### Conveners

#### Thursday afternoon session

- Jutta Kunz (University of Oldenburg)

Local properties of scalar, fermionic and electromagnetic vacua are discussed in the presence of cosmic string type topological defects. As important characteristics of the vacuum state we consider the expectation values of the squared fields, of the energy-momentum tensor and of the current density in the case of charged fields. The topological contributions are extracted from the vacuum...

General relativity (GR) and quantum theory form the basis of the modern physical picture of the universe. However, attempts to unify them inevitably lead to violations of the Einstein Equivalence Principle (EEP) which is the basis of GR. A promising kind of experiments to test the domain of validity of EEP is based on measuring the gravitational redshift. Recent progress in the stability and...

We consider the gravity assist maneuver, that is, a correction of spacecraft motion at its passing near a planet, as a tool for evaluating the Eddington post-Newtonian parameters $\beta$ and $\gamma$, characterizing vacuum spherically symmetric gravitation fields in metric theories of gravity. We estimate the effect of variation in $\beta$ and $\gamma$ on a particular trajectory of a probe...

We consider the generalized Tolman solution of general relativity, describing the evolution of a spherical dust cloud in the presence of an external electric or magnetic field. In such models, we study the possible existence of wormhole throats defined as spheres of minimum radius at a fixed time instant, and prove the existence of throats in the elliptic branch under certain conditions...

We study the quantum-gravitational corrections to the power spectrum of a gauge-invariant inflationary scalar perturbations in a closed model of a universe. We consider canonical quantum gravity as an approach to quantizing gravity. This leads to the Wheeler-DeWitt equation, which has been studied by applying a semiclassical Born–Oppenheimer type of approximation. At the corresponding orders...

The knowledge of electromagnetic field of charged particles in the vicinity of a black hole is important for the study of many astrophysical phenomena, in particular of gamma-ray bursts and jets of supermassive black holes. In the present work we determine multipole coefficients of electromagnetic field for charged particle, radially falling into Schwarzschild black hole and consider the limit...

Due to the high-density nuclear matter equation of state (EOS) being as yet unknown, neutron stars (NSs) do not have a confirmed limiting “Chandrasekhar” type maximum mass. However,observations of NSs (PSR J1614-2230, PSR J0348+0432, PSR J0740+6620, PSR J0952–0607) indicate that NS’s limiting mass, if there is any, could be well over $2M⊙$. On the other hand, there exists an observational mass...

We consider general radially moving frames realized in the background of nonextremal black holes having causal structure similar to that of the Schwarzschild metric. In doing so, we generalize the Lemaître approach, constructing free-falling frames which are built from the reference particles with an arbitrary specific energy $e_0$ including $e_0<0$ and a special case $e_0=0$. The general...

We consider a family of 4-dimensional black hole solutions

governed by natural number $q= 1, 2, 3 , \dots$, which appear in the model with anisotropic fluid and the equations of state: $p_r = -\rho (2q-1)^{-1}$, $p_t = - p_r$, where $p_r$ and $p_t$ are pressures in radial and transverse directions, respectively, and $\rho > 0$ is the density. These equations of state obey weak,...

We consider the motion of charged particles in Gutsunaev--Manko spacetime, which is the exact solution of the Einstein--Maxwell field equations for a massive dipole. In the present work we study periodic orbits symmetric with respect to the equatorial plane. The spacetime is static and axially symmetric, therefore the problem is reduced to the motion in two-dimentional effective potential. We...