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 Apr 15 comment Why do we assume local conformal transformations are symmetries in 2D CFT I'm also a little bit puzzled by: "the broken generators in this case cannot be unitarily implemented because they drive the vacuum outside the quantum Hilbert space." To my (probably wrong) understanding I thought that $\rho(L_n)|0>$ is either $0$ (for $n>-2$) or a new state in the Hilbert space. How plays this into the discussion? (Of course if this question is too long to answer, I'm happy to ask a separate stackexchange question) Apr 14 comment Why do we assume local conformal transformations are symmetries in 2D CFT Do I understand the logic of your first paragraph right? Suppose we want all $L_n$ to be symmetries. This means for all $n$ the vacuum is invariant: $\rho(L_n) |0>=0$ for all $n$. On the other hand the representation of a center is always proportional to the unity $\rho(Z)=c \times 1$. Now $[\rho(L_n),\rho(L_{-n})]|0>=0|0>=2n \rho(L_{0})|0>+c \times 1|0>=c \times 1|0>$ so we have $0=c \times 1|0>$ eventhough we assmumed $c \neq 0$. So the full Virasoro algebra can not be implemented at quantum level as a symmetry of the vacuum. Oct 27 revised Why do rainbows have distinct colors? Link fixed Sep 16 answered Review of Higher Spin Theory May 1 answered Any tips on evaluating Riemann tensor? Apr 22 comment Equivalence between Chern-Simons action and first order formalism I think you could figure out the answer by looking at physics.stackexchange.com/q/119953 Oct 11 asked CFT calculation of the Partitionfunction of $2+1$ dimensional gravity Jul 11 awarded Yearling Apr 4 comment Connection beween infinite gauge symmetries and UV finiteness 1.) One of the problems with the SUSY argument is, that Vasiliev theory is not supersymmetric and so it does not apply. 2.) I'm not sure if I understand you but let me rephrase your second statement to see if i maybe do: It is usually hard to find the right counterterm (of the many possible ones) and symmetries help (since they restict the possiblities of possible counterterms) to find the right one which finall helps to renormalize the theory. Apr 3 comment Connection beween infinite gauge symmetries and UV finiteness Thank you for the answer. So there seems to be a connection between more gauge symmetries and better quantum properties. Could you maybe explain (or be more explicit) about the systematics of that claim. There might be some (general) arguments for that claim? Apr 3 asked Connection beween infinite gauge symmetries and UV finiteness Mar 4 comment Regarding the possibility of Closed Timelike Curves @Danu Yes. So AdS in physics is usually a universal cover of the real AdS Mar 4 comment Regarding the possibility of Closed Timelike Curves @Danu When you connect two sides of a piece of paper (which is "real" Ads) you are able to go around it in circles (timelike closed curves). Since we do not want that we flatten the paper out again (i.e., we disconnect the two sides). Mar 3 comment Regarding the possibility of Closed Timelike Curves @Danu What physicists usually mean by AdS is the universal cover of AdS. Feb 21 awarded Enlightened Feb 21 awarded Nice Answer Jan 30 comment Asymptotic Symmetry Group of General Relativity @dingo_d From a pure GR point of view I think this is a standard reference home.uchicago.edu/~geroch/P464/AsympStr.pdf Nov 23 answered Peskin and Schroeder Equation 3.23 Nov 1 comment What is the CFT dual to pure gravity on AdS$_3$? Be aware that i could easily be not be up to date. So take that with a grain of salt. Hopefully a more knowledgeable user will add something. Nov 1 answered What is the CFT dual to pure gravity on AdS$_3$?