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We use Koll\'ar's gluing theory to prove the contraction theorem for generalized pairs. In particular, we show that we can run the MMP for any generalized log canonical pairs.

Algebraic Geometry · Mathematics 2022-11-22 Lingyao Xie

For a finite set of non-zero natural numbers that contains at least one element different from 1 and the least common multiple of any of its subsets, there exists a subset of at least half of its members which has a common divisor larger…

Number Theory · Mathematics 2018-08-29 Tom Fischer

We introduce a new axiomatization of matroid theory that requires the elimination property only among modular pairs of circuits, and we present a cryptomorphic phrasing thereof in terms of Crapo's axioms for flats. This new point of view…

Combinatorics · Mathematics 2016-08-23 Emanuele Delucchi

This is a survey and research note on the modified Orlik conjecture derived from the division theorem introduced in [2]. The division theorem is a generalization of classical addition-deletion theorems for free arrangements. The division…

Commutative Algebra · Mathematics 2016-03-15 Takuro Abe

We present an extension of Cluster Perturbation Theory to include many body correlations associated to local e-e repulsion in real materials. We show that this approach can describe the physics of complex correlated materials where…

Strongly Correlated Electrons · Physics 2013-06-25 F. Manghi

A simple binary matroid is called claw-free if none of its rank-3 flats are independent sets. These objects can be equivalently defined as the sets $E$ of points in $\mathrm{PG}(n-1,2)$ for which $|E \cap P|$ is not a basis of $P$ for any…

Combinatorics · Mathematics 2018-08-01 Peter Nelson , Kazuhiro Nomoto

The clustering of a data set is one of the core tasks in data analytics. Many clustering algorithms exhibit a strong contrast between a favorable performance in practice and bad theoretical worst-cases. Prime examples are least-squares…

Optimization and Control · Mathematics 2018-09-05 S. Borgwardt , F. Happach

A minor-closed class of matroids is (strongly) fractal if the number of n-element matroids in the class is dominated by the number of n-element excluded minors. We conjecture that when K is an infinite field, the class of K-representable…

Combinatorics · Mathematics 2019-08-01 Dillon Mayhew , Mike Newman , Geoff Whittle

We characterize 2-dimensional complexes associated canonically with basis graphs of matroids as simply connected triangle-square complexes satisfying some local conditions. This proves a version of a (disproved) conjecture by Stephen Maurer…

Combinatorics · Mathematics 2018-12-10 Jérémie Chalopin , Victor Chepoi , Damian Osajda

Clustering mechanisms are essential in certain multiuser networks for achieving efficient resource utilization. This lecture note presents the theory of coalition formation as a useful tool for distributed clustering problems. We reveal the…

Computer Science and Game Theory · Computer Science 2017-01-24 Rami Mochaourab , Eduard Jorswieck , Mats Bengtsson

A brick is a 3-connected graph such that the graph obtained from it by deleting any two distinct vertices has a perfect matching. A brick is minimal if for every edge e the deletion of e results in a graph that is not a brick. We prove a…

Combinatorics · Mathematics 2019-07-02 Serguei Norine , Robin Thomas

Clustering in image analysis is a central technique that allows to classify elements of an image. We describe a simple clustering technique that uses the method of similarity matrices. We expand upon recent results in spectral analysis for…

Statistics Theory · Mathematics 2022-03-23 Denis Gaidashev , Ralf Pihlström , Martin Ryner

We apply a recent duality theorem for tangles in abstract separation systems to derive tangle-type duality theorems for width-parameters in graphs and matroids. We further derive a duality theorem for the existence of clusters in large data…

Combinatorics · Mathematics 2020-01-24 Reinhard Diestel , Sang-il Oum

Rooted acyclic graphs appear naturally when the phylogenetic relationship of a set $X$ of taxa involves not only speciations but also recombination, horizontal transfer, or hybridization, that cannot be captured by trees. A variety of…

Populations and Evolution · Quantitative Biology 2022-04-29 Marc Hellmuth , David Schaller , Peter F. Stadler

Biclustering involves the simultaneous clustering of objects and their attributes, thus defining local two-way clustering models. Recently, efficient algorithms were conceived to enumerate all biclusters in real-valued datasets. In this…

Machine Learning · Computer Science 2015-06-04 Saullo Haniell Galvão de Oliveira , Rosana Veroneze , Fernando José Von Zuben

The compactness theorem for a logic states, roughly, that the satisfiability of a set of well-formed formulas can be determined from the satisfiability of its finite subsets, and vice versa. Usually, proofs of this theorem depend on the…

Logic · Mathematics 2025-07-04 Sayantan Roy , Sankha S. Basu , Mihir K. Chakraborty

A matroid M is cyclically orderable if there is a cyclic permutation of the elements of M such that any r consecutive elements form a basis in M. An old conjecture of Kajitani, Miyano, and Ueno states that a matroid M is cyclically…

Combinatorics · Mathematics 2024-08-06 Sean McGuinness

A distributive lattice structure ${\mathbf M}(G)$ has been established on the set of perfect matchings of a plane bipartite graph $G$. We call a lattice {\em matchable distributive lattice} (simply MDL) if it is isomorphic to such a…

Combinatorics · Mathematics 2015-03-09 Heping Zhang , Dewu Yang , Haiyuan Yao

Solving a problem of Diestel and Pott, we construct a large class of infinite matroids. These can be used to provide counterexamples against the natural extension of the Well-quasi-ordering-Conjecture to infinite matroids and to show that…

Combinatorics · Mathematics 2013-01-28 Nathan Bowler , Johannes Carmesin

We consider the problem of feature detection in the presence of clutter in spatial point processes. Classification methods have been developed in previous studies. Among these, Byers and Raftery (1998) models the observed Kth nearest…

Methodology · Statistics 2024-03-13 Nicoletta D'Angelo