Probing dark energy perturbations: The dark energy equation of state and speed of sound as measured by WMAP

Bean, Rachel; Doré, O.

doi:10.1103/physrevd.69.083503

Cited by 305 publications

(381 citation statements)

References 42 publications

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“…Given that the understanding the evolution of dark energy perturbations is crucial to making precise predictions for the observed power spectra, a variety of phenomenological models have been discussed [26,27,29,30,31]. In this section we attempt to make some contact between our work and these models.…”

Section: F Comparison To Generalized Fluid Systemsmentioning

confidence: 99%

“…The idea of generalized dark matter/energy has been considered previously by a number of authors [19,20,26,27,29,30,31]. We will attempt to discuss how the approaches suggested by others relate to those presented here.…”

Section: Introductionmentioning

confidence: 99%

“…This will require us to go back to the fundamentals of how formulate a generalized continuum medium in General Relativity and derive equations for the perturbations in the medium. These are essential in computing accurate predictions for observed power spectra [16,20,26,27]. We will show that the most obvious generalization of a perfect fluid is to allow for rigidity of the medium in a way analogous to a continuum elastic solid [19], and that this can be stable if the rigidity is sufficiently large even if the pressure is negative.…”

Section: Introductionmentioning

confidence: 99%

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Cosmological perturbations in elastic dark energy models

Battye

Moss

2007

Phys. Rev. D

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We discuss the general framework for a perfect continuum medium in cosmology and show that an interesting generalization of the fluids normally used is for the medium to have rigidity and, hence, be analogous to an elastic solid. Such models can provide perfect, adiabatic fluids which are stable even when the pressure is negative, if the rigidity is sufficiently large, making them natural candidates to describe the dark energy. In fact, if the medium is adiabatic and isotropic, they provide the most general description of linearized perturbations. We derive the equations of motion and wave propagation speeds in the isotropic case. We point out that anisotropic models can also be incorporated within the same formalism and that they are classified by the standard Bravais Lattices. We identify the adiabatic and isocurvature modes allowed in both the scalar and vector sectors and discuss the predictions they make for CMB and matter power spectra. We comment on the relationship between these models and other fluid-based approaches to dark energy, and discuss a possible microphysical manifestation of this class of models as a continuum description of defect-dominated scenarios.

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Section: F Comparison To Generalized Fluid Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cosmological perturbations in elastic dark energy models

Battye

Moss

2007

Phys. Rev. D

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“…More complicated models that have a sound speed (c 2 s = δp/δρ) much smaller than c allow fluctuations to grow on sub-horizon scales (e.g., Hu 1998;Erickson et al 2002;Weller and Lewis 2003;DeDeo et al 2003;Bean and Doré 2004). de Putter et al (2010) provide a clear discussion of the background physics and observable consequences of dark energy inhomogeneities.…”

Section: Model Parameterizationsmentioning

confidence: 99%

Observational probes of cosmic acceleration

et al. 2013

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The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H 0 . We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.

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“…Each fluid then evolves according to [31] 6 We also assume that V i follows the peculiar motion of the non-relativistic matter and therefore satisfies the geodesic equation (the c 2 s,I = 0 version of Eq. (4.12)).…”

Section: Conservation Of Curvaturementioning

confidence: 99%

On separate universes

Dai

Pajer

Schmidt

2015

J. Cosmol. Astropart. Phys.

188

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Abstract. The separate universe conjecture states that in General Relativity a density perturbation behaves locally (i.e. on scales much smaller than the wavelength of the mode) as a separate universe with different background density and curvature. We prove this conjecture for a spherical compensated tophat density perturbation of arbitrary amplitude and radius in ΛCDM. We then use Conformal Fermi Coordinates to generalize this result to scalar perturbations of arbitrary configuration and scale in a general cosmology with a mixture of fluids, but to linear order in perturbations. In this case, the separate universe conjecture holds for the isotropic part of the perturbations. The anisotropic part on the other hand is exactly captured by a tidal field in the Newtonian form. We show that the separate universe picture is restricted to scales larger than the sound horizons of all fluid components. We then derive an expression for the locally measured matter bispectrum induced by a long-wavelength mode of arbitrary wavelength, a new result which in standard perturbation theory is equivalent to a relativistic second-order calculation. We show that nonlinear gravitational dynamics does not generate observable contributions that scale like local-type non-Gaussianity f loc NL , and hence does not contribute to a scale-dependent galaxy bias ∆b ∝ k −2 on large scales; rather, the locally measurable long-short mode coupling assumes a form essentially identical to subhorizon perturbation theory results, once the long-mode density perturbation is replaced by the synchronous-comoving gauge density perturbation. Apparent f loc NL -type contributions arise through projection effects on photon propagation, which depend on the specific large-scale structure tracer and observable considered, and are in principle distinguishable from the local mode coupling induced by gravity. We conclude that any observation of f loc NL beyond these projection effects signals a departure from standard single-clock inflation.

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Probing dark energy perturbations: The dark energy equation of state and speed of sound as measured by WMAP

Cited by 305 publications

References 42 publications

Cosmological perturbations in elastic dark energy models

Cosmological perturbations in elastic dark energy models

Observational probes of cosmic acceleration

On separate universes

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