The Inkas had their own "Science", in all areas of knowledge. In this contribution, we will present their ancestral knowledge which refers to Astronomy, mainly we will present its constellations. This study is based on the triangulation of the chronicles, oral tradition and the complexes and archaeological elements that we can still locate.
The Incas worshipped the Sun, with light and shadow effects in their constructs commonly denoting such events as the solstices and equinoxes. They as well honored and venerated many features of both natural and man-made landscapes that they felt to be endowed with superhuman powers. In Quechua, these shrines were known as huacas, and at the time of the Spanish conquest there were thousands of...
We study the noncommutative formalism for black holes and their thermodynamics properties in the classical and quantum scenarios.
In the early 1980´s, Letelier introduced a gauge invariant model of a fluid of strings with the aim to treat gravity coupled to these array of strings, in the framework of general relativity. Thus, using the fluid formed by strings as a source of the gravitational field, he obtained a solution of the Einstein equations corresponding to a spherically symmetric space-time. In the case of...
The main goal of this work is to analyze the motion of diferent types of particles in a regular black hole solution obtained by Bronnikov in 2001. The trajectories are obtained through numerical integration of the equations of the orbits (using the program Maple), after the analysis of the effective potential of each case. The results are compared to those of the Reissner-Nordstrom black hole....
The Einstein equations describing the black-brane dynamics both in Minkowski and AdS background were recently recast in the form of coupled diffusion equations in the large-$D$(imension) limit. Using such results in the literature, we formulate a higher-order perturbation theory of black branes in time domain and present the general form of solutions for arbitrary initial conditions. For...
The evolution of main-sequence binaries resided in the galactic centre is influenced a lot by the central supermassive black hole (SMBH). Due to this perturbation, the stars in a dense environment are likely to experience mergers or collisions through secular or non-secular interactions. In this work, we study the dynamics of the stellar binaries at galactic centre, perturbed by another...
Astrometric microlensing provides a powerful tool to study white dwarfs, neutron stars and black holes, particularly the isolated ones. We have two such projects to study stellar remnants through astrometric microlensing, the details of which will be discussed: (i) In a reprise of the famous 1919 solar eclipse experiment that confirmed Einstein's general theory of relativity, the nearby white...
Quasi-periodic oscillations (QPOs) in the kHz range have been reported in the X-ray flux of several accreting black hole and neutron star systems. While several models have been suggested, such variability has been difficult to reproduce in numerical simulations. I will report on Radiative General Relativistic Hydrodynamic Simulations of accretion disks in which several high-frequency...
The direct detection of gravitational waves from binary black hole mergers by the advanced Laser Interferometer Gravitational-Wave Observatories has ushered astrophysics into a new era of observing cosmic events that were previously invisible. Using results for around two thousand star cluster models simulated using well-tested the MOCCA Monte Carlo code for star cluster evolution we...
Black holes (BHs) represent the most extreme objects in the universe and play an important role in astrophysics. We have been exploring various ideas of using gravitational lensing to probe the population and astrophysics of BHs. Supermassive BHs of million solar masses or greater are usually detected as active galactic nuclei (AGN). We show that the innermost X-ray-emitting structure of AGN...
Normal nuclei inside atoms are 2-flavored. What if normal baryonic matter is compressed intensely by gravity so that a huge number of nuclei would gradually merge to form a gigantic nucleus? It is proposed that gigantic nuclei could be 3-flavored, to be manifested in the form of compact stars, cosmic rays, and even dark matter.
We investigate the relativistic corrections to the standard model of formation of large scale structures. In matter domination and in the Poisson gauge, we use the weak-field approximation which allows to keep compact expressions even for the one-loop bispectrum. Whereas in the Newtonian limit, the choice of gauge is marginally important as all gauge coincides, when relativistic corrections...
In the context of a warm inflation scenario in this work we study the effects of a primordial magnetic field on the effective potential of a heavy charged scalar field in a magnetized thermal bath. It is known that models, based on global supersymmetry with a new-inflation-type potential and a coupling between the inflaton and a heavy intermediate superfield, preserve the flatness required...
The present study establishes a correlation between the neutron skin thickness and the infinite nuclear matter characteristics for the even−even isotopes of Fe, Ni, Zn, Ge, Se, and Kr. The axially deformed self-consistent relativistic mean field for the non-linear NL3$^*$ is used for the analysis. The coherent density functional method is adopted to formulate the symmetry energy, the neutron...
Different aspects of the behavior of quark and hadronic matter under intense magnetic fields are analyzed within the framework of Nambu-Jona-Lasinio models.
There is accumulating evidence that scalar fields may exist in nature. The gravitational collapse of a boson cloud would lead to the formation of a boson star just like white dwarfs and neutron star. In generally, as one of candidates of dark matter, a boson star holds a stable configuration and has deserved intensive attention and extensive researches in the past 50 years. At first, we...
The detection of gravitation waves by LIGO has allowed a great number of new tests of strong gravity and near-horizon models for black holes. One such model, pseudo-complex general relativity, agrees with Einstein gravity in the weak-field limit, but diverges dramatically in the near-horizon regime, with certain parameter ranges excluding the existence of black holes altogether. We show how...
We present the results of Relativistic Magnetohydrodynamic simulations utilizing a range of initial conditions in order to see if seed magnetic fields may be generated via the Biermann battery mechanism of magnetogenesis. These simulations occur in a simulated early universe around the time of the electroweak era ${10}^{-11}$ seconds after the Big Bang. Our results are characterized by the...
The NJL and PNJL approach had problems to describe the lattice equation of state for zero chemical potential. This made this Lagrangian, despite of its great merits, less attractive to study what happens for a finite baryon chemcial potential. A finite baryon chemical potential is expected for the experiments at FAIR/Germany and NICA, Russia but also during the merger of two neutron stars...
Dileptons are considered as one of the cleanest signals of the quark-gluon plasma (QGP), however, the QGP radiation is masked by many 'background' sources from either hadronic decays or semileptonic decays from correlated charm pairs.
We investigated the relative contribution of these channels in heavy-ion collisions from $\sqrt{s_{\rm NN}}=$ 8 GeV to 5 TeV with a focus on the competition...
Athena (the Advanced Telescope for High-Energy Astrophysics) will continue the series of large X-ray observatories inaugurated by Chandra and XMM-Newton, offering transformational capabilities in several key areas. It is the second large-class ESA mission (L2), and it is planned for a launch towards the end of the next decade.
In this talk, the main science objectives of Athena, and its main...
IXPE, the Imaging X-ray Polarimetry Explorer, has been selected by NASA on January 2017 as the next mission in the Small Explorer Program, for a launch in early 2021. IXPE, a collaboration between NASA and ASI (the Italian Space Agency), is led by M. Weisskopf (MSFC) and is composed by three identical telescopes with, at the focal plane, a Gax Pixel Detector based on the photoelectric effect....
The X-Ray Astronomy Recovery Mission (XARM), an international collaboration led by JAXA and involving major participation from NASA and ESA, will employ an advanced X-ray observatory with capabilities to carry out a science program to address some of the important questions of present-day astrophysics. XARM is essentially a rebuild of the the Hitomi (Astro-H) spacecraft that was lost due to an...
Transient low-mass X-ray binaries containing a neutron star which sporadically accrete matter from a low-mass companion provide a unique opportunity to study the internal structure of neutron stars. During accretion phase the neutron star is heated and driven out of thermal equilibrium. During the following quiescent phase, when no accretion is occurring, the thermal relaxation of the neutron...
Powerful radio sources and quasars emit relativistic jets of plasma and magnetic fields that travel hundreds of kilo-parsecs, ultimately depositing energy into the external medium. In the rest frame of the jet, the energy density of the cosmic microwave background is enhanced by the bulk Lorentz factor as $\Gamma^2$, and when this exceeds the magnetic energy density the primary loss mechanism...
The detection of the gravitational wave event GW170817 by LIGO and Virgo was accompanied by the independent detection of the short Gamma-ray Burst GRB 170817A by the Gamma-ray Burst Monitor (GBM) of NASA’s Fermi mission. This discovery was complemented by the detection of a weak coincident signal in the data of the Anti-Coincidence Shield ACS of Spectrometer SPI onboard ESA’s INTEGRAL mission....
The time domain astronomy will radically change in the coming decade, with the advent of facilities like LSST, SKA, CTA, etc that will find huge numbers of transients across the electromagnetic spectrum, and with the detections via non-electromagnetic signals, such as gravitational waves. Within this context, we plan to build the New Robotic Telescope (NRT), a 4 m optical and near infrared...
The Pierre Auger Observatory is the currently largest cosmic-ray detector covering ultra-high energies from 10$^{18}$ eV to 10$^{20}$ eV. The size of exposure accumulated since 2004 granted measurements of unprecedented precisions on energy spectrum, mass composition and anisotropy searches. These measurements guide us slowly to the sources of ultra-high energy cosmic rays, which is a...
Analysis of galaxy redshift data and theta-z data from the Sloan Digital Sky Survey (SDSS) provides surprising new insights in cosmology, which overturn prior results.
In the present study, we conduct a numerical analysis of the MacMillan problem in which the mass of the test particle varies in time according to the Jeans’ law. The MacMillan problem is a particular case of the circular three body problem, where the third body moves along an axis passing through the center of mass of the system, and is perpendicular to the plane of the primaries. Since the...
Local gravitational theories with more than four derivatives have remarkable quantum properties. Namely, they are super-renormalizable and may be unitary in the Lee-Wick sense, if the massive poles of the propagator are complex. It is important, therefore, to explore also the IR limit of these theories and identify possible observable signatures of the higher derivatives. In this talk we...
Measurements of the cosmic microwave background (CMB) polarization represent the best technique to study physical phenomena happening a split-second within the big bang and to test the standard cosmological model. In this scenario, the Large-Scale Polarization Explorer (LSPE) aims at the measurement of polarization at the largest angular scales, where cosmic inflation left its imprint in the...
Scattering of cosmic microwave background radiation in galaxy clusters induces polarization signals determined by the quadrupole anisotropy in the photon distribution at the location of clusters. This remote quadrupole derived from the measurements of the induced polarization in galaxy clusters provides the information of local CMB temperature anisotropies. Here we present an algorithm of the...
I will review ideas as to how a joint monitoring program at radio to submillimeter wavelengths may be used to study the relativistic jet formation and circumnuclear environment of supermassive black holes. At least some tidal disruption events (TDE) of (sub-)stellar objects around black holes form relativistic jets. Such a jet can first be detected in (sub)millimeter and only gradually become...
By using AMR cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code, we studied the mass transport processes onto galactic nuclei from high redshift up to $z\sim 6$. Due to the large dynamical range of the simulations we were able to study the mass accretion process on scales from $\sim 50$ kpc to $\sim$ pc. The SMBHs are modelled as a sink particles at the center of our...
The effect of a homogeneous weak magnetic field on the decay process of a neutral scalar field to a pair of charged fermions is studied. The decay rate is calculated through the imaginary part of the self-energy of the scalar particle interacting with the charged fermions, at one loop. We find that the effect depends on the kinematical regime of the progenitor particle: for low transverse...
The measurement of neutron star mass and radius is one of the most direct ways to distinguish between various dense matter equations of state. The mass and radius of accreting neutron stars hosted in low-mass X-ray binaries can be constrained by several methods, including photospheric radius expansion from type I X-ray bursts, gravitational redshift measurement and from quiescent spectra. In...
Strongly magnetized isolated neutron stars (NSs) are categorised into two families, according mainly to their magnetic field strength. The one with a higher magnetic field of $10^{14}$ - $10^{15}$ Gauss is called “magnetar”, and the other is the X-ray isolated neutron star (XINS) with $10^{13}$ Gauss. Both magnetars and XINSs show thermal emission in X-rays, whose spectra are different. The...
Abstract:
Pulsars are neutron stars, detected mainly through the pulses of electromagnetic radiation emitted from their poles, which is modulated by their stable rotation. Since their discovery in 1967 they have become fundamental tools for understanding subject such as stellar evolution, theories of gravity, the electron content of our Galaxy and understanding the behavior of matter at...
In this work, we investigate the Ohmic decay of surface dipole magnetic field of high-braking index pulsar PSR J1640$-$4631, and interpret the observed soft X-ray flux $F_{x}^{\infty}[2-10\rm keV]$ from $Chandra +NuStar$ telescopes. We obtain the ohmic decay timescale $\tau_{\rm ohm}\sim 3.23\times10^{6}$ yr. Observations indicate that magnetic multipole fields could exist in a neutron star...
We report the evidence for the anti-correlation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range $10^{35}$--$10^{37}$ erg s$^{-1}$ from observations spanning 15 years. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our pipeline analysis of other X-ray pulsars in the Small...
The behavior of pions is studied in systems where their normal leptonic decay is forbidden. When thermal fluctuations are present, a low decay rate is generated, and as a consequence of lepton recombination, the amount of pions remains almost unaltered. Compact stars conditions are favorable for the formation of such intermediate state of charged pions: near condensation and almost stable,...
Pulsars are among the most extreme objects in the universe, where physical processes work in regimes of extreme densities as well as gravitational and electromagnetic field strengths. It is widely agreed upon that pulsar activity is intimately connected to the copious generation of electron-positron pairs in the magnetosphere - a rapidly rotating magnetized neutron star is active as pulsar...
We perform cooling simulations for isolated neutron stars using recently developed equations of state for their core. The equations of state are obtained from new parametrizations of the FSU2 relativistic mean-field functional that reproduce the properties of nuclear matter and finite nuclei, while fulfilling the restrictions on high-density matter deduced from heavy-ion collisions,...
The merger of two compact stars is the celebrated event in Astrophysics which provides highest baryon densities and temperatures simultaneously as well as compact objects at the limit of stability, most likely in a transition stage to a black hole which, triggered by a gravitational wave signal, is then observable in all wavelengths of the electromagnetic spectrum, in some cases also in...
In this talk, we investigate the effect a crystalline quark-hadron mixed phase can have on the neutrino emissivity from the cores of neutron stars. To this end we use relativistic mean-field equations of state to model hadronic matter and a nonlocal extension of the three-flavor Nambu-Jona-Lasinio model for quark matter. The extent of the quark-hadron mixed phase and its crystalline structure...
The inflationary model was introduced by Guth in the 80's as a way of solving the so-called three cosmological problems: flatness of the space-time, the problem of the horizon, and the question of the magnetic monopoles. Since it was proposed, inflation has become much more than a cosmological model. The inflationary period may perhaps give us some clues about the transition from a continuum...
In this work we use the correspondence between a field theory in de Sitter space in 4-dimensions and the dual conformal field theory in an euclidean space in 3-dimensions to constraint the form of correlation functions of primordial perturbations. To this end, we use an inflationary model, in which the inflaton field is interacting with a vector field trough the term $f1(\phi)F_{μ\nu} F^{μ\nu}...
Abstract: Magnetars are incredible astrophysical objects with the largest ever observed magnetic fiels that are more than a thousand times larger than Pulsar magnetic fields.They are also associated with some of the most powerful flares ever seen. The origin of such strong magnetic fields is a fascinating problem in physics. I shall describe in this talk work done with V. Soni, with earlier...
The observed value $\Lambda_{obs}$ of the cosmological constant $\Lambda$ is extremely smaller than theoretical expectations, and the anthropic argument has been proposed as a solution to this problem because galaxies do not form when $\Lambda \gg \Lambda_{obs}$. However, the contemporary galaxy formation theory predicts that stars form even with a high value of $\Lambda / \Lambda_{obs} \sim...
We investigate a progenitor mass distribution of core-collapse supernova remnants (CCSNRs) in our Galaxy and the Large and Small Magellanic Clouds, for the first time. We use the zero-age main-sequence mass, $M_{\rm ZAMS}$, estimated from elemental abundances and count the number of the CCSNRs in three mass ranges:
A: $M_{\rm ZAMS} < 15\ {\rm M}_\odot$,
B: $15\ {\rm M}\odot < M{\rm ZAMS}...
We represent results of numerical simulation of magnetorotational (MR) instability which develops in MR core-collapsed supernova explosion. The MR instability leads to the exponential growth of all components of the magnetic field. It significantly reduce the time for the development of MR exlosion. The MR instability is of Tayler type with rotation. The maximal values of magnetic field found...
The observed GRB (170817A) that followed GW170817 confirmed the longstanding prediction of association of short GRBs with neutron star mergers. The unique large scale observational campaign that followed provided numerous surprising observations. I discuss past predictions concerning binary mergers. I then turn to current observations of GW 170817 and its EM counterpart and their...
The neutrinos’ burst from SN1987A were detected on different experiments around the World on February in 1987 until today it is theme of discussions and re-analysis. All events were approximately twenty five in the following detectors: Kamiokande II (KII) in Japan ~ 12, Irvine-Michigan-Brookhaven (IMB) in USA~8 and Baksan in Soviet Union ~ 5. The neutrinos play a key role on cooling mechanism...
The observation of a violation of baryon number conservation would have tremendous impact and implications for the fields of particle and astrophysics and cosmology. Observation of baryon number violating processes such as proton decay or neutron-antineutron oscillation would point to grand unification of the EM, strong, and weak forces at very high energies. This talk will present the...
Information Relativity Theory is a simple, axiom-free, epistemic relativizing of Newtonian physics. It attempts to answer the following question: What information will a proper measurement device in laboratory A, register about an occurrence in another laboratory B, which is in a state of motion relative to A. We assume that information about the respective occurrence (e.g., the start, and...
With the rapid development of the clock technology, the unprecedented accuracy and stability provides a potential to measure the solar gravitational redshift with the clock-comparison experiments in the laboratory. The clock-comparison model is discussed in both the Barycentric Celestial Reference System (BCRS) and the Geocentric Celestial Reference System (GCRS), in which the transformations...
Local Lorentz invariance (LLI) is an important component of General Relativity (GR). The test of LLI can not only probe the foundation stone of GR, but also help to explore the physics beyond GR and Standard Model. In the previous work, we have limited the LLI coefficients with the gravitational experiments (gravitational inverse square law) performed in our lab. As the Lorentz-violation...
Galileon theories are built with the purpose of having the most general scalar-tensor theory free of the Ostrogradski instability. Quite recently, the vector Galileon theories have been formulated, in particular its non-Abelian version (invariance under a global SU(2) symmetry). The theory, together with a cosmic triad configuration, is able to reproduce the present dark energy epoch,...
Recent analysis of the rotation curves of a large sample of galaxies with very diverse stellar properties reveal a relation between the radial acceleration purely due to the baryonic matter and the one inferred directly from the observed rotation curves. Assuming the dark matter (DM) exists, this acceleration relation is tantamount to an acceleration relation between DM and baryons. This leads...
We review some recent developments in describing cosmological inflation, dark energy, dark matter and primordial black holes in supergravity. Their relations to string cosmology on the one side, and to reheating after inflation, on the other side, are also outlined. Open problems of the theory are emphasised too.
Literature: our papers in arXiv:1708.05393, 1703.08993, 1701.08240, 1701.02450,...
I present several explicit examples of generalizations in relativistic quantum mechanics which may be used in astrophysics and cosmology.
First of all, I discuss the generalized spin-1/2 equations for neutrinos. They have been obtained by means of the Gersten-Sakurai method for derivations of arbitrary-spin relativistic equations. Possible physical consequences are discussed. Particularly, we...
For a modified theory of General Relativity, the pseudo-complex version, the stability of the Schwarzschild solution is investigated. The extended Zerilli equation is derived and the scattering of graviational waves investigated, which are the solutions of the Zerilli equation. Consequences for the ring-down frequency, after the fusion of two black holes, are studied.
We investigate the effects due to the introduction of delta resonances in the neutron star matter. We compare and contrast the mass-radius diagram obtained for four different nuclear equations of state in the relativistic mean field theory. More precisely we vary the coupling constants for the delta-mesons interactions in the limits defined by the constraints on the relativistic mean field of...
Magnetars are neutron stars presenting bursts and outbursts of X- and soft-gamma rays that can be understood with the presence of very large magnetic fields. In this setting, nonlinear electrodynamics should be taken into account for a more accurate description of such compact systems. We study that in the context of ideal magnetohydrodynamics and make a realization of our analysis to the case...
We focus on spacetime oscillations, the so-called w-modes, of gravitational waves emitted from a protoneutron star in the postbounce phase of core-collapse supernovae. By adopting numerical results from recent relativistic three-dimensional supernova models, we find that the w1-mode frequency multiplied by the radius of the protoneutron star is expressed as a linear function with respect to...
One of the most important prediction of Einstein's general theory of gravity is gravitational radiation. I will discuss the importance of the recent LIGO and Virgo direct detections of gravitational-waves. The observations of gravitational waves provide a different view on astrophysical processes hidden from electromagnetic astronomy and expand our knowledge of the Universe dramatically. I...
Magnetic null points can develop near the ergosphere boundary of a rotating black hole by the combined effects of strong gravitational field and the frame-dragging mechanism. The electric component does not vanish in the magnetic null and an efficient process or particle acceleration can occur. The situation is relevant for low-accretion-rate nuclei of some galaxies which exhibit episodic...
Gravitational waves from core-collapse Supernovae.
G.S. Bisnovatyi-Kogan, S.G. Moiseenko
A mechanism of formation of gravitational waves in the universe is considered for the nonspherical collapse of matter. Nonspherical collapse results are presented for a uniform spheroid of dust, and a finite entropy spheroid. Numerical simulation results on core-collapse supernova explosion are presented...
In this work, we study the behavior of nuclear matter at high densities considering the hadronic and quark phases at zero temperature. We describe the hadron-meson phase using a phenomenological Lagrangian, which exhibits a parametrization, through mathematical constants, of the intensity of the several meson-nucleon couplings. We have included in the formalism the chemical equilibrium...
In this work, a chemical analysis of a sample of B stars in the Orion Association is presented. This analysis consists in the calculation of the physical parameters: effective temperature ($T_{\rm eff}$) and surface gravity ($\log g$) by ionization equilibrium, and the determination of metal abundances of C, N, O, and Mg by a consistent analysis in non-LTE with TLUSTY. That is, the line...
We study the behavior of quark matter under an external magnetic field in the context of nonlocal chiral quark models, focusing on the features of the chiral restoration transition. It is seen that these models naturally lead to the inverse magnetic catalysis effect found in lattice QCD calculations.
The capabilities of telescopes allow us to make the plotting of light curves a routine task. This one shifts the main attention of astronomer from the plotting to research. To achieve this goal, we developed a new tool for automated reduction of photometric observations, which includes the computational method for the brightness assessment of the investigated and comparison stars; brightness...
We study a compatibility of the dark matter condensation inside the neutron stars with the observational constraints on the properties of these astrophysical objects. Effects of the baryon-lepton matter are taken under control based on the well tested novel equation of state of nuclear matter, which is able to fulfil a rich collection of constraints from nuclear physics and heavy ion collision...
Based on recent experimental and theoretical hints on possible formation of a resonant four-neutron system we study effects of appearance of such a cluster in neutron rich baryon matter inside NSs. For this purpose we employ a relativistic mean field approach which includes nucleons, Δ-baryons as well as light nuclear clusters. Our analysis demonstrates that tetraneutrons existing as the...
We examine crustal torsional oscillations, newly taking into account the effect of the pasta structure. We find from eigenmode analyses for various models of the equation of state of uniform nuclear matter that the fundamental frequencies of such oscillations are almost independent of the incompressibility of symmetric nuclear matter (K0), but strongly depend on the slope parameter of the...
The gravitational waves (GW) as standard siren directly determines the luminosity distance $d_L$ from progenitor source without assuming any cosmological model, of which the redshift $z$ can be obtained with the electromagnetic counterpart like GW events from coalescence binary neutron star (NS-NS) or neutron star/black hole (NS-BH) pair. In the near future, with the third generation GW...
Dark matter in the form of axions can be included in a model with $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$ symmetry with right handed neutrinos, where the strong CP problem can be solved. This version of the model has the appealing characteristic of giving the observed dark matter abundance measured by the Planck collaboration, for suitable values of the parameters in the model.
We studied the...
We analyze the dark matter problem in a class of models with gauge symmetry $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$, taking into account the constraints coming from Planck observations of the dark matter relic density, direct detection searches with Xenon1T and indirect detection experiments.
During the last decades the work involving objects known as $Active~Galactic~Nuclei$ (AGNs) has been gaining more and more attention from several authors aiming at improving the already acquired knowledge. This knowledge provide us with the understanding of the physical processes occurring in AGNs as well as with a better mapping of the Universe. The initial proposal of the thesis project...
The OGLE catalogue contains position and photometry information in the I band of 200000 variable stars in the direction of Bulge Galactic. Another project, MACHO, scanned the same region obtaining information from millions of variable stars but in bands b and r. We chose the OGLE fields that were intercepted with the MACHO fields and we calculated the light curves of the stars contained in the...
The aim of our contribution is to shed some light on open questions facing the high-density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role in the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings, the concept of naturalness has been adopted. In order to encourage possible...
In this contribution we combined our predictions for the tidal parameter with recent gravitational wave observation of merging system of binary neutron stars of the event GW170817 with quasi universal relations between the maximum mass of rotating and nonrotating neutron stars. Our results indicate that predictions of the tidal parameter represent an useful constraint of the EoS of neutron star matter.
On the scope of the pseudo-complex General Relativity (pc-GR), we investigate the role of many-body correlations in the maximum mass of rotating neutron stars with degrees of freedom of hyperons and weakly interacting massive dark matter particles (WIMPs) in their composition. In the baryon sector, we consider the effective relativistic QHD-model with parameterized couplings, which represents...
The second Law of Thermodynamics is an important approach to testing models and theories. If a model is not consistent with a constant or increasing entropy to achieve thermodynamic equilibrium must be discarded. Therefore, the study of Entropy suggests that it is possible to validate models or not. In this work, an approach is developed in light of the Second Law of Thermodynamics for Cold...
Abstract:
Pulsars are fundamental tools for astronomy and physics. Every single new pulsar has the potential to provide an outstanding laboratory for a wide variety of physics, ranging from a better understanding of the stellar evolution to testing theories of gravity and placing limits on the equation-of-state. The most stable pulsars, who's precision approaches that of atomic clocks, are...
Wolf-Rayet (WR) stars are massive stars that have evolved off the main-sequence and are undergoing advanced nuclear burning in their cores, rapidly approaching the end of their lives as supernovae. They are losing mass at very high rates and shocks associated with their metal-rich supersonic winds can produce strong X-ray emission, non-thermal (synchrotron) radio emission, and are potential...
Since 2013 the mass of pulsar PSR J0348+0432 ($M = 2.01\,M_{\odot}$) has provided a tight constraint on the neutron star equation of state. However, a number of different analyses of the recently detected binary neutron star merger (GW170817) point to a higher maximum neutron star mass of around $2.16\,M_{\odot}$. In addition, a recent study determined the mass of the millisecond pulsar PSR...
We study two macroscopic signals where the contribution of the magnetic field has an important role. The first one is related to kicks pulsar induced by neutrino emission from the core of neutron stars. The anisotropic neutrino emission produces a rocket effect that contributes to the star's kick velocity. We find that the computed values for the kick velocity lie within the range of the...
We investigate possibilities to determine a mass of primary particle from anomalous longitudinal profiles of extensive air showers. Such profiles are predicted utilizing a Monte Carlo technique together with the contemporal high-energy interaction models. The depth of shower maximum, that is commonly used for the mass composition analyses, is inspected and its performace to discriminate...
The development of multi-particle field method in the quarks scattering problem was considered. This method has been used to describe the differential cross section of elastic scattering by square of the transferred four-momentum. It is shown that the measurement of the interacting particles coordinates with simultaneity condition leads to impossible binding of probability amplitudes...
A QCD based analysis of the neutrino structure functions $xF2$, $xF3$ and $\Delta_{xF3}$, for charged current and neutral neutrino DIS is performed focusing on high energy and high precisions neutrino experiments. The investigation is done taking into account the color dipole formalism, considering a wide region of the kinematical variables Bjorken-$x$ and boson virtuality $Q^2$. We consider...
We study frequencies of axisymmetric and non-axisymmetric epicyclic modes of accretion disc oscillations and explore the influence of pressure forces present in the disc. We discuss the implications for estimations of black hole spin in the three Galactic microquasars, GRS 1915+105, GRO J1655-40, and XTE J1550-564, that have been carried out based on several models of 3:2 high-frequency...
The project is focused on the optimization and characterization of inorganic scintillators. Scintillators are materials that emit light (flashes), when an energy particle deposits energy in its volume, it serves to collect light from the ionization process and has a wide range of applications that are find from the study of high-energy physics, astrophysics, nuclear physics, cosmic rays,...
Motion of accreted gas approaching a neutron star (NS) in a NS low-mass X-ray binary (LMXB) system is determined by the relativistic scaling of orbital frequencies. The gas radiation dominates the NS LMXBs emissivity and accounts for most of the observed variability. As a likely consequence twin-peak quasi-periodic oscillations (QPOs) are observed in more than a dozen of sources. Motivated by...
Pseudo-complex General Relativity is an algebraic extension of the standard theory of gravitation that relies on pseudo-complex numbers in order to get new metric degrees of freedom. The pseudo-complex formalism has an extra contribution to the Einstein equations with a repulsive character that has been called dark energy. This dark energy is relevant only when intense gravitational fields...
We study the static stellar equilibrium configurations of uncharged and charged spheres composed by a relativistic polytropic fluid, and compare with those of spheres composed by a non-relativistic polytropic fluid, the later case already being studied in a previous work [J. D. Arbañil, P. S. Lemos, V. T. Zanchin, Phys. Rev. D 88, 084023 (2013)]. For the two fluids under study, it is assumed...
In the theory of pseudo-complex General Relativity (pc-GR), the field equations have an extra term, associated to the nature of spacetime, of repulsive character, which is believed to halt the gravitational attractive collapse of matter distributions in the evolution process of compact stars. This additional term arises from micro-scale phenomena due to vacuum fluctuations, which simulate the...
Standard models of non-rotating compact stars assumes perfect spherical symmetry. However, due to high magnetic fields, these compact stellar objects can be deformed making them oblate or prolate spheroids with distinct equatorial and polar radii. Recent work on models of the global structure of highly magnetized neutron stars indicate the macroscopic stellar properties such as masses and...
A new constraint on the equation of state and matter composition of neutron stars has been provided by the measurement of the mass of PSR J0348+0432 (2.01 $M_\odot$). In this contribution, we investigate, in the domain of the pseudo-complex General Relativity (pc-GR) with baryons, mesons, electrons and weakly interacting massive dark matter particles (WIMPs) degrees of freedom, the role of the...
In a recent paper McGaugh, Lelli, and Schombert showed that in an empirical plot of the observed centripetal accelerations in spiral galaxies against those predicted by the Newtonian gravity of the luminous matter in those galaxies the data points occupied a remarkably narrow band. While one could summarize the mean properties of the band by drawing a single mean curve through it, by fitting...
