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Dec 4, 2016 at 21:17 answer added Raziel timeline score: 2
Dec 17, 2011 at 14:16 history edited Daniel Tausk CC BY-SA 3.0
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Dec 17, 2011 at 14:05 vote accept Daniel Tausk
Dec 15, 2011 at 6:00 answer added Terry Tao timeline score: 10
Nov 24, 2010 at 4:15 comment added Daniel Tausk Correcting small imprecision of my previous comment: if $L$ is first-order (symmetric) then $L=-i\big(X+\frac12\mathrm{div}(X)\big)+V$, with $V$ the multiplication operator by a smooth real-valued function. Since $V$ is bounded self-adjoint, the conclusion is the same...
Nov 23, 2010 at 19:33 comment added Daniel Tausk ($F_t$ denotes the flow of $X$).
Nov 23, 2010 at 19:33 comment added Daniel Tausk By the way, the answer is also affirmative if $L$ is first-order. In that case, $L=-i\big(X+\frac12\mathrm{div}(X)\big)$, with $X$ a smooth vector field in $M$. Since $M$ is compact, $X$ is complete and we obtain $L$ as the generator of a one-parameter unitary group $U_t(f)=(f\circ F_t)\sqrt{\det\mathrm{d}F_t}$, which leaves $C^\infty(M)$ invariant. Thus $L$ is essentially self-adjoint on $C^\infty(M)$.
Nov 23, 2010 at 18:12 history edited Daniel Tausk CC BY-SA 2.5
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Nov 23, 2010 at 17:45 history asked Daniel Tausk CC BY-SA 2.5