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1:47 AM

When a gas atom gains kinetic energy by interacting with a hot solid. Is it that the solid's atoms/molecules are mechanically moving alot? Or is it the charges within the solid is moving alot, which then imparts kinetic energy to the gas?

Then again, I suppose on that level, what is a moving atom/molecule except a moving charge....

I'm not sure how helpful that thought is for this application though...

Ryan Unger

2:43 AM

@Slereah his email list is about a hundred people long

I think he took names from various GR conferences

bolbteppa

3:42 AM

@RyanUnger maybe he found your physics criticism sympatico :p

1 hour later…

John Rennie

4:44 AM

@antimony In a solid the atoms/molecules vibrate around their equilibrium position so they have vibrational energy. When a gas molecule hits the surface it can transfer its KE to the solid and increase the energy of the vibrations, or the vibrational energy can be transferred to the gas molecule and increase its KE.

satan 29

5:31 AM

@RewCie ?

John Rennie

awk is a text processing tool.

Omni man

6:12 AM

LSD is creativity enhancing tool

3 hours later…

123

9:17 AM

Hi All...

Hello @JohnRennie after long nice to see you.

Hello @ACuriousMind

antimony

9:48 AM

Ahh lovely thanks @JohnRennie , so they are mechanically vibrating around the equilibrium, which is governed by the electric forces binding them to their surrounding atoms/molecules?

John Rennie

@antimony Yes. The energy of the vibration is the way heat is stored in the solid, so increasingly the vibrational energy makes the solid hotter and decraesing it makes the solid colder.

antimony

lovely thanks @JohnRennie and when eg. a solid vaporises is it because the vibrational energy overcomes the electric force binding them to surrounding atoms/molecules?

John Rennie

@antimony Yes, exactly. As you increase the temperature the amplitude of the vibration increases, and eventually the atoms just shake themselves loose.

antimony

10:06 AM

incredible thanks @JohnRennie, one thing i puzzle over is how this vibration leads to emission in solids. since if this mechanical vibration creates an oscillation in charge density which creates the emission.

yet it seems incredible to think the atoms/molecules are mechanically vibrating at eg. 30 THz at room temperature (say 290K). So is there some mechanism by which the charge densities are oscillating at much higher frequency than the vibration frequency?

or can they actually vibrate at 30 THz? If I understand what you taught me previously, in gases such an emission is a quantum photon emission from a state transition. So the vibration doesn't need to be at 30 THz. but in solids it really puzzles me

is it because there are so many adjacent charges in a solid, that the effective acceleration of charges relative to eachother is enough to effectively "upconvert" the lower frequency vibrations into higher frequency charge density oscillations?

i suppose its not inconceivable there could be a nonlinearity between different modes, ie. vibration vs charge oscillation....

John Rennie

Black body radiation is related to oscillations in the electron density rather than directly to the oscillations of the atoms (i.e. oscillations of the nuclei since the nucleus makes up 99.99% of the mass of the atoms).

antimony

ahh i see

John Rennie

The electrons are much lighter than the nuclei so they oscillate at a much higher frequency.

antimony

ohh!

lovely

makes sense :)

is it ok to think of it in a very very simple way like an harmonic oscillator. since a lower mass will have a higher frequency?

John Rennie

10:44 AM

@antimony well it's a whole array of coupled simple harmonic oscillators, but basically yes you can think of it that way.

Nihar Karve

11:39 AM

one thing which I realise I have no clue about: why is the moduli space of a supersymmetric gauge theory equivalent to the space of single-trace scalar operator VEVs?

is this something obvious?

ACuriousMind

@NiharKarve I'm not 100% sure what you mean but vacua are classified by scalar values because non-scalar values would contradict the Lorentz invariance of the vacuum

Nihar Karve

yes, of course

but why single-trace?

and why all such VEVs

the prototypical example I'm thinking of here is SQCD, where the moduli space can be parameterised by mesons and two baryons

ah wait I think it's shown in arxiv.org/abs/hep-th/9506098

antimony

12:37 PM

lovely, thanks alot @JohnRennie everytime you teach me so much great stuff!! :)

7 hours later…