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Mar
7
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
well, can we or can't we? Do you agree that there is a time-varying charge distribution?
Mar
7
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
no, it was about whether defining it as a mixed state meant we couldn't talk about the time-varying charge distribution. Did you read the whole question?
Mar
7
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
to be clear: of course there is a time-varying charge distribution. Asyou point out in your answer, the whole universe is in a pure state. That means the charges are distributed somewhere, including the tungsten filament. If you cant FIND the charges by writing down the state function for the isolated tungsten filament...and I don't buy that for one minute...even if you can't, you can still evaluate the wave function of the whole universe. The charges in the tungsten filament are oscillating. It is ridiculous to claim, as Pisanty does, that they are stationary.
Mar
7
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
Pisanty has laid down the claim that because the tungsten filament is in a mixed state, specifically a thermal state, that it we therefore cannot talk about a time-varying charge distribution. In short: the charge is stationary, so classically it cannot radiate. I don't believe this is what Quantum Mechanics tells us, and it's not helpful to try and come up with a better definition of pure vs mixed states. The entanglement with the environment is nothing but a red herring when it comes to the real issue of whether there is a time-varying charge distribution.
Mar
7
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
I think you should let Emilio speak for himself.
Mar
7
comment Quantum entanglement vs classical analogy
Thanks. I'm not used to people agreeing with me.
Mar
7
reviewed Approve Is a heated tungsten filament in a “pure state” or a “mixed state”?
Mar
7
comment Quantum entanglement vs classical analogy
Because classically, it is perfectly normal for 50% of the light which gets through a vertical polarizer to then also get through a 45 degree offset polarizer. I think Greg is just wrong when he claims a particle that gets through an x polarizer will always be blocked by a y polarizer.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
So what exactly did you mean last year when you said "black-body radiation can be explained...with discrete energy levels on the emitters rather than the radiation"....what did you mean if not exactly what I am saying?
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
I'm fine with that.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
We make these choices all the time. When I solve a Grade 11 trajectory problem with a cannonball going at 100 m/s, I choose to treat the earth as flat. Only an idiot would treat it as round.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
You can write the pure state of a hydrogen atom, and if you bring another hydrogen atom nearby, it screws up the state of each hydrogen atom. But there is nothing to stop you from writing the pure state of the resulting hydrogen molecule.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
I choose not to consider the tensor product of the tungsten filament with the states of the surrounding environment because it is a pointless and needless complication. What I don't understand is why you insist on bringing it in.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
Okay, I'm fine with that.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
I have no idea what you're talking about.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
So take a filament with 200 atoms and then remove the heat bath once you've brought the filament up to temperature. Pure state or not?
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
@emilio I have no idea what you're trying to tell me. But exactly one year ago we were in a similar discussion and you said: "black-body radiation can be explained equally well with discrete energy levels on the emitters rather than the radiation". How is this different from what I'm saying about solving the filament mechanically in QM and then using Maxwell to get the radiation?
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
Why don't you tell me how many tungsten atoms I need to have in my filament before it ceases to be "ridiculous", and then we'll talk about it.
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
OK, then for the purpose of my question I am takingt my tungsten filament to be in the state A+B. And from that I am going to calcdulate a time-varying charge distribution. Do you consider that "reasonable"?
Mar
6
comment Is a heated tungsten filament in a “pure state” or a “mixed state”?
By your logic, a hydrogen atom in a superposition of the s1 and p2 states cannot be in a "pure" state because it is entangled with the X and Y states of the surrounding environment. And therefore I'm not allowed to talk about the time-varying charge distribution of the hydrogen atom. Is that what you're saying? Because it sounds like that's what you're saying.