Cyclic coverings of Fano threefolds

Sławomir Cynk

Displaying similar documents to “Cyclic coverings of Fano threefolds”

Linear and cyclic radio k-labelings of trees

Mustapha Kchikech, Riadh Khennoufa, Olivier Togni (2007)

Discussiones Mathematicae Graph Theory

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Motivated by problems in radio channel assignments, we consider radio k-labelings of graphs. For a connected graph G and an integer k ≥ 1, a linear radio k-labeling of G is an assignment f of nonnegative integers to the vertices of G such that $| f (x) - f (y) | \geq k + 1 - d_{G} (x, y)$ , for any two distinct vertices x and y, where $d_{G} (x, y)$ is the distance between x and y in G. A cyclic k-labeling of G is defined analogously by using the cyclic metric on the labels. In both cases, we are interested in minimizing the span of the labeling....

A note on cyclic chromatic number

Jana Zlámalová (2010)

Discussiones Mathematicae Graph Theory

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A cyclic colouring of a graph G embedded in a surface is a vertex colouring of G in which any two distinct vertices sharing a face receive distinct colours. The cyclic chromatic number $χ_{c} (G)$ of G is the smallest number of colours in a cyclic colouring of G. Plummer and Toft in 1987 conjectured that $χ_{c} (G) \leq Δ * + 2$ for any 3-connected plane graph G with maximum face degree Δ*. It is known that the conjecture holds true for Δ* ≤ 4 and Δ* ≥ 18. The validity of the conjecture is proved in the paper for some...

Subnormality and cyclicity

Franciszek Hugon Szafraniec (2005)

Banach Center Publications

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For an unbounded operator S the question whether its subnormality can be built up from that of every $S_{f}$ , the restriction of S to a cyclic space generated by f in the domain of S, is analyzed. Though the question at large has been left open some partial results are presented and a possible way to prove it is suggested as well.

Note on cyclic decompositions of complete bipartite graphs into cubes

Dalibor Fronček (1999)

Discussiones Mathematicae Graph Theory

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So far, the smallest complete bipartite graph which was known to have a cyclic decomposition into cubes $Q_{d}$ of a given dimension d was $K_{d 2^{d - 1}, d 2^{d - 2}}$ . We improve this result and show that also $K_{d 2^{d - 2}, d 2^{d - 2}}$ allows a cyclic decomposition into $Q_{d}$ . We also present a cyclic factorization of $K_{8, 8}$ into Q₄.

Circles passing through five or more integer points

Shaunna M. Plunkett-Levin (2013)

Acta Arithmetica

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We find an improvement to Huxley and Konyagin’s current lower bound for the number of circles passing through five integer points. We conjecture that the improved lower bound is the asymptotic formula for the number of circles passing through five integer points. We generalise the result to circles passing through more than five integer points, giving the main theorem in terms of cyclic polygons with m integer point vertices. Theorem. Let m ≥ 4 be a fixed integer. Let $W_{m} (R)$ be the number...

Strictly cyclic algebra of operators acting on Banach spaces $H^{p} (β)$

Bahmann Yousefi (2004)

Czechoslovak Mathematical Journal

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Let ${β (n)}_{n = 0}^{\infty}$ be a sequence of positive numbers and $1 \leq p < \infty$ . We consider the space $H^{p} (β)$ of all power series $f (z) = \sum_{n = 0}^{\infty} \hat{f} (n) z^{n}$ such that $\sum_{n = 0}^{\infty} {| \hat{f} (n) |}^{p} β {(n)}^{p} < \infty$ . We investigate strict cyclicity of $H_{p}^{\infty} (β)$ , the weakly closed algebra generated by the operator of multiplication by $z$ acting on $H^{p} (β)$ , and determine the maximal ideal space, the dual space and the reflexivity of the algebra $H_{p}^{\infty} (β)$ . We also give a necessary condition for a composition operator to be bounded on $H^{p} (β)$ when $H_{p}^{\infty} (β)$ is strictly cyclic.

$Z_{n}$ -actions on 3-manifolds

Józef H. Przytycki (1982)

Colloquium Mathematicae

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Explicit Selmer groups for cyclic covers of ℙ¹

Michael Stoll, Ronald van Luijk (2013)

Acta Arithmetica

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For any abelian variety J over a global field k and an isogeny ϕ: J → J, the Selmer group $S e l^{ϕ} (J, k)$ is a subgroup of the Galois cohomology group $H ¹ (G a l (k^{s} / k), J [ϕ])$ , defined in terms of local data. When J is the Jacobian of a cyclic cover of ℙ¹ of prime degree p, the Selmer group has a quotient by a subgroup of order at most p that is isomorphic to the ‘fake Selmer group’, whose definition is more amenable to explicit computations. In this paper we define in the same setting the ‘explicit Selmer group’, which...

Variations of mixed Hodge structure attached to the deformation theory of a complex variation of Hodge structures

Philippe Eyssidieux, Carlos Simpson (2011)

Journal of the European Mathematical Society

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Let $X$ be a compact Kähler manifold, $x \in X$ be a base point and $ρ : π_{1} (X, x) \to G L_{N} (C)$ be the monodromy representation of a $𝒞$ -VHS. Building on Goldman–Millson’s classical work, we construct a mixed Hodge structure on the complete local ring of the representation variety at $ρ$ and a variation of mixed Hodge structures whose monodromy is the universal deformation of $ρ$ .

Kannan-type cyclic contraction results in $2$ -Menger space

Binayak S. Choudhury, Samir Kumar BHANDARI (2016)

Mathematica Bohemica

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In this paper we establish Kannan-type cyclic contraction results in probabilistic 2-metric spaces. We use two different types of $t$ -norm in our theorems. In our first theorem we use a Hadzic-type $t$ -norm. We use the minimum $t$ -norm in our second theorem. We prove our second theorem by different arguments than the first theorem. A control function is used in our second theorem. These results generalize some existing results in probabilistic 2-metric spaces. Our results are illustrated with...

Bounded point evaluations for multicyclic operators

M. EL Guendafi, M. Mbekhta, E. H. Zerouali (2005)

Banach Center Publications

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Let T be a multicyclic operator defined on some Banach space. Bounded point evaluations and analytic bounded point evaluations for T are defined to generalize the cyclic case. We extend some known results on cyclic operators to the more general setting of multicyclic operators on Banach spaces. In particular we show that if T satisfies Bishop’s property (β), then $ℬ_{a} = ℬ ∖ σ_{a p} (T)$ . We introduce the concept of analytic structures and we link it to different spectral quantities. We apply this concept...

Cyclic actions on $S^{2}$ - and $P^{2}$ -bundles over $S^{1}$

Józef H. Przytycki (1982)

Colloquium Mathematicae

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Cyclic vectors and invariant subspaces for the backward shift operator

R. G. Douglas, H. S. Shapiro, A. L. Shields (1970)

Annales de l'institut Fourier

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The operator $U$ of multiplication by $z$ on the Hardy space $H^{2}$ of square summable power series has been studied by many authors. In this paper we make a similar study of the adjoint operator $U^{*}$ (the “backward shift”). Let $K_{f}$ denote the cyclic subspace generated by $f (f \in H^{2})$ , that is, the smallest closed subspace of $H^{2}$ that contains ${U^{* n} f}$ $(n \geq 0)$ . If $K_{f} = H^{2}$ , then $f$ is called a cyclic vector for $U^{*}$ . Theorem : $f$ is a cyclic vector if and only if there is a function $g$ , meromorphic and of bounded Nevanlinna...

Cyclic Type Fixed Point Results in 2-Menger Spaces

Binayak S. CHOUDHURY, Samir Kumar BHANDARI, Parbati SAHA (2015)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

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In this paper we introduce generalized cyclic contractions through $r$ number of subsets of a probabilistic 2-metric space and establish two fixed point results for such contractions. In our first theorem we use the Hadzic type $t$ -norm. In another theorem we use a control function with minimum $t$ -norm. Our results generalizes some existing fixed point theorem in 2-Menger spaces. The results are supported with some examples.

On the index of length four minimal zero-sum sequences

Caixia Shen, Li-meng Xia, Yuanlin Li (2014)

Colloquium Mathematicae

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Let G be a finite cyclic group. Every sequence S over G can be written in the form $S = (n ₁ g) \cdot . . . \cdot (n_{l} g)$ where g ∈ G and $n ₁, . . ., n_{l} i \in [1, o r d (g)]$ , and the index ind(S) is defined to be the minimum of $(n ₁ + \dots + n_{l}) / o r d (g)$ over all possible g ∈ G such that ⟨g⟩ = G. A conjecture says that every minimal zero-sum sequence of length 4 over a finite cyclic group G with gcd(|G|,6) = 1 has index 1. This conjecture was confirmed recently for the case when |G| is a product of at most two prime powers. However, the general case is still open. In this paper,...

Degenerations in the module varieties of almost cyclic coherent Auslander-Reiten components

Piotr Malicki (2009)

Colloquium Mathematicae

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We establish when the partial orders $\leq_{e x t}$ and $\leq_{d e g}$ coincide for all modules of the same dimension from the additive category of a generalized standard almost cyclic coherent component of the Auslander-Reiten quiver of a finite-dimensional algebra.