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1. Hydrodynamics of body–body interactions in dense synchronous elongated fish schools

   https://doi.org/10.1063/5.0142950  

   Kelly, J.; Pan, Y.; Menzer, A.; Dong, H. (April 2023, Physics of Fluids)

   Mechanisms for hydrodynamic benefit via fluid interactions in large planar fish schools ( n ≥ 10) are investigated by two-dimensional numerical simulations of carangiform fish swimming. It is observed that the average swimming efficiency of the 10-fish school is increased by 30% over a single swimmer, along with a thrust production improvement of 114%. The performance and flow analyses characterize the associated hydrodynamic interaction mechanisms in large dense schools leading to enhanced performance. First, anterior body suction arises from the proximity of the suction side of the flapping tail to the head of the following fish. Next, the block effect is observed as another fish body blocks the flow behind a fish. Finally, the wall effect enhances the flow of momentum downstream where the body of a neighboring fish acts as a wall for the flapping of a fish tail moving toward it. Because these primary body–body interactions are based on the arrangement of surrounding fish, a classification of the individual fish within the school is presented based on the intra-fish interactions and is reflected in the performance of the individuals. It is shown that the school can be separated as front fish, middle fish, edge fish, and back fish based on the geometric position, performance, and wake characteristics. Finally, groupings and mechanisms observed are proven to be consistent over a range of Reynolds numbers and school arrangements. 

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2. Many-Body Resonances in the Avalanche Instability of Many-Body Localization

   https://doi.org/10.1103/PhysRevLett.130.250405  

   Ha, Hyunsoo; Morningstar, Alan; Huse, David A. (June 2023, Physical Review Letters)

   Many-body localized (MBL) systems fail to reach thermal equilibrium under their own dynamics, even though they are interacting, nonintegrable, and in an extensively excited state. One instability toward thermalization of MBL systems is the so-called “avalanche,” where a locally thermalizing rare region is able to spread thermalization through the full system. The spreading of the avalanche may be modeled and numerically studied in finite one-dimensional MBL systems by weakly coupling an infinite-temperature bath to one end of the system. We find that the avalanche spreads primarily via strong many-body resonances between rare near-resonant eigenstates of the closed system. Thus we find and explore a detailed connection between many-body resonances and avalanches in MBL systems. 

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3. Implementing Chiral Three-Body Forces in Terms of Medium-Dependent Two-Body Forces

   https://doi.org/10.3389/fphy.2020.00100  

   Holt, Jeremy W.; Kawaguchi, Mamiya; Kaiser, Norbert (April 2020, Frontiers in Physics)
4. Quantum many-body scars in few-body dipole-dipole interactions

   https://doi.org/10.1103/PhysRevResearch.6.043086  

   Spielman, Sarah E; Handian, Alicia; Inman, Nina P; Carroll, Thomas J; Noel, Michael W (November 2024, Physical Review Research)

   We simulate the dynamics of Rydberg atoms resonantly exchanging energy via two-, three-, and four-body dipole-dipole interactions in a one-dimensional array. Using simplified models of a realistic experimental system, we study the initial-state survival probability, mean level spacing, spread of entanglement, and properties of the energy eigenstates. By exploring a range of disorders and interaction strengths, we find regions in parameter space where the three- and four-body dynamics either fail to thermalize or do so slowly. The interplay between the stronger hopping and weaker field-tuned interactions gives rise to quantum many-body scar states, which play a critical role in slowing the dynamics of the three- and four-body interactions. Published by the American Physical Society2024 

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5. Untangling the evolution of body-part terminology in Pano: conservative versus innovative traits in body-part lexicalization

   https://doi.org/10.1098/rsfs.2022.0053  

   Zariquiey, Roberto; Vera, Javier; Greenhill, Simon J.; Valenzuela, Pilar; Gray, Russell D.; List, Johann-Mattis (February 2023, Interface Focus)

   Although language-family specific traits which do not find direct counterparts outside a given language family are usually ignored in quantitative phylogenetic studies, scholars have made ample use of them in qualitative investigations, revealing their potential for identifying language relationships. An example of such a family specific trait are body-part expressions in Pano languages, which are often lexicalized forms, composed of bound roots (also called body-part prefixes in the literature) and non-productive derivative morphemes (called here body-part formatives). We use various statistical methods to demonstrate that whereas body-part roots are generally conservative, body-part formatives exhibit diverse chronologies and are often the result of recent and parallel innovations. In line with this, the phylogenetic structure of body-part roots projects the major branches of the family, while formatives are highly non-tree-like. Beyond its contribution to the phylogenetic analysis of Pano languages, this study provides significative insights into the role of grammatical innovations for language classification, the origin of morphological complexity in the Amazon and the phylogenetic signal of specific grammatical traits in language families. 

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