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Articles de revues sur le sujet « Analog cosmology »

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Auteur : Grafiati
Publié le 11 mars 2023

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1

Bilic, Neven, et Dijana Tolic. « Analogue cosmology in a hadronic fluid ». Facta universitatis - series : Physics, Chemistry and Technology 12, no 2 (2014) : 77–83. http://dx.doi.org/10.2298/fupct1402077b.

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Analog gravity models of general relativity seem promising routes to providing laboratory tests of the foundation of quantum field theory in curved space-time. In contrast to general relativity, where geometry of a spacetime is determined by the Einstein equations, in analog models geometry and evolution of analog spacetime are determined by the equations of fluid mechanics. In this paper we study the analogue gravity model based on massless pions propagating in a expanding hadronic fluid. The analog expanding spacetime takes the form of an FRW universe, with the apparent and trapping horizons defined in the standard way.
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ELLIS, JOHN, D. V. NANOPOULOS et N. E. MAVROMATOS. « A STRING SCENARIO FOR INFLATIONARY COSMOLOGY ». Modern Physics Letters A 10, no 23 (30 juillet 1995) : 1685–98. http://dx.doi.org/10.1142/s0217732395001800.

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We describe a scenario for inflation in the framework of noncritical string theory, which does not employ an inflaton field. There is an exponential expansion of the volume of the Universe, induced by enormous entropy production in the early stages of cosmological evolution. This is associated with the loss of information carried by global string modes that cross the particle horizon. It is the same loss of information that induces irreversible time flow when target time is identified with the worldsheet Liouville mode. The resulting scenario for inflation is described by a string analog of the Fokker-Planck equation that incorporates diffusion and dissipative effects. Cosmological density perturbations are naturally small.
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Falomir, Horacio, Jorge Gamboa et Fernando Mendez. « A Noncommutative Model of Cosmology with Two Metrics ». Symmetry 12, no 3 (9 mars 2020) : 435. http://dx.doi.org/10.3390/sym12030435.

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We propose a bicosmology model which reduces to the classical analog of noncommutative quantum mechanics. From this point of view, one of the sources in the so modified Friedmann-Robertson- Walker equations is a kind of dark energy governed by a Chapligyn-like equation of state. The parameters of noncommutativity θ and B are interpreted in terms of the Planck area and a magnetic-like field, which presumably acts as a seed for magnetogenesis.
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4

Socorro, J., Luis O. Pimentel et Abraham Espinoza-García. « Classical Bianchi Type I Cosmology in K-Essence Theory ». Advances in High Energy Physics 2014 (2014) : 1–11. http://dx.doi.org/10.1155/2014/805164.

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We use one of the simplest forms of the K-essence theory and we apply it to the classical anisotropic Bianchi type I cosmological model, with a barotropic perfect fluid (p=γρ) modeling the usual matter content and with cosmological constantΛ. Classical exact solutions for anyγ≠1andΛ=0are found in closed form, whereas solutions forΛ≠0are found for particular values in the barotropic parameter. We present the possible isotropization of the cosmological model Bianchi I using the ratio between the anisotropic parameters and the volume of the universe. We also include a qualitative analysis of the analog of the Friedmann equation.
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GÓRKA, PRZEMYSŁAW, TOMASZ KOSTRZEWA et ENRIQUE G. REYES. « THE RELLICH LEMMA ON COMPACT ABELIAN GROUPS AND EQUATIONS OF INFINITE ORDER ». International Journal of Geometric Methods in Modern Physics 10, no 02 (5 décembre 2012) : 1220030. http://dx.doi.org/10.1142/s0219887812200307.

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Partially motivated by a class of nonlinear equations of interest for string theory, cosmology and p-adic analysis, we continue our research on Sobolev spaces on arbitrary locally compact abelian (LCA) groups. In this paper we focus on an analog for LCA groups of the classical Rellich compactness theorem. As an application, we prove the existence of continuous solutions to a generalized Euclidean bosonic string equation posed on a compact abelian group.
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Górka, Przemysław, Tomasz Kostrzewa et Enrique G. Reyes. « Sobolev Spaces on Locally Compact Abelian Groups : Compact Embeddings and Local Spaces ». Journal of Function Spaces 2014 (2014) : 1–6. http://dx.doi.org/10.1155/2014/404738.

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We continue our research on Sobolev spaces on locally compact abelian (LCA) groups motivated by our work on equations with infinitely many derivatives of interest for string theory and cosmology. In this paper, we focus on compact embedding results and we prove an analog for LCA groups of the classical Rellich lemma and of the Rellich-Kondrachov compactness theorem. Furthermore, we introduce Sobolev spaces on subsets of LCA groups and study its main properties, including the existence of compact embeddings intoLp-spaces.
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7

GIANG, DAN, et CHARLES C. DYER. « CONSTRUCTING AN INHOMOGENEOUS BRANEWORLD THROUGH SPACE–TIME MATCHING ». International Journal of Modern Physics D 18, no 12 (30 novembre 2009) : 1913–41. http://dx.doi.org/10.1142/s021827180901576x.

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We attempt to construct the braneworld analog of the cheese slice universe, an inhomogeneous cosmology constructed from alternating layers of Kasner and FLRW space–times. This construction is possible in four dimensions and we find that the energy conditions can be satisfied in the braneworld context. However, an extension into the bulk becomes more problematic. We use a 3 + 1 + 1 decomposition inspired by the ADM decompositions to show that structure is required in the bulk to support an inhomogeneous brane.
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8

Gorobey, Natalia, et Alexander Lukyanenko. « Ground state of the universe in quantum cosmology ». International Journal of Modern Physics A 31, no 02n03 (20 janvier 2016) : 1641014. http://dx.doi.org/10.1142/s0217751x16410141.

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We find a physical state of a closed universe with the minimal excitation of the universe expansion energy in quantum gravity. It is an analog of the vacuum state of the ordinary quantum field theory in the Minkowsky space, but in our approach an energy of space of a closed universe together with the energy of its matter content are minimized. This ground state is chosen among an enlarged set of physical states, compared with the ordinary covariant quantum gravity. In our approach, physical states are determined by weak constraints: quantum mechanical averages of gravitational constraint operators equal zero. As a result, they appear to be non-static in such a modification of quantum gravity. Quantum dynamics of the universe is described by Schrödinger equation with a cosmic time determined by weak gravitational constraints. In order to obtain the observed megascopic universe with the inflation stage just after its quantum beginning, a lot of the energy in the form of the inflaton scalar field condensate is prescribed to the initial state. Parameters of the initial state for a homogeneous model of the universe are calculated.
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9

K.Shchigolev, V. « Applying He's variational iteration method to FRW cosmology ». International Journal of Advanced Astronomy 7, no 2 (20 septembre 2019) : 39. http://dx.doi.org/10.14419/ijaa.v7i2.29428.

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This work is devoted to the investigation of Friedmann-Robertson-Walker (FRW) cosmological models with the help of the so-called Variational Iteration Method (VIM). For this end, we briefly recall the main equations of the cosmological models and the basic idea of VIM. In order to approbate the VIM in FRW cosmology and demonstrate the main steps in solving by this method, we consider the test example of the universe with dust for which the exact solution of the model is known. Then, a solution for the spatially flat FRW model of the universe filled with the dust and quintessence is obtained when the exact analytic solution cannot be found. A comparison of our solution with the corresponding numerical solution shows that it is of a high degree of accuracy. Moreover, the Dynamical System Analysis to the dynamics of the homogeneous and isotropic FRW universes is used as a special case of generalized Lotka–Volterra system where the competitive species are the barotropic fluids filling the Universe. With the help of VIM, we have found the iterative formulae for the density parameters of the cosmological analog of the generalized Lotka–Volterra set of equations. All solutions illustrated graphically by means of Maple software.
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10

Nojiri, Shin'ichi, et Sergei D. Odintsov. « Multiple lambda cosmology : Dark fluid with time-dependent equation of state as classical analog of cosmological landscape ». Physics Letters B 649, no 5-6 (juin 2007) : 440–44. http://dx.doi.org/10.1016/j.physletb.2007.02.042.

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11

CASTRO, CARLOS. « THE CLIFFORD SPACE GEOMETRY BEHIND THE PIONEER AND FLYBY ANOMALIES ». International Journal of Modern Physics A 25, no 04 (10 février 2010) : 815–36. http://dx.doi.org/10.1142/s0217751x10047555.

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It is rigorously shown how the extended relativity theory in Clifford spaces (C-spaces) can explain the variable radial dependence ap(r) of the Pioneer anomaly; its sign (pointing towards the Sun); why planets do not experience the anomalous acceleration and why the present day value of the Hubble scale RH appears. It is the curvature–spin coupling of the planetary motions that hold the key. The difference in the rate at which clocks tick in C-space translates into the C-space analog of Doppler shifts which may explain the anomalous redshifts in cosmology, where objects which are not that far apart from each other exhibit very different redshifts. We conclude by showing how the empirical formula for the flybys anomalies obtained by Anderson et al.17 can be derived within the framework of Clifford geometry.
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12

Haas, Fernando. « Relativistic Ermakov–Milne–Pinney Systems and First Integrals ». Physics 3, no 1 (12 février 2021) : 59–70. http://dx.doi.org/10.3390/physics3010006.

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The Ermakov–Milne–Pinney equation is ubiquitous in many areas of physics that have an explicit time-dependence, including quantum systems with time-dependent Hamiltonian, cosmology, time-dependent harmonic oscillators, accelerator dynamics, etc. The Eliezer and Gray physical interpretation of the Ermakov–Lewis invariant is applied as a guiding principle for the derivation of the special relativistic analog of the Ermakov–Milne–Pinney equation and associated first integral. The special relativistic extension of the Ray–Reid system and invariant is obtained. General properties of the relativistic Ermakov–Milne–Pinney are analyzed. The conservative case of the relativistic Ermakov–Milne–Pinney equation is described in terms of a pseudo-potential, reducing the problem to an effective Newtonian form. The non-relativistic limit is considered to be well. A relativistic nonlinear superposition law for relativistic Ermakov systems is identified. The generalized Ermakov–Milne–Pinney equation has additional nonlinearities, due to the relativistic effects.
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13

BABAK, S. V., et L. P. GRISHCHUK. « FINITE-RANGE GRAVITY AND ITS ROLE IN GRAVITATIONAL WAVES, BLACK HOLES AND COSMOLOGY ». International Journal of Modern Physics D 12, no 10 (décembre 2003) : 1905–59. http://dx.doi.org/10.1142/s0218271803004250.

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Theoretical considerations of fundamental physics, as well as certain cosmological observations, persistently point out to permissibility, and maybe necessity, of macroscopic modifications of the Einstein general relativity. The field theoretical formulation of general relativity helped us to identify the phenomenological seeds of such modifications. They take place in the form of very specific mass terms, which appear in addition to the field theoretical analog of the usual Hilbert–Einstein Lagrangian. We derive and study exact nonlinear equations of the theory, along with its linear approximation. We interpret the added terms as masses of spin-2 and spin-0 gravitons. The arising finite-range gravity is a fully consistent theory, which smoothly approaches general relativity in the massless limit, that is, when both masses tend to zero and the range of gravity tends to infinity. We show that all local weak-field predictions of the theory are in perfect agreement with the available experimental data. However, some other conclusions of the nonlinear massive theory are in a striking contrast with those of general relativity. We show in detail how the arbitrarily small mass terms eliminate the black hole event horizon and replace a permanent power-law expansion of a homogeneous isotropic universe with an oscillatory behaviour. One variant of the theory allows the cosmological scale factor to exhibit an 'accelerated expansion' instead of slowing down to a regular maximum of expansion. We show in detail why the traditional, Fierz–Pauli, massive gravity is in conflict not only with the static-field experiments, but also with the available indirect gravitational-wave observations. At the same time, we demonstrate the incorrectness of the widely held belief that the non-Fierz–Pauli theories possess "negative energies" and "instabilities."
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14

Albertini, Emma, Stephon Alexander, Gabriel Herczeg et João Magueijo. « Torsion and the probability of inflation ». Journal of Cosmology and Astroparticle Physics 2022, no 11 (1 novembre 2022) : 036. http://dx.doi.org/10.1088/1475-7516/2022/11/036.

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Abstract We revisit the problem of the “probability of inflation” from the point of view of the Einstein-Cartan theory, where torsion can be present off-shell even in the absence of spinorial currents. An informal estimate suggests that the barrier for tunneling from “nothing” into a classical universe becomes thinner and lower, should torsion be present, even if only off-shell. We perform a detailed calculation that supports this informal estimate for the case of torsion eigenstates. Finally, we impose a quantum mechanical analog of the zero-torsion condition by restricting to states for which the expectation value of the torsion vanishes. An explicit family of such states is obtained by building wave-packets from linear superpositions of torsion eigenstates with Gaussian weights centered around zero torsion. The tunneling probability for these wave packets is maximized when the variance of the torsion goes to zero. Hence, by considering these wave-packets as the physical states, we recover a sensible model of quantum cosmology that incorporates quantum fluctuations in the torsion, despite the apparently unacceptable conclusions one draws from naïvely considering the tunneling probabilities for the torsion eigenstates.
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15

Khlopunov, M., et D. V. Gal'tsov. « Gravitational radiation from a binary system in odd-dimensional spacetime ». Journal of Cosmology and Astroparticle Physics 2022, no 04 (1 avril 2022) : 014. http://dx.doi.org/10.1088/1475-7516/2022/04/014.

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Abstract We explore possible manifestations of an odd number of extra dimensions in gravitational radiation, which are associated with violation of Huygens' principle in flat odd-dimensional spacetime. Our setup can be regarded as the limit of an infinite compactification radius in ADD model and is not viable as realistic cosmology, but it still may be useful as a simple analytically solvable model catching certain features of more realistic scenarios. The model consists of two point masses moving inside a flat three-dimensional brane, embedded in a five-dimensional Minkowski space and interacting only through a massless scalar field localized on the same brane, while gravitational radiation is emitted into the bulk. This setup avoids the difficulties associated with taking into account the gravitational stresses binding the system, which require the cubic terms in the perturbative gravitational Lagrangian, and permits to limit ourselves to linearized theory. We calculate radiation in a linearized five-dimensional gravity generalizing the Rohrlich-Teitelboim approach to extract the emitted part of the retarded gravitational field. The source term consists of a local contribution from point particles and a non-local contribution from scalar field stresses, which is calculated using the DIRE approach to post-Newtonian expansions. In the nonrelativistic limit, we find an analog of the quadrupole formula containing an integral over the history of the particles' motion preceding the retarded time. We also show that, for an observer on the brane, the radiation contains a third polarization: the breathing mode.
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16

Friend, David B., et Kevin Forkey. « A Portable Demonstration of Orbits in Curved Space-Time ». International Astronomical Union Colloquium 105 (1990) : 223–24. http://dx.doi.org/10.1017/s0252921100086802.

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Many introductory astronomy students, when confronted with the idea of curved space-time in discussions of relativity and cosmology, don’t have a very good grasp of what this really means. They are told that the presence of mass “curves” space-time, but it is often not clear to them what is meant by that statement. We have developed a simple portable demonstration of what is meant by curved space-time, by using a two-dimensional analog. We have stretched a thin rubber sheet over a circular metal frame which is supported a few inches above a table top. By placing a heavy weight (about a kilogram) in the center of the sheet, we can mimic the effect of the curvature of space-time around a massive object on an orbiting body (such as a planet orbiting a star). We roll a small ball around the sheet, and the ball describes approximately elliptical orbits around the weight (see the photograph). The orbits aren’t exactly elliptical for two reasons: energy is dissipated by friction between the ball and the sheet, and the sheet doesn’t quite have the correct shape (it is shaped roughly like In r instead of 1/r: see this by solving Laplace’s equation in two dimensions with circular symmetry). We like to project this demonstration with a video camera placed directly above the sheet, so that the students can see the “orbit” without actually seeing the curvature of the sheet.
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TARTAGLIA, A. « COSMIC DEFECT COSMOLOGY ». International Journal of Modern Physics A 24, no 08n09 (10 avril 2009) : 1620–24. http://dx.doi.org/10.1142/s0217751x0904511x.

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The accelerated expansion of the universe is interpreted as an effect of a defect in space-time treated as a four-dimensional continuum endowed with physical properties. The analogy is with texture defects in material continua, like dislocations and disclinations, described in terms of a singular displacement vector field. A Lagrangian for empty space-time is proposed exploiting one further analogy between the phase space of a Robertson-Walker universe and the phase space of a point particle moving across an homogeneous isotropic medium. The model, named Cosmic Defect theory, produces, as a byproduct, also inflation near the initial singularity. The theory has been applied to fit the luminosity data of 192 type Ia supernovae. The results are satisfying and comparable with the ones obtained by means of the Λ Cold Dark Matter standard model.
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Szydłowski, Marek, et Adam Krawiec. « Viscous Matter in FRW Cosmology ». Symmetry 12, no 8 (1 août 2020) : 1269. http://dx.doi.org/10.3390/sym12081269.

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We investigate the dynamics of dust matter with bulk viscosity effects. We explored the analogy dynamical problem to Chaplygin gas. Due to this analogy we give exact solutions for the FRW cosmology with viscosity coefficient parameterized by the Belinskii–Khalatnikov power law dependence with respect to energy density. These exact solutions are given in the form of hypergeometrical functions. We proved simple theorem which illustrated as viscosity effects can solved the initial singularity problem present in standard cosmological model.
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19

Faraoni, Valerio, et Adriana M. Cardini. « Analogues of glacial valley profiles in particle mechanics and in cosmology ». FACETS 2, no 1 (1 mai 2017) : 286–300. http://dx.doi.org/10.1139/facets-2016-0045.

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An ordinary differential equation describing the transverse profiles of U-shaped glacial valleys has two formal analogies, which we explore in detail, bridging these different areas of research. First, an analogy with point particle mechanics completes the description of the solutions. Second, an analogy with the Friedmann equation of relativistic cosmology shows that the analogue of a glacial valley profile is a universe with a future singularity of interest in theoretical models of cosmology. A Big Freeze singularity, which was not previously observed for positive curvature index, is also contained in the dynamics.
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Smith, Q. « Stephen Hawking's cosmology and theism ». Analysis 54, no 4 (1 octobre 1994) : 236–43. http://dx.doi.org/10.1093/analys/54.4.236.

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21

Eltsov, V. B., T. W. B. Kibble, M. Krusius, V. M. H. Ruutu et G. E. Volovik. « Composite Defect Extends Analogy between Cosmology andH3e ». Physical Review Letters 85, no 22 (27 novembre 2000) : 4739–42. http://dx.doi.org/10.1103/physrevlett.85.4739.

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22

Campbell, M. K. « Written in the stars [biodiversity-cosmology analogy] ». IEEE Potentials 21, no 5 (décembre 2002) : 4–5. http://dx.doi.org/10.1109/mp.2002.1166616.

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23

Deltete, R. J., et R. A. Guy. « Hartle-Hawking cosmology and unconditional probabilities ». Analysis 57, no 4 (1 octobre 1997) : 304–15. http://dx.doi.org/10.1093/analys/57.4.304.

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Goldstein, L. « A non-theistic cosmology and natural history ». Analysis 66, no 3 (1 juillet 2006) : 256–60. http://dx.doi.org/10.1093/analys/66.3.256.

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Robles-Pérez, Salvador J. « Quantum Cosmology in the Light of Quantum Mechanics ». Galaxies 7, no 2 (24 avril 2019) : 50. http://dx.doi.org/10.3390/galaxies7020050.

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There is a formal analogy between the evolution of the universe, when it is seen as a trajectory in the minisuperspace, and the worldline followed by a test particle in a curved spacetime. The analogy can be extended to the quantum realm, where the trajectories are transformed into wave packets that give us the probability of finding the universe or the particle in a given point of their respective spaces: the spacetime in the case of the particle and the minisuperspace in the case of the universe. The wave function of the spacetime and the matter fields, all together, can then be seen as a super-field that propagates in the minisuperspace and the so-called third quantisation procedure can be applied in a parallel way as the second quantisation procedure is performed with a matter field that propagates in the spacetime. The super-field can thus be interpreted as made up of universes propagating, i.e., evolving, in the minisuperspace. The analogy can also be used in the opposite direction. The way in which the semiclassical state of the universe is obtained in quantum cosmology allows us to obtain, from the quantum state of a field that propagates in the spacetime, the geodesics of the underlying spacetime as well as their quantum uncertainties or dispersions. This might settle a new starting point for a different quantisation of the spacetime.
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Markosian, N. « On the argument from quantum cosmology against theism ». Analysis 55, no 4 (1 octobre 1995) : 247–51. http://dx.doi.org/10.1093/analys/55.4.247.

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Mansoori, Seyed Ali Hosseini, et Zahra Molaee. « Multi-field Cuscuton cosmology ». Journal of Cosmology and Astroparticle Physics 2023, no 01 (1 janvier 2023) : 022. http://dx.doi.org/10.1088/1475-7516/2023/01/022.

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Abstract In this paper, we first introduce a multi-field setup of Cuscuton gravity in a curved field space manifold. Then, we show that this model allows for a regular bouncing cosmology and it does not lead to ghosts or other instabilities at the level of perturbations. More precisely, by decomposing the scalar fields perturbations into the tangential and normal components with respect to the background field space trajectory, the entropy mode perpendicular to the background trajectory is healthy which directly depends on the signature of the field-space metric, whereas the adiabatic perturbation tangential to the background trajectory is frozen. In analogy with the standard Cuscuton theory equipped with an extra dynamical scalar field, the adiabatic field does not have its own dynamics, but it modifies the dynamics of other dynamical fields like entropy mode in our scenario. Finally, we perform a Hamiltonian analysis of our model in order to count the degrees of freedom propagated by dynamical fields.
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NADDEO, A., et G. SCELZA. « A NOTE ON THE ANALOGY BETWEEN SUPERFLUIDS AND COSMOLOGY ». Modern Physics Letters B 24, no 06 (10 mars 2010) : 513–20. http://dx.doi.org/10.1142/s0217984910022573.

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A new analogy between superfluid systems and cosmology is here presented, which relies strongly on the following ingredient: the back-reaction of the vacuum to the quanta of sound waves. We show how the presence of thermal phonons, the excitations above the quantum vacuum for T > 0, enable us to deduce an hydrodynamical equation formally similar to the one obtained for a perfect fluid in a Universe obeying the Friedmann–Robertson–Walker metric.
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Bini, D., et S. Succi. « Analogy between capillary motion and Friedmann-Robertson-Walker cosmology ». EPL (Europhysics Letters) 82, no 3 (21 avril 2008) : 34003. http://dx.doi.org/10.1209/0295-5075/82/34003.

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Smiga, Joseph, et Jacob Taylor. « Optomechanical Analogy for Toy Cosmology with Quantized Scale Factor ». Entropy 19, no 9 (12 septembre 2017) : 485. http://dx.doi.org/10.3390/e19090485.

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31

Kafatos, Menas. « Knowledge Limits in Cosmology ». Symposium - International Astronomical Union 168 (1996) : 431–38. http://dx.doi.org/10.1017/s0074180900110307.

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In cosmology one faces the observational challenge that knowledge about distant regions of the universe is dependent on assumptions one makes about these regions which are themselves coupled to the observations. Within the framework of the Friedmann-Robertson-Walker big bang models the universe becomes opaque to its own radiation at z ≈ 1,000 and the earlier, and more distant, regions of the universe are not directly accessible through observations. Other challenges exist such as possible merging of extended distant sources and confusion of spectra from distant galaxies. One, therefore, encounters horizons in our understanding of the universe. Such horizons exist in any mode of description. To use the quantum analogy, the observer is always part of the system under study, the universe, and a description of the universe entails including the observer and observing apparatus. Since the early universe should be described in quantum terms, it follows that non-locality in the universe is not an a-priori requirement but the outcome of the observing process itself. As such, the flatness and horizon problems may not be preconditions on theoretical models.
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Tartaglia, Angelo. « The strained state cosmology ». International Journal of Modern Physics A 31, no 02n03 (20 janvier 2016) : 1641015. http://dx.doi.org/10.1142/s0217751x16410153.

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Starting from some relevant facts concerning the behavior of the universe over large scale and time span, the analogy between the geometric approach of General Relativity and the classical description of an elastic strained material continuum is discussed. Extending the elastic deformation approach to four dimensions it is shown that the accelerated expansion of the universe is recovered. The strain field of space-time reproduces properties similar to the ones ascribed to the dark energy currently called in to explain the accelerated expansion. The strain field in the primordial universe behaves as radiation, but asymptotically it reproduces the cosmological constant. Subjecting the theory to a number of cosmological tests confirms the soundness of the approach and gives an optimal value for the one parameter of the model, i.e. the bulk modulus of the space-time continuum. Finally various aspects of the Strained State Cosmology (SSC) are discussed and contrasted with some non-linear massive gravity theories. The possible role of structure topological defects is also mentioned. The conclusion is that SSC is at least as good as the [Formula: see text]CDM standard cosmology, giving a more intuitive interpretation of the physical nature of the phenomena.
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Leonhardt, Ulf. « The case for a Casimir cosmology ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, no 2177 (20 juillet 2020) : 20190229. http://dx.doi.org/10.1098/rsta.2019.0229.

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The cosmological constant, also known as dark energy, was believed to be caused by vacuum fluctuations, but naive calculations give results in stark disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces in dielectric media, which is very well described by Lifshitz theory. Recently, using the analogy between geometries and media, a cosmological constant of the correct order of magnitude was calculated with Lifshitz theory (Leonhardt 2019 Ann. Phys. ( New York ) 411 , 167973. ( doi:10.1016/j.aop.2019.167973 )). This paper discusses the empirical evidence and the ideas behind the Lifshitz theory of the cosmological constant without requiring prior knowledge of cosmology and quantum field theory. This article is part of a discussion meeting issue ‘The next generation of analogue gravity experiments’.
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PATOMÄKI, HEIKKI. « Cosmological sources of critical cosmopolitanism ». Review of International Studies 36, S1 (2 septembre 2010) : 181–200. http://dx.doi.org/10.1017/s0260210510001063.

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AbstractCritical cosmopolitan orientation has usually been embedded in a non-geocentric physical (NGP) cosmology that locates the human drama on the surface of planet Earth within wide scales of time and space. Although neither a necessary nor a sufficient condition for critical cosmopolitanism, NGP cosmology provides a contrast to the underpinnings of centric cosmologies, such as those of Aristotle, which see the world as revolving around a particular observer, theorist and/or communal identity. NGP cosmology makes it plausible to envisage all humans as part of the same species. The connection works also through homology and analogy. An astronomic theory can be isomorphic with an ethico-political theory, that is, a structure-preserving mapping from one to the other is possible. Key cosmopolitan theorists have situated morality within a cosmic framework. However, the ethico-political implications of the NGP cosmology are ambiguous. Nietzsche was among the first to articulate its sceptical and nihilist implications. Various reactions have encouraged territorial nationalism and geopolitics. I suggest that critical cosmopolitical orientation should now be grounded on the notion of cosmic evolution, which is not only contextual, historical, pluralist and open-ended but also suggests that humanity is not a mere accident of the cosmos.
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Dumin, Yurii V. « Nonlocal Quantum Effects in Cosmology ». Advances in High Energy Physics 2014 (2014) : 1–8. http://dx.doi.org/10.1155/2014/241831.

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Since it is commonly believed that the observed large-scale structure of the universe is an imprint of quantum fluctuations existing at the very early stage of its evolution, it is reasonable to pose the question: do the effects of quantum nonlocality, which are well established now by the laboratory studies, manifest themselves also in the early universe? We try to answer this question by utilizing the results of a few experiments, namely, with the superconducting multi-Josephson-junction loops and the ultracold gases in periodic potentials. Employing a close analogy between the above-mentioned setups and the simplest one-dimensional Friedmann-Robertson-Walker cosmological model, we show that the specific nonlocal correlations revealed in the laboratory studies might be of considerable importance also in treating the strongly nonequilibrium phase transitions of Higgs fields in the early universe. Particularly, they should substantially reduce the number of topological defects (e.g., domain walls) expected due to independent establishment of the new phases in the remote spatial regions. This gives us a hint on resolving a long-standing problem of the excessive concentration of topological defects, inconsistent with observational constraints. The same effect may be also relevant to the recent problem of the anomalous behavior of cosmic microwave background fluctuations at large angular scales.
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Ahmed, Nasr, Anirudh Pradhan et F. Salama. « A new topological perspective of expanding space-times with applications to cosmology ». International Journal of Geometric Methods in Modern Physics 18, no 08 (12 mai 2021) : 2150130. http://dx.doi.org/10.1142/s0219887821501309.

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We discuss the possible role of the Tietze extension theorem in providing a rigorous topological base to the expanding space-time in cosmology. A simple toy model has been introduced to show the analogy between the topological extension from a circle [Formula: see text] to the whole space [Formula: see text] and the cosmic expansion from a non-zero volume to the whole space-time in non-singular cosmological models. A topological analogy to the cosmic scale factor function has been suggested, the paper refers to the possible applications of the topological extension in mathematical physics.
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Smith, Q. « Quantum cosmology's implication of atheism ». Analysis 57, no 4 (1 octobre 1997) : 295–304. http://dx.doi.org/10.1093/analys/57.4.295.

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Repnik, R., A. Ranjkesh, V. Simonka, M. Ambrozic, Z. Bradac et S. Kralj. « Symmetry breaking in nematic liquid crystals : analogy with cosmology and magnetism ». Journal of Physics : Condensed Matter 25, no 40 (11 septembre 2013) : 404201. http://dx.doi.org/10.1088/0953-8984/25/40/404201.

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Lucier, Richard E., et James F. Dooley. « Cosmology and the changing role of libraries : An analogy and reflections ». Journal of the American Society for Information Science 36, no 1 (janvier 1985) : 44–47. http://dx.doi.org/10.1002/asi.4630360105.

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Höhn, Philipp. « Switching Internal Times and a New Perspective on the ‘Wave Function of the Universe’ ». Universe 5, no 5 (14 mai 2019) : 116. http://dx.doi.org/10.3390/universe5050116.

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Despite its importance in general relativity, a quantum notion of general covariance has not yet been established in quantum gravity and cosmology, where, given the a priori absence of coordinates, it is necessary to replace classical frames with dynamical quantum reference systems. As such, quantum general covariance bears on the ability to consistently switch between the descriptions of the same physics relative to arbitrary choices of quantum reference system. Recently, a systematic approach for such switches has been developed. It links the descriptions relative to different choices of quantum reference system, identified as the correspondingly reduced quantum theories, via the reference-system-neutral Dirac quantization, in analogy to coordinate changes on a manifold. In this work, we apply this method to a simple cosmological model to demonstrate how to consistently switch between different internal time choices in quantum cosmology. We substantiate the argument that the conjunction of Dirac and reduced quantized versions of the theory defines a complete relational quantum theory that not only admits a quantum general covariance, but, we argue, also suggests a new perspective on the ‘wave function of the universe’. It assumes the role of a perspective-neutral global state, without immediate physical interpretation that, however, encodes all the descriptions of the universe relative to all possible choices of reference system at once and constitutes the crucial link between these internal perspectives. While, for simplicity, we use the Wheeler-DeWitt formulation, the method and arguments might be also adaptable to loop quantum cosmology.
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Müller, Oliver, Marcel S. Pawlowski, Federico Lelli, Katja Fahrion, Marina Rejkuba, Michael Hilker, Jamie Kanehisa, Noam Libeskind et Helmut Jerjen. « The coherent motion of Cen A dwarf satellite galaxies remains a challenge for ΛCDM cosmology ». Astronomy & ; Astrophysics 645 (janvier 2021) : L5. http://dx.doi.org/10.1051/0004-6361/202039973.

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The plane-of-satellites problem is one of the most severe small-scale challenges for the standard Λ cold dark matter (ΛCDM) cosmological model: Several dwarf galaxies around the Milky Way and Andromeda co-orbit in thin, planar structures. A similar case has been identified around the nearby elliptical galaxy Centaurus A (Cen A). In this Letter, we study the satellite system of Cen A, adding twelve new galaxies with line-of-sight velocities from VLT/MUSE observations. We find that 21 out of 28 dwarf galaxies with measured velocities share a coherent motion. Similarly, flattened and coherently moving structures are found only in 0.2% of Cen A analogs in the Illustris-TNG100 cosmological simulation, independently of whether we use its dark-matter-only or hydrodynamical run. These analogs are not co-orbiting, and they arise only by chance projection, thus they are short-lived structures in such simulations. Our findings indicate that the observed co-rotating planes of satellites are a persistent challenge for ΛCDM, which is largely independent from baryon physics.
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AREF’EVA, I. YA, B. DRAGOVICH, P. H. FRAMPTON et I. V. VOLOVICH. « THE WAVE FUNCTION OF THE UNIVERSE AND p-ADIC GRAVITY ». International Journal of Modern Physics A 06, no 24 (10 octobre 1991) : 4341–58. http://dx.doi.org/10.1142/s0217751x91002094.

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A new approach to the wave function of the universe is suggested. The key idea is to take into account fluctuating number fields and present the wave function in the form of a Euler product. For this purpose we define a p-adic generalization of both classical and quantum gravitational theory. Elements of p-adic differential geometry are described. The action and gravitation field equations over the p-adic number field are investigated. p-adic analogs of some known solutions to the Einstein equations are presented. It follows that in quantum cosmology one should consider summation only over algebraic manifolds. The correspondence principle with the standard approach is considered.
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Willerslev, Rane, et Martin Holbraad. « Transcendental Perspectivism : Anonymous Viewpoints from Inner Asia ». Inner Asia 9, no 2 (2007) : 329–45. http://dx.doi.org/10.1163/146481707793646511.

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AbstractAfter Spinoza, and apropos Buddhist cosmology in Tibet, Da Col asks:What can a body do? In perspectivism this is always the question. Viveiros de Castro proposes it by analogy to themore familiar concern, intuitive to usWestern intellectuals: ‘What can a mind do?’We are accustomed to worrying about our minds because we assume that even if our mental powers are ultimately generated by our brains (bodily parts we have in common with others), it is what we can do with our minds – the ideas we come up with, our way of thinking about things – that makes us different from others (other people, other cultures, or even other species or spirits).
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NADDEO, A., et G. SCELZA. « WAVE EQUATION OF THE SCALAR FIELD AND SUPERFLUIDS ». Modern Physics Letters A 24, no 40 (28 décembre 2009) : 3249–56. http://dx.doi.org/10.1142/s0217732309032162.

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The new formal analogy between superfluid systems and cosmology, which emerges by taking into account the back-reaction of the vacuum to the quanta of sound waves,1 enables us to put forward some common features between these two different areas of physics. We find the condition that allows us to justify a General Relativity (GR) derivation of the hydrodynamical equation for the superfluid in a four-dimensional space whose metric is the Unruh one.2 Furthermore, we show how, in the particular case taken into account, our hydrodynamical equation can be deduced within a four-dimensional space from the wave equation of a massless scalar field.
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SOSNOVSKIY, Leonid A., et Sergei S. SHERBAKOV. « DEVELOPMENT OF THE CONCEPT OF ENTROPY : FROM THERMODYNAMICS TO COSMOLOGY. PART 2. HYPOTHESIS OF ENTROPY IN COSMOLOGY AND ITS DEVELOPMENT ». Mechanics of Machines, Mechanisms and Materials 1, no 54 (mars 2021) : 80–88. http://dx.doi.org/10.46864/1995-0470-2020-1-54-80-88.

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In the work [7], the classical concepts of thermodynamic entropy are systematized and modern approaches to assessing the tribo-fatigue and mechanothermodynamic entropy of non-additive systems are outlined. In this article, the concept of the analogy of thermodynamics and mechanics of black holes is presented and analyzed, which made it possible to estimate their (thermodynamic) entropy. The insufficiency of this concept is that thermodynamic entropy is a characteristic of energy dissipation, whereas black holes are characterized by the absorption of energy and matter. In this regard, it is proposed to consider the event horizon as a hermodynamic medium, and a black hole as a tribo-fatigue object. And then the “black hole — event horizon” system is presented as a combined mechanothermodynamic non-additive multisystem. Methods for estimating the total (mechanothermodynamic) entropy and its components — tribo-fatigue and thermodynamic entropy in black hole mechanics are presented. With regard to individual (specific) zones and objects of the universe, the well-known theory of Zeldovich is accordingly modified: the universe is a thermodynamic medium with discretely distributed (scattered) dense and/or solid bodies (objects) — stars, galaxies, etc. Behavior of such a system (direct and back effects in the universe) are described. The peculiarity of the action of the medium on the stars and, conversely, the action of the cluster of stars on the interaction between them consists in the fact that it is non-Newtonian: action is not equal to reaction. It is the inequality of action against counteraction, which has radically different mechanisms and consequences (results), or, in other words, the imbalance of the universe that determine its general motion in space–time. The changing set of all states is the evolution of the universe. The analysis of possible strategies for the evolution of mechanothermodynamic systems is carried out on the basis of the fundamental principle: the damageability of everything that exists has no conceivable boundaries. This principle is formulated in mechanothermodynamics and used in philosophy to create a generalized theory of the evolution of the material world.
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Roshan, Mahmood, et Bahram Mashhoon. « Characteristics of Effective Dark Matter in Nonlocal Gravity ». Astrophysical Journal 934, no 1 (1 juillet 2022) : 9. http://dx.doi.org/10.3847/1538-4357/ac75d6.

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Abstract Nonlocal gravity (NLG) is a classical nonlocal generalization of Einstein’s theory of gravitation that has been constructed in close analogy with the nonlocal electrodynamics of media. According to NLG, what appears as dark matter in astrophysics and cosmology is in reality the nonlocal aspect of the universal gravitational interaction. We focus here on two main features of the effective dark matter in NLG, namely, (a) the density of effective dark matter in NLG is always finite and therefore cusp-free, and (b) there is less effective dark matter in dwarf galaxies than is generally assumed in the standard particle dark matter paradigm. The corresponding astrophysical implications of NLG in connection with three ultra-diffuse galaxies AGC 114905, 242019, and 219533 are discussed.
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Matthews, William. « Encompassing the Horse : Analogy, Category, and Scale in the Yijing ». British Journal of Chinese Studies 8, no 1 (3 avril 2019) : 32–61. http://dx.doi.org/10.51661/bjocs.v8i1.19.

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The canonised Yijing had a decisive influence over the development of so-called “correlative cosmology” in China’s early imperial period, presenting the cosmos as knowable through sixty-four hexagrams and classifiable according to eight trigrams. The exact nature of these correlative categories continues to inspire debate. On the one hand, they appear to be defined relationally, but on the other they purport to describe everything in the cosmos in terms of fixed principles. These apparently discordant properties can be reconciled by paying due attention to the role of scale. This is revealed through a focus on the hexagram images as two distinct but interrelated forms of analogy, as human constructs for symbolic manipulation and as empirical descriptors of cosmic circumstances. Adopting perspectives from cognitive linguistics and anthropology, this symbolic manipulation allows unknown situations to be understood metaphorically via the hexagrams, and then metonymically incorporated into a natural category of cosmic circumstances. This transition between metaphoric and metonymic relations is a function of scale, and is reflected in the Yijing’s correlative categories. These correspond to perceived absolute natural kinds, but maintain a relational character dependant on the salience of metaphorical and metonymic relations at different scales. At time of publication, the journal operated under the old name. When quoting please refer to the citation on the left using British Journal of Chinese Studies. The pdf of the article still reflects the old journal name; issue number and page range are consistent.
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Ian Bradley, D., Shaun N. Fisher, Anthony M. Guénault, Richard P. Haley, Juha Kopu, Hazel Martin, George R. Pickett, John E. Roberts et Viktor Tsepelin. « Annihilation of an AB/BA interface pair in superfluid helium-3 as a simulation of cosmological brane interaction ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 366, no 1877 (5 juin 2008) : 2803–12. http://dx.doi.org/10.1098/rsta.2008.0078.

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This study presents measurements of the transport of quasiparticle excitations in the B phase of superfluid 3 He at temperatures below 0.2 T c . We find that creating and then removing a layer of A-phase superfluid leads to a measurable increase in the thermal impedance of the background B phase. This increase must be due to the survival of defects created as the AB and BA interfaces on either side of the A-phase layer annihilate. We speculate that a new type of defect may have been formed. The highly ordered A–B interface may be a good analogy for branes discussed in current cosmology. If so, these experiments may provide insight into how the annihilation of branes can lead to the formation of topological defects such as cosmic strings.
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Wentink, Karsten. « Crafting axes, producing meaning. Neolithic axe depositions in the northern Netherlands ». Archaeological Dialogues 15, no 2 (décembre 2008) : 151–73. http://dx.doi.org/10.1017/s1380203808002651.

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AbstractThis paper deals with Dutch flint axe depositions associated with the Middle Neolithic Funnelbeaker Culture (Trichterbecher Kultur – TRB). Large flint axes were acquired as finished products from southern Scandinavia and were deposited in specific, waterlogged places in the landscape. The application of new empirical research techniques has revealed unexpected patterns of use and treatment of these axes. Moreover, contextual analysis shows significant differences in terms of size and wear patterns compared with axes retrieved from megalithic tombs. The evidence strongly suggests that the observed differences may have been linked to completely different use-lives between the two classes of axes. Drawing on ethnographic analogy, it will be argued that the large flint axes deposited in natural places in the landscape became animated with special powers through the act of production. Given the highly ritualized treatment that accompanied their exchange, they must have played an important role in TRB cosmology.
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Tenev, T. G., et M. F. Horstemeyer. « Mechanics of spacetime — A Solid Mechanics perspective on the theory of General Relativity ». International Journal of Modern Physics D 27, no 08 (30 mai 2018) : 1850083. http://dx.doi.org/10.1142/s0218271818500839.

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We present an elastic constitutive model of gravity where we identify physical space with the mid-hypersurface of an elastic hyperplate called the “cosmic fabric” and spacetime with the fabric’s worldvolume. Using a Lagrangian formulation, we show that the fabric’s behavior as derived from Hooke’s Law is analogous to that of spacetime per the Field Equations of General Relativity (GR). The study is conducted in the limit of small strains, or analogously, in the limit of weak and nearly static gravitational fields. The Fabric’s Lagrangian outside of inclusions is shown to have the same form as the Einstein–Hilbert Lagrangian for free space. Properties of the fabric such as strain, stress, vibrations and elastic moduli are related to properties of gravity and space, such as the gravitational potential, gravitational acceleration, gravitational waves and the energy density of free space. By introducing a mechanical analogy of GR, we enable the application of Solid Mechanics tools to address problems in Cosmology.
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