1,630 research outputs found
Spin Asymmetry and Gerasimov-Drell-Hearn Sum Rule for the Deuteron
An explicit evaluation of the spin asymmetry of the deuteron and the
associated GDH sum rule is presented which includes photodisintegration, single
and double pion and eta production as well. Photodisintegration is treated with
a realistic retarded potential and a corresponding meson exchange current. For
single pion and eta production the elementary operator from MAID is employed
whereas for double pion production an effective Lagrangean approach is used. A
large cancellation between the disintegration and the meson production channels
yields for the explicit GDH integral a value of 27.31 b to be compared to
the sum rule value 0.65 b.Comment: 4 pages, 5 figures, revtex
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
We develop a formalism to calculate form factor and charge density
distribution of pion in the chiral limit using the holographic dual model of
QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and
present analytic expressions for these functions and for the pion form factor.
They allow to relate such observables as the pion decay constant and the pion
charge electric radius to the values of chiral condensate and hard-wall cutoff
scale. The evolution of the pion form factor to large values of the momentum
transfer is discussed, and results are compared to existing experimental data.Comment: 21 page, 7 figures. Short comparison with NJL predictions for pion
radius and new references added. To be published in Phys.Rev.
Towards Integrability of Topological Strings I: Three-forms on Calabi-Yau manifolds
The precise relation between Kodaira-Spencer path integral and a particular
wave function in seven dimensional quadratic field theory is established. The
special properties of three-forms in 6d, as well as Hitchin's action
functional, play an important role. The latter defines a quantum field theory
similar to Polyakov's formulation of 2d gravity; the curious analogy with
world-sheet action of bosonic string is also pointed out.Comment: 31 page
Status of Spin Physics - Experimental Summary
The current status of spin physics experiments, based on talks presented at
the Third Circum-Pan-Pacific Symposium on High Energy Spin Physics held in
Beijing, 2001, is summarized in this article. Highlights of recent experimental
results at SLAC, JLab, and DESY, as well as future plans at these facilities
and at RHIC-spin are discussed.Comment: 18 pages, 7 figures, Invited talk presented at the Third
Circum-Pan-Pacific Symposium on High Energy Spin Physics held in Beijing,
October, 200
On quantization of singular varieties and applications to D-branes
We calculate the ring of differential operators on some singular affine
varieties (intersecting stacks, a point on a singular curve or an orbifold).
Our results support the proposed connection of the ring of differential
operators with geometry of D-branes in (bosonic) string theory. In particular,
the answer does know about the resolution of singularities in accordance with
the string theory predictions.Comment: LaTeX2e, 17 pages, misprints correcte
Nonperturbative QCD Coupling and its function from Light-Front Holography
The light-front holographic mapping of classical gravity in AdS space,
modified by a positive-sign dilaton background, leads to a nonperturbative
effective coupling . It agrees with hadron physics data
extracted from different observables, such as the effective charge defined by
the Bjorken sum rule, as well as with the predictions of models with built-in
confinement and lattice simulations. It also displays a transition from
perturbative to nonperturbative conformal regimes at a momentum scale
GeV. The resulting function appears to capture the essential
characteristics of the full function of QCD, thus giving further
support to the application of the gauge/gravity duality to the confining
dynamics of strongly coupled QCD. Commensurate scale relations relate
observables to each other without scheme or scale ambiguity. In this paper we
extrapolate these relations to the nonperturbative domain, thus extending the
range of predictions based on .Comment: 32 pages, 7 figures. Final version published in Phys. Rev.
String theory and classical integrable systems
We discuss different formulations and approaches to string theory and
quantum gravity. The generic idea to get a unique description of {\it many}
different string vacua altogether is demonstrated on the examples in
conformal, topological and matrix formulations. The last one naturally brings
us to the appearance of classical integrable systems in string theory. Physical
meaning of the appearing structures is discussed and some attempts to find
directions of possible generalizations to ``higher-dimensional" models are
made. We also speculate on the possible appearence of quantum integrable
structures in string theory.Comment: lecture given at III Baltic Rim student seminar, Helsinki, September
1993} 33pp, late
Proton structure corrections to electronic and muonic hydrogen hyperfine splitting
We present a precise determination of the polarizability and other proton
structure dependent contributions to the hydrogen hyperfine splitting, based
heavily on the most recent published data on proton spin dependent structure
functions from the EG1 experiment at the Jefferson Laboratory. As a result, the
total calculated hyperfine splitting now has a standard deviation slightly
under 1 part-per-million, and is about 1 standard deviation away from the
measured value. We also present results for muonic hydrogen hyperfine
splitting, taking care to ensure the compatibility of the recoil and
polarizability terms.Comment: 9 pages, 1 figur
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