Sharif Digital Repository

The Quantum nonlocality problem, which has been tested with the Bell experiment, is one of the problems that doesn't have any explanation. Some people believed that there is a conflict between Quantum nonlocality and Special Relativity, the reason why, is Special Relativity based on Lorentz Transformations that don't allow us exceeding from speed of light. But in the nonlocality problem we understand that data transmition is instantaneous (at least is faster than speed of light). So it seems that we must look for transformations in which there is a possibility for exceeding from speed of light, the Lorentz Transformations is the special case of them. Then we can explain nonlocality with... 

One of the biggest challenges facing cosmologists is finding the nature of dark matter. The cosmological observations, like the Rotation Curve, Gravitational Weak Lensing and Cosmic Microwave Background radiation indicate that baryonic matter alone cannot explain the density of matter in the universe. In the context of standard cosmological models, it means that the universe is made of an unknown component(Dark Matter), which aprroximately has 27% of total energy-momentum of the universe. The Modify Gravity and General Relativity are alternative theories that introduced to describe this observation. In This thesis, we introduce the issue of the measurements of accelerated observers in... 

Quantum correlations are among most intriguing problems in physics. Bell’s inequality which was proved in 1964 provides with us the possibility of comparing the predictions of quantum theory with what an underlying local realistic theory may reproduce for some given observables in correlated states. The violation of Bell’s inequality in practice prohibits the existance of such underlying theories. Yet, it is not clear which of the assumption, i.e., locality or reality is responsible for explaining the experimentally verified violations. In 2003, a Nobel prizewinner A. J. Leggett proved a new inequality in which the locality assumption was not crucial. Here, we explore different aspects of... 

In this investigation has been tried to indagate the Bell’s inequality both theoretically and experimentally. This inequality published by John Bell in 1964 on the EPR argument. In the EPR argument they reasonably deduced that quantum mechanics with the wave function interpretation is incomplete (but proposing correct results), so we must looking for a deterministic and more fundamental and underlying theory than common quantum mechanics, the alternative theory shall contain Reality and Locality assumptions and also could produce current quantum mechanics results. Afterward, scientific probation started for finding a deterministic theory that including hidden variables, infact supplement... 

Up to this day, no conflict ever observed between experiments and the predictions of quantum mechanics. Scientists are in the belief that quantum mechanics is a universal theory and all the systems, even the classical ones, are quantum mechanical in their nature. In this regard, modeling the Earth-Sun dynamics using Hydrogen atom Hamiltonian has been addressed. Since we understand the classical systems with trajectories, we used Bohmian mechanics as an alternative way to study the Earth-Sun dynamics in a quantum fashion. Moreover, for better understanding the concept of the quantum to classical transition, we studied quantum thermodynamics. Accordingly, we described open quantum systems in... 

Despite the astonishing successes of quantum mechanics, due to some fundamental problems such as the measurement problem and quantum arrival time problem, the predictions of the theory are in some cases not quite clear and unique. Especially, there are various predictions for the joint spatiotemporal distribution of particle detection events on a screen, which are derived from different formulations and interpretations of the quantum theory. Although the differences are typically small, we show that these predictions can be experimentally distinguished by a proposed unconventional double-slit configuration, which is realizable using present-day single-atom interferometry. Furthermore, we...