Evolutionary Channels for the Formation of Double Neutron Stars

We analyze binary population models of double-neutron stars and compare results to the accurately measured orbital periods and eccentricities of the eight known such systems in our Galaxy. In contrast to past similar studies, we especially focus on the dominant evolutionary channels (we identify three); for the first time, we use a detailed understanding of the evolutionary history of three double neutron stars as actual constraints on the population models. We find that the evolutionary constraints derived from the double pulsar are particularly tight, and less than half of the examined models survive the full set of constraints. The top-likelihood surviving models yield constraints on the key binary evolution parameters, but most interestingly reveal (i) the need for electron-capture supernovae from relatively low-mass degenerate, progenitor cores, and (ii) the most likely evolutionary paths for the rest of the known double neutron stars. In particular, we find that J1913+16 likely went through a phase of Case BB mass transfer, and J1906+0746 and J1756-2251 are consistent with having been formed in electron-capture supernovae.Comment: 17 pages, 9 figure

Polynomial Interpretation of Multipole Vectors

Copi, Huterer, Starkman and Schwarz introduced multipole vectors in a tensor context and used them to demonstrate that the first-year WMAP quadrupole and octopole planes align at roughly the 99.9% confidence level. In the present article the language of polynomials provides a new and independent derivation of the multipole vector concept. Bezout's Theorem supports an elementary proof that the multipole vectors exist and are unique (up to rescaling). The constructive nature of the proof leads to a fast, practical algorithm for computing multipole vectors. We illustrate the algorithm by finding exact solutions for some simple toy examples, and numerical solutions for the first-year WMAP quadrupole and octopole. We then apply our algorithm to Monte Carlo skies to independently re-confirm the estimate that the WMAP quadrupole and octopole planes align at the 99.9% level.Comment: Version 1: 6 pages. Version 2: added uniqueness proof to Corollary 2; added proper citation (to Starkman et al.) for Open Question; other minor improvement

High resolution spectroscopy of the 11.3 micron emission band

High resolution spectra of the 11.3 micron emission band in M82 and NGC 7027 were obtained using the University of Texas IR echelle spectrometer on the IRTF in April 1988. The spectral resolution was 0.004 micron, with coverage from 11.0 to 11.6 microns. Spectra were measured at ten positions along a 10 min. long slit. Analysis of the data is still in progress, but initial results show no clear evidence of narrow structure within the feature. The analysis will involve comparison of the observed spectra to laboratory and predicted spectra of Polycylic Aromatic Hydrocarbons (PAHs) and Quenched Carbonaceous Composite (QCCs) to determine which may be responsible for the emission. The spectra will be examined with a goal of determining whether the emission is caused by molecular or solid state material. The data are also examined for evidence of variations in the shape and strength of the 11.3 micron feature with position on the sky. In NGC 7027 the 10 min. long slit went across the edge of the ionized nebulae, allowing comparison of emission from both ionized and neutral regions

Darwin Meets Einstein: LISA Data Analysis Using Genetic Algorithms

This work presents the first application of the method of Genetic Algorithms (GAs) to data analysis for the Laser Interferometer Space Antenna (LISA). In the low frequency regime of the LISA band there are expected to be tens of thousands galactic binary systems that will be emitting gravitational waves detectable by LISA. The challenge of parameter extraction of such a large number of sources in the LISA data stream requires a search method that can efficiently explore the large parameter spaces involved. As signals of many of these sources will overlap, a global search method is desired. GAs represent such a global search method for parameter extraction of multiple overlapping sources in the LISA data stream. We find that GAs are able to correctly extract source parameters for overlapping sources. Several optimizations of a basic GA are presented with results derived from applications of the GA searches to simulated LISA data.Comment: 8 pages, 12 figure

Towards a Realization of the Condensed-Matter/Gravity Correspondence in String Theory via Consistent Abelian Truncation

We present an embedding of the 3-dimensional relativistic Landau-Ginzburg model for condensed matter systems in an $\mathcal{N}=6$, $U(N)\times U(N)$ Chern-Simons-matter theory (the ABJM model) by consistently truncating the latter to an abelian effective field theory encoding the collective dynamics of ${\cal O}(N)$ of the ${\cal O}(N^2)$ modes. In fact, depending on the VEV on one of the ABJM scalars, a mass deformation parameter $\mu$ and the Chern-Simons level number $k$, our abelianization prescription allows us to interpolate between the abelian Higgs model with its usual multi-vortex solutions and a $\phi^4$ theory. We sketch a simple condensed matter model that reproduces all the salient features of the abelianization. In this context, the abelianization can be interpreted as giving a dimensional reduction from four dimensions.Comment: 4 pages, revtex; reference added, typo corrected; added clarifying paragraphs at end of introduction and on pages 3-4. Version accepted to PR

Embedded motivational interviewing combined with a smartphone app to increase physical activity in people with sub-acute low back pain: study protocol of a cluster randomised control trial

Background: Motivational Interviewing is an evidence-based, client-centred counselling technique that has been used effectively to increase physical activity, including for people with low back pain. One barrier to implementing Motivational Interviewing in health care settings more broadly is the extra treatment time with therapists. The aim of this paper is to describe the design of a cluster randomised controlled trial evaluating the effect of an intervention that pairs Motivational Interviewing embedded into usual physiotherapy care with a specifically designed app to increase physical activity in people with sub-acute low back pain. Methods: The study is a cluster randomised controlled in which patients aged over 18 years who have sub-acute low back pain (3–12 weeks duration) are recruited from four public hospital outpatient clinics. Based on the recruitment site, participants either receive usual physiotherapy care or the Motivational Interviewing intervention over 6 consecutive weekly outpatient sessions with a specifically designed app designed to facilitate participant-led physical activity behaviour change in between sessions. Outcome measures assessed at baseline and 7 weeks are: physical activity as measured by accelerometer (primary outcome), and pain-related activity restriction and pain self-efficacy (secondary outcomes). Postintervention interviews with physiotherapists and participants will be conducted as part of a process evaluation. Discussion: This intervention, which comprises trained physiotherapists conducting conversations about increasing physical activity with their patients in a manner consistent with Motivational Interviewing as part of usual care combined with a specifically designed app, has potential to facilitate behaviour change with minimal extra therapist time

Polarity-dependent reversible resistance switching in Ge–Sb–Te phase-change thin films

In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge–Sb–Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed in current-voltage characteristics. Moreover, voltage pulses less than 1.25 V showed this switching within time scales of microseconds with more than 40% contrast between the resistance states. The latter are found to be nonvolatile for months. The switching could also be achieved at nanoscales with atomic force microscopy with a better resistance contrast of three orders of magnitude.