Fixing the conformal window in QCD

Abstract

A physical characterization of Landau singularities is emphasized, which should trace the lower boundary N_f^* of the conformal window in QCD and supersymmetric QCD. A natural way to disentangle ``perturbative'' from ``non-perturbative'' contributions to amplitudes below N_f^* is suggested. Assuming an infrared fixed point persists in the perturbative part of the QCD coupling even below N_f^* leads to the condition γ(N_f^*)=1, where γis the critical exponent. Using the Banks-Zaks expansion, one gets 4<N_f^*<6. This result is incompatible with the existence of an analogue of Seiberg duality in QCD. The presence of a negative ultraviolet fixed point is required both in QCD and in supersymmetric QCD to preserve causality within the conformal window. Evidence for the existence of such a fixed point in QCD is provided.

10 pages, 1 figure, extended version of a talk given at the QCDNET2000 meeting, Paris, September 11-14 2000; main new material added is evidence for negative ultraviolet fixed point in QCD

References in corpus (6)

• Disentangling running coupling and conformal effects in QCD
• Constraints on ultraviolet-stable fixed points in supersymmetric gauge theories
• The Pinch Technique at Two Loops
• The pinch technique at two-loops: The case of mass-less Yang-Mills theories
• Conformal window and Landau singularities
• Computing the perturbative gluon condensate

Cited by in corpus (10)

• Light Composite Higgs from Higher Representations versus Electroweak Precision Measurements -- Predictions for LHC
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• Conformal Window of Gauge Theories with Four-Fermion Interactions and Ideal Walking
• Infrared Features of the Landau Gauge QCD
• Dynamical Stabilization of the Fermi Scale: Phase Diagram of Strongly Coupled Theories for (Minimal) Walking Technicolor and Unparticles
• Axial anomaly and the triality symmetry of octonion
• Phase Diagrams of Strongly Interacting Theories
• Computing the perturbative gluon condensate
• Infrared finite coupling in Sudakov resummation: the precise set-up