Gary Steigman OSU Physics Colloquium, November 21, 2006 PROBING THE UNIVERSE AT 20 MINUTES AND 400 THOUSAND YEARS The Ohio State University
Feb 03, 2016
Gary Steigman
OSU Physics Colloquium, November 21, 2006
PROBING THE UNIVERSE AT
20 MINUTES AND 400 THOUSAND YEARS
The Ohio State University
The Universe is expanding and is filled with radiation
~ 0.1 s after the Big BangNeutrinos Decouple
~ 400 kyr after the Big BangRelic Photons (CBR) are free
~ 100 s after the Big BangPrimordial Nucleosynthesis
BBN & The CBR Provide Complementary
Probes Of The Early Universe
Do predictions and observations of the
baryon density and the expansion rate
agree at 20 minutes and at 400 kyr ?
Baryon Density Parameter
Note : Baryons Nucleons
nN / n ; 10 = 274 Bh2
where : B B / c
and : h H0 / 100 km / s / Mpc 0.7
H0-1 = 9.8 / h Gyr 14 Gyr
BBN “begins” at T 70 keV
(when n / p 1 / 7)
Coulomb barriers and the absence of
free neutrons end BBN at T 30 keV
tBBN 4 24 min.
The Early, Hot, Dense Universe Is A
Cosmic Nuclear Reactor
10
More nucleons less D
Evolution of Deuterium
n / p 1 / 7 Y 0.25
All / most neutrons are incorporated in 4He
Y is VERY WEAKLY dependent on the nucleon abundance
Y 4He Mass Fraction
Y is neutron limited
10
Evolution of Helium - 4
BBN Abundances of D, 3He, 7Li
are RATE (Density) LIMITED
D, 3He, 7Li are potential BARYOMETERS
BBN – Predicted Primordial Abundances
7Li 7Be
Two pathways to mass - 7
DEUTERIUM --- The Baryometer Of Choice
• As the Universe evolves, D is only DESTROYED
* Anywhere, Anytime : (D/H) t (D/H) P
* For Z << Z : (D/H) t (D/H) P (Deuterium Plateau)
• H and D are seen in Absorption BUT …
* H and D spectra are identical H Interlopers?
* Unresolved velocity structure Errors in N(H ) ?
• (D/H) P is sensitive to the baryon density ( )
Ly - Absorption
D/H vs. Metallicity
Deuterium Plateau ?
Low – Z / High – z QSOALS
Real variations,systematic differences, statistical uncertainties ?
D/H vs. H I Column Density
D/H Correlated With N(H I) ?
D/H vs. H I Column Density
NEW (2006)
D/H vs. H I Column Density
D/H Correlated With N(H I) ?
D/H vs. Metallicity
For Primordial D/H adopt the mean and the
dispersion around the mean
105(D/H)P = 2.65 ± 0.25
(D/H)P + SBBN Constrains 10 (@ ~ 7 %)
SBBN
CBR
B h2 = 0.018, 0.023, 0.028
CBR (WMAP) constrains B h2
CBR Temperature Anisotropy Spectrum
(T2 vs. ) Encodes The Baryon Density
The CBR is an early - Universe Baryometer
Barger et al. (2003)
Amplitudes of odd/even
peaks depend on Bh2
CBR Constrains 10 (@ ~ 3 %)
CBR
BBN (20 min) & CBR (380 kyr) AGREE !
BBN CBR
BBN + WMAP
D/H vs. Metallicity
The CBR is a good Deuteronometer !
• S H / H (/)1/2 (1 + 7N / 43)1/2
The Expansion Rate (H Hubble Parameter)
provides a probe of Non-Standard Physics
• 4He is sensitive to S while D probes
for : + N and N 3 + N
0.23
0.24
0.25
4.0 3.0 2.0
YP & yD 105 (D/H)
D & 4He Isoabundance Contours
Kneller & Steigman (2004)
4He is an early – Universe Chronometer
SBBN Prediction
As O/H 0, Y 0
BBN (D, 4He)
4.0 3.0 2.0
0.25
0.24
0.23
For N ≈ 2.5 ± 0.3
YP & yD 105 (D/H)
Low Reheat Temp.
(TR MeV)
Kawasaki, Kohri & Sugiyama
Late Decay of a
Massive Particle
&
Relic Neutrinos Not
Fully (Re) Populated
Neff < 3
Non-Standard BBN (Example of Neff < 3)
N = 1, 2.75, 5, 7
CBR constrains N (S)
CBR Temperature Anisotropy Spectrum
Encodes the Radiation Density R (S or N)
The CBR is an early - Universe Chronometer
Barger et al. (2003)
Peak locations vary with N
BBN (D & 4He) + CBR (WMAP)
BBN
CBR
Barger et al. (2003)
BBN & CBRConsistent !
Barger et al. (2003)
Joint BBN (D & 4He) & CBR Fit
Barger et al. (2003)
N < 4
But, is Li Consistent ?
N > 1
Barger et al. (2003)
[Li]OBS 12 + log(Li/H) 2.1
[Li]BBN 12 + log(Li/H) 2.6 – 2.7
Li too low ?
BBN and Primordial (Pop ) Lithium
Even for N 3
Y + D H
[Li] 2.60 0.07
(vs. [Li]OBS 2.1)
Li depleted / diluted
in Pop stars ?
4.0
yLi 1010 (Li/H)
4.0 3.0 2.0
Or, New Physics ?
Baryon Density () Determinations
N < 3 ?
?
?
N < 3 ?
2σ
?
X ?
Observational Uncertainties Or New Physics?
2σ
N (S) Determinations
BBN is a betterChronometer than
the CBR
V. Simha
SUMMARY
• SBBN (N = 3) D / H & CBR
• BBN (D & 4He) & CBR agree for :
10 = 6.1 (Bh2 = 0.022) & N = 2.5 (?)
* 95% Ranges :
1.9 N 3.1
5.5 10 6.6 (B ≈ 0.04 – 0.05)
BBN and the CBR Agree !
(The Theorist’s Mantra)
More & Better Data Are Needed !
SUCCESS
CHALLENGE
But, what’s up with Lithium ?