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Jnanadeva Maharana

Publications and source records attributed to Jnanadeva Maharana.

At least 37 records · Page 2Linked to original sources
arXiv2005

The Algebra of Transition Matrices for the AdS_5 x S^5 Superstring

We consider integrability properties of the superstring on $AdS_{5}\times S^{5}$ background and construct a new one parameter family of currents which satisfies the vanishing curvature condition. We present the Hamiltonian analysis for the sigma model action and determine the Poisson algebra of the transition matrices. We reveal the generalization of the $\mathbb{Z}_{4}$ automorphism analogous to the sigma models defined on a symmetric space coset. A possible regularization scheme for the ambiguities present, which respects the generalized automorphism, is also discussed.

hep-th↗
arXiv2004

Symmetries of Axion-dilaton String Cosmology

The axion-dilaton string effective action is expressed in Einstein frame metric in a manifestly S-duality invariant form. It is shown that the moduli can be redefined to describe surface of a 2+1 dimensional pseudosphere. The classical cosmological solutions are of axion-dilaton are revisited. The Wheeler De Witt equation for the system is exactly solved and complete set of eigenfunctions are presented. The wave function factorizes and the one depending on the moduli is obtained by appealing to the underlying S-duality symmetry. Axion and dilaton parametrize the coset SU(1,1)/U(1), the S-duality group, and the Hamiltonian is expressed as a sum of the Ricci scalar and the Casimir of SU(1,1). Therefore, the complete set of wave functions, depending on the moduli, is obtained from group theory technique. The evidence for the existence of a W-infinity algebra in axion-dilaton cosmology is presented and the origin of the algebra is primarily due to high degree of degeneracies in the wave functions. It is qualitatively argued that axion-dilaton quantum cosmology exhibits chaotic behaviour in the semiclassical limit.

hep-th↗
arXiv2002

Novel Symmetries in Axion-Dilaton Cosmology

The symmetry structure of axion-dilaton quantum string cosmology is investigated. The invariance of the string effective action under S-duality group, SU(1,1), facilitates solution of Wheeler-De Witt equation from group theoretic considerations; revealing existence of a new class of wave functions. We discover the an underlying ${W}$-infinity algebra in this formulation.

hep-th↗
arXiv2002

From Big Crunch to Big Bang: A Quantum String Cosmology Perspective

The scenario that the Universe contracts towards a big crunch and then undergoes a transition to expanding Universe in envisaged in the quantum string cosmology approach. The Wheeler-De Witt equation is solved exactly for an exponential dilaton potential. S-duality invariant cosmological effective action, for type IIB theory, is considered to derive classical solutions and solve WDW equations.

gr-qc↗
arXiv1999

Recent Developments in String Theory

The purpose of this short review is to present progresses in string theory in the recent past. There have been very important developments in our understanding of string dynamics, especially in the nonperturbative aspects. In this context, dualities play a cardinal role. The string theory provides a deeper understanding of the physics of special class of black holes from a microscopical point of view and has resolved several important questions. It is also recognized that M-theory provides a unified description of the five perturbatively consistent string theories. The article covers some of these aspects and highlights important progress made in string theory.

hep-th↗
arXiv1998

Hidden Symmetries of M Theory

A worldvolume action for membrane is considered to study the target space local symmetries. We introduce a set of generators of canonical transformations to exhibit the target space symmetries such as the general coordinate transformation and the gauge transformation of antisymmetric tensor field. Similar results are derived for type IIB string with manifestly S-duality-invariant worldsheet action.

hep-th↗
arXiv1997

An SL(2, Z) Multiplet of Black Holes in $D = 4$ Type II Superstring Theory

It is well-known that the conjectured SL(2, Z) invariance of type IIB string theory in ten dimensions also persists in lower dimensions when the theory is compactified on tori. By making use of this recent observation, we construct an infinite family of magnetically charged black hole solutions of type II superstring theory in four space-time dimensions. These solutions are characterized by two relatively prime integers corresponding to the magnetic charges associated with the two gauge fields (from NS-NS and R-R sectors) of the theory and form an SL(2, Z) multiplet. In the extremal limit these solutions are stable as they are prevented from decaying into black holes of lower masses by a `mass gap' equation.

hep-th↗
arXiv1997

S-duality and Compactification of type IIB Superstring Action

The SL(2,R) invaraint ten dimensional type IIB superstring effective action is compactified on a torus to D spacetime dimensions. The transformation properties of scalar, vector and tensor fields, appearing after the dimensional reduction, are obtained in order to maintain the SL(2,R)} invariance of the reduced effective action. The symmetry of the action enables one to generate new string vacua from known configurations. As illustrative examples, new black hole solutions are obtained in five and four dimensions from a given set of solutions of the equations of motion.

hep-th↗
arXiv1995

Dualities in Five Dimensions and Charged String Solutions

We consider an eleven dimensional supergravity compactified on $K3\times T^2$ and show that the resulting five dimensional theory has identical massless states as that of heterotic string compactified on a specific five torus $T^5$. The strong-weak coupling duality of the five dimensional theory is argued to represent a ten dimensional Type $IIA$ string compactified on $K3 \times S^1$, supporting the conjecture of string-string duality in six dimensions. In this perspective, we present magnetically charged solution of the low energy heterotic string effective action in five dimensions with a charge defined on a three sphere $S^3$ due to the two form potential. We use the Poincare duality to replace the antisymmetric two form with a gauge field in the effective action and obtain a string solution with charge on a two sphere $S^2$ instead of that on a three sphere $S^3$ in the five dimensional spacetime. We note that the string-particle duality is accompanied by a change of topology from $S^3$ to $S^2$ and viceversa.

hep-th↗
arXiv1995

M Theory and P-Branes

Ten dimensional type IIA and IIB theories with p-branes are compactified to 8-dimensions. It is shown that resulting branes can be classified according to the representations of $\bf {SL(3,Z) \times SL(2,Z)}$. These p-branes can also be obtained by compactification of M theory on three torus and various wrappings of membrane and five brane of the eleven dimensional theory. It is argued that there is evidence for bound states of the branes in eight dimensions as is the case in the interpretation of $\bf {SL(2,Z)}$ family of string solutions obtained by Schwarz.

hep-th↗
arXiv1995

S-DUALITY AND THE ENTROPY OF BLACK HOLES IN HETEROTIC STRING THEORY

Four dimensional heterotic string effective action is known to admit non-rotating electrically and magnetically charged black hole solutions. It is shown that the partition functions and entropies in both the cases are identical when these black hole solutions are related by S-duality transformations. The entropy is computed and is vanishing for each black hole in the extremal limit.

hep-th↗
arXiv1995

HIDDEN SYMMETRIES OF TWO DIMENSIONAL STRING EFFECTIVE ACTION

The ten dimensional heterotic string effective action with graviton, dilaton and antisymmetric tensor fields is dimensionally reduced to two spacetime dimensions. The resulting theory, with some constraints on backgrounds, admits infinite sequence of conserved nonlocal currents. It is shown that generators of the infinitesimal transformations associated with these currents satisfy Kac-Moody algebra.

hep-th↗
arXiv1995

SYMMETRIES OF THE DIMENSIONALLY REDUCED STRING EFFECTIVE ACTION

A two dimensional string effective action is obtained by dimensionally reducing the bosonic part of the ten dimensional heterotic string effective action. It is shown that this effective action, with a few restrictions on some backgrounds describes a two dimensional model which admits an infinite sequence of nonlocal conserved currents.

hep-th↗
arXiv1994

Four Dimensional String-String Solutions and Symmetries of String Effective Action

A string action is considered in four spacetime dimensions which is obtained by dimensionally reducing the ten dimensional effective action. The equations of motion admit string like solutions. The symmetry properties of the four dimensional action is discussed. It is shown that new background configurations can be generated by implementing suitable $O(d,d)$ transformations.

hep-th↗
arXiv1994

Planckian Scattering of Non-abelian Gauge Particles

We present a systematic study of high energy scattering of non-abelian gauge particles in (3+1) dimensional Einstein gravity using semi-classical techniques of Verlinde and Verlinde. It is shown that the BRST gauge invariance of the Yang-Mills action in presence of quantum gravity at Planckian energy regime is maintained and the vertex operator is invariant under the BRST transformations. The presence of gravitational shock wave describing the gauge particles is discussed in the resulting (3+1) dimensional effective theory of Yang-Mills gravity.

hep-th↗
arXiv1994

Duality of the Superstring in Superspace

The evolution of a closed NSR string is considered in the background of constant graviton and antisymmetric fields. The $σ$-model action is written in a manifestly supersymmetric form in terms of superfields. The first order formalism adopted for the closed bosonic string is generalised to implement duality transformations and the constant dual backgrounds are obtained for the dual theory. We recover the $G \rightarrow G^{-1}$ duality for the case when antisymmetric tensor field is set to zero. Next, the case when the backgrounds depend on one superfield, is also analysed. This scenario is similar to the cosmological case envisaged for the bosonic string. The explicit form of the duality transformation is given for this case.

hep-th↗