29,283 research outputs found
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
Continuous topological phase transitions between clean quantum Hall states
Continuous transitions between states with the {\em same} symmetry but
different topological orders are studied. Clean quantum Hall (QH) liquids with
neutral quasiparticles are shown to have such transitions. For clean bilayer
(nnm) states, a continous transition to other QH states (including non-Abelian
states) can be driven by increasing interlayer repulsion/tunneling. The
effective theories describing the critical points at some transitions are
derived.Comment: 4 pages, RevTeX, 2 eps figure
Classification of Gapped Symmetric Phases in 1D Spin Systems
Quantum many-body systems divide into a variety of phases with very different
physical properties. The question of what kind of phases exist and how to
identify them seems hard especially for strongly interacting systems. Here we
make an attempt to answer this question for gapped interacting quantum spin
systems whose ground states are short-range correlated. Based on the local
unitary equivalence relation between short-range correlated states in the same
phase, we classify possible quantum phases for 1D matrix product states, which
represent well the class of 1D gapped ground states. We find that in the
absence of any symmetry all states are equivalent to trivial product states,
which means that there is no topological order in 1D. However, if certain
symmetry is required, many phases exist with different symmetry protected
topological orders. The symmetric local unitary equivalence relation also
allows us to obtain some simple results for quantum phases in higher dimensions
when some symmetries are present.Comment: 21 pages, 7 figures. Version 2, classification for parity and
translation symmetry update
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
Rapid Communicatio
Broken symmetry, hyper-fermions, and universal conductance in transport through a fractional quantum Hall edge
We have found solution to a model of tunneling between a multi-channel Fermi
liquid reservoir and an edge of the principal fractional quantum Hall liquid
(FQHL) in the strong coupling limit. The solution explains how the absence of
the time-reversal symmetry at high energies due to chiral edge propagation
makes the universal two-terminal conductance of the FQHL fractionally quantized
and different from that of a 1D Tomonaga-Luttinger liquid wire, where a similar
model but preserving the time-reversal symmetry predicts unsuppressed
free-electron conductance.Comment: 5 twocolumn pages in RevTex, no figures, more explanations added, a
short version was published in JETP Letters, vol.74, 87 (2001
Effect of folic acid supplementation in pregnancy on preeclampsia: The folic acid clinical trial study
Copyright © 2013 Shi Wu Wen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Preeclampsia (PE) is hypertension with proteinuria that develops during pregnancy and affects at least 5% of pregnancies. The Effect of Folic Acid Supplementation in Pregnancy on Preeclampsia: the Folic Acid Clinical Trial (FACT) aims to recruit 3,656 high risk women to evaluate a new prevention strategy for PE: supplementation of folic acid throughout pregnancy. Pregnant women with increased risk of developing PE presenting to a trial participating center between 80/7 and 166/7 weeks of gestation are randomized in a 1: 1 ratio to folic acid 4.0 mg or placebo after written consent is obtained. Intent-to-treat population will be analyzed. The FACT study was funded by the Canadian Institutes of Health Research in 2009, and regulatory approval from Health Canada was obtained in 2010. A web-based randomization system and electronic data collection system provide the platform for participating centers to randomize their eligible participants and enter data in real time. To date we have twenty participating Canadian centers, of which eighteen are actively recruiting, and seven participating Australian centers, of which two are actively recruiting. Recruitment in Argentina, UK, Netherlands, Brazil, West Indies, and United States is expected to begin by the second or third quarter of 2013. This trial is registered with NCT01355159. © 2013 Shi Wu Wen et al.The Canadian Institutes of Healt
Thermalized Displaced Squeezed Thermal States
In the coordinate representation of thermofield dynamics, we investigate the
thermalized displaced squeezed thermal state which involves two temperatures
successively. We give the wavefunction and the matrix element of the density
operator at any time, and accordingly calculate some quantities related to the
position, momentum and particle number operator, special cases of which are
consistent with the results in the literature. The two temperatures have
diffenent correlations with the squeeze and coherence components. Moreover,
different from the properties of the position and momentum, the average value
and variance of the particle number operator as well as the second-order
correlation function are time-independent.Comment: 7 pages, no figures, Revtex fil
Elimination of pain improves specificity of clinical diagnostic criteria for adult chronic rhinosinusitis
Objective
Determine whether the elimination of pain improves accuracy of clinical diagnostic criteria for adult chronic rhinosinusitis. Study Design
Retrospective cohort study. Methods
History, symptoms, nasal endoscopy, and computed tomography (CT) results were analyzed for 1,186 adults referred to an academic otolaryngology clinic with presumptive diagnosis of chronic rhinosinusitis. Clinical diagnosis was rendered using the 1997 Rhinosinusitis Taskforce (RSTF) Guidelines and a modified version eliminating facial pain, ear pain, dental pain, and headache. Results
Four hundred seventy-nine subjects (40%) met inclusion criteria. Among subjects positive by RSTF guidelines, 45% lacked objective evidence of sinonasal inflammation by CT, 48% by endoscopy, and 34% by either modality. Applying modified RSTF diagnostic criteria, 39% lacked sinonasal inflammation by CT, 38% by endoscopy, and 24% by either modality. Using either abnormal CT or endoscopy as the reference standard, modified diagnostic criteria yielded a statistically significant increase in specificity from 37.1% to 65.1%, with a nonsignificant decrease in sensitivity from 79.2% to 70.3%. Analysis of comorbidities revealed temporomandibular joint disorder, chronic cervical pain, depression/anxiety, and psychiatric medication use to be negatively associated with objective inflammation on CT or endoscopy. Conclusion
Clinical diagnostic criteria overestimate the prevalence of chronic rhinosinusitis. Removing facial pain, ear pain, dental pain, and headache increased specificity without a concordant loss in sensitivity. Given the high prevalence of sinusitis, improved clinical diagnostic criteria may assist primary care providers in more accurately predicting the presence of inflammation, thereby reducing inappropriate antibiotic use or delayed referral for evaluation of primary headache syndromes. Level of Evidence4. Laryngoscope, 127:1011-1016, 201
Non-Universal Fractional Quantum Hall States in a Quantum wire
The ground state as well as low-lying excitations in a 2D electron system in
strong magnetic fields and a parabolic potential is investigated by the
variational Monte Calro method. Trial wave functions analogous to the Laughlin
state are used with the power-law exponent as the variational parameter. Finite
size scaling of the excitation energy shows that the correlation function at
long distance is characterized by anon-universal exponent in sharp contrast to
the standard Laughlin state.The Laughlin-type state becomes unstable depending
on strength of the confining potential.Comment: 10 pages, REVTE
Non-Newtonian gravity in finite nuclei
In this talk, we report our recent study of constraining the non-Newtonian
gravity at femtometer scale. We incorporate the Yukawa-type non-Newtonian
gravitational potential consistently to the Skyrme functional form using the
exact treatment for the direct contribution and density-matrix expansion method
for the exchange contribution. The effects from the non-Newtonian potential on
finite nuclei properties are then studied together with a well-tested Skyrme
force. Assuming that the framework without non-Newtonian gravity can explain
the binding energies and charge radii of medium to heavy nuclei within 2%
error, we set an upper limit for the strength of the non-Newtonian
gravitational potential at femtometer scale.Comment: Talk given at the 11th International Conference on Nucleus-Nucleus
Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear
in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS
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