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Results for "Kwing To Lai"

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Pressure-induced enhancement of non-polar to polar transition temperature in metallic LiOsO$_3$Jun 02 2018Jun 06 2018LiOsO$_3$ undergoes a continuous transition from a centrosymmetric $R\bar{3}c$ structure to a polar $R3c$ structure at $T_s=140$~K. By combining transport measurements and first-principles calculations, we find that $T_s$ is enhanced by applied pressure, ... More
Nonsaturating large magnetoresistance in the high carrier density nonsymmorphic metal CrPMar 14 2019The band structure of high carrier density metal CrP features an interesting crossing at the Y point of the Brillouin zone. The crossing, which is protected by the nonsymmorphic symmetry of the space group, results in a hybrid, semi-Dirac-like energy-momentum ... More
Angular dependence of the upper critical field in the high-pressure $1T'$ phase of MoTe$_2$Mar 13 2019Superconductivity in the type-II Weyl semimetal candidate MoTe$_2$ has attracted much attention due to the possible realization of topological superconductivity. Under applied pressure, the superconducting transition temperature is significantly enhanced, ... More
A free-boundary problem for the evolution $p$-Laplacian equation with a combustion boundary conditionNov 20 2007We study the existence, uniqueness and regularity of solutions of the equation $f_t = \Delta_p f = \text{div} (|Df|^{p-2} Df)$ under over-determined boundary conditions $f = 0$ and $|Df| = 1$. We show that if the initial data is concave and Lipschitz ... More
The mass distribution of dwarf spheroidal galaxies from stellar kinematics: Draco, Ursa Minor and FornaxFeb 08 2007We model three dSph galaxies, Draco, Ursa Minor and Fornax, as axisymmetric stellar systems embedded in spherical dark-matter potentials, which are in dynamical equilibrium without significant external tidal forces. We construct non-parametric two- and ... More
Point Group Symmetry and Deformation Induced Symmetry Breaking of Superlattice MaterialsAug 12 2015The point group symmetry of materials is closely related to their physical properties and quite important for material modeling. However, superlattice materials have more complex symmetry conditions than crystals due to their multilevel structural feature. ... More
Proportional Topology Optimization: A new non-gradient method for solving stress constrained and minimum compliance problems and its implementation in MATLABNov 21 2014A new topology optimization method called the Proportional Topology Optimization (PTO) is presented. As a non-gradient method, PTO is simple to understand, easy to implement, and is also efficient and accurate at the same time. It is implemented into ... More
Characterization of polynomials whose large powers have all positive coefficientsJan 08 2017Mar 30 2017We give a criterion which characterizes a homogeneous real multi-variate polynomial to have the property that all sufficiently large powers of the polynomial (as well as their products with any given positive homogeneous polynomial) have positive coefficients. ... More
Multipole order and global/site symmetry in the hidden order phase of URu2Si2Sep 19 2014Oct 20 2014On the basis of group theory and the first-principles calculations, we investigate high-rank multipole orderings in URu2Si2, which have been proposed as a genuine primary order parameter in the hidden order phase below 17.5K. We apply Shubnikov group ... More
Active Sensing of Social NetworksJan 21 2016This paper develops an active sensing method to estimate the relative weight (or trust) agents place on their neighbors' information in a social network. The model used for the regression is based on the steady state equation in the linear DeGroot model ... More
Key Exchange Protocol in the Trusted Data Servers ContextSep 11 2015The aim of this technical report is to complement the work in [To et al. 2014] by proposing a Group Key Exchange protocol so that the Querier and TDSs (and TDSs themselves) can securely create and exchange the shared key. Then, the security of this protocol ... More
Singular limit and long-time dynamics of Bresse systemsNov 20 2015Oct 07 2016The Bresse system is a valid model for arched beams which reduces to the classical Timoshenko system when the arch curvature $\ell=0$. Our first result shows the Timoshenko system as a singular limit of the Bresse system as $\ell \to 0$. The remaining ... More
Logical Queries over Views: Decidability and ExpressivenessMar 18 2008We study the problem of deciding satisfiability of first order logic queries over views, our aim being to delimit the boundary between the decidable and the undecidable fragments of this language. Views currently occupy a central place in database research, ... More
Regularity of the minimizers in the composite membrane problem in R^2Apr 07 2008We study the regularity of minimizers to the composite membrane problem in the plane (ie given a domain omega and a positive number A, smaller than the measure of omega, minimize the first Dirichlet eigenvalue for the Schrodinger operator with potential ... More
Magnetically Driven Warping and Precession of Accretion Disks: Implications for "Exotic" Stellar VariabilitiesNov 13 2002The inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. ... More
Secular Instability of g-Modes in Rotating Neutron StarsJun 29 1998Apr 09 1999Gravitational radiation tends to drive gravity modes in rotating neutron stars unstable. For an inviscid star, the instability sets in when the rotation frequency is about 0.7 times the corresponding mode frequency of the nonrotating star. Neutron stars ... More
Tidal Stablization of Neutron Stars and White DwarfsMay 16 1996What happens to a neutron star or white dwarf near its maximum mass limit when it is brought into a close binary orbit with a companion? Such situation may occur in the progenitors of Type Ia supernovae and in coalescing neutron star binaries. Using an ... More
An extremal problem on potentially $K_{m}-P_{k}$-graphic sequencesSep 24 2004Jul 07 2006A sequence $S$ is potentially $K_{m}-P_{k}$ graphical if it has a realization containing a $K_{m}-P_{k}$ as a subgraph. Let $\sigma(K_{m}-P_{k}, n)$ denote the smallest degree sum such that every $n$-term graphical sequence $S$ with $\sigma(S)\geq \sigma(K_{m}-P_{k}, ... More
The smallest degree sum that yields potentially $C_k$-graphical sequenceJun 06 2002Aug 22 2004In this paper we consider a variation of the classical Tur\'{a}n-type extremal problems. Let $S$ be an $n$-term graphical sequence, and $\sigma(S)$ be the sum of the terms in $S$. Let $H$ be a graph. The problem is to determine the smallest even $l$ such ... More
Approximate Model Counting by Partial Knowledge CompilationMay 18 2018Model counting is the problem of computing the number of satisfying assignments of a given propositional formula. Although exact model counters can be naturally furnished by most of the knowledge compilation (KC) methods, in practice, they fail to generate ... More
A Generalization of Aztec DragonsApr 01 2015Oct 28 2015Aztec dragons are lattice regions first introduced by James Propp, which have the number of tilings given by a power of $2$. This family of regions has been investigated further by a number of authors. In this paper, we consider a generalization of the ... More
Tiling enumeration of doubly-intruded halved hexagonsDec 31 2017Feb 08 2019Inspired by Propp's intruded Aztec diamond regions, we consider halved hexagons in which two aligned arrays of triangular holes have been removed from their boundaries. Unlike the intruded Aztec diamonds (whose numbers of domino tilings contain some large ... More
Proof of a conjecture of Kenyon and Wilson on semicontiguous minorsJul 09 2015Jul 31 2018Kenyon and Wilson showed how to test if a circular planar electrical network with $n$ nodes is well-connected by checking the positivity of $\binom{n}{2}$ central minors of the response matrix. Their test is based on the fact that any contiguous minor ... More
Strict Deformation Quantisation of the G-connections via Lie GroupoidJan 17 2014Motivated by the compactification process of the space of connections in loop quantum gravity literature. A description of the space of G-connections using the tangent groupoid is given. As the tangent groupoid parameter is away from zero, the G-connections ... More
A new two weight estimates for a vector-valued positive operatorMar 23 2015Mar 24 2015We give a new characterization of the two weight inequality for a vector-valued positive operator. Our characterization has a different flavor than the one of Scurry's and H\"{a}nninen's. The proof can be essentially derived from the scalar-valued case. ... More
The Bellman functions of the Carleson Embedding Theorem and the Doob's martingale inequalityNov 20 2014Feb 11 2015Evaluation of the Bellman functions is a difficult task. The exact Bellman functions of the dyadic Carleson Embedding Theorem 1.1 and the dyadic maximal operators are obtained in [3] and [4]. Actually, the same Bellman functions also work for the tree-like ... More
Physics in Very Strong Magnetic Fields: Introduction and OverviewNov 28 2014This paper provides an introduction to a number of astrophysics problems related to strong magnetic fields. The first part deals with issues related to atoms, condensed matter and high-energy processes in very strong magnetic fields, and how these issues ... More
Global Nonradial Instabilities of Dynamically Collapsing Gas SpheresApr 05 2000Apr 18 2000Self-similar solutions provide good descriptions for the gravitational collapse of spherical clouds or stars when the gas obeys a polytropic equation of state, $p=K\rho^\gamma$ (with $\gamma\le 4/3$). We study the behaviors of nonradial perturbations ... More
Orbital Decay of the PSR J0045-7319/B Star Binary System: Age of Radio Pulsar and Initial Spin of Neutron StarMay 16 1996Recent timing observations of PSR J0045-7319 reveal that the neutron star/B star binary orbit is decaying on a time scale of $|\Porb/\dot\Porb|=0.5$ Myr, shorter than the characteristic age ($\tau_c=3$ Myr) of the pulsar (Kaspi et al.~1996a). We study ... More
Solar Obliquity Induced by Planet Nine: Simple CalculationAug 04 2016Bailey et al.~(2016) and Gomes et al.~(2016) recently suggested that the 6 degree misalignment between the Sun's rotational equator and the orbital plane of the major planets may be produced by the forcing from the hypothetical Planet Nine on an inclined ... More
Dynamics of PSR J0045-7319/B-star Binary and Neutron Star FormationApr 14 1997Recent timing observations have revealed the presence of orbital precession due to spin-orbit coupling and rapid orbital decay due to dynamical tidal interaction in the PSR J0045-7319/B-star binary system. They can be used to put concrete constraints ... More
Dynamical Tides in Rotating Binary StarsApr 14 1997We study the effect of rotation on the excitation of internal oscillation modes of a star by the external gravitational potential of its companion. Unlike the nonrotating case, there are difficulties with the usual mode decomposition for rotating stars ... More
On the numbers of perfect matchings of trimmed Aztec rectanglesApr 01 2015We consider several new families of graphs obtained from Aztec rectangle and augmented Aztec rectangle graphs by trimming two opposite corners. We prove that the perfect matchings of these new graphs are enumerated by powers of $2$, $3$, $5$, and $11$. ... More
A $q$-enumeration of lozenge tilings of a hexagon with four adjacent triangles removed from the boundaryFeb 05 2015Apr 10 2017MacMahon proved a simple product formula for the generating function of plane partitions fitting in a given box. The theorem implies a $q$-enumeration of lozenge tilings of a semi-regular hexagon on the triangular lattice. In this paper we generalize ... More
A $q$-enumeration of lozenge tilings of a hexagon with three dentsFeb 20 2015Oct 03 2015We $q$-enumerate lozenge tilings of a hexagon with three bowtie-shaped regions have been removed from three non-consecutive sides. The unweighted version of the result generalizes a problem posed by James Propp on enumeration of lozenge tilings of a hexagon ... More
Double Aztec RectanglesNov 01 2014Sep 29 2015We investigate the connection between lozenge tilings and domino tilings by introducing a new family of regions obtained by attaching two different Aztec rectangles. We prove a simple product formula for the generating functions of the tilings of the ... More
Enumeration of Hybrid Domino-Lozenge TilingsSep 20 2013We solve and generalize an open problem posted by James Propp (Problem 16 in New Perspectives in Geometric Combinatorics, Cambridge University Press, 1999) on the number of tilings of quasi-hexagonal regions on the square lattice with every third diagonal ... More
Markets are Dead, Long Live MarketsFeb 04 2005Researchers have long proposed using economic approaches to resource allocation in computer systems. However, few of these proposals became operational, let alone commercial. Questions persist about the economic approach regarding its assumptions, value, ... More
Emergent loop-nodal s$_\pm$-wave superconductivity in CeCu$_2$Si$_2$: similarities to the iron-based superconductorsApr 28 2015Heavy-fermion superconductors are prime candidates for novel electron-pairing states due to the spin-orbital coupled degrees of freedom and electron correlations. Superconductivity in CeCu$_2$Si$_2$ discovered in 1979, which is a prototype of unconventional ... More
C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric DistanceMar 06 2019We present a photometric and dynamical study of comet C/2010 U3 (Boattini), which was seen active in prediscovery data as early as 2005 November at a new inbound record heliocentric distance $r_{\rm H} = 25.8$ au. Two outburst events around 2009 and 2017 ... More
An Early Look of Comet C/2013 A1 (Siding Spring): Breathtaker or Nightmare?Mar 27 2014The dynamically new comet, C/2013 A1 (Siding Spring), is to make a close approach to Mars on 2014 October 19 at 18:30 UT at a distance of 40+/-1 Martian radius. Such extremely rare event offers a precious opportunity for the spacecrafts on Mars to closely ... More
First-principles study of magnetic properties in Fe-ladder compound BaFe2S3Jul 21 2015We study the magnetic, structural, and electronic properties of the recently discovered iron- based superconductor BaFe2S3 based on density functional theory with the generalized gradient approximation. The calculations show that the magnetic alignment ... More
Theory of Disk Accretion onto Magnetic StarsFeb 09 2014Disk accretion onto magnetic stars occurs in a variety of systems, including accreting neutron stars (with both high and low magnetic fields), white dwarfs, and protostars. We review some of the key physical processes in magnetosphere-disk interaction, ... More
Merging neutron star binaries: equation of state and electrodynamicsDec 25 2012Merging neutron star (NS) binaries may be detected by ground-based gravitational wave (GW) interferometers (e.g. LIGO/VIRGO) within this decade and may also generate electromagnetic radiation detectable by wide-field, fast imaging telescopes that are ... More
Tidal Dissipation in Planet-Hosting Stars: Damping of Spin-Orbit Misalignment and Survival of Hot JupitersSep 22 2011Jun 19 2012Observations of hot Jupiters around solar-type stars with very short orbital periods (~day) suggest that tidal dissipation in such stars is not too efficient so that these planets can survive against rapid orbital decay. This is consistent with recent ... More
Neutron Star Kicks and Supernova AsymmetryDec 19 2003Observations over the last decade have shown that neutron stars receive a large kick velocity (of order a hundred to a thousand km/s) at birth. The physical origin of the kicks and the related supernova asymmetry is one of the central unsolved mysteries ... More
Warping of Accretion Disks with Magnetically Driven Outflows: A Possible Origin for Jet PrecessionMay 31 2003Current theoretical models for the outflows/jets from AGN, X-ray binaries and young stellar objects involve large-scale magnetic fields threading an underlying accretion disk. We suggest that such a disk is subjected to warping instability and retrograde ... More
Physics of Neutron Star KicksDec 27 1999It is no longer necessary to `sell' the idea of pulsar kicks, the notion that neutron stars receive a large velocity (a few hundred to a thousand km s$^{-1}$) at birth. However, the origin of the kicks remains mysterious. We review the physics of different ... More
Magnetically Driven Warping, Precession and Resonances in Accretion DisksApr 09 1999Dec 27 1999The inner region of the accretion disk onto a rotating magnetized central star (neutron star, white dwarf or T Tauri star) is subjected to magnetic torques which induce warping and precession of the disk. The origin of these torques lies in the interaction ... More
Superfluidity of Hydrogenlike Gas in a Strong Magnetic Field ?May 10 1995The recent claim that in a strong magnetic field hydrogenlike gas (e.g., excitons in certain semiconductors, neutron star surface layers) becomes superfluid is refuted. Molecules form by strong covalent bond along the magnetic field axis, which prohibits ... More
Resonant Oscillations and Tidal Heating in Coalescing Binary Neutron StarsApr 25 1994Tidal interaction in a coalescing neutron star binary can resonantly excite the g-mode oscillations of the neutron star when the frequency of the tidal driving force equals the intrinsic g-mode frequencies. We study the g-mode oscillations of cold neutron ... More
Matter in Strong Magnetic FieldsSep 20 2000Jan 24 2001The properties of matter are significantly modified by strong magnetic fields, $B>>2.35\times 10^9$ Gauss ($1 G =10^{-4} Tesla$), as are typically found on the surfaces of neutron stars. In such strong magnetic fields, the Coulomb force on an electron ... More
Transonic Magnetic Slim Accretion Disks and kilo-Hertz Quasi-Periodic Oscillations in Low-Mass X-Ray BinariesNov 12 1997Feb 24 1998The inner regions of accretion disks of weakly magnetized neutron stars are affected by general relativity and stellar magnetic fields. Even for field strengths sufficiently small so that there is no well-defined magnetosphere surrounding the neutron ... More
Deep Learning for Medical Image SegmentationMay 08 2015This report provides an overview of the current state of the art deep learning architectures and optimisation techniques, and uses the ADNI hippocampus MRI dataset as an example to compare the effectiveness and efficiency of different convolutional architectures ... More
The rightness of the Riemann hypothesisAug 08 2016Aug 11 2016Applying the properties of increasing functions and the limitation theory of one variable, we show that the Riemann hypothesis is correct. Namely, it is proved that all zeros of {\zeta} function are 1/2+b_0i where b_0 represents many constants.
Enumeration of Hybrid Domino-Lozenge Tilings III: Symmetric TilingsSep 11 2016We use the subgraph replacement method to investigate new properties of regions on the square lattice with diagonals drawn in. In particular, we show that cyclically symmetric tilings of a generalization of the Aztec diamond are always enumerated by a ... More
Proof of a conjecture of Kenyon and Wilson on semicontiguous minorsJul 09 2015Oct 26 2015Kenyon and Wilson showed how to test if a circular planar electrical network with $n$ nodes is well-connected by checking the positivity of $\binom{n}{2}$ central minors of the response matrix (arXiv:1411.7425). Their test is based on the fact that any ... More
An extremal problem on potentially $K_{m}-C_{4}$-graphic sequencesSep 03 2004Jul 07 2006A sequence $S$ is potentially $K_{m}-C_{4}$-graphical if it has a realization containing a $K_{m}-C_{4}$ as a subgraph. Let $\sigma(K_{m}-C_{4}, n)$ denote the smallest degree sum such that every $n$-term graphical sequence $S$ with $\sigma(S)\geq \sigma(K_{m}-C_{4}, ... More
A note on potentially $K_4-e$ graphical sequencesAug 11 2003A sequence $S$ is potentially $K_4-e$ graphical if it has a realization containing a $K_4-e$ as a subgraph. Let $\sigma(K_4-e, n)$ denote the smallest degree sum such that every $n$-term graphical sequence $S$ with $\sigma(S)\geq \sigma(K_4-e, n)$ is ... More
Lozenge tilings of hexagons with central holes and dentsMar 07 2018Jan 04 2019Ciucu showed that the number of a hexagon in which a chain of equilateral triangles of alternating orientations, called a `\emph{fern}', has been removed in the center is given by a simple product formula (Adv. Math. 2017). In the first part of this paper, ... More
A note on martingale Hardy spacesNov 20 2014Feb 13 2015We investigate the relation between Carleson sequence and balayage, and use this to give an easy proof of the equivalence of the L1-norms of the maximal function and the square function in non-honogeneous martingale settings.
A $q$-enumeration of generalized plane partitionsFeb 05 2015Aug 04 2015MacMahon proved a simple product formula for the generating function of the plane partitions fitting in a given rectangular box. The theorem implies the number of lozenge tilings of a semi-regular hexagon on the triangular lattice. By investigating the ... More
Lozenge tilings of a halved hexagon with an array of triangles removedOct 20 2016Proctor's work on staircase plane partitions yields an enumeration of lozenge tilings of a halved hexagon on the triangular lattice. Recently, Rohatgi extended this tiling enumeration by proving an exact tiling formula for a halved hexagon with a triangle ... More
A proof to the Riemann HypothesisAug 08 2016Dec 05 2018The properties of several functions are employed to investigate the zeros of the Riemann zeta function $\zeta(a+bi)$. We show that if $0<a<1$, the zeros of the zeta function have the form $\frac{1}{2}+ib$ where $i=\sqrt{-1}$.
Word and Document Embeddings based on Neural Network ApproachesNov 18 2016Data representation is a fundamental task in machine learning. The representation of data affects the performance of the whole machine learning system. In a long history, the representation of data is done by feature engineering, and researchers aim at ... More
The smallest degree sum that yields potentially K_{r+1}-Z-graphical SequencesAug 10 2006Nov 17 2009Let $K_{m}-H$ be the graph obtained from $K_{m}$ by removing the edges set $E(H)$ of the graph $H$ ($H$ is a subgraph of $K_{m}$). We use the symbol $Z_4$ to denote $K_4-P_2.$ A sequence $S$ is potentially $K_{m}-H$-graphical if it has a realization containing ... More
An extremal problem on potentially $K_{p,1,1}$-graphic sequencesAug 22 2004Jul 07 2006A sequence $S$ is potentially $K_{p,1,1}$ graphical if it has a realization containing a $K_{p,1,1}$ as a subgraph, where $K_{p,1,1}$ is a complete 3-partite graph with partition sizes $p,1,1$. Let $\sigma(K_{p,1,1}, n)$ denote the smallest degree sum ... More
Bilinear endpoint estimates for Calderón commutator with rough kernelOct 26 2017In this paper, we establish some bilinear endpoint estimates of Calder\'on commutator $\mathcal{C}[\nabla A,f](x)$ with a homogeneous kernel when $\Omega\in L\log^+L(\mathbf{S}^{d-1})$. More precisely, we prove that $\mathcal{C}[\nabla A,f]$ maps $L^q(\mathbb{R}^d)\times ... More
A Lower Bound for the Number of Edges in a Graph Containing No Two Cycles of the Same LengthJun 06 2002Jun 07 2002In 1975, P. Erd\"{o}s proposed the problem of determining the maximum number $f(n)$ of edges in a graph of $n$ vertices in which any two cycles are of different lengths. In this paper, it is proved that $$f(n)\geq n+32t-1$$ for $t=27720r+169 (r\geq 1)$ ... More
Multilinear estimates for Calderón commutatorsDec 25 2017Aug 01 2018In this paper, we investigate the multilinear boundedness properties of the higher ($n$-th) order Calder\'on commutator for dimensions larger than two. We establish all multilinear endpoint estimates for the target space $L^{\frac{d}{d+n},\infty}(\mathbb{R}^d)$, ... More
Enumeration of Hybrid Domino-Lozenge Tilings III: Centrally Symmetric TilingsSep 11 2016Dec 25 2018We use the subgraph replacement method to investigate new properties of the tilings of regions on the square lattice with diagonals drawn in. In particular, we show that the centrally symmetric tilings of a generalization of the Aztec diamond are always ... More
DC Circuit Powered by Orbital Motion: Magnetic Interactions in Compact Object Binaries and Exoplanetary SystemsJun 17 2012The unipolar induction DC circuit model, originally developed by Goldreich & Lynden-Bell for the Jupiter-Io system, has been applied to different types of binary systems in recent years. We show that there exists an upper limit to the magnetic interaction ... More
Secular Bar-Mode Evolution and Gravitational Waves From Neutron StarsJan 03 2001The secular instability and nonlinear evolution of the m=2 f-mode (bar-mode) driven by gravitational radiation reaction in a rapidly rotating, newly formed neutron star are reviewed. There are two types of rotating bars which generate quite different ... More
Neutron Star Kicks and Asymmetric SupernovaeDec 03 2000Observational advances over the last decade have left little doubt that neutron stars received a large kick velocity (of order a few hundred to a thousand km/s) at birth. The physical origin of the kicks and the related supernova asymmetry is one of the ... More
A Family of Gravitational Waveforms from Rapidly Rotating Neutron StarsFeb 22 1999This note describes fitting formulae for the gravitational waveforms generated by a rapidly rotating neutron star (e.g., newly-formed in the core collapse of a supernova) as it evolves from an initial axisymmetric configuration toward a triaxial ellipsoid. ... More
Core-Collapse Supernovae and Neutron Star KicksDec 05 2002Recent observations have revealed many new puzzles related to core-collapse supernovae, including the formation of magnetars and black holes and their possible GRB connections. We review our current understanding of the origin of pulsar kicks and supernova ... More
Giraffe: Using Deep Reinforcement Learning to Play ChessSep 04 2015Sep 14 2015This report presents Giraffe, a chess engine that uses self-play to discover all its domain-specific knowledge, with minimal hand-crafted knowledge given by the programmer. Unlike previous attempts using machine learning only to perform parameter-tuning ... More
An Effective Compactness Theorem for Coxeter GroupsFeb 16 2009Through highly non-constructive methods, works by Bestvina, Culler, Feighn, Morgan, Paulin, Rips, Shalen, and Thurston show that if a finitely presented group does not split over a virtually solvable subgroup, then the space of its discrete and faithful ... More
Ricci flow under local almost non-negative curvature conditionsApr 22 2018Jun 12 2018We find a local solution to the Ricci flow equation under a negative lower bound for many known curvature conditions. The flow exists for a uniform amount of time, during which the curvature stays bounded below by a controllable negative number. The curvature ... More
An extremal problem on potentially $K_{p_{1},p_{2},...,p_{t}}$-graphic sequencesAug 24 2004A sequence $S$ is potentially $K_{p_{1},p_{2},...,p_{t}}$ graphical if it has a realization containing a $K_{p_{1},p_{2},...,p_{t}}$ as a subgraph, where $K_{p_{1},p_{2},...,p_{t}}$ is a complete t-partite graph with partition sizes $p_{1},p_{2},...,p_{t} ... More
Lozenge tilings of a halved hexagon with an array of triangles removed from the boundaryOct 20 2016Sep 07 2017Proctor's work on staircase plane partitions yields an enumeration of lozenge tilings of a halved hexagon on the triangular lattice. Rohatgi recently extended this tiling enumeration to a halved hexagon with a triangle removed from the boundary. In this ... More
Star Formation Rate and Extinction in Faint z~4 Lyman-Break GalaxiesApr 14 2014Jul 24 2014We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z~4 Lyman-break galaxies (LBGs). LBGs are key tracers of the high-redshift star formation history and important sources of UV photons that ionized the intergalactic ... More
Non-asymptotic Analysis of Biased Stochastic Approximation SchemeFeb 02 2019Stochastic approximation (SA) is a key method used in statistical learning. Recently, its non-asymptotic convergence analysis has been considered in many papers. However, most of the prior analyses are made under restrictive assumptions such as unbiased ... More
Ab initio downfolding study of the iron-based ladder superconductor BaFe$_2$S$_3$Jul 21 2015Aug 27 2015Motivated by the recent discovery of superconductivity in the iron-based ladder compound BaFe$_2$S$_3$ under high pressure, we derive low-energy effective Hamiltonians from first principles. We show that the complex band structure around the Fermi level ... More
Geometrical aspects of expansions in complex basesMay 22 2011We study the set of the representable numbers in base $q=pe^{i\frac{2\pi}{n}}$ with $\rho>1$ and $n\in \mathbb N$ and with digits in a arbitrary finite real alphabet $A$. We give a geometrical description of the convex hull of the representable numbers ... More
Spectrins in Axonal Cytoskeletons: Dynamics Revealed by Extensions and FluctuationsDec 04 2013Jun 18 2014The macroscopic properties, the properties of individual components and how those components interact with each other are three important aspects of a composited structure. An understanding of the interplay between them is essential in the study of complex ... More
On Weyl modules over affine Lie algebras in prime characteristicOct 14 2013Jan 25 2016We construct a family of homomorphisms between Weyl modules for affine Lie algebras in characteristic p, which supports our conjecture on the strong linkage principle in this context. We also exhibit a large class of reducible Weyl modules beyond level ... More
Polarization Evolution in A Strongly Magnetized Vacuum: QED Effect and Polarized X-ray Emission from Magnetized Neutron StarsMar 12 2009Apr 06 2009X-ray photons emitted from the surface or atmosphere of a magnetized neutron star is highly polarized. However, the observed polarization may be modified due to photon propagation through the star's magnetosphere. For photon frequencies much larger than ... More
Induced Lorentz-Violating Chern-Simons Term in QED and Anomalous Contributions to Effective Action ExpansionsJul 14 1999Aug 23 2000I present a unified formulation of anomalous contributions in quantum field theories by calculating directly the effective action using the background field and covariant-derivative expansion technique. I use this method to determine uniquely the induced ... More
Corotation resonance and overstable oscillations in black-hole accretion discs: general-relativistic calculationsJul 30 2013We study the dynamics of spiral waves and oscillation modes in relativistic rotating discs around black holes. Generalizing the Newtonian theory, we show that wave absorption can take place at the corotation resonance, where the pattern frequency of the ... More
Hiding Planets Behind a Big Friend: Mutual Inclinations of Multi-Planet Systems with External CompanionsJun 28 2016Nov 03 2016The {\it Kepler} mission has detected thousands of planetary systems with 1-7 transiting planets packed within 0.7~au from their host stars. There is an apparent excess of single-transit planet systems that cannot be explained by transit geometries alone, ... More
Rossby Wave Instability in Accretion Discs with Large-Scale Poloidal Magnetic FieldsDec 06 2012We study the effect of large-scale magnetic fields on the non-axisymmetric Rossby wave instability (RWI) in accretion discs. The instability develops around a density bump, which is likely present in the transition region between the active zone and dead ... More
Corotational Instability of Inertial-Acoustic Modes in Black Hole Accretion Discs and Quasi-Periodic OscillationsOct 01 2008Nov 14 2008We study the global stability of non-axisymmetric p-modes (also called inertial-acoustic modes) trapped in the inner-most regions of accretion discs around black holes. We show that the lowest-order (highest-frequency) p-modes, with frequencies $\omega=(0.5-0.7) ... More
On the definition and K-theory realization of a modular functorOct 18 2013Aug 10 2014We present a definition of a (super)-modular functor which includes certain interesting cases that previous definitions do not allow. We also introduce a notion of topological twisting of a modular functor, and construct formally a realization by a 2-dimensional ... More
The Hidden Magnetic Field of The Young Neutron Star in Kesteven 79Oct 14 2011Mar 16 2012Recent observations of the central compact object in the Kesteven 79 supernova remnant show that this neutron star (NS) has a weak dipole magnetic field (a few x 10^{10} G) but an anomalously large (~ 64%) pulse fraction in its surface X-ray emission. ... More
Tidal Novae in Compact Binary White DwarfsJun 03 2012Sep 20 2012Compact binary white dwarfs (WDs) undergoing orbital decay due to gravitational radiation can experience significant tidal heating prior to merger. In these WDs, the dominant tidal effect involves the excitation of outgoing gravity waves in the inner ... More
Correlation effects in double-Weyl semimetalsFeb 09 2015Jun 19 2015We study the long-range Coulomb interaction effects on the double-Weyl fermion system which is possibly realized in the three dimensional semimetal HgCr$_2$Se$_4$ in the ferromagnetic phase. Within the one-loop renormalization group analysis, we find ... More
Convergence of general inverse $σ_k$-flow on Kähler manifolds with Calabi AnsatzMar 23 2012We study the convergence behavior of the general inverse $\sigma_k$-flow on K\"{a}hler manifolds with initial metrics satisfying the Calabi Ansatz. The limiting metrics can be either smooth or singular. In the latter case, interesting conic singularities ... More
Second Kind Integral Equation Formulation for the Mode Calculation of Optical WaveguidesDec 03 2015We present a second kind integral equation (SKIE) formulation for calculating the electromagnetic modes of optical waveguides, where the unknowns are only on material interfaces. The resulting numerical algorithm can handle optical waveguides with a large ... More
Regularity of the extremal solution for a fourth-order elliptic problem with singular nonlinearityJan 13 2010Oct 28 2010In this paper, we consider the relation between $p > 1$ and critical dimension of the extremal solution of the semilinear equation $$\{\begin{array}{lllllll} \beta \Delta^{2}u-\tau \Delta u=\frac{\lambda}{(1-u)^{p}} & in\ \ B, 0<u\leq 1 & in\ \ B, u=\Delta ... More