Results for "Fei Dai"

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Ultrabroadband Super-Planckian Radiative Heat Transfer with Profile-Patterned Hyperbolic MetamaterialSep 14 2016We demonstrate the possibility of ultrabroadband super-Planckian radiative heat transfer be- tween two metal plates patterned with tapered hyperbolic metamaterial arrays. It is shown that, by employing profile-patterned hyperbolic media, one can design ... More
ADMM-IDNN: Iteratively Double-reweighted Nuclear Norm Algorithm for Group-prior based Nonconvex Compressed Sensing via ADMMMar 23 2019Group-prior based regularization method has led to great successes in various image processing tasks, which can usually be considered as a low-rank matrix minimization problem. As a widely used surrogate function of low-rank, the nuclear norm based convex ... More
WiPIN: Operation-free Person Identification using WiFi SignalsOct 06 2018Person identification is critical for sensitive applications such as system login/unlock, access control and payment. In this paper, we present an operation-free person identification system, namely WiPIN, that identifies biometric features of users using ... More
An Efficient Deep Reinforcement Learning Model for Urban Traffic ControlAug 06 2018Aug 24 2018Urban Traffic Control (UTC) plays an essential role in Intelligent Transportation System (ITS) but remains difficult. Since model-based UTC methods may not accurately describe the complex nature of traffic dynamics in all situations, model-free data-driven ... More
Dusty outflows in planetary atmospheres: Understanding "super-puffs" and transmission spectra of sub-NeptunesFeb 11 2019`Super-puffs' are planets with anomalously low mean densities ($\lesssim 10^{-1}~{\rm g\ cm}^{-3}$). With a low surface gravity, the extended atmosphere is susceptible to extreme hydrodynamic mass loss (`boil off') on a timescale much shorter than the ... More
Stellar obliquities and magnetic activities of Planet-Hosting Stars and Eclipsing Binaries based on Transit Chord CorrelationMar 13 2018The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity $\Psi$ of the eclipsed star. Here ... More
Hybrid Weyl SemimetalJul 28 2016We construct a tight-binding model realizing one pair of Weyl nodes and three distinct Weyl semimetals. In the type-I (type-II) Weyl semimetal, both nodes belong to type-I (type-II) Weyl nodes. In addition, there exists a novel type, dubbed "hybrid Weyl ... More
Discovery of Six Optical Phase Curves with K2Dec 21 2018Mar 07 2019We have systematically searched for the phase curves among the planets discovered by \textit{K2}. Using the reported planetary parameters, we screen out the best potential candidates, and examine their light curves in detail. For our work, we consider ... More
The Apparently Decaying Orbit of WASP-12Mar 20 2017May 24 2017We present new transit and occultation times for the hot Jupiter WASP-12b. The data are compatible with a constant period derivative: $\dot{P}=-29 \pm 3$ ms yr$^{-1}$ and $P/\dot{P}= 3.2$ Myr. However, it is difficult to tell whether we have observed ... More
DeepTrend: A Deep Hierarchical Neural Network for Traffic Flow PredictionJul 11 2017In this paper, we consider the temporal pattern in traffic flow time series, and implement a deep learning model for traffic flow prediction. Detrending based methods decompose original flow series into trend and residual series, in which trend describes ... More
Integrated four-channel all-fiber up-conversion single-photon-detector with adjustable efficiency and dark countSep 30 2016Oct 03 2016Up-conversion single photon detector (UCSPD) has been widely used in many research fields including quantum key distribution (QKD), lidar, optical time domain reflectrometry (OTDR) and deep space communication. For the first time in laboratory, we have ... More
FBNet: Hardware-Aware Efficient ConvNet Design via Differentiable Neural Architecture SearchDec 09 2018Dec 14 2018Designing accurate and efficient ConvNets for mobile devices is challenging because the design space is combinatorially large. Due to this, previous neural architecture search (NAS) methods are computationally expensive. ConvNet architecture optimality ... More
Experimental protection of the coherence of a molecular qubit exceeding a millisecondJun 28 2017There are several important solid-state systems, such as defects in solids, superconducting circuits and molecular qubits, for attractive candidates of quantum computations. Molecular qubits, which benefit from the power of chemistry for the tailored ... More
Visualization of electronic topology in ZrSiSe by scanning tunneling microscopyJan 30 2018As emerging topological nodal-line semimetals, the family of ZrSiX (X = O, S, Se, Te) has attracted broad interests in condensed matter physics due to their future applications in spintonics. Here, we apply a scanning tunneling microscopy (STM) to study ... More
On exponential stability for stochastic differential equations disturbed by G-Brownian motionNov 28 2013We first introduce the calculus of Peng's G-Brownian motion on a sublinear expectation space $(\Omega, {\cal H}, \hat{\mathbb{E}})$. Then we investigate the exponential stability of paths for a class of stochastic differential equations disturbed by a ... More
Doping effects of Cr on the physical properties of BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$Jul 04 2018We present a systematic study on the heavily Cr doped iron pnictides BaFe$_{1.9-x}$Ni$_{0.1}$Cr$_{x}$As$_{2}$ by using elastic neutron scattering, high-resolution synchrotron X-ray diffraction (XRD), resistivity and Hall transport measurements. When the ... More
A Ni-Fe Layered Double Hydroxide-Carbon Nanotube Complex for Water OxidationMar 13 2013May 24 2013Highly active, durable and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions including water splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin ... More
ChamNet: Towards Efficient Network Design through Platform-Aware Model AdaptationDec 21 2018This paper proposes an efficient neural network (NN) architecture design methodology called Chameleon that honors given resource constraints. Instead of developing new building blocks or using computationally-intensive reinforcement learning algorithms, ... More
Magellan/PFS Radial Velocities of GJ 9827, a late K dwarf at 30 pc with Three Transiting Super-EarthsNov 03 2017Feb 28 2018The Kepler mission showed us that planets with sizes between that of Earth and Neptune appear to be the most common type in our Galaxy. These "super-Earths" continue to be of great interest for exoplanet formation, evolution, and composition studies. ... More
Optimal stochastic control and optimal consumption and portfolio with G-Brownian motionSep 01 2013By the calculus of Peng's G-sublinear expectation and G-Brownian motion on a sublinear expectation space $(\Omega, {\cal H}, \hat{\mathbb{E}})$, we first set up an optimality principle of stochastic control problem. Then we investigate an optimal consumption ... More
Optimal control of uncertain stochastic systems with Markovian switching and its applications to portfolio decisionsJan 11 2014This paper first describes a class of uncertain stochastic control systems with Markovian switching, and derives an It\^o-Liu formula for Markov-modulated processes. And we characterize an optimal control law, which satisfies the generalized Hamilton-Jacobi-Bellman ... More
Emergent Geometric Hamiltonian and Insulator-Superfluid Phase TransitionsMar 22 2005May 05 2005I argue that certain bosonic insulator-superfluid phase transitions as an interaction constant varies are driven by emergent geometric properties of insulating states. The {\em renormalized} chemical potential and distribution of disordered bosons define ... More
Quantum Spin Nematic States in Bose-Einstein CondensatesAug 28 2001Dec 19 2002We review some recent results on discrete symmetries and topological order in spinor Bose-Einstein condensates (BECs) of $^{23}Na$. For spin one bosons with two-body scatterings dominated by a total spin equal to two channel, the BECs are in quantum spin ... More
A method to determine algebraically integral Cayley digraphs on finite Abelian groupJun 05 2012Apr 29 2018Researchers in the past have studied eigenvalues of Cayley digraphs or graphs. We are interested in characterizing Cayley digraphs on a finite Abelian group G whose eigenvalues are algebraic integers in a given number field K. And we succeed in finding ... More
Arithmetic compactifications of natural numbers and its applicationsNov 27 2018Jan 07 2019To study the arithmetic structure of natural numbers, we introduce a notion of entropy of arithmetic functions. This entropy possesses properties common both to Shannon's and Kolmogorov's entropies. We show that all zero-entropy arithmetic functions form ... More
Vacuum Stability Bounds On Higgs Mass With Gravitational ContributionsDec 06 2013May 22 2014We calculate the gravitational contributions to $\phi^4$ theory with general $R_\xi$ gauge-fixing choice and find that the result is gauge independent. Based on weak coupling expansion of gravity and ignoring the possible higher dimensional operators ... More
Existence, Lifespan and Transfer Rate of Ricci Flows on Manifolds with Small Ricci CurvatureApr 27 2016We show that in dimension 4 and above, the lifespan of Ricci flows depends on the relative smallness of the Ricci curvature compared to the Riemann curvature on the initial manifold. We can generalize this lifespan estimate to the local Ricci flow, using ... More
Existence and applications of Ricci flows via pseudolocalityOct 06 2016We prove the short-time existence of Ricci flows on complete manifolds with scalar curvature bounded below uniformly, Ricci curvature bounded below by a negative quadratic function, and with almost Euclidean isoperimetric inequality holds locally. In ... More
Counting Using Hall Algebras I. QuiversNov 28 2011Sep 24 2012We survey some results on counting the rational points of moduli spaces of quiver representations. We then make generalizations to Grassmannians and flags of quiver representations. These results have nice applications to the cluster algebra. Along the ... More
Log del Pezzo Surfaces of Rank 2 and Cartier Index 3 with a Unique SingularityDec 05 2010Log del Pezzo surfaces play the role of the opposite of surfaces of general type. We will completely classify all the log del Pezzo surfaces of rank 2 and Cartier index 3 with a unique singularity.
Cluster Algebras and Semi-invariant Rings II. ProjectionsAug 23 2015Aug 30 2015Let ${\rm SI}_\beta(Q)$ be the semi-invariant ring of $\beta$-dimensional representations of a quiver $Q$. Suppose that $(Q,\beta)$ projects to another quiver with dimension vector $(Q',\beta')$ through an exceptional representation $E$. We show that ... More
Cluster Algebras and Semi-invariant Rings I. Triple FlagsNov 17 2014Mar 03 2015We prove that each semi-invariant ring of the complete triple flag of length $n$ is an upper cluster algebra associated to an ice hive quiver. We find a rational polyhedral cone ${\sf G}_n$ such that the generic cluster character maps its lattice points ... More
Cluster Algebras, Invariant Theory, and Kronecker Coefficients IApr 12 2015Aug 25 2015We relate the $m$-truncated Kronecker products of symmetric functions to the semi-invariant rings of a family of quiver representations. We find cluster algebra structures for these semi-invariant rings when $m=2$. Each {\sf g}-vector cone ${\sf G}_{\Diamond_l}$ ... More
Cluster Algebras, Invariant Theory, and Kronecker Coefficients IINov 01 2017We prove that the semi-invariant ring of the standard representation space of the $l$-flagged $m$-arrow Kronecker quiver is an upper cluster algebra for any $l,m\in \mathbb{N}$. The quiver and cluster are explicitly given. We prove that the quiver with ... More
Hardy-Littlewood Conjecture and Exceptional real ZeroJul 27 2014Sep 08 2016In this paper, assume that Hardy-Littlewood Conjecture, we got a better upper bound of the exceptional real zero for a class of modulo, and thus we generalized the results of reference [3].
The Upper Cluster Algebras of iARt Quivers I. DynkinMar 08 2016Mar 14 2016For each valued quiver $Q$ of Dynkin type, we construct a valued ice quiver $\Delta_Q^2$ called the iARt quiver of $C^2Q$. Let $G$ be a simple connected Lie group with Dynkin diagram the underlying valued graph of $Q$. The upper cluster algebra of $\Delta_Q^2$ ... More
An Improved Result on Rayleigh--Taylor Instability of Nonhomogeneous Incompressible Viscous FlowsJan 02 2015In [F. Jiang, S. Jiang, On instability and stability of three-dimensional gravity driven viscous flows in a bounded domain, Adv. Math., 264 (2014) 831--863], Jiang investigated the instability of Rayleigh--Taylor steady-state of a three-dimensional ... More
Local Representation Theory of Transporter CategoriesMar 03 2017We attempt to generalize the $p$-modular representation theory of finite groups to finite transporter categories, which are regarded as generalized groups. We shall carry on our tasks through modules of transporter category algebras, a type of Gorenstein ... More
Categorical Homotopy I. QuiversNov 25 2012Nov 27 2012We quiver-interpret the classical simplicial theory - including the cosimplex category $\Delta$, Dold-Kan correspondence, and Hochschild homology - as a certain Q-homotopy theory of type $A$. For the cyclic and cubical theories, we proceed analogously. ... More
Constructing Coherently G-invariant ModulesFeb 25 2014Mar 15 2016Let $G$ be a reductive group acting on a path algebra $kQ$ as automorphisms. We assume that $G$ admits a graded polynomial representation theory, and the action is polynomial. We describe the quiver $Q_G$ of the smash product algebra $kQ\# k[M_G]^*$, ... More
Tensor Product Multiplicities via Upper Cluster AlgebrasMar 08 2016Dec 20 2017For each valued quiver $Q$ of Dynkin type, we construct a valued ice quiver $\Delta_Q^2$. Let $G$ be a simple connected Lie group with Dynkin diagram the underlying valued graph of $Q$. The upper cluster algebra of $\Delta_Q^2$ is graded by the triple ... More
On the cohomology of meromorphic open-string vertex algebrasApr 20 2018This paper generalizes Huang's cohomology theory of grading-restricted vertex algebras to meromorphic open-string vertex algebras (MOSVAs hereafter), which are noncommutative generalizations of grading-restricted vertex algebras introduced by Huang. The ... More
Representations of meromorphic open-string vertex algebrasJan 26 2018Mar 27 2018We study representations of the meromorphic open-string vertex algebra (MOSVAs hereafter) defined in [H3], a noncommutative generalization of vertex (operator) algebra. We start by recalling the definition of a MOSVA $V$ and left $V$-modules in [H3]. ... More
On the lattice point covering problem in dimension 2Oct 08 2018In this paper we study the lattice point covering property of some regular polygons in dimension 2.
Some Torsional Local Models of Heterotic StringsAug 23 2015Oct 06 2015We construct solutions to the Strominger system on a class of noncompact Calabi-Yau 3-folds. These spaces include $\mathbb{C}^3$ and resolved conifold $\mathcal{O}(-1,-1)$ as special examples.
A Construction of Non-Kähler Calabi-Yau Manifolds and New Solutions to the Strominger SystemJul 01 2015Oct 08 2015We propose a new construction of compact non-K\"ahler Calabi-Yau manifolds with balanced metrics and study the Strominger system on them. In particular, we obtain explicit solutions to the Strominger system with degeneracies on $\Sigma_g\times T^4$, where ... More
Mott states under the influence of fermion-boson conversion: invasion of superfluidityMay 30 2005Jun 28 2005I study the influence of fermion-boson conversion near Feshbach resonances on Mott states of Cooper pairs and demonstrate possible invasion of superfluidity. The quantum dynamics of Fermi-Bose gases is studied using both an effective coupled $U(1)\otimes ... More
Spin-1/2 Collective Excitations in BEC of Interacting Spin-1 AtomsJun 07 2001We construct spin-1/2 collective excitations in BEC of interacting spin-1 atoms. These excitations exist in states with a maximal global degeneracy. The stability and energy of these objects are determined by interactions with spin fluctuations and are ... More
Spin correlation and Discrete symmetry in Spinor Bose-Einstein CondensatesFeb 21 2001Aug 25 2001We study spin correlations in Bose-Einstein condensates of spin 1 bosons with scatterings dominated by a total spin equal 2 channel. We show the low energy spin dynamics in the system can be mapped into an $o(n)$ nonlinear sigma model(NL$\sigma$M). $n=3$ ... More
Spin Ordering and Quasiparticles in Spin Triplet Superconducting LiquidsJan 28 2002Jul 18 2002Spin ordering and its effect on low energy quasiparticles in a p-wave superconducting liquid are investigated. We show that there is a new 2D p-wave superconducting liquid where the ground state is rotation invariant. In quantum spin disordered liquids, ... More
Hidden topological order in $^{23}Na (F=1)$ Bose-Einstein CondensatesJul 12 2001Jul 13 2001We show the existence of a new hidden topological order in $^{23}Na$ (F=1) Bose-Einstein condensates (BEC) with antiferromagnetic interactions. Occurrence of this order is due to the confinement of hedgehogs in BEC where a spin Josephson effect takes ... More
Counting using Hall Algebras II. Extensions from QuiversFeb 07 2013Apr 13 2015We count the $\mathbb{F}_q$-rational points of GIT quotients of quiver representations with relations. We focus on two types of algebras -- one is one-point extended from a quiver $Q$, and the other is the Dynkin $A_2$ tensored with $Q$. For both, we ... More
Eigenvalues of Curvature, Lyapunov exponents and Harder-Narasimhan filtrationsAug 07 2014Oct 11 2016Inspired by Katz-Mazur theorem on crystalline cohomology and by Eskin-Kontsevich-Zorich's numerical experiments, we conjecture that the polygon of Lyapunov spectrum lies above (or on) the Harder-Narasimhan polygon of the Hodge bundle over any Teichm\"uller ... More
The dimension of automorphism groups of algebraic varieties with pseudo-effective log canonical divisorsNov 03 2016Jul 15 2017Let $(X,D)$ be a log smooth pair of dimension $n$, where $D$ is a reduced effective divisor such that the log canonical divisor $K_X + D$ is pseudo-effective. Let $G$ be a connected algebraic subgroup of $\mathrm{Aut}(X,D)$. We show that $G$ is a semi-abelian ... More
Parabolic and near-parabolic renormalization for local degree threeSep 30 2015Oct 25 2016The invariant class under parabolic and near-parabolic renormalization constructed by Inou and Shishikura has proved extremely useful in recent years. It leads to several important progresses on the dynamics of certain holomorphic maps with a local degree ... More
On the Banach-Mazur Distance between the Cube and the CrosspolytopeMay 03 2017In this note we study the Banach-Mazur distance between the $n$-dimensional cube and the crosspolytope. Previous work shows that the distance has order $\sqrt{n}$, and here we will prove some explicit bounds improving on former results. Even in dimension ... More
On Some Quiver Determinantal VarietiesMay 26 2014Apr 08 2015We introduce certain quiver analogue of the determinantal variety. We study the Kempf-Lascoux-Weyman's complex associated to a line bundle on the variety. In the case of generalized Kronecker quivers, we give a sufficient condition on when the complex ... More
Hochschild and ordinary cohomology rings of small categoriesMay 21 2008Jul 29 2008Let C be a small category and k a field. There are two interesting mathematical subjects: the category algebra kC and the classifying space |C|=BC. We study the ring homomorphism HH*(kC) --> H*(|C|,k) and prove it is split surjective. This generalizes ... More
Spin rotation invariant spin triplet superconducting liquidsFeb 19 2002Mar 26 2002Spin ordering and its effect on the low energy quasiparticles in a p-wave superconducting fluid are investigated. We study the properties of a new 2D quantum spin triplet superconducting liquid where the ground state is spin rotation invariant. In quantum ... More
A novel superconducting glass state in disordered thin films in Clogston limitJun 16 1999A theory of mesoscopic fluctuations in disordered thin superconducting films in a parallel magnetic field is developed. At zero temperature, the superconducting state undergoes a phase transition into a state characterized by superfluid densities of random ... More
Topological spin pumps INov 26 2003Jul 08 2004We have established a semiclassical kinetic approach for various spin correlated pumping phenomena incorporating spin rotation in wave functions into transport equations. We employ this technique to study topological pumps and illustrate spin pumping ... More
A Note on Large Time Behavior of Velocity in the Baratropic Compressible Navier-Stokes EquationsJun 20 2012Recently, for periodic initial data with initial density allowed to vanish, Huang and Li [1] establish the global existence of strong and weak solutions for the two-dimensional compressible Navier{Stokes equations with no restrictions on the size of initial ... More
On homology with coefficients and generalized inductionsFeb 15 2017Oct 22 2018In group representations several inductions given by tensoring with appropriate bimodules may be reconstructed via homology of $G$-posets with $G$-equivariant coefficients. For this purpose, we need various local categories of a finite group $G$, which ... More
Weight hierarchy of a class of linear codes relating to non-degenerate quadratic formsAug 18 2017Sep 03 2017In this paper, we discuss the generalized Hamming weights of a class of linear codes associated with non-degenerate quadratic forms. In order to do so, we study the quadratic forms over subspaces of finite field and obtain some interesting results about ... More
On the Hessian of Shape Matching EnergyApr 08 2016Apr 13 2016In this technical report we derive the analytic form of the Hessian matrix for shape matching energy. Shape matching is a useful technique for meshless deformation, which can be easily combined with multiple techniques in real-time dynamics. Nevertheless, ... More
Toric surfaces over an arbitrary fieldOct 20 2016Sep 13 2018We study toric varieties over an arbitrary field with an emphasis on toric surfaces in the Merkurjev-Panin motivic category of "K-motives". We explore the decomposition of certain toric varieties as K-motives into products of central simple algebras, ... More
On existence and uniqueness of solutions to uncertain backward stochastic differential equationsJan 29 2014This paper is concerned with a class of uncertain backward stochastic differential equations (UBSDEs) driven by both an $m$-dimensional Brownian motion and a $d$-dimensional canonical process with uniform Lipschitzian coefficients. Such equations can ... More
Circulant Digraphs Integral over Number FieldsJan 04 2012A number field K is a finite extension of rational number field Q. A circulant digraph integral over K means that all its eigenvalues are algebraic integers of K. In this paper we give the sufficient and necessary condition for circulant digraphs which ... More
Superconductivity, charge- or spin-density wave, and metal-nonmetal transition in BaTi$_{2}$(Sb$_{1-x}$Bi$_{x}$)$_{2}$ONov 09 2012Mar 09 2013We have performed an isovalent substitution study in a layered titanium oxypnictide system BaTi$_{2}$(Sb$_{1-x}$Bi$_{x}$)$_{2}$O (0$\leq x\leq$ 0.40) by the measurements of x-ray diffraction, electrical resistivity and magnetic susceptibility. The parent ... More
A tidal encounter caught in the act: modelling a star-disc fly-by in the young RW Aurigae systemFeb 23 2015Apr 04 2015RW Aurigae (RW Aur) is a binary star system with a long molecular arm trailing the primary star. Cabrit et al. (2006) noted the resemblance between this extended structure and the tidal arm stripped from the primary star in the simulations of star-disc ... More
Maximum-entropy calculation of end-to-end distance distribution of force stretching chainsDec 12 2002Using the maximum-entropy method, we calculate the end-to-end distance distribution of the force stretched chain from the moments of the distribution, which can be obtained from the extension-force curves recorded in single-molecule experiments. If one ... More
A model for the force stretching double-stranded chain moleculesDec 12 2002We modify and extend the recently developed statistical mechanical model for predicting the thermodynamic properties of chain molecules having noncovalent double-stranded conformations, as in RNA or ssDNA, and $\beta-$sheets in protein, by including the ... More
A constant extension ensembles model of double-stranded chain moleculesDec 16 2002Because the constant extension ensemble of single chain molecule is not always equivalent with constant force ensemble, a model of double-stranded conformations, as in RNA molecules and $\beta$-sheets in proteins, with fixed extension constraint is built ... More
Ultra-Broadband Super-Planckian Radiative Heat Transfer with Artificial Continuum Cavity States in Patterned Hyperbolic MetamaterialSep 14 2016Mar 31 2017Localized cavity resonances due to nanostructures at material surfaces can greatly enhance radiative heat transfer (RHT) between two closely placed bodies owing to stretching of cavity states in momentum space beyond light line. Based on such understanding, ... More
Edge and surface plasmons in graphene nanoribbonsDec 21 2015We report on nano-infrared (IR) imaging studies of confined plasmon modes inside patterned graphene nanoribbons (GNRs) fabricated with high-quality chemical-vapor-deposited (CVD) graphene on Al2O3 substrates. The confined geometry of these ribbons leads ... More
Electronic and plasmonic phenomena at graphene grain boundariesNov 26 2013Graphene, a two-dimensional honeycomb lattice of carbon atoms, is of great interest in (opto)electronics and plasmonics and can be obtained by means of diverse fabrication techniques, among which chemical vapor deposition (CVD) is one of the most promising ... More
The stellar obliquity, planet mass, and very low albedo of Qatar-2 from K2 PhotometrySep 05 2016Nov 15 2016The Qatar-2 transiting exoplanet system was recently observed by the {\it Kepler} telescope as part of {\it K2} Campaign 6. The photometric time series has one-minute time sampling and a precision of about 690~ppm, after filtering out artifacts and spurious ... More
Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic materialFeb 13 2015Apr 26 2015Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials light propagation is unusual, leading to novel and often non-intuitive optical phenomena. Here we report ... More
Raman evidence for dimerization and Mott collapse in $α$-RuCl$_3$ under pressuresJul 21 2018We perform Raman spectroscopy studies on $\alpha$-RuCl$_3$ at room temperature to explore its phase transitions of magnetism and chemical bonding under pressures. The Raman measurements resolve two critical pressures, about $p_1=1.1$~GPa and $p_2=1.7$~GPa, ... More
The stellar obliquity, planet mass, and very low albedo of Qatar-2 from K2 PhotometrySep 05 2016The Qatar-2 transiting exoplanet system was recently observed by the {\it Kepler} telescope as part of {\it K2} Campaign 6. The photometric time series has one-minute time sampling and a precision of about 690~ppm, after filtering out artifacts and spurious ... More
Electronic structure of BaNi$_2$As$_2$Oct 10 2010Jan 26 2011BaNi$_2$As$_2$, with a first order phase transition around 131 K, is studied by the angle-resolved photoemission spectroscopy. The measured electronic structure is compared to the local density approximation calculations, revealing similar large electronlike ... More
The K2-ESPRINT Project VI: K2-105 b, a Hot-Neptune around a Metal-rich G-dwarfJan 05 2017We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26$\pm$0.05) G-dwarf (T_eff = 5430$\pm$70 ... More
Graphene on hexagonal boron nitride as a tunable hyperbolic metamaterialJan 28 2015Jun 23 2015Hexagonal boron nitride (h-BN) is a natural hyperbolic material, for which the dielectric constants are the same in the basal plane (epsilon^t = epsilon^x = epsilon^y) but have opposite signs (epsilon^t*epsilon^z < 0) from that in the normal plane (epsilon^z). ... More
Doppler Monitoring of the WASP-47 Multiplanet SystemOct 13 2015Oct 28 2015We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses ... More
The Grothendieck Construction and Gradings for Enriched CategoriesJul 01 2009The Grothendieck construction is a process to form a single category from a diagram of small categories. In this paper, we extend the definition of the Grothendieck construction to diagrams of small categories enriched over a symmetric monoidal category ... More
Local well-posedness for the Hall-MHD system in optimal Sobolev SpacesMar 26 2018Jun 08 2018We show that the viscous resistive magneto-hydrodynamics system with Hall effect is locally well-posed in $H^s(\mathbb R^n)\times H^{s+1-\varepsilon}(\mathbb R^n)$ with $s>\frac{n}2-1$ and any small enough $\varepsilon>0$ such that $s+1-\varepsilon>\frac{n}2$. ... More
Propagation of regularity for the MHD system in optimal Sobolev spaceJul 24 2017Mar 14 2018We study the problem of propagation of regularity of solutions to the incompressible viscous non-resistive magneto-hydrodynamics system. According to scaling, the Sobolev space $H^{\frac n2-1}(\mathbb R^n)\times H^{\frac n2}(\mathbb R^n)$ is critical ... More
Regularity problem for the nematic LCD system with Q-tensor in $\mathbb R^3$Aug 26 2016We study the regularity problem of a nematic liquid crystal model with local configuration represented by Q-tensor in three dimensions. It was an open question whether the classical Prodi-Serrin condition implies regularity for this model. Applying a ... More
Regularity criterion and energy conservation for the supercritical Quasi-Geostrophic equationMay 09 2015Jul 12 2016This paper studies the regularity and energy conservation problems for the 2D supercritical quasi-geostrophic (SQG) equation. We apply an approach of splitting the dissipation wavenumber to obtain a new regularity condition which is weaker than all the ... More
On $\mathrm{C}^1$-class local diffeomorphisms whose periodic points are nonuniformly expandingJun 11 2012Using a sifting-shadowing combination, we prove in this paper that an arbitrary $\mathrm{C}^1$-class local diffeomorphism $f$ of a closed manifold $M^n$ is uniformly expanding on the closure $\mathrm{Cl}_{M^n}(\mathrm{Per}(f))$ of its periodic point set ... More
Time-preserving structural stability of hyperbolic differential dynamics with noncompact phase spacesMay 17 2008In this paper, we study the structural stability of hyperbolic differential systems on Euclidean spaces using Liao theory.
A positive solution to a conjecture of A. Katok for diffeomorphism caseJun 10 2008In this paper, using Pesin theory and Liao theory, we give a positive solution to a conjecture of A. Katok.
The McMahon pseudo-metrics of minimal transformation semigroups with invariant measuresJun 25 2018Let $T\times X\rightarrow X$ be any minimal semiflow with phase semigroup $T$. When $(T,X)$ admits an invariant Borel probability measure, using McMahon pseudo-metrics we mainly show in this paper the following results: \begin{itemize} \item[(1)] $S_{\textit{eq}}(X)=Q(X)$, ... More
Mean-variance hedging based on an incomplete market with external risk factors of non-Gaussian OU processesOct 03 2014Aug 26 2015In this paper, we prove the global risk optimality of the hedging strategy of contingent claim, which is explicitly (or called semi-explicitly) constructed for an incomplete financial market with external risk factors of non-Gaussian Ornstein-Uhlenbeck ... More
On chaotic minimal center of attraction of a Lagrange stable motion for topological semi flowsJul 02 2015Jul 09 2015In this paper, we study the chaotic dynamics of a minimal center of attraction of a Lagrange stable motion for semi flows.
Chaotic dynamics of continuous-time topological semi-flows on Polish spacesJan 09 2015In this paper, we study the chaotic dynamics of a continuous-time topological semi-flow on a Polish space.
Eigenvalue, global bifurcation and positive solutions for a class of fully nonlinear problemsMar 23 2014In this paper, we shall study global bifurcation phenomenon for the following Kirchhoff type problem \begin{equation} \left\{ \begin{array}{l} -\left(a+b\int_\Omega \vert \nabla u\vert^2\,dx\right)\Delta u=\lambda u+h(x,u,\lambda)\,\,\text{in}\,\, \Omega,\\ ... More
Stability of Solutions to the Quasi-Geostrophic Equations in $\mathbb R^2$Mar 16 2015We consider the stationary Quasi-Geostrophic equation in the whole space $\mathbb R^2$ driven by a force $f$. Under certain assumptions of $f$, we establish the existence of solutions with finite $L^2$ norm. This solution is unique among all solutions ... More
Cellular Stratified Spaces I: Face Categories and Classifying SpacesJun 19 2011Sep 16 2016The notion of cellular stratified spaces was introduced in a joint work of the author with Basabe, Gonz\'alez, and Rudyak [1009.1851] with the aim of constructing a cellular model of the configuration space of a sphere. In particular, it was shown that ... More