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Jan
1
comment Show $S_4$ is not isomorphic to $D_{24}$ by looking at their centers
Proof for the triviality of the center of $S_4$: the conjugate $gag^{-1}$ of $a$ is just a relabeling of $a$. For example, if $a=(123)$, then $gag^{-1}=(g(1)g(2)g(3))$. It's not hard to show that if $a\neq 1$, the identity, then the conjugate class of $a$ isn't a singleton.
Dec
30
asked Does the implicit function theorem imply Peano existence theorem
Dec
29
comment Question about integral on hypersurface
Note that the ordinary surface integral gives a positive linear functional on $C_c(S)$, the space of continuous compactly supported functions on $S$, where $S\subseteq\mathbb R^n$ is locally compact Hausdorff. The Riesz representation theorem furnishes a Riesz measure on the surface $S$.
Dec
29
awarded  Custodian
Dec
29
revised Solving recurrences with summation factors (Concrete Mathematics)
edited tags
Dec
29
revised Should diffeomorphisms preserving arc length be affine?
edited title
Dec
29
revised Newton polygon and asymptotic behavior near a singular point
added 67 characters in body; edited tags
Dec
28
revised Simultaneously (generalized) diagonalizable matrices
added 58 characters in body
Dec
28
comment What is the interpretation of the eigenvectors of the jacobian matrix?
I think you cannot obtain a good interpretation since that linear map (usually called the tangent map) is between different vector spaces (tangent spaces, even of distinct dimensions), therefore not a linear operator.
Dec
28
revised Newton polygon and asymptotic behavior near a singular point
added 20 characters in body
Dec
28
asked Newton polygon and asymptotic behavior near a singular point
Dec
28
comment Computing the monodromy for a cover of the Riemann sphere (and Puiseux expansions)
Is there any proof or reference of proofs for this method?
Dec
27
comment Composition of Number Fields
What about $\operatorname{Gal}(KL/F)\cong\operatorname{Gal}(K/F)\times\operatorname{Gal}(L/‌​F)$ where $F=K\cap L$ even when $K/F,L/F$ aren't finite but Galois?
Dec
26
comment Should diffeomorphisms preserving arc length be affine?
If $f$ preserves the (non-degenerate) symplectic structure, then $f$ is affine. I meant that I had less interest in the symplectic case, and I guessed (wrongly) for the symplectic case just because of the preceding statement.
Dec
26
comment Should diffeomorphisms preserving arc length be affine?
Informed and informative. However, the original problem arises in Lorentz quadratic form, therefore I'm more interested in the psuedo-Euclidean case. I guessed the symplectic case since it seems that the proof of my old problem also works for the symplectic structure.
Dec
26
revised Should diffeomorphisms preserving arc length be affine?
added 78 characters in body
Dec
22
asked Should diffeomorphisms preserving arc length be affine?
Dec
5
comment Show that $f\circ \gamma$ is a regular surface.
@B11b It's certainly a handwork to me.
Dec
1
comment Show that $f\circ \gamma$ is a regular surface.
You need to input $\LaTeX$ rather than images. I've edited.
Dec
1
revised Show that $f\circ \gamma$ is a regular surface.
LaTeXize