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Sunandan Gangopadhyay

Publications and source records attributed to Sunandan Gangopadhyay.

At least 199 records · Page 11Linked to original sources
arXiv2009

Harmonic oscillator in a background magnetic field in noncommutative quantum phase-space

We solve explicitly the two-dimensional harmonic oscillator and the harmonic oscillator in a background magnetic field in noncommutative phase-space without making use of any type of representation. A key observation that we make is that for a specific choice of the noncommutative parameters, the time reversal symmetry of the systems get restored since the energy spectrum becomes degenerate. This is in contrast to the noncommutative configuration space where the time reversal symmetry of the harmonic oscillator is always broken.

hep-th↗
arXiv2008

Free particle on noncommutative plane -- a coherent state path integral approach

We formulate the coherent state path integral on a two dimensional noncommutative plane using the fact that noncommuative quantum mechanics can be viewed as a quantum system on the Hilbert space of Hilbert-Schmidt operators acting on noncommutative configuration space. The propagation kernel for the free particle shows ultra-violet cutoff which agrees with the earlier investigations made in the literature but the approach differs substantially from the earlier studies.

math-ph↗
arXiv2008

Anomalies, Horizons and Hawking radiation

Hawking radiation is obtained from the Reissner-Nordström blackhole with a global monopole and the Garfinkle-Horowitz-Strominger blackhole falling in the class of the most general spherically symmetric blackholes $(\sqrt{-g}\neq1)$, using only chiral anomaly near the event horizon and covariant boundary condition at the event horizon. The approach differs from the anomaly cancellation approach since apart from the covariant boundary condition, the chiral anomaly near the horizon is the only input to derive the Hawking flux.

hep-th↗
arXiv2008

Hawking radiation and near horizon universality of chiral Virasoro algebra

We show that the diffeomorphism anomaly together with the trace anomaly reveal a chiral Virasoro algebra near the event horizon of a black hole. This algebra is the same irrespective of whether the anomaly is covariant or consistent, thereby manifesting its universal character and the fact that only the outgoing modes are relevant near the horizon. Our analysis therefore clarifies the role of the trace anomaly in the diffeomorphism anomaly approach \cite{wilczek, isowilczek, shailesh, shailesh2, sunandan, sunandan10, rabin10} to the Hawking radiation.

hep-th↗
arXiv2008

Some Studies in Noncommutative Quantum Field Theories

The central theme of this thesis is to study some aspects of noncommutative quantum mechanics and noncommutative quantum field theory. We explore how noncommutative structures can emerge and study the consequences of such structures in various physical models.

hep-th↗
arXiv2008

$κ$-Minkowski and Snyder algebra from reparametrisation symmetry

Following our earlier work \cite{sunandan1, sunandan2}, we derive noncommuting phase-space structures which are combinations of both the $κ$-Minkowski and Snyder algebra by exploiting the reparametrisation symmetry of the recently proposed Lagrangian for a point particle \cite{subir} satisfying the exact Doubly Special Relativity dispersion relation in the Magueijo-Smolin framework.

hep-th↗
arXiv2008

Hawking radiation in GHS blackhole, Effective action and Covariant Boundary condition

We exploit the expression for the anomalous (chiral) effective action to obtain the Hawking radiation from the GHS (stringy) blackhole falling in the class of the most general spherically symmetric blackholes $(\sqrt{-g}\neq1)$, using only covariant boundary condition at the event horizon. The connection between the anomalous and the normal energy-momentum tensors is also established from the effective action approach.

hep-th↗
arXiv2008

A study of the efficiency of the class of $W$-states as a quantum channel

Recently, a new class of $W$-states has been defined by Agarwal and Pati \cite{agarwal} and it has been shown that they can be used as a quantum channel for teleportation and superdense coding. In this work, we identify those three-qubit states from the set of the new class of $W$-states which are most efficient or suitable for quantum teleportation. We show that with some probability $|W_1>=(1/2)(|100>+|010>+\sqrt{2}|001>)$ is best suited for teleportation channel in the sense that it does not depend on the input state.

quant-ph↗
arXiv2007

Strings in pp-wave background and background B-field from membrane and its symplectic quantization

The symplectic quantization technique is applied to open free membrane and strings in pp-wave background and background gauge field obtained by compactifying the open membrane in the presence of a background anti-symmetric 3--form field. In both cases, first the Poisson brackets among the Fourier modes are obtained and then the Poisson brackets among the membrane(string) coordinates are computed. The full noncommutative phase-space structure is reproduced in case of strings in pp-wave background and background gauge field. We feel that this method of obtaining the Poisson algebra is more elegant than previous approaches discussed in the literature.

hep-th↗
arXiv2007

Hawking radiation in GHS and non-extremal D1-D5 blackhole via covariant anomalies

We apply the method of Banerjee and Kulkarni (arXiv:0707.2449, [hep-th]) to provide a derivation of Hawking radiation from the GHS (stringy) blackhole which falls in the class of the most general spherically symmetric blackholes ($\sqrt{-g}\neq 1$) and also the non-extremal $D1-D5$ blackhole using only covariant gravitational anomalies.

hep-th↗
arXiv2007

Lie algebraic noncommuting structures from reparametrisation symmetry

We extend our earlier work of revealing both space-space and space-time noncommuting structures in various models in particle mechanics exhibiting reparametrisation symmetry. We show explicitly (in contrast to the earlier results in our paper \cite{sg}) that for some special choices of the reparametrisation parameter $ε$, one can obtain space-space noncommuting structures which are Lie-algebraic in form even in the case of the relativistic free particle. The connection of these structures with the existing models in the literature is also briefly discussed. Further, there exists some values of $ε$ for which the noncommutativity in the space-space sector can be made to vanish. As a matter of internal consistency of our approach, we also study the angular momentum algebra in details.

hep-th↗
arXiv2007

Normal ordering and non(anti)commutativity in open super strings

Nonanticommutativity in an open super string moving in the presence of a background antisymmetric tensor field $\mathcal{B}_{μν}$ is investigated in a conformal field theoretic approach, leading to nonanticommutative structures. In contrast to several discussions, in which boundary conditions are taken as Dirac constraints, we first obtain the mode algebra by using the newly proposed normal ordering, which satisfies both equations of motion and boundary conditions. Using these the anticommutator among the fermionic string coordinates is obtained. Interestingly, in contrast to the bosonic case, this new normal ordering plays an important role in uncovering the underlying nonanticommutative structure between the fermionic string coordinates. We feel that our approach is more transparent than the previous ones and the results we obtain match with the existing results in the literature.

hep-th↗
arXiv2007

Noncommutativity in interpolating string: A study of gauge symmetries in noncommutative framework

A new Lagrangian description that interpolates between the Nambu--Goto and Polyakov version of interacting strings is given. Certain essential modifications in the Poission bracket structure of this interpolating theory generates noncommutativity among the string coordinates for both free and interacting strings. The noncommutativity is shown to be a direct consequence of the nontrivial boundary conditions. A thorough analysis of the gauge symmetry is presented taking into account the new modified constraint algebra, which follows from the noncommutative structures and finally a smooth correspondence between gauge symmetry and reparametrisation is established.

hep-th↗
arXiv2006

Normal ordering and noncommutativity in open bosonic strings

Noncommutativity in an open bosonic string moving in the presence of a background Neveu-Schwarz two-form field $B_{μν}$ is investigated in a conformal field theory approach, leading to noncommutativity at the boundaries. In contrast to several discussions, in which boundary conditions are taken as Dirac constraints, we first obtain the mode algebra by using the newly proposed normal ordering, which satisfies both equations of motion and boundary conditions. Using these the commutator among the string coordinates is obtained. Interestingly, this new normal ordering yields the same algebra between the modes as the one satisfying only the equations of motion. In this approach, we find that noncommutativity originates more transparently and our results match with the existing results in the literature.

hep-th↗
arXiv2006

Twisted Galilean symmetry and the Pauli principle at low energies

We show the twisted Galilean invariance of the noncommutative parameter, even in presence of space-time noncommutativity. We then obtain the deformed algebra of the Schrödinger field in configuration and momentum space by studying the action of the twisted Galilean group on the non-relativistic limit of the Klein-Gordon field. Using this deformed algebra we compute the two particle correlation function to study the possible extent to which the previously proposed violation of the Pauli principle may impact at low energies. It is concluded that any possible effect is probably well beyond detection at current energies.

hep-th↗
arXiv2005

Non(anti) commutativity for open superstrings

Non(anti)commutativity in an open free superstring and also one moving in a background anti-symmetric tensor field is investigated. In both cases, the non(anti)commutativity is shown to be a direct consequence of the non-trivial boundary conditions which, contrary to several approaches, are not treated as constraints. The above non(anti)commutative structures lead to new results in the algebra of super constraints which still remain involutive, indicating the internal consistency of our analysis.

hep-th↗
arXiv2005

Dual families of non-commutative quantum systems

We demonstrate how a one parameter family of interacting non-commuting Hamiltonians, which are physically equivalent, can be constructed in non-commutative quantum mechanics. This construction is carried out exactly (to all orders in the non-commutative parameter) and analytically in two dimensions for a free particle and a harmonic oscillator moving in a constant magnetic field. We discuss the significance of the Seiberg-Witten map in this context. It is shown for the harmonic oscillator potential that an approximate duality, valid in the low energy sector, can be constructed between the interacting commutative and a non-interacting non-commutative Hamiltonian. This approximation holds to order 1/B and is therefore valid in the case of strong magnetic fields and weak Landau-level mixing.

hep-th↗