9,068 research outputs found
Evidence for inbreeding depression in a species with limited opportunity for maternal effects
It is often assumed that mating with close relatives reduces offspring fitness. In such cases, reduced offspring fitness may arise from inbreeding depression (i.e., genetic effects of elevated homozygosity) or from post-mating maternal investment. This can be due to a reduction in female investment after mating with genetically incompatible males ("differential allocation") or compensation for incompatibility ("reproductive compensation"). Here, we looked at the effects of mating with relatives on offspring fitness in mosquitofish, Gambusia holbrooki. In this species, females are assumed to be nonplacental and to allocate resources to eggs before fertilization, limiting differential allocation. We looked at the effects of mating with a brother or with an unrelated male on brood size, offspring size, gestation period, and early offspring growth. Mating with a relative reduced the number of offspring at birth, but there was no difference in the likelihood of breeding, gestation time, nor in the size or growth of these offspring. We suggest that due to limited potential for maternal effects to influence these traits that any reduction in offspring fitness, or lack thereof, can be explained by inbreeding depression rather than by maternal effects. We highlight the importance of considering the potential role of maternal effects when studying inbreeding depression and encourage further studies in other Poeciliid species with different degrees of placentation to test whether maternal effects mask or amplify any genetic effects of mating with relatives.This work was supported bythe Australian Research Council (DP120100339). R.V.-T. is supported by fellowships from Consejo Nacion-al de Ciencia y Tecnologıa-Mexico and the ResearchSchool of Biology
Revisiting Minimal Lepton Flavour Violation in the Light of Leptonic CP Violation
The Minimal Lepton Flavour Violation (MLFV) framework is discussed after the
recent indication for CP violation in the leptonic sector. Among the three
distinct versions of MLFV, the one with degenerate right-handed neutrinos will
be disfavoured, if this indication is confirmed. The predictions for leptonic
radiative rare decays and muon conversion in nuclei are analysed, identifying
strategies to disentangle the different MLFV scenarios. The claim that the
present anomalies in the semi-leptonic -meson decays can be explained within
the MLFV context is critically re-examined concluding that such an explanation
is not compatible with the present bounds from purely leptonic processes.Comment: 36 pages, 4 figures. V2: References added; version accepted for
publication on JHE
Bilinear identities involving the -plane transform and Fourier extension operators
We prove certain bilinear estimates for Fourier extension operators associated to spheres and hyperboloids under the action of the -plane transform. As the estimates are -based, they follow from bilinear identities: in particular, these are the analogues of a known identity for paraboloids, and may be seen as higher-dimensional versions of the classical -bilinear identity for Fourier extension operators associated to curves in
Dynamical renormalization group approach to the Altarelli-Parisi-Lipatov equations
The Altarelli-Parisi-Lipatov equations for the parton distribution functions
are rederived using the dynamical renormalization group approach to quantum
kinetics. This method systematically treats the ln Q^2 corrections that arises
in perturbation theory as a renormalization of the parton distribution function
and unambiguously indicates that the strong coupling must be allowed to run
with the scale in the evolution kernel. To leading logarithmic accuracy the
evolution equation is Markovian and the logarithmic divergences in the
perturbative expansion are identified with the secular divergences (terms that
grow in time) that emerge in a perturbative treatment of the kinetic equations
in nonequilibrium systems. The resummation of the leading logarithms by the
Altarelli-Parisi-Lipatov equation is thus similar to the resummation of the
leading secular terms by the Boltzmann kinetic equation.Comment: 8 pages, version to appear in Phys. Rev.
Absence of eigenvalues of two-dimensional magnetic Schr ̈odinger operators
By developing the method of multipliers, we establish sufficient conditions on the electric potential and magnetic field which guarantee that the corresponding two-dimensional Schr ̈odinger operator possesses no point spectrum. The settings of complex-valued electric potentials and singular magnetic potentials of Aharonov-Bohm field are also covered
String dynamics in cosmological and black hole backgrounds: The null string expansion
We study the classical dynamics of a bosonic string in the --dimensional
flat Friedmann--Robertson--Walker and Schwarzschild backgrounds. We make a
perturbative development in the string coordinates around a {\it null} string
configuration; the background geometry is taken into account exactly. In the
cosmological case we uncouple and solve the first order fluctuations; the
string time evolution with the conformal gauge world-sheet --coordinate
is given by , where
are given by Eqs.\ (3.15), and is the exponent of the conformal factor
in the Friedmann--Robertson--Walker metric, i.e. . The string
proper size, at first order in the fluctuations, grows like the conformal
factor and the string energy--momentum tensor corresponds to that of
a null fluid. For a string in the black hole background, we study the planar
case, but keep the dimensionality of the spacetime generic. In the null
string expansion, the radial, azimuthal, and time coordinates are
and The first terms of the series represent a
{\it generic} approach to the Schwarzschild singularity at . First and
higher order string perturbations contribute with higher powers of . The
integrated string energy-momentum tensor corresponds to that of a null fluid in
dimensions. As the string approaches the singularity its proper
size grows indefinitely like . We end the paper
giving three particular exact string solutions inside the black hole.Comment: 17 pages, REVTEX, no figure
Spectral stability of Schrödinger operators with subordinated complex potentials
We prove that the spectrum of Schroedinger operators in three dimensions is purely continuous and coincides with the non-negative semiaxis for all potentials satisfying a form-subordinate smallness condition. By developing the method of multipliers, we also establish the absence of point spectrum for Schroedinger operators in all dimensions under various alternative hypotheses, still allowing complex-valued potentials with critical singularities
Absence of eigenvalues of two-dimensional magnetic Schroedinger operators
By developing the method of multipliers, we establish sufficient conditions on the electric potential and magnetic field which guarantee that the corresponding two-dimensional Schroedinger operator possesses no point spectrum. The settings of complex-valued electric potentials and singular magnetic potentials of Aharonov-Bohm field are also covered
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