713 research outputs found
The BIC of a singular foliation defined by an abelian group of isometries
We study the cohomology properties of the singular foliation \F determined
by an action where the abelian Lie group
preserves a riemannian metric on the compact manifold . More precisely, we
prove that the basic intersection cohomology \lau{\IH}{*}{\per{p}}{\mf} is
finite dimensional and verifies the Poincar\'e Duality. This duality includes
two well-known situations:
-- Poincar\'e Duality for basic cohomology (the action is almost
free).
-- Poincar\'e Duality for intersection cohomology (the group is compact
and connected)
Leaves of foliations with a transverse geometric structure of finite type
In this short note we find some conditions which ensure that a G foliation of finite type with all leaves compact is a Riemannian foliation or equivalently the space of leaves of such a foliation is a Satake manifold. A particular attention is paid to transversely affine foliations. We present several conditions such ensure completeness of these foliations
Top dimensional group of the basic intersection cohomology for singular riemannian foliations
It is known that, for a regular riemannian foliation on a compact manifold,
the properties of its basic cohomology (non-vanishing of the top-dimensional
group and Poincar\'e Duality) and the tautness of the foliation are closely
related. If we consider singular riemannian foliations, there is little or no
relation between these properties. We present an example of a singular
isometric flow for which the top dimensional basic cohomology group is
non-trivial, but its basic cohomology does not satisfy the Poincar\'e Duality
property. We recover this property in the basic intersection cohomology. It is
not by chance that the top dimensional basic intersection cohomology groups of
the example are isomorphic to either 0 or . We prove in this Note
that this holds for any singular riemannian foliation of a compact connected
manifold. As a Corollary, we get that the tautness of the regular stratum of
the singular riemannian foliation can be detected by the basic intersection
cohomology.Comment: 11 pages. Accepted for publication in the Bulletin of the Polish
Academy of Science
Effects of geometric variables on rub characteristics of Ti-6Al-4V
Experiments simulating rub interactions between Ti-6Al-4V blade tips and various seal materials were conducted. The number of blade tips and the blade tip geometry were varied to determine their effects on rub forces and on wear phenomena. Contact was found to be quite unsteady for all blade tip geometries except for those incorporating deliberately rounded blade tips. The unsteady contact was characterized by long periods of rubbing contact and increasing blade tip that terminated in sudden rapid metal removal, sometimes accompanied by tearing and disruption of porous seal material under the rub surface. A model describing the blade tip loading is proposed and is based on the propagation of an elastic stress wave through the seal material as the seal material is dynamically compressed by the blade tip leading edge
Finite temperature QMC study of the one-dimensional polarized Fermi gas
Quantum Monte Carlo (QMC) techniques are used to provide an
approximation-free investigation of the phases of the one-dimensional
attractive Hubbard Hamiltonian in the presence of population imbalance. The
temperature at which the "Fulde-Ferrell-Larkin-Ovchinnikov" (FFLO) phase is
destroyed by thermal fluctuations is determined as a function of the
polarization. It is shown that the presence of a confining potential does not
dramatically alter the FFLO regime, and that recent experiments on trapped
atomic gases likely lie just within the stable temperature range.Comment: 10 pages, 13 figures We added a discussion of the behaviour of the
FFLO peak as a function of the attractive interaction strengt
Individual repeatability and heritability of divorce in a wild population
Funding All authors were supported by a European Research Council grant to JMR. Fieldwork was supported by the Natural Sciences and Engineering Research Council of Canada and the University of British Columbia. Acknowledgments We thank the Tsawout and Tseycum First Nation bands for access to Mandarte, Peter Arcese, Lukas Keller, Pirmin Nietlisbach, and the University of Aberdeen Maxwell High Performance Computing cluster.Peer reviewedPostprin
Equivariant quantization of orbifolds
Equivariant quantization is a new theory that highlights the role of
symmetries in the relationship between classical and quantum dynamical systems.
These symmetries are also one of the reasons for the recent interest in
quantization of singular spaces, orbifolds, stratified spaces... In this work,
we prove existence of an equivariant quantization for orbifolds. Our
construction combines an appropriate desingularization of any Riemannian
orbifold by a foliated smooth manifold, with the foliated equivariant
quantization that we built in \cite{PoRaWo}. Further, we suggest definitions of
the common geometric objects on orbifolds, which capture the nature of these
spaces and guarantee, together with the properties of the mentioned foliated
resolution, the needed correspondences between singular objects of the orbifold
and the respective foliated objects of its desingularization.Comment: 13 page
Quantifying inbreeding avoidance through extra-pair reproduction
© 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.Peer reviewedPublisher PD
Validation of polish version of the Basel extent of rationing of nursing care revised questionnaire
Development of simple, valid and reliable instruments to determine nursing care rationing is a subject of ongoing research. One such instrument, which is gaining popularity worldwide and has significant research applicability, is the Basel Extent of Rationing of Nursing Care (BERNCA) and its revised version, the BERNCA-R. The aim of this study was to translate and adapt the BERNCA-R into a Polish-language version and to assess its reliability and validity in evaluating the level of implicit rationing of nursing care in Poland. Standard methodological requirements were followed during translation and cultural adaptation of the English version of the BERNCA-R questionnaire into Polish. The cross-sectional validation study was conducted between May and September 2017, which included 175 nurses undergoing specialisation and qualification courses at the European Postgraduate Education Centre in Wrocław, Poland. Cronbach’s alpha and inter-item correlations were used to analyse the internal consistency of the Polish BERNCA-R questionnaire. The mean total BERNCA-R score was 1.9 points (SD = 0.74) on a scale of 0-4. Cronbach’s alpha for the unidimensional scale was 0.96. The mean inter-item correlation was 0.4 (range 0.1-0.84), which indicates high internal consistency. A single-factor solution demonstrated stable loadings above 0.5 for almost all items of the Polish BERNCA-R questionnaire. The study using the Polish BERNCA-R questionnaire demonstrated that the instrument is valid and reliable for use in investigating care rationing in groups of Polish nurses
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