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 $N=2$, $d=1$ supersymmetric quantum mechanics algebras. These two algebras can be combined under certain circumstances to form a central charge extended $N=4$ 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

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 $xz$-plane. As we shall demonstrate, the fermionic scattered states are associated to two $N=2$ one dimensional supersymmetric quantum mechanical algebras with zero central charge. These two symmetries are combined to form a non-trivial one dimensional $N=4$ superalgebra with various central charges. In addition, we form higher dimensional irreducible representations of the two $N=2$ 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 $z$-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 $N=2$ supersymmetric structure

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

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

Transverse Wave Propagation in Relativistic Two-fluid Plasmas around Schwarzschild-anti-de Sitter Black Hole

The 3+1 formalism of Thorne and Macdonald has been used to derive the linear two-fluid equations for transverse waves in the plasma closed to the Schwarzschild-anti-de Sitter (SAdS) black hole. We reformulate the relativistic two-fluid equations to take account of gravitational effects due to the event horizon and negative cosmological constant and describe the set of simultaneous linear equations for the perturbations. Using a local approximation we investigate the one-dimensional radial propagation of Alfven and high frequency electromagnetic waves. We derive the dispersion relation for these waves and solve it for the wave number k numerically.Comment: 11 pages. arXiv admin note: substantial text overlap with arXiv:1008.4838, arXiv:0807.4595, arXiv:0902.3766, arXiv:0806.2740, arXiv:0904.337