459 research outputs found
Asymptotic degeneracy of dyonic N=4 string states and black hole entropy
It is shown that the asymptotic growth of the microscopic degeneracy of BPS
dyons in four-dimensional N=4 string theory captures the known corrections to
the macroscopic entropy of four-dimensional extremal black holes. These
corrections are subleading in the limit of large charges and originate both
from the presence of interactions in the effective action quadratic in the
Riemann tensor and from non-holomorphic terms. The presence of the
non-holomorphic corrections and their contribution to the thermodynamic free
energy is discussed. It is pointed out that the expression for the microscopic
entropy, written as a function of the dilaton field, is stationary at the
horizon by virtue of the attractor equations.Comment: 16 pages Late
Perturbative gravitational couplings and Siegel modular forms in string models
We consider four-parameter string models with Hodge numbers
and , and we express their perturbative Wilsonian
gravitational coupling in terms of Siegel modular forms.Comment: 8 pages, Latex 2.09, Contribution to the Proceedings of the 30th
International Symposium Ahrenshoop on the Theory of Elementary Particles,
Buckow, August 27-31, 199
Holographic Gravitational Anomalies
In the AdS/CFT correspondence one encounters theories that are not invariant
under diffeomorphisms. In the boundary theory this is a gravitational anomaly,
and can arise in 4k+2 dimensions. In the bulk, there can be gravitational
Chern-Simons terms which vary by a total derivative. We work out the
holographic stress tensor for such theories, and demonstrate agreement between
the bulk and boundary. Anomalies lead to novel effects, such as a nonzero
angular momentum for global AdS(3). In string theory such Chern-Simons terms
are known with exact coefficients. The resulting anomalies, combined with
symmetries, imply corrections to the Bekenstein-Hawking entropy of black holes
that agree exactly with the microscopic counting.Comment: 25 page
Polyploid plants have faster rates of multivariate niche differentiation than their diploid relatives
Polyploid speciation entails substantial and rapid postzygotic reproductive isolation of nascent species that are initially sympatric with one or both parents. Despite strong postzygotic isolation, ecological niche differentiation has long been thought to be important for polyploid success. Using biogeographic data from across vascular plants, we tested whether the climatic niches of polyploid species are more differentiated than their diploid relatives and if the climatic niches of polyploid species differentiated faster than those of related diploids. We found that polyploids are often more climatically differentiated from their diploid parents than the diploids are from each other. Consistent with this pattern, we estimated that polyploid species generally have higher rates of multivariate niche differentiation than their diploid relatives. In contrast to recent analyses, our results confirm that ecological niche differentiation is an important component of polyploid speciation and that niche differentiation is often significantly faster in polyploids.Polyploid speciation entails substantial and rapid postzygotic reproductive isolation of nascent species that are initially sympatric with one or both parents. Despite strong postzygotic isolation, ecological niche differentiation has long been thought to be important for polyploid success. Using biogeographic data from across vascular plants, we tested whether the climatic niches of polyploid species are more differentiated than their diploid relatives and if the climatic niches of polyploid species differentiated faster than those of related diploids.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/1/ele13402-sup-0001-TableS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/2/ele13402_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/3/ele13402-sup-0007-TableS7.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/4/ele13402-sup-0003-TableS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/5/ele13402-sup-0005-TableS5.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/6/ele13402.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/7/ele13402-sup-0006-TableS6.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/8/ele13402-sup-0002-TableS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153074/9/ele13402-sup-0004-TableS4.pd
Leptogenesis through direct inflaton decay to light particles
We present a scenario of nonthermal leptogenesis following supersymmetric
hybrid inflation, in the case where inflaton decay to both heavy right handed
neutrino and SU(2)_L triplet superfields is kinematically disallowed. Lepton
asymmetry is generated through the decay of the inflaton into light particles
by the interference of one-loop diagrams with right handed neutrino and SU(2)_L
triplet exchange respectively. We require superpotential couplings explicitly
violating a U(1) R-symmetry and R-parity. However, the broken R-parity need not
have currently observable low-energy signatures. Also, the lightest sparticle
can be stable. Some R-parity violating slepton decays may, though, be
detectable in the future colliders. We take into account the constraints from
neutrino masses and mixing and the preservation of the primordial lepton
asymmetry.Comment: 11 pages including 3 figures, uses Revtex, minor corrections,
references adde
Are Labour Markets Necessarily Local? Spatiality, Segmentation and Scale
This paper draws on recent debates about scale to approach the geography of labour markets from a dynamic perspective sensitive to the spatiality and scale of labour market
restructuring. Its exploration of labour market reconfigurations after the collapse of a major firm (Ansett Airlines) raises questions about geographyâs faith in the inherently âlocalâ constitution of labour markets. Through an examination of the job reallocation process after redundancy, the paper suggests that multiple labour markets use and articulate scale in different ways. It argues that labour market rescaling processes are enacted at the critical moment of recruitment, where social networks, personal aspirations and employer preferences combine to shape workersâ destinations
The spinorial geometry of supersymmetric heterotic string backgrounds
We determine the geometry of supersymmetric heterotic string backgrounds for
which all parallel spinors with respect to the connection with
torsion , the NSNS three-form field strength, are Killing. We find
that there are two classes of such backgrounds, the null and the timelike. The
Killing spinors of the null backgrounds have stability subgroups
K\ltimes\bR^8 in , for , SU(4), , and , and the Killing spinors of the timelike backgrounds have
stability subgroups , SU(3), SU(2) and . The former admit a single
null -parallel vector field while the latter admit a timelike and
two, three, five and nine spacelike -parallel vector fields,
respectively. The spacetime of the null backgrounds is a Lorentzian
two-parameter family of Riemannian manifolds with skew-symmetric torsion.
If the rotation of the null vector field vanishes, the holonomy of the
connection with torsion of is contained in . The spacetime of time-like
backgrounds is a principal bundle with fibre a Lorentzian Lie group and
base space a suitable Riemannian manifold with skew-symmetric torsion. The
principal bundle is equipped with a connection which determines the
non-horizontal part of the spacetime metric and of . The curvature of
takes values in an appropriate Lie algebra constructed from that of
. In addition has only horizontal components and contains the
Pontrjagin class of . We have computed in all cases the Killing spinor
bilinears, expressed the fluxes in terms of the geometry and determine the
field equations that are implied by the Killing spinor equations.Comment: 73pp. v2: minor change
An Exploratory Analysis of the âWas It Worth It?â Questionnaire as a Novel Metric to Capture Patient Perceptions of Cancer Treatment
Objectives: Asking âWas it worth it?â (WIWI) potentially captures the patient perception of a treatment's benefit weighed against its harms. This exploratory analysis evaluates the WIWI questionnaire as a metric of patientsâ perspectives on the worthwhileness of cancer treatment. Methods: A 3-item WIWI questionnaire was assessed at end of treatment in patients with cancer on the COMET-2 trial (NCT01522443). WIWI items were evaluated to determine their association with quality of life (QOL), treatment duration, end-of-treatment reason, patient-reported adverse events (AEs), and disease response. Results: A total of 65 patients completed the questionnaire; 40 (62%), 16 (25%), and 9 (14%) patients replied yes, uncertain, and no to âWas it worthwhile for you to receive the cancer treatment given in this study?â (item 1), respectively; 39 (60%), 12 (18%), and 14 (22%) to âIf you had to do it over again, would you choose to have this cancer treatment?â; and 40 (62%), 14 (22%), and 11 (17%) to âWould you recommend this cancer treatment to others?â Patients responding yes to item 1 remained on treatment longer than those responding uncertain or no (mean 23.0 vs 11.3 weeks, P<.001). Patients responding uncertain/no to item 1 discontinued treatment because of AEs more frequently than those responding yes (36% vs 7.5%, P=.004) and demonstrated meaningful decline in QOL from baseline (â2.5 vs â0.2 mean change, P<.001). Associations between WIWI responses and most patient-reported AEs or treatment efficacy did not reach statistical significance. Conclusions: Patients who responded affirmatively on WIWI items remained on therapy longer, were less likely to stop treatment because of AEs, and demonstrated superior QOL. The WIWI may inform clinical practice, oncology research, and value frameworks
Resonant leptogenesis in a predictive SO(10) grand unified model
An SO(10) grand unified model considered previously by the authors featuring
lopsided down quark and charged lepton mass matrices is successfully predictive
and requires that the lightest two right-handed Majorana neutrinons be nearly
degenerate in order to obtain the LMA solar neutrino solution. Here we use this
model to test its predictions for baryogenesis through resonant-enhanced
leptogenesis. With the conventional type I seesaw mechanism, the best
predictions for baryogenesis appear to fall a factor of three short of the
observed value. However, with a proposed type III seesaw mechanism leading to
three pairs of massive pseudo-Dirac neutrinos, resonant leptogenesis is
decoupled from the neutrino mass and mixing issues with successful baryogenesis
easily obtained.Comment: 22 pages including 1 figure; published version with reference adde
Leptogenesis and neutrino parameters
We calculate the baryonic asymmetry of the universe in the
baryogenesis-via-leptogenesis framework, assuming first a quark-lepton symmetry
and then a charged-neutral lepton symmetry. We match the results with the
experimentally favoured range. In the first case all the oscillation solutions
to the solar neutrino problem, except the large mixing matter solution, can
lead to the allowed range, but with fine tuning of the parameters. In the
second case the general result is quite similar. Some related theoretical hints
are discussed.Comment: RevTex, 21 pages with 8 figure
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