Summary
A « dynamical » Lagrangian approach to the many body problem in the collective co-ordinate formulation is made possible with the aid of the two-body correlation function. As a consequence, the values of the flctitious masses and frequencies for the collective co-ordinate harmonic oscillators, which represent the physical problem, are dependent on the average motion of the system. Moreover, the introduction of the center of mass and relative co-ordinates for theq k occasions no difficulty in the present approach. In Part B of the paper, preliminary considerations are presented on the physical extent of the domain of action ofq-space; various techniques are utilized to probe its structure. It is found in this way that the « diameter » ofq-space is of the order ofN 1/2. Application is made to the speed of sound in a fluid.
Riassunto
L’attacco del problema di più corpi nella formulazione con coordinate collettive per mezzo di un lagrangiano «dinamico» è reso possibile ricorrendo alla funzione di correlazione di due corpi. Come conseguenza i valori delle masse e delle frequenze fittizie per gli oscillatori armonici delle coordinate collettive che rappresentano il probleme fisico dipendono dal moto medio del sistema. Inoltre, l’introduzione del centro di masse e delle relative coordinate per iq k non offrono alcuna difficoltà in questo procedimento Nella parte B del lavoro si espongono considerazioni preliminari sull’estensione fisica del dominio d’azione dello spazioq; si utilizzano varie tecniche per saggiare la sua struttura. In tal modo si trova che il «diametro» dello spazioq è dell’ordine diN 1/2. Se ne fa un’applicazione alla velocità del suono in un fluido.
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References
G. J. Yevick andJ. K. Percus:A New Approach to the Many Body Problem andJ. K. Percus andG. J. Yevick:Some Dynamical Considerations in the New Approach to the Many Body Prbolem (Phys. Rev.,101, 1186 (1956), hereafter referred to as papers I and II).
A. Bohr andB. Mottelson:Kgl. Danske Viden. Selskab, Mat.-fys. Medd.,27, No. 16 (1953).
If explicit many body correlations are neglected as inJ. G. Kirkwood andE. M. Boggs:Journ. Chem. Phys.,10, 394 (1942), effective many body correlations are obtained in terms ofσ(x) alone, but the resulting form is not particularly appropriate for computations.
SeeW. Feller:Introduction to Probability Theory (New York, 1950), p. 192.
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Supported in part by the Office of Naval Research.
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Percus, J.K., Yevick, G.J. « Dynamical » lagrangian for the many body problem. Nuovo Cim 5, 65–82 (1957). https://doi.org/10.1007/BF02812818
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DOI: https://doi.org/10.1007/BF02812818