This question is unsourced and hence may be wiped out as hearsay, but perhaps some kind person might answer anyway. I remember (but cannot find the original source) that I once read a speculation that a "particle with negative energy" (not referring to anti-matter, but some sort of exotic matter) might result if one shot an ordinary particle through a region of negative energy (such as between the plates in the Casimir effect). This sounds off the wall to me, but does it have any sense whatsoever? [The idea of the speculation was to try to figure out how, if wormholes exist, negative energy might be fed to them to prolong their lifetime. Speculation cubed, as it were.] Thanks.