In this letter we calculate the energy loss of highly magnetized neutron star due to friction with quantum vacuum, namely Quantum Vacuum Friction (QVF). Taking into account one-loop corrections in the effective Heisenberg-Euler Lagrangian of the light-light interaction, we derive an analytic expression for QVF allowing us to consider magnetic field at the surface of the star as high as $10^{11} $T. In the case of magnetars with high magnetic field above the QED critical field, we show that the energy loss by QVF dominates the energy loss process. This has important consequences, in particular on the inferred value of the magnetic field. This also indicates the need for independent measurements of magnetic field, energy loss rate, and of the braking index to fully characterize magnetars.
We have recently shown that in a highly magnetized neutron star atmospheric plasma, vacuum polarization can induce resonant conversion of photon polarization modes via a mechanism analogous to MSW neutrino oscillation. In a recent paper Ozel has dismissed this mode conversion effect as ``mistakes''. Here we explain why our arguments/calculations of this effect are correct.
In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein like resonance across which a X-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to an unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized X-rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magn…
It is known that vacuum polarization can modify the photon propagation modes in the atmospheric plasma of a strongly magnetized neutron star. A resonance occurs when the effect of vacuum polarization on the photon modes balances that of the plasma. We show that a photon (with energy $E\go$ a few keV) propagating outward in the atmosphere can convert from one polarization mode into another as it traverses the resonant density, $ρ_{res}\simeq Y_e^{-1}η^{-2}(B/10^{14} G)^2(E/1 keV)^2$ g cm$^{-3}$, where $Y_e$ is the electron fraction, and $η\sim 1$ is a slowly varying function of the magnetic fie…
Charge separation effects in the expansion of magnetized relativistic electron-ion plasmas into a vacuum are examined using 2-1/2-dimensional particle-in-cell plasma simulations. The electrostatic field at the plasma surface decelerates electrons and accelerates ions. A fraction of the surface electrons are trapped and accelerated by the pondermotive force of the propagating electromagnetic pulse, a mechanism we call the DRPA (diamagnetic relativistic pulse accelerator). This charge separation is enhanced as the initial plasma temperature is decreased. The overall energy gain of the plasma par…
We consider the phenomenon of a gamma-ray burst as a nonlinear collapse of a magnetic cavity surrounding a neutron star with very strong magnetic field B = 10^15 - 10^16 G due to the process of the bubble shape instability in a resonant MHD field of the accreting plasma. The QED effect of vacuum polarizability by the strong magnetic field is taken into account. We develop an analogy with the phenomenon of sonoluminescence (SL) when the gas bubble is located in the surrounding liquid with a driven sound intensity. We show that this analogy between GRB and SL phenomena really exists.
We consider the effects of vacuum polarization and proton cyclotron resonances on the propagation of radiation through a strongly magnetized plasma. We analyze the conditions under which the photons evolve adiabatically through the resonant density and find that the adibaticity condition is satisfied for most photon energies of interest, allowing for a normal-mode treatment of the photon propagation. We then construct radiative equilibrium atmosphere models of strongly magnetized neutron stars that includes these effects, employing a new numerical method that resolves accurately the sharp chan…
We present a theoretical study of radiative transfer in strongly magnetized electron-ion plasmas, focusing on the effect of vacuum polarization due to quantum electrodynamics. This study is directly relevant to thermal radiation from the surfaces of highly magnetized neutron stars, which have been detected in recent years. Strong-field vacuum polarization modifies the photon propagation modes in the plasma, and induces a ``vacuum resonance'' at which a polarized X-ray photon propagating outward in the neutron star atmosphere can convert from a low-opacity mode to a high-opacity mode and vice v…
We make use of a flat, axisymmetric Bianchi I metric to investigate the effects of a magnetic field upon the dynamics of the universe for the case in which the accompanying fluid is a cosmological constant and derive two exact solutions to the dynamical equations for this situation. We examine the behaviour of the scale factor perpendicular and parallel to the field lines, A(t) and W(t) respectively, and find the expected behaviour. The field has the strongest effect when A(t) is small, decelerating collapse perpendicular to the field lines, due to magnetic pressure, and accelerating collapse …
We construct hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with surface fields B=10^12-5x10^14 G and effective temperatures T_eff a few x 10^5-10^6 K by solving the full radiative transfer equations for both polarization modes in the magnetized hydrogen plasma. The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars. We study the effects of vacuum polarization and bound atoms on the atmosphere structure and spectra. For the lower magnetic field models (B 10^12 G), the spectral features due to neutral atoms lie at…
Theoretical modeling of surface emission from magnetized neutron stars (NSs) requires proper treatment of QED effects, in particular the effect of photon mode conversion due to the ``vacuum resonance'' between plasma and vacuum polarization. Previous NS atmosphere models incorporated this effect approximately, using transfer equations for the photon modes which are inadequate near the vacuum resonance, particularly for field strengths around $B_l\simeq 7\times 10^{13}$ G, where the vacuum resonance occurs near the photosphere. In this paper, we provide an accurate treatment of the QED-induced …
The process of photon splitting, becomes allowed in the presence of strong magnetic field. We calculate the influence of magnetized plasma on the photon splitting absorption coefficient. We calculate the refraction coefficients and polarization vectors with the inclusion of the vacuum terms at an arbitrary value of the magnetic field, and then find photon splitting matrix element taking into account the terms that vanish in vacuum, but may be nonzero in the presence of plasma. We find the photon splitting rate in plasma with the density typical for a neutron star star atmosphere and identify a…
We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B=10^14-10^15 G, as appropriate for magnetars. Vacuum polarization modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the MSW mechanism for neutrino oscillation. We construct atmosphere models in radiative equilibrium wit…
The structure and magnitude of the electromagnetic field produced by a rotating accretion disk around a black hole were determined. The disk matter is assumed to be a magnetized plasma with a frozenin poloidal magnetic field. The vacuum approximation is used outside the disk.
In this letter we study the propagation of light in the neighbourhood of magnetised neutron stars. Thanks to the optical properties of quantum vacuum in the presence of a magnetic field, light emitted by background astronomical objects is deviated giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect and we discuss the possibility of its observation. We show that this effect could be detected monitoring the evolution of the recently discovered double neutron star system J0737-3039.
In continuation to our earlier work, in which the structure of the vacuum polarisation tensor in a medium was analysed in presence of a background electro-magnetic field, we discuss the absorptive part of the vacuum polarization tensor. Using the real time formalism of finite temperature field theory we calculate the absorptive part of 1-loop vacuum polarisation tensor in the weak field limit ($eB < m^2$). Estimates of the absorption probability are also made for different physical conditions of the background medium.
In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect couples the direction of the polarization of photons leaving the NS surface, to the direction of the magnetic field along the ray's path. We analyze the consequences that this effect has on aligning the polarization vectors to generate large net polarizations, while considering thermal radiation originating from a thermal hydrogen atmosphere. Counter to previous predictions, we show that the thermal radiation should be highly polarized even in the optical. When detected, this polar…
We study electric potential of a charge placed in a strong magnetic field B>>4.4x10^{13}G, as modified by the vacuum polarization. In such field the electron Larmour radius is much less than its Compton length. At the Larmour distances a scaling law occurs, with the potential determined by a magnetic-field-independent function. The scaling regime implies short-range interaction, expressed by Yukawa law. The electromagnetic interaction regains its long-range character at distances larger than the Compton length, the potential decreasing across the magnetic field faster than along. Correction to…
Using a 2-1/2-dimensional particle-in-cell (PIC) code to simulate the relativistic expansion of a magnetized collisionless plasma into a vacuum, we report a new mechanism in which the magnetic energy is efficiently converted into the directed kinetic energy of a small fraction of surface particles. We study this mechanism for both electron-positron and electron-ion (mi/me=100, me is the electron rest mass) plasmas. For the electron-positron case the pairs can be accelerated to ultra-relativistic energies. For electron-ion plasmas most of the energy gain goes to the ions.
The thermal emission of strongly magnetized neutron-star atmospheres is thought to be highly polarized. However, because of the different orientations of the magnetic field over the surface of the neutron star (NS), it is commonly assumed that the net observed polarization will be significantly reduced as the polarization from different regions will cancel each other. We show that the birefringence of the magnetized QED vacuum decouples the polarization modes in the magnetosphere; therefore, the direction of the polarization follows the direction of the magnetic field up to a large distance fr…
We study the electron-positron vacuum in a strong magnetic field $B$ in parallel with Casimir effect. Use is made of the energy-momentum tensor, taken as the zero temperature and zero density limit of the relativistic quantum statistical tensor. In both magnetic field and Casimir cases it is shown the arising of anisotropic pressures. In the first case the pressure transversal to the field $B$ is negative, whereas along $B$ an usual positive pressure arises. Similarly, in addition to the usual negative Casimir pressure perpendicular to the plates, the existence of a positive pressure along the…
Following the general formalism presented by Rezzolla, Ahmedov and Miller (MNRAS, 322, 723 2001), we here derive analytic solutions of the electromagnetic fields equations in the internal and external background spacetime of a slowly rotating highly conducting magnetized neutron star. The star is assumed to be isolated and in vacuum, with a dipolar magnetic field not aligned with the axis of rotation. Our results indicate that the electromagnetic fields of a slowly rotating neutron star are modified by general relativistic effects arising from both the monopolar and the dipolar parts of the gr…
Axions are pseudo-scalar particles, those arise because of breaking of Peccei Queen (PQ) symmetry. Axions have a tree level coupling to two photons. As a consequence there exists a tree level coupling of axion to photon in a magnetic field. However, in an external magnetic field, there exists a new loop induced, axion photon vertex, that gives rise to axion photon coupling. The strength of the tree level axion photon coupling in magnetic field is known to be model dependent. However in a magnetic field, the new loop induced coupling has some interesting features. This note discusses the new ax…
