2,992 research outputs found
Leading Order QED Electrical Conductivity from the 3PI Effective Action
In this article we study the electrical conductivity in QED using the
resummed 3PI effective action. We work to 3-loop order in the effective action.
We show that the resulting expression for the conductivity is explicitly gauge
invariant, and that the integral equations that resum the pinching and colinear
contributions are produced naturally by the formalism. All leading order terms
are included, without the need for any kind of power counting arguments.Comment: 10 pages, 15 figure
Next-to-Leading Order Transport Coefficients from the Four-Particle Irreducible Effective Action
Transport coefficients can be obtained from 2-point correlators using the
Kubo formulae. It has been shown that the full leading order result for
electrical conductivity and (QCD) shear viscosity is contained in the re-summed
2-point function that is obtained from the 3-loop 3PI re-summed effective
action. The theory produces all leading order contributions without the
necessity for power counting, and in this sense it provides a natural framework
for the calculation. In this article we study the 4-loop 4PI effective action
for a scalar theory with cubic and quartic interactions in the presence of
spontaneous symmetry breaking. We obtain a set of integral equations that
determine the re-summed 2-point vertex function. A next-to-leading order
contribution to the viscosity could be obtained from this set of coupled
equations.Comment: 24 pages, 18 figures. Added references and minor rewordings:
published versio
QED Electrical Conductivity using the 2PI Effective Action
In this article we calculate the electrical conductivity in QED using the 2PI
effective action. We use a modified version of the usual 2PI effective action
which is defined with respect to self-consistent solutions of the 2-point
functions. We show that the green functions obtained from this modified
effective action satisfy ward identities and that the conductivity obtained
from the kubo relation is gauge invariant. We work to 3-loop order in the
modified 2PI effective action and show explicitly that the resulting expression
for the conductivity contains the square of the amplitude that corresponds to
all binary collision and production processes.Comment: 24 pages, 21 figure
Quasiclassical and Quantum Systems of Angular Momentum. Part II. Quantum Mechanics on Lie Groups and Methods of Group Algebras
In Part I of this series we presented the general ideas of applying
group-algebraic methods for describing quantum systems. The treatment was there
very "ascetic" in that only the structure of a locally compact topological
group was used. Below we explicitly make use of the Lie group structure. Basing
on differential geometry enables one to introduce explicitly representation of
important physical quantities and formulate the general ideas of quasiclassical
representation and classical analogy
- …