Sudipta Mukherji

Null vectors and extra states in c=1 string theory

Abstract The structure of the null vectors in c=25 Liouville theory is analysed, and used to study the spectrum of physical states in the c=1 string. The occurrence and nature of two kinds of “extra states” is examined: the Polyakov-type states of fixed ghost number, and the Lian-Zuckerman-type states of increasing ghost number.

ANISOTROPIC POWER-LAW INFLATION FROM ROLLING TACHYONS

We provide an explicit solution representing an anisotropic power-law inflation within the framework of rolling tachyon model. This is generated by allowing a non-minimal coupling between the tachyon and the world-volume gauge field on non-BPS D3 brane. We also show that this solution is perturbatively stable.

A note on AdS cosmology and gauge theory correlator

A bstractUsing AdS/CFT prescription, we compute two point Yang-Mills correlator on a constant time slice for the Kasner background. Pushing the surface close to the initial singularity, we find, in some cases, the correlator does not develop pole. We further numerically calculate similar correlator where the bulk is a Kasner AdS soliton. We find that the qualitative behaviour of the correlator remains unchanged.

Some all-order classical solutions in non-polynomial closed string field theory

If a conformal field theory is perturbed by a nearly marginal operator of dimension ( 1 h, 1 h ), then, under certain conditions and for a certain value of the perturbing parameter, we get a new conformal field theory. Starting from a string field theory based on the original conformal field theory, we show how to construct a classical solution in this string field theory to all orders in h , which represents string field theory formulated around the perturbed conformal field theory. We also show that the equation of motion of string field theory forces us to have a time-dependent dilaton background of the form ax 0 to order h 3 , which compensates for the change in the central charge of the conformal field theory under the perturbation.

Notes on Axion, Inflation and Graceful Exit in Stringy Cosmology

We study the classical equations of motion and the corresponding Wheeler–De Witt equations for tree level string effective action with dilaton and axion. The graceful exit problem in certain cases is then analyzed.

A Note on Brans–Dicke Cosmology with Axion

We study the Brans-Dicke model in the presence of an axion. The dynamical equations are solved when the fields are space independent and the metric is spatially flat. It is found that at late time the scale factor undergoes decelerated expansion but the dilaton grows large. At early time, scale factor and the dilaton approach constants.

Black hole solution and its infinite parameter generalization in c=1 string field theory

Abstract We construct a string field theory describing c = 1 conformal field theory coupled to two dimensional gravity, and look for classical solutions of the equations of motion of the string field. We show the existence of a solution labelled by an infinite number of parameters, which satisfies the classical equations to all orders. For certain values of the parameters, this can be identified with the recently discovered black hole solution in c = 1 string theory, by comparing their asymptotic forms. We also discuss a certain duality symmetry of these solutions.

Nonvacuum AdS cosmology and comments on gauge theory correlator

Several time dependent backgrounds, with perfect fluid matter, can be used to construct solutions of Einstein equations in the presence of a negative cosmological constant along with some matter sources. In this work we focus on the non-vacuum Kasner-AdS geometry and its solitonic generalization. To characterize these space-times, we provide ways to embed them in higher dimensional flat space-times. General space-like geodesics are then studied and used to compute the two point boundary correlators within the geodesic approximation.

Gauge transformations in string field theory and canonical transformations in string theory

We study how canonical transformations in first quantized string theory can be understood as gauge transformations in string field theory. We establish this fact by working out some examples. As a by product, we could identify some of the fields appearing in string field theory with their counterparts in the σ-model.

TARGET SPACE INTERPRETATION OF NEW MODULI IN 2D STRING THEORY

We analyze the new states that have recently been discovered in 2D string theory by E. Witten and B. Zwiebach. Since the Liouville direction is uncompactified, we show that the deformations by the new ghost number two states generate equivalent classical solutions of the string fields. We argue that the new ghost number one states are responsible for generating transformations which relate such equivalent solutions. We also discuss the possible interpretation of higher ghost number states of these.