2019-present. Assistant Professor. Texas State University.
2019. Associate Professor. University of Massachusetts, Amherst. (On leave)
2014-2019. Assistant Professor. University of Massachusetts, Amherst.
2011-2014. E.R. Hedrick Assistant Professor. University of California, Los Angeles
Spring 2011. Postdoctoral Fellow. Mathematics Research Institute, Berkeley.
Winter 2009. Visiting Scholar. Institute for Advanced Study, Princeton.

2006-2011 University of Texas at Austin. Ph.D. Advisor: Luis Caffarelli.
2001-2006 Universidad Simon Bolivar. Licenciatura en Matematicas. Mentor: Lazaro Recht.

PhD Students
Rene Cabrera (University of Massachusetts, Amherst). Graduating May '22.

Awards and Fellowships
National Science Foundartion Collaborative Research Grant DMS-1700307.
National Science Foundation Research Grant DMS-1201413.
Fall 2014. Visiting Researcher at the Fields Institute.

Selected publications
Guillen, N. and Kitagawa, J., Pointwise estimates and regularity in geometric optics and other Generated Jacobian Equations.
Communications on Pure and Applied Mathematics 70.6 (2017): 1146-1220.

Gualdani, M. and Guillen, N., Estimates for radial solutions of the homogeneous Landau equation with Coulomb potential.
Analysis & PDE 9.8 (2016): 1773-1810.

Guillen, N. and Schwab, R.W., 2012. Aleksandrov-Bakelman-Pucci type estimates for integro-differential equations.
Archive for Rational Mechanics and Analysis 206.1 (2012): 111-157.

Invited talks
Recent trends on elliptic nonlocal equations. Fields Institute. Toronto, June 2016.
3rd Conference on Nonlocal Operators and Partial Differential Equations. Banach Center. Będlewo, June 2016.
Nonlocal PDEs Workshop. IPAM. Los Angeles, February 2012.

Coorganizer (with Jun Kitagawa and Robert McCann) of workshop "Generated Jacobian Equations: from Geometric Optics to Economics", at Banff International Research Station, April 2017.
Coorganizer (with Russell Schwab) "Non-local equations: perspectives from Probability and PDEs" session at SIAM PDE 2011
Coorganizer (with Dima Shlyakhtenko and Christoph Thiele) of Optimal Transport School at Lake Arrowhead, October 2013.
Coorganizer (with Luis Caffarelli) "Topics in fractional and geometric PDE" session at SIAM PDE 2009.