Gravity Asymptotics with Topological Parameters

In four dimensional gravity theory, the Barbero-Immirzi parameter has a topological origin, and can be identified as the coefficient multiplying the Nieh-Yan topological density in the gravity Lagrangian, as proposed by Date et al.[1]. Based on this fact, a first order action formulation for spacetimes with boundaries is introduced. The bulk Lagrangian, containing the Nieh-Yan density, needs to be supplemented with suitable boundary terms so that it leads to a well-defined variational principle. Within this general framework, we analyse spacetimes with and without a cosmological constant. For locally Anti de Sitter (or de Sitter) asymptotia, the action principle has non-trivial implications. It admits an extremum for all such solutions provided the SO(3,1) Pontryagin and Euler topological densities are added to it with fixed coefficients. The resulting Lagrangian, while containing all three topological densities, has only one independent topological coupling constant, namely, the Barbero-Immirzi parameter. In the final analysis, it emerges as a coefficient of the SO(3,2) (or SO(4,1)) Pontryagin density, and is present in the action only for manifolds for which the corresponding topological index is non-zero.Comment: References added; Published versio

Electronic and optical properties of SnX2(X=S, Se)-InSe van der Waals heterostructures from first- principle calculations

In this work from first-principles simulations we investigate bilayer van der Waals heterostructures (vdWh) of emerging 2-dimensional (2D) optical materials SnS 2 and SnSe 2 with monolayer InSe. With density functional theory (DFT) calculations, we study the structural, electronic, optical and carrier transport properties of the SnX 2 (X=S,Se)-InSe vdWh. Calculations show SnX 2 -InSe in its most stable stacking form (named AB-1) to be a material with a small (0.6- 0.7eV) indirect band-gap. The bilayer vdWh shows broad spectrum optical response, with number of peaks in the infra-red to visible region. In terms of carrier transport properties, asymmetry in conductance was observed with respect to the transport direction and electron and hole transmission. The findings are promising from the viewpoint of nanoelectronics and photonics.Comment: The following article has been submitted for peer-review. After it is published, it will be found at Lin

Confronting the Inert Doublet Model with results from Run 1 of the LHC

The Inert Doublet Model (IDM) is a simple extension of the Standard Model (SM) that aims to address the naturalness problem, electroweak baryogenesis and accommodate a viable dark matter (DM) candidate, along with a rich phenomenlogy in terms of collider signatures. In this note, we address the constraints on the IDM by recasting dilepton + missing energy searches performed for Supersymmetry at LHC run-1 using Madanalysis5.Comment: Contribution to the 18th International Conference From the Planck Scale to the Electroweak Scale, Ioannina, Greece. (admin note :Text overlap with arXiv: 1503.07367

GENERAL RELATIVISTIC EFFECTS ON THE INDUCED ELECTRIC FIELD EXTERIOR TO PULSARS

The importance of general relativity to the induced electric field exterior to pulsars has been investigated by assuming aligned vacuum and non-vacuum magnetosphere models. For this purpose the stationary and axisymmetric vector potential in Schwarzschild geometry has been considered and the corresponding expressions for the induced electric field due to the rotation of the magnetic dipole have been derived for both vacuum and non-vacuum conditions. Due to the change in the magnetic dipole field in curved spacetime the induced electric field also changes its magnitude and direction and increases significantly near the surface of the star. As a consequence the surface charge density, the acceleration of charged particles in vacuum magnetospheres and the space charge density in non-vacuum magnetosphere greatly increase near the surface of the star. The results provide the most general feature of the important role played by gravitation and could have several potentially important implications for the production of high-energy radiation from pulsars.Comment: 16 pages, LATEX, 7 figures available upon request, to appear in The Astrophysical Journa

Investigating Antigram Behaviour using Distributional Semantics

Language is an extremely interesting subject to study, each day presenting new challenges and new topics for research. Words in particular have several unique characteristics which when explored, prove to be astonishing. Anagrams and Antigrams are such words possessing these amazing properties. The presented work is an exploration into generating anagrams from a given word and determining whether there exists antigram relationships between the pairs of generated anagrams in light of the Word2Vec distributional semantic similarity model. The experiments conducted, showed promising results for detecting antigrams.Comment: 4 page