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Self-duality and pointwise Osserman manifolds

Dimitri V. Alekseevsky, Novica Blažić, Neda Bokan, Zoran Rakić (1999)

Archivum Mathematicum

This paper is a contribution to the mathematical modelling of the hump effect. We present a mathematical study (existence, homogenization) of a Hamilton-Jacobi problem which represents the propagation of a front f lame in a striated media.

Semi-symmetric four dimensional neutral Lie groups

Ali Haji-Badali, Amirhesam Zaeim (2020)

Czechoslovak Mathematical Journal

The present paper is concerned with obtaining a classification regarding to four-dimensional semi-symmetric neutral Lie groups. Moreover, we discuss some geometric properties of these spaces. We exhibit a rich class of non-Einstein Ricci soliton examples.

Some Para-Hermitian Related Complex Structures and Non-existence of Semi-Riemannian Metric on Some Spheres

Erdem, Sadettin (1999)

Serdica Mathematical Journal

It is shown that the spheres S^(2n) (resp: S^k with k ≡ 1 mod 4) can be given neither an indefinite metric of any signature (resp: of signature (r, k − r) with 2 ≤ r ≤ k − 2) nor an almost paracomplex structure. Further for every given Riemannian metric on an almost para-Hermitian manifold with the associated 2-form φ one can construct an almost Hermitian structure (under certain conditions, two different almost Hermitian structures) whose associated 2-form(s) is φ.

Some results on the existence of geodesics in static Lorentz manifolds with singular boundary

Vieri Benci, Donato Fortunato, Fabio Giannoni (1991)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

In this Note we deal with the problem of the existence of geodesies joining two given points of certain non-complete Lorentz manifolds, of which the Schwarzschild spacetime is the simplest physical example.

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