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Impact of Rattlers on Thermal Conductivity of a Thermoelectric Clathrate: A First-Principles StudyDec 18 2014Jan 25 2015We investigate the role of rattling guest atoms on the lattice thermal-conductivity of a type-I clathrate Ba$_{8}$Ga$_{16}$Ge$_{30}$ by first-principles lattice dynamics. Comparing phonon properties of filled and empty clathrates, we show that rattlers ... More

Numerical Investigation of Triexciton Stabilization in Diamond with Multiple Valleys and BandsSep 08 2016The existence of polyexcitons, the $N$-body complexes of excitons for $N > 2$ in 3D bulk systems, has been controversial for more than 40 years since its first theoretical suggestion. We investigated the stability of fundamental excitonic complexes in ... More

Anisotropic superconducting gaps in YNi$_2$B$_2$C: A first-principles investigationOct 24 2016We calculate superconducting gaps and quasiparticle density of states of YNi$_2$B$_2$C in the framework of the density functional theory for superconductors to investigate the origin of a highly anisotropic superconducting gaps in this material. Calculated ... More

An efficient method for calculating spatially extended electronic states of large systems with a divide-and-conquer approachNov 19 2016We present an efficient post-processing method for calculating the electronic structure of nanosystems based on the divide-and-conquer approach to density functional theory (DC-DFT), in which a system is divided into subsystems whose electronic structure ... More

Optical Absorption Study by Ab initio Downfolding Approach: Application to GaAsOct 24 2007We examine whether essence and quantitative aspects of electronic excitation spectra are correctly captured by an effective low-energy model constructed from an {\em ab initio} downfolding scheme. A global electronic structure is first calculated by {\em ... More

First-principles study of the pressure and crystal-structure dependences of the superconducting transition temperature in compressed sulfur hydridesFeb 03 2015Jul 07 2015We calculate superconducting transition temperatures ($T_{\rm c}$) in sulfur hydrides H$_{2}$S and H$_{3}$S from first principles using the density functional theory for superconductors. At pressures of $\lesssim$150 GPa, the high values of $T_{\rm c}$ ... More

Possible "Magnéli" phases and self-alloying in the superconducting sulfur hydrideDec 21 2015Aug 11 2016We theoretically give an infinite number of metastable crystal structures for the superconducting sulfur hydride H$_{x}$S under pressure. It has been thought that theoretically predicted structures of H$_{2}$S and H$_{3}$S exhibit low and high $T_{\rm ... More

Iterative diagonalization of the non-Hermitian transcorrelated Hamiltonian using a plane-wave basis set: Application to $sp$-electron systems with deep core statesMar 14 2016We develop an iterative diagonalization scheme in solving a one-body self-consistent-field equation in the transcorrelated (TC) method using a plane-wave basis set. Non-Hermiticity in the TC method is well handled with a block-Davidson algorithm. We verify ... More

Neural-network Kohn-Sham exchange-correlation potential and its out-of-training transferabilityFeb 08 2018We incorporate in the Kohn-Sham self consistent equation a trained neural-network projection from the charge density distribution to the Hartree-exchange-correlation potential $n \rightarrow V_{\rm Hxc}$ for possible numerical approach to the exact Kohn-Sham ... More

First-principles Calculation of Effective Onsite Coulomb Interaction of 3d Transition Metals: Constrained Local Density Functional Approach with Maximally Localized Wannier FunctionOct 17 2005We present a new ab initio method for calculating effective onsite Coulomb interactions of itinerant and strongly correlated electron systems. The method is based on constrained local density functional theory formulated in terms of maximally localized ... More

New Parameterization in Muon Decay and the Type of Emitted NeutrinoFeb 15 2005Sep 30 2005Normal muon decay, $\mu^{+} \to e^{+}\nu_{e}\bar{\nu_{\mu}}$, is studied as a tool to discriminate between the Dirac and Majorana types of neutrinos and to survey the structure of the weak interaction. It is assumed that massive neutrinos mix with one ... More

New Parameterization in Muon Decay and the Type of Emitted Neutrino. IIApr 17 2007Oct 02 2009In a previous paper, new sets of parameters to replace the Michel parameters were proposed to analyze data for the muon decay $\mu^{+} \to e^{+}\nu_{e}\bar{\nu_{\mu}}$. Both $(V-A)$ and $(V+A)$ charged currents with finite neutrino mass have been used ... More

Models with Quartic Potential of Dynamical SUSY Breaking in Meta-Stable VacuaMar 29 2007Apr 04 2007We search for models of dynamical SUSY breaking in meta-stable vacua which might have dual string descriptions with a few brane probes. Two models with quartic superpotential are proposed: One of them might be closely related to the dual gauge theory ... More

Dark energy: investigation and modelingApr 09 2010Constantly accumulating observational data continue to confirm that about 70% of the energy density today consists of dark energy responsible for the accelerated expansion of the Universe. We present recent observational bounds on dark energy constrained ... More

Cosmologies from higher-order string correctionsJun 06 2006Aug 03 2006We study cosmologies based on low-energy effective string theory with higher-order string corrections to a tree-level action and with a modulus scalar field (dilaton or compactification modulus). In the presence of such corrections it is possible to construct ... More

General analytic formulae for attractor solutions of scalar-field dark energy models and their multi-field generalizationsJan 24 2006May 01 2006We study general properties of attractors for scalar-field dark energy scenarios which possess cosmological scaling solutions. In all such models there exists a scalar-field dominant solution with an energy fraction \Omega_{\phi}=1 together with a scaling ... More

Lattice QCD at finite temperatureNov 01 2000Nov 17 2000Recent developments in finite-temperature QCD with dynamical quarks are reviewed focusing on the topics of critical temperature, the equation of state, and critical behaviors around the chiral phase transition.

A novel operation associated with Gauss' arithmetic-geometric meansAug 27 2007The arithmetic mean is the mean for addition and the geometric mean is that for multiplication. Then what kind of binary operation is associated with the arithmetic-geometric mean (AGM) due to C. F. Gauss? If it is possible to construct an arithmetic ... More

Combinatorics in the group of parity alternating permutationsDec 10 2008We call a permutation parity alternating, if its entries assume even and odd integers alternately. Parity alternating permutations form a subgroup of the symmetric group. This paper deals with such permutations classified by two permutation statistics; ... More

On the maximum value of ground states for the scalar field equation with double power nonlinearityJan 30 2009We evaluate the maximum value of the unique positive solution to semilinear elliptic equations with double power nonlinearities. It is known that a positive solution to this problem exists under some condition.Moreover, Ouyang and Shi in 1998 found that ... More

Phase structure of hot dense QCD by a histogram methodJun 03 2013Jul 24 2013We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. The quark mass dependence and the chemical potential dependence of the nature of phase transition are investigated focusing on ... More

Lattice QCD thermodynamics with Wilson quarksApr 27 2007We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the ... More

Canonical partition function and finite density phase transition in lattice QCDApr 21 2008Oct 16 2008We discuss the nature of the phase transition for lattice QCD at finite temperature and density. We propose a method to calculate the canonical partition function by fixing the total quark number introducing approximations allowed in the low density region. ... More

Remarks on the multi-parameter reweighting method for the study of lattice QCD at non-zero temperature and densityJan 07 2004Mar 04 2004We comment on the reweighting method for the study of finite density lattice QCD. We discuss the applicable parameter range of the reweighting method for models which have more than one simulation parameter. The applicability range is determined by the ... More

Charge separation instability in an unmagnetized disk plasma around a Kerr black holeSep 30 2010Dec 25 2010In almost all of plasma theories for astrophysical objects, we have assumed the charge quasi-neutrality of unmagnetized plasmas in global scales. This assumption has been justified because if there is a charged plasma, it induces electric field which ... More

Generalized General Relativistic MHD Equations and Distinctive Plasma Dynamics around Rotating Black HolesDec 26 2009To study phenomena of plasmas around rotating black holes, we have derived a set of 3+1 formalism of generalized general relativistic magnetohydrodynamic (GRMHD) equations. Especially, we investigated general relativistic phenomena with respect to the ... More

The effective field theory of inflation/dark energy and the Horndeski theoryApr 10 2014Sep 01 2014The effective field theory (EFT) of cosmological perturbations is a useful framework to deal with the low-energy degrees of freedom present for inflation and dark energy. We review the EFT for modified gravitational theories by starting from the most ... More

Modified gravity models of dark energyDec 31 2010We review recent progress of modified gravity models of dark energy--based on f(R) gravity, scalar-tensor theories, braneworld gravity, Galileon gravity, and other theories. In f(R) gravity and Brans-Dicke theory it is possible to design viable models ... More

Epidemic spreading with immunization on bipartite networksMay 17 2011Bipartite networks are composed of two types of nodes and there are no links between nodes of the same type. Thus the study of epidemic spread and control on such networks is relevant to sexually transmitted diseases (STDs). When entire populations of ... More

Dimensional Analysis and Physical LawsSep 14 2006Dimensional analysis provides many simple and useful tools for various situations in science. The objective of this paper is to investigate its relations to functions, i.e., the dimensions for functions that yield physical quantities and those for the ... More

Epidemic thresholds in directed complex networksMar 09 2011The spread of a disease, a computer virus or information is discussed in a directed complex network. We are concerned with a steady state of the spread for the SIR and SIS dynamic models. In a scale-free directed network it is shown that the threshold ... More

Magnetization Process in the One-Dimensional Doped Kondo Lattice ModelAug 02 1999Dec 20 1999The magnetization process in the one-dimensional Kondo lattice model for the doped (n_{c}<1) case is studied by the density matrix renormalization group (DMRG) method. A rapid increase of the magnetization is caused by the collapse of the intersite incommensurate ... More

A New Approach to Signed Eulerian NumbersFeb 13 2006The numbers of even and odd permutations with a given ascent number are investigated using an operator that was previously introduced by the author. Their difference is called a signed Eulerian number. By means of the operator the recurrence relation ... More

Hecke operators on weighted Dedekind symbolsDec 05 2004Dedekind symbols generalize the classical Dedekind sums (symbols). The symbols are determined uniquely by their reciprocity laws up to an additive constant. There is a natural isomorphism between the space of Dedekind symbols with polynomial (Laurent ... More

Uniqueness of positive solutions to semilinear elliptic equations with double power nonlinearities, revised edditionJan 16 2009We consider uniqueness of positive solutions to semilinear elliptic equations with double power nonlinearities. The condition to assure the existence of positive solutions to these types of equations has long been known. On the other hand for uniqueness, ... More

Lunar Laser Ranging constraints on nonminimally coupled dark energy and standard sirensMar 17 2019In dark energy models where a scalar field $\phi$ is coupled to the Ricci scalar $R$ of the form $e^{-2Q (\phi-\phi_0)/M_{\rm pl}}R$, where $Q$ is a coupling constant, $\phi_0$ is today's value of $\phi$, and $M_{\rm pl}$ is the reduced Planck mass, we ... More

Stealth magnetic field in de Sitter spacetimeJul 24 2016In the context of a U(1) gauge theory non-minimally coupled to scalar-tensor gravity, we find a cosmological attractor solution that represents a de Sitter universe with a homogeneous magnetic field. The solution fully takes into account backreaction ... More

Monopoles and Spatial String Tension in the High Temperature Phase of SU(2) QCDOct 17 1995We studied a behavior of monopole currents in the high temperature (deconfinement) phase of abelian projected finite temperature SU(2) QCD in maximally abelian gauge. Wrapped monopole currents closed by periodic boundary play an important role for the ... More

Monopole Condensation and Polyakov Loop in Finite-Temperature Pure QCDAug 01 1996We study the relation between the abelian monopole condensation and the deconfinement phase transition of the finite-temperature pure QCD. The expectation value of the monopole contribution to the Polyakov loop becomes zero when a long monopole loop is ... More

Lattice QCD at finite temperature and densitySep 07 2010We study the phase structure of QCD at finite temperature and density by numerical simulations on a lattice. The most important point for the numerical study at finite density is treatment of the sign problem. We propose a method to avoid the sign problem, ... More

Study of the critical point in lattice QCD at high temperature and densityOct 02 2007We propose a method to probe the nature of phase transitions in lattice QCD at finite temperature and density, which is based on the investigation of an effective potential as a function of the average plaquette. We analyze data obtained in a simulation ... More

Generalized Relativistic Magnetohydrodynamic Equations for Pair and Electron-Ion PlasmasFeb 25 2009We derived one-fluid equations based on a relativistic two-fluid approximation of e$^\pm$ pair plasma and electron-ion plasma to reveal the specific relativistic nature of their behavior. Assuming simple condition on the relativistic one-fluid equations, ... More

Propagation of Electromagnetic Waves in Resistive Pair Plasma and Causal Relativistic MagnetohydrodynamicsOct 07 2008We investigate the propagation of electromagnetic waves in resistive pair plasmas using a onefluid theory derived from the relativistic two-fluid equations. When the resistivity normalized by the electron/positron inertia variable exceeds a critical value, ... More

Quintessence: A ReviewApr 07 2013Oct 05 2013Quintessence is a canonical scalar field introduced to explain the late-time cosmic acceleration. The cosmological dynamics of quintessence is reviewed, paying particular attention to the evolution of the dark energy equation of state w. For the field ... More

Observational tests of inflation with a field derivative coupling to gravityJan 28 2012Apr 20 2012A field kinetic coupling with the Einstein tensor leads to a gravitationally enhanced friction during inflation, by which even steep potentials with theoretically natural model parameters can drive cosmic acceleration. In the presence of this non-minimal ... More

Observational signatures of f(R) dark energy models that satisfy cosmological and local gravity constraintsSep 10 2007Nov 19 2007We discuss observational consequences of f(R) dark energy scenarios that satisfy local gravity constraints (LGC) as well as conditions of the cosmological viability. The model we study is given by m(r)=C(-r-1)^p (C>0, p>1) with m=Rf_{,RR}/f_{,R} and r=-Rf_{,R}/f, ... More

Introductory review of cosmic inflationApr 28 2003These lecture notes provide an introduction to cosmic inflation. In particular I will review the basic concepts of inflation, generation of density perturbations, and reheating after inflation.

Natural growth model of weighted complex networksAug 17 2011We propose a natural model of evolving weighted networks in which new links are not necessarily connected to new nodes. The model allows a newly added link to connect directly two nodes already present in the network. This is plausible in modeling many ... More

Power laws of the in-degree and out-degree distributions of complex networksDec 15 2009A model for directed networks is proposed and power laws for their in-degree and/or out-degree distributions are derived from the model. It is based on the Barabasi-Albert model and contains two parameters. The parameters serve as regulatory factors for ... More

Stealth magnetic field in de Sitter spacetimeJul 24 2016Nov 23 2016In the context of a U(1) gauge theory non-minimally coupled to scalar-tensor gravity, we find a cosmological attractor solution that represents a de Sitter universe with a homogeneous magnetic field. The solution fully takes into account backreaction ... More

Energy Quantisation in Bulk Bouncing TachyonFeb 22 2005Feb 27 2005We argue that the closed string energy in the bulk bouncing tachyon background is to be quantised in a simple manner as if strings were trapped in a finite time interval. We discuss it from three different viewpoints; (1) the timelike continuation of ... More

A formulation of domain-wall fermions in the Schrödinger functionalOct 18 2010We present a formulation of domain-wall fermions in the Schr\"odinger functional by following a universality argument. To examine the formulation, we numerically investigate the spectrum of the free operator and perform a one-loop analysis to confirm ... More

Universality check of the overlap fermions in the Schroedinger functionalAug 21 2008I examine some properties of the overlap operator in the Schroedinger functional formulated by Luescher at perturbative level. By investigating spectra of the free operator and one-loop coefficient of the Schroedinger functional coupling, I confirm the ... More

Parity-Alternate Permutations and Signed Eulerian NumbersDec 06 2006In order to study signed Eulerian numbers, we introduce permutations of a particular type, called parity-alternate permutations, because they take even and odd entries alternately. The objective of this paper is twofold. The first is to derive several ... More

Explicit formulas for Hecke operators on cusp forms, Dedekind symbols and period polynomialsJun 19 2005Mar 28 2006Let S_{w+2} be the vector space of cusp forms of weight w+2 on the full modular group, and let S_{w+2}^* denote its dual space. Periods of cusp forms can be regarded as elements of S_{w+2}^*. The Eichler-Shimura isomorphism theorem asserts that odd (or ... More

Classification of double power nonlinear functionsNov 06 2008In this article we investigate the nature of the functions, including important double power terms which arise naturally in considering typical nonlinear Schroedinger equations.

A new basis for the space of modular formsAug 24 2010Let $G_{2n}$ be the Eisenstein series of weight $2n$ for the full modular group $\Gamma=SL_2(\ZZ)$. It is well-known that the space $M_{2k}$ of modular forms of weight $2k$ on $\Gamma$ has a basis $\{G_{4}^\alpha G_{6}^\beta\ |\ \alpha,\beta\in\ZZ,\ \alpha,\beta\geq ... More

Cuntz-Krieger type uniqueness theorem for topological higher-rank graph C*-algebrasNov 16 2009Oct 14 2010We study Sims-Yeend's product system C*-algebras and topological higher-rank graph C*-algebras by Yeend. We give a relation between Katsura's Cuntz-Pimsner covariance and Sims-Yeend's one by a direct approach and an explicit form of the core of product ... More

Monopoles in High Temperature Phase of SU(2) QCDSep 09 1995Sep 11 1995We investigated a behavior of monopole currents in the high temperature phase of abelian projected finite temperature SU(2) QCD in maximally abelian gauge. Wrapped monopole currents which are closed by periodic boundary play an important role for the ... More

On the existence of the critical point in finite density lattice QCDJun 25 2007Dec 11 2007We propose a method to probe the nature of phase transitions in lattice QCD at finite temperature and density, which is based on the investigation of an effective potential as a function of the average plaquette. We analyze data obtained in a simulation ... More

Epidemic spreading with immunization rate on complex networksApr 13 2011We investigate the spread of diseases, computer viruses or information on complex networks and also immunization strategies to prevent or control the spread. When an entire population cannot be immunized and the effect of immunization is not perfect, ... More

Possibility of realizing weak gravity in redshift space distortion measurementsMay 11 2015Aug 19 2015We study the possibility of realizing a growth rate of matter density perturbations lower than that in General Relativity. Using the approach of the effective field theory of modified gravity encompassing theories beyond Horndeski, we derive the effective ... More

Distinguishing between inflationary models from cosmic microwave backgroundJan 19 2014Jun 12 2014In this paper, inflationary cosmology is reviewed, paying particular attention to its observational signatures associated with large-scale density perturbations generated from quantum fluctuations. In the most general scalar-tensor theories with second-order ... More

Matter density perturbations and effective gravitational constant in modified gravity models of dark energyMay 08 2007Nov 06 2007We derive the equation of matter density perturbations on sub-horizon scales for a general Lagrangian density f(R, phi, X) that is a function of a Ricci scalar R, a scalar field phi and a kinetic term X=-(nabla phi)^2/2. This is useful to constrain modified ... More

Reconstruction of general scalar-field dark energy modelsAug 25 2005Oct 19 2005The reconstruction of scalar-field dark energy models is studied for a general Lagrangian density $p(\phi, X)$, where $X$ is a kinematic term of a scalar field $\phi$. We implement the coupling $Q$ between dark energy and dark matter and express reconstruction ... More

Construction of nonsingular cosmological solutions in string theoriesFeb 24 2003We study nonsingular cosmological scenarios in a general $D$-dimensional string effective action of the dilaton-modulus-axion system in the presence of the matter source. In the standard dilatonic Brans-Dicke parameter ($\omega=-1$) with radiation, we ... More

Cosmological disformal transformations to the Einstein frame and gravitational couplings with matter perturbationsJun 29 2015Oct 06 2015The disformal transformation of metric $g_{\mu \nu} \to \Omega^2 (\phi)g_{\mu \nu}+\Gamma(\phi,X) \partial_{\mu}\phi \partial_{\nu}\phi$, where $\phi$ is a scalar field with the kinetic energy $X= \partial_{\mu}\phi \partial^{\mu}\phi/2$, preserves the ... More

Cosmological density perturbations from perturbed couplingsMay 29 2003Aug 15 2003The density perturbations generated when the inflaton decay rate is perturbed by a light scalar field $\chi$ are studied. By explicitly solving the perturbation equations for the system of two scalar fields and radiation, we show that even in low energy-scale ... More

Perturbative analysis of the Neuberger-Dirac operator in the Schrödinger functionalDec 10 2007We investigate the spectrum of the free Neuberger-Dirac operator $\Dov$ on the Schr\"odinger functional (SF). We check that the lowest few eigen-values of the Hermitian operator $\Dov^{\dag}\Dov$ in unit of $L^{-2}$ converge to the continuum limit properly. ... More

Fat MagnonOct 02 2006Mar 30 2007We consider a D-brane type state which shares the characteristic of the recently found giant magnon of Hofman and Maldacena. More specifically we find a bound state of giant graviton (D3-brane) and giant magnon (F-string), which has exactly the same anomalous ... More

A remark on the uniqueness of positive solutions to semilinear elliptic equations with double power nonlinearitiesOct 31 2008We consider the uniqueness of positive solutions to semilinear elliptic equations with double power nonlinearities. We deduce the uniqueness from the argument in the classical paper by Peletier and Serrin, thereby recovering a part of the uniqueness result ... More

Uniqueness of positive solutions to semilinear elliptic equations with double power nonlinearitiesNov 06 2008We consider semilinear elliptic equations with double power nonlineaities. The condition to assure the existence of positive solutions is well-known. In the present paper, we remark that the additional condition to assure uniqueness proposed by Ouyang ... More

Cuntz's $ax+b$-semigroup C*-algebra over $\mathbb{N}$ and product system C*-algebrasJun 10 2009Jun 18 2009We investigate $C^*$-algebras associated with row-finite topological higher-rank graphs with no source, which are based on product system $C^*$-algebras. We prove the Cuntz-Krieger uniqueness theorem, and provide the condition of simplicity and purely ... More

The elliptic Apostol-Dedekind sums generate odd Dedekind symbols with Laurent polynomial reciprocity lawsJul 23 2009Dedekind symbols are generalizations of the classical Dedekind sums (symbols). There is a natural isomorphism between the space of Dedekind symbols with Laurent polynomial reciprocity laws and the space of modular forms. We will define a new elliptic ... More

On semilinear elliptic equations with global couplingOct 31 2008We consider nonlinear elliptic equations which contains global coupling as a nonlinear term. We classify the existence of all possible positive solutions to this problem.

A formulation of domain wall fermions in the Schroedinger functionalOct 13 2009We present a formulation of domain wall fermions in the Schroedinger functional by following the universality argument given by L\"uscher. To check whether the formulation works, we examine the lowest eigenmode of the free domain wall fermion operator. ... More

Automatic generation of Feynman rules in the Schroedinger functionalAug 22 2008We provide an algorithm to generate vertices for the Schr\"odinger functional with an abelian background gauge field. The background field has a non-trivial color structure, therefore we mainly focus on a manipulation of the color matrix part. We propose ... More

Lee-Yang zero analysis for the study of QCD phase structureJun 25 2005Mar 09 2006We comment on the Lee-Yang zero analysis for the study of the phase structure of QCD at high temperature and baryon number density by Monte-Carlo simulations. We find that the sign problem for non-zero density QCD induces a serious problem in the finite ... More

Critical point in finite density lattice QCD by canonical approachAug 04 2009Sep 18 2009We propose a method to find the QCD critical point at finite density calculating the canonical partition function ${\cal Z}_{\rm C} (T,N)$ by Monte-Carlo simulations of lattice QCD, and analyze data obtained by a simulation with two-flavor p4-improved ... More

Recent progress in lattice QCD at finite densityDec 08 2008We review recent progress in lattice QCD at finite density. The phase diagram of QCD and the equation of state at finite temperature and density are discussed. In particular, we focus on the critical point terminating a first order phase transition line ... More

Remarks on the reweighting method in the chemical potential directionDec 13 2002We comment on the reweighting method in the chemical potential $(\mu_{\rm q})$ direction. We study the fluctuation of the reweighting factor during Monte-Carlo steps. We find that it is the absolute value of the reweighting factor that mainly contributes ... More

Disformal invariance of cosmological perturbations in a generalized class of Horndeski theoriesDec 19 2014Apr 27 2015It is known that Horndeski theories can be transformed to a sub-class of Gleyzes-Langlois-Piazza-Vernizzi (GLPV) theories under the disformal transformation of the metric $g_{\mu \nu} \to \Omega^2(\phi)g_{\mu \nu}+\Gamma (\phi,X) \nabla_{\mu} \phi \nabla_{\nu} ... More

Density perturbations in the Ekpyrotic Universe and string-inspired generalizationsOct 31 2001Dec 31 2001We study density perturbations in several cosmological models motivated by string theory. The evolution and the spectra of curvature perturbations ${\cal R}$ are analyzed in the Ekpyrotic scenario and nonsingular string cosmologies. We find that these ... More

A remark on the BA model of scale-free networksFeb 10 2009May 19 2009The degree distributions of many real world networks follow power-laws whose exponents tend to fall between two and three. Within the framework of the Barabasi-Albert model (BA model), we explain this empirical observation by a simple fact. To that end ... More

Exact Renormalization Group and Loop EquationOct 31 1999Mar 06 2000We propose a gauge invariant formulation of the exact renormalization group equation for nonsupersymmetric pure U(N) Yang-Mills theory, based on the construction by Tim Morris. In fact we show that our renormalization group equation amounts to a regularized ... More

Janus within JanusMar 14 2006Oct 02 2006We found a simple and interesting generalization of the non-supersymmetric Janus solution in type IIB string theory. The Janus solution can be thought of as a thick AdS_d-sliced domain wall in AdS_{d+1} space. It turns out that the AdS_d-sliced domain ... More

Existence and uniqueness conditions of positive solutions to semilinear elliptic equations with double power nonlinearitiesNov 06 2008In this article we find the equivalent conditions to assure the existence and uniqueness of positive solutions to semilinear elliptic equations wih double power nonlinearities. As a bonus, we give a simpler proof of our former result that the uniqueness ... More

Circle correspondence $C^*$-algebrasAug 10 2008We investigate Cuntz-Pimsner $C^*$-algebras associated with certain correspondences of the unit circle $\mathbb{T}$. We analyze these $C^*$-algebras by analogy with irrational rotation algebras $A_\theta$ and Cuntz algebras $\mathcal{O}_n$. We construct ... More

WKB and "Cubic-WKB" methods as an adiabatic approximationMar 11 2019This paper shows that WKB wave function can be expressed in the form of an adiabatic expansion. To build a bridge between two widely invoked approximation schemes seems pedagogically instructive. Further "cubic-WKB" method that has been devised in order ... More

Role of Conduction Electrons in the ortho-KC$_{60}$ PolymerDec 24 1997We present first-principles band calculations as well as structural optimization of the orthorhombic K$_1$C$_{60}$ polymerized phase. We found three-dimensional inter-fullerene bonding/anti-bonding characters consisting of $t_{1u}$ molecular orbitals ... More

Density perturbations in general modified gravitational theoriesJun 02 2010We derive the equations of linear cosmological perturbations for the general Lagrangian density $f (R,\phi, X)/2+L_c$, where $R$ is a Ricci scalar, $\phi$ is a scalar field, and $X=-(\nabla \phi)^2/2$ is a field kinetic energy. We take into account a ... More

Epitaxially stabilized iron thin films via effective strain relief from stepsMay 22 2016We show a new way to stabilize epitaxial structures against transforming bulk stable phases for Fe thin films on a vicinal Cu(001) surface. Atomically-resolved observations by scanning tunneling microscopy reveal that high-density Cu steps serve as strain ... More

Explanation of the tunneling phenomena between the edges of two lateral quantum Hall systemsOct 22 2002We identify the physics behind the results of recent measurements [W. Kang et al., Nature 403, 59 (2000)] of electron transfer between the edges of two two-dimensional electron systems (2DES). We find that a consistent explanation of all of the observed ... More

Quantum railroads and directed localization at the juncture of quantum Hall systemsAug 31 2002The integer quantum Hall effect (QHE) and one-dimensional Anderson localization (AL) are limiting special cases of a more general phenomenon, directed localization (DL), predicted to occur in disordered one-dimensional wave guides called "quantum railroads" ... More

A Symmetry Property of Momentum Distribution Functions in the Nonequilibrium Steady State of Lattice Thermal ConductionDec 16 2005We study a symmetry property of momentum distribution functions in the steady state of heat conduction. When the equation of motion is symmetric under change of signs for all dynamical variables, the distribution function is also symmetric. This symmetry ... More

Moving-mirror entropySep 05 2000We consider a quantized scalar field in a two-dimensional Minkowski spacetime with a moving mirror and propose a definition of moving-mirror entropy associated with temporarily inaccessible information about the future.

Scattering of Closed String States from a Quantized D-ParticleDec 06 1996Mar 22 1997By developing an appropriate path-integral formalism, we compute, in bosonic string theory, the disk amplitude for the scattering of closed string states from a D-particle, in which the collective coordinate of the D-particle is fully quantized. As a ... More

Universal upper limit on inflation energy scale from cosmic magnetic fieldMay 22 2012Oct 22 2012Recently observational lower bounds on the strength of cosmic magnetic fields were reported, based on gamma-ray flux from distant blazars. If inflation is responsible for the generation of such magnetic fields then the inflation energy scale is bounded ... More

Effects of Light Fields During InflationFeb 27 2010May 06 2010In the inflationary universe, there can be light fields other than the inflaton. We explore a possibility that such light fields source the primordial perturbations, while minimally affecting the inflaton dynamics. We show that during inflation, fluctuations ... More

Noise-Induced Spatial Pattern Formation in Stochastic Reaction-Diffusion SystemsJan 02 2013This paper is concerned with stochastic reaction-diffusion kinetics governed by the reaction-diffusion master equation. Specifically, the primary goal of this paper is to provide a mechanistic basis of Turing pattern formation that is induced by intrinsic ... More