I work in quantum field theory in curved spacetime. Within QFTCS, we have a bunch of phenomena showing that the notion of "particle" is quite subtle. For example, the Unruh effect let's us know that the notion of particle is actually observer-dependent. As a consequence, I tend to be quite skeptic about fundamental theories that rely too much on the notion of particle.

While I am far from being an expert in string theory, the things I've heard about it make me feel as if that is precisely what string theory does: to take the notion of particle seriously and change it into a quantum string, which would then be able to solve numerous problem within quantum field theory and quantum gravity.

I have also heard one or two words about "string field theory", which appears to be a quantum field theory with infinitely many fields. The name, of course, also suggests it is somehow related to string theory.

With this in mind, my question is:

QFT is a theory about fields, in which particles sometimes appear as cute interpretations. Does the same thing happen in string theory? How exactly (to the best possible presentation for someone who knows nearly nothing about string theory)? Has string theory (or string field theory, or any other similar idea) successfully derived the Unruh effect or is it only "likely to be there" based on being a generalization of QFT?



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