Results for "Kenji Watanabe"

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Anisotropic Dielectric Breakdown Strength of Single Crystal Hexagonal Boron NitrideOct 31 2016Dielectric breakdown has historically been of great interest from the perspectives of fundamental physics and electrical reliability. However, to date, the anisotropy in the dielectric breakdown has not been discussed. Here, we report an anisotropic dielectric ... More
Phase diagram of nuclear "pasta" and its uncertainties in supernova coresDec 01 2007Mar 11 2010We examine the model dependence of the phase diagram of inhomogeneous nulcear matter in supernova cores using the quantum molecular dynamics (QMD). Inhomogeneous matter includes crystallized matter with nonspherical nuclei - "pasta" phases - and the liquid-gas ... More
Simulation of Transitions between "Pasta" Phases in Dense MatterAug 24 2004Jan 28 2005Calculations of equilibrium properties of dense matter predict that at subnuclear densities nuclei can be rodlike or slablike. To investigate whether transitions between phases with non-spherical nuclei can occur during the collapse of a star, we perform ... More
Dry transfer of CVD graphene using MoS$_2$-based stampsJun 01 2017Recently, a contamination-free dry transfer method for graphene grown by chemical vapor deposition (CVD) has been reported that allows to directly pick-up graphene from the copper growth substrate using a flake of hexagonal boron nitride (hBN), resulting ... More
A Stochastic Temporal Model of Polyphonic MIDI Performance with OrnamentsApr 08 2014Aug 03 2016We study indeterminacies in realization of ornaments and how they can be incorporated in a stochastic performance model applicable for music information processing such as score-performance matching. We point out the importance of temporal information, ... 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
Tunneling transport in a few monolayer-thick WS2/graphene heterojunctionNov 18 2014Dec 09 2014This paper demonstrates the high-quality tunnel barrier characteristics and layer number controlled tunnel resistance of a transition metal dichalcogenide (TMD) measuring just a few monolayers in thickness. Investigation of vertical transport in WS2 and ... 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
Dry-transferred CVD graphene for inverted spin valve devicesSep 05 2017Integrating high-mobility graphene grown by chemical vapor deposition (CVD) into spin transport devices is one of the key tasks in graphene spintronics. We use a van der Waals pickup technique to transfer CVD graphene by hexagonal boron nitride (hBN) ... More
BN/Graphene/BN Transistors for RF ApplicationsAug 09 2011In this letter, we demonstrate the first BN/Graphene/BN field effect transistor for RF applications. The BN/Graphene/BN structure can preserve the high mobility of graphene, even when it is sandwiched between a substrate and a gate dielectric. Field effect ... More
Boundary Scattering in Ballistic GrapheneMay 23 2012We report magnetotransport measurements in ballistic graphene/hexagonal boron nitride mesoscopic wires where the charge carrier mean free path is comparable to wire width $W$. Magnetoresistance curves show characteristic peak structures where the peak ... More
Robust nonabelian ground states and continuous quantum phase transitions in a half filled bilayer graphene Landau levelNov 22 2016In a topological quantum bit, quantum information is protected from decoherence by the energy gap separating the nonabelian vacuum from higher energy modes. Experimental systems predicted to harbor nonabelions range from p-wave superfluids to superconducting ... More
Ballistic transport exceeding 28 μm in CVD grown grapheneNov 27 2015Jan 12 2016We report on ballistic transport over more than 28 \mu m in graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride. The structures are fabricated by an advanced dry van-der-Waals transfer method and exhibit ... 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
Generation and detection of pure valley current by electrically induced Berry curvature in bilayer grapheneJan 20 2015Valley is a useful degree of freedom for non-dissipative electronics since valley current that can flow even in an insulating material does not accompany electronic current. We use dual-gated bilayer graphene in the Hall bar geometry to electrically control ... More
High-quality dry transferred CVD bilayer grapheneApr 14 2017We report on the fabrication and characterization of high-quality chemical vapor-deposited (CVD) bilayer graphene (BLG). In particular, we demonstrate that CVD-grown BLG can mechanically be detached from the copper foil by an hexagonal boron nitride (hBN) ... 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
Impact of nuclear "pasta" on neutrino transport in collapsing stellar coresJan 12 2007Apr 18 2007Nuclear ``pasta'', nonspherical nuclei in dense matter, is predicted to occur in collapsing supernova cores. We show how pasta phases affect the neutrino transport cross section via weak neutral current using several nuclear models. This is the first ... More
Absorptive pinhole collimators for ballistic Dirac fermions in grapheneNov 16 2016Nov 17 2016Ballistic electrons in solids can have mean free paths far larger than the smallest features patterned by lithography. This has allowed development and study of solid-state electron-optical devices such as beam splitters and quantum point contacts, which ... More
Possibility of Deconfined Criticality in SU(N) Heisenberg Models at Small NJul 01 2013Dec 15 2013To examine the validity of the scenario of the deconfined critical phenomena, we carry out a quantum Monte Carlo simulation for the SU($N$) generalization of the Heisenberg model with four-body and six-body interactions. The quantum phase transition between ... More
Nanosecond spin lifetimes in bottom-up fabricated bilayer graphene spin-valves with atomic layer deposited Al$_2$O$_3$ spin injection and detection barriersJul 09 2015We present spin transport studies on bi- and trilayer graphene non-local spin-valves which have been fabricated by a bottom-up fabrication method. By this technique, spin injection electrodes are first deposited onto Si$^{++}$/SiO$_2$ substrates with ... More
From diffusive to ballistic transport in etched graphene constrictions and nanoribbonsJun 29 2017Graphene nanoribbons and constrictions are envisaged as fundamental components of future carbon-based nanoelectronic and spintronic devices. At nanoscale, electronic effects in these devices depend heavily on the dimensions of the active channel and the ... More
Aharonov-Bohm oscillations and magnetic focusing in ballistic graphene ringsSep 02 2017We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. We investigate phase-coherent transport and show Aharonov-Bohm (AB) oscillations in quasi-ballistic graphene rings with hard confinement. ... More
Angular Power Spectrum in Modular Invariant Inflation ModelSep 25 2006Nov 28 2006We propose a scalar potential of inflation, motivated by modular invariant supergravity, and compute the angular power spectra of the adiabatic density perturbations that result from this model. The potential consists of three scalar fields, S, Y and ... More
Quantum Hall Effect, Screening and Layer-Polarized Insulating States in Twisted Bilayer GrapheneOct 20 2011We investigate electronic transport in dual-gated twisted bilayer graphene. Despite the sub-nanometer proximity between the layers, we identify independent contributions to the magnetoresistance from the graphene Landau level spectrum of each layer. We ... More
Imaging Electron Motion in a Few Layer MoS2 DeviceAug 07 2016Ultrathin sheets of MoS2 are a newly discovered 2D semiconductor that holds great promise for nanoelectronics. Understanding the pattern of current flow will be crucial for developing devices. In this talk, we present images of current flow in MoS2 obtained ... More
Multiple point adsorption in a heteropolymer gel and the Tanaka approach to imprinting: Experiment and TheorySep 13 2003Heteropolymer gels can be engineered to release specific molecules into or absorb molecules from a surrounding solution. This remarkable ability is the basis for developing gel applications in extensive areas such as drug delivery, waste cleanup, and ... More
Electrical spin injection into graphene through monolayer hexagonal boron nitrideMay 30 2013We demonstrate electrical spin injection from a ferromagnet to a bilayer graphene (BLG) through a monolayer (ML) of single-crystal hexagonal boron nitride (h-BN). A Ni81Fe19/ML h-BN/BLG/h-BN structure is fabricated using a micromechanical cleavage and ... More
Weak Localization and Electron-electron Interactions in Few Layer Black Phosphorus DevicesAug 01 2016Few layer phosphorene(FLP) devices are extensively studied due to its unique electronic properties and potential applications on nano-electronics . Here we present magnetotransport studies which reveal electron-electron interactions as the dominant scattering ... More
A high-mobility electronic system at an electrolyte-gated oxide surfaceOct 11 2014Electrolyte gating is a powerful technique for accumulating large carrier densities in surface two-dimensional electron systems (2DES). Yet this approach suffers from significant sources of disorder: electrochemical reactions can damage or alter the surface ... 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
Exciton energy-momentum map of hexagonal boron nitrideAug 07 2015Understanding and controlling the way excitons propagate in solids is a key for tailoring materials with improved optoelectronic properties. A fundamental step in this direction is the determination of the exciton energy-momentum dispersion. Here, thanks ... More
Band gap and broken chirality in single-layer and bilayer grapheneAug 11 2015Aug 21 2015Chirality is one of the key features governing the electronic properties of single- and bilayer graphene: the basics of this concept and its consequences on transport are presented in this review. By breaking the inversion symmetry, a band gap can be ... More
Line Shape of the Raman 2D Peak of Graphene in Van Der Waals HeterostructuresAug 09 2016The Raman 2D line of graphene is widely used for device characterization and during device fabrication as it contains valuable information on e.g. the direction and magnitude of mechanical strain and doping. Here we present systematic asymmetries in the ... More
Spatial control of laser-induced doping profiles in graphene on hexagonal boron nitrideNov 02 2015We present a method to create and erase spatially resolved doping profiles in graphene-hexagonal boron nitride (hBN) heterostructures. The technique is based on photo-induced doping by a focused laser and does neither require masks nor photo resists. ... More
Quantum transport through MoS$_2$ constrictions defined by photodopingDec 04 2016We present a device scheme to explore mesoscopic transport through molybdenum disulfide (MoS$_2$) constrictions using photodoping. The devices are based on van-der-Waals heterostructures where few-layer MoS$_2$ flakes are partially encapsulated by hexagonal ... More
Identifying suitable substrates for high-quality graphene-based heterostructuresOct 27 2016We report on a scanning confocal Raman spectroscopy study investigating the strain-uniformity and the overall strain and doping of high-quality chemical vapour deposited (CVD) graphene-based heterostuctures on a large number of different substrate materials, ... More
Spin lifetimes exceeding 12 nanoseconds in graphene non-local spin valve devicesFeb 08 2016We show spin lifetimes of 12.6 ns and spin diffusion lengths as long as 30.5 \mu m in single layer graphene non-local spin transport devices at room temperature. This is accomplished by the fabrication of Co/MgO-electrodes on a Si/SiO$_2$ substrate and ... 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
Nanosecond spin lifetimes in single- and few-layer graphene-hBN heterostructures at room temperatureJun 10 2014We present a new fabrication method of graphene spin-valve devices which yields enhanced spin and charge transport properties by improving both the electrode-to-graphene and graphene-to-substrate interface. First, we prepare Co/MgO spin injection electrodes ... More
Disorder From the Bulk Ionic Liquid in Electric Double Layer TransistorsJan 23 2018Ionic liquid gating has a number of advantages over solid-state gating, especially for flexible or transparent devices and for applications requiring high carrier densities. However, the large number of charged ions near the channel inevitably results ... More
Probing electronic lifetimes and phonon anharmonicities in high-quality chemical vapor deposited graphene by magneto-Raman spectroscopyNov 29 2015We present a magneto-Raman study on high-quality single-layer graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride by a dry transfer technique. By analyzing the Raman D, G, and 2D peaks, we find that ... More
Low B Field Magneto-Phonon Resonances in Single-Layer and Bilayer GrapheneApr 14 2015Apr 16 2015Many-body effects resulting from strong electron-electron and electron-phonon interactions play a significant role in graphene physics. We report on their manifestation in low B field magneto-phonon resonances in high quality exfoliated single-layer and ... More
Electrical generation and detection of spin waves in a quantum Hall ferromagnetJan 25 2018Spin waves are essential to understanding the intrinsic ordering and thermodynamic properties of magnetic systems. An attractive candidate for studying long-lived spin-wave physics is the quantum Hall (QH) ferromagnet, which forms spontaneously in clean ... More
Large spin relaxation anisotropy and valley-Zeeman spin-orbit coupling in WSe2/Gr/hBN heterostructuresDec 15 2017Dec 18 2017Large spin-orbital proximity effects have been predicted in graphene interfaced with a transition metal dichalcogenide layer. Whereas clear evidence for an enhanced spin-orbit coupling has been found at large carrier densities, the type of spin-orbit ... More
Photo-thermionic effect in vertical graphene heterostructuresJan 16 2016Jun 10 2016Finding alternative optoelectronic mechanisms that overcome the limitations of conventional semiconductor devices is paramount for detecting and harvesting low-energy photons. A highly promising approach is to drive a current from the thermal energy added ... More
Evidence for a Spin Phase Transition at ν=0 in Bilayer GrapheneDec 16 2012Feb 16 2013The most celebrated property of the quantum spin Hall effect is the presence of spin-polarized counter-propagating edge states. This novel edge state configuration has also been predicted to occur in graphene when spin-split electron- and hole-like Landau ... More
Electrical characterization of fully encapsulated ultra thin black phosphorus-based heterostructures with graphene contactsDec 03 2014The presence of finite bandgap and high mobility in semiconductor few-layer black phosphorus offers an attractive prospect for using this material in future two-dimensional electronic devices. Here we demonstrate for the first time fully encapsulated ... More
Nonlinear Transport of Graphene in the Quantum Hall RegimeNov 14 2016We have studied the breakdown of the integer quantum Hall (QH) effect with fully broken symmetry, in an ultra-high mobility graphene device sandwiched between two single crystal hexagonal boron nitride substrates. The evolution and stabilities of the ... More
Electrically Tunable Excitonic Light Emitting Diodes based on Monolayer WSe2 p-n JunctionsDec 05 2013Mar 04 2014Light-emitting diodes are of importance for lighting, displays, optical interconnects, logic and sensors. Hence the development of new systems that allow improvements in their efficiency, spectral properties, compactness and integrability could have significant ... 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
High-Mobility Holes in Dual-Gated WSe$_2$ Field-Effect TransistorsSep 13 2015We demonstrate dual-gated $p$-type field-effect transistors (FETs) based on few-layer tungsten diselenide (WSe$_2$) using high work-function platinum source/drain contacts, and a hexagonal boron nitride top-gate dielectric. A device topology with contacts ... More
Quantum Oscillations in Black Phosphorus Two-dimensional Electron GasNov 24 2014Two-dimensional electron gases (2DEG) have been an important source of experimental discovery and conceptual development in condensed matter physics for decades. When combined with the unique electronic properties of two-dimensional (2D) crystals, rich ... More
Fabry-Pérot interference in gapped bilayer graphene with broken anti-Klein tunnelingJun 13 2014Sep 30 2014We report the experimental observation of Fabry-P\'erot (FP) interference in the conductance of a gate-defined cavity in a dual-gated bilayer graphene (BLG) device. The high quality of the BLG flake, combined with the device's electrical robustness provided ... 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
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
Unconventional Correlation between Quantum Hall Transport Quantization and Bulk State Filling in Gated Graphene DevicesNov 04 2015Oct 28 2016We report simultaneous transport and scanning microwave impedance microscopy to examine the correlation between transport quantization and filling of the bulk Landau levels in the quantum Hall regime in gated graphene devices. Surprisingly, a comparison ... More
Stacking transition in bilayer graphene caused by thermally activated rotationDec 07 2016Crystallographic alignment between two-dimensional crystals in van der Waals heterostructures brought a number of profound physical phenomena, including observation of Hofstadter butterfly and topological currents, and promising novel applications, such ... 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
Emergence of Topologically Protected Helical States in Minimally Twisted Bilayer GrapheneFeb 08 2018Bilayer graphene samples in which inversion symmetry is broken have quantum valley Hall ground states that support counterpropogating topologically protected helical (TPH) edge states localized along domain walls between AB and BA stacking regions. Moreover, ... More
Direct exciton emission from atomically thin transition metal dichalcogenide heterostructures near the lifetime limitApr 30 2017We demonstrate the reduction of the inhomogeneous linewidth of the free excitons in atomically thin transition metal dichalcogenides (TMDCs) MoSe$_{2}$, WSe$_{2}$ and MoS$_{2}$ by encapsulation within few nanometer thick hBN. Encapsulation is shown to ... More
Anisotropic Etching of Graphite and Graphene in a Remote Hydrogen PlasmaMar 14 2017We investigate the etching of a pure hydrogen plasma on graphite samples and graphene flakes on SiO$_2$ and hexagonal Boron-Nitride (hBN) substrates. The pressure and distance dependence of the graphite exposure experiments reveals the existence of two ... 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
Tunable $Γ- K$ Valley Populations in Hole-Doped Trilayer WSe$_2$Jan 10 2018We present a combined experimental and theoretical study of valley populations in the valence bands of trilayer WSe$_2$. Shubnikov$-$de Haas oscillations show that trilayer holes populate two distinct subbands associated with the $K$ and $\Gamma$ valleys, ... 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
Hot Carrier-Assisted Intrinsic Photoresponse in GrapheneAug 18 2011Nov 17 2011Graphene is a new material showing high promise in optoelectronics, photonics, and energy-harvesting applications. However, the underlying physical mechanism of optoelectronic response has not been established. Here, we report on the intrinsic optoelectronic ... More
Spin and valley quantum Hall ferromagnetism in grapheneJan 19 2012In a graphene Landau level (LL), strong Coulomb interactions and the fourfold spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At partial filling, exchange interactions can spontaneously break this symmetry, manifesting as additional ... More
Raman spectroscopy as probe of nanometer-scale strain variations in grapheneJun 30 2014Mar 30 2015Confocal Raman spectroscopy is a versatile, non-invasive investigation tool and a major workhorse for graphene characterization. Here we show that the experimentally observed Raman 2D line width is a measure of nanometer-scale strain variations in graphene. ... More
Large N Expansion for Strongly-coupled Boson-Fermion MixturesOct 20 2010We study a many-body mixture of an equal number of bosons and two-component fermions with a strong contact attraction. In this system bosons and fermions can be paired into composite fermions. We construct a large N extension where both bosons and fermions ... More
Noise Response Data Reveal Novel Controllability Gramian for Nonlinear Network DynamicsJun 03 2016Control of nonlinear large-scale dynamical networks, e.g., collective behavior of agents interacting via a scale-free connection topology, is a central problem in many scientific and engineering fields. For the linear version of this problem, the so-called ... More
Asymptotic States in Two Black Hole Moduli SpaceJul 27 2004Oct 14 2004We discuss the quantum states in the moduli space, which constructed with maximally charged dilaton black holes. Considering the quantum mechanics in the moduli space, we obtain the asymptotic states for the near-coincident black holes and the widely ... More
On the symmetry of commuting differential operators with singularities along hyperplanesSep 03 2003Feb 14 2004We study the commutants of a Schr\"{o}dinger operator whose potential function possesses inverse square singularities along some hyperplanes passing through the origin. It is shown that the Weyl group symmetry of the potential function and the commutants ... 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
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
Bounded Optimal Exploration in MDPApr 05 2016Within the framework of probably approximately correct Markov decision processes (PAC-MDP), much theoretical work has focused on methods to attain near optimality after a relatively long period of learning and exploration. However, practical concerns ... More
Formation and evolution of molecular hydrogen in disk galaxies with different masses and Hubble typesJul 24 2014We investigate the physical properties of molecular hydrogen (H2) in isolated and interacting disk galaxies with different masses and Hubble types by using chemodynamical simulations with H2 formation on dust grains and dust growth and destruction in ... More
Rotation and multiple stellar population in globular clustersOct 19 2010We investigate structure and kinematics of the second generation of stars (SG) formed from gaseous ejecta of the first generation of stars (FG) in forming globular clusters (GCs). We consider that SG can be formed from gaseous ejecta from AGB stars of ... More
Ram pressure stripping of halo gas in disk galaxies: Implications on galactic star formation in different environmentsJul 25 2009We numerically investigate evolution of gaseous halos around disk galaxies in different environments ranging from small groups to rich clusters in order to understand galaxy evolution in these environments. Our simulations self-consistently incorporate ... More
Origin of lower velocity dispersions of ultra-compact dwarf galaxy populations in clusters of galaxiesJul 31 2007Recent observations have revealed that velocity dispersions of ``ultra-compact dwarf'' (UCD) galaxies are significantly smaller than those of other galaxy populations in the Fornax and the Virgo clusters of galaxies. In order to understand the origin ... More
Galactic star formation enhanced and quenched by ram pressure in groups and clustersNov 13 2013We investigate how ram pressure of intragroup and intracluster medium can influence the spatial and temporal variations of star formation (SF) of disk galaxies with halo masses (M_h) ranging from 10^10 M_sun to 10^12 M_sun (i.e., from dwarf irregular ... More
The influences of the Magellanic Clouds on the Galaxy: Pole shift, warp, and star formation historyFeb 02 2012We investigate how the Large Magellanic Cloud (LMC) influences the evolution of the Galaxy after the LMC enters into the virial radius of the dark matter halo of the Galaxy for the first time. Both the Galaxy and the LMC are modeled as N-body particles ... More
Turbulent pattern formation and diffusion in the early-time dynamics in the relativistic heavy-ion collisionJul 03 2013Oct 19 2013We propose a picture of turbulent pattern formation in the relativistic heavy-ion collision, which follows an efficient process to break color strings and dispose energy in the whole phase space. We perform numerical simulations using the SU(2) pure Yang-Mills ... More
Effects of chiral restoration on the behaviour of the Polyakov loop at strong couplingSep 26 2002Nov 28 2002We discuss the relation between the Polyakov loop and the chiral order parameter at finite temperature. For that purpose we analyse an effective model proposed by Gocksch and Ogilvie, which is constructed by the double expansion of strong coupling and ... More
Generic features of the phase transition in cold and dense quark matterApr 03 2012Aug 17 2012We investigate the phase transition in cold and dense quark matter in an intuitive way that shares common features of the effective model approaches. We first express the quasi-particle contribution to the thermodynamic potential with the dynamical mass ... More
Evolving Glasma and Kolmogorov SpectrumNov 04 2011Nov 13 2011We present a pedagogical introduction to the theoretical framework of the Color Glass Condensate (CGC) and the McLerran-Venugopalan (MV) model. We discuss the application of the MV model to describe the early-time dynamics of the relativistic heavy-ion ... More
Relation between color deconfinement and chiral restoration at finite temperature and densityMar 14 2004We discuss the relation between color deconfinement characterized by the Polyakov loop and chiral restoration characterized by the chiral condensate. We clarify how and why these two phenomena should take place at the same pseudo-critical temperature. ... More
Wave Operators for Schrödinger Operators with Threshold Singuralities, RevisitedAug 24 2015The continuity property in the Sobolev space $W^{k,p}({\bf R}^m)$ of wave operators of scattering theory for $m$-dimensional single-body Schr\"odinger operator is considered when the resolvent of the operator has singularities at the bottom of the continuous ... More
Dark impact and galactic star formation: Origin of the Gould beltJun 28 2009The Milky Way has a giant stellar structure in the solar neighborhood, which has a size of $\sim 1$ kpc, a mass of $\sim 10^6 {\rm M}_{\odot}$, and a ring-like distribution of young stars. Fundamental physical properties of this local enigmatic structure, ... More
Formation of blue compact dwarf galaxies from merging and interacting gas-rich dwarfsMay 06 2008We present the results of numerical simulations which show the formation of blue compact dwarf (BCD) galaxies from merging between very gas-rich dwarfs with extended HI gas disks. We show that dwarf-dwarf merging can trigger central starbursts and form ... More
The Galactic globular cluster system as a fossil record of reionizationJun 22 2005We propose that structural, kinematical, and chemical properties of the Galactic globular clusters (GCs) can contain fossil information of the cosmic reionization history. We first summarize possible observational evidences for the influence of reionization ... More
Formation of metal-poor gaseous halo in gas-rich galaxy mergersApr 18 1998We numerically investigate chemodynamical evolution of interstellar medium (ISM) in gas-rich disk-disk galaxy mergers in order to explore the origin of fundamental chemical properties of halo ISM observed in elliptical galaxies. Main results obtained ... More
Formation of ultra-compact blue dwarf galaxies and their evolution into nucleated dwarfsOct 15 2015We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf-dwarf merging. We consider the observational fact that ... More
A possible physical connection between helium-rich stellar populations of massive globular clusters and the UV upturn of galactic spheroidsDec 22 2011We discuss a possible physical connection between helium-rich (Y > 0.35) stellar populations of massive globular clusters (GCs) and the ultraviolet (UV) upturn of galactic spheroids by using analytical and numerical models. In our model, all stars are ... More
When was the Large Magellanic Cloud accreted onto the Galaxy ?Jun 13 2011Using fully self-consistent N-body models for the dynamical evolution of the Large Magellanic Cloud (LMC) in the Galaxy, we show that if the LMC initially has an extended old stellar halo before its commencement of tidal interaction with the Galaxy, physical ... More