Incredulous

I was in Koffee today, and a math graduate student beside me peeked at my notes on Grothendieck groups, then commented that "I feel I should know you..."

After telling him I am a physicist (to which he replied, "That's why I don't know you"), and that Grothendieck groups are applied in condensed matter physics, he expressed his incredulity. "Grothendieck groups are as far away from physics as anything I know. This goes against everything I learnt."