9052236
Zero-mode Spectrum of Eleven-dimensional Theory on the Plane-wave Background
In this doctoral thesis we study zero-mode spectra of Matrix theory and eleven-dimensional supergravity on the plane-wave background. This background is obtained via the Penrose limit of AdS_4 x S^7 and AdS_7 x S^4. The plane-wave background is a maximally supersymmetric spacetime supported by non-vanishing constant four-form flux in eleven-dimensional spacetime. First, we discuss the Matrix theory on the plane-wave background suggested by Berenstein, Maldacena and Nastase. We construct the Hamiltonian, 32 supercharges and their commutation relations. We discuss a spectrum of one specific supermultiplet which represents the center of mass degrees of freedom of N D0-branes. This supermultiplet would also represent a superparticle of the eleven-dimensional supergravity in the large-N limit. Second, we study the linearized supergravity on the plane-wave background in eleven dimensions. Fixing the bosonic and fermionic fields in the light-cone gauge, we obtain the spectrum of physical modes. We obtain the fact that the energies of the states in Matrix theory completely correspond to those of fields in supergravity. Thus, we find that the Matrix theory on the plane-wave background contains the zero-mode spectrum of the eleven-dimensional supergravity completely. Through this result, we can argue the Matrix theory on the plane-wave as a candidate of quantum extension of eleven-dimensional supergravity, or as a candidate which describes M-theory.
119194039
Canonical approach to Courant brackets for D-branes
A bstractWe present an extension of the Courant bracket to the ones for Dp-branes by analyzing Hamiltonians and local superalgebras. Contrast to the basis of the bracket for a fundamental string which consists of the momentum and the winding modes, the ones for Dp-branes contain higher rank R-R coupling tensors. We show that the R-R gauge transformation rules are obtained by these Courant brackets for Dp-branes where the Dirac-Born-Infeld gauge field and the “two-vierbein field” play an essential role. Canonical analysis of the worldvolume theories naturally gives the basis of the brackets and the target space backgrounds keeping T-duality manifest at least for NS-NS sector. In a D3-brane analysis S-duality is manifest as a symmetry of interchanging the NS-NS coupling and the R-R coupling.
118872049
Worldsheet description of exotic five-brane with two gauged isometries
A bstractWe study the string worldsheet description of the background geometry of the exotic $ 5_2^2 $-brane where two isometries are gauged. This is an extension of the gauged linear sigma model (GLSM) for the exotic $ 5_2^2 $-brane with a single gauged isometry. The new GLSM with two gauged isometries has only $ \mathcal{N} $ = (2, 2) supersymmetry rather than $ \mathcal{N} $ = (4, 4) supersymmetry of the original GLSM. This is caused by a conflict between two different SU(2)R associated with the two gauge symmetries. However, if we take a certain limit, we can find the genuine string sigma model of the background geometry of the exotic $ 5_2^2 $-brane with $ \mathcal{N} $ = (4, 4) supersymmetry. We also investigate the worldsheet instanton corrections to the background geometry of the exotic $ 5_2^2 $-brane. The worldsheet instanton corrections to the string sigma model can be traced in terms of the two gauge fields in the new GLSM. This new GLSM gives rise to a different feature of the quantum corrections from the one in the GLSM with the single gauged isometry.
651290
A note on conifolds
Abstract We present the Ricci-flat metric and its Kahler potential on the conifold with the O ( N ) isometry, whose conical singularity is repaired by the complex quadric surface Q N −2 = SO ( N )/ SO ( N −2)× U (1).
15429929
Supersymmetric nonlinear sigma models on Ricci-flat Kähler manifolds with O(N) symmetry
Abstract We propose a class of N =2 supersymmetric nonlinear sigma models on the Ricci-flat Kahler manifolds with O( N ) symmetry.
8177695
Gauged linear sigma models for noncompact Calabi-Yau varieties
Abstract We study gauged linear sigma models for noncompact Calabi–Yau manifolds described as a line bundle on a hypersurface in a projective space. This gauge theory has a unique phase if the Fayet–Iliopoulos parameter is positive, while there exist two distinct phases if the parameter is negative. We find four massless effective theories in the infrared limit, which are related to each other under the Calabi–Yau/Landau–Ginzburg correspondence and the topology change. In the T-dual theory, on the other hand, we obtain two types of exact massless effective theories: one is the sigma model on a newly obtained Calabi–Yau geometry as a mirror dual, while the other is given by a Landau–Ginzburg theory with a negative power term, indicating N = 2 superconformal field theory on SL ( 2 , R ) / U ( 1 ) . We argue that the effective theories in the original gauged linear sigma model are exactly realized as N = 2 Liouville theories coupled to well-defined Landau–Ginzburg minimal models.
106401419
Phase structure of two-dimensional topological insulators by lattice strong-coupling expansion
The phase structure of 2-dimensional topological insulators under a sufficiently strong electron- electron interaction is investigated. The effective theory is constructed by extending the idea of the Kane-Mele model on the graphenelike honeycomb lattice, in terms of U(1) lattice gauge theory (quantum electrodynamics, QED). We analyze the phase structure by the techniques of strong coupling expansion of lattice gauge theory. As a result, we find that the topological phase structure of the system is modified by the electron-electron interaction. There evolves a new phase with the antiferromagnetism not parallel to the direction pointed by the spin-orbit coupling, in between the conventional and the topological insulator phases. We also discuss the physical implication of the new phase structure found here, in analogy to the parity-broken phase in lattice quantum chromodynamics (QCD), known as "Aoki phase".
119294442
Towards Holographic Spintronics
We study transport phenomena of total angular momentum in holography, as a first step toward holographic understanding of spin transport phenomena. Spin current, which has both the local Lorentz index for spins and the space-time vector index for current, couples naturally to the bulk spin connection. Therefore the bulk spin connection becomes the source for the boundary spin current. This allows us to evaluate the spin current holographically, with a relation to the stress tensor and metric fluctuations in the bulk. We examine the spin transport coefficients and the thermal spin Hall conductivity in a simple holographic setup.
15561541
Classification and Generalization of Minimal-doubling actions
We propose a method to control the number of species of lattice fermions, which yields new classes of minimally doubled lattice fermions with one exact chiral symmetry and exact locality. We classify all the known minimally doubled fermions into two types based on the locations of the propagator poles in the Brillouin zone. We also study higher-dimensional extension of them and show it tends to be more difficult to realize minimal-doub ling in higher dimensions.
15996221
Aoki phases in the lattice Gross-Neveu model with flavored mass terms
We investigate the parity-broken phase structure for staggered and naive fermions in the Gross-Neveu model as a toy model of QCD. We consider a generalized staggered Gross-Neveu model including two types of four-point interactions. We use generalized mass terms to split the doublers for both staggered and naive fermions. The phase boundaries derived from the gap equations show that the mass splitting of tastes results in an Aoki phase both in the staggered and naive cases. We also discuss the continuum limit of these models and explore taking the chirally symmetric limit by fine-tuning a mass parameter and two-coupling constants. This supports the idea that in lattice QCD we can derive one- or two-flavor staggered fermions by tuning the mass parameter, which are likely to be less expensive than Wilson fermions in QCD simulation.
20098388
Characters of Lattice Fermions Based on the Hyperdiamond Lattice
We study minimal-doubling fermion actions on hyperdiamond and deformed hyperdiamond lattices, with emphasis on the real-space construction of them and Lorentz covariance of excitations from fermion poles. We propose the improved spatial construction of Creutz fermion action on a deformed hyperdiamond lattice, and discuss conditions for a hyperdiamond-lattice action to produce Lorentz-covariant excitations from poles of fermion propagators. It is pointed out that the non-nearest-site hoppings are essential for the correct excitations. We propose a class of minimal-doubling actions defined on a deformed hypercubic lattice as a generalization of Creutz-type actions. In addition we introduce a two-parameter class of Wilczek-type minimal-doubling actions.