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$SU(\infty)-QGR$ is a foundationally quantum approach to cosmology and gravity. It assumes that the Hilbert space of the Universe as a whole represents the symmetry group $SU(\infty)$, and demonstrates this symmetry for Hilbert spaces of…

General Relativity and Quantum Cosmology · Physics 2025-02-21 Houri Ziaeepour

We report model calculations of the time-dependent internal energy and entropy for a single quasi-free massive quantum particle at a constant temperature. We show that the whole process started from a fully coherent quantum state to…

Statistical Mechanics · Physics 2013-03-20 Jian-Ping Peng

I review several different calculations, coming from string theory, nonperturbative quantum gravity and analyses of black holes that lead to predictions of phenomena that would uniquely be signatures of quantum gravitational effects. These…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Lee Smolin

Based on trajectory dependent path probability formalism in state space, we derive generalized entropy production fluctuation relations for a quantum system in the presence of measurement and feedback. We have obtained these results for…

Statistical Mechanics · Physics 2015-06-04 Shubhashis Rana , Sourabh Lahiri , A. M. Jayannavar

Combining gravity with quantum theory is still work in progress. On the one hand, classical gravity, is the geometry of space-time determined by the energy-momentum tensor of matter and the resulting nonlinear equations; on the other hand,…

Quantum Physics · Physics 2024-01-26 P. Gusin , D. Burys , A. Radosz

Whether gravity must be quantized remains one of the biggest open problems in fundamental physics. Classical-quantum hybrid theories have recently attracted attention as a possible framework in which gravity is treated classically yet…

Quantum Physics · Physics 2026-04-14 Masahiro Hotta , Sebastian Murk , Daniel R. Terno

We introduce a new model of background independent physics in which the degrees of freedom live on a complete graph and the physics is invariant under the permutations of all the points. We argue that the model has a low energy phase in…

High Energy Physics - Theory · Physics 2007-05-23 Tomasz Konopka , Fotini Markopoulou , Lee Smolin

Blocking transformation is performed in quantum field theory at finite temperature. It is found that the manner temperature deforms the renormalized trajectories can be used to understand better the role played by the quantum fluctuations.…

High Energy Physics - Theory · Physics 2009-10-28 Sen-Ben Liao , Janos Polonyi , Dapeng Xu

Path integration is a respected form of quantization that all theoretical quantum physicists should welcome. This elaboration begins with simple examples of three different versions of path integration. After an important clarification of…

General Relativity and Quantum Cosmology · Physics 2023-01-10 John R. Klauder

The problem of finding the quantum theory of the gravitational field, and thus understanding what is quantum spacetime, is still open. One of the most active of the current approaches is loop quantum gravity. Loop quantum gravity is a…

General Relativity and Quantum Cosmology · Physics 2016-10-19 Carlo Rovelli

We describe the basic assumptions and key results of loop quantum gravity, which is a background independent approach to quantum gravity. The emphasis is on the basic physical principles and how one deduces predictions from them, at a level…

High Energy Physics - Theory · Physics 2017-08-23 Lee Smolin

General covariance in quantum gravity is seen once one integrates over all possible metrics. In recent years topological field theories have given us a different route to general covariance without integrating over all possible metrics.…

High Energy Physics - Theory · Physics 2010-04-06 Andrew Toon

A fluctuation theorem for the nonequilibrium entropy production in quantum phase space is derived, which enables the consistent thermodynamic description of arbitrary quantum systems, open and closed. The new treatment naturally generalizes…

Statistical Mechanics · Physics 2013-08-13 Sebastian Deffner

We discuss some aspects of the metric configuration space in quantum gravity in the background field formalism. We give a necessary and sufficient condition for the parameterization of Euclidean metric fluctuations such that i) the…

High Energy Physics - Theory · Physics 2022-12-14 Benjamin Knorr , Alessia Platania , Marc Schiffer

In this paper we expand our previous investigation of a quantum particle subject to the action of a random potential plus a fixed harmonic potential at a finite temperature T. In the classical limit the system reduces to a well-known…

Condensed Matter · Physics 2009-10-28 Yadin Y. Goldschmidt

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

Predictions from early universe cosmology typically concern primordial perturbations generated during epochs where effects arising from the quantum nature of gravity may be important; quantum vacuum fluctuations being stretched to…

General Relativity and Quantum Cosmology · Physics 2025-12-09 Kratika Mazde , Lisa Mickel , Patrick Peter

The aim of this paper is to explain carefully the arguments behind the assertion that the correct quantum theory of gravity must be background independent. We begin by recounting how the debate over whether quantum gravity must be…

High Energy Physics - Theory · Physics 2007-05-23 Lee Smolin

The asymptotic-safety paradigm posits that the symmetry of quantum theories of gravity and matter is enhanced to quantum scale symmetry, i.e., scale symmetry in the presence of quantum fluctuations, at very high energies. To achieve such a…

High Energy Physics - Theory · Physics 2022-12-16 Astrid Eichhorn , Marc Schiffer

There ought to exist a reformulation of quantum theory which does not depend on classical time. To achieve such a reformulation, we introduce the concept of an atom of space-time-matter (STM). An STM atom is a classical non-commutative…

General Relativity and Quantum Cosmology · Physics 2019-07-17 Shounak De , Tejinder P. Singh , Abhinav Varma