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Apr
16
awarded  Good Question
Feb
28
comment Is the Boltzmann brain problem really clearly established as a problem?
I do not understand what the relevance is of the level of additional complexity. If you are only trying to give some kind of vague "hint" it would be better served in the comments rather than as a proposed answer to the question.
Feb
27
comment Is the Boltzmann brain problem really clearly established as a problem?
This answer doesn't have much substance to it. It's not at all clear why a "trivial addition to the model" isn't all that is needed to solve it.
Feb
16
comment Many worlds interpretation of quantum mechanics
Yes your impression is false. Many-world explains the specificity of our experience as due to our indexical uncertainty in the quantum wave function. There is nothing mysterious here. If there are two copies of you, then there are two version of you asking "why me?" in the exact same sense that you can ask "why is an apple an apple and not an orange" in an ordinary non-many-worlds universe. Of course the reason an apple is an applie and not an orange is not a particularly difficult or deep question.
Feb
7
comment Is the video “How to Reveal Subatomic Particles at Home”'s explanation of its experiment misleading?
A very fast electron or muon has enough energy that it can ionize atoms it passes by without significantly affecting its trajectory, just as a bullet can stir the air without the bullet being "shot into a different path." Also, in the experiment in question the Heisenberg uncertainty principle is only relevant to much smaller distances than what is visible to the naked eye when looking at the condensation trail.
Feb
7
comment Decoherence and interpretations
@Jke, by taking the wave function "seriously", you are inadvertently making the philosophic commitment that the wavefunction is "ontic," i.e. "real," and not "epistemic," i.e. just a tool for accounting for our lack of knowledge about the state of a system. These are useful google keywords to help you understand the situation. Under Everett et al there is indeed an explanation for how superposed states can appear to reduce to a definite state despite not admitting that state reduction is "real": that is just the many worlds argument. But decoherence does not commit one to that position.
Feb
6
comment Decoherence and interpretations
Decoherence doesn't at all explain "collapse." It only explains the loss of coherence (ie interference effects). State reduction is still a "mystery" given an understanding of decoherence, and as such, all the various interpretational issues are still relevant. Long before Zurek et al even Bohm (of pilot wave theory) and Everett (of Many Worlds) had a basic development of decoherence in order to explain the loss of coherence in their interpretations. The main interpretational dichotomy comes into how you explain state reduction and whether you take the wave function as 'epistemic' or 'ontic'.
Feb
2
accepted What is the physical intuition behind the Bragg peak?
Feb
1
comment What is the physical intuition behind the Bragg peak?
But doesn't the number of electrons encountered per unit time increase with the velocity, and wouldn't that cancel out the 'v' on the bottom of your delta-p expression above?
Jan
31
comment What is the physical intuition behind the Bragg peak?
@Ernie, thanks. The Bethe-Bloch formula itself isn't helpful, but above the formula is a line that comes close to what I am looking for: "The faster the particle is, the less energy is given to the electron (the less time it has to spend imparting energy to the electron)," although while this makes sense for a single electron, I still am left wondering why this effect is still true in a material where the faster the particle the more electrons per unit time are encountered, such that a faster particle should be subject to a similar average field strength as a slower particle.
Jan
31
asked What is the physical intuition behind the Bragg peak?
Jan
22
reviewed Approve Do we need wires for current conduction in ionosphere?
Jan
21
comment From the photons perspective
It is instructive to go through the motions of calculating what the perspective of a scientist made out of parallel-moving photons would look like, and to find the root of the inconsistency. Hint: parallel-moving photons have zero invariant mass and therefore have zero interaction cross-section.
Jan
21
comment From the photons perspective
This is a common but unsatisfying answer: one can surely imagine an observer who is made out of photons. Therefore the repetition "there is no such perspective" is incomplete. The reason such observers don't constitute a valid reference frame is because of the subtle fact that the notion of a reference frame is only valid for bodies whose observational interactions to a good approximation do not affect their motion. Generally speaking, for photons any observational interaction non-negligibly affects its direction of motion (though one can imagine interactions that only change its frequency).
Jan
20
awarded  Popular Question
Jan
13
awarded  Yearling
Jan
11
comment Confusion about quantum probabilities depending on how coarsely grained the measurement apparatus is
Oh, you're right, I mis-read what you were doing.
Jan
11
comment Confusion about quantum probabilities depending on how coarsely grained the measurement apparatus is
Wait, actually, it doesn't work in the general case, for example if you had 5 states, and wanted to compare the probability of getting a 2-state degenerate subset to a 3-state degenerate subset... you would need to add an additional item to your list to be able to treat such cases in general, no?
Jan
11
comment Confusion about quantum probabilities depending on how coarsely grained the measurement apparatus is
I did do those steps, but you are "cheating" by using the fact that you know the probabilities have to add up to one, so you used the Born rule for the non-composite piece (|100>) in order to infer the probability for the composite piece (|211>+|210>). I guess maybe that is OK (and maybe you can always do that in more general cases), but that's what I meant by it not being in your list.
Jan
11
comment Confusion about quantum probabilities depending on how coarsely grained the measurement apparatus is
If you can't parse it then I better try to make sure you understand, because it seems to be a pretty big assumption. When you write "Then afterwards you end up with |100⟩⊗|13.6eV⟩ 50% of the time," how do you justify that statement using any of your nine steps?