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Feb
5
comment Roots of iterations of polynomials
Some interesting things to look at that might be related: Late work of Thurston (e.g. arxiv.org/pdf/1402.2008v1.pdf) and this discussion of roots of polynomials by Baez (math.ucr.edu/home/baez/roots).
Feb
5
answered Raising e to the power of both sides of an equation
Feb
5
comment Raising e to the power of both sides of an equation
$e^z = e^{\ln(x) + 0} = e^{\ln(x)}\cdot e^0 = e^{\ln(x)}\cdot 1 = x\cdot 1 $, not $x+1$ ...
Feb
4
comment Conceptual Differences among Galerkin Methods
Good answer. To your discussion of quasi-optimal approximation --- the error of approximation also depend on the approximating subspace $V_n$, yes? In a finite element solver, I can make the constant as bad as I want by using very thin triangles in my triangulation.
Feb
3
comment How does Green's theorem apply here?
The boundary is a union of closed curves, so you'll take orientations on each of them (so that you have a consistent choice of inward/outward normal) and then the integral over the boundary will just be the sum of the integrals over each of those curves.
Feb
2
comment Use the Fourier transform to find value of definite integral from negative infinity to infinity
Side note: If you find $\hat{f}$, then $\int_{-\infty}^{\infty} f(x)\ dx = \hat{f}(0)$.
Feb
1
awarded  Enlightened
Feb
1
awarded  Nice Answer
Feb
1
answered Is any smooth deformation of a metric in dimension 1 conformal?
Jan
30
comment derivative of a projection matrix
(It may also help to remember that transposition commutes with differentiation.)
Jan
30
answered Christoffel symbols of $S^n$ in polar coordinates
Jan
30
comment Christoffel symbols of $S^n$ in polar coordinates
Tricks using the symmetry of $S^n$ aside, where did you run into difficulty using the standard formula in terms of derivatives of the coordinate functions of the Riemannian metric? (c.f. en.wikipedia.org/wiki/Christoffel_symbols#Definition)
Jan
26
answered Proving path-connectedness of $\mathbb{R}^2\setminus\mathbb{E}$ where $\mathbb{E}$ is the set of points with both coordinates rational
Jan
26
comment Angle between position and velocity vectors is constant?
@TedShifrin True, I'll take that back.
Jan
22
answered Why does convolution of delta function commute (test distribution perspective)?
Jan
22
revised Why does convolution of delta function commute (test distribution perspective)?
added 103 characters in body
Jan
22
comment Why does convolution of delta function commute (test distribution perspective)?
TeX note: If you use \langle and \rangle for your brackets, it looks better. Compare $<\delta, f>$ to $\langle \delta, f\rangle$.
Jan
22
comment Basic question on cohomology ring
Nitpick: maps are homotopic. Spaces are homotopy-equivalent.
Jan
14
answered Mixed portfolio
Jan
14
revised Mixed portfolio
spelling error