Physics – Atomic Physics
Scientific paper
Aug 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt.........8h&link_type=abstract
Thesis (PHD). UNIVERSITY OF CALIFORNIA, SANTA CRUZ , Source DAI-B 59/02, p. 693, Aug 1998, 245 pages.
Physics
Atomic Physics
1
Quantum Electrodynamics
Scientific paper
In this thesis, I will examine how intense magnetic fields influence physical processes in the vicinity of and inside neutron stars. An intense magnetic field can have dramatic effects on the propagation of electromagnetic radiation and the structure of a dipole field. We first derive a compact analytic form for the effective Lagrangian of quantum electrodynamics (QED) with an external field. An intense field modifies the propagators of the virtual electron-positron pairs formed as a photon travels. We first treat the effects of QED as an effective magnetic permeability and electric permittivity. We derive compact expressions for the index of refraction of a low-frequency photon traveling through an electric or magnetic field. We examine the one-loop corrections to a macroscopic magnetic dipole and find that the nonlinear paramagnetic properties of the vacuum result in dipole, hexapole, 2n-pole moments which are a function of distance from the dipole. The speed of light in a magnetized vacuum is a function of the strength of the fields. We propose an experiment using the existing LIGO testbed interferometer which can measure this effect with a signal-to-noise ratio of twenty. We expect an intense magnetic field to affect the propagation of an electromagnetic wave. We treat the electromagnetic field as a relativistic fluid and derive the equations for the characteristics. The characteristics of the wave begin to cross after a number of wavelengths. A shock forms. The energy of the wave dissipates into electron-positron pairs shortly thereafter. We next discuss how an intense magnetic field affects atomic structure. We find that the bound electron shields the nucleus quite effectively and that the cross section for nuclear fusion reactions is dramatically increased. We then develop both an analytic and a numerical technique to study the properties of simple atoms and molecules in an intense magnetic field. We increase the scale from atomic physics to solid-state physics to understand how an intense magnetic field affects the transmission of heat through the envelope of a cooling neutron star. We develop a plane-parallel analytic treatment of the neutron star envelope in an intense magnetic field. The surface emission in this limit is proportional to the square of the cosine of the angle between the radial direction and the magnetic field, the cos2/psi rule. We reexamine the problem of heat flow for weaker fields by numerically integrating the thermal structure of the envelope. We derive the relationship between core temperature and transmitted flux over a wide range of field strengths and geometries. We find that in weaker fields cos2/psi rule is less accurate. We explore how an intense magnetic field affects the observed flux from neutron stars with both iron and light-element envelopes. Although a magnetic field strongly affects the thermal evolution of the neutron star the effect of altering the composition of the envelope is more dramatic. We propose that the emission from anomalous X-ray pulsars is simply the surface thermal emission from isolated neutron stars. (Abstract shortened by UMI.)
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