When battling Labor Day traffic, an irritated motorist might respond with the sort of language that comic strips represent by a string of symbols. For Benjamin Seibold, assistant professor of mathematics at Temple, traffic evokes different kinds of symbols: Greek letters and differential equations. Seibold studies "phantom" traffic jams — those aggravating road delays that occur for no apparent cause other than high volume. Seibold and his colleagues gained notice last year when they reported that, mathematically speaking, these waves of slowing traffic behave like shock waves from an explosion.