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1. Nonlinear Reconnection in Magnetized Turbulence

   https://doi.org/10.3847/1538-4357/ab6a95  

   Loureiro, Nuno F.; Boldyrev, Stanislav (February 2020, The Astrophysical Journal)
2. Turbulence in Magnetized Pair Plasmas

   https://doi.org/10.3847/2041-8213/aae483  

   Loureiro, Nuno F.; Boldyrev, Stanislav (October 2018, The Astrophysical Journal)
3. Magnetized Fingering Convection in Stars

   https://doi.org/10.3847/1538-4357/ad26fe  

   Fraser, Adrian E.; Reifenstein, Sam A.; Garaud, Pascale (March 2024, The Astrophysical Journal)

   Abstract Fingering convection (also known as thermohaline convection) is a process that drives the vertical transport of chemical elements in regions of stellar radiative zones where the mean molecular weight increases with radius. Recently, Harrington & Garaud used three-dimensional direct numerical simulations (DNS) to show that a vertical magnetic field can dramatically enhance the rate of chemical mixing by fingering convection. Furthermore, they proposed a so-called “parasitic saturation” theory to model this process. Here, we test their model over a broad range of parameter space, using a suite of DNS of magnetized fingering convection, varying the magnetic Prandtl number, magnetic field strength, and composition gradient. We find that the rate of chemical mixing measured in the simulations is not always predicted accurately by their existing model, in particular when the magnetic diffusivity is large. We then present an extension of the Harrington & Garaud model which resolves this issue. When applied to stellar parameters, it recovers the results of Harrington & Garaud except in the limit where fingering convection becomes marginally stable, where the new model is preferred. We discuss the implications of our findings for stellar structure and evolution. 

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4. Magnetized Oscillatory Double-diffusive Convection

   https://doi.org/10.3847/1538-4357/ac73ed  

   Sanghi, A.; Fraser, A_E; Tian, E_W; Garaud, P. (August 2022, The Astrophysical Journal)

   Abstract We study the properties of oscillatory double-diffusive convection (ODDC) in the presence of a uniform vertical background magnetic field. ODDC takes place in stellar regions that are unstable according to the Schwarzschild criterion and stable according to the Ledoux criterion (sometimes called semiconvective regions), which are often predicted to reside just outside the core of intermediate-mass main-sequence stars. Previous hydrodynamic studies of ODDC have shown that the basic instability saturates into a state of weak wave-like convection, but that a secondary instability can sometimes transform it into a state of layered convection, where layers then rapidly merge and grow until the entire region is fully convective. We find that magnetized ODDC has very similar properties overall, with some important quantitative differences. A linear stability analysis reveals that the fastest-growing modes are unaffected by the field, but that other modes are. Numerically, the magnetic field is seen to influence the saturation of the basic instability, overall reducing the turbulent fluxes of temperature and composition. This in turn affects layer formation, usually delaying it, and occasionally suppressing it entirely for sufficiently strong fields. Further work will be needed, however, to determine the field strength above which layer formation is actually suppressed in stars. Potential observational implications are briefly discussed. 

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5. Metaplectic flavor symmetries from magnetized tori

   https://doi.org/10.1007/jhep05(2021)078  

   Almumin, Yahya; Chen, Mu-Chun; Knapp-Pérez, Víctor; Ramos-Sánchez, Saúl; Ratz, Michael; Shukla, Shreya (May 2021, Journal of High Energy Physics)

   null (Ed.)

   A bstract We revisit the flavor symmetries arising from compactifications on tori with magnetic background fluxes. Using Euler’s Theorem, we derive closed form analytic expressions for the Yukawa couplings that are valid for arbitrary flux parameters. We discuss the modular transformations for even and odd units of magnetic flux, M , and show that they give rise to finite metaplectic groups the order of which is determined by the least common multiple of the number of zero-mode flavors involved. Unlike in models in which modular flavor symmetries are postulated, in this approach they derive from an underlying torus. This allows us to retain control over parameters, such as those governing the kinetic terms, that are free in the bottom-up approach, thus leading to an increased predictivity. In addition, the geometric picture allows us to understand the relative suppression of Yukawa couplings from their localization properties in the compact space. We also comment on the role supersymmetry plays in these constructions, and outline a path towards non-supersymmetric models with modular flavor symmetries. 

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