Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userScreening of the Coulomb potential in superstrong magnetic field: atomic levels and spontaneous production of positrons
103
0
0.0
(
0
)
Authors
M. I. Vysotsky
Ask ChatGPT about the research
No Arabic abstract
The expanded variant of the lectures delivered at the 39th ITEP Winter School in 2011
rate research
Read More
We obtain the following analytical formula which describes the dependence of the electric potential of a point-like charge on the distance away from it in the direction of an external magnetic field B: Phi(z) = e/|z| [ 1- exp(-sqrt{6m_e^2}|z|) + exp(-sqrt{(2/pi) e^3 B + 6m_e^2} |z|) ]. The deviation from Coulombs law becomes essential for B > 3pi B_{cr}/alpha = 3 pi m_e^2/e^3 approx 6 10^{16} G. In such superstrong fields, electrons are ultra-relativistic except those which occupy the lowest Landau level (LLL) and which have the energy epsilon_0^2 = m_e^2 + p_z^2. The energy spectrum on which LLL splits in the presence of the atomic nucleus is found analytically. For B > 3 pi B_{cr}/alpha, it substantially differs from the one obtained without accounting for the modification of the atomic potential.
We solve the one-dimensional Poisson equation along a magnetic field line, both analytically and numerically, for a given current density incorporating effects of returning positrons. We find that the number of returning positrons per one primary electrons should be smaller than unity, and the returning of positrons occurs only in a very short braking distance scale. As a result, for realistic polar cap parameters, the accelerating electric field will not be screened out; thus, the model fails to be self-consistent. A previous belief that pair creation with a pair density higher than the Goldreich-Julian density immediately screens out the electric field is unjustified. We suggest some possibilities to resolve this difficulty.
The process of neutrino production of electron positron pairs in a magnetic field of arbitrary strength, where electrons and positrons can be created in the states corresponding to excited Landau levels, is analysed. The mean value of the neutrino energy loss due to the process $ u to u e^- e^+$ is calculated. The result can be applied for calculating the efficiency of the electron-positron plasma production by neutrinos in the conditions of the Kerr black hole accretion disc considered by experts as the most possible source of a short cosmological gamma burst. The presented research can be also useful for further development of the calculation technic for an analysis of quantum processes in external active medium, and in part in the conditions of moderately strong magnetic field, when taking account of the ground Landau level appears to be insufficient.
We reexamine the process $gammato e^++ e^-$ in a background magnetic field comparable to $B_cequiv m_e^2/e$. This process is known to be non-perturbative in the magnetic-field strength. However, it can be shown that the {it moments} of the above pair production width is proportional to the derivatives of photon polarization function at the zero energy, which is perturbative in $B$. Hence, the pair-production width can be easily obtained from the latter by the inverse Mellin transform. The implications of our approach are discussed.
We study nonlinear trident in laser pulses in the high-energy limit, where the initial electron experiences, in its rest frame, an electromagnetic field strength above Schwingers critical field. At lower energies the dominant contribution comes from the two-step part, but in the high-energy limit the dominant contribution comes instead from the one-step term. We obtain new approximations that explain the relation between the high-energy limit of trident and pair production by a Coulomb field, as well as the role of the Weizsacker-Williams approximation and why it does not agree with the high-$chi$ limit of the locally-constant-field approximation. We also show that the next-to-leading order in the large-$a_0$ expansion is, in the high-energy limit, nonlocal and is numerically very important even for quite large $a_0$. We show that the small-$a_0$ perturbation series has a finite radius of convergence, but using Pade-conformal methods we obtain resummations that go beyond the radius of convergence and have a large numerical overlap with the large-$a_0$ approximation. We use Borel-Pade-conformal methods to resum the small-$chi$ expansion and obtain a high precision up to very large $chi$. We also use newer resummation methods based on hypergeometric/Meijer-G and confluent hypergeometric functions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
