
Roderich Tumulka started the topic Paradoxes and Primitive Ontology in Collapse Theories of Quantum Mechanics in the forum 2017 International Workshop: Collapse of the Wave Function 3 years, 11 months ago
Collapse theories are versions of quantum mechanics according to which the collapse of the wave function is a real physical process. They propose precise mathematical laws to govern this process and to replace the vague conventional prescription that a collapse occurs whenever an
observer” makes a
measurement.” The
primitive ontology” of a…[Read more]


Roderich Tumulka replied to the topic in the forum Roderich Tumulka 5 years, 10 months ago
Here are some general remarks on the practical usefulness of Bohmian mechanics (in a rather random order). They don’t address Maximilian’s specific question but contribute to the overall theme of ways in which Bohmian mechanics is helpful.
* Consider two theories making the same predictions: one clear, precise, and simple, the other unclear,…[Read more]

Roderich Tumulka replied to the topic in the forum Roderich Tumulka 5 years, 10 months ago
Hi Maximilian, I have a few examples. I am not sure whether they are of the kind you are interested in, but I thought I mention them nevertheless.
Bell has a paper [Intl.J.Quant.Chem. 14 (1980) 155; reprinted in “Speakable and unspeakable in quantum mechanics” p. 111] on how Bohmian mechanics answers the question of whether a delayedchoice…[Read more]

Roderich Tumulka replied to the topic A problem of Bohmian mechanics in the forum Bohm's theory 5 years, 10 months ago
Hi Rainer, here are three remarks on the problem you raised.
First, the situation is in a certain respect the same in Bohmian mechanics and in standard quantum mechanics. That is because if we consider the wave function of object and apparatus together (or of the whole solar system) then Bohmian mechanics and standard quantum mechanics both use…[Read more]

Roderich Tumulka started the topic Some advantages of Bohmian mechanics in the forum Bohm's theory 5 years, 10 months ago
A big advantage of Bohmian mechanics is its clarity. It has simple, clear statements about what exists in the world (wave function and particles), and how that evolves with time. Everything else is a matter of analysis of the theory. In particular, one can analyze measurement situations (which are dealt with by axiom, not by analysis, in standard…[Read more]


Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 2 months ago
Dear Richard,
Perhaps I understand better now the root of our disagreement. It seems to have something to do with whether the definition of locality refers to actions of an agent on one side having consequences on the other side, or whether it refers to events on one side having consequences on the other side, where events may include random…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Bob,
Yes, let’s agree to disagree. Thank you for the discussion.
All the best, Roderich

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Richard, (in response to your #1901)
I agree that “we can’t decide whether B is a function of events on all or part of H without applying some theory” if “theory” means laws governing a possible reality (i.e., what I called a “scenario” in my paper). Quantum theory is often understood as not talking about reality but only about empirical…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Bob, (at #1900)
Yes, it would good to find out what exactly we disagree about. So let me answer your questions about my position. By “English properties” I did not mean macroscopic properties. In your example, I assume that S is 1dimensional. I agree that with “cat is alive” is associated a (highdimensional) subspace A of the Hilbert space…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Bob,
Thank you for your replies #1860 and 1861. There are two relevant meanings of the word “property”: let me call them “English property” (the ordinary meaning of “property” in English) and “quantum property.” An English property of a system is something that a system either has or has not, while a “quantum property” of a system is a…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Richard (at #1859 and 1894),
I like that you point specifically to the step in the reasoning that you are objecting to. That helps for a good discussion.
I see that the word “predetermines” has connotations that are irrelevant to the argument. For my purposes, “x predetermines y” just means “y is a function of x.” It is not necessary to…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Richard,
Indeed one might suspect that statements about probability, or even fixity, must be relativized in the way you suggest. So let me go through the reasoning in more detail. The stateofaffairs (i.e., the “real, factual situation,” the “beables”) on that hypersurface includes Alice’s outcome, so it predetermines Bob’s outcome (as Bob…[Read more]

Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Dear Bob,
Let me first address the CarolDonald issue. I was, in fact, paying attention to the distinction you emphasize; let me elaborate some more. Let n_k be the unit vector in the direction in which Carol has prepared the spin of particle k. She predicts that if one were to make a SternGerlach experiment on particle k in the direction n_k,…[Read more]

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Roderich Tumulka replied to the topic The Assumptions of Bell’s Proof in the forum John Bell Workshop 2014 6 years, 3 months ago
Thank you to all of the commentators for your remarks!
To Dieter at 1674:
You may be surprised but I completely agree with you that Everett’s manyworlds proposal is a realist theory. In my paper, I considered the conditions (R1) through (R4) for their potential relevance to Bell’s theorem, not for categorizing interpretations of quantum…[Read more]

Roderich Tumulka joined the group John Bell Workshop 2014 6 years, 3 months ago
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