Lattice analysis of semi-leptonic form factors

We present preliminary results from simulations done on 170 $32^3 \times 64$ lattices at $\beta = 6.0$ using quenched Wilson fermions. This talk focuses on the $Q^2$ behavior of the form-factors, extrapolation in quark masses, dependence on renormalization scheme, and comparison with heavy-quark effective theory (HQET). Even though we cannot estimate errors due to quenching and discretization, our results are consistent with experimental results for $D$ decays. We present results for the Isgur-Wise function and estimate $\xi'(w=1) = 0.97(6)$.Comment: 4 pages. Talk presented at Lattice 95. Latex. Modified "axis" source for figures also include

Exploring N-rich phases in LixNy clusters for hydrogen storage at nano-scale

We have performed cascade genetic algorithm and ab initio atomistic thermodynamics under the framework of first-principles density functional theory to study the (meta-)stability of a wide range of LixNy clusters. We found that hybrid xc-functional is essential to address this problem as a local/semi-local functional simply fails even to predict a qualitative prediction. Most importantly, we find that though in bulk Lithium Nitride, Li rich phase, i.e. Li3N, is the stable stoichiometry, in small LixNy clusters N-rich phases are more stable at thermodynamic equilibrium. We further show a that these N-rich clusters are promising hydrogen storage material because of their easy adsorption and desorption ability at respectively low (< 300K) and moderately high temperature (> 600K).Comment: 5 pages, 4 figure

Evolution of the Modern Phase of Written Bangla: A Statistical Study

Active languages such as Bangla (or Bengali) evolve over time due to a variety of social, cultural, economic, and political issues. In this paper, we analyze the change in the written form of the modern phase of Bangla quantitatively in terms of character-level, syllable-level, morpheme-level and word-level features. We collect three different types of corpora---classical, newspapers and blogs---and test whether the differences in their features are statistically significant. Results suggest that there are significant changes in the length of a word when measured in terms of characters, but there is not much difference in usage of different characters, syllables and morphemes in a word or of different words in a sentence. To the best of our knowledge, this is the first work on Bangla of this kind.Comment: LCC 201

A note on entropy of de Sitter black holes

A de Sitter black hole or a black hole spacetime endowed with a positive cosmological constant has two Killing horizons -- a black hole and a cosmological event horizon surrounding it. It is natural to expect that the total Bekenstein-Hawking entropy of such spacetimes should be the sum of the two horizons' areas. In this work we apply the recently developed formalism using the Gibbons-Hawking-York boundary term and the near horizon symmetries to derive the total entropy of such two horizon spacetimes. We construct a suitable general geometric set up for general stationary axisymmetric spacetimes with two or more than two commuting Killing vector fields in an arbitrary spacetime dimensions. This framework helps us to deal with both the horizons in an equal footing. We show that in order to obtain the total entropy of such spacetimes, the near horizon mode functions for the diffeomorphism generating vector fields have to be restricted in a certain manner, compared to the single horizon spacetimes. We next discuss specific known exact solutions belonging to the Kerr-Newman- or the Plebanski-Demianski-de Sitter families to show that they fall into the category of our general framework. We end with a sketch of further possible extensions of this work.Comment: v2, 16pp; added references and discussions, results unchange

Exploring semiconductor substrates for Silicene epitaxy

We have carried out first-principles based DFT calculation on electronic properties of silicene monolayer on various (111) semi-conducting surfaces. We find that the relative stability and other properties of the silicene overlayer depends sensitively on whether the interacting top layer of the substrate is metal or non-metal terminated. The nature of silicene-monolayer on the metal termi- nated surface can be metallic or even magnetic, depending upon the choice of the substrate. The silicene overlayer undergoes n-type doping on metal terminated surface while it undergoes p-type doping on non metal terminated surfaces of the semiconductor substrates.Comment: 5 journal pages, 3 figure