1,879 research outputs found
Modeling the nonlinear clustering in modified gravity models I: A fitting formula for matter power spectrum of f(R) gravity
Based on a suite of N-body simulations of the Hu-Sawicki model of f(R)
gravity with different sets of model and cosmological parameters, we develop a
new fitting formula with a numeric code, MGHalofit, to calculate the nonlinear
matter power spectrum P(k) for the Hu-Sawicki model. We compare the MGHalofit
predictions at various redshifts (z<=1) to the f(R) simulations and find that
the accuracy on P(k) is 6% at k<1 h/Mpc and 12% at 1<k<10 h/Mpc respectively.
Based on a sensitivity study of an ongoing and a future spectroscopic survey,
we estimate the detectability of a signal of modified gravity described by the
Hu-Sawicki model using the power spectrum up to quasi-nonlinear scales.
MGHalofit is publicly available at
http://icosmology.info/website/MGHalofit.html.Comment: 28 AAS pages, 6 figures. Minor revision reflecting the accepted
version by The Astrophysical Journal Supplement Series. The MGHalofit code is
publicly available at http://icosmology.info/website/MGHalofit.htm
Constraining the dark matter-vacuum energy interaction using the EDGES 21-cm absorption signal
The recent measurement of the global 21-cm absorption signal reported by the
Experiment to Detect the Global Epoch of Reionization Signature (EDGES)
Collaboration is in tension with the prediction of the CDM model at a
significance level. In this work, we report that this tension can
be released by introducing an interaction between dark matter and vacuum
energy. We perform a model parameter estimation using a combined dataset
including EDGES and other recent cosmological observations, and find that the
EDGES measurement can marginally improve the constraint on parameters that
quantify the interacting vacuum, and that the combined dataset favours the
CDM at 68\% CL. This proof-of-the-concept study demonstrates the
potential power of future 21-cm experiments to constrain the interacting dark
energy models.Comment: 6 pages, 5 figures, 1 table; accepted for publication in Ap
Cosmological tests of gravity with latest observations
We perform observational tests of modified gravity on cosmological scales
following model-dependent and model-independent approaches using the latest
astronomical observations, including measurements of the local Hubble constant,
cosmic microwave background, the baryonic acoustic oscillations and redshift
space distortions derived from galaxy surveys including the SDSS BOSS and
eBOSS, as well as the weak lensing observations performed by the CFHTLenS team.
Using all data combined, we find a deviation from the prediction of general
relativity in both the effective Newton's constant, , and in the
gravitational slip, . The deviation is at a level in the
joint space using a two-parameter phenomenological
model for and , and it reaches a level if a general
parametrisation is used. This signal, which may be subject to unknown
observational systematics, or a sign of new physics, is worth further
investigating with forthcoming observations.Comment: 12 pages, 8 figures; ApJ accepte
Dark energy imprints on the kinematic Sunyaev-Zel'dovich signal
We investigate the imprint of dark energy on the kinetic Sunyaev-Zel'dovich
(kSZ) angular power spectrum on scales of to , and find that
the kSZ signal is sensitive to the dark energy parameter. For example, varying
the constant by 20\% around results in a change on the
kSZ spectrum; changing the dark energy dynamics parametrized by by
, a 30\% change on the kSZ spectrum is expected. We discuss the
observational aspects and develop a fitting formula for the kSZ power spectrum.
Finally, we discuss how the precise modeling of the post-reionization signal
would help the constraints on patchy reionization signal, which is crucial for
measuring the duration of reionization.Comment: 12 pages, 9 figures, 2 table
Detecting Features in the Dark Energy Equation of State: A Wavelet Approach
We study the utility of wavelets for detecting the redshift evolution of the
dark energy equation of state w(z) from the combination of supernovae, CMB and
BAO data. We show that local features in w, such as bumps, can be detected
efficiently using wavelets. To demonstrate, we first generate a mock supernovae
(SNe) data sample for a SNAP-like survey with a bump feature in w(z) hidden in,
then successfully discover it by performing a blind wavelet analysis. We also
apply our method to analyze the recently released "Constitution" SNe data,
combined with WMAP and BAO from SDSS, and find weak hints of dark energy
dynamics. Namely, we find that models with w(z) < -1 for 0.2 < z < 0.5, and
w(z)> -1 for 0.5 < z <1, are mildly favored at 95% confidence level. This is in
good agreement with several recent studies using other methods, such as
redshift binning with principal component analysis (PCA) (e.g. Zhao and Zhang,
arXiv:0908.1568)Comment: 8 pages, 6 figures. Minor changes from v1, matches the version
published in JCAP
A measurement of the Hubble constant using galaxy redshift surveys
We perform a measurement of the Hubble constant, , using the latest
baryonic acoustic oscillations (BAO) measurements from galaxy surveys of 6dFGS,
SDSS DR7 Main Galaxy Sample, BOSS DR12 sample, and eBOSS DR14 quasar sample, in
the framework of a flat CDM model. Based on the Kullback-Leibler (KL)
divergence, we examine the consistency of values derived from various
data sets. We find that our measurement is consistent with that derived from
Planck and with the local measurement of using the Cepheids and type Ia
supernovae. We perform forecasts on from future BAO measurements, and
find that the uncertainty of determined by future BAO data alone,
including complete eBOSS, DESI and Euclid-like, is comparable with that from
local measurements.Comment: 5 pages, 2 figures, 2 tables; accepted for publication in Ap
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