Comment on `Smooth and Discontinuous Signature Type Change in General Relativity'

Abstract

Kossowski and Kriele derived boundary conditions on the metric at a surface of signature change. We point out that their derivation is based not only on certain smoothness assumptions but also on a postulated form of the Einstein field equations. Since there is no canonical form of the field equations at a change of signature, their conclusions are not inescapable. We show here that a weaker formulation is possible, in which less restrictive smoothness assumptions are made, and (a slightly different form of) the Einstein field equations are satisfied. In particular, in this formulation it is possible to have a bounded energy-momentum tensor at a change of signature without satisfying their condition that the extrinsic curvature vanish.

Plain TeX, 6 pages; Comment on Kossowski and Kriele: Class. Quantum Grav. 10, 2363 (1993); Reply by Kriele: Gen. Rel. Grav. 28, 1409-1413 (1996)

References in corpus (6)

• The Scalar Field Equation in the Presence of Signature Change
• Failure of Standard Conservation Laws at a Classical Change of Signature
• Einstein's Equations in the Presence of Signature Change
• Actions for signature change
• Reply Comment: Comparison of Approaches to Classical Signature Change
• Tensor Distributions in the Presence of Degenerate Metrics

Cited by in corpus (11)

• Signature change events: A challenge for quantum gravity?
• Einstein's Equations in the Presence of Signature Change
• Note on Signature Change and Colombeau Theory
• Tensor distributions on signature-changing space-times
• Riemann-Cartan gravity with dynamical signature
• Magnetic solutions in Einstein-massive gravity with linear and nonlinear fields
• Emergent spacetimes
• Isochronous Spacetimes
• Singularity at the demise of a black hole
• Distinguished solutions for discontinuous signature change with weak junction conditions
• Isochronous solutions of Einstein's equations and their Newtonian limit