817,383 research outputs found
Optical Identification of Cepheids in 19 Host Galaxies of Type Ia Supernovae and NGC 4258 with the Hubble Space Telescope
We present results of an optical search for Cepheid variable stars using the
Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the
maser-host galaxy NGC 4258, conducted as part of the SH0ES project (Supernovae
and H0 for the Equation of State of dark energy). The targets include 9 newly
imaged SN Ia hosts using a novel strategy based on a long-pass filter that
minimizes the number of HST orbits required to detect and accurately determine
Cepheid properties. We carried out a homogeneous reduction and analysis of all
observations, including new universal variability searches in all SN Ia hosts,
that yielded a total of 2200 variables with well-defined selection criteria --
the largest such sample identified outside the Local Group. These objects are
used in a companion paper to determine the local value of H0 with a total
uncertainty of 2.4%.Comment: ApJ, in press. v2 adds missing co-author to arXiv metadata and text
in acknowledgment
Theory of quasiparticle interference in mirror symmetric 2D systems and its application to surface states of topological crystalline insulators
We study symmetry protected features in the quasiparticle interference (QPI)
pattern of 2D systems with mirror symmetries and time-reversal symmetry, around
a single static point impurity. We show that, in the Fourier transformed local
density of states (FT-LDOS), \rho(\bq,\omega), while the position of high
intensity peaks generically depends on the geometric features of the iso-energy
contour at energy , the \emph{absence} of certain peaks is guaranteed
by the opposite mirror eigenvalues of the two Bloch states that are (i) on the
mirror symmetric lines in the Brillouin zone (BZ) and (ii) separated by
scattering vector \bq. We apply the general result to the QPI on the -surface of topological crystalline insulator PbSnTe and predict
all vanishing peaks in \rho(\bq,\omega). The model-independent analysis is
supported by numerical calculations using an effective four-band model derived
from symmetry analysis.Comment: Six-page text plus 2.5-page appendices, three figures and one table.
Accepted versio
Planar diagrams from optimization
We propose a new toy model of a heteropolymer chain capable of forming planar
secondary structures typical for RNA molecules. In this model the sequential
intervals between neighboring monomers along a chain are considered as quenched
random variables. Using the optimization procedure for a special class of
concave--type potentials, borrowed from optimal transport analysis, we derive
the local difference equation for the ground state free energy of the chain
with the planar (RNA--like) architecture of paired links. We consider various
distribution functions of intervals between neighboring monomers (truncated
Gaussian and scale--free) and demonstrate the existence of a topological
crossover from sequential to essentially embedded (nested) configurations of
paired links.Comment: 10 pages, 10 figures, the proof is added. arXiv admin note: text
overlap with arXiv:1102.155
Density profiles of supernova matter and determination of neutrino parameters
The flavor conversion of supernova neutrinos can lead to observable
signatures related to the unknown neutrino parameters. As one of the
determinants in dictating the efficiency of resonant flavor conversion, the
local density profile near the MSW resonance in a supernova environment is,
however, not so well understood. In this analysis, variable power-law functions
are adopted to represent the independent local density profiles near the
locations of resonance. It is shown that the uncertain matter density profile
in a supernova, the possible neutrino mass hierarchies, and the undetermined
1-3 mixing angle would result in six distinct scenarios in terms of the
survival probabilities of and . The feasibility of
probing the undetermined neutrino mass hierarchy and the 1-3 mixing angle with
the supernova neutrinos is then examined using several proposed experimental
observables. Given the incomplete knowledge of the supernova matter profile,
the analysis is further expanded to incorporate the Earth matter effect. The
possible impact due to the choice of models, which differ in the average energy
and in the luminosity of neutrinos, is also addressed in the analysis.Comment: 27 pages, 10 figures. text and figures revised, references added, to
appear in Phys. Rev.
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