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.