@article{14660, abstract = {The classical Steinitz theorem states that if the origin belongs to the interior of the convex hull of a set 𝑆⊂ℝ𝑑, then there are at most 2𝑑 points of 𝑆 whose convex hull contains the origin in the interior. Bárány, Katchalski,and Pach proved the following quantitative version of Steinitz’s theorem. Let 𝑄 be a convex polytope in ℝ𝑑 containing the standard Euclidean unit ball 𝐁𝑑. Then there exist at most 2𝑑 vertices of 𝑄 whose convex hull 𝑄′ satisfies 𝑟𝐁𝑑⊂𝑄′ with 𝑟⩾𝑑−2𝑑. They conjectured that 𝑟⩾𝑐𝑑−1∕2 holds with a universal constant 𝑐>0. We prove 𝑟⩾15𝑑2, the first polynomial lower bound on 𝑟. Furthermore, we show that 𝑟 is not greater than 2/√𝑑.}, author = {Ivanov, Grigory and Naszódi, Márton}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {2}, pages = {796--802}, publisher = {London Mathematical Society}, title = {{Quantitative Steinitz theorem: A polynomial bound}}, doi = {10.1112/blms.12965}, volume = {56}, year = {2024}, } @article{17127, abstract = {Let P(x)∈Z[x] be a polynomial with at least two distinct complex roots. We prove that the number of solutions (x1,…,xk,y1,…,yk)∈[N]2k to the equation ∏1≤i≤kP(xi)=∏1≤j≤kP(yj)≠0 (for any k≥1 ) is asymptotically k!Nk as N→+∞. This solves a question first proposed and studied by Najnudel. The result can also be interpreted as saying that all even moments of random partial sums 1N√∑n≤Nf(P(n)) match standard complex Gaussian moments as N→+∞ , where f is the Steinhaus random multiplicative function.}, author = {Wang, Victor and Xu, Max Wenqiang}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {8}, pages = {2718--2726}, publisher = {London Mathematical Society}, title = {{Paucity phenomena for polynomial products}}, doi = {10.1112/blms.13095}, volume = {56}, year = {2024}, } @article{17376, abstract = {The inertia bound and ratio bound (also known as the Cvetković bound and Hoffman bound) are two fundamental inequalities in spectral graph theory, giving upper bounds on the independence number α(G) of a graph G in terms of spectral information about a weighted adjacency matrix of G. For both inequalities, given a graph G, one needs to make a judicious choice of weighted adjacency matrix to obtain as strong a bound as possible. While there is a well-established theory surrounding the ratio bound, the inertia bound is much more mysterious, and its limits are rather unclear. In fact, only recently did Sinkovic find the first example of a graph for which the inertia bound is not tight (for any weighted adjacency matrix), answering a longstanding question of Godsil. We show that the inertia bound can be extremely far from tight, and in fact can significantly underperform the ratio bound: for example, one of our results is that for infinitely many n, there is an n-vertex graph for which even the unweighted ratio bound can prove α(G)≤4n3/4, but the inertia bound is always at least n/4. In particular, these results address questions of Rooney, Sinkovic, and Wocjan--Elphick--Abiad.}, author = {Kwan, Matthew Alan and Wigderson, Yuval}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {10}, pages = {3196--3208}, publisher = {London Mathematical Society}, title = {{The inertia bound is far from tight}}, doi = {10.1112/blms.13127}, volume = {56}, year = {2024}, } @article{11186, abstract = {In this note, we study large deviations of the number 𝐍 of intercalates ( 2×2 combinatorial subsquares which are themselves Latin squares) in a random 𝑛×𝑛 Latin square. In particular, for constant 𝛿>0 we prove that exp(−𝑂(𝑛2log𝑛))⩽Pr(𝐍⩽(1−𝛿)𝑛2/4)⩽exp(−Ω(𝑛2)) and exp(−𝑂(𝑛4/3(log𝑛)))⩽Pr(𝐍⩾(1+𝛿)𝑛2/4)⩽exp(−Ω(𝑛4/3(log𝑛)2/3)) . As a consequence, we deduce that a typical order- 𝑛 Latin square has (1+𝑜(1))𝑛2/4 intercalates, matching a lower bound due to Kwan and Sudakov and resolving an old conjecture of McKay and Wanless.}, author = {Kwan, Matthew Alan and Sah, Ashwin and Sawhney, Mehtaab}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {4}, pages = {1420--1438}, publisher = {Wiley}, title = {{Large deviations in random latin squares}}, doi = {10.1112/blms.12638}, volume = {54}, year = {2022}, } @article{9037, abstract = {We continue our study of ‘no‐dimension’ analogues of basic theorems in combinatorial and convex geometry in Banach spaces. We generalize some results of the paper (Adiprasito, Bárány and Mustafa, ‘Theorems of Carathéodory, Helly, and Tverberg without dimension’, Proceedings of the Thirtieth Annual ACM‐SIAM Symposium on Discrete Algorithms (Society for Industrial and Applied Mathematics, San Diego, California, 2019) 2350–2360) and prove no‐dimension versions of the colored Tverberg theorem, the selection lemma and the weak 𝜀 ‐net theorem in Banach spaces of type 𝑝>1 . To prove these results, we use the original ideas of Adiprasito, Bárány and Mustafa for the Euclidean case, our no‐dimension version of the Radon theorem and slightly modified version of the celebrated Maurey lemma.}, author = {Ivanov, Grigory}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {2}, pages = {631--641}, publisher = {London Mathematical Society}, title = {{No-dimension Tverberg's theorem and its corollaries in Banach spaces of type p}}, doi = {10.1112/blms.12449}, volume = {53}, year = {2021}, } @article{9572, abstract = {We prove that every n-vertex tournament G has an acyclic subgraph with chromatic number at least n5/9−o(1), while there exists an n-vertex tournament G whose every acyclic subgraph has chromatic number at most n3/4+o(1). This establishes in a strong form a conjecture of Nassar and Yuster and improves on another result of theirs. Our proof combines probabilistic and spectral techniques together with some additional ideas. In particular, we prove a lemma showing that every tournament with many transitive subtournaments has a large subtournament that is almost transitive. This may be of independent interest.}, author = {Fox, Jacob and Kwan, Matthew Alan and Sudakov, Benny}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {2}, pages = {619--630}, publisher = {Wiley}, title = {{Acyclic subgraphs of tournaments with high chromatic number}}, doi = {10.1112/blms.12446}, volume = {53}, year = {2021}, } @article{6965, abstract = {The central object of investigation of this paper is the Hirzebruch class, a deformation of the Todd class, given by Hirzebruch (for smooth varieties). The generalization for singular varieties is due to Brasselet–Schürmann–Yokura. Following the work of Weber, we investigate its equivariant version for (possibly singular) toric varieties. The local decomposition of the Hirzebruch class to the fixed points of the torus action and a formula for the local class in terms of the defining fan are recalled. After this review part, we prove the positivity of local Hirzebruch classes for all toric varieties, thus proving false the alleged counterexample given by Weber.}, author = {Rychlewicz, Kamil P}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {2}, pages = {560--574}, publisher = {Wiley}, title = {{The positivity of local equivariant Hirzebruch class for toric varieties}}, doi = {10.1112/blms.12442}, volume = {53}, year = {2021}, } @article{9573, abstract = {It is a classical fact that for any ε>0, a random permutation of length n=(1+ε)k2/4 typically contains a monotone subsequence of length k. As a far-reaching generalization, Alon conjectured that a random permutation of this same length n is typically k-universal, meaning that it simultaneously contains every pattern of length k. He also made the simple observation that for n=O(k2logk), a random length-n permutation is typically k-universal. We make the first significant progress towards Alon's conjecture by showing that n=2000k2loglogk suffices.}, author = {He, Xiaoyu and Kwan, Matthew Alan}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {3}, pages = {515--529}, publisher = {Wiley}, title = {{Universality of random permutations}}, doi = {10.1112/blms.12345}, volume = {52}, year = {2020}, } @article{6793, abstract = {The Regge symmetry is a set of remarkable relations between two tetrahedra whose edge lengths are related in a simple fashion. It was first discovered as a consequence of an asymptotic formula in mathematical physics. Here, we give a simple geometric proof of Regge symmetries in Euclidean, spherical, and hyperbolic geometry.}, author = {Akopyan, Arseniy and Izmestiev, Ivan}, issn = {1469-2120}, journal = {Bulletin of the London Mathematical Society}, number = {5}, pages = {765--775}, publisher = {London Mathematical Society}, title = {{The Regge symmetry, confocal conics, and the Schläfli formula}}, doi = {10.1112/blms.12276}, volume = {51}, year = {2019}, } @article{707, abstract = {We answer a question of M. Gromov on the waist of the unit ball.}, author = {Akopyan, Arseniy and Karasev, Roman}, issn = {0024-6093}, journal = {Bulletin of the London Mathematical Society}, number = {4}, pages = {690 -- 693}, publisher = {Wiley}, title = {{A tight estimate for the waist of the ball }}, doi = {10.1112/blms.12062}, volume = {49}, year = {2017}, }