Gregor
@coexact.bsky.social
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I guess it depends on what is conserved by the fundamental Hamiltonian. We believe in charge superselection because we really believe in gauge symmetry
December 5, 2025 at 12:14 PM
I guess it depends on what is conserved by the fundamental Hamiltonian. We believe in charge superselection because we really believe in gauge symmetry
imo it's not an interdiction, it's just that when Hilbert space decomposes globally as a direct sum where all available operations preserve the summands, you in principle can't distinguish a state from its projection onto a summand, so we just discard the remainder
December 4, 2025 at 7:10 PM
imo it's not an interdiction, it's just that when Hilbert space decomposes globally as a direct sum where all available operations preserve the summands, you in principle can't distinguish a state from its projection onto a summand, so we just discard the remainder
I didn't mean to say that the charge superselection rule is what's relevant here. Angular momentum conservation is. The paper I linked has that name but I linked it for the concept of quantum reference frames
December 4, 2025 at 7:04 PM
I didn't mean to say that the charge superselection rule is what's relevant here. Angular momentum conservation is. The paper I linked has that name but I linked it for the concept of quantum reference frames
yeah, there is a superselection rule that makes it impossible to operationally cash out on such a superposition. (except via quantum reference frames, e.g. www.tesble.com/10.1103/Phys.... but then I suppose there will again be a frame with respect to which one rotates)
Charge Superselection Rule | 10.1103/PhysRev.155.1428_Science Hub
www.tesble.com
December 4, 2025 at 6:26 PM
yeah, there is a superselection rule that makes it impossible to operationally cash out on such a superposition. (except via quantum reference frames, e.g. www.tesble.com/10.1103/Phys.... but then I suppose there will again be a frame with respect to which one rotates)
though a rotation by 2pi really does give a different state if you have a superposition of different fermion numbers, or say a single fermion with location a superposition of two boxes and you think rotating one of them should be a thing you can do
December 4, 2025 at 4:29 PM
though a rotation by 2pi really does give a different state if you have a superposition of different fermion numbers, or say a single fermion with location a superposition of two boxes and you think rotating one of them should be a thing you can do
Another hint that cdp is connected to locality despite its asymptotic form is that it follows from locality (in the vanishing commutators sense) using Wightman axioms, at least if there is a mass gap
November 30, 2025 at 7:41 PM
Another hint that cdp is connected to locality despite its asymptotic form is that it follows from locality (in the vanishing commutators sense) using Wightman axioms, at least if there is a mass gap
is so constrained that things outside of D(O) are determined alongside those inside of it. Is there signaling? The question seems meaningless because how could there be localized agents or interventions?
November 30, 2025 at 7:41 PM
is so constrained that things outside of D(O) are determined alongside those inside of it. Is there signaling? The question seems meaningless because how could there be localized agents or interventions?
I'm not sure but I get confused when I try to think about what 'signaling' even means in the absence of something like CDP. Consider the most extreme failure of CDP: All distant happenings perfectly correlated with local ones. LQD could still hold, it's just that the solution space to the theory
November 30, 2025 at 7:41 PM
I'm not sure but I get confused when I try to think about what 'signaling' even means in the absence of something like CDP. Consider the most extreme failure of CDP: All distant happenings perfectly correlated with local ones. LQD could still hold, it's just that the solution space to the theory
I still don't see how the CDP implies that I'm afraid. What is the actual signal you measure after I switch on my accelerator? CDP a priori says something abt probabilities of scatterings involving two clusters, to measure these I need to be present at both clusters..
November 29, 2025 at 1:28 PM
I still don't see how the CDP implies that I'm afraid. What is the actual signal you measure after I switch on my accelerator? CDP a priori says something abt probabilities of scatterings involving two clusters, to measure these I need to be present at both clusters..
I've thought for a while that most likely MWI is true but simultaneously the Born rule not strictly provable in the sense that its critics demand because somehow it refers to concepts in whose definition the statement dissolves.
I hope you'll write something clever about it!
I hope you'll write something clever about it!
November 21, 2025 at 10:26 PM
I've thought for a while that most likely MWI is true but simultaneously the Born rule not strictly provable in the sense that its critics demand because somehow it refers to concepts in whose definition the statement dissolves.
I hope you'll write something clever about it!
I hope you'll write something clever about it!
Do you have a picture of the derived structure, beyond 'extra shimmery fuzz'? I always wanted to see the homotopy on the geometric side. 'loop-shaped fuzz' ?
November 15, 2025 at 5:21 PM
Do you have a picture of the derived structure, beyond 'extra shimmery fuzz'? I always wanted to see the homotopy on the geometric side. 'loop-shaped fuzz' ?
ok that does seem like refusing to engage w what she's saying yea
November 15, 2025 at 12:15 PM
ok that does seem like refusing to engage w what she's saying yea
starting with a Gaussian wavepacket, we could make a rough guess for its mass by taking a single position measurement after some time has passed, bc it spreads out more slowly for heavy particles
November 15, 2025 at 10:07 AM
starting with a Gaussian wavepacket, we could make a rough guess for its mass by taking a single position measurement after some time has passed, bc it spreads out more slowly for heavy particles
but idk the context here
November 15, 2025 at 9:58 AM
but idk the context here
isn't it the opposite? If only the proposition mattered he'd be happy with any proof but he strongly prefers the general one, presumably bc he feels that the special case doesn't get at the right conceptual reason. At least this is how I often feel about proofs of special cases in math
November 15, 2025 at 9:58 AM
isn't it the opposite? If only the proposition mattered he'd be happy with any proof but he strongly prefers the general one, presumably bc he feels that the special case doesn't get at the right conceptual reason. At least this is how I often feel about proofs of special cases in math
If you really know the wavefunction, then in a momentum eigenstate you can read off energy, and from those two you get the mass. in general you should be able to get at it by Fourier analysis
November 14, 2025 at 10:14 PM
If you really know the wavefunction, then in a momentum eigenstate you can read off energy, and from those two you get the mass. in general you should be able to get at it by Fourier analysis
I wonder if there are even expected to be a lot of high-energy gravitons flying around. like I think the waves that Ligo detects are hundreds of km long right so individual particles would be basically impossible to detect
November 14, 2025 at 1:09 AM
I wonder if there are even expected to be a lot of high-energy gravitons flying around. like I think the waves that Ligo detects are hundreds of km long right so individual particles would be basically impossible to detect
So we still need at least a limit in which both measurement of the things we can actually measure and free particle states make sense and don't imply superluminal signaling imo
November 11, 2025 at 8:25 PM
So we still need at least a limit in which both measurement of the things we can actually measure and free particle states make sense and don't imply superluminal signaling imo
don't exist at the most fundamental level, but that doesn't mean that they don't exist. Even if they're emergent, we want a formalism to describe them, along with an understanding of where that description breaks down and why.
November 11, 2025 at 8:25 PM
don't exist at the most fundamental level, but that doesn't mean that they don't exist. Even if they're emergent, we want a formalism to describe them, along with an understanding of where that description breaks down and why.
I don't think Haag's theorem makes this entirely moot. In practice people do use perturbations on effectively free Fock spaces, and if this is the formalism that is empirically successful we must be able to interpret it, no?
I'm happy saying particles, measurement, free propagators and other things
I'm happy saying particles, measurement, free propagators and other things
November 11, 2025 at 8:25 PM
I don't think Haag's theorem makes this entirely moot. In practice people do use perturbations on effectively free Fock spaces, and if this is the formalism that is empirically successful we must be able to interpret it, no?
I'm happy saying particles, measurement, free propagators and other things
I'm happy saying particles, measurement, free propagators and other things
Maybe there was a certain amplitude of not seeing a cloud-chamber track. Alice would trace over these outcomes. But like none of this implies that I have an electron number projection operator at my disposal that I can apply to any arbitrary state
November 11, 2025 at 7:29 PM
Maybe there was a certain amplitude of not seeing a cloud-chamber track. Alice would trace over these outcomes. But like none of this implies that I have an electron number projection operator at my disposal that I can apply to any arbitrary state
can interpret as measurement, we analyze them by a unitary local time-evolution, and as I've said that's where non-signaling applies imo.
We see a cloud chamber track. We analyze the possible scattering processes under H and find an overwhelming amplitude of an electron state.
We see a cloud chamber track. We analyze the possible scattering processes under H and find an overwhelming amplitude of an electron state.
November 11, 2025 at 7:29 PM
can interpret as measurement, we analyze them by a unitary local time-evolution, and as I've said that's where non-signaling applies imo.
We see a cloud chamber track. We analyze the possible scattering processes under H and find an overwhelming amplitude of an electron state.
We see a cloud chamber track. We analyze the possible scattering processes under H and find an overwhelming amplitude of an electron state.
Fock basis makes exact sense (because then the whole space is at our disposal). But maybe I'm reading too much into things there.
But I think the reason I'm not as bothered by this stuff as you is that I just don't think of measurement as fundamental at all. Whenever we have situations that we
But I think the reason I'm not as bothered by this stuff as you is that I just don't think of measurement as fundamental at all. Whenever we have situations that we
November 11, 2025 at 7:29 PM
Fock basis makes exact sense (because then the whole space is at our disposal). But maybe I'm reading too much into things there.
But I think the reason I'm not as bothered by this stuff as you is that I just don't think of measurement as fundamental at all. Whenever we have situations that we
But I think the reason I'm not as bothered by this stuff as you is that I just don't think of measurement as fundamental at all. Whenever we have situations that we
such evolution, converge on a Fock measurement basis in the macroscopic limit. So these must be compatible. It is also suggestive to me that the limit in which QM projection operators can hope to be a precise description--infinite spread of decoherence--seems like the same limit in which the
November 11, 2025 at 7:29 PM
such evolution, converge on a Fock measurement basis in the macroscopic limit. So these must be compatible. It is also suggestive to me that the limit in which QM projection operators can hope to be a precise description--infinite spread of decoherence--seems like the same limit in which the
aargh sorry I shouldn't write at 2am. A Bell measurement basis cannot be nonlocally entangled, only the state being measured, you are abs right there. But still we have the two observations/principles: Time-evolution is local and unitary, and also scattering processes, which are well-described by
November 11, 2025 at 7:29 PM
aargh sorry I shouldn't write at 2am. A Bell measurement basis cannot be nonlocally entangled, only the state being measured, you are abs right there. But still we have the two observations/principles: Time-evolution is local and unitary, and also scattering processes, which are well-described by