Results for "Fumitaka Nakamura"

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On the Mass of Population III StarsDec 21 1998Performing 1D hydrodynamical calculations coupled with non-equilibrium processes for H2 formation, we pursue the thermal and dynamical evolution of filamentary primordial clouds and attempt to make an estimate on the mass of population III stars. It is ... More
The Stellar IMF in Very Metal-Deficient GasJun 01 2001In the context of the star formation through the fragmentation of an extremely metal-deficient protogalactic cloud, the gravitational collapse of filamentary gas clouds is explored with H$_2$ and HD chemistry. It is found by 1D hydrodynamical simulations ... More
On the Initial Mass Function of Population III StarsOct 23 2000The collapse and fragmentation of filamentary primordial gas clouds are explored using 1D and 2D hydrodynamical simulations coupled with the nonequilibrium processes of H2 formation. The simulations show that depending upon the initial density,there are ... More
The Stellar Initial Mass Function in Primordial GalaxiesJan 30 2002In the context of star formation through fragmentation of an extremely metal-deficient protogalactic cloud, the gravitational collapse of filamentary gas clouds is explored with 1D numerical hydrodynamics coupled with non-equilibrium chemistry of H$_2$ ... More
GMC Collisions as Triggers of Star Formation. VI. Collision-Induced TurbulenceNov 03 2017We investigate collisions between giant molecular clouds (GMCs) as potential generators of their internal turbulence. Using magnetohydrodynamic (MHD) simulations of self-gravitating, magnetized, turbulent, GMCs, we compare kinematic and dynamic properties ... More
Hankel Determinant Solution for Elliptic SequenceNov 25 2014Dec 05 2014We show that the Hankel determinants of a generalized Catalan sequence satisfy the equations of the elliptic sequence. As a consequence, the coordinates of the multiples of an arbitrary point on the elliptic curve are expressed by the Hankel determinants. ... More
Solitons with nested structure over finite fieldsMay 08 2014We propose a solitonic dynamical system over finite fields that may be regarded as an analogue of the box-ball systems. The one-soliton solutions of the system, which have nested structures similar to fractals, are also proved. The solitonic system in ... More
Fragmentation of a Magnetized Filamentary Molecular Cloud Rotating around its AxisMay 09 1994The dynamical instability of a self-gravitating magnetized filamentary cloud was investigated while taking account of rotation around its axis. The filamentary cloud of our model is supported against self-gravity in part by both a magnetic field and rotation. ... More
Near-Infrared Imaging Polarimetry toward M17 SWexJun 28 2019We conducted near-infrared (JHKs) imaging polarimetry toward the infrared dark cloud (IRDC) M17 SWex, including almost all of the IRDC filaments as well as its outskirts, with the polarimeter SIRPOL on the IRSF 1.4 m telescope. We revealed the magnetic ... More
Substellar-Mass Condensations in Prestellar CoresSep 17 2012We present combined Submillimeter-Array (SMA) + single-dish images of the (sub)millimeter dust continuum emission toward two prestellar cores SM1 and B2-N5 in the nearest star cluster forming region, $\rho$ Ophiuchus. Our combined images indicate that ... More
On a Periodic Soliton Cellular AutomatonDec 25 2001We propose a box and ball system with a periodic boundary condition (pBBS). The time evolution rule of the pBBS is represented as a Boolean recurrence formula, an inverse ultradiscretization of which is shown to be equivalent with the algorithm of the ... More
Physical Properties of Dense Cores in the Rho Ophiuchi Main Cloud and A Significant Role of External Pressures in Clustered Star FormationJul 15 2009Jan 19 2010Using the archive data of the H13CO+ (J=1-0) line emission taken with the Nobeyama 45 m radio telescope with a spatial resolution of about 0.01pc, we have identified 68 dense cores in the central dense region of the rho Ophiuchi main cloud. The H13CO+ ... More
High-Resolution Studies of the Multiple-Core Systems toward Cluster-Forming Regions Including Massive StarsJul 14 2008We present the results of C18O observations by the Nobeyama Millimeter Array toward dense clumps with radii of ~ 0.3 pc in six cluster-forming regions including massive (proto)stars. We identified 171 cores, whose radius, line width, and molecular mass ... More
Cloud-cloud collision in the DR 21 cloud as a trigger of massive star formationMay 17 2019We report on a possible cloud-cloud collision in the DR 21 region, which we found through molecular observations with the Nobeyama 45-m telescope. We mapped an area of 8'x12' around the region with twenty molecular lines including the 12CO(J=1-0) and ... More
Filamentary Accretion Flows in the Infrared Dark Cloud G14.225-0.506 Revealed by ALMAMar 11 2019Filaments are ubiquitous structures in molecular clouds and play an important role in the mass assembly of stars. We present results of dynamical stability analyses for filaments in the infrared dark cloud G14.225$-$0.506, where a delayed onset of massive ... More
Discovery of Infalling Motion with Rotation of the Cluster-Forming Clump S235AB and Its Implication to the Clump StructuresOct 04 2016We report the discovery of infalling motion with rotation of S235AB the massive cluster-forming clump (~10^3 Mo) in the S235 region. Our C18O observations with the 45m telescope at the Nobeyama Radio Observatory have revealed the elliptical shape of the ... More
Low-Mass Star Formation, Triggered by Supernova in Primordial CloudsDec 13 2004The evolution of a gas shell, swept by the supernova remnant of a massive first generation star, is studied with H_2 and HD chemistry taken into account. When a first-generation star explodes as a supernova, H_2 and HD molecules are formed in the swept ... More
Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming ClumpsAug 28 2009(Abridged) We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using Enzo-based MHD simulations with accreting sink particles and effective resolution $2048^3$. ... More
Wide-Field $^{12}$CO ($J=2-1$) and $^{13}$CO ($J=2-1$) Observations toward the Aquila Rift and Serpens Molecular Cloud Complexes. I. Molecular Clouds and Their Physical PropertiesFeb 06 2017We present results of wide-field $^{12}$CO ($J = 2 - 1$) and $^{13}$CO ($J = 2 - 1$) observations toward the Aquila Rift and Serpens molecular cloud complexes (25$^\circ < l < 33^\circ$ and $1^\circ < b < 6^\circ$) at an angular resolution of 3$'$.4 ($\approx$ ... More
Lowering the Characteristic Mass of Cluster Stars by Magnetic Fields and Outflow FeedbackAug 02 2010Magnetic fields are generally expected to increase the characteristic mass of stars formed in stellar clusters, because they tend to increase the effective Jeans mass. We test this expectation using adaptive mesh refinement (AMR) magnetohydrodynamic simulations ... More
A Statistical Study of Massive Cluster-Forming ClumpsFeb 02 2018We report results of the observations of 15 regions in several molecular lines for a statistical study of massive cluster-forming clumps. We identified 24 clumps based on the C18O (J=1-0) data obtained by the NRO 45 m telescope, and found that 16 of them ... More
Cluster formation in the W40 and Serpens South complex triggered by the expanding HII regionSep 26 2018We present results of the mapping observations covering a large area of 1 square degree around W40 and Serpens South carried out in the 12CO (J=1-0), 13CO (J=1-0), C18O (J=1-0), CCS (J_{N}=8_{7}-7_{6}), and N_2H+ (J=1-0) emission lines with the 45 m Nobeyama ... More
Magnetic Flux Expulsion in Star FormationMay 28 2011Stars form in dense cores of magnetized molecular clouds. If the magnetic flux threading the cores is dragged into the stars, the stellar field would be orders of magnitude stronger than observed. This well-known "magnetic flux problem" demands that most ... More
Protostellar Disk Formation Enabled by Removal of Small Dust GrainsFeb 08 2016It has been shown that a realistic level of magnetization of dense molecular cloud cores can suppress the formation of a rotationally supported disk (RSD) through catastrophic magnetic braking in the axisymmetric ideal MHD limit. In this study, we present ... More
GMC Collisions as Triggers of Star Formation. V. Observational SignaturesJun 21 2017Oct 17 2017We present calculations of molecular, atomic and ionic line emission from simulations of giant molecular cloud (GMC) collisions. We post-process snapshots of the magneto-hydrodynamical simulations presented in an earlier paper in this series by Wu et ... More
Defect Energy with Conjugate Boundary Conditions in Spin Glass Models in Two DimensionsJun 29 1998We calculate the naive defect energy $\Delta E$ of Ising spin glass(SG) models in two dimensions using conjugate boundary conditions. We predict that, in the $\pm J$ model, the averaged value $\bar{\Delta E}$ converges to some non-zero value in the thermodynamic ... More
GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized SimulationsJun 04 2016Nov 29 2016We investigate giant molecular cloud (GMCs) collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of three dimensional, ... More
Interferometric Observations of Cyanopolyynes toward the G28.28-0.36 High-Mass Star-Forming RegionAug 25 2018We have carried out interferometric observations of cyanopolyynes, HC$_{3}$N, HC$_{5}$N, and HC$_{7}$N, in the 36 GHz band toward the G28.28$-$0.36 high-mass star-forming region using the Karl G. Jansky Very Large Array (VLA) Ka-band receiver. The spatial ... More
Discovery of CCS Velocity-Coherent Substructures in the Taurus Molecular Cloud 1May 29 2019We present the results of mapping observations toward a nearby starless filamentary cloud, the Taurus Molecular Cloud 1 (TMC-1), in the CCS(JN=43-32, 45.379033 GHz) emission line, using the Nobeyama 45-m telescope. The map shows that the TMC-1 filament ... More
Dense Clumps and Candidates for Molecular Outflows in W40May 11 2015May 12 2015We report results of the CO(J=3-2) and HCO+(J=4-3) observations of the W40 HII region with the ASTE 10 m telescope (HPBW~22 arcsec) to search for molecular outflows and dense clumps.We found that the velocity field in the region is highly complex, consisting ... More
Implication of Formation Mechanisms of HC5N in TMC-1 as Studied by 13C Isotopic FractionationDec 17 2015We observed the J = 9-8 and 16-15 rotational transitions of the normal species and five 13C isotopologues of HC5N to study its formation mechanisms toward the cyanopolyyne peak in Taurus Molecular Cloud-1, with the 45-m radio telescope of Nobeyama Radio ... More
GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star FormationFeb 27 2017Apr 26 2017We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. We further develop our three dimensional magnetized, turbulent, colliding GMC simulations by implementing star formation sub-grid models. Two such models ... More
On the Hydrodynamic Interaction of Shock Waves with Interstellar Clouds. II. The Effect of Smooth Cloud Boundaries on Cloud Destruction and Cloud TurbulenceNov 01 2005The effect of smooth cloud boundaries on the interaction of steady planar shock waves with interstellar clouds is studied using a high-resolution local AMR technique with a second-order accurate axisymmetric Godunov hydrodynamic scheme. A 3D calculation ... More
GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized SimulationsJun 04 2016We investigate giant molecular cloud (GMCs) collisions and their ability to induce gravitational instability and thus star formation. This mechanism may be a major driver of star formation activity in galactic disks. We carry out a series of three dimensional, ... More
A survey of molecular cores in M17 SWexMay 20 2019A survey of molecular cores covering the infrared dark cloud known as the M17 southwest extension (M17 SWex) has been carried out with the 45 m Nobeyama Radio Telescope. Based on the N2H+ (J= 1-0) data obtained, we have identified 46 individual cores ... More
Interaction between Northern Coal Sack in the Cyg OB 7 cloud complex and the multiple super nova remnants including HB 21May 17 2019We report possible interaction between multiple super nova remnants (SNRs) and Northern Coal Sack (NCS) which is a massive clump (~1000 Mo) in the Cyg OB 7 cloud complex and is forming a massive Class 0 object. We performed molecular observations of the ... More
Magnetic stability of massive star forming clumps in RCW 106Apr 12 2019Apr 16 2019The RCW 106 molecular cloud complex is an active massive star-forming region where a ministarburst is taking place. We examined its magnetic structure by near-IR polarimetric observations with the imaging polarimeter SIRPOL on the IRSF 1.4 m telescope. ... More
The Deuterium Fraction in Massive Starless Cores and Dynamical ImplicationsSep 29 2015May 08 2016We study deuterium fractionation in two massive starless/early-stage cores C1-N and C1-S in Infrared Dark Cloud (IRDC) G028.37+00.07, first identified by Tan et al. (2013) with ALMA. Line emission from multiple transitions of $\rm N_2H^+$ and $\rm N_2D^+$ ... More
Software Polarization Spectrometer "PolariS"Dec 03 2014We have developed a software-based polarization spectrometer, PolariS, to acquire full-Stokes spectra with a very high spectral resolution of 61 Hz. The primary aim of PolariS is to measure the magnetic fields in dense star-forming cores by detecting ... More
Magnetic stability of massive star forming clumps in RCW 106Apr 12 2019The RCW~106 molecular cloud complex is an active massive star-forming region where a ministarburst is taking place. We examined its magnetic structure by near-IR polarimetric observations with the imaging polarimeter SIRPOL on the IRSF 1.4 m telescope. ... More
The Dynamical State of The Serpens South Filamentary Infrared Dark CloudSep 10 2013We present the results of N$_2$H$^+$ ($J=1-0$) observations toward Serpens South, the nearest cluster-forming, infrared dark cloud. The physical quantities are derived by fitting the hyperfine structure of N$_2$H$^+$. The Herschel and 1.1-mm continuum ... More
Near-Infrared Imaging Polarimetry of the Serpens Cloud Core: Magnetic Field Structure, Outflows, and Inflows in A Cluster Forming ClumpApr 20 2010We made deep NIR imaging polarimetry toward the Serpens cloud core. The polarization vector maps enable us to newly detect 24 small IR reflection nebulae with YSOs. Polarization measurements of NIR point sources indicate an hourglass-shaped magnetic field, ... More
Expanding CO Shells in the Orion A Molecular CloudJun 05 2018We present the discovery of expanding spherical shells around low to intermediate-mass young stars in the Orion A giant molecular cloud using observations of $^{12}$CO (1-0) and $^{13}$CO (1-0) from the Nobeyama Radio Observatory 45-meter telescope. The ... More
Dense core properties in the Infrared Dark cloud G14.225-0.506 revealed by ALMAOct 27 2016We have performed a dense core survey toward the Infrared Dark Cloud G14.225-0.506 at 3 mm continuum emission with the Atacama Large Millimeter/Submillimeter Array (ALMA). This survey covers the two hub-filament systems with an angular resolution of $\sim3$\arcsec ... More
Emergence of magnetism and controlling factors of superconductivity in Li/Na-ammonia co-intercalated FeSe1-zTezJun 14 2014Dec 06 2014The discovery of superconductivity in alkali-ammonia co-intercalated FeSe has generated intensive interest because of their highest Tc (~ 45 K) among iron-chalcogenide superconductors with bulk form. Here, we report the phase diagrams of two series of ... More
Uniform Magnetic Order in a Ferromagnetic-Antiferromagnetic Random Alternating Quantum Spin ChainFeb 16 2004An $S=1/2$ ferromagnetic (F) - antiferromagnetic (AF) random alternating Heisenberg quantum spin chain model is investigated in connection to its realization compound: (CH$_3$)$_2$CHNH$_3$Cu(Cl$_x$Br$_{1-x}$)$_3$. The exchange interaction bonds have alternating ... More
Vanishing of the negative-sign problem of quantum Monte Carlo simulations in one-dimensional frustrated spin systemsJul 02 1997The negative-sign problem in one-dimensional frustrated quantum spin systems is solved. We can remove negative signs of the local Boltzmann weights by using a dimer basis that has the spin-reversal symmetry. Validity of this new basis is checked in a ... More
A generalization of Kato's local epsilon-conjecture for (phi,Gamma)-modules over the Robba ringMay 04 2013Feb 15 2015The aim of this article is to generalize Kato's (commutative) p-adic local epsilon-conjecture [Ka93b] for families of (phi,Gamma)-modules over the Robba ring. In particular, we prove the generalized local epsilon-conjecture for rank one (phi,Gamma)-modules, ... More
Decomposition of linear metric perturbations on generic background spacetime -- Toward higher-order general-relativistic gauge-invariant perturbation theoryJan 06 2011The decomposition of the linear-order metric perturbation is discussed in the context of the higher-order gauge-invariant perturbation theory. We show that the linear order metric perturbation is decomposed into gauge-invariant and gauge-variant parts ... More
Construction of gauge-invariant variables for linear-order metric perturbations on some background spacetimesDec 07 2010Gauge-invariant treatments of general-relativistic higher-order perturbations on generic background spacetime is proposed. We show the fact that the linear-order metric perturbation is decomposed into gauge-invariant and gauge-variant parts, which was ... More
Second-order Gauge-invariant Cosmological Perturbation Theory: Current StatusJan 15 2010Dec 10 2010The current status of the recent developments of the second-order gauge-invariant cosmological perturbation theory is reviewed. To show the essence of this perturbation theory, we concentrate only on the universe filled with a single scalar field. Through ... More
Consistency of Equations in the Second-order Gauge-invariant Cosmological Perturbation TheoryDec 29 2008Jan 03 2009Along the general framework of the gauge-invariant perturbation theory developed in the papers [K. Nakamura, Prog. Theor. Phys. {\bf 110} (2003), 723; {\it ibid}, {\bf 113} (2005), 481.], we re-derive the second-order Einstein equations on four-dimensional ... More
Initial condition of a thick loop cosmic string and linear perturbationsJan 17 2001Jan 07 2002The initial data of the gravitational field produced by a loop thick string is considered. We show that a thick loop is not a geodesic on the initial hypersurface, while a loop conical singularity is. This suggests that there is the ``{\it critical thickness}'' ... More
Alternative Approach to Noncommutative Quantum Mechanics on a Curved SpaceDec 01 2015Oct 05 2016Starting with the first-order singular Lagrangian containing the redundant variables, the noncommutative quantum mechanics on a curved space is investigated by the constraint star-product quantization formalism of the projection operator method. Imposing ... More
Noncommutative Quantum Mechanics on a Curved SpaceMar 23 2015Starting with the first-order singular Lagrangian, the canonical structures of the noncommutative quantum system on a submanifold embedded in the higher-dimensional Euclidean space are investigated with the projection operator method (POM) and the Dirac-bracket ... More
Canonical Structure of Noncommutative Quantum Mechanics as Constraint SystemFeb 10 2014Dec 23 2014Starting with the first-order singular Lagrangian, the canonical structure in the noncommutative quantum mechanics with the noncommutativities both of coordinates and momenta is investgated. Using the projection operator method (POM) for the constraint ... More
Polarisations of the $Z$ and $W$ bosons in the processes $pp \to ZH$ and $pp \to W^{\pm}_{}H$Jun 06 2017Nov 21 2017The $Z$ boson in the process $pp \to ZH$ and the $W^+_{}$ and $W^-_{}$ in the process $pp \to W^{\pm}_{}H$ can be in polarised states. The polarisation density matrix of the $Z$ ($W$) boson contains the complete information about a state of polarisation ... More
Simplifying branched covering surface-knots by chart moves involving black verticesSep 21 2017Apr 12 2018A branched covering surface-knot is a surface-knot in the form of a branched covering over an oriented surface-knot $F$, where we include the case when the covering has no branch points. A branched covering surface-knot is presented by a graph called ... More
Surface links which are coverings over the standard torusMay 01 2009Feb 12 2011We introduce a new construction of a surface link in the 4-space. We construct a surface link as a branched covering over the standard torus, which we call a torus-covering link. We show that a certain torus-covering $T^2$-link is equivalent to the split ... More
Simplifying branched covering surface-knots by an addition of 1-handles with chart loopsJul 25 2017Feb 27 2018A branched covering surface-knot over an oriented surface-knot $F$ is a surface-knot in the form of a branched covering over $F$. A branched covering surface-knot over $F$ is presented by a graph called a chart on a surface diagram of $F$. For a branched ... More
Simple proof of the functional relation for the Lerch type Tornheim double zeta functionDec 06 2010Dec 07 2010In this paper, we give a simple proof of the functional relation for the Lerch type Tornheim double zeta function. By using it, we obtain simple proofs of some explicit evaluation formulas for double $L$-values.
Large-time behavior of the $H^{-m}$-gradient flow of length for closed plane curvesMay 15 2019We consider the $H^{-m}$-gradient flow of length for closed plane curves. This flow is a generalization of curve diffusion flow. We investigate the large-time behavior assuming the global existence of the flow. Then we show that the evolving curve converges ... More
Real zeros of Hurwitz-Lerch zeta functions in the interval $(-1,0)$Dec 01 2015For $0 < a \le 1$, $s,z \in {\mathbb{C}}$ and $0 < |z|\le 1$, the Hurwitz-Lerch zeta function is defined by $\Phi (s,a,z) := \sum_{n=0}^\infty z^n(n+a)^{-s}$ when $\sigma :=\Re (s) >1$. In this paper, we show that $\Phi (\sigma,a,z) \ne 0$ when $\sigma ... More
Triple linking numbers and triple point numbers of certain $T^2$-linksFeb 18 2011Feb 14 2012The triple linking number of an oriented surface link was defined as an analogical notion of the linking number of a classical link. We consider a certain $m$-component $T^2$-link ($m \geq 3$) determined from two commutative pure $m$-braids $a$ and $b$. ... More
Invitation to higher local fields, Part I, section 4: Cohomological symbol for henselian discrete valuation fields of mixed characteristicDec 18 2000This is a sketch of main steps of the proof of Bloch--Kato's theorem which states that the norm residue homomorphism K_q(K)/m\to H^q(K,\Bbb Z/m(q)) is an isomorphism for a henselian discrete valuation field K of characteristic 0 with residue field of ... More
A compactification of the moduli scheme of abelian varietiesJul 23 2001We construct a canonical compactification $SQ^{toric}_{g,K}$ of the moduli of abelian varieties over $Z[\zeta_N, 1/N]$ where $\zeta_N$ is a primitive $N$-th root of unity. This is very similar to, but slightly diferent from the compactification constructed ... More
Hessian of the Ricci Calabi functionalJan 08 2018The Ricci Calabi functional is a functional on the space of K\"ahler metrics of Fano manifolds. Its critical points are called generalized K\"ahler Einstein metrics. In this article, we show that the Hessian of the Ricci Calabi functional is non-negative ... More
Negative Differential Resistivity from HolographyJun 21 2010Sep 16 2011Negative differential resistivity (NDR) in a (3+1)-dimensional quantum system of strongly correlated charge carriers is theoretically reproduced by using the AdS/CFT correspondence. Our system is microscopically defined, and the analysis does not rely ... More
Comments on Chemical Potentials in AdS/CFTNov 10 2007Dec 30 2008We propose a method for identifying holographic chemical potentials of conserved charges. The guiding principle is the consistency of the identification with the thermodynamic relations and the Legendre transformation. We consider the baryon-charge chemical ... More
Fox reimbedding and Bing submanifoldsFeb 18 2012Dec 28 2012Let M be an orientable closed connected 3-manifold. We introduce the notion of amalgamated Heegaard genus of M with respect to a closed separating 2-manifold F, and use it to show that the following two statements are equivalent: (i) a compact connected ... More
Supramolecule Structure for Amphiphilic Molecule by Dissipative Particle Dynamics SimulationApr 12 2006Meso-scale simulation of structure formation for AB-dimers in solution W monomers was performed by dissipative particle dynamics (DPD) algorithm. As a simulation model, modified Jury Model was adopted Jury, S. et al. "Simulation of amphiphilic mesophases ... More
A Rohlin Type Theorem for Automorphisms of Certain Purely Infinite $C^{\ast}$-AlgebrasDec 22 1997We show a noncommutative Rohlin type theorem for automorphisms of a certain class of purely infinite simple $C^{\ast}$-algebras. This class consists of the purely infinite unital simple $C^{\ast}$-algebras which are in the bootstrap category ${\cal N}$ ... More
A simple proof of the generalized strong recurrence for any non-zero parameterJun 16 2010Sep 22 2010The strong recurrence is equivalent to the Riemann hypothesis. In the present paper, we give a simple proof of the generalized strong recurrence for all non-zero parameters.
The generalized strong recurrence for non-zero rational parametersJun 09 2010The strong recurrence is equivalent to the Riemann hypothesis. On the other hand, the generalized strong recurrence holds for any irrational number. In this paper, we show the generalized strong recurrence for all non-zero rational numbers. Moreover, ... More
Efficient Monte Carlo algorithm in quasi-one-dimensional Ising spin systemsSep 17 2008We have developed an efficient Monte Carlo algorithm, which accelerates slow Monte Carlo dynamics in quasi-one-dimensional Ising spin systems. The loop algorithm of the quantum Monte Carlo method is applied to the classical spin models with highly anisotropic ... More
Off-axis Emission from the Beamed Afterglow of Gamma Ray Bursts and a Possible Interpretation of Slowly Declining X-Ray Afterglow of GRB980425Jul 16 1999A formula for off-axis emissions from the beamed afterglow of GRBs in a synchrotron model is derived. The formula is applied to an inhomogeneous circumstellar matter obeying n proportional to 1/r**2 suggested for SN1998bw/GRB980425. The slow decline rate ... More
Iwasawa theory of de Rham (φ,Γ)-modules over the Robba ringsJan 31 2012Dec 02 2012The aim of this article is to study Bloch-Kato's exponential map and Perrin-Riou's "big" exponential map purely in terms of (\phi,\Gamma)-modules over the Robba ring. We first generalize the definition of Bloch-Kato's exponential map for all the (\phi,\Gamma)-modules ... More
Short note on construction of gauge-invariant variables of linear metric perturbations on an arbitrary background spacetimeDec 05 2011An outline of a proof of the decomposition of linear metric perturbations into gauge-invariant and gauge-variant parts on an arbitrary background spacetime which admits ADM decomposition is briefly discussed. We explicitly construct the gauge-invariant ... More
Alternative construction of gauge-invariant variables for linear metric perturbation on general background spacetimeMar 16 2011Construction of the gauge-invariant variables for the linear metric perturbation, which was proposed in the paper [K. Nakamura, arXiv:1101.1147], is discussed through an alternative approach. Our starting point of the construction of the gauge-invariant ... More
General formulation of general-relativistic higher-order gauge-invariant perturbation theoryNov 24 2010Feb 02 2011Gauge-invariant treatments of general-relativistic higher-order perturbations on generic background spacetime is proposed. After reviewing the general framework of the second-order gauge-invariant perturbation theory, we show the fact that the linear-order ... More
The girth alternative for mapping class groupsMay 26 2011The girth of a finitely generated group G is the supremum of the girth of Cayley graphs for G over all finite generating sets. Let G be a finitely generated subgroup of the mapping class group Mod(S), where S is a compact orientable surface. Then, either ... More
Consistency of Equations for the Single Scalar Field Case in Second-order Gauge-invariant Cosmological Perturbation TheoryJan 25 2010We derived the second-order perturbations of the Einstein equations and the Klein-Gordon equation for a generic situation in terms of gauge-invariant variables. The consistency of all the equations is confirmed. This confirmation implies that all the ... More
Does a Nambu-Goto wall emit gravitational waves? -- Cylindrical Nambu-Goto wall as an example of gravitating non-spherical walls --May 08 2002Jul 26 2002Gravitational field of a cylindrical Nambu-Goto wall in the vacuum spacetime is considered in order to clarify the interaction between Nambu-Goto membranes and gravitational waves. If one neglects the emission of gravitational waves by the wall motion, ... More
On the derivation of several second order partial differential equations from a generalization of the Einstein equationMar 15 2016A generalization of the Einstein equation is considered for complex line elements. Several second order semilinear partial differential equations are derived from it as semilinear field equations in uniform and isotropic spaces. The nonrelativistic limits ... More
Mechanism of CDW-SDW Transition in One DimensionMar 15 1999The phase transition between charge- and spin-density-wave (CDW, SDW) phases is studied in the one-dimensional extended Hubbard model at half-filling. We discuss whether the transition can be described by the Gaussian and the spin-gap transitions under ... More
Tricritical Behavior in the Extended Hubbard ChainsSep 20 1999Jul 16 2000Phase diagrams of the one-dimensional extended Hubbard model (including nearest-neighbor interaction $V$) at half- and quarter-filling are studied by observing level crossings of excitation spectra using the exact diagonalization. This method is based ... More
Hurwitz-Lerch zeta and Hurwitz-Lerch type of Euler-Zagier double zeta distributionsMay 08 2014Sep 16 2015In this paper, we give Hurwitz-Lerch zeta distributions with $0 < \sigma \ne 1$ by using the Gamma function. Moreover, we define Hurwitz-Lerch type of Euler-Zagier double zeta distributions not only in the region of absolute convergence but also the outside ... More
Unknotting numbers and triple point cancelling numbers of torus-covering knotsJun 06 2012Feb 10 2013It is known that any surface knot can be transformed to an unknotted surface knot or a surface knot which has a diagram with no triple points by a finite number of 1-handle additions. The minimum number of such 1-handles is called the unknotting number ... More
H-functional and Matsushima type decomposition theoremMay 14 2019The H-functional characterizes K\"ahler-Ricci solitons as its critical points, and also plays an important role of the existence problem for K\"ahler-Einstein metrics. In this paper we prove the Hessian formula for the H-functional at its critical points, ... More
On semi-continuity problems for minimal log discrepanciesMay 07 2013Jul 19 2014We show the semi-continuity property of minimal log discrepancies for varieties which have a crepant resolution in the category of Deligne-Mumford stacks. Using this property, we also prove the ideal-adic semi-continuity problem for toric pairs.
Surface links with free abelian link groupsNov 22 2009Sep 25 2012It is known that if a classical link group is a free abelian group, then its rank is at most two. It is also known that a $k$-component 2-link group ($k>1$) is not free abelian. In this paper, we give examples of $T^2$-links each of whose link groups ... More
H-functional and Matsushima type decomposition theoremMay 14 2019May 17 2019The H-functional characterizes K\"ahler-Ricci solitons as its critical points, and also plays an important role of the existence problem for K\"ahler-Einstein metrics. In this paper we prove the Hessian formula for the H-functional at its critical points, ... More
Closed-string Tachyon Condensation and the On-shell Effective Action of Open-string TachyonsMay 07 2001Dec 12 2001We study how the effect of closed-string tachyon condensation can enter into the on-shell effective action of open-string tachyons in the bosonic case. We also consider open-string one-loop quantum corrections to the on-shell action. We use a sigma-model ... More
The local-global principle for integral bends in orthoplicial Apollonian sphere packingsJan 13 2014We introduce an orthoplicial Apollonian sphere packing, which is a sphere packing obtained by successively inverting a configuration of 8 spheres with 4-orthplicial tangency graph. We will show that there are such packings in which the bends of all constituent ... More
A Remark on the Mourre Theory for Two Body Schrödinger operatorsMay 21 2013May 31 2013On this short note, we apply the Mourre theory of the limiting absorption with {\it difference} type conditions on the potential, instead of conditions on the derivatives. In order that we modify the definition of the conjugate operator, and we apply ... More
The deformations of symplectic structures by moment mapsMay 09 2016We study deformations of symplectic structures on a smooth manifold $M$ via the quasi-Poisson theory. By a fact, we can deform a given symplectic structure $\omega $ to a new symplectic structure $\omega_t$ parametrized by some element $t$ in $\Lambda^2\mathfrak{g}$, ... More
The Rohlin Property for Actions of $Z^{2}$ on UHF AlgebrasOct 09 1996Dec 22 1997We define a Rohlin property for actions of $Z^{2}$ on UHF algebras and show a noncommutative Rohlin type theorem. Among those actions with the Rohlin property, we classify product type actions up to outer conjugacy. In particular we present two classes ... More
Smoothability of Z\times Z-actions on 4-manifoldsFeb 18 2009Nov 24 2009We construct a nonsmoothable Z\times Z-action on the connected sum of an Enriques surface and S^2\times S^2, such that each of generators is smoothable. We also construct a nonsmoothable self-homeomorphism on an Enriques surface.
Bauer-Furuta invariants under Z_2-actionsMay 11 2007Apr 28 2008S.Bauer and M.Furuta defined a stable cohomotopy refinement of the Seiberg-Witten invariants. In this paper, we prove a vanishing theorem of Bauer-Furuta invariants for 4-manifolds with smooth Z/2-actions. As an application, we give a constraint on smooth ... More
Hom-Poisson-Nijenhuis structures on Hom-Lie algebroids and Hom-Dirac structures on Hom-Courant algebroidsJul 11 2019In this paper, we develop the theory of Hom-Lie algebroids, Hom-Lie bialgebroids and Hom-Courant algebroids introduced by Cai, Liu and Sheng. Specifically, we introduce the notions of Hom-Poisson, Hom-Nijenhuis and Hom-Poisson-Nijenhuis structures on ... More