Turbulence model reduction by deep learning

A central problem of turbulence theory is to produce a predictive model for turbulent fluxes. These have profound implications for virtually all aspects of the turbulence dynamics. In magnetic confinement devices, drift-wave turbulence produces anomalous fluxes via cross-correlations between fluctuations. In this work, we introduce a new, data-driven method for parameterizing these fluxes. The method uses deep supervised learning to infer a reduced mean-field model from a set of numerical simulations. We apply the method to a simple drift-wave turbulence system and find a significant new effect which couples the particle flux to the local \emph{gradient} of vorticity. Notably, here, this effect is much stronger than the oft-invoked shear suppression effect. We also recover the result via a simple calculation. The vorticity gradient effect tends to modulate the density profile. In addition, our method recovers a model for spontaneous zonal flow generation by negative viscosity, stabilized by nonlinear and hyperviscous terms. We highlight the important role of symmetry to implementation of the new method.Comment: To be published in Phys. Rev. E Rap. Comm. 6 pages, 7 figure

“The best solution would probably be to never travel anywhere”:exploring consumers’ perceptions of low-carbon holiday travel

Abstract. More ecological, low-carbon holiday transport modes can offer a more sustainable option to conventional tourism travel such as airplane travel. This thesis aims to map out the overall perceptions as well as the enablers and barriers that consumers attach to low-carbon modes of holiday travel in the age of growing climate concern and “flight shame”. It does this by way of qualitative focus group interviews, where 15 Finnish individuals between the ages 23 and 38 are interviewed. The research draws from sustainable consumer behavior literature and sustainable holiday travel research as well as research concerned with the “intention-behavior gap” that is recognized in consumer behavior research related to pro-environmental consumption. Based on the previous literature and the findings of the qualitative interviews, an abductive approach is utilized in combining them to formulate a low-carbon travel perception framework. Based on the research, while low-carbon travel and its environmental impact are regarded positively, it is not seen as a form of holiday travel that would fit all needs and contexts. Low-carbon travel is regarded as having future potential but is deemed unfitting for certain situations and groups, such as inexperienced travelers. The experience-related aspects of such travel are appreciated but the perceived unattainability and other reportedly inferior qualities in comparison to airplane travel are not appreciated. The findings offer new insights for academic research in that they illustrate how consumers view low-carbon modes of holiday travel and by proposing a framework that illustrates factors that affect these perceptions. For managers and practitioners, the findings offer information about how consumers view different modes of transport and their potential in holiday travel now and in the future. The generalizability of the findings of this research is limited due to the somewhat homogenous nature of the interviewed population, all of whom are Finnish and represent a narrow age range. In future studies interviewees from different backgrounds could offer new insights. In the future, research that would focus on differences between avid holiday plane travelers and engaged low-carbon travelers could illustrate how different groups view such alternative forms of holiday transport

Odd Decays from Even Anomalies: Gauge Mediation Signatures Without SUSY

We analyze the theory and phenomenology of anomalous global chiral symmetries in the presence of an extra dimension. We propose a simple extension of the Standard Model in 5D whose signatures closely resemble those of supersymmetry with gauge mediation, and we suggest a novel scalar dark matter candidate.Comment: 26 pages, 1 figure; v2: references added; discussion of direct collider constraints added; v3: corrected dark matter calculation in chapter 4.2 and replaced figure 1

Mesoscopic transport beyond linear response

We present an approach to steady-state mesoscopic transport based on the maximum entropy principle formulation of nonequilibrium statistical mechanics. Our approach is not limited to the linear response regime. We show that this approach yields the quantization observed in the integer quantum Hall effect at large currents, which until now has been unexplained. We also predict new behaviors of non-local resistances at large currents in the presence of dirty contacts.Comment: 14 pages plus one figure (with an insert) (post-script codes appended), RevTeX 3.0, UCF-CM-93-004 (Revised