ممتحن داخلي۱: مسلم زارعي; ممتحن داخلي۲: غلامرضا خسروي

1397/01/20

كتابنامه

فيزيك

فيزيك

ID12249

Investigation of Lovelock Theory and Higher Derivatives Gravitational Systems at the Critical Point Sahar Dadkhah Tehrani Sahar Dadkhah@ph iut ac ir January 13 2018 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran University Code IUT 77142 Degree M S c Language Farsi supervisor Dr Ahmad Shirzad Shirzad@ipm ir Abstract General relativity is a classical theory of gravity at low energies or large distances There are di erent motivations for modifying and completing this theory In this thesis we investigate the higher derivatives theories of gravity Lovelock models are those with similar characteristics with general relativity For example the equivalence of the Palatini and metric formulations is a propery of Einestein gravity theory This is also the case for the Lovelock theories As a special case we investigate the Einestein Gauss Bonnet gravity in details We linearize this model around the AdS solution and nd that propagator of this model is massless graviton We nd that this theory contains ghost like solution There is a critical point in which kinetic term vanishes and Einestein Gauss Bonnet gravity describes a gravity theory without graviton We add curvature squared terms to Einestein Hilbert action and linearize this model as well We consider this theories of gravity in four dimensions and D di mensions This theories of gravity describe a massless spin 2 graviton a massive spin 2 part and a massive scalar This theories of gravity also su er from having ghosts There is a critical point in which massive scalar is absent massive spin 2 eld becomes massless and the energies of excitations of the remaining massless graviton vanish The lacking of kinetic term is unusual from the point of view of eld theories and its physical implication is not clear We study AdS wave solutions in these models and nd that at the critical points these models ad mit logarithmic solutions Within the framework of the AdS CFT duality these models may provide gravity descriptions for logarithmic conformal eld theories in the boundary Keywords Lovelock theory Einestein Gauss Bonnet theory of gravity Higher derivatives theory ofgravity Critical point Ghost like instability Logarithmic solution

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ممتحن داخلي۱: مسلم زارعي; ممتحن داخلي۲: غلامرضا خسروي