Hawking radiation as tunneling for spherically symmetric black holes: A generalized treatment

We present a derivation of Hawking radiation through tunneling mechanism for a general class of asymptotically flat, spherically symmetric spacetimes. The tunneling rate $\Gamma \sim \exp{(\Delta S)}$ arises as a consequence of the first law of thermodynamics, TdS=dE + PdV. Therefore, this approach demonstrates how tunneling is intimately connected with the first law of thermodynamics through the principle of conservation of energy. The analysis is also generally applicable to any reasonable theory of gravity so long as the first law of thermodynamics for horizons holds in the form, TdS=dE + PdV.Comment: RevTeX 4; 11 pages; no figure

Physical process first law and caustic avoidance for Rindler horizon

We study the perturbation induced by a slowly rotating massive object as it passes through a Rindler horizon. It is shown that the passage of this object can be approximately modeled as Delta\,function type tidal distortions hitting the horizon. Further, following the analysis presented by Amsel, Marolf and Virmani related to the issue of the validity of physical process first law, we establish a condition on the size of the object so that this law holds for the Rindler horizon.Comment: 15 pages, 2 figure

Hawking radiation from stationary black holes using gravitational anomaly

Among all the different techniques to derive the Hawking effect, the approach based on gravitational anomaly by Robinson and Wilczek provides a simple and satisfactory origin of the black hole radiation. In this picture, the effective near horizon physics becomes chiral and contains gravitational anomaly. Nevertheless, the underlying description must be generally covariant, and therefore we require a compensating energy-momentum flux whose divergence cancels the anomaly at the horizon. Remarkably, the energy flux associated with the Hawking emission from the horizon exactly cancels the gravitational anomaly and restores the general covariance at the quantum level. In this work, we present a generalization of the original derivation for a stationary axisymmetric black hole solution of any gravity theory which differs perturbatively from general relativity. The crucial input of the calculation is a remarkable simplification of the near horizon geometry and the validity of the zeroth law of black hole mechanics.Comment: 6 pages, no figure

Social Exclusion and Child Nutritional Status among the Scheduled Population in India

The concept of social exclusion covers a wide range of economic and social problems commonly related poverty, inequality, deprivation and discrimination. The child nutritional status is one of the important areas where the concept has serious applicability. The proportions of undernourished children in India is significantly higher along with wide spread socio-economic inequalities. The disadvantaged scheduled population (i.e. SC’s & ST’s) in the country are tremendously affected by multidimensional poverty and thus bearing the immense burden of undernourishment especially among the young children. Using the 3rd round of National Family and Health Survey (NFHS-3; 2005-06) dataset the study broadly suggests that the problem is deeply rooted in larger form social exclusion and deprivation among the lower most segments of the population. It explores the different contours exclusion related to the lesser access of the basic health care facilities, one of the leading causes for the very high rate of child undernourishment among the children. Keywords: Social Exclusion, Poverty, Inequality, Deprivation, Discrimination, Scheduled Children, Nutritional Status

Thermodynamics of Local Causal Horizons

We propose an expression for the entropy density associated with the Local Causal Horizons in any diffeomorphism invariant theory of gravity. If the black-hole entropy of the theory satisfies the physical process version of the first law of thermodynamics then our proposed entropy satisfies the Clausius relation. Thus, our study shows that the thermodynamic nature of the spacetime horizons is not restricted to the black holes; it also applies to the local causal horizons in the neighborhood of any point in the spacetime.Comment: 6 pages, 1 figur

Thermodynamics of horizons from a dual quantum system

It was shown recently that, in the case of Schwarschild black hole, one can obtain the correct thermodynamic relations by studying a model quantum system and using a particular duality transformation. We study this approach further for the case a general spherically symmetric horizon. We show that the idea works for a general case only if we define the entropy S as a congruence ("observer") dependent quantity and the energy E as the integral over the source of the gravitational acceleration for the congruence. In fact, in this case, one recovers the relation S=E/2T between entropy, energy and temperature previously proposed by one of us in gr-qc/0308070. This approach also enables us to calculate the quantum corrections of the Bekenstein-Hawking entropy formula for all spherically symmetric horizons.Comment: 5 pages; no figure