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Hindawi Publishing CorporationAbstract and Applied AnalysisVolume 2013 Article ID 757824 9 pageshttpdxdoiorg1011552013757824
Research ArticleExistence and Houmllder Regularity of the FractionalLandau-Lifshitz Equation without Gilbert Damping Term
Lijun Wang1 Jingna Li1 and Li Xia2
1 Department of Mathematics Jinan University Guangzhou 510632 China2Department of Mathematics Guangdong University of Finance amp Economics Guangzhou 510320 China
Correspondence should be addressed to Jingna Li jingna8005hotmailcom
Received 15 September 2013 Accepted 6 November 2013
Academic Editor Natig M Atakishiyev
Copyright copy 2013 Lijun Wang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Existence and Holder regularity of weak solutions to the fractional Landau-Lifshitz equation without Gilbert damping term isproved through viscosity approximation Since the nonlinear term is nonlocal and of full order of the equation a commutator isconstructed to get the convergence of the approximating solutions
1 Introduction
We study the fractional Landau-Lifshitz equation
120597119898
120597119905= minus1205821119898 times Λ
2120572119898 + 120582
2119898 times (119898 times Λ
2120572119898) (1)
where 119898(119909 119905) is a three-dimensional vector representing themagnetization and 120572 120582
1 1205822
ge 0 are real numbers Λ =
(minusΔ)12 is the square root of the Laplacian and the so-called
Zygmund operator and times denotes the cross product of R3-valued vectors The first term 119898 times Λ
2120572119898 is the gyromagnetic
term and the second term 119898 times (119898 times Λ2120572
119898) is called theGilbert damping term The fractional diffusion operator Λ
2120572
is nonlocal except120572 = 0 1 2 3 whichmeans thatΛ2120572
119906(119909)
depends not only on 119906(119910) for 119910 near 119909 but also on 119906(119910) for all119910
Equation (1) plays a fundamental role in the understand-ing of nonequilibrium magnetism which is an interestingproblem from both scientific and technological points ofview Besides their traditional applications in the magneticrecording industry these films are also currently beingexplored as alternatives to semiconductors asmagneticmem-ory devices (MRAMs) which has given greater incentiveto study this subject Since defects impurities and thermalnoise play important roles in the dynamics of the mag-netization field in nanometer thick films they also make
an ideal playground for studying some of the nanoscalephysics branches [1ndash4]
Fractional differential equations which appear in severalbranches of physics such as viscoelasticity electrochemistrycontrol porous media and electromagnetic now attract theinterests of many mathematicians see for example [5 6]A good case in point is the quasi-geostrophic equationwith fractional dissipation which has been extensively stud-ied in the last decade see [7ndash9] The fractional Landau-Lifshitz equation shares some similar difficulties with quasi-geostrophic equation however the equation studied here ismuchmore complicated in several waysThe derivative in thenonlinear convective term is local in the quasi-geostrophicequation and the fluid velocity is divergence free but here for1205822
= 0 (1) is degenerate and even worse the derivative inthe nonlinear term is nonlocal and of the same order as theequation which brings new difficulties in the convergence ofthe approximate solutions Hence subtle techniques must beused to overcome the difficulties
Let us recall some previous results of the equation When120572 = 1 (1) becomes the standard Landau-Lifshitz equationintroduced first by Landau and Lifshitz in [10] which waswidely studied in [11ndash16] For general 120572 isin (0 1] the interestedreader can refer to [17] for mathematical theory When 120582
2=
0 (1) corresponds to Schrodinger flow which representsthe conservation of angular momentum [18ndash21] Numericaltreatments can be found in [22 23]
2 Abstract and Applied Analysis
In this paper we will study local existence of weaksolutions in the spatial domain (0 2120587) with 120582
2= 0 and 120572 isin
[12 1] The main difficulty as in many partial differentialequations is the convergence of the nonlinear terms In oursituation we even face the problem of nonlocal differentialoperators degeneracy and nonlocal nonlinear term Forthese reasons the structure of (1) must be explored in detail
It is straightforward to check the following conclusions
(1) The matrix 119861(119898) is ldquozero definiterdquo namely
120585120591119861 (119898) 120585 = 0 forall120585 119898 isin R
3 (6)
(2) The matrix 119861(119898) is singular that is
det119861 (119898) = 0 forall119898 isin R3 (7)
Hence (2) is quite different from usual quasilinear parabolicequations for the above reasons
To approximate (2) we consider the following mollifiedequation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (8)
which can be written as
120597119898
120597119905+ (120576119864 minus 119861 (119898)) Λ
2120572119898 = 0 (9)
The rest of this paper is divided into three parts firstwe consider the corresponding linear equation and get theregularity as a preparation to deal with (9) second positive-definition and uniform ellipticity of matrix 120576119864 minus 119861(119898) andchoice of norm space 119871
infin ensure that Leray-Schauder fixed-point theorem can be applied to prove the existence of weaksolution to (9) and the necessary a priori estimates in orderto guarantee convergence are obtained finally existence andHolder regularity of weak solution to (2) is proved by takingthe limit of the solution to (9) in which a commutator isconstructed to get the convergence
2 Cauchy Problem for the CorrespondingLinear Equation
Our starting point is the linear equation
120597119898
120597119905+ 119860 (119909 119905) Λ
2120572119898 = 119891 (119909 119905) in T
119899times (0 119879) (10)
119898 (119909 0) = 1198980
(119909) on T119899 (11)
where T119899 = R119899119885119899 is the flat torus and 119898(119909 119905) and 119898
0(119909)
are N-dimensional vector-valued functions We have thefollowing theorem about existence of solution to (10)-(11)
Theorem 1 Suppose that119873times119873matrix119860(119909 119905) defined on T119899times(0 119879) is measurable bounded and uniformly elliptic namelythere exists a constant 119870 such that
119860 (119909 119905) 120578 sdot 120578 ge 1198701003816100381610038161003816120578
10038161003816100381610038162
(12)
for all 119873-dimensional vectors 119891(119909 119905) isin 1198712(0 119879 119871
2(T119899))
and 1198980(119909) isin 119867
120572(T119899)Then there exists a unique vector-valued
solution to (10)-(11) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(T119899)) ⋂ 119871
2(0 119879 119867
2120572(T119899))
120597119898
120597119905isin 1198712
(0 119879 1198712
(T119899))
(13)
Proof of Theorem 1 Weapply theGalerkinmethod let 120593119895 be
an orthogonal basis of 1198712(T119899) consisting of all the eigenfunc-
tions for the operator
Λ2120572
120593119895
= 120582119895120593119895
120593119895
(0) = 120593119895
(2120587)
(14)
We are looking for approximate solutions 119898119899(119909 119905) to (10)-(11)
under the form
119898119899
(119909 119905) =
119899
sum
119895=1
119892119895
(119905) 120593119895
(119909) (15)
where 119892119895are vector-valued functions such that for 1 ⩽ 119894 ⩽ 119899
there holds
intΩ
[120597119898119899
120597119905+ 119860 (119909 119905) Λ
2120572119898119899
minus 119891 (119909 119905)] 120593119894119889119909 = 0 (16)
intΩ
[119898119899
(119909 0) minus 1198980
(119909)] 120593119894119889119909 = 0 (17)
These relations produce an ordinary differential system thatcan be writeen as
120597119892
120597119905= 119865 (119892) 119892 (0) = 119892
0 (18)
where 119892 = (1198921 1198922 119892
119899) and 119892
0is the projection of
1198980on (120593
1 1205932 120593119899) The existence of a local solution to
system (18) is a classical matter We now proceed to estimate
Abstract and Applied Analysis 3
the approximate solution 119898119899 Multiplying equality (16) by 119892
119894
and summing for 1 le 119894 le 119899 we have
1
2
1003817100381710038171003817119898119899
(sdot 119905)10038171003817100381710038172
1198712(T119899)
= int
119879
0
intT119899
(119891 sdot 119898119899
minus 119860 (119909 119905) Λ2120572
119898119899
sdot 119898119899) 119889119909 119889119905
+1
2
10038171003817100381710038171198980
10038171003817100381710038172
1198712(T119899)
(19)
Multiplying equality (16) by 120582119894119892119894and summing for 1 le 119894 le 119899
Actually if the matrix 119860(119909 119905) is retrained to a small classof good function matrix one can get higher regularity ofsolution to (10)-(11)
Since the right-hand member of equality (22) and (24) isuniformly bounded thus the solution g can be extended to alltime andwe can extract from119898
119899a subsequence (still denoted
by 119898119899) such that
119898119899
119898119904119908 in 1198712
(0 119879 1198672120572
(T119899))weaklylowast
120597119898119899
120597119905
120597119898
120597119905 in 119871
2(0 119879 119871
2(T119899))weakly
(25)
Hence we know that [24]
119898119899
997888rarr 119898 strongly in 1198712
(0 119879 1198712
(T119899))
ae in T119899
times [0 119879]
(26)
Passing to the limit (119899 rarr infin) we find a weak solution to(10)-(11) From (16) and taking the limit 119899 rarr infin we deducethat for all 120593 in vectors (120593
To get existence of weak solution to (2) we consider the fol-lowing approximate equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (36)
which is called mollified equation In this section and nextsection we assume that the spatial variable 119909 isin (0 2120587) ByLeray-Schauder fixed-point theorem we have the followingtheorem
Theorem3 Suppose that1198980(119909) isin 119867
120572(0 2120587) then there exists
a unique weak solution to (36)with initial-boundary condition(4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(0 2120587)) (37)
where 119876119879
= (0 2120587) times (0 119879)
Proof First themapping119879120582
119871infin
(119876119879
) rarr 119871infin
(119876119879
) is definedas follows For each 119906 isin 119871
infin(119876119879
) 119898 = 119879120582(119906) is a solution to
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119906 times Λ
2120572119898 (38)
with initial condition (4) in which 0 le 120582 le 1 By Theorem 1we know that 119898 = 119879
120582(119906) is the unique solution to (38)
with initial-boundary condition (4) and (5) moreover 119898 isin
119871infin
(0 119879 1198671(0 2120587))
Obviously for all 120582 the mapping 119879120582is continuous and
for any bounded closed set of 119871infin
(119876119879
) 119879120582is uniformly
continuous with respect to 0 le 120582 le 1To apply Leray-Schauder fixed-point theorem wemake a
priori estimate on all fixed points of 119879120582
Abstract and Applied Analysis 5
Taking the inner product of 119898(119909 119905) and equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119898 times Λ
2120572119898 (39)
we have
119898 sdot120597119898
120597119905= minus120576119898 sdot Λ
2120572119898 minus 120582 (119898 times Λ
2120572119898) sdot 119898 (40)
Integrating (40) over 119876120591(0 le 120591 le 119879) we get
119898 (sdot 120591)2
1198712(02120587)
+ 21205761003817100381710038171003817Λ120572
11989810038171003817100381710038172
1198712(119876120591)
le10038171003817100381710038171198980
10038171003817100381710038172
1198712(02120587)
(41)
in which 0 le 120582 le 1 0 le 120591 le 119879 Hence
sup0le119905le119879
119898 (sdot 119905)1198712(02120587)
le 1198621 (42)
in which 1198621is a constant independent of 120576 120582
Taking the inner product of Λ2120572
119898(119909 119905) and (39) weobtain
Λ2120572
119898 sdot120597119898
120597119905= minus120576Λ
2120572119898 sdot Λ2120572
119898 minus 120582Λ2120572
119898 sdot (119898 times Λ2120572
119898)
(43)
Integrating (43) over (0 2120587) with respect to variable 119909 leadsto
1
2
119889
119889119905
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038172
1198712(02120587)
+ 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572
11989810038161003816100381610038161003816
2
119889119909 le 0 (44)
Obviously
sup0le119905le119879
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038171198712(02120587) le 119862
2 (45)
in which 1198622is a constant independent of 120582 120576 From (42) for
each 120576 gt 0 we have
1198981198712(01198791198672120572(02120587)) le 119862 (46)
In view of (42) (45) and (46) Sobolev embedding theoremgives the desired result
For small initial data 1198980(119909) we can get higher regularity
of the solution to (36)
Theorem 4 Suppose that 1198980(119909) isin 119867
120572+2(0 2120587) 120572 isin (12 1]
and 1198980(119909)2
119867120572+2 le 1119872119879 where 119872 = 119900(1120576) is a certain
constant then there exists a unique weak solution to (36) withinitial-boundary condition (4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572+2
(0 2120587)) (47)
Proof Let the operator Λ2 act on (39) we get
minusΔ119898119905
= minus 120576Λ2120572+2
119898 + 120582Δ119898 times Λ2120572
119898
minus 120582119898 times Λ2120572+2
119898 + 120582nabla119898 times nablaΛ2120572
119898
(48)
Taking the inner product of Λ2120572+2
119898 and (48) and integratingover (0 2120587) we have
1
2
119889
119889119905int
2120587
0
10038161003816100381610038161003816Λ120572+2
11989810038161003816100381610038161003816
2
119889119909 + 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572+2
11989810038161003816100381610038161003816
2
119889119909
= 120582 int
2120587
0
(Δ119898 times Λ2120572
119898) sdot Λ2120572+2
119898 119889119909
+ 120582 int
2120587
0
(nabla119898 times nablaΛ2120572
119898) sdot Λ2120572+2
119898 119889119909
le1
120576
10038171003817100381710038171003817Λ2120572
11989810038171003817100381710038171003817
2
119871infin
Δ1198982
1198712
+1
120576nabla119898
2
119871infin
10038171003817100381710038171003817nablaΛ2120572
11989810038171003817100381710038171003817
2
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
le119872
2
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
4
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
(49)
Note that119872 = 119900(1120576) is a constant hence by Lemma 5 whichwill be proved later we have
sup0le119905le119879
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
2
1198712(02120587)
le 1198623 (50)
in which 1198623is independent of 120576 120582 From (49) for each 120576 gt 0
we have
1198981198712(01198791198672120572+2(02120587)) le 119862 (51)
Lemma 5 Let 119891(119905) be nonnegative continuous functions for0 le 119905 le 119879 Suppose that 119891(0) lt 1119896119879 and
119891 (119905) le 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) 0 le 119905 le 119879 (52)
where 119896 is a constant Then
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0)(53)
holds for 0 le 119905 le 119879
Proof Define
V (119905) = 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) (54)
Then the function V(119905) is nondecreasing V(0) = 119891(0) and
119889V (119905)
119889119905= 1198961198912
(119905) le 119896V2 (119905) (55)
since 119891(119905) le V(119905) le V(119879) According to (55) the function119911(119905) = minus1V(119905) satisfies
119889119911 (119905)
119889119905=
V1015840 (119905)
V2 (119905)=
1198961198912
(119905)
V2 (119905)le 119896 (56)
6 Abstract and Applied Analysis
Integrating (56) from 0 to 119905 yields
119911 (119905) le 119896119905 + 119911 (0) (57)
orminus
1
V (119905)le 119896119905 minus
1
V (0) (58)
that isV (119905) le
V (0)
1 minus 119896119905V (0) (59)
Hence
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0) (60)
4 Convergence Process
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
In this paper we will study local existence of weaksolutions in the spatial domain (0 2120587) with 120582
2= 0 and 120572 isin
[12 1] The main difficulty as in many partial differentialequations is the convergence of the nonlinear terms In oursituation we even face the problem of nonlocal differentialoperators degeneracy and nonlocal nonlinear term Forthese reasons the structure of (1) must be explored in detail
It is straightforward to check the following conclusions
(1) The matrix 119861(119898) is ldquozero definiterdquo namely
120585120591119861 (119898) 120585 = 0 forall120585 119898 isin R
3 (6)
(2) The matrix 119861(119898) is singular that is
det119861 (119898) = 0 forall119898 isin R3 (7)
Hence (2) is quite different from usual quasilinear parabolicequations for the above reasons
To approximate (2) we consider the following mollifiedequation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (8)
which can be written as
120597119898
120597119905+ (120576119864 minus 119861 (119898)) Λ
2120572119898 = 0 (9)
The rest of this paper is divided into three parts firstwe consider the corresponding linear equation and get theregularity as a preparation to deal with (9) second positive-definition and uniform ellipticity of matrix 120576119864 minus 119861(119898) andchoice of norm space 119871
infin ensure that Leray-Schauder fixed-point theorem can be applied to prove the existence of weaksolution to (9) and the necessary a priori estimates in orderto guarantee convergence are obtained finally existence andHolder regularity of weak solution to (2) is proved by takingthe limit of the solution to (9) in which a commutator isconstructed to get the convergence
2 Cauchy Problem for the CorrespondingLinear Equation
Our starting point is the linear equation
120597119898
120597119905+ 119860 (119909 119905) Λ
2120572119898 = 119891 (119909 119905) in T
119899times (0 119879) (10)
119898 (119909 0) = 1198980
(119909) on T119899 (11)
where T119899 = R119899119885119899 is the flat torus and 119898(119909 119905) and 119898
0(119909)
are N-dimensional vector-valued functions We have thefollowing theorem about existence of solution to (10)-(11)
Theorem 1 Suppose that119873times119873matrix119860(119909 119905) defined on T119899times(0 119879) is measurable bounded and uniformly elliptic namelythere exists a constant 119870 such that
119860 (119909 119905) 120578 sdot 120578 ge 1198701003816100381610038161003816120578
10038161003816100381610038162
(12)
for all 119873-dimensional vectors 119891(119909 119905) isin 1198712(0 119879 119871
2(T119899))
and 1198980(119909) isin 119867
120572(T119899)Then there exists a unique vector-valued
solution to (10)-(11) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(T119899)) ⋂ 119871
2(0 119879 119867
2120572(T119899))
120597119898
120597119905isin 1198712
(0 119879 1198712
(T119899))
(13)
Proof of Theorem 1 Weapply theGalerkinmethod let 120593119895 be
an orthogonal basis of 1198712(T119899) consisting of all the eigenfunc-
tions for the operator
Λ2120572
120593119895
= 120582119895120593119895
120593119895
(0) = 120593119895
(2120587)
(14)
We are looking for approximate solutions 119898119899(119909 119905) to (10)-(11)
under the form
119898119899
(119909 119905) =
119899
sum
119895=1
119892119895
(119905) 120593119895
(119909) (15)
where 119892119895are vector-valued functions such that for 1 ⩽ 119894 ⩽ 119899
there holds
intΩ
[120597119898119899
120597119905+ 119860 (119909 119905) Λ
2120572119898119899
minus 119891 (119909 119905)] 120593119894119889119909 = 0 (16)
intΩ
[119898119899
(119909 0) minus 1198980
(119909)] 120593119894119889119909 = 0 (17)
These relations produce an ordinary differential system thatcan be writeen as
120597119892
120597119905= 119865 (119892) 119892 (0) = 119892
0 (18)
where 119892 = (1198921 1198922 119892
119899) and 119892
0is the projection of
1198980on (120593
1 1205932 120593119899) The existence of a local solution to
system (18) is a classical matter We now proceed to estimate
Abstract and Applied Analysis 3
the approximate solution 119898119899 Multiplying equality (16) by 119892
119894
and summing for 1 le 119894 le 119899 we have
1
2
1003817100381710038171003817119898119899
(sdot 119905)10038171003817100381710038172
1198712(T119899)
= int
119879
0
intT119899
(119891 sdot 119898119899
minus 119860 (119909 119905) Λ2120572
119898119899
sdot 119898119899) 119889119909 119889119905
+1
2
10038171003817100381710038171198980
10038171003817100381710038172
1198712(T119899)
(19)
Multiplying equality (16) by 120582119894119892119894and summing for 1 le 119894 le 119899
Actually if the matrix 119860(119909 119905) is retrained to a small classof good function matrix one can get higher regularity ofsolution to (10)-(11)
Since the right-hand member of equality (22) and (24) isuniformly bounded thus the solution g can be extended to alltime andwe can extract from119898
119899a subsequence (still denoted
by 119898119899) such that
119898119899
119898119904119908 in 1198712
(0 119879 1198672120572
(T119899))weaklylowast
120597119898119899
120597119905
120597119898
120597119905 in 119871
2(0 119879 119871
2(T119899))weakly
(25)
Hence we know that [24]
119898119899
997888rarr 119898 strongly in 1198712
(0 119879 1198712
(T119899))
ae in T119899
times [0 119879]
(26)
Passing to the limit (119899 rarr infin) we find a weak solution to(10)-(11) From (16) and taking the limit 119899 rarr infin we deducethat for all 120593 in vectors (120593
To get existence of weak solution to (2) we consider the fol-lowing approximate equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (36)
which is called mollified equation In this section and nextsection we assume that the spatial variable 119909 isin (0 2120587) ByLeray-Schauder fixed-point theorem we have the followingtheorem
Theorem3 Suppose that1198980(119909) isin 119867
120572(0 2120587) then there exists
a unique weak solution to (36)with initial-boundary condition(4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(0 2120587)) (37)
where 119876119879
= (0 2120587) times (0 119879)
Proof First themapping119879120582
119871infin
(119876119879
) rarr 119871infin
(119876119879
) is definedas follows For each 119906 isin 119871
infin(119876119879
) 119898 = 119879120582(119906) is a solution to
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119906 times Λ
2120572119898 (38)
with initial condition (4) in which 0 le 120582 le 1 By Theorem 1we know that 119898 = 119879
120582(119906) is the unique solution to (38)
with initial-boundary condition (4) and (5) moreover 119898 isin
119871infin
(0 119879 1198671(0 2120587))
Obviously for all 120582 the mapping 119879120582is continuous and
for any bounded closed set of 119871infin
(119876119879
) 119879120582is uniformly
continuous with respect to 0 le 120582 le 1To apply Leray-Schauder fixed-point theorem wemake a
priori estimate on all fixed points of 119879120582
Abstract and Applied Analysis 5
Taking the inner product of 119898(119909 119905) and equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119898 times Λ
2120572119898 (39)
we have
119898 sdot120597119898
120597119905= minus120576119898 sdot Λ
2120572119898 minus 120582 (119898 times Λ
2120572119898) sdot 119898 (40)
Integrating (40) over 119876120591(0 le 120591 le 119879) we get
119898 (sdot 120591)2
1198712(02120587)
+ 21205761003817100381710038171003817Λ120572
11989810038171003817100381710038172
1198712(119876120591)
le10038171003817100381710038171198980
10038171003817100381710038172
1198712(02120587)
(41)
in which 0 le 120582 le 1 0 le 120591 le 119879 Hence
sup0le119905le119879
119898 (sdot 119905)1198712(02120587)
le 1198621 (42)
in which 1198621is a constant independent of 120576 120582
Taking the inner product of Λ2120572
119898(119909 119905) and (39) weobtain
Λ2120572
119898 sdot120597119898
120597119905= minus120576Λ
2120572119898 sdot Λ2120572
119898 minus 120582Λ2120572
119898 sdot (119898 times Λ2120572
119898)
(43)
Integrating (43) over (0 2120587) with respect to variable 119909 leadsto
1
2
119889
119889119905
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038172
1198712(02120587)
+ 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572
11989810038161003816100381610038161003816
2
119889119909 le 0 (44)
Obviously
sup0le119905le119879
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038171198712(02120587) le 119862
2 (45)
in which 1198622is a constant independent of 120582 120576 From (42) for
each 120576 gt 0 we have
1198981198712(01198791198672120572(02120587)) le 119862 (46)
In view of (42) (45) and (46) Sobolev embedding theoremgives the desired result
For small initial data 1198980(119909) we can get higher regularity
of the solution to (36)
Theorem 4 Suppose that 1198980(119909) isin 119867
120572+2(0 2120587) 120572 isin (12 1]
and 1198980(119909)2
119867120572+2 le 1119872119879 where 119872 = 119900(1120576) is a certain
constant then there exists a unique weak solution to (36) withinitial-boundary condition (4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572+2
(0 2120587)) (47)
Proof Let the operator Λ2 act on (39) we get
minusΔ119898119905
= minus 120576Λ2120572+2
119898 + 120582Δ119898 times Λ2120572
119898
minus 120582119898 times Λ2120572+2
119898 + 120582nabla119898 times nablaΛ2120572
119898
(48)
Taking the inner product of Λ2120572+2
119898 and (48) and integratingover (0 2120587) we have
1
2
119889
119889119905int
2120587
0
10038161003816100381610038161003816Λ120572+2
11989810038161003816100381610038161003816
2
119889119909 + 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572+2
11989810038161003816100381610038161003816
2
119889119909
= 120582 int
2120587
0
(Δ119898 times Λ2120572
119898) sdot Λ2120572+2
119898 119889119909
+ 120582 int
2120587
0
(nabla119898 times nablaΛ2120572
119898) sdot Λ2120572+2
119898 119889119909
le1
120576
10038171003817100381710038171003817Λ2120572
11989810038171003817100381710038171003817
2
119871infin
Δ1198982
1198712
+1
120576nabla119898
2
119871infin
10038171003817100381710038171003817nablaΛ2120572
11989810038171003817100381710038171003817
2
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
le119872
2
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
4
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
(49)
Note that119872 = 119900(1120576) is a constant hence by Lemma 5 whichwill be proved later we have
sup0le119905le119879
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
2
1198712(02120587)
le 1198623 (50)
in which 1198623is independent of 120576 120582 From (49) for each 120576 gt 0
we have
1198981198712(01198791198672120572+2(02120587)) le 119862 (51)
Lemma 5 Let 119891(119905) be nonnegative continuous functions for0 le 119905 le 119879 Suppose that 119891(0) lt 1119896119879 and
119891 (119905) le 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) 0 le 119905 le 119879 (52)
where 119896 is a constant Then
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0)(53)
holds for 0 le 119905 le 119879
Proof Define
V (119905) = 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) (54)
Then the function V(119905) is nondecreasing V(0) = 119891(0) and
119889V (119905)
119889119905= 1198961198912
(119905) le 119896V2 (119905) (55)
since 119891(119905) le V(119905) le V(119879) According to (55) the function119911(119905) = minus1V(119905) satisfies
119889119911 (119905)
119889119905=
V1015840 (119905)
V2 (119905)=
1198961198912
(119905)
V2 (119905)le 119896 (56)
6 Abstract and Applied Analysis
Integrating (56) from 0 to 119905 yields
119911 (119905) le 119896119905 + 119911 (0) (57)
orminus
1
V (119905)le 119896119905 minus
1
V (0) (58)
that isV (119905) le
V (0)
1 minus 119896119905V (0) (59)
Hence
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0) (60)
4 Convergence Process
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
Actually if the matrix 119860(119909 119905) is retrained to a small classof good function matrix one can get higher regularity ofsolution to (10)-(11)
Since the right-hand member of equality (22) and (24) isuniformly bounded thus the solution g can be extended to alltime andwe can extract from119898
119899a subsequence (still denoted
by 119898119899) such that
119898119899
119898119904119908 in 1198712
(0 119879 1198672120572
(T119899))weaklylowast
120597119898119899
120597119905
120597119898
120597119905 in 119871
2(0 119879 119871
2(T119899))weakly
(25)
Hence we know that [24]
119898119899
997888rarr 119898 strongly in 1198712
(0 119879 1198712
(T119899))
ae in T119899
times [0 119879]
(26)
Passing to the limit (119899 rarr infin) we find a weak solution to(10)-(11) From (16) and taking the limit 119899 rarr infin we deducethat for all 120593 in vectors (120593
To get existence of weak solution to (2) we consider the fol-lowing approximate equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (36)
which is called mollified equation In this section and nextsection we assume that the spatial variable 119909 isin (0 2120587) ByLeray-Schauder fixed-point theorem we have the followingtheorem
Theorem3 Suppose that1198980(119909) isin 119867
120572(0 2120587) then there exists
a unique weak solution to (36)with initial-boundary condition(4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(0 2120587)) (37)
where 119876119879
= (0 2120587) times (0 119879)
Proof First themapping119879120582
119871infin
(119876119879
) rarr 119871infin
(119876119879
) is definedas follows For each 119906 isin 119871
infin(119876119879
) 119898 = 119879120582(119906) is a solution to
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119906 times Λ
2120572119898 (38)
with initial condition (4) in which 0 le 120582 le 1 By Theorem 1we know that 119898 = 119879
120582(119906) is the unique solution to (38)
with initial-boundary condition (4) and (5) moreover 119898 isin
119871infin
(0 119879 1198671(0 2120587))
Obviously for all 120582 the mapping 119879120582is continuous and
for any bounded closed set of 119871infin
(119876119879
) 119879120582is uniformly
continuous with respect to 0 le 120582 le 1To apply Leray-Schauder fixed-point theorem wemake a
priori estimate on all fixed points of 119879120582
Abstract and Applied Analysis 5
Taking the inner product of 119898(119909 119905) and equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119898 times Λ
2120572119898 (39)
we have
119898 sdot120597119898
120597119905= minus120576119898 sdot Λ
2120572119898 minus 120582 (119898 times Λ
2120572119898) sdot 119898 (40)
Integrating (40) over 119876120591(0 le 120591 le 119879) we get
119898 (sdot 120591)2
1198712(02120587)
+ 21205761003817100381710038171003817Λ120572
11989810038171003817100381710038172
1198712(119876120591)
le10038171003817100381710038171198980
10038171003817100381710038172
1198712(02120587)
(41)
in which 0 le 120582 le 1 0 le 120591 le 119879 Hence
sup0le119905le119879
119898 (sdot 119905)1198712(02120587)
le 1198621 (42)
in which 1198621is a constant independent of 120576 120582
Taking the inner product of Λ2120572
119898(119909 119905) and (39) weobtain
Λ2120572
119898 sdot120597119898
120597119905= minus120576Λ
2120572119898 sdot Λ2120572
119898 minus 120582Λ2120572
119898 sdot (119898 times Λ2120572
119898)
(43)
Integrating (43) over (0 2120587) with respect to variable 119909 leadsto
1
2
119889
119889119905
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038172
1198712(02120587)
+ 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572
11989810038161003816100381610038161003816
2
119889119909 le 0 (44)
Obviously
sup0le119905le119879
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038171198712(02120587) le 119862
2 (45)
in which 1198622is a constant independent of 120582 120576 From (42) for
each 120576 gt 0 we have
1198981198712(01198791198672120572(02120587)) le 119862 (46)
In view of (42) (45) and (46) Sobolev embedding theoremgives the desired result
For small initial data 1198980(119909) we can get higher regularity
of the solution to (36)
Theorem 4 Suppose that 1198980(119909) isin 119867
120572+2(0 2120587) 120572 isin (12 1]
and 1198980(119909)2
119867120572+2 le 1119872119879 where 119872 = 119900(1120576) is a certain
constant then there exists a unique weak solution to (36) withinitial-boundary condition (4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572+2
(0 2120587)) (47)
Proof Let the operator Λ2 act on (39) we get
minusΔ119898119905
= minus 120576Λ2120572+2
119898 + 120582Δ119898 times Λ2120572
119898
minus 120582119898 times Λ2120572+2
119898 + 120582nabla119898 times nablaΛ2120572
119898
(48)
Taking the inner product of Λ2120572+2
119898 and (48) and integratingover (0 2120587) we have
1
2
119889
119889119905int
2120587
0
10038161003816100381610038161003816Λ120572+2
11989810038161003816100381610038161003816
2
119889119909 + 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572+2
11989810038161003816100381610038161003816
2
119889119909
= 120582 int
2120587
0
(Δ119898 times Λ2120572
119898) sdot Λ2120572+2
119898 119889119909
+ 120582 int
2120587
0
(nabla119898 times nablaΛ2120572
119898) sdot Λ2120572+2
119898 119889119909
le1
120576
10038171003817100381710038171003817Λ2120572
11989810038171003817100381710038171003817
2
119871infin
Δ1198982
1198712
+1
120576nabla119898
2
119871infin
10038171003817100381710038171003817nablaΛ2120572
11989810038171003817100381710038171003817
2
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
le119872
2
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
4
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
(49)
Note that119872 = 119900(1120576) is a constant hence by Lemma 5 whichwill be proved later we have
sup0le119905le119879
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
2
1198712(02120587)
le 1198623 (50)
in which 1198623is independent of 120576 120582 From (49) for each 120576 gt 0
we have
1198981198712(01198791198672120572+2(02120587)) le 119862 (51)
Lemma 5 Let 119891(119905) be nonnegative continuous functions for0 le 119905 le 119879 Suppose that 119891(0) lt 1119896119879 and
119891 (119905) le 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) 0 le 119905 le 119879 (52)
where 119896 is a constant Then
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0)(53)
holds for 0 le 119905 le 119879
Proof Define
V (119905) = 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) (54)
Then the function V(119905) is nondecreasing V(0) = 119891(0) and
119889V (119905)
119889119905= 1198961198912
(119905) le 119896V2 (119905) (55)
since 119891(119905) le V(119905) le V(119879) According to (55) the function119911(119905) = minus1V(119905) satisfies
119889119911 (119905)
119889119905=
V1015840 (119905)
V2 (119905)=
1198961198912
(119905)
V2 (119905)le 119896 (56)
6 Abstract and Applied Analysis
Integrating (56) from 0 to 119905 yields
119911 (119905) le 119896119905 + 119911 (0) (57)
orminus
1
V (119905)le 119896119905 minus
1
V (0) (58)
that isV (119905) le
V (0)
1 minus 119896119905V (0) (59)
Hence
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0) (60)
4 Convergence Process
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
To get existence of weak solution to (2) we consider the fol-lowing approximate equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 119898 times Λ
2120572119898 (36)
which is called mollified equation In this section and nextsection we assume that the spatial variable 119909 isin (0 2120587) ByLeray-Schauder fixed-point theorem we have the followingtheorem
Theorem3 Suppose that1198980(119909) isin 119867
120572(0 2120587) then there exists
a unique weak solution to (36)with initial-boundary condition(4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572
(0 2120587)) (37)
where 119876119879
= (0 2120587) times (0 119879)
Proof First themapping119879120582
119871infin
(119876119879
) rarr 119871infin
(119876119879
) is definedas follows For each 119906 isin 119871
infin(119876119879
) 119898 = 119879120582(119906) is a solution to
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119906 times Λ
2120572119898 (38)
with initial condition (4) in which 0 le 120582 le 1 By Theorem 1we know that 119898 = 119879
120582(119906) is the unique solution to (38)
with initial-boundary condition (4) and (5) moreover 119898 isin
119871infin
(0 119879 1198671(0 2120587))
Obviously for all 120582 the mapping 119879120582is continuous and
for any bounded closed set of 119871infin
(119876119879
) 119879120582is uniformly
continuous with respect to 0 le 120582 le 1To apply Leray-Schauder fixed-point theorem wemake a
priori estimate on all fixed points of 119879120582
Abstract and Applied Analysis 5
Taking the inner product of 119898(119909 119905) and equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119898 times Λ
2120572119898 (39)
we have
119898 sdot120597119898
120597119905= minus120576119898 sdot Λ
2120572119898 minus 120582 (119898 times Λ
2120572119898) sdot 119898 (40)
Integrating (40) over 119876120591(0 le 120591 le 119879) we get
119898 (sdot 120591)2
1198712(02120587)
+ 21205761003817100381710038171003817Λ120572
11989810038171003817100381710038172
1198712(119876120591)
le10038171003817100381710038171198980
10038171003817100381710038172
1198712(02120587)
(41)
in which 0 le 120582 le 1 0 le 120591 le 119879 Hence
sup0le119905le119879
119898 (sdot 119905)1198712(02120587)
le 1198621 (42)
in which 1198621is a constant independent of 120576 120582
Taking the inner product of Λ2120572
119898(119909 119905) and (39) weobtain
Λ2120572
119898 sdot120597119898
120597119905= minus120576Λ
2120572119898 sdot Λ2120572
119898 minus 120582Λ2120572
119898 sdot (119898 times Λ2120572
119898)
(43)
Integrating (43) over (0 2120587) with respect to variable 119909 leadsto
1
2
119889
119889119905
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038172
1198712(02120587)
+ 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572
11989810038161003816100381610038161003816
2
119889119909 le 0 (44)
Obviously
sup0le119905le119879
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038171198712(02120587) le 119862
2 (45)
in which 1198622is a constant independent of 120582 120576 From (42) for
each 120576 gt 0 we have
1198981198712(01198791198672120572(02120587)) le 119862 (46)
In view of (42) (45) and (46) Sobolev embedding theoremgives the desired result
For small initial data 1198980(119909) we can get higher regularity
of the solution to (36)
Theorem 4 Suppose that 1198980(119909) isin 119867
120572+2(0 2120587) 120572 isin (12 1]
and 1198980(119909)2
119867120572+2 le 1119872119879 where 119872 = 119900(1120576) is a certain
constant then there exists a unique weak solution to (36) withinitial-boundary condition (4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572+2
(0 2120587)) (47)
Proof Let the operator Λ2 act on (39) we get
minusΔ119898119905
= minus 120576Λ2120572+2
119898 + 120582Δ119898 times Λ2120572
119898
minus 120582119898 times Λ2120572+2
119898 + 120582nabla119898 times nablaΛ2120572
119898
(48)
Taking the inner product of Λ2120572+2
119898 and (48) and integratingover (0 2120587) we have
1
2
119889
119889119905int
2120587
0
10038161003816100381610038161003816Λ120572+2
11989810038161003816100381610038161003816
2
119889119909 + 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572+2
11989810038161003816100381610038161003816
2
119889119909
= 120582 int
2120587
0
(Δ119898 times Λ2120572
119898) sdot Λ2120572+2
119898 119889119909
+ 120582 int
2120587
0
(nabla119898 times nablaΛ2120572
119898) sdot Λ2120572+2
119898 119889119909
le1
120576
10038171003817100381710038171003817Λ2120572
11989810038171003817100381710038171003817
2
119871infin
Δ1198982
1198712
+1
120576nabla119898
2
119871infin
10038171003817100381710038171003817nablaΛ2120572
11989810038171003817100381710038171003817
2
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
le119872
2
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
4
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
(49)
Note that119872 = 119900(1120576) is a constant hence by Lemma 5 whichwill be proved later we have
sup0le119905le119879
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
2
1198712(02120587)
le 1198623 (50)
in which 1198623is independent of 120576 120582 From (49) for each 120576 gt 0
we have
1198981198712(01198791198672120572+2(02120587)) le 119862 (51)
Lemma 5 Let 119891(119905) be nonnegative continuous functions for0 le 119905 le 119879 Suppose that 119891(0) lt 1119896119879 and
119891 (119905) le 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) 0 le 119905 le 119879 (52)
where 119896 is a constant Then
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0)(53)
holds for 0 le 119905 le 119879
Proof Define
V (119905) = 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) (54)
Then the function V(119905) is nondecreasing V(0) = 119891(0) and
119889V (119905)
119889119905= 1198961198912
(119905) le 119896V2 (119905) (55)
since 119891(119905) le V(119905) le V(119879) According to (55) the function119911(119905) = minus1V(119905) satisfies
119889119911 (119905)
119889119905=
V1015840 (119905)
V2 (119905)=
1198961198912
(119905)
V2 (119905)le 119896 (56)
6 Abstract and Applied Analysis
Integrating (56) from 0 to 119905 yields
119911 (119905) le 119896119905 + 119911 (0) (57)
orminus
1
V (119905)le 119896119905 minus
1
V (0) (58)
that isV (119905) le
V (0)
1 minus 119896119905V (0) (59)
Hence
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0) (60)
4 Convergence Process
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
Taking the inner product of 119898(119909 119905) and equation
120597119898
120597119905= minus120576Λ
2120572119898 minus 120582119898 times Λ
2120572119898 (39)
we have
119898 sdot120597119898
120597119905= minus120576119898 sdot Λ
2120572119898 minus 120582 (119898 times Λ
2120572119898) sdot 119898 (40)
Integrating (40) over 119876120591(0 le 120591 le 119879) we get
119898 (sdot 120591)2
1198712(02120587)
+ 21205761003817100381710038171003817Λ120572
11989810038171003817100381710038172
1198712(119876120591)
le10038171003817100381710038171198980
10038171003817100381710038172
1198712(02120587)
(41)
in which 0 le 120582 le 1 0 le 120591 le 119879 Hence
sup0le119905le119879
119898 (sdot 119905)1198712(02120587)
le 1198621 (42)
in which 1198621is a constant independent of 120576 120582
Taking the inner product of Λ2120572
119898(119909 119905) and (39) weobtain
Λ2120572
119898 sdot120597119898
120597119905= minus120576Λ
2120572119898 sdot Λ2120572
119898 minus 120582Λ2120572
119898 sdot (119898 times Λ2120572
119898)
(43)
Integrating (43) over (0 2120587) with respect to variable 119909 leadsto
1
2
119889
119889119905
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038172
1198712(02120587)
+ 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572
11989810038161003816100381610038161003816
2
119889119909 le 0 (44)
Obviously
sup0le119905le119879
1003817100381710038171003817Λ120572
119898 (sdot 119905)10038171003817100381710038171198712(02120587) le 119862
2 (45)
in which 1198622is a constant independent of 120582 120576 From (42) for
each 120576 gt 0 we have
1198981198712(01198791198672120572(02120587)) le 119862 (46)
In view of (42) (45) and (46) Sobolev embedding theoremgives the desired result
For small initial data 1198980(119909) we can get higher regularity
of the solution to (36)
Theorem 4 Suppose that 1198980(119909) isin 119867
120572+2(0 2120587) 120572 isin (12 1]
and 1198980(119909)2
119867120572+2 le 1119872119879 where 119872 = 119900(1120576) is a certain
constant then there exists a unique weak solution to (36) withinitial-boundary condition (4) and (5) such that
119898 (119909 119905) isin 119871infin
(0 119879 119867120572+2
(0 2120587)) (47)
Proof Let the operator Λ2 act on (39) we get
minusΔ119898119905
= minus 120576Λ2120572+2
119898 + 120582Δ119898 times Λ2120572
119898
minus 120582119898 times Λ2120572+2
119898 + 120582nabla119898 times nablaΛ2120572
119898
(48)
Taking the inner product of Λ2120572+2
119898 and (48) and integratingover (0 2120587) we have
1
2
119889
119889119905int
2120587
0
10038161003816100381610038161003816Λ120572+2
11989810038161003816100381610038161003816
2
119889119909 + 120576 int
2120587
0
10038161003816100381610038161003816Λ2120572+2
11989810038161003816100381610038161003816
2
119889119909
= 120582 int
2120587
0
(Δ119898 times Λ2120572
119898) sdot Λ2120572+2
119898 119889119909
+ 120582 int
2120587
0
(nabla119898 times nablaΛ2120572
119898) sdot Λ2120572+2
119898 119889119909
le1
120576
10038171003817100381710038171003817Λ2120572
11989810038171003817100381710038171003817
2
119871infin
Δ1198982
1198712
+1
120576nabla119898
2
119871infin
10038171003817100381710038171003817nablaΛ2120572
11989810038171003817100381710038171003817
2
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
le119872
2
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
4
1198712
+120576
2
10038171003817100381710038171003817Λ2120572+2
11989810038171003817100381710038171003817
2
1198712
(49)
Note that119872 = 119900(1120576) is a constant hence by Lemma 5 whichwill be proved later we have
sup0le119905le119879
10038171003817100381710038171003817Λ120572+2
11989810038171003817100381710038171003817
2
1198712(02120587)
le 1198623 (50)
in which 1198623is independent of 120576 120582 From (49) for each 120576 gt 0
we have
1198981198712(01198791198672120572+2(02120587)) le 119862 (51)
Lemma 5 Let 119891(119905) be nonnegative continuous functions for0 le 119905 le 119879 Suppose that 119891(0) lt 1119896119879 and
119891 (119905) le 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) 0 le 119905 le 119879 (52)
where 119896 is a constant Then
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0)(53)
holds for 0 le 119905 le 119879
Proof Define
V (119905) = 119896 int
119905
0
1198912
(120591) 119889120591 + 119891 (0) (54)
Then the function V(119905) is nondecreasing V(0) = 119891(0) and
119889V (119905)
119889119905= 1198961198912
(119905) le 119896V2 (119905) (55)
since 119891(119905) le V(119905) le V(119879) According to (55) the function119911(119905) = minus1V(119905) satisfies
119889119911 (119905)
119889119905=
V1015840 (119905)
V2 (119905)=
1198961198912
(119905)
V2 (119905)le 119896 (56)
6 Abstract and Applied Analysis
Integrating (56) from 0 to 119905 yields
119911 (119905) le 119896119905 + 119911 (0) (57)
orminus
1
V (119905)le 119896119905 minus
1
V (0) (58)
that isV (119905) le
V (0)
1 minus 119896119905V (0) (59)
Hence
119891 (119905) le119891 (0)
1 minus 119896119879119891 (0) (60)
4 Convergence Process
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
Before we prove existence of weak solution to the fractionalLandau-Lifshitz model without Gilbert term (2) we firstrecall two Lemmas in [25 26] respectively
Lemma 6 Suppose that 119904 gt 0 and 119901 isin (1 +infin) If 119891 119892 isin Sthe Schwartz class then
1003817100381710038171003817Λ119904
(119891119892) minus 119891Λ119904119892
1003817100381710038171003817119871119901
le 119862 (1003817100381710038171003817nabla119891
If 119898 minus 119895 minus (119899119903) is a nonnegative integer then (65) holds for119886 = 119895119898 The constant 119862 depends only on 119903 119902 119898 119895 119886 and theshape of Ω
From (45) we conclude the following
Lemma 8 Solutions to (36) satisfy
sup0le119905le119879
1003817100381710038171003817119898120576
(sdot 119905)1003817100381710038171003817119867120572(02120587) le 119862 (66)
in which 119862 is independent of 120576
For the uniform bound of 120597119898120576120597119905 we have the following
lemma
Lemma 9 120597119898120576120597119905 in (36) satisfies
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
minus 11989810038171003817100381710038171198712(0119879119867120573(02120587)) 997888rarr 0 as 120576 997888rarr 0
(86)
As 120576 rarr 0 in (76) we have
int int119876119879
[120597119898
120597119905120593 + Λ
120572(120593 times 119898) sdot Λ
120572119898] 119889119909 119889119905
+ int
2120587
0
120593 (119909 0) sdot 1198980
(119909) 119889119909 = 0
(87)
for all test functions 120593 isin (119862infin
(119876119879
))3
Acknowledgment
The paper is supported by the National Natural ScienceFoundation of China (no 11201181 no 11201311)
References
[1] A Hubert and R Schafer Magnetic Domains The Analysis ofMagnetic Microstructures Springer Berlin Germany 1998
[2] J M Daughton ldquoMagnetoresistive memory technologyrdquo ThinSolid Films vol 216 no 1 pp 162ndash168 1992
[3] B Heinrich and J A C Bland Ultrathin Magnetic Structures ISpringer Berlin Germany 1994
[4] G A Prinz ldquoMagnetoelectronicsrdquo Science vol 282 no 5394pp 1660ndash1663 1998
[5] K S Miller and B Ross An Introduction to the FractionalCalculus and Differential Equations JohnWiley New Youk NYUSA 1993
[6] I Podlubny Fractional Differential Equations Mathematics inScience and Engeineering 198 Academic Press San Diego CalifUSA 1999
[7] P Constantin D Cordoba and J Wu ldquoOn the critical dissipa-tive quasi-geostrophic equationrdquo Indiana University Mathemat-ics Journal vol 50 pp 97ndash106 2001
[8] P Constantin A J Majda and E Tabak ldquoFormation ofstrong fronts in the 2-D quasigeostrophic thermal active scalarrdquoNonlinearity vol 7 no 6 pp 1495ndash1533 1994
[9] P Constantin and J Wu ldquoBehavior of solutions of 2D quasi-geostrophic equationsrdquo SIAM Journal on Mathematical Analy-sis vol 30 no 5 pp 937ndash948 1999
[10] L Landau and E Lifshitz ldquoOn the theory of the dispersionof magnetic permeability in ferromagnetic bodiesrdquo UkrainianJournal of Physics vol 8 pp 153ndash169 1935
[11] B L Guo and M C Hong ldquoThe Landau-Lifshitz equation ofthe ferromagnetic spin chain and harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 1 no 3 pp311ndash334 1993
[12] M C Yunmei J D Shijin and L G Boling ldquoPartial regularityfor two dimensional Landau-Lifshitz equationsrdquo Acta Mathe-matica Sinica vol 14 no 3 pp 423ndash432 1998
Abstract and Applied Analysis 9
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969
[13] F Alouges and A Soyeur ldquoOn global weak solutions forLandau-Lifshitz equations existence and nonuniquenessrdquoNon-linear Analysis vol 18 no 11 pp 1071ndash1084 1992
[14] A Visintin ldquoOn Landau-Lifshitzrsquo equations for ferromag-netismrdquo Japan Journal of Applied Mathematics vol 2 no 1 pp69ndash84 1985
[15] J L Joly GMetivier and J Rauch ldquoGlobal solutions toMaxwellequations in a ferromagnetic mediumrdquoAnnales Henri Poincarevol 1 no 2 pp 307ndash340 2000
[16] G Carbou and P Fabrie ldquoRegular solutions for Landau-Lifshitzequation in a bounded domainrdquoDifferential Integral Equationsvol 14 pp 213ndash229 2001
[17] B Guo and X Pu ldquoThe fractional Landau-Lifshitz-Gilbertequation and the heat flow of harmonic mapsrdquo Calculus ofVariations and Partial Differential Equations vol 42 no 1-2 pp1ndash19 2011
[18] P L Sulem C Sulem and C Bardos ldquoOn the continuous limitfor a system of classical spinsrdquo Communications in Mathemati-cal Physics vol 107 no 3 pp 431ndash454 1986
[19] N Chang J Shatah and K Uhlenbeck ldquoSchrodinger mapsrdquoCommunications on Pure and Applied Mathematics vol 53 no5 pp 590ndash602 2000
[20] J Shatah and C Zeng ldquoSchrodinger maps and anti-ferromagnetic chainsrdquo Communications in MathematicalPhysics vol 262 no 2 pp 299ndash315 2006
[21] W Ding H Tang and C Zeng ldquoSelf-similar solutions ofSchrodinger flowsrdquo Calculus of Variations and Partial Differen-tial Equations vol 34 no 2 pp 267ndash277 2009
[22] N E Weinan and X P Wang ldquoNumerical methods for theLandau-Lifshitz equationrdquo SIAM Journal on Numerical Analy-sis vol 38 no 5 pp 1647ndash1665 2001
[23] C J Garcıa-Cervera and X Wang ldquoSpin-polarized currents inferromagnetic multilayersrdquo Journal of Computational Physicsvol 224 no 2 pp 699ndash711 2007
[24] J L Lions Quelques Methodes de Resolution des Problems AuxLimites Non Lineaire Chinese Edition Sun Yat-sen UniversityPress GuangZhou China 1996
[25] R Coifman and Y MeyerNolinear Harmonic Analysis OpertorTheory and PDE Princeton University Press Princeton NJUSA 1986
[26] A Friedman Partial Differential Equations Holt Rinehart andWinston New York NY USA 1969