Hundreds of Princetonians — including undergraduate and graduate students, the Tiger mascot, members of the band, faculty members, public-safety officers, and President Tilghman — make brief appearances in a video as they form the shape of a heart with their fingers. The simple message? We love Princeton. “I <3 Princeton,” produced by the University’s communications office, has been viewed more than 34,000 times on YouTube and social-media sites.