How does pressure gravitate? Cosmological constant problem confronts observational cosmology
Abstract
An important and longstanding puzzle in the history of modern physics is the gross inconsistency between theoretical expectations and cosmological observations of the vacuum energy density, by at least 60 orders of magnitude, otherwise known as the cosmological constant problem. A characteristic feature of vacuum energy is that it has a pressure with the same amplitude, but opposite sign to its energy density, while all the precision tests of General Relativity are either in vacuum, or for media with negligible pressure. Therefore, one may wonder whether an anomalous coupling to pressure might be responsible for decoupling vacuum from gravity. We test this possibility in the context of the Gravitational Aether proposal, using current cosmological observations, which probe the gravity of relativistic pressure in the radiation era. Interestingly, we find that the best fit for anomalous pressure coupling is about halfway between General Relativity (GR), and Gravitational Aether (GA), if we include Planck together with WMAP and BICEP2 polarization cosmic microwave background (CMB) observations. Taken at face value, this data combination excludes both GR and GA at around the 3 σ level. However, including higher resolution CMB observations (''highL'') or baryonic acoustic oscillations (BAO) pushes the best fit closer to GR, excludingmore »
 Authors:
 Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, V6T 1Z1 Canada (Canada)
 Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada)
 Publication Date:
 OSTI Identifier:
 22373380
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 08; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGICAL CONSTANT; COSMOLOGY; ENERGY DENSITY; GENERAL RELATIVITY THEORY; GRAVITATION; RELATIVISTIC RANGE; RELICT RADIATION
Citation Formats
Narimani, Ali, Scott, Douglas, and Afshordi, Niayesh, Email: anariman@phas.ubc.ca, Email: nafshordi@pitp.ca, Email: dscott@phas.ubc.ca. How does pressure gravitate? Cosmological constant problem confronts observational cosmology. United States: N. p., 2014.
Web. doi:10.1088/14757516/2014/08/049.
Narimani, Ali, Scott, Douglas, & Afshordi, Niayesh, Email: anariman@phas.ubc.ca, Email: nafshordi@pitp.ca, Email: dscott@phas.ubc.ca. How does pressure gravitate? Cosmological constant problem confronts observational cosmology. United States. doi:10.1088/14757516/2014/08/049.
Narimani, Ali, Scott, Douglas, and Afshordi, Niayesh, Email: anariman@phas.ubc.ca, Email: nafshordi@pitp.ca, Email: dscott@phas.ubc.ca. 2014.
"How does pressure gravitate? Cosmological constant problem confronts observational cosmology". United States.
doi:10.1088/14757516/2014/08/049.
@article{osti_22373380,
title = {How does pressure gravitate? Cosmological constant problem confronts observational cosmology},
author = {Narimani, Ali and Scott, Douglas and Afshordi, Niayesh, Email: anariman@phas.ubc.ca, Email: nafshordi@pitp.ca, Email: dscott@phas.ubc.ca},
abstractNote = {An important and longstanding puzzle in the history of modern physics is the gross inconsistency between theoretical expectations and cosmological observations of the vacuum energy density, by at least 60 orders of magnitude, otherwise known as the cosmological constant problem. A characteristic feature of vacuum energy is that it has a pressure with the same amplitude, but opposite sign to its energy density, while all the precision tests of General Relativity are either in vacuum, or for media with negligible pressure. Therefore, one may wonder whether an anomalous coupling to pressure might be responsible for decoupling vacuum from gravity. We test this possibility in the context of the Gravitational Aether proposal, using current cosmological observations, which probe the gravity of relativistic pressure in the radiation era. Interestingly, we find that the best fit for anomalous pressure coupling is about halfway between General Relativity (GR), and Gravitational Aether (GA), if we include Planck together with WMAP and BICEP2 polarization cosmic microwave background (CMB) observations. Taken at face value, this data combination excludes both GR and GA at around the 3 σ level. However, including higher resolution CMB observations (''highL'') or baryonic acoustic oscillations (BAO) pushes the best fit closer to GR, excluding the Gravitational Aether solution to the cosmological constant problem at the 4 5 σ level. This constraint effectively places a limit on the anomalous coupling to pressure in the parametrized postNewtonian (PPN) expansion, ζ{sub 4} = 0.105 ± 0.049 (+highL CMB), or ζ{sub 4} = 0.066 ± 0.039 (+BAO). These represent the most precise measurement of this parameter to date, indicating a mild tension with GR (for ΛCDM including tensors, with 0ζ{sub 4}=), and also among different data sets.},
doi = {10.1088/14757516/2014/08/049},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 08,
volume = 2014,
place = {United States},
year = 2014,
month = 8
}

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