16,380 research outputs found
Spinor model of a perfect fluid
Different characteristic of matter influencing the evolution of the Universe
has been simulated by means of a nonlinear spinor field. We have considered two
cases where the spinor field nonlinearity occurs either as a result of
self-action or due to the interaction with a scalar field.Comment: 5 pages, some misprints are corrected, some new expressions are adde
Anisotropic cosmological models with spinor and scalar fields and viscous fluid in presence of a term: qualitative solutions
The study of a self-consistent system of interacting spinor and scalar fields
within the scope of a Bianchi type I (BI) gravitational field in presence of a
viscous fluid and term has been carried out. The system of equations
defining the evolution of the volume scale of BI universe, energy density and
corresponding Hubble constant has been derived. The system in question has been
thoroughly studied qualitatively. Corresponding solutions are graphically
illustrated. The system in question is also studied from the view point of blow
up. It has been shown that the blow up takes place only in presence of
viscosity.Comment: 18 pages, 14 figures, 12 Tables, section "Basic equations" has been
rewritte
Interplay between topology and disorder in a two-dimensional semi-Dirac material
We investigate the role of disorder in a two-dimensional semi-Dirac material
characterized by a linear dispersion in one, and a parabolic dispersion in the
orthogonal, direction. Using the self-consistent Born approximation, we show
that disorder can drive a topological Lifshitz transition from an insulator to
a semi-metal, as it generates a momentum independent off-diagonal contribution
to the self-energy. Breaking time-reversal symmetry enriches the topological
phase diagram with three distinct regimes-- single-node trivial, two-node
trivial and two-node Chern. We find that disorder can drive topological
transitions from both the single- and two-node trivial to the two-node Chern
regime. We further analyze these transitions in an appropriate tight-binding
Hamiltonian of an anisotropic hexagonal lattice, by calculating the real-space
Chern number. Additionally we compute the disorder-averaged entanglement
entropy which signals both the topological Lifshitz and Chern transition as a
function of the anisotropy of the hexagonal lattice. Finally, we discuss
experimental aspects of our results.Comment: 8 pages, 9 figure
- …