Sharif Digital Repository

Given an element "H" in H^3 (X,Z), one can define the twisted K-group K(X,H). These groups have been appeared in physics and in particular in String Theory. As an explicit example, we study the twisted K-group of principle circle bundle E. An important notion related is the T-duality. We introduce (E,H), with E a principle circle bundle and H an element in H^3 (E,Z). Under certain circumstances we call (E,H) and (E,H)T-Dual. We study twisted K-theory of dual pair (E,H) and (E,H)  

In 2004 Ooguri, Strominger, and Vafa could write the partition function of 4D N=2 extremal black holes in type IIA superstring theory as the square of the absolute value of the partition function of type A closed topological string theory, which had already been introduced by Edward Witten in 1990. In this study, T and S dualities were applied to the original conjecture of Ooguri, Strominger, and Vafa. By using T duality, we have verified that the conjecture holds for 4D N=2 extremal black holes of type IIB superstring theory to the one loop order in string coupling. In other words, one can write the partition function of these kinds of black holes as the square of the absolute value of... 

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... 

Studying the puzzling aspects of quantum phenomenon is quite important subject from different points of view. It must be specially regarded through some major aspects such as: wave-particle dualty, Bell’s theorem no-go theorems, complementarity, entanglement and measurement problem. In this project, we survey subsequently the above topics with a careful attention regarding the measurement problem. One of the most relevant ways claiming to solve measurement problem is the decoherence theory. Scrutinizing the details of formalism and description basis of decoherence, we critically explain and asses the different aspects of this theory  

This Thesis presents a new approach for determining the day-ahead bidding strategies of a hybrid electric energy company. The company has both energy generation and energy retailing businesses in a competitive electricity market. Demand response programs are also considered in the retail side of the company in order to hedge the risk of participation in wholesale market. Price-taker and price maker companies are considered in this thesis separateky.For the price-taker hybrid structure, the predivtion of day-ahead prices are used to evaluate the optimum bidding and offering strategies. Also, day-ahead market price uncertainty is modeled, using non-probabilistic Information Gap Decision Theory... 

One of the approaches to study the plasma phase of quantum chromodynamics is to investigate the motion of probes in the quark-gluon plasma. In the case of a moving heavy quark, the medium affects the quark by exerting a drag force on it. Since we finally detect hadron jets in detectors, the goal is to compute the darg force formula in a form compatible with the espectrum of final hadrons. On the other hand due to strong coupling, perturbative methods fail in the medium. So a nonperturbative method is needed. We use gauge gravity duality and compute the drag force exerted on a heavy quark in the hydrodynamic regime, up to first order in derivative expansion