The calculation of the conductance of disordered rings requires a theory that goes beyond the Kubo-Drude formulation. Assuming "mesoscopic" circumstances the analysis of the electro-driven transitions show similarities with a percolation problem in energy space. We argue that the texture and the sparsity of the perturbation matrix dictate the value of the conductance, and study its dependence on the disorder strength, ranging from the ballistic to the Anderson localization regime. An improved sparse random matrix model is introduced to captures the essential ingredients of the problem, and leads to a generalized variable range hopping picture. ‡ Hence there is no issue of quantum recurrences which would arise for a strictly linear or periodic driving. From here on we use units such that = 1. § The terminology of this paper, and in particular our notion of "conductance" are the same as in the theoretical review [4] and in the experimental work [5].
This article discusses a case study of a pair of students mentored by a physics teacher as they engaged in a long‐term (15 months) engineering maker‐based inquiry (EMBI), a mandatory part of these students' formal learning of physics at the advanced high school level. We conceptualize the students' engagement as participating in a particular figured world, which is distinct from the figured world of authentic scientific inquiry. Using fine‐grained discourse analysis of mentor–mentee interactions in authentic working sessions, complemented by interviews and other ethnographic accounts, we: (a) characterize this figured world; (b) identify central legitimate forms of participation that were enacted by the students and influenced their learning; (c) articulate how these forms of participation were socially communicated, constructed, and enforced over time in the interaction between the two students and the educational staff; and (d) examine how these forms of participation facilitated (or impaired) the learning of content and practices of the related physics. Two legitimate forms of participation, which contributed extensively to the EMBI's goal of creating a working artifact, are discussed in detail. The analysis articulates the social construction of these forms of participation and shows that (a) participating as an engineer facilitated many foundational aspects of learning of physics, (b) participating as a technician fostered a sense of agency and efficacy with regard to physics in a student who did not find ways to express himself in the regular physics classroom; however, it did not facilitate the learning of scientific content and practices. The implications for the instruction of physics in school, particularly given recent calls for integrated STEM education and Making in education, are discussed.
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