Interaction elementary excitations in ultrarelativistic plasmas: damping mechanisms and plasma thermodynamics
Vanderheyden, Benoit Jose
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https://hdl.handle.net/2142/30858
Description
Title
Interaction elementary excitations in ultrarelativistic plasmas: damping mechanisms and plasma thermodynamics
Author(s)
Vanderheyden, Benoit Jose
Issue Date
1998
Doctoral Committee Chair(s)
Baym, Gordon A.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
elementary excitations
quark-gluon plasma
electromagnetic plasma
damping mechanisms
Language
en
Abstract
This dissertation examines the properties of the elementary excitations in quark-gluon and
electromagnetic plasmas. Due to Debye screening and Landau damping mechanisms, the
interaction fields fall off at large distances, except for static magnetic and color-magnetic fields. The lack of screening of the magnetic interaction leads to a singularity at small momentum transfer in the matrix element for fermion-fermion scattering via the exchange of a single gluon, or a single photon. We analyze the effects of this singularity on the
quasiparticle lifetimes in plasmas at zero and at finite temperature T. First, at T = 0,
we find that the fermion excitations above the ground state are long-lived, as the Pauli
exclusion principle limits the collision phase space. Because the magnetic interaction is long-ranged, the damping rates of the excitations near the edge of the Fermi sea vary linearly with the excitation energy. The quasiparticles are therefore not as well-defined as those
encountered in non-relativistic plasmas, with short-ranged interactions, where the variation of the damping rates away from the Fermi surface is quadratic, thus slower. Second, we find that in plasmas at finite temperatures, the magnetic interaction introduces correlations between the successive scatterings of the fermion quasi particles on the charges in the system.
This effect leads to a decay law that decreases in time more rapidly than an exponential; however the quasiparticles are long-lived. In addition to the analysis of the quasiparticle lifetimes, we derive a framework for ascertaining the effects of the long-ranged magnetic interaction on the thermodynamic properties of relativistic plasmas. Our method generalizes
the concept of conserving, φ-derivable, approximations to relativistic field theories. By treating the interaction field as a dynamical degree of freedom, we are able to derive the thermodynamical potential in terms of fully dressed propagators. This approach allows us to resolve the entropy into contributions from its interacting elementary excitations.
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