Constraining a possible time variation of the gravitational constant G with terrestrial nuclear laboratory data

Testing the constancy of the gravitational constant G has been a longstanding fundamental question in natural science. As first suggested by Jofr\'{e}, Reisenegger and Fern\'{a}ndez [1], Dirac's hypothesis of a decreasing gravitational constant $G$ with time due to the expansion of the Universe would induce changes in the composition of neutron stars, causing dissipation and internal heating. Eventually, neutron stars reach their quasi-stationary states where cooling due to neutrino and photon emissions balances the internal heating. The correlation of surface temperatures and radii of some old neutron stars may thus carry useful information about the changing rate of G. Using the density dependence of the nuclear symmetry energy constrained by recent terrestrial laboratory data on isospin diffusion in heavy-ion reactions at intermediate energies and the size of neutron skin in $^{208}Pb$ within the gravitochemical heating formalism, we obtain an upper limit of the relative changing rate of $|\dot{G}/G|\le4\times 10^{-12}yr^{-1}$ consistent with the best available estimates in the literature.Comment: 27 pages, 11 figures, and 2 tables. Accepted version to appear in PRC (2007

Constraining a possible time-variation of the gravitational constant through "gravitochemical heating" of neutron stars

A hypothetical time-variation of the gravitational constant $G$ would cause neutron star matter to depart from beta equilibrium, due to the changing hydrostatic equilibrium. This forces non-equilibrium beta processes to occur, which release energy that is invested partly in neutrino emission and partly in heating the stellar interior. Eventually, the star arrives at a stationary state in which the temperature remains nearly constant, as the forcing through the change of $G$ is balanced by the ongoing reactions. Comparing the surface temperature of the nearest millisecond pulsar, PSR J0437-4715, inferred from ultraviolet observations, with our predicted stationary temperature, we estimate two upper limits for this variation: (1) $|\dot G/G| < 2 \times 10^{-10}$ yr$^{-1}$, if we allow direct Urca reactions operating in the neutron star core, and (2) $|\dot G/G| < 4 \times 10^{-12}$ yr$^{-1}$, considering only modified Urca reactions. Both results are competitive with those obtained by other methods, with (2) being among the most restrictive.Comment: 4 pages, including 2 figures. Accepted for publication in Phys. Rev. Lett. Revised version includes minor changes in the wording, and more substantial changes in the last 2 paragraphs (Discussion and Conclusions). Equations, figures, and results are unchange

Anisotropy in the Distribution of Galactic Radio Polarizations

Radiation traversing the observable universe provides powerful ways to probe anisotropy of electromagnetic propagation. A controversial recent study claimed a signal of dipole character. Here we test a new and independent data set of 361 points under the null proposal of {\it statistical independence} of linear polarization alignments relative to galaxy axes, versus angular positions. The null hypothesis is tested via maximum likelihood analysis of best fits among numerous independent types of factored distributions. We also examine single-number correlations which are parameter free, invariant under coordinate transformations, and distributed very robustly. The statistics are shown explicitly not to depend on the uneven distribution of sources on the sky. We find that the null proposal is not supported at the level of less than 5% to less than 0.1% by several independent statistics. The signal of correlation violates parity, that is, symmetry under spatial inversion, and requires a statistic which transforms properly. The data indicate an axis of correlation, on the basis of likelihood determined to be $[{\rm R.A.}=(0^{\rm h},9^{\rm m}) \pm (1^{\rm h},0^{\rm m})$, ${\rm Decl.} = -1^o\pm 15^o]$.Comment: 10 pages, Late

Internal heating and thermal emission from old neutron stars: Constraints on dense-matter and gravitational physics

The equilibrium composition of neutron star matter is achieved through weak interactions (direct and inverse beta decays), which proceed on relatively long time scales. If the density of a matter element is perturbed, it will relax to the new chemical equilibrium through non-equilibrium reactions, which produce entropy that is partly released through neutrino emission, while a similar fraction heats the matter and is eventually radiated as thermal photons. We examined two possible mechanisms causing such density perturbations: 1) the reduction in centrifugal force caused by spin-down (particularly in millisecond pulsars), leading to "rotochemical heating", and 2) a hypothetical time-variation of the gravitational constant, as predicted by some theories of gravity and current cosmological models, leading to "gravitochemical heating". If only slow weak interactions are allowed in the neutron star (modified Urca reactions, with or without Cooper pairing), rotochemical heating can account for the observed ultraviolet emission from the closest millisecond pulsar, PSR J0437-4715, which also provides a constraint on |dG/dt| of the same order as the best available in the literature.Comment: 6 pages, 7 figures. To appear in the proceedings of "Isolated Neutron Stars: from the Interior to the Surface", a conference held in London in April 2006 (special issue of Astrophysics and Space Science, edited by Dany Page, Roberto Turolla, & Silvia Zane

An HST Survey of the mid-UV Morphology of Nearby Galaxies

(Abbreviated) We present an imaging survey of 37 nearby galaxies observed with HST/WFPC2 in the mid-UV F300W filter and in F814W. 11 galaxies were also imaged in F255W. These galaxies were selected to be detectable with WFPC2 in one orbit, and cover a wide range of Hubble types and inclinations. The mid-UV spans the gap between our groundbased optical/NIR images and far-UV images available from the Astro/UIT missions. Our first qualitative results are: (1) Early-type galaxies show a significant decrease in surface brightness going from the red to the mid-UV, and in some cases the presence of dust lanes. Some galaxies would be classified different when viewed in the mid-UV, some become dominated by a blue nuclear feature or point source. (2) Half of the mid-type spiral and star-forming galaxies appear as a later morphological type in the mid-UV, as Astro/UIT also found in the far-UV. Some- times these differences are dramatic. The mid-UV images show a considerable range in the scale and surface brightness of individual star-forming regions. Almost all mid-type spirals have their small bulges bi-sected by a dust-lane. (3) Most of the heterogeneous subset of late-type, irregular, peculiar, and merging galaxies display F300W morphologies that are similar to those seen in F814W, but with differences due to recognizable dust features absorbing the bluer light, and due to UV-bright hot stars, star-clusters, and star-forming ridges. In the rest-frame mid-UV, early- to mid-type galaxies are more likely to be misclassified as later types than vice versa. This morphological K-correction explains only part of the excess faint blue galaxies seen in deep HST fields.Comment: 30 pages, LateX (AASTeX5.0), 2 figures and 3 tables included, mid-UV atlas and pan-chromatic atlas provided as 63 JPG figures. Full resolution PS version (~100Mb) available upon request. Accepted for publication in ApJ

Vision zero: from accident prevention to the promotion of health, safety and well-being at work

There is growing attention in industry for the Vision Zero strategy, which in terms of work-related health and safety is often labelled as Zero Accident Vision or Zero Harm. The consequences of a genuine commitment to Vision Zero for addressing health, safety and well-being and their synergies are discussed. The Vision Zero for work-related health, safety and well-being is based on the assumption that all accidents, harm and work-related diseases are preventable. Vision Zero for health, safety and well-being is then the ambition and commitment to create and ensure safe and healthy work and to prevent all accidents, harm and work-related diseases in order to achieve excellence in health, safety and well-being. Implementation of Vision Zero is a process – rather than a target, and healthy organizations make use of a wide range of options to facilitate this process. There is sufficient evidence that fatigue, stress and work organization factors are important determinants of safety behaviour and safety performance. Even with a focus on preventing accidents these additional factors should also be addressed. A relevant challenge is the integration of the Vision Zero into broader business policy and practice. There is a continued need more empirical research in this area

UV, Optical and IR Observations of the Cepheid R Muscae

Ultraviolet IUE spectra, optical 12A mm-1 red and blue spectra, optical BV photometry and infrared JHKL photometry of the 7.5-d classical Cepheid R Muscae = HD 110 311 is presented and discussed together with some earlier photometric and radial velocity data. Using the CORS method, a newly derived radius is given, as well as new values for T.tT and log g. The UV spectra confirrned the predicted trend to increasing amplitudes with decreasing wavelength and indicate that R Mus has a shallow chromosphere, while no transition region lines could be detected. From all our data from 1200 A to 5 μm we conclude that R Mus does not have a companion detectable with the sensitivity given, contrary to earlier results