2,453 research outputs found
Light-Cone Quantization of the Liouville Model
We present the quantization of the Liouville model defined in light-cone
coordinates in (1,1) signature space. We take advantage of the representation
of the Liouville field by the free field of the Backl\"{u}nd transformation and
adapt the approch by Braaten, Curtright and Thorn.
Quantum operators of the Liouville field ,
, , are constructed consistently in
terms of the free field. The Liouville model field theory space is found to be
restricted to the sector with field momentum , , which
is a closed subspace for the Liouville theory operator algebra.Comment: 16 p, EFI-92-6
Photon Production from a Quark-Gluon-Plasma at Finite Baryon Chemical Potential
We compute the photon production of a QCD plasma at leading order in the
strong coupling with a finite baryon chemical potential. Our approach starts
from the real time formalism of finite temperature field theory. We identify
the class of diagrams contributing at leading order when a finite chemical
potential is added and resum them to perform a full treatment of the LPM effect
similar to the one performed by Arnold, Moore, and Yaffe at zero chemical
potential. Our results show that the contribution of and processes grows as the chemical potential grows.Comment: 28 pages, 14 figure
Soliton quantization and internal symmetry
We apply the method of collective coordinate quantization to a model of
solitons in two spacetime dimensions with a global symmetry. In
particular we consider the dynamics of the charged states associated with
rotational excitations of the soliton in the internal space and their
interactions with the quanta of the background field (mesons). By solving a
system of coupled saddle-point equations we effectively sum all tree-graphs
contributing to the one-point Green's function of the meson field in the
background of a rotating soliton. We find that the resulting one-point function
evaluated between soliton states of definite charge exhibits a pole on
the meson mass shell and we extract the corresponding S-matrix element for the
decay of an excited state via the emission of a single meson using the standard
LSZ reduction formula. This S-matrix element has a natural interpretation in
terms of an effective Lagrangian for the charged soliton states with an
explicit Yukawa coupling to the meson field. We calculate the leading-order
semi-classical decay width of the excited soliton states discuss the
consequences of these results for the hadronic decay of the resonance
in the Skyrme model.Comment: 23 pages, LA-UR-93-299
Correlation functions in super Liouville theory
We calculate three- and four-point functions in super Liouville theory
coupled to super Coulomb gas on world sheets with spherical topology. We first
integrate over the zero mode and assume that a parameter takes an integer
value. After calculating the amplitudes, we formally continue the parameter to
an arbitrary real number. Remarkably the result is completely parallel to the
bosonic case, the amplitudes being of the same form as those of the bosonic
case.Comment: 11 page
Quantum Hamilton-Jacobi equation
The nontrivial transformation of the phase space path integral measure under
certain discretized analogues of canonical transformations is computed. This
Jacobian is used to derive a quantum analogue of the Hamilton-Jacobi equation
for the generating function of a canonical transformation that maps any quantum
system to a system with a vanishing Hamiltonian. A formal perturbative solution
of the quantum Hamilton-Jacobi equation is given.Comment: 4 pages, RevTe
Classical A_n--W-Geometry
This is a detailed development for the case, of our previous article
entitled "W-Geometries" to be published in Phys. Lett. It is shown that the
--W-geometry corresponds to chiral surfaces in . This is comes out
by discussing 1) the extrinsic geometries of chiral surfaces (Frenet-Serret and
Gauss-Codazzi equations) 2) the KP coordinates (W-parametrizations) of the
target-manifold, and their fermionic (tau-function) description, 3) the
intrinsic geometries of the associated chiral surfaces in the Grassmannians,
and the associated higher instanton- numbers of W-surfaces. For regular points,
the Frenet-Serret equations for --W-surfaces are shown to give the
geometrical meaning of the -Toda Lax pair, and of the conformally-reduced
WZNW models, and Drinfeld-Sokolov equations. KP coordinates are used to show
that W-transformations may be extended as particular diffeomorphisms of the
target-space. This leads to higher-dimensional generalizations of the WZNW and
DS equations. These are related with the Zakharov- Shabat equations. For
singular points, global Pl\"ucker formulae are derived by combining the
-Toda equations with the Gauss-Bonnet theorem written for each of the
associated surfaces.Comment: (60 pages
Nucleon-Nucleon Scattering under Spin-Isospin Reversal in Large-N_c QCD
The spin-flavor structure of certain nucleon-nucleon scattering observables
derived from the large N_c limit of QCD in the kinematical regime where
time-dependent mean-field theory is valid is discussed. In previous work, this
regime was taken to be where the external momentum was of order N_c which
precluded the study of differential cross sections in elastic scattering. Here
it is shown that the regime extends down to order N_c^{1/2} which includes the
higher end of the elastic regime. The prediction is that in the large N_c
limit, observables describable via mean-field theory are unchanged when the
spin and isospin of either nucleon are both flipped. This prediction is tested
for proton-proton and neutron-proton elastic scattering data and found to fail
badly. We argue that this failure can be traced to a lack of a clear separation
of scales between momentum of order N_c^{1/2} and N_c^1 when N_c is as small as
three. The situation is compounded by an anomalously low particle production
threshold due to approximate chiral symmetry.Comment: 5 pages, 1 figur
Quantum Liouville Field Theory as Solution of a Flow Equation
A general framework for the Weyl invariant quantization of Liouville field
theory by means of an exact renormalization group equation is proposed. This
flow equation describes the scale dependence of the effective average action
which has a built-in infrared cutoff. For c<1 it is solved approximately by a
truncation of the space of action functionals. We derive the Ward identities
associated to Weyl transformations in presence of the infrared cutoff. They are
used to select a specific universality class for the renormalization group
trajectory which is found to connect two conformal field theories with central
charges 25-c and 26-c, respectively.Comment: 49 pages, late
On anomalies in classical dynamical systems
The definition of "classical anomaly" is introduced. It describes the
situation in which a purely classical dynamical system which presents both a
lagrangian and a hamiltonian formulation admits symmetries of the action for
which the Noether conserved charges, endorsed with the Poisson bracket
structure, close an algebra which is just the centrally extended version of the
original symmetry algebra. The consistency conditions for this to occur are
derived. Explicit examples are given based on simple two-dimensional models.
Applications of the above scheme and lines of further investigations are
suggested.Comment: arXiv version is already officia
Masses of the 70- Baryons in Large Nc QCD
The masses of the negative parity 70-plet baryons are analyzed in large N_c
QCD to order 1/N_c and to first order in SU(3) symmetry breaking. The existing
experimental data are well reproduced and twenty new observables are predicted.
The leading order SU(6) spin-flavor symmetry breaking is small and, as it
occurs in the quark model, the subleading in 1/N_c hyperfine interaction is the
dominant source of the breaking. It is found that the Lambda(1405) and
Lambda(1520) are well described as three-quark states and spin-orbit partners.
New relations between splittings in different SU(3) multiplets are found.Comment: 11 pages; references were added and a couple of improvements to the
text were mad
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