# DaPhil

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bio website location Marburg, Germany age 28 member for 1 year, 6 months seen 12 hours ago profile views 33

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

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 Jun27 revised Convolution theorem for product of functions edited body Jun27 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? Jun27 asked Convolution theorem for product of functions Mar21 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. Mar21 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. Jan28 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? Jan17 awarded Yearling Nov6 comment Rotate vector in spherical coordinates @tpg2114 Ok I see your point. Nov6 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. Nov6 awarded Popular Question Aug21 asked Is it possible to excite a semiconductor @ k=0? May3 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. May3 comment Coulomb interaction and conservation laws @MichaelBrown I suggest you convert your comment into an answer. May3 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 :) May3 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. May3 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... May2 accepted Hydrogen wave function in momentum space May2 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. May2 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. May2 asked Hydrogen wave function in momentum space