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In this paper we obtain a stability theorem of generalized Kahler structures with one pure spinor under small deformations of generalized complex structures. (This is analogous to the stability theorem of Kahler manifolds by…

Differential Geometry · Mathematics 2010-09-21 Ryushi Goto

In this article we give a classification of the binary, simple, $\omega$-categorical structures with SU-rank 1 and trivial pregeometry. This is done both by showing that they satisfy certain extension properties, but also by noting that…

Logic · Mathematics 2017-04-11 Ove Ahlman

For an increasing sequence $(T_n)$ of one-parameter semigroups of sub Markovian kernel operators over a Polish space, we study the limit semigroup and prove sufficient conditions for it to be strongly Feller. In particular, we show that the…

Functional Analysis · Mathematics 2022-04-06 Christian Budde , Alexander Dobrick , Jochen Glück , Markus Kunze

There exist NIP and non-NTP$_2$ theories satisfying all the following conditions: It is not o-minimal; All models are strongly locally o-minimal; It has a model which is an expansion of the linearly ordered abelian group over the reals…

Logic · Mathematics 2022-08-18 Masato Fujita

We first partly develop a mathematical notion of stable consistency intended to reflect the actual consistency property of human beings. Then we give a generalization of the first and second G\"odel incompleteness theorem to stably…

Logic in Computer Science · Computer Science 2022-08-16 Yasha Savelyev

We develop a general framework (multidimensional asymptotic classes, or m.a.c.s) for handling classes of finite first order structures with a strong uniformity condition on cardinalities of definable sets: The condition asserts that…

Logic · Mathematics 2024-08-02 Sylvy Anscombe , Dugald Macpherson , Charles Steinhorn , Daniel Wolf

We describe a new way to construct finite geometric objects. For every k we obtain a symmetric configuration E(k-1) with k points on a line. In particular, we have a constructive existence proof for such configurations. The method is very…

Combinatorics · Mathematics 2012-11-09 Christoph Hering , Andreas Krebs , Thomas Edgar

We introduce a new compactness principle which we call the gluing property. For a measurable cardinal $\kappa$ and a cardinal $\lambda$, we say that $\kappa$ has the $\lambda$-gluing property if every sequence of $\lambda$-many…

Logic · Mathematics 2026-03-27 Yair Hayut , Alejandro Poveda

We construct finitely generated groups with strong fixed point properties. Let $\mathcal{X}_{ac}$ be the class of Hausdorff spaces of finite covering dimension which are mod-$p$ acyclic for at least one prime $p$. We produce the first…

Group Theory · Mathematics 2014-11-11 G. Arzhantseva , M. R. Bridson , T. Januszkiewicz , I. J. Leary , A. Minasyan , J. Swiatkowski

Building off of recent results on Keisler's order, we show that consistently, $\leq_{SP}$ has infinitely many classes. In particular, we define the property of $\leq k$-type amalgamation for simple theories, for each $2 \leq k < \omega$. If…

Logic · Mathematics 2024-09-24 Saharon Shelah , Danielle Ulrich

We introduce the notion of the $k$-closure of a group of automorphisms of a locally finite tree, and give several examples of the construction. We show that the $k$-closure satisfies a new property of automorphism groups of trees that…

Group Theory · Mathematics 2014-10-07 Christopher C. Banks , Murray Elder , George A. Willis

Ando, Matsuzawa, Thom, and T\"ornquist have resolved a problem by Sorin Popa by constructing an example of a Polish group of unitary operators with the strong operator topology, whose left and right uniform structures coincide, but which…

Operator Algebras · Mathematics 2021-02-17 Vladimir Pestov

In 1963, Greenberg proved that every finite group appears as the monodromy group of some morphism of Riemann surfaces. In this paper, we give two constructive proofs of Greenberg's result. First, we utilize free groups, which given with the…

Group Theory · Mathematics 2021-03-19 Ra-Zakee Muhammad , Javier Santiago , Eyob Tsegaye

We present a construction, called the limit of a tree system of spaces (or, less formally, a tree of spaces). The construction is designed to produce compact metric spaces that resemble fractals, out of more regular spaces, such as closed…

Geometric Topology · Mathematics 2020-09-30 Jacek Swiatkowski

Justification theory is an abstract unifying formalism that captures semantics of various non-monotonic logics. One intriguing problem that has received significant attention is the consistency problem: under which conditions are…

Artificial Intelligence · Computer Science 2022-08-08 Simon Marynissen , Bart Bogaerts

In this paper we prove a strong nonstructure theorem for kappa (T)-saturated models of a stable theory T with dop.

Logic · Mathematics 2009-09-25 Tapani Hyttinen , Saharon Shelah

Universality has been an important concept in computable structure theory. A class $\mathcal{C}$ of structures is universal if, informally, for any structure, of any kind, there is a structure in $\mathcal{C}$ with the same…

Logic · Mathematics 2017-12-05 Matthew Harrison-Trainor , Meng-Che Ho

This paper forms the second part of a series by the authors [GMV1,GMV3] concerning the structure theory of nilspaces of Antol\'in Camarena and Szegedy. A nilspace is a compact space $X$ together with closed collections of cubes…

Dynamical Systems · Mathematics 2018-01-03 Yonatan Gutman , Freddie Manners , Péter P. Varjú

Two graphs are of the same topological type if they can be mutually embedded into each other topologically. We show that there are exactly $\aleph_1$ distinct topological types of countable trees. In general, for any infinite cardinal…

Combinatorics · Mathematics 2023-05-24 Thilo Krill , Max Pitz

We prove Gray--Moser stability theorems for complementary pairs of forms of constant class defining symplectic pairs, contact-symplectic pairs and contact pairs. We also consider the case of contact-symplectic and contact-contact…

Symplectic Geometry · Mathematics 2007-05-23 G. Bande , P. Ghiggini , D. Kotschick