The Time Machine Factory [unspeakable, speakable] on Time Travel -TM2019

Session

The Mathematical side of Causality

Session III

9 Oct 2019, 09:00

Turin

32. The role of causality in quantum gravity

Prof. Sumati Surya (Raman Research Institute)

09/10/2019, 09:00

talk

The notion of causality, both local or global, is tied inextricably to the Lorentzian character of spacetime.
This is embodied by the causal structure poset which, given weak causality constriants, determines the conformal
spacetime geometry. This is the starting point for the causal set approach to quantum gravity, where the
underlying continuum is replaced by a locally finite partially...

8. On the unique evolution of solutions to wave equations

Dr Jan Sbierski

09/10/2019, 09:45

talk

The well-known theorem of Choquet-Bruhat and Geroch states that for given smooth initial data for the Einstein equations there exists a unique maximal globally hyperbolic development. In particular, the time-evolution of globally hyperbolic solutions is unique. This talk investigates whether the same results hold for quasilinear wave equations defined on a fixed background. We first present an...

15. A gravitational collapse singularity theorem which does not require chronology

Prof. Ettore Minguzzi

09/10/2019, 10:50

talk

I present a new gravitational collapse singularity theorem which improves Penrose's and which does not assume predictability (global hyperbolicity) while it is compatible with chronology violation (closed timelike curves) and black hole evaporation.

54. A time machine allowing travel to the past by free fall

Prof. Livio Pizzocchero (Dipartimento di Matematica, Universit`a degli Studi di Milano and INFN, Sezione di Milano )

09/10/2019, 11:25

talk

This talk illustrates a model of spacetime with closed timelike curves proposed in a recent paper (D. Fermi and L. Pizzocchero, Class. Quantum Grav. 35 (2018), 165003, 42pp). This spacetime is diffeomorphic to R4 and carries an ad hoc metric; it consists of a flat outer region and of a “time machine”, formed by a toroidal interface and by an inner flat region. The timelike geodesics of this...

57. Locally Covariant Quantum Field Theory on Causally Compatible Sets

Prof. James Vickers (Mathematical Sciences, University of Southampton, UK)

10/10/2019, 17:30

talk

In this talk I describe the mathematics required in order to provide a description of the observables for quantum fields on low-regularity spacetimes. The first step involves constructing low-regularity advanced and retarded Green operators as maps between suitable function spaces. In specifying these we need to use graph norms on Sobolev spaces to ensure that the Green operators are...