Sharif Digital Repository

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... 

The search for an empirically proven quantum theory of gravity is one of the greatest open problems of fundamental physics. Obstacles are formal and conceptual in nature. Our goal is to find a theory that somehow unites general relativity (Einstein's classical field gravity theory) and quantum field theory. In this research work, the problem of quantum gravity and the reason for its importance are investigated, as well as the proposed solutions; and what philosophical issues do these approaches and the issue itself create. Research has been carefully selected to remain managed in terms of size and content, however, some basic formalism is introduced to enter physics and the philosophy of... 

According to Penrose-Hameroff's theory, Consciousness as an undeniable reality can, in some cases, be explained by a kind of orchestrated objective reduction of the wave function in the cytoskeleton of the brain neurons. Here, I have presented the subject, problem, and claim of this theory, as well as its argument, which consists of three main premises. In the first premise, first by rejecting the opposing theories and then by presenting reasons, it is shown that human thinking is, in some manner, sound but non-computable, and at the same time, accepting the Non-computability of human thinking requires believing in the objects in the universe that are non-computable, but They can be... 

In this thesis, we study two important quantum effects at deSitter spacetime and using the Schrödinger field theory, the power spectrum of massive non-interacting, minimally coupled scalars in a fixed de Sitter background would be obtained. To calculate the N-point function in Schrödinger field theory, the ”in-in” formalism is extended in the Friedmann- Lemaître-Robertson-Walker (FLRW) universe. This formalism in such picture would have a crucial role for evaluating the correlation functions of those quantum states naturally written in Schrödinger picture. We compute the three-point function for primordial scalar field fluctuation in the single field inflation by this in-in formalism. The... 

Investigation of the consistency between physical theories has always resulted in the advancement of physics. Meanwhile, study of the consistency between quantum mechanics and thermodynamics has led to the development of a branch in theoretical physics called quantum thermodynamics. In addition to the consistency problem,employing other features of quantum mechanics such as coherency and entanglement, to enhance thermodynamic processes is another ongoing subject of research. In order to study the thermodynamics of quantum systems, we use the first law of thermodynamics to present a derivation of quantum potential. Quantum potential is a term in the equations of motion of a quantum system of... 

Paul Feyerabend, an Austrian philosopher of science, is known as one of major critics of science and philosophy of science in 20th century. This inquiry is an attempt to study and criticize the bedrock of Feyerabend's philosophy of science. In the first chapter there will be an intruduction to enter the subject. In the second chapter the method of this study will be explained. Third chapter is a reconstruction of Feyerabend's philosophy of science. In the 4th chapter bedrock of Feyerabend's philosophy of science is derived to be: scepticism and fighting against dogmatism, defying monopolization, humanistic concerns and his personal character. In the last chapter there will be criticisms on... 

General Relativity is a generally covariant and deterministic theory of space-time. The Hole Argument requires that there is no substantivalist interpretation of general relativistic space-time. In this thesis, I am intended to show that this conclusion is not compelling. Through this, a deeper understanding of philosophical and mathematical content of General Relativity is investigated  

In this thesis, inspired by foundational discussions about the concepts of energy and entropy in the gravitational theory, we study the definitions of these concepts and the roles they play in that theory. The definitions considered in this thesis are derived from canonical formalism. To this end, first of all, the variational principle and the canonical structure in the gravitational theory, especially in situations where the spacetime is bounded, is carefully studied and the boundary and corner actions as well as the canonical structure on the boundaries in three cases of non-null, null and general boundaries are derived. Based on this study, two canonical approaches, namely the... 

The relation of mind and brain has always been a fundamental and challenging problem for science. The study of this subject with the help of modern physics, considering the failure of classical physics and materialistic philosophy in explaining spiritual and mental phenomena, has attracted the attention of contemporary eminent physicist and biologists. This area is known as "quantum consciousness" and involves theories about mind and brain. Among these theories are: Eccles-Beck theory, Heisenberg-James theory (presented by Stapp) and Penrose-Hameroff theory. In dealing with the problem of mind-matter interaction and consciousness, modern physics, psychology and some philosophical schools are... 

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... 

The universe appears to be homogeneous and isotropic as far as we can detect, which is called the Cosmological Principle. Standard big-bang model was successful in describing the universe. For example, it predicts the Hubble’s law of expansion for the universe, existence of the Cosmological background radiation and the correct abundance for the light atomic nuclei. Nevertheless, this model was unable to explain some problems in cosmology, for example horizon problem, smoothness problem and flatness problem. In the early 1980s, Inflation Theory was proposed by Alun Guth and others to resolve these problems in Standard Cosmology; but in two recent decades some contemporary prominent... 

The concept of symmetry has long been the focus of numerous debates in different fields; some have come up with an artistic approach looking for a beautiful notion germane to the concept of symmetry. Others have examined this issue from a philosophical viewpoint and studied the ontology of symmetry and philosophers like Kant moved beyond the limits and have given their symmetry a transcendental position. On the other hand, in an anti-realist position relying on the fact that the goal of science is not truth but merely it’s an empirical adequacy, Van Fraassen argued that “science was rapidly gaining autonomy not only from theology but from all of philosophy, and was exploiting concepts and... 

The purpose of this study is to investigate the causes and reasons of the decline of Iran. The beginnings of decline can be traced to factors such as determinism, esotericism, fundamentalism, the absence of skilled men, as well as the lack of a stable legal system and the emigration of Iranians to foreign countries. Lack of attention and lack of thought about the causes of the decline of Iranian civilization is the main problem of Iran's backwardness. On the other hand, this is the main reason for the growth of Western civilizations. Westerners have made good use of this feature and provided the means for their civilization to flourish. The lack of the concept of decline in a culture does... 

In recent decades, the idea of multiverse has been raised in several areas of physics for different reasons. One of the interpretations of quantum mechanics, the inflation theory in cosmology and string theory in fundamental physics have led to the multiverse idea. On the other hand, after the problem of fine-tuning of the constants of nature became a hot topic in recent decades, physicists have tried to find a way to explain this puzzle. One of the most important approaches that have been suggested by some physicists, as a scientific explanation for this problem, is the idea of multiverse and they are even willing to set aside the principle of observability to confirm physical... 

To answer the explanabilty of consciousness, we have first clarified the terms “consciousness”, “explanation”, and “physic”, concluding that consciousness and physics should be integrated in a single unified explanatory system. The common problem we have targeted in this work is “direct observation”. Then, inspired by Bergson, we have suggested that ,in direct observation, there is a unity between observer and the observed, out of which the qualitative characteristic of experience or qualia is constructed. Following computer graphic courses, this unity is called “rendering unity”. In the next scientific step, by analyzing the Wigner’s friend paradox, we have stipulated that, in direct... 

In recent decades, the growing number of eminent contemporary physicists, including Weinberg, Penrose, Isham, Susskind and etc. have doubted about the durability of quantum theory, and in the last year Weinberg, after analyzing the well-known interpretations of Standard quantum theory sees all of them as difficult and concludes that quantum theory needs to be replaced by a more comprehensive theory. The purpose of this dissertation is to analyze the critiques of Weinberg and others to the standard quantum theory and to study some of the alternative theories proposed, including the Bohemian quantum theory and the holographic universe  

From 1990’s the Cosmological Constant Problem was brought back to spotlight and physicists have tried to find out its source. But the value that particle physic anticipates for cosmological constant is not harmonic with cosmological considerations. This thesis investigates the studies in this field  

The history of an Episteme is part of that Episteme. Without understanding the history of Episteme, one cannot get the right understanding of the Episteme. In order to understand the current coordinates of philosophy in Iran (as well as understanding the current state of philosophy in Iran), it must examine the history of its emergence and development. Part of the sources of recognition of this history is the “Erlbnis” of those who lived the event. Those who have been trying for its birth and development. Some other sources in understanding this history are the previous published works in this area. Another is the educational effort and the establishment and development of the institutions... 

In 1917 Einstein used Λ as a cosmological constant in his theory of general relativity, but after a while he receded for some reasons. This constant has been reconsidered again recently. But using it in general relativity has caused some problems. In this thesis, after a short review of important elements in studying cosmological constant problem, like a short introduction to general relativity and cosmology in the first chapter as well as a short review of quantum field theory and supersymmetry in the second chapter, we will study the history and introduction of the problem in the third chapter.in the third chapter , different solutions to this problem ,like supersymmetry,anthropic... 

In this thesis a brief review of the concept of vacuum has been studied. In addition, we shall see how we can determine the vacuum energy in a flat space-time. Also the renormalization and the regularization of zero point energy, which is 122 order of magnitude more than the critical density energy, has been represented. Then, we study supersymmetry which is a candidate to solve this problem. Furthermore, different ways to determine cosmological constant and the orbits of planets has been studied.Finally, by studying free fall experiments, the gravitational properties of vacuum has been represented.Caisimir effect, one of the most amazing predictions in the history of physics, and Lamb...