arXiv subjects

P. Nurowski

Publications and source records attributed to P. Nurowski.

3 recordsLinked to original sources

arXiv2024

Unique Carrollian manifolds emerging from Einstein spacetimes

We explicitly determine all shear-free null hypersurfaces embedded in an Einstein spacetime, including vacuum asymptotically flat spacetimes. We characterize these hypersurfaces as oriented 3-dimensional manifolds where each is equipped with a coframe basis, a structure group and a connection. Such manifolds are known as null hypersurface structures (NHSs). The coframe and connection one-forms for an NHS appear as solutions to the projection of the Cartan structure equations onto the null hypersurface. We then show that each NHS corresponds to a Carrollian structure equipped with a unique pair of Ehresmann connection and affine connection.

gr-qc↗

arXiv2012

Structures in the microwave background radiation

We compare the actual WMAP maps with artificial, purely statistical maps of the same harmonic content to argue that there are, with confidence level 99.7 %, ring-type structures in the observed cosmic microwave background.

astro-ph.CO↗

arXiv1996

Twistor Bundles, Einstein Equations and Real Structures

We consider sphere bundles P and P' of totally null planes of maximal dimension and opposite self-duality over a 4-dimensional manifold equipped with a Weyl or Riemannian geometry. The fibre product PP' of P and P' is found to be appropriate for the encoding of both the selfdual and the Einstein-Weyl equations for the 4-metric. This encoding is realized in terms of the properties of certain well defined geometrical objects on PP'. The formulation is suitable for both complex- and real-valued metrics. It unifies results for all three possible real signatures. In the purely Riemannian positive definite case it implies the existence of a natural almost hermitian structure on PP' whose integrability conditions correspond to the self-dual Einstein equations of the 4-metric. All Einstein equations for the 4-metric are also encoded in the properties of this almost hermitian structure on PP'.

dg-ga↗