Good old email remains the best way to contact me:
Normally, I reply within one workday. If I did not, please wait a couple of days before sending a gentle reminder.
Although I’m present in most major social networks, I tend to ignore any requests from people I have not contacted by other means.
If you want to meet in person at the ENS, you may find me in the Rataud building, office S15. Doing so without previous arrangement is useless.