Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Anencephalus in Scotland 1961-72.

Data relating to the incidence of anencephalus for the 12-year period 1961-72 were abstracted from the Statistical Reviews of the Registrar General for Scotland. It was shown that considerable geographical variation is still apparent with the highlands having, in general, the lower incidences. In comparison with the earlier study of Edwards (1958), there were some changes: the incidence in the areas to the west had increased and that in those to the east decreased. During the 12-year period there was an overall decline in the incidence of the lesion; this was most marked in births to women under 20 years, and to those of social classes III, IV, and V. The decline was least apparent for births to women of high social class and the unmarried. It was shown that there was little seasonal variation in the time of delivery, but that even when the trend had been taken into account the yearly fluctuation was significantly different from that expected, with an excess of cases in 1961 and 1971