Will it hurt my chances if I apply undecided major to Brown University?
Nope.
I’ll second bruno14. Makes no difference.
I’ll third. Usually about 15% of those admitted apply as undecideds.
Some other posters have claimed Brown looks for applicants who would be able to navigate the open curriculum though. Wouldn’t applying as undecided or with two wildly different concentration choices tell the school you may have difficulty with that?
There’s a difference between “undecided” and “no direction”