2,720 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

### Time-Reversal Symmetry Breaking and Spontaneous Anomalous Hall Effect in Fermi Fluids

We study the spontaneous non-magnetic time-reversal symmetry breaking in a
two-dimensional Fermi liquid without breaking either the translation symmetry
or the U(1) charge symmetry. Assuming that the low-energy physics is described
by fermionic quasiparticle excitations, we identified an "emergent" local
$U(1)^N$ symmetry in momentum space for an $N$-band model. For a large class of
models, including all one-band and two-band models, we found that the
time-reversal and chiral symmetry breaking can be described by the $U(1)^N$
gauge theory associated with this emergent local $U(1)^N$ symmetry. This
conclusion enables the classification of the time-reversal symmetry-breaking
states as types I and II, depending on the type of accompanying spatial
symmetry breaking. The properties of each class are studied. In particular, we
show that the states breaking both time-reversal and chiral symmetries are
described by spontaneously generated Berry phases. We also show examples of the
time-reversal symmetry-breaking phases in several different microscopically
motivated models and calculate their associated Hall conductance within a
mean-field approximation. The fermionic nematic phase with time-reversal
symmetry breaking is also presented and the possible realizations in strongly
correlated models such as the Emery model are discussed.Comment: 18 pages, 8 figure

### 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

### Real time correlations at finite Temperature for the Ising model

After having developed a method that measures real time evolution of quantum
systems at a finite temperature, we present here the simplest field theory
where this scheme can be applied to, namely the 1+1 Ising model.
We will compute the probability that if a given spin is up, some other spin
will be up after a time $t$, the whole system being at temperature $T$. We can
thus study spatial correlations and relaxation times at finite $T$. The fixed
points that enable the continuum real time limit can be easily found for this
model.
The ultimate aim is to get to understand real time evolution in more
complicated field theories, with quantum effects such as tunneling at finite
temperature.Comment: 3 pp in Latex, 2 ps Figs., presented at the Latt98 Conf. in Boulder
C

### Duality picture between antiferromagnetism and d-wave superconductivity in t-J model at two dimensions

We show in this paper an interesting relation between elementary and
topological excitations in the antiferromagnetic and d-wave superconducting
phases of the t-J model at two dimenions. The topological spin and charge
excitations in one phase have the same dynamics as elementary excitations in
the other phase, except the appearance of energy gaps. Moreover, the transition
from one phase to another can be described as a quantum disordering transition
associated with the topological excitations. Based on the above picture, a
plausible phase diagram of t-J model is constructed.Comment: 28 pages, 3 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

### 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

### Charge-Density-Wave and Superconductor Competition in Stripe Phases of High Temperature Superconductors

We discuss the problem of competition between a superconducting (SC) ordered
state with a charge density wave (CDW) state in stripe phases of high $T_c$
superconductors. We consider an effective model for each stripe motivated by
studies of spin-gapped electronic ladder systems. We analyze the problem of
dimensional crossover arising from inter-stripe SC and CDW couplings using
non-Abelian bosonization and renormalization group (RG) arguments to derive an
effective $O(4)$-symmetric nonlinear $\sigma$-model in $D=2+1$ for the case of
when both inter-stripe couplings are of equal magnitude as well as equally RG
relevant. By studying the effects of various symmetry lowering perturbations,
we determine the structure of the phase diagram and show that, in general, it
has a broad regime in which both orders coexist. The quantum and thermal
critical behavior is discussed in detail, and the phase coexistence region is
found to end at associated $T=0$ as well as $T>0$ tetracritical points. The
possible role of hedgehog topological excitations of the theory is considered
and argued to be RG irrelevant at the spatially anisotropic higher dimensional
low-energy fixed point theory. Our results are also relevant to the case of
competing N\'eel and valence bond solid (VBS) orders in quantum magnets on 2D
isotropic square as well as rectangular lattices interacting via nearest
neighbor Heisenberg exchange interactions.Comment: 9 pages, 3 figures (one with 3 subfigures

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