Quantum hadrodynamics (QHD) is a framework for describing the nuclear many-body problem as a relativistic system of baryons and mesons. Motivation is given for the utility of such an approach and for the importance of basing it on a local, Lorentz-invariant lagrangian density. Calculations of nuclear matter and finite nuclei in both renormalizable and nonrenormalizable, effective QHD models are discussed. Connections are made between the effective and renormalizable models, as well as between relativistic mean-field theory and more sophisticated treatments. Recent work in QHD involving nuclear structure, electroweak interactions in nuclei, relativistic transport theory, nuclear matter under extreme conditions, and the evaluation of loop diagrams is reviewed.
Two-loop corrections with scalar and vector form factors are calculated for nuclear matter in the Walecka model. The on-shell form factors are derived from vertex corrections within the framework of the model and are highly damped at large spacelike momenta. The two-loop corrections are evaluated first by using the one-loop parameters and mean fields and then by refitting the total energy/baryon to empirical nuclear matter saturation properties. The modified two-loop corrections are significantly smaller than those computed with bare vertices. Contributions from the anomalous isoscalar form factor of the nucleon are included for the first time. The effects of the implicit density dependence of the form factors, which arise from the shift in the baryon mass, are also considered. Finally, necessary extensions of these calculations are discussed.Typeset using REVT E X where F µν = ∂ µ V ν − ∂ ν V µ and δL contains the counterterms. We observe that the off-shell vertex functions should be used in a fully satisfactory calculation with loops. A full offshell calculation is quite complicated, however, as one needs to know the off-shell behavior of the vertices at all spacelike momenta, as well as the modification of the vertices in the presence of valence nucleons at finite density. Calculations exploring these off-shell vertex functions are in progress [19]. Here, as a first step, we use an on-shell approximation, in which the off-shell vertex functions are replaced by their on-shell forms at zero density. This procedure is analogous to that used in Refs. [15] and [16], where parametrized, on-shell form factors were used at the vertices, except that we use form factors obtained from within our model. Note also that the form factors used in Refs. [15] and [16] were chosen to have
An effective hadronic lagrangian consistent with the symmetries of quantum chromodynamics and intended for applications to finite-density systems is constructed. The degrees of freedom are (valence) nucleons, pions, and the low-lying non-Goldstone bosons, which account for the intermediate-range nucleon-nucleon interactions and conveniently describe the nonvanishing expectation values of nucleon bilinears. Chiral symmetry is realized nonlinearly, with a light scalar meson included as a chiral singlet to describe the mid-range nucleon-nucleon attraction. The low-energy electromagnetic structure of the nucleon is described within the theory using vector-meson dominance, so that external form factors are not needed. The effective lagrangian is expanded in powers of the fields and their derivatives, with the terms organized using Georgi's "naive dimensional analysis". Results are presented for finite nuclei and nuclear matter at one-baryon-loop order, using the single-nucleon structure determined within the model. Parameters obtained from fits to nuclear properties show that naive dimensional analysis is a useful principle and that * Present address: School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455.
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