Recent content by Joe Cool

Thanks a lot for your answers!

Hello, how can you imagine the geometrically meaning of the minus sign in ds2=-dx02+dx12+dx22+dx32, maybe similar to ds2=x12+dx22 is the length in a triangle with the Pythagoras theorem?

Okay, I now get the idea of taking it as an paradox free macroscopic thing. Before talking with you about the classical limit or black holes I surely need to learn more advanced QT first ... Thanks everyone for taking so much time to explain it to me in detail!

Sorry for asking again, but I sill ponder on that. I haven't learned quantum statistics yet, just undergraduate quantum mechanics. So I would write the state of a (macroscopic) Geiger counter (I understand a cat is not in equilibrium and that makes it more complicated) measuring if the atom...

Nice quotes, they really made the point of the cat story more clear for me, thanks! Maybe future experiments will confirm that macroscopic classical observables can't be described by the concept of pure quantum states, who knows ;-)

:-D So does the "state" vector represent not a physical state of the cat but our knowledge(or "quantum ignorance") about it? But we are not able to interpretate the superposition just as "with 50% probability the cat is alive", are we?

Thank you for the answers :-). Have I understand it correctly that (if quantum mechanics is applied to the cat as if it would be single atom with two states) the cat and the atom$$(\frac 1 {\sqrt{2}} |decay> + \frac 1 {\sqrt{2}}|no~decay>) |cat>$$evolves to$$U(\frac 1 {\sqrt{2}} |decay>|cat> +...

Hello, does someone know where to find a calculation of Schrödinger's cat experiment? (like psi(cat)=|dead> + |alive>...)

Hi Mohamed, you can also watch the videos on this side: http://theoreticalminimum.com/courses They include modern topics like black holes or the Higgs particle that are not in the Feynman lectures from 1964, but are a bit more difficult and they probably explain everything in much more detail...

Thanks a lot, now I get it :-)

Hi, maybe someone can help me with this problem? Homework Statement A system consist of N Atoms that have a magnetic moment m. The Hamiltonian in the presence of a magnetic field H is $$\mathcal{H}(p,q) - mH \sum_{i=1}^N cos(\alpha_{i})$$ where ##\alpha_i## is the angle between the magnetic...

Thanks for your hint. I read about the surface tension and understand it like this: The water molecules attract each other stronger than an air molecule. So there is a force that put the volume of the water in the form that has the minimal surface. This force can balance the deforming of the...

Hello, after I read in an exercise that the pressure inside of a spherical water drop is different than the pressure outside, I'm a little bit confused. Which is the pressure used in Gibb's phase rule and why don't the pressure change the form of the water drop?

Thanks for your Tip. Should it be like that? ##ln((1+aP)^2)=ln\frac 1 V+lnV_0=ln\frac {V_0} V## with ##V_0=e^{const.}##

Homework Statement The internal Energy of a system is ##U=aP^2V## with a positive constant a. Find the adiabats of this system in the P-V plane. The solution is $$P=\frac 1 a\left( \sqrt{\frac {V_0} V}-1\right)$$ 2. The attempt at a solution the first law with the given internal energy...