Double scaling limit of a broken symmetry quantum field theory

Jul, 2000
27 pages
Published in:
  • J.Math.Phys. 42 (2001) 1960-1973
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Abstract:
The Ising limit of a conventional Hermitian parity-symmetric scalar quantum field theory is a correlated limit in which two bare Lagrangian parameters, the coupling constant gg and the {\it negative} mass squared m2-m^2, both approach infinity with the ratio m2/g=α>0-m^2/g=\alpha>0 held fixed. In this limit the renormalized mass of the asymptotic theory is finite. Moreover, the limiting theory exhibits universal properties. For a non-Hermitian PT\cal PT-symmetric Lagrangian lacking parity symmetry, whose interaction term has the form g(iϕ)N/N-g(i\phi)^N/N, the renormalized mass diverges in this correlated limit. Nevertheless, the asymptotic theory still has interesting properties. For example, the one-point Green's function approaches the value iα1/(N2)-i\alpha^{1/(N-2)} independently of the space-time dimension DD for D<2D<2. Moreover, while the Ising limit of a parity-symmetric quantum field theory is dominated by a dilute instanton gas, the corresponding correlated limit of a PT\cal PT-symmetric quantum field theory without parity symmetry is dominated by a constant-field configuration with corrections determined by a weak-coupling expansion in which the expansion parameter (the amplitude of the vertices of the graphs in this expansion) is proportional to an inverse power of gg. We thus observe a weak-coupling/strong-coupling duality in that while the Ising limit is a strong-coupling limit of the quantum field theory, the expansion about this limit takes the form of a conventional weak-coupling expansion. A possible generalization of the Ising limit to dimensions D<4D<4 is briefly discussed.
Note:
  • 27 pages, 2 figures
  • field theory: scalar
  • field theory: Euclidean
  • any-dimensional
  • spontaneous symmetry breaking
  • effective action: expansion
  • scaling
  • correlation function
  • Schroedinger equation
  • Ising model
  • parity: invariance