167 research outputs found
Analyzing eta' photoproduction data on the proton at energies of 1.5--2.3 GeV
The recent high-precision data for the reaction at
photon energies in the range 1.5--2.3 GeV obtained by the CLAS collaboration at
the Jefferson Laboratory have been analyzed within an extended version of the
photoproduction model developed previously by the authors based on a
relativistic meson-exchange model of hadronic interactions [Phys. Rev. C
\textbf{69}, 065212 (2004)]. The photoproduction can be described quite
well over the entire energy range of available data by considering ,
, , and resonances, in addition to the -channel
mesonic currents. The observed angular distribution is due to the interference
between the -channel and the nucleon - and -channel resonance
contributions. The resonances are required to reproduce some of the
details of the measured angular distribution. For the resonances considered,
our analysis yields mass values compatible with those advocated by the Particle
Data Group. We emphasize, however, that cross-section data alone are unable to
pin down the resonance parameters and it is shown that the beam and/or target
asymmetries impose more stringent constraints on these parameter values. It is
found that the nucleonic current is relatively small and that the
coupling constant is not expected to be much larger than 2.Comment: Revised version based on revised (finalized) CLAS data (14 pages, 10
figures, RevTeX4
Stable quantum systems in anti-de Sitter space: Causality, independence and spectral properties
If a state is passive for uniformly accelerated observers in n-dimensional
anti-de Sitter space-time (i.e. cannot be used by them to operate a perpetuum
mobile), they will (a) register a universal value of the Unruh temperature, (b)
discover a PCT symmetry, and (c) find that observables in complementary
wedge-shaped regions necessarily commute with each other in this state. The
stability properties of such a passive state induce a "geodesic causal
structure" on AdS and concommitant locality relations. It is shown that
observables in these complementary wedge-shaped regions fulfill strong
additional independence conditions. In two-dimensional AdS these even suffice
to enable the derivation of a nontrivial, local, covariant net indexed by
bounded spacetime regions. All these results are model-independent and hold in
any theory which is compatible with a weak notion of space-time localization.
Examples are provided of models satisfying the hypotheses of these theorems.Comment: 27 pages, 1 figure: dedicated to Jacques Bros on the occasion of his
70th birthday. Revised version: typos corrected; as to appear in J. Math.
Phy
Conformal Field Theory Correlators from Classical Scalar Field Theory on
We use the correspondence between scalar field theory on and a
conformal field theory on to calculate the 3- and 4-point functions of
the latter. The classical scalar field theory action is evaluated at tree
level.Comment: 9 pages, LaTeX2e with amsmath, amsfonts packages, section 2
rewritten, references adde
High Spin Gauge Fields and Two-Time Physics
All possible interactions of a point particle with background
electromagnetic, gravitational and higher-spin fields is considered in the
two-time physics worldline formalism in (d,2) dimensions. This system has a
counterpart in a recent formulation of two-time physics in non-commutative
field theory with local Sp(2) symmetry. In either the worldline or field theory
formulation, a general Sp(2) algebraic constraint governs the interactions, and
determines equations that the background fields of any spin must obey. The
constraints are solved in the classical worldline formalism (h-bar=0 limit) as
well as in the field theory formalism (all powers of h-bar). The solution in
both cases coincide for a certain 2T to 1T holographic image which describes a
relativistic particle interacting with background fields of any spin in (d-1,1)
dimensions. Two disconnected branches of solutions exist, which seem to have a
correspondence as massless states in string theory, one containing low spins in
the zero Regge slope limit, and the other containing high spins in the infinite
Regge slope limit.Comment: LaTeX 22 pages. Typos corrected in version
The minimal conformal O(N) vector sigma model at d=3
For the minimal O(N) sigma model, which is defined to be generated by the
O(N) scalar auxiliary field alone, all n-point functions, till order 1/N
included, can be expressed by elementary functions without logarithms.
Consequently, the conformal composite fields of m auxiliary fields possess at
the same order such dimensions, which are m times the dimension of the
auxiliary field plus the order of differentiation.Comment: 15 page
Open string fluctuations in AdS_5xS^5 and operators with large R-charge
A semiclassical string description is given for correlators of Wilson loops
with local operators in N=4 SYM theory in the regime when operators carry
parametrically large R-charge. The OPE coefficients of the circular Wilson loop
in chiral primary operators are computed to all orders in the alpha' expansion
in AdS_5xS^5 string theory. The results agree with field-theory predictions.Comment: 16 pages, 2 figures; v2: five misprints correcte
Pion-delta sigma-term
We use a configuration space chiral model in order to evaluate nucleon and
delta sigma-terms. Analytic expressions are consistent with chiral counting
rules and give rise to expected non-analytic terms in the chiral limit. We
obtain the results MeV and MeV, which are
very close to values extracted from experiment and produced by other groups.Comment: 18 pages, 4 figure
Constant Curvature Algebras and Higher Spin Action Generating Functions
The algebra of differential geometry operations on symmetric tensors over
constant curvature manifolds forms a novel deformation of the sl(2,R)
[semidirect product] R^2 Lie algebra. We present a simple calculus for
calculations in its universal enveloping algebra. As an application, we derive
generating functions for the actions and gauge invariances of massive,
partially massless and massless (for both bose and fermi statistics) higher
spins on constant curvature backgrounds. These are formulated in terms of a
minimal set of covariant, unconstrained, fields rather than towers of auxiliary
fields. Partially massless gauge transformations are shown to arise as
degeneracies of the flat, massless gauge transformation in one dimension
higher. Moreover, our results and calculus offer a considerable simplification
over existing techniques for handling higher spins. In particular, we show how
theories of arbitrary spin in dimension d can be rewritten in terms of a single
scalar field in dimension 2d where the d additional dimensions correspond to
coordinate differentials. We also develop an analogous framework for
spinor-tensor fields in terms of the corresponding superalgebra.Comment: 44 pages, LaTeX, 2 .eps figure
A dual lagrangian for non-Abelian tensor gauge fields
For non-Abelian tensor gauge fields of the lower rank we have found an
alternative expression for the field strength tensors, which transform
homogeneously with respect to the complementary gauge transformations and allow
us to construct the dual Lagrangian.Comment: 13 pages, LaTex fil
The exponential map for representations of
For the quantum group and the corresponding quantum algebra
Fronsdal and Galindo explicitly constructed the so-called
universal -matrix. In a previous paper we showed how this universal
-matrix can be used to exponentiate representations from the quantum algebra
to get representations (left comodules) for the quantum group. Here, further
properties of the universal -matrix are illustrated. In particular, it is
shown how to obtain comodules of the quantum algebra by exponentiating modules
of the quantum group. Also the relation with the universal -matrix is
discussed.Comment: LaTeX-file, 7 pages. Submitted for the Proceedings of the 4th
International Colloquium ``Quantum Groups and Integrable Systems,'' Prague,
22-24 June 199
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