Black Hole entropy in D=2+1 dimensions from extended Chern-Simons term in a gravitational background

We study the contribution to entropy of Black Holes in D=2+1 dimensions from an extension of the Chern Simons theory including higher derivative in a curved space-time.Comment: 8 pages, AMSte

An alternative calculation of the Casimir energy for kappa-deformed electrodynamics

A simple, but effcient way of calculating regularized Casimir energies suitable for non-trivial frequency spectra is briefly described and applied to the case of a kappa-deformed scalar field theory. The results are consistent with the ones obtained by other means.Comment: Four pages, latex file. Submitted for the Proceedings of the XXIV Brazilian National Meeting on Particles and Fields held in Caxambu MG, Brazil, September 30 -- October 4, 200

Non-Abelian Magnetic Monopoles in a Background of Gravitation with Fermions

The purpose of this paper is to study static solution configuration which describes the magnetic monopoles in a scenary where the gravitation is coupled with Higgs, Yang-Mills and fermions. We are looking for analysis of the energy functional and Bogomol'nyi equations. The Einstein equations now take into consideration the fermions' contribution for energy-momentum tensor. The interesting aspect here is to verify that the fermion field gives a contribution for non abelian magnetic field and for potential which minimise the energy functional

G\"{o}del Type solution with rotation, expansion and closed time-like curves

We propose a time-varying parameter $\underline{\alpha}$ for G\"{o}del metric and an energy momentum tensor corresponding to this geometry is found. To satisfy covariance arguments time-varying gravitational and cosmological term are introduced. The ``Einstein's equation'' for this special evolution for the Universe are written down where expansion, rotation and closed time-like curves appear as a combination between standard model, G\"{o}del and steady state properties are obtained.Comment: 10 pages, AMSte

Black Hole Entropy in 1+1 Dimensions from a Quasi-Chern Simons term in a Gravitational Background

We introduce a 'quasi-topological` term [1] in D=1+1 dimensions and the entropy for black holes is calculated [2]. The source of entropy in this case is justified by a non-null stress-energy tensor

Analysis of Maxwell Equations in a Gravitational Field

In a gravitational field, we analyze the Maxwell equations, the correponding electromagnetic wave and continuity equations. A particular solution for parellel electric and magnetic fields in a gravitational background is presented. These solutions also satisfy the free-wave equations and the phenomenology suggested by plasma physics.Comment: 10 pages, AMSte

Some Comments of Vlasov-Liouville Equation and its Relation with Gravitational Field

We discuss here the possibility to write the Liouville-Vlasov equation for the Wigner-function of a spinor field coupled to a gauge field with field strength tensor $F^{\mu\nu}$ in a curved space-time versus a local Lorentz manifold (introduction of local Lorentz coordinates) with an appropriate definition of a covariant derivative carried out using a spin connection $B_{\mu}^{ab}(x)$.Comment: 11 pages, AMSte

Some Comments on Wheeler De Witt Equation for Gravitational Collapse and the Problem of Time

We write the Hamiltonian for a gravitational spherically symmetric scalar field collapse with massive scalar field source, and we discuss the application of Wheeler De Witt equation as well as the appearence of time in this context. Using an Ansatz for Wheeler De Witt equation, solutions are discussed including the appearence of time evolution.Comment: 9 pages, AMSte

Molding the flow of light with a magnetic field: plasmonic cloaking and directional scattering

We investigate electromagnetic scattering and plasmonic cloaking in a system composed by a dielectric cylinder coated with a magneto-optical shell. In the long-wavelength limit we demonstrate that the application of an external magnetic field can not only switch on and off the cloaking mechanism but also mitigate losses, as the absorption cross-section is shown to be minimal precisely at the cloaking operation frequency band. We also show that the angular distribution of the scattered radiation can be effectively controlled by applying an external magnetic field, allowing for a swift change in the scattering pattern. By demonstrating that these results are feasible with realistic, existing magneto-optical materials, such as graphene epitaxially grown on SiC, we suggest that magnetic fields could be used as an effective, versatile external agent to tune plasmonic cloaks and to dynamically control electromagnetic scattering in an unprecedented way, we hope that these results may find use in disruptive photonic technologies.Comment: 7 pages, 8 figure

Tuning plasmonic cloaks with an external magnetic field

We propose a mechanism to actively tune the operation of plasmonic cloaks with an external magnetic field by investigating electromagnetic scattering by a dielectric cylinder coated with a magneto-optical shell. In the long wavelength limit we show that the presence of an external magnetic field may drastically reduce the scattering cross-section at all observation angles. We demonstrate that the application of external magnetic fields can modify the operation wavelength without the need of changing material and/or geometrical parameters. We also show that applied magnetic fields can reversibly switch on and off the cloak operation. These results, which could be achieved for existing magneto-optical materials, are shown to be robust to material losses, so that they may pave the way for developing actively tunable, versatile plasmonic cloaks.Comment: 5 pages and 4 figures Figure 4 has been remad