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Автор: Grafiati

Опубліковано: 14 березня 2023

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Статті в журналах з теми "G-bundles"

MURRAY, MICHAEL K., and RAYMOND F. VOZZO. "CIRCLE ACTIONS, CENTRAL EXTENSIONS AND STRING STRUCTURES." International Journal of Geometric Methods in Modern Physics 07, no. 06 (September 2010): 1065–92. http://dx.doi.org/10.1142/s0219887810004725.

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The caloron correspondence can be understood as an equivalence of categories between G-bundles over circle bundles and LG ⋊ρ S1-bundles where LG is the group of smooth loops in G. We use it, and lifting bundle gerbes, to derive an explicit differential form based formula for the (real) string class of an LG ⋊ρ S1-bundle.

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Choe, Insong, and George H. Hitching. "Non-defectivity of Grassmannian bundles over a curve." International Journal of Mathematics 27, no. 07 (June 2016): 1640002. http://dx.doi.org/10.1142/s0129167x16400024.

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Let [Formula: see text] be the Grassmann bundle of two-planes associated to a general bundle [Formula: see text] over a curve [Formula: see text]. We prove that an embedding of [Formula: see text] by a certain twist of the relative Plücker map is not secant defective. This yields a new and more geometric proof of the Hirschowitz-type bound on the isotropic Segre invariant for maximal isotropic sub-bundles of orthogonal bundles over [Formula: see text], analogous to those given for vector bundles and symplectic bundles in [I. Choe and G. H. Hitching, Secant varieties and Hirschowitz bound on vector bundles over a curve, Manuscripta Math. 133 (2010) 465–477, I. Choe and G. H. Hitching, Lagrangian sub-bundles of symplectic vector bundles over a curve, Math. Proc. Cambridge Phil. Soc. 153 (2012) 193–214]. From the non-defectivity, we also deduce an interesting feature of a general orthogonal bundle of even rank over [Formula: see text], contrasting with the classical and symplectic cases: a general maximal isotropic sub-bundle of maximal degree intersects at least one other such sub-bundle in positive rank.

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Deaconu, Valentin, Alex Kumjian, and Birant Ramazan. "Fell bundles associated to groupoid morphisms." MATHEMATICA SCANDINAVICA 102, no. 2 (June 1, 2008): 305. http://dx.doi.org/10.7146/math.scand.a-15064.

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Given a continuous open surjective morphism $\pi :G\rightarrow H$ of étale groupoids with amenable kernel, we construct a Fell bundle $E$ over $H$ and prove that its $C^*$-algebra $C^*_r(E)$ is isomorphic to $C^*_r(G)$. This is related to results of Fell concerning $C^*$-algebraic bundles over groups. The case $H=X$, a locally compact space, was treated earlier by Ramazan. We conclude that $C^*_r(G)$ is strongly Morita equivalent to a crossed product, the $C^*$-algebra of a Fell bundle arising from an action of the groupoid $H$ on a $C^*$-bundle over $H^0$. We apply the theory to groupoid morphisms obtained from extensions of dynamical systems and from morphisms of directed graphs with the path lifting property. We also prove a structure theorem for abelian Fell bundles.

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BISWAS, INDRANIL, and GÜNTHER TRAUTMANN. "A CRITERION FOR HOMOGENEOUS PRINCIPAL BUNDLES." International Journal of Mathematics 21, no. 12 (December 2010): 1633–38. http://dx.doi.org/10.1142/s0129167x10006689.

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We consider principal bundles over G/P, where P is a parabolic subgroup of a semi-simple and simply connected linear algebraic group G defined over ℂ. We prove that a holomorphic principal H-bundle EH → G/P, where H is a complex reductive group, and is homogeneous if the adjoint vector bundle ad (EH) is homogeneous. Fix a faithful H-module V. We also show that EH is homogeneous if the vector bundle EH ×H V associated to it for the H-module V is homogeneous.

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Perego, Arvid. "Kobayashi—Hitchin correspondence for twisted vector bundles." Complex Manifolds 8, no. 1 (January 1, 2021): 1–95. http://dx.doi.org/10.1515/coma-2020-0107.

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Abstract We prove the Kobayashi—Hitchin correspondence and the approximate Kobayashi—Hitchin correspondence for twisted holomorphic vector bundles on compact Kähler manifolds. More precisely, if X is a compact manifold and g is a Gauduchon metric on X, a twisted holomorphic vector bundle on X is g−polystable if and only if it is g−Hermite-Einstein, and if X is a compact Kähler manifold and g is a Kähler metric on X, then a twisted holomorphic vector bundle on X is g−semistable if and only if it is approximate g−Hermite-Einstein.

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Lashof, R. "Homogeneous Hamiltonian G-Bundles." Proceedings of the American Mathematical Society 121, no. 2 (June 1994): 599. http://dx.doi.org/10.2307/2160442.

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Lashof, R. "Homogeneous Hamiltonian $G$-bundles." Proceedings of the American Mathematical Society 121, no. 2 (February 1, 1994): 599. http://dx.doi.org/10.1090/s0002-9939-1994-1218116-6.

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Mozgovoy, Sergey, and Olivier Schiffmann. "Counting Higgs bundles and type quiver bundles." Compositio Mathematica 156, no. 4 (February 27, 2020): 744–69. http://dx.doi.org/10.1112/s0010437x20007010.

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We prove a closed formula counting semistable twisted (or meromorphic) Higgs bundles of fixed rank and degree over a smooth projective curve of genus $g$ defined over a finite field, when the twisting line bundle degree is at least $2g-2$ (this includes the case of usual Higgs bundles). This yields a closed expression for the Donaldson–Thomas invariants of the moduli spaces of twisted Higgs bundles. We similarly deal with twisted quiver sheaves of type $A$ (finite or affine), obtaining in particular a Harder–Narasimhan-type formula counting semistable $U(p,q)$-Higgs bundles over a smooth projective curve defined over a finite field.

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Krepski, Derek. "Central Extensions of Loop Groups and Obstruction to Pre-Quantization." Canadian Mathematical Bulletin 56, no. 1 (March 1, 2013): 116–26. http://dx.doi.org/10.4153/cmb-2011-131-6.

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AbstractAn explicit construction of a pre-quantumline bundle for themoduli space of flat G-bundles over a Riemann surface is given, where G is any non-simply connected compact simple Lie group. This work helps to explain a curious coincidence previously observed between Toledano Laredo's work classifying central extensions of loop groups LG and the author's previous work on the obstruction to pre-quantization of the moduli space of flat G-bundles.

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BISWAS, INDRANIL, and JOHN LOFTIN. "HERMITIAN–EINSTEIN CONNECTIONS ON PRINCIPAL BUNDLES OVER FLAT AFFINE MANIFOLDS." International Journal of Mathematics 23, no. 04 (April 2012): 1250039. http://dx.doi.org/10.1142/s0129167x12500395.

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Let M be a compact connected special flat affine manifold without boundary equipped with a Gauduchon metric g and a covariant constant volume form. Let G be either a connected reductive complex linear algebraic group or the real locus of a split real form of a complex reductive group. We prove that a flat principal G-bundle EG over M admits a Hermitian–Einstein structure if and only if EG is polystable. A polystable flat principal G-bundle over M admits a unique Hermitian–Einstein connection. We also prove the existence and uniqueness of a Harder–Narasimhan filtration for flat vector bundles over M. We prove a Bogomolov type inequality for semistable vector bundles under the assumption that the Gauduchon metric g is astheno-Kähler.

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Дисертації з теми "G-bundles"

Grguric, Izak. "Equivariant bordism and G-bundles." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/7567.

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Let G be the cyclic group of 4 elements and H the subgroup of G of order 2. We study the actions of G on manifolds modulo the equivariant bordism relation by studying the equivariant bordism relation on G-vector bundles; specifically, we focus on G-vector bundles such that G action is free away from the zero section, and the isotropy group of each point in the base is equal to H. We obtain a complete set of characteristic numbers that deter mines when such a G-vector bundle is nulibordant. Using this result, we obtain a geometric splitting of the bordism classes of these bundles into ge ometrically simpler components. Furthermore, we determine a complete set of characteristic numbers for the bordism ring of G-manifolds. Finally, we generalize our results to a larger family of finite groups G.

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Schaposnik, Laura P. "Spectral data for G-Higgs bundles." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:7b483c4c-53e4-4449-88c2-7a75d98ac861.

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We develop a new geometric method of understanding principal G-Higgs bundles through their spectral data, for G a real form of a complex Lie group. In particular, we consider the case of G a split real form, as well as G = SL(2,R), U(p,p), SU(p,p), and Sp(2p,2p). Further, we give some applications of our results, and discuss open questions.

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Zucca, Alessandro. "Dirac Operators on Quantum Principal G-Bundles." Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4108.

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In this thesis I discuss some results on the noncommutative (spin) geometry of quantum principal G-bundles. The first part of the thesis is devoted to the study of spectral triples over toral bundles; extending some recent results by L. Dabrowski and A. Sitarz, we introduce the notion of projectable spectral triple for T^n-bundles. Moreover, we work out twisted Dirac operators. We discuss, in particular, the application of these results to noncommutative tori. In the second part of the thesis, instead, we work out a method for constructing real spectral triples over cleft quantum principal G-bundles and we study the properties of these triples and their behaviour under gauge transformations. Some of the results discussed in this thesis can also be found in the following papers: arXiv:1305.6185 arXiv:1308.4738

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Coiai, Fabrizio. "Boundedness problem for semistable G-bundles in positive characteristic." Doctoral thesis, SISSA, 2004. http://hdl.handle.net/20.500.11767/4248.

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Muñoz, Castañeda Ángel Luis [Verfasser]. "Principal G-bundles on nodal curves / Ángel Luis Muñoz Castañeda." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1139709437/34.

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Duarte, Gustavo Ignácio. "Integrabilidade de G-Estruturas." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/45/45131/tde-05072018-111337/.

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Esta dissertação tem como objetivo discutir sob quais condições uma G- estrutura é integrável. Primeiro apresentam-se fibrados principais, vetoriais e outras estruturas a elas associados como torção, espaços verticais, espaços horizontais e conexões. Depois apresentam-se a definição de G-estrutura, de integrabilidade de G-estruturas, com exemplos e as respectivas versões de integrabilidade e equivalência de G-estruturas. Finalmente, são descritas condições mais gerais que garantem a integrabilidade de G-estruturas.
This dissertation aims to discuss what are the conditions for the inte- grability of a G-structure. We begin presenting principal bundles, vectoer bundles, associated bundles and other structures related to them like torsion, vertical spaces, horizontal spaces and connections. After this, we present the definition of G-structure, integrability os G-structures with examples ans respectives versions of integrabilities and the equivalence of G-estructures. Finally, we describe more general conditions that ensure the integrability of G-structures.

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Stein, Luba [Verfasser]. "On the Hilbert uniformization of moduli spaces of flat G-bundles over Riemann surfaces / Luba Stein." Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1047145499/34.

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Souza, Taciana Oliveira. "Teoremas de (H,G)-coincidências para variedades e classificação global de singularidades isoladas em dimensões (6,3)." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/55/55135/tde-10062013-161959/.

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Este trabalho é constituido por duas partes. Na primeira parte, obtivemos algumas generalizações do clássico Teorema de Borsuk-Ulam em termos de (H,G)-coincidências. Na segunda parte, estendemos a caracterização dos germes de aplicações triviais, em codimensão 3, pelas fibrações de Milnor iniciada por Church e Lamotke em [11]. Usamos essa caracterização na classificação global de singularidades isoladas em dimensões (6, 3)
This work consists of two parts. In the first part, we obtain some generalizations of the classical Borsuk-Ulam Theorem in terms of (H,G)-coincidences. In the second part, we extend the characterization of trivial map germs, in codimension 3, by the Milnor fibrations started by Church and Lamotke in [11]. We use this characterization in the global classification of isolated singularities in dimensions (6, 3)

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Balčiūnas, Aidas. "Baigtinio tipo g- struktūrų vidinės sietys." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100702_112749-84649.

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Vienas svarbiausių šiuolaikinės diferencialinės geometrijos skyrių yra glodžių G- struktūrų teorija, kuriai pradžią davė klasikinės Rymano erdvės struktūros nagrinėjimas. G- struktūra glodžioje daugdaroje yra gaunama paėmus jos reperių sluoksniuotės redukciją , atitinkantį neišsigimusių matricų grupės pogrupį G. G-struktūros egzistuoja ne bet kurioje daugdaroje. Šiame darbe yra nagrinėjama tik baigtinio tipo G- struktūrų vidinės sietys. Yra įrodoma, kad kiekvieną baigtinio tipo G- struktūrą atitinka baigtinio tipo diferencialinė lygtis ant daugdaros . G- struktūrų geometrija nagrinėjama netradiciniu būdu nagrinėjant jų infinitezimalių simetrijų diferencialines lygtis. Šiuo metodu yra išnagrinėtos G- struktūrų afininės sietys, taip pat ir normalinės sietys. Paskutiniosios G- struktūrų geometrijoje nebuvo iki šiol tyrinėtos.
The most important part of differential geometry in our days is the theory of smooth G- structures, which started with the analyses of clasical construction of Riemannian space. G-structure in smooth manifold is acquired, when we take reduction of its frame bundle corresponding to subgroup G of non-degeneracy matrix group . It‘s important to note, that G- structures do not exist in every manifold. In this paper are considering intrisic connections only of finite type of G- structures. It is proved, that every finite type of G- structure corresponds to finite type of differential equation on the manifold . The Geometry of G- structures is investigated not traditionally while analyzing differential equations of infetisimal simmetrics of G- structures. There are analysed affine connections of G- structures, also and normal connections. The former haven‘t been investigated in geometry of G- structures.

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Grégoire, Chloé. "Espace de modules des G2-fibrés principaux sur une courbe algébrique." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20086.

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L'objet de cette thèse est l'étude de l'espace de modules des G_2-fibrés principaux sur une courbe complexe projective connexe lisse, où G_2 désigne le groupe de Lie exceptionnel de plus petit rang. Le groupe G_2 est tout d'abord présenté comme le groupe des automorphismes de l'algèbre complexe des octaves de Cayley. D'autres définitions sont ensuite proposées. Les différentes réductions et extensions que peut admettre un G_2-fibré principal sont étudiées ainsi que la relation entre la stabilité d'un G_2-fibré principal et celle de son fibré vectoriel associé. L'espace de modules des G_2-fibrés principaux semistables est analysé. Nous obtenons notamment une caractérisation de son lieu lisse, une décomposition explicite de son lieu singulier en trois composantes connexes et une analyse de l'espace de Verlinde de niveau 1 pour le groupe G_2
This thesis studies the moduli space of principal G_2-bundles over a smooth connected projective curve, where G_2 is the exceptional Lie group of smallest rank. The group G_2 is first introduced as the group of automorphisms of the complex algebra of the Cayley numbers. Other equivalent definitions are also proposed. We study the reductions and extensions that a principal G_2_bundle can admit, as well as the link between a principal G_2-bundle and its associated vector bundle in relation to the notion of (semi)stability. The moduli space of semistable principal G_2-bundles is analysed. We notably obtain a characterisation of its smooth locus, with an explicit decomposition of its singular locus into three connected componants. We also give an analysis of the Verlinde space of G_2 at level 1

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Книги з теми "G-bundles"

Scognamillo, Renata. Principal G-bundles and abelian varieties: The Hitchin system. Edizioni della Normale, 2013.

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Gaitsgory, Dennis, and Jacob Lurie. Weil's Conjecture for Function Fields. Princeton University Press, 2019. http://dx.doi.org/10.23943/princeton/9780691182148.001.0001.

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A central concern of number theory is the study of local-to-global principles, which describe the behavior of a global field K in terms of the behavior of various completions of K. This book looks at a specific example of a local-to-global principle: Weil's conjecture on the Tamagawa number of a semisimple algebraic group G over K. In the case where K is the function field of an algebraic curve X, this conjecture counts the number of G-bundles on X (global information) in terms of the reduction of G at the points of X (local information). The goal of this book is to give a conceptual proof of Weil's conjecture, based on the geometry of the moduli stack of G-bundles. Inspired by ideas from algebraic topology, it introduces a theory of factorization homology in the setting ℓ-adic sheaves. Using this theory, the authors articulate a different local-to-global principle: a product formula that expresses the cohomology of the moduli stack of G-bundles (a global object) as a tensor product of local factors. Using a version of the Grothendieck–Lefschetz trace formula, the book shows that this product formula implies Weil's conjecture. The proof of the product formula will appear in a sequel volume.

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Schlieter, Jens. The Final Configuration of Near-Death Experiences (1960–1975). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190888848.003.0011.

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The final chapter of the discursive history outlines how Robert Crookall’s and Robert A. Monroe’s books on “astral projection,” but also C. G. Jung and other researchers discussing paranormal and parapsychological phenomena in the 1960s and early 1970s, already assembled almost all phenomena that Moody could bundle in 1975 under the new term “near-death experiences.” However, the chapter points to the fact that, in contrast to the opinio communis, the term had already been introduced by John C. Lilly in 1972. Other influences discussed are the use of LSD, which sometimes triggered near-death experiences, and the growing interest of psychologists and psychotherapists in such experiences (e.g., Russell Noyes and Roy Kletti or Stanislav Grof). It concludes with the institutionalization of the term as grasped in the post-Moodian “Greyson scale.” The latter serves as an example for the still-dominant religious interest in the experiences, i.e., their mystic, esoteric, and transformative qualities.

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Schmidt, Steffen W., Barbara A. Bardes, and Mack C. Shelley. Bundle : American Government and Politics Today : Essentials 2017-2018 Edition, Loose-Leaf Version, 19th + California: The Politics of Diversity, 9th + MindTap Political Science, 1 Term Printed Access Card for Bardes/Shelley/Schmidt's American G. Wadsworth, 2017.

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Частини книг з теми "G-bundles"

Kumar, Shrawan. "Infinite grassmannians and moduli spaces of G-bundles." In Vector Bundles on Curves — New Directions, 1–49. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/bfb0094424.

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García Pérez, P. L., and J. Muñoz Masqué. "Differential invariants on the bundles of g-structures." In Lecture Notes in Mathematics, 177–201. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/bfb0086422.

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Kawakami, Tomohiro. "G-Manifolds and G-Vector Bundles in Algebraic, Semialgebraic, and Definable Categories." In K-Monographs in Mathematics, 37–51. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-009-0003-5_3.

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Hoffmann, Norbert. "On Moduli Stacks of G-bundles over a Curve." In Affine Flag Manifolds and Principal Bundles, 155–63. Basel: Springer Basel, 2010. http://dx.doi.org/10.1007/978-3-0346-0288-4_5.

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Baranovsky, Vladimir, Sam Evens, and Victor Ginzburg. "Representations of Quantum Tori and G-bundles on Elliptic Curves." In The Orbit Method in Geometry and Physics, 29–48. Boston, MA: Birkhäuser Boston, 2003. http://dx.doi.org/10.1007/978-1-4612-0029-1_3.

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Morgan, John W., and Kieran G. O’Grady. "Certain moduli spaces for bundles on elliptic surfaces with p g = 1." In Differential Topology of Complex Surfaces, 57–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/bfb0086769.

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Feigin, B. L. "Differential operators on the moduli space of G-bundles on algebraic curve and Lie algebra cohomologies." In ICM-90 Satellite Conference Proceedings, 90–103. Tokyo: Springer Japan, 1991. http://dx.doi.org/10.1007/978-4-431-68170-0_5.

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Cordero, Luis A., C. T. J. Dodson, and Manuel de León. "Constructing G-structures on FM." In Differential Geometry of Frame Bundles, 137–69. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1265-6_8.

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Cordero, Luis A., C. T. J. Dodson, and Manuel de León. "Prolongation of G-structures to FM." In Differential Geometry of Frame Bundles, 17–37. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1265-6_2.

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Cordero, Luis A., C. T. J. Dodson, and Manuel de León. "Lift GD of a Riemannian G to FM." In Differential Geometry of Frame Bundles, 107–35. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-1265-6_7.

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Тези доповідей конференцій з теми "G-bundles"

Kowalski, Oldřich, and Masami Sekizawa. "Invariance of g-natural metrics on tangent bundles." In Proceedings of the 10th International Conference on DGA2007. WORLD SCIENTIFIC, 2008. http://dx.doi.org/10.1142/9789812790613_0015.

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Morandin, Greg, Eric Araujo, and David J. Ribbans. "Evaluation of CANDU Spent Nuclear Fuel Bundle Structural Integrity During Normal Transport Conditions." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-2143.

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The International Atomic Energy Agency requires that the transport of spent nuclear fuel in containers be able to handle certain loads in the axial, lateral and vertical direction under normal off-site handling scenarios. During transport, CANDU nuclear fuel bundles may experience axial impact loads due to possible sliding within a transport tube resulting in impact with the container wall. This paper presents a series of postulated fuel bundle impact scenarios in order to determine the enveloping dynamic g load that a bundle can experience before possible plastic deformation to the bundle fuel sheath. The IAEA load factors for envelope design are used as a reference to ramp the impact velocities and are not equivalent to the dynamic loads used in the analysis. Based on the transportation induced g loads outlined in the IAEA regulations for safe transport of spent fuel under normal handling conditions (IAEA 1985), these g loads are used to calculate a terminal velocity for the bundle whose motion impacts a rigid plate. One type of CANDU nuclear fuel bundle consists of 28 Zircaloy-4 fuel pencils loaded with Uranium Dioxide fuel pellets. The ends of the pencils are fitted with end caps and each end cap is spot welded to a Zircaloy-4 end plate at either end. The finite element model of the fuel bundle consists of 4-noded shell elements representing the fuel sheaths and end plates and 8-noded continuum elements representing the Uranium Dioxide pellets. For the purpose of the analysis, the fuel bundle is housed inside a transport tube, which limits the bundle lateral and vertical motion during impact rebound. The impact target is conservatively modelled as an infinitely rigid plate. Contact surfaces are modelled between the fuel bundle and transport tube, between the fuel bundle and impact plate and between each individual fuel pencil. Two bundle scenarios are considered. The first is a single fuel bundle impacting the plate and the second is two fuel bundles in series in a single transport tube impacting the plate. The second scenario considers the interaction between the two bundles during initial impact and rebound. The analysis covers these scenarios under various magnitudes of applied dynamic loading including 2g, 5g, and 8g. The objective is to determine at what applied load the fuel bundle will experience plastic damage to the fuel pencil sheath. This will effectively provide a bounding g load for CANDU spent fuel transport. The results of the analysis show that for a single bundle in a transport tube, a dynamic load of 8g results in plastic deformation of and the target are modeled using 4-noded shell elements. The pencil end caps are attached to the endplates using an area of common nodes (Fig. 3). Although the actual endcap to endplate connection is through a round spot-welded cross section, for modeling ease the interface is several fuel pencil sheaths. For the two-bundle case, a dynamic load of 8g does not result in any plastic deformation in the fuel pencil sheaths. Thus, a limiting dynamic load between 5g and 8g is determined for the fuel handling scenarios. This paper presents the methodology and models used in the analysis as well as the results of the simulations.

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KADAOUI ABBASSI, MOHAMED TAHAR, and OLDŘICH KOWALSKI. "ON G-NATURAL METRICS WITH CONSTANT SCALAR CURVATURE ON UNIT TANGENT SPHERE BUNDLES." In Proceedings in Honor of Professor K Sekigawa's 60th Birthday. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701701_0001.

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Summers, Michael P., Jonathan A. Holst, and John P. Parmigiani. "The Complex Shear Modulus of Humpback Whale Blubber." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14848.

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Further investigations of the mechanical properties of whale blubber will benefit its morphology and those who use it. Located below the dermas, blubber is an insular tissue constructed of a lipid matrix cross-weaved with strong, structural collagen and elastic fiber bundles. The blubber transitions into the superficial fascia layer, a loose connective tissue, which sheaths the muscle surrounding the whale. [1] Blubber should behave viscoelastically because it is a soft tissue. [2] The complex shear modulus G* = G′+iG″ is a viscoelastic property commonly used in defining soft tissues. It is comprised of both an elastic energy storage term (G′) and a viscous energy dissipation term (G″). Apart from adding to the morphology of whale blubber, these properties can currently be used for the improvement of certain whale tracking tag designs. The tags that would gain from these measurements deploy remotely and anchor subdermally in the body of the whale, near the dorsal fin. Once attached, they transmit a radio signal to a monitoring satellite. Knowing the migratory and behavioral patterns of whales allows for the adjustment of human activities to help in the recovery of endangered species.

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Jacques, Steven L. "Origins of Tissue Optical Properties in the UVA, Visible, and NIR Regions." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.opc364.

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This paper describes the relationship between the ultrastructure of biological tissues and the observed macroscopic optical scattering properties. A summary of the tissue absorption spectrum is also presented. The scattering of soft tissues (liver, prostate, etc.) and fibrous tissues such as dermis are considered. The scattering of soft tissues is attribued to membranous structures and modeled as Mie scattering from spheres in the 0.2-2-μm diameter range, where membrane lipids occupy about 1-20% of the cellular volume and the refractive index mismatch is 1.46/1.35. The scattering of dermis is modeled as scattering from collagen fiber bundles in the 2.8-μm diameter range occupying 21% of the dermal volume and the refractive index mismatch is 1.38/1.35. The effects of a component of small-scale particle scattering in the Rayleigh limit is also considered. The models are compared with tissue values from the literature for the reduced scattering coefficient, μs(1-g), and the anisotropy, g. The models roughly match the absolute value and wavelength dependence of scattering in the 300-1100 nm wavelength range.

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Davies, Peter, and Leif A. Carlsson. "Influence of Delamination on Strength of Externally Pressurized Glass/Epoxy Cylinders." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0908.

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Abstract The delamination resistance of filament wound glass/epoxy cylinders has been characterized for a range of winding angles and fracture mode ratios using beam fracture specimens. The results reveal that the fracture resistance increases with increasing winding angle and mode II (shear) fraction (GII/G). It was also found that interlaced fiber bundles in the filament wound cylinder wall acted as effective crack arresters in mode I loading. To examine the sensitivity of delamination damage on the implosion behavior of cylinders, external pressure tests were performed on filament-wound glass/epoxy composite cylinders with artificial defects and impact damage. The results revealed that the cylinder strength was insensitive to the presence of single delaminations but impact damage caused reductions in failure pressure. The insensitivity of the failure pressure to a single delamination is attributed to the absence of buckling of the delaminated sublaminates before the cylinder wall collapsed. The impacted cylinders contained multiple delaminations, which caused local reduction in the compressive load capability and reduction in failure pressure.

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Megías Díaz, Raquel, Ricardo Belda González, Ana Vercher Martínez, and Eugenio Giner Maravilla. "Explicit expressions for elastic constants of osteoporotic lamellar tissue and damage assessment using Hashin failure criterion." In VI ECCOMAS Young Investigators Conference. València: Editorial Universitat Politècnica de València, 2021. http://dx.doi.org/10.4995/yic2021.2021.12442.

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Osteoporosis is one of the most prevalent diseases in the last decades. The ageing of the population has led to a large increase in the number of people who suﬀer this musculoskeletal disease. For this reason, an early diagnosis of osteoporosis in order to improve bone fracture risk assessment is essential. To this end, eﬀorts to enhance the knowledge in the elastic, post-yielding and fracture properties of bone are required.In this work, we have derived explicit equations to estimate the orthotropic elastic constants of lamellar tissue as a function of the porosity at tissue level (microporosity) and the bone mineral density, following the multiscale approach presented in [1]. Microporosity has been explicitly mod-elled in a range from 1% to 25% [2]. Two types of pores, ellipsoid and sphere-shaped, have been modelled. On the other side, we have obtained the elastic constants of lamellar tissue in a range of bone mineral density comprised from 0,653 g/cm3 to 1,50 g/cm3 [3]. A non-linear multivariable regression by means of the least square ﬁtting has been performed and the explicit expressions for the elastic constants of lamellar tissue have been provided as a function of the volumetric bone mineral density and porosity.Moreover, independent quasi-static load cases are numerically simulated. Bone failure onset has been modeled by Hashin’s orthotropic failure criterion and damage evolution has been assessed through the material property degradation (MPD) method. Strength limits of lamellar tissue have been inferred from Ascenzi and Bonucci [4] and Giner et al. [5]. Results reveal that failure onset is mainly due to the tension in the transversal direction of the mineralized collagen bundles.

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Monreal, Gabriel, Frank Zamora, Hans Henrik Ovrebo, Peter Orizondo, and Otto Soidinsalo. "Characterization of a New Green Material for Offshore Well Completions and Downhole Treatments." In Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/31870-ms.

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Abstract In oil and gas well construction during the drillouts or wellbore cleaning process, one of the most critical functions of land and offshore completions fluids is the ability to suspend solids effectively under extreme downhole conditions. Conventional agents such as xanthan gum, HEC and numerous other polymers have historically been used to accomplish this function, albeit with limitations. Functionally, these commonly used polymers depend primarily upon viscosity rather than elastic characteristics to suspend solids and require intensive chemical processing that leads to high deployment cost. Recently microfibrillated cellulose (MFC) has been investigated as a prospective suspending agent in carrier fluids for extreme downhole conditions. MFC is a unique type of superfine cellulose fibrils obtained from fully sustainable sources that have been subjected to proprietary treatment procedures, resulting in fibril bundles consisting of lateral dimensions in the sub-micron scale and lengths up to micron scale with abundant terminal hydroxyl functional groups. When dispersed into aqueous solutions, the resulting fluid has been characterized to have several favorable rheological, chemical and mechanical properties. Rheological measurements show the viscoelasticity of MFC dispersions is dominated by their storage modulus (G′ > G″) even with fluids formulated with as low as 0.25 wt% (about 20 lbm MFC /1000 gallons). The result is a suspension that exhibits superior particle suspension properties compared on a mass basis to conventional materials such as guar, CMC, HEC and xanthan gum. In addition, MFC solutions exhibit comparatively high viscosities at low shear rates but thin by several orders of magnitude at high shear, a characteristic that implies less work on surface equipment while having the ability to suspend solids at very low pump rates. MFC dispersions also have an excellent brine tolerance, demonstrating stable suspensions over weeks in fluids containing up to 150,000 mg/L TDS. The dispersions are stable at downhole relevant temperatures, applicable at low and high pH levels and resistant to shear degradation. Finally, MFC originates from natural resources and is environmentally benign and biodegradable. This paper describes the comprehensive characterization of the rheological and suspension properties that distinguish MFC from other conventionally used materials and make it fit-for-purpose as a robust, environmentally benign and high-performance suspending agent for downhole applications.

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Stuckert, Juri, Mirco Große, Leo Sepold, and Martin Steinbru¨ck. "Experimental Results of Reflood Bundle Test QUENCH-14 With M5® Cladding Tubes." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75266.

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The QUENCH-14 experiment investigated the effect of M5® cladding material on bundle oxidation and core reflood, in comparison with tests QUENCH-06 (ISP-45) that used standard Zircaloy-4 and QUENCH-12 that used VVER E110-claddings. The PWR bundle configuration of QUENCH-14 with a single unheated rod, 20 heated rods, and four corner rods was otherwise identical to QUENCH-06. The test was conducted in principle with the same protocol as QUENCH-06, so that the effects of the change of cladding material could be observed more easily. Pre-test calculations were performed by the Paul Scherrer Institute (Switzerland) using SCDAPSIM, SCDAP/RELAP5 and MELCOR codes. The experiment started with a pre-oxidation phase in steam, lasting 3100 s at 1500 K peak bundle temperature. After a further temperature increase to maximal bundle temperature of 2050 K the bundle was flooded with 41 g/s water from the bottom. The peak temperature of ∼2300 K was measured on the bundle shroud, shortly after quench initiation. The electrical power was reduced to 3.9 kW during the reflood phase to simulate effective decay heat levels. The complete bundle cooling was reached in 300 s after reflood initiation. The development of the oxide layer growth during the test was rather defined by measurements performed on the three Zircaloy-4 corner rods withdrawn successively from the bundle. The withdrawal of Zircaloy-4 and E110 corner rods after the test allowed a comparison of the different alloys in one test. One heated rod with M5 cladding was withdrawn after the test for a detailed analysis of oxidation degree and measurement of absorbed hydrogen. Post-test examinations showed neither breakaway cladding oxidation nor noticeable melt relocation between rods. Different from the QUENCH-14 (M5) findings, the QUENCH-12 test with the E110 claddings performed under similar conditions had resulted in intensive breakaway effect at cladding and shroud surfaces during the pre-oxidation phase and local melt relocation on reflood initiation. The hydrogen production in QUENCH-14 up to reflood was similar to QUENCH-06 and QUENCH-12 bundle tests. During reflood 5 g hydrogen were released which is similar to QUENCH-06 (4 g) but much less than during quench phase of QUENCH-12 (24 g). The reason for the different behaviour of the Zr1%Nb cladding alloys is the different oxide scale properties of both materials.

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Zhang, Zhenning, Boxin Du, and Hanghang Tong. "S u G e R: A Subgraph-based Graph Convolutional Network Method for Bundle Recommendation." In CIKM '22: The 31st ACM International Conference on Information and Knowledge Management. New York, NY, USA: ACM, 2022. http://dx.doi.org/10.1145/3511808.3557707.

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