3,903 research outputs found
Holographic classification of Topological Insulators and its 8-fold periodicity
Using generic properties of Clifford algebras in any spatial dimension, we
explicitly classify Dirac hamiltonians with zero modes protected by the
discrete symmetries of time-reversal, particle-hole symmetry, and chirality.
Assuming the boundary states of topological insulators are Dirac fermions, we
thereby holographically reproduce the Periodic Table of topological insulators
found by Kitaev and Ryu. et. al, without using topological invariants nor
K-theory. In addition we find candidate Z_2 topological insulators in classes
AI, AII in dimensions 0,4 mod 8 and in classes C, D in dimensions 2,6 mod 8.Comment: 19 pages, 4 Table
Multiple Schramm-Loewner Evolutions and Statistical Mechanics Martingales
A statistical mechanics argument relating partition functions to martingales
is used to get a condition under which random geometric processes can describe
interfaces in 2d statistical mechanics at criticality. Requiring multiple SLEs
to satisfy this condition leads to some natural processes, which we study in
this note. We give examples of such multiple SLEs and discuss how a choice of
conformal block is related to geometric configuration of the interfaces and
what is the physical meaning of mixed conformal blocks. We illustrate the
general ideas on concrete computations, with applications to percolation and
the Ising model.Comment: 40 pages, 6 figures. V2: well, it looks better with the addresse
A Classification of random Dirac fermions
We present a detailed classification of random Dirac hamiltonians in two
spatial dimensions based on the implementation of discrete symmetries. Our
classification is slightly finer than that of random matrices, and contains
thirteen classes. We also extend this classification to non-hermitian
hamiltonians with and without Dirac structure.Comment: 15 pages, version2: typos in the table of classes are correcte
Are Domain Walls in Spin Glasses Described by Stochastic Loewner Evolutions?
Domain walls for spin glasses are believed to be scale invariant invariant; a
stronger symmetry, conformal invariance, has the potential to hold. The
statistics of zero-temperature Ising spin glass domain walls in two dimensions
are used to test the hypothesis that these domain walls are described by a
Schramm-Loewner evolution SLE. Multiple tests are consistent with
SLE, where . Both conformal invariance and the domain
Markov property are tested. The latter does not hold in small systems, but
detailed numerical evidence suggests that it holds in the continuum limit.Comment: 4 pages, 3 figures, see related work by Amoruso, Hartmann, Hastings,
Moore at cond-mat/060171
Disparate effects of chronic and acute theophylline on cyclosporine A nephrotoxicity
Abstract : We previously developed a model of acute cyclosporine A (CsA)-induced vasomotor nephrotoxicity in rabbits. As exogenous adenosine infusion mimics the haemodynamic changes that characterize acute renal failure (ARF), we wanted to know whether adenosine was a mediator in this model and whether an adenosine receptor blocker could prevent the CsA-induced ARF. Group 1 were untreated controls. Group 2 received CsA (25 mg/kg per day) for 5 days. Renal function parameters were measured, showing ARF in all animals compared to controls. Theophylline (1 mg/kg i.v. bolus) was then administered and renal function was reassessed. Theophylline significantly reduced renal vascular resistance (-8%) and increased renal blood flow (RBF) (+20%), glomerular filtration rate (GFR) (+50%), filtration fraction (+24%) and diuresis (+73%), suggesting that adenosine was involved in the CsA-induced ARF. In group 3, theophylline (30 mg/kg per day) was given concomitantly with CsA for 5 days. GFR was normalized, but theophylline did not hinder the drop in RBF seen with CsA alone in group 2. Microscopy observation of the kidneys showed that chronic theophylline administration aggravated the morphological changes induced by CsA alone. We conclude that CsA administration for 5 days induced a vasomotor nephropathy with an adenosine-mediated afferent arteriolar constriction which cannot be prevented by concomitant theophylline administratio
SMaRT-OnlineWDN: A Franco-German Project For The Online Security Management Of Water Distribution Networks
Water Distribution Networks (WDNs) are critical infrastructures that are exposed to deliberate or accidental chemical, biological or radioactive contamination which need to be detected in due time. However, until now, no monitoring system is capable of protecting a WDN in real time. Powerful online sensor systems are currently developed and the prototypes are able to detect a small change in water quality. In the immediate future, water service utilities will install their networks with water quantity and water quality sensors. For taking appropriate decisions and countermeasures, WDN operators will need to dispose of: 1) a fast and reliable detection of abnormal events in the WDNs; 2) reliable online models both for the hydraulics and water quality predictions; 3) methods for contaminant source identification backtracking from the data history. Actually, in general none of these issues (1) – (3) are available at the water suppliers. Consequently, the main objective of the project SMaRT-OnlineWDN is the development of an online security management toolkit for WDNs that is based on sensor measurements of water quality as well as water quantity. Its main innovations are the detection of abnormal events with a binary classifier of high accuracy and the generation of real-time, reliable (i) flow and pressure predictions, (ii) water quality indicator predictions of the whole water network. Detailed information regarding contamination sources (localization and intensity) will be explored by means of the online running model, which is automatically calibrated to the measured sensor data. Its field of application ranges from the detection of deliberate contamination including source identification and decision support for effective countermeasures to improved operation and control of a WDN under normal and abnormal conditions (dual benefit).In this project, the technical research work is completed with a sociological, economical and management analysis
A Decade of Multiwavelength Observations of the TeV Blazar 1ES 1215+303: Extreme Shift of the Synchrotron Peak Frequency and Long-term Optical-Gamma-Ray Flux Increase
Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multiwavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z = 0.130), with a focus on its gamma-ray emission from 100 MeV to 30 TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline, and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by Very Long Baseline Array at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed
Convergence of repeated quantum non-demolition measurements and wave function collapse
Motivated by recent experiments on quantum trapped fields, we give a rigorous
proof that repeated indirect quantum non-demolition (QND) measurements converge
to the collapse of the wave function as predicted by the postulates of quantum
mechanics for direct measurements. We also relate the rate of convergence
toward the collapsed wave function to the relative entropy of each indirect
measurement, a result which makes contact with information theory.Comment: 4 pages, 1 figur
Freezing transitions and the density of states of 2D random Dirac Hamiltonians
Using an exact mapping to disordered Coulomb gases, we introduce a novel
method to study two dimensional Dirac fermions with quenched disorder in two
dimensions which allows to treat non perturbative freezing phenomena. For
purely random gauge disorder it is known that the exact zero energy eigenstate
exhibits a freezing-like transition at a threshold value of disorder
. Here we compute the dynamical exponent which
characterizes the critical behaviour of the density of states around zero
energy, and find that it also exhibits a phase transition. Specifically, we
find that (and ) with for and
for . For a finite system size we find large
sample to sample fluctuations with a typical .
Adding a scalar random potential of small variance , as in the
corresponding quantum Hall system, yields a finite noncritical whose scaling exponent exhibits two transitions, one
at and the other at . These transitions are shown
to be related to the one of a directed polymer on a Cayley tree with random
signs (or complex) Boltzmann weights. Some observations are made for the strong
disorder regime relevant to describe transport in the quantum Hall system
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