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Confinement-induced Berry phase and helicity-dependent photocurrentsNov 18 2009The photocurrent in an optically active metal is known to contain a component that switches sign with the helicity of the incident radiation. At low frequencies, this current depends on the orbital Berry phase of the Bloch electrons via the "anomalous ... More

Stability of the quantum spin Hall effect: effects of interactions, disorder, and Z_2 topologyAug 11 2005The stability to interactions and disorder of the quantum spin Hall effect (QSHE) proposed for time-reversal-invariant 2D systems is discussed. The QSHE requires an energy gap in the bulk and gapless edge modes that conduct spin-up and spin-down excitations ... More

Geometric criticality between plaquette phases in integer-spin kagome XXZ antiferromagnetsJan 25 2005Jul 25 2005The phase diagram of the uniaxially anisotropic $s=1$ antiferromagnet on the kagom\'e lattice includes a critical line exactly described by the classical three-color model. This line is distinct from the standard geometric classical criticality that appears ... More

Entanglement entropy of random quantum critical points in one dimensionJun 30 2004For quantum critical spin chains without disorder, it is known that the entanglement of a segment of N>>1 spins with the remainder is logarithmic in N with a prefactor fixed by the central charge of the associated conformal field theory. We show that ... More

Doping dependence of thermopower and thermoelectricity in strongly correlated systemsSep 07 2006The search for semiconductors with high thermoelectric figure of merit has been greatly aided by theoretical modeling of electron and phonon transport, both in bulk materials and in nanocomposites. Recent experiments have studied thermoelectric transport ... More

Nonequilibrium charge density wave ordering from anomalous velocity in itinerant helical magnetsJun 13 2005The Karplus-Luttinger anomalous velocity is shown to lead to electric-field-induced charge accumulation in nearly ferromagnetic noncollinear magnets with itinerant electrons, like $MnSi$. For helical magnetic ordering, the balance between this accumulation ... More

Luttinger liquid physics from infinite-system DMRGJun 29 2012Oct 31 2012We study one-dimensional spinless fermions at zero and finite temperature T using the density matrix renormalization group. We consider nearest as well as next-nearest neighbor interactions; the latter render the system inaccessible by a Bethe ansatz ... More

Topological invariants of time-reversal-invariant band structuresJul 12 2006Jul 28 2006The topological invariants of a time-reversal-invariant band structure in two dimensions are multiple copies of the $\mathbb{Z}_2$ invariant found by Kane and Mele. Such invariants protect the topological insulator and give rise to a spin Hall effect ... More

Approaching Many-Body Localization from Disordered Luttinger Liquids via the Functional Renormalization GroupJun 02 2015Sep 08 2015We study the interplay of interactions and disorder in a one-dimensional fermion lattice coupled adiabatically to infinite reservoirs. We employ both the functional renormalization group (FRG) as well as matrix product state techniques, which serve as ... More

Berry phase mechanism for optical gyrotropy in stripe-ordered cupratesDec 12 2012Optical gyrotropy, the lifting of degeneracy between left and right circularly polarized light, can be generated by either time-reversal or chiral symmetry breaking. In the high-$T_c$ superconductor La$_{2-x}$Ba$_x$CuO$_4$ (LBCO), gyrotropy onsets at ... More

Dimensional reduction in superconducting arrays and frustrated magnetsMay 12 2004Jul 02 2004Some frustrated magnets and superconducting arrays possess unusual symmetries that cause the free energy or other physics of a $D$-dimensional quantum or classical problem to be that of a different problem in a reduced dimension $d<D$. Examples in two ... More

Scaling of electrical and thermal conductivities in an almost integrable chainNov 30 2012Oct 01 2013Many low-dimensional materials are well described by integrable one-dimensional models such as the Hubbard model of electrons or the Heisenberg model of spins. However, the small perturbations to these models required to describe real materials are expected ... More

Majorana fermion chain at the Quantum Spin Hall edgeApr 26 2010May 03 2010We study a realization of a 1d chain of Majorana bound states at the interfaces between alternating ferromagnetic and superconducting regions at a quantum spin Hall insulator edge. In the limit of well separated Majoranas, the system can be mapped to ... More

Edge Excitations of the $ν= 2/3$ Spin-Singlet Quantum Hall StateJun 21 1996The spectrum of edge excitations is derived for the spin-unpolarized $\nu = 2$ and $\nu = 2/3$ FQHE. Numerical diagonalization of a system of six electrons on a disc confirms that the edge $\nu = 2/3$ spin-singlet FQHE state consists of oppositely directed ... More

Nonequilibrium thermal transport and its relation to linear responseNov 09 2012Nov 15 2013We study the real-time dynamics of spin chains driven out of thermal equilibrium by an initial temperature gradient T_L \neq T_R using density matrix renormalization group methods. We demonstrate that the nonequilibrium energy current saturates fast to ... More

Exciton condensation and charge fractionalization in a topological insulator filmFeb 06 2009Jul 16 2009An odd number of gapless Dirac fermions is guaranteed to exist at a surface of a strong topological insulator. We show that in a thin-film geometry and under external bias, electron-hole pairs that reside in these surface states can condense to form a ... More

Exact solution of site and bond percolation on small-world networksJan 26 2000We study percolation on small-world networks, which has been proposed as a simple model of the propagation of disease. The occupation probabilities of sites and bonds correspond to the susceptibility of individuals to the disease and the transmissibility ... More

On The Formation of Disk Galaxies and Massive Central ObjectsJul 01 1998We propose that massive central objects form in the centers of the bars which must develop in young high-surface density galactic disks. Large-scale dynamics shuts off the growth of the central mass before it reaches $\sim 2%$ of the disk mass at the ... More

Modeling Quantum Gravity Effects in InflationJan 29 2014Jan 31 2014Cosmological models in 1+1 dimensions are an ideal setting for investigating the quantum structure of inflationary dynamics -- gravity is renormalizable, while there is room for spatial structure not present in the minisuperspace approximation. We use ... More

On the evolution of abelian-Higgs string networksAug 16 1998We study the evolution of abelian-Higgs string networks in numerical simulations. These are compared against a modified velocity-dependent one scale model for cosmic string network evolution. This incorporates the contributions of loop production, massive ... More

Glassy dynamics and aging in an exactly solvable spin modelJul 25 1997Aug 24 1999We introduce a simple two-dimensional spin model with short-range interactions which shows glassy behavior despite a Hamiltonian which is completely homogeneous and possesses no randomness. We solve exactly for both the static partition function of the ... More

Height representation, critical exponents, and ergodicity in the four-state triangular Potts antiferromagnetFeb 22 1999We study the four-state antiferromagnetic Potts model on the triangular lattice. We show that the model has six types of defects which diffuse and annihilate according to certain conservation laws consistent with their having a vector-valued topological ... More

Topological insulators beyond the Brillouin zone via Chern parityMay 02 2007The topological insulator is an electronic phase stabilized by spin-orbit coupling that supports propagating edge states and is not adiabatically connected to the ordinary insulator. In several ways it is a spin-orbit-induced analogue in time-reversal-invariant ... More

Coherent phonon scattering effects on thermal transport in thin semiconductor nanowiresJan 29 2007Feb 26 2007The thermal conductance by phonons of a quasi-one-dimensional solid with isotope or defect scattering is studied using the Landauer formalism for thermal transport. The conductance shows a crossover from localized to Ohmic behavior, just as for electrons, ... More

Topological defects and the superfluid transition of the $s=1$ spinor condensate in two dimensionsMay 03 2006Oct 03 2006The $s=1$ spinor Bose condensate at zero temperature supports ferromagnetic and polar phases that combine magnetic and superfluid ordering. We analyze the topological defects of the polar condensate, correcting previous studies, and show that the polar ... More

Quantum destruction of stiffness in diluted antiferromagnets and superconductorsMay 01 2003Oct 10 2003The reduction of 2D superconducting or antiferromagnetic order by random dilution is studied as a model for the 2D diluted Heisenberg antiferromagnet (DHAF) La$_2$Cu$_{1-p}$(Zn,Mg)$_p$O$_4$ and randomly inhomogeneous 2D suerconductors. We show in simplified ... More

Epidemics and percolation in small-world networksNov 30 1999Jan 07 2000We study some simple models of disease transmission on small-world networks, in which either the probability of infection by a disease or the probability of its transmission is varied, or both. The resulting models display epidemic behavior when the infection ... More

Reducing the numerical effort of finite-temperature density matrix renormalization group transport calculationsMar 16 2013Aug 27 2013Finite-temperature transport properties of one-dimensional systems can be studied using the time dependent density matrix renormalization group via the introduction of auxiliary degrees of freedom which purify the thermal statistical operator. We demonstrate ... More

Mean-field solution of the small-world network modelSep 10 1999Sep 21 1999The small-world network model is a simple model of the structure of social networks, which simultaneously possesses characteristics of both regular lattices and random graphs. The model consists of a one-dimensional lattice with a low density of shortcuts ... More

Finite temperature dynamical DMRG and the Drude weight of spin-1/2 chainsNov 18 2011Jun 07 2012We propose an easily implemented approach to study time-dependent correlation functions of one dimensional systems at finite temperature T using the density matrix renormalization group. The entanglement growth inherent to any time-dependent calculation ... More

Aharonov-Bohm oscillations in disordered topological insulator nanowiresMay 20 2010Oct 07 2010A direct signature of electron transport at the metallic surface of a topological insulator is the Aharonov-Bohm oscillation observed in a recent study of Bi_2Se_3 nanowires [Peng et al., Nature Mater. 9, 225 (2010)] where conductance was found to oscillate ... More

Universal nonequilibrium signatures of Majorana zero modes in quench dynamicsMay 22 2014Oct 14 2014The quantum evolution after a metallic lead is suddenly connected to an electron system contains information about the excitation spectrum of the combined system. We exploit this type of "quantum quench" to probe the presence of Majorana fermions at the ... More

An Unbiased Survey for Outflows in the W3 and W5 Star-Formation RegionsOct 15 2001During their birth all stars undergo periods of copious mass loss, frequently characterized by the occurrence of bipolar outflows. These outflows are believed to play a fundamental role in the star formation process. However the exact outflow generating ... More

Tension is DimensionSep 10 1999Jan 31 2000We propose a simple universal formula for the tension of a D-brane in terms of a regularized dimension of the associated conformal field theory statespace.

Relaxation energies and excited state structures of poly(para-phenylene)Oct 26 2004We investigate the relaxation energies and excited state geometries of the light emitting polymer, poly(para-phenylene). We solve the Pariser-Parr-Pople-Peierls model using the density matrix renormalization group method. We find that the lattice relaxation ... More

Quantum revivals and many-body localizationJul 16 2014Apr 27 2015We show that the magnetization of a single `qubit' spin weakly coupled to an otherwise isolated disordered spin chain exhibits periodic revivals in the localized regime, and retains an imprint of its initial magnetization at infinite time. We demonstrate ... More

Electronic-vibrational coupling in single-molecule devicesFeb 12 2003Mar 10 2003Experiments studying vibrational effects on electronic transport through single molecules have observed several seemingly inconsistent behaviors, ranging from up to 30 harmonics of a vibrational frequency in one experiment, to an absence of higher-harmonic ... More

Community detection in networks with unequal groupsSep 01 2015Sep 10 2015Recently, a phase transition has been discovered in the network community detection problem below which no algorithm can tell which nodes belong to which communities with success any better than a random guess. This result has, however, so far been limited ... More

Exact solutions for models of evolving networks with addition and deletion of nodesApr 04 2006There has been considerable recent interest in the properties of networks, such as citation networks and the worldwide web, that grow by the addition of vertices, and a number of simple solvable models of network growth have been studied. In the real ... More

Random graph models for dynamic networksJul 26 2016We propose generalizations of a number of standard network models, including the classic random graph, the configuration model, and the stochastic block model, to the case of time-varying networks. We assume that the presence and absence of edges are ... More

Finding community structure in very large networksAug 09 2004Aug 30 2004The discovery and analysis of community structure in networks is a topic of considerable recent interest within the physics community, but most methods proposed so far are unsuitable for very large networks because of their computational cost. Here we ... More

Optimal Determination of the Equilibrium Displacement of a Damped Harmonic Oscillator in the Presence of Thermal NoiseDec 17 2004Using a matched filter technique, we derive the minimum variance, unbiased estimator for the equilibrium displacement of a damped harmonic oscillator in thermal equilibrium when interactions with the thermal bath are the leading source of noise. We compare ... More

Transport properties of the one-dimensional Hubbard model at finite temperatureAug 08 2014Oct 06 2014We study finite-temperature transport properties of the one-dimensional Hubbard model using the density matrix renormalization group. Our aim is two-fold: First, we compute both the charge and the spin current correlation function of the integrable model ... More

Real-time and real-space spin- and energy dynamics in one-dimensional spin-1/2 systems induced by local quantum quenches at finite temperaturesDec 10 2013Mar 07 2014We study the spin- and energy dynamics in one-dimensional spin-1/2 systems induced by local quantum quenches at finite temperatures using a time-dependent density matrix renormalization group method. System sizes are chosen large enough to ensure that ... More

Ordering near the percolation threshold in models of 2D interacting bosons with quenched dilutionJul 25 2005Randomly diluted quantum boson and spin models in two dimensions combine the physics of classical percolation with the well-known dimensionality dependence of ordering in quantum lattice models. This combination is rather subtle for models that order ... More

An improved model of an actively contracting lymphatic vessel composed of several lymphangions: pumping characteristicsDec 03 2015Using essentially our 2011 numerical model of a multi-lymphangion segment of a collecting lymphatic vessel, but augmented by inclusion of a refractory period and definition of a mid lymphangion pressure, we explore the effect of several parameters on ... More

Hierarchical structure and the prediction of missing links in networksNov 04 2008Networks have in recent years emerged as an invaluable tool for describing and quantifying complex systems in many branches of science. Recent studies suggest that networks often exhibit hierarchical organization, where vertices divide into groups that ... More

Structural Inference of Hierarchies in NetworksOct 09 2006One property of networks that has received comparatively little attention is hierarchy, i.e., the property of having vertices that cluster together in groups, which then join to form groups of groups, and so forth, up through all levels of organization ... More

The physical limits of communicationJul 30 1999It has been well-known since the pioneering work of Claude Shannon in the 1940s that a message transmitted with optimal efficiency over a channel of limited bandwidth is indistinguishable from random noise to a receiver who is unfamiliar with the language ... More

Discontinuous Galerkin Isogeometric Analysis for The Biharmonic EquationMar 08 2017May 11 2018We present and analyze an interior penalty discontinuous Galerkin Isogeometric Analysis (dG-IgA) method for the biharmonic equation in computational domain in $\mathbb{R}^d$ with $d =2,3.$ The computational domain consist of several non-overlapping sub-domains ... More

Area and perimeter distribution of a surface in two dimensionsMay 15 1995May 18 1995We consider the number of configurations of a surface in two dimensions that has a prescribed length and encloses a prescribed perimeter with respect to a baseline. An approximate analytical treatment in a semi--continuum compares favourably with results ... More

Conservation laws in the quantum Hall Liouvillian theory and its generalizationsSep 12 2002Apr 09 2003It is known that the localization length scaling of noninteracting electrons near the quantum Hall plateau transition can be described in a theory of the bosonic density operators, with no reference to the underlying fermions. The resulting ``Liouvillian'' ... More

Mobility edge scaling at semiclassical and dissipative Hall transitionsApr 23 2002The universal anomalous diffusion scaling is obtained for the semiclassical quantum Hall transition, which has been argued to describe samples with dissipation or correlated impurities. The results explain a discrepancy between existing numerics and the ... More

Primordial fluctuations in extended Liouville theoryNov 10 2014Liouville gravity can be used to precisely model features of 3+1 dimensional cosmology in a simplified 1+1d setting. We study primordial fluctuations in a generally covariant extension of Liouville theory, in the context of single field inflation. The ... More

Nonlinear Radiation Pressure and Stochasticity in Ultraintense Laser FieldsFeb 13 1998May 01 1998The radiation force on a single electron in an ultraintense plane wave ($a = eE/mc\omega \sim 1$) is calculated and shown to be proportional to $a^4$ in the high-$a$ limit for arbitrary waveform and polarization. The cyclotron motion of an electron in ... More

Connecting polymers to the quantum Hall plateau transitionApr 02 2001Oct 04 2001A mapping is developed between the quantum Hall plateau transition and two-dimensional self-interacting lattice polymers. This mapping is exact in the classical percolation limit of the plateau transition, and diffusive behavior at the critical energy ... More

Efficacy of multimedia learning modules as preparation for lecture-based tutorials in electromagnetismSep 26 2014We have investigated the efficacy of online, multimedia learning modules (MLMs) as preparation for in-class, lecture-based tutorials in electromagnetism in a physics course for natural science majors (biology and marine science). Specifically, we report ... More

A predictive coding account of OCDApr 25 2015Jun 08 2015This paper presents a predictive coding account of obsessive-compulsive disorder (OCD). We extend the predictive coding model to include the concept of a 'formal narrative', or temporal sequence of cognitive states inferred from sense data. We propose ... More

A hierarchical narrative framework for OCDMar 03 2015This paper gives an explanatory framework for obsessive-compulsive disorder (OCD) based on a generative model of cognition. The framework is constructed using the new concept of a 'formal narrative' which is a sequence of cognitive states inferred from ... More

Stateman: Using Metafunctions to Manage Large Terms Representing Machine StatesSep 21 2015When ACL2 is used to model the operational semantics of computing machines, machine states are typically represented by terms recording the contents of the state components. When models are realistic and are stepped through thousands of machine cycles, ... More

Blue straggler stars in dwarf spheroidal galaxies II: Sculptor and FornaxApr 03 2009The existence of blue straggler stars (BSSs) in dwarf spheroidal galaxies (dSphs) is still an open question. In fact, many BSS candidates have been observed in the Local Group dSphs, but it is unclear whether they are real BSSs or young stars. Shedding ... More

The sensitivity of pulsar timing arraysAug 04 2014Simple analytic expressions are derived for the sensitivity curve of a pulsar timing array (PTA) to both a monochromatic source of gravitational waves and an isotropic stochastic background of gravitational waves. These derivations are performed in both ... More

Investigation of Quasi--Realistic Heterotic String Models with Reduced Higgs SpectrumMay 02 2011Quasi--realistic heterotic-string models in the free fermionic formulation typically contain an anomalous U(1), which gives rise to a Fayet-Iliopolous term that breaks supersymmetry at the one--loop level in string perturbation theory. Supersymmetry is ... More

Quasi Many-body Localization in Translation Invariant SystemsOct 27 2014It is typically assumed that disorder is essential to realize Anderson localization. Recently, a number of proposals have suggested that an interacting, translation invariant system can also exhibit localization. We examine these claims in the context ... More

Unified model for vortex-string network evolutionOct 21 2003May 02 2004We describe and numerically test the velocity-dependent one-scale (VOS) string evolution model, a simple analytic approach describing a string network with the averaged correlation length and velocity. We show that it accurately reproduces the large-scale ... More

Observation of spin Coulomb drag in a two-dimensional electron gasDec 01 2005An electron propagating through a solid carries spin angular momentum in addition to its mass and charge. Of late there has been considerable interest in developing electronic devices based on the transport of spin, which offer potential advantages in ... More

Phase diagram of the frustrated, spatially anisotropic S=1 antiferromagnet on a square latticeJan 20 2009We study the S=1 square lattice Heisenberg antiferromagnet with spatially anisotropic nearest neighbor couplings $J_{1x}$, $J_{1y}$ frustrated by a next-nearest neighbor coupling $J_{2}$ numerically using the density-matrix renormalization group (DMRG) ... More

Excited-state entanglement and thermal mutual information in random spin chainsMay 08 2014Dec 11 2014Entanglement properties of excited eigenstates (or of thermal mixed states) are difficult to study with conventional analytical methods. We approach this problem for random spin chains using a recently developed real-space renormalization group technique ... More

Edge states generated by spin-orbit coupling at domain walls in magnetic semiconductorsMar 06 2006Apr 04 2006Electronic states localized at domain walls between ferromagnetically ordered phases in two-dimensional electron systems are generated by moderate spin-orbit coupling. The spin carried by these states depends on the slope of the magnetic background at ... More

Entanglement entropy of 2D conformal quantum critical points: hearing the shape of a quantum drumMay 29 2006The entanglement entropy of a pure quantum state of a bipartite system $A \cup B$ is defined as the von Neumann entropy of the reduced density matrix obtained by tracing over one of the two parts. Critical ground states of local Hamiltonians in one dimension ... More

On the Evolution of Abelian-Higgs String NetworksJul 16 2001Jul 30 2001We study the evolution of Abelian-Higgs string networks in large-scale numerical simulations in both a static and expanding background. We measure the properties of the network by tracing the motion of the string cores, for the first time estimating the ... More

Entanglement entropy of the random spin-1 Heisenberg chainMar 01 2007Mar 14 2007Random spin chains at quantum critical points exhibit an entanglement entropy between a segment of length L and the rest of the chain that scales as log_2 L with a universal coefficient. Since for pure quantum critical spin chains this coefficient is ... More

Nonequilibrium quantum dynamics and transport: from integrability to many-body localizationMar 21 2016Jul 05 2016We review the non-equilibrium dynamics of many-body quantum systems after a quantum quench with spatial inhomogeneities, either in the Hamiltonian or in the initial state. We focus on integrable and many-body localized systems that fail to self-thermalize ... More

Multifractal Orthogonality Catastrophe in 1D Random Quantum Critical PointsMay 21 2015Aug 16 2015We study the response of random singlet quantum critical points to local perturbations. Despite being insulating, these systems are dramatically affected by a local cut in the system, so that the overlap $G=\left|\langle \Psi_B |\Psi_A \rangle\right|$ ... More

Loop-Generated Bounds on Changes to the Graviton Dispersion RelationJan 10 2002We identify the effective theory appropriate to the propagation of massless bulk fields in brane-world scenarios, to show that the dominant low-energy effect of asymmetric warping in the bulk is to modify the dispersion relation of the effective 4-dimensional ... More

Changing the lattice position of a bistable single magnetic dopant in a semiconductor using a scanning tunneling microscopeMay 14 2015We report a reversible and hysteretic change in the topography measured with a scanning tunneling microscope near a single Fe dopant in a GaAs surface when a small positive bias voltage is applied. First-principles calculations of the formation energy ... More

Criticality and entanglement in random quantum systemsAug 13 2009We review studies of entanglement entropy in systems with quenched randomness, concentrating on universal behavior at strongly random quantum critical points. The disorder-averaged entanglement entropy provides insight into the quantum criticality of ... More

Spectral statistics across the many-body localization transitionAug 28 2015The many-body localization transition (MBLT) between ergodic and many-body localized phase in disordered interacting systems is a subject of much recent interest. Statistics of eigenenergies is known to be a powerful probe of crossovers between ergodic ... More

Spin Wave Analysis of Low-Temperature Thermal Hall Effect in the Candidate Kitaev Spin Liquid $α$-RuCl${}_3$Jul 10 2018Proposed effective Hamiltonians from the literature for the material $\alpha$-RuCl${}_3$ are used to compute the magnon thermal Hall conductivity, $\kappa_{xy}$, using linear spin wave theory for the magnetically ordered state. No model previously proposed ... More

Neutral Hydrogen and the Missing Satellites of the Local GroupOct 18 2001We present a comparison of the leftover satellites at z=0 in a cold dark matter dominated simulation of the formation of the Local Group to the distribution of observed neutral hydrogen high-velocity clouds and compact high-velocity clouds. The ~2000 ... More

The Neutral Excitations in the Gaffnian StateJun 16 2016We study a model fractional quantum Hall (FQH) wavefunction called the Gaffnian state, which is believed to represent a gapless, strongly correlated state that is very different from conventional metals. To understand this exotic gapless state better, ... More

Global phase diagram of the spin-1 antiferromagnet with uniaxial anisotropy on the kagome latticeJan 25 2007The phase diagram of the XXZ spin-1 quantum magnet on the kagome lattice is studied for all cases where the $J_z$ coupling is antiferromagnetic. In the zero magnetic field case, the six previously introduced phases, found using various methods, are: the ... More

Strong-weak coupling self-duality in the two-dimensional quantum phase transition of $p+ip$ superconducting arraysDec 22 2003Jun 25 2004The 2D quantum phase transition that occurs in a square lattice of $p+ip$ superconductors is used to show how four-body interactions in $d=2$ reproduce nonperturbative effects familiar from the study of two-body interactions in $d=1$. This model can be ... More

Edge Physics of the Quantum Spin Hall Insulator from a Quantum Dot Excited by Optical AbsorptionDec 12 2013Apr 10 2014The gapless edge modes of the Quantum Spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states ... More

Current fluctuations near to the 2D superconductor-insulator quantum critical pointMay 24 2006Systems near to quantum critical points show universal scaling in their response functions. We consider whether this scaling is reflected in their fluctuations; namely in current-noise. Naive scaling predicts low-temperature Johnson noise crossing over ... More

Quadratic Sinusoidal Analysis of Neurons in Voltage ClampJul 06 2010Nonlinear biophysical properties of individual neurons are known to play a major role in the nervous system. Earlier electrophysiological studies have made use of piecewise linear characterization of voltage clamped neurons, which consists of a sequence ... More

An estimate of the inter-system crossing time in light-emitting polymersOct 26 2004The reported enhanced singlet-exciton yields in light-emitting polymers over the statistical limit of 25% has attracted wide experimental and theoretical attention. Most theoretical estimates of the singlet-exciton yield depend crucially on estimates ... More

Entanglement spectra of critical and near-critical systems in one dimensionSep 30 2009The entanglement spectrum of a pure state of a bipartite system is the full set of eigenvalues of the reduced density matrix obtained from tracing out one part. Such spectra are known in several cases to contain important information beyond that in the ... More

Stability of 1-D Excitons in Carbon Nanotubes under High Laser ExcitationsAug 30 2004Through ultrafast pump-probe spectroscopy with intense pump pulses and a wide continuum probe, we show that interband exciton peaks in single-walled carbon nanotubes (SWNTs) are extremely stable under high laser excitations. Estimates of the initial densities ... More

Study of off-diagonal disorder using the typical medium dynamical cluster approximationJun 04 2014We generalize the typical medium dynamical cluster approximation (TMDCA) and the local Blackman, Esterling, and Berk (BEB) method for systems with off-diagonal disorder. Using our extended formalism we perform a systematic study of the effects of non-local ... More

A Survey for Transient Astronomical Radio Emission at 611 MHzApr 14 2003We have constructed and operated the Survey for Transient Astronomical Radio Emission (STARE) to detect transient astronomical radio emission at 611 MHz originating from the sky over the northeastern United States. The system is sensitive to transient ... More

Universal Substructure Distributions in LCDM halos: Can we find a Fossil Group?Apr 19 2007We use large cosmological N-body simulations to study the subhalo population in galaxy group sized halos. In particular, we look for fossil group candidates with typical masses ~10-25% of Virgo cluster but with an order of magnitude less substructure. ... More

Shock-triggered formation of magnetically-dominated cloudsJun 04 2007To understand the formation of a magnetically dominated molecular cloud out of an atomic cloud, we follow the dynamical evolution of the cloud with a time-dependent axisymmetric magnetohydrodynamic code. A thermally stable warm atomic cloud is initially ... More

The STARE Project: A Progress ReportDec 26 1997The Survey for Transient Astronomical Radio Emission (STARE) is a wide-field monitor for transient radio emission at 611 MHz on timescales of fractions of a second to minutes. Consisting of multiple geographically separated total-power radiometers which ... More

Reflections and Thoughts on Tired LightJul 23 2007The position of the various tired light theories is reviewed briefly and it is noted that one of the biggest objections to them concerns the mechanism by which light might lose energy as it travels through space. Here some new work relating to the constancy ... More

Enhancements to ACL2 in Versions 5.0, 6.0, and 6.1Apr 30 2013We report on highlights of the ACL2 enhancements introduced in ACL2 releases since the 2011 ACL2 Workshop. Although many enhancements are critical for soundness or robustness, we focus in this paper on those improvements that could benefit users who are ... More

Tree Codes and a Conjecture on Exponential SumsAug 27 2013Dec 09 2013We propose a new conjecture on some exponential sums. These particular sums have not apparently been considered in the literature. Subject to the conjecture we obtain the first effective construction of asymptotically good tree codes. The available numerical ... More

Improvement and protection of niobium surface superconductivity by Atomic Layer Deposition and heat treatmentAug 26 2008A method to treat the surface of Nb is described which potentially can improve the performance of superconducting RF cavities. We present tunneling and x-ray photoemission spectroscopy (XPS) measurements at the surface of cavity-grade niobium samples ... More

The Initiation and Propagation of Helium Detonations in White Dwarf EnvelopesSep 11 2014Oct 16 2014Detonations in helium-rich envelopes surrounding white dwarfs have garnered attention as triggers of faint thermonuclear ".Ia" supernovae and double detonation Type Ia supernovae. However, recent studies have found that the minimum size of a hotspot that ... More

Tidal streams in a MOND potential: constraints from SagittariusJan 14 2005May 26 2005We compare orbits in a thin axisymmetric disc potential in MOND to those in a thin disc plus near-spherical dark matter halo predicted by a $\Lambda$CDM cosmology. Remarkably, the amount of orbital precession in MOND is nearly identical to that which ... More