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Pietro Menotti - One of the best experts on this subject based on the ideXlab platform.
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On the semiclassical treatment of the Hawking radiation
Classical and Quantum Gravity, 2010Co-Authors: Pietro MenottiAbstract:In the context of the semiclassical treatment of Hawking radiation we prove the universality of the reduced canonical momentum for the system of a massive shell self gravitating in a spherical gravitational field within the Painlevé family of gauges. We show that one can construct modes which are regular on the horizon both by considering as Hamiltonian the exterior Boundary Term and by using as Hamiltonian the interior Boundary Term. The late time expansion is given in both approaches and their time Fourier expansion computed to reproduce the self reaction correction to the Hawking spectrum.
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On the semiclassical treatment of the Hawking radiation
Classical and Quantum Gravity, 2010Co-Authors: Pietro MenottiAbstract:In the context of the semiclassical treatment of the Hawking radiation, we prove the universality of the reduced canonical momentum for the system of a massive shell self-gravitating in a spherical gravitational field within the Painleve family of gauges. We show that one can construct modes which are regular on the horizon both by considering as a Hamiltonian the exterior Boundary Term and by using as a Hamiltonian the interior Boundary Term. The late-time expansion is given in both approaches and their time Fourier expansion is computed to reproduce the self-reaction correction to the Hawking spectrum.
Y. Kucukakca - One of the best experts on this subject based on the ideXlab platform.
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Scalar–tensor teleparallel gravity with Boundary Term by Noether symmetries
International Journal of Geometric Methods in Modern Physics, 2018Co-Authors: G. Gecim, Y. KucukakcaAbstract:In the framework of teleparallel gravity, the Friedman–Robertson–Walker (FRW) cosmological model with scalar tensor theory, where scalar field is non-minimally coupled to both the torsion scalar and Boundary Term, is studied. Utilizing the Noether symmetry approach in such a theory, we obtain the explicit forms of the couplings and potential as a function of the scalar field. We present some important cosmological solutions for the modified field equations using these functions gotten via the Noether symmetry approach. Finally, the interesting cosmological properties of these solutions are discussed in detail, and it is shown that they can describe a universe leading to the late-time accelerating expansion.
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Scalar–tensor teleparallel gravity with Boundary Term by Noether symmetries
International Journal of Geometric Methods in Modern Physics, 2018Co-Authors: G. Gecim, Y. KucukakcaAbstract:In the framework of teleparallel gravity, the Friedman–Robertson–Walker (FRW) cosmological model with scalar tensor theory, where scalar field is non-minimally coupled to both the torsion scalar an...
Rodrigo Olea - One of the best experts on this subject based on the ideXlab platform.
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Topological Terms, AdS2n gravity, and renormalized entanglement entropy of holographic CFTs
Physical Review D, 2018Co-Authors: Giorgos Anastasiou, Ignacio J. Araya, Rodrigo OleaAbstract:We extend our topological renormalization scheme for entanglement entropy to holographic CFTs of arbitrary odd dimensions in the context of the AdS/CFT correspondence. The procedure consists in adding the Chern form as a Boundary Term to the area functional of the Ryu-Takayanagi minimal surface. The renormalized entanglement entropy thus obtained can be rewritten in Terms of the Euler characteristic and the AdS curvature of the minimal surface. This prescription considers the use of the replica trick to express the renormalized entanglement entropy in Terms of the renormalized gravitational action evaluated on the conically singular replica manifold extended to the bulk. This renormalized action is obtained in turn by adding the Chern form as the counterTerm at the Boundary of the 2n-dimensional asymptotically AdS bulk manifold. We explicitly show that, up to next-to-leading order in the holographic radial coordinate, the addition of this Boundary Term cancels the divergent part of the entanglement entropy. We discuss possible applications of the method for studying CFT parameters like central charges.
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Renormalization of entanglement entropy from topological Terms
Physical Review D, 2018Co-Authors: Giorgos Anastasiou, Ignacio J. Araya, Rodrigo OleaAbstract:We propose a renormalization scheme for Entanglement Entropy of 3D CFTs with a 4D asymptotically AdS gravity dual in the context of the gauge/gravity correspondence. The procedure consists in adding the Chern form as a Boundary Term to the area functional of the Ryu-Takayanagi minimal surface. We provide an explicit prescription for the renormalized Entanglement Entropy, which is derived via the replica trick. This is achieved by considering a Euclidean gravitational action renormalized by the addition of the Chern form at the spacetime Boundary, evaluated in the conically-singular replica manifold. We show that the addition of this Boundary Term cancels the divergent part of the Entanglement Entropy, recovering the results obtained by Taylor and Woodhead. We comment on how this prescription for renormalizing the Entanglement Entropy is in line with the general program of topological renormalization in asymptotically AdS gravity.
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Einstein-Gauss-Bonnet theory of gravity : The Gauss-Bonnet-Katz Boundary Term
Physical Review D, 2018Co-Authors: Nathalie Deruelle, Nelson Merino, Rodrigo OleaAbstract:We propose a Boundary Term to the Einstein-Gauss-Bonnet action for gravity, which is constructed as the dimensional continuation of the Chern-Weil theorem, and such that the extremization of the full action yields the equations of motion when Dirichlet Boundary conditions are imposed. When translated into tensorial language, this Boundary Term is the generalization to this theory of the Katz Boundary Term and vector for general relativity. The construction allows to deal with a general background and includes the Gibbons-Hawking-Myers Boundary Term as a special case, when the background is taken to be a product manifold. As a first application we show that this Einstein Gauss-Bonnet Katz action yields, without any extra ingredients or regularization, the expected mass of the Boulware-Deser black hole.
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Einstein-Gauss-Bonnet theory of gravity: The Gauss-Bonnet-Katz Boundary Term
Phys.Rev.D, 2018Co-Authors: Nathalie Deruelle, Nelson Merino, Rodrigo OleaAbstract:We propose a Boundary Term to the Einstein-Gauss-Bonnet action for gravity, which uses the Chern-Weil theorem plus a dimensional continuation process, such that the extremization of the full action yields the equations of motion when Dirichlet Boundary conditions are imposed. When translated into tensorial language, this Boundary Term is the generalization to this theory of the Katz Boundary Term and vector for general relativity. The Boundary Term constructed in this paper allows to deal with a general background and is not equivalent to the Gibbons-Hawking-Myers Boundary Term. However, we show that they coincide if one replaces the background of the Katz procedure by a product manifold. As a first application we show that this Einstein Gauss-Bonnet Katz action yields, without any extra ingredients, the expected mass of the Boulware-Deser black hole.
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Universal KounterTerms in Lovelock AdS gravity
Fortschritte der Physik, 2008Co-Authors: Georgios Kofinas, Rodrigo OleaAbstract:We show the universal form of the Boundary Term (KounterTerm series) which regularizes the Euclidean action and background-independent definition of conserved quantities for any Lovelock gravity theory with AdS asymptotics (including Einstein-Hilbert and Einstein-Gauss-Bonnet). We discuss on the connection of this procedure to the existence of topological invariants and Chern-Simons forms in the corresponding dimensions.
G. Gecim - One of the best experts on this subject based on the ideXlab platform.
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Scalar–tensor teleparallel gravity with Boundary Term by Noether symmetries
International Journal of Geometric Methods in Modern Physics, 2018Co-Authors: G. Gecim, Y. KucukakcaAbstract:In the framework of teleparallel gravity, the Friedman–Robertson–Walker (FRW) cosmological model with scalar tensor theory, where scalar field is non-minimally coupled to both the torsion scalar and Boundary Term, is studied. Utilizing the Noether symmetry approach in such a theory, we obtain the explicit forms of the couplings and potential as a function of the scalar field. We present some important cosmological solutions for the modified field equations using these functions gotten via the Noether symmetry approach. Finally, the interesting cosmological properties of these solutions are discussed in detail, and it is shown that they can describe a universe leading to the late-time accelerating expansion.
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Scalar–tensor teleparallel gravity with Boundary Term by Noether symmetries
International Journal of Geometric Methods in Modern Physics, 2018Co-Authors: G. Gecim, Y. KucukakcaAbstract:In the framework of teleparallel gravity, the Friedman–Robertson–Walker (FRW) cosmological model with scalar tensor theory, where scalar field is non-minimally coupled to both the torsion scalar an...
H. Mohseni Sadjadi - One of the best experts on this subject based on the ideXlab platform.
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Parameterized post-Newtonian approximation in a teleparallel model of dark energy with a Boundary Term
The European Physical Journal C, 2017Co-Authors: H. Mohseni SadjadiAbstract:We study the parameterized post-Newtonian approximation in teleparallel model of gravity with a scalar field. The scalar field is non-minimally coupled to the scalar torsion as well as to the Boundary Term introduced in Bahamonde and Wright (Phys Rev D 92:084034 arXiv:1508.06580v4 [gr-qc], 2015). We show that, in contrast to the case where the scalar field is only coupled to the scalar torsion, the presence of the new coupling affects the parameterized post-Newtonian parameters. These parameters for different situations are obtained and discussed.
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Parameterized post Newtonian approximation in a teleparallel model of dark energy with a Boundary Term
arXiv: General Relativity and Quantum Cosmology, 2016Co-Authors: H. Mohseni SadjadiAbstract:We study the parameterized post-Newtonian approximation in teleparallel model of gravity with a scalar field. The scalar field is non-minimally coupled to the scalar torsion as well as to the Boundary Term introduced in [1]. We show that, in contrast to the case where the scalar field is only coupled to the scalar torsion, the presence of the new coupling affects the parameterized post-Newtonian parameters. These parameters for different situations are obtained and discussed.
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Parametrized post Newtonian approximation in teleparallel model with a scalar field coupled to torsion and Boundary Term
arXiv: General Relativity and Quantum Cosmology, 2016Co-Authors: H. Mohseni SadjadiAbstract:We study the parameterized post Newtonian approximation in teleparallel model of gravity with a scalar field. The scalar field is non-minimally coupled to the scalar torsion as well as to the Boundary Term introduced in [1]. We show that, in contrast to the case where the scalar field is only coupled to the scalar torsion, the presence of the new coupling affects the parameterized post Newtonian parameters. These parameters for different situations are obtained and discussed.