Browsing by Author "Hajj, George Antoine"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Nonperturbative studies of scalar and scalar-fermion quantum field theories at zero and finite temperature using the Gaussian effective potential
    (1988) Hajj, George Antoine; Stevenson, Paul M.
    The Gaussian effective potential (GEP), a non-perturbative approach to study quantum field theory, is applied to scalar and scalar-fermion models. We study the scalar $\phi\sp6$ field coupled to fermions through g$\sb{\rm B}\phi\overline{\psi}\psi$ or g$\sb{\rm B}\phi\sp2\overline{\psi}\psi$ in 2 and 3 space-time dimensions. In addition, we derive the finite temperature (T $>$ 0) GEP from first principles and apply it to study these models at T $>$ 0. Also the Autonomous $\lambda\phi\sp4$, coupled to fermions through a Yukawa term (g$\sb{\rm B}\phi\overline{\psi}\psi$), is examined in 4 dimensions at T $>$ 0. In all these models, in order to obtain stable theories, it is found that g$\sb{\rm B}$ must vanish as 1/log(M$\sb{\rm uv}$), 1/M$\sb{\rm uv}$ or 1/M$\sbsp{\rm uv}{2}$ in 2, 3 or 4 dimensions respectively, M$\sb{\rm uv}$ being an ultraviolet cutoff which is sent to infinity. The contribution of fermions to the GEP, however, is nonvanishing. It is also found that for the class of theories discussed, symmetry, if broken, is restored above a critical temperature. The coupling constant parameter space for each model is studied carefully, and regions where symmetry breaking occurs are determined both at zero and finite temperature.