On the rigidity of special and exceptional geometries with torsion a closed $3$-form

This paper establishes that Riemannian manifolds admitting a connection with closed, covariantly constant torsion decompose locally into a product of a semisimple Lie group and a torsion-free manifold, a result used to simplify proofs for special geometries like KT and HKT manifolds and to fully characterize the geometry of complete, simply connected G2G_2, Spin(7)\mathrm{Spin}(7), and compact 8-dimensional HKT manifolds under these conditions.

Georgios PapadopoulosTue, 10 Ma🔢 math

\del\delbar\del\delbar-Lemma and Bott-Chern cohomology of twistor spaces

This paper investigates the Bott-Chern and Aeppli cohomologies of twistor spaces associated with compact self-dual 4-manifolds to characterize the validity of the ˉ\partial\bar{\partial}-lemma, while explicitly computing the Dolbeault cohomology for the twistor space of the flat 4-torus as a specific example where the lemma fails.

Anna Fino, Gueo Grantcharov, Nicoletta Tardini, Adriano Tomassini, Luigi VezzoniTue, 10 Ma🔢 math

On sporadic symmetry breaking operators for principal series representations of the de Sitter and Lorentz groups

This paper constructs and classifies all differential symmetry breaking operators between principal series representations of the de Sitter and Lorentz groups SO0(4,1)SO0(3,1)SO_0(4,1) \supset SO_0(3,1), proving that all such operators are necessarily differential and constitute "sporadic" cases that cannot be derived from meromorphic families via residue formulas.

Víctor Pérez-ValdésTue, 10 Ma🔢 math

On the DJ+\mathcal{D}^+_J operator on higher-dimensional almost Kähler manifolds

This paper introduces the DJ+\mathcal{D}^+_J operator on higher-dimensional almost Kähler manifolds to investigate the ˉ\bar{\partial}-problem and establish uniqueness and local existence results for a generalized Monge-Ampère equation, ultimately providing an elliptic system for the operator and reorganizing the work of Tosatti-Weinkove-Yau.

Qiang Tan, Hongyu Wang, Ken Wang, Zuyi ZhangTue, 10 Ma🔢 math

Rigidity of spin fill-ins with non-negative scalar curvature

This paper establishes new mean curvature rigidity theorems for spin fill-ins with non-negative scalar curvature by employing two distinct spinorial techniques—an APS boundary value problem extension and an index-theoretic comparison—to resolve questions posed by Miao and Gromov, while also deriving a novel Witten-type mass inequality for asymptotically Schwarzschild manifolds.

Simone Cecchini, Sven Hirsch, Rudolf ZeidlerTue, 10 Ma🔢 math

A gluing construction of singular solutions for a fully non-linear equation in conformal geometry

This paper demonstrates that the classical Mazzeo-Pacard gluing method can be successfully extended to construct singular solutions for the fully non-linear σ2\sigma_2-Yamabe equation in dimensions n>4n>4, provided the singular set consists of disjoint closed submanifolds with dimensions strictly less than (nn2)/2(n-\sqrt{n}-2)/2.

María Fernanda Espinal, María del Mar GonzálezTue, 10 Ma🔢 math

An index bound for smooth umbilic points

This paper proves that the local index of an isolated umbilic point on a C3+αC^{3+\alpha}-smooth convex surface in Euclidean 3-space is strictly less than two by employing a "totally real blow-up" technique to reduce the local problem to a global result regarding Lagrangian surfaces, thereby suggesting the potential existence of exotic umbilic points with index 3/2 that exceed the bounds known for real analytic surfaces.

Brendan Guilfoyle, Wilhelm KlingenbergTue, 10 Ma🔢 math

Flexibility of Codimension One C1,θC^{1,\theta} Isometric Immersions

This paper improves the known threshold for the flexibility of C1,θC^{1,\theta} isometric immersions of nn-dimensional Riemannian metrics into Rn+1\mathbb{R}^{n+1} by proving that any short immersion can be approximated by such immersions for θ<1/(1+2(n1))\theta < 1/(1+2(n-1)) when n3n \geq 3, utilizing a refined convex integration scheme with enhanced iterative integration by parts.

Dominik InauenTue, 10 Ma🔢 math