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#### Numerical investigation of fast axial flow high power CW CO2 laser: Considering the effect of intensity variation

, Article Scientia Iranica ; Volume 10, Issue 4 , 2003 , Pages 443-448 ; 10263098 (ISSN) ; Imangholi, B ; Sharif University of Technology
Sharif University of Technology
2003

Abstract

The effect of intensity variation on the quantum densities of active medium and thermodynamic characteristics of a high turbulent flow CO2 laser has been investigated. Comparison between the calculation of constant and variant intensity on the quantum densities and thermodynamic characteristics of turbulent gas flow shows a ∼ 10% drop in the output power of the laser, which is only 50 cm long. © Sharif University of Technology, October 2003

#### 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...

#### QBism is not so simply dismissed

, Article Foundations of Physics ; Volume 50, Issue 7 , 2020 , Pages 693-707 ; Sharif University of Technology
Springer
2020

Abstract

QBism is one of the main candidates for an epistemic interpretation of quantum mechanics. According to QBism, the quantum state or the wavefunction represents the subjective degrees of belief of the agent assigning the state. But, although the quantum state is not part of the furniture of the world, quantum mechanics grasps the real via the Born rule which is a consistency condition for the probability assignments of the agent. In this paper, we evaluate the plausibility of recent criticism of QBism. We focus on the consequences of the subjective character of the quantum state, the issue of realism and the problem of the evolution of the quantum state in QBism. In particular, drawing upon...

#### A critique of Mohrhoff's interpretation of quantum mechanics

, Article Studies in History and Philosophy of Science Part B - Studies in History and Philosophy of Modern Physics ; Volume 37, Issue 2 , 2006 , Pages 316-329 ; 13552198 (ISSN) ; Jafar Aghdami, M ; Golshani, M ; Sharif University of Technology
2006

Abstract

Assuming the completeness of quantum mechanics, Mohrhoff has recently presented a new interpretation in which the probabilistic description of quantum mechanics is introduced on the basis of counterfactual statements. The macroscopic positions are assumed to be intrinsic, self-indicating and real, while the properties of the microscopic world are contingent and extrinsic, depending on what happens in the macro-world. Mohrhoff's interpretation emphasizes the objective fuzziness of all quantum phenomena, assigning objective probabilities to the possible outcomes of unperformed measurements. He extends this non-valuedness and fuzziness to the concepts of space and time and introduces a new...

#### An overview of tight-binding method for two-dimensional carbon structures

, Article Graphene: Properties, Synthesis and Applications ; 2012 , Pages 1-36 ; 9781614709497 (ISBN) ; Khorasani, S ; Sharif University of Technology
2012

Abstract

Since the advent of graphene, the two-dimension allotrope of carbon, there has been a growing interest in calculation of quantum mechanical properties of this crystal and its derivatives. To this end, the tight-binding model has been in frequent use for a relatively long period of time. This review, presents an in-depth survey on this method as possible to graphene and two of the most important related structures, graphene anti-dot lattice, and graphane. The two latter derivatives of graphene are semiconducting, while graphane is semimetallic. We present band structure and quantum mechanical orbital calculations and justify the results with the density function theory

#### Quantum ergodicity for a class of non-generic systems

, Article Journal of Physics A: Mathematical and Theoretical ; Volume 49, Issue 5 , 2015 ; 17518113 (ISSN) ; Bakhshinezhad, F ; Rezakhani, A. T ; Sharif University of Technology
2015

Abstract

We examine quantum normal typicality and ergodicity properties for quantum systems whose dynamics are generated by Hamiltonians which have residual degeneracy in their spectrum and resonance in their energy gaps. Such systems can be considered atypical in the sense that degeneracy, which is usually a sign of symmetry, is naturally broken in typical systems due to stochastic perturbations. In particular, we prove a version of von Neumann's quantum ergodic theorem, where a modified condition needs to hold in order to have normal typicality and ergodicity. As a result, we show that degeneracy of spectrum does not considerably modify the condition of the theorem, whereas the existence of...

#### A proof for poisson bracket in non-commutative algebra of quantum mechanics

, Article Electronic Journal of Theoretical Physics ; Volume 13, Issue 35 , 2016 , Pages 57-71 ; 17295254 (ISSN) ; Sharif University of Technology
EJTP Publisher
2016

Abstract

The widely accepted approach to the foundation of quantum mechanics is that the Poisson bracket, governing the non-commutative algebra of operators, is taken as a postulate with no underlying physics. In this manuscript, it is shown that this postulation is in fact unnecessary and may be replaced by a few deeper concepts, which ultimately lead to the derivation of Poisson bracket. One would only need to use Fourier transform pairs and Kramers- Kronig identities in the complex domain. We present a definition of Hermitian time-operator and discuss some of its basic properties. © Electronic Journal of Theoretical Physics

#### Some clarifications on the relation between bohmian quantum potential and mach’s principle

, Article International Journal of Theoretical Physics ; Volume 56, Issue 10 , 2017 , Pages 3096-3107 ; 00207748 (ISSN) ; Golshani, M ; Sharif University of Technology
Abstract

Mach’s principle asserts that the inertial mass of a body is related to the distribution of other distant bodies. This means that in the absence of other bodies, a single body has no mass. In this case, talking about motion is not possible, because the detection of motion is possible only relative to other bodies. But in physics we are faced with situations that are not fully Machian. As in the case of general theory of relativity where geodesics exist in the absence of any matter, the motion has meaning. Another example which is the main topic of our discussion, refers to Bohmian quantum mechanics, where the inertial mass of a single particle does not vanish, but is modified. We can call...

#### Information and the Brukner-Zeilinger interpretation of quantum mechanics: A critical investigation

, Article Foundations of Physics Letters ; Volume 19, Issue 1 , 2006 , Pages 1-20 ; 08949875 (ISSN) ; Safinejad, F ; Naqsh, F ; Sharif University of Technology
2006

Abstract

In Brukner and Zeilinger's interpretation of quantum mechanics, information is introduced as the most fundamental notion and the finiteness of information is considered as an essential feature of quantum systems. They also define a new measure of information which is inherently different from the Shannon information and try to show that the latter is not useful in defining the information content in a quantum object. Here, we show that there are serious problems in their approach which make their efforts unsatisfactory. The finiteness of information does not explain how objective results appear in experiments and what an instantaneous change in the so-called information vector (or catalog of...

#### Particle creation by moving spherical shell in the dynamical Casimir effect

, Article Modern Physics Letters A ; Volume 16, Issue 14 , 2001 , Pages 927-935 ; 02177323 (ISSN) ; Saharian, A. A ; Sharif University of Technology
2001

Abstract

The creation of massless scalar particles from the quantum vacuum by spherical shell with time varying radius is studied. In the general case of motion the equations are derived for the instantaneous basis expansion coefficients. The examples are considered when the mean number of particles can be explicitly evaluated in the adiabatic approximation

#### Entanglemant: Standard QM nersus Bohmian QM

, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract

The1935 EPR thought experiment, introduced the concept of entanglement of quantum states, and this brought up the problems of faster than light signaling and faster than light influencing.The quantum entanglement has becomeone of the most important aspects of quantum information in the last thirty years.But the standard quantum theory has not been able to solve the dilemma of quantum entanglement and has confined itselfto deny faster than light signaling, but admitting faster than light influencing.But the followers of Bohmian mechanics,which have appealed to hidden variables,see no problem with quantum entanglement.The aim of this thesis is to compare the status of the standard quantum...

#### A proposed mechanism for mind-brain interaction using extended Bohmian quantum mechanics in Avicenna's monotheistic perspective

, Article Heliyon ; Volume 5, Issue 7 , July , 2019 ; 24058440(ISSN) ; Golshani, M ; Jamali, Y ; Sharif University of Technology
Elsevier Ltd
2019

Abstract

In quantum approaches to consciousness, the authors try to propose a model and mechanism for the mind-brain interaction using modern physics and some quantum concepts which do not exist in the classical physics. The independent effect of mind on the brain has been one of the challenging issues in the history of science and philosophy. In some recent mind-brain interaction models, the direct influence of mind on matter is either not accepted (as in Stapp's model) or not clear, and there have not been any clear mechanism for it (as in Penrose-Hameroff's model or in Eccles's model). In this manuscript we propose a model and mechanism for mind's effect on the matter using an extended Bohmian...

#### A proposed mechanism for mind-brain interaction using extended Bohmian quantum mechanics in Avicenna's monotheistic perspective

, Article Heliyon ; Volume 5, Issue 7 , 2019 ; 24058440 (ISSN) ; Golshani, M ; Jamali, Y ; Sharif University of Technology
Elsevier Ltd
2019

Abstract

In quantum approaches to consciousness, the authors try to propose a model and mechanism for the mind-brain interaction using modern physics and some quantum concepts which do not exist in the classical physics. The independent effect of mind on the brain has been one of the challenging issues in the history of science and philosophy. In some recent mind-brain interaction models, the direct influence of mind on matter is either not accepted (as in Stapp's model) or not clear, and there have not been any clear mechanism for it (as in Penrose-Hameroff's model or in Eccles's model). In this manuscript we propose a model and mechanism for mind's effect on the matter using an extended Bohmian...

#### Some Innovations in Expantion of Causal Quantum Mechanics to Quantum Field Theory

, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract

The advent of Quantum Mechanics in the beginning of twentieth century created a fundamental evolution on physics. The ability and performance of Quantum Mechanics in perception of natural phenomena have spread its penetration farther than physics and affected different realms of science, and especially Philosophy. As a result, several philosophic and logical principles defined according to the Quantum Mechanics, and also several of them were rejected because of their inconsistency with Quantum Mechanics. Since Quantum Mechanics was not flawless theory, some of these evolutions have created profound deviations in interpretation and perception of nature. One of these changes was denial of...

#### Ab initio calculations of characteristic lengths of crystalline materials in first strain gradient elasticity

, Article Mechanics of Materials ; Volume 61 , 2013 , Pages 73-78 ; 01676636 (ISSN) ; Zaheri, A ; Tehranchi, A ; Sharif University of Technology
2013

Abstract

Incorporation of the first gradient of strain, in addition to the strain itself, into the strain energy density of an elastic solid leads to Mindlin's first strain gradient theory, which is useful for examination of size effect as well as other mechanical phenomena at the nano-scale. For isotropic elastic solids, the first strain gradient theory, in addition to the two independent Lamé constants, gives rise to five new material constants which in turn reduce to two material parameters, ℓ1 and ℓ2 with dimension of length. The evaluation of these parameters, however, has posed serious challenges, both experimentally and theoretically. In this work ab initio method is used to compute the...

#### Deriving relativistic Bohmian quantum potential using variational method and conformal transformations

, Article Pramana - Journal of Physics ; Volume 86, Issue 4 , 2016 , Pages 747-761 ; 03044289 (ISSN) ; Golshani, M ; Sarbishei, M ; Sharif University of Technology
Abstract

In this paper we shall argue that conformal transformations give some new aspects to a metric and changes the physics that arises from the classical metric. It is equivalent to adding a new potential to relativistic Hamilton-Jacobi equation. We start by using conformal transformations on a metric and obtain modified geodesics. Then, we try to show that extra terms in the modified geodesics are indications of a background force. We obtain this potential by using variational method. Then, we see that this background potential is the same as the Bohmian non-local quantum potential. This approach gives a method stronger than Bohm's original method in deriving Bohmian quantum potential. We do not...

#### Analogies and Differences Between Auantum Mechanics and Quanmtum Field Theory (Causality and Locality)

, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract

Causality and locality are two of the fundamental problems in physics and physicists have different interpretations of them. In new physics theories like Quantum mechanics and Quantum field theory, the main point of discussion is that whether these two theories are local and causal or not? In first chapter, we introduce the principle of causality. The second and third chapters cover causality in Quantum mechanics and Quantum field theory.The last chapter is about locality

#### Consciousness in Quantum View: An Inspection of Stapp and Penrose Viewpoints

, M.Sc. Thesis Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract

In order to study the phenomenon of consciousness, many physicists have presented their views. In this thesis, the phenomenon of consciousness is analyzed from Henrry Stapp and Penrose-Hameroffs’ viewpoints. Assuming the subjective reduction of state vector, Stapp considers conscious mind as prerequisite for the reduction of wave function. In his view, consciousness is a selection agent which has a top-level control over brain stimulations,and every conscious experience is the feeling of the top-level event in the brain. He also considers physical world as a structure of tendencies and probabilities. He speaks about creative events which occur among Heisenberg probability distributions. On...

#### Expounding the Meaning of Time in Evolutionary Process

, M.Sc. Thesis Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract

The question of the time is one of the obscure and challenging subjects which has been discussed as a mysterious problem in various civilizations. In ancient Greece, the question has been debated among the supporters of existence and eternity. We observe the words of Plato, on the existence of the absolute essence of eternity against the change and transition time instantiated as a conducted river in the Heraclitus view. Other discussions focused on the relationship between the change and displacement, or the the spatial relations to which Aristotle paid attention. With the passing of time from the ancient and medieval eras to the Renaissance period, along with the growth of the science in...

####
Studying of Chaotic Behavior in Some Classical and Quantum Systems

,
M.Sc. Thesis
Sharif University of Technology
;
Shafiee, Afshin
(Supervisor)
Abstract

Chaos is defined as an unpredictable and unrepeatable motion which has been observed in many classical systems such as unharmonic oscillators and turbulent currents in fluids. The common aspect of these types of motions is the deterministic nonlinear equation. On the other hand, quantum mechanics is a stochastic theory which is based on probabilistic description of quantum systems. These approaches lead to quantum chaos phenomenon which has been a controversial issue in the recent years. In the thesis, by studying the classical chaotic models such as kicked rotor, billiard model, excited hydrogen atom under microwave field and etc, we examine the existence of chaotic behavior in quantum...