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Marcori OH, Pitrou C, Uzan JP, Pereira TS. Direction and redshift drifts for general observers and their applications in cosmology. Int J Clin Exp Med 2018. [DOI: 10.1103/physrevd.98.023517] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Cusin G, Dvorkin I, Pitrou C, Uzan JP. First Predictions of the Angular Power Spectrum of the Astrophysical Gravitational Wave Background. Phys Rev Lett 2018; 120:231101. [PMID: 29932710 DOI: 10.1103/physrevlett.120.231101] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Indexed: 06/08/2023]
Abstract
We present the first predictions for the angular power spectrum of the astrophysical gravitational wave background constituted of the radiation emitted by all resolved and unresolved astrophysical sources. Its shape and amplitude depend on both the astrophysical properties on galactic scales and on cosmological properties. We show that the angular power spectrum behaves as C_{ℓ}∝1/ℓ on large scales and that relative fluctuations of the signal are of order 30% at 100 Hz. We also present the correlations of the astrophysical gravitational wave background with weak lensing and galaxy distribution. These numerical results pave the way to the study of a new observable at the crossroad between general relativity, astrophysics, and cosmology.
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Affiliation(s)
- Giulia Cusin
- Astrophysics Department, University of Oxford, DWB, Keble Road, Oxford OX1 3RH, United Kingdom
| | - Irina Dvorkin
- Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, Potsdam-Golm 14476, Germany
| | - Cyril Pitrou
- Institut d'Astrophysique de Paris, CNRS UMR 7095, Sorbonne Université, Institut Lagrange de Paris, 98 bis, Bd Arago, 75014 Paris, France
| | - Jean-Philippe Uzan
- Institut d'Astrophysique de Paris, CNRS UMR 7095, Sorbonne Université, Institut Lagrange de Paris, 98 bis, Bd Arago, 75014 Paris, France
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Bergé J, Brax P, Métris G, Pernot-Borràs M, Touboul P, Uzan JP. MICROSCOPE Mission: First Constraints on the Violation of the Weak Equivalence Principle by a Light Scalar Dilaton. Phys Rev Lett 2018; 120:141101. [PMID: 29694146 DOI: 10.1103/physrevlett.120.141101] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/09/2018] [Indexed: 06/08/2023]
Abstract
The existence of a light or massive scalar field with a coupling to matter weaker than gravitational strength is a possible source of violation of the weak equivalence principle. We use the first results on the Eötvös parameter by the MICROSCOPE experiment to set new constraints on such scalar fields. For a massive scalar field of mass smaller than 10^{-12} eV (i.e., range larger than a few 10^{5} m), we improve existing constraints by one order of magnitude to |α|<10^{-11} if the scalar field couples to the baryon number and to |α|<10^{-12} if the scalar field couples to the difference between the baryon and the lepton numbers. We also consider a model describing the coupling of a generic dilaton to the standard matter fields with five parameters, for a light field: We find that, for masses smaller than 10^{-12} eV, the constraints on the dilaton coupling parameters are improved by one order of magnitude compared to previous equivalence principle tests.
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Affiliation(s)
- Joel Bergé
- DPHY, ONERA, Université Paris Saclay, F-92322 Châtillon, France
| | - Philippe Brax
- Institut de Physique Théorique, Université Paris-Saclay, CEA, CNRS, F-91191 Gif-sur-Yvette Cedex, France
| | - Gilles Métris
- Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, IRD, Géoazur, 250 avenue Albert Einstein, F-06560 Valbonne, France
| | - Martin Pernot-Borràs
- DPHY, ONERA, Université Paris Saclay, F-92322 Châtillon, France
- Sorbonne Université, CNRS, Institut d'Astrophysique de Paris, IAP, F-75014 Paris, France
| | - Pierre Touboul
- DPHY, ONERA, Université Paris Saclay, F-92322 Châtillon, France
| | - Jean-Philippe Uzan
- Institut d'Astrophysique de Paris, CNRS UMR 7095, Université Pierre et Marie Curie-Paris VI, 98 bis Boulevard Arago, 75014 Paris, France
- Sorbonne Universités, Institut Lagrange de Paris, 98 bis, Boulevard Arago, 75014 Paris, France
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Abstract
The standard theory of weak gravitational lensing relies on the infinitesimal light beam approximation. In this context, images are distorted by convergence and shear, the respective sources of which unphysically depend on the resolution of the distribution of matter-the so-called Ricci-Weyl problem. In this Letter, we propose a strong-lensing-inspired formalism to describe the lensing of finite beams. We address the Ricci-Weyl problem by showing explicitly that convergence is caused by the matter enclosed by the beam, regardless of its distribution. Furthermore, shear turns out to be systematically enhanced by the finiteness of the beam. This implies, in particular, that the Kaiser-Squires relation between shear and convergence is violated, which could have profound consequences on the interpretation of weak-lensing surveys.
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Affiliation(s)
- Pierre Fleury
- Départment de Physique Théorique, Université de Genève, 24 quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Julien Larena
- Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, South Africa
| | - Jean-Philippe Uzan
- Institut d'Astrophysique de Paris, CNRS UMR 7095, Université Pierre et Marie Curie-Paris VI, 98 bis Boulevard Arago, 75014 Paris, France, and Sorbonne Universités, Institut Lagrange de Paris, 98 bis Boulevard Arago, 75014 Paris, France
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Fleury P, Dupuy H, Uzan JP. Can all cosmological observations be accurately interpreted with a unique geometry? Phys Rev Lett 2013; 111:091302. [PMID: 24033020 DOI: 10.1103/physrevlett.111.091302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Indexed: 06/02/2023]
Abstract
The recent analysis of the Planck results reveals a tension between the best fits for (Ω(m0), H(0)) derived from the cosmic microwave background or baryonic acoustic oscillations on the one hand, and the Hubble diagram on the other hand. These observations probe the Universe on very different scales since they involve light beams of very different angular sizes; hence, the tension between them may indicate that they should not be interpreted the same way. More precisely, this Letter questions the accuracy of using only the (perturbed) Friedmann-Lemaître geometry to interpret all the cosmological observations, regardless of their angular or spatial resolution. We show that using an inhomogeneous "Swiss-cheese" model to interpret the Hubble diagram allows us to reconcile the inferred value of Ω(m0) with the Planck results. Such an approach does not require us to invoke new physics nor to violate the Copernican principle.
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Affiliation(s)
- Pierre Fleury
- Institut d'Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, 98 bis boulevard Arago, 75014 Paris, France and Sorbonne Universités, Institut Lagrange de Paris, 98 bis boulevard Arago, 75014 Paris, France
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Ellis GFR, Poltis R, Uzan JP, Weltman A. Blackness of the cosmic microwave background spectrum as a probe of the distance-duality relation. Int J Clin Exp Med 2013. [DOI: 10.1103/physrevd.87.103530] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
I summarize various tests of general relativity on astrophysical scales, based on the large-scale structure of the universe but also on other systems, in particular the constants of physics. I emphasize the importance of hypotheses on the geometric structures of our universe while performing such tests and discuss their complementarity as well as their possible extensions.
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Affiliation(s)
- Jean-Philippe Uzan
- Institut d'Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, 98 bis bd Arago, 75014 Paris, France.
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Abstract
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
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Affiliation(s)
- Jean-Philippe Uzan
- Institut d’Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, 98 bis bd Arago, 75014 Paris, France
- Department of Mathematics and Applied Mathematics, Cape Town University, Rondebosch, 7701 South Africa
- National Institute for Theoretical Physics (NITheP), Stellenbosch, 7600 South Africa
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Uzan JP, Clarkson C, Ellis GFR. Time drift of cosmological redshifts as a test of the Copernican principle. Phys Rev Lett 2008; 100:191303. [PMID: 18518435 DOI: 10.1103/physrevlett.100.191303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Indexed: 05/26/2023]
Abstract
We present the time drift of the cosmological redshift in a general spherically symmetric spacetime. We demonstrate that its observation would allow us to test the Copernican principle and so determine if our Universe is radially inhomogeneous, an important issue in our understanding of dark energy. In particular, when combined with distance data, this extra observable allows one to fully reconstruct the geometry of a spacetime describing a spherically symmetric underdense region around us, purely from background observations.
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Affiliation(s)
- Jean-Philippe Uzan
- Institut d'Astrophysique de Paris, Université Pierre and Marie Curie-Paris VI, CNRS-UMR 7095, Paris, France.
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Abstract
BACKGROUND Various definitions of biological complexity have been proposed: the number of genes, cell types, or metabolic processes within an organism. As knowledge of biological systems has increased, it has become apparent that these metrics are often incongruent. METHODOLOGY Here we propose an alternative complexity metric based on the number of genetically uncorrelated phenotypic traits contributing to an organism's fitness. This metric, phenotypic complexity, is more objective than previous suggestions, as complexity is measured from a fundamental biological perspective, that of natural selection. We utilize a model linking the equilibrium fitness (drift load) of a population to phenotypic complexity. We then use results from viral evolution experiments to compare the phenotypic complexities of two viruses, the bacteriophage X174 and vesicular stomatitis virus, and to illustrate the consistency of our approach and its applicability. CONCLUSIONS/SIGNIFICANCE Because Darwinian evolution through natural selection is the fundamental element unifying all biological organisms, we propose that our metric of complexity is potentially a more relevant metric than others, based on the count of artificially defined set of objects.
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Affiliation(s)
- Olivier Tenaillon
- Institut National de la Santé et de la Recherche Médicale (INSERM) U722, Faculté de Médecine Xavier Bichat, Université Denis Diderot-Paris VII, Paris, France.
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Abstract
In scalar-tensor theories of gravity, the equation of state of dark energy, w, can become smaller than -1 without violating any energy condition. The value of w today is tied to the level of deviations from general relativity which, in turn, is constrained by solar system and pulsars timing experiments. The conditions on these local constraints for w to be significantly less than -1 are established. It is demonstrated that this requires us to consider theories that differ from the Jordan-Fierz-Brans-Dicke theory and that involve either a steep coupling function or a steep potential. It is also shown how a robust measurement of w could probe scalar-tensor theories.
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Affiliation(s)
- Jérôme Martin
- Institut d'Astrophysique de Paris, GReCO-CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France.
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Luminet JP, Weeks JR, Riazuelo A, Lehoucq R, Uzan JP. Dodecahedral space topology as an explanation for weak wide-angle temperature correlations in the cosmic microwave background. Nature 2003; 425:593-5. [PMID: 14534579 DOI: 10.1038/nature01944] [Citation(s) in RCA: 279] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Accepted: 07/28/2003] [Indexed: 11/09/2022]
Abstract
The current 'standard model' of cosmology posits an infinite flat universe forever expanding under the pressure of dark energy. First-year data from the Wilkinson Microwave Anisotropy Probe (WMAP) confirm this model to spectacular precision on all but the largest scales. Temperature correlations across the microwave sky match expectations on angular scales narrower than 60 degrees but, contrary to predictions, vanish on scales wider than 60 degrees. Several explanations have been proposed. One natural approach questions the underlying geometry of space--namely, its curvature and topology. In an infinite flat space, waves from the Big Bang would fill the universe on all length scales. The observed lack of temperature correlations on scales beyond 60 degrees means that the broadest waves are missing, perhaps because space itself is not big enough to support them. Here we present a simple geometrical model of a finite space--the Poincaré dodecahedral space--which accounts for WMAP's observations with no fine-tuning required. The predicted density is Omega(0) approximately 1.013 > 1, and the model also predicts temperature correlations in matching circles on the sky.
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