545 research outputs found
Unparticle constraints from SN1987A
The existence of an unparticle sector, weakly coupled to the standard model,
would have a profound impact on supernova (SN) physics. Emission of energy into
the unparticle sector from the core of SN1987A would have significantly
shortened the observed neutrino burst. The unparticle interaction with
nucleons, neutrinos, electrons and muons is constrained to be so weak that it
is unlikely to provide any missing-energy signature at colliders. One important
exception are models where scale invariance in the hidden sector is broken by
the Higgs vacuum expectation value. In this case the SN emission is suppressed
by threshold effects.Comment: 4 pages, 1 figur
Axion hot dark matter bounds
We derive cosmological limits on two-component hot dark matter consisting of
neutrinos and axions. We restrict the large-scale structure data to the safely
linear regime, excluding the Lyman-alpha forest. We derive Bayesian credible
regions in the two-parameter space consisting of m_a and sum(m_nu).
Marginalizing over sum(m_nu) provides m_a<1.02 eV (95% CL). In the absence of
axions the same data and methods give sum(m_nu)< 0.63 eV (95% CL).Comment: Contribution to Proc. 4th Patras Workshop on Axions, WIMPs and WISPs
(18-21 June 2008, DESY
Getting leverage on inflation with a large photometric redshift survey
We assess the potential of a future large-volume photometric redshift survey
to constrain observational inflationary parameters using three large-scale
structure observables: the angular shear and galaxy power spectra, and the
cluster mass function measured through weak lensing. When used in combination
with Planck-like CMB measurements, we find that the spectral index n_s can be
constrained to a 1 sigma precision of up to 0.0025. The sensitivity to the
running of the spectral index can potentially improve to 0.0017, roughly a
factor of five better than the present 1 sigma~constraint from Planck and
auxiliary CMB data, allowing us to test the assumptions of the slow-roll
scenario with unprecedented accuracy. Interestingly, neither CMB+shear nor
CMB+galaxy nor CMB+clusters alone can achieve this level of sensitivity; it is
the combined power of all three probes that conspires to break the different
parameter degeneracies inherent in each type of observations. We make our
forecast software publicly available via download or upon request from the
authors.Comment: 22 pages, 6 figures; the forecast software can be downloaded from
http://jhamann.web.cern.ch/jhamann/simdata/simdata.tar.g
Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes
We revisit the issue of ripples in the primordial power spectra caused by
trans-Planckian physics, and the potential for their detection by future
cosmological probes. We find that for reasonably large values of the first
slow-roll parameter epsilon (> 0.001), a positive detection of trans-Planckian
ripples can be made even if the amplitude is as low as 10^-4. Data from the
Large Synoptic Survey Telescope (LSST) and the proposed future 21 cm survey
with the Fast Fourier Transform Telescope (FFTT) will be particularly useful in
this regard. If the scale of inflation is close to its present upper bound, a
scale of new physics as high as 0.2 M_Planck could lead to observable
signatures.Comment: 20 pages, 3 figures, uses iopart.cls; v2: 21 pages, added references,
to appear in JCA
Axion hot dark matter bounds after Planck
We use cosmological observations in the post-Planck era to derive limits on
thermally produced cosmological axions. In the early universe such axions
contribute to the radiation density and later to the hot dark matter fraction.
We find an upper limit m_a < 0.67 eV at 95% C.L. after marginalising over the
unknown neutrino masses, using CMB temperature and polarisation data from
Planck and WMAP respectively, the halo matter power spectrum extracted from
SDSS-DR7, and the local Hubble expansion rate H_0 released by the Carnegie
Hubble Program based on a recalibration of the Hubble Space Telescope Key
Project sample. Leaving out the local H_0 measurement relaxes the limit
somewhat to 0.86 eV, while Planck+WMAP alone constrain the axion mass to 1.01
eV, the first time an upper limit on m_a has been obtained from CMB data alone.
Our axion limit is therefore not very sensitive to the tension between the
Planck-inferred H_0 and the locally measured value. This is in contrast with
the upper limit on the neutrino mass sum, which we find here to range from 0.27
eV at 95% C.L. combining all of the aforementioned observations, to 0.84 eV
from CMB data alone.Comment: 20 pages, 8 figures, matches version published in JCAP 1310 (2013)
02
Neutrino mass from future high redshift galaxy surveys: sensitivity and detection threshold
We calculate the sensitivity of future cosmic microwave background probes and large scale structure measurements from galaxy redshift surveys to the neutrino mass. We find that, for minimal models with few parameters, a measurement of the matter power spectrum over a large range of redshifts has more constraining power than a single measurement at low redshifts. However, this improvement in sensitivity does not extend to larger models. We also quantify how the non-Gaussian nature of the posterior distribution function with respect to the individual cosmological parameter influences such quantities as the sensitivity and the detection threshold. For realistic assumptions about future large scale structure data, the minimum detectable neutrino mass at 95 % C.L. is about 0.05 eV in the context of a minimal 8-parameter cosmological model. In a more general model framework, however, the detection threshold can increase by as much as a factor of three
Observational bounds on the cosmic radiation density
We consider the inference of the cosmic radiation density, traditionally
parameterised as the effective number of neutrino species N_eff, from precision
cosmological data. Paying particular attention to systematic effects, notably
scale-dependent biasing in the galaxy power spectrum, we find no evidence for a
significant deviation of N_eff from the standard value of N_eff^0=3.046 in any
combination of cosmological data sets, in contrast to some recent conclusions
of other authors. The combination of all available data in the linear regime
prefers, in the context of a ``vanilla+N_eff'' cosmological model,
1.1<N_eff<4.8 (95% C.L.) with a best-fit value of 2.6. Adding data at smaller
scales, notably the Lyman-alpha forest, we find 2.2<N_eff<5.8 (95% C.L.) with
3.8 as the best fit. Inclusion of the Lyman-alpha data shifts the preferred
N_eff upwards because the sigma_8 value derived from the SDSS Lyman-alpha data
is inconsistent with that inferred from CMB. In an extended cosmological model
that includes a nonzero mass for N_eff neutrino flavours, a running scalar
spectral index and a w parameter for the dark energy, we find 0.8<N_eff<6.1
(95% C.L.) with 3.0 as the best fit.Comment: 23 pages, 3 figures, uses iopart.cls; v2: 1 new figure, references
added, matches published versio
Cosmology seeking friendship with sterile neutrinos
Precision cosmology and big-bang nucleosynthesis mildly favor extra radiation
in the universe beyond photons and ordinary neutrinos, lending support to the
existence of low-mass sterile neutrinos. We use the WMAP 7-year data,
small-scale CMB observations from ACBAR, BICEP and QuAD, the SDSS 7th data
release, and measurement of the Hubble parameter from HST observations to
derive credible regions for the assumed common mass scale m_s and effective
number N_s of thermally excited sterile neutrino states. Our results are
compatible with the existence of one or perhaps two sterile neutrinos, as
suggested by LSND and MiniBooNE, if m_s is in the sub-eV range.Comment: 4 pages, 1 figure, matches version published in PR
Cosmological axion bounds
We discuss current cosmological constraints on axions, as well as future
sensitivities. Bounds on axion hot dark matter are discussed first, and
subsequently we discuss both current and future sensitivity to models in which
axions play the role as cold dark matter, but where the Peccei-Quinn symmetry
is not restored during reheating.Comment: 4 pages, 2 figures, To appear in the proceedings of 5th Patras
Workshop on Axions, WIMPs and WISPs, Durham 13-17 July 200
Dark energy properties from large future galaxy surveys
We perform a detailed forecast on how well a {\sc Euclid}-like survey will be
able to constrain dark energy and neutrino parameters from a combination of its
cosmic shear power spectrum, galaxy power spectrum, and cluster mass function
measurements. We find that the combination of these three probes vastly
improves the survey's potential to measure the time evolution of dark energy.
In terms of a dark energy figure-of-merit defined as , we find a value of 690 for {\sc Euclid}-like data combined
with {\sc Planck}-like measurements of the cosmic microwave background (CMB)
anisotropies in a 10-dimensional cosmological parameter space, assuming a
CDM fiducial cosmology. For the more commonly used 7-parameter model,
we find a figure-of-merit of 1900 for the same data combination. We consider
also the survey's potential to measure dark energy perturbations in models
wherein the dark energy is parameterised as a fluid with a nonstandard
non-adiabatic sound speed, and find that in an \emph{optimistic} scenario in
which deviates by as much as is currently observationally allowed from
, models with and can be distinguished at more than significance. We emphasise that
constraints on the dark energy sound speed from cluster measurements are
strongly dependent on the modelling of the cluster mass function; significantly
weaker sensitivities ensue if we modify our model to include fewer features of
nonlinear dark energy clustering. Finally, we find that the sum of neutrino
masses can be measured with a precision of 0.015~eV, (abridged)Comment: 26 pages, 5 figures, matches JCAP versio
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