Implementation of the frequency-modulated sideband search method for gravitational waves from low mass X-ray binaries

We describe the practical implementation of the sideband search, a search for periodic gravitational waves from neutron stars in binary systems. The orbital motion of the source in its binary system causes frequency-modulation in the combination of matched filters known as the $\mathcal{F}$-statistic. The sideband search is based on the incoherent summation of these frequency-modulated $\mathcal{F}$-statistic sidebands. It provides a new detection statistic for sources in binary systems, called the $\mathcal{C}$-statistic. The search is well suited to low-mass X-ray binaries, the brightest of which, called Sco X-1, is an ideal target candidate. For sources like Sco X-1, with well constrained orbital parameters, a slight variation on the search is possible. The extra orbital information can be used to approximately demodulate the data from the binary orbital motion in the coherent stage, before incoherently summing the now reduced number of sidebands. We investigate this approach and show that it improves the sensitivity of the standard Sco X-1 directed sideband search. Prior information on the neutron star inclination and gravitational wave polarization can also be used to improve upper limit sensitivity. We estimate the sensitivity of a Sco X-1 directed sideband search on 10 days of LIGO data and show that it can beat previous upper limits in current LIGO data, with a possibility of constraining theoretical upper limits using future advanced instruments.Comment: 20 pages, 5 figure

An Asymptotic Preserving Maxwell Solver Resulting in the Darwin Limit of Electrodynamics

In plasma simulations, where the speed of light divided by a characteristic length is at a much higher frequency than other relevant parameters in the underlying system, such as the plasma frequency, implicit methods begin to play an important role in generating efficient solutions in these multi-scale problems. Under conditions of scale separation, one can rescale Maxwell's equations in such a way as to give a magneto static limit known as the Darwin approximation of electromagnetics. In this work, we present a new approach to solve Maxwell's equations based on a Method of Lines Transpose (MOL$^T$) formulation, combined with a fast summation method with computational complexity $O(N\log{N})$, where $N$ is the number of grid points (particles). Under appropriate scaling, we show that the proposed schemes result in asymptotic preserving methods that can recover the Darwin limit of electrodynamics

Non-equilibrium steady states in the Klein-Gordon theory

We construct non-equilibrium steady states in the Klein-Gordon theory in arbitrary space dimension $d$ following a local quench. We consider the approach where two independently thermalized semi-infinite systems, with temperatures $T_{\rm L}$ and $T_{\rm R}$, are connected along a $d-1$-dimensional hypersurface. A current-carrying steady state, described by thermally distributed modes with temperatures $T_{\rm L}$ and $T_{\rm R}$ for left and right-moving modes, respectively, emerges at late times. The non-equilibrium density matrix is the exponential of a non-local conserved charge. We obtain exact results for the average energy current and the complete distribution of energy current fluctuations. The latter shows that the long-time energy transfer can be described by a continuum of independent Poisson processes, for which we provide the exact weights. We further describe the full time evolution of local observables following the quench. Averages of generic local observables, including the stress-energy tensor, approach the steady state with a power-law in time, where the exponent depends on the initial conditions at the connection hypersurface. We describe boundary conditions and special operators for which the steady state is reached instantaneously on the connection hypersurface. A semiclassical analysis of freely propagating modes yields the average energy current at large distances and late times. We conclude by comparing and contrasting our findings with results for interacting theories and provide an estimate for the timescale governing the crossover to hydrodynamics. As a modification of our Klein-Gordon analysis we also include exact results for free Dirac fermions.Comment: 42 pages, 7 figure

A Test of the Theory of Planned Behaviour and an Implementation Intentions Intervention for Condom Use Behaviours among Men Who Have Sex with Men

Despite many years of promotion of safe sex practices, men who have sex with men continue to be vastly over-represented in new HIV diagnoses and infection rates continue (Sullivan et al., 2009). This has been attributed to a reduction in condom use associated with the reduced disease burden and reduced infectivity resulting from antiretroviral therapy uptake. Theories of health behaviour may assist in understanding the processes involved in condom use among MSM. The aims of this study are to test the utility of the Theory of Planned Behaviour (TPB; Ajzen, 1991) in explaining condom use among MSM, and the utility of an implementation intentions intervention in increasing condom use. These aims were achieved through the following phases; demonstration of the utility of the TPB as a predictive model of condom use among MSM based on a meta-analytic review of the literature; the conduct of a cross-sectional online study to assess the TPB construct associations when assessing condom preparatory, and use behaviours among MSM; and the conduct of an implementation intentions intervention which was assessed over a three month period. The meta-analysis revealed moderate to strong effect sizes between all purported TPB construct relationships, indicating that it is an appropriate model. The cross sectional study (N=81) found that the TPB was able to explain a intention and behaviour for a number of condom behaviours, in particular condom use, but was subject to low power. The intervention study (N=28) was also underpowered, and interaction effects of time and condition on condom use and main effects of time and condition on condom use were non-significant. The findings of all three studies are discussed in terms of implications for research and theory, and in particular, the need for further predictive and experimental TPB studies among MSM