Theory of Magneto--Acoustic Transport in Modulated Quantum Hall Systems Near ν=1/2\nu=1/2

Motivated by the experimental results of Willett et al [Phys.Rev. Lett., {\bf 78}, 4478 (1997)] we develop a magneto-transport theory for the response of a two dimensional electron gas (2DEG) in the Fractional Quantum Hall Regime near Landau level filling factor $\nu = 1/2$ to the surface acoustic wave (SAW) in the presence of an added periodic density modulation. We assume there exists a Composite Fermion Fermi Surface (CF-FS) at $\nu = 1/2$, and we show that the deformation of the (CF-FS) due to the density modulation can be at the origin of the observed transport anomalies for the experimental conditions. Our analysis is carried out particularly for the non-local case which corresponds to the SAW experiments. We introduce a new model of a deformed CF-FS. The model permits us to explain anomalous features of the response of the modulated 2DEG to the SAW near $\nu = 1/2:$ namely the nonlinear wave vector dependence of the electron conductivity, the appearance of peaks in the SAW velocity shift and attenuation and the anisotropy of the effect, all of which originate from contributions to the conductivity tensor due to the regions of the CF-FS which are flattened by the applied modulation.Comment: 13 pages, 4 figures, the published versio

Standards and Standardization: an Interdisciplinary Literature Review

Standardisation and standards are long-held and essential features of our society, but their field of study is fragmented. This paper reviews recent developments (2012-2021) of the scientific literature on standardisation and standards by adopting an interdisciplinary and systematic approach. Investigating over 1350 published papers, we analyse both their horizontal topics (theory-oriented) and vertical topics (context or the industry of application). Standards have become an ubiquitous feature of our society, and this is indeed reflected by the richness of insights and disciplinary perspectives we observe in this content analysis. Making use of a bibliometric analysis, we find that (1) especially in the last 5 years, there is a surge of studies on technical standardisation (IT & Engineering), triggered by developments such as IoT and 5G; (2) a set of classical, long-held research domains that was well established even before our time frame and continues to exist, and (3) there is an increasing focus on the role of standardisation with regard to societal impact, such as environment and sustainability. We also describe the recurring theme of the (apparent) paradoxical nature of standardisation – the problems it addresses and the challenges it creates by doing so – and the complex way standardisation relates to innovation