Here’s the abstract to their paper, “Evaluating Donald Trump’s Allegations of Voter Fraud in the 2016 Presidential Election”:

During the 2016 presidential campaign, Donald Trump repeatedly claimed that the presidential election would be tainted by massive voter fraud. Despite winning the presidency, Trump has maintained that position through November. We suspected prior to the election that fraud allegations might dominate the post-election political landscape, and to this end we initiated a research project with the objective of evaluating the relationship between election returns and potential sources of fraud in the vein of Trump’s claims. Our research focuses on non-citizen populations, deceased individuals, the timing of results, and voting technology, and we do not uncover any evidence consistent with Trump’s assertions about widespread voter fraud. Moreover, we do not observe any striking abnormalities in two sets of states recently highlighted as potentially problematic: Michigan, Pennsylvania, and Wisconsin (the subject of ongoing recount efforts) and California, New Hampshire, and Virginia (three states cited personally by Trump). Our results do not imply that there was no fraud at all in the 2016 presidential contest, nor do they imply that this contest was error-free. They do strongly suggest, however, that the voter fraud concerns fomented and espoused by the Trump campaign are not grounded in any observable features of the 2016 presidential election.