112 research outputs found
Modified gravity. Problems and observational manifestations
Some models of modified gravity and their observational manifestations are
considered. It is shown, that gravitating systems with mass density rising with
time evolve to a singular state with infinite curvature scalar. The universe
evolution during the radiation dominated epoch is studied in -extended
gravity theory. Particle production rate by the oscillating curvature is
calculated. Possible implications of the model for cosmological creation of
non-thermal dark matter are discussed.Comment: 8 pages, 4 figures, talk presented at Les Rencontres de Physique de
la Vallee d'Aoste, 26 February - 3 March, 201
New Options for SUSY-kind Dark Matter
In the conventional cosmology masses of the stable supersymmetric relics,
candidates for the dark matter (DM) particles, should be typically below 1 TeV.
This is in conflict with the LHC bounds on the low energy SUSY. However, in
-gravity the masses of the stable particles with the interaction strength
typical for SUSY could be much higher depending upon the dominant decay mode of
the scalaron. We discuss the bounds on the masses of DM particles for the
following dominant decay modes: to minimally coupled massless scalars, to
massive fermions, and to gauge bosons.Comment: 5 pages, 1 table. Talk presented at 20th Lomonosov Conference on
Elementary Particle Physics, Moscow, MSU, 19-25 August, 202
On Influence of Intensive Stationary Electromagnetic Field on the Behavior of Fermionic Systems
Exact solutions of Schroedinger and Pauli equations for charged particles in
an external stationary electromagnetic field of an arbitrary configuration are
constructed. Green functions of scalar and spinor particles are calculated in
this field. The corresponding equations for complex energy of particles bounded
by short range potential are deduced. Boundary condition typical for delta -
potential is not used in the treatment. Explicit analytical expressions are
given for the shift and width of a quasistationary level for different
configurations of the external field. The critical value of electric field in
which the idea of quasistationary level becomes meaningless is calculated. It
is shown that the common view on the stabilizing role of magnetic field
concerns only scalar particles.Comment: 15 pages, no figures, LaTeX2
Jeans Instability in Classical and Modified Gravity
Gravitational instability in classical Jeans theory, General Relativity, and
modified gravity is considered. The background density increase leads to a
faster growth of perturbations in comparison with the standard theory. The
transition to the Newtonian gauge in the case of coordinate dependent
background metric functions is studied. For modified gravity a new high
frequency stable solution is found
Curvature Oscillations in Modified Gravity and High Energy Cosmic Rays
It is shown that F(R)-modified gravitational theories lead to curvature
oscillations in astrophysical systems with rising energy density. The frequency
and the amplitude of such oscillations could be very high and would lead to
noticeable production of energetic cosmic ray particles.Comment: 7 pages, 2 figures, author's affiliation is correcte
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