Relativistic corrections to the long range interaction between closed shell atoms

The complete $O(\alpha^2)$ correction to the long range interaction between neutral closed shell atoms is obtained, the relation to the asymptotic expansion of the known short range interaction at the atomic scale is presented and a general interaction potential which is valid in the whole range of the inter atomic distances is constructed.Comment: 9 pages, accepted for Phys. Rev.

Quadrupolar contact terms and Hyperfine Structure

In the interaction of two electric quadrupoles, there is at short distances a contact term proportional to the second derivative of a delta function. This contact term contributes to the hyperfine splitting of bound states of two particles with spin one or higher-for example the bound states of Omega minus and a nucleus of spin one.The contact hyperfine splitting occurs in states with orbital angular momentum one(p-wave), in contrast to the Fermi contact interaction which is in s-states.We find that these contact splittings will be observable with Omega minus atoms and help measure the quadrupole moment and charge radius of the hyperon.Comment: 19 pages; two sentences deleted from first versio

Synchrotron radiation by fast fermions in heavy-ion collisions

We study the synchrotron radiation of gluons by fast quarks in strong magnetic field produced by colliding relativistic heavy-ions. We argue that due to high electric conductivity of plasma, time variation of the magnetic field is slow and estimate its relaxation time. We calculate the energy loss due to synchrotron radiation of gluons by fast quarks. We find that the typical energy loss per unit length for a light quark at LHC is a few GeV per fm. This effect alone predicts quenching of jets with $p_\bot$ up to about 20 GeV. We also show that the spin-flip transition effect accompanying the synchrotron radiation leads to a strong polarization of quarks and leptons with respect to the direction of the magnetic field. Observation of the lepton polarization may provide a direct evidence of existence of strong magnetic field in heavy-ion collisions.Comment: 10 pages, 6 figures; v3: estimate of the relaxation time of magnetic field is revised, acknowledgment adde

Coulomb problem for vector bosons versus Standard Model

The Coulomb problem for vector bosons W(+/-) propagating in an attractive Coulomb field incorporates a known difficulty, i.e. the total charge of the boson localized on the Coulomb center turns out infinite. This fact contradicts the renormalizability of the Standard model, which presumes that at small distances all physical quantities are well defined. The paradox is shown to be resolved by the QED vacuum polarization, which brings in a strong effective repulsion and eradicates the infinite charge of the boson on the Coulomb center. The effect makes the Coulomb problem for vector bosons well defined and consistent with the Standard Model.Comment: 4 page

Classical Noncommutative Electrodynamics with External Source

In a $U(1)_{\star}$-noncommutative (NC) gauge field theory we extend the Seiberg-Witten (SW) map to include the (gauge-invariance-violating) external current and formulate - to the first order in the NC parameter - gauge-covariant classical field equations. We find solutions to these equations in the vacuum and in an external magnetic field, when the 4-current is a static electric charge of a finite size $a$, restricted from below by the elementary length. We impose extra boundary conditions, which we use to rule out all singularities, $1/r$ included, from the solutions. The static charge proves to be a magnetic dipole, with its magnetic moment being inversely proportional to its size $a$. The external magnetic field modifies the long-range Coulomb field and some electromagnetic form-factors. We also analyze the ambiguity in the SW map and show that at least to the order studied here it is equivalent to the ambiguity of adding a homogeneous solution to the current-conservation equation

Relativistic Coulomb problem for particles with arbitrary half-integer spin

Using relativistic tensor-bispinorial equations proposed in hep-th/0412213 we solve the Kepler problem for a charged particle with arbitrary half-integer spin interacting with the Coulomb potential.Comment: Misprints are correcte

Quantum Theory and Galois Fields

We discuss the motivation and main results of a quantum theory over a Galois field (GFQT). The goal of the paper is to describe main ideas of GFQT in a simplest possible way and to give clear and simple arguments that GFQT is a more natural quantum theory than the standard one. The paper has been prepared as a presentation to the ICSSUR' 2005 conference (Besancon, France, May 2-6, 2005).Comment: Latex, 24 pages, 1 figur

Interelectronic-interaction effects on the two-photon decay rates of heavy He-like ions

Based on a rigorous QED approach a theoretical analysis is performed for the two-photon transitions in heavy He-like ions. Special attention is paid to the interelectronic-interaction corrections to the decay rates that are taken into account within the two-time Green-function method. Detailed calculations are carried out for the two-photon transitions 2^1S_0 -> 1^1S_0 and 2^3S_1 -> 1^1S_0 in He-like ions within the range of nuclear numbers Z=28-92. The total decay rates together with the spectral distributions are given. The obtained results are compared with experimental values and previous calculations.Comment: 17 pages, 7 figure

Non-Linear Compton Scattering of Ultrashort and Ultraintense Laser Pulses

The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed, which is independent of the considered pulse shape and pulse length. A broad distribution of scatted photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase space region is identified where the differential photon distribution is strongly modified by quantum effects.Comment: 31 pages, 10 figure

Laser assisted decay of quasistationary states

The effects of intense electromagnetic fields on the decay of quasistationary states are investigated theoretically. We focus on the parameter regime of strong laser fields and nonlinear effects where an essentially nonperturbative description is required. Our approach is based on the imaginary time method previously introduced in the theory of strong-field ionization. Spectra and total decay rates are presented for a test case and the results are compared with exact numerical calculations. The potential of this method is confirmed by good quantitative agreement with the numerical results.Comment: 24 pages, 5 figure