23,409 results
Search Results
102. Fekete-Szegö problem for starlike functions connected withk-Fibonacci numbers
- Author
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Serap Bulut
- Subjects
Combinatorics ,Subordination (linguistics) ,Fibonacci number ,General Mathematics ,010102 general mathematics ,010103 numerical & computational mathematics ,0101 mathematics ,01 natural sciences ,Analytic function ,Mathematics - Abstract
In a recent paper, Sokół et al. [Applications of k-Fibonacci numbers for the starlike analytic functions, Hacet. J. Math. Stat. 44(1) (2015), 121{127] obtained an upper bound for the Fekete-Szegö functionalϕλwhenλ 2R of functions belong to the classSLkconnected withk-Fibonacci numbers. The main purpose of this paper is to obtain sharp bounds forϕλbothλ 2R andλ 2C.
- Published
- 2021
103. Maximal families of nodal varieties with defect
- Author
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REMKE NANNE KLOOSTERMAN
- Subjects
Surface (mathematics) ,Double cover ,Degree (graph theory) ,Plane (geometry) ,General Mathematics ,010102 general mathematics ,01 natural sciences ,Combinatorics ,Mathematics - Algebraic Geometry ,Hypersurface ,0103 physical sciences ,FOS: Mathematics ,010307 mathematical physics ,0101 mathematics ,NODAL ,Algebraic Geometry (math.AG) ,Mathematics - Abstract
In this paper we prove that a nodal hypersurface in P^4 with defect has at least (d-1)^2 nodes, and if it has at most 2(d-2)(d-1) nodes and d>6 then it contains either a plane or a quadric surface. Furthermore, we prove that a nodal double cover of P^3 ramified along a surface of degree 2d with defect has at least d(2d-1) nodes. We construct the largest dimensional family of nodal degree d hypersurfaces in P^(2n+2) with defect for d sufficiently large., v2: A proof for the Ciliberto-Di Gennaro conjecture is added (Section 5); Some minor corrections in the other sections. v3: some minor corrections in the abstract v4: The proof for the Ciliberto-Di Gennaro conjecture has been modified; The paper is split into two parts, the complete intersection case will be discussed in a different paper
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- 2021
104. Fragility of nonconvergence in preferential attachment graphs with three types
- Author
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Ben Andrews and Jonathan Jordan
- Subjects
Random graph ,Vertex (graph theory) ,05C82 ,General Mathematics ,Probability (math.PR) ,Type (model theory) ,Preferential attachment ,Graph ,Combinatorics ,Fragility ,FOS: Mathematics ,Tournament ,Node (circuits) ,Mathematics - Probability ,Mathematics - Abstract
Preferential attachment networks are a type of random network where new nodes are connected to existing ones at random, and are more likely to connect to those that already have many connections. We investigate further a family of models introduced by Antunovi\'{c}, Mossel and R\'{a}cz where each vertex in a preferential attachment graph is assigned a type, based on the types of its neighbours. Instances of this type of process where the proportions of each type present do not converge over time seem to be rare. Previous work found that a "rock-paper-scissors" setup where each new node's type was determined by a rock-paper-scissors contest between its two neighbours does not converge. Here, two cases similar to that are considered, one which is like the above but with an arbitrarily small chance of picking a random type and one where there are four neighbours which perform a knockout tournament to determine the new type. These two new setups, despite seeming very similar to the rock-paper-scissors model, do in fact converge, perhaps surprisingly., Comment: 7 pages, 2 figures
- Published
- 2021
105. Inverse problems of the Erdős-Ko-Rado type theorems for families of vector spaces and permutations
- Author
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Xiangliang Kong, Bingchen Qian, Yuanxiao Xi, and Gennian Ge
- Subjects
Combinatorics ,Matrix (mathematics) ,Intersection ,General Mathematics ,Structure (category theory) ,Intersection number ,Inverse problem ,Type (model theory) ,Linear subspace ,Mathematics ,Vector space - Abstract
Ever since the famous Erdős-Ko-Rado theorem initiated the study of intersecting families of subsets, extremal problems regarding intersecting properties of families of various combinatorial objects have been extensively investigated. Among them, studies about families of subsets, vector spaces and permutations are of particular concerns. Recently, we proposed a new quantitative intersection problem for families of subsets: For $${\cal F} \subseteq \left({\matrix{{[n]} \cr k \cr}} \right)$$ , define its total intersection number as $${\cal I}({\cal F}) = \sum\nolimits_{{F_1},{F_2} \in {\cal F}} {\left| {{F_1} \cap {F_2}} \right|} $$ . Then, what is the structure of $${\cal F}$$ when it has the maximal total intersection number among all the families in $$\left({\matrix{{[n]} \cr k \cr}} \right)$$ with the same family size? In a recent paper, Kong and Ge (2020) studied this problem and characterized extremal structures of families maximizing the total intersection number of given sizes. In this paper, we consider the analogues of this problem for families of vector spaces and permutations. For certain ranges of family size, we provide structural characterizations for both families of subspaces and families of permutations having maximal total intersection numbers. To some extent, these results determine the unique structure of the optimal family for some certain values of $$\left| {\cal F} \right|$$ and characterize the relationship between having maximal total intersection number and being intersecting. Besides, we also show several upper bounds on the total intersection numbers for both families of subspaces and families of permutations of given sizes.
- Published
- 2021
106. Sumsets of Wythoff sequences, Fibonacci representation, and beyond
- Author
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Jeffrey Shallit
- Subjects
FOS: Computer and information sciences ,Fibonacci number ,Mathematics - Number Theory ,Discrete Mathematics (cs.DM) ,Formal Languages and Automata Theory (cs.FL) ,General Mathematics ,Computer Science - Formal Languages and Automata Theory ,Of the form ,Combinatorics ,Alpha (programming language) ,Simple (abstract algebra) ,FOS: Mathematics ,Mathematics - Combinatorics ,Combinatorics (math.CO) ,Number Theory (math.NT) ,Representation (mathematics) ,Computer Science - Discrete Mathematics ,Mathematics - Abstract
Let $$\alpha = (1+\sqrt{5})/2$$ and define the lower and upper Wythoff sequences by $$a_i = \lfloor i \alpha \rfloor $$ , $$b_i = \lfloor i \alpha ^2 \rfloor $$ for $$i \ge 1$$ . In a recent interesting paper, Kawsumarng et al. proved a number of results about numbers representable as sums of the form $$a_i + a_j$$ , $$b_i + b_j$$ , $$a_i + b_j$$ , and so forth. In this paper I show how to derive all of their results, using one simple idea and existing free software called Walnut. The key idea is that for each of their sumsets, there is a relatively small automaton accepting the Fibonacci representation of the numbers represented. I also show how the automaton approach can easily prove other results.
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- 2021
107. Finite Homogeneous Subspaces of Euclidean Spaces
- Author
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V. N. Berestovskiĭ and Yu. G. Nikonorov
- Subjects
Convex hull ,General Mathematics ,Archimedean solid ,Combinatorics ,symbols.namesake ,Polyhedron ,Metric space ,symbols ,Tetrahedron ,Mathematics::Metric Geometry ,Cube ,Isometry group ,Mathematics ,Regular polytope - Abstract
The paper is devoted to the study of the metric properties of regular and semiregular polyhedra in Euclidean spaces. In the first part, we prove that every regular polytope of dimension greater or equal than 4, and different from 120-cell in $$\mathbb {E}^4 $$ is such that the set of its vertices is a Clifford–Wolf homogeneous finite metric space. The second part of the paper is devoted to the study of special properties of Archimedean solids. In particular, for each Archimedean solid, its description is given as the convex hull of the orbit of a suitable point of a regular tetrahedron, cube or dodecahedron under the action of the corresponding isometry group.
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- 2021
108. A fractional $$p(x,\cdot )$$-Laplacian problem involving a singular term
- Author
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K. Saoudi, A. Mokhtari, and N. T. Chung
- Subjects
Symmetric function ,Sobolev space ,Combinatorics ,Continuous function (set theory) ,Applied Mathematics ,General Mathematics ,Bounded function ,Domain (ring theory) ,Lambda ,Laplace operator ,Omega ,Mathematics - Abstract
This paper deals with a class of singular problems involving the fractional $$p(x,\cdot )$$ -Laplace operator of the form $$\begin{aligned} \left\{ \begin{array}{ll} (-\Delta )^{s}_{p(x,\cdot )}u(x)= \frac{\lambda }{u^{\gamma (x)}}+u^{q(x)-1} &{} \hbox {in }\Omega , \\ u>0, \;\;\text {in}\;\; \Omega &{} \hbox {} \\ u=0 \;\;\text {on}\;\;{\mathbb {R}}^N\setminus \Omega , &{} \hbox {} \end{array} \right. \end{aligned}$$ where $$\Omega $$ is a smooth bounded domain in $${\mathbb {R}}^N$$ ( $$N\ge 3$$ ), $$00$$ small enough. To our best knowledge, this paper is one of the first attempts in the study of singular problems involving fractional $$p(x,\cdot )$$ -Laplace operators.
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- 2021
109. Limit theorems for linear random fields with tapered innovations. II: The stable case
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Vygantas Paulauskas and Julius Damarackas
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Combinatorics ,010104 statistics & probability ,Number theory ,Random field ,General Mathematics ,010102 general mathematics ,Limit (mathematics) ,0101 mathematics ,01 natural sciences ,Mathematics - Abstract
In the paper, we consider the limit behavior of partial-sum random field (r.f.) $$ \left.{S}_n\left({t}_1,{t}_2;\right)X\left(b\left(\mathbf{n}\right)\right)\right)={\sum}_{k=1}^{\left[{n}_1{t}_1\right]}{\sum}_{l=1}^{\left[{n}_2{t}_2\right]}{X}_{k,l}\left(b\left(\mathbf{n}\right)\right), $$ where $$ \left\{{X}_{k,l}\left(b\left(\mathbf{n}\right)\right)={\sum}_{i=0}^{\infty }{\sum}_{j=0}^{\infty }{c}_{i,j}{\upxi}_{k-i,l-j}\left(b\left(\mathbf{n}\right)\right),k,l\in \mathrm{\mathbb{Z}}\right\},n\ge 1, $$ is a family (indexed by n = (n1, n2), ni ≥ 1) of linear r.f.s with filter ci,j = aibj and innovations ξk,l(b(n)) having heavy-tailed tapered distributions with tapering parameter b(n) growing to infinity as n → ∞. In [V. Paulauskas, Limit theorems for linear random fields with tapered innovations. I: The Gaussian case, Lith. Math. J., 61(2):261–273, 2021], we considered the so-called hard tapering as b(n) grows relatively slowly and the limit r.f.s for appropriately normalized Sn(t1, t2;X(b(n))) are Gaussian. In this paper, we consider the case of soft tapering where b(n) grows more rapidly in comparison with the case of hard tapering and stable limit r.f.s.We consider cases where the sequences {ai} and {bj} are long-range, short-range, and negatively dependent.
- Published
- 2021
110. A group of Pythagorean triples using the inradius
- Author
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Howard Sporn
- Subjects
Combinatorics ,Coprime integers ,Group (mathematics) ,General Mathematics ,Pythagorean triple ,Right triangle ,Mathematics ,Incircle and excircles of a triangle - Abstract
Pythagorean triples are triples of integers (a, b, c) satisfying the equation a2 + b2 = c2. For the purpose of this paper, we will take a, b and c to be positive, unless otherwise stated. Then, of course, it follows that a triple represents the lengths of sides of a right triangle. Also, for the purpose of this paper, we will consider the triples (a, b, c) and (b, a, c) to be distinct, even though they represent the same right triangle. A primitive Pythagorean triple is one for which a, b and c are relatively prime.
- Published
- 2021
111. An improvement on Furstenberg’s intersection problem
- Author
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Han Yu
- Subjects
Combinatorics ,Intersection ,Applied Mathematics ,General Mathematics ,Bounded function ,010102 general mathematics ,Dimension (graph theory) ,Zero (complex analysis) ,0101 mathematics ,Invariant (mathematics) ,Dynamical system (definition) ,01 natural sciences ,Mathematics - Abstract
In this paper, we study a problem posed by Furstenberg on intersections between × 2 , × 3 \times 2, \times 3 invariant sets. We present here a direct geometrical counting argument to revisit a theorem of Wu and Shmerkin. This argument can be used to obtain further improvements. For example, we show that if A 2 , A 3 ⊂ [ 0 , 1 ] A_2,A_3\subset [0,1] are closed and × 2 , × 3 \times 2, \times 3 invariant respectively, assuming that dim A 2 + dim A 3 > 1 \dim A_2+\dim A_3>1 then A 2 ∩ ( u A 3 + v ) A_2\cap (uA_3+v) is sparse (defined in this paper) and has box dimension zero uniformly with respect to the real parameters u , v u,v such that u u and u − 1 u^{-1} are both bounded away from 0 0 .
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- 2021
112. Generalization of some fractional versions of Hadamard inequalities via exponentially (α,h−m)-convex functions
- Author
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Ghulam Farid, Waqas Nazeer, Hafsa Yasmeen, Yu-Pei Lv, and Chahn Yong Jung
- Subjects
Generalization ,General Mathematics ,Regular polygon ,Function (mathematics) ,Hadamard inequality ,h−m)-convex function ,hadamard inequality ,exponentionally (α ,Combinatorics ,Alpha (programming language) ,Exponential growth ,Hadamard transform ,riemann-liouville fractional integrals ,(α ,QA1-939 ,Convex function ,Mathematics - Abstract
In this paper we give Hadamard inequalities for exponentially $ (\alpha, h-m) $-convex functions using Riemann-Liouville fractional integrals for strictly increasing function. Results for Riemann-Liouville fractional integrals of convex, $ m $-convex, $ s $-convex, $ (\alpha, m) $-convex, $ (s, m) $-convex, $ (h-m) $-convex, $ (\alpha, h-m) $-convex, exponentially convex, exponentially $ m $-convex, exponentially $ s $-convex, exponentially $ (s, m) $-convex, exponentially $ (h-m) $-convex, exponentially $ (\alpha, h-m) $-convex functions are particular cases of the results of this paper. The error estimations of these inequalities by using two fractional integral identities are also given.
- Published
- 2021
113. Degrees of Enumerations of Countable Wehner-Like Families
- Author
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I. Sh. Kalimullin and M. Kh. Faizrahmanov
- Subjects
Statistics and Probability ,Class (set theory) ,Degree (graph theory) ,Applied Mathematics ,General Mathematics ,010102 general mathematics ,01 natural sciences ,Spectrum (topology) ,010305 fluids & plasmas ,Combinatorics ,0103 physical sciences ,Enumeration ,Countable set ,Family of sets ,0101 mathematics ,Turing ,computer ,Finite set ,computer.programming_language ,Mathematics - Abstract
This paper is a survey of results on countable families with natural degree spectra. These results were obtained by a modification of the methodology proposed by Wechner, who first found a family of sets with the spectrum consisting precisely of nonzero Turing degrees. Based on this method, many researchers obtained examples of families with other natural spectra. In addition, in this paper we extend these results and present new examples of natural spectra. In particular, we construct a family of finite sets with the spectrum consisting of exactly non-K-trivial degrees and also we find new sufficient conditions on $$ {\Delta}_2^0 $$ -degree a, which guarantees that the class {x : x ≰ a} is the degree spectrum of some family. Finally, we give a survey of our recent results on the degree spectra of α-families, where α is an arbitrary computable ordinal.
- Published
- 2021
114. On a class number formula of Hurwitz
- Author
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William Duke, Árpád Tóth, and Özlem Imamoglu
- Subjects
Binary quadratic forms ,Combinatorics ,class numbers ,Hurwitz ,Applied Mathematics ,General Mathematics ,Binary quadratic form ,Class number formula ,Mathematics - Abstract
In a little-known paper Hurwitz gave an infinite series representation of the class number for positive definite binary quadratic forms. In this paper we give a similar formula in the indefinite case. We also give a simple proof of Hurwitz's formula and indicate some extensions., Journal of the European Mathematical Society, 23 (12), ISSN:1435-9855, ISSN:1435-9863
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- 2021
115. Generation of colored graphs with isomorphism rejection
- Author
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P. V. Razumovsky and M. B. Abrosimov
- Subjects
General Computer Science ,generator ,Mechanical Engineering ,General Mathematics ,Colored graph ,Computational Mechanics ,graph labeling ,color graph ,graph ,Combinatorics ,Mechanics of Materials ,graph coloring ,QA1-939 ,Isomorphism ,Mathematics ,MathematicsofComputing_DISCRETEMATHEMATICS - Abstract
In the article we consider graphs whose vertices or edges are colored in a given number of colors — vertex and edge colorings. The study of colorings of graphs began in the middle of the 19th century, but the main attention is paid to proper colorings, in which the restriction applies that the colors of adjacent vertices or edges must be different. This paper considers colorings of graphs without any restrictions. We study the problem of generating all non-isomorphic vertex and edge $k$-colorings of a given graph without direct checking for isomorphism. The problem of generating non-isomorphic edge $k$-colorings is reduced to the problem of constructing all vertex $k$-colorings of a graph. Methods for generating graphs without direct checking for isomorphism or isomorphism rejection are based on the method of canonical representatives. The idea of the method is that a method for encoding graphs is proposed and a certain rule is chosen according to which one of all isomorphic graphs is declared canonical. All codes are built and only the canonical ones are accepted. Often, the representative with the largest or smallest code is chosen as the canonical one. In practice, generating all codes requires large computational resources; therefore, various methods of enumeration optimization are used. The paper proposes two algorithms for solving the problem of generating vertex $k$-colorings with isomorphism rejection by McKay and Reed – Faradzhev methods. A comparison of the proposed algorithms for generating colorings on two classes of graphs — paths and cycles is made. Computational experiments show that the Reed – Faradzhev method is faster for paths and cycles.
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- 2021
116. Variations of Weyl Type Theorems for Upper Triangular Operator Matrices
- Author
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M. H. M. Rashid
- Subjects
Set (abstract data type) ,Combinatorics ,Operator matrix ,General Mathematics ,Triangular matrix ,Banach space ,Extension (predicate logic) ,Type (model theory) ,Lambda ,Mathematics ,Bounded operator - Abstract
Let $\mathcal X$ be a Banach space and let T be a bounded linear operator on $\mathcal {X}$ . We denote by S(T) the set of all complex $\lambda \in \mathcal {C}$ such that T does not have the single-valued extension property. In this paper it is shown that if MC is a 2 × 2 upper triangular operator matrix acting on the Banach space $\mathcal {X} \oplus \mathcal {Y}$ , then the passage from σLD(A) ∪ σLD(B) to σLD(MC) is accomplished by removing certain open subsets of σd(A) ∩ σLD(B) from the former, that is, there is the equality σLD(A) ∪ σLD(B) = σLD(MC) ∪ℵ, where ℵ is the union of certain of the holes in σLD(MC) which happen to be subsets of σd(A) ∩ σLD(B). Generalized Weyl’s theorem and generalized Browder’s theorem are liable to fail for 2 × 2 operator matrices. In this paper, we also explore how generalized Weyl’ theorem, generalized Browder’s theorem, generalized a-Weyl’s theorem and generalized a-Browder’s theorem survive for 2 × 2 upper triangular operator matrices on the Banach space.
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- 2021
117. Noncommutative Counting Invariants and Curve Complexes
- Author
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Ludmil Katzarkov and George Dimitrov
- Subjects
Intersection theory ,medicine.medical_specialty ,Functor ,Conjecture ,Group (mathematics) ,General Mathematics ,010102 general mathematics ,Quiver ,Type (model theory) ,01 natural sciences ,Combinatorics ,0103 physical sciences ,medicine ,010307 mathematical physics ,0101 mathematics ,Partially ordered set ,Commutative property ,Mathematics - Abstract
In our previous paper, viewing $D^b(K(l))$ as a noncommutative curve, where $K(l)$ is the Kronecker quiver with $l$-arrows, we introduced categorical invariants via counting of noncommutative curves. Roughly, these invariants are sets of subcategories in a given category and their quotients. The noncommutative curve-counting invariants are obtained by restricting the subcategories to be equivalent to $D^b(K(l))$. The general definition, however, defines a larger class of invariants and many of them behave properly with respect to fully faithful functors. Here, after recalling the definition, we focus on the examples and extend our studies beyond counting. We enrich our invariants with the following structures: the inclusion of subcategories makes them partially ordered sets and considering semi-orthogonal pairs of subcategories as edges amounts to directed graphs. It turns out that the problem for counting $D^b(A_k)$ in $D^b(A_n)$ has a geometric combinatorial parallel - counting of maps between polygons. Estimating the numbers counting noncommutative curves in $D^b({\mathbb P}^2)$ modulo the group of autoequivalences, we prove finiteness and that the exact determining of these numbers leads to a solution of Markov problem. Via homological mirror symmetry, this gives a new approach to this problem. Regarding the structure of a partially ordered set mentioned above, we initiate intersection theory of noncommutative curves focusing on the case of noncommutative genus zero. The above-mentioned structure of a directed graph (and related simplicial complex) is a categorical analogue of the classical curve complex, introduced by Harvey and Harrer. The paper contains pictures of the graphs in many examples and also presents an approach to Markov conjecture via counting of subgraphs in a graph associated with $D^b({{\mathbb{P}}}^2)$. Some of the results proved here were announced in a previous work.
- Published
- 2021
118. On the size of subsets of $$\mathbb{F}_p^n$$ without p distinct elements summing to zero
- Author
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Lisa Sauermann
- Subjects
Mathematics - Number Theory ,General Mathematics ,media_common.quotation_subject ,010102 general mathematics ,Zero (complex analysis) ,Lattice (group) ,0102 computer and information sciences ,Infinity ,01 natural sciences ,Upper and lower bounds ,Prime (order theory) ,Combinatorics ,Integer ,010201 computation theory & mathematics ,FOS: Mathematics ,Mathematics - Combinatorics ,Maximum size ,Combinatorics (math.CO) ,Number Theory (math.NT) ,0101 mathematics ,Constant (mathematics) ,media_common ,Mathematics - Abstract
Let us fix a prime $p$. The Erd\H{o}s-Ginzburg-Ziv problem asks for the minimum integer $s$ such that any collection of $s$ points in the lattice $\mathbb{Z}^n$ contains $p$ points whose centroid is also a lattice point in $\mathbb{Z}^n$. For large $n$, this is essentially equivalent to asking for the maximum size of a subset of $\mathbb{F}_p^n$ without $p$ distinct elements summing to zero. In this paper, we give a new upper bound for this problem for any fixed prime $p\geq 5$ and large $n$. In particular, we prove that any subset of $\mathbb{F}_p^n$ without $p$ distinct elements summing to zero has size at most $C_p\cdot \left(2\sqrt{p}\right)^n$, where $C_p$ is a constant only depending on $p$. For $p$ and $n$ going to infinity, our bound is of the form $p^{(1/2)\cdot (1+o(1))n}$, whereas all previously known upper bounds were of the form $p^{(1-o(1))n}$ (with $p^n$ being a trivial bound). Our proof uses the so-called multi-colored sum-free theorem which is a consequence of the Croot-Lev-Pach polynomial method. This method and its consequences were already applied by Naslund as well as by Fox and the author to prove bounds for the problem studied in this paper. However, using some key new ideas, we significantly improve their bounds., Comment: 11 pages
- Published
- 2021
119. A new obstruction for normal spanning trees
- Author
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Max Pitz
- Subjects
Aleph ,Spanning tree ,General Mathematics ,010102 general mathematics ,Minor (linear algebra) ,Type (model theory) ,01 natural sciences ,Graph ,Combinatorics ,Mathematics::Logic ,Arbitrarily large ,Cardinality ,FOS: Mathematics ,Mathematics - Combinatorics ,Combinatorics (math.CO) ,0101 mathematics ,Connectivity ,05C83, 05C05, 05C63 ,Mathematics - Abstract
In a paper from 2001 (Journal of the LMS), Diestel and Leader offered a proof that a connected graph has a normal spanning tree if and only if it does not contain a minor from two specific forbidden classes of graphs, all of cardinality $\aleph_1$. Unfortunately, their proof contains a gap, and their result is incorrect. In this paper, we construct a third type of obstruction: an $\aleph_1$-sized graph without a normal spanning tree that contains neither of the two types described by Diestel and Leader as a minor. Further, we show that any list of forbidden minors characterising the graphs with normal spanning trees must contain graphs of arbitrarily large cardinality., Comment: 9 pages. arXiv admin note: text overlap with arXiv:2005.02833
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- 2021
120. On Classes of Subcompact Spaces
- Author
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Alexander V. Osipov, E. G. Pytkeev, and V. I. Belugin
- Subjects
Condensed Matter::Quantum Gases ,Combinatorics ,Compact space ,High Energy Physics::Lattice ,General Mathematics ,Cardinal number ,Hausdorff space ,Space (mathematics) ,Mathematics - Abstract
This paper continues the study of P. S. Alexandroff’s problem: When can a Hausdorff space $$X$$ be one-to-one continuously mapped onto a compact Hausdorff space? For a cardinal number $$\tau$$ , the classes of $$a_\tau$$ -spaces and strict $$a_\tau$$ -spaces are defined. A compact space $$X$$ is called an $$a_\tau$$ -space if, for any $$C\in[X]^{\le\tau}$$ , there exists a one-to-one continuous mapping of $$X\setminus C$$ onto a compact space. A compact space $$X$$ is called a strict $$a_\tau$$ -space if, for any $$C\in[X]^{\le\tau}$$ , there exits a one-to-one continuous mapping of $$X\setminus C$$ onto a compact space $$Y$$ , and this mapping can be continuously extended to the whole space $$X$$ . In this paper, we study properties of the classes of $$a_\tau$$ - and strict $$a_\tau$$ -spaces by using Raukhvarger’s method of special continuous paritions.
- Published
- 2021
121. Fourier restriction in low fractal dimensions
- Author
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Bassam Shayya
- Subjects
Conjecture ,Measurable function ,Characteristic function (probability theory) ,General Mathematics ,Second fundamental form ,010102 general mathematics ,42B10, 42B20 (Primary), 28A75 (Secondary) ,0102 computer and information sciences ,Function (mathematics) ,Lebesgue integration ,01 natural sciences ,Measure (mathematics) ,Combinatorics ,symbols.namesake ,Hypersurface ,Mathematics - Classical Analysis and ODEs ,010201 computation theory & mathematics ,Classical Analysis and ODEs (math.CA) ,FOS: Mathematics ,symbols ,0101 mathematics ,Mathematics - Abstract
Let $S \subset \Bbb R^n$ be a smooth compact hypersurface with a strictly positive second fundamental form, $E$ be the Fourier extension operator on $S$, and $X$ be a Lebesgue measurable subset of $\Bbb R^n$. If $X$ contains a ball of each radius, then the problem of determining the range of exponents $(p,q)$ for which the estimate $\| Ef \|_{L^q(X)} \leq C \| f \|_{L^p(S)}$ holds is equivalent to the restriction conjecture. In this paper, we study the estimate under the following assumption on the set $X$: there is a number $0 < \alpha \leq n$ such that $|X \cap B_R| \leq c \, R^\alpha$ for all balls $B_R$ in $\Bbb R^n$ of radius $R \geq 1$. On the left-hand side of this estimate, we are integrating the function $|Ef(x)|^q$ against the measure $\chi_X dx$. Our approach consists of replacing the characteristic function $\chi_X$ of $X$ by an appropriate weight function $H$, and studying the resulting estimate in three different regimes: small values of $\alpha$, intermediate values of $\alpha$, and large values of $\alpha$. In the first regime, we establish the estimate by using already available methods. In the second regime, we prove a weighted H\"{o}lder-type inequality that holds for general non-negative Lebesgue measurable functions on $\Bbb R^n$, and combine it with the result from the first regime. In the third regime, we borrow a recent fractal Fourier restriction theorem of Du and Zhang and combine it with the result from the second regime. In the opposite direction, the results of this paper improve on the Du-Zhang theorem in the range $0 < \alpha < n/2$., Comment: 31 pages. Minor revision
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- 2021
122. Approximations in $$L^1$$ with convergent Fourier series
- Author
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Michael Ruzhansky, Zhirayr Avetisyan, and M. G. Grigoryan
- Subjects
Measurable function ,General Mathematics ,010102 general mathematics ,Hausdorff space ,Second-countable space ,Space (mathematics) ,01 natural sciences ,Functional Analysis (math.FA) ,Separable space ,Mathematics - Functional Analysis ,010101 applied mathematics ,Combinatorics ,Mathematics and Statistics ,Bounded function ,41A99, 43A15, 43A50, 43A85, 46E30 ,Homogeneous space ,FOS: Mathematics ,Orthonormal basis ,0101 mathematics ,Mathematics - Abstract
For a separable finite diffuse measure space $${\mathcal {M}}$$ M and an orthonormal basis $$\{\varphi _n\}$$ { φ n } of $$L^2({\mathcal {M}})$$ L 2 ( M ) consisting of bounded functions $$\varphi _n\in L^\infty ({\mathcal {M}})$$ φ n ∈ L ∞ ( M ) , we find a measurable subset $$E\subset {\mathcal {M}}$$ E ⊂ M of arbitrarily small complement $$|{\mathcal {M}}{\setminus } E| | M \ E | < ϵ , such that every measurable function $$f\in L^1({\mathcal {M}})$$ f ∈ L 1 ( M ) has an approximant $$g\in L^1({\mathcal {M}})$$ g ∈ L 1 ( M ) with $$g=f$$ g = f on E and the Fourier series of g converges to g, and a few further properties. The subset E is universal in the sense that it does not depend on the function f to be approximated. Further in the paper this result is adapted to the case of $${\mathcal {M}}=G/H$$ M = G / H being a homogeneous space of an infinite compact second countable Hausdorff group. As a useful illustration the case of n-spheres with spherical harmonics is discussed. The construction of the subset E and approximant g is sketched briefly at the end of the paper.
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- 2021
123. High perturbations of quasilinear problems with double criticality
- Author
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Prashanta Garain, Vicenţiu D. Rădulescu, Claudianor O. Alves, Universidade Federal de Campina Grande, Department of Mathematics and Systems Analysis, AGH University of Science and Technology, Aalto-yliopisto, and Aalto University
- Subjects
General Mathematics ,010102 general mathematics ,01 natural sciences ,Omega ,010101 applied mathematics ,Combinatorics ,Qualitative analysis ,Variational methods ,Domain (ring theory) ,Musielak–Sobolev space ,Nabla symbol ,0101 mathematics ,Quasilinear problems ,Mathematics - Abstract
This paper is concerned with the qualitative analysis of solutions to the following class of quasilinear problems $$\begin{aligned} \left\{ \begin{array}{ll} -\Delta _{\Phi }u=f(x,u) &{}\quad \text {in } \Omega ,\\ u=0 &{}\quad \text {on }\partial \Omega , \end{array} \right. \end{aligned}$$ - Δ Φ u = f ( x , u ) in Ω , u = 0 on ∂ Ω , where $$\Delta _{\Phi }u=\mathrm{div}\,(\varphi (x,|\nabla u|)\nabla u)$$ Δ Φ u = div ( φ ( x , | ∇ u | ) ∇ u ) and $$\Phi (x,t)=\int _{0}^{|t|}\varphi (x,s)s\,ds$$ Φ ( x , t ) = ∫ 0 | t | φ ( x , s ) s d s is a generalized N-function. We assume that $$\Omega \subset {\mathbb {R}}^N$$ Ω ⊂ R N is a smooth bounded domain that contains two open regions $$\Omega _N,\Omega _p$$ Ω N , Ω p with $${\overline{\Omega }}_N \cap {\overline{\Omega }}_p=\emptyset $$ Ω ¯ N ∩ Ω ¯ p = ∅ . The features of this paper are that $$-\Delta _{\Phi }u$$ - Δ Φ u behaves like $$-\Delta _N u $$ - Δ N u on $$\Omega _N$$ Ω N and $$-\Delta _p u $$ - Δ p u on $$\Omega _p$$ Ω p , and that the growth of $$f:\Omega \times {\mathbb {R}} \rightarrow {\mathbb {R}}$$ f : Ω × R → R is like that of $$e^{\alpha |t|^{\frac{N}{N-1}}}$$ e α | t | N N - 1 on $$\Omega _N$$ Ω N and as $$|t|^{p^{*}-2}t$$ | t | p ∗ - 2 t on $$\Omega _p$$ Ω p when |t| is large enough. The main result establishes the existence of solutions in a suitable Musielak–Sobolev space in the case of high perturbations with respect to the values of a positive parameter.
- Published
- 2021
124. On the pair correlations of powers of real numbers
- Author
-
Christoph Aistleitner and Simon Baker
- Subjects
11K06, 11K60 ,General Mathematics ,Modulo ,FOS: Physical sciences ,0102 computer and information sciences ,Lebesgue integration ,01 natural sciences ,Combinatorics ,symbols.namesake ,Pair correlation ,FOS: Mathematics ,Number Theory (math.NT) ,0101 mathematics ,Algebra over a field ,Classical theorem ,Mathematical Physics ,Real number ,Mathematics ,Sequence ,Mathematics - Number Theory ,Probability (math.PR) ,010102 general mathematics ,Mathematical Physics (math-ph) ,010201 computation theory & mathematics ,symbols ,Martingale (probability theory) ,Mathematics - Probability - Abstract
A classical theorem of Koksma states that for Lebesgue almost every $x>1$ the sequence $(x^n)_{n=1}^{\infty}$ is uniformly distributed modulo one. In the present paper we extend Koksma's theorem to the pair correlation setting. More precisely, we show that for Lebesgue almost every $x>1$ the pair correlations of the fractional parts of $(x^n)_{n=1}^{\infty}$ are asymptotically Poissonian. The proof is based on a martingale approximation method., Version 2: some minor changes. The paper will appear in the Israel Journal of Mathematics
- Published
- 2021
125. On additive and multiplicative decompositions of sets of integers with restricted prime factors, I. (Smooth numbers)
- Author
-
Kálmán Győry, Lajos Hajdu, and András Sárközy
- Subjects
Sequence ,Conjecture ,Mathematics - Number Theory ,General Mathematics ,Sieve (category theory) ,010102 general mathematics ,Multiplicative function ,010103 numerical & computational mathematics ,01 natural sciences ,Combinatorics ,Prime factor ,FOS: Mathematics ,Number Theory (math.NT) ,0101 mathematics ,Unit (ring theory) ,Mathematics - Abstract
In Sarkozy (2001) the third author of this paper presented two conjectures on the additive decomposability of the sequence of ”smooth” (or ”friable”) numbers. Elsholtz and Harper (2015) proved (by using sieve methods) the second (less demanding) conjecture. The goal of this paper is to extend and sharpen their result in three directions by using a different approach (based on the theory of S -unit equations).
- Published
- 2021
126. Simpson filtration and oper stratum conjecture
- Author
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Zhi Hu and Pengfei Huang
- Subjects
Mathematics::Dynamical Systems ,Conjecture ,Mathematics::Commutative Algebra ,General Mathematics ,010102 general mathematics ,Dimension (graph theory) ,Vector bundle ,Algebraic geometry ,01 natural sciences ,Moduli space ,Combinatorics ,Mathematics - Algebraic Geometry ,Mathematics::Algebraic Geometry ,Number theory ,0103 physical sciences ,FOS: Mathematics ,Filtration (mathematics) ,010307 mathematical physics ,0101 mathematics ,Algebraic Geometry (math.AG) ,Mathematics::Symplectic Geometry ,Mathematics ,Stratum - Abstract
In this paper, we prove that for the oper stratification of the de Rham moduli space $M_{\mathrm{dR}}(X,r)$, the closed oper stratum is the unique minimal stratum with dimension $r^2(g-1)+g+1$, and the open dense stratum consisting of irreducible flat bundles with stable underlying vector bundles is the unique maximal stratum., Comment: This paper comes from the last section of arXiv:1905.10765v1 as an independent paper. Comments are welcome! To appear in manuscripta mathematica
- Published
- 2021
127. Results on a Conjecture of Chen and Yi
- Author
-
Yan Liu, Xiao-Min Li, and Hong-Xun Yi
- Subjects
010101 applied mathematics ,Combinatorics ,Conjecture ,Integer ,General Mathematics ,Operator (physics) ,010102 general mathematics ,Order (ring theory) ,0101 mathematics ,01 natural sciences ,Meromorphic function ,Mathematics - Abstract
In this paper, we prove that if a nonconstant finite order meromorphic function f and its n-th order difference operator $$\Delta ^n_{\eta }f$$ share $$a_1,$$ $$a_2,$$ $$a_3$$ CM, where n is a positive integer, $$\eta \ne 0$$ is a finite complex value, and $$a_1,$$ $$a_2,$$ $$a_3$$ are three distinct finite complex values, then $$f(z)=\Delta ^n_{\eta }f(z)$$ for each $$z\in \mathbb {C}.$$ The main results in this paper improve and extend many known results concerning a conjecture posed by Chen and Yi in 2013.
- Published
- 2021
128. Minimizing closed geodesics on polygons and disks
- Author
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Ian M. Adelstein, Arthur Azvolinsky, Alexander Schlesinger, and Joshua Hinman
- Subjects
Mathematics - Differential Geometry ,Sequence ,Geodesic ,General Mathematics ,010102 general mathematics ,0102 computer and information sciences ,01 natural sciences ,Closed geodesic ,Combinatorics ,Differential Geometry (math.DG) ,010201 computation theory & mathematics ,FOS: Mathematics ,Mathematics::Metric Geometry ,Mathematics::Differential Geometry ,0101 mathematics ,Mathematics - Abstract
In this paper we study 1/k geodesics, those closed geodesics that minimize on all subintervals of length $L/k$, where $L$ is the length of the geodesic. We develop new techniques to study the minimizing properties of these curves on doubled polygons, and demonstrate a sequence of doubled polygons whose closed geodesics exhibit unbounded minimizing properties. We also compute the length of the shortest closed geodesic on doubled odd-gons and show that this length approaches 4 times the diameter., Comment: This paper is a result of a SUMRY (REU) project at Yale
- Published
- 2021
129. Continuous Extension of Functions from a Segment to Functions in $\mathbb{R}^n$ with Zero Ball Means
- Author
-
V. V. Volchkov and Vit. V. Volchkov
- Subjects
Continuous function ,Euclidean space ,General Mathematics ,010102 general mathematics ,Dimension (graph theory) ,Zero (complex analysis) ,Function (mathematics) ,01 natural sciences ,Domain (mathematical analysis) ,Modulus of continuity ,010101 applied mathematics ,Combinatorics ,Bounded function ,0101 mathematics ,Mathematics - Abstract
Let $\mathbb{R}^n$ be a Euclidean space of dimension $n\geq 2$ . For a domain $G\subset \mathbb{R}^n$ , we denote by $V_r(G)$ the set of functions $f\in L_{\mathrm{loc}}(G)$ having zero integrals over all closed balls of radius r contained in G (if domain G does not contain such balls, we set $V_r(G)=L_{\mathrm{loc}}(G)$ ). Let E be a nonempty subset of $\mathbb{R}^n$ . In this paper we study the following questions related to the extension problem. 1) Which conditions guarantee the extension of a continuous function defined on E to a continuous function of class $V_r(\mathbb{R}^n)$ defined on the whole $\mathbb{R}^n$ ? 2) If the above extension exists, obtain growth estimates of the extended function at infinity. Theorem 1 of this paper shows that for a wide class of continuous functions on segment E defined in terms of the modulus of continuity, there exists an extension to a bounded function of class $(V_r\cap C)(\mathbb{R}^n)$ regardless of the length of segment E. A similar result is not true for open sets E with a diameter greater than 2r, even without conditions for extension growth. Theorem 1 also contains an estimate of the velocity decrease of the extended function at infinity in directions orthogonal to the segment E.
- Published
- 2021
130. Estimates of Derivatives in Sobolev Spaces in Terms of Hypergeometric Functions
- Author
-
T. A. Garmanova
- Subjects
Sobolev space ,Combinatorics ,General Mathematics ,Order (ring theory) ,Interval (graph theory) ,Hypergeometric function ,Legendre polynomials ,Mathematics - Abstract
The paper deals with sharp estimates of derivatives of intermediate order $$k\le n-1$$ in the Sobolev space $$\mathring W^n_2[0;1]$$ , $$n\in\mathbb N$$ . The functions $$A_{n,k}(x)$$ under study are the smallest possible quantities in inequalities of the form $$|y^{(k)}(x)|\le A_{n,k}(x)\|y^{(n)}\|_{L_2[0;1]}.$$ The properties of the primitives of shifted Legendre polynomials on the interval $$[0;1]$$ are used to obtain an explicit description of these functions in terms of hypergeometric functions. In the paper, a new relation connecting the derivatives and primitives of Legendre polynomials is also proved.
- Published
- 2021
131. Totally $T$-adic functions of small height
- Author
-
Xander Faber and Clayton Petsche
- Subjects
Mathematics - Number Theory ,General Mathematics ,Zero (complex analysis) ,Field (mathematics) ,Rational function ,Arithmetic dynamics ,Upper and lower bounds ,Combinatorics ,Minimal polynomial (field theory) ,Finite field ,Bounded function ,FOS: Mathematics ,Number Theory (math.NT) ,Mathematics - Abstract
Let $\mathbb{F}_q(T)$ be the field of rational functions in one variable over a finite field. We introduce the notion of a totally $T$-adic function: one that is algebraic over $\mathbb{F}_q(T)$ and whose minimal polynomial splits completely over the completion $\mathbb{F}_q(\!(T)\!)$. We give two proofs that the height of a nonconstant totally $T$-adic function is bounded away from zero, each of which provides a sharp lower bound. We spend the majority of the paper providing explicit constructions of totally $T$-adic functions of small height (via arithmetic dynamics) and minimum height (via geometry and computer search). We also execute a large computer search that proves certain kinds of totally $T$-adic functions of minimum height over $\mathbb{F}_2(T)$ do not exist. The problem of whether there exist infinitely many totally $T$-adic functions of minimum positive height over $\mathbb{F}_q(T)$ remains open. Finally, we consider analogues of these notions under additional integrality hypotheses., 25 pages; source code for computations in the paper available at https://github.com/RationalPoint/T-adic
- Published
- 2021
132. $$k-$$Fibonacci powers as sums of powers of some fixed primes
- Author
-
Jhonny C. Gómez, Carlos A. Gómez, and Florian Luca
- Subjects
Fibonacci number ,Sums of powers ,010505 oceanography ,General Mathematics ,Diophantine equation ,010102 general mathematics ,Prime number ,Order (ring theory) ,01 natural sciences ,Combinatorics ,Integer ,0101 mathematics ,Finite set ,0105 earth and related environmental sciences ,Mathematics - Abstract
Let $$S=\{p_{1},\ldots ,p_{t}\}$$ be a fixed finite set of prime numbers listed in increasing order. In this paper, we prove that the Diophantine equation $$(F_n^{(k)})^s=p_{1}^{a_{1}}+\cdots +p_{t}^{a_{t}}$$ , in integer unknowns $$n\ge 1$$ , $$s\ge 1,~k\ge 2$$ and $$a_i\ge 0$$ for $$i=1,\ldots ,t$$ such that $$\max \left\{ a_{i}: 1\le i\le t\right\} =a_t$$ has only finitely many effectively computable solutions. Here, $$F_n^{(k)}$$ is the nth k–generalized Fibonacci number. We compute all these solutions when $$S=\{2,3,5\}$$ . This paper extends the main results of [15] where the particular case $$k=2$$ was treated.
- Published
- 2021
133. The Alternating Block Decomposition of Iterated Integrals and Cyclic Insertion on Multiple Zeta Values
- Author
-
Steven Charlton
- Subjects
Combinatorics ,Identity (mathematics) ,Conjecture ,Mathematics - Number Theory ,Iterated integrals ,General Mathematics ,FOS: Mathematics ,Pi ,Block (permutation group theory) ,Structure (category theory) ,Number Theory (math.NT) ,11M32 ,Mathematics - Abstract
The cyclic insertion conjecture of Borwein, Bradley, Broadhurst and Lison\v{e}k states that by inserting all cyclic permutations of some initial blocks of 2's into the multiple zeta value $ \zeta(1,3,\ldots,1,3) $ and summing, one obtains an explicit rational multiple of a power of $ \pi $. Hoffman gives a conjectural identity of a similar flavour concerning $ 2 \zeta(3,3,\{2\}^m) - \zeta(3,\{2\}^m,(1,2)) $. In this paper we introduce the 'generalised cyclic insertion conjecture', which we describe using a new combinatorial structure on iterated integrals -- the so-called alternating block decomposition. We see that both the original BBBL cyclic insertion conjecture, and Hoffman's conjectural identity, are special cases of this 'generalised' cyclic insertion conjecture. By using Brown's motivic MZV framework, we establish that some symmetrised version of the generalised cyclic insertion conjecture always holds, up to a rational; this provides some evidence for the generalised conjecture., Comment: 40 pages, 1 figure created with Inkscape. Added an observation due to Panzer about the structure of D_odd cycle I(\ell_1, \ldots, \ell_n), in the odd weight case. Added a reference to the recent paper from Hirose and Sato, which proves Hoffman's conjectural identity exactly
- Published
- 2021
134. CUBE PACKINGS IN EUCLIDEAN SPACES
- Author
-
Han Yu
- Subjects
General Mathematics ,010102 general mathematics ,Dimension (graph theory) ,05B30, 28A78, 52C17 ,0102 computer and information sciences ,01 natural sciences ,Combinatorics ,Packing problems ,Mathematics - Classical Analysis and ODEs ,010201 computation theory & mathematics ,Euclidean geometry ,Classical Analysis and ODEs (math.CA) ,FOS: Mathematics ,0101 mathematics ,Cube ,Mathematics - Abstract
In this paper we study some cube packing problems. In particular we are interested in compact subsets of $\mathbb{R}^n,n\geq 2$, which contain boundaries of cubes with all side lengths in $(0,1)$. We show here that such sets must have lower box dimension at least $n-0.5$ and we will also provide sharp examples. We also show here that such sets must be large in general in a precise sense which is also introduced in this paper., 9 pages. arXiv admin note: text overlap with arXiv:1711.06533
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- 2021
135. Properties of triangulated and quotient categories arising from n-Calabi–Yau triples
- Author
-
Francesca Fedele
- Subjects
Derived category ,Endomorphism ,Triangulated category ,General Mathematics ,010102 general mathematics ,Field (mathematics) ,01 natural sciences ,Cluster algebra ,Combinatorics ,Mathematics::Category Theory ,0103 physical sciences ,FOS: Mathematics ,Homological algebra ,010307 mathematical physics ,Gap theorem ,Representation Theory (math.RT) ,0101 mathematics ,Mathematics - Representation Theory ,Quotient ,Mathematics - Abstract
The original definition of cluster algebras by Fomin and Zelevinsky has been categorified and generalised in several ways over the course of the past 20 years, giving rise to cluster theory. This study lead to Iyama and Yang's generalised cluster categories $\mathcal{T}/\mathcal{T}^{fd}$ coming from $n$-Calabi-Yau triples $(\mathcal{T}, \mathcal{T}^{fd}, \mathcal{M})$. In this paper, we use some classic tools of homological algebra to give a deeper understanding of such categories $\mathcal{T}/\mathcal{T}^{fd}$. Let $k$ be a field, $n\geq 3$ an integer and $\mathcal{T}$ a $k$-linear triangulated category with a triangulated subcategory $\mathcal{T}^{fd}$ and a subcategory $\mathcal{M}=\text{add}(M)$ such that $(\mathcal{T}, \mathcal{T}^{fd}, \mathcal{M})$ is an $n$-Calabi-Yau triple. In this paper, we prove some properties of the triangulated categories $\mathcal{T}$ and $\mathcal{T}/\mathcal{T}^{fd}$. Our first result gives a relation between the Hom-spaces in these categories, using limits and colimits. Our second result is a Gap Theorem in $\mathcal{T}$, showing when the truncation triangles split. Moreover, we apply our two theorems to present an alternative proof to a result by Guo, originally stated in a more specific setup of dg $k$-algebras $A$ and subcategories of the derived category of dg $A$-modules. This proves that $\mathcal{T}/\mathcal{T}^{fd}$ is Hom-finite and $(n-1)$-Calabi-Yau, its object $M$ is $(n-1)$-cluster tilting and the endomorphism algebras of $M$ over $\mathcal{T}$ and over $\mathcal{T}/\mathcal{T}^{fd}$ are isomorphic. Note that these properties make $\mathcal{T}/\mathcal{T}^{fd}$ a generalisation of the cluster category., Comment: 17 pages. Final accepted version to appear in the Pacific Journal of Mathematics
- Published
- 2021
136. The Benson - Symonds Invariant for Permutation Modules
- Author
-
Aparna Upadhyay
- Subjects
Combinatorics ,Finite group ,Permutation ,Symmetric group ,General Mathematics ,Projective test ,Invariant (mathematics) ,Representation theory ,Mathematics - Abstract
In a recent paper, Dave Benson and Peter Symonds defined a new invariant γG(M) for a finite dimensional module M of a finite group G which attempts to quantify how close a module is to being projective. In this paper, we determine this invariant for permutation modules of the symmetric group corresponding to two-part partitions using tools from representation theory and combinatorics.
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- 2021
137. On graphs with equal total domination and Grundy total domination numbers
- Author
-
Tilen Marc, Tim Kos, Tanja Dravec, and Marko Jakovac
- Subjects
Sequence ,Domination analysis ,Applied Mathematics ,General Mathematics ,010102 general mathematics ,010103 numerical & computational mathematics ,Characterization (mathematics) ,01 natural sciences ,Vertex (geometry) ,Combinatorics ,Dominating set ,Chordal graph ,Bipartite graph ,Discrete Mathematics and Combinatorics ,Projective plane ,0101 mathematics ,Mathematics - Abstract
A sequence $$(v_1,\ldots ,v_k)$$ of vertices in a graph G without isolated vertices is called a total dominating sequence if every vertex $$v_i$$ in the sequence totally dominates at least one vertex that was not totally dominated by $$\{v_1,\ldots , v_{i-1}\}$$ and $$\{v_1,\ldots ,v_k\}$$ is a total dominating set of G. The length of a shortest such sequence is the total domination number of G ( $$\gamma _{t}(G)$$ ), while the length of a longest such sequence is the Grundy total domination number of G ( $$\gamma _{gr}^t(G)$$ ). In this paper we study graphs with equal total and Grundy total domination numbers. We characterize bipartite graphs with both total and Grundy total dominations number equal to 4, and show that there is no connected chordal graph G with $$\gamma _{t}(G)=\gamma _{gr}^t(G)=4$$ . The main result of the paper is a characterization of bipartite graphs with $$\gamma _{t}(G)=\gamma _{gr}^t(G)=6$$ proved by establishing a surprising correspondence between the existence of such graphs and a classical but still open problem of the existence of certain finite projective planes.
- Published
- 2021
138. THE COHOMOLOGY OF UNRAMIFIED RAPOPORT–ZINK SPACES OF EL-TYPE AND HARRIS’S CONJECTURE
- Author
-
Alexander Bertoloni Meli
- Subjects
Conjecture ,Mathematics - Number Theory ,General Mathematics ,Prove it ,Type (model theory) ,Cohomology ,Combinatorics ,Mathematics - Algebraic Geometry ,Mathematics::Algebraic Geometry ,Morphism ,Square-integrable function ,FOS: Mathematics ,Number Theory (math.NT) ,Mathematics::Representation Theory ,Algebraic Geometry (math.AG) ,Mathematics - Abstract
We study the $l$-adic cohomology of unramified Rapoport-Zink spaces of EL-type. These spaces were used in Harris and Taylor's proof of the local Langlands correspondence for $\mathrm{GL_n}$ and to show local-global compatibilities of the Langlands correspondence. In this paper we consider certain morphisms, $\mathrm{Mant}_{b, \mu}$, of Grothendieck groups of representations constructed from the cohomology of the above spaces, as studied by Harris and Taylor, Mantovan, Fargues, Shin, and others. Due to earlier work of Fargues and Shin we have a description of $\mathrm{Mant}_{b, \mu}(\rho)$ for $\rho$ a supercuspidal representation. In this paper, we give a conjectural formula for $\mathrm{Mant}_{b, \mu}(\rho)$ for all $\rho$ and prove it when $\rho$ is essentially square integrable. Our proof works for general $\rho$ conditionally on a conjecture appearing in Shin's work. We show that our description agrees with a conjecture of Harris in the case of parabolic inductions of supercuspidal representations of a Levi subgroup., Comment: 50 pages, published version
- Published
- 2021
139. Phase transitions of Best‐of‐two and Best‐of‐three on stochastic block models
- Author
-
Takeharu Shiraga and Nobutaka Shimizu
- Subjects
Vertex (graph theory) ,Random graph ,Applied Mathematics ,General Mathematics ,Block (permutation group theory) ,0102 computer and information sciences ,Binary logarithm ,01 natural sciences ,Computer Graphics and Computer-Aided Design ,Omega ,Combinatorics ,010201 computation theory & mathematics ,Stochastic block model ,Expander graph ,Constant (mathematics) ,Software ,Mathematics - Abstract
This paper is concerned with voting processes on graphs where each vertex holds one of two different opinions. In particular, we study the \emph{Best-of-two} and the \emph{Best-of-three}. Here at each synchronous and discrete time step, each vertex updates its opinion to match the majority among the opinions of two random neighbors and itself (the Best-of-two) or the opinions of three random neighbors (the Best-of-three). Previous studies have explored these processes on complete graphs and expander graphs, but we understand significantly less about their properties on graphs with more complicated structures. In this paper, we study the Best-of-two and the Best-of-three on the stochastic block model $G(2n,p,q)$, which is a random graph consisting of two distinct Erdős-Renyi graphs $G(n,p)$ joined by random edges with density $q\leq p$. We obtain two main results. First, if $p=\omega(\log n/n)$ and $r=q/p$ is a constant, we show that there is a phase transition in $r$ with threshold $r^*$ (specifically, $r^*=\sqrt{5}-2$ for the Best-of-two, and $r^*=1/7$ for the Best-of-three). If $r>r^*$, the process reaches consensus within $O(\log \log n+\log n/\log (np))$ steps for any initial opinion configuration with a bias of $\Omega(n)$. By contrast, if $r r^*$, we show that, for any initial opinion configuration, the process reaches consensus within $O(\log n)$ steps. To the best of our knowledge, this is the first result concerning multiple-choice voting for arbitrary initial opinion configurations on non-complete graphs.
- Published
- 2021
140. Simplest Test for the Three-Dimensional Dynamical Inverse Problem (The BC-Method)
- Author
-
Mikhail I. Belishev, N. A. Karazeeva, and A. S. Blagoveshchensky
- Subjects
Statistics and Probability ,Applied Mathematics ,General Mathematics ,Operator (physics) ,010102 general mathematics ,Boundary (topology) ,Function (mathematics) ,Inverse problem ,Positive function ,01 natural sciences ,010305 fluids & plasmas ,Combinatorics ,0103 physical sciences ,Nabla symbol ,0101 mathematics ,Dynamical system (definition) ,Realization (systems) ,Mathematics - Abstract
A dynamical system $$ {\displaystyle \begin{array}{ll}{u}_{tt}-\Delta u-\nabla 1\mathrm{n}\;\rho \cdot \nabla u=0& in\kern0.6em {\mathrm{\mathbb{R}}}_{+}^3\times \left(0,T\right),\\ {}{\left.u\right|}_{t=0}={\left.{u}_t\right|}_{t=0}=0& in\kern0.6em \overline{{\mathrm{\mathbb{R}}}_{+}^3},\\ {}{\left.{u}_z\right|}_{z=0}=f& for\kern0.36em 0\le t\le T,\end{array}} $$ is under consideration, where ρ = ρ(x, y, z) is a smooth positive function; f = f(x, y, t) is a boundary control; u = uf (x, y, z, t) is a solution. With the system one associates a response operator R : f ↦ uf|z = 0. The inverse problem is to recover the function ρ via the response operator. A short representation of the local version of the BC-method, which recovers ρ via the data given on a part of the boundary, is provided. If ρ is constant, the forward problem is solved in explicit form. In the paper, the corresponding representations for the solutions and response operator are derived. A way to use them for testing the BC-algorithm, which solves the inverse problem, is outlined. The goal of the paper is to extend the circle of the BC-method users, who are interested in numerical realization of methods for solving inverse problems.
- Published
- 2021
141. Khintchine-type theorems for values of subhomogeneous functions at integer points
- Author
-
Mishel Skenderi and Dmitry Kleinbock
- Subjects
Mathematics - Number Theory ,010505 oceanography ,General Mathematics ,010102 general mathematics ,Second moment of area ,Function (mathematics) ,Type (model theory) ,01 natural sciences ,Minimax approximation algorithm ,Combinatorics ,Integer ,FOS: Mathematics ,11J25, 11J54, 11J83, 11H06, 11H60, 37A17 ,Number Theory (math.NT) ,0101 mathematics ,Element (category theory) ,Axiom ,0105 earth and related environmental sciences ,Mathematics - Abstract
This work has been motivated by recent papers that quantify the density of values of generic quadratic forms and other polynomials at integer points, in particular ones that use Rogers' second moment estimates. In this paper we establish such results in a very general framework. Given any subhomogeneous function (a notion to be defined) $f: \mathbb{R}^n \to \mathbb{R}$, we derive a necessary and sufficient condition on the approximating function $\psi$ for guaranteeing that a generic element $f\circ g$ in the $G$-orbit of $f$ is $\psi$-approximable; that is, $|f\circ g(\mathbf{v})| \le \psi(\|\mathbf{v}\|)$ for infinitely many $\mathbf{v} \in \mathbb{Z}^n$. We also deduce a sufficient condition in the case of uniform approximation. Here, $G$ can be any closed subgroup of $\rm{ASL}_n(\mathbb{R})$ satisfying certain axioms that allow for the use of Rogers-type estimates., Comment: 26 pages; misprints corrected, concluding remarks added
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- 2021
142. Polyadic Liouville numbers
- Subjects
Combinatorics ,Integer ,Series (mathematics) ,Simple (abstract algebra) ,Approximations of π ,General Mathematics ,Field (mathematics) ,Algebraic independence ,Transcendental number ,Liouville number ,Mathematics - Abstract
We study here polyadic Liouville numbers, which are involved in a series of recent papers. The author considered the series 𝑓0(𝜆) =∞Σ𝑛=0(𝜆)𝑛𝜆𝑛, 𝑓1(𝜆) =∞Σ𝑛=0(𝜆 + 1)𝑛𝜆𝑛, where 𝜆 is a certain polyadic Liouville number. The series considered converge in any field Q𝑝 . Here (𝛾)𝑛 denotes Pochhammer symbol, i.e. (𝛾)0 = 1 , and for 𝑛 ≥ 1 we have(𝛾)𝑛 = 𝛾(𝛾 + 1)...(𝛾 + 𝑛 − 1). The values of these series were also calculated at polyadic Liouville number. The canonic expansion of a polyadic number 𝜆 is of the form 𝜆 =∞Σ𝑛=0𝑎𝑛𝑛!, 𝑎𝑛 ∈ Z, 0 ≤ 𝑎𝑛 ≤ 𝑛. This series converges in any field of 𝑝-adic numbers Q𝑝. We call a polyadic number 𝜆 a polyadic Liouville number, if for any 𝑛 and 𝑃 there exists a positive integer 𝐴 such that for all primes 𝑝 ,satisfying 𝑝 ≤ 𝑃 the inequality |𝜆 − 𝐴|𝑝 < 𝐴−𝑛 holds. The paper gives a simple proof that the Liouville polyadic number is transcendental in any field Q𝑝. In other words,the Liouville polyadic number is globally transcendental. We prove here a theorem on approximations of a set of 𝑝−adic numbers and it’s corollary — a sufficient condition of the algebraic independence of a set of 𝑝−adic numbers. We also present a theorem on global algebraic independence of polyadic numbers.
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- 2021
143. THE NUMBER OF RATIONAL SOLUTIONS OF ABEL EQUATIONS
- Author
-
Yang Shen, Jiazhong Yang, and Xinjie Qian
- Subjects
Combinatorics ,Degree (graph theory) ,Differential equation ,General Mathematics ,Upper and lower bounds ,Mathematics - Abstract
In this paper, we study rational solutions of the Abel differential equations $ dy/dx = f_m(x)y^2+g_n(x)y^3 $, where $ f_m(x) $ and $ g_n(x) $ are real polynomials of degree $ m $ and $ n $ respectively. The main result of the paper is as follows: We give a systematic upper bound on the number of the nontrivial rational solutions of such equations in all these cases. Then we prove that these upper bounds can be reached in most cases. Finally, we present some examples of Abel equations having exactly $ i $ nontrivial rational solutions, where $ 1\leq i\leq 5 $.
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- 2021
144. The limit of reciprocal sum of some subsequential Fibonacci numbers
- Author
-
Jong Do Park and Ho Hyeong Lee
- Subjects
Physics ,Subsequential limit ,Fibonacci number ,General Mathematics ,fibonacci number ,floor function ,convergent series ,Combinatorics ,QA1-939 ,reciprocal sum ,catalan's identity ,Limit (mathematics) ,Mathematics ,Convergent series ,Reciprocal - Abstract
This paper deals with the sum of reciprocal Fibonacci numbers. Let $ f_0 = 0 $, $ f_1 = 1 $ and $ f_{n+1} = f_n+f_{n-1} $ for any $ n\in\mathbb{N} $. In this paper, we prove new estimates on $ \sum\limits^\infty_{k = n}\frac{1}{f_{mk-\ell}} $, where $ m\in\mathbb{N} $ and $ 0\leq\ell\leq m-1 $. As a consequence of some inequalities, we prove \begin{document}$ \lim\limits_{n\rightarrow \infty}\left\{\left(\sum\limits^\infty_{k = n}\frac{1}{f_{mk-\ell}} \right)^{-1} -(f_{mn-\ell}-f_{m(n-1)-\ell})\right\} = 0. $\end{document} And we also compute the explicit value of $ \left\lfloor\left(\sum\limits^\infty_{k = n}\frac{1}{f_{mk-\ell}}\right)^{-1}\right\rfloor $. The interesting observation is that the value depends on $ m(n+1)+\ell $.
- Published
- 2021
145. A Bijective Proof of the ASM Theorem Part II: ASM Enumeration and ASM–DPP Relation
- Author
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Ilse Fischer and Matjaž Konvalinka
- Subjects
Mathematics::Combinatorics ,Series (mathematics) ,General Mathematics ,010102 general mathematics ,Mathematical proof ,01 natural sciences ,Bijective proof ,Combinatorics ,Matrix (mathematics) ,Bijection ,Alternating sign matrix ,0101 mathematics ,Bijection, injection and surjection ,Sign (mathematics) ,Mathematics - Abstract
This paper is the 2nd in a series of planned papers that provide 1st bijective proofs of alternating sign matrix (ASM) results. Based on the main result from the 1st paper, we construct a bijective proof of the enumeration formula for ASMs and of the fact that ASMs are equinumerous with descending plane partitions. We are also able to refine these bijections by including the position of the unique $1$ in the top row of the matrix. Our constructions rely on signed sets and related notions. The starting point for these constructions were known “computational” proofs, but the combinatorial point of view led to several drastic modifications. We also provide computer code where all of our constructions have been implemented.
- Published
- 2020
146. Tate (Co)homology of invariant group chains
- Author
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Angelina López Madrigal and Rolando Jimenez
- Subjects
Combinatorics ,Finite group ,Mathematics::K-Theory and Homology ,Computer Science::Information Retrieval ,General Mathematics ,Astrophysics::Instrumentation and Methods for Astrophysics ,Computer Science::General Literature ,Computer Science::Computation and Language (Computational Linguistics and Natural Language and Speech Processing) ,Invariant (mathematics) ,Homology (mathematics) ,Automorphism ,Cohomology ,Mathematics - Abstract
Let [Formula: see text] be a finite group acting on a group [Formula: see text] as a group automorphisms, [Formula: see text] the bar complex, [Formula: see text] the homology of invariant group chains and [Formula: see text] the cohomology invariant, both defined in Knudson’s paper “The homology of invariant group chains”. In this paper, we define the Tate homology of invariants [Formula: see text] and the Tate cohomology of invariants [Formula: see text]. When the coefficient [Formula: see text] is the abelian group of the integers, we proved that these groups are isomorphics, [Formula: see text]. Further, we prove that the homology and cohomology of invariant group chains are duals, [Formula: see text], [Formula: see text].
- Published
- 2020
147. Peg solitaire in three colors on graphs
- Author
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Tara C. Davis, Melissa Wong, Roberto C. Soto, Alexxis De Lamere, Gustavo Sopena, and Sonali Vyas
- Subjects
Computer Science::Computer Science and Game Theory ,Solitaire Cryptographic Algorithm ,combinatorial games ,General Mathematics ,games on graphs ,peg solitaire ,Combinatorial game theory ,Star (graph theory) ,Cartesian product ,Combinatorics ,symbols.namesake ,TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES ,Computer Science::Discrete Mathematics ,Path (graph theory) ,91A43 ,symbols ,Bipartite graph ,Astrophysics::Solar and Stellar Astrophysics ,05C57 ,MathematicsofComputing_DISCRETEMATHEMATICS ,Mathematics - Abstract
Peg solitaire is a classical one-person game that has been played in various countries on different types of boards. Numerous studies have focused on the solvability of the games on these traditional boards and more recently on mathematical graphs. In this paper, we go beyond traditional peg solitaire and explore the solvability on graphs with pegs of more than one color and arrive at results that differ from previous works on the subject. This paper focuses on classifying the solvability of peg solitaire in three colors on several different types of common mathematical graphs, including the path, complete bipartite, and star. We also consider the solvability of peg solitaire on the Cartesian products of graphs.
- Published
- 2020
148. Ideal, non-extended formulations for disjunctive constraints admitting a network representation
- Author
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Markó Horváth and Tamás Kis
- Subjects
Combinatorics ,Cardinality ,Series (mathematics) ,Unit vector ,General Mathematics ,Embedding ,Polytope ,QA75 Electronic computers. Computer science / számítástechnika, számítógéptudomány ,Ideal (ring theory) ,Characterization (mathematics) ,Type (model theory) ,Software ,Mathematics - Abstract
In this paper we reconsider a known technique for constructing strong MIP formulations for disjunctive constraints of the form $$x \in \bigcup _{i=1}^m P_i$$ x ∈ ⋃ i = 1 m P i , where the $$P_i$$ P i are polytopes. The formulation is based on the Cayley Embedding of the union of polytopes, namely, $$Q := \mathrm {conv}(\bigcup _{i=1}^m P_i\times \{\epsilon ^i\})$$ Q : = conv ( ⋃ i = 1 m P i × { ϵ i } ) , where $$\epsilon ^i$$ ϵ i is the ith unit vector in $${\mathbb {R}}^m$$ R m . Our main contribution is a full characterization of the facets of Q, provided it has a certain network representation. In the second half of the paper, we work-out a number of applications from the literature, e.g., special ordered sets of type 2, logical constraints, the cardinality indicating polytope, union of simplicies, etc., along with a more complex recent example. Furthermore, we describe a new formulation for piecewise linear functions defined on a grid triangulation of a rectangular region $$D \subset {\mathbb {R}}^d$$ D ⊂ R d using a logarithmic number of auxilirary variables in the number of gridpoints in D for any fixed d. The series of applications demonstrates the richness of the class of disjunctive constraints for which our method can be applied.
- Published
- 2022
149. Further study on the Brück conjecture and some non-linear complex differential equations
- Author
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Dilip Chandra Pramanik and Kapil Roy
- Subjects
Monomial ,021103 operations research ,Current (mathematics) ,Conjecture ,Complex differential equation ,General Mathematics ,Entire function ,0211 other engineering and technologies ,02 engineering and technology ,Function (mathematics) ,01 natural sciences ,010101 applied mathematics ,Combinatorics ,0101 mathematics ,Complex number ,Differential (mathematics) ,Mathematics - Abstract
PurposeThe purpose of this current paper is to deal with the study of non-constant entire solutions of some non-linear complex differential equations in connection to Brück conjecture, by using the theory of complex differential equation. The results generalize the results due to Pramanik et al.Design/methodology/approach39B32, 30D35.FindingsIn the current paper, we mainly study the Brück conjecture and the various works that confirm this conjecture. In our study we find that the conjecture can be generalized for differential monomials under some additional conditions and it generalizes some works related to the conjecture. Also we can take the complex number a in the conjecture to be a small function. More precisely, we obtain a result which can be restate in the following way: Let f be a non-constant entire function such that σ2(f)<∞, σ2(f) is not a positive integer and δ(0, f)>0. Let M[f] be a differential monomial of f of degree γM and α(z), β(z)∈S(f) be such that max{σ(α), σ(β)} <σ(f). If M[f]+β and fγM−α share the value 0 CM, then M[f]+βfγM−α=c,where c≠0 is a constant.Originality/valueThis is an original work of the authors.
- Published
- 2020
150. The Absolutely Strongly Star-Hurewicz Property with Respect to an Ideal
- Author
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B. K. Tyagi, Sumit Singh, and Manoj Bhardwaj
- Subjects
Class (set theory) ,Sequence ,Property (philosophy) ,Dense set ,General Mathematics ,010102 general mathematics ,Star (graph theory) ,Space (mathematics) ,01 natural sciences ,010101 applied mathematics ,Combinatorics ,Ideal (ring theory) ,0101 mathematics ,Mathematics - Abstract
Aspace X is said to have the absolutely strongly star --Hurewicz (ASSH) property if for each sequence (𝒰 n : n ∈ )of opencovers of X and each dense subset Y of X, there is a sequence (Fn : n ∈ ) of finite subsets of Y such that for each x ∈ X, {n ∈ : x ∉ St(Fn , 𝒰 n )}∈ , where is the proper admissible ideal of . In this paper, we investigate the relationship between the ASSH property and other related properties and study the topological properties of the ASSH property. This paper generalizes several results of Song [25] to the larger class of spaces having the ASSH properties.
- Published
- 2020
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