13 research outputs found
Axial torsion waves in metric-affine gravity
We construct new explicit vacuum solutions of quadratic metric-affine
gravity. The approach of metric-affine gravity in using an independent affine
connection produces a theory with 10+64 unknowns, which implies admitting
torsion and possible nonmetricity. Our spacetimes are generalisations of
classical pp-waves, four-dimensional Lorentzian spacetimes which admit a
nonvanishing parallel spinor field. We generalize this definition to metric
compatible spacetimes with pp-metric and purely axial torsion. It has been
suggested that one can interpret that the axial component of torsion as the
Hodge dual of the electromagnetic vector potential. We compare these solutions
with our previous results and other solutions of classical models describing
the interaction of gravitational and neutrino fields.Comment: 6 pages. Proceedings of the MG14 Meeting on General Relativity,
University of Rome "La Sapienza", Italy, 12 - 18 July 2015. Edited by:
Massimo Bianchi (Universit\`a degli Studi di Roma "Tor Vergata", Italy),
Robert T Jantzen (Villanova University, USA), Remo Ruffini (International
Center for Relativistic Astrophysics Network (ICRANet), Italy and University
of Rome "La Sapienza", Italy
Physical interpretation of pp-waves with axial torsion
We consider generalised pp-waves with purely axial torsion, which we
previously showed to be new vacuum solutions of quadratic metric-affine
gravity. Our analysis shows that classical pp-waves of parallel Ricci curvature
should not be viewed on their own. They are a particular representation of a
wider class of solutions, namely generalised pp-waves of parallel Ricci
curvature. We compare our pp-waves with purely axial torsion to solutions of
Einstein-Weyl theory, the classical model describing the interaction of
gravitational and massless neutrino fields.Comment: 5 pages. Proceedings of the MG14 Meeting on General Relativity,
University of Rome "La Sapienza", Italy, 12 - 18 July 2015. Edited by:
Massimo Bianchi (Universit\`a degli Studi di Roma "Tor Vergata", Italy),
Robert T Jantzen (Villanova University, USA), Remo Ruffini (International
Center for Relativistic Astrophysics Network (ICRANet), Italy and University
of Rome "La Sapienza", Italy
Torsion Wave Solutions in Yang-Mielke Theory of Gravity
The approach of metric-affine gravity initially distinguishes it from Einstein’s general relativity. Using an
independent affine connection produces a theory with 10 + 64 unknowns. We write down the Yang-Mills action
for the affine connection and produce the Yang-Mills equation and the so-called complementary Yang-Mills
equation by independently varying with respect to the connection and the metric, respectively. We call this
theory the Yang-Mielke theory of gravity. We construct explicit spacetimes with pp-metric and purely axial
torsion and show that they represent a solution of Yang-Mills theory. Finally we compare these spacetimes to
existing solutions of metric-affine gravity and present future research possibilities
Black holes in the classical and quantum world
These are the lecture notes for an introductory course on black holes and
some aspects of their interaction with the classical and quantum world. The
focus is on phenomena of "fundamental physics" in the immediate surroundings of
the black hole (classical and quantum fields, with little astrophysics). We aim
more at qualitative, intuitive understanding than at quantitative rigor or
detail. Accordingly, we only assume previous exposure to a conventional
introduction to the elements of General Relativity and a glancing acquaintance
with the Schwarzschild solution, but not more. We use many figures for
illustrations and provide a set of carefully guided exercises.
Topics: (1) The black hole as a tale of light and darkness. (2) The black
hole that vibrates. (3) The black hole that rotates. (4) The black hole that
evaporates. (A) Guided problems.Comment: Lectures at Second Training School of COST Action "Quantum gravity
phenomenology in the multi-messenger approach", to be published in PoS. 51
pages, 17 figures. v2: minor corrections, final versio