Meson field theories

This method has been successfully applied to the photoionization of Hg and Xe [103,101] as well as to the evaluation of the polarizabilities of heavy closed-shell atoms [104] (using a direct time-dependent extension of the LDA for the xc-functional). A concept to deal with excited states in the framework of RDFT has been put forward by Nagy [105]. The derivation and first applications of relativistic extended Thomas-Fermi models may be found in Refs.[106-112]. Furthermore, an RDFT approach to meson field theory for hadronic matter (quantum hadrodynamics) [113] has been established by Speicher et al. [114]. This hadronic RDFT has been successfully applied to the description of nuclear ground states both within the extended Thomas-Fermi model [115-118] and within the KS scheme [119-121]. A corresponding formalism for finite temperature is also available [122,123]. 

FIGURE 8.4 Typical structure of the fullerene The double bindings are illustrated by double lines. In the nuclear case the Carbon atoms are replaced by a particles and the double bindings by the additional neutrons. Such a structure would immediately explain the semi-hollowness of that superheavy nucleus, which is revealed in the mean-field calculations within meson-field theories. For a colour reproduction of this figure see the colour plate section, near the end of this book. 

In the framework of meson field theory the energy spectrum of baryons has a peculiar structure, depicted in Figure 8.21. It consists of an upper and a lower con-... 

The mechanism is similar for the production of multi-hyper nuclei A, E, S, Q). Meson field theory predicts also for the A energy spectrum at finite primary nucleon density the existence of upper and lower wells. The lower well belongs to the vacuum and is fully occupied by yl s. 

FIGURE 8.24 The potential structure of the shell model and the vacuum for various primary densities p = po. 4po, 14po. At left the predictions of ordinary Durr-Teller-Walecka-type theories are shown at right those for a chirally symmetric meson field theory as developed by P. Papazoglu, S. Schramm et al. [36,13]. Note however, that this particular chiral mean-field theory does contain a> terms. If introduced in both effective models, they seem to predict quantitatively similar results. 

FIGURE 8.25 The strong phase transition inherent in Dtirr-Teller-Walecka-type meson field theories, as predicted by J. Theis et al. [37]. Note that there is a first-order transition along the p-axis (i.e. with density), but a simple transition along the temperature T-axis. Note also that this is very similar to the phase transition obtained recently from the Nambu-Jona-Lasinio-approximation of QCD [38]. 

Nucleon-Nucleon Potentials from Meson Field Theories. 49... 

Despite the successes, even with its generalizations, difficulties in thermal field theory remain to be overcome in order to deal with experimental and theoretical demands. In fact, numerous studies, in particular using quantum chromodynamics (A. Smilga, 2001), have been carried out in an attempt to understand, for instance, the quark-gluon plasma at finite temperature and in this common effort, some underlying aspects have been identified. For example, the coupling constants for 7r,a,w and p mesons decrease to zero at a certain critical temperature, which are, respectively, given by = 360 MeV, Tj = 95... 

The relativistic mean meson field (R.MF) theory formulated by Teller and others [8, 9, 10] and by Walecka [11] is quite successful in both infinite nuclear matter and finite nuclei[12, 13, 14]. In the RMF model, only positive-energy baryonic states are considered to study the properties of ordinary nuclei. This is the so-called no-sea-approximation . However, an interesting feature of the RMF theory is the existence of bound negative-energy baryonic states. This happens because the interaction with the vector field generated by the baryon-... 

The weak interactions that cause atomic PNC violate not only the symmetry of parity, P, but also the symmetry of charge conjugation, C. However, the product of these, CP, is conserved. Because any quantum field theory conserves CPT, where T is time reversal this is equivalent to saying that T is conserved. However, even this symmetry is known to be violated. To date, this incompletely understood phenomenon has been seen in only two systems, the neutral kaon system, and, quite recently, the neutral B meson system. However, as noted already in the 1950 s by Ramsey and Purcell [62], an elementary particle possessing an intrinsic electric dipole moment also violates T invariance, so that detection of such a moment would be a third way of seeing T noninvariance. 

Quantum kwan-t9m [L, neuter of quantus] (1567) n. Unit quantity of energy postulated in the quantum theory. The photon is a quantum of the electromagnetic field, and in nuclear field theories, the meson is considered to be the quantum of the nuclear field. 

CPT invariance is so far fiilly supported by the available experimental evidence and it is absolutely fundamental in field theory. Nevertheless, there are many experiments trying to test it. The simplest way to do that is to compare the mass or charge of particles and antiparticles. The most precise measurement of this type is that of the relative mass difference between the neutral K meson and its antiparticle that has so far been found to be less than 10 (Amsler et al. 2008). In 1999, an Antiproton Decelerator facility (CERN 2009) was constructed at the European Particle Physics Laboratory, CERN, in order to test the CPT invariance by comparing the spectra of hydrogen and antihydrogen, the latter being the bound state of an antiproton and a positron (see Chap. 28 in Vol. 3). 

Relativistic quantum field theories with nucleons and mesons and relativistic nucleon-nucleus scattering models should also be pursued further, as such work provides important tools for dealing with the relativistic nuclear many-body problem and indicates the level at which relativistic effects might manifest themselves in nuclear systems. This work also provides an important step along the way towards a covariant description of nuclear physics. Recent work in which QCD-inspired models of NN systems and nuclear matter [We 90, Me 91, Co 91] are studied is significant and may someday provide an important link between QCD and nuclear phenomenology. 

Efforts to use relativistic dynamics to describe nuclear phenomena began in the 1950s with application to infinite nuclear matter. Johnson and Teller [Jo 55] developed a nonrelativistic field theory for interacting nucleons and neutral, scalar mesons which served as a catalyst for Duerr, who, in a landmark paper [Du 56], developed a relativistic invariant version of the Johnson and Teller model which included both scalar and vector meson fields. He showed that nuclear saturation and the strong spin-orbit potential of the shell model could be readily understood. He also predicted a single particle potential which qualitatively reproduced the real part of the central optical potential well depth and its energy dependence for incident kinetic energies up to 200 MeV. 

In 1974 Walecka [Wa 74] introduced the first relativistic quantum field theory for nuclear matter. The mesonic degrees of freedom included scalar and vector fields. This model, referred to as the quantum hadrodynamic (QHD) model, accounts for spin-orbit splitting in the shell model and the ground state properties of many nuclei [Se 85]. Noble [No 79] demonstrated the consistency between the strengths of the scalar and vector potentisds in Walecka s QHD theory and those obtained from relativistic one-meson exchange potentials for the free NN interaction. 

Sooner or later, changes in scientific subjects start to affect the school science curriculum. In the case of biology, it has been sooner rather than later DNA is, at 50 years of age, already firmly part of school biology. In physics, change is patchy, often later rather than sooner. Some glamorous parts of astronomy are present, if only as an option so are simplified accounts of the quark structure of nucleons and mesons. But, with rare exceptions, the revolution introduced by quantum field theory remains unremarked so indeed in large measure do Maxwell s equations, and relativity, aneient ftiough both are. 

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