Blar i UiS Brage på forfatter "Hervik, Sigbjørn"
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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, ... -
Some factors affecting the grades of technology students
Gregersen, Øyvind Weiby; Kløkstad, Geir Øivind; Hervik, Sigbjørn; Plesser, Hans Ekkehard; Pettersen, Ivar (Peer reviewed; Journal article, 2017)In this study factors that affect the grades of Norwegian technology students have been investigated. The total data set contained 355.706 individual exams from 63 different engineering master programs during the 2010 to ... -
A study of inhomogeneous massless scalar gauge fields in cosmology
Normann, Ben David; Ricciardone, Angelo; Hervik, Sigbjørn; Thorsrud, Mikjel (Peer reviewed; Journal article, 2022)Why is the Universe so homogeneous and isotropic? We summarize a general study of a γ-law perfect fluid alongside an inhomogeneous, massless scalar gauge field (with homogeneous gradient) in anisotropic spaces with General ... -
Tales from Wonderland
Normann, Ben David (Doctoral thesis, 2020-06)Knowing that the Universe is quite isotropic, one may, as already discussed in Chapter 1, wonder how likely such a Universe is. We take the following research question. Question 1. Is the asymptotic future of a cosmology ... -
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 ... -
Universal Black Holes
Hervik, Sigbjørn; Ortaggio, Marcello (Peer reviewed; Journal article, 2020-02)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 ... -
Universal p-form black holes in generalized theories of gravity
Hervik, Sigbjørn; Ortaggio, Marcello (Peer reviewed; Journal article, 2020-10)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 ... -
Universal spacetimes in four dimensions
Hervik, Sigbjørn; Pravda, Vojtech; Pravdova, Alena (Journal article; Peer reviewed, 2017-10)Universal spacetimes are exact solutions to all higher-order theories of gravity. We study these spacetimes in four dimensions and provide necessary and sufficient conditions for universality for all Petrov types except ...