This paper presents the derivation of formal, exact expressions for "generalized response coeffIcients, " quantities which characterize the response of a system to conservative forces of arbitrary strength and time dependence. The development avoids all expansions of the response in powers of the driving forces. The generalized response coefBcients thus provide the basis for calculations of nonlinear effects in those situations for which expansions in powers of the forces are not suitable.It is shown how the linear and higher-order response functions obtained first by Kubo can be obtained in a relatively more compact way. The expressions corresponding to static forces are considered in some detail. Generalized response coeKcients are also derived for systems in equilibrium; the lowest order of these is just the isothermal susceptibility as usually defined.

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Articles you may be interested inZero-crossing Shapiro step generated in an asymmetric and nonhysteretic rf-current-driven two-junction superconducting quantum interference deviceThe average voltage and circulating current of a superconducting interferometer containing two Josephson junctions (a dc SQUID) are calculated analytically, in various approximations, as functions of bias current and applied magnetic field or control current. The results are useful in calculations of the noise characteristics of the dc SQUID, as well as in other applications. PACS numbers: 74.50. + r, 85.25. + k [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 132.