Journal of the London Mathematical Society-Second Series最新文献

In the Lebesgue decomposition of a lower semibounded sesquilinear form, the corresponding regular and singular parts are mutually singular. The more general Lebesgue-type decompositions studied here allow components that need not be mutually singular anymore. In the new situation, the earlier basic orthogonal space decomposition in the background is now replaced by a nonorthogonal decomposition in the sense of de Branges and Rovnyak. The relevant theory is based on Lebesgue-type decompositions for linear operators and relations via a so-called representing map. This map also makes it possible to formulate explicit analogs for representation theorems for lower semibounded forms that are not necessarily closed or closable. This new representation also appears naturally in the convergence of monotone sequences of lower semibounded forms.

For any compactly generated triangulated category, we introduce two topological spaces, the shift spectrum and the shift-homological spectrum. We use them to parametrise a family of thick subcategories of the compact objects, which we call radical. These spaces can be viewed as non-monoidal analogues of the Balmer and homological spectra arising in tensor-triangular geometry: we prove that for monogenic tensor-triangulated categories, the Balmer spectrum is a subspace of the shift spectrum. To construct these analogues, we utilise quotients of the module category, rather than the lattice theoretic methods which have been adopted in other approaches. We characterise radical thick subcategories and show in certain cases, such as the perfect derived categories of tame hereditary algebras or monogenic tensor-triangulated categories, that every thick subcategory is radical. We establish a close relationship between the shift-homological spectrum and the set of irreducible integral rank functions, and provide necessary and sufficient conditions for every radical thick subcategory to be given by an intersection of kernels of rank functions. In order to facilitate these results, we prove that both spaces we introduce may equivalently be described in terms of the Ziegler spectrum.

Studying Manin's program for a family of spherical log Fano threefolds, we determine the asymptotic number of integral points whose height associated with an arbitrary ample line bundle is bounded. This confirms a recent conjecture by Santens and sheds new light on the logarithmic analog of Iitaka fibrations, which have not yet been adequately formulated.

This article investigates the splitting problem for finitely generated projective modules $�P$ over affine algebras over algebraically closed fields and their polynomial extensions. We then address an open question due to M. Roitman on monic inversion principle for projective modules and prove it in the affirmative for finitely generated rings. For affine algebras over $�{\overline{F}}_p$, we prove a monic inversion principle for ideals. We also exhibit some applications.

Very recently in [Das et al., Expo. Math. 43(3):125653, 2025], statistically characterized subgroups have been investigated for certain types of nonarithmetic sequences. Building on this work, we investigate further and demonstrate that, for a particular class of nonarithmetic sequences, the statistically characterized subgroups coincide with the corresponding characterized subgroups. It had already been shown that statistically characterized subgroups corresponding to arithmetic sequences cannot be characterized by any sequence [Das et al., Bull. Sci. Math. 179(2):103157, 2022], and further, they are always of the size of the continuum. From the very beginning, it has been an open question as to whether statistically characterized subgroups can be small in size, that is, countably infinite. Our observation thus sheds new light on the crucial role of sequences generating subgroups of the circle group, and at the same time, one can subsequently identify a class of sequences for which statistically characterized subgroups are countably infinite. This result provides a negative solution to Problem 2.16 posed in [Das et al., Expo. Math. 43(3):125653, 2025] and Question 6.3 from [Dikranjan et al., Fund. Math. 249:185-209, 2020]. Additionally, our findings resolve several open problems from [Dikranjan et al., Topo. Appl., 2025].

We investigate the concept of Pauli pairs and a discrete counterpart to it. In particular, we make substantial progress on the question of when a discrete Pauli pair is automatically a classical Pauli pair. Effectively, if one of the functions has space and frequency Gaussian decay, and one has that $��\left|�f�\right|�=�\left|�g�\right|�$ and $���|��\hat{f}��|�=�|��\hat{g}��|��$ on two sets which accumulate like suitable small multiples of $�\sqrt{�n�}$ at infinity, then $��\left|�f�\right|�\equiv �\left|�g�\right|�$ and $���|��\hat{f}��|�=�|��\hat{g}��|��$. Furthermore, we show that if one drops either the assumption that one of the functions has space–frequency decay or that the discrete sets accumulate at a hig

We provide a new description of the hom functor on weak $�\omega$-categories, and show that it admits a left adjoint that we call the suspension functor. We then show that the hom functor preserves the property of being free on a computad, in contrast to the hom functor for strict $�\omega$-categories. Using the same technique, we define the opposite of an $�\omega$-category with respect to a set of dimensions, and show that this construction also preserves the property of being free on a computad. Finally, we show that the constructions of opposites and homs commute.