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 ?