Hiroshi Isono

Exactly Marginal Deformations of Quiver Gauge Theories as Seen from Brane Tilings

We study the relation between exactly marginal deformations in a large class of N=1 superconformal quiver gauge theories described by brane tilings and the degrees of freedom in the corresponding 5-brane systems. We show, with the help of NSVZ exact beta functions, that there are generically d-1 complex exactly marginal deformations of a gauge theory, where d is the perimeter of the corresponding n it, and the other two, the diagonal gauge coupling and a beta-like deformation, as background supergravity fields.toric diagram. We identify d-3 complex marginal deformations as deformations of the brane system and the Wilson lines on it, and the other two, the diagonal gauge coupling and a beta-like deformation, as background supergravity fields.

Boundary States in the Open String Channel and CFT near a Corner

We generalize the idea of boundary states to the open string channel. They describe emission and absorption of open strings in the presence of intersecting D-branes. We construct the explicit oscillator representation for the free boson and fermionic ghost. The inner product of such states describes a disk amplitude of rectangular shape and possesses modular covariance with a nontrivial conformal weight. We compare the result obtained here with those obtained using two different methods, one employing the path integral formalism and one employing the conformal anomaly. We find that all these methods give consistent results. In our method, we must be careful in our treatment of the singularity of the CFT near the corners. Specifically, we derive the correction to the conformal weight of the primary field inserted at the corner, and it gives the modular weight of the rectangle amplitude. We also carry out explicit computations of the correlation functions.

Nonlinear Dielectric Spectroscopy of Antiferroelectric Liquid Crystals in Various Smectic Phases

Nonlinear dielectric spectroscopy in frequency domain has been applied to antiferroelectric liquid crystals in various smectic phases including antiferroelectric SmC A *, SmC FI2 * and incommensurate SmCα* phases. We have observed different characteristic third-order nonlinear dielectric spectra ϵη3* in respective phases. In SmC A * and SmC FI2 * phases, nonlinear dielectric response originated from Goldstone-like fluctuation with long relaxation time along the helical structure have been observed, which cannot be usually observed in linear spectrum. In the SmCα* phases, we have observed the critical behavior of soft mode that condenses in the SmCα* phase by ϵ3*. The obtained nonlinear dielectric spectra are discussed by using phenomenological models for respective relaxation.

Boundary State of Superstring in Open String Channel

We derive boundary state of superstring in the open string channel. It describes the superconformal field theory of open string emission and absorption by D-brane. We define the boundary state by conformal mappings from upper half plane with operators inserted at two points corresponding to the corners of semi-infinite strip. We obtain explicit oscillator forms analytically for the fermion and superconformal ghost sectors. For the fermion sector we compare this with numerical result obtained by using naive boundary condition.

Nonlinear dielectric response of antiferroelectric liquid crystals

We measure the nonlinear dielectric response of antiferroelectric liquid crystals in the SmC A * and SmC f * phase. In the SmC A * phase, the spectrum of the third-order nonlinear permittivity l 3 * shows a Debye-type relaxation and is ascribed to the deformation of helical structure due to the coupling between dielectric anisotropy and electric field. In the SmC f * phase, the spectrum of l 3 * shows a complicated form and is explained by the Landau-type phenomenological free-energy which is composed of the ferroelectric and the antiferroelectric order parameter.

BOUNDARY STATE OF SUPERSTRING IN OPEN STRING CHANNEL

We report on the boundary state of superstring in the open string channel, which describes the superconformal field theory of open string emission and absorption by D-brane.