269 research outputs found
The Worldvolume Action of Kink Solitons in AdS Spacetime
A formalism is presented for computing the higher-order corrections to the
worldvolume action of co-dimension one solitons. By modifying its potential, an
explicit "kink" solution of a real scalar field in AdS spacetime is found. The
formalism is then applied to explicitly compute the kink worldvolume action to
quadratic order in two expansion parameters--associated with the hypersurface
fluctuation length and the radius of AdS spacetime respectively. Two
alternative methods are given for doing this. The results are expressed in
terms of the trace of the extrinsic curvature and the intrinsic scalar
curvature. In addition to conformal Galileon interactions, we find a
non-Galileon term which is never sub-dominant. This method can be extended to
any conformally flat bulk spacetime.Comment: 32 pages, 3 figures, typos corrected and additional comments adde
Closed String Tachyon Condensation: An Overview
These notes are an expanded version of a review lecture on closed string
tachyon condensation at the RTN workshop in Copenhagen in September 2003. We
begin with a lightning review of open string tachyon condensation, and then
proceed to review recent results on localized closed string tachyon
condensation, focusing on two simple systems, C/Z_n orbifolds and twisted
circle compactifications.Comment: harvmac, 59 pages; references adde
Bouncing Braneworlds Go Crunch!
Recently, interesting braneworld cosmologies in the Randall-Sundrum scenario
have been constructed using a bulk spacetime which corresponds to a charged AdS
black hole. In particular, these solutions appear to `bounce', making a smooth
transition from a contracting to an expanding phase. By considering the
spacetime geometry more carefully, we demonstrate that generically in these
solutions the brane will encounter a singularity in the transition region.Comment: 17 pages, 4 figures, ref adde
On the nature of the FBS blue stellar objects and the completeness of the Bright Quasar Survey. II
In Paper I (Mickaelian et al. 1999), we compared the surface density of QSOs
in the Bright Quasar Survey (BQS) and in the First Byurakan Survey (FBS) and
concluded that the completeness of the BQS is of the order of 70% rather than
30-50% as suggested by several authors. A number of new observations recently
became available, allowing a re-evaluation of this completeness. We now obtain
a surface density of QSOs brighter than B = 16.16 in a subarea of the FBS
covering ~2250 deg^2, equal to 0.012 deg^-2 (26 QSOs), implying a completeness
of 53+/-10%.Comment: LaTeX 2e, 11 pages, 3 tables and 3 figures (included in text). To
appear in Astrophysics. Uses a modified aaspp4.sty (my_aaspp4.sty), included
in packag
Middle Miocene Tectonic Boundary Conditions for Use in Climate Models
Utilizing general circulation models (GCMs) for paleoclimate study requires the construction of appropriate model boundary conditions. We present a middle Miocene paleotopographic and paleobathymetric reconstruction geographically constrained at 15 Ma for use in GCMs. Paleotopography and paleogeography are reconstructed using a published global plate rotation model and published geological data. Paleobathymetry is reconstructed through application of an age-depth relationship to a middle Miocene global digital isochron map, followed by the overlay of reconstructed sediment thickness and large igneous provinces. Adjustments are subsequently made to ensure our reconstruction may be utilized in GCMs
The Bekenstein Formula and String Theory (N-brane Theory)
A review of recent progress in string theory concerning the Bekenstein
formula for black hole entropy is given. Topics discussed include p-branes,
D-branes and supersymmetry; the correspondence principle; the D- and M-brane
approach to black hole entropy; the D-brane analogue of Hawking radiation, and
information loss; D-branes as probes of black holes; and the Matrix theory
approach to charged and neutral black holes. Some introductory material is
included.Comment: 53 pages, LaTeX. v3: Typos fixed, minor updates, references added,
brief Note Added on AdS/CF
The fitness consequences of inbreeding in natural populations and their implications for species conservation – a systematic map
Background: Threatened species often have small and isolated populations where mating among relatives can
result in inbreeding depression increasing extinction risk. Effective management is hampered by a lack of syntheses
summarising the magnitude of, and variation in inbreeding depression. Here we describe the nature and scope
of the literature examining phenotypic/fitness consequences of inbreeding, to provide a foundation for future
syntheses and management.
Methods: We searched the literature for articles documenting the impact of inbreeding in natural populations.
Article titles, abstracts and full-texts were assessed against a priori defined criteria, and information relating to study
design, quality and other factors that may influence inbreeding responses (e.g. population size) was extracted from
relevant articles.
Results: The searches identified 11457 articles, of which 614 were assessed as relevant and included in the systematic
map (corresponding to 703 distinct studies). Most studies (663) assessed within-population inbreeding resulting from
self-fertilisation or consanguineous pairings, while 118 studies assessed among-population inbreeding due to drift load.
Plants were the most studied taxon (469 studies) followed by insects (52 studies) and birds (43 studies). Most studies
investigated the effects of inbreeding on components of fitness (e.g. survival or fecundity; 648 studies) but measurements
were typically under laboratory/greenhouse conditions (486 studies). Observations were also often restricted to the first
inbred generation (607 studies) and studies frequently lacked contextual information (e.g. population size).
Conclusions: Our systematic map describes the scope and quality of the evidence describing the phenotypic
consequences of inbreeding. The map reveals substantial evidence relating to inbreeding responses exists,
but highlights information is still limited for some aspects, including the effects of multiple generations of
inbreeding. The systematic map allowed us to define several conservation-relevant questions, where sufficient
data exists to support systematic reviews, e.g. How do inbreeding responses vary with population size? However,
we found that such syntheses are likely to be constrained by incomplete reporting of critical contextual information.
Our systematic map employed the same rigorous literature assessment methods as systematic review, including a
novel survey of study quality and thus provides a robust foundation to guide future research and syntheses seeking to
inform conservation decision-making
From Sound to Significance: Exploring the Mechanisms Underlying Emotional Reactions to Music
A common approach to studying emotional reactions to music is to attempt to obtain direct links between musical surface features such as tempo and a listener’s responses. however, such an analysis ultimately fails to explain why emotions are aroused in the listener. in this article we explore an alternative approach, which aims to account for musical emotions in terms of a set of psychological mechanisms that are activated by different types of information in a musical event. this approach was tested in 4 experiments that manipulated 4 mechanisms (brain stem reflex, contagion, episodic memory, musical expectancy) by selecting existing musical pieces that featured information relevant for each mechanism. the excerpts were played to 60 listeners, who were asked to rate their felt emotions on 15 scales. skin conductance levels and facial expressions were measured, and listeners reported subjective impressions of relevance to specific mechanisms. results indicated that the target mechanism conditions evoked emotions largely as predicted by a multimechanism framework and that mostly similar effects occurred across the experiments that included different pieces of music. we conclude that a satisfactory account of musical emotions requires consideration of how musical features and responses are mediated by a range of underlying mechanisms
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