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All gauge theories need ``something fixed'' even as ``something changes.'' Underlying the implementation of these ideas all major physical theories make indispensable use of an elaborately designed spacetime model as the ``something…

General Relativity and Quantum Cosmology · Physics 2011-04-15 Carl H. Brans

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

Time-symmetric cosmological theories, in which the initial and final states are arranged to have similar features or are independently fixed, have been quite extensively discussed in the literature. However, a more general and perhaps more…

General Relativity and Quantum Cosmology · Physics 2012-04-20 Adrian Kent

We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no…

High Energy Physics - Theory · Physics 2012-04-24 Kurt Hinterbichler , Justin Khoury

Can we infer whether all of physical reality began to exist? Several novel results are offered suggesting a negative verdict. First, a common strategy for defending a cosmic beginning involves showing that individual beginningless…

History and Philosophy of Physics · Physics 2026-05-12 Daniel Linford

If the Past Hypothesis underlies the arrows of time, what is the status of the Past Hypothesis? In this paper, I examine the role of the Past Hypothesis in the Boltzmannian account and defend the view that the Past Hypothesis is a candidate…

History and Philosophy of Physics · Physics 2020-09-21 Eddy Keming Chen

Experiments are once again under way at the LHC. This time around, however, the mood in the high-energy physics community is pessimistic. There is a growing suspicion that naturalness arguments that predict new physics near the weak scale…

High Energy Physics - Phenomenology · Physics 2015-07-08 Andrew Fowlie

The apparent dominance of matter over antimatter in our universe is an obvious and puzzling fact which cannot be adequately explained in present physical frameworks that assume matter-antimatter symmetry at the big bang. However, our…

High Energy Physics - Phenomenology · Physics 2016-04-20 Lorenz Willmann , Klaus Jungmann

The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete---if not incorrect---and that new physics is out there, waiting to be discovered. A…

Cosmology and Nongalactic Astrophysics · Physics 2017-09-12 C. J. A. P. Martins

There exists a stark tension among different formulations of quantum theory as some are inherently time-symmetric while others are time-asymmetric. This tension is crisply captured when considering physical theories as theories of…

Quantum Physics · Physics 2024-11-12 John H. Selby , Maria E. Stasinou , Stefano Gogioso , Bob Coecke

A finite non-classical framework for physical theory is described which challenges the conclusion that the Bell Inequality has been shown to have been violated experimentally, even approximately. This framework postulates the universe as a…

Quantum Physics · Physics 2018-05-23 T. N. Palmer

The present discussion concerning certain fundamental physical theories (such as string theory and multiverse cosmology) has reopened the demarcation problem between science and non-science. While parts of the physics community see the…

History and Philosophy of Physics · Physics 2017-02-23 Helge Kragh

Discussions on indeterminism in physics focus on the possibility of an open future, i.e. the possibility of having potential alternative future events, the realisation of one of which is not fully determined by the present state of affairs.…

History and Philosophy of Physics · Physics 2023-02-21 Flavio Del Santo , Nicolas Gisin

The Standard Model is in good shape, apart possibly from g_\mu - 2 and some niggling doubts about the electroweak data. Something like a Higgs boson is required to provide particle masses, but theorists are actively considering…

High Energy Physics - Phenomenology · Physics 2023-03-30 John Ellis

In this review we present the problem of time in quantum physics, including a short history of the problem and the known objections about considering time a quantum observable. The need to deal with time as an observable is elaborated…

Quantum Physics · Physics 2022-06-13 M. Basil Altaie , Daniel Hodgson , Almut Beige

Time-asymmetric behavior as embodied in the second law of thermodynamics is observed in {\it individual macroscopic} systems. It can be understood as arising naturally from time-symmetric microscopic laws when account is taken of a) the…

Statistical Mechanics · Physics 2007-09-06 Joel L. Lebowitz

We investigate the cosmological behavior in a universe governed by time asymmetric extensions of general relativity, which is a novel modified gravity based on the addition of new, time-asymmetric, terms on the Hamiltonian framework, in a…

General Relativity and Quantum Cosmology · Physics 2015-11-11 Genly Leon , Emmanuel N. Saridakis

Physical systems are usually assumed to evolve relative to an external time parameter, which is problematic because in quantum theory that parameter is not a physical observable. Page & Wootters (1984) solved this by proposing that the…

Quantum Physics · Physics 2026-04-08 Sam Kuypers , Simone Rijavec

If there are fundamental laws of nature, can they fail to be exact? In this paper, I consider the possibility that some fundamental laws are vague. I call this phenomenon 'fundamental nomic vagueness.' I characterize fundamental nomic…

History and Philosophy of Physics · Physics 2022-07-08 Eddy Keming Chen

The problem of the Nature of Time is twofold: whether or not time is a fundamental quantity of Nature, and how does clock time of metrology emerge in the experimental description of dynamics. This work strongly supports the fundamental…

Classical Physics · Physics 2013-11-05 Enrico Prati