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In this paper, we investigate an important issue addressed by several approaches to quantum cosmology, like that based on loop quantum gravity and string theory: the existence of an arrow of time driving the cosmological evolution according…

General Relativity and Quantum Cosmology · Physics 2026-03-25 Carlos Silva , Renan Aragão , Francisco A. Brito

The standard method for observationally confirming the existence of a predicted finite topology of the universe involves searching for the repetition of the same finite or extended source in different directions. However, serious problems…

Astrophysics · Physics 2007-05-23 Reuven Opher

Within the framework of loop quantum cosmology, there exists a semi-classical regime where spacetime may be approximated in terms of a continuous manifold, but where the standard Friedmann equations of classical Einstein gravity receive…

General Relativity and Quantum Cosmology · Physics 2009-11-10 James E. Lidsey

This contribution consists of two parts. In the first part, I review the tunneling approach to quantum cosmology and comment on the alternative approaches. In the second part, I discuss the relation between quantum cosmology and eternal…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Alexander Vilenkin

After reviewing the general ideas of quantum cosmology (Wheeler-DeWitt equation, boundary conditions, interpretation of $\psi$), I discuss how these ideas can be tested observationally. Observational predictions differ for different choices…

General Relativity and Quantum Cosmology · Physics 2008-02-03 Alexander Vilenkin

What is the quantum state of the universe? That is the central question of quantum cosmology. This essay describes the place of that quantum state in a final theory governing the regularities exhibited universally by all physical systems in…

General Relativity and Quantum Cosmology · Physics 2020-04-29 James B. Hartle

Following a paper by Berman and Marinho Jr (2001), where it was established an equation of state (p=-(1/3)rho), for the very early Universe, under which, Einstein's equations with lambda=0, render a scale-factor proportional to the time…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Marcelo Samuel Berman

The role of topology in elementary quantum physics is discussed in detail. It is argued that attributes of classical spatial topology emerge from properties of state vectors with suitably smooth time evolution. Equivalently, they emerge…

General Relativity and Quantum Cosmology · Physics 2009-10-28 A. P. Balachandran , G. Bimonte , G. Marmo , A. Simoni

An interesting consequence of the modern cosmological paradigm is the spatial infinity of the universe. When coupled with naturalistic understanding of the origin of life and intelligence, which follows the basic tenets of astrobiology, and…

Astrophysics · Physics 2008-11-26 Milan M. Cirkovic

Based on the conjecture that rather than the second law of thermodynamics inevitably be breached as matter approaches a big crunch or a black hole singularity, the order of events should reverse, a model of the universe that resolves a…

General Physics · Physics 2007-05-23 Peter Lynds

Inspired by String T-duality and taking into account the zero-point length correction, $l_0$, to the gravitational potential, we construct modified Friedmann equations by applying the first law of thermodynamics on the apparent horizon of…

General Relativity and Quantum Cosmology · Physics 2024-12-17 Giuseppe Gaetano Luciano , Ahmad Sheykhi

This paper deals with the philosophical issues of the notion of nothingness and pre-inflationary stage of the universe in physical cosmology. We presuppose that, in addition to cosmological limits, there may be both anthropic and…

History and Philosophy of Physics · Physics 2020-06-19 Kristina Šekrst

Inflation, a period of exponential expansion in the early Universe, is considered an important part of the standard $\Lambda$CDM cosmological model, and plays a crucial role in explaining a wide range of current observations. The standard…

General Relativity and Quantum Cosmology · Physics 2023-12-08 Maria Pia Piccirilli , Gabriel Leon

In this paper we build on our previous work and the work of Peter Lynds within a Bohmian framework to consider the intervallic structure of thermodynamic reversibility as well as presenting new considerations for the measurement of…

General Physics · Physics 2011-05-10 Maurice Passman , Philip V. Fellman , Jonathan Vos Post

Observational cosmology is in its "golden age" with a vast amount of recent data on the distribution of matter and light in the universe. This data can be used to probe theories of the very early universe. It is small amplitude cosmological…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-19 Robert H. Brandenberger

We review the most recent progress in our understanding of quantum mechanical observables in cosmology in the perturbative regime. It relies on an approach that considers them directly as functions of the data at the space-like boundary at…

High Energy Physics - Theory · Physics 2022-12-07 Paolo Benincasa

If the parameters defining the physics of our universe departed from their present values, the observed rich structure and complexity would not be supported. This article considers whether similar fine-tuning of parameters applies to…

Popular Physics · Physics 2020-08-26 Jeffrey M. Shainline

Why is it interesting to try to understand the origin of the universe? Everything we observe today, including our existence, arose from that event. Although we still do not have a theory that allows us to describe the origin itself, the…

General Physics · Physics 2020-07-08 Gabriel R. Bengochea

According to the orthodox interpretation of bounce cosmologies, the universe was born from an entropy reducing phase in a previous universe. To defend the thesis that the whole of physical reality was caused to exist a finite time ago,…

History and Philosophy of Physics · Physics 2020-06-17 Daniel Linford

Informed by a quantum information perspective, we interpret cosmological expansion of space as growing entanglement between underlying degrees of freedom. In particular, we focus on inflationary cosmology, which, while being a successful…

General Physics · Physics 2021-09-10 Ashmeet Singh , Olivier Doré