Exotic QED processes and atoms in strong external fields

Abstract

The discovery of very intense magnetic fields in compact cosmic objects (white dwarf stars with B ≈ 10² − 10⁵ Tesla, neutron stars with B ≈ 10⁷ − 10⁹ Tesla) has opened the possibility of studying the properties of matter under extreme conditions which can never be realized in terrestrial laboratories. Since in neutron star magnetic fields the characteristic quantum energy, the cyclotron energy, becomes of the order of the electron rest energy, it is obvious that even quantum electrodynamical processes are strongly influenced by these magnetic fields. In white dwarf magnetic fields the cyclotron energy is on the order of the binding energy of atoms, and therefore at these field strengths the properties of atoms will be drastically altered by the presence of the fields. I report on the progress that has been made in recent years in recalculating the properties of QED processes and atoms in these intense fields and the way this has helped in understanding the physical processes that occur in the vicinity of white dwarfs and neutron stars.

Highly excited atoms in strong laboratory field strengths (B ~ several Tesla) are exposed to an intense-field situation, because of their small binding energies, in the same way as are low-lying states of atoms in strong cosmic magnetic fields. Moreover, from a classical point of view these atoms serve as a real and physical example of simple nonintegrable systems with classical chaos. Therefore in this lecture I also elaborate on the important rôle studies of the properties of Rydberg atoms in strong terrestrial magnetic fields have played in answering the exciting question as to the existence of “quantum” chaos.