The influence of strong magnetic fields on proto-quark stars
TL;DR: In this article, different stages of magnetized quark star evolution incorporating baryon number conservation and using an anisotropic energy momentum tensor were analyzed, and the first stages of the evolution were simulated through the inclusion of trapped neutrinos and fixed entropy per particle, while in the last stage the star was taken to be deleptonized and cold.
Abstract: We analyze different stages of magnetized quark star evolution incorporating baryon number conservation and using an anisotropic energy momentum tensor. The first stages of the evolution are simulated through the inclusion of trapped neutrinos and fixed entropy per particle, while in the last stage the star is taken to be deleptonized and cold. We find that, although strong magnetic fields modify quark star masses, the evolution of isolated stars needs to be constrained by fixed baryon number, which necessarily lowers the possible star masses. Moreover, magnetic field effects, measured by the difference between the parallel and perpendicular pressures, are more pronounced in the beginning of the star evolution, when there is a larger number of charged leptons and up quarks. We also show that having a spatially varying magnetic field allows for larger magnetic fields to be supported.
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TL;DR: In this paper, a self-consistent model for the study of the structure of a neutron star in strong magnetic fields is presented, which includes the effect of the magnetic field on the equation of state, the interaction of the electromagnetic field with matter, and anisotropies in the energy-momentum tensor, as well as general relativistic aspects.
Abstract: We present a self-consistent model for the study of the structure of a neutron star in strong magnetic fields. Starting from a microscopic Lagrangian, this model includes the effect of the magnetic field on the equation of state, the interaction of the electromagnetic field with matter (magnetisation), and anisotropies in the energy-momentum tensor, as well as general relativistic aspects. We build numerical axisymmetric stationary models and show the applicability of the approach with one example quark matter equation of state (EoS) often employed in the recent literature for studies of strongly magnetised neutron stars. For this EoS, the effect of inclusion of magnetic field dependence or the magnetisation do not increase the maximum mass significantly in contrast to what has been claimed by previous studies.
136 citations
Cites background or methods or result from "The influence of strong magnetic fi..."
...…on the EoS, computed the corresponding mass-radius relations using isotropic Tolman-OppenheimerVolkoff (TOV) equations, see e.g. Rabhi et al. (2009); Ferrer et al. (2010); Paulucci et al. (2011); Strickland et al. (2012); Lopes & Menezes (2012); Dexheimer et al. (2014); Casali et al. (2014)....
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...This should answer some discussion in the recent literature c© 2014 RAS, MNRAS 000, 1–13 on the role of magnetisation, see e.g. Dexheimer et al. (2014) and Potekhin & Yakovlev (2012)....
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...In contrast to the results obtained previously by other authors, see Paulucci et al. (2011); Dexheimer et al. (2014); Sinha et al. (2013), we found that the effect of inclusion of the magnetic field dependence on the EoS does not change significantly the star’s structure....
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TL;DR: In this paper, the inverse magnetic catalysis in the Nambu-Jona-Lasinio model was studied and the feed-down from mesons to quarks was embedded in an effective coupling constant at finite temperature and magnetic field.
73 citations
TL;DR: In this paper, the meson propagators in terms of quark bubbles in Ritus and Schwinger schemes are derived, and pion masses are numerically calculated in the Ritus scheme for neutral and charged pions.
Abstract: Pions in an external magnetic field are investigated in the frame of a Pauli-Villars regularized Nambu--Jona-Lasinio model The meson propagators in terms of quark bubbles in Ritus and Schwinger schemes are analytically derived, and pion masses are numerically calculated in the Ritus scheme For neutral and charged pions at finite temperature, there exist mass jumps at the Mott transition points due to the discrete energy levels of the two constituent quarks in the magnetic field
54 citations
TL;DR: In this article, the effect of the magnetic field on the mass and shape of a star was studied and the excess mass and change in the equatorial radius of the star due to the non-uniform magnetic field was found to be about 3-4% compared to the spherical solution.
Abstract: Magnetars are compact stars which are observationally determined to have very strong surface magnetic fields of the order of $10^{14}-10^{15}$G. The centre of the star can potentially have a magnetic field several orders of magnitude larger. We study the effect of the field on the mass and shape of such a star. In general, we assume a non-uniform magnetic field inside the star which varies with density. The magnetic energy and pressure as well as the metric are expanded as multipoles in spherical harmonics up to the quadrupole term. Solving the Einstein equations for the gravitational potential, one obtains the correction terms as functions of the magnetic field. Using a nonlinear model for the hadronic EoS the excess mass and change in equatorial radius of the star due to the magnetic field are quite significant if the surface field is $10^{15}$G and the central field is about $10^{18}$ G. For a value of the central magnetic field strength of $1.75\times10^{18}$ G, we find that both the excess mass and the equatorial radius of the star changes by about $3-4\%$ compared to the spherical solution.
47 citations
Journal Article•
TL;DR: The magnetic susceptibility of the degenerate free electrons in the crust of a neutron star is computed for a range of densities, temperatures, and field strengths as discussed by the authors, and it is shown that when the temperature is low enough (typically less than 107K for densities of about 107 g cm-3 and 1012 G fields), the susceptibility undergoes large de Haas-van Alphen oscillations.
Abstract: The magnetic susceptibility of the degenerate free electrons in the crust of a neutron star is computed for a range of densities, temperatures, and field strengths. It is shown that when the temperature is low enough (typically less than 107K for densities of about 107 g cm-3 and 1012 G fields), the susceptibility undergoes large de Haas-van Alphen oscillations. The crust is then unstable to the formation of layers of domains of alternating magnetisation. Associated with these domains are magnetic field fluctuations of a few per cent amplitude and anisotropic magnetostrictive stresses which may be large enough to crumble the crust. It is argued that these domains are unlikely to directly influence the surface properties of the neutron star but may possibly be coupled indirectly to observable effects.
45 citations
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TL;DR: Radio timing observations of the binary millisecond pulsar J1614-2230 that show a strong Shapiro delay signature are presented and the pulsar mass is calculated to be (1.97 ± 0.04)M⊙, which rules out almost all currently proposed hyperon or boson condensate equations of state.
Abstract: Neutron stars comprise the densest form of matter known to exist in our Universe, but their composition and properties are uncertain. Measurements of their masses and radii can constrain theoretical predictions of their composition, but so far it has not been possible to rule out many predictions of 'exotic' non-nucleonic components. Here, radio timing observations of the binary millisecond pulsar J1614-2230 are presented, allowing almost all currently proposed hyperon or boson condensate equations of state to be ruled out.
3,338 citations
TL;DR: In this paper, the authors studied the gravitational equilibrium of masses of neutrons, using the equation of state for a cold Fermi gas, and general relativity, and showed that for masses under 1/3, there are no static equilibrium solutions.
Abstract: It has been suggested that, when the pressure within stellar matter becomes high enough, a new phase consisting of neutrons will be formed. In this paper we study the gravitational equilibrium of masses of neutrons, using the equation of state for a cold Fermi gas, and general relativity. For masses under $\frac{1}{3}\ensuremath{\bigodot}$ only one equilibrium solution exists, which is approximately described by the nonrelativistic Fermi equation of state and Newtonian gravitational theory. For masses $\frac{1}{3}\ensuremath{\bigodot}lml\frac{3}{4}\ensuremath{\bigodot}$ two solutions exist, one stable and quasi-Newtonian, one more condensed, and unstable. For masses greater than $\frac{3}{4}\ensuremath{\bigodot}$ there are no static equilibrium solutions. These results are qualitatively confirmed by comparison with suitably chosen special cases of the analytic solutions recently discovered by Tolman. A discussion of the probable effect of deviations from the Fermi equation of state suggests that actual stellar matter after the exhaustion of thermonuclear sources of energy will, if massive enough, contract indefinitely, although more and more slowly, never reaching true equilibrium.
2,962 citations
TL;DR: In this paper, a first-order QCD phase transition that occurred reversibly in the early universe would lead to a surprisingly rich cosmological scenario, which is at least conceivable that the phase transition would concentrate most of the quark excess in dense, invisible quark nuggets, providing an explanation for the dark matter in terms of QCD effects only.
Abstract: A first-order QCD phase transition that occurred reversibly in the early universe would lead to a surprisingly rich cosmological scenario. Although observable consequences would not necessarily survive, it is at least conceivable that the phase transition would concentrate most of the quark excess in dense, invisible quark nuggets, providing an explanation for the dark matter in terms of QCD effects only. This possibility is viable only if quark matter has energy per baryon less than 938 MeV. Two related issues are considered in appendices: the possibility that neutron stars generate a quark-matter component of cosmic rays, and the possibility that the QCD phase transition may have produced a detectable gravitational signal.
2,553 citations
TL;DR: In this article, it is argued that a convective dynamo can also generate a very strong dipole field after the merger of a neutron star binary, but only if the merged star survives for as long as about 10-100 ms.
Abstract: It is proposed that the main observational signature of magnetars, high-field neutron stars, is gamma-ray bursts powered by their vast reservoirs of magnetic energy. If they acquire large recoils, most magnetars are unbound from the Galaxy or reside in an extended, weakly bound Galactic corona. There is evidence that the soft gamma repeaters are young magnetars. It is argued that a convective dynamo can also generate a very strong dipole field after the merger of a neutron star binary, but only if the merged star survives for as long as about 10-100 ms. Several mechanisms which could impart a large recoil to these stars at birth, sufficient to escape from the Galactic disk, are discussed.
2,482 citations
TL;DR: In this article, a method is developed for treating Einstein's field equations, applied to static spheres of fluid, in such a manner as to provide explicit solutions in terms of known analytic functions.
Abstract: A method is developed for treating Einstein's field equations, applied to static spheres of fluid, in such a manner as to provide explicit solutions in terms of known analytic functions. A number of new solutions are thus obtained, and the properties of three of the new solutions are examined in detail. It is hoped that the investigation may be of some help in connection with studies of stellar structure. (See the accompanying article by Professor Oppenheimer and Mr. Volkoff.)
2,264 citations