830 research outputs found
Heavy Meson Masses in the \epsilon-Regime of HM\chi PT
The pseudoscalar and vector heavy meson masses are calculated in the
\epsilon-regime of Heavy Meson Chiral Perturbation Theory to order \epsilon^4.
The results of this calculation will allow the determination of low-energy
coefficients (LECs) directly from Lattice QCD calculations of the heavy mesons
masses for lattices that satisfy the \epsilon-regime criteria. In particular,
the LECs that parametrize the NLO volume dependance of the heavy meson masses
are necessary for evaluating the light pseudoscalar meson (\pi, K, \eta) and
heavy meson ({D^0, D^+, D^+_s}, {B^-,\bar{B}^0,\bar{B}^0_s}) scattering phase
shifts.Comment: 16 pages, 6 figure
A Perturbation Framework for Convex Minimization and Monotone Inclusion Problems with Nonlinear Compositions
We introduce a framework based on Rockafellar's perturbation theory to
analyze and solve general nonsmooth convex minimization and monotone inclusion
problems involving nonlinearly composed functions as well as linear
compositions. Such problems have been investigated only from a primal
perspective and only for nonlinear compositions of smooth functions in
finite-dimensional spaces in the absence of linear compositions. In the context
of Banach spaces, the proposed perturbation analysis leads to the construction
of a dual problem and of a maximally monotone Kuhn--Tucker operator which is
decomposable as the sum of simpler monotone operators. In the Hilbertian
setting, this decomposition leads to block-iterative primal-dual proximal
algorithms that fully split all the components of the problem and capture
state-of-the-art existing methods as special cases
Proximal methods for stationary mean field games with local couplings
© 2018 Society for Industrial and Applied Mathematics. We address the numerical approximation of mean field games with local couplings. For power-like Hamiltonians, we consider a stationary system and also a system involving density constraints modeling hard congestion effects. For finite difference discretization of the mean field game system developed in [Y. Achdou and I. Capuzzo-Dolcetta, SIAM J. Numer. Anal., 48 (2010), pp. 1136-1162], we follow a variational approach. We prove that the aforementioned schemes can be obtained as the optimality system of suitably defined optimization problems. In order to prove the existence of solutions of the scheme with a variational argument, monotonicity assumptions on the coupling term are not needed, which allows us to recover general existence results proved by Achdou and Capuzzo-Dolcetta. Next, assuming that the coupling term is nondecreasing, the variational problem is cast as a convex optimization problem, for which we study and compare several proximal-type methods. These algorithms have several interesting features, such as global convergence and stability with respect to the viscosity parameter, which can eventually be zero. We assess the performance of the methods via numerical experiments
17 new very low-mass members in Taurus. The brown dwarf deficit revisited
Recent studies of the substellar population in the Taurus cloud have revealed
a deficit of brown dwarfs (BD) compared to the Trapezium cluster population
(Briceno et al 1998; Luhman 2000; Luhman et al 2003a; Luhman 2004). However,
these works have concentrated on the highest stellar density regions of the
Taurus cloud. We have performed a large scale optical survey of this region,
covering a total area of 30 deg^2, and encompassing the densest part of the
cloud as well as their surroundings, down to a mass detection limits of 15
Jupiter Masses (MJ). In this paper, we present the optical spectroscopic
follow-up observations of 97 photometrically selected potential new low-mass
Taurus members, of which 27 are strong late-M (SpT < M4V) candidates. These
observations reveal 5 new very low mass (VLM) Taurus members and 12 new BDs.
Combining our observations with previously published results, we derive an
updated substellar to stellar ratio in Taurus of Rss =0.23 +/- 0.05. This ratio
now appears consistent with the value previously derived in the Trapezium
cluster under similar assumptions of 0.26 +/- 0.04. We find strong indication
that the relative numbers of BDs with respect to stars is decreased by a factor
2 in the central regions of the aggregates with respect to the more distributed
population. Our findings are best explained in the context of the
embryo-ejection model where brown dwarfs originate from dynamical interactions
in small N unstable multiple systems.Comment: 20 pages, 15 figure
Peroxidase expression in a cereal cyst nematode (Heterodera avenae) resistant hexaploid wheat line.
The incompatible interaction between plant and pathogen is often determined by the hypersensitive reaction (HR). This response is associated with accumulation of reactive oxygen species (ROS), which results in adverse growth conditions for pathogens. Two major mechanisms involving either NADPH oxidases or peroxidases have been proposed for generation of ROS. Peroxidases (PER, EC 1.11.1.7), present in all land plants, are members of a large multigenic family with high number of isoforms involved in a broad range of physiological processes. PER genes, which are expressed in nematode feeding sites, have been identified in several plant species (Zacheo et al. 1997). A strong correlation between HR and PER activities at four and seven days post nematode infection, was detected in roots of wheat lines carrying Cre2, Cre5 (from Ae. ventricosa) or Cre7 (from Ae. triuncialis) Heterodera avenae resistance genes (Andrés et al. 2001; Montes et al. 2003, 2004). We have studied changes in root of peroxidase mRNAs levels after infection by H. avenae of a wheat/Ae. ventricosa introgression line (H-93-8) carrying Cre2 (Delibes et al. 1993). We also report and classify the predicted protein sequences derived from complete peroxidase transcripts
The Coevality of Young Binary Systems
Multiple star systems are commonly assumed to form coevally; they thus
provide the anchor for most calibrations of stellar evolutionary models. In
this paper we study the binary population of the Taurus-Auriga association,
using the component positions in an HR diagram in order to quantify the
frequency and degree of coevality in young binary systems. After identifying
and rejecting the systems that are known to be affected by systematic errors
(due to further multiplicity or obscuration by circumstellar material), we find
that the relative binary ages, |Delta log(tau)|, have an overall dispersion of
sigma~0.40 dex. Random pairs of Taurus members are coeval only to within
sigma~0.58 dex, indicating that Taurus binaries are indeed more coeval than the
association as a whole. However, the distribution of |Delta log(tau)| suggests
two populations, with ~2/3 of the sample appearing coeval to within the errors
(sigma~0.16 dex) and the other ~1/3 distributed in an extended tail reaching
|Delta log(tau)|~0.4-0.9 dex. To explain the finding of a multi-peaked
distribution, we suggest that the tail of the differential age distribution
includes unrecognized hierarchical multiples, stars seen in scattered light, or
stars with disk contamination; additional followup is required to rule out or
correct for these explanations. The relative coevality of binary systems does
not depend significantly on the system mass, mass ratio, or separation. Indeed,
any pair of Taurus members wider than ~10' (~0.7 pc) shows the full age spread
of the association.Comment: 23 pages, 11 figures; accepted to Ap
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