ar X iv : 1 40 1 . 48 40 v 2 [ cs . D B ] 1 4 Fe b 20 14 All – instances termination of chase is undecidable

ar X iv : 0 90 1 . 39 84 v 1 [ cs . D B ] 2 6 Ja n 20 09 Stop the Chase

The chase procedure, an algorithm proposed 25+ years ago to fix constraint violations in database instances, has been successfully applied in a variety of contexts, such as query optimization, data exchange, and data integration. Its practicability, however, is limited by the fact that – for an arbitrary set of constraints – it might not terminate; even worse, chase termination is an undecidabl...

ar X iv : 1 40 6 . 46 48 v 1 [ cs . F L ] 1 8 Ju n 20 14 Optimal Strategy Synthesis for Request - Response Games ∗ Florian Horn

We show the existence and effective computability of optimal winning strategies for request-response games in case the quality of a play is measured by the limit superior of the mean accumulated waiting times between requests and their responses.

ar X iv : 1 30 2 . 24 55 v 1 [ m at h . G R ] 1 1 Fe b 20 13 Rational subsets and submonoids of wreath products ⋆

It is shown that membership in rational subsets of wreath products H ≀ V with H a finite group and V a virtually free group is decidable. On the other hand, it is shown that there exists a fixed finitely generated submonoid in the wreath product Z ≀ Z with an undecidable membership problem.

ar X iv : 1 40 2 . 47 75 v 1 [ m at h . A T ] 1 9 Fe b 20 14 HIGHER HOMOTOPY EXCISION AND BLAKERS – MASSEY THEOREMS FOR STRUCTURED RING SPECTRA

Working in the context of symmetric spectra, we prove higher homotopy excision and higher Blakers–Massey theorems, and their duals, for algebras and left modules over operads in the category of modules over a commutative ring spectrum (e.g., structured ring spectra). We also prove analogous results for algebras and left modules over operads in unbounded chain complexes.

ar X iv : 0 80 1 . 48 21 v 2 [ he p - ph ] 2 8 Fe b 20 08 X ( 1835 ) and η ( 1760 ) observed by BES Collaboration