### The cosmological QCD transition

When the early Universe had a temperature of about 150 MeV it made
a transition from a
quark-gluon plasma to a gas of hadrons. The cosmological
QCD transition might have observable consequences today:
- Baryon number fluctuations from a first-order QCD transition
might give rise to inhomogeneous nucleosynthesis. The scale
is set by the mean bubble nucleation distance. We found that
a new mechanism for the QCD transition, inhomogeneous nucleation,
might indeed give rise to effects on primordial nucleosynthesis,
for more details see a poster of my collaborator J. Ignatius:
The Effect of Primordial Temperature Fluctuations on the QCD Transition
- During a first-order transition the sound speed vanishes at scales
above the bubble scale. This leads to the amplification of
primordial inhomogeneities. In the further evolution of the Universe
these large inhomogeneities may produce clumps of cold dark
matter on very small scales. More details may be found in my talk
at the Texas symposium 98, Paris: Clumping of
CDM from the cosmological QCD transition.
- The primordial spectrum of gravitational waves is modified,
independently of the order of the transition.

My habilitation thesis (Frankfurt am Main, February 1999):

**The Cosmological QCD Transition** (ps-file)

1. Introduction

2. The early universe at the QCD scale

3. A first-order QCD transition

4. Isothermal baryon fluctuations

5. Amplification of inhomogeneities

6. A smooth QCD crossover

7. Conclusions and open questions

A The Friedmann model

B Cosmological perturbations

Dominik J. Schwarz

* Last modified: * December 3, 1999