Tiny Graviton Matrix Theory On Time-Dependent Background

In this article we construct a tiny graviton matrix model for type IIB string theory on a plane-wave background with null dilaton. For the linear null dilaton case, we analyze its vacuum and the excitation spectrum around the vacuum, and discuss the time-dependent fuzzy three-sphere solutions and their evolution. It turns out that at very late time the non-Abelian fuzzy degrees of freedom disappear, which indicates the appearance of perturbative strings.Comment: 20 pages and 4 figures; published version, with more clarification

D1-D3 (or D3ˉ\bar{\textrm{D}3}) Systems with Fluxes

In this article we study D1-D3 (or $\bar{\textrm{D}3}$) brane systems with generic constant electric and magnetic fluxes in IIB string theory. We work out all possible supersymmetric configurations and find out via T-duality all of them and corresponding supersymmetry conditions could be related to the supersymmetric intersecting D1-D1 pairs. And we do D1-D3 (or $\bar{\textrm{D}3}$) open string quantization for a class of configurations. We find that there are many near massless states in NS sector for near-BPS configurations. Furthermore we calculate open string pair creation rate in generic nonsupersymmetric configurations.Comment: 31 pages. References adde

Strong Subadditivity and Emergent Surface

In this paper, we introduce two bounds which we call the Upper Differential Entropy and the Lower Differential Entropy for an infinite family of intervals(strips) in quantum field theory. The two bounds are equal provided that the theory is translational invariant and the entanglement entropy varies smoothly with respect to the interval. When the theory has a holographic dual, strong subadditivity of entanglement entropy indicates that there is always an emergent surface whose gravitational entropy is exactly given by the bound.Comment: 18 pages, 8 figures, replace "residual entropy" to "differential entropy

Hidden Conformal Symmetry and Quasi-normal Modes

We provide an algebraic way to calculate the quasi-normal modes of a black hole, which possesses a hidden conformal symmetry. We construct an infinite tower of quasi-normal modes from the highest-weight mode, in a simple and elegant way. For the scalar, the hidden conformal symmetry manifest itself in the fact that the scalar Laplacian could be rewritten in terms of the $SL(2,R)$ quadratic Casimir. For the vector and the tensor, the hidden conformal symmetry acts on them through Lie derivatives. We show that for three-dimensional black holes, with appropriate combination of the components the radial equations of the vector and the tensor could be written in terms of the Lie-induced quadratic Casimir. This allows the algebraic construction of the quasi-normal modes feasible. Our results are in good agreement with the previous study.Comment: 23 pages; references added; typos corrected, more clarifications, published versio

Note on DBI dynamics of Dbrane Near NS5-branes

In this note, we investigate the homogeneous radial dynamics of (Dp, NS5)-systems without and with one compactified transverse direction, in the framework of DBI effective action. During the homogeneous evolution, the electric field on the D-brane is always conserved and the radial motion could be reduced to an one-dimension dynamical system with an effective potential. When the Dp-brane energy is not high, the brane moves in a restricted region, with the orbits depending on the conserved energy, angular momentum through the form of the effective potential. When the Dp-brane energy is high enough, it can escape to the infinity. It turns out that the conserved angular momentum plays an interesting role in the dynamics. Moreover, we discuss the gauge dynamics around the tachyon vacuum and find that the dynamics is very reminiscent of the string fluid in the rolling tachyon case.Comment: 13 pages, 2 figures; typos corrected, discussions improved; gauge dynamics has been include

On short interval expansion of R\'enyi entropy

R\'enyi entanglement entropy provides a new window to study the AdS/CFT correspondence. In this paper we consider the short interval expansion of R\'enyi entanglement entropy in two-dimensional conformal field theory. This amounts to do the operator product expansion of the twist operators. We focus on the vacuum Verma module and consider the quasiprimary operators constructed from the stress tensors. After obtaining the expansion coefficients of the twist operators to level 6 in vacuum Verma module, we compute the leading contributions to the R\'enyi entropy, to order 6 in the short interval expansion. In the case of one short interval on cylinder, we reproduce the first several leading contributions to the R\'enyi entropy. In the case of two short disjoint intervals with a small cross ratio $x$, we obtain not only the classical and 1-loop quantum contributions to the R\'enyi entropy to order $x^6$, both of which are in perfect match with the ones found in gravity, but also the leading $1/c$ contributions, which corresponds to 2-loop corrections in the bulk.Comment: V1, 23 pages, 5 figures; V2, published version, typos corrected, references adde