199 research outputs found
The maximum size of a partial spread in H(5, q²) is q³+1
AbstractIn this paper, we show that the largest maximal partial spreads of the hermitian variety H(5,q2) consist of q3+1 generators. Previously, it was only known that q4 is an upper bound for the size of these partial spreads. We also show for q⩾7 that every maximal partial spread of H(5,q2) contains at least 2q+3 planes. Previously, only the lower bound q+1 was known
Partial ovoids and partial spreads in symplectic and orthogonal polar spaces
We present improved lower bounds on the sizes of small maximal partial ovoids and small maximal partial spreads in the classical symplectic and orthogonal polar spaces, and improved upper bounds on the sizes of large maximal partial ovoids and large maximal partial spreads in the classical symplectic and orthogonal polar spaces. An overview of the status regarding these results is given in tables. The similar results for the hermitian classical polar spaces are presented in [J. De Beule, A. Klein, K. Metsch, L. Storme, Partial ovoids and partial spreads in hermitian polar spaces, Des. Codes Cryptogr. (in press)]
The Theorem of Totten for planar spaces
It is shown that an irreducible planar space S with v points and π
planes such that n3 ≤ v < (n + 1)3 and π ≤ v + n2 + n for some integer n ≥ 4 exists iff
n is a prime power and S either can be embedded in P G(3, n), or S is the affine space
AG(3, n) with a generalized projective 3-space at infinity. This result is an analogue to
the classification of restricted linear spaces by Totten
Partial Ovoids and Partial Spreads of Classical Finite Polar Spaces
2000 Mathematics Subject Classification: 05B25, 51E20.We survey the main results on ovoids and spreads, large maximal partial ovoids and large maximal partial spreads, and on small maximal partial ovoids and small maximal partial spreads in classical finite polar spaces. We also discuss the main results on the spectrum problem on maximal partial ovoids and maximal partial spreads in classical finite polar spaces.The research of the fourth author was also supported by the Project Combined algorithmic and the oretical study of combinatorial structur es between the Fund for Scientific Research Flanders-Belgium (FWO-Flanders) and the Bulgarian Academy of Science
Relativistic quark models of baryons with instantaneous forces
This is the first of a series of three papers treating light baryon resonances (up to 3 GeV) within a relativistically covariant quark model based on the three-fermion Bethe-Salpeter equation with instantaneous two- and three-body forces. In this paper we give a unified description of the theoretical background and demonstrate how to solve the Bethe-Salpeter equation by a reduction to the Salpeter equation. The specific new features of our covariant Salpeter model with respect to the usual nonrelativistic quark model are discussed in detail. The purely theoretical results obtained in this paper will be applied numerically to explicit quark models for light baryons in two subsequent papers
Electromagnetic Meson Form Factors in the Salpeter Model
We present a covariant scheme to calculate mesonic transitions in the
framework of the Salpeter equation for -states. The full Bethe
Salpeter amplitudes are reconstructed from equal time amplitudes which were
obtained in a previous paper\cite{Mue} by solving the Salpeter equation for a
confining plus an instanton induced interaction. This method is applied to
calculate electromagnetic form factors and decay widths of low lying
pseudoscalar and vector mesons including predictions for CEBAF experiments. We
also describe the momentum transfer dependence for the processes
.Comment: 22 pages including 10 figure
Food insecurity is associated with anxiety, stress, and symptoms of posttraumatic stress disorder in a cohort of women with or at risk of HIV in the United States
Background: Food insecurity, which disproportionately affects marginalized women in the United States, is associated with depressive symptoms. Few studies have examined relations of food insecurity with other mental health outcomes. Objective: The aim of this study was to investigate the associations of food insecurity with symptoms of generalized anxiety disorder (GAD), stress, and posttraumatic stress disorder (PTSD) in the Women's Interagency HIV Study (WIHS), a prospective cohort study of women with or at risk of HIV in the United States. Methods: Participants were 2553 women with or at risk of HIV, predominantly African American/black (71.6%). Structured questionnaires were conducted during April 2013-March 2016 every 6 mo. Food security (FS) was the primary predictor, measured using the Household Food Security Survey Module. We measured longitudinal outcomes for GAD (GAD-7 score and a binary GAD-7 screener for moderate-to-severe GAD). Only cross-sectional data were available for outcomes measuring perceived stress (PSS-10 score) and PTSD (PCL-C score and a binary PCL-C screener for PTSD). We examined associations of FS with the outcomes through use of multivariable linear and logistic regression, including lagged associations with GAD outcomes. Results: After adjusting for sociodemographic and health-related factors including HIV serostatus, current marginal, low, and very low FS were associated with increasingly higher GAD-7 scores, and with 1.41 (95% CI: 1.10, 1.80; P < 0.01), 2.03 (95% CI: 1.59, 2.61; P < 0.001), and 3.23 (95% CI: 2.43, 4.29; P < 0.001) times higher odds of screening positive for moderate-to-severe GAD, respectively. Low and very low FS at the previous visit (6 mo earlier) were independently associated with GAD outcomes at current visit. Associations of FS with PSS-10 and PCL-C scores exhibited similar dose-response relations. Very low FS was associated with 1.93 (95% CI: 1.15, 3.24; P < 0.05) times higher odds of screening positive for PTSD. Conclusions: Food insecurity may be associated with a range of poor mental health outcomes among women in the United States with or at risk of HIV
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