Nucleosynthesis Constraints on Scalar-Tensor Theories of Gravity

We study the cosmological evolution of massless single-field scalar-tensor theories of gravitation from the time before the onset of $e^+e^-$ annihilation and nucleosynthesis up to the present. The cosmological evolution together with the observational bounds on the abundances of the lightest elements (those mostly produced in the early universe) place constraints on the coefficients of the Taylor series expansion of $a(\phi)$, which specifies the coupling of the scalar field to matter and is the only free function in the theory. In the case when $a(\phi)$ has a minimum (i.e., when the theory evolves towards general relativity) these constraints translate into a stronger limit on the Post-Newtonian parameters $\gamma$ and $\beta$ than any other observational test. Moreover, our bounds imply that, even at the epoch of annihilation and nucleosynthesis, the evolution of the universe must be very close to that predicted by general relativity if we do not want to over- or underproduce $^{4}$He. Thus the amount of scalar field contribution to gravity is very small even at such an early epoch.Comment: 15 pages, 2 figures, ReVTeX 3.1, submitted to Phys. Rev. D1

Deconvolving the information from an imperfect spherical gravitational wave antenna

We have studied the effects of imperfections in spherical gravitational wave antenna on our ability to properly interpret the data it will produce. The results of a numerical simulation are reported that quantitatively describe the systematic errors resulting from imperfections in various components of the antenna. In addition, the results of measurements on a room-temperature prototype are presented that verify it is possible to accurately deconvolve the data in practice.Comment: 5 pages, 2 figures, to be published in Europhysics Letter

Corotation Resonance and Diskoseismology Modes of Black Hole Accretion Disks

We demonstrate that the corotation resonance affects only some non-axisymmetric g-mode oscillations of thin accretion disks, since it is located within their capture zones. Using a more general (weaker radial WKB approximation) formulation of the governing equations, such g-modes, treated as perfect fluid perturbations, are shown to formally diverge at the position of the corotation resonance. A small amount of viscosity adds a small imaginary part to the eigenfrequency which has been shown to induce a secular instability (mode growth) if it acts hydrodynamically. The g-mode corotation resonance divergence disappears, but the mode magnitude can remain largest at the place of the corotation resonance. For the known g-modes with moderate values of the radial mode number and axial mode number (and any vertical mode number), the corotation resonance lies well outside their trapping region (and inside the innermost stable circular orbit), so the observationally relevant modes are unaffected by the resonance. The axisymmetric g-mode has been seen by Reynolds & Miller in a recent inviscid hydrodynamic accretion disk global numerical simulation. We also point out that the g-mode eigenfrequencies are approximately proportional to m for axial mode numbers |m|>0.Comment: 16 pages, no figures. Submitted to The Astrophysical Journa

Errors on the inverse problem solution for a noisy spherical gravitational wave antenna

A single spherical antenna is capable of measuring the direction and polarization of a gravitational wave. It is possible to solve the inverse problem using only linear algebra even in the presence of noise. The simplicity of this solution enables one to explore the error on the solution using standard techniques. In this paper we derive the error on the direction and polarization measurements of a gravitational wave. We show that the solid angle error and the uncertainty on the wave amplitude are direction independent. We also discuss the possibility of determining the polarization amplitudes with isotropic sensitivity for any given gravitational wave source.Comment: 13 pages, 4 figures, LaTeX2e, IOP style, submitted to CQ

Motivating citizens to participate in public policymaking: Identification, trust and cost-benefit analyses

Under what conditions do citizens of nations and states comply with governmental requests to participate in public policymaking? Drawing on the dual pathway model of collective action (Stürmer & Simon, 2004) but with a focus on compliance with the status quo, rather than participation in collective protest, two studies examined citizens’ motivation to participate in public policymaking. Study 1 (N = 169) was an MTurk hosted survey that recruited participants from California, while Study 2 (N = 198) was a field experiment that recruited participants in Sardinia, Italy. Study 1 measured cost-benefit analyses, societal identification, and willingness to participate in public policymaking. Study 2 repeated the same procedures except we manipulated costs of participation, and also measured participants’ trust in government. Study 1 confirmed our initial hypotheses – fewer costs predicted more willingness to participate, as did stronger state identification. However, Study 2 found an interactive effect of costs, identification, and trust on willingness to participate in public policymaking. Results confirm our hypotheses by showing both costs and identification independently influence willingness to participate in public policymaking. Results also add to the literature by showing these additive pathways can be influenced by trust in the source of governance

Electrophysiological and arrhythmogenic effects of 5-hydroxytryptamine on human atrial cells are reduced in atrial fibrillation

5-Hydroxytryptamine (5-HT) is proarrhythmic in atrial cells from patients in sinus rhythm (SR) via activation of 5-HT<sub>4</sub> receptors, but its effects in atrial cells from patients with atrial fibrillation (AF) are unknown. The whole-cell perforated patch-clamp technique was used to record L-type Ca<sup>2+</sup> current (<i>I</i><sub>CaL</sub>), action potential duration (APD) and arrhythmic activity at 37 °C in enzymatically isolated atrial cells obtained from patients undergoing cardiac surgery, in SR or with chronic AF. In the AF group, 5-HT (10 μM) produced an increase in <i>I</i><sub>CaL</sub> of 115 ± 21% above control (<i>n</i> = 10 cells, 6 patients) that was significantly smaller than that in the SR group (232 ± 33%; <i>p</i> 0.05; <i>n</i> = 27 cells, 12 patients). Subsequent co-application of isoproterenol (1 μM) caused a further increase in <i>I</i><sub>CaL</sub> in the AF group (by 256 ± 94%) that was greater than that in the SR group (22 ± 6%; p < 0.05). The APD at 50% repolarisation (APD<sub>50</sub>) was prolonged by 14 ± 3 ms by 5-HT in the AF group (<i>n</i> = 37 cells, 14 patients). This was less than that in the SR group (27 ± 4 ms; <i>p</i> < 0.05; <i>n</i> = 58 cells, 24 patients). Arrhythmic activity in response to 5-HT was observed in 22% of cells in the SR group, but none was observed in the AF group (p < 0.05). Atrial fibrillation was associated with reduced effects of 5-HT, but not of isoproterenol, on <i>I</i><sub>CaL</sub> in human atrial cells. This reduced effect on <i>I</i><sub>CaL</sub> was associated with a reduced APD<sub>50</sub> and arrhythmic activity with 5-HT. Thus, the potentially arrhythmogenic influence of 5-HT may be suppressed in AF-remodelled human atrium

Why people attend science festivals : interests, motivations and self-reported benefits of public engagement with research

As a form of public engagement, science festivals have rapidly expanded in size and number over recent years. However, as with other domains of informal public engagement that are not linked to policy outcomes, existing research does not fully address science festivals’ impacts and popularity.This study adduces evidence from surveys and focus groups to elucidate the perspectives of visitors at a large UK science festival. Results show that visitors value the opportunities science festivals afford to interact with scientific researchers and to encounter different types of science engagement aimed at adults, children and families. The most significant self-reported impact of attending a science festival was the development of increased interest and curiosity about new areas of scientific knowledge within a socially stimulating and enjoyable setting

Relativistic Diskoseismology. I. Analytical Results for 'Gravity Modes'

We generalize previous calculations to a fully relativistic treatment of adiabatic oscillations which are trapped in the inner regions of accretion disks by non-Newtonian gravitational effects of a black hole. We employ the Kerr geometry within the scalar potential formalism of Ipser and Lindblom, neglecting the gravitational field of the disk. This approach treats perturbations of arbitrary stationary, axisymmetric, perfect fluid models. It is applied here to thin accretion disks. Approximate analytic eigenfunctions and eigenfrequencies are obtained for the most robust and observable class of modes, which corresponds roughly to the gravity (internal) oscillations of stars. The dependence of the oscillation frequencies on the mass and angular momentum of the black hole is exhibited. These trapped modes do not exist in Newtonian gravity, and thus provide a signature and probe of the strong-field structure of black holes. Our predictions are relevant to observations which could detect modulation of the X-ray luminosity from stellar mass black holes in our galaxy and the UV and optical luminosity from supermassive black holes in active galactic nuclei.Comment: 31 pages, 6 figures, uses style file aaspp4.sty, prepared with the AAS LATEX macros v4.0, significant revision of earlier submission to include modes with axial index m>

Precision Prediction for the Big-Bang Abundance of Primordial Helium

Within the standard models of particle physics and cosmology we have calculated the big-bang prediction for the primordial abundance of \he to a theoretical uncertainty of less than 0.1 \pct $(\delta Y_P < \pm 0.0002)$, improving the current theoretical precision by a factor of 10. At this accuracy the uncertainty in the abundance is dominated by the experimental uncertainty in the neutron mean lifetime, $\tau_n = 885.4 \pm 2.0 sec$. The following physical effects were included in the calculation: the zero and finite-temperature radiative, Coulomb and finite-nucleon-mass corrections to the weak rates; order-$\alpha$ quantum-electrodynamic correction to the plasma density, electron mass, and neutrino temperature; and incomplete neutrino decoupling. New results for the finite-temperature radiative correction and the QED plasma correction were used. In addition, we wrote a new and independent nucleosynthesis code designed to control numerical errors to be less than 0.1\pct. Our predictions for the \EL[4]{He} abundance are presented in the form of an accurate fitting formula. Summarizing our work in one number, $Y_P(\eta = 5\times 10^{-10}) = 0.2462 \pm 0.0004 (expt) \pm < 0.0002 (theory)$. Further, the baryon density inferred from the Burles-Tytler determination of the primordial D abundance, $\Omega_B h^2 = 0.019\pm 0.001$, leads to the prediction: $Y_P = 0.2464 \pm 0.0005 (D/H) \pm < 0.0002 (theory) \pm 0.0005 (expt)$. This ``prediction'' and an accurate measurement of the primeval \he abundance will allow an important consistency test of primordial nucleosynthesis.Comment: Replaced fitting formulas - new versions differ by small but significant amount. Other minor changes. 30 pages, 17 figures, 5 table

Influence of the r-mode instability on hypercritically accreting neutron stars

We have investigated an influence of the r-mode instability on hypercritically accreting ($\dot{M}\sim 1M_\odot {y}^{-1}$) neutron stars in close binary systems during their common envelope phases based on the scenario proposed by Bethe et al. \shortcite{bethe-brown-lee}. On the one hand neutron stars are heated by the accreted matter at the stellar surface, but on the other hand they are also cooled down by the neutrino radiation. At the same time, the accreted matter transports its angular momentum and mass to the star. We have studied the evolution of the stellar mass, temperature and rotational frequency. The gravitational-wave-driven instability of the r-mode oscillation strongly suppresses spinning-up of the star, whose final rotational frequency is well below the mass-shedding limit, typically as small as 10% of that of the mass-shedding state. On a very short time scale the rotational frequency tends to approach a certain constant value and saturates there as far as the amount of the accreted mass does not exceed a certain limit to collapse to a black hole. This implies that the similar mechanism of gravitational radiation as the so-called Wagoner star may work in this process. The star is spun up by accretion until the angular momentum loss by gravitational radiation balances the accretion torque. The time-integrated dimensionless strain of the radiated gravitational wave may be large enough to be detectable by the gravitational wave detectors such as LIGO II.Comment: 6 pages, 3 figure