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Results for "J. D. Lee"

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Calculation of the electrostatic energy of two charged helices on rods in a generalized braid geometryFeb 06 2013Feb 11 2013This is a technical document that outlines a calculation of an electrostatic interaction energy between two rods, with charge helices on them, forming a braid. We deal here with screened electrostatics. A general braid geometry is considered, though to ... More
A statistical mechanical study of mechanical dual molecular braidingDec 05 2013Mar 28 2014This is an archival document; the work contains theoretical development to be used in new publications and to stimulate further development. Here, we develop a statistical mechanical treatment of a braid formed of two molecules subject to an external ... More
The D-Gauge: a solution to the i-r problem for fermion mass generation in QED3 in the Matsubara formalismJun 03 1998A serious problem with the Schwinger-Dyson approach to dynamical mass generation in QED3 at finite temperature is that the contribution from the transverse part of the photon propagator, in the Landau gauge, leads to infrared divergences in both the mass ... More
The effect of undulations on Spontaneous Braid formationFeb 14 2013This paper extends on a recent work where it was shown that forces dependent on the helical structure may cause two DNA molecules to spontaneously braid [R. Cortini et Al, Biophys. J. 101, 875 (2011)]. Here, bending fluctuations of DNA centre lines about ... More
Statistical Mechanical Model for a closed loop plectoneme with weak helix specific forcesSep 08 2016We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure ... More
Undulations in a weakly interacting mechanically generated molecular braid under tensionDec 19 2013Dec 20 2013We consider mechanically generated molecular braids composed of two molecules where long range interactions between them can be considered to be very weak. We describe a model that takes account of the thermal fluctuations of the braid, steric interactions ... More
Statistical Mechanical Model for a closed loop plectoneme with weak helix specific forcesSep 08 2016Jan 13 2017We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure ... More
Statistical Mechanical Model for a closed loop plectoneme with weak helix specific forcesSep 08 2016Oct 06 2016We develop a statistical mechanical framework, based on a variational approximation, to describe closed loop plectonemes. This framework incorporates weak helix structure dependent forces into the determination of the free energy and average structure ... More
Effect of retardation on dynamical mass generation in two-dimensional QED at finite temperatureMar 13 1998Jun 03 1998The effect of retardation on dynamical mass generation in is studied, in the imaginary time formalism. The photon porarization tensor is evaluated to leading order in 1/N (N is the number of flavours), and simple closed form expressions are found for ... More
Torsional fluctuations in columnar DNA assembliesNov 01 2005In columnar assemblies of helical bio-molecules the azimuthal degrees of freedom, i.e. rotations about the long axes of molecules, may be important in determining the structure of the assemblies especially when the interaction energy between neighbouring ... More
Small ball probabilities, maximum density and rearrangementsMar 31 2015Apr 01 2015We prove that the probability that a sum of independent random variables in $\mathbb{R}^d$ with bounded densities lies in a ball is maximized by taking uniform distributions on balls. This in turn generalizes a result by Rogozin on the maximum density ... More
External losses in photoemission from strongly correlated quasi two-dimensional solidsJan 09 2001Jun 26 2001New expressions are derived for photoemission, which allow experimental electron energy loss data to be used for estimating losses in photoemission. The derivation builds on new results for dielectric response and mean free paths of strongly correlated ... More
The sudden approximation in photoemission and beyondSep 27 2001The conditions behind the sudden approximation are critically examined. The fuzzy band expression is derived in detail from first principles. We go beyond the sudden approximation to account for both extrinsic losses and interference effects. In an extension ... More
Typical growth behavior of the out-of-time-ordered commutator in many-body localized systemsDec 02 2018We investigate the typicality of the growth behavior of the out-of-time-ordered commutator (OTOC) in the many-body localized (MBL) quantum spin chains across random disorder realizations. In the MBL phase of the Heisenberg XXZ chain, we find that the ... More
Typical growth behavior of the out-of-time-ordered commutator in many-body localized systemsDec 02 2018May 31 2019We investigate the typicality of the growth behavior of the out-of-time-ordered commutator (OTOC) in the many-body localized (MBL) quantum spin chains across random disorder realizations. In the MBL phase of the Heisenberg XXZ chain, we find that the ... More
Charge ordering in doped manganese oxides: lattice dynamics and magnetic structureApr 07 1997Based on the Hamiltonian of small polarons with the strong nearest neighbor repulsion, we have investigated the charge ordering phenomena observed in half-doped manganites R_{1/2}A_{1/2}MnO_3. We have explored possible consequences of the charge ordering ... More
Renormalization group and 1/N expansion for 3-dimensional Ginzburg-Landau-Wilson modelsJul 19 2001A renormalization-group scheme is developed for the 3-dimensional O($2N$)-symmetric Ginzburg-Landau-Wilson model, which is consistent with the use of a 1/N expansion as a systematic method of approximation. It is motivated by an application to the critical ... More
Bragg spectroscopic interferometer and quantum measurement-induced correlations in atomic Bose-Einstein condensatesApr 20 2012Aug 02 2012We theoretically analyze the Bragg spectroscopic interferometer of two spatially separated atomic Bose-Einstein condensates that was experimentally realized by Saba et al. [Science 2005 v307 p1945] by continuously monitoring the relative phase evolution. ... More
Sloshing of the Magnetized Cool Gas in the Cores of Galaxy ClustersAug 22 2011Sep 19 2011X-ray observations of many clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts". In relaxed clusters with cool cores, these edges have been interpreted as evidence for the "sloshing" of the core ... More
The transition from the adiabatic to the sudden limit in core level photoemission: A model study of a localized systemApr 23 1999We consider core electron photoemission in a localized system, where there is a charge transfer excitation. The system is modelled by three electron levels, one core level and two outer levels. The model has a Coulomb interaction between these levels ... More
Control of carrier transport in GaAs by longitudinal-optical phonon-carrier scattering using a pair of laser pump pulsesJan 13 2011Jan 31 2011We demonstrate optical control of the LO phonon-plasmon coupled (LOPC) modes in GaAs by using a femtosecond pump-pulse pair. The relaxation time of the plasmon-like LOPC mode significantly depends on the separation time (\Delta t) of the pump-pulse pair. ... More
Polaron transport and lattice dynamics in colossal magnetoresistance manganitesApr 07 1997Based on the model combining the spin double exchange and the lattice polaron, we have studied the colossal magnetoresistance phenomena observed in perovskite manganites R_{1-x}A_xMnO_3. First, effects of both the double exchange and the electron-phonon ... More
Entanglement of a two-mode squeezed state in a Gaussian environmentJun 28 2002Jul 21 2002Some non-classical properties such as squeezing, sub-Poissonian photon statistics or oscillations in photon-number distributions may survive longer in a phase-sensitive environment than in a phase-insensitive environment. We examine if entanglement, which ... More
Structure of exciton condensates in imbalanced electron-hole bilayersNov 29 2016We investigate the possibility of excitonic superfluidity in electron-hole bilayers. We calculate the phase diagram of the system for the whole range of electron-hole density imbalance and for different degrees of electrostatic screening, using mean-field ... More
$sp^{2}$/$sp^{3}$ carbon ratio in graphite oxide with different preparation timesJul 02 2010Mar 02 2011Graphite oxide is an amorphous insulator. Although several models have been suggested, its structure remains controversial. To elucidate this issue, 5 samples were prepared by the Brodie process and the Staudenmaier process. The electronic structure of ... More
Photoemission in the system of linear chains : application to PrBa$_2$Cu$_3$O$_7$ and La$_{\rm 2-x-y}$Nd$_{\rm y}$Sr$_{\rm x}$CuO$_4$Sep 26 2000Photoemission in the system of linear charged chains has been studied with the dipole matrix incorporated, from which its dependencies on the photoelectron momentum (${\bf k}$), photon polarization ($\hat{\bf E}$), and photon energy ($\omega$) can be ... More
Critical-point scaling function for the specific heat of a Ginzburg-Landau superconductorJul 19 2001If the zero-field transition in high temperature superconductors such as YBa_2Cu_3O_7-\delta is a critical point in the universality class of the 3-dimensional XY model, then the general theory of critical phenomena predicts the existence of a critical ... More
Dijkgraaf-Witten Type Invariants of Seifert Surfaces in 3-ManifoldsJul 03 2015We introduce defects, with internal gauge symmetries, on a knot and Seifert surface to a knot into the combinatorial construction of finite gauge-group Dijkgraaf-Witten theory. The appropriate initial data for the construction are certain three object ... More
Stratified spaces, Directed Algebraic Topology, and State-Sum TQFTsJul 20 2018We apply the theory of directed topology developed by Grandis [9, 10] to the study of stratified spaces by describing several ways in which a stratification or a stratification with orientations on the strata can be used to produce a related directed ... More
A Unified Model for Two Localisation Problems: Electron States in Spin-Degenerate Landau Levels, and in a Random Magnetic FieldNov 20 1993A single model is presented which represents both of the two apparently unrelated localisation problems of the title. The phase diagram of this model is examined using scaling ideas and numerical simulations. It is argued that the localisation length ... More
Preparation of carbon nanotubes from graphite powder at room temperatureJul 07 2010Feb 23 2011We develop a new chemical route to prepare carbon nanotubes at room temperature. Graphite powder is immersed in a mixed solution of nitric and sulfuric acid with potassium chlorate. After heating the solution up to 70{\deg}C and leaving them in the air ... More
Optimal tuning of a confined Brownian information engineDec 22 2015A Brownian information engine is a device extracting a mechanical work from a single heat bath by exploiting the information on the state of a Brownian particle immersed in the bath. As for engines, it is important to find the optimal operating condition ... More
Herschel Key Program, "Dust, Ice, and Gas In Time" (DIGIT): the origin of molecular and atomic emission in low-mass protostars in TaurusJul 11 2014Six low-mass embedded sources (L1489, L1551-IRS5, TMR1, TMC1-A, L1527, and TMC1) in Taurus have been observed with Herschel-PACS to cover the full spectrum from 50 to 210 $\mu$m as part of the Herschel key program, "Dust, Ice, and Gas In Time (DIGIT)". ... More
Scale-free random branching tree in supercritical phaseFeb 01 2007We study the size and the lifetime distributions of scale-free random branching tree in which $k$ branches are generated from a node at each time step with probability $q_k\sim k^{-\gamma}$. In particular, we focus on finite-size trees in a supercritical ... More
Some new identities on the twisted (h, q)- Euler numbers and q-Bernstein polynomialsApr 30 2011In this paper we give some interesting relationships between twisted (h,q)-Euler numbers and q-Berstein polynomnials by using fermionic p-adic q-integrals on Zp
Exchange coupled perpendicular mediaMay 12 2008The potential of exchange spring bilayers and graded media is reviewed. An analytical model for the optimization of graded media gives an optimal value of the magnetic polarization of Js = 0.8 T. The optimum design allows for thermally stable grains with ... More
A Metric for Performance PortabilityNov 22 2016The term "performance portability" has been informally used in computing to refer to a variety of notions which generally include: 1) the ability to run one application across multiple hardware platforms; and 2) achieving some notional level of performance ... More
Current-induced asymmetric magnetoresistance due to energy transfer via quantum spin-flip processMar 29 2016Current-induced magnetization excitation is a core phenomenon for next-generation magnetic nanodevices, and has been attributed to the spin-transfer torque (STT) that originates from the transfer of the spin angular momentum between a conduction electron ... More
A Multiwavelength Study on the Fate of Ionizing Radiation in Local StarburstsOct 13 2010The fate of ionizing radiation is vital for understanding cosmic ionization, energy budgets in the interstellar and intergalactic medium, and star formation rate indicators. The low observed escape fractions of ionizing radiation have not been adequately ... More
Statistical mechanics of columnar DNA assembliesAug 13 2004Many physical systems can be mapped onto solved or "solvable" models of magnetism. In this work, we have mapped the statistical mechanics of columnar phases of ideally helical rigid DNA -- subject to the earlier found unusual, frustrated pair potential ... More
Composite Fermion Hall Conductance at $ν=1/2$Jul 22 1996We show that in the limit of vanishing bare electron effective mass, and in the presence of particle-hole symmetric disorder (which can be of vanishing strength), the composite fermion Hall conductance is constrained to be $-{1\over 2}\frac{e^2}{h}$. ... More
Nonabelian Vortices on Surfaces and Their StatisticsJan 14 1997We discuss the physics of topological vortices moving on an arbitrary surface M in a Yang-Mills-Higgs theory in which the gauge group G breaks to a finite subgroup H. We concentrate on the case where M is compact and/or nonorientable. Interesting new ... More
Spinning Particles, Braid Groups and SolitonsJan 14 1994We develop general techniques for computing the fundamental group of the configuration space of $n$ identical particles, possessing a generic internal structure, moving on a manifold $M$. This group generalizes the $n$-string braid group of $M$ which ... More
Intrinsic degree-correlations in static model of scale-free networksNov 07 2005Jan 04 2006We calculate the mean neighboring degree function $\bar k_{\rm{nn}}(k)$ and the mean clustering function $C(k)$ of vertices with degree $k$ as a function of $k$ in finite scale-free random networks through the static model. While both are independent ... More
Lost in Space: Geolocation in Event DataNov 14 2016Extracting the "correct" location information from text data, i.e., determining the place of event, has long been a goal for automated text processing. To approximate human-like coding schema, we introduce a supervised machine learning algorithm that ... More
Many-body dynamics of p-wave Feshbach molecule production: a mean-field approachOct 08 2012Jan 16 2013We study the mean-field dynamics of p-wave Feshbach molecule production in an ultra cold gas of Fermi atoms in the same internal state. We derive a separable potential to describe the low-energy scattering properties of such atoms, and use this potential ... More
The magnetic field and pressure dependence of the magnetic ordering transition in NaxCoO2 (0.6<x<0.72)Oct 26 2005Apr 27 2006We have measured the magnetic field (H<90 kOe) and pressure (P<10 kbar) dependence of the magnetic ordering temperature, Tmag, in single crystal samples of NaxCoO2 for a range of Na concentrations (0.60<x<0.72). We show that in zero field, Tmag remains ... More
Trapping and Assembly of Living Colloids at Water/Water InterfacesDec 11 2014We study the assembly of colloids in a two phase water-water system that provides an environment that can sustain bacteria, providing a new structure with rich potential to confine and structure living colloids. The water-water system, formed via phase ... More
Holomorphic Supersymmetric Nambu--Jona-Lasinio Model with Application to Electroweak Symmetry BreakingJun 19 2009Feb 08 2010Based on our idea of an alternative supersymmetrization of the Nambu--Jona-Lasinio model for dynamical symmetry breaking, we analyze the resulted new model with a holomorphic dimension-five operator in the superpotential. The approach provides a new direction ... More
Entanglement induced by a single-mode heat environmentSep 12 2001A thermal field, which frequently appears in problems of decoherence, provides us with minimal information about the field. We study the interaction of the thermal field and a quantum system composed of two qubits and find that such a chaotic field with ... More
Relativity of EntanglementNov 02 2000Jan 18 2003It has recently been suggested that various entanglement measures for bipartite mixed states do not in general give the same ordering even in the asymptotic cases [S. Virmani and M. B. Plenio, Phys. Lett. A {\bf 268}, 31 (2000)]. That is, for two certain ... More
Dirty quantum Hall ferromagnets and quantum Hall spin glassesOct 19 2002We study quantum Hall ferromagnets in the presence of a random electrostatic impurity potential, within the framework of a classical non-linear sigma model. We discuss the behaviour of the system using a heuristic picture for the competition between exchange ... More
Spin textures, screening and excitations in dirty quantum Hall ferromagnetsSep 18 2001We study quantum Hall ferromagnets in the presence of a random electrostatic impurity potential. Describing these systems with a classical non-linear sigma model and using analytical estimates supported by results from numerical simulations, we examine ... More
Cold Fronts and Gas Sloshing in Galaxy Clusters with Anisotropic Thermal ConductionApr 26 2012Nov 11 2012(Abridged) Cold fronts in cluster cool cores should be erased on short timescales by thermal conduction, unless protected by magnetic fields that are "draped" parallel to the front surfaces, suppressing conduction perpendicular to the fronts. We present ... More
The NSNS High Energy Beam Transport LineSep 09 1997In the National Spallation Neutron Source (NSNS) design, a 180 meter long transport line connects the 1 GeV linac to an accumulator ring. The linac beam has a current of 28 mA, pulse length of 1 ms, and 60 Hz rep rate. The high energy transport line consists ... More
Robustness of the avalanche dynamics in data packet transport on scale-free networksOct 27 2004Jan 11 2006We study the avalanche dynamics in the data packet transport on scale-free networks through a simple model. In the model, each vertex is assigned a capacity proportional to the load with a proportionality constant $1+a$. When the system is perturbed by ... More
Investigation of the Spin Density Wave in NaxCoO2Jun 22 2004Oct 04 2004Magnetic susceptibility, transport and heat capacity measurements of single crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave (SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac) data in which a cusp is ... More
Assumed Density Filtering Q-learningDec 09 2017Oct 05 2018While off-policy temporal difference (TD) methods have widely been used in reinforcement learning due to their efficiency and simple implementation, their Bayesian counterparts have not been utilized as frequently. One reason is that the non-linear max ... More
Disorder and superfluid density in overdoped cuprate superconductorsApr 16 2017Jun 15 2018We calculate superfluid density for a dirty d-wave superconductor. The effects of impurity scattering are treated within the self-consistent t-matrix approximation, in weak-coupling BCS theory. Working from a realistic tight-binding parameterization of ... More
Chiral symmetry breaking in a uniform external magnetic field II. Symmetry restoration at high temperatures and chemical potentialsNov 17 1997Chiral symmetry is dynamically broken in quenched, ladder QED at weak gauge couplings when an external magnetic field is present. In this paper, we show that chiral symmetry is restored above a critical chemical potential and the corresponding phase transition ... More
Textured Superconductivity in the Presence of a Coexisting Order: Ce115s and Other Heavy-Fermion CompoundsAug 01 2012Superconductivity in strongly correlated electron systems frequently emerges in proximity to another broken symmetry. In heavy-electron superconductors, the nearby ordered state most commonly is magnetism, and the so-called Ce115 heavy-electron compounds ... More
Constraining the Envelope Structure of L1527 IRS: Infrared Scattered Light ModelingFeb 19 2008We model Spitzer Space Telescope observations of the Taurus Class 0 protostar L1527 IRS (IRAS 04368+2557) to provide constraints on its protostellar envelope structure. The nearly edge-on inclination of L1527 IRS, coupled with the highly spatially-resolved ... More
Finding a faint polarized signal in wide-band radio dataNov 29 2016We develop two algorithms, based on maximum likelihood (ML) inference, for estimating the parameters of polarized radio sources which emit at a single rotation measure (RM), e.g., pulsars. These algorithms incorporate the flux density spectrum of the ... More
Chiral anomaly without Landau levels: From the quantum to the classical regimeMay 01 2018Jan 23 2019We study the chiral anomaly in disordered Weyl semimetals, where the broken translational symmetry prevents the direct application of Nielsen and Ninomiya's mechanism and disorder is strong enough that quantum effects are important. In the weak disorder ... More
Solitary waves and supersonic reaction front in metastable solidsDec 28 2000Motivated by an increasing number of remarkable experimental observations on the role of pressure and shear stress in solid reactions,explosions and detonations,we present a simple toy model that embodies nonlinear elasticity and dispersion as well as ... More
Chiral Symmetry Breaking in a Uniform External Magnetic FieldJan 29 1997Using the nonperturbative Schwinger-Dyson equation, we show that chiral symmetry is dynamically broken in QED at weak couplings when an external magnetic field is present, and that chiral symmetry is restored at temperatures above $T_c \simeq \alpha\pi^2/\sqrt{2 ... More
Rings and BallsJan 15 1993Feb 10 1993We examine the various linkings in space-time of ``ball-like'' and ``ring-like'' topological solitons in certain nonlinear sigma models in 2+1 and 3+1 dimensions. By going to theories where soliton overlaps are forbidden, these linkings become homotopically ... More
Interactive Execution Monitoring of Agent TeamsJun 22 2011There is an increasing need for automated support for humans monitoring the activity of distributed teams of cooperating agents, both human and machine. We characterize the domain-independent challenges posed by this problem, and describe how properties ... More
Terahertz wave generation via optical rectification from multiferroic BiFeO3Nov 06 2008We detected broadband coherent terahertz (THz) emission from multiferroic BiFeO3 after illuminating a high-quality bulk single ferroelectric domain crystal with a ~100 fs optical pulse. The dependence of the emitted THz waveform on the energy and polarization ... More
Dark matter and Higgs boson collider implications of fermions in an abelian-gauged hidden sectorApr 13 2009We add fermions to an abelian-gauged hidden sector. We show that the lightest can be the dark matter with the right thermal relic abundance, and discovery is within reach of upcoming dark matter detectors. We also show that these fermions change Higgs ... More
Assumed Density Filtering Q-learningDec 09 2017Jun 03 2019While off-policy temporal difference (TD) methods have widely been used in reinforcement learning due to their efficiency and simple implementation, their Bayesian counterparts have not been utilized as frequently. One reason is that the non-linear max ... More
Fast Object Localization Using a CNN Feature Map Based Multi-Scale SearchApr 12 2016Object localization is an important task in computer vision but requires a large amount of computational power due mainly to an exhaustive multiscale search on the input image. In this paper, we describe a near real-time multiscale search on a deep CNN ... More
Exciton-exciton interaction and biexciton formation in bilayer systemsNov 20 2008We report quantum Monte Carlo calculations of biexciton binding energies in ideal two-dimensional bilayer systems with isotropic electron and hole masses. We have also calculated exciton-exciton interaction potentials, and pair distribution functions ... More
Spin chirality on a two-dimensional frustrated latticeApr 05 2005Apr 05 2005The collective behavior of interacting magnetic moments can be strongly influenced by the topology of the underlying lattice. In geometrically frustrated spin systems, interesting chiral correlations may develop that are related to the spin arrangement ... More
Intrusion-aware Alert Validation Algorithm for Cooperative Distributed Intrusion Detection Schemes of Wireless Sensor NetworksDec 29 2009Existing anomaly and intrusion detection schemes of wireless sensor networks have mainly focused on the detection of intrusions. Once the intrusion is detected, an alerts or claims will be generated. However, any unidentified malicious nodes in the network ... More
Long-range surface plasmon polariton excitation at the quantum levelJan 26 2009Jun 02 2009We provide the quantum mechanical description of the excitation of long-range surface plasmon polaritons (LRSPPs) on thin metallic strips. The excitation process consists of an attenuated-reflection setup, where efficient photon-to-LRSPP wavepacket-transfer ... More
"Dust, Ice, and Gas In Time" (DIGIT) Herschel Observations of GSS30-IRS1 in OphiuchusJan 21 2015As a part of the "Dust, Ice, and Gas In Time" (DIGIT) key program on Herschel, we observed GSS30-IRS1, a Class I protostar located in Ophiuchus (d = 120 pc), with Herschel/Photodetector Array Camera and Spectrometer (PACS). More than 70 lines were detected ... More
Laser-induced antiferromagnetic-like resonance in amorphous ferrimagnetsAug 17 2018The magnetization dynamics for ferrimagnets at the angular momentum compensation temperature T_A is believed to be analogous to that for antiferromagnets. We investigated the pulsed-laser-induced magnetization dynamics in amorphous rare-earth transition-metal ... More
Compact objects for everyone: I. White dwarf starsSep 14 2004Jul 19 2005Based upon previous discussions on the structure of compact stars geared towards undergraduate physics students, a real experiment involving two upper-level undergraduate physics students, a beginning physics graduate, and two advanced graduate students ... More
Fermion Damping in a Fermion-Scalar PlasmaOct 16 1998Jan 13 1999In this article we study the dynamics of fermions in a fermion-scalar plasma. We begin by obtaining the effective in-medium Dirac equation in real time which is fully renormalized and causal and leads to the initial value problem. For a heavy scalar we ... More
Damping Rates and Mean Free Paths of Soft Fermion Collective Excitations in a Hot Fermion-Gauge-Scalar TheoryFeb 01 1999Feb 24 2000We study the transport coefficients, damping rates and mean free paths of soft fermion collective excitations in a hot fermion-gauge-scalar plasma with the goal of understanding the main physical mechanisms that determine transport of chirality in scenarios ... More
Reheating and Thermalization, Linear Vs. Non-Linear RelaxationJul 25 1995We consider the case of a scalar field, the inflaton, coupled to both lighter scalars and fermions, and the study the relaxation of the inflaton via particle production in both the linear and non-linear regimes. This has an immediate application to the ... More
New Aspects of ReheatingNov 17 1995Nov 21 1995The reheating stage in post-inflationary cosmologies is reanalyzed. New techniques from non-equilibrium quantum field theory allow a consistent derivation of the equation of motion including the non-linearity of the dynamics. These offer a rationale for ... More
Nonlinear optical probe of tunable surface electrons on a topological insulatorJan 07 2011We use ultrafast laser pulses to experimentally demonstrate that the second-order optical response of bulk single crystals of the topological insulator Bi$_2$Se$_3$ is sensitive to its surface electrons. By performing surface doping dependence measurements ... More
Reheating the Post Inflationary UniverseMay 03 1995We consider the non-equilibrium evolution of the inflaton field coupled to both lighter scalars and fermions. The dissipational dynamics of this field is studied and found to be quite different than that believed in inflationary models. In particular, ... More
Spectroscopically resolving the Algol triple systemJun 03 2015Algol ($\beta$ Persei) is the prototypical semi-detached eclipsing binary and a hierarchical triple system. From 2006 to 2010 we obtained 121 high-resolution and high-S/N \'{e}chelle spectra of this object. Spectral disentangling yields the individual ... More
The Effects of Post-Thermal Annealing on the Emission Spectra of GaAs/AlGaAs Quantum Dots grown by Droplet EpitaxyAug 22 2012We fabricated GaAs/AlGaAs quantum dots by droplet epitaxy method, and obtained the geometries of the dots from scanning transmission electron microscopy data. Post-thermal annealing is essential for the optical activation of quantum dots grown by droplet ... More
Photoluminescence of patterned arrays of vertically stacked InAs/GaAs quantum dotsDec 16 2010We report on photoluminescence measurements of vertically stacked InAs/GaAs quantum dots grown by molecular-beam epitaxy on focused ion beam patterned hole arrays with varying array spacing. Quantum dot emission at 1.24 eV was observed only on patterned ... More
Pair production and electron capture in relativistic heavy-ion collisionsJun 09 2000Results are presented for simulations of electron-positron pair production in relativistic heavy-ion collisions leading to electron capture and positron ejection. We apply a two-center relativistic continuum distorted-wave model to represent the electron/positron ... More
Dynamic Locomotion For Passive-Ankle Biped Robots And Humanoids Using Whole-Body Locomotion ControlJan 23 2019Whole-body control (WBC) is a generic task-oriented control method for feedback control of loco-manipulation behaviors in humanoid robots. The combination of WBC and model-based walking controllers has been widely utilized in various humanoid robots. ... More
On Pulsar Distance Measurements and their UncertaintiesJun 03 2012Accurate distances to pulsars can be used for a variety of studies of the Galaxy and its electron content. However, most distance measures to pulsars have been derived from the absorption (or lack thereof) of pulsar emission by Galactic HI gas, which ... More
Oxygen vacancy induced re-entrant spin glass behavior in multiferroic ErMnO3 thin filmsJan 29 2009Epitaxial thin films of hexagonal ErMnO3 fabricated on Pt(111)/Al2O3(0001) and YSZ(111) substrates exhibited both ferroelectric character and magnetic ordering at low temperatures. As the temperature was reduced, the ErMnO3 films first showed antiferromagnetism. ... More
A semiconductor photon-sorterMay 20 2016Photons do not interact directly with each other, but conditional control of one beam by another can be achieved with non-linear optical media at high field intensities. It is exceedingly difficult to reach such intensities at the single photon level ... More
Electronic structures of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin filmsAug 17 2007We investigated the electronic structure of multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films using both optical spectroscopy and first-principles calculations. Using artificially stabilized hexagonal RMnO3, we extended the optical spectroscopic ... More
Determinable Solutions for One-dimensional Quantum Potentials: Scattering, Quasi-bound and Bound State ProblemsNov 19 2006Jan 06 2007We derive analytic expressions of the recursive solutions to the Schr\"{o}dinger's equation by means of a cutoff potential technique for one-dimensional piecewise constant potentials. These solutions provide a method for accurately determining the transmission ... More
Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy and specific-heat measurementsMay 05 2011Specific heat has been measured down to 600 mK and up to 8 Tesla by the highly sensitive AC microcalorimetry on the MgCNi3 single crystals with Tc ~ 7 K. Exponential decay of the electronic specific heat at low temperatures proved that a superconducting ... More
Star-Forming or Starbursting? The Ultraviolet ConundrumOct 05 2009Compared to starburst galaxies, normal star forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-beta diagram (the IR/UV ratio "IRX" versus the UV color "beta"). To ... More
Low energy fast events from radon progenies at the surface of a CsI(Tl) scintillatorAug 22 2011Aug 27 2012In searches for rare phenomena such as elastic scattering of dark matter particles or neutrinoless double beta decay, alpha decays of Rn222 progenies attached to the surfaces of the detection material have been identified as a serious source of background. ... More
Real-time nonequilibrium dynamics in hot QED plasmas: dynamical renormalization group approachMay 22 2000Oct 20 2000We study the real-time nonequilibrium dynamics in hot QED plasmas implementing a dynamical renormalization group and using the hard thermal loop (HTL) approximation. The focus is on the study of the relaxation of gauge and fermionic mean fields and on ... More
Quantum Statistical Metastability RevisitedMay 11 1993We calculate the decay rate for a state prepared in a thermal density matrix centered on a metastable ground state. We find a rate that is intrinsically time {\it dependent}, as opposed to the {\it constant} rates of previous works. The rate vanishes ... More