qm italia, 2009 (roma 22,23,24 aprile)
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QM Italia, 2009 (Roma 22,23,24 aprile)
QCD & cosmology
The quest for cosmologicalsignals of QCD dynamics
Silvio BonomettoPhysics dep., Milano-Bicocca Univ. &INFN – Sezione di Milano-Bicocca
Why signals from cosmological context could be significant ?
Q-H cosmological transition necessarily occurred(otherwise, no room to allocate existing baryon number)
Today: average cosmic B-B distance 1 mWhen a/ao was 10^-15 10^-13 cm T then \sim GeV
Q-H cosmological transition characterized by
high T, low
only context where these conditions naturally occurred
observational value of B-density/Ndensity
definition & value
Assumption (?): homogeneity & isotropy on very large scales
Stress-energy tensor shape (generic ref. frame)
Metrics (generic ref. frame)
Stress-energy tensor components in peculiar reference frameMetric form in peculiar reference frame
Einstein eqn. Friedmann eqn. Hubble (energy conserv….. mechanical) -a eqn. (energy conserv…... thermodynamical)
acceleration eqn.
definitions: critical density qo parameter parameter(s)
Entropy in cosmologyFree-energy -p relation E – definitions
Phase transitions (order)
Entropy conserv./non-conserv.in first-order phase transitions
Stress-energy tensor for free particle distributionDensity/pressure rel./non-rel.
- p - n – for Bose-Fermi distributionsfor thermal soup
T-a relationT-t & a-t relations in radiative era
Generalized Bag-Model expressionsHagedorn expression
Cheng, M. et al., arXiv:0710.0354v2 [hep-lat]McGuigan M. & Soeldner W., arXiv:0810.0265v2 [hep-th]
so
so
TTT
TsTsE
TT
dtTdE
TTp
TTE
)/)(ln33
1(13
)/(1
/3
)(
)(4
4
define
ext. BagModel
)]/1/1([)/( 2/54
HoHHo TTmEiTTTp
Hagedorn
Ipotheticalphase transition
s=const. state eq.
s value from best fit offirst 5 pressure points
Hadron gas state eq.:Hagedorn
A benchmark
From S - conservation
Phase-transitionno-phase transition
vs. no transition at all [ aT = const. ] meaning of
“vertical” evolution
Phase-transitionno-phase transition
vs. no transition at all
How can 1-ordertransition occur ?
a(t) during transition
Which signal of different evolution ?
Ta : final behavior depends just on entropy conservation
time delay ?recall: t \sim 10^-5 sec. ……
Formation of cold remnantse.g. neutralino decoupling
(hot decoupling, cold decoupling ….. )
a-t relation must matter when annihilationstill going on at significant rate
Q-H transition & primeval nucleosynthesis (BBN)
a connection (perhaps) if transition is 1° order
• Why a connection ?• Could cosmological transition, in spite of all, still be a 1° order phase transition ?
A quick outline of BBN (at the origins of scientific cosmology)
• He abundance in stars• Why not from H burning in previous stellar gen. (4p + 2e He + 28.3 MeV)• neutron-proton equilibrium up to 900 keV (m=1.4MeV n/b \sim 0.17)• – decay rate vs. cosmic expansion rate• deuterium bottleneck ( B=2.2 MeV - opens at T \sim 100 keV )• nuclear reaction network• astration - observational abundances
b from BBN vs WMAP etc. determination Why can we determine b from WMAP etc. data
BBN 6.1 \pm 0.6WMAP etc. 6.25
decreasing errors…
No significant chemical potential associated to BCould there be Lepton number ?Would it matter ?Can B easily transfered from plasma to hadron gas ?
Concentration discrepancy could causephase transition ?
A general conclusion:
Cosmological Q-H transition did occur, but …. did it leave any imprints ?
How could Q-H transition affect all that ?
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