199,003 research outputs found
The Mumford-Tate group of 1-motives
No full textIn this paper we study the structure and the degeneracies of the Mumford-Tate group MT(M) of a 1-motive M defined over C. This group is an algebraic Q-group acting on the Hodge realization of M and endowed with an increasing filtration W•. We prove that the unipotent radical of MT(M), which is W-1(MT(M)), injects into a "generalized" Heisenberg group. We then explain how to reduce to the study of the Mumford-Tate group of a direct sum of 1-motives whose torus'character group and whose lattice are both of rank 1. Next we classify and we study the degeneracies of MT(M), i.e., those phenomena which imply the decrement of the dimension of MT(M)
Périodes de 1-motifs et transcendance
No full textAbstractThe generalized Grothendieck's conjecture of periods (CPG)K predicts that if M is a 1-motive defined over an algebraically closed subfield K of C, then deg.transcQK(périodes(M))⩾dimQMT(MC). In this article we propose a conjecture of transcendance that we call the elliptico-toric conjecture (CET). Our main result is that (CET) is equivalent to (CPG)K applied to 1-motives defined over K of the kind M=[Zr∏j=1nEj×Gms]. (CET) implies some classical conjectures, as the Schanuel's conjecture or its elliptic analogue, but it implies new conjectures as well. All these conjectures following from (CET) are equivalent to (CPG)K applied to well chosed 1-motives: for example the Schanuel's conjecture is equivalent to (CPG)K applied to 1-motives of the kind M=[ZrGms]
Third kind elliptic integrals and 1-motives
No full textIn [4] we have showed that the Generalized Grothendieck's Period Conjecture applied to 1-motives, whose underlying semi-abelian variety is a product of elliptic curves and of tori, is equivalent to a transcendental conjecture involving elliptic integrals of the first and second kind, and logarithms of complex numbers. In this paper we investigate the Generalized Grothendieck's Period Conjecture in the case of a 1-motive M whose underlying semi-abelian variety is a non trivial extension of a product of elliptic curves by a torus. This will imply the introduction of elliptic integrals of the third kind for the computation of the periods of M and therefore the Generalized Grothendieck's Period Conjecture applied to M will be equivalent to a transcendental conjecture involving elliptic integrals of the first, second and third kind
Brauer groups of 1-motives
No full textOver a normal base scheme, we prove the generalized Theorem of the Cube for 1-motives and that a torsion class of the group He ́t2(M,Gm,M) of a 1-motive M, whose pull-back via the unit section ε:S→M is zero, comes from an Azumaya algebra. In particular, we deduce that over an algebraically closed field of characteristic zero, all classes of He ́t2(M,Gm,M) come from Azumaya algebras
A note on divisorial Correspondences of extensions of abelian schemes by tori
No full textLet S be a locally noetherian scheme and consider two extensions G1 and G2 of abelian S-schemes by S-tori. In this note we prove that the fppf-sheaf (Formula presented.) of divisorial correspondences between G1 and G2 is representable. Moreover, using divisorial correspondences, we show that line bundles on an extension G of an abelian scheme by a torus define group homomorphisms between G and (Formula presented.) Dedicated to M. Raynaud
Novel risk assessment tools for the climate-induced mechanical decay of wooden structures: Empirical and machine learning approaches
No full textThe microclimate in which historical buildings and objects are placed strongly influences the mechanical decay and properties of the constituent materials, especially if they are susceptible to fluctuations of temperature (T) and relative humidity (RH). For this reason, in this work, the attention is focused on the indoor microclimate of an historic building completely made of Scots pine wood: Ringebu Church (Norway). In particular, the indoor RH of Ringebu church has been analyzed by means of the European Standard EN15757, which establishes guidelines on assessing whether the RH fluctuations are risky for the conservation of historic hygroscopic materials (such as wood). However, for conservation purposes, it is useful to further study the entity of the RH fluctuations. In this framework, a novel simple strategy, named Median of Data Strategy (MoDS), for identifying RH drops is here proposed; the new approach, by scanning the RH time series and being tested on several examples, displays potential for better assessing the risk of degradation of wooden assets, objects, and artefacts. Then, based on evidence available in literature, a simple empirical model for computing the levels of hygro-mechanical stress developed due to hygric changes has been described and a novel tool for assessing the climate-induced mechanical risk for wooden structures has been proposed. Finally, a machine learning approach for predicting whether climatic fluctuations may have catastrophic effects on the historical wooden materials is presented as well. The obtained results show that the different proposed approaches may be useful for general assessments on the risk of decay of wooden samples and they open a pathway for future investigations in the fields of fracture mechanics, fatigue behavior and smart timeseries prediction for conservation and preservation purposes
Analysing the Main Standards for Climate-Induced Mechanical Risk in Heritage Wooden Structures: The Case of the Ringebu and Heddal Stave Churches (Norway)
No full textStudying, controlling and extrapolating the indoor microclimate of historical buildings have always been at the forefront among numerous preventive conservation strategies, especially in case of buildings made of organic hygroscopic materials, e.g., wood. The variations and fluctuations of the microclimatic variables, namely temperature (T) and relative humidity (RH), could have a detrimental effect on the mechanical properties of wooden objects, works of art and structures. For this reason, through the years, several guidelines have been provided by standards and protocols about the optimal microclimatic conditions that should be ensured to avoid the decay and the eventual catastrophic failure of heritage objects and buildings. In this work, two historical buildings entirely made of Scots pine wood have been analysed: the Ringebu and Heddal stave churches (Norway). These churches store several wooden medieval statues and paintings that are also susceptible to the effects of the microclimate. For this reason, the timeseries of the indoor relative humidity of the two churches have been analysed, in the framework of the indications provided by the standards. The criticalities of the existing protocols have been pointed out, emphasizing the need for systematically and periodically updated specifications, tailorable to a given case study of concern, without forgetting the ever-present needs of energy- and money-saving approaches
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Foraging patterns of the Antarctic Shag Phalacrocorax bransfieldensis at Harmony Point, Antarctica
No full textDuring the 1995 and1996 summer seasons the foraging patterns of the Antarctic Shag Phalacrocorax bransfieldensis werestudied by direct observation at Harmony Point, Nelson Island, South ShetlandIslands. During pre-laying and incubation, individuals of both sexes usuallyforaged once a day, females early in the morning and males when their partnersreturned to their nests. Due to increasing energy requirements at the nest, rearingindividuals incremented the daily time invested in foraging activitiesdisplaying more, but shorter, foraging trips. The reduction in the duration ofthe foraging trips through the breeding season suggests that Antarctic shags budgettheir activities in order to buffer variable food abundance or energyrequirements at the nests. The possibility of using the foraging parametersconsidered in this study in ecosystem monitoring programmes is discussed.Fil: Casaux, Ricardo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Bertolin M.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentin
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
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