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J. Serreau

Publications and source records attributed to J. Serreau.

25 records · Page 2Linked to original sources
arXiv2003

Thermalization of fermionic quantum fields

We solve the nonequilibrium dynamics of a 3+1 dimensional theory with Dirac fermions coupled to scalars via a chirally invariant Yukawa interaction. The results are obtained from a systematic coupling expansion of the 2PI effective action to lowest non-trivial order, which includes scattering as well as memory and off-shell effects. The dynamics is solved numerically without further approximation, for different far-from-equilibrium initial conditions. The late-time behavior is demonstrated to be insensitive to the details of the initial conditions and to be uniquely determined by the initial energy density. Moreover, we show that at late time the system is very well characterized by a thermal ensemble. In particular, we are able to observe the emergence of Fermi--Dirac and Bose--Einstein distributions from the nonequilibrium dynamics.

hep-ph↗
arXiv2002

Far-from-equilibrium dynamics with broken symmetries from the 2PI-1/N expansion

We derive the nonequilibrium real-time evolution of an O(N) - invariant scalar quantum field theory in the presence of a nonvanishing expectation value of the quantum field. Using a systematic 1/N expansion of the 2PI effective action to next-to-leading order, we obtain nonperturbative evolution equations which include scattering and memory effects. The equivalence of the direct method, which requires the resummation of an infinite number of skeleton diagrams, with the auxiliary-field formalism, which involves only one diagram at next-to-leading order, is shown.

hep-ph↗
arXiv2001

Kinetic equilibration in heavy ion collisions: The role of elastic processes

We study the kinetic equilibration of gluons produced in the very early stages of a high energy heavy ion collision in a ``self-consistent'' relaxation time approximation. We compare two scenarios describing the initial state of the gluon system, namely the saturation and the minijet scenarios, both at RHIC and LHC energies. We argue that, in order to characterize kinetic equilibration, it is relevant to test the isotropy of various observables. As a consequence, we find in particular that in both scenarios elastic processes are not sufficient for the system to reach kinetic equilibrium at RHIC energies. More generally, we show that, contrary to what is often assumed in the literature, elastic collisions alone are not sufficient to rapidly achieve kinetic equilibration. Because of longitudinal expansion at early times, the actual equilibration time is at least of the order of a few fermis.

hep-ph↗
arXiv2001

A simple out-of-equilibrium field theory formalism ?

In this paper, we determine a condition of applicability of a very simple formalism for the calculation of a fast process taking place in a non-equilibrium medium, in which the particle distribution functions are frozen in time. Indeed, a well known obstacle for the use of such a naive formalism is the appearance of the so-called ``pinch singularities''. We argue that these potentially dangerous terms can be regularized, and that they are negligible if the characteristic time-scale of the process under study is small compared to the relaxation time of the system.

hep-ph↗
arXiv2000

On the microscopic dynamics of DCC formation

The dynamics of the pion field after a quench is studied in the framework of the linear sigma model. Our aim is to determine to what extent the amplified pion field resembles the DCC picture originally proposed in the early '90s. We present the result of a computer experiment where, among other things, we study in detail the correlation between isospin orientations of the distinct modes of the field. We show that this correlation is absent. In a sense, the distinct modes behave as distinct DCCs. The implications of this observation are discussed.

hep-ph↗
arXiv1999

The Likelihood of DCC Formation

We estimate the probability that a disoriented chiral condensate forms during the spherical expansion of a hot medium described by the linear sigma model.

hep-ph↗