Histoire de l’univers infinite, G 8 H 3 0 k 2 0 c finite, c 1 k infinite, c 1 k
Early universe: photons + ultra-relativistic particles radiation era
42rad Tc
2
22
radt
G32/c3c
2/1tT 2/1tRR1
T
Thermal equilibrium: interaction rate> volume expansion
interaction rate per unit time (one particle): (n=density)
volume expansion:
relative expansion per unit time:
0Hvn
dt)x(H3)x()dtH1(x)x( 30
330
3 nvN
0H
relativistic particles loose energy between interactions because of expansion
hc
hE
E'
hc'h'E
When kt<2mc2= 280 MeV, t=10-4 s, the last hadrons annihilate ,
except for a few non relativistic protons and neutrons, surviving thanks to a small asymmetry between matter and antimatter ( ). This is today’s matter!
This requires
1) small B non conservation, not included in the SM GUT
2) CP non conservation
CKM q mixing contributes, but may not be sufficient
neutrino mixing matrix also has a CP non conservation phase, which may do the job
3) Non equilibrium
910
pn
np
W W
s1t,MeV3kTfordecouple
kTEEm
g: cm
2cm4
W
4
e e
e e
W
e
e e
e e
e
e
e
,
onlyeofsurplussmallleaving
s'boosting,annihilatee,e
s10t
MeV1cm2kTwhenends 2e
t<1 s:
Neutrino freeze out at kT=0.8 MeV :
t> 10 s: primordial nucleosynthesis
remain photons, and a few electrons and non relativistic p, n in thermal equilibrium
Deuterium 2H is then the start of other fusion reactions, leading to light nuclei
s887epn
nep
pen
ne
e
e
MeV293.1c)mm(mckTmc
expN
N 2pn
22
p
n
20.0N
N
p
n
npH
MeV2.2QQHpn
epn
2
2
e
ends when MeV05.0kT
LiHeH
LieBe
BeHeHe
ppHeHeHe
HHn
HeHp
Hnp
743
e77
743
433
32
32
2
Nucleosynthesis
No stable nuclei with A=5, 8, primordial nucleosynthesis ends here!
After that the universe is filled with photons, electrons and light nuclei in thermal equilibrium
e-+p H(atom)+
slows down when ends for kT 0.3 eV, t=105 yr
,eV6.13IkT
t>105 yr matter (neutral atoms) and radiation decouple
no more Compton interaction with charged particles:
Universe becomes transparent to radiation (photons) relic photons
now cooled down to Cosmic Microwave Background (CMB)
e
e
BIG BANG
10-43 sec
10-32 sec
10-11 sec
10-4 sec
100 sec
300’000 yr109 yr
15x109 yr
gravity separates
EW Weak+Elec
inflation ends
quarks p, n
p, n He
formation of atoms
galaxy formationtoday
normal expansion
COBE
T=2.735 K
waves/cm
inte
nsity
, 10
-4er
g/cm
2 sr
sec
cm-1
3cm5410n
d
1e
h
c
8d)T,(ukTh3
2
black body, Planck
Relic of the early universe