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Title: Nonlinear fields in generalized cosmologies

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1324017
Grant/Contract Number:
AC02-76SF00515
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 94; Journal Issue: 6; Related Information: CHORUS Timestamp: 2016-09-12 18:08:36; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Fasiello, Matteo, and Vlah, Zvonimir. Nonlinear fields in generalized cosmologies. United States: N. p., 2016. Web. doi:10.1103/PhysRevD.94.063516.
Fasiello, Matteo, & Vlah, Zvonimir. Nonlinear fields in generalized cosmologies. United States. doi:10.1103/PhysRevD.94.063516.
Fasiello, Matteo, and Vlah, Zvonimir. 2016. "Nonlinear fields in generalized cosmologies". United States. doi:10.1103/PhysRevD.94.063516.
@article{osti_1324017,
title = {Nonlinear fields in generalized cosmologies},
author = {Fasiello, Matteo and Vlah, Zvonimir},
abstractNote = {},
doi = {10.1103/PhysRevD.94.063516},
journal = {Physical Review D},
number = 6,
volume = 94,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevD.94.063516

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

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  • We study the formation of large-scale structure in universes dominated by dark matter and driven to accelerated expansion by f(R) gravity in the Palatini formalism. If the dark matter is cold, practically all of these models are ruled out because they fail to reproduce the observed matter power spectrum. We point out that if the assumption that dark matter is perfect and pressureless at all scales is relaxed, nontrivial alternatives to a cosmological constant become viable within this class of modified gravity models.
  • We consider linear perturbation equations for long-wavelength scalar metric perturbations in generalized gravity, applicable to nonsingular cosmological models including a bounce from collapse to expansion in the very early universe. We present the general form for the perturbation equations, which follows from requiring that the inhomogeneous universe on large scales obeys the same local equations as the homogeneous Friedmann-Robertson-Walker background cosmology (the separate universes approach). In a pseudolongitudinal gauge this becomes a homogeneous second-order differential equation for adiabatic perturbations, which reduces to the usual equation for the longitudinal gauge metric perturbation in general relativity with vanishing anisotropic stress. As anmore » application we show that the scale-invariant spectrum of perturbations in the longitudinal gauge generated during an ekpyrotic collapse are not transferred to the growing mode of adiabatic density perturbations in the expanding phase in a simple bounce model.« less
  • We generalize the Swiss-cheese cosmologies so as to include nonzero linear momenta of the associated boundary surfaces. The evolution of mass scales in these generalized cosmologies is studied for a variety of models for the background without having to specify any details within the local inhomogeneities. We find that the final effective gravitational mass and size of the evolving inhomogeneities depends on their linear momenta but these properties are essentially unaffected by the details of the background model.
  • The generalized Swiss-cheese model, consisting of a Lemaitre-Tolman (inhomogeneous dust) region matched, by way of a comoving boundary surface, onto a Robertson-Walker background of homogeneous dust, has become a standard construction in modern cosmology. Here, we ask if this construction can be made more realistic by introducing some evolution of the boundary surface. The answer we find is no. To maintain a boundary surface using the Darmois-Israel junction conditions, as opposed to the introduction of a surface layer, the boundary must remain exactly comoving. The options are to drop the assumption of dust or allow the development of surface layers.more » Either option fundamentally changes the original construction.« less
  • We evaluate our capability to constrain the abundance of primordial tensor perturbations (primordial gravitational waves, PGWs) in cosmologies with generalized expansion histories in the epoch of cosmic acceleration. Forthcoming satellite and sub-orbital experiments probing polarization in the Cosmic Microwave Background (CMB) are expected to measure the B−mode power in CMB polarization, coming from PGWs on the degree scale, as well as gravitational lensing on arcminute scales; the latter is the main competitor for the measurement of PGWs, and is directly affected by the underlying expansion history, determined by the presence of a Dark Energy (DE) component. In particular, we considermore » early DE possible scenarios, in which the expansion history is substantially modified at the epoch in which the CMB lensing is most relevant. We show that the introduction of a parametrized DE may induce a variation as large as 30% in the ratio of the power of lensing and PGWs on the degree scale. We find that adopting the nominal specifications of upcoming satellite measurements, the constraining power on PGWs is weakened by the inclusion of the extra degrees of freedom, resulting in a reduction of about 10% of the upper limits on r in fiducial models with no GWs, as well as a comparable increase in the error bars in models with non-zero tensor power. Moreover, we find that the inclusion of sub-orbital CMB experiments, capable of mapping the B−mode power up to the angular scales which are affected by lensing, has the effect of restoring the forecasted performances with a fixed cosmological expansion history corresponding to a cosmological constant. Finally, we show how the combination of CMB data with Type Ia SuperNovae (SNe), Baryonic Acoustic Oscillations (BAO) and Hubble constant allows to constrain simultaneously the primordial tensor power and the DE quantities in the parametrization we consider, consisting of present abundance and first redshift derivative of the energy density. We compare this study with results obtained using the forecasted lensing potential measurement precision from CMB satellite observations, finding consistent results.« less