Results for "Kenji Watanabe"

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Tunneling spin valves based on Fe$_3$GeTe$_2$/hBN/Fe$_3$GeTe$_2$ van der Waals heterostructuresJun 14 2018Thin van der Waals (vdW) layered magnetic materials disclose the possibility to realize vdW heterostructures with new functionalities. Here we report on the realization and investigation of tunneling spin valves based on van der Waals heterostructures ... More
Hybridized indirect excitons in MoS2/WS2 heterobilayersDec 27 2018Ensembles of indirect or interlayer excitons (IXs) are intriguing systems to explore classical and quantum phases of interacting bosonic ensembles. IXs are composite bosons that feature enlarged lifetimes due to the reduced overlap of the electron-hole ... More
Graph Zeta Function in the Bethe Free Energy and Loopy Belief PropagationFeb 17 2010We propose a new approach to the analysis of Loopy Belief Propagation (LBP) by establishing a formula that connects the Hessian of the Bethe free energy with the edge zeta function. The formula has a number of theoretical implications on LBP. It is applied ... More
Loopy Belief Propagation, Bethe Free Energy and Graph Zeta FunctionMar 03 2011We propose a new approach to the theoretical analysis of Loopy Belief Propagation (LBP) and the Bethe free energy (BFE) by establishing a formula to connect LBP and BFE with a graph zeta function. The proposed approach is applicable to a wide class of ... More
Loop series expansion with propagation diagramsAug 08 2008Nov 13 2008The Bethe approximation is a successful method for approximating partition functions of probabilistic models associated with a graph. Recently, Chertkov and Chernyak derived an interesting formula called Loop Series Expansion, which is an expansion of ... More
New graph polynomials from the Bethe approximation of the Ising partition functionAug 26 2009Jun 04 2010We introduce two graph polynomials and discuss their properties. One is a polynomial of two variables whose investigation is motivated by the performance analysis of the Bethe approximation of the Ising partition function. The other is a polynomial of ... More
Suppressed out-of-plane polarizability of free excitons in monolayer WSe$_{2}$Dec 03 2018Monolayer semiconductors are atomically thin quantum wells with strong confinement of electrons in two-dimensional (2D) plane. Here, we experimentally study the out-of-plane polarizability of excitons in hBN-encapsulated monolayer WSe$_{2}$ in strong ... More
Coulomb drag between carbon nanotube and grapheneDec 18 2016Oct 18 2017We report the observation of Coulomb drag between a two-dimensional (2D) electron gas in graphene and a one-dimensional (1D) wire composed of a carbon nanotube. We find that drag occurs when the bulk of graphene is conducting, but is strongly suppressed ... More
Thermal Conductivity and Phonon Transport in Suspended Few-Layer Hexagonal Boron NitrideFeb 07 2013The thermal conductivity of suspended few-layer hexagonal boron nitride (h-BN) was measured using a micro-bridge device with built-in resistance thermometers. Based on the measured thermal resistance values of 11-12 atomic layer h-BN samples with suspended ... More
Visualizing Strain-induced Pseudo magnetic Fields in Graphene through an hBN Magnifying GlassMar 01 2017The remarkable properties of graphene are inherent to its 2D honeycomb lattice structure. Its low dimensionality, which makes it possible to rearrange the atoms by applying an external force, offers the intriguing prospect of mechanically controlling ... More
Skyrmion solids in monolayer grapheneApr 25 2019Partially filled Landau levels host competing orders, with electron solids prevailing close to integer fillings before giving way to fractional quantum Hall liquids as the Landau level fills. Here, we report the observation of an electron solid with noncolinear ... More
Reliable post-processing improvement of van der Waals heterostructuresMar 25 2019The successful assembly of heterostructures consisting of several layers of different 2D materials in arbitrary order by exploiting van der Waals forces has truly been a game changer in the field of low dimensional physics. For instance, the encapsulation ... More
Low Magnetic Field Regime of a Gate-Defined Constriction in High-Mobility GrapheneJun 26 2018Dec 02 2018We report on the evolution of the coherent electronic transport through a gate-defined constriction in a high-mobility graphene device from ballistic transport to quantum Hall regime upon increasing the magnetic field. At low field, the conductance exhibits ... More
Graph polynomials and approximation of partition functions with Loopy Belief PropagationMar 26 2009Nov 14 2009The Bethe approximation, or loopy belief propagation algorithm is a successful method for approximating partition functions of probabilistic models associated with a graph. Chertkov and Chernyak derived an interesting formula called Loop Series Expansion, ... More
Giant Frictional Drag in Double Bilayer Graphene HeterostructuresMar 02 2016We study the frictional drag between carriers in two bilayer graphene flakes separated by a 2 $-$ 5 nm thick hexagonal boron nitride dielectric. At temperatures ($T$) lower than $\sim$ 10 K, we observe a large anomalous negative drag emerging predominantly ... More
Metallic Phase and Temperature Dependence of the $ν= 0$ Quantum Hall State in Bilayer GrapheneMar 11 2019The $\nu = 0$ quantum Hall state of bilayer graphene is a fertile playground to realize many-body ground states with various broken symmetries. Here we report the experimental observations of a previously unreported metallic phase. The metallic phase ... More
Electrically Tunable Energy Bandgap in Dual-Gated Ultra-Thin Black Phosphorus Field Effect TransistorsMar 24 2017The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is of great importance not only to device ... More
Quantitative transport measurements of fractional quantum Hall energy gaps in edgeless graphene devicesMay 10 2018Sep 05 2018Owing to their wide tunability, spin- and valley internal degrees of freedom, and low disorder, graphene heterostructures are emerging as a promising experimental platform for fractional quantum Hall (FQH) studies. Surprisingly, however, transport measurements ... More
Tunnelling Spectroscopy of Andreev States in GrapheneMar 30 2017Apr 13 2017A normal conductor placed in good contact with a superconductor can inherit its remarkable electronic properties. This proximity effect microscopically originates from the formation in the conductor of entangled electron-hole states, called Andreev states. ... More
Waveguide-integrated van der Waals heterostructure photodetector at telecom band with high speed and high responsivityApr 23 2019Intensive efforts have been devoted to exploit novel optoelectronic devices based on two-dimensional (2D) transition-metal dichalcogenides (TMDCs) owing to their strong light-matter interaction and distinctive material properties. In particular, photodetectors ... More
Graphene photodetector integrated on a photonic crystal defect waveguideMar 07 2019We present a graphene photodetector for telecom applications based on a silicon photonic crystal defect waveguide. The photonic structure is used to confine the propagating light in a narrow region in the graphene layer to enhance light-matter interaction. ... More
Visualizing Encapsulated Graphene, its Defects and its Charge Environment by Sub-Micrometer Resolution Electrical ImagingNov 14 2018Devices made from two-dimensional (2D) materials such as graphene or transition metal dichalcogenides possess interesting electronic properties that can become accessible to experimental probes when the samples are protected from deleterious environmental ... More
In-situ strain tuning in hBN-encapsulated graphene electronic devicesApr 14 2019Using a simple setup to bend a flexible substrate, we demonstrate deterministic and reproducible in-situ strain tuning of graphene electronic devices. Central to this method is the full hBN encapsulation of graphene, which preserves the exceptional quality ... More
Magnetic Properties of One-Dimensional Quantum Spin System Rb2Cu2Mo3O12 Studied by Muon Spin RelaxationOct 27 2017Magnetic properties of a one-dimensional frustrated quantum spin system Rb2Cu2Mo3O12 is investigated by the muon spin relaxation (muSR) technique. Although this system shows an incommensurate spin correlation in neutron scattering, it has not yet been ... More
Graphene Nanoribbons on Hexagonal Boron Nitride: Deposition and Transport CharacterizationOct 16 2018May 02 2019Chemically synthesized "cove"-type graphene nanoribbons (cGNRs) of different widths were brought into dispersion and drop-cast onto exfoliated hexagonal boron nitride (hBN) on a Si/SiO2 chip. With AFM we observed that the cGNRs form ordered domains aligned ... More
Electric Field Tunable Correlated States and Magnetic Phase Transitions in Twisted Bilayer-Bilayer GrapheneMar 20 2019Mar 25 2019The recent discovery of correlated insulator states and superconductivity in magic-angle twisted bilayer graphene has paved the way to the experimental investigation of electronic correlations in tunable flat band systems realized in twisted van der Waals ... More
New generation of moiré superlattices in doubly aligned hBN/graphene/hBN heterostructuresDec 25 2018The specific rotational alignment of two-dimensional lattices results in a moir\'e superlattice with a larger period than the original lattices and allows one to engineer the electronic band structure of such materials. So far, transport signatures of ... More
Chemical Potential and Quantum Hall Ferromagnetism in Bilayer GrapheneJan 03 2014Jul 07 2014Bilayer graphene has a unique electronic structure influenced by a complex interplay between various degrees of freedom. We probe its chemical potential using double bilayer graphene heterostructures, separated by a hexagonal boron nitride dielectric. ... More
Tunneling spectroscopy of graphene nanodevices coupled to large-gap superconductorsSep 25 2018We performed tunneling spectroscopy measurements of graphene coupled to niobium/niobium-nitride superconducting electrodes. Due to the proximity effect, the graphene density of states depends on the phase difference between the superconductors and exhibits ... More
Tunable transmission of quantum Hall edge channels with full degeneracy lifting in split-gated graphene devicesMay 27 2016Mar 05 2017Charge carriers in the quantum Hall regime propagate via one-dimensional conducting channels that form along the edges of a two-dimensional electron gas. Controlling their transmission through a gate-tunable constriction, also called quantum point contact ... More
Boron Nitride Nanosheets as Improved and Reusable Substrates for Gold Nanoparticles Enabled Surface Enhanced Raman SpectroscopyMar 11 2015Atomically thin boron nitride (BN) nanosheets have been found an excellent substrate for noble metal particles enabled surface enhanced Raman spectroscopy (SERS), thanks to their good adsorption of aromatic molecules, high thermal stability and weak Raman ... More
Enhanced Superconductivity and Suppression of Charge-density Wave Order in 2H-TaS$_2$ in the Two-dimensional LimitOct 31 2017Feb 27 2018As superconductors are thinned down to the 2D limit, their critical temperature $T_c$ typically decreases. Here we report the opposite behavior, a substantial enhancement of $T_c$ with decreasing thickness, in 2D crystalline superconductor 2H-TaS$_2$. ... More
A valley valve and electron beam splitterAug 07 2017Dec 08 2018Developing alternative paradigms of electronics beyond silicon technology requires the exploration of fundamentally new physical mechanisms, such as the valley specific phenomena in hexagonal two-dimensional materials. We realize ballistic valley Hall ... More
Inducing Superconducting Correlation in Quantum Hall Edge StatesSep 26 2016Sep 28 2016The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a 2-dimensional electron gas (2DEG) system. A superconductor (SC) contacting these states induces correlation of the quasi-particles in the dissipationless 1D chiral ... More
Nanospot Angle-Resolved Photoemission Study of Bernal-Stacked Bilayer Graphene on Hexagonal Boron Nitride: Band Structure and Local Variation of Lattice AlignmentApr 24 2019Hexagonal boron nitride (hBN) is the supporting substrate of choice for two-dimensional material devices because it is atomically flat and chemically inert. However, due to the small size of mechanically exfoliated hBN flakes, electronic structure studies ... More
Substrate-Induced Shifts and Screening in the Fluorescence Spectra of Supramolecular Adsorbed Organic MonolayersMay 29 2018We have investigated the influence of the substrate on the fluorescence of adsorbed organic molecules. Monolayer films of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI), a supramolecular network formed from PTCDI and melamine, and perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride ... More
Interlayer excitons in bilayer MoS2 with strong oscillator strength up to room temperatureNov 15 2018Feb 06 2019Coulomb bound electron-hole pairs, excitons, govern the optical properties of semi-conducting transition metal dichalcogenides like MoS$_2$ and WSe$_2$. We study optical transitions at the K-point for 2H homobilayer MoS$_2$ in Density Functional Theory ... More
Visualization and Control of Single Electron Charging in Bilayer Graphene Quantum DotsSep 13 2018Graphene p-n junctions provide an ideal platform for investigating novel behavior at the boundary between electronics and optics that arise from massless Dirac fermions, such as whispering gallery modes and Veselago lensing. Bilayer graphene also hosts ... More
Unconventional Quantum Hall Edge-Bulk Correlation in Gated Graphene DevicesNov 04 2015The quantum Hall effect in a two dimensional electron system has been understood as chiral edge states circulating a highly insulating bulk when the bulk Landau levels are completely filled. We report simultaneous transport and scanning Microwave Impedance ... More
Order parameters with higher dimensionful composite fieldsDec 23 2003We discuss the possibility of the spontaneous symmetry breaking characterized by order parameters with higher dimensionful composite fields. By analyzing general Ginzburg-Landau potential for a complex scalar field \phi=\phi_1 + i \phi_2 with O(2) symmetry, ... More
Supercurrent Flow in Multi-Terminal Graphene Josephson JunctionsOct 27 2018We investigate the electronic properties of ballistic planar Josephson junctions with multiple superconducting terminals. Our devices consist of monolayer graphene encapsulated in boron nitride with molybdenum-rhenium contacts. Resistance measurements ... More
Surface Transport and Quantum Hall Effect in Ambipolar Black Phosphorus Double Quantum WellsMar 15 2017Mar 27 2017Quantum wells constitute one of the most important classes of devices in the study of 2D systems. In a double layer QW, the additional "which-layer" degree of freedom gives rise to celebrated phenomena such as Coulomb drag, Hall drag and exciton condensation. ... More
Observation of Ultralong Valley Lifetime in WSe2/MoS2 HeterostructuresDec 16 2016The valley degree of freedom in two-dimensional (2D) crystals recently emerged as a novel information carrier in addition to spin and charge. The intrinsic valley lifetime in 2D transition metal dichalcoginides (TMD) is expected to be remarkably long ... More
Imaging bulk and edge transport near the Dirac point in graphene moiré superlatticesNov 21 2017Van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride exhibit a moir\'e superlattice that is expected to break sublattice symmetry. Despite an energy gap of several tens of millielectron volts ... More
Quantum Critical Transition and Kondo Screening of Magnetic Moments in GrapheneNov 19 2017Jan 11 2018In normal metals, the magnetic moment of impurity spins disappears below a characteristic Kondo temperature, TK, where coupling with the conduction-band electrons produces an entangled state that screens the local moment. In contrast, moments embedded ... More
Multiple Hot-Carrier Collection in Photo-Excited Graphene Moire SuperlatticesMar 16 2016In conventional light harvesting devices, the absorption of a single photon only excites one electron, which sets the standard limit of power-conversion efficiency, such as the Shockley-Queisser limit. In principle, generating and harnessing multiple ... More
A New Room-Temperature Quantum Emitter in High-Quality Hexagonal Boron NitrideApr 27 2019May 09 2019Light emitters in wide band gap semiconductors are of great fundamental interest and have potential as optically addressable qubits. Here we describe the discovery of a new quantum emitter in high-quality hexagonal boron nitride (h-BN) with a sharp emission ... More
LHC constraints and prospects for $S_1$ scalar leptoquark explaining the $\bar B \to D^{(*)} τ\barν$ anomalyMar 16 2016Recently, deviations in flavor observables of B -> D(*) tau nu have been shown between the predictions in the Standard Model and the experimental results reported by BaBar, Belle, and LHCb collaborations. One of the solutions to this anomaly is obtained ... More
Tunable Lifshitz Transitions and Multiband Transport in Tetralayer GrapheneFeb 21 2018As the Fermi level and band structure of two-dimensional materials are readily tunable, they constitute an ideal platform for exploring Lifshitz transition, a change in the topology of a material's Fermi surface. Using tetralayer graphene that host two ... More
Cubic BN optical gap and intragap optically active defectsJun 29 2018We report a comprehensive study on the optical properties of cubic boron nitride (c-BN) and its optically active defects. Using electron energy-loss spectroscopy (EELS) within a monochromated scanning transmission electron microscope (STEM) on the highest-quality ... More
Zeeman Splitting and Inverted Polarization of Biexciton Emission in Monolayer WS2Jan 28 2018We investigate the magnetic-field-induced splitting of biexcitons in monolayer WS$_2$ using polarization-resolved photoluminescence spectroscopy in out-of-plane magnetic fields up to 30 T. The observed $g$ factor of the biexciton amounts to $-3.89$, closely ... More
Visualizing the Effect of an Electrostatic Gate with Angle-Resolved Photoemission SpectroscopyApr 20 2019Electrostatic gating is pervasive in materials science, yet its effects on the electronic band structure of materials has never been revealed directly by angle-resolved photoemission spectroscopy (ARPES), the technique of choice to non-invasively probe ... More
Mach-Zehnder interferometry using spin- and valley-polarized quantum Hall edge states in grapheneMar 01 2017Confined to a two-dimensional plane, electrons in a strong magnetic field travel along the edge in one-dimensional quantum Hall channels that are protected against backscattering. These channels can be used as solid-state analogues of monochromatic beams ... More
Flat Bands in Buckled Graphene SuperlatticesApr 23 2019Interactions between stacked two-dimensional (2D) atomic crystals can radically change their properties, leading to essentially new materials in terms of the electronic structure. Here we show that monolayers placed on an atomically flat substrate can ... More
Integration of atomically thin layers of transition metal dichalcogenides into high-Q, monolithic Bragg-cavities - an experimental platform for the enhancement of optical interaction in 2D-materialsDec 03 2018Dec 05 2018We demonstrate a new approach to integrate single layer MoSeR2R and WSeR2R flakes into monolithic all-dielectric planar high-quality micro-cavities. These distributed-Bragg-reflector (DBR) cavities may e.g. be tuned to match the exciton resonance of the ... More
Imaging ballistic carrier trajectories in graphene using scanning gate microscopyAug 02 2015Dec 15 2015We use scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and subject to a weak magnetic field. We employ a magnetic focusing geometry to image carriers that emerge ... More
Integer and Fractional Quantum Hall effect in Ultra-high Quality Few-layer Black Phosphorus TransistorsApr 06 2018As a high mobility two-dimensional semiconductor with strong structural and electronic anisotropy, atomically thin black phosphorus (BP) provides a new playground for investigating the quantum Hall (QH) effect, including outstanding questions such as ... More
Genuine Ohmic van der Waals contact between indium and MoS2Apr 23 2019May 03 2019The formation of an ideal van der Waals (vdW) contacts at metal/transition-metal dichalcogenide (TMDC) interfaces is a critical step for the development of high-performance and energy-efficient electronic and optoelectronic applications based on the two-dimensional ... More
Strain-modulated Bandgap and Piezo-resistive Effect in Black Phosphorus Field-effect TransistorsJan 27 2017Energy bandgap largely determines the optical and electronic properties of a semiconductor. Variable bandgap therefore makes versatile functionality possible in a single material. In layered material black phosphorus, the bandgap can be modulated by the ... More
Probing magnetism in 2D van der Waals crystalline insulators via electron tunnelingJan 26 2018Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises ultrathin insulating multiferroics, spin liquids, and ferromagnets, but new characterization methods are required ... More
Van der Waals epitaxial growth of topological insulator Bi$_{2-x}$Sb$_x$Te$_{3-y}$Se$_y$ ultrathin nanoplate on electrically insulating fluorophlogopite micaJul 29 2014We report the growth of high quality Bi$_{2-x}$Sb$_x$Te$_{3-y}$Se$_y$ ultrathin nanoplates (BSTS-NPs) on an electrically insulating fluorophlogopite mica substrate using a catalyst-free vapor solid method. Under an optimized pressure and suitable Ar gas ... More
Measuring valley polarization in transition metal dichalcogenides with second-harmonic spectroscopyMar 04 2019Inducing a population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such valley imbalance (a valley polarization) that directly exploits this symmetry reduction as ... More
Emergence of Tertiary Dirac Points in Graphene Moiré SuperlatticesFeb 10 2017The electronic structure of a crystalline solid is largely determined by its lattice structure. Recent advances in van der Waals solids, artificial crystals with controlled stacking of two-dimensional (2D) atomic films, have enabled the creation of materials ... More
X-ray pumping of the Th-229 nuclear clock isomerFeb 13 2019Thorium-229 is a unique case in nuclear physics: it presents a metastable first excited state Th-229m, just a few electronvolts above the nuclear ground state. This so-called isomer is accessible by VUV lasers, which allows transferring the amazing precision ... More
Rolling Tachyon with Electromagnetic Field in Linear Dilaton BackgroundDec 13 2003Apr 08 2004Rolling tachyon in linear dilaton background is examined by using an effective field theory with gauge field on an unstable D-brane in bosonic string theory. Several solutions are identified with tachyon matter equipped with constant electromagnetic field ... More
Origin of a bottom-heavy stellar initial mass function in elliptical galaxiesNov 07 2013We investigate the origin of a bottom-heavy stellar initial mass function (IMF) recently observed in elliptical galaxies by using chemical evolution models with a non-universal IMF. We adopt the Kroupa IMF with the three slopes (alpha_1, alpha_2, and ... More
Formation of massive globular clusters with heavy element abundance spread in the Galactic building blocksDec 16 2011A growing number of recent observations have revealed that the Galactic globular cluster (GC) omega Cen is not the only GC that shows abundance spread in heavy elements (e.g., Fe). In order to understand the origin of the Galactic GCs with heavy element ... More
Merging between a Central Massive Black Hole and a Compact Stellar System: A Clue to the Origin of M31'S NucleusDec 16 2000The central bulge of M31 is observed to have two distinct brightness peaks with the separation of $\sim$ 2 pc. Tremaine (1995) recently proposed a new idea that the M31's nucleus is actually a single thick eccentric disk surrounding the central super-massive ... More
Gas fueling and nuclear disk formation in merging between a central black hole and a gas clumpDec 14 2000We numerically investigate dynamical evolution of a merger between a central massive black hole (MBH) and a gas clump with the mass of $10^6$ $-$ $10^7$ $M_{\odot}$ in the central tens pc of a galactic bulge. We found that strong tidal gravitational field ... More
Formation of emission line dots and extremely metal-deficient dwarfs from almost dark galaxiesSep 14 2015Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-mass dark matter halos. We investigate star formation histories of these gas-rich dwarf ("almost dark") galaxies both for isolated and ... More
Simulating galaxy evolution with a non-universal stellar initial mass functionSep 16 2013We consider that the stellar initial mass function (IMF) depends on physical properties of star-forming molecular clouds in galaxies and thereby investigate how such a non-universal IMF (NUIMF) influences galaxy evolution. We incorporate a NUIMF model ... More
Evolution of the Small Magellanic CloudJul 31 2007Based on the results of N-body simulations on the last 2.5 Gyr evolution of the Large and Small Magellanic Clouds (LMC and SMC, respectively) interacting with the Galaxy, we firstly show when and where the leading arms (LAs) of the Magellanic stream (MS) ... More
Formation of a polar-ring galaxy in a galaxy mergerApr 22 1998We numerically investigate stellar and gas dynamics in star-forming and dissipative galaxy mergers between two disk galaxies with specific orbital configurations. We find that violent relaxation combined with gaseous dissipation in galaxy merging transforms ... More
Critical surface in hot and dense QCD with the vector interactionSep 18 2008Nov 05 2008We discuss the chiral phase transition of hot and dense quark matter. We illustrate that the first-order phase transition is generally favored at high baryon density and the repulsive vector-vector interaction weakens the first-order phase transition. ... More
Initial fields and instability in the classical model of the heavy-ion collisionApr 26 2007May 22 2007Color Glass Condensate (CGC) provides a classical description of dense gluon matter at high energies. Using the McLerran-Venugopalan (MV) model we calculate the initial energy density \epsilon(\tau) in the early stage of the relativistic nucleus-nucleus ... More
Characterizing the Larkin-Ovchinnikov-Fulde-Ferrel phase induced by the chromomagnetic instabilityMar 26 2006Apr 04 2006We discuss possible destinations from the chromomagnetic instability in color superconductors with Fermi surface mismatch $\delta\mu$. In the two-flavor superconducting (2SC) phase we calculate the effective potential for color vector potentials $A_\alpha$ ... More
Deconfinement and Chiral Restoration in Hot and Dense MatterSep 13 2004We propose a picture that the chiral phase transition at zero quark mass and the deconfinement transition at infinite quark mass are continuously connected. This gives a simple interpretation on the coincidence of the pseudo-critical temperatures observed ... More
Phase diagram of hot and dense QCD constrained by the Statistical ModelJun 14 2010Jun 30 2010We propose a prescription to constrain the chiral effective model approach to the QCD phase diagram using the thermal Statistical Model, which is a description consistent with the experimental data at the freeze-out. In the transition region where thermal ... More
Chiral effective model with the Polyakov loopOct 09 2003Apr 11 2004We discuss how the simultaneous crossovers of deconfinement and chiral restoration can be realized. We propose a dynamical mechanism assuming that the effective potential gives a finite value of the chiral condensate if the Polyakov loop vanishes. Using ... More
Deformations of reducible SL(n,C) representations of fibered 3-manifold groupsSep 24 2015Sep 27 2015Let $M_\phi$ be a surface bundle over a circle with monodromy $\phi:S \rightarrow S$. We study deformations of certain reducible representations of $\pi_1(M_\phi)$ into $\text{SL}(n,\mathbb{C})$, obtained by composing a reducible representation into $\text{SL}(2,\mathbb{C})$ ... More
On a q-difference Painlevé III equation: II. Rational solutionsMay 29 2002Mar 13 2004Rational solutions for a $q$-difference analogue of the Painlev\'e III equation are considered. A Determinant formula of Jacobi-Trudi type for the solutions is constructed.
Dust-regulated galaxy formation and evolution:A new chemodynamical model with live dust particlesJan 22 2015Interstellar dust plays decisive roles in the conversion of neutral to molecular hydrogen (H_2), the thermodynamical evolution of interstellar medium (ISM), and the modification of spectral energy distributions (SEDs) of galaxies. These important roles ... More
Coevolution of dust, gas, and stars in galaxies - I. Spatial distributions and scaling-relations of dust and molecular hydrogenApr 05 2013We investigate the time evolution of dust properties, molecular hydrogen (H_2) contents, and star formation histories in galaxies by using our original chemodynamical simulations. The simulations include the formation of dust in the stellar winds of supernovae ... More
A possible common halo of the Magellanic CloudsJul 12 2008Recent observational and theoretical studies on the three-dimensional (3D) space motions of the Large and the Small Magellanic Clouds (LMC and SMC, respectively) have strongly suggested that the latest proper motion measurements of the Magellanic Clouds ... More
Origin of dwarf irregular galaxies with outer early-type structuresMay 15 2008Recent observations have reported that some gas-rich dwarf irregular (dIrr) galaxies appear to have spherical distributions in the outer underlying old and intermediate-age stellar populations (e.g., NGC 6822). These observations imply that some dIrr's ... More
Primordial pollution of globular clusters within their host dwarfs embedded in dark matter halos at high redshiftsDec 19 2005Recent observational studies have revealed star-to-star abundance inhomogeneity among light elements (e.g., C, N, O, Na, and Al) of stars on the main sequence in the Galactic globular clusters (GCs). One of promising interpretations for this result is ... More
Star clusters and galactic chemodynamics: Implosive formation of super star clustersAug 14 2003We numerically investigate dynamical and chemical properties of star clusters (open and globular clusters, and ``super star clusters'', SSC) formed in interacting/merging galaxies. The investigation is two-fold: (1) large-scale (100pc-100kpc) SPH simulations ... More
The Fundamental Plane and merger scenario I. Star formation history of galaxy mergers and origin of the Fundamental PlaneApr 07 1998We perform numerical simulations of galaxy mergers between star-forming and gas-rich spirals in order to explore the origin of the Fundamental Plane (FP) of elliptical galaxies. We consider particularly that the origin of the slope of the FP is essentially ... More
Origin of rotational kinematics in the globular cluster system of M31: A new clue to the bulge formationDec 13 2009We propose that the rotational kinematics of the globular cluster system (GCS) in M31 can result from a past major merger event that could have formed its bulge component. We numerically investigate kinematical properties of globular clusters (GCs) in ... More
Dynamical friction of star clusters against disk field stars in galaxies: Implications on stellar nucleus formation and globular cluster luminosity functionsNov 29 2009We numerically investigate orbital evolution of star clusters (SCs) under the influence of dynamical friction by field stars of their host disk galaxies embedded in dark matter halos. We find that SCs with masses larger than 2 * 10^5 M_sun can show significant ... More
On the Origin of the Kinematical Differences Between the Stellar Halo and the Old Globular Cluster System in the Large Magellanic CloudJul 15 2007We discuss structural and kinematical properties of the stellar halo and the old globular cluster system (GCS) in the Large Magellanic Cloud (LMC) based on numerical simulations of the LMC formation. We particularly discuss the observed possible GCS's ... More
Group-cluster merging and the formation of starburst galaxiesNov 08 1998A significant fraction of clusters of galaxies are observed to have substructure, which implies that merging between clusters and subclusters is a rather common physical process of cluster formation. It still remains unclear how cluster merging affects ... More
Bosonic representations of Yangian Double $\cD Y_{\hbar}(\gtg)$ with $\gtg=\gtgl_N,\gtsl_N$Apr 01 1996On the basis of `$RTT=TTR$' formalism, we introduce the quantum double of the Yangian $Y_{\hbar}(\gtg)$ for $\gtg=\gtgl_N,\gtsl_N$ with a central extension. The Gauss decomposition of T-matrices gives us the so-called Drinfel'd generators. Using these ... More
Closed String Emission from Unstable D-brane with Background Electric FieldSep 01 2003Jan 22 2004We study the closed string emission from an unstable D$p$-brane with constant background electric field in bosonic string theory. The average total number density and the average total energy density of emitted closed strings are explicitly calculated ... More
Floer homology of Lagrangian submanifoldsJun 24 2011This is a translation of an article appeared in Japanese in Suugaku 63 (2011), no. 1, 43-66 (MR2790665) and is a survey of Lagrangian Floer homology which the author studies jointly with Y.-G.Oh, H. Ohta, and K. Ono. It also contains some explanation ... More
Exceptional String: Instanton Expansions and Seiberg-Witten CurveOct 15 2001Feb 25 2002We investigate instanton expansions of partition functions of several toric E-string models using local mirror symmetry and elliptic modular forms. We also develop a method to obtain the Seiberg--Witten curve of E-string with arbitrary Wilson lines with ... More
Kähler Moduli Space of a D-Brane at Orbifold SingularitiesJun 08 1998Jun 10 1998We develop a method to analyze systematically the configuration space of a D-brane localized at the orbifold singular point of a Calabi--Yau $d$-fold of the form ${\Bbb C}^d/\Gamma$ using the theory of toric quotients. This approach elucidates the structure ... More
D-Branes and Quotient Singularities of Calabi-Yau FourfoldsJul 01 1997Mar 02 1998We investigate a (0,2) gauge theory realized on the world volume of the type IIB D1-brane at the singular point of a Calabi-Yau fourfold. It is argued that the gauge anomaly can be canceled via coupling to the R-R chiral bosons in bulk IIB string. We ... More
Baryonic matter and beyondAug 03 2014Oct 01 2014We summarize recent developments in identifying the ground state of dense baryonic matter and beyond. The topics include deconfinement from baryonic matter to quark matter, a diquark mixture, topological effect coupled with chirality and density, and ... More
Effective Model Approach to the Dense State of QCD MatterAug 25 2010The first-principle approach to the dense state of QCD matter, i.e. the lattice-QCD simulation at finite baryon density, is not under theoretical control for the moment. The effective model study based on QCD symmetries is a practical alternative. However ... More