2,616 research outputs found
The right choice of moment for anisotropic fluid dynamics
We study anisotropic fluid dynamics derived from the Boltzmann equation based
on a particular choice for the anisotropic distribution function within a
boost-invariant expansion of the fluid in one spatial dimension. In order to
close the conservation equations we need to choose an additional moment of the
Boltzmann equation. We discuss the influence of this choice of closure on the
time evolution of fluid-dynamical variables and search for the best agreement
to the solution of the Boltzmann equation in the relaxation-time approximation.Comment: 4 pages, 4 figures, proceedings for Quark Matter 201
Exact Path Integrals by Equivariant Cohomology
It is a common belief among field theorists that path integrals can be
computed exactly only in a limited number of special cases, and that most of
these cases are already known. However recent developments, which generalize
the WKBJ method using equivariant cohomology, appear to contradict this folk
wisdom. At the formal level, equivariant localization would seem to allow exact
computation of phase space path integrals for an arbitrary partition function!
To see how, and if, these methods really work in practice, we have applied them
in explicit quantum mechanics examples. We show that the path integral for the
1-d hydrogen atom, which is not WKBJ exact, is localizable and computable using
the more general formalism. We find however considerable ambiguities in this
approach, which we can only partially resolve. In addition, we find a large
class of quantum mechanics examples where the localization procedure breaks
down completely.Comment: LATE
On Lorentz Invariance, Spin-Charge Separation And SU(2) Yang-Mills Theory
Previously it has been shown that in spin-charge separated SU(2) Yang-Mills
theory Lorentz invariance can become broken by a one-cocycle that appears in
the Lorentz boosts. Here we study in detail the structure of this one-cocycle.
In particular we show that its non-triviality relates to the presence of a
(Dirac) magnetic monopole bundle. We also explicitely present the finite
version of the cocycle.Comment: 4 page
Fixed Charge Ensembles and Parity Breaking Terms
Recently derived results for the exact induced parity-breaking term in 2+1
dimensions at finite temperature are shown to be relevant to the determination
of the free energy for fixed-charge ensembles. The partition functions for
fixed total charge corresponding to massive fermions in the presence of Abelian
and non-Abelian magnetic fields are discussed. We show that the presence of the
induced Chern-Simons term manifests itself in that the free energy depends
strongly on the relation between the external magnetic flux and the value of
the fixed charge.Comment: 10 pages, Revte
Embedding Brans-Dicke gravity into electroweak theory
We argue that a version of the four dimensional Brans-Dicke theory can be
embedded in the standard flat spacetime electroweak theory. The embedding
involves a change of variables that separates the isospin from the hypercharge
in the electroweak theory.Comment: 4 pages, no figures; replaced to match published versio
Abelian and Non-Abelian Induced Parity Breaking Terms at Finite Temperature
We compute the exact canonically induced parity breaking part of the
effective action for 2+1 massive fermions in particular Abelian and non Abelian
gauge field backgrounds. The method of computation resorts to the chiral
anomaly of the dimensionally reduced theory.Comment: 13 pages, RevTeX, no figure
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