Research Papers (TP)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/3

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Start date: 2010Subject: search.filters.subject.Entropy

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    Entropy increase during physical processes for black holes in Lanczos-Lovelock gravity
    (American physical society, 2012-07-03) Padmanabhan, T.; Kolekar, Sanved; Sarkar, Sudipta
    We study quasistationary physical process for black holes within the context of Lanczos-Lovelock gravity. We show that the Wald entropy of the stationary black holes in Lanczos-Lovelock gravity monotonically increases for quasistationary physical processes in which the horizon is perturbed by the accretion of positive energy matter and the black hole ultimately settles down to a stationary state. This result reinforces the physical interpretation of Wald entropy for Lanczos-Lovelockmodels and takes a step towards proving the analogue of the black hole area increase theorem in a wider class of gravitational theories.
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    Noether Current, Horizon Virasoro Algebra, and Entropy
    (American physical society, 2012-04-08) Bibhas, Ranjan Majhi; Padmanabhan, T.
    We provide a simple and straightforward procedure for defining a Virasoro algebra based on the diffeomorphisms near a null surface in a space-time and obtain the entropy density of the null surface from its central charge.We use the off-shell Noether current corresponding to the diffeomorphism invariance of a gravitational Lagrangian Lðgab; RabcdÞ and define the Virasoro algebra from its variation. This allows us to identify the central charge and the zero-mode eigenvalue with which we obtain the entropy density of the Killing horizon. Our approach works for all Lanczos-Lovelock models and reproduces the correct Wald entropy. The entire analysis is done off-shell without using the field equations and allows us to define an entropy density for any null surface which acts as a local Rindler horizon for a particular class of observers.
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    Ideal gas in a strong gravitational field: Area dependence of entropy
    (American Physical Society, 2011-03-24) Kolekar, Sanved; Padmanabhan, T.
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    Finite entanglement entropy from the zero-point area of spacetime
    (American Physical Society, 2010-12-13) Padmanabhan, T.
    The calculation of entanglement entropy S of quantum fields in spacetimes with horizon shows that, quite generically, S is (a) proportional to the area A of the horizon and (b) divergent. I argue that this divergence, which arises even in the case of Rindler horizon in flat spacetime, is yet another indication of a deep connection between horizon thermodynamics and gravitational dynamics. In an emergent perspec- tive of gravity, which accommodates this connection, the fluctuations around the equipartition value in the area elements will lead to a minimal quantum of area Oð1ÞL2 P, which will act as a regulator for this divergence. In a particular prescription for incorporating the L2 P as zero-point-area of spacetime, this does happen and the divergence in entanglement entropy is regularized, leading to S / A=L2 P in Einstein gravity. In more general models of gravity, the surface density of microscopic degrees of freedom is different which leads to a modified regularization procedure and the possibility that the entanglement entropy—when appropriately regularized—matches the Wald entropy.