arXiv subjects

V. K. Oikonomou

Publications and source records attributed to V. K. Oikonomou.

At least 253 records · Page 14Linked to original sources

arXiv2014

Supersymmetric Chern-Simons Vortex Systems and Extended Supersymmetric Quantum Mechanics Algebras

We study N=2 supersymmetric Chern-Simons Higgs models in $(2+1)$-dimensions and the existence of extended underlying supersymmetric quantum mechanics algebras. Our findings indicate that the fermionic zero modes quantum system in conjunction with the system of zero modes corresponding to bosonic fluctuations, are related to an N=4 extended 1-dimensional supersymmetric algebra with central charge, a result closely connected to the N=2 spacetime supersymmetry of the total system. We also add soft supersymmetric terms to the fermionic sector in order to examine how this affects the index of the corresponding Dirac operator, with the latter characterizing the degeneracy of the solitonic solutions. In addition, we analyze the impact of the underlying supersymmetric quantum algebras to the zero mode bosonic fluctuations. This is relevant to the quantum theory of self-dual vortices and particularly for the symmetries of the metric of the space of vortices solutions and also for the non-zero mode states of bosonic fluctuations.

hep-th↗

arXiv2014

Low Dimensional Supersymmetries in SUSY Chern-Simons Systems and Geometrical Implications

We study in detail the underlying graded geometric structure of abelian N=2 supersymmetric Chern-Simons theory in $(2+1)$-dimensions. This structure is an attribute of the hidden unbroken one dimensional N=2 supersymmetries that the system also possesses. We establish the result that the geometric structures corresponding to the bosonic and to the fermionic sectors are equivalent fibre bundles over the $(2+1)$-dimensional manifold. Moreover, we find a geometrical answer to the question why some and not all of the fermionic sections are related to a N=2 supersymmetric algebra. Our findings are useful for the quantum theory of Chern-Simons vortices.

math-ph↗

arXiv2014

Superconducting Cosmic Strings and One Dimensional Extended Supersymmetric Algebras

In this article we study in detail the supersymmetric structures that underlie the system of fermionic zero modes around a superconducting cosmic string. Particularly, we extend the analysis existing in the literature on the one dimensional $N=2$ supersymmetry and we find multiple $N=2$, $d=1$ supersymmetries. In addition, compact perturbations of the Witten index of the system are performed and we find to which physical situations these perturbations correspond. More importantly, we demonstrate that there exists a much more rich supersymmetric structure underlying the system of fermions with $N_f$ flavors and these are $N$-extended supersymmetric structures with non-trivial topological charges, with "$N$" depending on the fermion flavors.

hep-th↗

arXiv2014

Color Superconductivity, Fermionic Quasinormal Modes in Reissner-Nordström-anti-de Sitter Spacetimes and Supersymmetry

We study two fermionic systems that have an underlying supersymmetric structure, namely a color superconductor and Dirac fermion in a Reissner-Nordström-anti-de Sitter gravitational background. In the chiral limit of the color superconductor, the localized fermionic zero modes around the vortex form an N=2 with zero central charge $d=1$ quantum algebra, with all the operators being Fredholm. We compute the Witten index of this algebra and we find an unbroken supersymmetry. The fermionic gravitational system in the chiral limit too, has two underlying unbroken N=2, $d=1$ supersymmetric algebras. The unbroken supersymmetry in the later is guaranteed by the existence of fermionic quasinormal modes in the Reissner-Nordström-anti-de Sitter background. In this case the operators are not Fredholm and regularized indices are deployed.

hep-th↗

arXiv2014

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.

hep-th↗

arXiv2013

Localized Fermions on Domain Walls and Extended Supersymmetric Quantum Mechanics

We study fermionic fields localized on topologically unstable domain walls bounded by strings in a grand unified theory theoretical framework. Particularly, we found that the localized fermionic degrees of freedom, which are up and down quarks as long as charged leptons, are connected to three independent N=2, $d=1$ supersymmetric quantum mechanics algebras. As we demonstrate, these algebras can be combined to form higher order representations of N=2, $d=1$ supersymmetry. Due to the uniform coupling of the domain wall solutions to the down-quarks and leptons, we also show that a higher order N=2, $d=1$ representation of the down-quark--lepton system is invariant under a duality transformation between the couplings. In addition, the two N=2, $d=1$ supersymmetries of the down-quark--lepton system, combine at the coupling unification scale to an N=4, $d=1$ supersymmetry. Furthermore, we present the various extra geometric and algebraic attributes that the fermionic systems acquire, owing to the underlying N=2, $d=1$ algebras.

hep-th↗

arXiv2013

An Exponential F(R) Dark Energy Model

We present an exponential $F(R)$ modified gravity model in the Jordan and the Einstein frame. We use a general approach in order to investigate and demonstrate the viability of the model. Apart from the general features that this models has, which actually render it viable at a first step, we address the issues of finite time singularities, Newton's law corrections and the scalaron mass. As we will evince, the model passes these latter two tests successfully and also has no finite time singularities, a feature inherent to other well studied exponential models.

gr-qc↗

arXiv2013

Casimir Force of Fermions Coupled to Monopoles in Six Dimensional Spacetime

We calculate the Casimir force for a fermionic quantum field in a piston geometry with three parallel plates. The fermion satisfies bag boundary conditions on the plates and the spacetime is assumed to have compact extra dimensions. The calculation is performed in the cases where the extra space has toroidal and spherical topology. We are mainly interested in the case in which the fermion is coupled non-trivially to an extra dimensional defect, with a torus extra dimensional topological background. We found that in certain limits, the Casimir force corresponding to the defect-fermion system and to the sphere, has opposite sign, in reference to those corresponding to the toroidal extra dimensional spaces.

hep-th↗

arXiv2013

An Electric Analogue to Gravity Induced Vacuum Dominance

It is shown that when a strong electric field is turned on as a background in a charged scalar field, the vacuum state of the scalar field becomes exponentially amplified. This is an analogue to gravity induced vacuum amplification, where the vacuum state becomes exponentially amplified for some geometries.

gr-qc↗

arXiv2013

Extended Supersymmetries and 2+1 Dimensional Supersymmetric Chern Simons Theories

We study N=2 supersymmetric Chern-Simons Higgs models in $(2+1)$-dimensions. As we will demonstrate, an extended supersymmetric quantum mechanics algebras underlies the fermionic zero modes quantum system and the zero modes corresponding to bosonic fluctuations. These two algebras, in turn, combine to give an N=4 extended 1-dimensional supersymmetric algebra with central charge

hep-th↗

arXiv2013

Graded Geometric Structures Underlying F-Theory Related Defect Theories

In the context of F-theory, we study the related eight dimensional super-Yang-Mills theory and reveal the underlying supersymmetric quantum mechanics algebra that the fermionic fields localized on the corresponding defect theory are related to. Particularly, the localized fermionic fields constitute a graded vector space, and in turn this graded space enriches the geometric structures that can be built on the initial eight-dimensional space. We construct the implied composite fibre bundles, which include the graded affine vector space and demonstrate that the composite sections of this fibre bundle are in one-to-one correspondence to the sections of the square root of the canonical bundle corresponding to the submanifold on which the zero modes are localized.

math-ph↗

arXiv2013

Hidden Supersymmetry in Dirac Fermion Quasinormal Modes of Black Holes

We connect the quasinormal modes corresponding to Dirac fermions in various black holes backgrounds to an N=2 supersymmetric quantum mechanics algebra, which can be constructed from the radial part of the fermionic solutions of the Dirac equation. In the massless fermion case, the quasinormal modes are in bijective correspondence with the zero modes of the fermionic system and this results to unbroken supersymmetry. The massive case is more evolved but as we prove, supersymmetry remains unbroken even in this case.

gr-qc↗

arXiv2013

Singularities of the Casimir Energy for Quantum Field Theories with Lifshitz Dimensions

We study the singularities that the Casimir energy of a scalar field in spacetimes with Lifshitz dimensions exhibits, and provide expressions of the energy in terms of multidimensional zeta functions for the massless case. Using the zeta-regularization method, we found that when the 4-dimensional spacetime has Lifshitz dimensions, then for specific values of the critical exponents, the Casimir energy is singular, in contrast to the non-Lifshitz case. Particularly we found that when the value of the critical exponent is $z=2$, the Casimir energy is singular, while for $z\geq 3$ the Casimir energy is regular. In addition, when flat extra dimensions are considered, the critical exponents of the Lifshitz dimensions affect drastically the Casimir energy, introducing singularities that are absent in the non-Lifshitz case. We also discuss the Casimir energy in the context of braneworld models and the perspective of Lifshitz dimensions in such framework.

hep-th↗

arXiv2012

De Sitter Cosmic Strings and Supersymmetry

We study massive spinor fields in the geometry of a straight cosmic string in a de Sitter background. We find a hidden N=2 supersymmetry in the fermionic solutions of the equations of motion. We connect the zero mode solutions to the heat-kernel regularized Witten index of the supersymmetric algebra.

hep-th↗

arXiv2011

A Criterion for Physically Acceptable Extra Dimensions with Boundaries

We present a criterion for deciding which compact extra dimensional spaces yield physically reliable Newton's law corrections. We study compact manifolds with boundary and without boundary. The boundary conditions which we use on the boundaries are Dirichlet or Neumann. We find that compact connected Riemannian manifolds with Dirichlet boundaries are completely excluded as extra dimensional spaces.

hep-th↗

arXiv2011

The 2d Gross-Neveu Model for Pseudovector Fermions and Tachyonic Mass Generation

Recent observations in the OPERA experiment suggest that the neutrino could propagate with speed that is superluminal. Based on early theoretical work on tachyonic fermions we shall study a modification of the Gross-Neveu model in two dimensions. We shall see that the theory results to the dynamical generation of real and imaginary masses. These imaginary masses indicate the possibility that tachyonic solutions (or instabilities) could exist in the theory. The implications of a tachyonic neutrino coming from astrophysical sources are critically discussed. Moreover, we present a toy model that consists of an U(2,2) invariant Dirac Lagrangian. This theory can have tachyonic masses as solutions. A natural mass splitting between the solutions is a natural outcome of the formalism.

hep-th↗

arXiv2011

F-theory Yukawa Couplings and Supersymmetric Quantum Mechanics

The localized fermions on the intersection curve $Σ$ of D7-branes, are connected to a N=2 supersymmetric quantum mechanics algebra. Due to this algebra the fields obey a global U(1) symmetry. This symmetry restricts the proton decay operators and the neutrino mass terms. Particularly, we find that several proton decay operators are forbidden and the Majorana mass term is the only one allowed in the theory. A special SUSY QM algebra is studied at the end of the paper. In addition we study the impact of a non-trivial holomorphic metric perturbation on the localized solutions along each matter curve. Moreover, we study the connection of the localized solutions to an N=2 supersymmetric quantum mechanics algebra when background fluxes are turned on.

hep-th↗

arXiv2011

Testing extra dimensions with boundaries using Newton's law modifications

Extra dimensions with boundaries are often used in the literature, to provide phenomenological models that mimic the standard model. In this context, we explore possible modifications to Newton's law due to the existence of an extra-dimensional space, at the boundary of which the gravitational field obeys Dirichlet, Neumann or mixed boundary conditions. We focus on two types of extra space, namely, the disk and the interval. As we prove, in order to have a consistent Newton's law modification (i.e., of the Yukawa-type), some of the extra-dimensional spaces that have been used in the literature, must be ruled out.

hep-th↗