137 research outputs found
CP asymmetry in the Higgs decay into the top pair due to the stop mixing
We investigate a potentially large CP violating asymmetry in the decay of a
neutral scalar or pseudoscalar Higgs boson into the top-anti-top pair. The
source of the CP nonconservation is the complex mixing in the (left-right) stop
sector. One of the interesting consequence is the different rates of the Higgs
boson decays into CP conjugate polarized states.Comment: 14 pages, 8 figures include
The ecology of sex explains patterns of helping in arthropod societies
Authors thank the Natural Sciences and Engineering Research Council of Canada (NGD), the Clarendon Fund (NGD) and the Natural Environment Research Council (LR, NE/K009516/1; AG, NE/K009524/1) for funding.Across arthropod societies, sib-rearing (e.g. nursing or nest defence) may be provided by females, by males or by both sexes. According to Hamilton's ‘haplodiploidy hypothesis’, this diversity reflects the relatedness consequences of diploid vs. haplodiploid inheritance. However, an alternative ‘preadaptation hypothesis’ instead emphasises an interplay of ecology and the co-option of ancestral, sexually dimorphic traits for sib-rearing. The preadaptation hypothesis has recently received empirical support, but remains to be formalised. Here, we mathematically model the coevolution of sex-specific helping and sex allocation, contrasting these hypotheses. We find that ploidy per se has little effect. Rather, the ecology of sex shapes patterns of helping: sex-specific preadaptation strongly influences who helps; a freely adjustable sex ratio magnifies sex biases and promotes helping; and sib-mating, promiscuity, and reproductive autonomy also modulate the sex and abundance of helpers. An empirical survey reveals that patterns of sex-specific helping in arthropod taxa are consistent with the preadaptation hypothesis.Publisher PDFPeer reviewe
Range shifting species reduce phylogenetic diversity in high latitude communities via competition
Acknowledgements We thank Heather Bodie and Debbie Young for assistance in the field, and local landowners for permissions to study and sample damselflies on their land. Brad Duthie provided helpful comments on an earlier version of this manuscript. The project was supported by a NERC DTP fellowship to R.N.L.F. and a start-up grant to L.T.L. provided by the University of Aberdeen. Data accessibility All data used in this study have been deposited in Dryad Digital Repository: https://doi.org/10.5061/dryad.kp89j (Fitt & Lancaster 2017).Peer reviewedPostprin
CP--odd Correlation in the Decay of Neutral Higgs Boson into , , or
We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
pair, a pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.Comment: 16 pages, plus 8 postscript graphs not posted befor
Come back Marshall, all is forgiven? : Complexity, evolution, mathematics and Marshallian exceptionalism
Marshall was the great synthesiser of neoclassical economics. Yet with his qualified assumption of self-interest, his emphasis on variation in economic evolution and his cautious attitude to the use of mathematics, Marshall differs fundamentally from other leading neoclassical contemporaries. Metaphors inspire more specific analogies and ontological assumptions, and Marshall used the guiding metaphor of Spencerian evolution. But unfortunately, the further development of a Marshallian evolutionary approach was undermined in part by theoretical problems within Spencer's theory. Yet some things can be salvaged from the Marshallian evolutionary vision. They may even be placed in a more viable Darwinian framework.Peer reviewedFinal Accepted Versio
Typification and authorship of Drosera intermedia (Droseraceae)
Drosera intermedia is lectotypified with the herbarium specimen on which the type drawing in the 1798 protologue was based. The collection history of the specimen, the history of the botanical drawing as original material, and the correct nomenclatural author and publication date of the name are presented based on historical notes and literature. Additionally, the global distribution of the species is given, including the first record from Africa
How Fitch-Margoliash Algorithm can Benefit from Multi Dimensional Scaling
Whatever the phylogenetic method, genetic sequences are often described as strings of characters, thus molecular sequences can be viewed as elements of a multi-dimensional space. As a consequence, studying motion in this space (ie, the evolutionary process) must deal with the amazing features of high-dimensional spaces like concentration of measured phenomenon
Gravitational Lensing by Black Holes
We review the theoretical aspects of gravitational lensing by black holes,
and discuss the perspectives for realistic observations. We will first treat
lensing by spherically symmetric black holes, in which the formation of
infinite sequences of higher order images emerges in the clearest way. We will
then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the
perspectives for observations of black hole lensing, from the detection of
secondary images of stellar sources and spots on the accretion disk to the
interpretation of iron K-lines and direct imaging of the shadow of the black
hole.Comment: Invited article for the GRG special issue on lensing (P. Jetzer, Y.
Mellier and V. Perlick Eds.). 31 pages, 12 figure
Genetic structure among Charadrius plovers on the African mainland and islands of Madagascar and St Helena
Colonisation of islands by long distance dispersers has great impact on genetic diversification among populations and may spearhead speciation events. We investigated intra‐ and interspecific divergence in Charadrius plovers with populations on mainland Africa, Madagascar and St Helena. We analysed microsatellite loci and sequence data from four nuclear and two mitochondrial gene regions. Charadrius plovers are shorebirds with high dispersal and mobility. Our results confirmed genetic differentiation between Madagascar and mainland populations of three plover species (White‐fronted Plovers, C. marginatus; Kittlitz's Plovers, C. pecuarius; and based on sequence data only, Three‐banded Plovers, C. tricollaris) but highlight substantial variation in levels of intraspecific divergence among the three species. Namely, the Kittlitz's Plover, a dispersive habitat generalist with a polygamous mating system, exhibited lower island‐mainland differentiation (0.05% COI sequence divergence) than two monogamous species, the White‐fronted Plover (0.6% COI divergence) and Three‐banded Plover (1.6% COI divergence). In addition, past colonisation of the islands of St Helena and Madagascar by ancestors of today's Kittlitz's Plover led to the evolution of two endemic island species, the Madagascar Plover C. thoracicus and the more closely‐related St Helena Plover C. sanctaehelenae. We discuss the factors driving species differences in island‐mainland divergence, and highlight the importance of conserving genetically unique island populations and island habitats to safe‐guard future evolutionary potential
Caste development and reproduction: a genome-wide analysis of hallmarks of insect eusociality
The honey bee queen and worker castes are a model system for developmental plasticity. We used established expressed sequence tag information for a Gene Ontology based annotation of genes that are differentially expressed during caste development. Metabolic regulation emerged as a major theme, with a caste-specific difference in the expression of oxidoreductases vs. hydrolases. Motif searches in upstream regions revealed group-specific motifs, providing an entry point to cis-regulatory network studies on caste genes. For genes putatively involved in reproduction, meiosis-associated factors came out as highly conserved, whereas some determinants of embryonic axes either do not have clear orthologs (bag of marbles, gurken, torso), or appear to be lacking (trunk) in the bee genome. Our results are the outcome of a first genome-based initiative to provide an annotated framework for trends in gene regulation during female caste differentiation (representing developmental plasticity) and reproduction
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