Timeline for Positive inuequality of Laplacian with a variable coefficient [closed]

11 events

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May 26, 2014 at 20:53	comment	added	username		It's a question of notations. If $\partial_x^2 a =(\partial_x a)^2$ my counter example works. If $\partial_x^2 a = \partial_{xx} a$ the answer below gives the counter example.
May 26, 2014 at 0:30	review	Reopen votes
May 26, 2014 at 9:30
May 26, 2014 at 0:14	comment	added	Wang Ming		Thanks for your answer. For your example, the right hand side is 0, which does not give a contradiction.
May 26, 2014 at 0:13	history	edited	Wang Ming	CC BY-SA 3.0	added 10 characters in body
May 25, 2014 at 9:38	history	closed	José Figueroa-O'Farrill Stefan Kohl♦ Chris Godsil Ben Webster♦		Not suitable for this site
May 24, 2014 at 22:16	comment	added	username		counterexample: $\phi(x)=\cos(x)$ $a(x)= 2+\sin(Nx)$ gives $$ 2\pi > N^2\frac{\pi}{2}.$$
May 24, 2014 at 19:15	review	Close votes
May 25, 2014 at 9:38
May 24, 2014 at 18:56	comment	added	José Figueroa-O'Farrill		This reads like homework. Voted to close.
May 24, 2014 at 9:35	answer	added	marcoromito		timeline score: 2
May 24, 2014 at 3:29	history	edited	Wang Ming	CC BY-SA 3.0	added 15 characters in body
May 24, 2014 at 2:59	history	asked	Wang Ming	CC BY-SA 3.0