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Good luck!

When the electron hits the metal, it gets absorbed and hence "collapsed". But when it hits one of the slits, it goes through it hence does not get absorbed. The electron wave is an extended object that does both; a part of the wave hits the metal and another part of the wave hits the slits. This...

True, in general there is no any reason why the Landau functional should have any exact symmetry. But close to the minimum ##x=x_{\rm red}## the functional can be expanded $$\psi(x,...)=a+b(x-x_{\rm red})^2+...$$ which at least has an approximate symmetry. EDIT: Or maybe there is always some...

One can answer this question formally, without understanding physics. Shift the variable ##x## such that the red minimum of the plotted function is at ##x=0##. The minimum ##x=0## is hence invariant under the transformation ##x\to -x##. The green minimum is not invariant under ##x\to -x##, so...

Imagine that someone came to the body-builder forum and said: "I don't have much of muscles but I think I know how to pose in front of mirror, can I apply to the professional body-builder competition? Or should I build some muscles first?" What do you think how the "peers" would reply, do you...

If you have one equation for two variables ##x## and ##t##, then you cannot find the definite values of ##x## and ##t##. You can only find a general relation between ##x## and ##t##, meaning that the value of one variable is arbitrary, while only the other variable is determined by this...

This is not what space is. First, space is not the same thing as empty space, so it does not need to be without matter. Second, which seems to be the main source of your confusion, even if there is no matter, why do you think that space does not have physical properties? In fact, what exactly do...

If you developed an intuitive idea without any math, you cannot be finished. Your intuitive understanding of GR without math is almost certainly wrong, and you must be ready to gradually revise your intuition as you learn more and more math of GR. Einstein himself changed his view of GR several...

That assumption is not as clear as you think it is. When I was 20, I had the same biological age as my dad when he was 20. But we didn't have the same biological age at the same time. Perhaps you wanted us to imagine two people who have the same biological age at the same time, but then you have...

Are you talking about Carroll and Ostlie?

What I had in mind was not the maximal extension, but only this:

That's because it isn't. The Kruskal coordinates are related to the freely falling observer in a weaker sense. Such observer has access to the whole spacetime, and Kruskal coordinates cover the whole spacetime. That's all.

Before understanding that, consider first Minkowski and Rindler coordinates in flat spacetime. Do you agree that Minkowski coordinates are related to inertial observers and Rindler coordinates to non-inertial ones?

To see why reflection from the mirror does not produce decoherence (i.e. why it preserves coherence) see e.g. my http://thphys.irb.hr/wiki/main/images/5/50/QFound3.pdf page 15.

Physics is usually viewed as a natural science, based on empirical evidence. Computer science and math are formal sciences, based on pure thought. Since philosophy is also based on pure thought, this probably explains why philosophy is generally more accepted in the latter than in the former.

Do you know a book that studies such stuff?

The is a philosophy itself. SCNR.

Those who say "that's just philosophy" are usually not interested in philosophy, so it's not to be expected that they distinguish different branches of it. All philosophy often sounds like "postmodern nonsense" to them. In the case of philosophy it's not a risk, it's their intention. They just...

The formula ##d'Q=TdS## does not imply that ##T## is constant. For analogy, consider classical mechanics of a particle moving in one dimension. The infinitesimal path ##dx## during the time ##dt## is ##dx=vdt##, but it does not imply that the velocity ##v(t)## is constant. Instead, it means...

Exactly.

Can you elaborate a bit, why is QM necessary to understand how oven mitt works?

https://en.wikipedia.org/wiki/Inexact_differential

How do you define interacting vacuum? How do you define particle number density?

The interacting vacuum is complicated when expressed in terms of eigenstates of the free Hamiltonian. But it is simple when expressed in terms of eigenstates of the interacting Hamiltonian. In the latter sense, it has zero particles and lowest possible energy.

Every material partially reflects and partially absorbs. The absorption is a quantum effect. First, it requires that the atoms/molecules/crystals have empty excited states the energy of which (relative to the nonempty state) is equal to the energy of photons. Second, even if such excited states...

It's general. It's my signature, not a part of my reply to your question.

Can you give a theoretical explanation why this can't happen?

It can, but the probability for that happening is smaller when the energy difference (between photon energy and required energy) is larger. https://physics.stackexchange.com/questions/297474/how-does-an-atom-interact-with-a-photon-off-resonance

Did you read Sec. 1.3?

Unknown state cannot be cloned. Known state can be cloned. When the preparation is known, the state is known.

How? I see this as a confirmation that his view agrees with mine.

See my post #47, the last paragraph. And also #49.

They lost me when they said that probability can be negative or larger than one.

Here is one example. At page 207 of his book he writes: "It is possible to prepare the lowest energy state of a system simply by waiting for the system to decay to its ground state." He says "system", not "ensemble". To me, it looks as confirmation of my claim that in the case of known...

My impression (which could be wrong) is that my view of SEI is very similar to that of Ballentine, but that he sometimes uses wording that creates more confusion than clarity, so I tried to further simplify the explanation of SEI in a way which avoids confusion. Now it seems that I wasn't very...

It's relevant, if we want to understand how exactly statistical aspects of QM differ from statistical aspects of classical physics. In my opinion, the former cannot be understood correctly before first understanding the latter. In the context of quantum interpretations, the word "physical" has...

Yes, you summarized it very well. I see SEI as a rather practical approach, it always seemed to me that SEI is an attempt to formulate QM with a minimal amount of philosophy. Now I am becoming aware that not everybody sees SEI that way.

But the difference is only in rhetoric, I don't see any substantial physical difference, at least in the classical case. Do you see a substantial physical difference? Or maybe, as an adherent of consistent histories, you see framing, i.e. rhetoric, as physical?

Can you be more explicit, what exactly do I deny? In the first post I wrote about several versions of SEI, is there a possibility that I didn't mention there?

In my view, all three are legitimate applications of SEI.

OK, but Ballentine does not deny that something similar exists also behind the Born rule in QM. On the contrary, in several places he writes (I can make quotes if someone is interested) that it is a reasonable possibility. So the Ballentine's version of SEI at least does not involve a denial of it.

Do you think that 4) makes sense in the classical case of coin flipping?

It's probably written somewhere in a way I would be satisfied, but I don't know where exactly. In any case, I wanted to write it by myself, in a way I would like someone explained it to me.

I'm not sure that the difference is relevant. Let us consider a classical analogy, in which preparation is a coin flipping. The flipping prepares the state $$S=[p({\rm heads})=1/2,p({\rm tails})=1/2]$$ where ##p## is the probability. What is the distinction between the following claims? 1. We...

Maybe, but I see it as a virtue, not a drawback.

If we know how much winky, and if this is the only source of uncertainty, we can associate a well defined mixed state with the source. This is still too vague, so I cannot comment it. I didn't intend to be binary. I explained two cases, but I didn't say that intermediate cases don't exist...

Can you give an example of such "rough idea"?