2,212 research outputs found
Imaginaries in separably closed valued fields
We show that separably closed valued fields of finite imperfection degree
(either with lambda-functions or commuting Hasse derivations) eliminate
imaginaries in the geometric language. We then use this classification of
interpretable sets to study stably dominated types in those structures. We show
that separably closed valued fields of finite imperfection degree are
metastable and that the space of stably dominated types is strict
pro-definable
On sets with rank one in simple homogeneous structures
We study definable sets of SU-rank 1 in , where is a
countable homogeneous and simple structure in a language with finite relational
vocabulary. Each such can be seen as a `canonically embedded structure',
which inherits all relations on which are definable in , and has no
other definable relations. Our results imply that if no relation symbol of the
language of has arity higher than 2, then there is a close relationship
between triviality of dependence and being a reduct of a binary random
structure. Somewhat more preciely: (a) if for every , every -type
which is realized in is determined by its sub-2-types
, then the algebraic closure restricted to is
trivial; (b) if has trivial dependence, then is a reduct of a binary
random structure
Absoluteness via Resurrection
The resurrection axioms are forcing axioms introduced recently by Hamkins and
Johnstone, developing on ideas of Chalons and Velickovi\'c. We introduce a
stronger form of resurrection axioms (the \emph{iterated} resurrection axioms
for a class of forcings and a given
ordinal ), and show that implies generic
absoluteness for the first-order theory of with respect to
forcings in preserving the axiom, where is a
cardinal which depends on ( if is any
among the classes of countably closed, proper, semiproper, stationary set
preserving forcings).
We also prove that the consistency strength of these axioms is below that of
a Mahlo cardinal for most forcing classes, and below that of a stationary limit
of supercompact cardinals for the class of stationary set preserving posets.
Moreover we outline that simultaneous generic absoluteness for
with respect to and for with respect to
with is in principle
possible, and we present several natural models of the Morse Kelley set theory
where this phenomenon occurs (even for all simultaneously). Finally,
we compare the iterated resurrection axioms (and the generic absoluteness
results we can draw from them) with a variety of other forcing axioms, and also
with the generic absoluteness results by Woodin and the second author.Comment: 34 page
Decision-Making in the Context of Imprecise Probabilistic Beliefs
Coherent imprecise probabilistic beliefs are modelled as incomplete comparative likelihood relations admitting a multiple-prior representation. Under a structural assumption of Equidivisibility, we provide an axiomatization of such relations and show uniqueness of the representation. In the second part of the paper, we formulate a behaviorally general axiom relating preferences and probabilistic beliefs which implies that preferences over unambiguous acts are probabilistically sophisticated and which entails representability of preferences over Savage acts in an Anscombe-Aumann-style framework. The motivation for an explicit and separate axiomatization of beliefs for the study of decision-making under ambiguity is discussed in some detail.
Arithmetic-arboreal residue structures induced by Prufer extensions : An axiomatic approach
We present an axiomatic framework for the residue structures induced by
Prufer extensions with a stress upon the intimate connection between their
arithmetic and arboreal theoretic properties. The main result of the paper
provides an adjunction relationship between two naturally defined functors
relating Prufer extensions and superrigid directed commutative regular
quasi-semirings.Comment: 56 page
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