Results for "T. -H. Chung"

total 149907took 0.14s
Alternative subtraction scheme using Nagy Soper dipolesJan 15 2010We present an alternative subtraction scheme for the treatment of infrared divergences in NLO QCD calculations. In this scheme, the number of transformations is greatly reduced with respect to the standard subtraction scheme by Catani and Seymour. We ... More
IPA-CuCl$_3$: a S=1/2 Ladder with Ferromagnetic RungsJun 15 2005The spin gap material IPA-CuCl3 has been extensively studied as a ferromagnetic-antiferromagnetic bondalternating S = 1/2 chain. This description of the system was derived from structural considerations and bulk measurements. New inelastic neutron scattering ... More
Inflationary Cosmology Connecting Dark Energy and Dark MatterApr 24 2007Oct 09 2007Kination dominated quintessence models of dark energy have the intriguing feature that the relic abundance of thermal cold dark matter can be significantly enhanced compared to the predictions from standard cosmology. Previous treatments of such models ... More
Stabilization of ultra-short pulses in cubic nonlinear mediaDec 13 2005Apr 07 2006We study the propagation of ultra-short pulses in a cubic nonlinear medium. Using multiple-scale technique, we derive a new wave equation that preserves the nonlocal dispersion present in Maxwell's equations. As a result, we are able to understand how ... More
Engineering of selective carrier injection in patterned arrays of single-quantum-dot entangled photon light-emitting diodesJul 19 2017Scalability and foundry compatibility (as for example in conventional silicon based integrated computer processors) in developing quantum technologies are exceptional challenges facing current research. Here we introduce a quantum photonic technology ... More
Statistical study of stacked/coupled site-controlled pyramidal quantum dots and their excitonic propertiesAug 31 2017We report on stacked multiple quantum dots (QDs) formed inside inverted pyramidal recesses, which allow for the precise positioning of the QDs themselves. Specifically we fabricated double QDs with varying inter-dot distance and ensembles with more than ... More
Ward Identity and Basis Tensor Gauge Theory at One LoopDec 29 2017May 11 2018Basis tensor gauge theory (BTGT) is a reformulation of ordinary gauge theory that is an analog of the vierbein formulation of gravity and is related to the Wilson line formulation. To match ordinary gauge theories coupled to matter, the BTGT formalism ... More
Large Blue Spectral Isocurvature Spectral Index Signals Time-Dependent MassSep 19 2015We show that if a spectator linear isocurvature dark matter field degree of freedom has a constant mass through its entire evolution history, the maximum measurable isocurvature spectral index that is consistent with the current tensor-to-scalar ratio ... More
A partial inventory of observational anisotropies in single-dish line-intensity mappingMay 01 2019Line-intensity mapping, being an imperfect observation of the line-intensity field in a cosmological volume, will be subject to various anisotropies introduced in observation. Existing literature in the context of CO and [C II] line-intensity mapping ... More
Dynamics of composite Haldane spin chains in IPA-CuCl3Nov 06 2005Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl3 are studied by cold neutron inelastic scattering. Strongly dispersive gap excitations are observed. Contrary to previously proposed models, the system is best described as an ... More
Classical inflaton field induced creation of superheavy dark matterSep 23 1998We calculate analytically and numerically the production of superheavy dark matter (X) when it is coupled to the inflaton field \phi within the context of a slow-roll m_\phi^2 \phi^2/2 inflationary model with coupling g^2 X^2 \phi^2/2. We find that X ... More
Superheavy Dark MatterAug 14 1998If there exist fields of mass of the order of $10^{13}$ GeV and large field inflation occurs, their interaction with classical gravitation will generate enough particles to give the universe critical density today regardless of their nongravitational ... More
Erratum: Dynamics and scaling in a quantum spin chain material with bond randomnessApr 28 2004Apr 13 2006Follow-up neutron measurements, performed on a sample much larger than the one used in the original study, show that in the energy range 0.5-45 meV the magnetic excitations in BaCu2SiGeO7 are indistinguishable from those in conventional (disorder-free) ... More
On estimation of contamination from hydrogen cyanide in carbon monoxide line intensity mappingJun 09 2017Aug 31 2017Line-intensity mapping surveys probe large-scale structure through spatial variations in molecular line emission from a population of unresolved cosmological sources. Future such surveys of carbon monoxide line emission, specifically the CO(1-0) line, ... More
Conditions for entangled photon emission from (111)B site-controlled Pyramidal quantum dotsFeb 13 2015A study of highly symmetric site-controlled Pyramidal In0.25Ga0.75As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from Pyramidal QDs of different designs from the one already reported in Juska ... More
Constraints on Resonant Particle Production during Inflation from the Matter and CMB Power SpectraJun 01 2004Aug 25 2004We analyze the limits on resonant particle production during inflation based upon the power spectrum of fluctuations in matter and the cosmic microwave background. We show that such a model is consistent with features observed in the matter power spectrum ... More
Connecting LHC, ILC, and QuintessenceJun 15 2007Oct 09 2007If the cold dark matter consists of weakly interacting massive particles (WIMPs), anticipated measurements of the WIMP properties at the Large Hadron Collider (LHC) and the International Linear Collider (ILC) will provide an unprecedented experimental ... More
Forecasting [C II] line-intensity mapping measurements between the end of reionization and the epoch of galaxy assemblyDec 19 2018We combine recent simulation work on the SFR--[C II] correlation at high redshift with empirical modeling of the galaxy--halo connection (via UniverseMachine) to forecast [C II] auto power spectra from $z\sim4$ to $z\sim8$. We compare these to sensitivities ... More
Strange superconductivity near an antiferromagnetic heavy fermion quantum critical pointJun 11 2018The heavy fermion CeMIn5 family with M = Co, Rh, Ir provide a prototypical example of strange superconductors with unconventional d-wave pairing and strange metal normal state, emerged near an antiferromagnetic quantum critical point. The microscopic ... More
Development of a Smart Modulator and Efficiency Evaluation of 500-GeV e+e- C-Band Linear ColliderAug 18 2000An e+e- linear collider at 500-GeV C.M. (center of mass) has been proposed as a future accelerator. The C-band linear collider has more than a thousand klystrons and matching modulators. The linear colliders require smart modulators with high reliability, ... More
Adaptive generalized multiscale finite element methods for H(curl)-elliptic problems with heterogeneous coefficientsFeb 08 2018In this paper, we construct an adaptive multiscale method for solving H(curl)-elliptic problems in highly heterogeneous media. Our method is based on the generalized multiscale finite element method. We will first construct a suitable snapshot space, ... More
An analysis of the NLMC upscaling method for high contrast problemsApr 25 2019In this paper we propose simple multiscale basis functions with constraint energy minimization to solve elliptic problems with high contrast medium. Our methodology is based on the recently developed non-local multicontinuum method (NLMC). The main ingredient ... More
Constraint Energy Minimizing Generalized Multiscale Finite Element Method for high-contrast linear elasticity problemSep 11 2018In this paper, we consider the offline and online Constraint Energy Minimizing Generalized Mul- tiscale Finite Element Method (CEM-GMsFEM) for high-contrast linear elasticity problem. Offline basis construction starts with an auxiliary multiscale space ... More
Strain-stress study of AlxGa1-xN/AlN heterostructures on c-plane sapphire and related optical propertiesMay 10 2019This work presents a systematic study of stress and strain of AlxGa1-xN/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using synchrotron radiation high-resolution X-ray diffraction ... More
Dispersive resonance bands within the space charge layer of metal- semiconductor junctionJun 03 2010Based on measurements of angle resolved photoemission, we report that in the Pb/Ge(111)- \sqrt{3}x\sqrt{3} R30^\circ structure, in addition to three bands resembling Ge heavy hole (HH), light hole (LH), and split off (SO) bulk band edges, a fourth dispersive ... More
AMiBA: Array for Microwave Background AnisotropyDec 13 2000Jan 13 2001As part of a 4-year Cosmology and Particle Astrophysics (CosPA) Research Excellence Initiative in Taiwan, AMiBA $-$ a 19-element dual-channel 85-105 GHz interferometer array is being specifically built to search for high redshift clusters of galaxies ... 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
Statics and dynamics of an incommensurate spin order in a geometrically frustrated antiferromagnet CdCr$_2$O$_4$Oct 13 2005Using elastic and inelastic neutron scattering we show that a cubic spinel, CdCr$_2$O$_4$, undergoes an elongation along the c-axis ($c > a = b$) at its spin-Peierls-like phase transition at $T_N$ = 7.8 K. The N\'{e}el phase ($T < T_N$) has an incommesurate ... More
Nonlinear Photoelasticity to Explicate Acoustic Phonon Phase under Anharmonic and Extrinsic DecayMar 06 2018Mar 07 2018By measuring the continuously varying phase of optically detected acoustic (AC) wavepackets in degenerate pump-probe schemes as functions of compositional strain profiles and time, the previously concealed nonlinear interrelation between the refractive ... More
Signatures of Electronic Nematic Phase at Isotropic-Nematic Phase TransitionApr 21 2003Oct 16 2003The electronic nematic phase occurs when the point-group symmetry of the lattice structure is broken, due to electron-electron interactions. We study a model for the nematic phase on a square lattice with emphasis on the phase transition between isotropic ... More
The influence of the cluster environment on the large-scale radio continuum emission of 8 Virgo cluster spiralsJan 20 2010The influence of the environment on the polarized and total power radio continuum emission of cluster spiral galaxies is investigated. We present deep scaled array VLA 20 and 6 cm observations including polarization of 8 Virgo spiral galaxies. These data ... More
The Fincher-Burke spin excitations and omega/T scaling in the insulating 5% Sr-doped La2CuO4Apr 09 2007Oct 23 2007Insulating La1.95Sr0.05CuO4 shares with superconducting cuprates the same Fincher-Burke-like spin excitations, which usually are observed in itinerant antiferromagnets. The local spectral function satisfies omega/T scaling above ~16 K for this incommensurate ... More
Nanoscale femtosecond imaging of transient hot solid density plasmas with elemental and charge state sensitivity using resonant coherent diffractionAug 17 2015Here we propose to exploit the low energy bandwidth, small wavelength and penetration power of ultrashort pulses from XFELs for resonant Small Angle Scattering (SAXS) on plasma structures in laser excited plasmas. Small angle scattering allows to detect ... More
Universal Nonequilibrium I-V Curve at an Interacting Impurity Quantum Critical PointSep 15 2016Aug 03 2017The nonlinear I-V curve at an interacting quantum critical point (QCP) is typically out of reach theoretically. Here, however, we provide an analytical calculation of the I-V curve at a QCP under nonequilibrium conditions and, furthermore, present experimental ... More
Initial growth behavior and resulting microstructural properties of heteroepitaxial ZnO thin films on sapphire (0001) substratesAug 22 2006We have investigated the initial growth behavior and resulting microstructural properties of heteroepitaxial ZnO thin films prepared by pulsed laser deposition on sapphire (0001) substrates. High-resolution x-ray diffraction and transmission electron ... More
Universal Nonequilibrium I-V Curve at an Interacting Impurity Quantum Critical PointSep 15 2016The nonlinear I-V curve at an interacting quantum critical point (QCP) is typically out of reach theoretically. Here, however, we provide an analytical calculation of the I-V curve at a QCP under nonequilibrium conditions and, furthermore, present experimental ... More
Ferroelectric properties of SrRuO3/BaTiO3/SrRuO3 ultrathin film capacitors free from passive layJun 20 2005Structural studies on ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors, with BaTiO3 thicknesses of between 5 nm and 30 nm, show well-defined interfaces between ferroelectric BaTiO3 and electrode SrRuO3 layers. In these capacitors, we cannot observe any extrinsic ... More
An adaptive GMsFEM for high-contrast flow problemsSep 24 2013In this paper, we derive an a-posteriori error indicator for the Generalized Multiscale Finite Element Method (GMsFEM) framework. This error indicator is further used to develop an adaptive enrichment algorithm for the linear elliptic equation with multiscale ... More
Thermal rectification properties of multiple-quantum-dot junctionsJan 08 2010It is illustrated that semiconductor quantum dots (QDs) embedded into an insulating matrix connected with metallic electrodes and some vacuum space can lead to significant thermal rectification effect. A multilevel Anderson model is used to investigate ... More
Light emitting single electron transistorsJun 03 2006Jun 22 2006The dynamic properties of light-emitting single-electron transistors (LESETs) made from quantum dots are theoretically studied by using nonequilibrium Green's function method. Holes residing at QD created by small ac signals added in the base electrode ... More
Stark effect on the exciton complexes of individual quantum dotsOct 17 2005The emission spectrum of exciton complexes formed in individual self-assembled quantum dots (QDs) embedded into a p-n junction is theoretically studied using an effective mass model. We calculate the particle Coulomb interactions, eletron-hole overlaps ... More
Tunneling current spectroscopy of a nanostructure junction involving multiple energy levelsFeb 05 2007A multi-level Anderson model is employed to simulate the system of a nanostructure tunnel junction with any number of one-particle energy levels. The tunneling current, including both shell-tunneling and shell-filling cases, is theoretically investigated ... More
Superlattice nanowire heat engines with direction-dependent power output and heat currentApr 15 2019Heat engines (HEs) made of low dimensional structures offer promising applications in energy harvesting due to their reduced phonon thermal conductance. Many efforts have been devoted to the design of HEs made of quantum-dot (QD) superlattice nanowire ... More
Residual driven online mortar mixed finite element methods and applicationsOct 04 2017In this paper, we develop an online basis enrichment method with the mortar mixed finite element method, using the oversampling technique, to solve for flow problems in highly heterogeneous media. We first compute a coarse grid solution with a certain ... More
Stokes tomography of radio pulsar magnetospheres. I. Linear polarizationOct 14 2010Dec 20 2010Polarimetric studies of pulsar radio emission traditionally concentrate on how the Stokes vector (I, Q, U, V) varies with pulse longitude, with special emphasis on the position angle (PA) swing of the linearly polarized component. The interpretation of ... More
Effects of electron correlation on the photocurrent in quantum dot infrared photodetectorsOct 16 2002The effect of electron correlation on the photocurrent of self-assembled InAs/InGaAs quantum dot infrared photo-detector (QDIPs) is studied. It is found that Coulomb interaction and level mixing in the many-body open system lead to double peaks associated ... More
Mixed GMsFEM for the simulation of waves in highly heterogeneous mediaSep 08 2015Numerical simulations of waves in highly heterogeneous media have important applications, but direct computations are prohibitively expensive. In this paper, we develop a new generalized multiscale finite element method with the aim of simulating waves ... More
Generalized Multiscale Finite Element Method for Elasticity EquationsAug 25 2014In this paper, we discuss the application of Generalized Multiscale Finite Element Method (GMsFEM) to elasticity equation in heterogeneous media. Our applications are motivated by elastic wave propagation in subsurface where the subsurface properties ... More
A two-grid preconditioner with an adaptive coarse space for flow simulations in highly heterogeneous mediaJul 19 2018In this paper, we consider flow simulation in highly heterogeneous media that has many practical applications in industry. To enhance mass conservation, we write the elliptic problem in a mixed formulation and introduce a robust two-grid preconditioner ... More
Mapping Luminosity-Redshift Relationship to LTB CosmologyAug 18 2006We derive a direct general map from the luminosity distance D(z) to the inhomogeneous matter distribution M(r) in the Lemaitre-Tolman-Bondi (LTB) cosmology and compute several examples. One of our examples explicitly demonstrates that it is possible to ... More
Standard Model baryogenesis through four-fermion operators in braneworldsDec 30 2001Jan 30 2002We study a new baryogenesis scenario in a class of braneworld models with low fundamental scale, which typically have difficulty with baryogenesis. The scenario is characterized by its minimal nature: the field content is that of the Standard Model and ... More
The MSW Effect in Quantum Field TheoryApr 12 1999We show in detail the general relationship between the Schr\"{o}dinger equation approach to calculating the MSW effect and the quantum field theoretical S-matrix approach. We show the precise form a generic neutrino propagator must have to allow a physically ... More
A quantitative estimate for quasi-integral points in orbitsOct 23 2009Let f(z) be a rational function of degree at least 2 with coefficients in a number field K, and assume that the second iterate f^2(z) of f(z) is not a polynomial. The second author previously proved that for any b in K, the forward orbit O_f(b) contains ... More
Non-Abelian basis tensor gauge theoryMay 20 2019Basis tensor gauge theory is a vierbein analog reformulation of ordinary gauge theories in which the difference of local field degrees of freedom has the interpretation of an object similar to a Wilson line. Here we present a non-Abelian basis tensor ... More
Thermoelectric Properties of a Semiconductor Quantum Dot Chain Connected to Metallic ElectrodesSep 04 2012Jan 10 2013The thermoelectric properties of a semiconduct quantum dot chain (SQDC) connected to metallic electrodes are theoretically investigated in the Coulomb blockade regime. An extended Hubbard model is employed to simulate the SQDC system consisted of {\color{blue}N=2,3,4, ... More
Bistable states of quantum dot array junctions for high-density memoryDec 29 2008We demonstrate that two-dimensional (2D) arrays of coupled quantum dots (QDs) with six-fold degenerate p orbitals can display bistable states, suitable for application in high-density memory device with low power consumption. Due to the inter-dot coupling ... More
Dynamics of quantum spin liquid and spin solid phases in IPA-CuCl3 under fieldMay 09 2007Inelastic and elastic neutron scattering is used to study spin correlations in the quasi-one dimensional quantum antiferromagnet IPA-CuCl3 in strong applied magnetic fields. A condensation of magnons and commensurate transverse long-range ordering is ... More
A conservative local multiscale model reduction technique for Stokes flows in heterogeneous perforated domainsAug 25 2016In this paper, we present a new multiscale model reduction technique for the Stokes flows in heterogeneous perforated domains. The challenge in the numerical simulations of this problem lies in the fact that the solution contains many multiscale features ... More
Stokes tomography of radio pulsar magnetospheres. II. Millisecond pulsarsApr 06 2011The radio polarization characteristics of millisecond pulsars (MSPs) differ significantly from those of non-recycled pulsars. In particular, the position angle (PA) swings of many MSPs deviate from the S-shape predicted by the rotating vector model, even ... More
An enriched multiscale mortar space for high contrast flow problemsSep 08 2016Mortar methods are widely used techniques for discretizations of partial differential equations and preconditioners for the algebraic systems resulting from the discretizations. For problems with high contrast and multiple scales, the standard mortar ... More
An embedded SDG method for the convection-diffusion equationJun 18 2018In this paper, we present an embedded staggered discontinuous Galerkin method for the convection-diffusion equation. The new method combines the advantages of staggered discontinuous Galerkin (SDG) and embedded discontinuous Galerkin (EDG) method, and ... More
Long distance coherent tunneling effect on the charge and heat currents in serially coupled triple quantum dotsSep 06 2013Mar 12 2014The effect of long distance coherent tunneling (LDCT) on the charge and heat currents in serially coupled triple quantum dots (TQDs) connected to electrodes is illustrated by using a combination of the extended Hurbbard model and Anderson model. The charge ... More
Bipolar thermoelectric effect in a srially coupled quantum dot systemApr 14 2011Nov 01 2011The Seebeck coefficient (S) of a serially coupled quantum dot (SCQD) junction system is theoretically studied via a two-level Anderson model. A change of sign in S with respect to temperature is found, which arises from the competition between tunneling ... More
Thermoelectric and thermal rectification properties of quantum dot junctionsFeb 21 2010The electrical conductance, thermal conductance, thermal power and figure of merit (ZT) of semiconductor quantum dots (QDs) embedded into an insulator matrix connected with metallic electrodes are theoretically investigated in the Coulomb blockade regime. ... More
Tunnelling current and emission spectrum of a single electron transistor under optical pumpingJun 01 2005Theoretical studies of the tunnelling current and emission spectrum of a single electron transistor (SET) under optical pumping are presented. The calculation is performed via Keldysh Green's function method within the Anderson model with two energy levels. ... More
Online adaptive basis enrichment for mixed CEM-GMsFEMOct 25 2018Nov 16 2018In this paper, an online basis construction for constraint energy minimizing generalized multiscale finite element method (CEM-GMsFEM) in mixed formulation is proposed. The online approach is based on the strategy of oversampling and makes use of the ... More
Online mixed multiscale finite element method with oversampling and its applicationsJul 02 2018In this paper, we consider an online basis enrichment mixed generalized multiscale method with oversampling, for solving flow problems in highly heterogeneous porous media. This is an exten- sion of the online mixed generalized multiscale method [6]. ... More
Excitations from a Bose-Einstein condensate of magnons in coupled spin laddersAug 25 2006Apr 19 2007The weakly coupled quasi-one-dimensional spin ladder compound (CH$_3$)$_2$CHNH$_3$CuCl$_3$ is studied by neutron scattering in magnetic fields exceeding the critical field of Bose-Einstein condensation of magnons. Commensurate long-range order and the ... More
Analysis and Control of Period-Doubling Bifurcation in Buck Converters Using Harmonic BalanceOct 27 2012Period doubling bifurcation in buck converters is studied by using the harmonic balance method. A simple dynamic model of a buck converter in continuous conduction mode under voltage mode or current mode control is derived. This model consists of the ... More
Elementary Theorems Regarding Blue Isocurvature PerturbationsJan 22 2015Jan 23 2015Blue CDM-photon isocurvature perturbations are attractive in terms of observability and may be typical from the perspective of generic mass relations in supergravity. We present and apply three theorems useful for blue isocurvature perturbations arising ... More
Isocurvature Perturbations and Non-Gaussianity of Gravitationally Produced Nonthermal Dark MatterOct 26 2011Jan 09 2013Gravitational particle production naturally occurs during the transition from the inflationary phase to the non-inflationary phase. If the particles are stable and very weakly interacting, they are natural nonthermal dark matter candidates. We show that ... More
Lensed Density Perturbations in Braneworlds: An Alternative to Perturbations from InflationFeb 04 2002We consider a scenario in which our observable universe is a 3-dimensional surface (3-brane) living in extra dimensions with a warped geometry. We show that ``lensed'' density perturbations from other branes serve as possible seeds for structure formation ... More
Can Geodesics in Extra Dimensions Solve the Cosmological Horizon Problem?Oct 05 1999Oct 12 2000We demonstrate a non-inflationary solution to the cosmological horizon problem in scenarios in which our observable universe is confined to three spatial dimensions (a three-brane) embedded in a higher dimensional space. A signal traveling along an extra-dimensional ... More
Cosmological Challenges in Theories with Extra Dimensions and Remarks on the Horizon ProblemJun 29 1999Nov 02 1999We consider the cosmology that results if our observable universe is a 3-brane in a higher dimensional universe. In particular, we focus on the case where our 3-brane is located at the $Z_2$ symmetry fixed plane of a $Z_2$ symmetric five-dimensional spacetime, ... More
On a Dynamical Brauer-Manin ObstructionJan 19 2008Let F : X --> X be a morphism of a variety defined over a number field K, let V be a K-subvariety of X, and let O_F(P)= {F^n(P) :n=0,1,2,...} be the orbit of a point P in X(K). We describe a local-global principle for the intersection of V and O_F(P). ... More
Fully implicit time-stepping schemes and non-linear solvers for systems of reaction-diffusion equationsJan 23 2015In this article we present robust, efficient and accurate fully implicit time-stepping schemes and nonlinear solvers for systems of reaction-diffusion equations. The applications of reaction-diffusion systems is abundant in the literature, from modelling ... More
Local Bifurcations in DC-DC ConvertersOct 10 2012Three local bifurcations in DC-DC converters are reviewed. They are period-doubling bifurcation, saddle-node bifurcation, and Neimark bifurcation. A general sampled-data model is employed to study the types of loss of stability of the nominal (periodic) ... More
Cosmological Constant, Dark Matter, and Electroweak Phase TransitionAug 25 2011Aug 29 2011Accepting the fine tuned cosmological constant hypothesis, we have recently proposed that this hypothesis can be tested if the dark matter freeze out occurs at the electroweak scale and if one were to measure an anomalous shift in the dark matter relic ... More
Approximate Consistency Condition from Running Spectral Index in Slow-Roll Inflationary ModelsAug 19 2005Density perturbations generated from inflation almost always have a spectral index n_s which runs (varies with the wavelength). We explore a running spectral index scenario in which the scalar spectral index runs from blue (n_s >1) on large length scales ... More
Electroweak Phase Transition in the munuSSMApr 06 2010Sep 22 2010An extension of the MSSM called the munuSSM does not allow a conventional thermal leptogenesis scenario because of the low scale seesaw that it utilizes. Hence, we investigate the possibility of electroweak baryogenesis. Specifically, we identify a parameter ... More
Quantum Critical Scaling and origin of Non-Fermi-Liquid behavior in Sc$_{1-x}$U$_{x}$Pd$_3$Jan 01 2005We use inelastic neutron scattering to study magnetic excitations of Sc$_{1-x}$U$_{x}$Pd$_3$ for U concentrations ($x=0.25$, 0.35) near the spin glass quantum critical point (QCP). The excitations are spatially incoherent, broad in energy ($E=\hbar\omega$), ... More
Semiclassical Gravity Theory and Quantum FluctuationsApr 06 1993We discuss the limits of validity of the semiclassical theory of gravity in which a classical metric is coupled to the expectation value of the stress tensor. It is argued that this theory is a good approximation only when the fluctuations in the stress ... More
A Bump in the Blue Axion Isocurvature SpectrumOct 13 2016Blue axion isocurvature perturbations are both theoretically well-motivated and interesting from a detectability perspective. These power spectra generically have a break from the blue region to a flat region. Previous investigations of the power spectra ... More
Basis Tensor Gauge TheorySep 13 2016We reformulate gauge theories in analogy with the vierbein formalism of general relativity. More specifically, we reformulate gauge theories such that their gauge dynamical degrees of freedom are local fields that transform linearly under the dual representation ... More
Gravity Waves as a Probe of Hubble Expansion Rate During An Electroweak Scale Phase TransitionMar 12 2010Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate ... More
A Hint of a Blue Axion Isocurvature Spectrum?Nov 17 2017It is known that if the Peccei-Quinn symmetry breaking field is displaced from its minimum during inflation, the axion isocurvature spectrum is generically strongly blue tilted with a break transition to a flat spectrum. We fit this spectrum (incorporated ... More
Step bunching-induced vertical lattice mismatch and crystallographic tilt in vicinal BiFeO3(001) filmsJan 04 2011Epitaxial (001) BiFeO3 thin films grown on vicinal SrTiO3 substrates are under large anisotropic stress from the substrates. The variations of the crystallographic tilt angle and the c lattice constant, caused by the lattice mismatch, along the film thickness ... More
Electric-field-controlled directional growth of ferroelectric domains in multiferroic BiFeO3 filmsSep 30 2009We describe the directional growth of ferroelectric domains in a multiferroic BiFeO3 thin film, which was grown epitaxially on a vicinal (001) SrTiO3 substrate. A detailed structural analysis of the film shows that a strain gradient, which can create ... More
Anisotropy in the electronic screening of oxygen lattice modes in YBa(2)Cu(3)O(6.95)May 30 2001Inelastic neutron scattering data from a twinned single-crystal of YBa2Cu3O6.95 are presented that show a distinct a-b plane anisotropy in the oxygen vibrations. The Cu-O bond-stretching type phonons are simultaneously observed along the a and b directions ... More
Formation of Co nanoclusters in epitaxial Ti_{0.96} Co_{0.04} O_2 thin films and their ferromagnetismAug 03 2002Anatase Ti0.96Co0.04O2 films were grown epitaxially on SrTiO3 (001) substrates by using plused laser deposition with in-situ reflection high-energy electron diffraction. The oxygen partial pressure, PO2, during the growth was systematically varied. As ... More
Testing the validity of the Lorentz factorDec 19 2017Our proposed experiment aimed to test the validity of the Lorentz factor with two methods: The time of flight (TOF) of various particles at different momenta and the decay rate of pions at different momenta. Due to the high sensitivity required for the ... More
Complex optical signatures from quantum dot nanostructures and behavior in inverted pyramidal recessesJul 02 2014A study of previously overlooked structural and optical properties of InGaAs heterostructures grown on (111)B oriented GaAs substrates patterned with inverted 7.5 um pitch pyramidal recesses is presented. First, the composition of the confinement barrier ... More
Surface versus bulk characterization of the electronic inhomogeneity in a VO_{2} filmJul 31 2007We investigated the inhomogeneous electronic properties at the surface and interior of VO_{2} thin films that exhibit a strong first-order metal-insulator transition (MIT). Using the crystal structural change that accompanies a VO_{2} MIT, we used bulk-sensitive ... More
A UV to Mid-IR Study of AGN SelectionFeb 21 2014We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 sq. deg Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR ... More
Experimental evidence of the spin selection rule in KLL Auger transitionJul 11 2001Jul 12 2001With on- and off- resonant excitation photons, spin-resolved Auger electron spectra of epitaxial CrO$_{2}$ thin films show an experimental evidence of the spin-selective KLL Auger decay. The on-resonance O KLL Auger electrons are found to be highly spin-polarized, ... More
Spin excitations under fields in an anisotropic bond-alternating quantum S=1 chain: contrast with Haldane spin chainsJan 10 2005Inelastic neutron scattering experiments on the S=1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9D24N4)(NO2)ClO4 have been performed under magnetic fields below and above a critical field Hc at which the energy gap closes. Normal field ... More
Experimental verification of electrostatic boundary conditions in gate-patterned quantum devicesJun 24 2018In a model of a gate-patterned quantum device it is important to choose the correct electrostatic boundary conditions (BCs) in order to match experiment. In this study, we model gated-patterned devices in doped and undoped GaAs heterostructures for a ... More
Uncertainty Estimates for Theoretical Atomic and Molecular DataMar 18 2016Jul 02 2016Sources of uncertainty are reviewed for calculated atomic and molecular data that are important for plasma modeling: atomic and molecular structure and cross sections for electron-atom, electron-molecule, and heavy particle collisions. We concentrate ... More
Frustrated minority spins in GeNi2O4Aug 23 2007Recently, two consecutive phase transitions were observed, upon cooling, in an antiferromagnetic spinel GeNi$_2$O$_4$ at $T_{N1}=12.1$ K and $T_{N2}=11.4$ K, respectively \cite{matsuno, crawford}. Using unpolarized and polarized elastic neutron scattering ... More
The anomaly in the cosmic-ray positron spectrumOct 12 2007A recent analysis of cosmic-ray data from a space borne experiment by the AMS collaboration supports the observation of an excess in the cosmic-ray positron spectrum by previous balloon experiments. The combination of the various experimental data establishes ... More