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  • If two probability distributions (on the same measure space) are s.t they have p.d.fs and the $L^1$ distance between the p.d.f.s is large, then is there a choice of a ``nice" metric $d_{\rm smooth}$ and a positive integer $p$ s.t the two distributions are far in the Wasserstein $p-$norm in $d_{\rm smooth}$?

    If we use the trivial metric $d(x,y) = {\bf 1}(x \neq y)$ then the ${\rm W}_{1,d} = 0.5 {\rm TV}$ and TV is the $L^1$ distance between the p.d.fs when they exist. But suppose that I want to use a smoother metric than this.

  • Secondly if two probability distributions are such that their inverse CDFs are close (say in the sup norm) then are the two distributions close in some Wasserstein norm?

    Note that one can create examples where the two inverse CDFs are close in the sup norm but their TV distance is large hence their $1-$Wasserstein norm in the trivial metric is large.

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  • $\begingroup$ At least in the one-dimensional case the Lp distance between quantile functions happens to be exactely the Wasserstein-p metirc for the corresponding measures. $\endgroup$
    – Tobsn
    Commented May 5, 2020 at 10:56
  • $\begingroup$ Any reference you could give for this? $\endgroup$ Commented May 5, 2020 at 18:20
  • $\begingroup$ It's a fairly standard result which you will find in every book on optimal transport, e.g. Santambrogio "Optimal Transport for Applied Mathematicians" just to name one. $\endgroup$
    – Tobsn
    Commented May 6, 2020 at 8:22
  • $\begingroup$ Not really standard to beginners in the field :D Can you kindly point to the theorem number? $\endgroup$ Commented May 7, 2020 at 16:34

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