2,143 research outputs found
The Matsubara-Fradkin Thermodynamical Quantization of Podolsky Electrodynamics
In this work we apply the Matsubara-Fradkin formalism and the Nakanishi's
auxiliary field method to the quantization of the Podolsky electrodynamics in
thermodynamic equilibrium. This approach allows us to write consistently the
path integral representation for the partition function of gauge theories in a
simple manner. Furthermore, we find the Dyson-Schwinger-Fradkin equations and
the Ward-Fradkin-Takahashi identities for the Podolsky theory. We also write
the most general form for the polarization tensor in thermodynamic equilibrium.Comment: Submitted to Physical Review
Generating Functional for Gauge Invariant Actions: Examples of Nonrelativistic Gauge Theories
We propose a generating functional for nonrelativistic gauge invariant
actions. In particular, we consider actions without the usual magnetic term.
Like in the Born-Infeld theory, there is an upper bound to the electric field
strength in these gauge theories.Comment: 14 pages, 2 figures; v2: misprints correcte
Three-point Green function of massless QED in position space to lowest order
The transverse part of the three-point Green function of massless QED is
determined to the lowest order in position space. Taken together with the
evaluation of the longitudinal part in arXiv:0803.2630, this gives a relation
for QED which is analogous to the star-triangle relation. We relate our result
to conformal-invariant three-point functions.Comment: 8 page
Action for (Free) Open String Modes in AdS Space Using the Loop Variable Approach
The loop variable technique (for open strings in flat space) is a gauge
invariant generalization of the renormalization group method for obtaining
equations of motion. Unlike the beta functions, which are only proportional to
the equations of motion, here it gives the full equation of motion. In an
earlier paper, a technique was described for adapting this method to open
strings in gravitational backgrounds. However unlike the flat space case, these
equations cannot be derived from an action and are therefore not complete. This
is because there are ambiguities in the method that involve curvature couplings
that cannot be fixed by appealing to gauge invariance alone but need a more
complete treatment of the closed string background. An indirect method to
resolve these ambiguities is to require symmetricity of the second derivatives
of the action. In general this will involve modifying the equations by terms
with arbitrarily high powers of curvature tensors. This is illustrated for the
massive spin 2 field. It is shown that in the special case of an AdS or dS
background, the exact action can easily be determined in this way.Comment: 14 pages, Latex fil
One-particle and collective electron spectra in hot and dense QED and their gauge dependence
The one-particle electron spectrum is found for hot and dense QED and its
properties are investigated in comparison with the collective spectrum. It is
shown that the one-particle spectrum (in any case its zero momentum limit) is
gauge invariant, but the collective spectrum, being qualitatively different, is
always gauge dependent. The exception is the case for which the
collective spectrum long wavelength limit demonstrates the gauge invariance as
well.Comment: 9 pages, latex, no figure
On bipartite Rokhsar-Kivelson points and Cantor deconfinement
Quantum dimer models on bipartite lattices exhibit Rokhsar-Kivelson (RK)
points with exactly known critical ground states and deconfined spinons. We
examine generic, weak, perturbations around these points. In d=2+1 we find a
first order transition between a ``plaquette'' valence bond crystal and a
region with a devil's staircase of commensurate and incommensurate valence bond
crystals. In the part of the phase diagram where the staircase is incomplete,
the incommensurate states exhibit a gapless photon and deconfined spinons on a
set of finite measure, almost but not quite a deconfined phase in a compact
U(1) gauge theory in d=2+1! In d=3+1 we find a continuous transition between
the U(1) resonating valence bond (RVB) phase and a deconfined staggered valence
bond crystal. In an appendix we comment on analogous phenomena in quantum
vertex models, most notably the existence of a continuous transition on the
triangular lattice in d=2+1.Comment: 9 pages; expanded version to appear in Phys. Rev. B; presentation
improve
Dynamics of the particle - hole pair creation in graphene
The process of coherent creation of particle - hole excitations by an
electric field in graphene is quantitatively described. We calculate the
evolution of current density, number of pairs and energy after switching on the
electric field. In particular, it leads to a dynamical visualization of the
universal finite resistivity without dissipation in pure graphene. We show that
the DC conductivity of pure graphene is rather than the
often cited value of . This value coincides with the AC
conductivity calculated and measured recently at optical frequencies. The
effect of temperature and random chemical potential (charge puddles) are
considered and explain the recent experiment on suspended graphene. A
possibility of Bloch oscillations is discussed within the tight binding model.Comment: 4 pages, 2 figure
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