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One of the most fundamental open problems in physics is the unification of general relativity and quantum theory to a theory of quantum gravity. An aspect that might become relevant in such a theory is that the dynamical nature of causal…

Quantum Physics · Physics 2022-03-14 Veronika Baumann , Marius Krumm , Philippe Allard Guérin , Časlav Brukner

We argue that semiclassical gravity can be made consistent if quantum systems source gravity only when they participate in non-gravitational interactions that lead to environment-induced decoherence. Outside such decoherence-based events,…

General Relativity and Quantum Cosmology · Physics 2026-01-27 Francisco Pipa

It is unclear whether an observable notion of time exists in quantum gravity even in principle because spacetime itself fluctuates. We propose a form of observable time in perturbative quantum gravity. First, we define an elapsed proper…

High Energy Physics - Theory · Physics 2025-06-23 Allic Sivaramakrishnan

We consider Hilbert's problem of the axioms of Physics at a qualitative or conceptual level. This issue is more pressing than ever as we seek to understand how both General Relativity and quantum theory could emerge from some deeper theory…

Mathematical Physics · Physics 2018-05-09 Shahn Majid

The causal set approach to quantum gravity has gained traction over the past three decades, but numerical experiments involving causal sets have been limited to relatively small scales. The software suite presented here provides a new…

General Relativity and Quantum Cosmology · Physics 2018-09-17 William J. Cunningham , Dmitri Krioukov

Philosophical analyses of causation take many forms but one major difficulty they all aim to address is that of the spatio-temporal continuity between causes and their effects. Bertrand Russell in 1913 brought the problem to its most…

Quantum Physics · Physics 2016-10-26 Cynthia K. W. Ma

A discrete model of Lorentzian quantum gravity is proposed. The theory is completely background free, containing no reference to absolute space, time, or simultaneity. The states at one slice of time are networks in which each vertex is…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Aron C. Wall

Quantum mechanics emerged as the result of a successful resolution of stringent empirical and profound conceptual conflicts within the development of atomic physics at the beginning of the last century. At first glance, it seems to be…

Neurons and Cognition · Quantitative Biology 2014-10-16 Reinhard Blutner , Peter beim Graben

The problems connected with a causality of space-time universe and with the paradox of Einstein, Podolsky, and Rosen are considered. A main philosophical problem and its possible solutions are briefly discussed. A concept of unified local…

Quantum Physics · Physics 2007-05-23 Alexander A. Chernitskii

Quantum gravity (or quantum spacetime) is to unify general relativity and quantum mechanics into a single theoretical framework and presented as the most important open puzzle in fundamental physics. The development of a microscopic theory…

General Physics · Physics 2025-10-24 Su-Peng Kou

In quantum logic there is well-known arbitrariness in choosing a binary operation for conditional. Currently, we have at least three candidates, called the Sasaki conditional, the contrapositive Sasaki conditional, and the relevance…

Quantum Physics · Physics 2017-01-04 Masanao Ozawa

A discrete quantum gravity model given by a quantum sequential growth process (QSGP) is considered. The QSGP describes the growth of causal sets (causets) one element at a time in discrete steps. It is shown that the set $\pscript$ of…

General Relativity and Quantum Cosmology · Physics 2012-04-17 Stan Gudder

I take non-locality to be the Michaelson Morley experiment of the 21st Century, assume its universal validity, and try to derive its consequences. Spacetime, with its locality, cannot be fundamental, but emergent from entangled coherent…

General Physics · Physics 2022-04-27 Stuart Kauffman

We show that several interpretations of quantum mechanics admit an ontology of objects and events. This ontology reduces the breach between mind and matter. When humans act, their actions do not appear explainable in mechanical terms but…

Quantum Physics · Physics 2016-06-28 Rodolfo Gambini , Jorge Pullin

Quantum decision theory is introduced here, and new basis for this theory is proposed. It is first based upon the author's general arguments for the Hilbert space formalism in quantum theory, next on arguments for the Born rule, that is,…

Quantum Physics · Physics 2026-02-13 Inge S. Helland

In this work we establish a novel approach to the foundations of relativistic quantum theory, which is based on generalizing the quantum-mechanical Born rule for determining particle position probabilities to curved spacetime. A principal…

Mathematical Physics · Physics 2025-11-17 Maik Reddiger , Bill Poirier

It is postulated that quantum gravity is a sum over causal structures coupled to matter via scale evolution. Quantized causal structures can be described by studying simple matrix models where matrices are replaced by an algebra of quantum…

High Energy Physics - Theory · Physics 2015-07-01 R. Bonezzi , O. Corradini , E. Latini , A. Waldron

In this work, we give rigorous operational meaning to superposition of causal orders. This fits within a recent effort to understand how the standard operational perspective on quantum theory could be extended to include indefinite…

Quantum Physics · Physics 2021-09-07 Nicola Pinzani , Stefano Gogioso

In physics, there is the prevailing intuition that we are part of a unique external world, and that the goal of physics is to understand and describe this world. This assumption of the fundamentality of objective reality is often seen as a…

Quantum Physics · Physics 2019-07-22 Markus P. Mueller

In this brief note I argue that putting conscious observers at the center of the considerations clarifies and strengthens the many-worlds interpretation. The basic assumption, which seems extremely plausible based on our current…

Quantum Physics · Physics 2009-08-04 Christoph Simon