My point isn't that it is unreasonable to use symmetric (/antisymmetric) wavefunctions until we discover something that requires us to use a more complicated model. My objection is to an error in thinking that holds that such potential future discoveries are a-priori impossible. I'm with philosopher Bob on this one.

That is a great explanation. Thanks

I think quantum physicists here are making the same mistake that lead to the Gibbs paradox in classical phyiscs. Of course, my textbook in classical thermodynamics tried to sweep the Gibbs paradox under the quantum rug, and completely missed the point of what it was telling us about the subjective nature of classical entropy. Quantum physics is another deterministic reversible state-machine, so I don't see why it is different in principle from a "classical world".

While it is true that *a* wavefunction or something very much like it must be what the...

I have a counter-hypothesis: If the universe did distinguish between photons, but we didn't have any tests which could distinguish between photons, what this physically means is that our measuring devices, in their quantum-to-classical transitions (yes, I know this is a perception thing in MWI), are what is adding the amplitudes before taking the squared modulus. Our measurers can't distinguish, which is why we can get away with representing the hidden "true wavefunction" (or object carrying similar information) with a symmetric wavefunction. If ...

18y

If we had a destructive measurement device that reacted in the exact same way to
photon type A vs photon type B, it would be an information-destroying
irreversible process. Which would, I believe, require a drastic rewrite of much
of physics due to the CPT theorem.

08y

This seems like a great example of a theory that Occam's Razor should slash, or
assign low probability. Though our best formal definition of the Razor is wrong
[http://lesswrong.com/lw/jti/the_problem_with_aixi/].

(I don't claim to be *using* my notes to any great effect, but this is what I do with them):

To me, I've noticed that I seldom actually use my notes as a reference. When I need to refer to something, I go to a place in a book somewhere. Rather, during a lecture, my notebook for the class seems to function more as a way to keep me paying attention to the lecturer, and to run various complicated pieces of information (equations, etc) across my mind. (Okay, I do sort of refer to these during exam study, but the books tend to be more legible).

I also do a lot of m...

I've never understood why explaining the Born Rule is *less* of a problem for any of the other interpretations of QP than it is for MWI. Copenhagen, IIRC, simply asserts it as an axiom. (Rather, it seems to me that MWI is one of the few that even tries to explain it!)

08y

As I understand, it's less of a problem for a hardline Copenhagen interpretation
because no definite ontological status is assigned to the wavefunction, or
indeed the collapse of the wavefunction. CI can roughly be paraphrased as
"Consider this set of rules for predicting experimental outcomes. Look how well
it works! Of course, we're not asserting anything about actual reality here".
One of those rules is the Born rule. Another is the fact that physical
transformations correspond to unitary maps on the Hilbert space. All of them are
postulated, and their correctness is a matter of experimental
falsification/verification.
Conversely, MWI assigns definite reality to the wavefunction, but denies that
collapse is a real process, and does not postulate any rules about predictions
of experimental outcomes. Instead, the claim that a process of measurement
inevitably results in a single result being recorded - with probability given by
the square amplitude of the wavefunction - must be derived from the pre-existing
structure of the theory (possibly with some reasonable assumptions about
gambling commitments).
A conceivable alternative to MWI might have the Born rule as an additional
postulate, supported only by experiment rather than following from the structure
of the theory. I feel that this would be much less appealing to many of its
advocates.

28y

I think the Born rule falls out pretty nicely in the Bohmian interpretation.

The problem that I've always had with the "utility monster" idea is that it's a misuse of what information utility functions actually encode.

In game theory or economics, a utility function is a rank ordering of preferred states over less preferred states for a single agent (who presumably has some input he can adjust to solve for his preferred states). That's it. There are no "global" utility functions or "collective" utility measures that don't run into problems when individual goals conflict.

Given that an agent's utility fu...

2[anonymous]8y

I think the misunderstanding here is that some of you interpret the post as a
call to change your values. However, it is merely a suggestion for the
implementation of values that already exist, such as utilitarian preferences.
The idea is clearly never going to be attractive to people who care exactly zero
about the SWB of others. But those are not a target group of effective altruism
or any charity really.

Hmm. In a certain sense, is these sufficient conditions to actually define an organization with boundaries?

I don't think many of us have ever seen the outside of that university. :-P

Contrast this to the notion we have in probability theory, of an exact quantitative rational judgment. If 1% of women presenting for a routine screening have breast cancer, and 80% of women with breast cancer get positive mammographies, and 10% of women without breast cancer get false positives, what is the probability that a routinely screened woman with a positive mammography has breast cancer? 7.5%. You cannot say, "I believe she doesn't have breast cancer, because the experiment isn't definite enough." You cannot say, "I believe she... (read more)