Model-independent constraints on the cosmological anisotropic stress

Amendola, Luca; Fogli, Simone; Guarnizo, Alejandro; Kunz, M.; Vollmer, Adrian

doi:10.1103/physrevd.89.063538

Cited by 67 publications

(102 citation statements)

References 24 publications

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“…In principle, one can therefore measure the gravitational slip η (where η 1 is an unambiguous signature of modified gravity [227]) without making reference to galaxy bias [226,466]. Without assuming a value and form for the galaxy bias function, one cannot determine the underlying dark matter perturbation and so make a measurement of the effective Newton's constant µ, however.…”

Section: Model-independent Tests Of λCdm Discussion Session Chairs: Ementioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

460

210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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Section: Model-independent Tests Of λCdm Discussion Session Chairs: Ementioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

460

210

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“…Contributions to the gravitational slip also appear generically in modified gravity theories [24]. On large scales p ≃ 10 −4 h=Mpc, the gravitational slip could reach ϖ ≃ 10 −3 [25,26].…”

Section: Higgs Vacuum Expectation Valuementioning

confidence: 93%

Higgs effective potential in a perturbed Robertson-Walker background

Maroto

Prada

2014

Phys. Rev. D

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We calculate the one-loop effective potential of a scalar field in a Robertson-Walker background with scalar metric perturbations. A complete set of orthonormal solutions of the perturbed equations is obtained by using the adiabatic approximation for comoving observers. After analyzing the problem of renormalization in inhomogeneous backgrounds, we get the explicit contribution of metric perturbations to the effective potential. We apply these results to the Standard Model Higgs field and evaluate the effects of metric perturbations on the Higgs mass and on its vacuum expectation value. Space-time variations are found, which are proportional to the gravitational slip parameter, with a typical amplitude of the order of Δϕ=ϕ ≃ 10 −11 on cosmological scales. We also discuss possible astrophysical signatures in the Solar System and in the Milky Way that could open new possibilities to explore the symmetry breaking sector of the electroweak interactions.

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“…Therefore, in principle, its presence could be revealed in large scale structure observations. The growth of perturbations can also be affected by the anisotropic stress contributions [14,15,17] which lead to a damping in the velocity perturbations. In the parametrization used here, the damping effect is driven by the viscosity parameter c 2 vis which links the anisotropic stress to the velocity perturbation and the metric shear.…”

Section: Introductionmentioning

confidence: 99%

Current constraints on early and stressed dark energy models and future 21 cm perspectives

2014

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Despite the great progress of current cosmological measurements, the nature of the dominant component of the universe, coined dark energy, is still an open question. Early Dark Energy is a possible candidate which may also alleviate some fine tuning issues of the standard paradigm. Using the latest available cosmological data, we find that the 95% CL upper bound on the early dark energy density parameter is ΩeDE < 0.009. On the other hand, the dark energy component may be a stressed and inhomogeneous fluid. If this is the case, the effective sound speed and the viscosity parameters are unconstrained by current data. Future omniscope-like 21 cm surveys, combined with present CMB data, could be able to distinguish between standard quintessence scenarios from other possible models with 2σ significance, assuming a non-negligible early dark energy contribution. The precision achieved on the ΩeDE parameter from these 21 cm probes could be below O(10%).PACS numbers: 95.36.+x

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Model-independent constraints on the cosmological anisotropic stress

Cited by 67 publications

References 24 publications

BeyondΛCDM: Problems, solutions, and the road ahead

BeyondΛCDM: Problems, solutions, and the road ahead

Higgs effective potential in a perturbed Robertson-Walker background

Current constraints on early and stressed dark energy models and future 21 cm perspectives

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