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On the Concepts and Roles of Energy and Entropyin Gravitational Physics and Cosmology(Canonical Approaches in Definition of Conserved Quantities in Gravitational Physics)

Aghapour Hasiri, Sajad | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52615 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Golshani, Mehdi; Jafari, Ghadir
  7. Abstract:
  8. In this thesis, inspired by foundational discussions about the concepts of energy and entropy in the gravitational theory, we study the definitions of these concepts and the roles they play in that theory. The definitions considered in this thesis are derived from canonical formalism. To this end, first of all, the variational principle and the canonical structure in the gravitational theory, especially in situations where the spacetime is bounded, is carefully studied and the boundary and corner actions as well as the canonical structure on the boundaries in three cases of non-null, null and general boundaries are derived. Based on this study, two canonical approaches, namely the generalized Hamilton-Jacobi and the covariant phase space methods, are used to define the conserved quantities. Moreover, the essential role of the boundary action in the two approaches and its impact on the definitions of quantities are explained.These definitions are then applied in the context of general relativity to derive the energy-momentum and the entropy for Blackhole and cosmological solutions where the boundaries of the spacetime region is the null infinity and/or the event horizon. To perform the calculations, a suitable and useful formalism for a double-foliation of spacetime is developed and the relevant computational codes are produced
  9. Keywords:
  10. Energy ; Entropy ; Gravitation ; Black Holles ; Cosmology ; Conserves Charges

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