2,100 research outputs found
Scalar Field Dark Matter mass model and evolution of rotation curves for Lsb galaxies
We study the evolution of gas rotation curves within the scalar field dark
matter (SFDM) model. In this model the galactic haloes are astronomical
Bose-Einstein Condensate drops of scalar field. These haloes are characterized
by a constant-density core and are consistent with observed rotation curves of
dark matter dominated galaxies, a missing feature in CDM haloes resulting from
DM-only simulations. We add the baryonic component to the SFDM haloes and
simulate the evolution of the dark matter tracer in a set of grid-based
hydrodynamic simulations aimed to analyse the evolution of the rotation curves
and the gas density distribution in the case of dark matter dominated galaxies.
Previous works had found that when considering an exact analytic solution for a
static SF configuration, the free parameters of the model allows for good fits
to the rotation curves, we confirm that in our simulations but now taking into
account the evolution of the baryonic component in a static dark matter and
stellar disk potential. Including live gas is a step forward from the previous
work using SFDM, as for example, the rotation velocity of the gas is not always
exactly equal to the circular velocity of a test particle on a circular orbit.
Contrasting with the data the cored mass model presented here is preferred
instead of a cuspy one.Comment: 8 pages, 8 figures. Accepted for publication in MNRA
Empirical testing of Tsallis' Thermodynamics as a model for dark matter halos
We study a dark matter halo model from two points of view: the ``stellar
polytrope'' (SP) model coming from Tsallis' thermodynamics, and the one coming
from the Navarro-Frenk-White (NFW) paradigm. We make an appropriate comparison
between both halo models and analyzing the relations between the global
physical parameters of observed galactic disks, coming from a sample of actual
galaxies, with the ones of the unobserved dark matter halos, we conclude that
the SP model is favored over the NFW model in such a comparison.Comment: 5 pages, 1 figure, To appear in the Proceedings of X Mexican Workshop
on Particles and Fields, Morelia Michoac\'an, M\'exico, November 7-12, 200
Supersymmetry Breaking: Models of Gauge Mediation with Gauge Messengers
With the start of the LHC, it becomes increasingly important to understand
the experimental signatures that discriminate different extensions
of the standard model.
Supersymmetry (SUSY), in particular the Minimal Supersymmetric
Standard Model (MSSM), is one such extension that is specially attractive
by its simplicity and elegance. However, if this symmetry is to be
realized in nature, it must be spontaneously broken.
In this work we will try to understand the most general way in
which SUSY breaking can happen in renormalizable field theories and
the implications that this has on the minimal extension of the standard
model (MSSM) mass spectrum.
The first two chapters are the introductory material: in chapter 1
we will introduce some of the key ideas necessary to understand supersymmetric
field theories, and in chapter 2 we will briefly describe the
the simplest supersymmetric version of the Standard Model.
In chapter 3 we will focus on understanding the role of R-Symmetry
breaking in determining the soft terms gauge mediation of supersymmetry
breaking (GMSB) can lead to. To do this we consider a model where
both R-symmetry and SUSY are spontaneously broken. One starts
with the model proposed by Intriligator, Seiberg and Shih (ISS) and
adds a (dangerous) marginal operator, which we call a meson deformation.
The inclusion of this operator leads to the spontaneous breaking
of R-symmetry in the vacuum. One then gauges the SU(5) of flavour
and identifies it with the MSSM GUT gauge group, thus implementing
GMSB. This was the second explicit example where R-symmetry was
spontaneously broken in the vacuum. As in the first, gaugino masses
iii
turned out to be smaller than naively expected so that a mild splitting
between scalar (squark and slepton) and gaugino masses exists.
After this, a general argument showed that in fact gaugino masses
are always significantly smaller than scalar masses if the universe is
perturbatively stable. This arguments suggests that any viable vacuum
should be (perturbatively) metastable, as had been previously noticed
by Murayama and Nomura.
In chapter 4, we try to explore alternatives to this scenario by considering
the possibility that the vacuum doesn’t break supersymmetry
by F-term vevs alone, but by a having simultaneously non-zero F and
D-terms.
It turns out that this does not happen in models where the Kahler
potential is canonical, and the superpotential is a cubic polynomial in
the fields, but it can happen if either of these constraints is violated.
This leads us to consider a particular example, where we study a
hidden sector model with SU(3) gauge group, two flavours of quarks
and one singlet. The superpotential is the most general consistent with
the tree-level symmetries. The R-symmetry is anomalous, however, but
one can still derive selection rules that constrain the form of the effective
superpotential. The only extra term that is allowed is an instanton
induced contribution. This term explicitly breaks the R-symmetry, but
the resulting low energy superpotential is not generic and SUSY is still
spontaneously broken.
While not a complete example of GMSB, this class of hidden sector
models is interesting as it does not require metastability: the tension
between the spontaneous breaking of an R-symmetry and the massless
R-axion is bypassed by the naturally non-generic superpotential. These
models usually have both F and D-term SUSY breaking, but these two
vevs are not independent: in non-Abelian theories, the D-term vevs can
only be induced by the F-term vevs of fields that are not gauge singlets.
The implementation of GMSB in scenarios where the F-terms are
not gauge singlets is then considered in both its direct and semi-direct
forms:
iv
In chapter 5 we deal with direct gauge mediation with gauge messengers.
In this version of gauge mediation, the spontaneously broken
gauge group is identified with the MSSM GUT gauge group and generically
leads to tachyonic squark or slepton masses. In the particular
case where the GUT gauge group is SU(5), we show that this problem
can be solved if there are two independent sectors where SUSY is spontaneously
broken or simply by using a solution of the doublet-triplet
splitting problem where the vev responsible for the spontaneous breaking
of the GUT symmetry is larger than the SUSY breaking scale. In
both cases the effects gauge and non-gauge messengers have to combine
if a viable spectrum is to be reached.
We then finish out study in chapter 6 by considering the semi-direct
version of gauge mediation with gauge messengers. As it is known,
gaugino masses are screened from messenger interactions, at leading
order in the SUSY breaking parameter F. Because of this, gaugino soft
masses will be suppressed with respect to scalar soft masses. This leads
to a scenario of mildly split SUSY, i.e. scalars are at least one or two
orders of magnitude heavier than gauginos. This generically leads to
some extra fine-tuning to get the EW breaking scale to occur at the
correct scale
Distributed process execution in collaborative networks
Processes are a central entity in enterprise collaboration. Collaborative processes need to be executed and coordinated in a distributed Computational platform where computers are connected through heterogeneous networks and systems. Life cycle management of such collaborative processes requires a framework able to handle their diversity based on different computational and communication requirements. This paper proposes a rational for such framework, points out key requirements and proposes it strategy for a supporting technological infrastructure. Beyond the portability of collaborative process definitions among different technological bindings, a framework to handle different life cycle phases of those definitions is presented and discussed. (c) 2007 Elsevier Ltd. All rights reserved
Avaliação do potencial mineiro das escombreiras da mina de São Domingos, Faixa Piritosa Ibérica, Portugal
ABSTRACT: The outcropping São Domingos Iberian Pyrite Belt deposit was
mined since Roman time and between 1857 and 1966. The mine is
formed by a 120 m depth flooded open pit and galleries until 420 m
depth. Associated with felsic volcanic rocks and black shales of the
Volcano-Sedimentary Complex, the deposit is formed by massive
sulphide and stockwork ore (py, ccp, sp, ga, tt, apy) and related supergene
enrichment ore (hematite gossan and covellite/chalcocite). Different mine
wastes classes were mapped: gossan, felsic volcanic and shales, shales
and landfill. Considering the CONASA mining waste characterization
(162 shafts and 160 reverse circulation boreholes/LNEG database), new
inferred resources are presented, using block modelling software: 2.38 Mt
@ 0.77 g/t Au and 8.26 g/t Ag in non-conditioned volumes. Considering
all evaluated wastes, including urban areas, an inferred resource of 4.0 Mt
@ 0.64 g/t Au and 7.30 g/t Ag is presented, corresponding to a metal
content of 82,878 oz t Au and 955,753 oz t Ag.RESUMO: Localizado na Faixa Piritosa Ibérica, o jazigo de São Domingos
foi explorado na época Romana e no período entre 1857 e 1966, tendo
sido escavada uma corta com 120 m de profundidade e abertas galerias
mineiras até 420 m. O minério é formado por sulfuretos maciços e
stockwork (py, ccp, sp, ga, tt, apy) e respetivo enriquecimento
supergénico (chapéu de ferro hematítico e zona de covelite/calcocite),
encontrando-se associado a rochas vulcânicas félsicas e xistos negros do
Complexo Vulcano-Sedimentar. Cartografaram-se diferentes classes de
escombreiras: chapéu de ferro, rochas vulcânicas e xistos, xistos e aterros.
Considerando a sua caracterização efetuada pela empresa CONASA (162
poços e 160 sondagens de circulação inversa/base de dados LNEG),
foram inferidos novos recursos usando software de modelação por
blocos: 2,38 Mt @ 0,77 g/t Au e 8,26 g/t Ag (volumes não
condicionados). Considerando todos os recursos avaliados (incluindo
áreas urbanas) inferem-se valores de 4,0 Mt @ 0.64 g/t Au e 7,30 g/t Ag,
correspondendo a um conteúdo em metal de 82 878 oz t Au e 955 753 oz
t Ag.info:eu-repo/semantics/publishedVersio
Depth as Randomness Deficiency
Depth of an object concerns a tradeoff between computation time and excess of program length over the shortest program length required to obtain the object. It gives an unconditional lower bound on the computation time from a given program in absence of auxiliary information. Variants known as logical depth and computational depth are expressed in Kolmogorov complexity theory.
We derive quantitative relation between logical depth and computational depth and unify the different depth notions by relating them to A. Kolmogorov and L. Levin’s fruitful notion of randomness deficiency. Subsequently, we revisit the computational depth of infinite strings, study the notion of super deep sequences and relate it with other approaches
Evidence from cross-border mergers and acquisitions
Funding agencies: European Research Council, Fundacao para a Ciencia e Tecnologia (grant nr.: PTDC/IIM-FIN/2977/2014) and Mayo Center for Asset ManagementWe test the hypothesis that foreign direct investment promotes corporate governance spillovers in the host country. Using firm-level data from 64 countries during the period 2005-2014, we find that cross-border M&A activity is associated with subsequent improvements in the governance of nontarget firms when the acquirer country has stronger investor protection than the target country. The effect is more pronounced when the target industry is more competitive. Cross-border M&As are also associated with increases in investment and valuation of nontarget firms. Alternative explanations, such as access to global financial markets and cultural similarities, do not appear to explain our findings.authorsversionpublishe
Distinguishing two probability ensembles with one sample from each ensemble
We introduced a new method for distinguishing two probability ensembles called
one from each method, in which the distinguisher receives as input two samples, one from
each ensemble. We compare this new method with multi-sample from the same method
already exiting in the literature and prove that there are ensembles distinguishable by the
new method, but indistinguishable by the multi-sample from the same method. To evaluate
the power of the proposed method we also show that if non-uniform distinguishers ( ..
First morphological and molecular isolation of Talaromyces marneffei in beech marten (Martes foina) in Portugal
Talaromyces marneffei is a zoonotic fungus that mostly infects immunocompromised individuals. For the first
time, this fungus was isolated in an adult beech marten (Martes foina) hit by a car, found dead in Penamacor,
Portugal. During the necropsy, different samples (skin, fur, lymph nodes, lung, spleen, kidneys, and brain) were
collected and processed for microbiology (including mycology) and molecular biology. T. marneffei was identified through its mycological characteristics and confirmed by PCR in hair samples. No other lesions or alterations were reported, except a concomitant presence of M. avium subsp. paratuberculosis in lung, kidney and brain samples. To the authors’ knowledge, this is the first description of this fungus beech marten, as well as the first case of co-infection with M. avium subsp. paratuberculosis in wildlife fauna. These results suggest a sylvatic lifecycle of T. marneffei, involving beech martens, in Portugal.This work was funded by the project UID/CVT/00772/2019 supported by the Portuguese Foundation of Science and Technology - Fundaçao ˜ para a Ciˆencia e Tecnologia (FCT). This work was also supported by FCT under the grant 2021.04520.BD. The authors of the research unit CITAB received funding from FCT; reference of the project UIDB/04033/2020.info:eu-repo/semantics/publishedVersio
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