[PhilPhys] CHANGEMENT d"HORAIRE: seminaire de philosophie de la physique

[GRINBAUM Alexei]

Séminaire des fondements et de philosophie de la physique

CHANGEMENT D'HORAIRE ET NOUVELLE ANNONCE

15 octobre à 17h, IHPST (13 rue du Four 75006 Paris)

Christian Wüthrich (University of California, San Diego)
"An old and a new theorem in quantum mechanics and what they don't imply for indeterminism"
It is known, at least since Bell (1966), that Gleason's theorem does not rule out either hidden-variables interpretations of quantum mechanics or determinism, despite numerous assertions to the contrary. Recently, John Conway and Simon Kochen have published what they call the 'free will theorem' and proclaimed that it establishes that Nature herself is indeterministic. I will review the common argument why Gleason's theorem is thought to rule out determinism and Bell's response to it before I embark on an analysis of the free will theorem and its alleged implications. Alas, I will conclude that nothing as grand as what is claimed is in fact established.


16 octobre à 11h, LARSIM (CEA-Orme des Merisiers, bât. 774, salle 50)

Christian Wüthrich (University of California, San Diego)
"Let's go for a ride on a time machine"
For over a century, the science fiction literature has offered ever more fanciful scenarios involving time travel in one's own past, while science has never seriously entertained their possibility. Even Gödel's discovery in 1949 of a general-relativistic spacetime with causal loops did not change that. For the last two decades, however, physicists and philosophers have ventured more boldly - and more seriously - into the business of time travel. I will show why time travel and time machines, understood in a technical sense to be defined, become serious business in modern spacetime theories and how they illuminate important foundational issues such as the cosmic censorship hypotheses and the quest for a quantum theory of gravity.


29 octobre à 14h15, LARSIM (CEA-Orme des Merisiers, bât. 774, salle 50)

Christian de Ronde (Université libre de Bruxelles)
"For and Against Metaphysics in Modal Interpretations of Quantum"
The advent of quantum mechanics in physics was concomitant with the arrival of logical empiricism on the philosophical scene. While QM quickly led to philosophical speculation among physicists (which many scholars felt was metaphysical), logical positivism was a frontal assault on the deep seated tendency towards metaphysics in Western philosophical thought. However, the philosophical movement that grew out of logical empiricism - sometimes going by the name Anglo-Saxon philosophy but better know as analytic philosophy - "was subverted by reactionary forces. [...] And lo, even before mid-century, some of its ablest adherents began to make the world safe for metaphysics again" (van Fraassen, 2002, p. xviii.). Thus, the possibility or impossibility of a metaphysical development of physics - a discussion which has taken place mainly within the analytic domain - remains at stake at the beginning of the 21 century. Contrary to that other revolution in physics, relativity theory, QM was ambiguous with respect to metaphysics from the start. So even though metaphysics is again relevant in any domain of physics, including relativity theory, quantum mechanics - exactly because of its recalcitrant nature with respect to any kind of interpretation - remains an even more interesting locus for philosophical research into the nature of a contemporary metaphysics of science than relativity theory. Modal interpretations were developed in the early seventies by Bas van Fraassen formalizing what was known until then about possibility through modal logics. Although van Fraassen as an empiricists remained agnostic regarding the ontological character of the interpretation, the different versions which continued this line of research - such as those proposed by Kochen, Dieks, Bub, Clifton and Bacciagaluppi and Dickson - placed themselves within a realistic position. In this presentation we attempt to discuss the metaphysical commitments of modal interpretations of quantum mechanics in its different versions and analyze if such interpretations can provide a picture of what the world is like if quantum mechanics were to be true.
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