arXiv subjects
Publications and source records attributed to Dennis D. Dietrich.
Expressions for the absorption spectrum of a nucleus in a three- and a two-dimensional crystal respectively are obtained analytically at zero and at finite temperature respectively. It is found that for finite temperature in two dimensions the Moessbauer effect vanishes but is replaced by what we call a Quasi-Moessbauer effect. Possibilities to identify two-dimensional elastic behavior are discussed.
Considering cold, dense quark matter with two massless quark flavors, we demonstrate how, in a self-consistent calculation in the framework of QCD, the condensation of Cooper pairs induces a non-vanishing background color field. This background color field has precisely the right magnitude to cancel tadpole contributions and thus ensures overall color neutrality of the two-flavor color superconductor.
The exact fermion propagator in a classical time-dependent gauge field is derived by solving the equation of motion for the Dirac Green's functions. From the retarded propagator obtained in this way the momentum spectrum for the produced fermion pairs is calculated. Different approximations and the exact solution for the propagator and the momentum spectrum are presented.
We discuss the production mechanism of partons via vacuum polarization during the very early, gluon dominated phase of an ultrarelativistic heavy-ion collision in the framework of the background field method of quantum chromodynamics.
A medium modified gluon propagator is used to evaluate the scattering cross section for the process gg-->gg in the QCD medium by performing an explicit sum over the polarizations of the gluons. We incorporate a magnetic sreening mass from a non-perturbative study. It is shown that the medium modified cross section is finite, divergence free, and is independent of any ad-hoc momentum transfer cut-off parameters. The medium modified finite cross sections are necessary for a realistic investigation of the production and equilibration of the minijet plasma expected at RHIC and LHC.
We describe gluon-pair production from a space-time dependent chromofield via vacuum polarization within the framework of the background field method of QCD. The processes we consider are first order in the action. We derive the corresponding source terms for gluon pair production for situations that can be described by a 1+1 dimensional approach. Especially, we observe that within the range of applicability of our approach the principal contribution to gluon production is included. Gluon production from a space-time dependent chromofield will play an important role in the production and evolution of the quark-gluon plasma in ultra relativistic heavy-ion collisions at RHIC and LHC.
We derive source terms for the production of quarks and gluons from the QCD vacuum in the presence of a space-time dependent external chromofield A_{cl} to the order of S^{(1)}. We found that the source terms for the parton production processes A_{cl} -> q\bar{q} and A_{cl},A_{cl}A_{cl} -> gg also include the annihilation processes q\bar{q} -> A_{cl} and gg -> A_{cl},A_{cl}A_{cl}. The source terms we derive are applicable for the description of the production of partons with momentum p larger rhan gA which itself must be larger than Λ_{QCD}. We observe that these source terms for the production of partons from a space-time dependent chromofield can be used to study the production and equilibration of the quark-gluon plasma during the very early stages of an ultrarelativistic heavy-ion collision.
We investigate the production of gluon pairs from a space-time dependent classical chromofield via vacuum polarization within the framework of the background field method of QCD. The investigation of the production of gluon pairs is important in the study of the evolution of the quark-gluon plasma in ultra-relativistic heavy-ion collisions at RHIC and LHC.