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Littérature scientifique sur le sujet « Fibred threefold »

Auteur : Grafiati

Publié le 9 mars 2023

Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Fibred threefold"

Thompson, Alan. « Explicit Models for Threefolds Fibred by K3 Surfaces of Degree Two ». Canadian Journal of Mathematics 65, n^o 4 (1 août 2013) : 905–26. http://dx.doi.org/10.4153/cjm-2012-037-2.

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AbstractWe consider threefolds that admit a fibration by K3 surfaces over a nonsingular curve, equipped with a divisorial sheaf that defines a polarization of degree two on the general fibre. Under certain assumptions on the threefold we show that its relative log canonical model exists and can be explicitly reconstructed from a small set of data determined by the original fibration. Finally, we prove a converse to this statement: under certain assumptions, any such set of data determines a threefold that arises as the relative log canonical model of a threefold admitting a fibration by K3 surfaces of degree two.

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XU, JINSONG. « The third and fourth pluricanonical maps of threefolds of general type ». Mathematical Proceedings of the Cambridge Philosophical Society 157, n^o 2 (19 juin 2014) : 209–20. http://dx.doi.org/10.1017/s0305004114000267.

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AbstractFor a nonsingular projective threefold of general typeXover the field of complex numbers, we show that the fourth pluricanonical map ϕ4is not birational onto its image if and only ifXis birationally fibred by (1,2)-surfaces, provided that vol(X) ≥ 303. We also have similar characterization of birationality of ϕ3.

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HUNT, BRUCE. « K3-FIBERED CALABI–YAU THREEFOLDS II : SINGULAR FIBERS ». International Journal of Mathematics 10, n^o 07 (novembre 1999) : 871–96. http://dx.doi.org/10.1142/s0129167x99000379.

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Duneau, Michel, et Marc Audier. « Quasiperiodic packings of fibres with icosahedral symmetry ». Acta Crystallographica Section A Foundations of Crystallography 55, n^o 4 (1 juillet 1999) : 746–54. http://dx.doi.org/10.1107/s0108767399001142.

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Different icosahedral packings of fibres have been experimentally realized. A packing construction with straight fibres of the same circular cross section, only parallel to fivefold icosahedral axes and respecting the closest packing condition, is reported. Its characteristics of point-group symmetry and related two-dimensional tilings are analysed. But for determining unambiguously all the fibre positions it appears that a mathematical construction has to be made from the cut and projection of a five-dimensional space. Through such a method, the volume fraction of fibrous reinforcement in a composite material can be calculated. The related two-dimensional tiling can be proved to be different from a Penrose tiling. Finally, the characteristics of other icosahedral packings where fibres are parallel to threefold axes or to both threefold and fivefold axes are briefly discussed and a few further experiments on their elasticity properties and photonic band-gap structure are suggested.

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Colliot-Thélène, Jean-Louis, et Bruno Kahn. « Cycles de codimension 2 et H3 non ramifié pour les variétés sur les corps finis ». Journal of K-Theory 11, n^o 1 (février 2013) : 1–53. http://dx.doi.org/10.1017/is012009001jkt194.

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AbstractLet X be a smooth projective variety over a finite field $\mathbb{F}$. We discuss the unramified cohomology group H3nr(X, ℚ/ℤ(2)). Several conjectures put together imply that this group is finite. For certain classes of threefolds, H3nr(X, ℚ/ℤ(2)) actually vanishes. It is an open question whether this holds for arbitrary threefolds. For a threefold X equipped with a fibration onto a curve C, the generic fibre of which is a smooth projective surface V over the global field $\mathbb{F}$(C), the vanishing of H3nr(X, ℚ/ℤ(2)) together with the Tate conjecture for divisors on X implies a local-global principle of Brauer–Manin type for the Chow group of zero-cycles on V. This sheds new light on work started thirty years ago.

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ANDREAS, BJÖRN, GOTTFRIED CURIO et ALBRECHT KLEMM. « TOWARDS THE STANDARD MODEL SPECTRUM FROM ELLIPTIC CALABI–YAU MANIFOLDS ». International Journal of Modern Physics A 19, n^o 12 (10 mai 2004) : 1987–2014. http://dx.doi.org/10.1142/s0217751x04018087.

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We show that it is possible to construct supersymmetric three-generation models with the Standard Model gauge group in the framework of non-simply-connected elliptically fibered Calabi–Yau threefolds, without section but with a bi-section. The fibrations on a cover Calabi–Yau threefold, where the model has six generations of SU(5) and the bundle is given via the spectral cover description, use a different description of the elliptic fiber which leads to more than one global section. We present two examples of a possible cover Calabi–Yau threefold with a free involution: one is a fiber product of rational elliptic surfaces dP9; another example is an elliptic fibration over a Hirzebruch surface. We compute the necessary amount of chiral matter by "turning on" a further parameter which is related to singularities of the fibration and the branching of the spectral cover.

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BARJA, MIGUEL A. « LOWER BOUNDS OF THE SLOPE OF FIBRED THREEFOLDS ». International Journal of Mathematics 11, n^o 04 (juin 2000) : 461–91. http://dx.doi.org/10.1142/s0129167x00000234.

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We study from a geographical point of view fibrations of threefolds over smooth curves f:T→B such that the general fibre is of general type. We prove the non-negativity of certain relative invariants under general hypotheses and give lower bounds for [Formula: see text] depending on other relative invariants. We also study the influence of the relative irregularity q(T)-g(B) on these bounds. A more detailed study of the lowest cases of the bounds is given.

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Szendrői, Balázs. « Sheaves on Fibered Threefolds and Quiver Sheaves ». Communications in Mathematical Physics 278, n^o 3 (8 janvier 2008) : 627–41. http://dx.doi.org/10.1007/s00220-007-0408-y.

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Oguiso, Keiji. « On certain rigid fibered Calabi-Yau threefolds ». Mathematische Zeitschrift 221, n^o 1 (janvier 1996) : 437–48. http://dx.doi.org/10.1007/bf02622125.

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Oguiso, Keiji. « On certain rigid fibered Calabi–Yau threefolds ». Mathematische Zeitschrift 221, n^o 3 (15 mars 1996) : 437–48. http://dx.doi.org/10.1007/pl00004519.

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Thèses sur le sujet "Fibred threefold"

RIVA, ENEA. « Slope inequalities for fibred surfaces and fibreed threefolds ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/374266.

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Su una varieta algebrica fibrata si definesce un invariante relativo detto slope che ne specifica la natura. Per queste fibrazioni un ruolo importante è svolto del fibrato di Hodge e dagli invarianti geometrici delle fibre generiche. In particulare in questa tesi ci concentreremo su superfici e threefold fibrati su curve, dando un stima dal basso della slope che dipenda del rango unitario del fibrato di hodge e da: - indice di clifford cella curva generale, nel caso di superfici; -dal genere geometrico ($p_{g}$) della superficie generale nel caso di threefold. infine sfrutteremo i risultati ottenuti sui threefold per definere un upper bound del rango unitario $u_{f}$ in funzione di $p_{g}$ sotto l'ipotesi che il genere della curva base sia zero o uno.
On a fibred algebraic variety, is defined a relative invariant called slope which classifies the variety itself. For these fibration a main character is played by the Hodge bundle and by the geometric invariants of the general fibers. In particular in this thesis we focus on surfaces and threefolds fibred over curves, and we give a lower bound for the slope which depends on the unitary rank of the hodge bundle and on: -the clifford index of the general curve, in case of fibred surfaces; - the geometric genus ($p_{g}$) of the general surface, in case of threefolds. Finally we use these results on fibred threefolds to make a new upper bound for the unitary rank $u_{f}$ depending on $p_{g}$ under the hypothesis that the genus of the base curve is zero or one.

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Barja, Yáñez Miguel Ángel. « On the Slope and Geography of Fibred Surfaces and Threefolds ». Doctoral thesis, Universitat de Barcelona, 1998. http://hdl.handle.net/10803/655.

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In this tesis we study numerical propieties of surfaces and threefolds, mainly fibred over curves, the so called "slope" of the fibration. We prove partially a conjecture of Fujita on the semiampleness of the direct image of the relative dualizing sheaf of a fibration.
We give new lower bounds of the slope of a fibred surface depending on data of the general fibre (existence of involutions) and on data of the hole surface (the fibration not being the Albanese morphism, for example).
We study the case of threefolds over curves. We prove that, in general, the relative algebraic Euler characteristic is nonnegative and give lower bound for the slope. We classify the lowest cases of the invariants.

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Thompson, Alan Matthew. « Models for threefolds fibred by K3 surfaces of degree two ». Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542980.

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Chapitres de livres sur le sujet "Fibred threefold"

« Fibre products of elliptic surfaces ». Dans Modular Calabi-Yau Threefolds, 21–30. Providence, Rhode Island : American Mathematical Society, 2005. http://dx.doi.org/10.1090/fim/022/02.

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Actes de conférences sur le sujet "Fibred threefold"

Zhang, Yani, Qiang Xu, Sicong Liu et Ya Zhao. « Optimization of nearly zero ultra-flattened dispersion photonic crystal fibre with fluorine doped threefold symmetry core ». Dans Selected Papers of the Chinese Society for Optical Engineering Conferences held October and November 2016, sous la direction de Yueguang Lv, Jialing Le, Hesheng Chen, Jianyu Wang et Jianda Shao. SPIE, 2017. http://dx.doi.org/10.1117/12.2268376.

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Zeleny, R., et M. Lucki. « An improved non-linear nearly-zero dispersion flattened photonic crystal fiber with the threefold symmetry core ». Dans SPIE Photonics Europe, sous la direction de Kyriacos Kalli et Alexis Mendez. SPIE, 2012. http://dx.doi.org/10.1117/12.920064.

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Bergano, Neal S., Jennifer Aspell, C. R. Davidson, P. R. Trischitta, B. M. Nyman et F. W. Kerfoot. « Bit-Error-Rate Measurements of a Multi-Thousand-Kilometer Fiber-Amplifier Transmission System Using a Circulating Loop ». Dans Optical Amplifiers and Their Applications. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oaa.1991.tha5.

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Recently, we reported the results of a 2.4 Gb/s and 5 Gb/s feasibility demonstration of long distance erbium-doped fiber amplifier (EDFA) transmission systems using a circulating loop[1] The significance of this experiment was threefold. First, it demonstrated that high bit rate all-optical EDFA transmission systems are capable of achieving transoceanic distances. Second, it demonstrated a new measurement technique in which bit-error-rate (BER) is measured in a circulating loop. And, third, it achieved a new record in bit rate distance products.

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Konka, Hari Prasad, M. A. Wahab et Kun Lian. « Sandwich Structures With Smart Composite Face Skin ». Dans ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62170.

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Sandwich structures are one of the very important classes of composite structures that have been studied quite extensively in the past few years. The concepts of sandwich structures have been widely used in the aerospace, automobile, marine, and civil engineering applications; because it is suitable and amenable to the development of light-weight structures with high in-plane and flexural stiffness. A typical sandwich structure is usually comprised of two stiff face skins, which are separated by a thick, lightweight, and compliant core. The primary function of the face skin sheets in a sandwich structure is to provide required bending and in-plane shear stiffness and to carry edge-wise bending and in-plane loads. The composite face skins are usually made from resin impregnated glass fiber or a laminate of unidirectional fibers (prepregs), graphite prepregs, aluminum alloys or many other refractory metal alloys. In this study, smart composite face skins comprise of the composite layers with embedded Piezoelectric Fiber Composite Sensors (PFCS). The functions of PFCS as an embedded sensor inside the composite sandwich structure are threefold: (i) to detect all loading conditions acting on to the structure, (ii) to detect the damages while in-service under dynamic loads, and finally, (iii) to monitor the pre-existing damages in the structure so that their severity can be ascertained to avoid eventual catastrophic or premature failures. The PFCS are generally an ideal choice for this type of sandwich structures applications, as they are highly flexible, easily embeddable; their high compatibility to the composite manufacturing techniques; and more importantly, they produce significantly less interfacial stresses when embedded inside the composite structures. This research is focused on examining the effects on the structural integrity of the composite sandwich structure (with glass micro-balloons syntactic foam core and resin infused glass fiber face skins) with PFCS embedded inside face skin. In-plane tensile, and tension-tension fatigue tests are performed to evaluate the strengths/behavior of the composites containing embedded PFCS. The tensile tests showed that both the average ultimate strength and the modulus of elasticity of the tested laminate with or without embedded PFCS are within 7%. The Stress-Life (S-N) curves obtained from fatigue tests indicates that the fatigue lives and strengths with and without the PFCS are close to each other as well. Then carefully planned experiments are conducted to investigate the ability of the embedded PFCS to monitor the stress/strain levels and detect damages in composite sandwich structure. Experiments were performed to explore the ability of the embedded PFCS (MFC and PFC) to detect the damages in the structures using modal analysis method. Results from these experiments shows that the PFCS are effective in detecting the initiations of damages like delamination inside these composite sandwich structures through changes in natural frequency modes. Hence a smart composite face skin can be an effective method to monitor the health of the composite sandwich structures’ in-service conditions.

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