Results for "Teruaki Ikeda"

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Bees with attitude: the effect of gusts on flight dynamicsFeb 10 2018Flight is a complicated task at small scales in part due to the ubiquitous unsteady air which contains it. Flying organisms deal with these difficulties using active and passive control mechanisms to steer their body motion. Body attitudes of flapping ... More
Introduction to twisted Alexander polynomials and related topicsOct 12 2015Jan 16 2016This article is based on the lectures in the Winter Braids V (Pau, Feb. 2015). Main puposel of this is to explain how to compute twisted Alexander polynomials for non-experts.
Some numerical computations on Reidemeister torsion for homology 3-spheres obtained by Dehn surgeries along the figure-eight knotMar 11 2016We show some computations on representations of the fundamental group in SL(2;C) and Reidemeister torsion for a homology 3-sphere obtained by Dehn surgery along the figure-eight knot.
A polynomial defined by the SL(2;C)-Reidemeister torsion for a homology 3-sphere obtained by a Dehn surgery along a (2p,q)-torus knotJun 05 2015Sep 28 2015Let K be a (2p,q)-torus knot and M_n is a 3-manifold obtained by 1/n-Dehn surgery along K. We consider a polynomial whose zeros are the inverses of the Reideimeister torsion of M_n for SL(2;C)-irreducible representations. Johnson gave a formula for the ... More
Exact gravitational lensing by cosmic strings with junctionsJul 28 2008We point out that the results by Brandenberger et al. in Phys.Rev.D77:083502(2008) that the geometry around the straight cosmic strings with stationary junctions is flat to linear order in the string tension can be immediately extended to any order.
Added costs of insect-scale flapping flight in unsteady airflowsOct 28 2016The aerial environment in the operating domain of small-scale natural and artificial flapping wing fliers is highly complex, unsteady and generally turbulent. Considering flapping flight in an unsteady wind environment with a periodically varying lateral ... More
Instanton-noninstanton transition in nonintegrable tunneling processes: A renormalized perturbation approachMar 02 2015The instanton-noninstanton (I-NI) transition in the tunneling process, which has been numerically observed in classically nonintegrable quantum maps, can be described by a perturbation theory based on an integrable Hamiltonian renormalized so as to incorporate ... More
Loop contribution to inflationary magnetic fieldJan 07 2014Within the framework of the standard quantum electrodynamics, we compute contribution of vacuum polarization at one-loop order to the power spectrum of the magnetic field on inflationary (de Sitter) background. It is found that the one-loop term exhibits ... More
Third order equations of motion and the Ostrogradsky instabilityNov 13 2014Apr 15 2015It is known that any nondegenerate Lagrangian containing time derivative terms higher than first order suffers from the Ostrogradsky instability, pathological excitation of positive and negative energy degrees of freedom. We show that, within the framework ... More
Self-accelerating solutions in massive gravity on an isotropic reference metricAug 15 2012Oct 12 2012Within the framework of the recently proposed ghost-free massive gravity, a cosmological constant-type self-accelerating solution has been obtained for Minkowski and de Sitter reference metrics. We ease the assumption on the reference metric and find ... More
A Heuristic Method of Generating Diameter 3 Graphs for Order/Degree ProblemSep 11 2016We propose a heuristic method that generates a graph for order/degree problem. Target graphs of our heuristics have large order (> 4000) and diameter 3. We describe the ob- servation of smaller graphs and basic structure of our heuristics. We also explain ... More
Anisotropic neutrino effect on magnetar spin: constraint on inner toroidal fieldJul 17 2014The ultra-strong magnetic field of magnetars modifies the neutrino cross section due to the parity violation of the weak interaction and can induce asymmetric propagation of neutrinos. Such an anisotropic neutrino radiation transfers not only the linear ... More
SL(2;R)-representations of a Brieskorn homology 3-sphereFeb 24 2016Mar 03 2016We classify SL(2;C)-representations of a Brieskorn homology 3-sphere. We show any irreducible representation into SL(2;C) is conjugate to that into either SU(2) or SL(2;R). We also give a construction of SL(2;R)-representations for a Brieskorn homology ... More
Twisted Alexander polynomials and a partial order on the set of prime knotsApr 05 2009We give a survey of some recent papers by the authors and Masaaki Wada relating the twisted Alexander polynomial with a partial order on the set of prime knots. We also give examples and pose open problems.
Constraining Primordial Magnetic Fields by CMB Photon-Graviton ConversionSep 02 2013We revisit the method of using the photon-graviton conversion mechanism in the presence of the external magnetic field to probe small-scale primordial magnetic fields that may exist between the last scattering surface and present. Specifically, we investigate ... More
Non-Gaussianity from SymmetryApr 02 2008Sep 01 2008We point out that a light scalar field fluctuating around a symmetry-enhaced point can generate large non-Gaussianity in density fluctuations. We name such a particle as an "ungaussiton", a scalar field dominantly produced by the quantum fluctuations,generating ... More
Nucleon described by the chiral soliton in the chiral quark soliton modelJun 23 1997We give a survey of recent development and applications of the chiral quark soliton model (also called the Nambu-Jona-Lasinio soliton model) with $N_f$=2 and $N_f$=3 quark flavors for the structure of baryons. The model is an effective chiral quark model ... More
Non-Gaussianity in the modulated reheating scenarioSep 17 2007Jan 31 2008We investigate the non-Gaussianity of primordial curvature perturbation in the modulated reheating scenario where the primordial perturbation is generated due to the spacial fluctuation of the inflaton decay rate to radiation. We use the $\delta N$ formalism ... More
Curvature perturbation from velocity modulationJul 15 2011Sep 08 2011We propose a new variant model of the modulated reheating. If particles have large scale fluctuations on their velocities, or equivalently their Lorentz factors, the decay rate also fluctuates and the curvature perturbation is induced via their decay ... More
Majorana and Majorana-Weyl fermions in lattice gauge theoryJun 16 2004Aug 11 2004In various dimensional Euclidean lattice gauge theories, we examine a compatibility of the Majorana decomposition and the charge conjugation property of lattice Dirac operators. In $8n$ and $1+8n$ dimensions, we find a difficulty to decompose a classical ... More
Evolution of FLRW spacetime after the birth of a cosmic stringDec 12 2011May 01 2012We consider the evolution of an initially FLRW universe after the formation of a long, straight, cosmic string with arbitrary tension and mass per unit length. The birth of the string sources scalar and tensor-type perturbations in the background metric ... More
Primordial black holes as a novel probe of primordial gravitational waves. II: Detailed analysisMay 15 2016Aug 16 2016Recently we have proposed a novel method to probe primordial gravitational waves from upper bounds on the abundance of primordial black holes (PBHs). When the amplitude of primordial tensor perturbations generated in the early Universe is fairly large, ... More
Primordial black holes as a novel probe of primordial gravitational wavesJun 17 2015May 15 2016We propose a novel method to probe primordial gravitational waves by means of primordial black holes (PBHs). When the amplitude of primordial tensor perturbations on comoving scales much smaller than those relevant to Cosmic Microwave Background is very ... More
Black hole perturbation in parity violating gravitational theoriesJul 19 2011Dec 14 2011We study linear perturbations around the static and spherically symmetric spacetime for the gravitational theories whose Lagrangian depends on Ricci scalar and the parity violating Chern-Simons term. By an explicit construction, we show that Hamiltonian ... More
Statistics of general functions of a Gaussian field -application to non-Gaussianity from preheating-Mar 06 2013May 22 2013We provide a general formula for calculating correlators of arbitrary function of a Gaussian field. This work extends the standard leading-order approximation based on the delta N formalism to the case where truncation of the delta N at some low order ... More
Scalar mode propagation in modified gravity with a scalar fieldJul 30 2009We study the propagation of the scalar modes around a Friedmann-Lemaitre-Robertson-Walker universe for general modifications of gravity in the presence of a real scalar field. In general, there will be two propagating scalar perturbation fields, which ... More
Temporal enhancement of super-horizon curvature perturbations from decays of two curvatons and its cosmological consequencesJun 29 2011Aug 07 2011If more than one curvaton dominate the Universe at different epochs from each other, curvature perturbations can be temporarily enhanced to a value much larger than the observed one 10^{-5}. The traces of the enhancement may be left as higher order correlation ... More
Vacuum structure for scalar cosmological perturbations in Modified Gravity ModelsApr 14 2009Jun 30 2009We have found for the general class of Modified Gravity Models f(R,G) a new instability which can arise in vacuum for the scalar modes of the cosmological perturbations if the background is not de Sitter. In particular, the short-wavelength modes, if ... More
Metric perturbation from inflationary magnetic field and generic bound on inflation modelsApr 18 2012There is an observational indication of extragalactic magnetic fields. No known astrophysical process can explain the origin of such large scale magnetic fields, which motivates us to look for their origin in primordial inflation. By solving the linearized ... More
Linear growth of matter density perturbations in f(R,G) theoriesOct 19 2010May 12 2011We derive the equation of matter density perturbations on sub-horizon scales around a flat Friedmann-Lema\^\i tre-Robertson-Walker background for the general Lagrangian density $f(R,\GB)$ that is a function of a Ricci scalar $R$ and a Gauss-Bonnet term ... More
The decoupling of the glass transitions in the two-component $p$-spin spherical modelMar 21 2016Binary mixtures of large and small particles with disparate size ratio exhibit a rich phenomenology at their glass transition points. In order to gain insights on such systems, we introduce and study a two-component version of the $p$-spin spherical spin ... More
One-dimensional Kac model of dense amorphous hard spheresMay 28 2015We introduce a new model of hard spheres under confinement for the study of the glass and jamming transitions. The model is an one-dimensional chain of the $d$-dimensional boxes each of which contains the same number of hard spheres, and the particles ... More
Lifespan of solutions for the nonlinear Schrödinger equation without gauge invarianceNov 29 2012Dec 06 2012We study the lifespan of solutions for the nonlinear Schr\"odinger equation id_{t}u+{\Delta}u={\lambda}|u|^{p}, (t,x)\in[0,T)\timesR^{n}, with the initial condition, where 1<p\leq 1+2/n and {\lambda}\in C. Our main aim in this paper is to prove an upper ... More
Dressed Quark Propagator at Finite Temperature in the Schwinger-Dyson approach with the Rainbow Approximation - exact numerical solutions and their physical implicationJul 10 2001The Schwinger-Dyson equation for the quark in the rainbow approximation at finite temperature (T) is solved numerically without introducing any ansatz for the dressed quark propagator. The dymanical quark mass-function and the wave-function renormalization ... More
Absence of Quantum Metallic Behavior in Disordered Granular SuperconductorsJul 23 2003We examine the idea, postulated by Phillips et al., that a finite resistivity in $T \to 0$ limit in disordered granular superconducting (SC) films is explained as a consequence of the absence of phase stiffness in a phase glass (PG) peculiar to granular ... More
Fluctuation Effects in Underdoped Cuprate Superconductors under Magnetic FieldMar 11 2002Aug 30 2002Fluctuation effects in underdoped cuprates under high fields are examined by trying to fit theoretical results to resistivity and Nernst data in vortex states. The superconducting (SC) fluctuation in underdoped cuprates includes not only the ordinary ... More
Comment on "Disorder and Quantum Fluctuations in Superconducting Films in Strong Magnetic Fields"Nov 07 2001Sep 03 2002This is a Comment to the paper by Galitski and Larkin in Phys. Rev. Lett. 87 (2001) 087001 (cond-mat/0104247). It is pointed out that their argument that the quantumn glass transition field should be higher than the mean field H_{c2}(0) is incompatible ... More
Josephson Vortex States in Intermediate FieldsOct 10 2001Dec 03 2001Motivated by recent resistance data in high $T_c$ superconductors in fields {\it parallel} to the CuO layers, we address two issues on the Josephson-vortex phase diagram, the appearances of structural transitions on the observed first order transition ... More
Photon stimulated desorption of and nuclear resonant scattering by noble gas atoms at solid surfacesJan 18 2015Apr 20 2015When a noble gas atom approaches a solid surface, it is adsorbed via the Van der Waals force, which is called physisorption. In this thesis, several experimental results concerning physisorbed atoms at surfaces are presented. First, photon stimulated ... More
Lectures on AKSZ Sigma Models for PhysicistsApr 17 2012Apr 13 2016This is an introductory review of topological field theories (TFTs) called AKSZ sigma models. The AKSZ construction is a mathematical formulation for the construction and analyses of a large class of TFTs; it was inspired by the Batalin-Vilkovisky formalism ... More
The varieties of tangent lines to hypersurfaces in projective spacesDec 10 2010For a hypersurface in a projective space, we consider the set of pairs of a point and a line in the projective space such that the line intersects the hypersurface at the point with a fixed multiplicity. We prove that this set of pairs forms a smooth ... More
Pseudogap and Superconductivity in Iron-Based Layered Superconductor studied by Fluctuation-Exchange ApproximationOct 10 2008Oct 23 2008We investigate interplay between magnetic fluctuations and superconductivity in the effective five-band Hubbard model for iron-oxypnictide superconductors on the basis of the fluctuation-exchange approximation. As for the normal-state properties, we find ... More
Quantum Resistive Behaviors in the Vortex Liquid Regimes at Finite TemperaturesOct 29 2002Sep 02 2003Motivated by a {\it mean field-like} resistive behavior in magnetic fields commonly seen in various superconducting (SC) cuprates and organics with strong fluctuation, {\it quantum} SC fluctuation effects on resistive behaviors are reexamined by putting ... More
Ginzburg-Landau Theory of Vortex Phase Diagram in Layered Type II SuperconductorMay 07 2001Recent theoretical understanding of the vortex phase diagram in real layered type II superconductors is briefly described in both cases with fields perpendicular (B \parallel c) and parallel (B \perp c) to the superconducting layers. The description is ... More
Quantum Resistive Transition in Type II Superconductors under Magnetic FieldJun 16 1995It is shown that, within a Ginzburg-Landau (GL) formalism, the superconducting fluctuation is insulating at zero temperature even if the fluctuation dynamics is metallic (dissipative). Based on this fact, the low temperature behavior of the $H_{c2}$-line ... More
Deformation of Batalin-Vilkovisky StructuresApr 07 2006Aug 22 2006A Batalin-Vilkovisky formalism is most general framework to construct consistent quantum field theories. Its mathematical structure is called {\it a Batalin-Vilkovisky structure}. First we explain rather mathematical setting of a Batalin-Vilkovisky formalism. ... More
Stability conditions on $\text{CY}_N$ categories associated to $A_n$-quivers and period mapsMay 21 2014In this paper, we study the space of stability conditions on a certain $N$-Calabi-Yau ($\text{CY}_N$) category associated to an $A_n$-quiver. Recently, Bridgeland and Smith constructed stability conditions on some $\text{CY}_3$ categories from meromorphic ... More
Schubert classes in the equivariant cohomology of the Lagrangian GrassmannianAug 05 2005May 11 2006Let $LG_n$ denote the Lagrangian Grassmannian parametrizing maximal isotropic (Lagrangian) subspaces of a fixed symplectic vector space of dimension $2n.$ For each strict partition $\lambda=(\lambda_1,...,\lambda_k)$ with $\lambda_1\leq n$ there is a ... More
The effect of memory on relaxation in a scalar field theoryJan 09 2004We derive a kinetic equation with a non-Markovian collision term which includes a memory effect, from Kadanoff-Baym equations in $\phi^4$ theory within the three-loop level for the two-particle irreducible (2PI) effective action. The memory effect is ... More
On the functional equation of the Siegel seriesJun 03 2015It is well-known that the Fourier coefficients of Siegel-Eisenstein series can be expressed in terms of the Siegel series. The functional equation of the Siegel series of a quadratic form over $\mathbb{Q}_p$ was first proved by Katsurada. In this paper, ... More
On the Hodge structure of degenerating hypersurfaces in toric varietiesMar 13 2005We introduce an algebraic method for describing the Hodge filtration of degenerating hypersurfaces in projective toric varieties. For this purpose, we show some fundamental properties of logarithmic differential forms on proper equivariant morphisms of ... More
Topological Field Theories and Geometry of Batalin-Vilkovisky AlgebrasSep 05 2002Oct 31 2002The algebraic and geometric structures of deformations are analyzed concerning topological field theories of Schwarz type by means of the Batalin-Vilkovisky formalism. Deformations of the Chern-Simons-BF theory in three dimensions induces the Courant ... More
A Deformation of Three Dimensional BF TheoryOct 12 2000Feb 20 2001We consider a deformation of three dimensional BF theory by means of the antifield BRST formalism. Possible deformations for the action and the gauge symmetries are analyzed. We find a new class of gauge theories which include nonabelian BF theory, higher ... More
How to Solve Quantum Nonlinear Abelian Gauge Theory in Two Dimension in the Heisenberg PictureApr 07 1998The new method based on the operator formalism proposed by Abe and Nakanishi is applied to the quantum nonlinear abelian gauge theory in two dimension. The soluble models in this method are extended to wider class of quantum field theories. We obtain ... More
Anisotropic Strong Coupling Effects on Superfluid 3He in Aerogels - Conventional Spin-Fluctuation Approach -Jan 05 2015Motivated by recent experiments on liquid $^3$He reporting emergence of novel superfluid phases in globally anisotropic aerogels, our previous theory on superfluid $^3$He in globally anisotropic aerogels is extended to incorporate effects of an anisotropy ... More
Stability of vortex state of Fulde-Ferrell-Larkin-Ovchinnikov type in magnetic fields perpendicular to superconducting layersOct 31 2006Motivated by recent NMR data suggesting the presence of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex lattice in magnetic fields perpendicular to the superconducting plane in the heavy-fermion superconductor CeCoIn5, we examine here the stability of ... More
Conductivity in glass phases of disordered granular superconductors in magnetic fieldsJun 20 2006Jun 08 2009The electric conductivities in glass phases of three-dimensional (3D) granular superconductors in magnetic fields are examined based on a quantum disordered Josephson-junction array. A correct inclusion of the Ohmic dissipative dynamics leads to glass ... More
Vortex tilt modulus in Fulde-Ferrell-Larkin-Ovchinnikov stateOct 28 2006Jul 27 2007Vortex tilt response in Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex lattice is theoretically examined as a probe reflecting the spatial structure of this state. In the FFLO state with nodal planes perpendicular to the magnetic field in a quasi 2D material ... More
Comment on "History Effects and Phase Diagram near the Lower Critical Point in YBa_2Cu_3O_{7-δ} Single Crystals"Jan 17 2002This is a Comment on an experimental paper by Zhukov et al. on the issue of a lower critical point, seen only in YBCO clean samples, of the first order transition line implying a vortex liquid-freezing. An explanation with a firm theoretical basis of ... More
The double cover of cubic surfaces branched along their HessianDec 20 2010We prove the relation between the Hodge structure of the double cover of a nonsingular cubic surface branched along its Hessian and the Hodge structure of the triple cover of the ambient projective space branched along the cubic surface. And we introduce ... More
A new construction of the real numbers by alternating seriesAug 07 2012Oct 30 2013We put forward a new method of constructing the complete ordered field of real numbers from the ordered field of rational numbers. Our method is a generalization of that of A. Knopfmacher and J. Knopfmacher. Our result implies that there exist infinitely ... More
Deformation of BF theories, Topological Open Membrane and A Generalization of The Star DeformationMay 29 2001Aug 14 2001We consider a deformation of the BF theory in any dimension by means of the antifield BRST formalism. Possible consistent interaction terms for the action and the gauge symmetries are analyzed and we find a new class of topological gauge theories. Deformations ... More
Two-Dimensional Gravity and Nonlinear Gauge TheoryDec 08 1993We review nonlinear gauge theory and its application to two-dimensional gravity. We construct a gauge theory based on nonlinear Lie algebras, which is an extension of the usual gauge theory based on Lie algebras. It is a new approach to generalization ... More
The Suzaku Discovery of A Hard Power-Law Component in the Spectra of Short Bursts from SGR 0501+4516Jun 24 2011Using data with the Suzaku XIS and HXD, spectral studies of short bursts from the soft gamma repeater SGR 0501+4516 were performed. In total, 32 bursts were detected during the ~60 ks of observation conducted in the 2008 August activity. Excluding the ... More
CMB temperature trispectrum of cosmic stringsNov 06 2009Feb 22 2010We provide an analytical expression for the trispectrum of the Cosmic Microwave Background (CMB) temperature anisotropies induced by cosmic strings. Our result is derived for the small angular scales under the assumption that the temperature anisotropy ... More
The effects of the kaonic cloud on the neutron electric form factorJul 17 1995Mar 11 1997We investigate the effects of mesonic clouds on neutron electric and nucleon strange form factors in the framework of the chiral quark soliton model. We present a mechanism to identify the mesonic clouds and their Yukawa tail in the polarized Dirac sea. ... More
Black hole perturbation in the most general scalar-tensor theory with second-order field equations II: the even-parity sectorFeb 26 2014Nov 18 2014We perform a fully relativistic analysis of even-parity linear perturbations around a static and spherically symmetric solution in the most general scalar-tensor theory with second-order field equations. This paper is a sequel to Kobayashi {\em et al.} ... More
Ultra Slow-Roll Inflation and the non-Gaussianity Consistency RelationNov 01 2012Ultra slow-roll inflation has recently been used to challenge the non-Gaussianity consistency relation. We show that this inflationary scenario belongs to a one parameter class of models and we study its properties and observational predictions. We demonstrate ... More
Efficient diagrammatic computation method for higher order correlation functions of local type primordial curvature perturbationsOct 17 2008Jan 15 2009We present a new efficient method for computing the non-linearity parameters of the higher order correlation functions of local type curvature perturbations in inflation models having a $\cal N$-component scalar field, focusing on the non-Gaussianity ... More
Stability conditions for preprojective algebras and root systems of Kac-Moody Lie algebrasFeb 06 2014The aim of this paper is to study the space of stability conditions on the bounded derived category of nilpotent modules over the preprojective algebra associated with a quiver without loops. We describe this space as a covering space of some open set ... More
High field superconducting phase diagrams including Fulde-Ferrell-Larkin-Ovchinnikov vortex statesJun 03 2007Sep 08 2007Motivated by a striking observation of a Fulde-Ferell-Larkin-Ovchinnikov (FFLO) vortex state in the heavy fermion material CeCoIn5 in fields {\it perpendicular} to the superconducting planes (${\bf H} \parallel c$), superconducting phase diagrams including ... More
Impurity-induced broadening of the transition to a Fulde-Ferrell-Larkin-Ovchinnikov phaseDec 02 2009Mar 04 2010Recent study on doping effects in the heavy fermion superconductor CeCoIn$_5$ has shown that a small amount of doping induces unexpectedly large broadening of the second order transition into the high field and low temperature (HFLT) phase of this material. ... More
Superconducting transition in disordered granular superconductors in magnetic fieldsOct 14 2005Jul 28 2006Motivated by a recent argument that the superconducting (SC) transition field of three-dimensional (3D) disordered superconductors with granular structure in a nonzero magnetic field should lie above $H_{c2}(0)$ in low $T$ limit, the glass transition ... More
Hydrodynamics and Nonlocal Conductivities in Vortex States of Type II SuperconductorsJul 25 1995A hydrodynamical description for vortex states in type II superconductors is presented based on the time-dependent Ginzburg-Landau equation (TDGL). In contrast to the familiar extension of a single vortex dynamics based on the force balance, our description ... More
Hydrodynamics and Nonlocal Conductivities in Vortex StatesFeb 24 1995A hydrodynamical description for vortex states in type II superconductors with no pinning is presented based on the time-dependent GL equation, and the nonlocal conductivities are examined in terms of Kubo formula. Typically, the nonlocal conductivities ... More
Donaldson Invariants and Their Generalizations from AKSZ Topological Field TheoriesApr 12 2011Observable structures of a topological field theory of AKSZ type are analyzed. From a double (or multiple) complex structure of observable algebras, new topological invariants are constructed. Especially, Donaldson polynomial invariants and their generalizations ... More
Chern-Simons Gauge Theory coupled with BF TheoryMar 06 2002Jul 31 2002We couple three-dimensional Chern-Simons gauge theory with BF theory and study deformations of the theory by means of the antifield BRST formalism. We analyze all possible consistent interaction terms for the action under physical requirements and find ... More
Three Dimensional Topological Field Theory induced from Generalized Complex StructureDec 14 2004Mar 21 2005We construct a three-dimensional topological sigma model which is induced from a generalized complex structure on a target generalized complex manifold. This model is constructed from maps from a three-dimensional manifold $X$ to an arbitrary generalized ... More
The Exact Solution of Born-Infeld Theory in Two DimensionJul 03 1997We obtain the exact operator solution of two-dimensional quantum Born-Infeld theory. This theory has a Lagrangian density non-polynomial in the fundamental fields. So this analysis might shed some light on the analysis of non-perturbative effects of field ... More
Reidemeister torsion, twisted Alexander polynomial and fibered knotsNov 11 2003As a generalization of a classical result on the Alexander polynomial for fibered knots, we show in this paper that the Reidemeister torsion associated to a certain representation detects fiberedness of knots in the three sphere.
Quantum Optics in Dispersive and Absorptive MediaApr 11 1998Using microscopic models in which both photons and excitons are treated as microscopic degrees of freedom, we discuss polaritons of two cases: One is the case when excitonic parameters are time dependent. The time dependence causes creation of polaritons ... More
Magneto-reheating constraints from curvature perturbationsFeb 25 2013As additional perturbative degrees of freedom, it is known that magnetic fields of inflationary origin can source curvature perturbations on super-Hubble scales. By requiring the magnetic generated curvature to remain smaller than its inflationary adiabatic ... More
Fully non-linear equivalence of delta N and covariant formalismsJan 16 2012Apr 05 2012We explicitly show the fully non-linear equivalence of the $\delta$N and the covariant formalisms for the superhorizon curvature perturbations, which enables us to safely evaluate the non-Gaussian quantities of the curvature perturbation in either formalism. ... More
Supermassive black holes formed by direct collapse of inflationary perturbationsSep 08 2016We propose a mechanism of producing a new type of primordial perturbations which collapse to primordial black holes whose mass can be as large as necessary for them to grow to the supermassive black holes observed at high redshifts, without contradicting ... More
Testing scenarios of primordial black holes being the seeds of supermassive black holes by ultracompact minihalos and CMB $μ$-distortionsMay 23 2014Oct 16 2014Supermassive black holes and intermediate mass black holes are believed to exist in the Universe. There is no established astrophysical explanation for their origin and considerations have been made in the literature that those massive black holes (MBHs) ... More
Universal instability of hairy black holes in Lovelock-Galileon theories in D dimensionsNov 19 2015Mar 30 2016We analyze spherically symmetric black hole solutions with time-dependent scalar hair in a class of Lovelock-Galileon theories, which are the scalar-tensor theories with second-order field equations in arbitrary dimensions. We first show that known black ... More
Instability of hairy black holes in shift-symmetric Horndeski theoriesOct 26 2015Sep 11 2016Recently it was pointed out that in shift-symmetric scalar-tensor theories a black hole can have nontrivial scalar hair which depends linearly on time. We develop black hole perturbation theory for such solutions and compute the quadratic action of odd-parity ... More
Spontaneous scalarization: asymmetron as dark matterAug 06 2015We propose a new scalar-tensor model which induces significant deviation from general relativity inside dense objects like neutron stars, while passing solar-system and terrestrial experiments, extending a model proposed by Damour and Esposito-Farese. ... More
Fundamental theorem on gauge fixing at the action levelJul 30 2016Regardless of the long history of gauge theories, it is not well-recognized under which condition gauge fixing at the action level is legitimate. We address this issue from the Lagrangian point of view, and prove the following theorem on the relation ... More
A note on the replica liquid theory of binary mixturesSep 27 2016It has been known that the binary replica liquid theory (RLT) is inconsistent with its one-component counterpart; In the limit that all atoms are identical, the configurational entropy and thus the glass transition point calculated by the binary RLT differ ... More
Small data blow-up of L^{2}-solution for the nonlinear Schrödinger equation without gauge invarianceNov 01 2011Sep 25 2012We study the initial value problem for the nonlinear Schr\"odinger equation. We will prove that the blow-up of the L^{2}-norm of solutions with suitable initial data. We impose a condition related to the sign of the data but put no restriction on their ... More
Thermal fluctuations, mechanical response, and hyperuniformity in jammed solidsApr 10 2015Jul 15 2015Jamming is a geometric phase transition occurring in dense particle systems in the absence of temperature. We use computer simulations to analyse the effect of thermal fluctuations on several signatures of the transition. We show that scaling laws for ... More
Maximum Hands-off Control without Normality AssumptionNov 18 2015Maximum hands-off control is a control that has the minimum L0 norm among all feasible controls. It is known that the maximum hands-off (or L0-optimal) control problem is equivalent to the L1-optimal control under the assumption of normality. In this ... More
Antiferromagnetic Order oriented by Fulde-Ferrell-Larkin-Ovchinnikov Superconducting OrderDec 09 2014Mar 09 2015Resolving the high-field superconducting phase (HFSP), often called as the Q-phase, and the antiferromagnetic or spin-density-wave (SDW) order appearing in the phase remains a crucial issue on the superconductor CeCoIn$_5$. It is shown that a switching ... More
Strong-coupling approach to antiferromagnetic ordering driven by paramagnetic pair-breaking in d-wave superconducting phaseSep 18 2013Oct 04 2013The field-induced antiferromagnetic (AFM) ordering in the $d_{x^2-y^2}$-paired superconducting phase, which has been recently found in the weak-coupling approach as a basic mechanism due to the Pauli paramagnetic pair-breaking (PPB) in relation to the ... More
Fluctuation Conductivity in Unconventional Superconductors near Critical DisorderSep 21 2001Sep 23 2001The fluctuation conductivity $\sigma_{\rm s}$ in bulk superconductors with non s-wave pairing and with nonmagnetic disorder of strength $D$ is studied at low $T$ and within the Gaussian approximation. It is shown by assuming a quasi two-dimensional (2D) ... More
Suppression of the vortex glass transition due to correlated defects with a persistent direction perpendicular to an applied magnetic fieldJan 27 2004Apr 13 2004It is found on the basis of the lowest Landau level approach for the Ginzburg-Landau model that, in bulk type II superconductors with strong line disorder directed {\it perpendicularly} to an applied field, the continuous vortex-glass transition is depressed ... More
Fermions in (Anti) de Sitter Gravity in Four DimensionsApr 13 2009May 21 2009Fermions in (anti) de Sitter gravity theory in four dimensions are considered. Especially we propose new fermion actions to derive a Weyl or Majorana fermion action if we break the AdS (dS) group to the Lorentz group in curved spacetime.
QP-Structures of Degree 3 and 4D Topological Field TheoryApr 05 2010Feb 17 2011A A BV algebra and a QP-structure of degree 3 is formulated. A QP-structure of degree 3 gives rise to Lie algebroids up to homotopy and its algebraic and geometric structure is analyzed. A new algebroid is constructed, which derives a new topological ... More