1,815 research outputs found
Cosmological constraints on neutrino self-interactions with a light mediator
If active neutrinos undergo non-standard (`secret') interactions (NSI)
the cosmological evolution of the neutrino fluid might be altered, leaving an
imprint in cosmological observables. We use the latest publicly available CMB
data from Planck to constrain NSI inducing scattering, under the
assumption that the mediator of the secret interaction is very light. We
find that the effective coupling constant of the interaction, , is constrained at (95\% credible interval), which stregthens to
when Planck non-baseline small-scale
polarization is considered. Our findings imply that after decoupling at
MeV, cosmic neutrinos are free streaming at redshifts , or
if small-scale polarization is included. These bounds are only
marginally improved when data from geometrical expansion probes are included in
the analysis to complement Planck. We also find that the tensions between CMB
and low-redshift measurements of the expansion rate and the amplitude of
matter fluctuations are not significantly reduced. Our results are
independent on the underlying particle physics model as long as is very
light. Considering a model with Majorana neutrinos and a pseudoscalar mediator
we find that the coupling constant of the secret interaction is constrained
at . By further assuming that the pseudoscalar
interaction comes from a dynamical realization of the see-saw mechanism, as in
Majoron models, we can bound the scale of lepton number breaking as
.Comment: V2. Replaced to match version accepted for publication in PRD. Added
more detailed discussion about parameter degeneracies. 14 pages, 6 figures, 3
table
Decaying warm dark matter and neutrino masses
Neutrino masses may arise from spontaneous breaking of ungauged lepton
number. Due to quantum gravity effects the associated Goldstone boson - the
majoron - will pick up a mass. We determine the lifetime and mass required by
cosmic microwave background observations so that the massive majoron provides
the observed dark matter of the Universe. The majoron DDM scenario fits nicely
in models where neutrino masses arise a la seesaw, and may lead to other
possible cosmological implications.Comment: 4 pages, 3 figures. Replaced to match published version. Minor
changes made to address referees' comments. References adde
Can the WIMP annihilation boost factor be boosted by the Sommerfeld enhancement?
We demonstrate that the Sommerfeld correction to CDM annihilations can be
appreciable if even a small component of the dark matter is extremely cold.
Subhalo substructure provides such a possibility given that the smallest clumps
are relatively cold and contain even colder substructure due to incomplete
phase space mixing. Leptonic channels can be enhanced for plausible models and
the solar neighbourhood boost required to account for PAMELA/ATIC data is
plausibly obtained, especially in the case of a few TeV mass neutralino for
which the Sommerfeld-corrected boost is found to be Saturation
of the Sommerfeld effect is shown to occur below thereby
constraining the range of contributing substructures to be above We find that the associated diffuse gamma ray signal from
annihilations would exceed EGRET constraints unless the channels annihilating
to heavy quarks or to gauge bosons are suppressed. The lepton channel gamma
rays are potentially detectable by the FERMI satellite, not from the inner
galaxy where substructures are tidally disrupted, but rather as a
quasi-isotropic background from the outer halo, unless the outer substructures
are much less concentrated than the inner substructures and/or the CDM density
profile out to the virial radius steepens significantly.Comment: 8 pages, 5 figures. References added. Replaced to match published
versio
Dynamic Algorithms for the Massively Parallel Computation Model
The Massive Parallel Computing (MPC) model gained popularity during the last
decade and it is now seen as the standard model for processing large scale
data. One significant shortcoming of the model is that it assumes to work on
static datasets while, in practice, real-world datasets evolve continuously. To
overcome this issue, in this paper we initiate the study of dynamic algorithms
in the MPC model.
We first discuss the main requirements for a dynamic parallel model and we
show how to adapt the classic MPC model to capture them. Then we analyze the
connection between classic dynamic algorithms and dynamic algorithms in the MPC
model. Finally, we provide new efficient dynamic MPC algorithms for a variety
of fundamental graph problems, including connectivity, minimum spanning tree
and matching.Comment: Accepted to the 31st ACM Symposium on Parallelism in Algorithms and
Architectures (SPAA 2019
A general relativistic model for the light propagation in the gravitational field of the Solar System: the dynamical case
Modern astrometry is based on angular measurements at the micro-arcsecond
level. At this accuracy a fully general relativistic treatment of the data
reduction is required. This paper concludes a series of articles dedicated to
the problem of relativistic light propagation, presenting the final
microarcsecond version of a relativistic astrometric model which enable us to
trace back the light path to its emitting source throughout the non-stationary
gravity field of the moving bodies in the Solar System. The previous model is
used as test-bed for numerical comparisons to the present one. Here we also
test different versions of the computer code implementing the model at
different levels of complexity to start exploring the best trade-off between
numerical efficiency and the micro-arcsecond accuracy needed to be reached.Comment: 40 pages, 5 figures. Accepted for publication on The Astrophysical
Journal. Manuscript prepared with AASLaTeX macros v.5.
Fertilizer Nitrogen and Morphogenetic Response in Avena Sativa and Lolium Multiflorum
A field experiment was carried out at the EEA Balcarce, INTA, Argentina (37° 45’LS, 58° 18’LW) to determine whether Leaf Appearance Rate (LAR) was affected by N fertilization in Italian ryegrass (Lolium multiflorum Lam.) and forage oats (Avena sativa). N treatments (0, 50, 100, 150, 200 and 250 kg N ha-1) were applied in winter 1995, after a defoliation. Subsequently, number of leaves per tiller was determined on 45 labelled tillers in each treatment twice a week. LAR was calculated as the slope of the linear regression of number of leaves on thermal time (air temperature, base 0 °C). Leaf appearance was more rapid with N fertilization in ryegrass, but was not in oats. In situations in which N applied did not affect LAR similar phyllochrons of 112 (± 4,6) and 113 (± 3,6) GDD leaf1 were found for Italian ryegrass and oats, respectively
The Effect of the Perceived Utility of a Management Control System with a Broad Scope on the Use of Food Waste Information and on Financial and Non-Financial Performances in Restaurants
The purpose of this study is to analyse the effect of the perceived utility of a management control system with a broad scope on the use of food waste information and on financial and non-financial performances in restaurants. To collect data, a questionnaire was administered in Brazilian restaurants. Data from 206 restaurants were analysed with structural equation modelling, which was performed with SmartPLS software. The results reveal that a management control system of broad scope, which includes non-financial information, is oriented towards the future, and contains an external and long-term focus, assists in the use of information on food waste. In addition, the use of information about food waste by managers improves the financial and non-financial performance of restaurants. The study contributes to the literature by showing that broader information systems are effective in managing food waste, and they can also contribute to improving performance
Solving an open problem about the G-Drazin partial order
[EN] G-Drazin inverses and the G-Drazin partial order for square matrices have been both recently introduced by Wang and Liu. They proved the following implication: If A is below B under the G-Drazin partial order, then any G-Drazin inverse of B is also a G-Drazin inverse of A. However, this necessary condition could not be stated as a characterization and the validity (or not) of the converse implication was posed as an open problem. In this paper, this problem is completely solved. It is obtained that the converse, in general, is false, and a form to construct counterexamples is provided. It is also proved that the converse holds under an additional condition (which is also necessary) as well as for some special cases of matrices.Partially supported by Universidad Nacional de RÃo Cuarto (Grant PPI
18/C472), CONICET (Grant PIP 112-201501-00433CO), and by ANPCyT (Grant PICT 2018-03492)
Partially supported by Universidad Nacional de La Pampa, Facultad de IngenierÃa (Grant
Resol. Nro. 155/14)
Partially supported by Ministerio de EconomÃa, Industria y Competitividad of Spain (Grant Red
de Excelencia MTM2017-90682-REDT), and by Universidad Nacional del Sur of Argentina (Grant 24/L108)Ferreyra, DE.; Lattanzi, M.; Levis, FE.; Thome, N. (2020). Solving an open problem about the G-Drazin partial order. The Electronic Journal of Linear Algebra. 36:55-66. http://hdl.handle.net/10251/161871S55663
Astrometry with "Carte du Ciel" plates, San Fernando zone. I. Digitization and measurement using a flatbed scanner
We present an original method of digitizing and astrometrically reducing
"Carte du Ciel" plate material using an inexpensive flatbed scanner, to
demonstrate that for this material there is an alternative to more specialized
measuring machines that are very few in number and thus not readily available.
The sample of plates chosen to develop this method are original "Carte du Ciel"
plates of the San Fernando zone, photographic material with a mean epoch
1903.6, and a limiting photographic magnitude ~14.5, covering the declination
range of -10 < dec < -2. Digitization has been made using a commercial flatbed
scanner, demonstrating the internal precision that can be attained with such a
device. A variety of post-scan corrections are shown to be necessary. In
particular, the large distortion introduced by the non-uniform action of the
scanner is modelled using multiple scans of each plate. We also tackle the
specific problems associated with the triple-exposure images on some plates and
the grid lines present on all. The final measures are reduced to celestial
coordinates using the Tycho-2 Catalogue. The internal precision obtained over a
single plate, 3microns ~ 0.18" in each axis, is comparable to what is realized
with similar plate material using slower, less affordable, and less widely
available conventional measuring machines, such as a PDS microdensitometer. The
accuracy attained over large multi-plate areas, employing an overlapping plate
technique, is estimated at 0.2".Comment: 16 pages, 19 figures and 3 tables. Accepted for publication in A&
Inhibition of DNA damage response at telomeres improves the detrimental phenotypes of Hutchinson–Gilford Progeria Syndrome
Hutchinson–Gilford progeria syndrome (HGPS) is a genetic disorder characterized by premature aging features. Cells from HGPS patients express progerin, a truncated form of Lamin A, which perturbs cellular homeostasis leading to nuclear shape alterations, genome instability, heterochromatin loss, telomere dysfunction and premature entry into cellular senescence. Recently, we reported that telomere dysfunction induces the transcription of telomeric non-coding RNAs (tncRNAs) which control the DNA damage response (DDR) at dysfunctional telomeres. Here we show that progerin-induced telomere dysfunction induces the transcription of tncRNAs. Their functional inhibition by sequence-specific telomeric antisense oligonucleotides (tASOs) prevents full DDR activation and premature cellular senescence in various HGPS cell systems, including HGPS patient fibroblasts. We also show in vivo that tASO treatment significantly enhances skin homeostasis and lifespan in a transgenic HGPS mouse model. In summary, our results demonstrate an important role for telomeric DDR activation in HGPS progeroid detrimental phenotypes in vitro and in vivo
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