They can be mathematicians, or phycisist. Indeed INFJs are quite flexible in the abstract domain, being the most in between type when it comes to F/T.
I think the archetypical Ti heavy INFJ is a linguist with polymathic tendencies dabbling in anthropology and other fields to supplement. They are unable to operate effectively by zooming in and focusing on one subject alone, their Ni and Fe urging them to seek holistic understanding; they see most clearly when gazing on a panorama, not through the lenses of binoculars, Ni processing Se impressions and Fe urging them to serve humankind as a whole. This is true even in a Ti focused INFJ, look at people like Chomsky and Jung. They need their broad knowledge to propagate effectively.
If you take pathologically Ti heavy INFJs things change a bit. Wittgenstein being a good example of an Ni/Ti looper. Such INFJs may desperately attempt to find the one and only truth or just ideal. Hitler may have been one as well, though he certainly used Fe instrumentally his thoughts were circular. These INFJs are typically not in a good mental state, they may be antisocial, schizo's to some degree, or suffer some form of autism. Autism+Inferior Se can be hell for the sufferer.
