97 research outputs found
Central Charge Extended Supersymmetric Structures for Fundamental Fermions Around non-Abelian Vortices
Fermionic zero modes around non-abelian vortices are shown that they
constitute two , supersymmetric quantum mechanics algebras. These
two algebras can be combined under certain circumstances to form a central
charge extended supersymmetric quantum algebra. We thoroughly discuss the
implications of the existence of supersymmetric quantum mechanics algebras, in
the quantum Hilbert space of the fermionic zero modes
Dark Energy: The Shadowy Reflection of Dark Matter?
In this article, we review a series of recent theoretical results regarding a
conventional approach to the dark energy (DE) concept. This approach is
distinguished among others for its simplicity and its physical relevance. By
compromising General Relativity (GR) and Thermodynamics at cosmological scale,
we end up with a model without DE. Instead, the Universe we are proposing is
filled with a perfect fluid of self-interacting dark matter (DM), the volume
elements of which perform hydrodynamic flows. To the best of our knowledge, it
is the first time in a cosmological framework that the energy of the cosmic
fluid internal motions is also taken into account as a source of the universal
gravitational field. As we demonstrate, this form of energy may compensate for
the DE needed to compromise spatial flatness, while, depending on the
particular type of thermodynamic processes occurring in the interior of the DM
fluid (isothermal or polytropic), the Universe depicts itself as either
decelerating or accelerating (respectively). In both cases, there is no
disagreement between observations and the theoretical prediction of the distant
supernovae (SNe) Type Ia distribution. In fact, the cosmological model with
matter content in the form of a thermodynamically-involved DM fluid not only
interprets the observational data associated with the recent history of
Universe expansion, but also confronts successfully with every major
cosmological issue (such as the age and the coincidence problems). In this way,
depending on the type of thermodynamic processes in it, such a model may serve
either for a conventional DE cosmology or for a viable alternative one.Comment: Review article, 38 pages, 5 figures, accepted for publication in
Entrop
Extended Supersymmetric Quantum Mechanics Algebras in Scattering States of Fermions off Domain Walls
We study the underlying extended supersymmetric structure in a system
composed of fermions scattered off an infinitely extended static domain wall in
the -plane. As we shall demonstrate, the fermionic scattered states are
associated to two one dimensional supersymmetric quantum mechanical
algebras with zero central charge. These two symmetries are combined to form a
non-trivial one dimensional superalgebra with various central charges. In
addition, we form higher dimensional irreducible representations of the two
algebras. Moreover, we study how the Witten index behaves under compact
odd and even perturbations, coming from a background magnetic field and some
non-renormalizable Yukawa mass terms for the fermions. As we shall demonstrate,
the Witten index is invariant only when the magnetic field is taken into
account and particularly when only the -component of the field is taken into
account. Finally, we study the impact of this supersymmetric structures on the
Hilbert space of the fermionic states and also we present a deformed extension
of the supersymmetric structure
Higher-dimensional models in gravitational theories of quarticLagrangians
Ten-dimensional models, arising from a gravitational action which includes
terms up to the fourth order in curvature tensor, are discussed. The spacetime
consists of one timelike dimension and two maximally symmetric subspaces,
filled with matter in the form of an anisotropic fluid. Numerical integration
of the cosmological field equations indicates that exponential, as well as
power law, solutions are possible. We carry out a dynamical study of the
results in the H_{ext} - H_{int} plane and confirm the existence of
"attractors" in the evolution of the Universe. Those attracting points
correspond to "extended De Sitter" spacetimes, in which the external space
exhibits inflationary expansion, while the internal one contracts.Comment: LaTeXfile, 22 page
Parametric resonant acceleration of particles by gravitational waves
We study the resonant interaction of charged particles with a gravitational
wave propagating in the non-empty interstellar space in the presence of a
uniform magnetic field. It is found that this interaction can be cast in the
form of a parametric resonance problem which, besides the main resonance,
allows for the existence of many secondary ones. Each of them is associated
with a non-zero resonant width, depending on the amplitude of the wave and the
energy density of the interstellar plasma. Numerical estimates of the
particles' energisation and the ensuing damping of the wave are given.Comment: LaTeX file, 16 page
The Emission of Electromagnetic Radiation from Charges Accelerated by Gravitational Waves and its Astrophysical Implications
We provide calculations and theoretical arguments supporting the emission of
electromagnetic radiation from charged particles accelerated by gravitational
waves (GWs). These waves have significant indirect evidence to support their
existence, yet they interact weakly with ordinary matter. We show that the
induced oscillations of charged particles interacting with a GW, which lead to
the emission of electromagnetic radiation, will also result in wave
attenuation. These ideas are supported by a small body of literature, as well
as additional arguments for particle acceleration based on GW memory effects.
We derive order of magnitude power calculations for various initial charge
distributions accelerated by GWs. The resulting power emission is extremely
small for all but very strong GWs interacting with large quantities of charge.
If the results here are confirmed and supplemented, significant consequences
such as attenuation of early universe GWs could result. Additionally, this
effect could extend GW detection techniques into the electromagnetic regime.
These explorations are worthy of study to determine the presence of such
radiation, as it is extremely important to refine our theoretical framework in
an era of active GW astrophysics.Comment: Appears in Gravitational Wave Astrophysics, Editor C.F. Sopuerta,
Astrophysics and Space Science Proceedings, Volume 40. ISBN
978-3-319-10487-4. Springer International Publishing Switzerland, 2015, p.
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