{ "id": "1302.6374", "version": "v4", "published": "2013-02-26T09:53:15.000Z", "updated": "2014-05-20T13:43:05.000Z", "title": "On strongly indefinite systems involving the fractional Laplacian", "authors": [ "Woocheol Choi" ], "comment": "23 pages. The previous version had been written for the square root of Laplacian. We revised it with generalizsing the results for $(-Delta)_s$, $0