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1. Actions of 𝐴𝑙𝑡(𝑛) on groups of finite Morley rank without involutions

   https://doi.org/10.1090/proc/16530  

   Altınel, Tuna; Wiscons, Joshua (January 2024, Proceedings of the American Mathematical Society)

   We investigate faithful representations of Alt(n) as automorphisms of a connected group 𝐺 of finite Morley rank. We target a lower bound of 𝑛 on the rank of such a nonsolvable 𝐺, and our main result achieves this in the case when 𝐺 is without involutions. In the course of our analysis, we also prove a corresponding bound for solvable 𝐺 by leveraging recent results on the abelian case. We conclude with an application towards establishing natural limits to the degree of generic transitivity for permutation groups of finite Morley rank. 

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2. GROUPS OF MORLEY RANK 4

   https://doi.org/10.1017/jsl.2014.81  

   WISCONS, JOSHUA (March 2016, The Journal of Symbolic Logic)

   Abstract We show that any simple group of Morley rank 4 must be a bad group with no proper definable subgroups of rank larger than 1. We also give an application to groups acting on sets of Morley rank 2. 

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3. TRANSITIVITY, LOWNESS, AND RANKS IN NSOP THEORIES

   https://doi.org/10.1017/jsl.2023.36  

   CHERNIKOV, ARTEM; KIM, BYUNGHAN; RAMSEY, NICHOLAS (June 2023, The Journal of Symbolic Logic)

   Abstract We develop the theory of Kim-independence in the context of NSOP $$_{1}$$ theories satisfying the existence axiom. We show that, in such theories, Kim-independence is transitive and that -Morley sequences witness Kim-dividing. As applications, we show that, under the assumption of existence, in a low NSOP $$_{1}$$ theory, Shelah strong types and Lascar strong types coincide and, additionally, we introduce a notion of rank for NSOP $$_{1}$$ theories. 

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4. Positively curved Riemannian metrics with logarithmic symmetry rank bounds

   https://doi.org/10.4171/CMH/340  

   Kennard, Lee (November 2014, Commentarii Mathematici Helvetici)

   We prove an obstruction at the level of rational cohomology to the existence of positively curved metrics with large symmetry rank. The symmetry rank bound is logarithmic in the dimension of the manifold. As one application, we provide evidence for a generalized conjecture of H. Hopf, which states that no symmetric space of rank at least two admits a metric with positive curvature. Other applications concern product manifolds, connected sums, and manifolds with nontrivial fundamental group. 

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5. Meridional rank and bridge number of knotted 2-spheres

   https://doi.org/10.4153/S0008414X23000883  

   Joseph, Jason; Pongtanapaisan, Puttipong (February 2025, Canadian Journal of Mathematics)

   Abstract The meridional rank conjecture asks whether the bridge number of a knot in$$S^3$$is equal to the minimal number of meridians needed to generate the fundamental group of its complement. In this paper, we investigate the analogous conjecture for knotted spheres in$$S^4$$. Towards this end, we give a construction to produce classical knots with quotients sending meridians to elements of any finite order in Coxeter groups and alternating groups, which detect their meridional ranks. We establish the equality of bridge number and meridional rank for these knots and knotted spheres obtained from them by twist-spinning. On the other hand, we show that the meridional rank of knotted spheres is not additive under connected sum, so that either bridge number also collapses, or meridional rank is not equal to bridge number for knotted spheres. 

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