22,605 research outputs found
Random template banks and relaxed lattice coverings
Template-based searches for gravitational waves are often limited by the
computational cost associated with searching large parameter spaces. The study
of efficient template banks, in the sense of using the smallest number of
templates, is therefore of great practical interest. The "traditional" approach
to template-bank construction requires every point in parameter space to be
covered by at least one template, which rapidly becomes inefficient at higher
dimensions. Here we study an alternative approach, where any point in parameter
space is covered only with a given probability < 1. We find that by giving up
complete coverage in this way, large reductions in the number of templates are
possible, especially at higher dimensions. The prime examples studied here are
"random template banks", in which templates are placed randomly with uniform
probability over the parameter space. In addition to its obvious simplicity,
this method turns out to be surprisingly efficient. We analyze the statistical
properties of such random template banks, and compare their efficiency to
traditional lattice coverings. We further study "relaxed" lattice coverings
(using Zn and An* lattices), which similarly cover any signal location only
with probability < 1. The relaxed An* lattice is found to yield the most
efficient template banks at low dimensions (n < 10), while random template
banks increasingly outperform any other method at higher dimensions.Comment: 13 pages, 10 figures, submitted to PR
Entanglement Distillation Protocols and Number Theory
We show that the analysis of entanglement distillation protocols for qudits
of arbitrary dimension benefits from applying basic concepts from number
theory, since the set \zdn associated to Bell diagonal states is a module
rather than a vector space. We find that a partition of \zdn into divisor
classes characterizes the invariant properties of mixed Bell diagonal states
under local permutations. We construct a very general class of recursion
protocols by means of unitary operations implementing these local permutations.
We study these distillation protocols depending on whether we use twirling
operations in the intermediate steps or not, and we study them both
analitically and numerically with Monte Carlo methods. In the absence of
twirling operations, we construct extensions of the quantum privacy algorithms
valid for secure communications with qudits of any dimension . When is a
prime number, we show that distillation protocols are optimal both
qualitatively and quantitatively.Comment: REVTEX4 file, 7 color figures, 2 table
Déjà vu and the entorhinal cortex: dissociating recollective from familiarity disruptions in a single case patient
Past research has demonstrated a relationship between déjà vu and the entorhinal cortex in patients with wider medial temporal lobe damage. The aim of the present research was to investigate this crucial link in a patient (MR) with a selective lesion to the left lateral entorhinal cortex to provide a more direct exploration of this relationship. Two experiments investigated the experiences of déjà vécu (using the IDEA questionnaire) and déjà vu (using an adapted DRM paradigm) in MR and a set of matched controls. The results demonstrated that MR had quantitatively more and qualitatively richer recollective experiences of déjà vécu. In addition, under laboratory-based déjà vu conditions designed to elicit both false recollection (critical lures) and false familiarity (weakly-associated lures), MR only revealed greater memory impairments for the latter. The present results are therefore the first to demonstrate a direct relationship between the entorhinal cortex and the experience of both déjà vu and déjà vécu. They furthermore suggest that the entorhinal cortex is involved in both weakly-associative false memory as well as strongly-associative memory under conditions that promote familiarity-based processing
Pattern Selection in the Complex Ginzburg-Landau Equation with Multi-Resonant Forcing
We study the excitation of spatial patterns by resonant, multi-frequency
forcing in systems undergoing a Hopf bifurcation to spatially homogeneous
oscillations. Using weakly nonlinear analysis we show that for small amplitudes
only stripe or hexagon patterns are linearly stable, whereas square patterns
and patterns involving more than three modes are unstable. In the case of
hexagon patterns up- and down-hexagons can be simultaneously stable. The
third-order, weakly nonlinear analysis predicts stable square patterns and
super-hexagons for larger amplitudes. Direct simulations show, however, that in
this regime the third-order weakly nonlinear analysis is insufficient, and
these patterns are, in fact unstable
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Preliminary findings from geological mapping of the Hokusai (H5) quadrangle of Mercury
Quadrangle geological maps from Mariner 10 data cover 45% of the surface of Mercury at 1:5M scale. Orbital MESSENGER data, which cover the entire planetary surface, can now be used to produce finer scale geological maps, including regions unseen by Mariner 10.
Hokusai quadrangle (0–90° E; 22.5–66° N) is in the hemisphere unmapped by Mariner 10. It contains prominent features which are already being studied, including: Rachmaninoff basin, volcanic vents within and around Rachmaninoff, much of the Northern Plains and abundant wrinkle ridges. Its northern latitude makes it a prime candidate for regional geological mapping since compositional and topographical data, as well as Mercury Dual Imaging System (MDIS) data, are available for geological interpretation. This work aims to produce a map at 1:2M scale, compatible with other new quadrangle maps and to complement a global map now in progress
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Preliminary observations of Rustaveli basin, Mercury
Rustaveli basin on Mercury (82.76° E, 52.39° N) is a 200.5 km diameter peak-ring basin. Since the approval of its name on April 24, 2012, it has not featured prominently in the literature. It is a large and important feature within the Hokusai (H5) quadrangle of which we are currently producing a 1:2M scale geological map. Here, we describe our first observations of Rustaveli
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Candidate constructional volcanic edifices on Mercury
[Introduction] Studies using MESSENGER data suggest that Mercury’s crust is predominantly a product of effusive volcanism that occurred in the first billion years following the planet’s formation. Despite this planet-wide effusive volcanism, no constructional volcanic edifices, characterized by a topographic rise, have hitherto been robustly identified on Mercury, whereas constructional volcanoes are common on other planetary bodies in the solar system with volcanic histories. Here, we describe two candidate constructional volcanic edifices we have found on Mercury and discuss how these edifices may have formed
Professional boundaries: research report
In 2008 the General Social Care Council (GSCC) published Raising standards: Social work conduct in England 2003-2008. This constituted the GSCC’s first report covering the work undertaken to uphold standards and protect people who use social care services. The GSCC’s analysis revealed that a considerable proportion of conduct cases, some 40%, involved allegations of 'inappropriate relations'. In the light of this finding, and the release by the Council for Healthcare Regulatory Excellence (CHRE) of sexual boundaries guidance for healthcare workers at the beginning of this year (Halter et al, 2009), the GSCC committed itself to exploring the possibility of producing professional boundaries guidance for social workers.
To begin this exploration, the GSCC commissioned a study in early 2009.This is the report of that study. There were two main purposes. First, to establish what professional boundaries1 guidance currently exists for social workers, or for sections of the workforce that includes social workers in the United Kingdom, and the content of any such guidance. Secondly, to identify and discuss a number of other examples of professional boundaries guidance to act as points of reference for the GSCC’s project. The aim was to identify and discuss examples relevant to the GSCC’s project
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Spatial distribution and morphometric measurements of circum-Caloris knobs on Mercury: Application of novel shadow measurements
The Caloris basin (1550 km diameter) is the largest, well-preserved impact feature on Mercury. Its impact ejecta, excavated from the lower crust and uppermost mantle, provides an opportunity to investigate the interior materials of the planet. Based on Mariner 10 data, which cover only the eastern third of the basin, ‘hummocky plains’, associated with Caloris, consisting of ‘low, closely spaced to scattered hills 0.3-1 km across’ were interpreted as Caloris impact ejecta. These plains were subsequently named the Odin Formation, and the knobs associated with them were interpreted as degraded ejecta blocks. To test for an impact ejecta origin for the circum-Caloris knobs, we have mapped their locations and made morphometric measurements and high-resolution observations
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