33,819 research outputs found
Bosonization Theory of Excitons in One-dimensional Narrow Gap Semiconductors
Excitons in one-dimensional narrow gap semiconductors of anti-crossing
quantum Hall edge states are investigated using a bosonization method. The
excitonic states are studied by mapping the problem into a non-integrable
sine-Gordon type model. We also find that many-body interactions lead to a
strong enhancement of the band gap. We have estimated when an exciton
instability may occur.Comment: 4pages, 1 figure, to appear in Phys. Rev. B Brief Report
Anomaly inflow mechanism using Wilson line
It is shown that the anomaly inflow mechanism can be implemented using Wilson
line in odd dimensional gauge theories. An action of Wess-Zumino-Witten (WZW)
type can be constructed using Wilson line. The action is understood in the odd
dimensional bulk space-time rather than in the even dimensional boundary. This
action is not gauge invariant. It gives anomalous gauge variations of the
consistent form on boundary space-times. So it can be used to cancel the
quantum anomalies localized on boundary space-times. This offers a new way to
cancel the gauge anomaly and construct anomaly-free gauge theory in odd
dimensional space-time.Comment: 4 pages, 1 figure; title changed; text and figure improved;
references adde
Irrational charge from topological order
Topological or deconfined phases of matter exhibit emergent gauge fields and
quasiparticles that carry a corresponding gauge charge. In systems with an
intrinsic conserved U(1) charge, such as all electronic systems where the
Coulombic charge plays this role, these quasiparticles are also characterized
by their intrinsic charge. We show that one can take advantage of the
topological order fairly generally to produce periodic Hamiltonians which endow
the quasiparticles with continuously variable, generically irrational,
intrinsic charges. Examples include various topologically ordered lattice
models, the three dimensional RVB liquid on bipartite lattices as well as water
and spin ice. By contrast, the gauge charges of the quasiparticles retain their
quantized values.Comment: 4 pages, 1 figure with two panel
Quasi-adiabatic Continuation of Quantum States: The Stability of Topological Ground State Degeneracy and Emergent Gauge Invariance
We define for quantum many-body systems a quasi-adiabatic continuation of
quantum states. The continuation is valid when the Hamiltonian has a gap, or
else has a sufficiently small low-energy density of states, and thus is away
from a quantum phase transition. This continuation takes local operators into
local operators, while approximately preserving the ground state expectation
values. We apply this continuation to the problem of gauge theories coupled to
matter, and propose a new distinction, perimeter law versus "zero law" to
identify confinement. We also apply the continuation to local bosonic models
with emergent gauge theories. We show that local gauge invariance is
topological and cannot be broken by any local perturbations in the bosonic
models in either continuous or discrete gauge groups. We show that the ground
state degeneracy in emergent discrete gauge theories is a robust property of
the bosonic model, and we argue that the robustness of local gauge invariance
in the continuous case protects the gapless gauge boson.Comment: 15 pages, 6 figure
Resonating singlet valence plaquettes
We consider the simplest generalizations of the valence bond physics of SU(2)
singlets to SU(N) singlets that comprise objects with N sites -- these are
SU(N) singlet plaquettes with N=3 and N=4 in three spatial dimensions.
Specifically, we search for a quantum mechanical liquid of such objects -- a
resonating singlet valence plaquette phase that generalizes the celebrated
resonating valence bond phase for SU(2) spins. We extend the Rokhsar-Kivelson
construction of the quantum dimer model to the simplest SU(4) model for valence
plaquette dynamics on a cubic lattice. The phase diagram of the resulting
quantum plaquette model is analyzed both analytically and numerically. We find
that the ground state is solid everywhere, including at the Rokhsar-Kivelson
point where the ground state is an equal amplitude sum. By contrast, the equal
amplitude sum of SU(3) singlet triangular plaquettes on the face centered cubic
lattice is liquid and thus a candidate for describing a resonating single
valence plaquette phase, given a suitably defined local Hamiltonian.Comment: 12 pages, 15 figures, minor changes, references added, Phys Rev B
versio
Do the adult daughters of PCOS patients develop PCOS and is this due to an androgenized uterine environment-an online epidemiological survey
Objectives: Several inconsistent studies have investigated whether the uterine environment of androgenized pregnant women is a risk factor for an in-utero developmental imprinted predisposition towards subsequent
polycystic ovarian syndrome (PCOS) among their female offspring. These are difficult to compare due to variable parameters and subject selection criteria. Few epidemiological studies have analyzed the incidence of PCOS
amongst adult daughters of PCOS affected women previously. Our study aimed to investigate risk factors relating to the development of PCOS in the female offspring of PCOS patients.
Methods: We used a questionnaire to collect a mother-to-daughter medical history and relevant information, in order to understand risk factors, which might relate to the presence of PCOS daughters of PCOS patients.
Results: Of four hundred and one responses, 131 participants were included in the final analysis. There was no statistical association with the subsequent development of PCOS amongst female offspring of women with PCOS. However, there was a significantly higher prevalence of post-term birth among PCOS mothers. Nevertheless, the major determinant of risk of subsequent incidence of PCOS amongst daughters was a higher BMI, regardless of the mothers BMI.
Conclusion: Socio-economic family influences, affecting BMI, may be the reason for any mother to daughter association with PCOS
A competing order scenario of two-gap behavior in hole doped cuprates
Angle-dependent studies of the gap function provide evidence for the
coexistence of two distinct gaps in hole doped cuprates, where the gap near the
nodal direction scales with the superconducting transition temperature ,
while that in the antinodal direction scales with the pseudogap temperature. We
present model calculations which show that most of the characteristic features
observed in the recent angle-resolved photoemission spectroscopy (ARPES) as
well as scanning tunneling microscopy (STM) two-gap studies are consistent with
a scenario in which the pseudogap has a non-superconducting origin in a
competing phase. Our analysis indicates that, near optimal doping,
superconductivity can quench the competing order at low temperatures, and that
some of the key differences observed between the STM and ARPES results can give
insight into the superlattice symmetry of the competing order.Comment: 9 pages, 7 fig
Detecting extreme mass ratio inspirals with LISA using time-frequency methods II: search characterization
The inspirals of stellar-mass compact objects into supermassive black holes
constitute some of the most important sources for LISA. Detection of these
sources using fully coherent matched filtering is computationally intractable,
so alternative approaches are required. In a previous paper (Wen and Gair 2005,
gr-qc/0502100), we outlined a detection method based on looking for excess
power in a time-frequency spectrogram of the LISA data. The performance of the
algorithm was assessed using a single `typical' trial waveform and
approximations to the noise statistics. In this paper we present results of
Monte Carlo simulations of the search noise statistics and examine its
performance in detecting a wider range of trial waveforms. We show that typical
extreme mass ratio inspirals (EMRIs) can be detected at distances of up to 1--3
Gpc, depending on the source parameters. We also discuss some remaining issues
with the technique and possible ways in which the algorithm can be improved.Comment: 15 pages, 9 figures, to appear in proceedings of GWDAW 9, Annecy,
France, December 200
Mosaic spin models with topological order
We study a class of two-dimensional spin models with the Kitaev-type
couplings in mosaic structure lattices to implement topological orders. We show
that they are exactly solvable by reducing them to some free Majorana fermion
models with gauge symmetries. The typical case with a 4-8-8 close packing is
investigated in detail to display the quantum phases with Abelian and
non-Abelian anyons. Its topological properties characterized by Chern numbers
are revealed through the edge modes of its spectrum.Comment: 4 pages, 3 figures. Final version to appear in Phys. Rev. B as a
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