Abstract
We show that if a change of spatial topology is mediated by a spacetime with an everywhere-non-singular metric of Lorentzian signature which admits a spinor structure, then the Kervaire semicharacteristic of the boundary plus the kink number of the Lorentzian metric on the boundary must vanish modulo 2. The kink number is a measure of how many times the light cone tips over on the boundary. It vanishes if the boundary is everywhere spacelike. This result gives a generalization of a previous selection rule: The number of wormholes plus the number of kinks created during a topology change is conserved modulo 2.
- Received 10 July 1992
DOI:https://doi.org/10.1103/PhysRevLett.69.1719
©1992 American Physical Society
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The Work of Stephen Hawking in Physical Review
To mark the passing of Stephen Hawking, we gathered together his 55 papers in Physical Review D and Physical Review Letters. They probe the edges of space and time, from "Black holes and thermodynamics” to "Wave function of the Universe."
