Národní úložiště šedé literatury Nalezeno 3 záznamů.  Hledání trvalo 0.03 vteřin. 
VSI electromagnetic fields
Ortaggio, Marcello ; Pravda, Vojtěch
A p-form F is VSI (i.e., all its scalar invariants of arbitrary order vanish) in a n-dimensional spacetime if and only if it is of type N, its multiple null direction is "degenerate Kundt", and ...F = 0. This recent result is reviewed in the present contribution and its main consequences are summarized. In particular, a subset of VSI Maxwell fields possesses a universal property, i.e., they also solve (virtually) any generalized (non-linear and with higher derivatives) electrodynamics, possibly also coupled to Einstein's gravity.
On type II universal spacetimes
Hervik, S. ; Málek, Tomáš ; Pravda, Vojtěch ; Pravdová, Alena
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.
On type N and III universal spacetimes
Hervik, S. ; Pravda, Vojtěch ; Pravdová, Alena
We briefly summarize our recent results on type N and III universal spacetimes.

Chcete být upozorněni, pokud se objeví nové záznamy odpovídající tomuto dotazu?
Přihlásit se k odběru RSS.