1. North Carolina State UniversityDepartment of Mathematics Box 8205 Raleigh NC 27695 USA
2. CUNY Queens CollegeDepartment of Mathematics 65‐30 Kissena Blvd., Queens NY 11367 USA
3. CUNY Graduate CenterPh.D. Programs in Mathematics and Computer Science 365 Fifth Avenue New York NY 10016 USA
4. National Research UniversityHigher School of Economics, Department of Computer Science 11 Pokrovsky blvd Moscow 109028 Russia
5. LIX, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris 1 rue d'Estiennes d'Orves Palaiseau 91120 France
6. Courant Institute 251 Mercer Street New York NY 10012 USA