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visits member for 2 years, 4 months
seen 13 hours ago

Mar
29
asked Limiting argument when proving inequality in Sobolev space
Mar
26
awarded  Popular Question
Mar
21
accepted What does it mean for a distribution to be in $L_2$?
Mar
21
comment What does it mean for a distribution to be in $L_2$?
I am trying to get a little intuition here. So based on what you said, a lot of distributions are not in $L_2$ since for a general distribution, you are not even lucky enough to get that kind of representation. Am I right?
Mar
21
asked What does it mean for a distribution to be in $L_2$?
Mar
13
awarded  Yearling
Feb
10
comment What is the characteristics for the wave equation with space dimension more than 1?
What do you mean by there are no characteristics in higher spatial dimensions? I thought we need to just find a function $\phi(t,x,y)$, s.t. $\phi_t^2=\phi_x^2+\phi_y^2$. And the set$\{\phi=const\}$ would be the family of characteristic surfaces. When I tried to solve the equation, I got planes. But my intuition tells me that it should be something like the cone you mentioned. I don't know where I went wrong.
Feb
10
asked What is the characteristics for the wave equation with space dimension more than 1?
Jan
24
awarded  Popular Question
Jan
21
awarded  Nice Question
Oct
12
asked how to prove this function is harmonic (Fritz John 4.1 #5)
Apr
8
comment Approximating measurable function by continuous ones
@GiuseppeNegro I did check on that one. But isn't regularity of the measure needed there?
Apr
8
revised Approximating measurable function by continuous ones
deleted 49 characters in body
Apr
8
comment Approximating measurable function by continuous ones
@DavideGiraudo Let's say $X$ is $\mathbb{R}^n$ with the usual topology. And sorry that I made a mistake in my original problem. I should ask for almost everywhere convergence.
Apr
8
comment Steiner symmetrization preserves area?
This is just by the construction of Steiner symmetric action and Fubini's theorem( where you can get: in order to get area, you integrate length of chords with respect to proper measure)
Apr
7
revised approximate measurable function by continuous ones
deleted 59 characters in body
Apr
7
asked approximate measurable function by continuous ones
Apr
7
asked Approximating measurable function by continuous ones
Mar
13
awarded  Yearling
Feb
12
comment Topology on set of maps between manifolds
@Sigur thanks, man