67 research outputs found
Logical Dreams
We discuss the past and future of set theory, axiom systems and independence
results. We deal in particular with cardinal arithmetic
Non-archimedean integrals as limits of complex integrals
We explain how non-archimedean integrals considered by Chambert-Loir and
Ducros naturally arise in asymptotics of families of complex integrals. To
perform this analysis we work over a non-standard model of the field of complex
numbers, which is endowed at the same time with an archimedean and a
non-archimedean norm. Our main result states the existence of a natural
morphism between bicomplexes of archimedean and non-archimedean forms which is
compatible with integration.Comment: 55 page
Quantum advantage by relational queries about physically realizable equivalence classes
Relational quantum queries are sometimes capable to effectively decide
between collections of mutually exclusive elementary cases without completely
resolving and determining those individual instances. Thereby the set of
mutually exclusive elementary cases is effectively partitioned into equivalence
classes pertinent to the respective query. In the second part of the paper, we
review recent progress in theoretical certifications (relative to the
assumptions made) of quantum value indeterminacy as a means to build quantum
oracles for randomness.Comment: 8 Pages, one figure, invited contribution to TopHPC2019, Tehran,
Iran, April 22-25, 201
Growth in solvable subgroups of GL_r(Z/pZ)
Let and let be a subset of \GL_r(K) such that is
solvable. We reduce the study of the growth of $A$ under the group operation to
the nilpotent setting. Specifically we prove that either $A$ grows rapidly
(meaning $|A\cdot A\cdot A|\gg |A|^{1+\delta}$), or else there are groups $U_R$
and $S$, with $S/U_R$ nilpotent such that $A_k\cap S$ is large and
$U_R\subseteq A_k$, where $k$ is a bounded integer and $A_k = \{x_1 x_2...b x_k
: x_i \in A \cup A^{-1} \cup {1}}$. The implied constants depend only on the
rank $r$ of $\GL_r(K)$.
When combined with recent work by Pyber and Szab\'o, the main result of this
paper implies that it is possible to draw the same conclusions without
supposing that is solvable.Comment: 46 pages. This version includes revisions recommended by an anonymous
referee including, in particular, the statement of a new theorem, Theorem
Model theory of finite and pseudofinite groups
This is a survey, intended both for group theorists and model theorists, concerning the structure of pseudofinite groups, that is, infinite models of the first-order theory of finite groups. The focus is on concepts from stability theory and generalisations in the context of pseudofinite groups, and on the information this might provide for finite group theory
On theories of random variables
We study theories of spaces of random variables: first, we consider random
variables with values in the interval , then with values in an arbitrary
metric structure, generalising Keisler's randomisation of classical structures.
We prove preservation and non-preservation results for model theoretic
properties under this construction: i) The randomisation of a stable structure
is stable. ii) The randomisation of a simple unstable structure is not simple.
We also prove that in the randomised structure, every type is a Lascar type
Small doubling in groups
Let A be a subset of a group G = (G,.). We will survey the theory of sets A
with the property that |A.A| <= K|A|, where A.A = {a_1 a_2 : a_1, a_2 in A}.
The case G = (Z,+) is the famous Freiman--Ruzsa theorem.Comment: 23 pages, survey article submitted to Proceedings of the Erdos
Centenary conferenc
Tools, Objects, and Chimeras: Connes on the Role of Hyperreals in Mathematics
We examine some of Connes' criticisms of Robinson's infinitesimals starting
in 1995. Connes sought to exploit the Solovay model S as ammunition against
non-standard analysis, but the model tends to boomerang, undercutting Connes'
own earlier work in functional analysis. Connes described the hyperreals as
both a "virtual theory" and a "chimera", yet acknowledged that his argument
relies on the transfer principle. We analyze Connes' "dart-throwing" thought
experiment, but reach an opposite conclusion. In S, all definable sets of reals
are Lebesgue measurable, suggesting that Connes views a theory as being
"virtual" if it is not definable in a suitable model of ZFC. If so, Connes'
claim that a theory of the hyperreals is "virtual" is refuted by the existence
of a definable model of the hyperreal field due to Kanovei and Shelah. Free
ultrafilters aren't definable, yet Connes exploited such ultrafilters both in
his own earlier work on the classification of factors in the 1970s and 80s, and
in his Noncommutative Geometry, raising the question whether the latter may not
be vulnerable to Connes' criticism of virtuality. We analyze the philosophical
underpinnings of Connes' argument based on Goedel's incompleteness theorem, and
detect an apparent circularity in Connes' logic. We document the reliance on
non-constructive foundational material, and specifically on the Dixmier trace
(featured on the front cover of Connes' magnum opus) and the Hahn-Banach
theorem, in Connes' own framework. We also note an inaccuracy in Machover's
critique of infinitesimal-based pedagogy.Comment: 52 pages, 1 figur
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