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Hi, I am a string theorist and a publicist.


3h
comment $\mathrm{CO_2}$ rate of deposition
Despite widespread misconceptions, there is nothing such as "excess atmospheric CO2 problem". The economically and ecologically optimum concentration of CO2 would be around 4,000 ppm. The current concentration is 10 times lower than that. The Earth's ecosystem are CO2-starving, in a technical sense, but of course they got adapted to that. However, most existing plant species are unable to adapt to concentrations below 150 ppm. Dropping below that value would pretty much mean the end of life on Earth, at least temporarily.
7h
awarded  Guru
1d
comment Geodesic curvature and Weyl transformations
A timelike boundary is a boundary that is a timelike curve i.e. with $ds^2\gt 0$ for each infinitesimal segment, in some conventions, the spacelike one is spacelike. I am totally confident that the terms are self-explanatory. They're not realy new terms. They are combinations of 2 words you should have known since undergrad relativity and basic school geometry, respectively.
1d
awarded  Nice Answer
1d
revised Geodesic curvature and Weyl transformations
added 126 characters in body
1d
answered Geodesic curvature and Weyl transformations
Aug
30
awarded  Enlightened
Aug
28
awarded  Good Answer
Aug
28
comment Existence of Tripoles?
Right, firtree. I am personally always using $z=r\cos\theta$. In that convention, $\sin 3\theta$ isn't smooth near the poles and the function is a combination of infinitely many spherical harmonics (all odd $l$ $Y_{lm}$). If one uses the "latitude" $\theta$ going from $-\pi/2$ to $+\pi / 2$, then $\sin 3\theta$ i.e. roughly $\cos 3\theta$ in my normal language is smooth near the poles and the function is a simple combination of $Y_{10}$ and $Y_{30}$.
Aug
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reviewed Approve suggested edit on How do you add temperatures?
Aug
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answered Commutator algebra in exponents
Aug
28
comment Existence of Tripoles?
It is definitely not orthogonal to the other spherical harmonics, pretty much to none of them. The inner product with $Y_{l0}$ is nonzero for all odd values of $l$ - it's the integral over $\theta$ from zero to pi of the product of the functions times an extra $\sin\theta$. The spherical harmonics form a basis so they're complete - orthogonal to each other and you can't find any other that would be orthogonal to them.
Aug
28
comment Existence of Tripoles?
Sorry, I was inaccurate. You chose the function so nicely that the laplacian vanishes almost everywhere - but it doesn't on the $z$-axis i.e. for $\theta=0$ or $\theta=\pi$. Or maybe it's an eigenstate of the Laplacian with a nonzero eigenvalue? You may calculate those things.
Aug
28
comment Existence of Tripoles?
The particular potential you wrote down doesn't obey $\nabla^2 \phi = 0$ almost anywhere. It's easy to check. You can't fix this problem even by choosing a different dependence on $r$ exactly because the angular part isn't an eigenstate of the angular part of the Laplacian, i.e. the $L^2$ operator.
Aug
28
revised Existence of Tripoles?
added 391 characters in body
Aug
28
answered Existence of Tripoles?
Aug
28
awarded  Enlightened
Aug
27
awarded  Nice Answer
Aug
27
answered How do you add temperatures?
Aug
27
answered Do massive particles exchange Higgs bosons?