2,555 research outputs found
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
Testing Lorentz Invariance by Comparing Light Propagation in Vacuum and Matter
We present a Michelson-Morley type experiment for testing the isotropy of the
speed of light in vacuum and matter. The experiment compares the resonance
frequency of a monolithic optical sapphire resonator with the resonance
frequency of an orthogonal evacuated optical cavity made of fused silica while
the whole setup is rotated on an air bearing turntable once every 45 s.
Preliminary results yield an upper limit for the anisotropy of the speed of
light in matter (sapphire) of \Delta c/c < 4x10^(-15), limited by the frequency
stability of the sapphire resonator operated at room temperature. Work to
increase the measurement sensitivity by more than one order of magnitude by
cooling down the sapphire resonator to liquid helium temperatures (LHe) is
currently under way.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
Leading Order QCD Shear Viscosity from the 3PI Effective Action
In this article we calculate the leading order shear viscosity in QCD using
the resummed 3PI effective action. We work to 3-loop order in the effective
action. We show that the integral equations that resum the pinching and
collinear contributions are produced naturally by the formalism. All leading
order terms are included, without the need for any kind of power counting
arguments.Comment: 23 pages, 27 figure
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