Unification of gravity and electromagnetism revisited

Within the context of a $5D$ space-time, we construct a unified theory of gravity and electromagnetism from which the Einstein field equations and Maxwell equations emerge, with homogenous Maxwell equations appearing naturally. We also introduce a well-defined five dimensional energy-momentum tensor consistent with our unification scheme. A correction term appears in Maxwell equations which can be used to explain the recently discovered galactic magnetic fields.Comment: 10 page

Nano-structural, Electrical and Mechanical Characterization of Zirconium Oxide Thin Films as a Function of Annealing Temperature and Time

Zr thin films were deposited by DC magnetron sputtering technique on Si substrate and then post-annealed at different temperatures (150-750 °C in steps of 150 °C) and times (60 and 180 min) with flow of oxygen. X-ray diffraction (XRD) method was used for study of crystallographic structure. These results showed an orthorhombic structure for annealed films at 150 and a mixed structure of monoclinic and tetragonal for annealed films at higher temperatures (300-750 ºC). XRD result also showed that an increase in annealing temperature and time caused increasing of crystalline size. EDAX and AFM tech-niques were employed for investigation of chemical composition and surface morphology of samples, re-spectively. The results showed a granular structure for all samples, while the O / Zr ratio, grains size and surface roughness were increased with increasing of annealing temperature and time. A two probe instru-ment was used for electrical properties investigation, while hardness of films was measured by nano-indentation test. These results showed that increasing of annealing temperature and time caused increas-ing of electrical resistance and decreasing of hardness in the films. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3513

Brane f(R)f(\cal R) gravity

We consider a brane world scenario in which the bulk action is assumed to have the form of a generic function of the Ricci scalar $f(\mathcal{R})$ and derive the resulting Einstein field equations on the brane. In a constant curvature bulk a conserved geometric quantity appears in the field equations which can be associated with matter. We present cosmological and spherically symmetric solutions by assuming specific forms for $f(\mathcal{R})$ and show that the former can explain an accelerated expanding universe while the latter may account for galaxy rotation curves.Comment: 8 pages, 2 figures, to appear in EP

Detailed balance condition and ultraviolet stability of scalar field in Horava-Lifshitz gravity

Detailed balance and projectability conditions are two main assumptions when Horava recently formulated his theory of quantum gravity - the Horava-Lifshitz (HL) theory. While the latter represents an important ingredient, the former often believed needs to be abandoned, in order to obtain an ultraviolet stable scalar field, among other things. In this paper, because of several attractive features of this condition, we revisit it, and show that the scalar field can be stabilized, if the detailed balance condition is allowed to be softly broken. Although this is done explicitly in the non-relativistic general covariant setup of Horava-Melby-Thompson with an arbitrary coupling constant $\lambda$, generalized lately by da Silva, it is also true in other versions of the HL theory. With the detailed balance condition softly breaking, the number of independent coupling constants can be still significantly reduced. It is remarkable to note that, unlike other setups, in this da Silva generalization, there exists a master equation for the linear perturbations of the scalar field in the flat Friedmann-Robertson-Walker background.Comment: Some typos are corrected. To appear in JCA

Lifshitz-type Quantum Field Theories in Particle Physics

This introduction to Lifshitz-type field theories reviews some of its aspects in Particle Physics. Attractive features of these models are described with different examples, as the improvement of graphs convergence, the introduction of new renormalizable interactions, dynamical mass generation, asymptotic freedom, and other features related to more specific models. On the other hand, problems with the expected emergence of Lorentz symmetry in the IR are discussed, related to the different effective light cones seen by different particles when they interact.Comment: 26 pages, comments and references adde

Effective potential for Lifshitz type z=3 gauge theories

We consider the one-loop effective potential at zero temperature in field theories with anisotropic space-time scaling, with critical exponent $z=3$, including scalar, fermion and gauge fields. The fermion determinant generates a symmetry breaking term at one loop in the effective potential and a local minimum appears, for non zero scalar field, for every value of the Yukawa coupling. Depending on the relative strength of the coupling constants for the scalar and the gauge field, we find a second symmetry breaking local minimum in the effective potential for a bigger value of the scalar field.Comment: 12 pages, 3 figures. Minor corrections in the text, results unchange

f(R) theories

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in Relativity, Published version, Comments are welcom

Search for narrow resonances in dilepton mass spectra in proton-proton collisions at root s=13 TeV and combination with 8 TeV data

Peer reviewe

Search for top squark pair production in pp collisions at root s=13 TeV using single lepton events

Peer reviewe