3,940 research outputs found
Ultra-Light Dark Matter in Ultra-Faint Dwarf Galaxies
Cold Dark Matter (CDM) models struggle to match the observations at galactic
scales. The tension can be reduced either by dramatic baryonic feedback effects
or by modifying the particle physics of CDM. Here, we consider an ultra-light
scalar field DM particle manifesting a wave nature below a DM particle
mass-dependent Jeans scale. For DM mass , this scenario
delays galaxy formation and avoids cusps in the center of the dark matter
haloes. We use new measurements of half-light mass in ultra-faint dwarf
galaxies Draco II and Triangulum II to estimate the mass of the DM particle in
this model. We find that if the stellar populations are within the core of the
density profile then the data are in agreement with a wave dark matter model
having a DM particle with . The presence
of this extremely light particle will contribute to the formation of a central
solitonic core replacing the cusp of a Navarro-Frenk-White profile and bringing
predictions closer to observations of cored central density in dwarf galaxies.Comment: matching version accepted by MNRA
Distinguishing between Neutrinos and time-varying Dark Energy through Cosmic Time
We study the correlations between parameters characterizing neutrino physics
and the evolution of dark energy. Using a fluid approach, we show that
time-varying dark energy models exhibit degeneracies with the cosmic neutrino
background over extended periods of the cosmic history, leading to a degraded
estimation of the total mass and number of species of neutrinos. We investigate
how to break degeneracies and combine multiple probes across cosmic time to
anchor the behaviour of the two components. We use Planck CMB data and BAO
measurements from the BOSS, SDSS and 6dF surveys to present current limits on
the model parameters, and then forecast the future reach from the CMB Stage-4
and DESI experiments. We show that a multi-probe analysis of current data
provides only marginal improvement on the determination of the individual
parameters and no reduction of the correlations. Future observations will
better distinguish the neutrino mass and preserve the current sensitivity to
the number of species even in case of a time-varying dark energy component.Comment: 10 pages, 7 figures, minor updates to match the version accepted by
Phys. Rev.
Future CMB tests of dark matter: ultra-light axions and massive neutrinos
Measurements of cosmic microwave background (CMB) anisotropies provide strong
evidence for the existence of dark matter and dark energy. They can also test
its composition, probing the energy density and particle mass of different
dark-matter and dark-energy components. CMB data have already shown that
ultra-light axions (ULAs) with mass in the range compose a fraction of the cosmological critical
density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment
(assuming a 1 arcmin beam and noise levels over a sky
fraction of 0.4) to the density of ULAs and other dark-sector components is
assessed. CMB-S4 data should be times more sensitive to the ULA
energy-density than Planck data alone, across a wide range of ULA masses
, and will probe axion decay constants of
, at the grand unified scale. CMB-S4 could
improve the CMB lower bound on the ULA mass from to
, nearing the mass range probed by dwarf galaxy abundances
and dark-matter halo density profiles. These improvements will allow for a
multi- detection of percent-level departures from CDM over a wide range
of masses. Much of this improvement is driven by the effects of weak
gravitational lensing on the CMB, which breaks degeneracies between ULAs and
neutrinos. We also find that the addition of ULA parameters does not
significantly degrade the sensitivity of the CMB to neutrino masses. These
results were obtained using the axionCAMB code (a modification to the CAMB
Boltzmann code), presented here for public use.Comment: 16 pages, 12 figures. The axionCAMB code will be available online at
http://github.com/dgrin1/axionCAMB from 1 August 201
Complementing the ground-based CMB-S4 experiment on large scales with the PIXIE satellite
We present forecasts for cosmological parameters from future cosmic microwave background (CMB) data measured by the stage-4 (S4) generation of ground-based experiments in combination with large-scale anisotropy data from the PIXIE satellite. We demonstrate the complementarity of the two experiments and focus on science targets that benefit from their combination. We show that a cosmic-variance-limited measurement of the optical depth to reionization provided by PIXIE, with error σ(τ)=0.002, is vital for enabling a 5σ detection of the sum of the neutrino masses when combined with a CMB-S4 lensing measurement and with lower-redshift constraints on the growth of structure and the distance-redshift relation. Parameters characterizing the epoch of reionization will also be tightly constrained; PIXIE’s τ constraint converts into σ(zre)=0.2 for the mean time of reionization, and a kinematic Sunyaev-Zel’dovich measurement from S4 gives σ(Δzre)=0.03 for the duration of reionization. Both PIXIE and S4 will put strong constraints on primordial tensor fluctuations, vital for testing early-Universe models, and will do so at distinct angular scales. We forecast σ(r)≈5×10−4 for a signal with a tensor-to-scalar ratio r=10−3, after accounting for diffuse foreground removal and delensing. The wide and dense frequency coverage of PIXIE results in an expected foreground-degradation factor on r of only ≈25%. By measuring large and small scales PIXIE and S4 will together better limit the energy injection at recombination from dark matter annihilation, with pann<0.09×10−6 m3/s/kg projected at 95% confidence. Cosmological parameters measured from the damping tail with S4 will be best constrained by polarization, which has the advantage of minimal contamination from extragalactic emission
Entanglement of Stationary States in the Presence of Unstable Quasiparticles
The effect of unstable quasiparticles in the out-of-equilibrium dynamics of
certain integrable systems has been the subject of several recent studies. In
this paper we focus on the stationary value of the entanglement entropy
density, its growth rate, and related functions, after a quantum quench. We
consider several quenches, each of which is characterised by a corresponding
squeezed coherent state. In the quench action approach, the coherent state
amplitudes become input data that fully characterise the large-time
stationary state, thus also the corresponding Yang-Yang entropy. We find that,
as function of the mass of the unstable particle, the entropy growth rate has a
global minimum signalling the depletion of entropy that accompanies a slowdown
of stable quasiparticles at the threshold for the formation of an unstable
excitation. We also observe a separation of scales governed by the interplay
between the mass of the unstable particle and the quench parameter, separating
a non-interacting regime described by free fermions from an interacting regime
where the unstable particle is present. This separation of scales leads to a
double-plateau structure of many functions, where the relative height of the
plateaux is related to the ratio of central charges of the UV fixed points
associated with the two regimes, in full agreement with conformal field theory
predictions. The properties of several other functions of the entropy and its
growth rate are also studied in detail, both for fixed quench parameter and
varying unstable particle mass and viceversa
Update on quetiapine in the treatment of bipolar disorder: results from the BOLDER studies
The essential features of bipolar affective disorder involve the cyclical occurrence of high (manic or hypomanic episodes) and low mood states. Depressive episodes in both bipolar I and II disorder are more numerous and last for longer duration than either manic or hypomanic episodes. In addition depressive episodes are associated with higher morbidity and mortality. While multiple agents, including all 5 atypical antipsychotics, have demonstrated efficacy and earned US FDA indication for manic phase of bipolar illness, the acute treatment of bipolar depression is less well-studied. The first treatment approved by the US FDA for acute bipolar depression was the combination of the atypical antipsychotic olanzapine and the antidepressant fluoxetine. Recently, quetiapine monotherapy has demonstrated efficacy in the treatment of depressive episodes associated with both bipolar I and II disorder and has earned US FDA indication for the same
3D simulations of Einstein's equations: symmetric hyperbolicity, live gauges and dynamic control of the constraints
We present three-dimensional simulations of Einstein equations implementing a
symmetric hyperbolic system of equations with dynamical lapse. The numerical
implementation makes use of techniques that guarantee linear numerical
stability for the associated initial-boundary value problem. The code is first
tested with a gauge wave solution, where rather larger amplitudes and for
significantly longer times are obtained with respect to other state of the art
implementations. Additionally, by minimizing a suitably defined energy for the
constraints in terms of free constraint-functions in the formulation one can
dynamically single out preferred values of these functions for the problem at
hand. We apply the technique to fully three-dimensional simulations of a
stationary black hole spacetime with excision of the singularity, considerably
extending the lifetime of the simulations.Comment: 21 pages. To appear in PR
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