605 research outputs found
On the symplectic eightfold associated to a Pfaffian cubic fourfold
We show that the irreducible holomorphic symplectic eightfold Z associated to
a cubic fourfold Y not containing a plane is deformation-equivalent to the
Hilbert scheme of four points on a K3 surface. We do this by constructing for a
generic Pfaffian cubic Y a birational map Z ---> Hilb^4(X), where X is the K3
surface associated to Y by Beauville and Donagi. We interpret Z as a moduli
space of complexes on X and observe that at some point of Z, hence on a Zariski
open subset, the complex is just the ideal sheaf of four points.Comment: 9 pages. Minor changes; to appear in Crelle as an appendix to
1305.017
Hodge theory and derived categories of cubic fourfolds
Cubic fourfolds behave in many ways like K3 surfaces. Certain cubics -
conjecturally, the ones that are rational - have specific K3s associated to
them geometrically. Hassett has studied cubics with K3s associated to them at
the level of Hodge theory, and Kuznetsov has studied cubics with K3s associated
to them at the level of derived categories.
These two notions of having an associated K3 should coincide. We prove that
they coincide generically: Hassett's cubics form a countable union of
irreducible Noether-Lefschetz divisors in moduli space, and we show that
Kuznetsov's cubics are a dense subset of these, forming a non-empty, Zariski
open subset in each divisor.Comment: 37 pages. Applications to algebraic cycles added, and other
improvements following referees' suggestions. This is a slightly expanded
version of the paper to appear in Duke Math
Moduli spaces of torsion sheaves on K3 surfaces and derived equivalences
We show that for many moduli spaces M of torsion sheaves on K3 surfaces S,
the functor D(S) -> D(M) induced by the universal sheaf is a P-functor, hence
can be used to construct an autoequivalence of D(M), and that this
autoequivalence can be factored into geometrically meaningful equivalences
associated to abelian fibrations and Mukai flops. Along the way we produce a
derived equivalence between two compact hyperkaehler 2g-folds that are not
birational, for every g >= 2. We also speculate about an approach to showing
that birational moduli spaces of sheaves on K3 surfaces are derived-equivalent.Comment: 28 pages. typos corrected. final version to appear in JLM
Unirationality of moduli spaces of special cubic fourfolds and K3 surfaces
We provide explicit descriptions of the generic members of Hassett's divisors
for relevant and for . In doing so, we
prove that is unirational for . As a
corollary, we prove that the moduli space of polarized K3
surfaces of degree is unirational for . The case is
entirely new, while the other two cases have been previously proven by Mukai.Comment: 13 pages, 2 tables. Script for the computer calculations used are
provided on the author's websit
Hodge numbers are not derived invariants in positive characteristic
We study a pair of Calabi-Yau threefolds X and M, fibered in non-principally polarized Abelian surfaces and their duals, and an equivalence D^b(X) = D^b(M), building on work of Gross, Popescu, Bak, and Schnell. Over the complex numbers, X is simply connected while pi_1(M) = (Z/3)^2. In characteristic 3, we find that X and M have different Hodge numbers, which would be impossible in characteristic 0. In an appendix, we give a streamlined proof of Abuaf's result that the ring H^*(O) is a derived invariant of complex threefolds and fourfolds. A second appendix by Alexander Petrov gives a family of higher-dimensional examples to show that h^{0,3} is not a derived invariant in any positive characteristic
Formulation de cas dans la psychose débutante : Quels outils pour le travail en équipe? [Case Formulation in Early Psychosis: What are the Tools for Teamwork?]
Nous prĂ©sentons dâabord briĂšvement le programme TIPP et les concepts gĂ©nĂ©raux de la prise en charge prĂ©coce dans la psychose dĂ©butante. Un des objectifs de lâintervention dans la phase prĂ©coce des troubles psychotiques est notamment de proposer des soins spĂ©cifiques adaptĂ©s Ă cette phase de la maladie. En dĂ©but de prise en charge, lâĂ©quipe de soins et en particulier le gestionnaire de cas (case manager), chef dâorchestre de la prise en charge, sont confrontĂ©s Ă une quantitĂ© importante dâinformation dont il faut dĂ©gager les lignes de forces pour mettre en place une prise en charge adaptĂ©e. Cet article propose un modĂšle qui peut constituer un outil de travail prĂ©cieux pour les Ă©quipes travaillant dans lâintervention prĂ©coce pour faire Ă©merger une formulation de cas et synthĂ©tiser les situations cliniques des patients, en extraire une histoire qui fasse sens et ainsi faciliter la mise en place dâun projet thĂ©rapeutique
Substance use in clinical high risk for psychosis: a review of the literature
AimIn the literature, there is evidence suggesting an association between substance use and psychosis. However, little is known about substance use in those who may be in the pre-psychotic phase, that is, those who are putatively prodromal are considered to be at clinical high risk (CHR) of developing psychosis. MethodsWe conducted a review of publications measuring patterns and rates of substance use in CHR for psychosis individuals and the effects on the transition to psychosis. ResultsOf 5527 potentially relevant research papers, 10 met inclusion criteria of CHR subjects and specifically mentioned substance use in the sample. The results of these studies varied. Cannabis, alcohol and tobacco/nicotine were reported as the most commonly used substances. There was limited information on the changes in patterns of use over time. Two out of the ten studies found a significant association between the use of substances and subsequent transition to psychosis. In one of these studies, substance abuse was a predictor of psychosis when included as a variable in a prediction algorithm. In the other study, the abuse of cannabis and nicotine was associated with transition to psychosis. ConclusionsWe found limited evidence to suggest that increased rates of substance use may be associated with transition to psychosis. However, further prospective research examining the association between substance use and transition to psychosis is required before any firm conclusions can be made
Are lay people good at recognising the symptoms of schizophrenia?
©2013 Erritty, Wydell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This article has been made available through the Brunel Open Access Publishing Fund.Aim: The aim of this study was to explore the general publicâs perception of schizophrenia symptoms and the need to seekhelp for symptoms. The recognition (or âlabellingâ) of schizophrenia symptoms, help-seeking behaviours and public
awareness of schizophrenia have been suggested as potentially important factors relating to untreated psychosis.
Method: Participants were asked to rate to what extent they believe vignettes describing classic symptoms (positive and
negative) of schizophrenia indicate mental illness. They were also asked if the individuals depicted in the vignettes required help or treatment and asked to suggest what kind of help or treatment.
Results: Only three positive symptoms (i.e., Hallucinatory behaviour, Unusual thought content and Suspiciousness) of schizophrenia were reasonably well perceived (above 70%) as indicating mental illness more than the other positive or negative symptoms. Even when the participants recognised that the symptoms indicated mental illness, not everyone recommended professional help.
Conclusion: There may be a need to improve public awareness of schizophrenia and psychosis symptoms, particularly regarding an awareness of the importance of early intervention for psychosis
- âŠ