Results for "Hiroyuki Hirashita"

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Effects of grain growth mechanisms on the extinction curve and the metal depletion in the interstellar mediumOct 17 2013Dust grains grow their sizes in the interstellar clouds (especially in molecular clouds) by accretion and coagulation. Here we model and test these processes by examining the consistency with the observed variation of the extinction curves in the Milky ... More
Importance of far-infrared mapping in a spiral galaxy: AKARI observation of M81Oct 07 2010Oct 25 2010The importance of the far-infrared (FIR) mapping is demonstrated for a face-on spiral galaxy, M81, by analyzing its imaging data at 65, 90, and 140 {\mu}m taken by AKARI. Basic products are the dust temperature map, the dust optical depth map, and the ... More
Search for high column density systems with gamma ray burstsMar 17 2006We investigate the possibility to search for metal-poor high column density (> 10^{23} cm^{-2}) clouds at high redshift (z) by using gamma ray burst (GRB) afterglows. Such clouds could be related to primeval galaxies which may cause a burst of star formation. ... More
Mass-Metallicity Relation for the Local Group Dwarf Spheroidal Galaxies: A New Picture for the Chemical Enrichment of Galaxies in the Lowest Mass RangeApr 28 2001The virial mass ($M_{\rm vir}$)-metallicity relation among the Local Group dwarf spheroidal galaxies (dSphs) is examined. Hirashita, Takeuchi, & Tamura showed that the dSphs can be divided into two distinct classes with respect to the relation between ... More
Shattering by turbulence as a production source of very small grainsJun 11 2010The origin of grain size distribution in the interstellar medium is one of the most fundamental problems in the interstellar physics. In the Milky Way, smaller grains are more abundant in number, but their origins are not necessarily specified and quantified. ... More
Dust processing in elliptical galaxiesSep 14 2015We reconsider the origin and processing of dust in elliptical galaxies. We theoretically formulate the evolution of grain size distribution, taking into account dust supply from asymptotic giant branch (AGB) stars and dust destruction by sputtering in ... More
Central free-free-dominated 880 $\micron$ emission in II Zw 40Jul 29 2011The central star-forming region in a blue compact dwarf galaxy, II Zw 40, was observed in the 340 GHz ($880 \micron$) band at $\sim 5$ arcsec (250 pc) resolution with the Submillimetre Array (SMA). A source associated with the central star-forming complex ... More
Evolution of grain size distribution in high-redshift dusty quasars: Integrating large amounts of dust and unusual extinction curvesOct 29 2014The discoveries of huge amounts of dust and unusual extinction curves in high-redshift quasars (z > 4) cast challenging issues on the origin and properties of dust in the early universe. In this Letter, we investigate the evolutions of dust content and ... More
Two-size approximation: a simple way of treating the evolution of grain size distribution in galaxiesDec 12 2014Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy. In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing ... More
Dust Cooling in Supernova Remnants in the Large Magellanic CloudJun 26 2015The infrared-to-X-ray (IRX) flux ratio traces the relative importance of dust cooling to gas cooling in astrophysical plasma such as supernova remnants (SNRs). We derive IRX ratios of SNRs in the LMC using Spitzer and Chandra SNR survey data and compare ... More
Dust growth in the interstellar medium: How do accretion and coagulation interplay?Feb 07 2012Dust grains grow in interstellar clouds by accretion and coagulation. In this paper, we focus on these two grain growth processes and numerically investigate how they interplay to increase the grain radii. We show that accretion efficiently depletes grains ... More
Evolution of the extinction curves in galaxiesJan 28 2014We investigate the evolution of extinction curves in galaxies based on our evolution model of grain size distribution. In this model, we considered various processes: dust formation by SNe II and AGB stars, dust destruction by SN shocks in the ISM, metal ... More
What determines the grain size distribution in galaxies?Mar 22 2013We construct a dust evolution model taking into account the grain size distribution, and investigate what kind of dust processes determine the grain size distribution at each stage of galaxy evolution. In addition to the dust production by type II supernovae ... More
Extinction curves flattened by reverse shocks in supernovaeJan 17 2008We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). Since at high redshift (z>5), low-mass stars cannot be dominant sources for dust grains, SNe ... More
Properties of free-free, dust, and CO emissions in the starbursts of blue compact dwarf galaxiesDec 16 2012The central star-forming regions in three blue compact dwarf galaxies (He 2-10, NGC 5253, and II Zw 40) were observed in the 340 GHz (880 micron) band at 5 arcsec resolution with the Submillimetre Array (SMA). Continuum emission associated with the central ... More
Dust coagulation in star formation with different metallicitiesJul 17 2009Dust grains coagulate into larger aggregates in dense gas. This changes their size distribution and possibly affects the thermal evolution of star-forming clouds. We here investigate dust coagulation in collapsing pre-stellar cores with different metallicities ... More
Evolution of dust grain size distribution by shattering in the interstellar medium: robustness and uncertaintyMar 16 2013Shattering of dust grains in the interstellar medium is a viable mechanism of small grain production in galaxies. We examine the robustness or uncertainty in the theoretical predictions of shattering. We identify $P_1$ (the critical pressure above which ... More
H2 Formation in Low Metallicity GalaxiesApr 30 2001May 23 2001A possible formation mechanism of hydrogen molecules on a galactic scale is examined. We are interested especially in the role of hydrogen molecules for formation and evolution of primordial galaxies. Then, formation process of hydrogen molecules in a ... More
Synthesized grain size distribution in the interstellar mediumMar 20 2012We examine a synthetic way of constructing the grain size distribution in the interstellar medium (ISM). First we formulate a synthetic grain size distribution composed of three grain size distributions processed with the following mechanisms that govern ... More
Observational Test of Environmental Effects on The Local Group Dwarf Spheroidal GalaxiesSep 01 1999In this paper, we examine whether tidal forces exerted by the Galaxy or M31 have an influence on the Local Group dwarf spheroidal galaxies (dSphs) which are their companions. We focus on the surface brightness profiles of the dSphs, especially their core ... More
Shattering and coagulation of dust grains in interstellar turbulenceDec 18 2008We investigate shattering and coagulation of dust grains in turbulent interstellar medium (ISM). The typical velocity of dust grain as a function of grain size has been calculated for various ISM phases based on a theory of grain dynamics in compressible ... More
Dust properties in afterglow of GRB 071025 at z~5Oct 14 2011Oct 17 2011At high redshift, the universe was so young that core-collapse supernovae (SNe) are suspected to be the dominant source of dust production. However, some observations indicate that the dust production by SNe is an inefficient process, casting doubts on ... More
Planet Traps and First Planets: the Critical Metallicity for Gas Giant FormationApr 22 2014The ubiquity of planets poses an interesting question: when first planets are formed in galaxies. We investigate this problem by adopting a theoretical model developed for understanding the statistical properties of exoplanets. Our model is constructed ... More
Galaxy Simulation with Dust Formation and DestructionSep 24 2016Jan 18 2017We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova feedback. For ... More
Condition for the formation of micron-sized dust grains in dense molecular cloud coresJun 24 2013We investigate the condition for the formation of micron-sized grains in dense cores of molecular clouds. This is motivated by the detection of the mid-infrared emission from deep inside a number of dense cores, the so-called `coreshine,' which is thought ... More
Effects of grain growth on the interstellar polarization curveAug 20 2014We apply the time evolution of grain size distributions by accretion and coagulation found in our previous work to the modelling of the wavelength dependence of interstellar linear polarization. We especially focus on the parameters of the Serkowski curve ... More
Effects of grain size distribution on the interstellar dust mass growthMay 25 2011Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in ... More
Effects of dust abundance on the far-infrared colours of blue compact dwarf galaxiesMar 11 2009We investigate the FIR properties of a sample of BCDs observed by AKARI. By utilizing the data at wavelengths of $\lambda =65 \mu$m, 90 $\mu$m, and 140 $\mu$m, we find that the FIR colours of the BCDs are located at the natural high-temperature extension ... More
Radiation-pressure-driven dust transport to galaxy halos at $z\sim 10$May 14 2019The origin of dust in galaxy halos or in the circum-galactic medium (CGM) is still a mystery. We investigate if the radiation pressure in high-redshift ($z\sim 10$) galaxies can efficiently transport dust to halos. To clarify the first dust enrichment ... More
Impact of grain size distributions on the dust enrichment in high-redshift quasarsMay 28 2012May 29 2012In high-redshift ($z>5$) quasars, a large amount of dust ($\textstyle\sim 10^{8} \mathrm{M}_{\sun}$) has been observed. In order to explain the large dust content, we focus on a possibility that grain growth by the accretion of heavy elements is the dominant ... More
Two Species of the Local Group Dwarf SpheroidalsOct 20 1998We analyzed 10 dwarf spheroidal galaxies (dSphs) in the Local Group, and found two distinct sequences on the $M_{\rm vir} / L$ -- $M_{\rm vir}$ plane: $M_{\rm vir} / L \propto M_{\rm vir}^{1.6}$ for $M_{\rm vir} < 10^8 M_\odot$ whereas $M_{\rm vir} / ... More
Fate of clumps in damped Ly$α$ systemsSep 09 2005May 30 2006Recent observations have revealed that damped Ly$\alpha$ clouds (DLAs) host star formation activity. In order to examine if such star formation activity can be triggered by ionization fronts, we perform high-resolution hydrodynamics and radiative transfer ... More
Star Formation Efficiency in the Central 1 kpc Region of Early-Type Spiral GalaxiesJul 20 2000It has been reported recently that there are some early-type spiral (Sa--Sab) galaxies having evident star-forming regions which concentrate in their own central 1-kpc. In such central region, is the mechanism of the star formation distinct from that ... More
Star formation rate in galaxies from UV, IR, and H-alpha estimatorsAug 29 2003Infrared (IR) luminosity of galaxies originating from dust emission can be used as an indicator of the star formation rate (SFR). Inoue et al. (2000, IHK) have derived a formula for the conversion from IR luminosity to SFR by using the following three ... More
Evolution of dust content in galaxies probed by gamma-ray burst afterglowsApr 23 2014Because of their brightness, gamma-ray burst (GRB) afterglows are viable targets for investigating the dust content in their host galaxies. Simple intrinsic spectral shapes of GRB afterglows allow us to derive the dust extinction. Recently, the extinction ... More
Far-infrared dust properties in the Galaxy and the Magellanic CloudsMar 20 2007A recent data analysis of the far-infrared (FIR) map of the Galaxy and the Magellanic Clouds has shown that there is a tight correlation between two FIR colours: the 60 um-100 um and 100 um-140 um colours. This FIR colour relation called ``main correlation'' ... More
Detecting Lyman Alpha Emitters in the Sub-millimeterAug 11 2009Dec 07 2009Using the results from a previously developed Lyman Alpha/continuum production/transmission and dust enrichment model for Lyman Alpha Emitters (LAEs), based on cosmological SPH simulations, we assess the detectability of their dust-reprocessed sub-millimeter ... More
Origin of Chromatic Features in Multiple Quasars -Variability, Dust, or Microlensing -Sep 11 2007Aims:In some of the lensed quasars, color differences between multiple images are observed at optical/near-infrared wavelengths. There are three possible origins of the color differences: intrinsic variabilities of quasars, differential dust extinction, ... More
Exploring the Dust Population in Cold Diffuse CloudsDec 05 2017The formation and evolution of cold diffuse clouds (CDCs), the parent objects of dense molecular clouds, affects both the star formation process and that of larger-scale galactic evolution. We have begun a pilot study of one CDC's dust content, with the ... More
Effect of Dust Extinction on Estimating Star Formation Rate of Galaxies: Lyman Continuum ExtinctionMar 15 2001We re-examine the effect of Lyman continuum ($\lambda \leq 912$ \AA) extinction (LCE) by dust in H {\sc ii} regions in detail and discuss how it affects the estimation of the global star formation rate (SFR) of galaxies. To clarify the first issue, we ... More
The origin of dust extinction curves with or without the 2175 A bump in galaxies: The case of the Magellanic CloudsJul 13 2015The Large and Small Magellanic Clouds (LMC and SMC, respectively) are observed to have characteristic dust extinction curves that are quite different from those of the Galaxy (e.g., strength of the 2175 A bump). Although the dust composition and size ... More
Constraining dust formation in high-redshift young galaxiesJun 26 2014Core-collapse supernovae (SNe) are believed to be the first significant source of dust in the Universe. Such SNe are expected to be the main dust producers in young high-redshift Lyman $\alpha$ emitters (LAEs) given their young ages, providing an excellent ... More
Millimeter-sized grains in the protostellar envelopes: where do they come from?Jun 10 2016Jun 13 2016Grain growth during star formation affects the physical and chemical processes in the evolution of star-forming clouds. We investigate the origin of the millimeter (mm)-sized grains recently observed in Class I protostellar envelopes. We use the coagulation ... More
Effects of grain shattering by turbulence on extinction curves in starburst galaxiesJan 15 2010Dust grains can be efficiently accelerated and shattered in warm ionized medium (WIM) because of the turbulent motion. This effect is enhanced in starburst galaxies, where gas is ionized and turbulence is sustained by massive stars. Moreover, dust production ... More
Common Correlations between 60, 100 and 140 um Intensities in the Galactic Plane and Magellanic CloudsApr 10 2006Apr 11 2006We investigate the far-infrared SED of the Galaxy and the Magellanic Clouds by using the COBE (COsmic Background Explorer) / DIRBE (Diffuse InfraRed Background Experiment) ZSMA (Zodi - Subtracted Mission Average) maps at wavelengths of 60 um, 100 um and ... More
Absorption Measurement of Hydrogen Molecules in the Early UniverseJun 06 2001We investigate the observability of hydrogen molecules in absorption. The absorption efficiency of the hydrogen molecules become comparable with or larger than that of the dust grains in the metal-poor condition expected in the early Universe. If we can ... More
Far-Infrared Properties of Blue Compact Dwarf Galaxies Observed with AKARI/Far-Infrared Surveyor (FIS)Sep 03 2008We report basic far-infrared (FIR) properties of eight blue compact dwarf galaxies (BCDs) observed by AKARI. We measure the fluxes at the four FIS bands (wavelengths of 65 um, 90 um, 140 um, and 160 um). Based on these fluxes, we estimate basic quantities ... More
Revisiting the lifetime estimate of large presolar grains in the interstellar mediumFeb 23 2016Some very large (>0.1 um) presolar grains are sampled in meteorites. We reconsider the lifetime of very large grains (VLGs) in the interstellar medium focusing on interstellar shattering caused by turbulence-induced large velocity dispersions. This path ... More
Dust evolution processes constrained by extinction curves in nearby galaxiesAug 22 2016Extinction curves, especially those in the Milky Way (MW), the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC), have provided us with a clue to the dust properties in the nearby Universe. We examine whether or not these extinction curves ... More
Formation History of Polycyclic Aromatic Hydrocarbons in GalaxiesJan 16 2014Polycyclic aromatic hydrocarbons (PAHs) are some of the major dust components in the interstellar medium (ISM). We present our evolution models for the abundance of PAHs in the ISM on a galaxy-evolution timescale. We consider shattering of carbonaceous ... More
Testing Intermittency of the Galactic Star Formation History along with the Infall ModelApr 07 2000We analyze the star formation history (SFH) of the Galactic disk by using an infall model. Based on the observed SFH of the Galactic disk, we first determine the timescales of the gas infall into the Galactic disk ($t_{\rm in}$) and that of the gas consumption ... More
Impact of Future Submillimeter and Millimeter Large Facilities on the Studies of Galaxy Formation and EvolutionJan 31 2001We investigate what we can learn about galaxy formation and evolution from the data which will be obtained by the forthcoming large submillimeter/millimeter facilities, mainly by the Atacama Submillimeter Telescope Experiment (ASTE) and the Atacama Large ... More
A new era of sub-millimeter GRB afterglow follow-ups with the Greenland TelescopeMar 26 2015A planned rapid submillimeter (submm) Gamma Ray Burst (GRBs) follow-up observations conducted using the Greenland Telescope (GLT) is presented. The GLT is a 12-m submm telescope to be located at the top of the Greenland ice sheet, where the high-altitude ... More
The dust production rate of AGB stars in the Magellanic CloudsApr 28 2014We compare theoretical dust yields for stars with mass 1 Msun < mstar < 8 Msun, and metallicities 0.001 < Z < 0.008 with observed dust production rates (DPR) by carbon- rich and oxygen-rich Asymptotic Giant Branch (C-AGB and O-AGB) stars in the Large ... More
Dust scaling relations in a cosmological simulationJan 09 2019To study the dust evolution in the cosmological structure formation history, we perform a smoothed particle hydrodynamic simulation with a dust enrichment model in a cosmological volume. We adopt the dust evolution model that represents the grain size ... More
Galaxy Simulation with Dust Formation and DestructionSep 24 2016We perform smoothed particle hydrodynamics (SPH) simulations of an isolated galaxy with a new treatment for dust formation and destruction. To this aim, we treat dust and metal production self-consistently with star formation and supernova feedback. For ... More
Dense molecular cloud cores as a source of micrometer-sized grains in galaxiesJan 22 2014Coreshine in dense molecular cloud cores (dense cores) is interpreted as evidence for micrometer-sized grains (referred to as very large grains, VLGs). VLGs may have a significant influence on the total dust amount and the extinction curve. We estimate ... More
Dust formation history of galaxies: a critical role of metallicity for the dust mass growth by accreting materials in the interstellar mediumJun 05 2012This paper investigate what is the main driver of the dust mass growth in the interstellar medium (ISM) by using a chemical evolution model of galaxy with metals (elements heavier than helium) in dust phase in addition to the total amount of metals. We ... More
Populating H$_2$ and CO in galaxy simulation with dust evolutionNov 02 2017There are two major theoretical issues for the star formation law (the relation between the surface densities of molecular gas and star formation rate on a galaxy scale): (i) At low metallicity, it is not obvious that star-forming regions are rich in ... More
The Role of Dust in the Early Universe I : Protogalaxy EvolutionApr 05 2011Apr 06 2011We develop one-zone galaxy formation models in the early Universe, taking into account dust formation and evolution by supernova (SN) explosions. Especially we focus on the time evolution of dust size distribution, because ${\rm H}_{2}$ formation on the ... More
Extinction curves expected in young galaxiesJan 10 2005We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). We adopt Nozawa et al. (2003) for compositions and size distribution of grains formed in SNe ... More
Molecular hydrogen emission in the interstellar medium of the Large Magellanic CloudJul 29 2014Nov 03 2014We present the detection and analysis of molecular hydrogen emission toward ten interstellar regions in the Large Magellanic Cloud. We examined low-resolution infrared spectral maps of twelve regions obtained with the Spitzer infrared spectrograph (IRS). ... More
Cosmological simulation with dust formation and destructionFeb 12 2018Jul 22 2018To investigate the evolution of dust in a cosmological volume, we perform hydrodynamic simulations, in which the enrichment of metals and dust is treated self-consistently with star formation and stellar feedback. We consider dust evolution driven by ... More
Evolution of dust extinction curves in galaxy simulationApr 06 2017To understand the evolution of extinction curve, we calculate the dust evolution in a galaxy using smoothed particle hydrodynamics simulations incorporating stellar dust production, dust destruction in supernova shocks, grain growth by accretion and coagulation, ... More
Exploring Galaxy Evolution from Infrared Number Counts and Cosmic Infrared BackgroundSep 28 2000Recently reported infrared (IR) galaxy number counts and cosmic infrared background (CIRB) all suggest that galaxies have experienced a strong evolution sometime in their lifetime. We statistically estimate the galaxy evolution history from these data. ... More
The IRIS Far-Infrared Galaxy Survey : Expected Number Count, Redshift, and PerspectiveDec 11 1998Infrared Imaging Surveyor (IRIS) is a satellite which will be launched in the beginning of 2003. One of the main purposes of the IRIS mission is an all-sky survey at far-infrared (FIR) with a flux limit much deeper than that of IRAS. In order to examine ... More
A model for the infrared dust emission from forming galaxiesJun 25 2005In the early epoch of galaxy evolution, dust is only supplied by supernovae (SNe). With the aid of a new physical model of dust production by SNe developed by Nozawa et al. (2003) (N03), we constructed a model of dust emission from forming galaxies on ... More
Infrared Spectral Energy Distribution Model for Extremely Young GalaxiesApr 26 2003The small grain sizes produced by Type II supernova (SN II) models in young, metal-poor galaxies make the appearance of their infrared (IR) spectral energy distribution (SED) quite different from that of nearby, older galaxies. To study this effect, we ... More
Chemical Evolution of the Galaxy Based on the Oscillatory Star Formation HistoryJan 30 2001We model the star formation history (SFH) and the chemical evolution of the Galactic disk by combining an infall model and a limit-cycle model of the interstellar medium (ISM). Recent observations have shown that the SFH of the Galactic disk violently ... More
Buckling of Carbon Nanotubes: A State of the Art ReviewDec 20 2011The nonlinear mechanical response of carbon nanotubes, referred to as their "buckling" behavior, is a major topic in the nanotube research community. Buckling means a deformation process in which a large strain beyond a threshold causes an abrupt change ... More
Spontaneous and dynamical symmetry breaking in higher-dimensional space-time with boundary termsJul 01 2003In this thesis we study physics beyond the standard model focusing on the quantum field theory in higher-dimensional space-time with some boundary terms. The boundary term causes nontrivial consequences about the vacuum structure of the higher-dimensional ... More
General heart construction for twin torsion pairs on triangulated categoriesNov 08 2011In our previous article, we constructed an abelian category from any torsion pair on a triangulated category. This generalizes the heart of a $t$-structure and the ideal quotient by a cluster tilting subcategory. Recently, generalizing the quotient by ... More
Biset transformations of Tambara functorsMay 04 2011Nov 16 2013If we are given an $H$-$G$-biset $U$ for finite groups $G$ and $H$, then any Mackey functor on $G$ can be transformed by $U$ into a Mackey functor on $H$. In this article, we show that the biset transformation is also applicable to Tambara functors when ... More
Ideals of Tambara functorsJan 31 2011Mar 21 2011For a finite group $G$, a Tambara functor on $G$ is regarded as a $G$-bivariant analog of a commutative ring. In this article, we consider a $G$-bivariant analog of the ideal theory for Tambara functors.
A Mackey-functor theoretic interpretation of biset functorsNov 16 2013Dec 07 2015In this article, we consider a formulation of biset functors using the 2-category of finite sets with variable finite group actions. We introduce a 2-category $\mathbb{S}$, on which a biset functor can be regarded as a special kind of Mackey functors. ... More
Mean-field theory on a coupled system of ferromagnetism and electronic nematic orderDec 19 2012We analyze an effective model on a square lattice with two types of forward scattering interactions, which, respectively, drive ferromagnetism (FM) and electronic nematic order via a d-wave Pomeranchuk instability (dPI). The FM and dPI in general compete ... More
Universal crossover in interacting fermions within the low-energy expansionFeb 28 2019Mar 03 2019We generalize the Bardeen-Cooper-Schrieffer-Bose-Einstein-condensation (BCS-BEC) crossover of two-component fermions, which is realized by tuning the $s$-wave scattering length $a$ between the fermions, to the case of an arbitrary effective range $r_{\rm ... More
A finite number of defining relations and a UCE theorem of the elliptic Lie algebras and superalgebras with rank $\geq 2$Aug 26 2004In this paper, we give a finite number of defining relations satisfied by a finite number of generators for the elliptic Lie algebras and superalgebras ${\frak g}_R$ with rank $\geq 2$. Here the $R$'s denote the reduced and non-reduced elliptic root systems ... More
4 D Quantum N-Dilaton Gravity and One-Loop Divergence of Effective Action on Constant DilatonMay 04 1996We consider 4D quantum gravity with N-dilatons with the most general couplings. Especially, on constant dilaton and arbitrary metric background, we show the structure of the divergent terms. We show the constraint between the couplings necessary to cancel ... More
A generalization of The Dress construction for a Tambara functor, and polynomial Tambara functorsDec 09 2010May 24 2011For a finite group $G$, (semi-)Mackey functors and (semi-)Tambara functors are regarded as $G$-bivariant analogs of (semi-)groups and (semi-)rings respectively. In fact if $G$ is trivial, they agree with the ordinary (semi-)groups and (semi-)rings, and ... More
Limiting behaviors of the Brownian motions on hyperbolic spacesJan 26 2009Feb 02 2009Using the explicit representations of the Brownian motions on the hyperbolic spaces, we show that their almost sure convergence and the central limit theorems for the radial components as time tends to infinity are easily obtained. We also give a straightforward ... More
Resolvent estimates related with a class of dispersive equationsApr 03 2007Aug 02 2007We present a simple proof of the resolvent estimates of elliptic Fourier multipliers on the Euclidean space, and apply them to the analysis of time-global and spatially-local smoothing estimates of a class of dispersive equations. For this purpose we ... More
Simple perfect samplers using monotone birth-and-death processesFeb 19 2017Mar 26 2017This paper proposes simple perfect samplers using monotone birth-and-death processes (BD-processes), which draw samples from an arbitrary finite discrete target distribution. We first construct a monotone BD-process whose stationary distribution is equal ... More
General heart construction on a triangulated category (I): unifying t-structures and cluster tilting subcategoriesJul 13 2009Sep 15 2009In the paper of Keller and Reiten, it was shown that the quotient of a triangulated category (with some conditions) by a cluster tilting subcategory becomes an abelian category. After that, Koenig and Zhu showed in detail, how the abelian structure is ... More
Continuous-time block-monotone Markov chains and their block-augmented truncationsNov 15 2015Nov 19 2016This paper considers continuous-time block-monotone Markov chains (BMMCs) and their block-augmented truncations. We first introduce the block monotonicity and block-wise dominance relation for continuous-time Markov chains, and then provide some fundamental ... More
Well-posedness and scattering for a system of quadratic derivative nonlinear Schrödinger equations with low regularity initial dataSep 17 2013Nov 07 2013In the present paper, we consider the Cauchy problem of a system of quadratic derivative nonlinear Schr\"odinger equations which was introduced by M. Colin and T. Colin (2004) as a model of laser-plasma interaction. The local existence of the solution ... More
A Dai-Yuan-type Riemannian conjugate gradient method with the weak Wolfe conditionsMay 17 2014Jun 17 2016This article describes a new Riemannian conjugate gradient method and presents a global convergence analysis. The existing Fletcher-Reeves-type Riemannian conjugate gradient method is guaranteed to be globally convergent if it is implemented with the ... More
Biset functors as module Mackey functors, and its relation to derivatorsJan 22 2016In this article, we will show that the category of biset functors can be regarded as a reflective monoidal subcategory of the category of Mackey functors on the 2-category of finite groupoids. This reflective subcategory is equivalent to the category ... More
Several adjoint constructions for biset functors via Mackey-functorial interpretationJun 13 2014We consider analogs of Jacobson's $F$-Burnside construction and Boltje's $(-)_+$-construction for biset functors, using Mackey-functor theoretic interpretation of biset functors.
On Calculations of Zeros of Various L-functionsNov 09 1994As we have shown several years ago [Y2], zeros of $L(s, \Delta )$ and $L^(2)(s, \Delta )$ can be calculated quite efficiently by a certain experimental method. Here $\Delta$ denotes the cusp form of weight 12 with respect to SL$(2, Z)$ and $L(s, \Delta ... More
Low Energy Investigations at Kamioka ObservatoryJan 30 2013At Kamioka Observatory many activities for low energy rare event search are ongoing. Super-Kamiokande(SK), the largest water Cherenkov neutrino detector, currently continues data taking as the fourth phase of the experiment (SK-IV). In SK-IV, we have ... More
The interplay between electron-electron interactions and impurities in one-dimensional ringsNov 17 1994The persistent current and charge stiffness of a one-dimensional Luttinger liquid on a ring threaded by a magnetic flux are calculated by Monte Carlo simulation. By changing the random impurity potential strength and the electron-electron interaction, ... More
The initial value problem for a third order dispersive equation on the two-dimensional torusApr 01 2004May 01 2004We present the necessary and sufficient condition for the $L^2$-well-posedness of the initial problem for a third order linear dispersive equation on the two dimensional torus. Birkhoff's method of asymptotic solutions is used to prove the necessity. ... More
Magnetic excitations in La-based cuprate superconductors: slave-boson mean-field analysis of the two-dimensional t-J modelOct 22 2006Motivated by recent inelastic neutron scattering experiments up to a high-energy region for La-based cuprates, we compute (q,omega) maps of the imaginary part of the dynamical magnetic susceptibility chi(q,omega) in the slave-boson mean-field approximation ... More
The limit formula for the normalized fundamental matrix of the northwest-corner truncation of Markov chains: Matrix-infinite-product form solutions of block-Hessenberg Markov chainsMar 25 2016Jun 30 2016This paper considers the normalized fundamental matrix for the northwest-corner (NW-corner) truncation of ergodic continuous-time Markov chains, technically, of their infinitesimal generators. We first present a limit formula for the normalized fundamental ... More
Subexponential tail equivalence of the queue length distributions of BMAP/GI/1 queues with and without retrialsOct 17 2013Jul 06 2014The main contribution of this paper is to prove the subexponential tail equivalence of the stationary queue length distributions in the BMAP/GI/1 queues with and without retrials. We first present a stochastic-decomposition-like result of the stationary ... More
On the defining relations of the affine Lie superalgebras and their quantized universal enveloping superalgebrasMar 15 1996In this paper, we give defining relations of the affine Lie superalgebras an and defining relations of a super-version of the Drinfeld[D]-Jimbo[J] affine quantized universal enveloping algebras. As a result, we can exactly define the affine quantized ... More
Electroweak Sudakov corrections at 2 loop levelFeb 14 2001In processes at the energy much higher than electroweak scale, weak boson mass act as the infrared cutoff in weak boson loops and resulting Sudakov log corrections can be as large as 10%. Since electroweak theory is off-diagonally broken gauge theory, ... More
Analytic expression for pull-or-jerk experimentAug 27 2014This work focuses on a theoretical analysis of a well-known inertia demonstration, which uses a weight suspended by a string with an extra string that hangs below the weight. The point in question is which string, the upper or lower, will break when pulling ... More
Persistent current in quantum torus knotsApr 23 2012I consider the quantum interference of electrons moving along knotted trajectories under external magnetic field. The induced persistent current is formulated in terms of characteristic parameters that classify the torus knot geometry. The current is ... More