5,553 research outputs found
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
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