Later he worked as a postdoctoral fellow at UCLA and UC Berkeley in the USA.
He was a research scientist at the INFN section in Pisa, Italy, in collaboration with CERN, where he over the years has spent several periods,[1] before joining NYU in 1992.
[2] Among other things, Porrati is known for his work on the large-distance modification of gravity and its application to the cosmological constant problem.
Porrati held the Marie Curie Chair (2005–2007) at the Theoretical Physics Group in the Scuola Normale Superiore di Pisa, Italy.
[3] Massimo was featured on a video produced by the Wired YouTube channel titled 'Theoretical Physicist Brian Greene Explains Time in 5 Levels of Difficulty', where Greene mentioned their collaboration on research.