Nick P

Ich hab's mit sowas probiert wie "very nice cut". In meinem Lexikon steht auch cut = [textil.] Schnitt. Das hat aber zu gigantischen Missverstaendnissen gefuehrt. Es wurde so verstanden "hast Du aber huebsch selbst zusammengeschnippelt". Also: kompetenter Rat ist erwuenscht...

I saw this in a thread. I suspect that some people use it to point to themselves!

The index of refraction is a complex number if the mediums conductivity is non zero. We know that for real refractive index:

v=c/n

How is the corresponding relation for complex n? I would expect v=c/Re(n), but since Re(n) may become small for several media v would exceed the light speed which I doubt to be true!

I desire to calculate the intensities of spectral lines for the case of Hydrogene at temperature T contained inside a volume V.

I thnk that all I need is

1)The mean population of the upper energy level

2)The probability of transition between the levels

I believe that the mean population of a quantum state will be given by Bose statistics, so that of an energy level will be the same multiplied by the degeneracy of the energy level.

For the transition probabilities I need help. When we deal with atoms subjected to a field those are usually calculated by perturbation theory, for which one needs a perturbative Hamiltonian. I have no clue how to arrive at the latter here. Nor do I think that the influence of the whole surrounding would be small enough to be a perturbation.

I really wish to understand it!

We know to calculate the intensity emitted by a black body (total or inside a frequency interval) by Planck's formula. A realization of such is usually a cavity of constant temperature containing almost no matter.

But what do we do if we want to calculate the intensity emitted by matter? F.e. a box of hydrogen at constant temperature and are not fine with a black body approximation?

How could we get at least the intensities of the Hydrogene lines?

Thanks!

It is clear that the temperatures and pressures of the different phases are equal, due to the maximum entropy requirement. Though I can't proof why both are known to remain constant during transition.

That apparently holds, if the P(T) curve intersects the curve of phase coexistence at one point only. Then the transition happens at this very point of fixed T and P.

But couldn't one imagine the P(T) curve moving towards the coexistence curve, then moving ON it for a while and then leaving it. The part where both curves show congruence would represent the transition, during which temperature and pressure would change.

My book of statistical physics says that such a claim "obviously" holds. I don't get it. It seems natural to me, since I can't draw a corresponding diagram, but I don't manage to deliver a clear proof.

When I calculate it I get approximately the pion mass - roughly 135MeV. But ,as I read, that threshold equals 144.68MeV. Obviously I do something wrong. Can you help me and explain how to calculate the answer?

I have to give a talk and must programme the slides using LaTeX. Many images will be included, too. Which is a good quick way to learn making slides with LaTeX. I know the most elementary things (typesetting equations and so on) but have never made slides.

I feel that I have a really interesting 360 blog about strange animals (like flying squirrels, anglerfish and more), but I have only quite a few visitors. I would like to promote it among those who are truly interested.The search option hasn't helped so much yet. Has anyone got a better idea?

When I click on "edit my Info" it says "360 nickname not found", but I have a Y!360 page and want the link to appear on the Q&A page. What's wrong?

When I click on "edit my Info" it says "360 nickname not found", but I have a Y!360 page and want the link to appear on the Q&A page. What's wrong?

I very much need the exact definition of the Partial trace (corresponding to Ha) of an Operator acting on the Productspace (Tensorproduct) of 2 Hilbertspaces Ha and Hb in terms of the kets that constitute a basis of these Hilbertspaces.

I've been searching all day long. It keeps reapearing in important lecture notes, but I can't find the definition and it's gone to drive me mad unless someone helps!

The matter can occure only in the oher phases, regardless of temperature.

What is that due to?

I also have the impression, that this does not follow from Van-der-Wals's model. What effect does the latter model neglect?

this implies C(t)->0 in the limit t->0?

In other words:

C(t) is an arbitary function of t. t is always positive. I know that

Int(C(t)/t)dt, t=0...T is finite

and want to prove C(T)->0 for T->0

From the dogs behavior I deduced there's probably smth. in it's ear. It's seems to run a fever and not to hear well. I have not succeeded to contact a vet (Located in Greece, near Volos). What should I do?

In our thermodynamics lecture we defined a reversible process as:

1) A process during which every intermediate state deviates only infinitesimally from equilibrium.

OR,

2) A process that, when followed by the one in opposite direction, leaves no change in enviroment.

Now we see, that from 1) follows that every part of the process is rev. too. Does that follow from 2) as well? If so, why? If not, that apparently implies 1) and 2) not describing the same notion. Have we got to modify 2), adding "...for every part of which..."

What definition do you find most accurate? Do we need to start from entropy (We made use of reversibility to define it). Perhaps from a mikroskopic definition of it?

d(X,fist assymptote)*d(X,second assymptote) is constant. Specialy:

The hyperbola is given by (x/a)^2-(y/b)^2=1.

The assymptotes are: (x/a)-(x/b)=0 and (x/a)+(x/b)=0

The product above comes out to be: (ab)^2/(a^2+b^2)