1,591 research outputs found
The Effective Potential, the Renormalisation Group and Vacuum Stability
We review the calculation of the the effective potential with particular
emphasis on cases when the tree potential or the
renormalisation-group-improved, radiatively corrected potential exhibits
non-convex behaviour. We illustrate this in a simple Yukawa model which
exhibits a novel kind of dimensional transmutation. We also review briefly
earlier work on the Standard Model. We conclude that, despite some recent
claims to the contrary, it can be possible to infer reliably that the tree
vacuum does not represent the true ground state of the theory.Comment: 23 pages; 5 figures; v2 includes minor changes in text and additional
reference
Abelian Gauge Theory in de Sitter Space
Quantization of spinor and vector free fields in 4-dimensional de Sitter
space-time, in the ambient space notation, has been studied in the previous
works. Various two-points functions for the above fields are presented in this
paper. The interaction between the spinor field and the vector field is then
studied by the abelian gauge theory. The U(1) gauge invariant spinor field
equation is obtained in a coordinate independent way notation and their
corresponding conserved currents are computed. The solution of the field
equation is obtained by use of the perturbation method in terms of the Green's
function. The null curvature limit is discussed in the final stage.Comment: 10 pages, typos corrected, reference adde
de Sitter Vacua, Renormalization and Locality
We analyze the renormalization properties of quantum field theories in de
Sitter space and show that only two of the maximally invariant vacuum states of
free fields lead to consistent perturbation expansions. One is the Euclidean
vacuum, and the other can be viewed as an analytic continuation of Euclidean
functional integrals on . The corresponding Lorentzian manifold is the
future half of global de Sitter space with boundary conditions on fields at the
origin of time. We argue that the perturbation series in this case has
divergences at the origin, which render the future evolution of the system
indeterminate without a better understanding of high energy physics.Comment: JHEP Latex, 13 pages, v2. references adde
Off-Forward Parton Distributions in 1+1 Dimensional QCD
We use two-dimensional QCD as a toy laboratory to study off-forward parton
distributions (OFPDs) in a covariant field theory. Exact expressions (to
leading order in ) are presented for OFPDs in this model and are
evaluated for some specific numerical examples. Special emphasis is put on
comparing the and regimes as well as on analyzing the
implications for the light-cone description of form factors.Comment: Revtex, 6 pages, 4 figure
Supergrassmannian and large N limit of quantum field theory with bosons and fermions
We study a large N_{c} limit of a two-dimensional Yang-Mills theory coupled
to bosons and fermions in the fundamental representation. Extending an approach
due to Rajeev we show that the limiting theory can be described as a classical
Hamiltonian system whose phase space is an infinite-dimensional
supergrassmannian. The linear approximation to the equations of motion and the
constraint yields the 't Hooft equations for the mesonic spectrum. Two other
approximation schemes to the exact equations are discussed.Comment: 24 pages, Latex; v.3 appendix added, typos corrected, to appear in
JM
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