630 research outputs found
Pseudo-Riemannian manifolds with recurrent spinor fields
The existence of a recurrent spinor field on a pseudo-Riemannian spin
manifold is closely related to the existence of a parallel
1-dimensional complex subbundle of the spinor bundle of . We
characterize the following simply connected pseudo-Riemannian manifolds
admitting such subbundles in terms of their holonomy algebras: Riemannian
manifolds; Lorentzian manifolds; pseudo-Riemannian manifolds with irreducible
holonomy algebras; pseudo-Riemannian manifolds of neutral signature admitting
two complementary parallel isotropic distributions.Comment: 13 pages, the final versio
On the local structure of Lorentzian Einstein manifolds with parallel distribution of null lines
We study transformations of coordinates on a Lorentzian Einstein manifold
with a parallel distribution of null lines and show that the general Walker
coordinates can be simplified. In these coordinates, the full Lorentzian
Einstein equation is reduced to equations on a family of Einstein Riemannian
metrics.Comment: Dedicated to Dmitri Vladimirovich Alekseevsky on his 70th birthda
The efficiency of combined electrothermal and electrochemical accumulation of electricity of a photovoltaic power plant
The relevance of the research is caused by the fact that renewable energy, in particular, photovoltaic generation is becoming essential support in the decentralized systems in Russia. However, the high cost of the power equipment of photovoltaic power plants is a deterrent to their wide practical application. This paper presents the method for reducing the cost of photovoltaic power plants by optimizing energy conversion processes in isolated power supply systems. The characteristics of equipment for photovoltaic generation and the subsequent conversion of parameters and power storage is an urgent task are presented
How to find the holonomy algebra of a Lorentzian manifold
Manifolds with exceptional holonomy play an important role in string theory,
supergravity and M-theory. It is explained how one can find the holonomy
algebra of an arbitrary Riemannian or Lorentzian manifold. Using the de~Rham
and Wu decompositions, this problem is reduced to the case of locally
indecomposable manifolds. In the case of locally indecomposable Riemannian
manifolds, it is known that the holonomy algebra can be found from the analysis
of special geometric structures on the manifold. If the holonomy algebra
of a locally indecomposable
Lorentzian manifold of dimension is different from
, then it is contained in the similitude algebra
. There are 4 types of such holonomy algebras. Criterion
how to find the type of are given, and special geometric
structures corresponding to each type are described. To each
there is a canonically associated subalgebra
. An algorithm how to find
is provided.Comment: 15 pages; the final versio
Comments of the Max Planck Institute for Intellectual Property, Competition and Tax Law (Munich) on the DG Competition discussion paper of December 2005 on the application of Article 82 of the EC Treaty to exclusionary abuses
One component of the curvature tensor of a Lorentzian manifold
The holonomy algebra \g of an -dimensional Lorentzian manifold
admitting a parallel distribution of isotropic lines is contained in the
subalgebra \simil(n)=(\Real\oplus\so(n))\zr\Real^n\subset\so(1,n+1). An
important invariant of \g is its \so(n)-projection \h\subset\so(n), which
is a Riemannian holonomy algebra. One component of the curvature tensor of the
manifold belongs to the space \P(\h) consisting of linear maps from \Real^n
to \h satisfying an identity similar to the Bianchi one. In the present paper
the spaces \P(\h) are computed for each possible \h. This gives the
complete description of the values of the curvature tensor of the manifold
. These results can be applied e.g. to the holonomy classification of
the Einstein Lorentzian manifolds.Comment: An extended version of a part from arXiv:0906.132
Lack of association between the Serotonin Transporter Promoter Polymorphism (5-HTTLPR) and Panic Disorder: a systematic review and meta-analysis
<p>Abstract</p> <p>Background</p> <p>The aim of this study is to assess the association between the Serotonin Transporter Promoter Polymorphism (5-HTTLPR) and Panic Disorder (PD).</p> <p>Methods</p> <p>This is a systematic review and meta-analysis of case-control studies with unrelated individuals of any ethnic origin examining the role of the 5-HTTLPR in PD according to standard diagnostic criteria (DSM or ICD). Articles published in any language between January 1996 and April 2007 were eligible. The electronic databases searched included PubMed, PsychInfo, Lilacs and ISI. Two separate analyses were performed: an analysis by alleles and a stratified analysis separating studies by the quality of control groups. Asymptotic DerSimonian and Laird's Q test were used to assess heterogeneity. Results of individual studies were combined using the fixed effect model with respective 95% confidence intervals.</p> <p>Results</p> <p>Nineteen potential articles were identified, and 10 studies were included in this meta-analysis. No statistically significant association between 5-HTTLPR and PD was found, OR = 0.91 (CI95% 0.80 to 1.03, p = 0.14). Three sub-analyses divided by ethnicity, control group quality and Agoraphobia comorbidity also failed to find any significant association. No evidence of heterogeneity was found between studies in the analyses.</p> <p>Conclusion</p> <p>Results from this systematic review do not provide evidence to support an association between 5-HTTLPR and PD. However, more studies are needed in different ethnic populations in order to evaluate a possible minor effect.</p
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