University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Sexual Selection and Speciation

Abstract: Sexual selection has a reputation as a major cause of speciation, one of the most potent forces driving reproductive isolation. This reputation arises from observations that species differ most in traits involved with mating success and from successful models of sexual selection–driven speciation. But how well proven is the case? Models confirm that the process can occur, but is strongest in conjunction with ecological or niche specialization. Some models also show that strong sexual selection can act against speciation. Studies using the comparative method are equivocal and often inconclusive, but some phylogeographic studies are more convincing. Experimental evolution and genetic or genomic analyses are in their infancy, but look particularly promising for resolving the importance of sexual selection. The case for sexual selection is not as strongly supported as, for example, allopatric speciation. Sexual selection probably contributes most effectively alongside ecological selection or selection...

Why do we need slow light

Abstract: The extreme speed at which light moves, and the fact that photons do not tend to interact with transparent matter, is of enormous benefit to mankind. It allows us to see deep into the Universe and to transmit data over long distances in optical fibres. So, why slow light down?

The 2dF Galaxy Redshift Survey: The bias of galaxies and the density of the Universe

Abstract: We compute the bispectrum of the 2dF Galaxy Redshift Survey (2dFGRS) and use it to measure the bias parameter of the galaxies. This parameter quantifies the strength of clustering of the galaxies relative to the mass in the Universe. By analysing 80 x 10 6 triangle configurations in the wavenumber range 0.1 < k < 0.5 h Mpc - 1 (i.e. on scales roughly between 5 and 30 h - 1 Mpc) we find that the linear bias parameter is consistent with unity: b 1 = 1.04 ′ 0.11, and the quadratic (non-linear) bias is consistent with zero: b 2 = -0.054 ′ 0.08. Thus, at least on large scales, optically selected galaxies do indeed trace the underlying mass distribution. The bias parameter can be combined with the 2dFGRS measurement of the redshift distortion parameter β ≃ Ω 0 . 6 m /b 1 , to yield Ωm = 0.27 ′0.06 for the matter density of the Universe, a result that is determined entirely from this survey, independent of other data sets. Our measurement of the matter density of the Universe should be interpreted as Ω m at the effective redshift of the survey (z = 0.17).