This thesis aims to study how amending certain astrophysical observable of quark stars due to presence of magnetic field. To do this we need to obtain Equation of State (EOS) and consider the stability of Strange Quark Matter (made up of quarks u, d and s) cold dense and magnetized in stellar equilibrium (beta equilibrium, conservation of the baryonic number and charge neutrality). We will work using the phenomenological MIT Bag model. The stability of the Magnetized Strange Quark Matter (MSQM) is studied taking into account the variation of parameters from the model: s quark mass, baryonic density, magnetic field and the Bag parameter. Results obtained were compared with those of magnetized normal quark matter (only u and d quarks in beta equilibrium) as well as the Strange Quark Matter (SQM). It is found that the energy per baryon decreases with the increasing magnetic field which implies that the MSQM is more stable than SQM. The Equations of State previously obtained are used to obtain stable configurations of magnetized strange stars checking that the magnetic field helps to reduce Mass-Radius (M-R) ratio of the star.
We assess the fragmentation of strange quark matter in astrophysical events, showing that the application of statistical multifragmentation models suggests that most of the fragments (strangelets) should belong to an unstable baryon number $A$. While there are some caveats to be addressed, the flux of strangelets onto the Earth could be orders of magnitude lower than previous estimates, with negative prospects for the ongoing search experiments.
The conjecture of Bodmer-Witten-Terazawa suggesting a form of quark matter (Strange Quark Matter) as the ground state of hadronic interactions has been studied in laboratory and astrophysical contexts by a large number of authors. If strange stars exist, some violent events involving these compact objects, such as mergers and even their formation process, might eject some strange matter into the interstellar medium that could be detected as a trace signal in the cosmic ray flux. To evaluate this possibility, it is necessary to understand how this matter in bulk would fragment in the form of st…
In the current work an equation of state model with a first-order phase transition for astrophysical applications is presented. The model is based on a two-phase approach for quark-hadron phase transitions, which leads by construction to a first-order phase transition. The resulting model has already been successfully used in several astrophysical applications, such as cold neutron stars, core-collapse supernova explosions and binary neutron star mergers. Main goal of this work is to present the details of the model, discuss certain features and eventually publish it in a tabulated form for fu…
Explosive astrophysical systems, such as supernovae or compact star binary mergers, provide conditions where strange quark matter can appear. The high degree of isospin asymmetry and temperatures of several MeV in such systems may cause a transition to the quark phase already around saturation density. Observable signals from the appearance of quark matter can be predicted and studied in astrophysical simulations. As input in such simulations, an equation of state with an integrated quark matter phase transition for a large temperature, density and proton fraction range is required. Additional…
We study a possible mechanism for astrophysical jet production from a neutron star composed by a partially bosonized npe-gas. We obtain that the expulsion of a stable stream of matter might be triggered by the quantum magnetic collapse of one or various components of the gas, while its collimation is due to the formation of a strong self-generated magnetic field.
One of the fundamental properties of astrophysical magnetic fields is their ability to change topology through reconnection and in doing so, to release magnetic energy, sometimes violently. In this work, we review recent results on the role of magnetic reconnection and associated heating and particle acceleration in jet/accretion disk systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs).
This is our first study of the magnetic Rayleigh-Taylor instability at the inner edge of an astrophysical disk around a central back hole. We derive the equations governing small-amplitude oscillations in general relativistic ideal magnetodydrodynamics and obtain a criterion for the onset of the instability. We suggest that static disk configurations where magnetic field is held by the disk material are unstable around a Schwarzschild black hole. On the other hand, we find that such configurations are stabilized by the spacetime rotation around a Kerr black hole. We obtain a crude estimate of …
Rankine-Hugoniot condition has been solved to study phase transition in astrophysical scenario mainly in the case of phase transition from neutron star (NS) to quark star (QS). The phase transition is brought about by a combustion front, which travels from the center to the surface. The equations of state and temperature plays a huge role in determining the nature of the front propagation, which brings about the phase transition in neutron stars (NSs). Magnetic field has been introduced and the modified conservation condition for the perpendicular and oblique shocks is obtained. Numerical solu…
This review discusses the physics of magnetic reconnection, a process in which the magnetic field topology changes and magnetic energy is converted to kinetic energy, in pair plasmas in the relativistic regime. We focus on recent progress in the field driven by theory advances and the maturity of particle-in-cell codes. This work shows that fragmentation instabilities at the current sheet can play a critical role in setting the reconnection speed and affect the resulting particle acceleration, anisotropy, bulk flows, and radiation. Then, we discuss how this novel understanding of relativistic …
We investigate interacting quark matter (IQM), including the perturbative QCD correction and color superconductivity, for both up-down quark matter ($ud$QM) and strange quark matter (SQM). We first derive an equation of state (EOS) unifying all cases by a simple reparametrization and rescaling, through which we manage to maximally reduce the number of degrees of freedom. We find, in contrast to the conventional EOS $p=1/3(ρ-4B_{\rm eff})$ for non-interacting quark matter, that taking the extreme strongly interacting limit on the unified IQM EOS gives $p=ρ-2B_{\rm eff}$, where $B_{\rm eff}$ is …
Compact stars (CS) are stellar remnants of massive stars. Inside CSs the density is so high that matter is in subatomic form composed of nucleons. With increase of density of matter towards the centre of the objects other degrees of freedom like hyperons, heavier non-strange baryons, meson condensates may appear. Not only that at higher densities, the nucleons may get decomposed into quarks and form deconfined strange quark matter (SQM). If it is so then CSs may contain SQM in the core surrounded by nucleonic matter forming hybrid stars (HSs). However, the nature and composition of matter insi…
The aberrated radiation pressure at the inner edge of the accretion disk around an astrophysical black hole imparts a relative azimuthal velocity on the electrons with respect to the ions which gives rise to a ring electric current that generates large scale poloidal magnetic field loops. This is the Cosmic Battery established by Contopoulos and Kazanas in 1998. In the present work we perform realistic numerical simulations of this important astrophysical mechanism in advection-dominated accretion flows-ADAF. We confirm the original prediction that the inner parts of the loops are continuously…
We present simulations of magnetized astrophysical shocks taking into account the interplay between the thermal plasma of the shock and supra-thermal particles. Such interaction is depicted by combining a grid-based magneto-hydrodynamics description of the thermal fluid with particle in cell techniques devoted to the dynamics of supra-thermal particles. This approach, which incorporates the use of adaptive mesh refinement features, is potentially a key to simulate astrophysical systems on spatial scales that are beyond the reach of pure particle-in-cell simulations. We consider in this study n…
The conservation of the energy flux in turbulent jets which propagate in the intergalactic medium (IGM) allows deducing the law of motion in the classical and relativistic cases. Three types of IGM are considered: constant density, hyperbolic and inverse power law decrease of density. An analytical law for the evolution of the magnetic field along the radio-jets is deduced using a linear relation between the magnetic pressure and the rest density. Astrophysical applications are made to the centerline intensity of synchrotron emission in NGC315 and to the magnetic field of 3C273.
Quark matter with only $u$ and $d$ quarks ($ud$QM) might be the ground state of baryonic matter at large baryon number $A>A_{\rm min}$. With $A_{\rm min}\gtrsim 300$, this has no direct conflict with the stability of ordinary nuclei. An intriguing test of this scenario is to look for quantum nucleation of $ud$QM inside neutron stars due to their large baryon densities. In this paper, we study the transition rate of cold neutron stars to $ud$ quark stars ($ud$QSs) and the astrophysical implications, considering the relevant theoretical uncertainties and observational constraints. It turns out t…
We study the weak interaction processes taking place within a combustion flame that converts dense hadronic matter into quark matter in a compact star. Using the Boltzmann equation we follow the evolution of a small element of just deconfined quark matter all along the flame interior until it reaches chemical equilibrium at the back boundary of the flame. We obtain the reaction rates and neutrino emissivities of all the relevant weak interaction processes without making any assumption about the neutrino degeneracy. We analyse systematically the role the initial conditions of unburnt hadronic m…
Determination of the baryon number (or mass) distribution of the strangelets, that may fragment out of the warm and excited strange quark matter (SQM) ejected in the merger of strange stars (SSs) in compact binary stellar systems of the Galaxy, is attempted by using a statistical disassembly model (SMM). Finite mass of strange quarks is taken into account in the analysis. Strangelet charge and the resulting Coulomb correction are included to get a plausible mass distribution of galactic strangelets at their source.
Astrophysical plasmas can have parameters vastly different from the more studied laboratory and space plasmas. In particular, the magnetic fields can be the dominant component of the plasma, with energy-density exceeding the particle rest-mass energy density. Magnetic fields then determine the plasma dynamical evolution, energy dissipation and acceleration of non-thermal particles. Recent data coming from astrophysical high energy missions, like magnetar bursts and Crab nebula flares, point to the importance of magnetic reconnection in these objects. In this review we outline a broad spectrum …
Aim: To study the multimessenger nature of the signal that can result from the phase transition of a neutron star to a quark star and their corresponding astrophysical observations. Methods: The phase transition process is initiated by the abrupt pressure and density changes at the star center, giving rise to a shock which deconfines matter followed by a weak front converting excess down to strange quarks to attain absolute stability. This process's effects are investigated by understanding how the energy escapes from the star in the form of neutrino-antineutrino annihilation. For such annihil…
We develop a first-principles model for the relativistic magnetic reconnection rate in strongly magnetized pair plasmas. By considering the energy budget and required current density near the x-line, we analytically show that in the magnetically-dominated relativistic regime, the x-line thermal pressure is significantly lower than the upstream magnetic pressure due to the extreme energy needed to sustain the current density, consistent with kinetic simulations. This causes the upstream magnetic field lines to collapse in, producing the open outflow geometry which enables fast reconnection. The…
The origin of magnetic fields in clusters of galaxies is still an unsolved problem, which is largely due to our poor understanding of initial seed magnetic fields. If the seed magnetic fields have primordial origins, it is likely that large-scale pervasive magnetic fields were present before the formation of the large-scale structure. On the other hand, if they were ejected from astrophysical bodies, they were highly localized in space at the time of injection. In this paper, using turbulence dynamo models for high magnetic Prandtl number fluids, we find constraints on the seed magnetic fields…
Neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. Astrophysical observables, however, depend strongly on the star's internal structure, which is currently unknown due to uncertainties in the equation of state. Universal relations, however, exist among certain stellar observables that do not depend sensitively on the star's internal structure. One such set of relations is between the star's moment of inertia ($I$), its tidal Love number (Love) and its quadrupole moment ($Q$), the so-called I-Love-Q relat…
A phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. We investigate the quark deconfinement phase transition in cold (T = 0) and hot beta-stable hadronic matter. Assuming a first order phase transition, we calculate and compare the nucleation rate and the nucleation time due to quantum and thermal nucleation mechanisms. We show that above a threshold value of the central pressure a pure hadronic star (HS) (i.e. a compact star with no fraction of deconfined quark matter) is metastable to the conversion to a quark star (QS) (i.e. a hybrid …
We propose and examine a new high-density composite of $Λ^* \equiv K^-p = (s \bar{u}) \otimes (uud)$, which may be called {\it Kaonic Proton Matter (KPM)}, or simply, {\it $Λ^* $-Matter}, where substantial shrinkage of baryonic bound systems originating from the strong attraction of the $(\bar{K}N)^{I=0}$ interaction takes place, providing a ground-state neutral baryonic system with a huge energy gap. The mass of an ensemble of $(K^-p)_m$, where $m$, the number of the $K^-p$ pair, is larger than $m \approx 10$, is predicted to drop down below its corresponding neutron ensemble, $(n)_m$, since …
Magnetic reconnection is a fundamental process of magnetic field topology change. We analyze the connection of this process with turbulence which is ubiquitous in astrophysical environments. We show how Lazarian & Vishniac (1999) model of turbulent reconnection is connected to the experimentally proven concept of Richardson diffusion and discuss how turbulence violates the generally accepted notion of magnetic flux freezing. We note that in environments that are laminar initially turbulence can develop as a result of magnetic reconnection and this can result in flares of magnetic reconnection …
We have shown the simultaneous generation of macro-scale fast flows and strong magnetic fields in the 2-temperature relativistic electron-ion plasmas of astrophysical objects due to Unified Reverse Dynamo/Dynamo mechanism. The resulting dynamical magnetic field amplification and/or flow acceleration is directly proportional to the initial turbulent kinetic/magnetic (magnetic) energy; the process is very sensitive to relativistically hot electron-ion fraction temperature and magneto-fluid coupling. It is shown, that for realistic physical parameters of White Dwarfs accreting hot astrophysical f…
One of the most promising possibilities may be the appearance of quark matter in astrophysical phenomena in the light of recent progress in observations. The mechanism of deconfinement is not well understood, but the thermodynamical aspects of the hadron-quark (HQ) phase transition have been extensively studied in recent years. Then the mixed phase of hadron and quark matter becomes important; the proper treatment is needed to describe the HQ phase transition and derive the equation of state (EOS) for the HQ matter, based on the Gibbs conditions for phase equilibrium. We here adopt a EOS based…
We present an updated general purpose nuclear equation of state (EoS) for use in simulations of core-collapse supernovae, neutron star mergers and black hole collapse. This EoS is formulated in the context of Density Functional Theory (DFT) and is generalized to include all DFT EoSs consistent with known nuclear and astrophysical constraints. This EoS also allows for the possibility of the formation of material with a net proton excess ($Y_p > 0.5$) and has an improved treatment of the nuclear statistical equilibrium and the transition to heavy nuclei as the density approaches nuclear matter d…
We consider the quantum mechanics of a spinless charged particle on a 2-dimensional sphere. When threaded with a magnetic monopole field, this is the well-known Haldane sphere that furnishes a translationally-invariant, incompressible quantum fluid state of a gas of electrons confined to the sphere. This letter presents the results of a novel variant of the Haldane solution where the monopole field is replaced by that of a dipole. We argue that this system is relevant to the physics on the surface of compact astrophysical objects like neutron stars.
Recently it was shown that the centrifugal instability may be important in the dynamics of astrophysical jets undergoing reconfinement by external pressure. However, these studies were limited to the case of unmagnetised flows. Here we explore the role of the magnetic field within both the Newtonian and relativistic frameworks. Since the jet problem is rather complicated, we focus instead on the simpler problem of cylindrical rotation and axial magnetic field, which shares significant similarity with the jet problem, and consider only axisymmetric perturbations. The studied equilibrium configu…
Asymptotic Freedom and Vacuum Polarization Determine the Astrophysical End State of Relativistic Gravitational Collapse: Quark--Gluon Plasma Star Instead of Black Hole
Colciencias National Program for Basic Sciences, Space Science（Colciencias 基础科学国家计划，空间科学）；Valencia International University（瓦伦西亚国际大学）；Escuela de Fisica, Universidad Nacional de Colombia（哥伦比亚国立大学物理学院）；Instituto de Fisica, Universidad de Antioquia（安蒂奥基亚大学物理研究所）；Department of Physics and Astronomy, West Virginia University（西弗吉尼亚大学物理与天文学系）
We evaluate the three bulk viscosity coefficients $ζ_1, ζ_2$ and $ζ_3$ in the color-flavor locked (CFL) superfluid phase due to phonons and kaons, which are the lightest modes in that system. We first show that the computation is rather analogous to the computation of the same coefficients in superfluid $^4$He, as due to phonons and rotons. For astrophysical applications, we also find the value of the viscosities when there is a periodic disturbance, and the viscosities also depend on the frequency of the disturbance. In a temperature regime that might be of astrophysical relevance, we find th…
Radial oscillations of quark stars in light of current astrophysical constraints: A comparative study
Universidad de La Frontera（拉弗龙特拉大学）；Universidad del Bío-Bío（比奥比奥大学）；Silesian University in Opava（奥帕瓦西里西亚大学）；Institute of Physics, Silesian University in Opava（奥帕瓦西里西亚大学物理研究所）；Universidade de Lisboa（里斯本大学）
We study the propagation of neutrinos from compact astrophysical objects with strong magnetic field, such as magnetars. Both neutrino spin rotation and oscillations in a realistic three-flavor model are taken into account. We solve the neutrino evolution equation in the magnetic field near the object and obtain the probabilities of all possible spin-flavor transitions. Assuming that neutrinos are produced in the interior of the star being in their left-handed state with electron flavor, we use these spin-flavor transition probabilities to estimate the fraction of neutrinos, which change their …
We discuss a cornucopia of potential astrophysical signatures and constraints on magnetically charged black holes of various masses. As recently highlighted, being potentially viable astrophysical candidates with immense electromagnetic fields, they may be ideal windows to fundamental physics, electroweak symmetry restoration and non-perturbative quantum field theoretic phenomena. We investigate various potential astrophysical pointers and bounds -- including limits on charges, location of stable orbits and horizons in asymptotically flat and asymptotically de Sitter backgrounds, bounds from g…
We study the properties of strange quark stars by employing a 3-flavor Nambu-Jona-Lasinio model with both scalar-isovector and vector-isovector interactions. Using the constraint on the vector-isoscalar interaction strength obtained from the elliptic flow splitting between particles and their antiparticles in relativistic heavy-ion collisions, we investigate the dependence of the properties of strange quark stars on the vector-isovector and the scalar-isovector interactions, and compare the results with the state-of-art astrophysical constraints on the compact star radius and mass as well as i…
The shaping of astrophysical outflows into bright, dense and collimated jets due to magnetic pressure is here investigated using laboratory experiments. We notably look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collim…
The constraint imposed by magnetic helicity conservation on the alpha effect is considered for both magnetically and flow dominated self-organizing plasmas. Direct numerical simulations are presented for a dominant contribution to the alpha effect, which can be cast in the functional form of a total divergence of an averaged helicity flux, called the helicity-flux-driven alpha ( H$α$) effect. Direct numerical simulations of the H$α$ effect are prese nted for two examples---the magnetically dominated toroidal plasma unstable to tearing modes, and the flow-dominated accretion disk.
The possible role of a first order QCD phase transition at nonvanishing quark chemical potential and temperature for cold neutron stars and for supernovae is delineated. For cold neutron stars, we use the NJL model with nonvanishing color superconducting pairing gaps, which describes the phase transition to the 2SC and the CFL quark matter phases at high baryon densities. We demonstrate that these two phase transitions can both be present in the core of neutron stars and that they lead to the appearance of a third family of solution for compact stars. In particular, a core of CFL quark matter …
The appearance of quark matter in the centers of compact stars has a number of astrophysical implications. In this contribution I discuss the structure and stability of compact stars, gravitational radiation from non-axisymmetric deformations, and nucleation and dynamics of vortices (flux tubes) in the color superconducting phases.
Dissipation and particle acceleration in astrophysical jets with velocity and magnetic shear: Interaction of Kelvin-Helmholtz and Drift-Kink Instabilities
Photons may convert to axion-like particles (ALPs) in external magnetic fields. Under certain conditions, this effect should result in irregular features in observed spectra of astrophysical sources. Lack of such irregularities in particular spectra was used to constrain ALP parameters, with two most popular sources being the radio galaxy NGC 1275 and the blazar PKS 2155-304. The effect and, consequently, the constraints, depend on the magnetic fields through which the light from the source is propagated. Here, we revisit ALP constraints from gamma-ray observations of NGC 1275 taking into acco…
Collisionless shocks are ubiquitous in the Universe and often associated with strong magnetic field. Here we use large-scale particle-in-cell simulations of non-relativistic perpendicular shocks in the high-Mach-number regime to study the amplification of magnetic field within shocks. The magnetic field is amplified at the shock transition due to the ion-ion two-stream Weibel instability. The normalized magnetic-field strength strongly correlates with the Alfvénic Mach number. Mock spacecraft measurements derived from PIC simulations are fully consistent with those taken in-situ at Saturn's bo…
For quark matter studies in astrophysics the thermodynamic bag model (tdBAG) has been widely used. Despite its success it fails to account for various phenomena expected from Quantum-Chromo-Dynamics (QCD). We suggest a straightforward extension of tdBAG in order to take the dynamical breaking of chiral symmetry and the influence of vector interactions explicitly into account. As for tdBAG the model mimics confinement in a phenomenological approach. It is based on an analysis of the Nambu--Jona-Lasinio (NJL) model at finite density. Furthermore, we demonstrate how NJL and bag models in this reg…
We show that a primeval seed magnetic field arises due to spin-degeneracy breaking of fermions caused by the dragging of inertial frames in the curved spacetime of rotating astrophysical bodies. This seed magnetic field would arise even due to electrically neutral fermions such as neutrons. As an example, we show that an ideal neutron star rotating at $500$ revolutions per second, having mass $0.83$ M$_{\odot}$ and described by an ensemble of degenerate neutrons, would have $0.12$ Gauss seed magnetic field at its center arising through the breaking of spin-degeneracy.
We use particle-in-cell (PIC) simulations to study the nonlinear evolution of ion velocity space instabilities in an idealized problem in which a background velocity shear continuously amplifies the magnetic field. We simulate the astrophysically relevant regime where the shear timescale is long compared to the ion cyclotron period, and the plasma beta is ~ 1-100. The background field amplification in our calculation is meant to mimic processes such as turbulent fluctuations or MHD-scale instabilities. The field amplification continuously drives a pressure anisotropy with the perpendicular pre…
We study the surface tension of hot, highly magnetized three flavor quark matter droplets, focusing specifically on the thermodynamic conditions prevailing in neutron stars, hot lepton rich protoneutron stars and neutron star mergers. We explore the role of temperature, baryon number density, trapped neutrinos, droplet size and magnetic fields within the multiple reflection expansion formalism (MRE), assuming that astrophysical quark matter can be described as a mixture of free Fermi gases composed by quarks $u$, $d$, $s$, electrons and neutrinos, in chemical equilibrium under weak interaction…
Determination of baryon number (or mass) distribution of the strangelets, that may fragment out of the warm and excited strange quark matter ejected in the merger of strange stars in compact binary stellar systems in the Galaxy, is attempted here by using a statistical disassembly model. Finite mass of strange quarks is taken into account in the analysis. Resulting charges of the strangelets and the corresponding Coulomb corrections are included to get a plausible size distribution of those strangelets as they are produced in binary stellar mergers thus getting injected in the Galaxy. From thi…
We compute the fluxes of radio photons from conversion of axion-like particle dark matter in cosmic magnetic fields. We find that for axion-like particle masses around $10^{-6}\,$eV and effective coupling constants to photons $g_{aγ}\gtrsim10^{-13}\,{\rm GeV}^{-1}$ strongly magnetized nearby stellar winds may give detectable line-like radio photon signals, although predicted fluxes are highly uncertain due to the poorly known structure of the magnetic fields. Nevertheless, it may be worth while to conduct a dedicated search in the direction of such sources. When combined with a possible future…
We study the possibility that the transition from hadron matter to quark matter at vanishing temperatures proceeds via crossover, similar to the crossover behavior found with lattice QCD studies at high temperatures. The purpose is to examine astrophysical consequences of this postulate by constructing hybrid star sequences fulfilling current experimental data.
We consider applications of general relativistic uniformly-rotating white dwarfs to several astrophysical phenomena related to the spin-up and the spin-down epochs and to delayed type Ia supernova explosions of super-Chandrasekhar white dwarfs, where we estimate the "spinning down" lifetime due to magnetic-dipole braking. In addition, we describe the physical properties of Soft Gamma Repeaters and Anomalous X-Ray Pulsars as massive rapidly-rotating highly-magnetized white dwarfs. Particularly we consider one of the so-called low-magnetic-field magnetars SGR 0418+5729 as a massive rapidly-rotat…
