33 research outputs found
Bending AdS Waves with New Massive Gravity
We study AdS-waves in the three-dimensional new theory of massive gravity
recently proposed by Bergshoeff, Hohm, and Townsend. The general configuration
of this type is derived and shown to exhibit different branches, with different
asymptotic behaviors. In particular, for the special fine tuning
, solutions with logarithmic fall-off arise, while in the
range , spacetimes with Schrodinger isometry group are admitted
as solutions. Solutions that are asymptotically AdS, both for
Brown-Henneaux and for the weakened boundary conditions, are also identified.
The metric function that characterizes the profile of the AdS-wave behaves as a
massive excitation on the spacetime, with an effective mass given by
. For the critical value , the value of
the effective mass precisely saturates the Breitenlohner-Freedman bound for the
AdS space where the wave is propagating on. The analogies with the AdS-wave
solutions of topologically massive gravity are also discussed. Besides, we
consider the coupling of both massive deformations to Einstein gravity and find
the exact configurations for the complete theory, discussing all the different
branches exhaustively. One of the effects of introducing the Chern-Simons
gravitational term is that of breaking the degeneracy in the effective mass of
the generic modes of pure New Massive Gravity, producing a fine structure due
to parity violation. Another effect is that the zoo of exact logarithmic
specimens becomes considerably enlarged.Comment: 9 pages. Minor typos correcte
Patterns of non-randomness in the exotic avifauna of Florida
It is now generally recognized that human-mediated biological invasion is a multistage process, successively comprising transport, introduction, establishment, and spread, and that a complete understanding of the causes of invasion requires studies of all stages. However, while many studies address the characteristics that influence establishment, relatively few address the characteristics that influence whether or not a species transits the earlier stages of transport and introduction. Here, we use data on the rich exotic avifauna of Florida to assess non-randomness in the identities of species that have passed through the transport and introduction stages. Bird species transported and introduced to Florida are non-random with respect to their taxonomic affiliations, body mass, native geographical range size, and region of origin: introductions are more likely for widespread, large-bodied species from the Neotropics and belonging to the Anatidae, Psittacidae, Ciconiidae, and Passeridae. Data on the identities of species that have attempted to breed but failed, and on the breeding population size for most established species, also allowed us to assess the extent to which the same variables influenced various aspects of post-introduction establishment. Only native geographical range size and latitudinal range mid-point distinguish between these different classes of exotic species. Geographical range size is the most general correlate of different classes of invaders in our analyses.Tim M. Blackburn and Phillip Casse