*Pier A. Mello and Narendra Kumar*

- Published in print:
- 2004
- Published Online:
- September 2007
- ISBN:
- 9780198525820
- eISBN:
- 9780191712234
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198525820.003.0005
- Subject:
- Physics, Condensed Matter Physics / Materials

This chapter motivates and discusses the basic idea of information-theoretic entropy, i.e., the Shannon entropy, and the maximum-entropy approach (MEA) based on it. The concepts of the prior and of ...
More

This chapter motivates and discusses the basic idea of information-theoretic entropy, i.e., the Shannon entropy, and the maximum-entropy approach (MEA) based on it. The concepts of the prior and of the physically relevant constraints are introduced and illustrated through a number of simple examples. The contents of this chapter include the ideas of probability and the associated information entropy; the role of the relevant physical parameters as constraints; the role of symmetries in motivating a natural probability measure; applications to equilibrium statistical mechanics; the classical ensembles; the quantum-mechanical ensembles; and a discussion of the maximum-entropy criterion in the context of statistical inference.Less

This chapter motivates and discusses the basic idea of information-theoretic entropy, i.e., the Shannon entropy, and the maximum-entropy approach (MEA) based on it. The concepts of the prior and of the physically relevant constraints are introduced and illustrated through a number of simple examples. The contents of this chapter include the ideas of probability and the associated information entropy; the role of the relevant physical parameters as constraints; the role of symmetries in motivating a natural probability measure; applications to equilibrium statistical mechanics; the classical ensembles; the quantum-mechanical ensembles; and a discussion of the maximum-entropy criterion in the context of statistical inference.

*Pier A. Mello and Narendra Kumar*

- Published in print:
- 2004
- Published Online:
- September 2007
- ISBN:
- 9780198525820
- eISBN:
- 9780191712234
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198525820.003.0001
- Subject:
- Physics, Condensed Matter Physics / Materials

This chapter introduces the notion of complex scattering of waves, emphasizes the generality of the ideas involved, and explains its relevance to the field of nuclear physics and microwave cavities. ...
More

This chapter introduces the notion of complex scattering of waves, emphasizes the generality of the ideas involved, and explains its relevance to the field of nuclear physics and microwave cavities. It then introduces the subject of coherent wave transport through mesoscopic systems, e.g., disordered conductors and chaotic cavities, with emphasis on the statistics of fluctuations observed in these systems. These fluctuations, among them the universal conductance fluctuation, arise ultimately from the complex wave interference. Various length- and time-scales defining the mesoscopic system are discussed. The idea of maximum entropy approach (MEA) is introduced as distinct from, but related to, the idea of random-matrix theory (RMT) pioneered by Wigner originally in the context of isolated resonances of complex nuclei. The contents of this chapter include complex atomic nuclei and chaotic microwave cavities; wave localization; statistical fluctuations; mesoscopic conductors: time- and length-scales, ballistic mesoscopic cavities, diffusive mesoscopic conductors, and statistical approach to mesoscopic fluctuations.Less

This chapter introduces the notion of complex scattering of waves, emphasizes the generality of the ideas involved, and explains its relevance to the field of nuclear physics and microwave cavities. It then introduces the subject of coherent wave transport through mesoscopic systems, e.g., disordered conductors and chaotic cavities, with emphasis on the statistics of fluctuations observed in these systems. These fluctuations, among them the universal conductance fluctuation, arise ultimately from the complex wave interference. Various length- and time-scales defining the mesoscopic system are discussed. The idea of maximum entropy approach (MEA) is introduced as distinct from, but related to, the idea of random-matrix theory (RMT) pioneered by Wigner originally in the context of isolated resonances of complex nuclei. The contents of this chapter include complex atomic nuclei and chaotic microwave cavities; wave localization; statistical fluctuations; mesoscopic conductors: time- and length-scales, ballistic mesoscopic cavities, diffusive mesoscopic conductors, and statistical approach to mesoscopic fluctuations.

*Pier A. Mello and Narendra Kumar*

- Published in print:
- 2004
- Published Online:
- September 2007
- ISBN:
- 9780198525820
- eISBN:
- 9780191712234
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780198525820.003.0007
- Subject:
- Physics, Condensed Matter Physics / Materials

This chapter treats the problem of finding the probability distribution of quantities related to quantum transport through a strictly one-dimensional (i.e., 1-channel) and through an N-channel ...
More

This chapter treats the problem of finding the probability distribution of quantities related to quantum transport through a strictly one-dimensional (i.e., 1-channel) and through an N-channel quasi-one-dimensional disordered system. It uses the maximum entropy approach wherein the distribution for the random transfer matrix for an elementary building block is determined by maximizing the associated Shannon entropy, subject to the physically relevant constraints of flux conservation, time-reversal symmetry (when relevant), and the Ohmic small length-scale limit. The contents of this chapter include ensemble of transfer matrices; universality classes — the orthogonal and the unitary classes; invariant measure; the Fokker-Planck equation for a disordered one-dimensional conductor; the maximum-entropy ansatz for the building block; construction of the probability density for a system of finite length; the Fokker-Planck equation for a quasi-one-dimensional multi-channel disordered conductor; the diffusion equation for the orthogonal universality class, β = 1; the diffusion equation for the unitary universality class, β = 2; and universal conductance fluctuations in the good-metallic limit.Less

This chapter treats the problem of finding the probability distribution of quantities related to quantum transport through a strictly one-dimensional (i.e., 1-channel) and through an *N*-channel quasi-one-dimensional disordered system. It uses the maximum entropy approach wherein the distribution for the random transfer matrix for an elementary building block is determined by maximizing the associated Shannon entropy, subject to the physically relevant constraints of flux conservation, time-reversal symmetry (when relevant), and the Ohmic small length-scale limit. The contents of this chapter include ensemble of transfer matrices; universality classes — the orthogonal and the unitary classes; invariant measure; the Fokker-Planck equation for a disordered one-dimensional conductor; the maximum-entropy ansatz for the building block; construction of the probability density for a system of finite length; the Fokker-Planck equation for a quasi-one-dimensional multi-channel disordered conductor; the diffusion equation for the orthogonal universality class, β = 1; the diffusion equation for the unitary universality class, β = 2; and universal conductance fluctuations in the good-metallic limit.