“In the relatively short history of modern dance, an awkward chain of events has unfolded that goes something like this: a choreographer gets older, his dancers get younger and suddenly, plopped into the middle of a work, is a solo in which the aging choreographer tries to get his groove back. John Jasperse, 43, wants no part of it.” Which is why he’s created a work, premiering this week at Dance Theater Workshop, for himself and two 43-year-old colleagues.