The posters, seen around campus, called student activist Emma Sulkowicz a "pretty little liar."
The investigation will probe whether Columbia and Barnard mishandled sexual assault cases on campus.
Students gave Columbia President Lee Bollinger a mattress that looked like a mock check for $471.
Protesters demanded President Lee Bollinger change the university's sexual assault policies.
The university released a long-awaited report on campus sex assaults in the face of growing criticism.
A student activist will carry a mattress with her everywhere until her rapist is removed from campus.
The new policy focuses on changes to the hearing process, but students said it doesn't go far enough.
Capt. Keith Robinson flew halfway around the world to see his daughter graduate from Columbia.
Columbia is also adding another rape crisis center amid criticism over its handling of sexual assaults.
The building will be on Haven Avenue, with a view of the Hudson River.
Critics say Columbia hasn't hired enough African-American architects for its Manhattanville expansion.
Teachers College Community School will serve students in grades K-8 in West Harlem.
The city awarded Columbia $15 million to help it build a new engineering school.
Inwood residents want to know why Columbia has not broken ground on a promised public waterfront.
Columbia University president Lee Bollinger threw his support behind NYU's expansion plan.
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