6752160
Bound-valence-quark contributions to hadron structure functions.
The conventional separation of valence''- and sea''-quark distributions of a hadron implicitly assumes that the quark and antiquark contributions to the sea are identical in shape, although this cannot be strictly correct due to the exclusion principle. A new separation of bound-valence''- and - non-valence''- quark distributions of a hadron is proposed which incorporates the Pauli principle and relates the valence component to the wave functions of the bound-state valence constituents. With this new definition, the non-valence-quark distributions correspond to structure functions which would be measured if the valence quarks of the target hadron were chargeless. The bound-valence-quark distributions are not singular at small {ital x}, thus allowing for the calculation of sum rules and expectation values which would otherwise be divergent.
17276805
Glue drops inside hadrons
We present experimental evidences for the existence of a semi-hard scale in light hadrons. This includes the suppression of gluon radiation that is seen in high mass hadron diffraction; the weak energy dependence of hadronic total cross sections; the small value of the Pomeron trajectory slope measured in photoproduction of J / Ψ ; the weakness of gluon shadowing in nuclei; shortage of gluons in the proton revealed by an unusual behavior of the proton structure function in the soft limit, and the enhanced intrinsic transverse momentum of quarks and gluons, which considerably exceeds the inverse hadronic size. All these observations suggest that gluons in hadrons are located within spots of a small size relative to the confinement radius.
123339797
The Physics of the Chiral Schwinger Model: Taming an Anomalous Theory
Abstract We study the physical aspects of the chiral Schwinger model, comparing the content of this theory to that of the vector-like case. The theory is analyzed by bosonization with special attention to charged sectors and aspects of symmetry breaking. A generalized model with different left and right couplings is analyzed and the currents coupled to the gauge fields are shown to be conserved by using the equations of motion. The effects of the anomaly are studied and the mechanisms by which a new massless particle is introduced in the physical spectrum of the chiral model are clarified. We find that the longitudinal mode of the gauge field, acquiring dynamics because of the anomaly, is responsible for restoring the cluster property of chirality-carrying operators. The physics of the Wess-Zumino term is clarified and the equivalence between the theories with and without the Wess-Zumino term is spelled out. We construct the Hilbert spaces of the theories with and without the W-Z term and the physical subspaces are shown to be the same, with positive definite metric in both cases. The Ward identity Z 2 = Z 1 is shown to hold in the theory (without the W-Z term) despite its lack of local gauge invariance.
122242481
Delta electroproduction in nuclei
Abstract We compute delta electroproduction in nuclei using a relativistic nuclear model. Iron is predicted to have the largest per nucleon cross section and narrowest width, but the variation in A is no larger than an 18% effect. Predictions are made for the SLAC NPAS NE5 experiment and a recently completed Bates laboratory experiment.
119202959
Dilaton in a soft-wall holographic approach to mesons and baryons
We discuss a holographic soft-wall model developed for the description of mesons and baryons with adjustable quantum numbers n, J, L, S. This approach is based on an action which describes hadrons with broken conformal invariance and which incorporates confinement through the presence of a background dilaton field. We show that in the case of the bound-state problem (hadronic mass spectrum) two versions of the model with a positive and negative dilaton profile are equivalent to each other by a special transformation of the bulk field. We also comment on recent works which discuss the dilaton sign in the context of soft-wall approaches.
120008075
NUCLEON RESONANCES AND GPDS IN AdS/QCD
We discuss an holographic soft wall model to describe nucleon properties. We pay special attention to nucleon spectrum, GPDs in the skewness case for nucleons and electroproduction of the N (1440) Roper resonance in soft-wall AdS/QCD.
44869344
Stability and Hamiltonian formulation of higher derivative theories.
We analyze the presumptions which lead to instabilities in theories of order higher than second. That type of fourth order gravity which leads to an inflationary (quasi de Sitter) period of cosmic evolution by inclusion of one curvature squared term (i.e. the Starobinsky model) is used as an example. The corresponding Hamiltonian formulation (which is necessary for deducing the Wheeler de Witt equation) is found both in the Ostrogradski approach and in another form. As an example, a closed form solution of the Wheeler de Witt equation for a spatially flat Friedmann model and L = R2 is found. The method proposed by Simon to bring fourth order gravity to second order can be (if suitably generalized) applied to bring sixth order gravity to second order. PACS numbers: 0320 Classical mechanics of discrete systems: general mathematical aspects; 9880 Cosmology; 0450 Other theories of gravitation
20398756
Comment on "Conformal transformations single out a unique measure of distance"
We discuss the consequences of the incorrectness [see the Erratum Phys. Rev. D 49, 1145(E) (1994)] of Cotsakis' paper and add two related remarks. The scope of this Comment is to encourage further research on ``which of the conformally equivalent metrics is the physical one.''
27551183
Comment on "Stability of the semiclassical Einstein equation"
Some mathematical errors of the paper commented upon [W.-M. Suen, Phys. Rev. D 40, (1989) 315] are corrected.
31181088
Plane domain walls when coupled with the Brans-Dicke scalar field.
The space-times of plane thin domain walls are studied in the context of the Brans-Dicke (BD) theory of gravity by using distribution theory. In particular, the BD field equations are divided into two groups: one holding in the regions outside of the wall and the other holding on the wall. It is found that the equations on the wall take a very simple form, and are given explicitly in terms of the metric coefficients and the BD scalar field. As an application of the theory developed, a class of exact solutions, which represents a plane domain wall interacting with the BD scalar field, is given and studied. It is found that the surface energy density of the wall always exponentially decreases as the time develops; this is one possible solution of the domain wall problem in cosmological models founded on general relativity
12973910
Axigluon production in hadronic collisions.
Recently proposed chiral-color models predict the existence of a massive color octet of vector bosons, the axigluon. In this paper we investigate axigluon production in hadronic collisions. We compute the single-jet inclusive cross section and the two-jet invariant-mass distribution for the CERN collider, the Fermilab Tevatron, and the Superconducting Super Collider. We use CERN data to exclude axigluon masses between 125 and 275 GeV, subject to a mild constraint on the width.