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Relational particle mechanics are models in which there is, overall, no time, position, orientation (nor, sometimes, scale). They are useful for whole-universe modelling - the setting for quantum cosmology. This note concerns 3 particles in…

General Relativity and Quantum Cosmology · Physics 2012-06-20 Edward Anderson

A C*-algebra formulation of Quantum Mechanics is derived from purely operational axioms in which the primary role is played by the "transformations" that the system undergoes in the course of an "experiment". The notion of the {\em adjoint}…

Quantum Physics · Physics 2007-05-23 Giacomo Mauro D'Ariano

We construct the higher order terms of curvatures in Lagrangians of the scale factor for the Friedmann-Lemaitre-Robertson-Walker universe, which are linear in the second derivative of the scale factor with respect to cosmic time. It is…

General Relativity and Quantum Cosmology · Physics 2013-04-02 Nahomi Kan , Koichiro Kobayashi , Kiyoshi Shiraishi

Canonical quantization of general relativity does not yield a unique quantum theory for gravity. This is in part due to operator ordering ambiguities. In this paper, we investigate the role of different operator orderings on the question of…

General Relativity and Quantum Cosmology · Physics 2019-08-21 Thibaut Demaerel , Ward Struyve

Loop quantum cosmology is a symmetry reduced quantization of cosmological spacetimes based on loop quantum gravity. While it has been successful in resolution of various cosmological singularities and connecting Planck scale physics to…

General Relativity and Quantum Cosmology · Physics 2019-12-25 Klaus Liegener , Parampreet Singh

Recently, the research community has been exploring fractional calculus to address problems related to cosmology; in this approach, the gravitational action integral is altered, leading to a modified Friedmann equation, then the resulting…

General Relativity and Quantum Cosmology · Physics 2023-02-07 Bayron Micolta-Riascos , Alfredo D. Millano , Genly Leon , Cristián Erices , Andronikos Paliathanasis

Quantum theory in a global space-time gives rise to non-local correlations, which cannot be explained causally in a satisfactory way; this motivates the study of theories with reduced global assumptions. Oreshkov, Costa, and Brukner (2012)…

Quantum Physics · Physics 2014-10-10 Ämin Baumeler , Adrien Feix , Stefan Wolf

It is shown that causality violations [M. de Haan, Physica 132A, 375, 397 (1985)], emerging when the conventional definition of the time-normal operator ordering [P.L.Kelley and W.H.Kleiner, Phys.Rev. 136, A316 (1964)] is taken outside the…

Quantum Physics · Physics 2015-05-27 L. I. Plimak , S. T. Stenholm

The underlying physical concept of computing out-of-time-ordered correlation (OTOC) is a significant new tool within the framework of quantum field theory, which now-a-days is treated as a measure of random fluctuations. In this paper, by…

General Physics · Physics 2021-06-03 Sayantan Choudhury

We construct the algebra of operators acting on the Hilbert spaces of Quantum Mechanics for systems of $N$ identical particles from the field operators acting in the Fock space of Quantum Field Theory by providing the explicit relation…

Quantum Physics · Physics 2021-11-10 Nuno Barros e Sá , Cláudio Gomes

This article explores an algebraic-recursive approach to construct differential operators that commute with a central operator $\hat{H}$ in quantum mechanics. Starting from the Schr\"odinger equation for a free particle, the work derives…

Quantum Physics · Physics 2025-10-28 Enrique Casanova , Melvin Arias

The classical procedures which define the relativistic notion of space-time can be implemented in the framework of Quantum Field Theory. Only relying on the conformal symmetries of field propagation, time-frequency transfer and localization…

General Relativity and Quantum Cosmology · Physics 2013-02-27 Marc-Thierry Jaekel , Serge Reynaud

In theories of communication, it is usually presumed that the involved parties perform actions in a fixed causal order. However, practical and fundamental reasons can induce uncertainties in the causal order. Here we show that a maximal…

Quantum Physics · Physics 2019-11-20 Ding Jia , Fabio Costa

We provide an algebraic formulation of C.Rovelli's relational quantum theory that is based on suitable notions of "non-commutative" higher operator categories, originally developed in the study of categorical non-commutative geometry. As a…

Mathematical Physics · Physics 2025-10-20 Paolo Bertozzini

In the past decade, the toolkit of quantum information has been expanded to include processes in which the basic operations do not have definite causal relations. Originally considered in the context of the unification of quantum mechanics…

Quantum Physics · Physics 2024-07-22 Lee A. Rozema , Teodor Strömberg , Huan Cao , Yu Guo , Bi-Heng Liu , Philip Walther

We propose a formulation of quantum mechanics in an extended Fock space in which a tensor product structure is applied to time. Subspaces of histories consistent with the dynamics of a particular theory are defined by a direct quantum…

Quantum Physics · Physics 2021-03-29 N. L. Diaz , J. M. Matera , R. Rossignoli

A class of diffeomorphism invariant, physical observables, so-called astrometric observables, is introduced. A particularly simple example, the time delay, which expresses the difference between two initially synchronized proper time clocks…

General Relativity and Quantum Cosmology · Physics 2012-06-26 Igor Khavkine

We provide a reinterpretation of the quantum vacuum ambiguities that one encounters when studying particle creation phenomena due to an external and time-dependent agent. We propose a measurement-motivated understanding: Each way of…

In the framework of the concordance cosmological model the first-order scalar and vector perturbations of the homogeneous background are derived in the weak gravitational field limit without any supplementary approximations. The sources of…

General Relativity and Quantum Cosmology · Physics 2016-07-06 Maxim Eingorn

We sketch a quantum mechanical framework for the universe as a whole. Within that framework we propose a program for describing the ultimate origin in quantum cosmology of the quasiclassical domain of familiar experience and for…

General Relativity and Quantum Cosmology · Physics 2018-03-14 Murray Gell-Mann , James B. Hartle