v0.2:

  * Changed: more precise statement of the bound on the large x decay of u (Theorem 1.2)

  * Added: more details in the proof of the large x decay of u (Theorem 1.2)

  * Fixed: miscellaneous typos.


v0.1:

  * Added: references to [Nelson, 1964] and [Reed, Simon, 1975].

  * Fixed: sign of Laplacian in definition of \mathfrak K_e.

  * Added: references to proofs in introduction.

  * Fixed: miscellaneous typos.