NWA Route 5 meeting at Felix Meritis, Amsterdam, 22 March 2016. Philosophy of spacetime.

1. Philosophy of Spacetime
• 129: What is the real nature of spacetime and gravity?
• What is its ontology? Spacetime as a fundamental entity?
• Or is spacetime replaced by something else?
• Approaches: strings, loops, bottom-up…
• Common feature: spacetime/gravity emerge!
• Hooke’s law for a polymer in a heat bath:
• No microscopic force.
• Could gravity emerge? (E. Verlinde)
Sebastian De Haro (AUC/UvA)

2. Emergent Spacetime and Dualities
• ’t Hooft: the holographic principle: a gravitational theory
in a region of space is equivalent to a quantum theory,
without gravity, on the surface bounding this region.
• Important conceptual questions (physical/found./phil.):
• Does spacetime emerge? What does ‘emergence’ mean?
• What picture of space, time and gravity can we get from our best theories?
• Gravitons? As opposed to gravitational waves? • Or just dual theories?

3. An Interdisciplinary Research
• Use of these concepts (emergence, duality…) in the
literature is muddled: conceptual analysis needed.
• Duality relates to important philosophical questions:
• Individuation: when are two theories ‘the same’?
• Ontology: when are two theories about the same subject matter?
• New insights on reductionism and emergence, much (and, often, confusingly!)
debated in the literature.
• Foundations of space and time: a very Dutch topic going back to Lorentz!
• Many of these issues (ontology and emergence of spacetime…) relate directly to the
“big questions” submitted by the public.
• Opportunity for broad collaboration between physicists (over all ranges of energies!),
philosophers, outreach!