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1. Analytical external spherical solutions in entangled relativity

Author

Denis Arruga and Olivier Minazzoli

Subjects
Astrophysics, QB460-466, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract In this manuscript, we present analytical external spherical solutions of entangled relativity, which we compare to numerical solutions obtained in a Tolman–Oppenheimer–Volkoff framework. Analytical and numerical solutions match perfectly well outside spherical compact objects, therefore validating both types of solutions at the same time. The analytical external (hairy) solutions – which depend on two parameters only – may be used in order to easily compute observables – such as X-ray pulse profiles – without having to rely on an unknown equation of state for matter inside the compact object.

Published
2021
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2. Deformed General Relativity and Quantum Black Holes Interior

Author

Denis Arruga, Jibril Ben Achour, and Karim Noui

Subjects
black holes, loop quantum gravity, modified gravity, Elementary particle physics, QC793-793.5
Abstract

Effective models of black holes interior have led to several proposals for regular black holes. In the so-called polymer models, based on effective deformations of the phase space of spherically symmetric general relativity in vacuum, one considers a deformed Hamiltonian constraint while keeping a non-deformed vectorial constraint, leading under some conditions to a notion of deformed covariance. In this article, we revisit and study further the question of covariance in these deformed gravity models. In particular, we propose a Lagrangian formulation for these deformed gravity models where polymer-like deformations are introduced at the level of the full theory prior to the symmetry reduction and prior to the Legendre transformation. This enables us to test whether the concept of deformed covariance found in spherically symmetric vacuum gravity can be extended to the full theory, and we show that, in the large class of models we are considering, the deformed covariance cannot be realized beyond spherical symmetry in the sense that the only deformed theory which leads to a closed constraints algebra is general relativity. Hence, we focus on the spherically symmetric sector, where there exist non-trivial deformed but closed constraints algebras. We investigate the possibility to deform the vectorial constraint as well and we prove that non-trivial deformations of the vectorial constraint with the condition that the constraints algebra remains closed do not exist. Then, we compute the most general deformed Hamiltonian constraint which admits a closed constraints algebra and thus leads to a well-defined effective theory associated with a notion of deformed covariance. Finally, we study static solutions of these effective theories and, remarkably, we solve explicitly and in full generality the corresponding modified Einstein equations, even for the effective theories which do not satisfy the closeness condition. In particular, we give the expressions of the components of the effective metric (for spherically symmetric black holes interior) in terms of the functions that govern the deformations of the theory.

Published
2020
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3. Advanced Excitation Symmetry Analysis Method (ESAM) for improved automated ultrasonic testing within NDT4.0

Author

Morgan Brochard, Serge Dos Santos, and Denis Arruga

Subjects
Physics, Signal processing, business.industry, Acoustics, Ultrasonic testing, 02 engineering and technology, 01 natural sciences, Nonlinear system, 020303 mechanical engineering & transports, Nonlinear acoustics, 0203 mechanical engineering, Nondestructive testing, 0103 physical sciences, Chirp, Ultrasonic sensor, Sensitivity (control systems), business, 010301 acoustics
Abstract

Nonlinear acoustics and vibration has become increasingly important during the last forty years due to the increase of higher sensitivity of electronic instrumentation and its associate signal processing algorithms. The nonlinearity of materials results in nonlinear effects, which arise from defects in the materials present at all scales. The paper presents the Time Reversal based Nonlinear Elastic Wave Spectroscopy TR-NEWS device which is associated to the advanced Excitation Symmetry Analysis Method ESAM using chirp-coded excitations. The enhanced experimental device was tested with the V3 calibration block, improved and specially scaled in order to access to a wide range of multivalued parameters: mechanical properties, ultrasonic parameters (celerity and attenuation) and local geometric data. Linear and third order nonlinear signatures of material properties are measured and calibrated locally thanks to an optimized signal processing involving time reversal, correlation and pulse inversion algorithms. This experimental set-up fully controlled is considered as the first NDT4.0 based nonlinear NDT apparatus tagged “Industry 4.0”.

Published
2020
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4. Compact Objects in Entangled Relativity

Author

Olivier Rousselle, Olivier Minazzoli, Denis Arruga, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire Kastler Brossel (LKB [Collège de France]), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Collège de France (CdF (institution)), Astrophysique Relativiste Théories Expériences Métrologie Instrumentation Signaux (ARTEMIS), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Université Nice Sophia Antipolis (1965 - 2019) (UNS)

Subjects
star: compact, General relativity, alternative theories of gravity, FOS: Physical sciences, Quantum entanglement, General Relativity and Quantum Cosmology (gr-qc), Compact star, 01 natural sciences, General Relativity and Quantum Cosmology, Theoretical physics, Theory of relativity, 0103 physical sciences, conservation law, 010306 general physics, numerical calculations, neutron star, equation of state, Physics, Conservation law, Tolman-Oppenheimer-Volkoff equation, density, 010308 nuclear & particles physics, Equation of state (cosmology), Neutron star, relativity theory, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], entanglement, Free parameter
Abstract

We describe the first numerical Tolman-Oppenheimer-Volkoff solutions of compact objects in entangled relativity, which is an alternative to the framework of general relativity that does not have any additional free parameter. Assuming a simple polytropic equation of state and the conservation of the rest-mass density, we notably show that, for any given density, compact objects are always heavier (up to $\sim 8\%$) in entangled relativity than in general relativity -- for any given central density within the usual range of neutron stars' central densities, or for a given radius of the resulting compact object., Comment: 9 pages, 7 figures

Published
2020
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5. Deformed General Relativity and Quantum Black Holes Interior

Author

Karim Noui, Jibril Ben Achour, Denis Arruga, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Fédération de recherche Denis Poisson (FDP), Université d'Orléans (UO)-Université de Tours-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), and Université de Tours-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)

Subjects
lcsh:QC793-793.5, General relativity, Constraint algebra, gravitation: model, gravitation: deformation, FOS: Physical sciences, General Physics and Astronomy, polymer: model, General Relativity and Quantum Cosmology (gr-qc), Loop quantum gravity, constraint: algebra, 01 natural sciences, General Relativity and Quantum Cosmology, Legendre transformation, symbols.namesake, 0103 physical sciences, Effective field theory, general relativity, symmetry: rotation, 010306 general physics, modified gravity, Physics, black hole: quantum, loop quantum gravity, 010308 nuclear & particles physics, constraint: Hamiltonian, lcsh:Elementary particle physics, Covariance, black holes, Constraint (information theory), Hamiltonian constraint, Classical mechanics, covariance, black hole: model, symbols, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], phase space: deformation, Einstein equation
Abstract

Effective models of black holes interior have led to several proposals for regular black holes. In the so-called polymer models, based on effective deformations of the phase space of spherically symmetric general relativity in vacuum, one considers a deformed Hamiltonian constraint while keeping a non-deformed vectorial constraint. In this article, we revisit and study further the question of covariance in these deformed gravity models. In particular, we propose a Lagrangian formulation for these deformed gravity models where polymer-like deformations are introduced at the level of the full theory prior to the symmetry reduction and prior to the Legendre transformation. This enables us to test whether the concept of deformed covariance found in spherically symmetric vacuum gravity can be extended to the full theory, and we show that, in the large class of models we are considering, the deformed covariance can not be realized beyond spherical symmetry in the sense that the only deformed theory which leads to a closed constraints algebra is general relativity. Hence, we focus on the spherically symmetric sector, where there exist non-trivial deformed but closed constraints algebras. We investigate the possibility to deform the vectorial constraint as well and we prove that non-trivial deformations of the vectorial constraint with the condition that the constraints algebra remains closed do not exist. Then, we compute the most general deformed Hamiltonian constraint which admits a closed constraints algebra and thus leads to a well-defined effective theory associated with a notion of deformed covariance. Finally, we study homogeneous solutions of these effective theories and, remarkably, we solve explicitly and in full generality the corresponding modified Einstein equations, even for the effective theories which do not satisfy the closeness condition., 29 pages, invited contribution to special Issue: "Probing New Physics with Black holes", Matched the published version in Universe

Published
2019
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