French investigators are studying accusations that Dominique Strauss-Kahn may have been involved in a rape during a sex party in a Washington hotel in 2010 while he was chief of the International Monetary Fund, a judicial official said Friday. Strauss-Kahn, via his lawyers, denied any violence and said he’s the subject of a public “lynching campaign.’’ The prominent economist, once a top contender for France’s presidency, has seen his career and reputation crumble since he was accused of sexual assault in a New York hotel a year ago.