1,611 research outputs found
Candidates for non-baryonic dark matter
This report is a brief review of the efforts to explain the nature of
non-baryonic dark matter and of the studies devoted to the search for relic
particles. Among the different dark matter candidates, special attention is
devoted to relic neutralinos, by giving an overview of the recent calculations
of its relic abundance and detection rates in a wide variety of supersymmetric
schemes.Comment: 13 pages, 10 figures, typeset with ReVTeX, uses espcrc2.sty. Invited
review talk presented at "Topics in Astroparticle and Underground Physics
(TAUP 2001)" Laboratori Nazionali del Gran Sasso, Italy, September 8-12,
2001. References added. The paper may also be downloaded from
http://www.to.infn.it/~fornengo/proceedings/taup01.ps.g
Particle dark matter searches in the anisotropic sky
Anisotropies in the electromagnetic emission produced by dark matter
annihilation or decay in the extragalactic sky are a recent tool in the quest
for a particle dark matter evidence. We review the formalism to compute the
two-point angular power spectrum in the halo-model approach and discuss the
features and the relative size of the various auto- and cross-correlation
signals that can be envisaged for anisotropy studies. From the side of particle
dark matter signals, we consider the full multi-wavelength spectrum, from the
radio emission to X-ray and gamma-ray productions. We discuss the angular power
spectra of the auto-correlation of each of these signals and of the
cross-correlation between any pair of them. We then extend the search to
comprise specific gravitational tracers of dark matter distribution in the
Universe: weak-lensing cosmic shear, large-scale-structure matter distribution
and CMB-lensing. We have shown that cross-correlating a multi-wavelength dark
matter signal (which is a direct manifestation of its particle physics nature)
with a gravitational tracer (which is a manifestation of the presence of large
amounts of unseen matter in the Universe) may offer a promising tool to
demonstrate that what we call dark matter is indeed formed by elementary
particles.Comment: 16 pages, 11 figures. Prepared as inaugural article for Frontiers in
High-Energy and Astroparticle Physics. v2: few comments added, to appear in
Frontiers (Hypothesis and Theory Article
Prospects to verify a possible dark matter hint in cosmic antiprotons with antideuterons and antihelium
Cosmic rays are an important tool to study dark matter annihilation in our
Galaxy. Recently, a possible hint for dark matter annihilation was found in the
antiproton spectrum measured by AMS-02, even though the result might be
affected by theoretical uncertainties. A complementary way to test its dark
matter interpretation would be the observation of low-energy antinuclei in
cosmic rays. We determine the chances to observe antideuterons with GAPS and
AMS-02, and the implications for the ongoing AMS-02 antihelium searches. We
find that the corresponding antideuteron signal is within the GAPS and AMS-02
detection potential. If, more conservatively, the putative signal was
considered as an upper limit on DM annihilation, our results would indicate the
highest possible fluxes for antideuterons and antihelium compatible with
current antiproton data.Comment: 11 pages, 5 figures, matches published versio
Client-server multi-task learning from distributed datasets
A client-server architecture to simultaneously solve multiple learning tasks
from distributed datasets is described. In such architecture, each client is
associated with an individual learning task and the associated dataset of
examples. The goal of the architecture is to perform information fusion from
multiple datasets while preserving privacy of individual data. The role of the
server is to collect data in real-time from the clients and codify the
information in a common database. The information coded in this database can be
used by all the clients to solve their individual learning task, so that each
client can exploit the informative content of all the datasets without actually
having access to private data of others. The proposed algorithmic framework,
based on regularization theory and kernel methods, uses a suitable class of
mixed effect kernels. The new method is illustrated through a simulated music
recommendation system
Opinion influence and evolution in social networks: a Markovian agents model
In this paper, the effect on collective opinions of filtering algorithms
managed by social network platforms is modeled and investigated. A stochastic
multi-agent model for opinion dynamics is proposed, that accounts for a
centralized tuning of the strength of interaction between individuals. The
evolution of each individual opinion is described by a Markov chain, whose
transition rates are affected by the opinions of the neighbors through
influence parameters. The properties of this model are studied in a general
setting as well as in interesting special cases. A general result is that the
overall model of the social network behaves like a high-dimensional Markov
chain, which is viable to Monte Carlo simulation. Under the assumption of
identical agents and unbiased influence, it is shown that the influence
intensity affects the variance, but not the expectation, of the number of
individuals sharing a certain opinion. Moreover, a detailed analysis is carried
out for the so-called Peer Assembly, which describes the evolution of binary
opinions in a completely connected graph of identical agents. It is shown that
the Peer Assembly can be lumped into a birth-death chain that can be given a
complete analytical characterization. Both analytical results and simulation
experiments are used to highlight the emergence of particular collective
behaviours, e.g. consensus and herding, depending on the centralized tuning of
the influence parameters.Comment: Revised version (May 2018
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