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Number of found documents:
426
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Higher dimensional Robinson-Trautman spacetimes sourced by p-forms: static and radiating black holes
Ortaggio, Marcello; Podolský, J.; Žofka, M.
2017 - English
We summarize results about Robinson-Trautman spacetimes in the presence of an aligned p-form Maxwell field and an arbitrary cosmological constant in n >= 4 dimensions. While in odd dimensions the solutions reduce to static black holes dressed with an electric and a magnetic field (with an Einstein space horizon), in even dimensions 2p = n they may also describe black holes gaining (or losing) mass by receiving (or emitting) electromagnetic radiation. The Weyl type of the spacetimes is also briefly discussed in all the possible cases.
Keywords:
Robinson-Trautman spacetimes; p-form fields; black holes
Available on request at various institutes of the ASCR
Higher dimensional Robinson-Trautman spacetimes sourced by p-forms: static and radiating black holes
We summarize results about Robinson-Trautman spacetimes in the presence of an aligned p-form Maxwell field and an arbitrary cosmological constant in n >= 4 dimensions. While in odd dimensions the ...
Programs and Algorithms of Numerical Mathematics 18 : Janov nad Nisou, June 19-24, 2016 : proceedings of seminar
Chleboun, J.; Kůs, Pavel; Přikryl, Petr; Segeth, Karel; Šístek, Jakub; Vejchodský, Tomáš
2017 - English
This book comprises papers that originated from the invited lectures, survey lectures, short communications, and posters presented at the 18th seminar Programs and Algorithms of Numerical Mathematics (PANM) held in Janov nad Nisou, Czech Republic, June 19-24, 2016. All the papers have been peer-reviewed. The seminar was organized by the Institute of Mathematics of the Czech Academy of Sciences under the auspices of EU-MATHS-IN.cz, Czech Network for Mathematics in Industry. It continued the previous seminars on mathematical software and numerical methods held (biennially, with only one exception) in Al šovice, Bratří kov, Janov nad Nisou, Ko řenov, L ázně Libverda, Dolní Maxov, and Prague in the period 1983-2014. The objective of this series of seminars is to provide a forum for presenting and discussing advanced theoretical as well as practical topics in numerical analysis, computer implementation of algorithms, new approaches to mathematical modeling, and single- or multi-processor applications of computational methods.
Keywords:
numerical mathematics
Available in digital repository of the ASCR
Programs and Algorithms of Numerical Mathematics 18 : Janov nad Nisou, June 19-24, 2016 : proceedings of seminar
This book comprises papers that originated from the invited lectures, survey lectures, short communications, and posters presented at the 18th seminar Programs and Algorithms of Numerical Mathematics ...
On type N and III universal spacetimes
Hervik, S.; Pravda, Vojtěch; Pravdová, Alena
2017 - English
We briefly summarize our recent results on type N and III universal spacetimes.
Keywords:
generalized theories of gravity; universal spacetimes
Available on request at various institutes of the ASCR
On type N and III universal spacetimes
We briefly summarize our recent results on type N and III universal spacetimes.
On type II universal spacetimes
Hervik, S.; Málek, Tomáš; Pravda, Vojtěch; Pravdová, Alena
2017 - English
We briefly summarize our recent results on type II universal metrics of the Lorentzian signature. These metrics simultaneously solve all vacuum field equations of theories of gravity with the Lagrangian being a polynomial curvature invariant constructed from the metric, the Riemann tensor and its covariant derivatives of arbitrary order. It turns out that the results critically depend on the dimensionality of the spacetime. While we discuss examples of type II universal metrics for all composite number dimensions, we have no examples for prime number dimensions. Furthermore, we have proven the non-existence of type II universal spacetimes in five dimensions.
Keywords:
generalized theories of gravity; universal spacetimes
Available on request at various institutes of the ASCR
On type II universal spacetimes
We briefly summarize our recent results on type II universal metrics of the Lorentzian signature. These metrics simultaneously solve all vacuum field equations of theories of gravity with the ...
The effect of irregular interfaces on the BDDC method for the Navier-Stokes equations
Hanek, M.; Šístek, Jakub; Burda, P.
2017 - English
We investigate the effect of interface irregularity on the convergence of the BDDC method for Navier-Stokes equations. A benchmark problem of a sequence of contracting channels is proposed to evaluate the robustness of the iterative solver with respect to element aspect ratios at the interface. Partitioners based on graph of the mesh and the geometry of the domain are compared. It is shown, that the convergence is significantly improved by avoiding irregular interfaces for the benchmark problem as well as for an industrial problem of oil flow in hydrostatic bearing.
Keywords:
Navier Stokes equations; domain decomposition methods; hydrostatic bearings
Available at various institutes of the ASCR
The effect of irregular interfaces on the BDDC method for the Navier-Stokes equations
We investigate the effect of interface irregularity on the convergence of the BDDC method for Navier-Stokes equations. A benchmark problem of a sequence of contracting channels is proposed to evaluate ...
Observing how future primary school teachers reason about fractions
Samková, L.; Tichá, Marie
2017 - English
The contribution focuses on the possibility to use an educational tool called Concept Cartoons in future primary school teachers' education, especially as an instrument for observing how future primary school teachers reason about fractions. The task which we adapted to the Concept Cartoons form belongs to primary school mathematics, i.e. it focuses on the concept of a fraction per se, in particular on the parts-and-whole decision and on comparison of two pre-partitioned models with diverse wholes. Using Concept Cartoons, we observe which statements about the issue our respondents consider as correct, and which kinds of reasoning they use in their justifications. We also mention other related concepts (percentages), and related tasks from entrance exams to lower-secondary selective schools.
Keywords:
concept Cartoons; fractions; future primary school teachers
Available at various institutes of the ASCR
Observing how future primary school teachers reason about fractions
The contribution focuses on the possibility to use an educational tool called Concept Cartoons in future primary school teachers' education, especially as an instrument for observing how future ...
The role of Sommerville tetrahedra in numerical mathematics
Hošek, Radim
2017 - English
In this paper we summarize three recent results in computational geometry, that were motivated by applications in mathematical modelling of fluids. The cornerstone of all three results is the genuine construction developed by D. Sommerville already in 1923. We show Sommerville tetrahedra can be effectively used as an underlying mesh with additional properties and also can help us prove a result on boundary-fitted meshes. Finally we demonstrate the universality of the Sommerville's construction by its direct generalization to any dimension.
Keywords:
simplicial tessellations; simplicial mesh; Sommerville tetrahedron
Available in digital repository of the ASCR
The role of Sommerville tetrahedra in numerical mathematics
In this paper we summarize three recent results in computational geometry, that were motivated by applications in mathematical modelling of fluids. The cornerstone of all three results is the genuine ...
A particular smooth interpolation that generates splines
Segeth, Karel
2017 - English
There are two grounds the spline theory stems from -- the algebraic one (where splines are understood as piecewise smooth functions satisfying some continuity conditions) and the variational one (where splines are obtained via minimization of some quadratic functionals with constraints). We use the general variational approach called $it smooth interpolation$ introduced by Talmi and Gilat and show that it covers not only the cubic spline and its 2D and 3D analogues but also the well known tension spline (called also spline with tension). We present the results of a 1D numerical example that characterize some properties of the tension spline.
Keywords:
data interpolation; smooth interpolation; spline interpolation
Available in digital repository of the ASCR
A particular smooth interpolation that generates splines
There are two grounds the spline theory stems from -- the algebraic one (where splines are understood as piecewise smooth functions satisfying some continuity conditions) and the variational one ...
The Cramér-Rao inequality on singular statistical models
Le, Hong-Van; Jost, J.; Schwachhöfer, L.
2017 - English
We introduce the notions of essential tangent space and reduced Fisher metric and extend the classical Cramér-Rao inequality to $2$-integrable (possibly singular) statistical models for general $varphi$-estimators, where $varphi$ is a $V$-valued feature function and $V$ is a topological vector space. We show the existence of a $varphi$-efficient estimator on strictly singular statistical models associated with a finite sample space and on a class of infinite dimensional exponential models that have been discovered by Fukumizu. We conclude that our general Cramér-Rao inequality is optimal.
Keywords:
Cramér-Rao inequality; Singular Statistical Models
Available on request at various institutes of the ASCR
The Cramér-Rao inequality on singular statistical models
We introduce the notions of essential tangent space and reduced Fisher metric and extend the classical Cramér-Rao inequality to $2$-integrable (possibly singular) statistical models for general ...
Note on the problem of dissipative measure-valued solutions to the compressible non-Newtonian system
Al Baba, Hind; Caggio, Matteo; Ducomet, B.; Nečasová, Šárka
2017 - English
We introduce a dissipative measure-valued solution to the compressible non-Newtonian system. We generalized a result given by Novotný, Nečasová [14]. We derive a relative entropy inequality for measure-valued solution as an extension of the classical entropy inequality introduced by Dafermos [2], Mellet-Vasseur [11], Feireisl-Jin-Novotný [5].
Keywords:
dissipative measure-valued solution; non-Newtonian fluid; compressible fluid
Available on request at various institutes of the ASCR
Note on the problem of dissipative measure-valued solutions to the compressible non-Newtonian system
We introduce a dissipative measure-valued solution to the compressible non-Newtonian system. We generalized a result given by Novotný, Nečasová [14]. We derive a relative entropy inequality for ...
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