L. A. Vassilevskaya

Axion in an external electromagnetic field

We investigate the effective interaction of a pseudoscalar particle with two photons in an external electromagnetic field in the general case of all external particles being off the mass shell. This interaction is used to study the radiative decay

Axion self-energy in a magnetic field

stackrel{ensuremath{rightarrow}}{a}ensuremath{gamma}ensuremath{gamma}

FIELD-INDUCED AXION DECAY A E+E- IN PLASMA

of the axion, a pseudoscalar particle associated with the Peccei-Quinn symmetry, and the crossing channel of photon splitting

Magnetic-field influence on radiative axion decay into photons of the same polarization

stackrel{ensuremath{rightarrow}}{ensuremath{gamma}}ensuremath{gamma}a

FIELD-INDUCED AXION EMISSION VIA PROCESS e+e-→a IN PLASMA

. It is shown that the external field removes the suppression associated with the smallness of the axion mass and so leads to the strong catalysis of these processes. The field-induced axion emission by the photon is analyzed as one more possible source of energy loss by astrophysical objects.

MASS SHIFT OF AXION IN MAGNETIC FIELD

The axion self-energy in an external magnetic field is investigated. It is shown that, in addition to the standard contribution due to axion interaction with virtual fermions, there exists the contribution induced by photon exchange. For the two contributions, expressions that take exactly into account an external field are obtained, and the limit of an ultrastrong magnetic field is explored for them. The question of whether two-dimensional QED, which effectively arises in the limit of a strong magnetic field, is applicable to calculating the virtual-fermion-induced contribution to the axion self-energy is analyzed.

Field-induced axion decay a → e+e− via plasmon

Abstract The axion decay a → e + e − is investigated in the presence of a plasma and an external magnetic field. The results demonstrate a strong catalyzing influence of medium. The axion lifetime in the magnetic field of order 10 15 G and at the temperature of order 10 MeV is reduced to 10 4 s.

AXION DECAY OF A PHOTON IN AN EXTERNAL ELECTROMAGNETIC FIELD

The decays of a pseudoscalar particle, the axion, into two photons of the same polarization are studied in the model involving direct axion-electron coupling. These processes, which are forbidden in a vacuum because of a pseudoscalar nature of the axion, become possible in a magnetic field. It is shown that the kinematics of ultrarelativistic-axion decay substantially depends on photon polarizations. The probability of radiative axion decay in the limit of a strong magnetic field substantially exceeds the corresponding probability in a vacuum.

Axion-electron interaction induced by an external magnetic field

The annihilation into axion e+e-→a is investigated in a plasma and an external magnetic field. This process via a plasmon intermediate state has a resonant character at a particular energy of the emitted axion. The emissivity by e+e-→a is compared with the axion cyclotron emissivity.

Photon-axion processes in a crossed external field

A mass-shift of the axion propagating in an external constant homogenious magnetic field is calculated. The contributions via an electron loop and a virtual photon are examined. It is shown that the virtual photon contribution dominates substantially over the electron-loop one. Under the conditions of the early Universe the electron-loop contribution to the massless axion mass-shift is equal to zero while the virtual photon contribution is finite and can be of order of the recent restrictions on the axion mass.