*Helmut Hofmann*

- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780198504016
- eISBN:
- 9780191708480
- Item type:
- book

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198504016.001.0001
- Subject:
- Physics, Nuclear and Plasma Physics

This book offers a survey of nuclear physics at low energies and discusses similarities to mesoscopic systems. It addresses systems at finite excitations of the internal degrees of freedom where ...
More

This book offers a survey of nuclear physics at low energies and discusses similarities to mesoscopic systems. It addresses systems at finite excitations of the internal degrees of freedom where collective motion exhibits features typical of transport processes for small and isolated systems. The importance of quantum aspects is investigated both with respect to the microscopic damping mechanism and to the nature of the transport equations. It is vital to account for nuclear collective motion being self-sustained, which in the end implies a highly nonlinear coupling between internal and collective degrees of freedom, a feature which in the literature all too often is ignored. The book is to be considered self-contained. The first part introduces basic elements of nuclear physics and guides to a modern understanding of collective motion as a transport process. This overview is supplemented in the second part with more advanced approaches to nuclear dynamics. The third part deals with special aspects of mesoscopic systems for which close analogies with nuclear physics are given. In the fourth part, the theoretical tools are discussed in greater detail. These include nuclear reaction theory, thermostatics and statistical mechanics, linear response theory, functional integrals, and various aspects of transport theory.Less

This book offers a survey of nuclear physics at low energies and discusses similarities to mesoscopic systems. It addresses systems at finite excitations of the internal degrees of freedom where collective motion exhibits features typical of transport processes for small and isolated systems. The importance of quantum aspects is investigated both with respect to the microscopic damping mechanism and to the nature of the transport equations. It is vital to account for nuclear collective motion being self-sustained, which in the end implies a highly nonlinear coupling between internal and collective degrees of freedom, a feature which in the literature all too often is ignored. The book is to be considered self-contained. The first part introduces basic elements of nuclear physics and guides to a modern understanding of collective motion as a transport process. This overview is supplemented in the second part with more advanced approaches to nuclear dynamics. The third part deals with special aspects of mesoscopic systems for which close analogies with nuclear physics are given. In the fourth part, the theoretical tools are discussed in greater detail. These include nuclear reaction theory, thermostatics and statistical mechanics, linear response theory, functional integrals, and various aspects of transport theory.

*Helmut Hofmann*

- Published in print:
- 2008
- Published Online:
- September 2008
- ISBN:
- 9780198504016
- eISBN:
- 9780191708480
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198504016.003.0018
- Subject:
- Physics, Nuclear and Plasma Physics

This chapter derives formulas for gross sections of potential scattering, and shows their generalizations to nuclear reactions. A projection technique is introduced, which allows one to separate in ...
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This chapter derives formulas for gross sections of potential scattering, and shows their generalizations to nuclear reactions. A projection technique is introduced, which allows one to separate in the T-matrix the part which varies smoothly in energy from that for resonances. For the latter, general expressions are deduced which involve partial and total widths. Non-hermitean Hamiltonians for the optical model are obtained by applying suitable energy averages. The doorway mechanism is explained by which the intermediate structure in the resonances can be understood: it employs widths for decays to the continuum and to the compound states. The statistical theory is addressed, for which on the basis of general assumptions, analytic formulas for the fluctuating cross section are derived, which are in accord with N. Bohr's hypothesis of the independence of entrance and exit channels. The Weisskopf-Ewing relations and the Hauser-Feshbach theory are described, which involve branching ratios and formation probabilities. A critique of the statistical model is included.Less

This chapter derives formulas for gross sections of potential scattering, and shows their generalizations to nuclear reactions. A projection technique is introduced, which allows one to separate in the T-matrix the part which varies smoothly in energy from that for resonances. For the latter, general expressions are deduced which involve partial and total widths. Non-hermitean Hamiltonians for the optical model are obtained by applying suitable energy averages. The doorway mechanism is explained by which the intermediate structure in the resonances can be understood: it employs widths for decays to the continuum and to the compound states. The statistical theory is addressed, for which on the basis of general assumptions, analytic formulas for the fluctuating cross section are derived, which are in accord with N. Bohr's hypothesis of the independence of entrance and exit channels. The Weisskopf-Ewing relations and the Hauser-Feshbach theory are described, which involve branching ratios and formation probabilities. A critique of the statistical model is included.