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In his book (String Theory Volume 1, pp. 66-68), Polchinski explains state-operator correspondence and derives the vacuum state through the identity operator: $$Psi_1[X_b] propto exp left( -frac{1}{alpha'} right)...
Asked on 01/16/2021 by Darkseid
0 answerIn the Landau's book "Electrodynamics of Continuous Media" he derives the relation between the polarisation $vec P$ and the dipole moment $vec p$.Starting with the definition of the dipole...
Asked on 01/16/2021
3 answerI'm struggling to understand the physical interpretation behind the field operators $ phi(mathbf x)$ and $phi ^dagger (mathbf x)$ in quantum field theory. My understanding is ...
Asked on 01/16/2021 by Bentley Carr
1 answerThe Landauer formula for a one dimensional quantum system (potential step scattering) can be written as $$I(V)=frac{2e}{h}int_{-infty}^infty dE T(E) (f_S(E) - f_D(E)),$$ where $T(E)$ is the...
Asked on 01/16/2021 by user2820579
1 answerThe following paradox is mentioned in the Feynman Lectures on Physics Vol II, Chapter 17, Section 17-4. I have seen various solutions to this paradox across the internet and even...
Asked on 01/16/2021 by Aryamann
1 answerThe partial derivative of a tensor of rank $n$, $T_{...i}$, with respect to $x^j$ can be expressed using the transformation rule: begin{equation}frac{partial}{partial x^j}T'_{...i}=frac{partial}{partial x^j}sum_{...k}...frac{partial x^k}{partial...
Asked on 01/16/2021 by IchVerlore
1 answerI Landau & Lifshitz I mechanics introduces adiabatic through Hamiltonian that is dependent on some slowly changing parameter $lambda$. After some derivation they got$$I=frac{1}{2pi}oint pdq=const.$$This...
Asked on 01/15/2021
0 answerI know that Fraunhofer lines are certain wavelengths in the Sun's spectrum that are 'missing' because of absorption at the chromosphere. In other words, they are 'dark'.But my...
Asked on 01/15/2021
1 answerA motor is dragging a log up a slope with a cable. When the cable breaks, what happens to the forces? There is no more tension, but does the direction...
Asked on 01/15/2021 by borns
3 answerI am working with a Hamiltonian which looks like this (Heisenberg model)$$ hat{H} = -frac{1}{2}sum_{j=1}^N left( J_xsigma_j^xsigma_{j+1}^x+J_ysigma_j^ysigma_{j+1}^y+J_zsigma_j^zsigma_{j+1}^z + hsigma_j^zright). $$ I have made a...
Asked on 01/15/2021 by Trantidon
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