If you are from Central/Western Europe you might want to consider to take a train to Heidelberg Hbf.
Frankfurt Airport is close, so having landed there you can take a high-speed train to Mannheim Hbf and from there a local train to Heidelberg. This will take you 60 to 90 minutes.
From Heidelberg Hbf you can take tram 24 to Technologiepark. From there it is just a 100m walk to the math department.