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Arjona R, Nesseris S. Complementary consistency test of the Copernican principle via Noether’s theorem and machine learning forecasts. Int J Clin Exp Med 2021. [DOI: 10.1103/physrevd.104.103532] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [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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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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Bel J, Marinoni C. Proposal for a Real-Time Detection of our Acceleration through Space. Phys Rev Lett 2018; 121:021101. [PMID: 30085739 DOI: 10.1103/physrevlett.121.021101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 02/05/2018] [Indexed: 06/08/2023]
Abstract
Our proper acceleration with respect to the cosmic microwave background results in a real-time change of the angular position of distant extragalactic sources. The cosmological component of this aberration drift signal, the noninertial motion generated by the large-scale distribution of matter, can, in principle, be detected by future high-precision astrometric experiments. It will provide interesting consistency tests of the standard model of cosmology, set independent constraints on the amplitude of the Hubble constant and the linear growth rate of cosmic structures, and be instrumental in searching for evidence of new physics beyond the standard model. We present the formalism of this novel cosmological test, discuss the physics to which it is sensitive, and show simulated forecasts of the accuracy with which it can be implemented.
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Affiliation(s)
- Julien Bel
- Aix Marseille Univ, Université de Toulon, CNRS, CPT, Marseille, France
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Yu HR, Zhang TJ, Pen UL. Method for direct measurement of cosmic acceleration by 21-cm absorption systems. Phys Rev Lett 2014; 113:041303. [PMID: 25105607 DOI: 10.1103/physrevlett.113.041303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Indexed: 06/03/2023]
Abstract
So far there is only indirect evidence that the Universe is undergoing an accelerated expansion. The evidence for cosmic acceleration is based on the observation of different objects at different distances and requires invoking the Copernican cosmological principle and Einstein's equations of motion. We examine the direct observability using recession velocity drifts (Sandage-Loeb effect) of 21-cm hydrogen absorption systems in upcoming radio surveys. This measures the change in velocity of the same objects separated by a time interval and is a model-independent measure of acceleration. We forecast that for a CHIME-like survey with a decade time span, we can detect the acceleration of a ΛCDM universe with 5σ confidence. This acceleration test requires modest data analysis and storage changes from the normal processing and cannot be recovered retroactively.
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Affiliation(s)
- Hao-Ran Yu
- Department of Astronomy, Beijing Normal University, Beijing 100875, China and Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
| | - Tong-Jie Zhang
- Department of Astronomy, Beijing Normal University, Beijing 100875, China
| | - Ue-Li Pen
- Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, M5S 3H8, Ontario, Canada
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Abstract
The standard model of cosmology is based on the existence of homogeneous surfaces as the background arena for structure formation. Homogeneity underpins both general relativistic and modified gravity models and is central to the way in which we interpret observations of the cosmic microwave background (CMB) and the galaxy distribution. However, homogeneity cannot be directly observed in the galaxy distribution or CMB, even with perfect observations, since we observe on the past light cone and not on spatial surfaces. We can directly observe and test for isotropy, but to link this to homogeneity we need to assume the Copernican principle (CP). First, we discuss the link between isotropic observations on the past light cone and isotropic space-time geometry: what observations do we need to be isotropic in order to deduce space-time isotropy? Second, we discuss what we can say with the Copernican assumption. The most powerful result is based on the CMB: the vanishing of the dipole, quadrupole and octupole of the CMB is sufficient to impose homogeneity. Real observations lead to near-isotropy on large scales--does this lead to near-homogeneity? There are important partial results, and we discuss why this remains a difficult open question. Thus, we are currently unable to prove homogeneity of the Universe on large scales, even with the CP. However, we can use observations of the cosmic microwave background, galaxies and clusters to test homogeneity itself.
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Affiliation(s)
- Roy Maartens
- Department of Physics, University of Western Cape, Cape Town 7535, South Africa.
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Zhang P, Stebbins A. Confirmation of the Copernican principle through the anisotropic kinetic Sunyaev Zel'dovich effect. Philos Trans A Math Phys Eng Sci 2011; 369:5138-5145. [PMID: 22084299 DOI: 10.1098/rsta.2011.0294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The Copernican principle remains largely unproven at Gpc radial scale and above. Generally, violations of this type cause a first-order anisotropic kinetic Sunyaev Zel'dovich (kSZ) effect. Here we show that, if large-scale radial inhomogeneities have amplitude large enough to explain the 'dark energy' phenomena, the induced kSZ power spectrum will be orders of magnitude larger than the Atacama cosmology telescope/South Pole telescope upper limit. This single test rules out the void model as the cause of the apparent cosmic acceleration, confirms the Copernican principle on Gpc radial scale and above, and closes a loophole in the standard cosmology.
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Affiliation(s)
- Pengjie Zhang
- Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030, People's Republic of China.
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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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Zhang P, Stebbins A. Confirmation of the Copernican principle at Gpc radial scale and above from the kinetic Sunyaev-Zel'dovich effect power spectrum. Phys Rev Lett 2011; 107:041301. [PMID: 21866989 DOI: 10.1103/physrevlett.107.041301] [Citation(s) in RCA: 4] [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: 09/19/2010] [Revised: 04/14/2011] [Indexed: 05/27/2023]
Abstract
The Copernican principle, a cornerstone of modern cosmology, remains largely unproven at the Gpc radial scale and above. Here will show that violations of this type will inevitably cause a first order anisotropic kinetic Sunyaev-Zel'dovich effect. If large scale radial inhomogeneities have an amplitude large enough to explain the "dark energy" phenomena, the induced kinetic Sunyaev-Zel'dovich power spectrum will be much larger than the Atacama Cosmology Telescope and/or South Pole Telescope upper limit. This single test confirms the Copernican principle and rules out the adiabatic void model as a viable alternative to dark energy.
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Affiliation(s)
- Pengjie Zhang
- Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai, 200030, China.
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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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Quercellini C, Quartin M, Amendola L. Possibility of detecting anisotropic expansion of the universe by very accurate astrometry measurements. Phys Rev Lett 2009; 102:151302. [PMID: 19518616 DOI: 10.1103/physrevlett.102.151302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 12/22/2008] [Indexed: 05/27/2023]
Abstract
Refined astrometry measurements allow us to detect large-scale deviations from isotropy through real-time observations of changes in the angular separation between sources at cosmic distances. This "cosmic parallax" effect is a powerful consistency test of the Friedmann-Robertson-Walker metric and may set independent constraints on cosmic anisotropy. We apply this novel general test to Lemaitre-Tolman-Bondi cosmologies with off-center observers and show that future satellite missions such as Gaia might achieve accuracies that would put limits on the off-center distance which are competitive with cosmic microwave background dipole constraints.
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Abstract
The idea that we live near the center of a large, nonlinear void has attracted attention recently as an alternative to dark energy or modified gravity. We show that an appropriate void profile can fit both the latest cosmic microwave background and supernova data. However, this requires either a fine-tuned primordial spectrum or a Hubble rate so low as to rule these models out. We also show that measurements of the radial baryon acoustic scale can provide very strong constraints. Our results present a serious challenge to void models of acceleration.
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Affiliation(s)
- James P Zibin
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 Canada
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Clifton T, Ferreira PG, Land K. Living in a void: testing the Copernican principle with distant supernovae. Phys Rev Lett 2008; 101:131302. [PMID: 18851434 DOI: 10.1103/physrevlett.101.131302] [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: 07/09/2008] [Revised: 09/05/2008] [Indexed: 05/26/2023]
Abstract
We show that the local redshift dependence of the luminosity distance can be used to test the Copernican principle that we are not in a central or otherwise special region of the Universe. Future surveys of type Ia supernovae that focus on a redshift range of approximately 0.1-0.4 will be ideally suited to observationally determine the validity of the Copernican principle on new scales, as well as probing the degree to which dark energy must be considered a necessary ingredient in the Universe.
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Affiliation(s)
- Timothy Clifton
- Department of Physics, Oxford Astrophysics, DWB, Keble Road, Oxford, OX1 3RH, United Kingdom.
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Abstract
To date, there has been no general way of determining if the Copernican principle--that we live at a typical position in the Universe--is in fact a valid assumption, significantly weakening the foundations of cosmology as a scientific endeavor. Here we present an observational test for the Copernican assumption which can be automatically implemented while we search for dark energy in the coming decade. Our test is entirely independent of any model for dark energy or theory of gravity and thereby represents a model-independent test of the Copernican principle.
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Affiliation(s)
- Chris Clarkson
- Cosmology and Gravity Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, South Africa
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