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Fate of strong cosmic censorship conjecture in presence of higher spacetime dimensions

Abstract Strong cosmic censorship conjecture has been one of the most important leap of faith in the context of general relativity, providing assurance in the deterministic nature of the associated field equations. Though it holds well for asymptotically flat spacetimes, a potential failure of the strong cosmic censorship conjecture might arise for spacetimes inheriting Cauchy...

On some novel features of the Kerr–Newman-NUT spacetime

In this work we have presented a special class of Kerr–Newman-NUT black hole, having its horizon located precisely at \(r=2M\), for \(Q^{2}=l^{2}-a^{2}\), where M, l, a and Q are respectively mass, NUT, rotation and electric charge parameters of the black hole. Clearly this choice radically alters the causal structure as there exists no Cauchy horizon indicating spacelike nature...

A comment on generalized Schwinger effect

A spatially homogeneous, time-dependent, electric field can produce charged particle pairs from the vacuum. When the electric field is constant, the mean number of pairs which are produced depends on the electric field and the coupling constant in a non-analytic manner, showing that this result cannot be obtained from the standard perturbation theory of quantum electrodynamics...

Field Equations for Lovelock Gravity: An Alternative Route

Correspondence should be addressed to Sumanta Chakraborty; moc.liamg@scisyhp.catnamus Received 20 December 2017; Revised 9 February 2018; Accepted 20 February 2018; Published 19 April 2018 Academic Editor: Izzet ... Sakalli Copyright © 2018 Sumanta Chakraborty. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in

Unruh effect for inertial observers through vacuum correlations

We study a dynamic version of the Unruh effect in a two dimensional collapse model forming a black hole. In this two-dimensional collapse model a scalar field coupled to the dilaton gravity, moving leftwards, collapses to form a black hole. There are two sets of asymptotic (\(t\rightarrow \infty \)) observers, around \(x\rightarrow \infty \) and \(x\rightarrow -\infty \). The...

Gravity stabilizes itself

We show that a possible resolution to the stabilization of an extra spatial dimension (radion) can be obtained solely in the context of gravitational dynamics itself without the necessity of introducing any external stabilizing field. In this scenario the stabilized value of the radion field gets determined in terms of the parameters appearing in the higher curvature...

Kinematics of radion field: a possible source of dark matter

The discrepancy between observed virial and baryonic mass in galaxy clusters have lead to the missing mass problem. To resolve this, a new, non-baryonic matter field, known as dark matter, has been invoked. However, till date no possible constituents of the dark matter components are known. This has led to various models, by modifying gravity at large distances to explain the...

Solving higher curvature gravity theories

Solving field equations in the context of higher curvature gravity theories is a formidable task. However, in many situations, e.g., in the context of f(R) theories, the higher curvature gravity action can be written as an Einstein–Hilbert action plus a scalar field action. We show that not only the action but the field equations derived from the action are also equivalent...

Variational principle for gravity with null and non-null boundaries: a unified boundary counter-term

It is common knowledge that the Einstein–Hilbert action does not furnish a well-posed variational principle. The usual solution to this problem is to add an extra boundary term to the action, called a counter-term, so that the variational principle becomes well-posed. When the boundary is spacelike or timelike, the Gibbons–Hawking–York counter-term is the most widely used. For...

Lanczos-Lovelock gravity from a thermodynamic perspective

Abstract The deep connection between gravitational dynamics and horizon thermodynamics leads to several intriguing features both in general relativity and in Lanczos-Lovelock theories of gravity. Recently in arXiv:1312.3253 several additional results strengthening the above connection have been established within the framework of general relativity. In this work we provide a...

Brown-York quasilocal energy in Lanczos-Lovelock gravity and black hole horizons

Abstract A standard candidate for quasilocal energy in general relativity is the Brown-York energy, which is essentially a two dimensional surface integral of the extrinsic curvature on the two-boundary of a spacelike hypersurface referenced to flat spacetime. Several years back one of us had conjectured that the black hole horizon is defined by equipartition of gravitational and...

Effective gravitational field equations on m-brane embedded in n-dimensional bulk of Einstein and \(f(\mathcal {R})\) gravity

We have derived effective gravitational field equations on a lower dimensional hypersurface (known as a brane), placed in a higher dimensional bulk spacetime for both Einstein and \(f(\mathcal {R})\) gravity theories. We have started our analysis on the n-dimensional bulk from which the effective field equations on a \((n-1)\)-dimensional brane have been obtained by imposing \(Z_...

Gravitational field equations near an arbitrary null surface expressed as a thermodynamic identity

Abstract Previous work has demonstrated that the gravitational field equations in all Lanczos-Lovelock models imply a thermodynamic identity T δλ S = δλ E + P δλ V (where the variations are interpreted as changes due to virtual displacement along the affine parameter λ) in the near-horizon limit in static spacetimes. Here we generalize this result to any arbitrary null surface in...

Spherically symmetric brane spacetime with bulk \(f(\mathcal {R})\) gravity

Sumanta Chakraborty 1 Soumitra SenGupta 0 0 Department of Theoretical Physics, Indian Association for the Cultivation of Science , Kolkata 700032 , India 1 IUCAA, Ganeshkhind, Pune University Campus

A quantum peek inside the black hole event horizon

We solve the Klein-Gordon equation for a scalar field, in the background geometry of a dust cloud collapsing to form a black hole, everywhere in the (1+1) spacetime: that is, both inside and outside the event horizon and arbitrarily close to the curvature singularity. This allows us to determine the regularized stress tensor expectation value, everywhere in the appropriate...

Radion cosmology and stabilization

Sumanta Chakraborty 1 Soumitra SenGupta 0 0 Department of Theoretical Physics, Indian Association for the Cultivation of Science , Kolkata 700032, India 1 IUCAA, Ganeshkhind, Pune University Campus

Anomalous effective action, Noether current, Virasoro algebra and Horizon entropy

Several investigations show that in a very small length scale there exist corrections to the entropy of black hole horizon. Due to fluctuations of the background metric and the external fields the action incorporates corrections. In the low energy regime, the one-loop effective action in four dimensions leads to trace anomaly. We start from the Noether current corresponding to...

Biocontrol of larval mosquitoes by Acilius sulcatus (Coleoptera: Dytiscidae)

Sumanta Chakraborty 0 0 Address: Mosquito Research Unit, Department of Zoology, the University of Burdwan , West Bengal , India Background: Problems associated with resistant mosquitoes and the effects on