Testing gravity using cosmic voids

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Section: Introductionmentioning

confidence: 61%

Exploring the liminality: properties of haloes and subhaloes in borderlinef(R) gravity

Shi

Han

et al. 2015

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“…those with the chameleon screening mechanism, voids are expected to be emptier than their GR counterparts. The dark matter profile of voids can therefore provide powerful test for modified gravity (Clampitt, Cai & Li 2013;Barreira et al 2015;Cai, Padilla & Li 2015;Lam et al 2015). Our measurement suggests that it is possible to do this with CMB lensing.…”

Section: S U M M a Ry A N D C O N C L U S I O N Smentioning

confidence: 74%

The lensing and temperature imprints of voids on the cosmic microwave background

Cai

Neyrinck

Mao

et al. 2016

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We have searched for the signature of cosmic voids in the CMB, in both the Planck temperature and lensing-convergence maps; voids should give decrements in both. We use ZOBOV voids from the DR12 SDSS CMASS galaxy sample. We base our analysis on N -body simulations, to avoid a posteriori bias. For the first time, we detect the signature of voids in CMB lensing: the significance is 3.2σ, close to ΛCDM in both amplitude and projected densityprofile shape. A temperature dip is also seen, at modest significance (2.3σ), with amplitude about 6 times the prediction. This temperature signal is induced mostly by voids with radius between 100 and 150 h −1 Mpc, while the lensing signal is mostly contributed by smaller voids -as expected; lensing relates directly to density, while ISW depends on gravitational potential. The void abundance in observations and simulations agree, as well. We also repeated the analysis excluding lower-significance voids: no lensing signal is detected, with an upper limit of about twice the ΛCDM prediction. But the mean temperature decrement now becomes non-zero at the 3.7σ level (similar to that found by Granett et al.), with amplitude about 20 times the prediction. However, the observed dependence of temperature on void size is in poor agreement with simulations, whereas the lensing results are consistent with ΛCDM theory. Thus, the overall tension between theory and observations does not favour non-standard theories of gravity, despite the hints of an enhanced amplitude for the ISW effect from voids.

“…The various aspects of their formation and distribution of sizes and amplitudes have been developed by Sheth & van de Weygaert (2004) in the context of hierarchical scenarios of the large-scale structure formation. Investigations of last few years show that parameters of voids can be probe for cosmology and gravity theories since the void density profile, form, intrinsic dynamics, statistical properties and their dependences on voids sizes are sensitive to models of dark energy and modified gravity (Biswas et al 2010;Bos et al 2012;Li et al 2012;Jennings et al 2013;Dai 2015;Li & Zhao 2009;Clampitt et al 2013;Cai et al 2015;Hamaus et al 2015;Falck 2016). That is why the voids are extensively investigated using modern catalogues of galaxies as well as N-body simulations (Gottloeber et al 2003;Sutter et al 2014b,c,d;Woltak et al 2016;Demchenko et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Evolution of density and velocity profiles of dark matter and dark energy in spherical voids

Novosyadlyj¹,

Tsizh²,

Kulinich³

2016

We analyse the evolution of cosmological perturbations which leads to the formation of large isolated voids in the Universe. We assume that initial perturbations are spherical and all components of the Universe (radiation, matter and dark energy) are continuous media with perfect fluid energy-momentum tensors, which interact only gravitationally. Equations of the evolution of perturbations for every component in the comoving to cosmological background reference frame are obtained from equations of energy and momentum conservation and Einstein's ones and are integrated numerically. Initial conditions are set at the early stage of evolution in the radiation-dominated epoch, when the scale of perturbation is much larger than the particle horizon. Results show how the profiles of density and velocity of matter and dark energy are formed and how they depend on parameters of dark energy and initial conditions. In particular, it is shown that final matter density and velocity amplitudes change within range ∼4-7% when the value of equation-of-state parameter of dark energy w vary in the range from -0.8 to -1.2, and change within ∼1% only when the value of effective sound speed of dark energy vary over all allowable range of its values.