Dark matter in the framework of the shell-universe

We show that the shell-universe model (used to explain the observed expansion rate of the universe without a dark energy component) provides a natural mechanism for local increasing of the brane tension leading to the modified Newtons law alternative to galactic dark matter.     

Black Hole Information Problem and Wave Bursts

By reexamination of the boundary conditions of wave equation on a black hole horizon it is found not harmonic, but real-valued exponentially time-dependent solutions. This means that quantum particles probably do not cross the Schwarzschild horizon, but are absorbed and some are reflected by it, what potentially can solve the famous black hole information paradox. To study this strong gravitational lensing we are introducing an effective negative cosmological constant between the Schwarzschild and photon spheres. It is shown that the reflected particles can obtain their additional energy in this effective AdS space and could explain properties of some unusually strong signals, like LIGO events, gamma ray and fast radio bursts.     

New class of N-dimensional braneworlds

The new class of the non-stationary solutions to the system of N-dimensional equations for coupled gravitational and massless scalar field is found. The model represents a single (N-1)-brane in a space-time with one large (infinite) and (N-5) small (compact) space-like extra dimensions. In some particular cases the model corresponds to the gravitational and scalar field standing waves bounded by the brane. These braneworlds can be relevant in string and other higher dimensional models.     

Tensor-tensor model of gravity

The main problem with the standard gauge theory of the Poincaré group realized as a subgroup of GL(5, R) is that fields, whose physical sense is unclear, appear in connection with the non-Lorentz symmetries. Here, the Poincaré fields are treated as new Yang-Mills-type tensor fields and gravity is treated as a Higgs-Goldstone field. In this case, the effective metric tensor for matter is a hybrid of two tensor fields. In the linear approximation, the massive translation gauge field gives the Yukawa-type correction to the Newtonian potential. Also, corrections to the standard Einstein post-Newtonian formulas for light deflection and radar echo delay are obtained. A spherically symmetric solution to the equations of translation gauge fields is also found. The translation gauge field leads to the existence of a singular surface, which is impenetrable to matter and can prevent gravitational collapse of a large body, inside the Schwarzschild sphere. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 113, No. 3, pp. 448–460, December, 1997. This work was supported in part by the Georgian Government and the International Science Foundation (ISF Grant No. MXL 200).     

Gravitational repulsion of spherical domain walls

It is shown that the equations of motion and Tolman's formula require reverse flow of time on a spherical domain wall. Moreover, the active gravitational mass of the wall becomes negative. The critical mass and radius of a bubble are found for realistic models.Institute of Physics, Georgian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 100, No. 2, pp. 303–311, August, 1994.     

Coriolis force and Sagnac effect

The optical Sagnac effect is considered, when the fictitious gravitational field simulates the reflections from the mirrors. It is shown that no contradiction exists between the conclusions of the laboratory and rotated observers. Because of the acting of a gravity-like Coriolis force, the trajectories of coand anti-rotating photons have different radii in the rotating reference frame, while in the case of equal radii the effective gravitational potentials for the photons have to be different.     

Localization of gauge bosons in the 5D standing wave braneworld

We investigate the problem of localization of gauge fields within the 5D standing wave braneworld model and show that in the case of increasing warp factor there exist normalizable vector field zero modes on the brane.     

Gravitational repulsion of spherical domain walls

We consider the disagreements in gravitational properties of planar and spherical domain walls (bubbles). We argue that if the spherical domain walls are described by the same equation of state as the planar walls are, then they also exhibit gravitational repulsion just as the planar walls are assumed to do. In the thin-wall approximation we show the existence of the solution of Einstein equations with negative gravitational mass of bubbles and the reversed direction of time flow on the shell. The equilibrium radius and critical mass of such objects are found for realistic models.     

Information-Probabilistic Description of the Universe

We describe the universe as a single entangled ensemble of quantum particles. The total entropy of this world ensemble, which can be expressed as a sum of information, thermodynamic and entanglement components, is assumed to be always zero. This condition suggests information quantization, which we associate with the Planck’s action. Then the entropy neutrality condition for the universe leads to the zero-action principle. We show that the main concepts of classical space-time and gravity naturally emerge in this picture. A generalized least action principle, which embraces the maximal entropy principles of information theory, is introduced.     

Machian Origin of the Entropic Gravity and Cosmic Acceleration

We discuss the emergence of relativistic effects in the Machian universe with a global preferred frame and use thermodynamic considerations to clarify the origin of gravity as an entropic force and the origin of dark energy/cosmic acceleration as related to the Hawking-Unruh temperature at the universe’s horizon.