Teaching cosmology at the undergraduate or high school level requires simplifications and analogies, and inevitably brings the teacher into contact with at least one of the pedagogical ...interpretations of the expanding Universe. The by far most popular interpretation holds that galaxies in an expanding Universe are stationary, while space itself expands and thus causes the growing distances that characterize cosmic expansion. The alternative relativistic explosion interpretation regards cosmic expansion as a pattern of (relativistic) galaxy motion. The aim of this article is to discuss the two competing interpretations from the perspective of potential student preconceptions, taking into account both beneficial anchoring conceptions and potentially harmful preconceptions that can lead to misconceptions.
Scalar field effects on the orbit of S2 star Amorim, A; Bauböck, M; Benisty, M ...
Monthly notices of the Royal Astronomical Society,
11/2019, Letnik:
489, Številka:
4
Journal Article
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ABSTRACT
Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region ...is well established, but its neighbouring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark matter (e.g. stellar dark remnants or diffuse dark matter) is unknown. This article assumes it to be a scalar field of toroidal distribution, associated with ultralight dark matter particles, surrounding the Kerr black hole. Such a field is a form of ‘hair’ expected in the context of superradiance, a mechanism that extracts rotational energy from the black hole. Orbital signatures for the S2 star are computed and shown to be detectable by GRAVITY. The scalar field can be constrained because the variation of orbital elements depends both on the relative mass of the scalar field to the black hole and on the field mass coupling parameter.
Teaching cosmology at the undergraduate or high school level requiressimplifications and analogies, and inevitably brings the teacher into contactwith at least one of the pedagogical interpretations ...of the expanding Universe.The by far most popular interpretation holds that galaxies in an expandingUniverse are stationary, while space itself expands and thus causes the growingdistances that characterize cosmic expansion. The alternative relativisticexplosion interpretation regards cosmic expansion as a pattern of (relativistic)galaxy motion. The aim of this article is to discuss the two competinginterpretations from the perspective of potential student preconceptions, takinginto account both beneficial anchoring conceptions and potentially harmfulpreconceptions that can lead to misconceptions.
We give a brief overview of the role of quantum theory in cosmology, reviewing the standard model of classical cosmology, inflation and quantum cosmology.
We give a brief overview of the role of quantum theory in cosmology, reviewing the standard model of classical cosmology, inflation and quantum cosmology.
We study the hidden symmetries arising in the dimensional reduction of d=5, N=2 supergravity to three dimensions. Extending previous partial results for the bosonic part, we give a derivation that ...includes fermionic terms, shedding light on the appearance of the local hidden symmetry SO(4) in the reduction.
We show that the Gödel solution of five-dimensional gauged supergravity contains either closed time-like curves through every space–time point or none at all, dependent on the rotational parameter. ...In addition, we present a deformation of that solution with a parameter κ which characterizes the symmetry of four-dimensional base space: for κ=1,0,−1 it has spherical, flat and hyperbolic symmetry, respectively. Also investigated are the causal properties of the lifted solution in 10 dimensions.
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