# qft

1. ### QFT T-duality, Massless vector states

1. The problem statement, all variables and given/known data Part C) Please on first attachment 2. Relevant equations above,below 3. The attempt at a solution so I think I understand the background of these expressions well enough, very briefly, changing the manifold from $R^n$...
2. ### QFT T-duality, Massless vector states

1. The problem statement, all variables and given/known data Part C) Please: (attachment 1) 2. Relevant equations above,below 3. The attempt at a solution so I think I understand the background of these expressions well enough, very briefly, changing the manifold from $R^n$...
3. ### Why we can't build a QFT of gravity?

Why we can not consider the Einstein's equation as a motion equation of gravitation field in flat spacetime background.If we can,we would be able to construct a quantum field theory of gravity with the Lagrangian deduced from the Einstein's equation and the functional integral formalism.
4. ### A question in QFT of Weinberg.

The Goldstone's theorem was demonstrated base on the breaking of global symmetry of Lagrangian of scalar fields.Then why we know the existence of Goldstone bosons in fermion sector where the breaking symmetry happend for Lagrangian of fermion field?Example why we know the existence of pion when...
5. ### A question about effective action in QFT?

They say that for constant fields the effective potential in the tree approximately is given simply by minus the non-derivative terms in the Lagrangian density.I do not understand why the derivative terms are ''kinematic energy'' so that the potential equalling minimum expectation energy must...