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1. Revisiting the Relation Between Momentum and Scalar Roughness Lengths of Urban SurfacesRevisiting the Relation Between the Momentum and Scalar Roughness Lengths of Urban Surfaces

   https://doi.org/10.1002/qj.3839  

   Li, Qi ; Bou‐Zeid, Elie ; Grimmond, Sue ; Zilitinkevich, Sergej ; Katul, Gabriel ( June 2020 , Quarterly journal of the Royal Meteorological Society)

   Large Eddy Simulations (LES) of neutral flow over regular arrays of cuboids are conducted to explore connections between momentum (z 0m ) and scalar (z 0s ) roughness lengths in urban environments, and how they are influenced by surface geometry. As LES resolves the obstacles but not the micro‐scale boundary layers attached to them, the aforementioned roughness lengths are analyzed at two distinct spatial scales. At the micro‐scale (roughness of individual facets, e.g. roofs), it is assumed that both momentum and scalar transfer are governed by accepted arguments for smooth walls that form the basis for the LES wall model. At the macro‐scale, the roughness lengths are representative of the aggregate effects of momentum and scalar transfer over the resolved roughness elements of the whole surface, and hence they are directly computed from the LES. The results indicate that morphologically‐based parameterizations for macro‐scale z 0m are adequate overall. The relation between the momentum and scalar macro‐roughness values, as conventionally represented by log(z 0m /z 0s ) and assumed to scale with urn:x-wiley:00359009:media:qj3839:qj3839-math-0001 (where Re * is a roughness Reynolds number), is then interpreted using surface renewal theory (SRT). SRT predicts n = 1/4 when only Kolmogorov‐scale eddies dominate the scalarmore »exchange, whereas n = 1/2 is predicted when large eddies limit the renewal dynamics. The latter is found to better capture the LES results. However, both scaling relations indicate that z 0s decreases when z 0m increases for typical urban geometries and scales. This is opposite to how their relation is usually modeled for urban canopies (i.e. z 0s /z 0m is a fixed value smaller than unity).« less
2. Contracting asymptotics of the linearized lapse-scalar field sub-system of the Einstein-scalar field equations

   https://doi.org/10.1063/1.5115104  

   Ames, Ellery ; Beyer, Florian ; Isenberg, James ( October 2019 , Journal of Mathematical Physics)
3. Renormalization for a Scalar Field in an External Scalar Potential

   https://doi.org/10.3390/sym10030054  

   Fulling, Stephen ; Settlemyre, Thomas ; Milton, Kimball ( March 2018 , Symmetry)
4. Solar System constraints on massless scalar-tensor gravity with positive coupling constant upon cosmological evolution of the scalar field

   https://doi.org/10.1103/PhysRevD.96.064037  

   Anderson, David ; Yunes, Nicolás ( September 2017 , Physical Review D)
5. Implications of the scalar tilt for the tensor-to-scalar ratio

   https://doi.org/10.1103/PhysRevD.92.123528  

   Creminelli, Paolo ; Dubovsky, Sergei ; López Nacir, Diana ; Simonović, Marko ; Trevisan, Gabriele ; Villadoro, Giovanni ; Zaldarriaga, Matias ( December 2015 , Physical Review D)