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What is the quantum state of the universe? Although there have been several interesting suggestions, the question remains open. In this paper, I consider a natural choice for the universal quantum state arising from the Past Hypothesis, a…

Quantum Physics · Physics 2019-01-25 Eddy Keming Chen

In a quantum universe with a strong arrow of time, it is standard to postulate that the initial wave function started in a particular macrostate--the special low-entropy macrostate selected by the Past Hypothesis. Moreover, there is an…

Quantum Physics · Physics 2021-10-25 Eddy Keming Chen

Realism about quantum theory naturally leads to realism about the quantum state of the universe. It leaves open whether it is a pure state represented by a wave function, or an impure (mixed) one represented by a density matrix. I…

Quantum Physics · Physics 2024-11-05 Eddy Keming Chen

Two of the most difficult problems in the foundations of physics are (1) what gives rise to the arrow of time and (2) what the ontology of quantum mechanics is. They are difficult because the fundamental dynamical laws of physics do not…

Quantum Physics · Physics 2022-11-09 Eddy Keming Chen

An interpretation and re-formulation of modern physics which removes the presumption of the space-time continuum, and bases physical theory on a small number of rational and empirical principles. After briefly describing the philosophical…

General Physics · Physics 2014-05-13 Charles Francis

We investigate the origin of the arrow of time in quantum mechanics in the context of quantum cosmology. The ``Copenhagen'' quantum mechanics of measured subsystems incorporates a fundamental arrow of time. Extending discussions of…

General Relativity and Quantum Cosmology · Physics 2009-09-25 Murray Gell-Mann , James B. Hartle

It is proposed to give up the description of physical states in terms of ensembles of state vectors with various probabilities, relying instead solely on the density matrix as the description of reality. With this definition of a physical…

Quantum Physics · Physics 2015-06-19 Steven Weinberg

Quantum mechanics can emerge from classical statistics. A typical quantum system describes an isolated subsystem of a classical statistical ensemble with infinitely many classical states. The state of this subsystem can be characterized by…

Quantum Physics · Physics 2015-05-13 C. Wetterich

In this paper Quantum Mechanics with Fundamental Length is chosen as the theory for describing the early Universe. This is possible due to the presence in the theory of General Uncertainty Relations from which unavoidable it follows that in…

General Relativity and Quantum Cosmology · Physics 2016-08-31 A. E. Shalyt-Margolin , J. G. Suarez

A model quantum cosmology is used to illustrate how arrows of time emerge in a universe governed by a time-neutral dynamical theory constrained by time asymmetric initial and final boundary conditions represented by initial and final…

General Relativity and Quantum Cosmology · Physics 2020-02-18 James B. Hartle

Determining the initial state of the universe is a challenging problem in quantum cosmology and we argue that the issue is intractable if the basic postulates of quantum mechanics are not modified in a nontrivial way. Namely a "standard"…

General Relativity and Quantum Cosmology · Physics 2019-10-09 Ali Kaya

The pure state space of Quantum Mechanics is investigated as Hermitian Symmetric Kaehler manifold. The classical principles of Quantum Mechanics (Quantum Superposition Principle, Heisenberg Uncertainty Principle, Quantum Probability…

Quantum Physics · Physics 2009-11-07 R. Cirelli , M. Gatti , A. Maniá

Based on a number of experimentally verified physical observations, it is argued that the standard principles of quantum mechanics should be applied to the Universe as a whole. Thus, a paradigm is proposed in which the entire Universe is…

General Relativity and Quantum Cosmology · Physics 2007-05-23 J. S. Eakins

So far, none of attempts to quantize gravity has led to a satisfactory model that not only describe gravity in the realm of a quantum world, but also its relation to elementary particles and other fundamental forces. Here, we outline the…

General Relativity and Quantum Cosmology · Physics 2021-11-29 Houri Ziaeepour

The article explores challenges presented by revelations in physics and the questions they provoke concerning reality. It sheds light on the disparity between the indefinite nature of quantum reality and our perception of classical reality.…

General Physics · Physics 2024-05-14 Jahan N. Schad

The properties of the quantum universe on extremely small spacetime scales are studied in the semi-classical approach to the well-defined quantum model. It is shown that near the initial cosmological singularity point quantum gravity…

General Relativity and Quantum Cosmology · Physics 2010-04-30 V. E. Kuzmichev , V. V. Kuzmichev

A density matrix {\rho}(t) yields probabilistic information about the outcome of measurements on a quantum system. We introduce here the past quantum state, which, at time T, accounts for the state of a quantum system at earlier times t <…

Quantum Physics · Physics 2013-10-21 Søren Gammelmark , Brian Julsgaard , Klaus Mølmer

The observable universe is fundamentally inhomogeneous and anisotropic. Quantum description of the generation of these inhomogeneities and anisotropies is ill-understood and unsatisfactory. After providing a brief account of the standard…

General Relativity and Quantum Cosmology · Physics 2024-04-05 Sujoy K. Modak

In physical theories, boundary or initial conditions play the role of selecting special situations which can be described by a theory with its general laws. Cosmology has long been suspected to be different in that its fundamental theory…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Martin Bojowald

The subject of this study is Quantum and Statistical Mechanics of the Early Universe. In it a new approach to investigation of these two theories - density matrix deformation - is proposed. The distinguishing feature of the proposed…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Alex. E. Shalyt-Margolin
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