70 research outputs found
Spectral properties of the Laplacian of multiplex networks.
One of the more challenging tasks in the understanding of dynamical properties of models on top of complex networks is to capture the precise role of multiplex topologies. In a recent paper, Gómez et al. [ Phys. Rev. Lett. 110 028701 (2013)], some of the authors proposed a framework for the study of diffusion processes in such networks. Here, we extend the previous framework to deal with general configurations in several layers of networks and analyze the behavior of the spectrum of the Laplacian of the full multiplex. We derive an interesting decoupling of the problem that allow us to unravel the role played by the interconnections of the multiplex in the dynamical processes on top of them. Capitalizing on this decoupling we perform an asymptotic analysis that allow us to derive analytical expressions for the full spectrum of eigenvalues. This spectrum is used to gain insight into physical phenomena on top of multiplex, specifically, diffusion processes and synchronizability
Zero Sound in Neutron Stars with Dense Quark Matter under Strong Magnetic Fields
We study a neutron star with a quark matter core under extremely strong
magnetic fields. We investigate the possibility of an Urca process as a
mechanism for the cooling of such a star. We found that apart from very
particular cases, the Urca process cannot occur. We also study the stability of
zero sound modes under the same conditions. We derive limits for the coupling
constant of an effective theory, in order the zero sound to be undamped. We
show that zero sound modes can help kinematically to facilitate a cooling
process
Dark Matter Interference
We study different patterns of interference in WIMP-nuclei elastic scattering
that can accommodate the DAMA and CoGeNT experiments via an isospin violating
ratio . We study interference between the following pairs of
mediators: Z and Z', Z' and Higgs, and two Higgs fields. We show under what
conditions interference works. We also demonstrate that in the case of the two
Higgs interference, an explanation of the DAMA/CoGeNT is consistent with
Electroweak Baryogenesis scenarios based on two Higgs doublet models proposed
in the past.Comment: 14 pages, 2 figures, references and appendix added, match with the
published versio
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Innovative Technologies for District Heating and Cooling: InDeal Project
The paper discusses the outcomes of the conference organized by the InDeal project. The conference took place on 12 December 2018 in Montpellier as part of the EnerGaia energy forum 2018. A holistic interdisciplinary approach for district heating and cooling (DHC) networks is presented that integrates heterogeneous innovative technologies from various scientific sectors. The solution is based on a multi-layer control and modelling framework that has been designed to minimize the total plant production costs and optimize heating/cooling distribution. Artificial intelligence tools are employed to model uncertainties associated with weather and energy demand forecasts, as well as quantify the energy storage capacity. Smart metering devices are utilized to collect information about all the crucial heat substations’ parameters, whereas a web-based platform offers a unique user environment for network operators. Three new technologies have been further developed to improve the efficiency of pipe design of DHC systems: (i) A new sustainable insulation material for reducing heat losses, (ii) a new quick-fit joint for an easy installation, and (iii) a new coating for reducing pressure head losses. The results of a study on the development and optimization of two energy harvesting systems are also provided. The assessment of the environmental, economic and social impact of the proposed holistic approach is performed through a life cycle analysis. The validation methodology of the integrated solution is also described, whereas conclusions and future work are finally given
Scalar Bilepton Dark Matter
In this work we show that 3-3-1 model with right-handed neutrinos has a
natural weakly interacting massive particle (WIMP) dark mater candidate. It is
a complex scalar with mass of order of some hundreds of GeV which carries two
units of lepton number, a scalar bilepton. This makes it a very peculiar WIMP,
very distinct from Supersymmetric or Extra-dimension candidates. Besides,
although we have to make some reasonable assumptions concerning the several
parameters in the model, no fine tunning is required in order to get the
correct dark matter abundance. We also analyze the prospects for WIMP direct
detection by considering recent and projected sensitivities for WIMP-nucleon
elastic cross section from CDMS and XENON Collaborations.Comment: 21 pages, 8 figures, uses iopart.cls, same text as published version
with a small different arrangement of figure
Asymmetric Origin for Gravitino Relic Density in the Hybrid Gravity-Gauge Mediated Supersymmetry Breaking
We propose the hybrid gravity-gauge mediated supersymmetry breaking where the
gravitino mass is about several GeV. The strong constraints on supersymmetry
viable parameter space from the CMS and ATLAS experiments at the LHC can be
relaxed due to the heavy colored supersymmetric particles, and it is consistent
with null results in the dark matter (DM) direct search experiments such as
XENON100. In particular, the possible maximal flavor and CP violations from the
relatively small gravity mediation may naturally account for the recent LHCb
anomaly. In addition, because the gravitino mass is around the asymmetric DM
mass, we propose the asymmetric origin of the gravitino relic density and solve
the cosmological coincident problem on the DM and baryon densities \Omega_{\rm
DM}:\Omega_{B}\approx 5:1. The gravitino relic density arises from asymmetric
metastable particle (AMP) late decay. However, we show that there is no AMP
candidate in the minimal supersymmetric Standard Model (SM) due to the robust
gaugino/Higgsino mediated wash-out effects. Interestingly, AMP can be realized
in the well motivated supersymmetric SMs with vector-like particles or
continuous U(1)_R symmetry. Especially, the lightest CP-even Higgs boson mass
can be lifted in the supersymmetric SMs with vector-like particles.Comment: RevTex4, 21 pages, 1 figure, minor corrections, JHEP versio
Closing in on Asymmetric Dark Matter I: Model independent limits for interactions with quarks
It is argued that experimental constraints on theories of asymmetric dark
matter (ADM) almost certainly require that the DM be part of a richer hidden
sector of interacting states of comparable mass or lighter. A general requisite
of models of ADM is that the vast majority of the symmetric component of the DM
number density must be removed in order to explain the observed relationship
via the DM asymmetry. Demanding the efficient
annihilation of the symmetric component leads to a tension with experimental
limits if the annihilation is directly to Standard Model (SM) degrees of
freedom. A comprehensive effective operator analysis of the model independent
constraints on ADM from direct detection experiments and LHC monojet searches
is presented. Notably, the limits obtained essentially exclude models of ADM
with mass 1GeV 100GeV annihilating to SM quarks via
heavy mediator states. This motivates the study of portal interactions between
the dark and SM sectors mediated by light states. Resonances and threshold
effects involving the new light states are shown to be important for
determining the exclusion limits.Comment: 18+6 pages, 18 figures. v2: version accepted for publicatio
Resolution of dark matter problem in f(T) gravity
In this paper, we attempt to resolve the dark matter problem in f(T) gravity.
Specifically, from our model we successfully obtain the flat rotation curves of
galaxies containing dark matter. Further, we obtain the density profile of dark
matter in galaxies. Comparison of our analytical results shows that our
torsion-based toy model for dark matter is in good agreement with empirical
data-based models. It shows that we can address the dark matter as an effect of
torsion of the space.Comment: 14 pages, 3 figure
Dynamical Boson Stars
The idea of stable, localized bundles of energy has strong appeal as a model
for particles. In the 1950s John Wheeler envisioned such bundles as smooth
configurations of electromagnetic energy that he called {\em geons}, but none
were found. Instead, particle-like solutions were found in the late 1960s with
the addition of a scalar field, and these were given the name {\em boson
stars}. Since then, boson stars find use in a wide variety of models as sources
of dark matter, as black hole mimickers, in simple models of binary systems,
and as a tool in finding black holes in higher dimensions with only a single
killing vector. We discuss important varieties of boson stars, their dynamic
properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in
Relativity; major revision in 201
The physics of spreading processes in multilayer networks
The study of networks plays a crucial role in investigating the structure,
dynamics, and function of a wide variety of complex systems in myriad
disciplines. Despite the success of traditional network analysis, standard
networks provide a limited representation of complex systems, which often
include different types of relationships (i.e., "multiplexity") among their
constituent components and/or multiple interacting subsystems. Such structural
complexity has a significant effect on both dynamics and function. Throwing
away or aggregating available structural information can generate misleading
results and be a major obstacle towards attempts to understand complex systems.
The recent "multilayer" approach for modeling networked systems explicitly
allows the incorporation of multiplexity and other features of realistic
systems. On one hand, it allows one to couple different structural
relationships by encoding them in a convenient mathematical object. On the
other hand, it also allows one to couple different dynamical processes on top
of such interconnected structures. The resulting framework plays a crucial role
in helping achieve a thorough, accurate understanding of complex systems. The
study of multilayer networks has also revealed new physical phenomena that
remain hidden when using ordinary graphs, the traditional network
representation. Here we survey progress towards attaining a deeper
understanding of spreading processes on multilayer networks, and we highlight
some of the physical phenomena related to spreading processes that emerge from
multilayer structure.Comment: 25 pages, 4 figure
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