143 research outputs found
On function field Mordell-Lang: the semiabelian case and the socle theorem
We here aim to complete our model-theoretic account of the function field
Mordell-Lang conjecture, avoiding appeal to dichotomy theorems for Zariski
geometries, where we now consider the general case of semiabelian varieties.
The main result is a reduction, using model-theoretic tools, of the semiabelian
case to the abelian case.Comment: 43 pages. Some minor corrections and clarifications were made
following a referee's repor
On function field Mordell-Lang and Manin-Mumford
We present a reduction of the function field Mordell-Lang conjecture to the
function field Manin-Mumford conjecture, in all characteristics, via model
theory, but avoiding recourse to the dichotomy theorems for (generalized)
Zariski structures.
In this version 2, the quantifier elimination result in positive
characteristic is extended from simple abelian varieties to all abelian
varieties, completing the main theorem in the positive characteristic case.
In version 3, some corrections are made to the proof of quantifier
elimination in positive characteristic, and the paper is substantially
reorganized.Comment: 21 page
Dimension, matroids, and dense pairs of first-order structures
A structure M is pregeometric if the algebraic closure is a pregeometry in
all M' elementarily equivalent to M. We define a generalisation: structures
with an existential matroid. The main examples are superstable groups of U-rank
a power of omega and d-minimal expansion of fields. Ultraproducts of
pregeometric structures expanding a field, while not pregeometric in general,
do have an unique existential matroid.
Generalising previous results by van den Dries, we define dense elementary
pairs of structures expanding a field and with an existential matroid, and we
show that the corresponding theories have natural completions, whose models
also have a unique existential matroid. We extend the above result to dense
tuples of structures.Comment: Version 2.8. 61 page
Some Definability Results in Abstract Kummer Theory
Let be a semiabelian variety over an algebraically closed field, and let
be an irreducible subvariety not contained in a coset of a proper algebraic
subgroup of . We show that the number of irreducible components of
is bounded uniformly in , and moreover that the bound is
uniform in families .
We prove this by purely Galois-theoretic methods. This proof applies in the
more general context of divisible abelian groups of finite Morley rank. In this
latter context, we deduce a definability result under the assumption of the
Definable Multiplicity Property (DMP). We give sufficient conditions for finite
Morley rank groups to have the DMP, and hence give examples where our
definability result holds.Comment: 21 pages; minor notational fixe
Semiabelian varieties over separably closed fields, maximal divisible subgroups, and exact sequences
Given a separably closed field K of positive characteristic and finite degree
of imperfection we study the # functor which takes a semiabelian variety G over
K to the maximal divisible subgroup #G of G(K). We show that the # functor need
not preserve exact sequences. The main result is an example where #G does not
have "relative Morley rank", yielding a counterexample to a claim of
Hrushovski. The methods involve studying preservation of exact sequences by the
# functor as well as issues of descent. We also develop the notion of an
iterative D-structure on a group scheme over an iterative Hasse field, as well
as giving characteristic 0 versions of our results.Comment: 55 pages In this version 3, some corrections and clarifications are
made: in section 2.3 on relative Morley rank. Also in section 5.2 where more
explanation is given of D-structures in positive characteristic. In an
appendix we give a proof of the exactness of the functor taking a semiabelian
variety to its universal vectorial extensio
Beyond aspect: will be -ing and shall be -ing
This article discusses the synchronic status and diachronic development of will be -ing and shall be -ing (as in I’ll be leaving at noon).2 Although available since at least Middle English, the constructions did not establish a significant foothold in standard English until the twentieth century. Both types are also more prevalent in British English (BrE) than American English (AmE).
We argue that in present-day usage will/shall be -ing are aspectually underspecified: instances that clearly construe a situation as future-in-progress are in the minority. Similarly, although volition-neutrality has been identified as a key feature of will/shall be -ing, it is important to take account of other, generally richer meanings and associations, notably ‘future-as-matter-of-course’ (Leech 2004), ‘already-decided future’ (Huddleston & Pullum et al. 2002) and non-agentivity. Like volition-neutrality, these characteristics appear to be relevant not only in contemporary use, but also in their historical expansion. We show that the construction has evolved from progressive aspect towards more subjectivised evidential meaning
Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships
Purpose: To characterise hydration, cooling, body
mass loss, and core (Tcore) and skin (Tsk) temperatures
during World Athletics Championships in hot-humid
conditions.
Methods: Marathon and race-walk (20 km and 50
km) athletes (n=83, 36 women) completed a pre-race
questionnaire. Pre-race and post-race body weight
(n=74), Tcore (n=56) and Tsk (n=49; thermography) were
measured.
Results: Most athletes (93%) had a pre-planned
drinking strategy (electrolytes (83%), carbohydrates
(81%)) while ice slurry was less common (11%;
p<0.001). More men than women relied on
electrolytes and carbohydrates (91%–93% vs
67%–72%, p≤0.029). Drinking strategies were based
on personal experience (91%) rather than external
sources (p<0.001). Most athletes (80%) planned
pre-cooling (ice vests (53%), cold towels (45%), neck
collars (21%) and ice slurry (21%)) and/or midcooling (93%; head/face dousing (65%) and cold
water ingestion (52%)). Menthol usage was negligible
(1%–2%). Pre-race Tcore was lower in athletes
using ice vests (37.5°C±0.4°C vs 37.8°C±0.3°C,
p=0.024). Tcore (pre-race 37.7°C±0.3°C, post-race
39.6°C±0.6°C) was independent of event, ranking or
performance (p≥0.225). Pre-race Tsk was correlated
with faster race completion (r=0.32, p=0.046)
and was higher in non-finishers (did not finish
(DNF); 33.8°C±0.9°C vs 32.6°C±1.4°C, p=0.017).
Body mass loss was higher in men than women
(−2.8±1.5% vs −1.3±1.6%, p<0.001), although not
associated with performance.
Conclusion: Most athletes’ hydration strategies
were pre-planned based on personal experience. Ice
vests were the most adopted pre-cooling strategy
and the only one minimising Tcore, suggesting that
event organisers should be cognisant of logistics (ie,
freezers). Dehydration was moderate and unrelated to
performance. Pre-race Tsk was related to performance
and DNF, suggesting that Tsk modulation should be
incorporated into pre-race strategies
Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships.
PURPOSE: To characterise hydration, cooling, body mass loss, and core (Tcore) and skin (Tsk) temperatures during World Athletics Championships in hot-humid conditions. METHODS: Marathon and race-walk (20 km and 50 km) athletes (n=83, 36 women) completed a pre-race questionnaire. Pre-race and post-race body weight (n=74), Tcore (n=56) and Tsk (n=49; thermography) were measured. RESULTS: Most athletes (93%) had a pre-planned drinking strategy (electrolytes (83%), carbohydrates (81%)) while ice slurry was less common (11%; p<0.001). More men than women relied on electrolytes and carbohydrates (91%-93% vs 67%-72%, p≤0.029). Drinking strategies were based on personal experience (91%) rather than external sources (p<0.001). Most athletes (80%) planned pre-cooling (ice vests (53%), cold towels (45%), neck collars (21%) and ice slurry (21%)) and/or mid-cooling (93%; head/face dousing (65%) and cold water ingestion (52%)). Menthol usage was negligible (1%-2%). Pre-race Tcore was lower in athletes using ice vests (37.5°C±0.4°C vs 37.8°C±0.3°C, p=0.024). Tcore (pre-race 37.7°C±0.3°C, post-race 39.6°C±0.6°C) was independent of event, ranking or performance (p≥0.225). Pre-race Tsk was correlated with faster race completion (r=0.32, p=0.046) and was higher in non-finishers (did not finish (DNF); 33.8°C±0.9°C vs 32.6°C±1.4°C, p=0.017). Body mass loss was higher in men than women (-2.8±1.5% vs -1.3±1.6%, p<0.001), although not associated with performance. CONCLUSION: Most athletes' hydration strategies were pre-planned based on personal experience. Ice vests were the most adopted pre-cooling strategy and the only one minimising Tcore, suggesting that event organisers should be cognisant of logistics (ie, freezers). Dehydration was moderate and unrelated to performance. Pre-race Tsk was related to performance and DNF, suggesting that Tsk modulation should be incorporated into pre-race strategies
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