105 research outputs found
Distinguished self-adjoint extensions of Dirac operators via Hardy-Dirac inequalities
We prove some Hardy-Dirac inequalities with two different weights including
measure valued and Coulombic ones. Those inequalities are used to construct
distinguished self-adjoint extensions of Dirac operators for a class of
diagonal potentials related to the weights in the above mentioned inequalities.Comment: 16 page
2PI Effective Action and Evolution Equations of N = 4 super Yang-Mills
We employ nPI effective action techniques to study N = 4 super Yang-Mills,
and write down the 2PI effective action of the theory. We also supply the
evolution equations of two-point correlators within the theory.Comment: 16 pages, 6 figures. Figure 2 replaced, approximation scheme
clarified, references adde
Two-loop HTL Thermodynamics with Quarks
We calculate the quark contribution to the free energy of a hot quark-gluon
plasma to two-loop order using hard-thermal-loop (HTL) perturbation theory. All
ultraviolet divergences can be absorbed into renormalizations of the vacuum
energy and the HTL quark and gluon mass parameters. The quark and gluon HTL
mass parameters are determined self-consistently by a variational prescription.
Combining the quark contribution with the two-loop HTL perturbation theory free
energy for pure-glue we obtain the total two-loop QCD free energy. Comparisons
are made with lattice estimates of the free energy for N_f=2 and with exact
numerical results obtained in the large-N_f limit.Comment: 33 pages, 6 figure
Resummation in Hot Field Theories
There has been significant progress in our understanding of
finite-temperature field theory over the past decade. In this paper, we review
the progress in perturbative thermal field theory focusing on thermodynamic
quantities. We first discuss the breakdown of naive perturbation theory at
finite temperature and the need for an effective expansion that resums an
infinite class of diagrams in the perturbative expansion. This effective
expansion which is due to Braaten and Pisarski, can be used to systematically
calculate various static and dynamical quantities as a weak-coupling expansion
in powers of g. However, it turns that the weak-coupling expansion for
thermodynamic quantities are useless unless the coupling constant is very
small. We critically discuss various ways of reorganizing the perturbative
series for thermal field theories in order to improve its convergence. These
include screened perturbation theory (SPT), hard-thermal-loop perturbation
theory (HTLPT), the Phi-derivable approach, dimensionally reduced (DR) SPT, and
the DR Phi-derivable approach.Comment: 82 pages, 20 figures; v2 - typos corrected, references adde
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