The Time Machine Factory [unspeakable, speakable] on Time Travel - TMF2024

Session

Session II. Time travel and consistency

23 Sept 2024, 14:55

Vallauri Hall (INRiM historical building, Turin)

Conveners

Session II. Time travel and consistency

• Lorenzo Maccone

Session II. Time travel and consistency

• Seth Lloyd

110. Inner-extremal regular black holes from pure gravity

Prof. David Kubiznak (Institute for Theoretical Physics, Charles University, Prague)

23/09/2024, 14:55

talk

It is well known that (static) regular black hole spacetimes can be sourced by appropriately chosen theories of non-linear electrodynamics. More recently, it was shown that many such models can also be obtained as solutions of vacuum gravity equations, upon considering an infinite series of quasi-topological higher curvature corrections. After reviewing both these approaches, I will show that...

113. Beyond black holes, ultra-strong gravity spacetimes

Jose Maria Martin Senovilla (Istituto Nazionale di Astrofisica (INAF))

23/09/2024, 16:00

talk

The area of spatially stable marginally trapped surfaces (MTS) has a bound that depends on the minimum of a particular component of the Einstein tensor. I will prove that any spacetime containing spatially stable MTSs with area approaching the bound acquire universal properties generically. In particular, they possess marginally trapped tubes foliated by MTS of spherical topology, composed of...

106. Avoiding singularities in Lorentzian-Euclidean black holes: the role of atemporality

Salvatore Capozziello (Istituto Nazionale di Astrofisica (INAF))

23/09/2024, 16:35

talk

We investigate a Schwarzschild metric exhibiting a signature change across the event horizon, which gives rise to what we term a Lorentzian-Euclidean black hole. The resulting geometry is regularized by employing the Hadamard partie finie technique, which allows us to prove that the metric represents a solution of vacuum Einstein equations. In this framework, we introduce the concept of...

109. Quantum field theory in the presence of time-machines

Ana Alonso-Serrano (Institut für Physik, Humboldt-Universität zu Berlin)

23/09/2024, 17:15

talk

In this talk I analyze the construction of quantum field theory in spacetimes that contain regions with closed timelike curves (CTCs). Additionally, I explore how particle detectors can discern the presence of CTCs in causally disconnected regions and differentiate between various spacetime topologies.

89. Time Travel Paradoxes and Entangled Timelines

Barak Shoshany (Brock University)

23/09/2024, 17:50

talk

Before we can begin manufacturing time machines in our factory, we must consider whether those time machines could create time travel paradoxes, and if so, how these paradoxes might be resolved by existing or new laws of physics. We will first review the different types of time travel paradoxes and their proposed resolutions. Then we will present the results of our 3 recent papers...

96. Relational Quantum Dynamics for Toy Models of Time Travel

Sebastian Schuster (University of Sheffield/Stockholms Universitet)

24/09/2024, 09:00

talk

The “problem of time” that approaches to quantum gravity have to either tackle or circumvent should, naturally, also occur in models of time travel trying to move beyond (semi-)classical gravity. From a viewpoint of canonical gravity a first hurdle to time travel is that the underlying quantization procedure relies on global hyperbolicity of the space-time to be quantized. As with any new...

116. Geometric Event-Based quantum mechanics (GEB): a fully covariant relativistic quantum mechanics

Prof. Lorenzo Maccone (Università di Pavia, INFN Sez. Pavia)

24/09/2024, 09:25

talk

I present a fully covariant framework for quantum mechanics, where the
quantization is based on quantum events instead of quantum systems. The
dynamics is introduced through constraints. Hopefully, this means that
the same framework can be extended also to general relativity (up to now
we developed only the special relativistic case), where it should
account for CTCs using the, previously...

123. Resolution of The Quantum Clock-Time Observable

Dr Khai Bordon (Griffith University)

24/09/2024, 10:05

talk

Time is perhaps the most enigmatic concept in physics [1]. Indeed, we still lack an acceptable explanation for the observed preferred direction of time, and a universally-accepted quantum treatment of time as an observable [2 - 4]. The observations of discrete symmetry violations of charge conjugation (𝐶), parity inversion (𝑃), and time reversal (𝑇) observed in high energy particle decays,...

124. Black to White hole transitions as (forward) time machines

Marios Christodoulou (Institute for Quantum Optics and Quantum Information - Austria)

24/09/2024, 11:00

talk

I review ideas regarding the possibility that black holes can become white holes through a quantum gravity process. Indeed, an observer passing through such a region of spacetime would effectively be travelling in the far future compared to an observer far from the effect, and vice versa should a white hole become black!