Electric fields at the quark surface of strange stars in the color-flavor locked phase

It is shown that extremely strong electric fields may be generated at the surface of strange quark matter in the color-flavor locked phase because of the surface effects. Some properties of strange stars made of this matter are briefly discussed.Comment: 3 pages, no figures, Phys. Rev. D, matches published versio

PULSARS WITH STRONG MAGNETIC FIELDS: POLAR GAPS, BOUND PAIR CREATION AND NONTHERMAL LUMINOSITIES

Modifications to polar-gap models for pulsars are discussed for the case where the surface magnetic field, $B_\S$, of the neutron star is strong. For B\ga4\times10^8\rm\,T, the curvature $\gamma$-quanta emitted tangentially to the curved force lines of the magnetic field are captured near the threshold of bound pair creation and are channelled along the magnetic field as bound electron-positron pairs (positronium). The stability of such bound pairs against ionization by the parallel electric field, $E_\parallel$, in the polar cap, and against photoionization is discussed. Unlike free pairs, bound pairs do not screen $E_\parallel$ near the neutron star. As a consequence, the energy flux in highly relativistic particles and high-frequency (X-ray and/or $\gamma$-ray) radiation from the polar gaps can be much greater than in the absence of positronium formation. We discuss this enhancement for (a) Arons-type models, in which particles flow freely from the surface, and find any enhancement to be modest, and (b) Ruderman-Sutherland-type models, in which particles are tightly bound to the surface, and find that the enhancement can be substantial. In the latter case we argue for a self-consistent, time-independent model in which partial screening of $E_\parallel$ maintains it close to the threshold value for field ionization of the bound pairs, and in which a reverse flux of accelerated particles maintains the polar cap at a temperature such that thermionic emission supplies the particles needed for this screening. This model applies only in a restricted range of periods, $P_2<P<P_1$, and it implies an energy flux in high-energy particles that can correspond to a substantial fraction of the spin-down power of the pulsar. Nonthermal, high-frequency radiation has been observed from six radio pulsarsComment: TEX file, 47 pages. Accepted by Australian J. Phy

Effective Lagrangian in nonlinear electrodynamics and its properties of causality and unitarity

In nonlinear electrodynamics, by implementing the causality principle as the requirement that the group velocity of elementary excitations over a background field should not exceed the speed of light in the vacuum and the unitarity principle as the requirement that the residue of the propagator should be nonnegative, we establish the positive convexity of the effective Lagrangian on the class of constant fields, also the positivity of all characteristic dielectric and magnetic permittivity constants that are derivatives of the effective Lagrangian with respect to the field invariants. Violation of the general principles by the one-loop approximation in QED at exponentially large magnetic field is analyzed resulting in complex energy ghosts that signal the instability of the magnetized vacuum. Superluminal excitations (tachyons) appear, too, but for the magnetic field exceeding its instability threshold. Also other popular Lagrangians are tested to establish that the ones leading to spontaneous vacuum magnetization possess wrong convexity.Comment: Modified version of arXiv:0911.0640[hep-th] with Section IV and Appendix omitted, Subsections IIIC,D added, Subsection II D perfected, 33 pages, submitted to Phys. Rev.