The student filed a report with Chicago police on April 27, 2013, in connection with the alleged February 2012 incident, but apparently did not pursue criminal charges, a police department source said.
The Inquirer does not identify victims of sex crimes and is withholding the student's name.
A Rutgers spokesman would not discuss a report that the university had already made an offer to Ludlow and he had accepted.
In November, a philosophy and academia blog, Leiter Reports, announced that Ludlow "has accepted a senior offer from the department of philosophy at Rutgers University, New Brunswick, where he will also . . . serve as director of the Rutgers Center for Cognitive Science."
Ludlow was a visiting professor at that center in the fall of 2012, according to his website.
Brian Leiter, a professor at the University of Chicago's law school who teaches philosophy and the author of the blog, said Thursday that he had spoken with Ludlow at the time and Ludlow said he had accepted a Rutgers offer.
Rutgers had for months been considering Ludlow, whose work focuses on language and cognitive science. During that process, the school said, it was not told of the alleged incident or Northwestern's subsequent investigation. The accusation became public Monday with the filing of the civil lawsuit.
"This was not brought to our attention by either the candidate or his employer," Rutgers spokesman Greg Trevor said in a statement Thursday. "We are looking into this matter thoroughly, including requesting all relevant information to fully evaluate his candidacy."
Ludlow could not be reached. The Chicago law firm that represents him declined to comment Thursday, citing the privacy of both parties.
The lawsuit accuses Ludlow of harassing her sexually after taking her to an art event in Chicago. That night, according to the suit, Ludlow repeatedly ordered alcoholic drinks for the underage student, who said she did not want to drink. The student first met the professor when she took one of his courses in 2011.
After making sexual comments throughout the night, the suit says, Ludlow took her to his apartment and made unwanted advances, including kissing and groping her. At one point, according to the suit, the student awoke to find him sleeping with his arms around her.
Ludlow brought the student back to the campus in nearby Evanston the next day, the suit says. The student reported the incident to a faculty member the following day.
She was hospitalized after attempting suicide and was found to have post-traumatic stress disorder, the suit says.
It says Northwestern's investigation found that Ludlow "engaged in unwelcome and inappropriate sexual advances." It quotes an e-mail from Joan Slavin, Northwestern's director of sexual harassment prevention: "You . . . were incapacitated due to heavy consumption of alcohol purchased for you by respondent [Ludlow], and were therefore unable to offer meaningful consent to this physical touching that night."
But, the suit says, attempts by the student to find out what penalty was meted out to Ludlow went unanswered, with the university saying it was a personnel issue.
Ludlow continued to teach, and the student encountered him on campus, causing panic attacks "so severe that [she] could not even leave her house."
A spokesman for Northwestern confirmed that Ludlow was teaching this semester. The school will respond to the allegations "in federal court, where they were made," the spokesman said.
The student asks for a jury trial and seeks compensation, for medical bills, attorney's fees and other items, as well as punitive damages.