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1d
reviewed Approve Lower bounding the multiplicative order of 2 modulo p
Jul
15
comment Class of analytically-integrable divergence-free vector fields?
@Robert Bryant: It depends on what you mean by "explicit." On each level curve of the Hamiltonian, you have to solve an autonomous ODE in one dimension. This can always be done in terms of integrations and inverse functions. Of course, whether you can do those "explicitly" is another question, but one that is usually deemed at a "lower level."
Jul
15
answered Class of analytically-integrable divergence-free vector fields?
Jul
10
comment The $L^2\times L^2\to L^2$ norm of the bilinear multiplier operator
Consider what happens when you set $m=\hat f\hat g$.
Jul
10
answered Bandwidth approximation for a nonlinear problem
Jul
7
awarded  Good Answer
Jun
23
answered Convergence of sequence of polynomials defined by boundary conditions
Jun
19
comment Infinitesimal generator is bounded
A much more serious flaw in your reasoning is that you are overlooking the fact that $t$ is in the denominator and $t\to 0$.
Jun
17
comment Is $f(x,y)=\sum_{n\in\mathbb{Z}\backslash\{0\}}\frac{1}{n}e^{2\pi i(xn+yn^2)}$ essentially bounded?
No. Set y=0. You can do the sum explicitly in that case.
Jun
16
reviewed Edit for which values of $\theta$ does this equation $x_{n+1}=\cos(\theta)x^2_{n}-\sin(\theta)x^2_{n-1}$ have bounded solutions?
Jun
16
revised for which values of $\theta$ does this equation $x_{n+1}=\cos(\theta)x^2_{n}-\sin(\theta)x^2_{n-1}$ have bounded solutions?
The body text of the problem was so unregular.
Jun
16
comment [This might be a easy question]: A possible trace (inequality) defined under negative Sobolev scale
The problem is that if you pick $f\in H_0^{s+2}$, then $\partial f/\partial\nu$ will be zero on the boundary.
May
29
awarded  Good Answer
May
26
comment Existence of Solution steady navier stokes with do nothing outflow condition
First of all, the free boundary condition should be $pn-\nu(\nabla u+(\nabla u)^T)n=0$. Second, what kind of existence results are you looking for? For small data, standard methods work. For large data, there is not much hope if there are free surfaces, as demonstrated by phenomena such as wave breaking, jet breakup etc.
May
21
comment Derivatives of radial functions can be bounded by derivatives in terms of radial distance?
This example does not quite seem to work. Does not $d^2f/dr^2$ get large when you actually do the modification near 0?
May
20
answered Interpolation between weighted $L^p$ spaces
May
13
reviewed Approve Loop space of manifold
May
10
comment Mixed (anisotropic) Sobolev spaces
The correct inference is that $f\in H^s(L^2)\cap L^2(H^s)$. You should look at the equivalent statement for Fourier transforms.
May
10
answered Mixed (anisotropic) Sobolev spaces
May
4
reviewed Approve oa.operator-algebras tag wiki excerpt