Publicaties

This paper is an addendum to our paper [PS], where a closed model structure on the category C-dgwu(k) of small (Kontsevich-Soibelman) weakly unital dg categories is constructed, k a field of any characteristic. In [PS], we referred to our earlier preprint for proofs of the following results: (A) small (co)completeness of C-dgwu(k), and (B) the non-symmetric dg operad O' (which governs weakly unital dg categories acting on k-quivers, we recall ...

In this paper, which is subsequent to our previous paper (but can be read independently from it), we continue our study of the closed model structure on the category of small weakly unital dg categories (in the sense of Kontsevich-Soibelman) over a field. In our previous paper, we constructed a closed model structure on the category of weakly unital dg categories, imposing a technical condition on the weakly unital dg categories, namely the ...

Using singular perturbation theory and family blow-up we prove that nilpotent contact points in deformations of slow-fast Darboux integrable systems have finite cyclicity. The deformations are smooth or analytic depending on the region in the parameter space. This paper is a natural continuation of [3, 1] where one studies limit cycles in polynomial deformations of slow-fast Darboux integrable systems, around the "integrable" direction in the ...

The isotropic matroid M[IAS(G)] of a looped simple graph G is a binary matroid equivalent to the isotropic system of G. In general, M[IAS(G)] is not regular, so it cannot be represented over fields of characteristic not equal 2. The ground set of M[IAS(G)] is denoted W(G); it is partitioned into 3-element subsets corresponding to the vertices of G. When the rank function of M[IAS(G)] is restricted to subtransversals of this partition, the ...

Smoothing (and decay) spacetime estimates are discussed for evolution groups of self-adjoint operators in an abstract setting. The basic assumption is the existence (and weak continuity) of the spectral density in a functional setting. Spectral identities for the time evolution of such operators are derived, enabling results concerning U+201Cbest constantsU+201D for smoothing estimates. When combined with suitable U+201Ccomparison ...

Research has explained interviewer effects in face-to-face surveys: in terms of question, respondent and interviewer characteristics. In this paper, we relate interview speed to interviewer effects. Three interview types are operationalized (slow, moderate and fast) based on the residual speeds from a model controlling for respondent characteristics. Data from the European Social Survey is used. Results show larger interviewer effects among slow ...