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Strong absorption model for elastic nuclear scattering. Part I
ANNALS
OF PHYSICS:
Abstracts
23, 330-334
of
(1963)
Papers
to Appear
in Future
Issues
On Partially Conserved Currents. SIDNEY COLEMAN, Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts. It is observed that the hypothesis of partially conserved leptonic weak interaction currents, which has been proposed by several authors, implies that the fundamental mesonbaryon interaction be invariant under a certain group constructed from these currents. The only candidate for this group that is consistent with experiment and that does not require the introduction of an exorbitant number of spinless mesons is the eight-dimensional rotation group. The associated meson-baryon coupling is one first proposed by Gtirsey. This group does not seem to have any connection with the approximate symmetries of the strong interactions; thus we reject the notion of partially conserved currents. Strong Absorption Model for Elastic Nuclear Scattering. Part I. W. E. FRAHN AND It. H. VENTER, Department of Physics, University of Stellenbosch, Cape Province, South Africa. A phenomenological model is presented which is capable of describing the average entrance channel phenomena of neutral and charged particles strongly interacting with complex nuclei. Instead of postulating a complex single-particle interaction potential, we start from rather general assumptions on the asymptotic properties of the scattered wave function. This approach is similar to the diffraction models of Bethe and Placzek, Akhiezer and Pomeranchuk, the sharp-cutoff model of Blair, and their generalizations by Greider and Glassgold, and by McIntyre et al. However, by means of a somewhat different formulation it is possible to give an analytical treatment for fairly arbitrary shapes of the complex scattering function consistent with the strong absorption assumption, thereby extending and unifying the earlier models. Closed-form expressions are given for the elastic scattering amplitudes and total reaction cross sections, which exhibit all known general features of the observed angular distributions and excitation functions, and permit a detailed study of their dependence on the various scattering parameters. The relation of this model to alternative descriptions of scattering in the presence of strong absorption, in particular to the complex potential model, is discussed. 2’he Foundations of Nonequilibrium Statistical Mechanics, I. GLXDO SANDRI, Aeronautical Research Associates, Princeton, New Jersey. In this paper a novel philosophy of irreversible dynamics is formulated. This philosophy stems from the claim that the kinetic equations available (Boltzmann, LandauBogoliubovLenard) are essentially exact and cannot be improved. That is, for kinetic gases (those whose behavior is characterized by that of one typical particle) these equations constitute closed, statistically complete knowledge. This thesis is demonstrated by using a technique that separates completely the different time components exibited by the evolution of a gas when an appropriate parameter (characteristic of the regime in which the gas is found) is small. The expansion in this parameter is pushed up to its breaking point marked by t,he presence of an intrinsic divergence. With our technique we can pinch off the series at this point and remain with a closed, finite system of equations. The argument is made compelling by the fact that the sanle divergence occurs for all gaseous regimes (short-range, weak-coupling, dilute weak-coupling and Debye). 330
OF PHYSICS:
Abstracts
23, 330-334
of
(1963)
Papers
to Appear
in Future
Issues
On Partially Conserved Currents. SIDNEY COLEMAN, Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts. It is observed that the hypothesis of partially conserved leptonic weak interaction currents, which has been proposed by several authors, implies that the fundamental mesonbaryon interaction be invariant under a certain group constructed from these currents. The only candidate for this group that is consistent with experiment and that does not require the introduction of an exorbitant number of spinless mesons is the eight-dimensional rotation group. The associated meson-baryon coupling is one first proposed by Gtirsey. This group does not seem to have any connection with the approximate symmetries of the strong interactions; thus we reject the notion of partially conserved currents. Strong Absorption Model for Elastic Nuclear Scattering. Part I. W. E. FRAHN AND It. H. VENTER, Department of Physics, University of Stellenbosch, Cape Province, South Africa. A phenomenological model is presented which is capable of describing the average entrance channel phenomena of neutral and charged particles strongly interacting with complex nuclei. Instead of postulating a complex single-particle interaction potential, we start from rather general assumptions on the asymptotic properties of the scattered wave function. This approach is similar to the diffraction models of Bethe and Placzek, Akhiezer and Pomeranchuk, the sharp-cutoff model of Blair, and their generalizations by Greider and Glassgold, and by McIntyre et al. However, by means of a somewhat different formulation it is possible to give an analytical treatment for fairly arbitrary shapes of the complex scattering function consistent with the strong absorption assumption, thereby extending and unifying the earlier models. Closed-form expressions are given for the elastic scattering amplitudes and total reaction cross sections, which exhibit all known general features of the observed angular distributions and excitation functions, and permit a detailed study of their dependence on the various scattering parameters. The relation of this model to alternative descriptions of scattering in the presence of strong absorption, in particular to the complex potential model, is discussed. 2’he Foundations of Nonequilibrium Statistical Mechanics, I. GLXDO SANDRI, Aeronautical Research Associates, Princeton, New Jersey. In this paper a novel philosophy of irreversible dynamics is formulated. This philosophy stems from the claim that the kinetic equations available (Boltzmann, LandauBogoliubovLenard) are essentially exact and cannot be improved. That is, for kinetic gases (those whose behavior is characterized by that of one typical particle) these equations constitute closed, statistically complete knowledge. This thesis is demonstrated by using a technique that separates completely the different time components exibited by the evolution of a gas when an appropriate parameter (characteristic of the regime in which the gas is found) is small. The expansion in this parameter is pushed up to its breaking point marked by t,he presence of an intrinsic divergence. With our technique we can pinch off the series at this point and remain with a closed, finite system of equations. The argument is made compelling by the fact that the sanle divergence occurs for all gaseous regimes (short-range, weak-coupling, dilute weak-coupling and Debye). 330