I am very grateful of founding this website.

Actually this question is not related to this lecture, I would like to you personally you think what is the best approach for proving backward uniqueness of ricci flow? ]]>

It does seem that there are many different proofs of this result; I’ll ask Peter tomorrow what his favourite one is. :)

]]>although he doesn’t seem to state this explicitly. However, indeed he makes no use of that in proving Klingenberg’s lemma 5.9.16, so they are really independent ways of seeing that the injectivity radius is less than or equal to the conjugate radius. The second variation formula, however, is due to Synge. ]]>

http://arxiv.org/abs/0802.2408

and Section 8 of

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