The derived category of quasi-coherent sheaves and axiomatic stable homotopy

We prove in this paper that for a quasi-compact and semi-separated (non necessarily noetherian) scheme X, the derived category of quasi-coherent sheaves over X, D(A_qc(X)), is a stable homotopy category in the sense of Hovey, Palmieri and Strickland, answering a question posed by Strickland. Moreover we show that it is unital and algebraic. We also prove that for a noetherian semi-separated formal scheme X, its derived category of sheaves of modules with quasi-coherent torsion homologies D_qct(X) is a stable homotopy category. It is algebraic but if the formal scheme is not a usual scheme, it is not unital, therefore its abstract nature differs essentially from that of the derived category of a usual scheme.Comment: v2: 31 pages, some improvements in exposition; v3 updated bibliography, to appear Adv. Mat

Joint signal extraction from galaxy clusters in X-ray and SZ surveys: A matched-filter approach

The hot ionized gas of the intra-cluster medium emits thermal radiation in the X-ray band and also distorts the cosmic microwave radiation through the Sunyaev-Zel'dovich (SZ) effect. Combining these two complementary sources of information through innovative techniques can therefore potentially improve the cluster detection rate when compared to using only one of the probes. Our aim is to build such a joint X-ray-SZ analysis tool, which will allow us to detect fainter or more distant clusters while maintaining high catalogue purity. We present a method based on matched multifrequency filters (MMF) for extracting cluster catalogues from SZ and X-ray surveys. We first designed an X-ray matched-filter method, analogous to the classical MMF developed for SZ observations. Then, we built our joint X-ray-SZ algorithm by combining our X-ray matched filter with the classical SZ-MMF, for which we used the physical relation between SZ and X-ray observations. We show that the proposed X-ray matched filter provides correct photometry results, and that the joint matched filter also provides correct photometry when the $F_{\rm X}/Y_{500}$ relation of the clusters is known. Moreover, the proposed joint algorithm provides a better signal-to-noise ratio than single-map extractions, which improves the detection rate even if we do not exactly know the $F_{\rm X}/Y_{500}$ relation. The proposed methods were tested using data from the ROSAT all-sky survey and from the Planck survey.Comment: 22 pages (before appendices), 19 figures, 3 tables, 5 appendices. Accepted for publication in A&

Neutron-induced fission fragment angular distribution at CERN n TOF: The Th-232 case

This thesis work focuses on the measurement of the angular distribution of the fragments emitted in the neutron-induced fission in Th-232. This experiment was done at the CERN n_TOF facility using a setup based on fast and position-sensitive Parallel Plate Avalanche Counters (PPACs). Fission events were identified by detection of both fission fragments in time coincidence in the two PPAC detectors flanking the target. Both detectors and targets were tilted 45º with respect to the neutron beam direction to cover all the possible emission angles. Data from this experiment are analysed and the fission fragment angular distribution of Th-232(n,f) reaction is obtained, extending its knowledge up to 1 GeV neutron energy. The cross section of Th-232(n,f) is also obtained up to 1 GeV, after applying the efficiency corrections due to the anisotropic emission of fragments, according to our results

Classifying Compactly generated t-structures on the derived category of a Noetherian ring

We classify complactly generated t-structures on the derived category of modules over a commutative Noetherian ring R in terms of decreasing filtrations by supports on Spec(R). A decreasing filtration by supports \phi : Z -> Spec(R) satisfies the weak Cousin condition if for any integer i \in Z, the set \phi(i) contains all the inmediate generalizations of each point in \phi(i+1). Every t-structure on D^b_fg(R) (equivalently, on D^-_fg(R)) is induced by complactly generated t-structures on D(R) whose associated filtrations by supports satisfy the weak Cousin condition. If the ring R has dualizing complex we prove that these are exactly the t-structures on D^b_fg(R). More generally, if R has a pointwise dualizing complex we classify all compactly generated t-structures on D_fg(R).Comment: v2 41 pages, improved exposition

Memória e intencionalidade na transmissão humanística de material epigráfico. A propósito de uma inscrição da Gallaecia na Geographia do Dr. João de Barros (CIL II, 2422)

Este estudo aborda o carácter problemático ou pouco fidedigno de CIL II 2422, de transmissão unicamente textual, em que Callaecia aparece como dedicante a um dos filhos adoptivos de Augusto. Avança-se a hipótese de uma possível manipulação tendenciosa, à luz da transmissão humanística especificamente portuguesa e o seu contexto: a utilização jurídicoeclesiástica da Gallaecia antiga, romana e medieval, por parte do arcebispo de Braga D. Diogo de Sousa (curador da inscrição) e a valorização da mesma na Geographia de Entre Douro e Minho e Tras-os montes (Lisboa, 1548) de João de Barros, para quem Callaecia funciona como ascedente prestigiante de Portugal frente ao reino castelhano, em concorrência com a restauratio resendiana da Lusitania.This paper focus the problematic CIL II 2422, known only by textual transmission, dedicated to one of Augustus’ grandsons by Callaecia. The study of the specific Portuguese fifteenth transmission allows the hypothesis of a humanistic forgery, regarding the juridical use of Gallaecia by Braga’s archbishop D. Diogo de Sousa (the curator of this piece), and the use of this inscription by João de Barros in a section of his Geographia de Entre Douro e Minho e Tras-os montes (Lisbon, 1548) where Callaecia plays as a prestigious antecedent of Portugal against the Spanish kingdom’s appropriation and in concurrence with the Lusitaniae restauratio of André de Resende’s circle

Electric/magnetic duality and RG flows in AdS4/CFT3

A large set of relevant deformations of the ABJM field theory defined on a stack of M2 branes is captured holographically by D = 4 N = 8 SO(8)-gauged supergravity, which has accordingly been applied to study renormalisation group (RG) flows of the field theory between distinct superconformal phases. Recently, it has been discovered that this supergravity is not unique, and that a one-parameter family of gaugings of maximal supergravity exists. The parameter is an angle that measures the mixture of electric and magnetic vectors that gauge SO(8) dyonically. We construct and comprehensively characterise all domain walls between the critical points of the new supergravities with at least SU(3) invariance, which are expected to be dual to RG flows of new field theories defined at least at large N. We also construct some walls running off to infinity in scalar space, which we expect to be dual to Coulomb branch flows of these field theories