Finite Temperature Effective Action Research Articles

Finite-temperature effective actions for gauge fields.

We consider the problem of computing the kinetic terms in the one-loop effective action. General results are presented for an expansion of the heat kernel of a second-order operator in powers of covariant derivatives. This is used to find the kinetic terms in the high temperature limit of the effective action up to the square of the gauge field strength.

Mass gap of the nonlinear-σ model through the finite-temperature effective action

The $O(3)$ nonlinear $\sigma$ model is studied in the disordered phase, using the techniques of the effective action and finite temperature field theory. The nonlinear constraint is implemented through a Lagrange multiplier. The finite temperature effective potential for this multiplier is calculated at one loop. The existence of a nontrivial minimum for this potential is the signal of a disordered phase in which the lowest excited state is a massive triplet. The mass gap is easily calculated as a function of temperature in dimensions 1, 2 and 3. In dimension 1, this gap is known as the Haldane gap, and its temperature dependence is compared with experimental results.

Finite-temperature effective action for composite operators in the O( N) scalar model

A modified version of the Cornwall-Jackiw-Tomboulis effective action for composite operators is extended at finite temperature in the imaginary-time formalism. As a test, the application to the O( N) scalar model in the N → ∞ limit is presented, showing that it reproduces the known results.