Loading...
Search for:
faraji-astaneh--a
0.122 seconds
Total 14710 records
What surface maximizes entanglement entropy?
, Article Physical Review D - Particles, Fields, Gravitation and Cosmology ; Vol. 90, issue. 8 , 2014 ; Gibbons, G ; Solodukhin, S. N
2014
Abstract
For a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? We analyze the answer to this question in four and higher dimensions. Surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces that minimize the Willmore (bending) energy and eventually to the Willmore conjecture. We propose a generalization of the Willmore energy in higher dimensions and analyze its minimizers in a general class of topologies Sm×Sn and make certain observations and conjectures that may have some mathematical significance
Entropy discrepancy and total derivatives in trace anomaly
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 751 , 2015 , Pages 227-232 ; 03702693 (ISSN) ; Patrushev, A ; Solodukhin, S. N ; Sharif University of Technology
Elsevier
2015
Abstract
In this note we address the discrepancy found by Hung, Myers and Smolkin between the holographic calculation of entanglement entropy (using the Jacobson-Myers functional for the holographic minimal surface) and the CFT trace anomaly calculation if one uses the Wald prescription to compute the entropy in six dimensions. As anticipated in our previous work [1] the discrepancy originates entirely from a total derivative term present in the trace anomaly in six dimensions
Energy of decomposition and entanglement thermodynamics for T2-deformation
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 839 , 2023 ; 03702693 (ISSN) ; Allameh, K ; Sharif University of Technology
Elsevier B.V
2023
Abstract
We have presented a set of laws of entanglement thermodynamics for TT¯-deformed CFTs and in general for T2-deformed field theories. In particular, the first law of this set, states that although we are dealing with a non-trivial deformed theory, the change of the entanglement entropy is simply translated to the change of the bending energy of the entangling surface. We interpret this energy as the energy of decomposition. Probing the whole spectrum of the deformed theory, a second law also results, which suggests an inequality that the first law is derived from its saturation limit. We explain that this second law guarantees the preservation of the unitarity bound. The thermodynamical form...
Boundary conformal invariants and the conformal anomaly in five dimensions
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 816 , 2021 ; 03702693 (ISSN) ; Solodukhin, S. N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In odd dimensions the integrated conformal anomaly is entirely due to the boundary terms [1]. In this paper we present a detailed analysis of the anomaly in five dimensions. We give the complete list of the boundary conformal invariants that exist in five dimensions. Additionally to 8 invariants known before we find a new conformal invariant that contains the derivatives of the extrinsic curvature along the boundary. Then, for a conformal scalar field satisfying either the Dirichlet or the conformal invariant Robin boundary conditions we use the available general results for the heat kernel coefficient a5, compute the conformal anomaly and identify the corresponding values of all boundary...
Fermions, boundaries, and conformal and chiral anomalies in d=3, 4 and 5 dimensions
, Article Physical Review D ; Volume 108, Issue 8 , 2023 ; 24700010 (ISSN) ; Solodukhin, S. N ; Sharif University of Technology
American Physical Society
2023
Abstract
In the presence of boundaries, the quantum anomalies acquire additional boundary terms. In odd dimensions, the integrated conformal anomaly, for which the bulk contribution is known to be absent, is nontrivial due to the boundary terms. These terms became a subject of active study in the recent years. In the present paper, we continue our previous study [1,2] and compute explicitly the anomaly for fermions in dimensions d=3, 4 and 5. The calculation in dimension 5 is new. It contains both contributions of the gravitational field and the gauge fields to the anomaly. In dimensions d=3 and 4, we reproduce and clarify the derivation of the results available in the literature. Imposing the...
Investigation of Information Paradox in Charged Black Holes Using the Holography
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
Bonding gravity with Quantum mechanics has always been a challenging issue. So that, accomplishing a theory of quantum gravity is one of the most important research topics in High-Energy Physics.Information paradox in black holes is among such issues which connect quantum mechanics with gravity. Black holes as a natural solution of Einstein equations have a distinction, with other solutions, since there exists an event horizon that imparts space-time into two causally disconnected regions.According to Hawking’s calculations, black holes would evaporate over time by the thermal radiation. This resulting thermal radiation has less information than the initial collapsed matter in a pure state....
Investigation of the Information Paradox in Black Hole Solutions of the Higher Derivative Gravitational Models, Using the Holography
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
The information paradox is one of the most important questions around black hole physics. The problem is raised since the operators which are responsible for the evolutions in quantum mechanics are unitary while the black hole evaporation seems to be a nonunitary evolution (Since a black hole which has been formed from the collapse of matter in a pure state evaporates to a mixed thermal state eventually). This loss of information during the evaporation process is known as the information paradox.Recently many attempts have been made to investigate this problem holographically, actually to see if the information is really lost and if not how one can recover the information.Our main goal is to...
Swampland Program in String Theory and Its Consequences in Cosmology
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
Not all effective theories in the low energy limit are compatible with quantum gravity. The goal of the swampland program is bringing the necessary criteria to test these effective theories and examine their compatibility with quantum gravity. This set of conjectures determines which theory is effective in the perspective of the self-consistent theory of quantum gravity which is actually string theory. A very important connection (through the swamp program) between high energy physics (UV) And the physics of the low energy limit (IR) can provide very important explanations for our questions. Among them are the cosmological constant problem in general relativity and the hierarchy problem in...
Swampland Program in String Theory and its Consequences in Elementary Particle Physics
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
Not all low-energy effective theories are compatible with quantum gravity. The purpose of swampland program is to provide the necessary characteristics to test these theories and measure their compatibility with quantum gravity. Accordingly, this group of conjectures determine which effective theory is in the landscape of self-consistent quantum gravity which is String Theory. An important connection is provided through the swampland program between the high-energy limit physics (UV) and the low-energy limit physics (IR) that can provide immensely important fundamental explanations for our profound and consistent questions such as the hierarchy problem in elementary particle physics and...
Aspects of Two and Three Dimensional Quantum Gravity
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
Gravity models in lower dimensions, particularly in two and three dimensions, are powerful tools for gaining a deeper understanding of the fundamental structure of gravitational and quantum theories. Three-dimensional gravity, due to its simpler and more controllable properties, provides a unique laboratory for studying the geometric and topological features of black holes, as well as the holographic nature of spacetime. On the other hand, two-dimensional gravity models, such as dilaton gravity, play a crucial role in exploring the dynamic mechanisms of horizons and phenomena like black hole evaporation. These models not only allow us to grasp the complexities of quantum gravity in a more...
AdS Black Hole Evaporation Modeling with Emphasis on Partial-Dimensional Reduction
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
As a contribution to the subject of the information loss paradox in (1+1)-dimensional gravitational systems, we studied the evaporation of (1+1)-dimensional black holes in AdS gravity from a (3+1)-dimensional point of view. A partial dimensional reduction of Einstein-Hilbert action with a negative cosmological constant in four dimensions led to a black hole in AdS2 gravity. This method allowed us to effectively split the (3+1)-dimensional spacetime into a (1+1)-dimensional black hole and a remainder, which could be interpreted as a ‘bath’. We computed the fine-grained entropy of the radiation using geodesic lengths in the (3+1)-dimensional spacetime. We then focus on the finite temperature...
Holographic Investigation of Black Hole Evaporation
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
The problem of quantum gravity has always posed significant challenges, particularly evident in black hole evaporation and the information paradox. Numerous proposals have been offered. Solutions such as semi-classical gravitational approximations aim to reconcile gravitational collapse and black hole evaporation with unitary quantum evolution. Symmetries, such as conformal symmetry and Anti-de Sitter geometry, Simplify the explanation of information recovery during black hole evaporation. Near the horizon of a spherically symmetric 4D black hole, gravity can be effectively described by a 2D dilaton theory. Studying the problem in 2D magnifies the strength of conformal symmetry. Holography,...
Algebra of Operators and Observables in the Algebraic Theory of Quantum Fields and Their Generalization in the Presence of Gravity
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
In recent years, a series of deep connections have been found between the ideas that used to be in the Algebraic Theory of Quantum Fields and the important problems of High Energy and Fundamental Physics. In the 1960s and later, some people who were mostly closer to mathematicians were trying to formulate the basics and principles of Quantum Field Theory in mathematically precise way. Many and various efforts have been made in this direction. One of these important efforts has been the Algebraic Theory of Quantum Fields. The main motivation in the Algebraic Theory of Quantum Fields is to focus on the operators and observables of the theory and study the algebraic structure between them instead...
Infrared Structure of Gravity and Information Paradox of Black Holes
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
According to general theory of relativity, collapse of matter under gravitational force leads to the formation of black holes. Considering the quantum effect shows that black holes have thermal radiation which cause them to evaporate. After a complete evaporation, the state of radiation can not contain all information of initial matter. In other word, this process does not obey unitary evolution of quantum mechanics. This is called the black hole information paradox, which has been one of the most challenging problem of theoretical physics for several recent decades. Recently, a deep connections between asymptotic symmetries, soft graviton theorem and gravitational memory effect has been...
Aspects of Entanglement in Quantum Field Theory and Quantum Gravity, using the Holography
, Ph.D. Dissertation Sharif University of Technology ; Arfaei, Hessamaddin (Supervisor) ; Mosaffa, Amir Esmaeil (Supervisor) ; Alishahiha, Mohsen (Co-Advisor)
Abstract
Entanglement is an immediate consequence of quantum mechanical pos- tulates and is thus an indispensable part of studying quantum systems. A very useful quantity which can appropriately quantify entanglement between the degrees of freedom of a composite quantum system is En- tanglement Entropy (EE).
Over the last few years, this subject has attracted a lot of interest both in QFT and in the context of holography. On the one hand, an intu- itive geometrical Holographic model for entanglement entropy has been proposed in the context of gauge/gravity duality, and on the other, var- ious issues concerning entanglement have been explored, e.g. in quan- tum computation, quantum information...
Over the last few years, this subject has attracted a lot of interest both in QFT and in the context of holography. On the one hand, an intu- itive geometrical Holographic model for entanglement entropy has been proposed in the context of gauge/gravity duality, and on the other, var- ious issues concerning entanglement have been explored, e.g. in quan- tum computation, quantum information...
Holographic entanglement entropy for excited states in two dimensional CFT
, Article Journal of High Energy Physics ; Volume 2013, Issue 3 , March , 2013 ; 11266708 (ISSN) ; Mosaffa, A. E ; Sharif University of Technology
2013
Abstract
We use holographic methods to study the entanglement entropy for excited states in a two dimensional conformal field theory. The entangling area is a single interval and the excitations are produced by in and out vertex operators with given scaling dimensions. On the gravity side we provide the excitations by turning on a scalar field with an appropriate mass. The calculation amounts to using the gravitational background, with a singular boundary, to find the one point function of the vertex operators. The singular boundary is taken care of by introducing a nontrivial UV regulator surface to calculate gravitational partition functions. By means of holographic methods we reproduce the field...
Quantum local quench, AdS/BCFT and Yo-Yo string
, Article Journal of High Energy Physics ; Volume 2015, Issue 5 , May , 2015 ; 11266708 (ISSN) ; Mosaffa, A. E ; Sharif University of Technology
Springer Verlag
2015
Abstract
Abstract: We propose a holographic model for local quench in 1 + 1 dimensional Conformal Field Theory (CFT). The local quench is produced by joining two identical CFT’s on semi-infinite lines. When these theories have a zero boundary entropy, we use the AdS/Boundary CFT proposal to describe this process in terms of bulk physics. Boundaries of the original CFT’s are extended in AdS as dynamical surfaces. In our holographic picture these surfaces detach from the boundary and form a closed folded string which can propagate in the bulk. The dynamics of this string is governed by the tensionless Yo-Yo string solution and its subsequent evolution determines the time dependence after quench. We use...
Aspects of holographic entanglement entropy for TT¯-deformed CFTs
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 826 , 2022 ; 03702693 (ISSN) ; Faraji Astaneh, A ; Hassanzadeh, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
We use the holographic methods to calculate the entanglement entropy for field theories modified by TT¯ insertion. Based on the available holographic proposals, this calculation reduces to the holographic computations in AdS with finite cut-off. We perform a direct holographic calculation of the entanglement entropy for two dimensional deformed theory. By direct we mean the evaluation of the gravitational action in the bulk spacetime which has been reconstructed from a dual CFT2 on n-sheeted Riemann surface as a finite cut-off boundary. We also apply Ryu-Takayanagi's prescription to investigate the most general structure of the entanglement entropy for TT¯-deformed theories of arbitrary...
Island in the presence of higher derivative terms
, Article Journal of High Energy Physics ; Volume 2021, Issue 2 , 2021 ; 10298479 (ISSN) ; Faraji Astaneh, A. F ; Naseh, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Using extended island formula we compute entanglement entropy of Hawking radiation for black hole solutions of certain gravitational models containing higher derivative terms. To be concrete we consider two different four dimensional models to compute entropy for both asymptotically flat and AdS black holes. One observes that the resultant entropy follows the Page curve, thanks to the contribution of the island, despite the fact that the corresponding gravitational models might be non-unitary. © 2021, The Author(s)
Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity
, Article Journal of Photochemistry and Photobiology B: Biology ; Volume 178 , 2018 , Pages 124-132 ; 10111344 (ISSN) ; Mohaghegh, N ; Abedini, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
A series of g-C3N4-SnO2/TiO2 nanotubes/Ti plates were fabricated via simple dipping of TiO2 nanotubes/Ti in a solution containing SnCl2 and g-C3N4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C3N4-SnO2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis...