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    Double-horizon limit, AdS geometry and entropy function

    , Article Nuclear Physics B ; Volume 802, Issue 3 , 2008 , Pages 405-420 ; 05503213 (ISSN) Arfaei, H ; Fareghbal, R ; Sharif University of Technology
    We start from a generic metric which describes four-dimensional stationary black holes in an arbitrary theory of gravity and show that the AdS2 part of the near-horizon geometry is a consequence of the double-horizon limit and finiteness. We also show that the field configurations of the near horizon are determined if the same conditions are applied to the equations of motion. This is done by showing that in the double-horizon limit field equations at the horizon decouple from the bulk of the space. Solving these equations gives the near-horizon field configurations. It is shown that these decoupled equations can be obtained from an action derived from the original action by applying the... 

    On 5D small black holes

    , Article Journal of High Energy Physics ; Volume 2008, Issue 3 , 2008 ; 11266708 (ISSN) Alishahiha, M ; Ardalan, F ; Ebrahim, H ; Mukhopadhyay, S ; Sharif University of Technology
    Using higher order corrections we argue that five dimensional = 2 and = 4 small black holes exhibit supersymmetry enhancement in near horizon geometry leading to eight and sixteen supercharges, respectively. Using this enhancement at supergravity level we can identify the global supergroup of the near horizon geometry. In particular we show how this supergroup distinguishes between small and large black holes in = 2 case  

    Double-horizon limit and decoupling of the dynamics at the horizon

    , Article Journal of High Energy Physics ; Volume 2007, Issue 1 , 2007 ; 10298479 (ISSN) Arfaei, H ; Fareghbal, R ; Sharif University of Technology
    We show that the attractor mechanism for generic black hole is a consequence of the double-horizon. Investigation of equations of motion shows that in the case of the double-horizon black holes, the dynamics of the geometry, the scalars and the gauge fields at the horizon decouples from the rest of the space. In the general case, the value of the fields at the horizon satisfies a number of differential equations of functions of the θ coordinate. We show this for the case of rotating and non-rotating electrically charged black holes in the general two derivative theories of gravity and f(R) gravities including the theories with cosmological constant. © SISSA 2007  

    Quasi-normal modes of extremal BTZ black holes in TMG

    , Article Journal of High Energy Physics ; Volume 2010, Issue 8 , 2010 ; 11266708 (ISSN) Afshar, H. R ; Alishahiha, M ; Mosaffa, A. E ; Sharif University of Technology
    We study the spectrum of tensor perturbations on extremal BTZ black holes in topologically massive gravity for arbitrary values of the coefficient of the Chern-Simons term, μ. Imposing proper boundary conditions at the boundary of the space and at the horizon, we find that the spectrum contains quasi-normal modes  

    Nearing extremal intersecting giants and new decoupled sectors in N = 4 SYM

    , Article Journal of High Energy Physics ; Volume 2008, Issue 8 , 21 August , 2008 ; 11266708 (ISSN) Fareghbal, R ; Gowdigere, C. N ; Mosaffa, A. E ; Sheikh Jabbari, M. M ; Sharif University of Technology
    We study near-horizon limits of near-extremal charged black hole solutions to five-dimensional U(1) 3 gauged supergravity carrying two charges, extending the recent work of Balasubramanian et al. [1]. We show that there are two near-horizon decoupling limits for the near-extremal black holes, one corresponding to the near-BPS case and the other for the far from BPS case. Both of these limits are only defined on the 10d IIB uplift of the 5d black holes, resulting in a decoupled geometry with a six-dimensional part (conformal to) a rotating BTZ × S 3. We study various aspects of these decoupling limits both from the gravity side and the dual field theory side. For the latter we argue that... 

    Parallel D-Branes in Linear Background Kalb-Ramond Field

    , M.Sc. Thesis Sharif University of Technology Mehin Rasulian, Aida (Author) ; Arfaei, Hessamaddin (Supervisor)
    The purpose of this thesis is to study the behaviour of open strings between two parallel D-Branes in the presence of a background Kalb-Ramond field linearly varying perpendicular to D-Branes. In an attempt to solve the nonlinear equations of motion we found two sets of nontrivial solutions: String wrapped around a cylinder with constant velocity along its axis and a rotating string with oscillatory radius perpendicular to D-Branes, such that knots are shaped. Considering the boundary conditions, the constraints on these solutions, conserved currents and Mass are found. In particular calculated linear momentum for the first set of solutions suggests the possibility of using this setup as an... 

    Mass Spectrum of Open Bosonic Strings in the Presence of Classical Gravity with Geometry of the Randall-Sundrum Model

    , M.Sc. Thesis Sharif University of Technology Karkheiran, Mohsen (Author) ; Arfaei, Hessamaddin (Supervisor)
    Since 1980’s, String Theory is considered as one of the main candidates for the unified theory of nature. One of the important features of this theory, is describing the Gravity as a renormalizable quantum theory. An interesting and important problem is the interaction of the string with classical fields in spacetime such as gravity. The conclusions which can be deduced may be very different from the standard results in case of absence of these classical fields.On the other side, for giving a solution to one of the unsolved problems in standard model of particle physics, the hierarchy problem, Lisa Randall and Raman Sundrum in1999, suggested a model which assumes that spacetime may has... 

    String Theory Discription on Non-Relativistic QFT

    , Ph.D. Dissertation Sharif University of Technology Vahedi, Ali (Author) ; Ardalan, Farhad (Supervisor)
    In this Thesis we study the string theory discription of non-relativistic quantum ?eld theories.In other statement we study the duality between gravity and gauge theory with non-relativistic symmetry.We discuss that this duality works in non rel- ativistic sense.We study two kind of non-relativistic theories that one of them camefrom string theory and other model obtained by special transformation of original relativistic theory and we see that how duality can be work for these models.Also dual picture of semi-classical string in the background that found from string theorystudied.We also study the motion of particle in a hot plasma and we ?nd a sign of non-relativisic duality really works  

    Obstruction of black hole singularity by quantum field theory effects

    , Article Journal of High Energy Physics ; Volume 2016, Issue 3 , 2016 ; 11266708 (ISSN) Abedi, J ; Arfaei, H ; Sharif University of Technology
    Springer Verlag  2016
    Abstract: We consider the back reaction of the energy due to quantum fluctuation of the background fields considering the trace anomaly for Schwarzschild black hole. It is shown that it will result in modification of the horizon and also formation of an inner horizon. We show that the process of collapse of a thin shell stops before formation of the singularity at a radius slightly smaller than the inner horizon at the order of (Formula presented.). After the collapse stops the reverse process takes place. Thus we demonstrate that without turning on quantum gravity and just through the effects the coupling of field to gravity as trace anomaly of quantum fluctuations the formation of the... 

    Non-relativistic CFT and semi-classical strings

    , Article Journal of High Energy Physics ; Volume 2009, Issue 3 , 2009 ; 11266708 (ISSN) Akhavan, A ; Alishahiha, M ; Davody, A ; Vahedi, A ; Sharif University of Technology
    We study different features of 3D non-relativistic CFT using gravity description. As the corresponding gravity solution can be embedded into the type IIB string theory, we study semi-classical closed/open strings in this background. In particular we consider folded rotating and circular pulsating closed strings where we find the anomalous dimension of the dual operators as a function of their quantum numbers. We also consider moving open strings in this background which can be used to compute the drag force. In particular we find that for slowly moving particles, the energy is lost exponentially and the characteristic time is given in terms of the temperature, while for fast moving particles... 

    Magneto-transport in a chiral fluid from kinetic theory

    , Article Journal of High Energy Physics ; Volume 2019, Issue 3 , 2019 ; 11266708 (ISSN) Abbasi, N ; Taghinavaz, F ; Tavakol, O ; Sharif University of Technology
    Springer Verlag  2019
    We argue that in order to study the magneto-transport in a relativistic Weyl fluid, it is needed to take into account the associated quantum corrections, namely the side-jump effect, at least to second order. To this end, we impose Lorentz invariance to a system of free Weyl fermions in the presence of the magnetic field and find the second order correction to the energy dispersion. By developing a scheme to compute the integrals in the phase space, we show that the mentioned correction has non-trivial effects on the thermodynamics of the system. Specifically, we compute the expression of the negative magnetoresistivity in the system from the enthalpy density in equilibrium. Then in analogy... 

    Central charge for 2D gravity on AdS 2 and AdS 2/CFT 1 correspondence

    , Article Journal of High Energy Physics ; Volume 2008, Issue 8 , 26 August , 2008 ; 11266708 (ISSN) Alishahiha, M ; Ardalan, F ; Sharif University of Technology
    We study 2D Maxwell-dilaton gravity on AdS 2. We distinguish two distinctive cases depending on whether the AdS 2 solution can be lifted to an AdS 3 geometry. In both cases, in order to get a consistent boundary condition we need to work with a twisted energy momentum tensor which has non-zero central charge. With this central charge and the explicit form of the twisted Virasoro generators we compute the entropy of the system using the Cardy formula. The entropy is found to be the same as that obtained from gravity calculations for a specific value of the level of the U(1) current. The agreement is an indication of AdS 2/CFT 1 correspondence  

    Swampland Program in String Theory and Its Consequences in Cosmology

    , M.Sc. Thesis Sharif University of Technology Ahangar, Amir (Author) ; Faraji Astaneh, Amin (Supervisor)
    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 Salehi, Mohammad (Author) ; Faraji Astaneh, Amin (Supervisor)
    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... 

    Double Field Theory

    , M.Sc. Thesis Sharif University of Technology Ehsani, Masoud (Author) ; Arfaei, Hesamaddin (Supervisor)
    Double Field Theory tries to incorporate T-duality, one of fundamental features of string theory, as a symmetry of a field Theory on a doubled space. It sets fields depend on winding mode conjugate coordinates as well as conventional space-time coordinates. In this review after presenting a brief introduction to string theory we investigate O(d,d,ℤ) duality group. Subsequently, we focus on Double Field Theory construction putting our attention on massless sector of string theory. We investigate on 2D nonlinear sigma model action in DFT and its gauge algebra. We follow this review by discussing constraints of DFT and Double Geometry. At the end we present some unsolved questions in this... 

    Extremal Black Holes and Decoupled Dynamics of Horizon

    , Ph.D. Dissertation Sharif University of Technology Fareghbal Khameneh, Reza (Author) ; Arfaei, Hessamaddin (Supervisor)
    We study a speci?c class of black holes which are called extremal. By de?ning extremality asdouble-horizon condition and imposing ?niteness assumption, we show that the dynamics of ?eldsat the horizon decouples from the rest of space. This decoupling occurs by vanishing all radialderivatives. We show this decoupling for the extremal black holes in the theories of gravity correctedby f(R)terms.We also show that these two above conditions leads to AdS × S1 near horizon geometry2of rotating black holes. This geometry which preserve SO(2, 1) × U(1) isometry group, is recentlyused in improving the entropy function method. Finally we show that decoupled equations of horizon can be derived from a... 

    Inclusive b-jet production in pp collisions at √s = 7 TeV

    , Article Journal of High Energy Physics ; Volume 2012, Issue 4 , 2012 ; 11266708 (ISSN) Chatrchyan, S ; Khachatryan, V ; Sirunyan, A. M ; Tumasyan, A ; Adam, W ; Bergauer, T ; Dragicevic, M ; Ero, J ; Fabjan, C ; Friedl, M ; Fruhwirth, R ; Ghete, V. M ; Hammer, J ; Hoch, M ; Hormann, N ; Hrubec, J ; Jeitler, M ; Kiesenhofer, W ; Krammer, M ; Liko, D ; Mikulec, I ; Pernicka, M ; Rahbaran, B ; Rohringer, C ; Rohringer, H ; Schöfbeck, R ; Strauss, J ; Taurok, A ; Teischinger, F ; Wagner, P ; Waltenberger, W ; Walzel, G ; Widl, E ; Wulz, C. E ; Mossolov, V ; Shumeiko, N ; Gonzalez, J. S ; Bansal, S ; Benucci, L ; Cornelis, T ; De Wolf, E. A ; Janssen, X ; Luyckx, S ; Maes, T ; Mucibello, L ; Ochesanu, S ; Roland, B ; Rougny, R ; Selvaggi, M ; Van Haevermaet, H ; Van Mechelen, P ; Van Remortel, N ; Van Spilbeeck, A ; Blekman, F ; Blyweert, S ; DHondt, J ; Suarez, R.G ; Kalogeropoulos, A ; Maes, M ; Olbrechts, A ; Van Doninck, W ; Van Mulders, P ; Van Onsem, G.P ; Villella, I ; Charaf, O ; Clerbaux, B ; De Lentdecker, G ; Dero, V ; Gay, A. P. R ; Hammad, G. H ; Hreus, T ; Leonard, A ; Marage, P. E ; Thomas, L ; Vander Velde, C ; Vanlaer, P ; Wickens, J ; Adler, V ; Beernaert, K ; Cimmino, A ; Costantini, S ; Garcia, G ; Grunewald, M ; Klein, B ; Lellouch, J ; Marinov, A ; Mccartin, J ; Rios, A. A. O ; Ryckbosch, D ; Strobbe, N ; Thyssen, F ; Tytgat, M ; Vanelderen, L ; Verwilligen, P ; Walsh, S ; Yazgan, E ; Zaganidis, N ; Basegmez, S ; Bruno, G ; Ceard, L ; De Favereau De Jeneret, J ; Delaere, C ; Du Pree, T ; Favart, D ; Forthomme, L ; Giammanco, A ; Grégoire, G ; Hollar, J ; Lemaitre, V ; Liao, J ; Militaru, O ; Nuttens, C ; Pagano, D ; Pin, A ; Piotrzkowski, K ; Schul, N ; Beliy, N ; Caebergs, T ; Daubie, E ; Alves, G. A ; Martins Jr., M. C ; De Jesus Damiao, D ; Martins, T ; Pol, M.E ; Souza, M. H. G ; Aldá Jr., W. L ; Carvalho, W ; Custódio, A ; Da Costa, E. M ; De Oliveira Martins, C ; De Souza, S. F ; Figueiredo, D. M ; Mundim, L ; Nogima, H ; Oguri, V ; Da Silva, W. L. P ; Santoro, A ; Do Amaral, S. M. S ; Jorge, L. S ; Sznajder, A. A ; Anjos, T. S ; Bernardes, C. A ; Dias, F. A ; Tomei, T. R. F. P ; Gregores, E. M ; Lagana, C ; Marinho, F ; Mercadante, P. G ; Novaes, S. F ; Padula, S. S ; Genchev, V ; Iaydjiev, P ; Piperov, S ; Rodozov, M ; Stoykova, S ; Sultanov, G ; Tcholakov, V ; Trayanov, R ; Vutova, M ; Dimitrov, A ; Hadjiiska, R ; Karadzhinova, A ; Kozhuharov, V ; Litov, L ; Pavlov, B ; Petkov, P ; Bian, J. G ; Chen, G. M ; Chen, H. S ; Jiang, C. H ; Liang, D ; Liang, S ; Meng, X ; Tao, J ; Wang, J ; Wang, J ; Wang, X ; Wang, Z ; Xiao, H ; Xu, M ; Zang, J ; Zhang, Z ; Asawatangtrakuldee, C ; Ban, Y ; Guo, S ; Guo, Y ; Li, W ; Liu, S ; Mao, Y ; Qian, S. J ; Teng, H ; Wang, S ; Zhu, B ; Zou, W ; Cabrera, A ; Gomez Morenon,B ; Osorio Oliveros, A. F ; Sanabria, J. C ; Godinovic, N ; Lelas, D ; Plestina, R ; Polic, D ; Puljak, I ; Antunovic, Z ; Dzelalija, M ; Kovac, M ; Brigljevic, V ; Duric, S ; Kadija, K ; Luetic, J ; Morovic, S ; Attikis, A ; Galanti, M ; Mousa, J ; Nicolaou, C ; Ptochos, F ; Razis, P. A ; Finger, M ; Finger Jr., M ; Assran, Y ; Kamel, A. E ; Khalil, S ; Mahmoud, M. A ; Radi, A ; Hektor, A ; Kadastik, M ; Müntel, M ; Raidal, M ; Rebane, L ; Tiko, A ; Azzolini, V ; Eerola, P ; Fedi, G ; Voutilainen, M ; Czellar, S ; Harkonen, J ; Heikkinen, A ; Karimaki, V ; Kinnunen, R ; Kortelainen, M. J ; Lampen, T ; Lassila Perini, K ; Lehti, S ; Linden, T ; Luukka, P ; Mäenpaa, T ; Peltola, T ; Tuominen, E ; Tuominiemi, J ; Tuovinen, E ; Ungaro, D ; Wendland, L ; Banzuzi, K ; Korpela, A ; Tuuva, T ; Sillou, D ; Besancon, M ; Choudhury, S ; Dejardin, M ; Denegri, D ; Fabbro, B ; Faure, J. L ; Ferri, F ; Ganjour, S ; Givernaud, A ; Gras, P ; De Monchenault, G. H ; Jarry, P ; Locci, E ; Malcles, J ; Millischer, L ; Rander, J ; Rosowsky, A ; Shreyber, I ; Titov, M ; Baffioni, S ; Beaudette, F ; Benhabib, L ; Bianchini, L ; Bluj, M ; Broutin, C ; Busson, P ; Charlot, C ; Daci, N ; Dahms, T ; Dobrzynski, L ; Elgammal, S ; De Cassagnac, R. G ; Haguenauer, M ; Mine, P ; Mironov, C ; Ochando, C ; Paganini, P ; Sabes, D ; Salerno, R ; Sirois, Y ; Thiebaux, C ; Veelken, C ; Zabi, A ; Agram, J. L ; Andrea, J ; Bloch, D ; Bodin, D ; Brom, J. M ; Cardaci, M ; Chabert, E. C ; Collard, C ; Conte, E ; Drouhin, F ; Ferro, C ; Fontaine, J.-C ; Gele, D ; Goerlach, U ; Juillot, P ; Karim, M ; Le Bihan, A. C ; Van Hove, P ; Fassi, F ; Mercier, D ; Baty, C ; Beauceron, S ; Beaupere, N ; Bedjidian, M ; Bondu, O ; Boudoul, G ; Boumediene, D ; Brun, H ; Chasserat, J ; Chierici, R ; Contardo, D ; Depasse, P ; El Mamouni, H ; Falkiewicz, A ; Fay, J ; Gascon, S ; Gouzevitch, M ; Ille, B ; Kurca, T ; Le Grand, T ; Lethuillier, M ; Mirabito, L ; Perries, S ; Sordini, V ; Tosi, S ; Tschudi, Y ; Verdier, P ; Viret, S ; Lomidze, D ; Anagnostou, G ; Beranek, S ; Edelhoff, M ; Feld, L ; Heracleous, N ; Hindrichs, O ; Jussen, R ; Klein, K ; Merz, J ; Ostapchuk, A ; Perieanu, A ; Raupach, F ; Sammet, J ; Schael, S ; Sprenger, D ; Weber, H ; Wittmer, B ; Zhukov, V ; Ata, M ; Caudron, J ; Dietz Laursonn, E ; Erdmann, M ; Guth, A ; Hebbeker, T ; Heidemann, C ; Hoepfner, K ; Klimkovich, T ; Klingebiel, D ; Kreuzer, P ; Lanskey, D ; Lingemann, J ; Magass, C ; Merschmeyer, M ; Meyer, A ; Olschewski, M ; Papacz, P ; Pieta, H ; Reithler, H ; Schmitz, S. A ; Sonnenschein, L ; Steggemann, J ; Teyssier, D ; Weber, M ; Bontenackels, M ; Cherepanov, V ; Davids, M ; Flügge, G ; Geenen, H ; Geisler, M ; Ahmad, W. H ; Hoehle, F ; Kargoll, B ; Sharif University of Technology
    The inclusive b-jet production cross section in pp collisions at a center-ofmass energy of 7TeV is measured using data collected by the CMS experiment at the LHC. The cross section is presented as a function of the jet transverse momentum in the range 18 < pT < 200 GeV for several rapidity intervals. The results are also given as the ratio of the b-jet production cross section to the inclusive jet production cross section. The measurement is performed with two different analyses, which differ in their trigger selection and b-jet identification: a jet analysis that selects events with a b jet using a sample corresponding to an integrated luminosity of 34 pb -1, and a muon analysis requiring a... 

    Nonrelativistic AdS/CFT

    , Ph.D. Dissertation Sharif University of Technology Davody, Ali (Author) ; Ardalan, Farhad (Supervisor) ; Alishahiha, Mohsen (Supervisor)
    We extend the non-relativistic AdS/CFT correspondence to the fermionic fields. In particular we study the two point function of a fermionic perator in non-relativistic CFTs by making use of a massive fermion propagating in geometries with Schrodinger group isometry. Although the boundary of the geometries with Schrodinger group isometry differ from that in AdS geometries where the dictionary of AdS/CFT is established، using the general procedure of AdS/CFT correspondence، we see that the resultant two point function has the expected form for fermionic operators in non-relativistic CFTs، though a non-trivial regularization may be needed. Also we study Weyl symmetry for non-relativistic... 

    Challenges Against The Front Grand Unified Theories

    , M.Sc. Thesis Sharif University of Technology Zavarbashi, Amin (Author) ; Golshani, Mehdi (Supervisor)
    Many physicists believed that all four forces were once unified at high energy levels but as the universe reduced into a lower-energy states the inherent symmetry between the forces began to break down.this broken symmetry caused the creation of four distinct forces of nature. The goal of the unified theory is an attempt to look back in time to when these forces where unified as one. In this thesis I tried to give an overview of the challenges which is againsted theorists in the way of unification. In the first chapter explores the theory that try to unify the electromagnetic and weak forces are investigated.it is done by considering guage principle and spontaneous symmetry breaking.in the... 

    Critique and Survey of Various Formulation of Multiverse Theory

    , Ph.D. Dissertation Sharif University of Technology Masoumi, Saeed (Author) ; Golshani, Mehdi (Supervisor) ; Sheikh Jabbari, Mohammad Mehdi (Supervisor)
    Multiverse scenario has been recently addressed by physicists and they have found it useful in many areas of physics. In this dissertation, I have treated some issues about multiverse such as the kinds of multiverses, the arguments for or against multiverse, areas in which multiverse is introduced, etc. This dissertation has six chapters and an appendix. In the chapter one, some classifications of multiverse is introduced, and also some definitions of the concept of a world is presented. Then, my classification and definition of a multiverse and a world is introduced. In the chapter two, the concept of possible worlds in philosophy and its relationship with multiverse hypothesis is examined....