Results for "H. Sugawara"

total 85390took 0.14s
Unusual behaviors in the transport properties of REFe$_{4}$P$_{12}$ (RE: La, Ce, Pr, and Nd)Oct 02 2000We have investigated the resistivity ($\rho$), thermoelectric power (TEP) and Hall coefficient ($R_{H}$) on high quality single crystals of REFe$_{4}$P$_{12}$. TEP in CeFe$_{4}$P$_{12}$ is extremely large ($\sim$ 0.5mV/K at 290K) with a peak of $\sim$ ... More
Anomalous properties in the low-carrier ordered phase of PrRu4P12: Consequence of hybridization between conduction and Pr 4f electronsAug 04 2009The low-carrier ordered phase below the metal-non-metal transition temperature T_MI ~ 63 K of PrRu4P12 is explored by probing magnetoresistance, magnetic susceptibility, thermoelectric power, and Hall effect on high quality single crystals. All the measured ... More
Fermi surface of the filled-skutterudite superconductor LaRu4P12: A clue to the origin of the metal-insulator transition in PrRu4P12Apr 24 2005We report the de Haas-van Alphen (dHvA) effect and magnetoresistance in the filled-skutterudite superconductor LaRu4P12, which is a reference material of PrRu4P12 that exhibits a metal-insulator (M-I) transition at T_MI~60 K. The observed dHvA branches ... More
Fermi surface of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$Oct 28 2002Dec 11 2002We have investigated the de Haas-van Alphen effect in the Pr-based heavy fermion superconductor PrOs$_4$Sb$_{12}$.The topology of Fermi surface is close to the reference compound LaOs$_4$Sb$_{12}$ and well explained by the band structure calculation based ... More
Abrupt Emergence of Pressure-Induced Superconductivity of 34 K in SrFe2As2: A Resistivity Study under PressureOct 27 2008Nov 19 2008We report resistivity measurement under pressure in single crystals of SrFe_2As_2, which is one of the parent materials of Fe-based superconductors. The structural and antiferromagnetic (AFM) transition of T_0 = 198 K at ambient pressure is suppressed ... More
Novel features in the flux-flow resistivity of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$Apr 16 2005Jul 19 2005We have investigated the electrical resistivity of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$ in the mixed state. We found unusual double minima in the flux-flow resistivity as a function of magnetic field below the upper critical field for ... More
Effect of Uniaxial Stress for Pressure-Induced Superconductor SrFe_2As_2Apr 29 2009Jun 17 2009We report that the pressure-temperature phase diagram of single-crystalline SrFe$_2$As$_2$ is easily affected by the hydrostaticity of a pressure-transmitting medium. For all of the three mediums we used, superconductivity with zero resistance appears, ... More
Evidence for s-wave superconductivity with antiferromagnetic fluctuations in filled skutterudite LaFe$_{4}$P$_{12}$: $^{139}$La and $^{31}$P-NMR studiesOct 05 2005We have performed $^{139}$La,$^{31}$P-NMR studies on a filled skutterudite superconductor LaFe$_{4}$P$_{12}$ with a critical temperature $T_c=4.1$ K. In the normal state, the presence of antiferromagnetic (AFM) fluctuations at finite wave vectors is suggested ... More
Magnetic Phase Diagram of the Heavy-Fermion Superconductor PrOs4Sb12Mar 26 2003We investigated the magnetic phase diagram of the first Pr-based heavy fermion superconductor PrOs4Sb12 by means of high-resolution dc magnetization measurements in low temperatures down to 0.06K. The temperature dependence of the magnetization M(T) at ... More
On the Symmetry of Low-Field Ordered Phase of PrFe4P12 : 31P NMRJan 22 2007Apr 02 2007We have performed 31P nuclear magnetic resonance (NMR) experiments on the filled skutterudite compound PrFe4P12 to investigate the exotic ordered phase at low temperatures and low magnetic fields. Analysis of the NMR line splitting in the ordered phase ... More
BPS mass spectrum from D-brane actionMay 03 1996We derive the BPS mass formulae of the Dirichlet branes from the Born-Infeld type action. BPS saturation is realized when the brane has the minimal volume while keeping the appropriate winding numbers. We apply the idea to two cases, type IIA superstring ... More
Low-lying optical phonon modes in the filled skutterudite CeRu4Sb12Nov 02 2006The phonon dynamics of filled skutterudite CeRu4Sb12 have been studied at room temperature by inelastic neutron scattering. Optical phonons associated with a large vibration of Ce atoms are observed at a relatively low energy of E = 6 meV, and show anticrossing ... More
Topological String on AdS_3 x NSep 21 1999Feb 04 2000We study the topologically twisted string theory on the general back-ground $AdS_3\times {\cal N}$ which is compatible with the world-sheet N=2 superconformal symmetry and is extensively discussed in the recent works (hep-th/9904024, hep-th/9904040). ... More
Thermodynamics of Superstring on Near-extremal NS5 and Effective Hagedorn BehaviorAug 17 2012Oct 08 2012We study the thermodynamical torus partition function of superstring on the near-extremal black NS5-brane background. The exact partition function has been computed with the helps of our previous works:[arXiv:1012.5721 [hep-th]], [arXiv:1109.3365 [hep-th]], ... More
Thermal Partition Function of Superstring on Compactified PP-WaveJan 07 2003Jan 15 2003We study the thermal partition function of superstring on the pp-wave background with the circle compactification along a transverse direction. We calculate it in the two ways: the operator formalism and the path-integral calculation. The former gives ... More
Evolution of superconductivity in Pr$_{1-x}$La$_{x}$Os$_{4}$Sb$_{12}$: Upper critical field measurementsJun 28 2006Measurements of the upper critical field $H_{c2}$ near $T_c$ of Pr$_{1- x}$La$_{x}$Os$_{4}$Sb$_{12}$ were performed by specific heat. A positive curvature in $H_{c2}$ versus $T$ was observed in samples and concentrations exhibiting two superconducting ... More
On the Proof of Vanishing Cosmological Constant in String TheoryDec 15 2013The proof of 4-dimensional cosmological constant is given for the 10-dimensional supergravity-super-Yang-Mills theory. Supersymmetry is broken at will. The proof is very simple and it is based on the scale invariance of the theory but it assumes a nouvelle ... More
`Analytic Continuation' of N=2 Minimal ModelNov 19 2013In this paper we discuss what theory should be identified as the `analytic continuation' with $N \rightarrow -N$ of the ${\cal N}=2$ minimal model with the central charge $\hat{c} = 1 - \frac{2}{N}$. We clarify how the elliptic genus of the expected model ... More
Pressure-Temperature-Magnetic Field Phase Diagram of Ferromagnetic Kondo Lattice CeRuPONov 06 2013We report the temperature-pressure-magnetic field phase diagram made from electrical resistivity measurements for the ferromagnetic (FM) Kondo lattice CeRuPO. The ground state at zero field changes from the FM state to another state, which is suggested ... More
High magnetic field phase diagram of PrOs4Sb12May 08 2003Sep 02 2003The magnetic phase diagram of PrOs$_4$Sb$_{12}$ has been investigated by specific heat measurements between 8 and 32 T. A new Schottky anomaly due to excitations between two lowest crystalline-electric-field (CEF) singlets, has been found for both $H ... More
Thermal Amplitudes in DLCQ Superstrings on PP-WavesSep 18 2002Jan 15 2003We calculate the thermal partition function of DLCQ superstring on the maximally supersymmetric pp-wave background, which is realized as the Penrose limit of orbifolded $AdS_5\times S^5$ and known to be dual to the $\cN=2$ ``large'' quiver gauge theory ... More
On the String Actions for the Generalized Two-dimensional Yang-Mills TheoriesJan 19 1996Jun 13 1996We study the structures of partition functions of the large $N$ generalized two-dimensional Yang-Mills theories ($gYM_2$) by recasting the higher Casimirs. We clarify the appropriate interpretations of them and try to extend the Cordes-Moore-Ramgoolam's ... More
Thermal Partition Functions for S-branesJul 03 2003Jul 15 2003We calculate the thermal partition functions of open strings on the S-brane backgrounds (the bouncing or rolling tachyon backgrounds) both in the bosonic and superstring cases. According to hep-th/0302146, we consider the discretized temperatures compatible ... More
N=(0,4) Quiver $SCFT_2$ and Supergravity on $AdS_3 \times S^2$Mar 15 1999Jul 06 1999We study the proposed duality between the 5-dimensional supergravity/superstring on $AdS_3\times S^2$ and the 2-dimensional N=(0,4) SCFT defined on the boundary of AdS-space. We construct explicitly the N=(0,4) SCFT by imposing the `quiver projection' ... More
Sb-NQR probe for superconducting property in the Pr-based filled skutterudite compound PrRu4Sb12Mar 27 2003We report the electronic and superconducting properties in the Pr-based filled-skutterudite superconductor PrRu$_4$Sb$_{12}$ with $T_c = 1.3$ K via the measurements of nuclear-quadrupole-resonance (NQR) frequency $\nu_Q$ and nuclear-spin-lattice-relaxation ... More
Nonmagnetic Impurity Effect of the S=1/2 Spin Ladder System (pipdH)_2Cu_{1-x}Zn_xBr_4May 07 2013May 08 2013We report the synthesis and the magnetic susceptibility of (pipdH)2Cu1-xZnxBr4, which is a nonmagnetic impurity-doped S=1/2 spin ladder system. The samples were synthesized from a solution by using a slow evaporation method. Samples were confirmed to ... More
Comments on Non-holomorphic Modular Forms and Non-compact Superconformal Field TheoriesSep 15 2011Aug 01 2014We extend our previous work arXiv:1012.5721 [hep-th] on the non-compact N=2 SCFT_2 defined as the supersymmetric SL(2,R)/U(1)-gauged WZW model. Starting from path-integral calculations of torus partition functions of both the axial-type (`cigar') and ... More
Probing the superconducting gap symmetry of PrOs$_{4}$Sb$_{12}$: A penetration depth studyAug 22 2003Sep 11 2003We report measurements of the magnetic penetration depth $\lambda$ in single crystals of PrOs$_{4}$Sb$_{12}$ down to $\sim$0.1 K using a tunnel-diode based, self-inductive technique at 21 MHz, with the ac field applied along the \textit{a}, \textit{b} ... More
Magnetic, thermal, and transport properties on single crystals of antiferromagnetic Kondo-lattice Ce2PdSi3May 10 2000Magnetization, heat capacity, electrical resistivity, thermoelectric power, and Hall effect have been investigated on single-crystalline Ce_2PdSi_3. This compound is shown to order antiferromagnetically below N'eel temperature (T_N) \~3 K. The Sommerfeld ... More
Drastic change in transport of entropy with quadrupolar ordering in PrFe$_{4}$P$_{12}$Dec 19 2005May 16 2006The antiferroquadrupolar ordering of PrFe$_{4}$P$_{12}$ is explored by probing thermal and thermoelectric transport. The lattice thermal conductivity drastically increases with the ordering, as a consequence of a large drop in carrier concentration and ... More
Evolution of superconducting order in Pr(Os$_{1-x}$Ru$_{x}$)$_{4}$Sb$_{12}$Nov 16 2004Nov 17 2004We report measurements of the magnetic penetration depth $\lambda$ in single crystals of Pr(Os$_{1-x}$Ru$_{x}$)$_{4}$Sb$_{12}$ down to 0.1 K. Both $\lambda$ and superfluid density $\rho_{s}$ exhibit an exponential behavior for the $x$$\geq$0.4 samples, ... More
Collective Dynamics of Active Elements: Task Allocation and Pheromone TrailingAug 25 2004Collective behavior of active elements inspired by mass of biological organisms is addressed. Especially, two topics are focused on among amazing behaviors performed by colony of ants. First, task allocation phenomena are treated from the viewpoint of ... More
The effect of uniaxial pressure on the magnetic anomalies of the heavy-fermion metamagnet CeRu2Si2Jun 11 2002The effect of uniaxial pressure (P_u) on the magnetic susceptibility (X), magnetization (M), and magnetoresistance (MR) of the heavy-fermion metamagnet CeRu2Si2 has been investigated. For the magnetic field along the tetragonal c axis, it is found that ... More
Pressure suppression of spin-density-wave gap in the optical conductivity of SrFe2As2Mar 18 2013Optical reflectance R(w) of a pressure-induced superconductor SrFe2As2 has been measured under external pressure to 6 GPa and at temperatures to 8 K. Optical conductivity s(w) has been derived from the measured R(w). At ambient pressure, in the antiferromagnetic ... More
Anomalous Anisotropic Magnetoresistance in Heavy-Fermion PrFe4P12Jun 25 2008We have investigated the anisotropy of the magnetoresistance in the Pr-based HF compound PrFe4P12. The large anisotropy of effective mass and its strong field dependence have been confirmed by resistivity measurements. Particularly for H||[111], where ... More
Anomalous heavy-fermion and ordered states in the filled skutterudite PrFe4P12Jan 04 2002Specific heat and magnetization measurements have been performed on high-quality single crystals of filled-skutterudite PrFe_4P_{12} in order to study the high-field heavy-fermion state (HFS) and low-field ordered state (ODS). From a broad hump observed ... More
123Sb-NQR study of unconventional superconductivity in the filled skutterudite heavy-fermion compound PrOs4Sb12 under high pressure up to P = 3.82 GPaJun 30 2008We report $^{123}$Sb nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs$_4$Sb$_{12}$ under high pressure. The temperature dependence of NQR frequency and the spin-lattice relaxation rate $1/T_1$ ... More
Probing the superconducting gap symmetry of PrRu$_{4}$Sb$_{12}$: A comparison with PrOs$_{4}$Sb$_{12}$Feb 25 2004We report measurements of the magnetic penetration depth $\lambda$ in single crystals of PrRu$_{4}$Sb$_{12}$ down to 0.1 K. Both $\lambda$ and superfluid density $\rho_{s}$ exhibit an exponential behavior for $T$ $<$ 0.5$T_{c}$, with parameters $\Delta$(0)/\textit{k}$_{B}$\textit{T}$_{c}$ ... More
Transport properties of the heavy fermion superconductor PrOs$_{4}$Sb$_{12}$Apr 29 2005Jul 19 2005We have measured the electrical resistivity, thermoelectric power, Hall coefficient, and magnetoresistance (MR) on single crystals of PrOs$_{4}$Sb$_{12}$, LaOs$_{4}$Sb$_{12}$ and NdOs$_{4}$Sb$_{12}$. All the transport properties in PrOs$_{4}$Sb$_{12}$ ... More
Thermodynamical Study on the Heavy-Fermion Superconductor PrOs4Sb12: Evidence for Field-Induced Phase TransitionJun 11 2002Sep 10 2002We report measurements of low-temperature specific heat on the 4f^2-based heavy-fermion superconductor PrOs4Sb12. In magnetic fields above 4.5 T in the normal state, distinct anomalies are found which demonstrate the existence of a field-induced ordered ... More
Magnetic anisotropy, first-order-like metamagnetic transitions and large negative magnetoresistance in the single crystal of Gd$_{2}$PdSi$_3$Aug 09 1999Electrical resistivity ($\rho$), magnetoresistance (MR), magnetization, thermopower and Hall effect measurements on the single crystal Gd$_{2}$PdSi$_3$, crystallizing in an AlB$_2$-derived hexagonal structure are reported. The well-defined minimum in ... More
Specific Heat Study on Heavy-Fermion Pr compounds with filled skutterudite structureOct 27 2002Rare 4f^2-based heavy-fermion behaviors have been revealed recently in Pr-based filled skutterudites PrFe4P12 and PrOs4Sb12. Recent studies on the thermal properties on both compounds are reported, putting emphasis on the field-induced ordered phase found ... More
Transport properties in CeOs$_{4}$Sb$_{12}$: Possibility of the ground state being semiconductingDec 22 2004Apr 03 2005We have measured both magnetoresistance and Hall effect in CeOs$_4$Sb$_{12}$ to clarify the large resistivity state ascribed to the Kondo insulating one and the origin of the phase transition near 0.9 K reported in the specific heat measurement. We found ... More
Multiband Superconductivity in Filled-Skutterudite Compounds (Pr_{1-x}La_{x})Os_{4}Sb_{12}: An Sb Nuclear-Quadruple-Resonance (NQR) StudyOct 09 2006We report on Sb nuclear-quadrupole-resonance (NQR) study in filled-skutterudite compounds (Pr_1-xLa_x)Os_4Sb_12. The Sb-NQR spectra have split into two sets, arising from different Sb_12 cages containing either Pr or La, which enables us to measure two ... More
Optical Conductivity and Electronic Structure of CeRu4Sb12 under High PressureMar 04 2011Jan 13 2012Optical conductivity [s(w)] of Ce-filled skutterudite CeRu4Sb12 has been measured at high pressure to 8 GPa and at low temperature, to probe the pressure evolution of its electronic structures. At ambient pressure, a mid-infrared peak at 0.1 eV was formed ... More
Magnetic fluctuations and superconductivity in YbPd$_2$SnMay 29 2002Jun 10 2002We report muon spin relaxation and inelastic neutron measurements on the Heusler system YbPd$_2$Sn. Localised anisotropic and quasi-elastic Yb magnetic fluctuations are observed below $T = 150$K. Both $\mu$SR and neutron data indicate a slowing-down of ... More
Gap opening with ordering in PrFe4P12 studied by local tunneling spectroscopyApr 15 2008We present measurements of the local tunneling density of states in the low temperature ordered state of PrFe4P12. The temperature dependencies of the Fermi level density of states and of the integrated density of states at low bias voltages show anomalies ... More
Possible Kondo resonance in PrFe4P12 studied by bulk-sensitive photoemissionAug 21 2002Jul 16 2004Pr 4f electronic states in Pr-based filled skutterudites PrT4X12(T=Fe and Ru; X=P and Sb) have been studied by high-resolution bulk-sensitive Pr 3d-4f resonance photoemission. A very strong spectral intensity is observed just below the Fermi level in ... More
Superconducting phase diagram of the filled skuterrudite PrOs4Sb12Feb 27 2004Mar 16 2004We present new measurements of the specific heat of the heavy fermion superconductor PrOs4Sb12, on a sample which exhibits two sharp distinct anomalies at Tc1= 1.89K and Tc2= 1.72K. They are used to draw a precise magnetic field-temperature superconducting ... More
Exotic Heavy Fermion State in the Filled Skutterudite PrFe$_4$P$_{12}$ Uncovered by the de Haas-van Alphen EffectSep 30 2000Aug 19 2002We report the de Haas-van Alphen (dHvA) experiment on the filled skutterudite PrFe$_4$P$_{12}$ exhibiting apparent Kondo-like behaviors in the transport and thermal properties. We have found enormously enhanced cyclotron effective mass $m^{\rm \ast}_{\rm ... More
Multiple Superconducting Phases in New Heavy Fermion Superconductor PrOs4Sb12Sep 24 2002The superconducting gap structure of recently discovered heavy fermion superconductor PrOs4Sb12 was investigated by using thermal transport measurements in magnetic field rotated relative to the crystal axes. We demonstrate that a novel change in the ... More
Boundary States of D-branes in AdS_3 Based on Discrete SeriesJul 23 2001May 14 2002We study D-branes in the Lorentzian AdS_3 background from the viewpoint of boundary states, emphasizing the role of open-closed duality in string theory. Employing the world sheet with Lorentzian signature, we construct the Cardy states with the discrete ... More
Fractional Strings in (p,q) 5-brane and Quiver Matrix String TheoryMay 30 1998We study the (p,q)5-brane dynamics from the viewpoint of Matrix string theory in the T-dualized ALE background. The most remarkable feature in the (p,q)5-brane is the existence of ``fractional string'', which appears as the instanton of 5-brane gauge ... More
Compact Formulas for the Completed Mock Modular FormsJul 29 2014Nov 27 2014In this paper we present a new compact expression of the elliptic genus of SL(2)/U(1)-supercoset theory by making use of the `spectral flow method' of the path-integral evaluation. This new expression is written in a form like a Poincare series with a ... More
Modular Bootstrap for Boundary N=2 Liouville TheoryNov 17 2003Jan 29 2004We study the boundary N=2 Liouville theory based on the ``modular bootstrap'' approach. As fundamental conformal blocks we introduce the ``extended characters'' that are defined as the proper sums over spectral flows of irreducible characters of the N=2 ... More
D-branes in Singular Calabi-Yau n-fold and N=2 Liouville TheoryNov 16 2000Dec 26 2000Making use of the N=2 Liouville theory and world-sheet techniques, we study the properties of D-branes wrapped around vanishing SUSY cycles of singular Calabi-Yau n-folds (n=2,3,4). After constructing boundary states describing the wrapped branes, we ... More
A thermodynamic force generated by chemical gradient and adsorption reactionSep 05 2009Biological units such as macromolecules, organelles, and cells are directed to a proper location under gradients of relevant chemicals. By considering a macroscopic element that has binding sites for a chemical adsorption reaction to occur on its surface, ... More
Superconducting Gap Structure of LaFePO Studied by Thermal ConductivityJun 03 2009The superconducting gap structure of LaFePO ($T_c=7.4 $K) is studied by thermal conductivity ($\kappa$) at low temperatures in fields $H$ parallel and perpendicular to the c axis. A clear two-step field dependence of $\kappa(H)$ with a characteristic ... More
Double superconducting transition in the filled skutterudite PrOs4Sb12 and sample characterizationsMar 27 2007A thorough characterization of many samples of the filled skutterudite compound PrOs4Sb12 is provided. We find that the double superconducting transition in the specific heat Tc1~1.89K and Tc2~1.72K tends to appear in samples with a large residual resistivity ... More
Non-holomorphic Modular Forms and SL(2,R)/U(1) Superconformal Field TheoryDec 28 2010Mar 04 2011We study the torus partition function of the SL(2,R)/U(1) SUSY gauged WZW model coupled to N=2 U(1) current. Starting from the path-integral formulation of the theory, we introduce an infra-red regularization which preserves good modular properties and ... More
CFT Description of String Theory Compactified on Non-compact Manifolds with G_2 HolonomyAug 14 2001Aug 23 2001We construct modular invariant partition functions for strings propagating on non-compact manifolds of G_2 holonomy. Our amplitudes involve a pair of N=1 minimal models M_m, M_{m+2} (m=3,4,...) and are identified as describing strings on manifolds of ... More
Duality in N=4 Liouville Theory and Moonshine PhenomenaMar 09 2016May 20 2016We consider the ${\cal N}=4$ Liouville theory by varying the linear dilaton coupling constant $\cal{Q}$. It is known that at two different values of coupling constant ${\cal Q}=\sqrt{{2\over N}},-(N-1)\sqrt{{2\over N}}$ system exhibits two different small ... More
Multi-Strings on AdS_3 x S^3 from Matrix String TheoryMay 02 1999Aug 02 1999We analyze the Coulomb branch of Matrix string theory in the presence of NS5-branes. If we regard the components of U(1) gauge fields as the dualized longitudinal coordinates, we obtain the symmetric product of AdS_3 x S^3 x R^4 as the geometry of Coulomb ... More
Broken $S_3$ Symmetry in Flavor PhysicsNov 26 2010Dec 10 2010The $S_3$ symmetry is shown to be a very good approximate symmetry when it is broken in a specific way. This is true both in quark sector and in lepton sector. The way to break it is implied by the K-M mechanism applied not to the mixing matrix but to ... More
D-branes in T-fold conformal field theorySep 03 2007Feb 08 2008We investigate boundary dynamics of orbifold conformal field theory involving T-duality twists. Such models typically appear in contexts of non-geometric string compactifications that are called monodrofolds or T-folds in recent literature. We use the ... More
Mirrorfolds with K3 FibrationsNov 07 2007May 06 2008We study a class of non-geometric string vacua realized as completely soluble superconformal field theory (SCFT). These models are defined as `interpolating orbifolds' of $K3 \times S^1$ by the mirror transformation acting on the $K3$ fiber combined with ... More
Branches of N=1 Vacua and Argyres-Douglas PointsMay 07 2003May 30 2003We study the N=1 version of Argyres-Douglas (AD) points by making use of the recent developments in understanding the dynamics of the chiral sector of N=1 gauge theories. We shall consider N=1 U(N) gauge theories with an adjoint matter and look for the ... More
Modular Invariance in Superstring on Calabi-Yau n-fold with A-D-E SingularityFeb 12 2000Mar 09 2000We study the type II superstring theory on the background $\br^{d-1,1}\times X_n$, where $X_n$ is a Calabi-Yau $n$-fold ($2n+d=10$) with an isolated singularity, by making use of the holographically dual description proposed by Giveon-Kutasov-Pelc (hep-th/9907178). ... More
Superstrings on PP-Wave Backgrounds and Symmetric OrbifoldsMay 20 2002Jul 01 2002We study the superstring theory on pp-wave background with NSNS-flux that is realized as the Penrose limit of AdS_3 x S^3 x M^4, where M^4 is T^4 or T^4/Z_2(~ K3). Quantizing this system in the covariant gauge, we explicitly construct the space-time supersymmetry ... More
Superstring Vacua of 4-dimensional PP-Waves with Enhanced SupersymmetryJul 12 2002Nov 18 2002We study the superstring vacua constructed from the conformal field theories of the type H_4 x M, where H_4 denotes the super Nappi-Witten model (super WZW model on the 4-dimensional Heisenberg group H_4) and M denotes an arbitrary N=2 rational superconformal ... More
SL(2,R)/U(1) Supercoset and Elliptic Genera of Non-compact Calabi-Yau ManifoldsMar 19 2004Jul 31 2006We first discuss the relationship between the SL(2;R)/U(1) supercoset and N=2 Liouville theory and make a precise correspondence between their representations. We shall show that the discrete unitary representations of SL(2;R)/U(1) theory correspond exactly ... More
Conifold Type Singularities, N=2 Liouville and SL(2;R)/U(1) TheoriesNov 03 2004Jan 17 2005In this paper we discuss various aspects of non-compact models of CFT of the type: $ \prod_{j=1}^{N_L} {N=2 Liouville theory}_j \otimes \prod_{i=1}^{N_M} {N=2 minimal model}_i $ and $ \prod_{j=1}^{N_L}{SL(2;R)/U(1) supercoset}_j \otimes \prod_{i=1}^{N_M} ... More
More on Non-supersymmetric Asymmetric Orbifolds with Vanishing Cosmological ConstantMay 23 2016Jul 31 2016We explore various non-supersymmetric type II string vacua constructed based on asymmetric orbifolds of tori with vanishing cosmological constant at the one loop. The string vacua we present are modifications of the models studied in arXiv:1512.05155[hep-th], ... More
Instanton and Spectral Flow in Topological Conformal Field TheoriesApr 08 1993A class of two-dimensional topological conformal field theories (TCFTs) is studied within the framework of gauged WZW models in order to gain some insights on the global geometrical nature of TCFTs. The BRST quantizations of topological G/H gauged WZW ... More
Topological Gauged WZW Models and 2D GravityApr 16 1992Apr 17 1992We study the "topological gauged WZW model associated with $SU(2)/U(1)$",which is defined as the twisted version of the corresponding supersymmetric gauged WZW model. It is shown that this model is equivalent to a topological conformal field theory characterized ... More
D-brane Analyses for BPS Mass Spectra and U-dualityJul 24 1997Apr 06 1998We give a confirmation of U-duality of type II superstring by discussing mass spectrum of the BPS states. We first evaluate the mass spectrum of BPS solitons with one kind of R-R charges. Our analysis is based on the 1-loop effective action of D-brane, ... More
Lie algebra lattices and strings on T-foldsNov 24 2016We study the world-sheet conformal field theories for T-folds systematically based on the Lie algebra lattices representing the momenta of strings. The fixed point condition required for the T-duality twist restricts the possible Lie algebras. When the ... More
Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor La(O$_{1-x}$F$_x$)FeAsMay 20 2008We report high-resolution photoemission spectroscopy of newly-discovered iron-based layered superconductor La(O$_{0.93}$F$_{0.07}$)FeAs (Tc = 24 K). We found that the superconducting gap shows a marked deviation from the isotropic s-wave symmetry. The ... More
Atomic displacements and lattice distortion in the magnetic-field-induced charge ordered state of SmRu$_{4}$P$_{12}$Nov 02 2016Structural properties of SmRu$_4$P$_{12}$ in the anomalous magnetic ordered phase between $T^*\sim 14 $ K and $T_{\text{N}}=16.5$ K in magnetic fields has been studied by x-ray diffraction. Atomic displacements of Ru and P, reflecting the field-induced ... More
BRST-Fixed Points and Topological Conformal SymmetryApr 15 1992We study the twisted version of the supersymmetric $G/T=SU(n)/U(1)^{\otimes(n-1)} gauged Wess-Zumino-Witten model. By studying its fixed points under BRST transformation this model is shown to be reduced to a simple topological field theory, that is, ... More
Non-geometric Backgrounds Based on Topological InterfacesFeb 20 2015Jul 03 2015We study simple models of the world-sheet CFTs describing non-geometric backgrounds based on the topological interfaces, the `gluing condition' of which imposes T-duality- or analogous twists. To be more specific, we start with the torus partition function ... More
Hilbert Space of Space-time SCFT in AdS_3 Supersting and T^{4kp}/S_{kp} SCFTDec 11 1998Jan 14 1999We explore the superstring theory on AdS_3 x S^3 x T^4 in the framework given in hep-th/9806194. We argue on the Hilbert space of "space-time CFT", and especially construct a suitable vacuum of this CFT from the physical degrees of freedom of the superstring ... More
String Theory on G_2 Manifolds Based on Gepner ConstructionNov 01 2001Nov 30 2001We study the type II string theories compactified on manifolds of $G_2$ holonomy of the type $({Calabi-Yau 3-fold} \times S^1)/\bz_2$ where $CY_3$ sectors realized by the Gepner models. We construct modular invariant partition functions for $G_2$ manifold ... More
Pattern dynamics in a two-dimensional gas discharge system : Intermittent collapse and recreation, moving of spots, dynamic change of clustersMar 14 2005Apr 30 2009Reaction-diffusion equation model for a 2-dimensional gas discharge system is introduced in close relationship with the recent experiment by Nasuno. The model shows formation of spots, molecule-like organization of a cluster of spots, moving of spots, ... More
Universal scaling in the dynamical conductivity of heavy fermion Ce and Yb compoundsApr 27 2006Feb 01 2007Dynamical conductivity spectra s(w) have been measured for a diverse range of heavy-fermion (HF) Ce and Yb compounds. A characteristic excitation peak has been observed in the mid-infrared region of s(w) for all the compounds, and has been analyzed in ... More
Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor CrAsDec 22 2016In conventional metals, modification of electron trajectories under magnetic field gives rise to a magnetoresistance that varies quadratically at low field, followed by a saturation at high field for closed orbits on the Fermi surface. Deviations from ... More
Penetration depth study of LaOs$_4$Sb$_{12}$: Multiband s-wave superconductivityJun 11 2012We measured the magnetic penetration depth $\lambda(T)$ in single crystals of LaOs$_{4}$Sb$_{12}$ ($T_c$=0.74 K) down to 85 mK using a tunnel diode oscillator technique. The observed low-temperature exponential dependence indicates a s-wave gap. Fitting ... More
Evidence for Unconventional Strong-coupling Superconductivity in PrOs_4Sb_12 : An Sb Nuclear Quadrupole Resonance (NQR) StudySep 04 2002Sep 05 2002We report Sb-NQR results which evidence a heavy-fermion (HF) behavior and an unconventional superconducting (SC) property in the filled-skutterudite compound PrOs_4Sb_12 revealing a SC transition temperature T_c=1.85 K. The temperature (T) dependence ... More
ASTRO-H White Paper - Stars -- Accretion, Shocks, Charge Exchanges and Magnetic PhenomenaDec 03 2014X-ray emission from stars has origins as diverse as the stars themselves: accretion shocks, shocks generated in wind-wind collisions, or release of magnetic energy. Although the scenarios responsible for X-ray emission are thought to be known, the physical ... More
Time-Reversal Symmetry-Breaking Superconductivity in Heavy Fermion PrOs4Sb12 detected by Muon Spin RelaxationAug 11 2003We report on muon spin relaxation measurements of the 4f^2-based heavy-fermion superconductor filled-skutterudite PrOs4Sb12. The results reveal the spontaneous appearance of static internal magnetic fields below the superconducting transition temperature, ... More
Direct Observation of Quadrupolar Excitons in the Heavy-Fermion Superconductor PrOs$_{4}$Sb$_{12}$Feb 28 2005Sep 07 2005We report inelastic neutron scattering experiments performed to investigate the low energy magnetic excitations on single crystals of the heavy-fermion superconductor PrOs$_{4}$Sb$_{12}$. The observed excitation clearly softens at a wave vector Q = (1,0,0), ... More
Measurement of the 6Li(e,e'p) reaction cross sections at low momentum transferOct 27 1998Dec 18 1998The triple differential cross sections for the 6Li(e,e'p) reaction have been measured in the excitation energy region from 27 to 46 MeV in a search for evidence of the giant dipole resonance (GDR) in 6Li. The cross sections have no distinct structures ... More
Comment on "Pronounced Enhancement of the Lower Critical Field and Critical Current Deep in the Superconducting State of PrOs4Sb12"Jun 02 2010Cichorek et al. [Phys. Rev. Lett. 94, 107002 (2005)] reported enhancements of the lower critical field Hc1(T) and critical current in superconducting PrOs4Sb12 below a transition temperature Tc3 ~ 0.6 K, and speculated that this reflects a transition ... More
f-Electron-Nuclear Hyperfine-Coupled Multiplets in the Unconventional Charge Order Phase of Filled Skutterudite PrRu4P12May 11 2011In the unconventional f-electron-associated charge order phase of filled skutterudite PrRu4P12, the low-temperature behaviors of the triplet crystalline-electric-field ground state of Pr ions have been studied by specific heat and magnetization measurements ... More
Reverberation Measurements of the Inner Radius of the Dust Torus in 17 Seyfert GalaxiesJun 09 2014We present the results of a dust reverberation survey for 17 nearby Seyfert 1 galaxies, which provides the largest homogeneous data collection for the radius of the innermost dust torus. A delayed response of the K-band light curve after the V-band light ... More
Domain walls in (Ga,Mn)As diluted magnetic semiconductorFeb 12 2008We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization ... More
Electronic structure of semiconducting CeFe$_4$P$_{12}$: Strong hybridization and relevance of single-impurity Anderson modelJan 06 2006Semiconducting skutterudite CeFe$_4$P$_{12}$ is investigated by synchrotron x-ray photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Ce 3$d$ core-level PES and 3$d-4f$ XAS, in combination with single impurity Anderson model (SIAM) ... More
Pressure suppression of unconventional charge-density-wave state in PrRu4P12 studied by optical conductivityFeb 14 2012Apr 24 2012Optical conductivity s(w) of PrRu4P12 has been studied under high pressure to 14 GPa, at low temperatures to 8 K, and at photon energies 12 meV-1.1 eV. The energy gap in s(w) at ambient pressure, caused by a metal-insulator transition due to an unconventional ... More
Nonsaturating large magnetoresistance in the high carrier density nonsymmorphic metal CrPMar 14 2019The band structure of high carrier density metal CrP features an interesting crossing at the Y point of the Brillouin zone. The crossing, which is protected by the nonsymmorphic symmetry of the space group, results in a hybrid, semi-Dirac-like energy-momentum ... More
Liouville Field, Modular Forms and Elliptic GeneraNov 30 2006Mar 20 2007When we describe non-compact or singular Calabi-Yau manifolds by CFT, continuous as well as discrete representations appear in the theory. These representations mix in an intricate way under the modular transformations. In this article, we propose a method ... More