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Observations indicate that the universe is effectively flat, but they do not rule out a closed universe. The role of positive curvature is negligible at late times, but can be crucial in the early universe. In particular, positive curvature…

General Relativity and Quantum Cosmology · Physics 2010-04-06 George Ellis , Roy Maartens

Quantum mechanical unitarity in our universe is challenged both by the notion of the big bang, in which nothing transforms into something, and the expansion of space, in which something transforms into more something. This motivates the…

High Energy Physics - Theory · Physics 2022-02-08 Jordan Cotler , Andrew Strominger

This paper contains a discussion on the quantum cosmic models, starting with the interpretation that all of the accelerating effects in the current universe are originated from the existence of a nonzero entropy of entanglement. In such a…

General Relativity and Quantum Cosmology · Physics 2010-01-22 Pedro F. Gonzalez-Diaz , Alberto Rozas-Fernandez

We explain how quantum gravity can be defined by quantizing spacetime itself. A pinpoint is that the gravitational constant G = L_P^2 whose physical dimension is of (length)^2 in natural unit introduces a symplectic structure of spacetime…

High Energy Physics - Theory · Physics 2014-11-21 Hyun Seok Yang

We discuss how developments in physics often imply in the need that spacetime acquires an increasingly richer and complex structure. General Relativity was the first theory to show us the way to connect space and time with the physical…

General Relativity and Quantum Cosmology · Physics 2015-06-25 Orfeu Bertolami

A `quantum inequality' (a conjectured relation between the energy density of a free quantum field and the time during which this density is observed) has recently been used to rule out some of the macroscopic wormholes and warp drives. I…

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

There is a deep structural link between acausal spacetimes and quantum theory. As a consequence quantum theory may resolve some "paradoxes" of time travel. Conversely, non-time-orientable spacetimes naturally give rise to electric charges…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Mark J Hadley

A nonvanishing cosmological term in Einstein's equations implies a nonvanishing spacetime curvature even in absence of any kind of matter. It would, in consequence, affect many of the underlying kinematic tenets of physical theory. The…

General Relativity and Quantum Cosmology · Physics 2009-11-10 R. Aldrovandi , J. P. Beltran Almeida , J. G. Pereira

Space-time is one of the most essential, yet most mysterious concepts in physics. In quantum mechanics it is common to understand time as a marker of instances of evolution and define states around all the space but at one time; while in…

Quantum Physics · Physics 2020-12-01 Tian Zhang , Oscar Dahlsten , Vlatko Vedral

General relativity predicts a singularity in the beginning of the universe being called big bang. Recent developments in loop quantum cosmology avoid the singularity and the big bang is replaced by a big bounce. A classical theory of…

General Physics · Physics 2011-02-08 Walter Petry

In the Emergent scenario, the Universe should evolve from a non-singular state replacing the typical singularity of General Relativity, for any initial condition. For the scalar field model in [1] we show that only a set of measure zero of…

General Relativity and Quantum Cosmology · Physics 2024-08-13 Molly Burkmar , Marco Bruni

As a basis for epistemological study of ``time,'' we analyze three suspect phenomena introduced by modern physics: non-locality, asymmetric aging and advanced interaction. It is shown that all three arise in connection with what has to be…

Quantum Physics · Physics 2007-05-23 A. F. Kracklauer

One signature of an expanding universe is the time-variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments…

Cosmology and Nongalactic Astrophysics · Physics 2022-02-09 Keith R. Dienes , Lucien Heurtier , Fei Huang , Doojin Kim , Tim M. P. Tait , Brooks Thomas

We propose that at the beginning of the universe gravity existed in a limbo either because it was switched off or because it was only conformally coupled to all particles. This picture can be reverse-engineered from the requirement that the…

General Relativity and Quantum Cosmology · Physics 2015-12-09 Giovanni Amelino-Camelia , Michele Arzano , Giulia Gubitosi , Joao Magueijo

The IKKT matrix model yields an emergent space-time. We further develop these ideas and give a proposal for an emergent metric. Based on previous numerical studies of this model, we provide evidence that the emergent space-time is…

High Energy Physics - Theory · Physics 2022-09-21 Suddhasattwa Brahma , Robert Brandenberger , Samuel Laliberte

According to the principle of emergence, the expansion of the universe can be explained as the emergence of space with the progress of cosmic time. We have analytically solved the equation of emergence proposed by Padmanabhan by assuming…

General Relativity and Quantum Cosmology · Physics 2022-07-26 Hassan Basari V. T. , Krishna P. B. , Priyesh K. V. , Titus K. Mathew

A definition is proposed to give precise meaning to the counterfactual statements that often appear in discussions of the implications of quantum mechanics. Of particular interest are counterfactual statements which involve events occurring…

Quantum Physics · Physics 2007-05-23 J. Finkelstein

This paper is a continuation of the paper [V.S.Mashkevich, gr-qc/9409010]. Indeterministic quantum gravity is a theory that unifies general relativity and quantum theory involving indeterministic conception, i.e., quantum jumps. By the same…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Vladimir S. Mashkevich

According to \textit{effective realism}, scientific theories give us knowledge about the unobservable world, but not at the fundamental level. This view is justified by the well-received \textit{effective-field-theory} (EFT) approach to…

History and Philosophy of Physics · Physics 2023-09-11 Lu Chen

The developments of special relativity and quantum mechanics marked the beginning of the modern physics age. The former has taught us that while space and time are frame dependent notions, there is a quantity -- the space-time interval --…

Quantum Physics · Physics 2021-03-03 Matheus Fritsch Savi , Renato Moreira Angelo