arXiv subjects

M. Angeles Perez-Garcia

Publications and source records attributed to M. Angeles Perez-Garcia.

17 recordsLinked to original sources

arXiv2015

Constraining decaying dark matter with neutron stars

The amount of decaying dark matter, accumulated in the central regions in neutron stars together with the energy deposition rate from decays, may set a limit on the neutron star survival rate against transitions to more compact objects provided nuclear matter is not the ultimate stable state of matter and that dark matter indeed is unstable. More generally, this limit sets constraints on the dark matter particle decay time, $τ_χ$. We find that in the range of uncertainties intrinsic to such a scenario, masses $(m_χ/ \rm TeV) \gtrsim 9 \times 10^{-4}$ or $(m_χ/ \rm TeV) \gtrsim 5 \times 10^{-2}$ and lifetimes ${τ_χ}\lesssim 10^{55}$ s and ${τ_χ}\lesssim 10^{53}$ s can be excluded in the bosonic or fermionic decay cases, respectively, in an optimistic estimate, while more conservatively, it decreases $τ_χ$ by a factor $\gtrsim10^{20}$. We discuss the validity under which these results may improve with other current constraints.

astro-ph.SR↗

arXiv2014

Can Dark Matter explain the Braking Index of Neutron Stars?

We explore a new mechanism of slowing down the rotation of neutron stars via accretion of millicharged dark matter. We find that this mechanism yields pulsar braking indices that can be substantially smaller than the standard $n\sim 3$ of the magnetic dipole radiation model for millicharged dark matter particles that are not excluded by existing experimental constraints thus accommodating existing observations.

astro-ph.SR↗

arXiv2013

Anisotropy in Cosmic rays from internal transitions in neutron stars

We discuss the possibility that some recently measured anisotropic cosmic ray components in the TeV-PeV energy range may be an indication of the ejection of a peculiar type of matter. We present a model where a neutron star internal transition with nuclear deconfinement of the quark content takes place. This catastrophic event may cause a mass ejection process seeding the insterstelar medium with droplets of quark matter, so called nuclearites. Neutralization of these droplets in molecular clouds may drive the anisotropy since quasi-rectilinear trajectories are allowed. Complementary information from current experimental settings on earth or magnetic spectrometers on the ISS may shed light on this exotic form of matter.

astro-ph.HE↗

arXiv2013

Pulsar scintillation patterns and strangelets

We propose that interstellar extreme scattering events, usually observed as pulsar scintillations, may be caused by a coherent agent rather than the usually assumed turbulence of $\rm H_2$ clouds. We find that the penetration of a flux of ionizing, positively charged strangelets or quark nuggets into a dense interstellar hydrogen cloud may produce ionization trails. Depending on the specific nature and energy of the incoming droplets, diffusive propagation or even capture in the cloud are possible. As a result, enhanced electron densities may form and constitute a lens-like scattering screen for radio pulsars and possibly for quasars.

astro-ph.GA↗

arXiv2013

Deconfinement of quark content in neutron stars due to cosmic external agents

We summarize in this contribution to the the proceedings of "Compact Stars in the QCD Phase Diagram III (CSQCD III)", December 12-15, 2012, Guaruja, SP, Brazil the possibility of an scenario involving the existence of cosmic external agents able to deposit energy in neutron stars by (co-) or self-annihilation. This, in turn, may drive a internal phase transition in neutron stars in a sort of Trojan mechanism disrupting the original configuration. This event would have macroscopic consequences, by changing the EoS of the object and by the emission of a multimessenger signal, that in the photon range could be detected with gamma rays of $\sim10-100$ keV.

astro-ph.HE↗

arXiv2013

Short GRBs and dark matter seeding in neutron stars

We present a mechanism based on internal self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars that may trigger the full or partial conversion into a quark star. We explain how this effect may induce a gamma ray burst that could be classified as short, according to the usual definition based on time duration of the prompt gamma-ray emission. This mechanism differs in many aspects from the most discussed scenario associating short gamma-ray bursts with compact object binary mergers. We list possible observational signatures that should help to distinguish between these two possible classes of progenitors.

astro-ph.HE↗

arXiv2013

Strangelets and the TeV-PeV cosmic-ray anisotropies

Several experiments (e.g., Milagro and IceCube) have reported the presence in the sky of regions with significant excess in the arrival direction distributions of Galactic cosmic rays in the TeV to PeV energy range. Here we study the possibility that these hotspots are a manifestation of the peculiar nature of these cosmic rays, and of the presence of molecular clouds near the sources. We propose that stable quark matter lumps or so-called "strangelets" can be emitted in the course of the transition of a neutron star to a more compact astrophysical object. A fraction of these massive particles would lose their charge by spallation or electron capture in molecular clouds located in the immediate neighborhood of their source, and propagate rectilinearly without decaying further, hence inducing anisotropies of the order of the cloud size. With reasonable astrophysical assumptions regarding the neutron star transition rate, strangelet injection and neutralization rates, we can reproduce successfully the observed hotspot characteristics and their distribution in the sky.

astro-ph.HE↗

arXiv2012

GRB emission in Neutron Star transitions

In this contribution we briefly introduce a mechanism for short gamma ray burst emission different from the usually assumed compact object binary merger progenitor model. It is based on the energy release in the central regions of neutron stars. This energy injection may be due to internal self-annihilation of dark matter gravitationally accreted from the galactic halo. We explain how this effect may trigger its full or partial conversion into a quark star and, in such a case, induce a gamma ray burst with isotropic equivalent energies in agreement with those measured experimentally. Additionally, we show how the ejection of the outer crust in such events may be accelerated enough to produce Lorentz factors over those required for gamma ray emission.

astro-ph.HE↗

arXiv2012

Neutron star as laboratories for Cosmology

Neutron stars can be considered a useful and interesting laboratory for Cosmology. With their deep gravitational potential they may accrete dark matter from the galactic halo and subsequent self-annihilation processes could induce an indirect observable signal this type of matter. In addition, the large densities in the interior of these objects may constitute a test-bench to study hypothesized deviations of fundamental constant values complementary to existing works using constraints at low density from BBN.

astro-ph.HE↗

arXiv2011

Dark matter seeding and the kinematics and rotation of neutron stars

Self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars may affect their kinematical properties, namely velocity kicks and rotation patterns. We find that if a stable long-lived single or multiple strangelet off-center seed forms, there is an associated change in momentum and torque that may affect the kinematical observables of the star.

astro-ph.CO↗

arXiv2010

Dark matter, neutron stars and strange quark matter

We show that self-annihilating neutralino WIMP dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.

astro-ph.CO↗

arXiv2010

Neutrino mean free paths in spin-polarized neutron Fermi liquids

Neutrino mean free paths in magnetized neutron matter are calculated using the Hartree-Fock approximation with effective Skyrme and Gogny forces in the framework of the Landau Fermi Liquid Theory. It is shown that describing nuclear interaction with Skyrme forces and for magnetic field strengths $log_{10} B(G) \gtrsim 17$, the neutrino mean free paths stay almost unchanged at intermediate densities but they largely increase at high densities when they are compared to the field-free case results. However the description with Gogny forces differs from the previous and mean free paths stay almonst unchanged or decrease at densities $[1-2]ρ_0$. This different behaviour can be explained due to the combination of common mild variation of the Landau parameters with both types of forces and the values of the nucleon effective mass and induced magnetization of matter under presence of a strong magnetic field as described with the two parametrizations of the nuclear interaction.

nucl-th↗

arXiv2009

Response of spin polarized neutron matter under the presence of a strong magnetic field with Skyrme interactions

The effects of a strong magnetic field in the dynamical response of a pure neutron system to a weak neutrino probe are studied within the framework of the Landau Fermi Liquid Theory in the non-relativistic Hartree-Fock approximation. We use Skyrme forces to parametrize the partially magnetized nuclear interacting plasma and describe its collective modes. We study the vector and vector-axial matter response functions and the neutrino mean free path in this two-component fermion system with net spin polarization and density dependent in-medium correlations. We find a decrease in the neutrino opacity of magnetized matter with respect to the non-magnetized case for fields $log_{10} B(G) \gtrsim 17$.

nucl-th↗

arXiv2009

Neutron Fermi Liquids under the presence of a strong magnetic field with effective nuclear forces

Landau's Fermi Liquid parameters are calculated for non-superfluid pure neutron matter in the presence of a strong magnetic field at zero temperature. The particle-hole interactions in the system, where a net magnetization may be present, are characterized by these parameters in the framework of a multipolar formalism. We use either zero- or finite-range effective nuclear forces to describe the nuclear interaction. Using the obtained Fermi Liquid parameters, the effect of a strong magnetic field on some bulk magnitudes such as isothermal compressibility and spin susceptibility is also investigated.

nucl-th↗

arXiv2008

Simulation of symmetric nuclei and the role of Pauli potential in binding energies and radii

It is shown that the use of a density dependent effective Pauli potential together with a nucleon-nucleon interaction potential plays a crucial role to reproduce not only the binding energies but also the matter root mean square radii of medium mass range spin-isospin saturated nuclei. This study is performed with a semiclassical Monte Carlo many-body simulation within the context of a simplified nucleon-nucleon interaction to focus on the effect of the genuine correlations due to the fermionic nature of nucleons. The procedure obtained is rather robust and it does not depend on the detailed features of the nucleon-nucleon interaction. For nuclei below saturation the density dependence may be represented in terms either of the nucleon number, $A$, or the associated Fermi momenta. When testing the simulation procedure for idealized "infinite" symmetric nuclear matter within the corresponding range of densities, it turns out that finite size effects affect the Pauli potential strength parametrization in systems up to about 120 particles while remaining approximately stable for larger systems.

nucl-th↗

arXiv2008

Magnetization of a neutron plasma with Skyrme and Gogny forces in the presence of a strong magnetic field

Some thermodynamical magnitudes of interest in a pure neutron plasma are studied within the framework of the non-relativistic Brueckner-Hartree-Fock approximation at finite density and temperature. We use Skyrme and Gogny forces to describe such a neutron plasma and study the main differences that arise in these two effective parametrizations of the nuclear interaction when a strong magnetic field induces a permanent magnetization in the gas. The existence of a non-zero permanent spin polarization in a neutron plasma is explored in the density-temperature parameter space. We find that for moderate temperatures and in the low density range up to densities $\approx 0.5ρ_0$ both parametrizations predict that as density decreases an increasingly strong magnetization is allowed. In the range $0.5 ρ_0 \lesssim ρ\lesssim 3 ρ_0$ there is an approximately constant polarization that can be as big as $\approx 12%$ for the maximum allowed interior magnetic field $B \approx 10^{18}$ G. For higher densities there is a dramatic difference in the polarization trend followed by Skyrme an Gogny forces. While the former predict a ferromagnetic phase transition, the Gogny forces prevent it keeping the magnetization below 5%.

nucl-th↗

arXiv2008

Binding energies and modelling of nuclei in semiclassical simulations

We study the binding energies of spin-isospin saturated nuclei with nucleon number $8 \le A \le 100$ in semiclassical Monte Carlo many-body simulations. The model Hamiltonian consists of, (i) nucleon kinetic energy, (ii) a nucleon-nucleon interaction potential, and (iii) an effective Pauli potential which depends on density. The basic ingredients of the nucleon-nucleon potential are, a short-range repulsion, and a medium-range attraction. Our results demonstrate that one can always expect to obtain the empirical binding energies for a set of nuclei by introducing a proper density dependent Pauli potential. The present work suggests a simple, pragmatic procedure for modelling a set of nuclei calibrated by the empirical binding energies for a given NN interaction potential. Then, each set of modelled nuclei can be tested by studying other properties of nuclei in semiclassical simulations.

nucl-th↗