arXiv subjects

Indrajit Mitra

Publications and source records attributed to Indrajit Mitra.

31 records · Page 2Linked to original sources

arXiv2003

Perturbation theory including topological degrees of freedom: Yang-Mills theory in three Euclidean dimensions

A method for systematically including topological degrees of freedom in perturbation theory is developed. This is not bound by the restrictions of semi-classical techniques. The Yang-Mills theory in three Euclidean dimensions is considered here. A well-defined separation of the topological and the ``spin wave'' degrees of freedom is obtained, motivated by a singular gauge. This has ``photons'' distorting the spherically symmetric magnetic fields of Dirac monopoles, and massless charged vector bosons ``W'' scattering off the latter. It is explicitly shown that the Dirac string does not contribute. The mode of the charged vector bosons with total angular momentum J=0 provides precisely the core to give a finite energy to the monopole. The radial equation for W is remarkably simplified and only two polarization states survive exactly for the anomalous magnetic moment required by the Yang-Mills interaction.

hep-th↗

arXiv2003

Half-monopoles and half-vortices in the Yang-Mills theory

It is demonstrated that there are smooth Yang-Mills potentials which correspond to monopoles and vortices of one-half winding number. They are the generic configurations, in contrast to the integral winding number configurations like the 't Hooft-Polyakov monopole.

hep-th↗

arXiv2002

Topological field patterns of the Yang-Mills theory

It is shown that the SO(3) gauge field configurations can be completely characterised by certain gauge invariant vector fields. The singularities of these vector fields describe the topological aspects of the gauge field configurations. The topological (or monopole) charge is expressed in terms of an Abelian vector potential.

hep-th↗

arXiv2002

Double-trace operators and one-loop vacuum energy in AdS/CFT

We perform a one-loop calculation of the vacuum energy of a tachyon field in anti de-Sitter space with boundary conditions corresponding to the presence of a double-trace operator in the dual field theory. Such an operator can lead to a renormalization group flow between two different conformal field theories related to each other by a Legengre transformation in the large N limit. The calculation of the one-loop vacuum energy enables us to verify the holographic c-theorem one step beyond the classical supergravity approximation.

hep-th↗

arXiv2002

Some interesting violations of the Breitenlohner-Freedman bound

We demonstrate that AdS_5 x T^{pq} is unstable, in the sense of Breitenlohner and Freedman, for unequal p and q. This settles, negatively, the long-standing question of whether the T^{pq} manifolds for unequal p and q might correspond to non-supersymmetric fixed points of the renormalization group. We also show that the AdS_3 x S^7 vacuum of Sugimoto's USp(32) open string theory is unstable. This explains, at a heuristic level, the apparent absence of a heterotic string dual.

hep-th↗

arXiv2002

Some aspects of particle physics in thermal background

The work in this thesis uses the formalism of thermal field theory. The major problem considered by us is the gravitational interaction of charged leptons in a medium. Working in the context of the linearized theory of gravity, we have deduced general expressions for the matter-induced $O(α)$ corrections to the gravitational mass in normal matter background which contains electrons but not the other charged leptons. Explicit formulas are then given for the corrections in terms of the macroscopic parameters of the medium for a few special cases of the background gases. In the last part of the thesis, we have considered high-temperature, massless QED at zero chemical potential. We have investigated the gauge independence of the one-loop electron dispersion relation, taking subleading temperature dependence into account.

hep-ph↗

arXiv2001

The evolution of unstable black holes in anti-de Sitter space

We examine the thermodynamic stability of large black holes in four-dimensional anti-de Sitter space, and we demonstrate numerically that black holes which lack local thermodynamic stability often also lack stability against small perturbations. This shows that no-hair theorems do not apply in anti-de Sitter space. A heuristic argument, based on thermodynamics only, suggests that if there are any violations of Cosmic Censorship in the evolution of unstable black holes in anti-de Sitter space, they are beyond the reach of a perturbative analysis.

hep-th↗

arXiv2001

Gravitational couplings of charged leptons in a medium

We calculate the leading order matter-induced corrections to the gravitational interactions of charged leptons and their antiparticles in a medium that contains electrons but not the other charged leptons, such as normal matter. The gravitational coupling, which is universal at the tree level, is found to be flavor-dependent, and also different for the corresponding antiparticles, when the corrections of $O(α)$ are taken into account. General expressions are obtained for the matter-induced corrections to the gravitational mass in a generic matter background, and explicit formulas for those corrections are given in terms of the macroscopic parameters of the medium for particular conditions of the background gases.

hep-ph↗

arXiv2001

Stability of AdS_p x M_q Compactifications Without Supersymmetry

We study the stability of Freund-Rubin compactifications, AdS_p x M_q, of p+q-dimensional gravity theories with a q-form field strength and no cosmological term. We show that the general AdS_p x S^q vacuum is classically stable against small fluctuations, in the sense that all modes satisfy the Breitenlohner-Freedman bound. In particular, the compactifications used in the recent discussion of the proposed bosonic M-theory are perturbatively stable. Our analysis treats all modes arising from the graviton and the q-form, and is completely independent of supersymmetry. From the masses of the linearized perturbations, we obtain the dimensions of some operators in possible holographic dual CFT's. Solutions with more general compact Einstein spaces need not be stable, and in particular AdS_p x S^n x S^{q-n} is unstable for q < 9 but is stable for q >= 9. We also study the AdS_4 x S^6 compactification of massive type IIA supergravity, which differs from the usual Freund-Rubin compactification in that there is a cosmological term already in ten dimensions. This nonsupersymmetric vacuum is unstable.

hep-th↗

arXiv2000

Instability of charged black holes in anti-de Sitter space

We exhibit a tachyonic mode in a linearized analysis of perturbations of large anti-de Sitter Reissner-Nordstrom black holes in four dimensions. In the large black hole limit, and up to a 0.7% discrepancy which is probably round-off error in the numerical analysis, the tachyon appears precisely when the black hole becomes thermodynamically unstable.

hep-th↗

arXiv2000

Gauge Independence of Limiting Cases of One-Loop Electron Dispersion Relation in High-Temperature QED

Assuming high temperature and taking subleading temperature dependence into account, gauge dependence of one-loop electron dispersion relation is investigated in massless QED at zero chemical potential. The analysis is carried out using a general linear covariant gauge. The equation governing the gauge dependence of the dispersion relation is obtained and used to prove that the dispersion relation is gauge independent in the limiting case of momenta much larger than $eT$. It is also shown that the effective mass is not influenced by the leading temperature dependence of the gauge dependent part of the effective self-energy. As a result the effective mass, which is of order $eT$, does not receive a correction of order $e^2T$ from one loop, independent of the gauge parameter.

hep-ph↗

arXiv2000

The Equilibrium Distribution of Gas Molecules Adsorbed on an Active Surface

We evaluate the exact equilibrium distribution of gas molecules adsorbed on an active surface with an infinite number of attachment sites. Our result is a Poisson distribution having mean $X = {μP P_s \over P_e}$, with $μ$ the mean gas density, $ P_s$ the sticking probability, $P_e$ the evaporation probability in a time interval $τ$, and $P$ Smoluchowski's exit probability in time interval $τ$ for the surface in question. We then solve for the case of a finite number of attachment sites using the mean field approximation, recovering in this case the Langmuir isotherm.

physics.data-an↗

arXiv1997

The decay of the omega meson at finite temperature

The decay width of the $ω$ meson at finite temperature is calculated using the Gell-Mann Sharp Wagner model of $ρ$ pole dominance. Effective masses of the $ρ$ and $ω$ are determined within the framework of real-time formalism of finite temperature field theory. It is shown that even though the mass of the $ω$-meson decreases with temperature, its decay width increases because of an interesting interplay between the phase space factors, the transition matrix element and Bose enhancement.

nucl-th↗