Zobrazeno 1 - 10
of 126
pro vyhledávání: '"Hervik, Sigbjorn"'
Autor:
Hervik, Sigbjørn
We continue to study left-invariant pseudo-Riemannian metrics on Lie groups being in the null cone of the $O(p,q)$-action using the moving bracket approach. In particular, the Lie algebra being in the null cone implies that the pseudo-Riemannian metr
Externí odkaz:
http://arxiv.org/abs/2410.21161
Autor:
Hervik, Sigbjorn, Pantohan, Edmar G.
We consider Kundt solutions to vacuum Conformal Killing Gravity (CKG) proposed by Harada and find numerous solutions in four dimensions and in higher dimensions. In CKG theory the cosmological constant appears as an integration constant, and hence, i
Externí odkaz:
http://arxiv.org/abs/2409.14353
Autor:
Hervik, Sigbjorn
We study left-invariant pseudo-Riemannian metrics on Lie groups using the bracket flow of the corresponding Lie algebra. We focus on metrics where the Lie algebra is in the null cone of the $G=O(p,q)$-action; i.e., Lie algebras $\mu$ where zero is in
Externí odkaz:
http://arxiv.org/abs/2402.03536
Autor:
Hervik, Sigbjørn, Ortaggio, Marcello
Publikováno v:
Eur. Phys. J. C 80, 1020 (2020)
We explore how far one can go in constructing $d$-dimensional static black holes coupled to $p$-form and scalar fields before actually specifying the gravity and electrodynamics theory one wants to solve. At the same time, we study to what extent one
Externí odkaz:
http://arxiv.org/abs/2007.05464
Autor:
Hervik, Sigbjørn, Ortaggio, Marcello
Publikováno v:
Acta Phys. Pol. B Proc. Suppl. 13, 291 (2020)
Recent results of arXiv:1907.08788 on universal black holes in $d$ dimensions are summarized. These are static metrics with an isotropy-irreducible homogeneous base space which can be consistently employed to construct solutions to virtually any metr
Externí odkaz:
http://arxiv.org/abs/2007.00556
Autor:
Normann, Ben David, Hervik, Sigbjørn
Publikováno v:
2020 Class. Quantum Grav. 37 145002
What is the asymptotic future of a scalar-field model if the assumption of isotropy is relaxed in generic, homogeneous space-times with general relativity? This paper is a continuation of our previous work on Bianchi cosmologies with a $p$-form field
Externí odkaz:
http://arxiv.org/abs/1910.12083
Why is the Universe so homogeneous and isotropic? We summarize a general study of a $\gamma$-law perfect fluid alongside an inhomogeneous, massless scalar gauge field (with homogeneous gradient) in anisotropic spaces with General Relativity. The anis
Externí odkaz:
http://arxiv.org/abs/1909.11965
Autor:
Normann, Ben David, Hervik, Sigbjørn
Publikováno v:
Class. Quantum Grav. 37 (2020) 085002
Continuing previous work, we show the existence of stable, anisotropic future attractors in Bianchi invariant sets with a $p$-form field ($p\,\in\,\{1,3\}$) and a perfect fluid. In particular, we consider the not previously investigated Bianchi invar
Externí odkaz:
http://arxiv.org/abs/1909.11962
Autor:
Hervik, Sigbjørn, Ortaggio, Marcello
Publikováno v:
J. High Energ. Phys. 2020, 47 (2020)
We prove that a generalized Schwarzschild-like ansatz can be consistently employed to construct $d$-dimensional static vacuum black hole solutions in any metric theory of gravity for which the Lagrangian is a scalar invariant constructed from the Rie
Externí odkaz:
http://arxiv.org/abs/1907.08788
Autor:
Helleland, Christer, Hervik, Sigbjorn
Motivated by Wick-rotations of pseudo-Riemannian manifolds, we study real geometric invariant theory (GIT) and compatible representations. We extend some of the results from earlier works \cite{W2,W1}, in particular, we give some sufficient as well a
Externí odkaz:
http://arxiv.org/abs/1807.05879