4 papers · 1 filter
Cherenkov radiation as ghost instability
Eugeny Babichev
We demonstrate that Cherenkov radiation can be interpreted as ghost instability of a certain type. Solutions of modified gravity theories often contain ghost instabilities. One typ…
Properties of general stationary axisymmetric spacetimes: circularity and beyond
Eugeny Babichev, Jacopo Mazza
We analyse properties of general stationary and axisymmetric spacetimes, with a particular focus on circularity -- an accidental symmetry enjoyed by the Kerr metric, and therefore…
Large black-hole scalar charges induced by cosmology in Horndeski theories
Eugeny Babichev, Gilles Esposito-Farèse, Ignacy Sawicki +1
The regularity of black hole solutions, embedded in an expanding Universe, is studied in a subclass of Horndeski theories, namely the sum of the simplest quadratic, cubic and quint…
The cosmic trimmer: Black-hole hair in scalar-Gauss-Bonnet gravity is altered by cosmology
Eugeny Babichev, Ignacy Sawicki, Leonardo G. Trombetta
Static black holes in general relativity modified by a linear scalar coupling to the Gauss-Bonnet invariant always carry hair. We show that the same mechanism that creates the hair…