5,921 research outputs found
Indirect detection of light neutralino dark matter in the NMSSM
We explore the prospects for indirect detection of neutralino dark matter in
supersymmetric models with an extended Higgs sector (NMSSM). We compute, for
the first time, one-loop amplitudes for NMSSM neutralino pair annihilation into
two photons and two gluons, and point out that extra diagrams (with respect to
the MSSM), featuring a potentially light CP-odd Higgs boson exchange, can
strongly enhance these radiative modes. Expected signals in neutrino telescopes
due to the annihilation of relic neutralinos in the Sun and in the Earth are
evaluated, as well as the prospects of detection of a neutralino annihilation
signal in space-based gamma-ray, antiproton and positron search experiments,
and at low-energy antideuteron searches. We find that in the low mass regime
the signals from capture in the Earth are enhanced compared to the MSSM, and
that NMSSM neutralinos have a remote possibility of affecting solar dynamics.
Also, antimatter experiments are an excellent probe of galactic NMSSM dark
matter. We also find enhanced two photon decay modes that make the possibility
of the detection of a monochromatic gamma-ray line within the NMSSM more
promising than in the MSSM.Comment: 26 pages, 12 figures. Updated references and corrected discussion of
Upsilon decay
Comfort Women in Indonesia: A Consideration of the Prewar Socio-legal context in Indonesia and Japan
14 páginas, 5 figuras, 10 tablas.A mechanistic lactation model, based on a theory of mammary cell proliferation and cell death, was studied and compared to the equation of Wood (1967). Lactation curves of British Holstein Friesian cows (176 curves), Spanish Churra sheep (40 curves) and Spanish Murciano-Granadina goats (30 curves) were used for model evaluation. Both models were fitted in their original form using non-linear least squares estimation. The parameters were compared among species and among parity groups within species.
In general, both models provided highly significant fits to lactation data and described the data accurately. The mechanistic model performed well against Wood's 1967 equation (hereafter referred to as Wood's equation), resulting in smaller residual mean square values in more than two-thirds of the datasets investigated, and producing parameter estimates that allowed appropriate comparisons and noticeable trends attributed to shape. Using Akaike or Bayesian information criteria, goodness-of-fit with the mechanistic model was superior to that with Wood's equation for 1 Lie cow lactation curves, with no significant differences between models when fitted to goat or sheep lactation curves. The rate parameters of the mechanistic model, representing specific proliferation rate of mammary secretory cells at parturition, decay associated with reduction in cell proliferation capacity with time and specific death rate of mammary secretory cells, were smaller for primiparous than for multiparous cows. Greater lactation persistency of cows compared to goats and sheep, and decrease in persistency with parity, were shown to be represented by different values of the specific secretory cell death rate parameter in the mechanistic model. The plausible biological interpretation and fitting properties of the mechanistic model enable it to be used in complex models of whole-cow digestion and metabolism and as a tool in selection programmes and by dairy producers for management decisions.Canada Research Chairs ProgramPeer reviewe
Microscopic origin of the conducting channels in metallic atomic-size contacts
We present a theoretical approach which allows to determine the number and
orbital character of the conducting channels in metallic atomic contacts. We
show how the conducting channels arise from the atomic orbitals having a
significant contribution to the bands around the Fermi level. Our theory
predicts that the number of conducting channels with non negligible
transmission is 3 for Al and 5 for Nb one-atom contacts, in agreement with
recent experiments. These results are shown to be robust with respect to
disorder. The experimental values of the channels transmissions lie within the
calculated distributions.Comment: 11 pages, 4 ps-figures. Submitted to Phys. Rev. Let
Subgraphs in random networks
Understanding the subgraph distribution in random networks is important for
modelling complex systems. In classic Erdos networks, which exhibit a
Poissonian degree distribution, the number of appearances of a subgraph G with
n nodes and g edges scales with network size as \mean{G} ~ N^{n-g}. However,
many natural networks have a non-Poissonian degree distribution. Here we
present approximate equations for the average number of subgraphs in an
ensemble of random sparse directed networks, characterized by an arbitrary
degree sequence. We find new scaling rules for the commonly occurring case of
directed scale-free networks, in which the outgoing degree distribution scales
as P(k) ~ k^{-\gamma}. Considering the power exponent of the degree
distribution, \gamma, as a control parameter, we show that random networks
exhibit transitions between three regimes. In each regime the subgraph number
of appearances follows a different scaling law, \mean{G} ~ N^{\alpha}, where
\alpha=n-g+s-1 for \gamma<2, \alpha=n-g+s+1-\gamma for 2<\gamma<\gamma_c, and
\alpha=n-g for \gamma>\gamma_c, s is the maximal outdegree in the subgraph, and
\gamma_c=s+1. We find that certain subgraphs appear much more frequently than
in Erdos networks. These results are in very good agreement with numerical
simulations. This has implications for detecting network motifs, subgraphs that
occur in natural networks significantly more than in their randomized
counterparts.Comment: 8 pages, 5 figure
A Monte Carlo study of O(3) antiferromagnetic models in three dimensions
We study three antiferromagnetic formulations of the O(3) spin model in three
dimensions by means of Monte Carlo simulations: 1. a two parameter
model with nearest and next to nearest neighbors couplings in a cubic lattice;
2. a face centered cubic lattice with nearest neighbors interaction; 3. a cubic
lattice with a set of fully frustrating couplings. We discuss in all cases the
vacua properties and analyze the phase transitions. Using Finite Size Scaling
analysis we conclude that all phase transitions found are of first order.Comment: 24 pages, uuencoded gzipped postscript file. 13 figures include
Sub-millimeter Tests of the Gravitational Inverse-square Law
Motivated by a variety of theories that predict new effects, we tested the
gravitational 1/r^2 law at separations between 10.77 mm and 137 microns using
two different 10-fold azimuthally symmetric torsion pendulums and rotating
10-fold symmetric attractors. Our work improves upon other experiments by up to
a factor of about 100. We found no deviation from Newtonian physics at the 95%
confidence level and interpret these results as constraints on extensions of
the Standard Model that predict Yukawa or power-law forces. We set a constraint
on the largest single extra dimension (assuming toroidal compactification and
that one extra dimension is significantly larger than all the others) of R <=
160 microns, and on two equal-sized large extra dimensions of R <= 130 microns.
Yukawa interactions with |alpha| >= 1 are ruled out at 95% confidence for
lambda >= 197 microns. Extra-dimensions scenarios stabilized by radions are
restricted to unification masses M >= 3.0 TeV/c^2, regardless of the number of
large extra dimensions. We also provide new constraints on power-law potentials
V(r)\propto r^{-k} with k between 2 and 5 and on the gamma_5 couplings of
pseudoscalars with m <= 10 meV/c^2.Comment: 34 pages, 38 figure
Minimum mass of galaxies from BEC or scalar field dark matter
Many problems of cold dark matter models such as the cusp problem and the
missing satellite problem can be alleviated, if galactic halo dark matter
particles are ultra-light scalar particles and in Bose-Einstein condensate
(BEC), thanks to a characteristic length scale of the particles. We show that
this finite length scale of the dark matter can also explain the recently
observed common central mass of the Milky Way satellites ()
independent of their luminosity, if the mass of the dark matter particle is
about .Comment: 10 pages, 1 figure, accepted in JCA
QED Logarithms in the Electroweak Corrections to the Muon Anomalous Magnetic Moment
We employ an effective Lagrangian approach to derive the leading-logarithm
two-loop electroweak contributions to the muon anomalous magnetic moment, a_mu.
We show that these corrections can be obtained using known results on the
anomalous dimensions of composite operators. We confirm the result of Czarnecki
et al. for the bosonic part and present the complete sin^2 \theta_W dependence
of the fermionic contribution. The approach is then used to compute the
leading-logarithm three-loop electroweak contribution to a_mu. Finally we
derive, in a fairly model-independent way, the QED improvement of new-physics
contributions to a_mu and to the electric dipole moment (EDM) of the electron.
We find that the QED corrections reduce the effect of new physics at the
electroweak scale by 6% (for a_mu) and by 11% (for the electron EDM).Comment: 13 page
Iterated perturbation theory for the attractive Holstein and Hubbard models
A strictly truncated (weak-coupling) perturbation theory is applied to the
attractive Holstein and Hubbard models in infinite dimensions. These results
are qualified by comparison with essentially exact Monte Carlo results. The
second order iterated perturbation theory is shown to be quite accurate in
calculating transition temperatures for retarded interactions, but is not as
accurate for the self energy or the irreducible vertex functions themselves.
Iterated perturbation theory is carried out thru fourth order for the Hubbard
model. The self energy is quite accurately reproduced by the theory, but the
vertex functions are not. Anomalous behavior occurs near half filling because
the iterated perturbation theory is not a conserving approximation. (REPLACED
WITH UUENCODED FIGURES AT THE END. THE TEXT IS UNCHANGED)Comment: 27 pages, RevTex (figures appended at end
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