35 research outputs found
Effective Field Theories from QCD
We present a method for extracting effective Lagrangians from QCD. The
resulting effective Lagrangians are based on exact rewrites of cut-off QCD in
terms of these new collective field degrees of freedom. These cut-off
Lagrangians are thus ``effective'' in the sense that they explicitly contain
some of the physical long-distance degrees of freedom from the outset. As an
example we discuss the introduction of a new collective field carrying the
quantum numbers of the -meson. (Contribution presented by R. Sollacher
at the workshop ``QCD'94'', Montpellier, France, July 7-13, 1994. To appear in
those proceedings.)Comment: 6 pages, GSI-94-5
Qualitons from QCD
Qualitons, topological excitations with the quantum numbers of quarks, may
provide an accurate description of what is meant by constituent quarks in QCD.
Their existence hinges crucially on an effective Lagrangian description of QCD
in which a pseudoscalar colour-octet of fields enters as a new variable. We
show here how such new fields may be extracted from the fundamental QCD
Lagrangian using the gauge-symmetric collective field technique.Comment: LaTeX, 12 pages, CERN--TH-7073/9
BRST Gauge Fixing and Regularization
In the presence of consistent regulators, the standard procedure of BRST
gauge fixing (or moving from one gauge to another) can require non-trivial
modifications. These modifications occur at the quantum level, and gauges exist
which are only well-defined when quantum mechanical modifications are correctly
taken into account. We illustrate how this phenomenon manifests itself in the
solvable case of two-dimensional bosonization in the path-integral formalism.
As a by-product, we show how to derive smooth bosonization in
Batalin-Vilkovisky Lagrangian BRST quantization.Comment: LaTeX, 12 page
Collective Fields for QCD
A gauge-symmetric approach to effective Lagrangians is described with special
emphasis on derivations of effective low-energy Lagrangians from QCD. The
examples we discuss are based on exact rewritings of cut-off QCD in terms of
new collective degrees of freedom. These cut-off Lagrangians are thus
``effective'' in the sense that they explicitly contain some of the physical
long-distance degrees of freedom from the outset.(Talk presented by P.H.
Damgaard at the workshop on ``Quantum Field Theoretical Methods in High Energy
Physics'', Kyffhauser, Germany, Sept. 1993. To appear in those proceedings).Comment: LaTeX, 12 pages, CERN--TH-7035/9
Smooth Bosonization II: The Massive Case
The (1+1)-dimensional bosonization relations for fermionic mass terms are
derived by choosing a specific gauge in an enlarged gauge-invariant theory
containing both fermionic and bosonic fields. The fermionic part of the
generating functional subject to the gauge constraint can be cast into the form
of a strongly coupled Schwinger model, which can be solved exactly. The
resulting bosonic theory coupled to the scalar sources then exhibits directly
the bosonic counterparts of the fermionic scalar and pseudoscalar mass
densities.Comment: 8 pages, Latex, CERN-TH-6563/9
Quantum pattern recognition with liquid-state nuclear magnetic resonance
A novel quantum pattern recognition scheme is presented, which combines the
idea of a classic Hopfield neural network with adiabatic quantum computation.
Both the input and the memorized patterns are represented by means of the
problem Hamiltonian. In contrast to classic neural networks, the algorithm can
return a quantum superposition of multiple recognized patterns. A proof of
principle for the algorithm for two qubits is provided using a liquid state NMR
quantum computer.Comment: updated version, Journal-ref adde
Smooth Non-Abelian Bosonization
We present an extension of ``smooth bosonization'' to the non-Abelian case.
We construct an enlarged theory containing both bosonic and fermionic fields
which exhibits a local chiral gauge symmetry. A gauge fixing function depending
on one real parameter allows us to interpolate smoothly between a purely
fermionic and a purely bosonic representation. The procedure is, in the special
case of bosonization, complementary to the approach based on duality.Comment: LaTeX, 13 pages, CERN--TH-7347/9