Friedel oscillations due to Fermi arcs in Weyl semimetals

Weyl semimetals harbor unusual surface states known as Fermi arcs, which are essentially disjoint segments of a two dimensional Fermi surface. We describe a prescription for obtaining Fermi arcs of arbitrary shape and connectivity by stacking alternate two dimensional electron and hole Fermi surfaces and adding suitable interlayer coupling. Using this prescription, we compute the local density of states -- a quantity directly relevant to scanning tunneling microscopy -- on a Weyl semimetal surface in the presence of a point scatterer and present results for a particular model that is expected to apply to pyrochlore iridate Weyl semimetals. For thin samples, Fermi arcs on opposite surfaces conspire to allow nested backscattering, resulting in strong Friedel oscillations on the surface. These oscillations die out as the sample thickness is increased and Fermi arcs from the bottom surface retreat and weak oscillations, due to scattering between the top surface Fermi arcs alone, survive. The surface spectral function -- accessible to photoemission experiments -- is also computed. In the thermodynamic limit, this calculation can be done analytically and separate contributions from the Fermi arcs and the bulk states can be seen.Comment: 5 pages, 2 figures; minor changes in figures and text, typos correcte

Three dimensional Lifshitz black hole and the Korteweg-de Vries equation

We consider a solution of three dimensional New Massive Gravity with a negative cosmological constant and use the AdS/CTF correspondence to inquire about the equivalent two dimensional model at the boundary. We conclude that there should be a close relation with the Korteweg-de Vries equation.Comment: 4 page

Automatic Clustering with Single Optimal Solution

Determining optimal number of clusters in a dataset is a challenging task. Though some methods are available, there is no algorithm that produces unique clustering solution. The paper proposes an Automatic Merging for Single Optimal Solution (AMSOS) which aims to generate unique and nearly optimal clusters for the given datasets automatically. The AMSOS is iteratively merges the closest clusters automatically by validating with cluster validity measure to find single and nearly optimal clusters for the given data set. Experiments on both synthetic and real data have proved that the proposed algorithm finds single and nearly optimal clustering structure in terms of number of clusters, compactness and separation.Comment: 13 pages,4 Tables, 3 figure

Non-Universal Gaugino Masses, CDMS, and the LHC

We consider the possibility that the recently reported events at the CDMS-II direct dark matter detection experiment are the result of coherent scattering of supersymmetric neutralinos. In such a scenario we argue that non-universal soft supersymmetry breaking gaugino masses are favored with a resulting lightest neutralino with significant Higgsino and wino components. We discuss the accompanying signals which must be seen at liquid-xenon direct detection experiments and indirect detection experiments if such a supersymmetric interpretation is to be maintained. We illustrate the possible consequences for early discovery channels at the LHC via a set of benchmark points designed to give rise to an observed event rate comparable to the reported CDMS-II data.Comment: Typos corrected and references adde