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Jul 13, 2021 at 11:25 vote accept Ali
Jul 13, 2021 at 2:52 answer added Willie Wong timeline score: 4
Jul 13, 2021 at 0:56 comment added Ali The question can also be posed in Lorentzian setup but I stated it in Riemannian setting for simplicity.
Jul 13, 2021 at 0:55 comment added Ali $Z$ can be thought of as a vector field on $M$ that when restricted to $\Sigma$, is tangent to $\Sigma$. By the restriction of $D_{\nabla \phi}\nabla \phi$ to $\Sigma$ I mean the restriction, so the equation should be considered on $\Sigma$ only.
Jul 13, 2021 at 0:28 comment added Willie Wong Additionally, when $Z$ is said to be a smooth vector field on $\Sigma$, do you mean $Z$ is tangent to $\Sigma$, or a vector field of $M$ restricted to $\Sigma$? And when you say "restriction of $D_{\nabla \phi} \nabla \phi$ to $\Sigma$" do you mean the projection, to $T\Sigma$ or just the restriction?
Jul 13, 2021 at 0:26 comment added Willie Wong Why is this question tagged with lorentzian and semi-riemannian geometry? All the objects in sight seems to be Riemannian. Is there some connection to semi-Riemannian stuff? If so, can you make it explicit?
Jul 12, 2021 at 20:18 comment added Ali Indeed $f$ is redundant :)
Jul 12, 2021 at 20:13 comment added Leo Moos The Whitney extension theorem could be relevant. (Also, do you need $f$ at all?)
Jul 12, 2021 at 19:23 history asked Ali CC BY-SA 4.0