As an act of faith--one hopes rewarded--this collection of short stories is to be published simultaneously with Ann Beattie's Chilly Scenes of Winter. The temperature's the same--"It's hard to imagine that somewhere in the world it's warm today"--and a number of the pieces deal with similar unattached young people in dissolving relationships. Many of them seem to lounge through life, free or rather trapped, thinking of something they might do--perhaps write a letter to Nixon. Often they don't get around to it. Their existence is as much of a random option as the offhand way in which Miss Beattie uses interstices of experiences--cf. "Gaps," a clever story, a terrible one. Or the impermanence of Michael in "Fancy Flights," Michael who's lost his job and his wife and now his plant. There's the trivial adultery of "Parking Lot," but toward the end death takes over decisively whether by accident in "The Lifeguard" or by design with an old woman who anticipates its too slow course in "Victor Blue." Strangely enough, "Downhill," in spite of the title, is one of the few stories to reverse the direction and the general tenor of the book. This is a talented writer and she achieves a lien on life through almost imperceptible moments, identifiably true and very mortal. "We wave, they disappear. That was easy." Was it?