Gauge Invariant Extension of Linearized Horava Gravity

In the present paper we have constructed a gauge invariant extension of a generic Horava Gravity (HG) model (with quadratic curvature terms) in linearized version in a systematic procedure. No additional fields are introduced. The linearized HG model is explicitly shown to be a gauge fixed version of the Einstein Gravity (EG) thus proving the Bellorin-Restuccia conjecture in a robust way. In the process we have explicitly computed the correct Hamiltonian dynamics using Dirac Brackets appearing from the Second Class Constraints present in the HG model. We comment on applying this scheme to the full non-linear HG.Comment: 11 pages, no figures, some changes in the text but no change in the results, Journal reference: Mod. Phys. Lett. A, Vol. 26, No. 37 (2011) pp. 279

Electron-Electron Interactions on the Edge States of Graphene: A Many Body Configuration Interaction Study

We have studied zigzag and armchair graphene nano ribbons (GNRs), described by the Hubbard Hamiltonian using quantum many body configuration interaction methods. Due to finite termination, we find that the bipartite nature of the graphene lattice gets destroyed at the edges making the ground state of the zigzag GNRs a high spin state, whereas the ground state of the armchair GNRs remains a singlet. Our calculations of charge and spin densities suggest that, although the electron density prefers to accumulate on the edges, instead of spin polarization, the up and down spins prefer to mix throughout the GNR lattice. While the many body charge gap results in insulating behavior for both kinds of GNRs, the conduction upon application of electric field is still possible through the edge channels because of their high electron density. Analysis of optical states suggest differences in quantum efficiency of luminescence for zigzag and armchair GNRs, which can be probed by simple experiments.Comment: 5 pages, 4 figure

Sub-leading contributions to the black hole entropy in the brick wall approach

[Abridged] We compute the canonical entropy of a quantum scalar field around static and spherically symmetric black holes through the brick wall approach at the higher orders (in fact, up to the sixth order in \hbar) in the WKB approximation. We explicitly show that the brick wall model generally predicts corrections to the Bekenstein-Hawking entropy in all spacetime dimensions. In four dimensions, we find that the corrections to the Bekenstein-Hawking entropy are of the form (A^n \log A), while, in six dimensions, the corrections behave as (A^m + A^n \log A), where A denotes the area of the black hole event horizon, and (m, n) < 1. We compare our results with the corrections to the Bekenstein-Hawking entropy that have been obtained through the other approaches in the literature, and discuss the implications.Comment: 21 pages, Revtex 4; Final verson - 22 pages, References added, Accepted in Phys. Rev.

Nanoparticles of Cerium Oxide Targeted to an Amyloid-Beta Antigen of Alzheimer\u27s Disease and Associated Methods

Disclosed is a composition immunologically targeted to Alzheimer’s disease (AD), the composition containing amine functionalized nanoparticles of Cerium oxide coated with polyethylene glycol and bearing an antibody specific for an amyloid-beta antigen associated with AD. The invention also includes a medication manufactured with the targeted nanoceria particles and methods of treatment by administering the targeted nanoceria particles to patients in need thereof

Large magnetoelectric coupling in nanoscale BiFeO3_3 from direct electrical measurements

We report the results of direct measurement of remanent hysteresis loops on nanochains of BiFeO$_3$ at room temperature under zero and $\sim$20 kOe magnetic field. We noticed a suppression of remanent polarization by nearly $\sim$40\% under the magnetic field. The powder neutron diffraction data reveal significant ion displacements under a magnetic field which seems to be the origin of the suppression of polarization. The isolated nanoparticles, comprising the chains, exhibit evolution of ferroelectric domains under dc electric field and complete 180$^o$ switching in switching-spectroscopy piezoresponse force microscopy. They also exhibit stronger ferromagnetism with nearly an order of magnitude higher saturation magnetization than that of the bulk sample. These results show that the nanoscale BiFeO$_3$ exhibits coexistence of ferroelectric and ferromagnetic order and a strong magnetoelectric multiferroic coupling at room temperature comparable to what some of the type-II multiferroics show at a very low temperature.Comment: 7 pages with 5 figures, published in Phys. Rev.

Phase transitions in higher derivative gravity and gauge theory: R-charged black holes

This is a continuation of our earlier work where we constructed a phenomenologically motivated effective action of the boundary gauge theory at finite temperature and finite gauge coupling on $S^3 \times S^1$. In this paper, we argue that this effective action qualitatively reproduces the gauge theory representing various bulk phases of R-charged black hole with Gauss-Bonnet correction. We analyze the system both in canonical and grand canonical ensemble.Comment: 36 pages, 16 figures; v2: typos corrected, references adde