4,679 research outputs found
Leptogenesis with heavy neutrino flavours: from density matrix to Boltzmann equations
Leptogenesis with heavy neutrino flavours is discussed within a density
matrix formalism. We write the density matrix equation, describing the
generation of the matter-antimatter asymmetry, for an arbitrary choice of the
right-handed (RH) neutrino masses. For hierarchical RH neutrino masses lying in
the fully flavoured regimes, this reduces to multiple-stage Boltzmann
equations. In this case we recover and extend results previously derived within
a quantum state collapse description. We confirm the generic existence of
phantom terms. However, taking into account the effect of gauge interactions,
we show that they are washed out at the production with a wash-out rate that is
halved compared to that one acting on the total asymmetry. In the N_1-dominated
scenario they cancel without contributing to the final baryon asymmetry. In
other scenarios they do not in general and they have to be taken into account.
We also confirm that there is a (orthogonal) component in the asymmetry
produced by the heavier RH neutrinos which completely escapes the washout from
the lighter RH neutrinos and show that phantom terms additionally contribute to
it. The other (parallel) component is washed out with the usual exponential
factor, even for weak washout. Finally, as an illustration, we study the two RH
neutrino model in the light of the above findings, showing that phantom terms
can contribute to the final asymmetry also in this case.Comment: 39 pages, 5 figures; v2: added Appendix and discussion in 2.2 on
lepton-antilepton flavour compositions difference (eq. (28) is a new result);
footnotes 4 and 5; new effect of gauge interactions in inducing wash-out of
phantom terms but with halved wash-out rate compared to the total asymmetry
wash-out rate; matches JCAP versio
William H. Sorrell, Attorney General of Vermont, et al. v. IMS Health Inc., et al. - Amicus Brief in Support of Petitioners
On April 26, 2011, the US Supreme Court will hear oral arguments in the Vermont data mining case, Sorrell v. IMS Health Inc. Respondents claim this is the most important commercial speech case in a decade. Petitioner (the State of Vermont) argues this is the most important medical privacy case since Whalen v. Roe.
The is an amicus brief supporting Vermont, written by law professors and submitted on behalf of the New England Journal of Medicin
Extragalactic gamma-ray signal from dark matter annihilation: an appraisal
We re-evaluate the extragalactic gamma-ray flux prediction from dark matter
annihilation in the approach of integrating over the nonlinear matter power
spectrum, extrapolated to the free-streaming scale. We provide an estimate of
the uncertainty based entirely on available N-body simulation results and
minimal theoretical assumptions. We illustrate how an improvement in the
simulation resolution, exemplified by the comparison between the Millennium and
Millennium II simulations, affects our estimate of the flux uncertainty and we
provide a "best guess" value for the flux multiplier, based on the assumption
of stable clustering for the dark matter perturbations described as a
collision-less fluid. We achieve results comparable to traditional Halo Model
calculations, but with a much simpler procedure and a more general approach, as
it relies only on one, directly measurable quantity. In addition we discuss the
extension of our calculation to include baryonic effects as modeled in
hydrodynamical cosmological simulations and other possible sources of
uncertainty that would in turn affect indirect dark matter signals. Upper limit
on the integrated power spectrum from supernovae lensing magnification are also
derived and compared with theoretical expectations.Comment: 20 pages, 9 figures, 1 table. Updated to match the published version.
New material and figures added, conclusions unchange
A fuller flavour treatment of N_2-dominated leptogenesis
We discuss N_2-dominated leptogenesis in the presence of flavour dependent effects that have hitherto been neglected, in particular the off-diagonal entries of the flavour coupling matrix that connects the total flavour asymmetries, distributed in different particle species, to the lepton and Higgs doublet asymmetries. We derive analytical formulae for the final asymmetry including the flavour coupling at the N_2-decay stage as well as at the stage of washout by the lightest right-handed neutrino N_1. We point out that in general part of the electron and muon asymmetries can completely escape the wash-out at the production and a total B-L asymmetry can be generated by the lightest RH neutrino wash-out yielding so called phantom leptogenesis. Taking of all these new effects into account can enhance the final asymmetry produced by the decays of the next-to-lightest RH neutrinos by orders of magnitude, opening up new interesting possibilities for N_2-dominated thermal eptogenesis. We illustrate these effects for two models which describe realistic neutrino masses and mixing based on sequential dominance
AGN Feedback in Galaxy Groups: the two interesting cases of AWM 4 and NGC 5044
We present AGN feedback in the interesting cases of two groups: AWM 4 and NGC
5044. AWM 4 is characterized by a combination of properties which seems to defy
the paradigm for AGN heating in cluster cores: a flat inner temperature profile
indicative of a past, major heating episode which completely erased the cool
core, as testified by the high central cooling time (> 3 Gyrs) and by the high
central entropy level (~ 50 keV cm^2), and yet an active central radio galaxy
with extended radio lobes out to 100 kpc, revealing recent feeding of the
central massive black hole. A recent Chandra observation has revealed the
presence of a compact cool corona associated with the BCG, solving the puzzle
of the apparent lack of low entropy gas surrounding a bright radio source, but
opening the question of its origin. NGC 5044 shows in the inner 10 kpc a pair
of cavities together with a set of bright filaments. The cavities are
consistent with a recent AGN outburst as also indicated by the extent of dust
and H_alpha emission even though the absence of extended 1.4 GHz emission
remains to be explained. The soft X-ray filaments coincident with H_alpha and
dust emission are cooler than those which do not correlate with optical and
infrared emission, suggesting that dust-aided cooling can contribute to the
overall cooling. For the first time sloshing cold fronts at the scale of a
galaxy group have been observed in this object.Comment: 4 pages, 1 figure, to appear in proceedings of the conference "The
Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June
2009, Madison Wisconsi
ALMA observations of molecular clouds in three group centered elliptical galaxies: NGC 5846, NGC 4636, and NGC 5044
We present new ALMA CO(2--1) observations of two well studied group-centered
elliptical galaxies: NGC~4636 and NGC~5846. In addition, we include a revised
analysis of Cycle 0 ALMA observations of the central galaxy in the NGC~5044
group that has been previously published. We find evidence that molecular gas,
in the form of off-center orbiting clouds, is a common presence in bright
group-centered galaxies (BGG). CO line widths are times broader
than Galactic molecular clouds, and using the reference Milky Way , the
total molecular mass ranges from as low as in NGC~4636
to in NGC~5044. With these parameters the virial
parameters of the molecular structures is . Complementary observations
of NGC~5846 and NGC~4636 using the ALMA Compact Array (ACA) do not exhibit any
detection of a CO diffuse component at the sensitivity level achieved by
current exposures. The origin of the detected molecular features is still
uncertain, but these ALMA observations suggest that they are the end product of
the hot gas cooling process and not the result of merger events. Some of the
molecular clouds are associated with dust features as revealed by HST dust
extinction maps suggesting that these clouds formed from dust-enhanced cooling.
The global nonlinear condensation may be triggered via the chaotic turbulent
field or buoyant uplift. The large virial parameter of the molecular structures
and correlation with the warm ()/hot () phase velocity
dispersion provide evidence that they are unbound giant molecular associations
drifting in the turbulent field, consistently with numerical predictions of the
chaotic cold accretion process. Alternatively, the observed large CO line
widths may be generated by molecular gas flowing out from cloud surfaces due to
heating by the local hot gas atmosphere.Comment: Revised version to be published in ApJ, 16 pages, 10 figures, 4
table
Application of the Preisach and Jiles–Atherton models to the simulation of hysteresis in soft magnetic alloys
his article describes the advances in unification of model descriptions of hysteresis in magnetic materials and demonstrates the equivalence of two widely accepted models, the Preisach (PM) and Jiles–Atherton (JA) models. Recently it was shown that starting from general energy relations, the JA equation for a loop branch can be derived from PM. The unified approach is here applied to the interpretation of magnetization measured in nonoriented Si–Fe steels with variable grain size ⟨s⟩, and also in as-cast and annealed Fe amorphous alloys. In the case of NO Fe–Si, the modeling parameter k defined by the volume density of pinning centers is such that k≈A+B/⟨s⟩, where the parameters A and B are related to magnetocrystalline anisotropy and grain texture. The value of k in the amorphous alloys can be used to estimate the microstructural correlation length playing the role of effective grain size in these materials
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