# Presentation: 622431

## Workshop on Cosmological ImplicationsorObservable Implications of a Cosmological Phase Transition

- 2005 RHIC & AGS Users’ Meeting
- Organized by Vicki Greene,
- Vanderbilt University

## Time

**In the beginning ****quark – gluon plasma****             ****           **

**~ ****10 ms after Big Bang**
**hadron synthesis**
**strong force binds **
**quarks and gluons****  **

- ~ **100 s after Big Bang**
** ****nucleosynthesis **
**strong force binds nucleons**** **

- Temperature

**Notes:**
Look at the 
In the beginning
Expanded and cooled - Hadron synthesis
Light nuclei 
Atoms, stars , galaxies, supernovae explosions 
Now (the Thinker) we are looking back trying to solve the mysteries of the early Universe: Why almost massless quarks formed massive hadrons? How did colored objects conspire to bind into colorless matter ? We built RHIC hoping to find the answers of these questions.
In RHIC we can not make time go backward, but we can prepare in the laboratory a system that is as hot as the early Universe. 
In our detectors we can not detect the quark-gluon plasma – we see hadrons, leptons and gammas.

## Magic, Metaphor or Measurement?

- We are crossing into a new frontier of scientific inquiry.  Scientists from around the world will use this facility (RHIC) to answer some of the most basic questions about the properties of matter and the evolution of our universe.
- Energy Secretary Bill Richardson ,June 12, 2000
- Nuclear physicists have now demonstrated that the material essence of the universe at a time mere microseconds after the big bang consists of a ubiquitous quark-gluon liquid... RHIC is of course not a telescope pointed at the sky but an underground accelerator on Long Island; it is, nevertheless, in effect, a precision cosmology instrument for viewing a very early portion of the universe...
- Ben Stein, PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 728 April 20, 2005

## Workshop Agenda

- 1:30 Introduction - Vicki Greene 1:40 Hitchhiker's Guide to the Early Universe - Paul Stankus 2:15 Quarks and Cosmology - Robert Scherrer 2:45 The QCD Equation of State - Frithjof Karsch 3:15 From quantum black holes to relativistic heavy ions - Dmitri Kharzeev 3:45 Experimental results from RHIC - Mike Tannenbaum 4:30 Further questions and discussion 4:45 finish

## Golden Rule 1: Entropy per co-moving volume is conserved

- Golden Rule 2: All chemical potentials are negligible

- Golden Rule 3: All entropy is in relativistic species

- Expansion covers many decades in T, so typically either T>>m (relativistic) or T<<m (frozen out)

- Kolb & Turner, *The Early Universe,* Westview 1990

- P.Stankus

## Golden Rule 4:

- Kolb & Turner

- QCD Transition

- e+e- Annihilation

- Nucleosynthesis

-  Decoupling

- Mesons freeze out

- Heavy quarks and bosons freeze out

- P.Stankus

- Temperature (GeV)

**Effective number of degrees-of-freedom per relativistic particle **

## Golden Rule 5: Equilibrium is boring!

- Weinberg, *Gravitation and Cosmology,* Wiley 1972

- Would you like to live in thermal equilibrium at 2.75oK?

**Relics**  *T>m *but* *>*H* (CMB photons, neutrinos, gravitons,dark matter? free quarks, magnetic monopoles...)
**Remnants** *T<m *but* *≠0 (baryons /B~1010, electrons, dark matter?)

- Example of e+e- annihilation transferring entropy to photons, after neutrinos have already decoupled (relics).

- That which survives:

- P.Stankus

## The QCD quark-hadron transition is typically ignored by cosmologists as uninteresting

**Weinberg (1972):** Considers Hagedorn-style limiting-temperature model, leads to *a*(*t*)t2/3|ln*t*|1/2; but concludes “...the present contents...depends only on the entropy per baryon....  In order to learn something about the behavior of the universe before the temperature dropped below 1012oK we need to look for fossils [relics]....”

**Kolb & Turner (1990):** “While we will not discuss the quark/hadron transition, the details and the nature (1st order, 2nd order, etc.) of this transition are of some cosmological interest, as local inhomogeneities in the baryon number density could possibly affect...primordial nucleosythesis...”

- P.Stankus

## A Brief History of the Universe    

- T > 100 GeV             Inflation?  Baryogenesis?
- T ~ 100 GeV             Electroweak phase transition
- T ~ 100 MeV	      	 Quark-gluon phase transition
- T > 1 MeV                 Dark matter freezes out?
- T = 0.1 – 1 MeV        Primordial Nucleosynthesis
- T = 3000 K                Recombination – CMB
- 20 K < T < 3000 K    The “dark ages”
- T < 20 K	            Observational Astronomy

- 1 MeV = 1010 K

- We have precision measurements that constrain
- the nature of the universe at T = 3000 K ( = 1 eV)
- and T = 0.1 – 1 MeV.

- R. Scherrer

## What about the quark era?

- At T > 100 MeV:
- Universe is radiation-dominated (i.e., dominated by relativistic particles)
- Most particles are in thermal equilibrium and relativistic
- Cosmological constant is irrelevant

- R. Scherrer

## Quark-Hadron Phase Transition

- In the 1980’s, several groups investigated the effect of the QCD phase transition on primordial nucleosynthesis
- (Witten; Applegate, Hogan, RJS; Alcock, Fuller, Matthews)
- Assumed:  A first order phase transition, leading to inhomogeneities in the initial densities of hadrons.

- R. Scherrer

## Quark-Hadron Phase Transition

- Interest in this scenario was intense for a while, but died out:
- QCD Phase transition not first order, so no large inhomogenities?
- Initial motivation was to make baryon density much higher and allow for a “pure baryon” universe.  This is ruled out by other observations.

- R. Scherrer

## What happens in the quark era?

- Suppose the universe behaves differently than we expected at T > 100 MeV?  (Currently taken to be a perfect gas with zero viscosity, and pressure = density/3).   Any effects?  (unfortunately, currently part of the “dark ages”)
- Relic impact on nucleosynthesis?  Hard to do unless it produces inhomogeneities.  But small effects can be detectable here.
- What else happens at T > 100 MeV?
- 	Freeze-out of relic dark matter particle?
- 	Effects on baryogenesis?
- 3.   What are the cosmological effects of the observed RHIC quark-gluon phase?

- R. Scherrer

## Summary

- We have very good ideas of what happens at T = 3000 K and T = 0.1 – 1 MeV (CMB and Big-Bang nucleosynthesis), but the rest of the history of the universe is “dark”.
- 2.  Modifying the behavior of the quark phase of the universe may be hard to detect.  Best bets are nucleosynthesis, and possible effects on relic particle freeze-out.  The problem, however, remains unexplored.  Even specifying any changes in the expansion behavior would be interesting.  Interesting theoretical problem

- R. Scherrer

## F. Karsch

## F. Karsch

## Primordial black holes formation during the QCD phase transition in the Early Universe ?

- QCD phase transition in the Early Universe:
- sQGP: small pressure, high energy density =>
- gravitational collapse into a black hole is likely(?)
-                                                    K. Jedamzik, PRD55(97) 5871
- The _primordial black holes_, with a peak in the mass
- distribution at the QCD horizon mass scale (~ 1 Msun):
-      dark matter? MACHO’s? (MAssive Compact Halo Objects)

- D. Kharzeev

## A link between General Relativity and QCD?

-      solution to some of the RHIC puzzles?

- RHIC collisions

## Phase Diagram from Thermal Fit of particle ratios---``chemical”

**Hadron resonance ideal gas  ****(M. Kaneta and N. Xu, ****	****nucl-ex/0104021 & QM02)**
**T****CH**** = 175 ± 10 MeV**
** ********B****  =   40 ± 10 MeV**
**<E>/N ~ 1 GeV**
**	****(J. Cleymans and K. Redlich, Phys.Rev.C, 60, 054908, 1999 )**

-  Where is the QGP critical point?

- M. Tannenbaum

## Conclusions

- Cosmological implications of observations at RHIC is a thorny problem, but it is reasonable (essential?) to revisit – and an interesting cosmological problem in its own right.
- Places to look:
- Effects on nucleosynthesis resulting from fluctuations
- WIMPS
- Primoridal black holes
- Effects on baryogenesis
- Dark matter?, Machos?
- Metaphor or measurements – we will have to answer the question.
- My thanks to Paul, Bob, Frithof, Dima, and Mike!

## Spacetime evolution is important

## The New Standard Cosmology in Four Easy Steps

- Inflation, dominated by “inflaton field” vacuum energy
- Radiation-dominated thermal equilibrium
- Matter-dominated, non-uniformities grow (structure)
- Start of acceleration in *a*(*t*), return to domination by cosmological constant and/or vacuum energy.

*w*=*P*/

- -1/3

- +1/3

- -1

*a*e*Ht*

*a**t*1/2

*a**t*2/3

***t***

- now

- acc dec

- P.Stankus

## T(t)

***T*****(*****t*****)**

***a*****(*****t*****)**

********(*****t*****)**

***t***

- How do we relate ***T*** to ***a***,******?  i.e. thermodynamics

## Slide 24

## Outline

- Why black holes cannot be produced at RHIC
- Why black holes may anyway teach us about
-      the properties of QCD matter produced at RHIC
-      and in the Early Universe

## Can black holes anyway help usto understand the physics at RHIC?

- One new idea: use a mathematical correspondence between
-                        a gauge theory and gravity in AdS space

- Gauge theory                        Gravity

- Anti de Sitter space - solution of Einstein’s equations
- with a negative cosmological constant 
- (de Sitter space - solution with a positive inflation

- Maldacena

- deconfinement -
- black hole formation
- in AdS5xS3xT space

- Witten; Polyakov;
- Gubser, Klebanov;
- Son, Starinets, Kovtun;
- Nastase; ...

- boundary

## Black holes radiate

- Black holes emit
- thermal radiation
- with temperature

- S.Hawking ‘74

- acceleration of gravity
- at the surface, (4GM)-1

## Similar things happen in non-inertial frames

- Einstein’s Equivalence Principle:

- Gravity             Acceleration in a non-inertial frame

- An observer moving with an acceleration a detects
- a thermal radiation with temperature

- W.Unruh ‘76

## In both cases the radiation is due to the presence of event horizon 

-  Accelerated frame:  part of space-time is hidden
-                                   (causally disconnected) from
-                                   an accelerating observer;
-                                   Rindler metric

## Where on Earth can one achieve the largest

- acceleration (deceleration) ?

- Relativistic heavy ion collisions! -
- stronger color fields: