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We propose that the observed value of the cosmological constant may be explained by a fundamental uncertainty in the spacetime metric, which arises when combining the principle that mass and energy curve spacetime with the quantum…

General Relativity and Quantum Cosmology · Physics 2025-05-20 Ahmed Farag Ali , Nader Inan

In effective models of loop quantum gravity, the onset of quantum effects is controlled by a so-called polymerisation scale. It is sometimes necessary to make this scale phase space dependent in order to obtain sensible physics. A…

General Relativity and Quantum Cosmology · Physics 2019-10-28 Norbert Bodendorfer , Fabio M. Mele , Johannes Münch

We demonstrate that to all large scale cosmological structures where gravitation is the only overall relevant interaction assembling the system (e.g. galaxies), there is associated a characteristic unit of action per particle whose order of…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Salvatore Capozziello , Salvatore De Martino , Silvio De Siena , Fabrizio Illuminati

We assume that space-time at the Planck scale is discrete, quantised in Planck units and "qubitsed" (each pixel of Planck area encodes one qubit), that is, quantum space-time can be viewed as a quantum computer. Within this model, one finds…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Paola Zizzi

The inverse scale factor, which in classical cosmological models diverges at the singularity, is quantized in isotropic models of loop quantum cosmology by using techniques which have been developed in quantum geometry for a quantization of…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Martin Bojowald

By considering matter as a constraint on the availability of gravitational degrees of freedom and accounting for the statistical interpretation of Rindler horizons, the freedom to construct quantum gravity theories reproducing General…

General Physics · Physics 2019-01-25 P. A. Mandrin

Suppose the usual description of spacetime as a 4-dimensional manifold with a Lorentzian metric breaks down at Planck energies. Can we still construct sensible theoretical models of the universe? Are they testable? Do they lead to a…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Fotini Markopoulou

The Planck scale is usually believed to be an unpassable wall. Putting a cutoff there and thinking of it as a quantized spacetime entity shows that. However, this is exactly the cause of many problems in quantum gravity. The cosmological…

High Energy Physics - Theory · Physics 2023-07-13 Ken-ji Hamada

So far, none of attempts to quantize gravity has led to a satisfactory model that not only describe gravity in the realm of a quantum world, but also its relation to elementary particles and other fundamental forces. Here, we outline the…

General Relativity and Quantum Cosmology · Physics 2021-11-29 Houri Ziaeepour

In the standard approach to defining a Planck scale where gravity is brought into the quantum domain, the Schwarzschild gravitational radius is set equal to the Compton wavelength. However, ignored thereby are the charge and spin, the…

General Relativity and Quantum Cosmology · Physics 2009-11-10 F. I. Cooperstock , V. Faraoni

The proper resolution of the so-called measurement problem requires a "top-down" conception of the quantum world that is opposed to the usual "bottom-up" conception, which builds on an intrinsically and maximally differentiated manifold.…

Quantum Physics · Physics 2011-05-25 Ulrich Mohrhoff

Consider a proposed model of the universe with $\hbar$ much greater than its well-known value of $10^{-34} Js$. In this model universe, very large objects can show quantum behaviors. In a scenario with large extra dimensions, $\hbar$ can…

High Energy Physics - Theory · Physics 2015-06-26 Kourosh Nozari , Behnaz Fazlpour

Recently\cite{BQG}, it was shown that quantum effects of matter could be identified with the conformal degree of freedom of the space-time metric. Accordingly, one can introduce quantum effects either by making a scale transformation (i.e.…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Fatimah Shojai , Ali Shojai , Mehdi Golshani

The requirement that physical phenomena associated with gravitational collapse should be duly reconciled with the postulates of quantum mechanics implies that at a Planckian scale our world is not 3+1 dimensional. Rather, the observable…

General Relativity and Quantum Cosmology · Physics 2009-03-21 G. 't Hooft

When one takes into account gravitation, the measurement of space and time cannot be carried out with infinite accuracy. When quantum mechanics is reformulated taking into account this lack of accuracy, the resolution of the measurement…

General Relativity and Quantum Cosmology · Physics 2009-03-16 Rodolfo Gambini , Jorge Pullin

Phenomenological approaches to quantum gravity try to infer model-independent laws by analyzing thought experiments and combining both quantum, relativistic, and gravitational ingredients. We first review these ingredients -three basic…

General Relativity and Quantum Cosmology · Physics 2013-08-21 Jean-Philippe Bruneton

I argue that the linearity of quantum mechanics is an emergent feature at the Planck scale, along with the manifold structure of space-time. In this regime the usual causality violation objections to nonlinearity do not apply, and nonlinear…

Quantum Physics · Physics 2009-11-10 George Svetlichny

Classical limits of quantum systems are shown to lead to different conceptions of spaces different from the classical one underlying the process of quantization of such systems. The accent is put in situations where traces of…

Quantum Physics · Physics 2022-07-22 Thierry Paul

The new interpretation of Mach's principle of mass of a particle being a measure of the interactions of this particle with all other gravitating particles inside its causal spheres is introduced. It is shown that within some alternative…

High Energy Physics - Theory · Physics 2008-11-26 Merab Gogberashvili

In a natural extension of the relativity principle we argue that a quantum theory of gravity involves two fundamental scales associated with both dynamical space-time as well as dynamical momentum space. This view of quantum gravity is…

High Energy Physics - Theory · Physics 2015-06-19 Laurent Freidel , Robert G. Leigh , Djordje Minic