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Higher-order interactions in quantum optomechanics: Revisiting theoretical foundations
, Article Applied Sciences (Switzerland) ; Volume 7, Issue 7 , 2017 ; 20763417 (ISSN) ; Sharif University of Technology
MDPI AG
2017
Abstract
The theory of quantum optomechanics is reconstructed from first principles by finding a Lagrangian from light's equation of motion and then proceeding to the Hamiltonian. The nonlinear terms, including the quadratic and higher-order interactions, do not vanish under any possible choice of canonical parameters, and lead to coupling of momentum and field. The existence of quadratic mechanical parametric interaction is then demonstrated rigorously, which has been so far assumed phenomenologically in previous studies. Corrections to the quadratic terms are particularly significant when the mechanical frequency is of the same order or larger than the electromagnetic frequency. Further discussions...
Time operator in relativistic quantum mechanics
, Article Communications in Theoretical Physics ; Volume 68, Issue 1 , 2017 , Pages 35-38 ; 02536102 (ISSN) ; Sharif University of Technology
Abstract
It is first shown that the Dirac's equation in a relativistic frame could be modified to allow discrete time, in agreement to a recently published upper bound. Next, an exact self-adjoint 4 × 4 relativistic time operator for spin-1/2 particles is found and the time eigenstates for the non-relativistic case are obtained and discussed. Results confirm the quantum mechanical speculation that particles can indeed occupy negative energy levels with vanishingly small but non-zero probablity, contrary to the general expectation from classical physics. Hence, Wolfgang Pauli's objection regarding the existence of a self-adjoint time operator is fully resolved. It is shown that using the time...
The Necessity of a Privileged Frame of Reference in Physics
, M.Sc. Thesis Sharif University of Technology ; Golshani , Mehdi (Supervisor)
Abstract
In the special theory of relativity, it is not necessary to propose that there is no privileged frame of reference but because this formalism is of the epistemological level, we can not deduce this ontological conclusion. On the other hand, there are different physical motivations for a privileged frame of reference and also there is an alternative physical model for special relativity called inertial transformations which is similar to the special theory of relativity at the observational level, but there is a privileged frame of reference in that theory. In this paper, I have tried to collect motivations for a privileged frame of reference in physics, in order to prepare a source for those...
Critical study and discrimination of different formulations of electromagnetic force density and consequent stress tensors inside matter
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Vol. 89, issue. 4 , April , 2014 ; ISSN: 10502947 ; Mehrany, K ; Sharif University of Technology
Abstract
By examination of the exerted electromagnetic (EM) force on boundary of an object in a few examples, we look into the compatibility of the stress tensors corresponding to different formulas of the EM force density with special relativity. Ampere-Lorentz's formula of the EM force density is physically justifiable in that the electric field and the magnetic flux density act on the densities of the total charges and the total currents, unlike Minkowski's formula which completely excludes the densities of the bounded charges and the bounded currents inside homogeneous media. Abraham's formula is fanciful and devoid of physical meaning. Einstein-Laub's formula seems to include the densities of...
Is quantum theory compatible with special relativity?
, Article Pramana - Journal of Physics ; Volume 80, Issue 3 , 2013 , Pages 429-437 ; 03044289 (ISSN) ; Shafiee, A ; Saravani, M ; Golshani, M ; Sharif University of Technology
2013
Abstract
How a proposed quantum nonlocal phenomenon could be incompatible with the requirements of special relativity is studied. To show this, the least set of assumptions about the formalism and the interpretation of non-relativistic quantum theory is considered. Then, without any reference to the collapse assumption or any other stochastic processes, an experiment is proposed, involving two quantum systems, that interacted at an arbitrary time, with results which seem to be in conflict with requirements of special relativity
Teleparallel Gravity and Phenomenology of Dark Matter
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor) ; Baghram, Shant (Supervisor)
Abstract
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...
Are Quantum Mechanics and Special Relativity in Peaceful Coexistence?
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
Quantum mechanics is very succesful in the description and prediction of the microphysical world. So nowadays very few doubt its authenticity. Nevertheless, there are some conceptual issues that are still under debate, such as action at a distance. It took a while after the introduction of the EPR paradox in 1935 until John Stewart Bell derived an inequality, using local hidden variables. This inequality was in contrast with predictions of quantum mechanics. Experiments also contradicted this inequality. This implies that there is action at distance which, in turn suggests, the violation of the special relativity. In this thesis, we consider this issue and shall see that on the one hand we...