240 research outputs found
Detecting the cosmological recombination signal from space
Spectral distortions of the CMB have recently experienced an increased
interest. One of the inevitable distortion signals of our cosmological
concordance model is created by the cosmological recombination process, just a
little before photons last scatter at redshift . These
cosmological recombination lines, emitted by the hydrogen and helium plasma,
should still be observable as tiny deviation from the CMB blackbody spectrum in
the cm--dm spectral bands. In this paper, we present a forecast for the
detectability of the recombination signal with future satellite experiments. We
argue that serious consideration for future CMB experiments in space should be
given to probing spectral distortions and, in particular, the recombination
line signals. The cosmological recombination radiation not only allows
determination of standard cosmological parameters, but also provides a direct
observational confirmation for one of the key ingredients of our cosmological
model: the cosmological recombination history. We show that, with present
technology, such experiments are futuristic but feasible. The potential rewards
won by opening this new window to the very early universe could be
considerable.Comment: 12 pages, 6 figures. Comments welcom
An improved limit on the neutrino mass with CMB and redshift-dependent halo bias-mass relations from SDSS, DEEP2, and Lyman-Break Galaxies
We use measurements of luminosity-dependent galaxy bias at several different
redshifts, SDSS at , DEEP2 at and LBGs at , combined with
WMAP five-year cosmic microwave background anisotropy data and SDSS Red
Luminous Galaxy survey three-dimensional clustering power spectrum to put
constraints on cosmological parameters. Fitting this combined dataset, we show
that the luminosity-dependent bias data that probe the relation between halo
bias and halo mass and its redshift evolution are very sensitive to sum of the
neutrino masses: in particular we obtain the upper limit of eV at the 95% confidence level for a
model, with a equal to (1). When we
allow the dark energy equation of state parameter to vary we find
for a general model with the 95% confidence
level upper limit on the neutrino masses at eV. The
constraint on the dark energy equation of state further improves to
when using also ACBAR and supernovae Union data, in addition
to above, with a prior on the Hubble constant from the Hubble Space Telescope.Comment: 9 pages, 6 figures, submitted to PR
Future weak lensing constraints in a dark coupled universe
Coupled cosmologies can predict values for the cosmological parameters at low
redshifts which may differ substantially from the parameters values within
non-interacting cosmologies. Therefore, low redshift probes, as the growth of
structure and the dark matter distribution via galaxy and weak lensing surveys
constitute a unique tool to constrain interacting dark sector models. We focus
here on weak lensing forecasts from future Euclid and LSST-like surveys
combined with the ongoing Planck cosmic microwave background experiment. We
find that these future data could constrain the dimensionless coupling to be
smaller than a few . The coupling parameter is strongly
degenerate with the cold dark matter energy density and the
Hubble constant .These degeneracies may cause important biases in the
cosmological parameter values if in the universe there exists an interaction
among the dark matter and dark energy sectors.Comment: 8 pages, 6 figure
Visualizing probabilistic models: Intensive Principal Component Analysis
Unsupervised learning makes manifest the underlying structure of data without
curated training and specific problem definitions. However, the inference of
relationships between data points is frustrated by the `curse of
dimensionality' in high-dimensions. Inspired by replica theory from statistical
mechanics, we consider replicas of the system to tune the dimensionality and
take the limit as the number of replicas goes to zero. The result is the
intensive embedding, which is not only isometric (preserving local distances)
but allows global structure to be more transparently visualized. We develop the
Intensive Principal Component Analysis (InPCA) and demonstrate clear
improvements in visualizations of the Ising model of magnetic spins, a neural
network, and the dark energy cold dark matter ({\Lambda}CDM) model as applied
to the Cosmic Microwave Background.Comment: 6 pages, 5 figure
CMB Polarization Systematics, Cosmological Birefringence and the Gravitational Waves Background
Cosmic Microwave Background experiments must achieve very accurate
calibration of their polarization reference frame to avoid biasing the
cosmological parameters. In particular, a wrong or inaccurate calibration might
mimic the presence of a gravitational wave background, or a signal from
cosmological birefringence, a phenomenon characteristic of several
non-standard, symmetry breaking theories of electrodynamics that allow for
\textit{in vacuo} rotation if the polarization direction of the photon.
Noteworthly, several authors have claimed that the BOOMERanG 2003 (B2K)
published polarized power spectra of the CMB may hint at cosmological
birefringence. Such analyses, however, do not take into account the reported
calibration uncertainties of the BOOMERanG focal plane. We develop a formalism
to include this effect and apply it to the BOOMERanG dataset, finding a
cosmological rotation angle . We also
investigate the expected performances of future space borne experiment, finding
that an overall miscalibration larger then for Planck and
for EPIC, if not properly taken into account, will produce a bias on the
constraints on the cosmological parameters and could misleadingly suggest the
presence of a GW background.Comment: 10 pages, 3 figure
Determining the Neutrino Mass Hierarchy with Cosmology
The combination of current large scale structure and cosmic microwave
background (CMB) anisotropies data can place strong constraints on the sum of
the neutrino masses. Here we show that future cosmic shear experiments, in
combination with CMB constraints, can provide the statistical accuracy required
to answer questions about differences in the mass of individual neutrino
species. Allowing for the possibility that masses are non-degenerate we combine
Fisher matrix forecasts for a weak lensing survey like Euclid with those for
the forthcoming Planck experiment. Under the assumption that neutrino mass
splitting is described by a normal hierarchy we find that the combination
Planck and Euclid will possibly reach enough sensitivity to put a constraint on
the mass of a single species. Using a Bayesian evidence calculation we find
that such future experiments could provide strong evidence for either a normal
or an inverted neutrino hierachy. Finally we show that if a particular neutrino
hierachy is assumed then this could bias cosmological parameter constraints,
for example the dark energy equation of state parameter, by > 1\sigma, and the
sum of masses by 2.3\sigma.Comment: 9 pages, 6 figures, 3 table
Detecting the cosmological recombination signal from space
Spectral distortions of the cosmic microwave background (CMB) have recently experienced an increased interest. One of the inevitable distortion signals of our cosmological concordance model is created by the cosmological recombination process, just a little before photons last scatter at redshift z ≃ 1100. These cosmological recombination lines, emitted by the hydrogen and helium plasma, should still be observable as tiny deviation from the CMB blackbody spectrum in the cm-dm spectral bands. In this paper, we present a forecast for the detectability of the recombination signal with future satellite experiments. We argue that serious consideration for future CMB experiments in space should be given to probing spectral distortions and, in particular, the recombination line signals. The cosmological recombination radiation not only allows determination of standard cosmological parameters, but also provides a direct observational confirmation for one of the key ingredients of our cosmological model: the cosmological recombination history. We show that, with present technology, such experiments are futuristic but feasible. The potential rewards won by opening this new window to the very early universe could be considerabl
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