Narrow Results

We analyze the behavior of the energy spectrum of the Klein–Gordon equation in the presence of a truncated hyperbolic tangent potential. From our analysis we obtain that, for some values of the potential there is embedding of the bound states into the negative energy continuum, showing that, in opposition to the general belief, relativistic scalar particles in one-dimensional short range potentials can exhibit resonant behavior and also the Schiff–Snyder effect.

The oscillator representation is used for the nonperturbative description of vacuum particle creation in a strong time-dependent electric field in the framework of scalar QED. It is shown that the method can be more effective for the derivation of the quantum kinetic equation (KE) in comparison with the Bogoliubov method of time-dependent canonical transformations. This KE is used for the investigation of vacuum creation in periodical linear and circular polarized electric fields and also in the case of the presence of a constant magnetic field, including the back reaction problem. In particular, these examples are applied for a model illustration of some features of vacuum creation of electron–positron plasma within the planned experiments on the X-ray free electron lasers.

We discuss consistency of the concept of external background in QFT. Different restrictions on magnitude of magnetic and electric fields are analyzed. The back reaction due to strong electric field is calculated and restrictions on the magnitude and duration of such a field are obtained. The problem of consistency of Dirac equation with a superstrong Coulomb field is discussed.

We discuss consistency of the concept of external background in QFT. Different restrictions on magnitude of magnetic and electric fields are analyzed. The back reaction due to strong electric field is calculated and restrictions on the magnitude and duration of such a field are obtained. The problem of consistency of Dirac equation with a superstrong Coulomb field is discussed.

Strong gravity regions, like the neighborhood of black holes or neutron stars, can induce non-minimal couplings between electromagnetic fields(EM) and gravity. In these regions, gravitational fields behave as a non-linear medium in which the electromagnetic fields propagate. For a system of mass M and size R, the surface potential scales as M/R. Pulsar timing array, Double pulsar Shapiro delay, and Event horizon telescope probe that largest surface potentials [10⁻⁴ − 10⁻²]. With many future experiments, it is possible to constrain the non-minimal coupling between electromagnetic fields and gravity. As a step in this direction, we consider the non-minimal coupling of EM field tensor through Riemann tensor for a dynamical black-hole, described by Sultana-Dyer(SD) metric. The non-minimal coupling leads to modified dispersion relations of photons, which get simplified at $\tilde{E}/\tilde{L}>>1$ regime, where $\tilde{E}$ and $\tilde{L}$ are two conserved quantities obtained by taking into account the symmetries of the metric. We calculate polarization-dependent photon deflection angle and arrival time from these dispersion relations, which we evaluate considering different astrophysical sources of photons. We compare the analytical results with the current astrophysical observations to constraint the non-minimal coupling parameters to Riemann tensor more stringently.

The decay of the vacuum in supercritical Coulomb fields is discussed. Connected with that is the time delay in giant nuclear systems like U+Cm etc. This – in turn – is connected with the production of superheavy elements. Recent theoretical and experimental studies of extreme neutron-rich isotopes are also mentioned. A perspective for future research is given.