Answer:
Either way would probably be accepted. The "rules" state you must capitalize all parts of a "proper" noun, such as 'Golden Gate Bridge.' Problem is, there is no formal rule on whether a scientific theory is a "proper" noun, particularly when there is no name attached to it. For example, "Maxwell's Equations" would always be capitalized, while "quantum mechanics" is usually un-capitalized.
I searched half a dozen sites for an answer to this but found no clue about a rule. So go either way that makes you happy, but (most of all) be consistent.