19 Jan 19
How slow can an electron go?
I am particularly interested in why a Bose Einstein Condensate behaves in the way it does. I read that a BEC was predicted before observed by Satyendra Nath Bose. Is that prediction based on a slower electron? I was having a hard time finding out so I figured somebody on here might already know and save me time searching for the answer.
19 Jan 19
There is no strict limit on "how slow an electron can go" as long as the uncertainty principle is satisfied.
A BEC consists of bosons, and electrons are fermions, so electrons cannot Bose-condense except as a part of some composite boson. Bose-Einstein condensation can be explained purely on quantum statistical grounds, it doesn't rely on specific properties of the constituent bosons.
21 Jan 19
@kazetnagorra saidAren't the Bose condensates in one quantum state, a kind of single atom, quantumly speaking?
There is no strict limit on "how slow an electron can go" as long as the uncertainty principle is satisfied.
A BEC consists of bosons, and electrons are fermions, so electrons cannot Bose-condense except as a part of some composite boson. Bose-Einstein condensation can be explained purely on quantum statistical grounds, it doesn't rely on specific properties of the constituent bosons.
21 Jan 19
@kazetnagorra saidWhat is your source of info? You cannot lower temps to absolute zero so there has to be a limit to electron speed.
There is no strict limit on "how slow an electron can go" as long as the uncertainty principle is satisfied.
A BEC consists of bosons, and electrons are fermions, so electrons cannot Bose-condense except as a part of some composite boson. Bose-Einstein condensation can be explained purely on quantum statistical grounds, it doesn't rely on specific properties of the constituent bosons.
If the electrons of a BEC are not tugging on each other how does a BEC flow upwards seeming to defy gravity? A slower electron would explain this. How can a Boson explain that?
21 Jan 19
@sonhouse saidThat seems to be a popular theory, but just a theory.
Aren't the Bose condensates in one quantum state, a kind of single atom, quantumly speaking?
21 Jan 19
@metal-brain saidYou cannot reach absolute zero, but you can get arbitrarily close to it in principle. In practice, experiments using ultra-cold atoms achieving BEC can reach temperatures below 1 µK. As a source of information, you can consider reading Pethick & Smith's standard text on BECs in dilute atomic vapours.
What is your source of info? You cannot lower temps to absolute zero so there has to be a limit to electron speed.
If the electrons of a BEC are not tugging on each other how does a BEC flow upwards seeming to defy gravity? A slower electron would explain this. How can a Boson explain that?
Electrons in a BEC (if part of some composite boson) can interact, but that interaction isn't important for the principle of Bose-Einstein condensation, which just relies on the constituent particles being bosons. To understand how it works you need some understanding of basic quantum mechanics. In loose laymen's language: bosons like to be in the same state, and at low temperatures you can get a lot of them in the lowest momentum state.
21 Jan 19
@kazetnagorra saidSo electrons are a kind of contamination of the Bose, then? Do they interfere with any of the properties of the Bose?
You cannot reach absolute zero, but you can get arbitrarily close to it in principle. In practice, experiments using ultra-cold atoms achieving BEC can reach temperatures below 1 µK. As a source of information, you can consider reading Pethick & Smith's standard text on BECs in dilute atomic vapours.
Electrons in a BEC (if part of some composite boson) can interact, b ...[text shortened]... e in the same state, and at low temperatures you can get a lot of them in the lowest momentum state.
21 Jan 19
@kazetnagorra saidThat still doesn't explain why a BEC seems to defy gravity and runneth over cup.
You cannot reach absolute zero, but you can get arbitrarily close to it in principle. In practice, experiments using ultra-cold atoms achieving BEC can reach temperatures below 1 µK. As a source of information, you can consider reading Pethick & Smith's standard text on BECs in dilute atomic vapours.
Electrons in a BEC (if part of some composite boson) can interact, b ...[text shortened]... e in the same state, and at low temperatures you can get a lot of them in the lowest momentum state.
22 Jan 19
@metal-brain saidMassive particles in a BEC are affected by gravity in the same way as ordinary massive particles. I guess "runneth over cup" refers to superfluids in a container, which can run over the cup due to surface tension and the absence of viscosity. It's essentially the same effect that causes water in a cup to curl up at the edges (defying gravity, in your words), on steroids.
That still doesn't explain why a BEC seems to defy gravity and runneth over cup.
22 Jan 19
@sonhouse saidThey are not a contamination. In a BEC of ultra-cold atoms, it is the atoms as a whole that Bose-condense, which includes the nucleus and electrons. The internal structure of the atoms is not important for the principle of Bose-Einstein condensation, as long as the atoms in question are composite bosons.
So electrons are a kind of contamination of the Bose, then? Do they interfere with any of the properties of the Bose?
22 Jan 19
@kazetnagorra said" It's essentially the same effect that causes water in a cup to curl up at the edges"
Massive particles in a BEC are affected by gravity in the same way as ordinary massive particles. I guess "runneth over cup" refers to superfluids in a container, which can run over the cup due to surface tension and the absence of viscosity. It's essentially the same effect that causes water in a cup to curl up at the edges (defying gravity, in your words), on steroids.
Surface tension is caused by the cohesion of water. Isn't it adhesion that causes water in a cup to curl up at the edges? Water has both cohesive and adhesive properties. I thought the two went hand in hand, but perhaps I was mistaken.
Does a BEC superfluid retain adhesive properties while losing cohesive properties? Why is the BEC clinging to the rim of the cup as it runs over?