9. Large N Expansion as a String Theory, Part II

MIT 8.821 String Theory and Holographic Duality, Fall 2014
View the complete course: ocw.mit.edu/8-8...
Instructor: Hong Liu
In this lecture, Prof. Liu wraps up the mathematical connection between 1/N expansion of a large N matrix field theory with the perturbative expansion of a string theory. The second half of this lecture is an introduction to string theory.
License: Creative Commons BY-NC-SA
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[@peterpalumbo1963]

What about naked singularities and compactified Calaba-Yah spaces? How would they be brought into this matrix quantum mechanics.

[@mavzolej]

Why are we so afraid of the appearance of massless spin-2 paticles in 3+1 theory? Yes. QCD does not contain them. But the gravity in 4d does - so maybe it's even good that the string theory with 4 compact dimensions gives gravitons?

[@sb5403]

That is precisely why people do string theory, but if your goal is to find a description of QCD, you should deal with the graviton in some way, since QCD does not have it.

[@peterpalumbo1963]

You say string theory is only consistent in 10 or 26 dim, this may be true but what about 11 supergravity and 12 technicolor. As to 26 dimension why not 27 which would be a Majorana/gravity dim and 28 which could be a transition phase where a boson gains weight, maybe by the higgs mechanism and becomes a fermion.

[@sb5403]

The spacetime dimension of theories that have a well-defined perturbative expansion in terms of strings is always confined to be 26 or 10, depending on whether the strings are bosonic or super. Uncompactified 11-dimensional M-theory has no such perturbative expansion.