975 research outputs found
Aspects of production and kinetic decoupling of non-thermal dark matter
We reconsider non-thermal production of WIMP dark matter in a systematic way
and using a numerical code for accurate computations of dark matter relic
densities. Candidates with large pair annihilation rates are favored,
suggesting a connection with the anomalies in the lepton cosmic-ray flux
detected by Pamela and Fermi. Focussing on supersymmetric models we will
consider the impact of non-thermal production on the preferred mass scale for
dark matter neutralinos. We have also developed a new formalism to solve the
Boltzmann's equation for a system of coannihilating species without assuming
kinetic equilibrium and applied it to the case of pure Winos.Comment: Proceedings for the conference TAUP 201
A Tutorial on Estimating Time-Varying Vector Autoregressive Models
Time series of individual subjects have become a common data type in
psychological research. These data allow one to estimate models of
within-subject dynamics, and thereby avoid the notorious problem of making
within-subjects inferences from between-subjects data, and naturally address
heterogeneity between subjects. A popular model for these data is the Vector
Autoregressive (VAR) model, in which each variable is predicted as a linear
function of all variables at previous time points. A key assumption of this
model is that its parameters are constant (or stationary) across time. However,
in many areas of psychological research time-varying parameters are plausible
or even the subject of study. In this tutorial paper, we introduce methods to
estimate time-varying VAR models based on splines and kernel-smoothing
with/without regularization. We use simulations to evaluate the relative
performance of all methods in scenarios typical in applied research, and
discuss their strengths and weaknesses. Finally, we provide a step-by-step
tutorial showing how to apply the discussed methods to an openly available time
series of mood-related measurements
Inequalities for differences of Dyson's rank for all odd moduli
Kathrin Bringmann (Mathematisches Institut, UniversitÀt Köln, Weyertal 86-90, D-50931 Köln, Germany)
Ben Kane (Wiskunde Afdeling, Radboud Universiteit, Postbus 9010, 6500 GL, Nijmegen, Netherlands)postprin
New identities involving sums of the tails related to real quadratic fields
In previous work, the authors discovered new examples of q-hypergeometric series related to the arithmetic of and . Building on this work, we construct in this paper sum of the tails identities for which some which some of these functions occur as error terms. As an application, we obtain formulas for the generating function of a certain zeta functions for real quadratic fields at negative integers.postprin
Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matter
Events like inflation or phase transitions can produce large density
perturbations on very small scales in the early Universe. Probes of small
scales are therefore useful for e.g. discriminating between inflationary
models. Until recently, the only such constraint came from non-observation of
primordial black holes (PBHs), associated with the largest perturbations.
Moderate-amplitude perturbations can collapse shortly after matter-radiation
equality to form ultracompact minihalos (UCMHs) of dark matter, in far greater
abundance than PBHs. If dark matter self-annihilates, UCMHs become excellent
targets for indirect detection. Here we discuss the gamma-ray fluxes expected
from UCMHs, the prospects of observing them with gamma-ray telescopes, and
limits upon the primordial power spectrum derived from their non-observation by
the Fermi Large Area Space Telescope.Comment: 4 pages, 3 figures. To appear in J Phys Conf Series (Proceedings of
TAUP 2011, Munich
Duality and differential operators for harmonic Maass forms
Due to the graded ring nature of classical modular forms, there are many interesting relations between the coefficients of different modular forms. We discuss additional relations arising from Duality, Borcherds products, theta lifts. Using the explicit description of a lift for weakly holomorphic forms, we realize the differential operator acting on a harmonic Maass form for integers k > 2 in terms of acting on a different form. Using this interpretation, we compute the image of D k â 1. We also answer a question arising in recent work on the p-adic properties of mock modular forms. Additionally, since such lifts are defined up to a weakly holomorphic form, we demonstrate how to construct a canonical lift from holomorphic modular forms to harmonic Maass forms.postprin
P2X7 and A2A receptor endogenous activation protects against neuronal death caused by CoCl2-induced photoreceptor toxicity in the zebrafish retina
Injured retinas in mammals do not regenerate and heal with loss of function. The adult retina of zebrafish self-repairs after damage by activating cell-intrinsic mechanisms, which are regulated by extrinsic signal interactions. Among relevant regulatory extrinsic systems, purinergic signaling regulates progenitor proliferation during retinogenesis and regeneration and glia proliferation in proliferative retinopathies. ATP-activated P2X7 (P2RX7) and adenosine (P1R) receptors are involved in the progression of almost all retinopathies leading to blindness. Here, we examined P2RX7 and P1R participation in the retina regenerative response induced by photoreceptor damage caused by a specific dose of CoCl2. First, we found that treatment of uninjured retinas with a potent agonist of P2RX7 (BzATP) provoked photoreceptor damage and mitotic activation of multipotent progenitors. In CoCl2-injured retinas, blockade of endogenous extracellular ATP activity on P2RX7 caused further neurodegeneration, MĂŒller cell gliosis, progenitor proliferation, and microglia reactivity. P2RX7 inhibition in injured retinas also increased the expression of lin28a and tnfα genes, which are related to multipotent progenitor proliferation. Levels of hif1α, vegf3r, and vegfaa mRNA were enhanced by blockade of P2RX7 immediately after injury, indicating hypoxic like damage and endothelial cell growth and proliferation. Complete depletion of extracellular nucleotides with an apyrase treatment strongly potentiated cell death and progenitor proliferation induced with CoCl2. Blockade of adenosine P1 and A2A receptors (A2AR) had deleterious effects and deregulated normal timing for progenitor and precursor cell proliferation following photoreceptor damage. ATP via P2RX7 and adenosine via A2AR are survival extracellular signals key for retina regeneration in zebrafish.Fil: Medrano, Matias. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay; ArgentinaFil: Pisera Fuster, Antonella. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay; ArgentinaFil: Bernabeu, Ramon Oscar. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay; ArgentinaFil: Faillace, Maria Paula. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay; Argentin
Molecular Model of Dynamic Social Network Based on E-mail communication
In this work we consider an application of physically inspired sociodynamical model to the modelling of the evolution of email-based social network. Contrary to the standard approach of sociodynamics, which assumes expressing of system dynamics with heuristically defined simple rules, we postulate the inference of these rules from the real data and their application within a dynamic molecular model. We present how to embed the n-dimensional social space in Euclidean one. Then, inspired by the Lennard-Jones potential, we define a data-driven social potential function and apply the resultant force to a real e-mail communication network in a course of a molecular simulation, with network nodes taking on the role of interacting particles. We discuss all steps of the modelling process, from data preparation, through embedding and the molecular simulation itself, to transformation from the embedding space back to a graph structure. The conclusions, drawn from examining the resultant networks in stable, minimum-energy states, emphasize the role of the embedding process projecting the nonâmetric social graph into the Euclidean space, the significance of the unavoidable loss of information connected with this procedure and the resultant preservation of global rather than local properties of the initial network. We also argue applicability of our method to some classes of problems, while also signalling the areas which require further research in order to expand this applicability domain
Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA
The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs)
will play an important role in indirect dark matter searches. In this article,
we consider two particularly promising candidate sources for dark matter
annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study
the prospects of detecting such a signal for the soon-operating MAGIC II
telescope system as well as for the planned installation of CTA, taking special
care of describing the experimental features that affect the detectional
prospects. For the first time in such a study, we fully take into account the
effect of internal bremsstrahlung, which has recently been shown to
considerably enhance, in some cases, the gamma-ray flux at the high energies
where Atmospheric Cherenkov Telescopes operate, thus leading to significantly
harder annihilation spectra than traditionally considered. While the detection
of the spectral features introduced by internal bremsstrahlung would constitute
a smoking gun signature for dark matter annihilation, we find that for most
models the overall flux still remains at a level that will be challenging to
detect unless one adopts rather (though by no means overly) optimistic
astrophysical assumptions about the distribution of dark matter in the dwarfs.Comment: 10 pages, 4 figures, minor changes, matches the published version
(JCAP
- âŠ