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4
votes
3answers
244 views

What is meant by “non-perturbative” string theory?

I often hear people talk about finding a non-perturbative formulation of string theory. What does this mean exactly? To my knowledge string theory is a perturbative method. Just like Feynman graphs ...
4
votes
2answers
524 views

Meaning of perturbative and non-perturbative renormalizability

What is meant by a theory to be (1) perturbatively renormalizable, (2) perturbatively non-renormalizable, (3) non-perturbatively renormalizable, and non-perturbatively non-renormalizable? In each case,...
0
votes
1answer
312 views

Is the non-perturbative approach to QFT a path integral approach? If so then how, given we don't have simple path integral formula for Dirac equation?

Here is my understanding of the scenario. Please correct me if i go wrong somewhere. Initially, the perturbative approach to QED (Feynman diagrams​) was very successful. But the same approach to QCD ...
2
votes
1answer
463 views

complicated QCD Color factor formula?

I was doing higher order calculations for purely gluonic system and came across complicated color factors like the product of six structure constants product $f_{a_1a_2a_3}f_{a_4a_2a_7}f_{a_7a_8a_1}f_{...
14
votes
2answers
811 views

Non-Perturbative Feynman diagrams?

The Wikipedia page for Feynman Diagrams claims that Thinking of Feynman diagrams as a perturbation series, nonperturbative effects like tunnelling do not show up, because any effect that goes to ...