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1. Rural Smart Shrinkage and Perceptions of Quality of Life in the American Midwest

   https://doi.org/10.1007/978-3-030-50540-0_20  

   Zarecor, K.; Peters, D.; Hamideh, S. (January 2021, International handbooks of qualityoflife)

   null; null; null (Ed.)

   Rural communities in the American Midwest have experienced upheaval since the 1980s with shrinking populations, an exodus of younger people, job losses, and aging infrastructure. Evidence shows that these trends are unlikely to be reversed in most places. Despite this, high-cost and unproven economic growth strategies are still promoted as the most appropriate responses. This chapter presents findings from an interdisciplinary research project about quality of life (QoL) in rural Iowa that proposes changing the analytical paradigm in this context from growth to one that sees adaptation to population loss as a form of resiliency. Using qualitative and quantitative data, the research considers how some shrinking rural communities in Iowa have been better able to adapt than others. The research shows that negative trends in QoL perceptions in these towns were best mitigated by investing in community services and social capital, rather than in economic development. This process is described as rural smart shrinkage, a term borrowed from research on shrinking cities and applied here to rural communities for the first time. The framework shifts away from associating population loss with community decline and instead emphasizes intentional and low-cost strategies that may sustain shrinking rural communities into the future. 

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2. Impacts of urban decline on local climatology: A comparison of growing and shrinking cities in the post-industrial Rust Belt

   https://doi.org/10.3389/fclim.2023.1010849  

   Hwang, Kyotaek; Eklund, Alex; Valdez, Cecily; Papuga, Shirley A. (January 2023, Frontiers in Climate)

   Cities such as Detroit, MI in the post-industrial Rust Belt region of the United States, have been experiencing a decline in both population and economy since the 1970's. These “shrinking cities” are characterized by aging infrastructure and increasing vacant areas, potentially resulting in more green space. While in growing cities research has demonstrated an “urban heat island” effect resulting from increased temperatures with increased urbanization, little is known about how this may be different if a city shrinks due to urban decline. We hypothesize that the changes associated with shrinking cities will have a measurable impact on their local climatology that is different than in areas experiencing increased urbanization. Here we present our analysis of historical temperature and precipitation records (1900–2020) from weather stations positioned in multiple shrinking cities from within the Rust Belt region of the United States and in growing cities within and outside of this region. Our results suggest that while temperatures are increasing overall, these increases are lower in shrinking cities than those cities that are continuing to experience urban growth. Our analysis also suggests there are differences in precipitation trends between shrinking and growing cities. We also highlight recent climate data in Detroit, MI in the context of these longer-term changes in climatology to support urban planning and management decisions that may influence or be influenced by these trends. 

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3. Electric-magnetic duality in a class of G2-compactifications of M-theory

   https://doi.org/10.1007/JHEP04(2023)089  

   Halverson, James; Sung, Benjamin; Tian, Jiahua (April 2023, Journal of High Energy Physics)

   A bstract We study electric-magnetic duality in compactifications of M-theory on twisted connected sum (TCS) G 2 manifolds via duality with F-theory. Specifically, we study the physics of the D3-branes in F-theory compactified on a Calabi-Yau fourfold Y , dual to a compactification of M-theory on a TCS G 2 manifold X . $$ \mathcal{N} $$ N = 2 supersymmetry is restored in an appropriate geometric limit. In that limit, we demonstrate that the dual of D3-branes probing seven-branes corresponds to the shrinking of certain surfaces and curves, yielding light particles that may carry both electric and magnetic charges. We provide evidence that the Minahan-Nemeschansky theories with E n flavor symmetry may be realized in this way. The SL(2 , ℤ) monodromy of the 3/7-brane system is dual to a Fourier-Mukai transform of the dual IIA/M-theory geometry in this limit, and we extrapolate this monodromy action to the global compactification. Away from the limit, the theory is broken to $$ \mathcal{N} $$ N = 1 supersymmetry by a D-term. 

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4. Shrinking targets for the geodesic flow on geometrically finite hyperbolic manifolds

   https://doi.org/10.3934/jmd.2021014  

   Kelmer, Dubi; Oh, Hee (January 2021, Journal of Modern Dynamics)

   Let \begin{document}$$ \mathscr{M} $$\end{document} be a geometrically finite hyperbolic manifold. We present a very general theorem on the shrinking target problem for the geodesic flow, using its exponential mixing. This includes a strengthening of Sullivan's logarithm law for the excursion rate of the geodesic flow. More generally, we prove logarithm laws for the first hitting time for shrinking cusp neighborhoods, shrinking tubular neighborhoods of a closed geodesic, and shrinking metric balls, as well as give quantitative estimates for the time a generic geodesic spends in such shrinking targets. 

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5. Dynamical Borel–Cantelli lemma for recurrence under Lipschitz twists

   https://doi.org/10.1088/1361-6544/acafcb  

   Kleinbock, Dmitry; Zheng, Jiajie (January 2023, Nonlinearity)

   Abstract In the study of some dynamical systems the limsup set of a sequence of measurable sets is often of interest. The shrinking targets and recurrence are two of the most commonly studied problems that concern limsup sets. However, the zero–one laws for the shrinking targets and recurrence are usually treated separately and proved differently. In this paper, we introduce a generalized definition that can specialize into the shrinking targets and recurrence; our approach gives a unified proof of the zero–one laws for the two problems. 

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