English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

An immense class of physical counterexamples to the four dimensional strongcosmic censor conjecture---in its usual broad formulation---is exhibited. Moreprecisely, out of any closed and simply connected 4-manifold an open Ricci-flatLorentzian 4-manifold is constructed which is not globally hyperbolic and noperturbation of it, in any sense, can be globally hyperbolic. This very stablenon-global-hyperbolicity is the consequence of our open spaces having a"creased end" i.e., an end diffeomorphic to an exotic ${\mathbb R}^4$. Openmanifolds having an end like this is a typical phenomenon in four dimensions.  The construction is based on a collection of results of Gompf and Taubes onexotic and self-dual spaces, respectively, as well as applying Penrose'non-linear graviton construction (i.e., twistor theory) to solve the RiemannianEinstein's equation. These solutions then are converted into stablynon-globally-hyperbolic Lorentzian vacuum solutions. It follows that theplethora of vacuum solutions we found cannot be obtained via the initial valueformulation of the Einstein's equation because they are "too long" in a certainsense (explained in the text). This different (i.e., not based on the initialvalue formulation but twistorial) technical background might partially explainwhy the existence of vacuum solutions of this kind have not been realized sofar in spite of the fact that, apparently, their superabundance compared to thewell-known globally hyperbolic vacuum solutions is overwhelming.

Exotica and the status of the strong cosmic censor conjecture in four dimensions