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Copyright of Ergebnisse der Exakten Naturwissenschaften is the property of Springer eBooks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ergebnisse der Exakten Naturwissenschaften is the property of Springer eBooks and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Interaction of electrons or holes in narrow energy bands with both acoustic and polar phonons is investigated. Based upon a graphical expansion of the electron Green's function and of the transport vertex function, a Boltzmann equation is derived, which includes one-phonon and simultaneous two-phonon scattering. The general results are applied to a one-dimensional model of a narrow-band system. [ABSTRACT FROM AUTHOR]

The group dynamical prescriptions for constructing conserved currents of baryons of fixed internal quantum numbers are extended as to apply to the whole SU(3) octet of weak and electromagnetic curents. It is shown how for any dynamical group such a current octet can be found which satisfies the charge-current commutation rules at infinite momentum and is not proportional to the particle charges. The SU(3) symmetry described by these currents is broken, such that the masses within every SU(3) multiplet are split and strangeness changing currents are not conserved. Finally, some comments are made on a possible extension of the algebra by an axial-vector octet of currents in order to generate the full chiral SU(3)×SU(3) charge-current algebra. These lectures are based on work done in collaboration with D. Corrigan and B. Hamprecht. [ABSTRACT FROM AUTHOR]

We present a review of the basic theory of electron scattering from nuclei and of photonuclear processes, as well as a discussion of the analysis of electron scattering experiments. This includes cross sections in Born approximation, elastic scattering from nuclei for the study of nuclear moments, and continuum scattering. Particular attention is given to inelastic electron scattering with excitation of nuclear levels, both below and in the giant resonance region. Various theoretical models are discussed that describe excitations of nuclear states. [ABSTRACT FROM AUTHOR]

A recent controversy about the value of the sigma term in pion-nucleon scattering is reviewed, with particular attention to possible attempts to reconcile the large value of Cheng and Dashen with the (3, 3*) + (3*, 3) chiral symmetry breaking model of Gell-Mann. Grounds for reservations may be found for each one of three mechanisms considered here. Thus we confirm the general belief that the conventional theory of chiral symmetry breaking cannot be easily maintained, unless the value of Cheng and Dashen is given up in favour of a reestimate by Höhler, Jakob and Strauss. [ABSTRACT FROM AUTHOR]

We review properties of Schwinger terms contained in the equaltime commutators of the SU (3) ⊗ SU (3) charge densities with the SU (3) ⊗ SU (3) current divergences. [ABSTRACT FROM AUTHOR]

Amplitudes with total cross-sections rising asymptotically like (logs)\+ require shrinkage of the diffraction peak. For 0 <β+ ≦ 1, it is sufficient to have a leading positive signature trajectory which is regular at t = 0, but not a constant. For 1<β+≦2, the trajectory must have a branch point at t = 0. Explicit amplitudes with complex Pomeranchuk trajectories are given which are compatible with t channel unitarity. The limiting case of maximal absorption is considered briefly. [ABSTRACT FROM AUTHOR]

In this review first the considerable internal flexibility of Regge-cut models is emphasized. In order to reduce this flexibility, popular Regge-cut models (especially Argonne, Michigan) are confronted with a set of theoretical and decisive experimental constraints, the most important ones being the dual absorptive picture of Harari for the dip systematics and the new polarization data of πN-charge exchange. In general it is concluded that all current Regge-cut models are seriously affected by the set of constraints — even in the case of the "unproblematic" class of hadronic reactions, dominated by vector and tensor exchange. In particular the following results were found: i) the real parts of the helicity-nonflip amplitudes are wrong, i.e. by far too much absorbed, in the Michigan as well as in the Argonne model; moreover in the Michigan model the real parts of the helicity-flip amplitudes are wrong, too, ii) there is much support for wrong signature nonsense zeros in the Regge-pole input and iii) the correct crossover of elastic differential cross sections does not necessarily imply very strong absorption. Altogether a weak cut type model — if any — seems to be favoured for the imaginary parts of the amplitudes. The real parts should then be calculated from fixed t-dispersion relations. [ABSTRACT FROM AUTHOR]