285 research outputs found
Controlled delocalization of electronic states in a multi-strand quasiperiodic lattice
Finite strips, composed of a periodic stacking of infinite quasiperiodic
Fibonacci chains, have been investigated in terms of their electronic
properties. The system is described by a tight binding Hamiltonian. The
eigenvalue spectrum of such a multi-strand quasiperiodic network is found to be
sensitive on the mutual values of the intra-strand and inter-strand tunnel
hoppings, whose distribution displays a unique three-subband self-similar
pattern in a parameter subspace. In addition, it is observed that special
numerical correlations between the nearest and the next-nearest neighbor
hopping integrals can render a substantial part of the energy spectrum
absolutely continuous. Extended, Bloch like functions populate the above
continuous zones, signalling a complete delocalization of single particle
states even in such a non-translationally invariant system, and more
importantly, a phenomenon that can be engineered by tuning the relative
strengths of the hopping parameters. A commutation relation between the
potential and the hopping matrices enables us to work out the precise
correlation which helps to engineer the extended eigenfunctions and determine
the band positions at will.Comment: 8 pages, 6 figure
Implementation and characterization of BinaryWeave: A new search pipeline for continuous gravitational waves from Scorpius X-1
Scorpius X-1 (Sco X-1) has long been considered one of the most promising
targets for detecting continuous gravitational waves with ground-based
detectors. Observational searches for Sco X-1 have achieved substantial
sensitivity improvements in recent years, to the point of starting to rule out
emission at the torque-balance limit in the low-frequency range \sim 40--180
Hz. In order to further enhance the detection probability, however, there is
still much ground to cover for the full range of plausible signal frequencies
\sim 20--1500 Hz, as well as a wider range of uncertainties in binary orbital
parameters. Motivated by this challenge, we have developed BinaryWeave, a new
search pipeline for continuous waves from a neutron star in a known binary
system such as Sco X-1. This pipeline employs a semi-coherent StackSlide
F-statistic using efficient lattice-based metric template banks, which can
cover wide ranges in frequency and unknown orbital parameters. We present a
detailed timing model and extensive injection-and-recovery simulations that
illustrate that the pipeline can achieve high detection sensitivities over a
significant portion of the parameter space when assuming sufficiently large
(but realistic) computing budgets. Our studies further underline the need for
stricter constraints on the Sco X-1 orbital parameters from electromagnetic
observations, in order to be able to push sensitivity below the torque-balance
limit over the entire range of possible source parameters.Comment: 19 pages, 7 figures, 3 table
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