Local Transition Process Research Articles

Multifractality in monitored single-particle dynamics

We study multifractal properties in time evolution of a single particle subject to repeated measurements. For quantum systems, we consider circuit models consisting of local unitary gates and local projective measurements. For classical systems, we consider models for estimating the trajectory of a particle evolved under local transition processes by partially measuring particle occupations. In both cases, multifractal behaviors appear in the ensemble of wave functions or probability distributions conditioned on measurement outcomes after a sufficiently long time. While the nature of particle transport (diffusive or ballistic) qualitatively affects the multifractal properties, they are even quantitatively robust to the measurement rate or specific protocols. On the other hand, multifractality is generically lost by generalized measurements allowing erroneous outcomes or by postselection of the outcomes with no particle detection. We demonstrate these properties by numerical simulations and also propose several simplified models, which allow us to analytically obtain multifractal properties in the monitored single-particle systems. Published by the American Physical Society 2024

More than one story: remaking community and place in Sweden’s transition to a fossil free society

ABSTRACT In this article, we study how Sweden’s transition to a fossil free society is interpreted and experienced by communities whose livelihoods and cultural identities are entangled with carbon-intensive industries. The study draws upon interviews with citizen groups in the coastal city of Lysekil, located next to Scandinavia’s largest oil refinery. Our analysis speaks to a growing scholarly literature on just transitions where we argue that a better understanding of place attachment as an active and operating force in local transition processes, can provide important information for just transition policy design. Based on our research on place attachment in Lysekil, we suggest that inclusivity in just transitions, implies acknowledging and addressing more than material aspects of loss, involving loss of direction, loss of identities and loss of imagined futures. Moreover, we argue that the vision of an inclusive transition requires a more nuanced approach to the concept of “community” which recognises different stories, voices, and perspectives and challenges taken for granted assumptions about local people's priorities in debates on just transitions. Finally, based on our experiences from Lysekil we contend that inclusivity requires communicative spaces where citizens can meet to listen, speak, and discuss future pathways towards a fossil free society. The visions of just and inclusive transitions, we argue, can only be realised if driven by a place-based dialogue on future pathways and if agendas for a fossil free transformation are locally anchored.

A spatial approach for future-oriented heat planning in urban areas

The current climate protection goals will lead to unprecedented and profound changes to energy systems. The transition to a decarbonized heat supply system will be complex and the process will have deep impact on the urban subsystems (technical, economic, social and planning subsystems) with different spatial extents. For decision making in this context, the level of individual buildings provides a perspective which is too narrow. On the other hand a very broad view is also unhelpful for the local transition process. This article shows an innovative way to analyse heat demand data with the help of fuzzy logic and spatial mapping of the suitability of different heat supply systems. At the subsequent planning level, the results can be used as guard rails to make the urban planning process more consistent and transparent.

Modeling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJs) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semiempirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, recalibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

Transition Modeling for Vortex Generating Jets on Low-Pressure Turbine Profiles

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is≤100·103, an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modeled by a filtered Q vortex criterion the transition development itself is modeled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

Frequency Dependence of Quantum Localization in a Periodically Driven System

We study the quantum localization phenomena for a random matrix model belonging to the Gaussian orthogonal ensemble (GOE). An oscillating external field is applied on the system. After the transient time evolution, energy is saturated to various values depending on the frequencies. We investigate the frequency dependence of the saturated energy. This dependence cannot be explained by a naive picture of successive independent Landau-Zener transitions at avoided level crossing points. The effect of quantum interference is essential. We define the number of Floquet states which have large overlap with the initial state, and calculate its frequency dependence. The number of Floquet states shows approximately linear dependence on the frequency, when the frequency is small. Comparing the localization length in Floquet states and that in energy states from the viewpoint of the Anderson localization, we conclude that the Landau-Zener picture works for the local transition processes between levels.