Recent content by DrDu

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    I Do hyperbolic harmonics exist?

    https://projecteuclid.org/journals/communications-in-mathematical-physics/volume-8/issue-1/Matrix-elements-of-representations-of-non-compact-groups-in-a/cmp/1103840513.pdf
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    Unlocking the Secrets of Prof. Verschure's Rosetta Stones

    Usually, when talking about PPL, you assume that the polarizer is present, but the analyzer has been removed.
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    I Citation needed: Only multivariate rotationally invariant distribution with iid components is a multivariate normal distribution

    On a Characterization of the Normal Distribution M. Kac American Journal of Mathematics, Vol. 61, No. 3 (Jul., 1939), pp. 726-728 (3 pages) https://doi.org/10.2307/2371328•https://www.jstor.org/stable/2371328 Thank you guys, your comments helped me to locate the article mentioned above!
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    Unlocking the Secrets of Prof. Verschure's Rosetta Stones

    The orientation of the polariser is best detected by the pleochroism of biotite. Biotite, cut perpendicular to the sheets, appears dark if the polariser is oriented parallel to the sheets, and bright if perpendicular. And yes, a "head cut" (my translation of the german "Kopfschnitt") is a slice...
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    Unlocking the Secrets of Prof. Verschure's Rosetta Stones

    Yes, if it is quartz, it can only have formed diagenetically.
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    Unlocking the Secrets of Prof. Verschure's Rosetta Stones

    The white rim looks like quartz to me.
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    I Citation needed: Only multivariate rotationally invariant distribution with iid components is a multivariate normal distribution

    I need a citation for the following proposition: Assume a random vector ##X=(X_1, ..., X_n)^T## with iid components ##X_i## and mean 0, then the distribution of ##X## is only invariant with respect to orthogonal transformations, if the distribution of the ##X_i## is a normal distribution. Thank...
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    I Hartree-Fock: Feynman diagrams vs perturbation theory

    Well, if ##H=H_0+\epsilon V## and ##R=(H-\lambda)^{-1}## and similarly ##R_0##, then the one particle Greensfunction is something like ##G=\langle 1 | R| 1\rangle> ## where ##| 1 \rangle ## is some one particle state. Expanding R in powers of ##\epsilon## yields the Dyson equation for ##G##. If...
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    I Hartree-Fock: Feynman diagrams vs perturbation theory

    Basically, Feynman diagrams are related to a perturbation expansion of the resolvent (H-lambda)^{-1} and not of the hamiltonian itself. So it is not astonishing that a first order correction to energy yields a geometric series for the resolvent and vice versa to get exactly coincident expressions.
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    New Insight into the Chemistry of Solvents

    If you consider the electron gas as a solvent for the positive ionic cores in a metal, the Cooper mechanism in superconductors is just of this form
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    Separation of KCl from potassium chromium(III) PDTA

    There are syntheses which don't seem to have KCl as a byproduct, e.g. https://www.mdpi.com/2313-0105/9/12/573 or here https://www.cell.com/joule/pdf/S2542-4351(19)30318-6.pdf Even if both substances are in principle soluble in the same solvents, when you try to crystallize them, usually one of...
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    Classical Looking for a thermodynamics book that 'ties it all together'

    I would recommend Max Plancks book https://www.amazon.de/Treatise-Thermodynamics-Dover-Books-Physics/dp/048666371X He did his PhD on Thermodynamics and Thermodynamics was his route to discover quantum mechanics which earned him the Nobel Prize.
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    Unlocking the Secrets of Prof. Verschure's Rosetta Stones

    Very nice slide! You should also try to identify the pleochroism of the arfvedsonite. From your picture, one already recognizes a change from light blue to light green parallel or perpendicular to the longitudinal extension. How is your polarisatior oriented? (NS or EW)? Do you also find a...
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    A QFT Superposition of Final States

    See for example: https://en.wikipedia.org/wiki/Infraparticle
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    A QFT Superposition of Final States

    As far as I understand it, almost all different outcomes are in separate superselection sectors (differing by an infinite number of soft photons) so that no superpositions are possible.
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