1,921 research outputs found
Shutting the allowed mass range of the ultralight bosons with S2 star
It is well known that N-body simulations of ultralight bosons show the
formation of a solitonic dark matter core in the innermost part of the halo.
The scale length of such a soliton depends on the inverse of the mass of the
boson. On the other hand, the orbital motion of stars in the Galactic Center
depends on the distribution of matter whether be it baryonic or dark, providing
an excellent probe for the gravitational field of the region. In this Letter we
propose the S-stars in the Galactic Center as a new observational tool,
complementary to other astrophysical systems, to narrow down the range of
allowed values for an ultralight dark matter candidate boson mass. We built
mock catalogs mirroring the forthcoming astrometric and spectroscopic
observations of S2, and we used a MCMC analysis to predict the accuracy down to
which the mass of an ultralight boson may be bounded, and we showed that, once
complementary constraints are considered, this analysis will help to restrict
the allowed range of the boson mass. Our analysis forecasts the bound on the
mass of an ultralight boson to be eV at the 95% of confidence
level.Comment: 5 pages, 2 figures, 1 table, 5 appendices. Accepted for publication
in A&A Letter
Bounding the mass of ultralight bosonic Dark Matter particles with the motion of the S2 star around Sgr A*
Dark matter is undoubtedly one of the fundamental, albeit unknown, components
of the standard cosmological model. The failure to detect WIMPs, the most
promising candidate particle for cold dark matter, actually opens the way for
the exploration of viable alternatives, of which ultralight bosonic particles
with masses eV represent one of the most encouraging. Numerical
simulations have shown that such particles form solitonic cores in the
innermost parts of virialized galactic halos that are supported by internal
quantum pressure on characteristic kpc de Broglie scales. In the Galaxy,
this halo region can be probed by means of S-stars orbiting the supermassive
black hole Sagittarius A* to unveil the presence of such a solitonic core and,
ultimately, to bound the boson mass . Employing a Monte Carlo Markov
Chain algorithm, we compare the predicted orbital motion of S2 with publicly
available data and set an upper bound eV
on the boson mass, at 95 \% confidence level. When combined with other galactic
and cosmological probes, our constraints help to reduce the allowed range of
the bosonic mass to eV, at
the 95 \% confidence level, which opens the way to precision measurements of
the mass of the ultralight bosonic dark matter.Comment: 6 pages, 2 figures, 1 table. Accepted for publication on PRD.
Additional plot and related code at
http://produccioncientifica.usal.es/datos/6464bdb7a842f677be8feeb
Visualization and ontology to analyse categorical attributes in geographic metadata
No abstract availabl
Testing space-time geometries and theories of gravity at the Galactic Center with pulsar's time delay
We developed a numerical methodology to compute the fully-relativistic
propagation time of photons emitted by a pulsar in orbit around a massive
compact object, like the supermassive black hole Sagittarius A* in the Galactic
Center, whose gravitational field is described by a generic spherically
symmetric space-time. Pulsars at the Galactic Center are usually regarded as
the next major precision probe for theories of gravity, filling the current
experimental gap between horizon-scale gravity tests and those at larger
scales. We retain a completely general approach, which allows us to apply our
code to the Schwarzschild space-time (by which we successfully validate our
methodology) and to three different well-motivated alternatives to the standard
black hole paradigm. The results of our calculations highlight departures
spanning several orders of magnitudes in timing residuals, that are supposed to
be detectable with future observing facilities like the Square Kilometer Array.Comment: 15 pages, 8 figures, 1 table. Comments are welcom
Semantic Similarity Tailored on the Application Context
The paper proposes an approach to assess the semantic similarity among instances of an ontology. It aims to define a sensitive measurement of semantic similarity, which takes into account different hints hidden in the ontology definition and explicitly considers the application context. The similarity measurement is computed by analyzing, combining and extending some of the existing similarity measures and tailoring them according to the criteria induced by specific application context
The Galactic Center as a laboratory for theories of gravity and dark matter
The Galactic Center of the Milky Way, thanks to its proximity, allows to
perform astronomical observations that investigate physical phenomena at the
edge of astrophysics and fundamental physics. As such, it offers a unique
laboratory to probe gravity, where one can not only test the basic predictions
of General Relativity, but is also able to falsify theories that, over time,
have been proposed to modify or extend General Relativity; to test different
paradigms of dark matter; and to place constraints on putative models that have
been formulated as alternatives to the standard black hole paradigm in General
Relativity. In this review we provide a general overview of the history of
observations of the Galactic Center, emphasizing the importance, in particular
on the smallest-observable scales, that they had in opening a new avenue to
improve our understanding of the underlying theory of gravity in the
surrounding of a supermassive compact object.Comment: Comments and suggestions are welcome. Revised versio
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