3,858 research outputs found
On the Transition from Confinement to Screening in QCD_{1+1} Coupled to Adjoint Fermions at Finite N
We consider SU(N) QCD_{1+1} coupled to massless adjoint Majorana fermions,
where N is finite but arbitrary. We examine the spectrum for various values of
N, paying particular attention to the formation of multi-particle states, which
were recently identified by Gross, Hashimoto and Klebanov in the N -> infinity
limit of the theory. It is believed that in the limit of vanishing fermion
mass, there is a transition from confinement to screening in which string-like
states made out of adjoint fermion bits dissociate into stable constituent
``single particles''. In this work, we provide numerical evidence that such a
transition into stable constituent particles occurs not only at large N, but
for any finite value of N. In addition, we discuss certain issues concerning
the ``topological'' properties exhibited by the DLCQ spectrum.Comment: 14 pages, Late
Quantum Chromodynamics and Other Field Theories on the Light Cone
We discuss the light-cone quantization of gauge theories as a calculational
tool for representing hadrons as QCD bound-states of relativistic quarks and
gluons, and also as a novel method for simulating quantum field theory on a
computer. The light-cone Fock state expansion of wavefunctions provides a
precise definition of the parton model and a general calculus for hadronic
matrix elements. We present several new applications of light-cone Fock
methods, including calculations of exclusive weak decays of heavy hadrons, and
intrinsic heavy-quark contributions to structure functions. Discretized
light-cone quantization, is outlined and applied to several gauge theories. We
also discuss the construction of the light-cone Fock basis, the structure of
the light-cone vacuum, and outline the renormalization techniques required for
solving gauge theories within the Hamiltonian formalism on the light cone.Comment: 206 pages Latex, figures included, Submitted to Physics Report
Anomalously light mesons in a (1+1)-dimensional supersymmetric theory with fundamental matter
We consider N=1 supersymmetric Yang-Mills theory with fundamental matter in
the large-N_c approximation in 1+1 dimensions. We add a Chern-Simons term to
give the adjoint partons a mass and solve for the meson bound states. Here
mesons are color-singlet states with two partons in the fundamental
representation but are not necessarily bosons. We find that this theory has
anomalously light meson bound states at intermediate and strong coupling. We
also examine the structure functions for these states and find that they prefer
to have as many partons as possible at low longitudinal momentum fraction.Comment: 14 pages, 3 figures, LaTe
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