Cohen-Macaulayness of Local Models via Shellability of the Admissible Set

This paper proves that augmented admissible sets in Iwahori-Weyl groups are dual EL-shellable, thereby resolving a conjecture of Görtz and establishing the Cohen-Macaulayness of special fibers for local models with parahoric level structure—including previously open cases in residue characteristic 2 and non-reduced root systems—through a characteristic-free, intrinsic construction that yields an explicit shelling and inductive building procedure.

Xuhua He, Felix Schremmer, Qingchao Yu2026-03-09🔢 math

Ground States of Attractive Fermi Schrödinger Systems with Ring-Shaped Potentials

This paper establishes the existence and nonexistence of ground states for mass-critical N-coupled attractive Fermi nonlinear Schrödinger systems in ring-shaped potentials based on the strength of interactions relative to a critical constant derived from a finite-rank Lieb-Thirring inequality, while also characterizing the mass concentration behavior of these states as the interaction strength approaches this critical threshold.

Yujin Guo, Yan Li, Shuang Wu2026-03-09🔢 math

Beamforming Optimization for Extremely Large-Scale RIS-Aided Near-Field Secure Communications

This paper proposes a joint optimization algorithm for transmit precoding and discrete phase-shift reflection in an extremely large-scale RIS-aided near-field secure communication system with artificial jamming, effectively maximizing secrecy rates even when eavesdroppers are located close to the RIS and in the same direction as legitimate users.

Xiaotong Xu, Qian Zhang, Yunxiao Li, Xuejun Cheng, Meihui Liu, Ju Liu2026-03-09🔢 math

Shape-Resonance in Spectral density, Scattering Cross-section, Time delay and Bound on Sojourn time

This paper revisits the Friedrichs model to derive precise asymptotic results, including the Breit-Wigner formula and spectral concentration, for resonances near embedded eigenvalues, while also establishing exact properties for sojourn time, scattering amplitude, and time delay in the context of rank-one perturbations of the Laplacian.

Hemant Bansal, Alok Maharana, Lingaraj Sahu, Kalyan B. Sinha2026-03-09🔢 math

Space-time boundaries for random walks and their application to operator algebras

This paper investigates the Martin boundary of space-time Markov chains associated with finitely supported random walks to establish structural connections between various compactifications and harmonic function boundaries, ultimately demonstrating that the noncommutative Shilov boundary of the associated tensor algebra coincides with its Toeplitz CC^*-algebra.

Adam Dor-On, Matthieu Dussaule, Ilya Gekhtman, Pavel Prudnikov2026-03-09🔢 math

Vanishing orders and zero degree Turán densities

This paper investigates the structural implications of vanishing \ell-degree Turán densities in hypergraphs, proving that for kk-uniform hypergraphs with vanishing 2-degree Turán density, a specific global vertex ordering (2-vanishing order) must exist, thereby generalizing classical results on zero Turán density and demonstrating that unlike the classical case, 2-degree Turán densities accumulate at zero.

Laihao Ding, Hong Liu, Haotian Yang2026-03-09🔢 math

Metrical Distortion, Exterior Differential and Gauss's Lemma

This paper revises Gauss's Lemma by introducing the concept of "metrical distortion" as a non-identity isometry between double tangential and tangential spaces, and concretely defines the exterior differential via covariant gradient transport to incorporate a "differential slip" representing scalar gauge theory, ultimately distinguishing between geodesically radial volume preservation (metrical distortion) and length preservation (exponential mapping) through the example of the 2-sphere.

Stephan Voellinger2026-03-09🔢 math