FLORENCE.- Italian researchers on Wednesday began looking for the remains of a Renaissance woman many believed posed for the “Mona Lisa.” The researchers used a geo-radar device to search for underground tombs in a Florence convent where Lisa Gherardini is believed to be buried. Tradition has long linked Gherardini, the wife of a rich silk merchant named Francesco del Giocondo, to Leonardo da Vinci’s painting, which is known in Italian as “La Gioconda” and in French as “La Joconde.” Giorgio Vasari, a 16th-century artist and biographer of Leonardo, wrote that Leonardo painted a portrait of del Giocondo’s wife. Gherardini is believed to have died in 1542 and have been buried in the Convent of St. Ursula in central Florence. The researchers will use the geo-radar until Friday, covering an