250 reputation
110
bio website
location Marburg, Germany
age 28
visits member for 1 year, 6 months
seen 12 hours ago

I made a diploma in experimental physics. Now, I am a PhD student in theoretical physics.


Jun
27
revised Convolution theorem for product of functions
edited body
Jun
27
comment Convolution theorem for product of functions
yes, $\vec{k}$ only can take values from a discrete set. But the Fourier transform from r to k is an integral since r is continous right?
Jun
27
asked Convolution theorem for product of functions
Mar
21
comment Temperature of gases
@Danu You're right. I just wanted to give a hint into the right direction. That's why I just commented, and did not answered.
Mar
21
comment Temperature of gases
You should have a look at the ideal gas law: $pV=NRT$. If you decrease the volume $V$ but pressure $p$ and number of particles $N$ stay constant, the temperature $T$ must increase. And vice versa.
Jan
28
comment Can a mass matrix be asymmetric?
Could you be more precise? What mass matrix are you talking about, an effective mass tensor as for a semiconductor? Or the mass matrix of analytical mechanics?
Jan
17
awarded  Yearling
Nov
6
comment Rotate vector in spherical coordinates
@tpg2114 Ok I see your point.
Nov
6
comment Rotate vector in spherical coordinates
@tpg2114 Then think of an integral containing a Coulomb potential. In my opinion this is a very direct connection to physics.
Nov
6
awarded  Popular Question
Aug
21
asked Is it possible to excite a semiconductor @ k=0?
May
3
comment Coulomb interaction and conservation laws
So you are saying that these 2 Hamiltonians are not comparable? If the quantum chemistry Hamiltonian describes totally different situations (molecules instead of charge carriers), of course I can say nothing about it... I was assuming that the Hamiltonians describe the exact same thing.
May
3
comment Coulomb interaction and conservation laws
@MichaelBrown I suggest you convert your comment into an answer.
May
3
comment Coulomb interaction and conservation laws
Ok. I think the quantum chemistry book just took a bad convention... Always trust the physicists if you have the choice :)
May
3
comment Coulomb interaction and conservation laws
I agree with Michael Brown, the conservation laws must be somehow 'integrated' into the definitions of the indices. For a reference, see Haug/Koch, Quantum theory of the optical and electronic properties of semiconductors. They derive your first Hamiltonian.
May
3
comment Sign crazyness on the stress energy tensor?
I guess it depends on the definition of the relativistic position vector. One definition is $a^\mu = (x,y,z,ct)$, the other is $a^\mu = (x,y,z,ict)$. This can cause inconsistency of all quantities that are derived from them. Hope this helps to track this down...
May
2
accepted Hydrogen wave function in momentum space
May
2
comment Hydrogen wave function in momentum space
Ok, so the 'forminvariance' is a consequence of the Hamiltonian in the Schrödinger equation. I guess it is not easy (and though not a good idea) to show this using a Fourier transformation.
May
2
comment Hydrogen wave function in momentum space
I am not convinced. The Fourier transform contains $\exp (- \mathrm{i} \mathbf{k} \cdot \mathbf{r})$ which mixes the integration of the angles and the radius.
May
2
asked Hydrogen wave function in momentum space