1,975 research outputs found
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
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
The Measure of Cosmological Parameters
New, large, ground and space telescopes are contributing to an exciting and
rapid period of growth in observational cosmology. The subject is now far from
its earlier days of being data-starved and unconstrained, and new data are
fueling a healthy interplay between observations and experiment and theory. I
briefly review here the status of measurements of a number of quantities of
interest in cosmology: the Hubble constant, the total mass-energy density, the
matter density, the cosmological constant or dark energy component, and the
total optical background light.Comment: 12 pages, 4 figures, to be published in "2001: A Spacetime Odyssey:
Proceedings of the Inaugural Conference of the Michigan Center for
Theoretical Physics", Michael J. Duff & James T. Liu, eds., (World
Scientific, Singapore), in pres
ARGO CMB Anisotropy Measurement Constraints on Open and Flat-Lambda CDM Cosmogonies
We use data from the ARGO cosmic microwave background (CMB) anisotropy
experiment to constrain cosmogonies. We account for the ARGO beamwidth and
calibration uncertainties, and marginalize over the offset removed from the
data. Our derived amplitudes of the CMB anisotropy detected by the ARGO
experiment are smaller than those derived previously.
We consider open and spatially-flat-Lambda cold dark matter cosmogonies, with
clustered-mass density parameter Omega_0 in the range 0.1-1, baryonic-mass
density parameter Omega_B in the range (0.005-0.029)h^{-2}, and age of the
universe t_0 in the range (10--20) Gyr. Marginalizing over all parameters but
Omega_0, the ARGO data favors an open (spatially-flat-Lambda) model with
Omega_0= 0.23 (0.1). However, these numerical values are model dependent.
At the 2 sigma confidence level model normalizations deduced from the ARGO
data are consistent with those drawn from the UCSB South Pole 1994, MAX 4+5,
White Dish, and SuZIE data sets. The ARGO open model normalizations are also
consistent with those deduced from the DMR data. However, for most
spatially-flat-Lambda models the DMR normalizations are more than 2 sigma above
the ARGO ones.Comment: 21 pages of latex. Uses aaspp4.sty. 8 figures included. ApJ in pres
Constraining Modified Gravity with Euclid
Future proposed satellite missions as Euclid can offer the opportunity to
test general relativity on cosmic scales through mapping of the galaxy weak
lensing signal. In this paper we forecast the ability of these experiments to
constrain modified gravity scenarios as those predicted by scalar-tensor and
theories. We found that Euclid will improve constraints expected from
the PLANCK satellite on these modified gravity models by two orders of
magnitude. We discuss parameter degeneracies and the possible biases introduced
by modified gravity
Postural control deficit during Sit-To-Walk in patients with Parkinson\u2019s Disease and Freezing of Gait
Introduction
The intricate linkage between Freezing of Gait (FoG) and postural control in Parkinson's disease (PD) is unclear. We analyzed the impact of FoG on dynamic postural control.
Methods
24 PD patients, 12 with (PD\u202f+\u202fFoG), 12 without FoG (PD-FoG), and 12 healthy controls, were assessed in ON state. Mobility and postural control were measured with clinical scales (UPDRS III, BBS, MPAS) and with kinematic and kinetic analysis during three tasks, characterized by levels of increasing difficulty to plan sequential movement of postural control: walk (W), gait initiation (GI) and sit-to-walk (STW).
Results
The groups were balanced by age, disease duration, disease severity, mobility and balance. During STW, the spatial distribution of COP trajectories in PD\u202f+\u202fFoG patients are spread over medial-lateral space more than in the PD-FoG (p\u202f<\u202f.001). Moreover, the distribution of COP positions. in the transition between sit-to-stand and gait initiation, is not properly shifted toward the leading leg, as in PD-FoG and healthy controls, but it is more centrally dispersed (p\u202f<\u202f.01) with a delayed weight forward progression (p\u202f<\u202f.05). In GI task and walk task, COM and COP differences are less evident and even absent between PD patients.
Conclusion
PD\u202f+\u202fFoG show postural control differences in STW, compared with PD-FoG and healthy. Different spatial distribution of COP trajectories, between two PD groups are probably due to a deficit to plan postural control during a more demanding motor pattern, such as STW
Multi-mode TES bolometer optimization for the LSPE-SWIPE instrument
In this paper we explore the possibility of using transition edge sensor
(TES) detectors in multi-mode configuration in the focal plane of the Short
Wavelength Instrument for the Polarization Explorer (SWIPE) of the
balloon-borne polarimeter Large Scale Polarization Explorer (LSPE) for the
Cosmic Microwave Background (CMB) polarization. This study is motivated by the
fact that maximizing the sensitivity of TES bolometers, under the augmented
background due to the multi-mode design, requires a non trivial choice of
detector parameters. We evaluate the best parameter combination taking into
account scanning strategy, noise constraints, saturation power and operating
temperature of the cryostat during the flight.Comment: in Journal of Low Temperature Physics, 05 January 201
Amplitudes of thermal and kinetic Sunyaev-Zel'dovich signals from small-scale CMB anisotropies
While the arcminute-scale Cosmic Microwave Background (CMB) anisotropies are
due to secondary effects, point sources dominate the total anisotropy power
spectrum. At high frequencies the point sources are primarily in the form of
dusty, star-forming galaxies. Both Herschel and Planck have recently measured
the anisotropy power spectrum of cosmic infrared background (CIB) generated by
dusty, star-forming galaxies from degree to sub-arcminute angular scales,
including the non-linear clustering of these galaxies at multipoles of 3000 to
6000 relevant to CMB secondary anisotropy studies. We scale the CIB angular
power spectra to CMB frequencies and interpret the combined WMAP-7 year and
arcminute-scale Atacama Cosmology Telescope (ACT) and South Pole Telescope
(SPT) CMB power spectra measurements to constrain the Sunyaev-Zel'dovich (SZ)
effects. Allowing the CIB clustering amplitude to vary, we constrain the
amplitudes of thermal and kinetic SZ power spectra at 150 GHz.Comment: 8 pages, 3 figures, 2 table
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