Results 21 to 30 of about 208 (40)

Partner symmetries and non-invariant solutions of four-dimensional heavenly equations [PDF]

, 2004
We extend our method of partner symmetries to the hyperbolic complex Monge-Amp\`ere equation and the second heavenly equation of Pleba\~nski. We show the existence of partner symmetries and derive the relations between them for both equations.
A A Malykh, Aliev A N, Atiyah M F, Boyer C P, Dunajski M, Goldblatt E, Ivanov I T, Levi D, M B Sheftel, Malykh A A, Malykh A A, Mason L J, Mason L J, Olver P, Plebañski J F, Y Nutku   +15 more
core   +1 more source

Anti-self-dual Riemannian metrics without Killing vectors, can they be realized on K3?

, 2003
Explicit Riemannian metrics with Euclidean signature and anti-self dual curvature that do not admit any Killing vectors are presented. The metric and the Riemann curvature scalars are homogenous functions of degree zero in a single real potential and its
A A Malykh, Aliev A N, Atiyah M F, Boyer C P, Calabi E, Chern S S, Chern S S, Goldblatt E, Hitchin N J, Kummer E E, Lie S, M B Sheftel, Malykh A A Sheftel M B V K Andreev Yu V Shan'ko, Martina L, Mason L J, Nutku Y, Olver P, Ovsiannikov L V, Vessiot E, Y Nutku, Yau S-T   +20 more
core   +2 more sources

Critical Robertson-Walker universes [PDF]

, 2019
The integral of the energy density function $\mathfrak m$ of a closed Robertson-Walker (RW) spacetime with source a perfect fluid and cosmological constant $\Lambda$ gives rise to an action functional on the space of scale functions of RW spacetime ...
Eshkobilov, Olimjon, Musso, Emilio, Nicolodi, Lorenzo   +2 more
core   +2 more sources

A Special Universe and its Massless Scalar Field Mathematical Structure

Analele Stiintifice ale Universitatii Ovidius Constanta: Seria Matematica
The present paper highlights an exotic universe having a metric which is partially suggested by the metric of an universe without time seen in [2]. The new metric is globally defined and depends on an exotic matter created by some classical waves.
Boskoff Wladimir-Georges, Nicola Aurelian   +1 more
doaj   +1 more source

Flat deformation of a spacetime admitting two Killing fields [PDF]

, 2010
It is shown that given an analytic Lorentzian metric on a 4-manifold, $g$, which admits two Killing vector fields, then it exists a local deformation law $\eta = a g + b H$, where $H$ is a 2-dimensional projector, such that $\eta$ is flat and admits the ...
Choquet-Bruhat Y, Eisenhart L P, Garcia-Parrado A, Jaume Carot, John F, Josep Llosa, Kobayashi S, Llosa J, Llosa J, Rainich G Y   +9 more
core   +3 more sources

LRS Bianchi type-I cosmological model with constant deceleration parameter in $f(R,T)$ gravity

, 2017
A spatially homogeneous anisotropic LRS Bianchi type-I cosmological model is studied in $f(R,T)$ gravity with a special form of Hubble's parameter, which leads to constant deceleration parameter.
Bishi, Binaya K., Pacif, S. K. J., Sahoo, P. K., Singh, G. P.   +3 more
core   +1 more source

A mathematical note about a FLRW universe embedded in a universe without time

Analele Stiintifice ale Universitatii Ovidius Constanta: Seria Matematica
In this paper we propose to study a six-dimensional Friedmann-Lemaître-Robertson-Walker (FLRW) universe without time. The way we study this timeless universe is the classic one: we highlight future oriented time-like loops and closed chains of future ...
Sburlan Cristina
doaj   +1 more source

Exact Fermi coordinates for a class of spacetimes

, 2009
We find exact Fermi coordinates for timelike geodesic observers for a class of spacetimes that includes anti-de Sitter spacetime, de Sitter spacetime, the constant density interior Schwarzschild spacetime with positive, zero, and negative cosmological ...
David Klein, O’Neill B., Peter Collas, Synge J. L.   +3 more
core   +1 more source

Nonholonomic Ricci Flows and Running Cosmological Constant: I. 4D Taub-NUT Metrics [PDF]

, 2006
In this work we construct and analyze exact solutions describing Ricci flows and nonholonomic deformations of four dimensional (4D) Taub-NUT spacetimes. It is outlined a new geometric techniques of constructing Ricci flow solutions.
Astefanesei D., Astefanesei D., Bakas I., Bejancu A., Cao H.-D., Deligne P., MIHAI VISINESCU, SERGIU I. VACARU, Vacaru S.   +8 more
core   +3 more sources

Fractional Curve Flows and Solitonic Hierarchies in Gravity and Geometric Mechanics

, 2011
Methods from the geometry of nonholonomic manifolds and Lagrange-Finsler spaces are applied in fractional calculus with Caputo derivatives and for elaborating models of fractional gravity and fractional Lagrange mechanics.
Dumitru Baleanu, Gorenflo R., Kilbas A. A., Sergiu I. Vacaru   +3 more
core   +1 more source