1,916 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
Self-duality in Generalized Lorentz Superspaces
We extend the notion of self-duality to spaces built from a set of
representations of the Lorentz group with bosonic or fermionic behaviour, not
having the traditional spin-one upper-bound of super Minkowski space. The
generalized derivative vector fields on such superspaces are assumed to form a
superalgebra. Introducing corresponding gauge potentials and hence covariant
derivatives and curvatures, we define generalized self-duality as the Lorentz
covariant vanishing of certain irreducible parts of the curvatures.Comment: 6 pages, Late
Heat transport through quantum Hall edge states: Tunneling versus capacitive coupling to reservoirs
We study the heat transport along an edge state of a two-dimensional electron
gas in the quantum Hall regime, in contact to two reservoirs at different
temperatures. We consider two exactly solvable models for the edge state
coupled to the reservoirs. The first one corresponds to filling and
tunneling coupling to the reservoirs. The second one corresponds to integer or
fractional filling of the sequence (with odd), and capacitive
coupling to the reservoirs. In both cases we solve the problem by means of
non-equilibrium Green function formalism. We show that heat propagates chirally
along the edge in the two setups. We identify two temperature regimes, defined
by , the mean level spacing of the edge. At low temperatures, , finite size effects play an important role in heat transport, for both
types of contacts. The nature of the contacts manifest themselves in different
power laws for the thermal conductance as a function of the temperature. For
capacitive couplings a highly non-universal behavior takes place, through a
prefactor that depends on the length of the edge as well as on the coupling
strengths and the filling fraction. For larger temperatures, ,
finite-size effects become irrelevant, but the heat transport strongly depends
on the strength of the edge-reservoir interactions, in both cases. The thermal
conductance for tunneling coupling grows linearly with , whereas for the
capacitive case it saturates to a value that depends on the coupling strengths
and the filling factors of the edge and the contacts.Comment: 15 pages, 5 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
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Symmetric-Gapped Surface States of Fractional Topological Insulators
We construct the symmetric-gapped surface states of a fractional topological
insulator with electromagnetic -angle and
a discrete gauge field. They are the proper generalizations of
the T-pfaffian state and pfaffian/anti-semion state and feature an extended
periodicity compared with their of "integer" topological band insulators
counterparts. We demonstrate that the surface states have the correct anomalies
associated with time-reversal symmetry and charge conservation.Comment: 5 pages, 33 references and 2 pages of supplemental materia
Loops, Surfaces and Grassmann Representation in Two- and Three-Dimensional Ising Models
Starting from the known representation of the partition function of the 2-
and 3-D Ising models as an integral over Grassmann variables, we perform a
hopping expansion of the corresponding Pfaffian. We show that this expansion is
an exact, algebraic representation of the loop- and surface expansions (with
intrinsic geometry) of the 2- and 3-D Ising models. Such an algebraic calculus
is much simpler to deal with than working with the geometrical objects. For the
2-D case we show that the algebra of hopping generators allows a simple
algebraic treatment of the geometry factors and counting problems, and as a
result we obtain the corrected loop expansion of the free energy. We compute
the radius of convergence of this expansion and show that it is determined by
the critical temperature. In 3-D the hopping expansion leads to the surface
representation of the Ising model in terms of surfaces with intrinsic geometry.
Based on a representation of the 3-D model as a product of 2-D models coupled
to an auxiliary field, we give a simple derivation of the geometry factor which
prevents overcounting of surfaces and provide a classification of possible sets
of surfaces to be summed over. For 2- and 3-D we derive a compact formula for
2n-point functions in loop (surface) representation.Comment: 31 pages, 9 figure
The imbalanced antiferromagnet in an optical lattice
We study the rich properties of the imbalanced antiferromagnet in an optical
lattice. We present its phase diagram, discuss spin waves and explore the
emergence of topological excitations in two dimensions, known as merons, which
are responsible for a Kosterlitz-Thouless transition that has never
unambiguously been observed.Comment: 4 pages, 5 figures, RevTe
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