John Silbersack, noted science fiction editor at Penguin and Warner, and most recently head of the HarperEntertainment and HarperPrism imprints, is joining the Trident Media Group as a senior vice-president to bring new projects and authors to the year-old agency.... Pocket Books' Luke Dempsey, with the keen support of president Judith Curr, herself a keen golfer, has bought a new illustrated guide to the rules of the game by golf legend Arnold Palmer; he bought world rights, and the hardcover book will be published next February....Two recent sales by agent Andrew Blauner are of a first novel about time travel, Tunneling, by Beth Bosworth, sold to Crown's Shaye Areheart for her imprint there, and The Candle Café Cookbook by Joy Pierson and Bart Potenza, who run this highly successful vegetarian restaurant on New York's Upper East Side; Margot Schupf at Clarkson Potter preempted for world rights.