Blar i Vitenskapelige publikasjoner (TN-IMN) på forfatter "Hervik, Sigbjørn"

Viser treff 1-13 av 13

    • A spacetime not characterized by its invariants is of aligned type II 

      Hervik, Sigbjørn (Journal article; Peer reviewed, 2011)
      By using invariant theory we show that a (higher-dimensional) Lorentzian metric that is not characterised by its invariants must be of aligned type II; i.e., there exists a frame such that all the curvature tensors ...

    • All metrics have curvature tensors characterised by its invariants as a limit: the ϵ-property 

      Hervik, Sigbjørn (Journal article; Peer reviewed, 2011)
      We prove a generalisation of the ϵ-property, namely that for any dimension and signature, a metric which is not characterised by its polynomial scalar curvature invariants, there is a frame such that the components of the ...

    • Curvature operators and scalar curvature invariants 

      Hervik, Sigbjørn; Coley, Alan (Journal article; Peer reviewed, 2010)
      We continue the study of the question of when a pseudo-Riemannain manifold can be locally characterised by its scalar polynomial curvature invariants (constructed from the Riemann tensor and its covariant deriva- tives). ...

    • Discriminating the Weyl type in higher dimensions using scalar curvature invariants 

      Hervik, Sigbjørn; Coley, Alan (Journal article; Peer reviewed, 2011)
      We consider higher dimensional Lorentzian spacetimes which are currently of interest in theoretical physics. It is possible to algebraically classify any tensor in a Lorentzian spacetime of arbitrary dimensions using ...

    • Higher dimensional bivectors and classification of the Weyl operator 

      Hervik, Sigbjørn; Coley, Alan (Journal article; Peer reviewed, 2010)
      We develop the bivector formalism in higher dimensional Lorentzian spacetimes. We define the Weyl bivector operator in a manner consis- tent with its boost-weight decomposition. We then algebraically classify the Weyl ...

    • Inflation with stable anisotropic hair 

      Hervik, Sigbjørn; Mota, David F.; Thorsrud, Mikjel (Journal article; Peer reviewed, 2011)
      Recently an inflationary model with a vector field coupled to the inflaton was proposed and the phenomenology studied for the Bianchi type I spacetime. It was found that the model demonstrates a counter-example to the ...

    • Note on the invariant classification of vacuum type D spacetimes 

      Coley, Alan; Hervik, Sigbjørn (Journal article; Peer reviewed, 2009-12)
      We illustrate the fact that the class of vacuum type D spacetimes which are I-non-degenerate are invariantly classified by their scalar polynomial curvature invariants.

    • On the algebraic classification of pseudo-Riemannian spaces 

      Hervik, Sigbjørn; Coley, Alan (Journal article; Peer reviewed, 2011-12)
      We consider arbitrary-dimensional pseudo-Riemannian spaces of signature (k, k + m). We introduce a boost-weight decomposition and define a number of algebraic properties (e.g. the Si- and N-properties) and present a ...

    • Pseudo-Riemannian VSI spaces 

      Hervik, Sigbjørn; Coley, Alan (Journal article; Peer reviewed, 2011)
      In this paper we consider pseudo-Riemannian spaces of arbitrary sig- nature for which all of their polynomial curvature invariants vanish (VSI spaces). We discuss an algebraic classification of pseudo-Riemannian spaces ...

    • Pseudo-Riemannian VSI spaces II 

      Hervik, Sigbjørn (Journal article; Peer reviewed, 2012)
      In this paper we consider pseudo-Riemannian spaces of arbitrary signature for which all of the polynomial curvature invariants vanish (VSI spaces). Using an algebraic classification of pseudo-Riemannian spaces in terms of ...

    • Ricci nilsoliton black holes 

      Hervik, Sigbjørn (Journal article; Peer reviewed, 2008)
      We follow a constructive approach and find higher-dimensional black holes with Ricci nilsoliton horizons. The spacetimes are solutions to the Einstein equation with a negative cosmological constant and generalise therefore, ...

    • Type III and II universal spacetimes 

      Hervik, Sigbjørn; Pravdova, Alena; Pravda, Vojtech (Journal article; Peer reviewed, 2015)
      We briefly summarize our recent results on universal spacetimes. We show that universal spacetimes are necessarily CSI, i.e. for these spacetimes, all curvature invariants constructed from the Riemann tensor and its ...

    • Type N universal spacetimes 

      Hervik, Sigbjørn; Pravda, V; Pravdova, A (Journal article; Peer reviewed, 2015)
      Universal spacetimes are vacuum solutions to all theories of gravity with the Lagrangian L [...]. Well known examples of universal spacetimes are plane waves which are of the Weyl type N. Here, we discuss recent results ...