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  Subjects -> MATHEMATICS (Total: 874 journals)
    - APPLIED MATHEMATICS (71 journals)
    - GEOMETRY AND TOPOLOGY (19 journals)
    - MATHEMATICS (647 journals)
    - MATHEMATICS (GENERAL) (41 journals)
    - NUMERICAL ANALYSIS (19 journals)
    - PROBABILITIES AND MATH STATISTICS (77 journals)

MATHEMATICS (647 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 538 Journals sorted alphabetically
Abakós     Open Access   (Followers: 3)
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg     Hybrid Journal   (Followers: 2)
Academic Voices : A Multidisciplinary Journal     Open Access   (Followers: 2)
Accounting Perspectives     Full-text available via subscription   (Followers: 7)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 16)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 4)
ACM Transactions on Mathematical Software (TOMS)     Hybrid Journal   (Followers: 6)
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 21)
Acta Applicandae Mathematicae     Hybrid Journal   (Followers: 1)
Acta Mathematica     Hybrid Journal   (Followers: 11)
Acta Mathematica Hungarica     Hybrid Journal   (Followers: 2)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5)
Acta Mathematica Sinica, English Series     Hybrid Journal   (Followers: 5)
Acta Mathematica Vietnamica     Hybrid Journal  
Acta Mathematicae Applicatae Sinica, English Series     Hybrid Journal  
Advanced Science Letters     Full-text available via subscription   (Followers: 5)
Advances in Applied Clifford Algebras     Hybrid Journal   (Followers: 3)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 15)
Advances in Decision Sciences     Open Access   (Followers: 4)
Advances in Difference Equations     Open Access   (Followers: 1)
Advances in Fixed Point Theory     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Linear Algebra & Matrix Theory     Open Access   (Followers: 1)
Advances in Materials Sciences     Open Access   (Followers: 16)
Advances in Mathematical Physics     Open Access   (Followers: 6)
Advances in Mathematics     Full-text available via subscription   (Followers: 10)
Advances in Numerical Analysis     Open Access   (Followers: 4)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Pure and Applied Mathematics     Hybrid Journal   (Followers: 5)
Advances in Pure Mathematics     Open Access   (Followers: 4)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aequationes Mathematicae     Hybrid Journal   (Followers: 2)
African Journal of Educational Studies in Mathematics and Sciences     Full-text available via subscription   (Followers: 5)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Afrika Matematika     Hybrid Journal   (Followers: 1)
Air, Soil & Water Research     Open Access   (Followers: 7)
AKSIOMA Journal of Mathematics Education     Open Access   (Followers: 1)
Algebra and Logic     Hybrid Journal   (Followers: 3)
Algebra Colloquium     Hybrid Journal   (Followers: 4)
Algebra Universalis     Hybrid Journal   (Followers: 2)
Algorithmic Operations Research     Full-text available via subscription   (Followers: 5)
Algorithms     Open Access   (Followers: 9)
Algorithms Research     Open Access   (Followers: 1)
American Journal of Biostatistics     Open Access   (Followers: 9)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 3)
American Journal of Mathematical Analysis     Open Access  
American Journal of Mathematics     Full-text available via subscription   (Followers: 7)
American Journal of Operations Research     Open Access   (Followers: 5)
American Mathematical Monthly     Full-text available via subscription   (Followers: 6)
An International Journal of Optimization and Control: Theories & Applications     Open Access   (Followers: 7)
Analele Universitatii Ovidius Constanta - Seria Matematica     Open Access   (Followers: 1)
Analysis     Hybrid Journal   (Followers: 2)
Analysis and Applications     Hybrid Journal   (Followers: 1)
Analysis and Mathematical Physics     Hybrid Journal   (Followers: 4)
Analysis Mathematica     Full-text available via subscription  
Annales Mathematicae Silesianae     Open Access  
Annales mathématiques du Québec     Hybrid Journal   (Followers: 4)
Annales UMCS, Mathematica     Open Access   (Followers: 1)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica     Open Access  
Annali di Matematica Pura ed Applicata     Hybrid Journal   (Followers: 1)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Data Science     Hybrid Journal   (Followers: 8)
Annals of Discrete Mathematics     Full-text available via subscription   (Followers: 6)
Annals of Mathematics     Full-text available via subscription  
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 6)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of the Alexandru Ioan Cuza University - Mathematics     Open Access  
Annals of the Institute of Statistical Mathematics     Hybrid Journal   (Followers: 1)
Annals of West University of Timisoara - Mathematics     Open Access  
Annuaire du Collège de France     Open Access   (Followers: 5)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applications of Mathematics     Hybrid Journal   (Followers: 1)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Mathematics     Open Access   (Followers: 3)
Applied Mathematics     Open Access   (Followers: 4)
Applied Mathematics & Optimization     Hybrid Journal   (Followers: 4)
Applied Mathematics - A Journal of Chinese Universities     Hybrid Journal  
Applied Mathematics Letters     Full-text available via subscription   (Followers: 1)
Applied Mathematics Research eXpress     Hybrid Journal   (Followers: 1)
Applied Network Science     Open Access  
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arab Journal of Mathematical Sciences     Open Access   (Followers: 2)
Arabian Journal of Mathematics     Open Access   (Followers: 2)
Archive for Mathematical Logic     Hybrid Journal   (Followers: 1)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 4)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
Arnold Mathematical Journal     Hybrid Journal   (Followers: 1)
Artificial Satellites : The Journal of Space Research Centre of Polish Academy of Sciences     Open Access   (Followers: 18)
Asia-Pacific Journal of Operational Research     Hybrid Journal   (Followers: 3)
Asian Journal of Algebra     Open Access   (Followers: 1)
Asian Journal of Current Engineering & Maths     Open Access  
Asian-European Journal of Mathematics     Hybrid Journal   (Followers: 2)
Australian Mathematics Teacher, The     Full-text available via subscription   (Followers: 7)
Australian Primary Mathematics Classroom     Full-text available via subscription   (Followers: 2)
Australian Senior Mathematics Journal     Full-text available via subscription   (Followers: 1)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Axioms     Open Access  
Baltic International Yearbook of Cognition, Logic and Communication     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
BIBECHANA     Open Access  
BIT Numerical Mathematics     Hybrid Journal  
BoEM - Boletim online de Educação Matemática     Open Access  
Boletim Cearense de Educação e História da Matemática     Open Access  
Boletim de Educação Matemática     Open Access  
Boletín de la Sociedad Matemática Mexicana     Hybrid Journal  
Bollettino dell'Unione Matematica Italiana     Full-text available via subscription   (Followers: 1)
British Journal of Mathematical and Statistical Psychology     Full-text available via subscription   (Followers: 21)
Bruno Pini Mathematical Analysis Seminar     Open Access  
Buletinul Academiei de Stiinte a Republicii Moldova. Matematica     Open Access   (Followers: 7)
Bulletin des Sciences Mathamatiques     Full-text available via subscription   (Followers: 4)
Bulletin of Dnipropetrovsk University. Series : Communications in Mathematical Modeling and Differential Equations Theory     Open Access   (Followers: 1)
Bulletin of Mathematical Sciences     Open Access   (Followers: 1)
Bulletin of the Brazilian Mathematical Society, New Series     Hybrid Journal  
Bulletin of the London Mathematical Society     Hybrid Journal   (Followers: 3)
Bulletin of the Malaysian Mathematical Sciences Society     Hybrid Journal  
Calculus of Variations and Partial Differential Equations     Hybrid Journal  
Canadian Journal of Science, Mathematics and Technology Education     Hybrid Journal   (Followers: 17)
Carpathian Mathematical Publications     Open Access   (Followers: 1)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal  
CHANCE     Hybrid Journal   (Followers: 5)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Annals of Mathematics, Series B     Hybrid Journal  
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Mathematics     Open Access  
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Cogent Mathematics     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Collectanea Mathematica     Hybrid Journal  
College Mathematics Journal     Full-text available via subscription   (Followers: 2)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Commentarii Mathematici Helvetici     Hybrid Journal   (Followers: 1)
Communications in Contemporary Mathematics     Hybrid Journal  
Communications in Mathematical Physics     Hybrid Journal   (Followers: 1)
Communications On Pure & Applied Mathematics     Hybrid Journal   (Followers: 3)
Complex Analysis and its Synergies     Open Access   (Followers: 2)
Complex Variables and Elliptic Equations: An International Journal     Hybrid Journal  
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 9)
Comptes Rendus Mathematique     Full-text available via subscription   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 4)
Computational Methods and Function Theory     Hybrid Journal  
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Concrete Operators     Open Access   (Followers: 4)
Confluentes Mathematici     Hybrid Journal  
COSMOS     Hybrid Journal  
Cryptography and Communications     Hybrid Journal   (Followers: 14)
Cuadernos de Investigación y Formación en Educación Matemática     Open Access  
Cubo. A Mathematical Journal     Open Access  
Czechoslovak Mathematical Journal     Hybrid Journal   (Followers: 1)
Demographic Research     Open Access   (Followers: 12)
Demonstratio Mathematica     Open Access  
Dependence Modeling     Open Access  
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 29)
Developments in Clay Science     Full-text available via subscription   (Followers: 1)
Developments in Mineral Processing     Full-text available via subscription   (Followers: 3)
Dhaka University Journal of Science     Open Access  
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 2)
Discrete Mathematics     Hybrid Journal   (Followers: 7)
Discrete Mathematics & Theoretical Computer Science     Open Access  
Discrete Mathematics, Algorithms and Applications     Hybrid Journal   (Followers: 2)
Discussiones Mathematicae Graph Theory     Open Access   (Followers: 1)
Doklady Mathematics     Hybrid Journal  
Duke Mathematical Journal     Full-text available via subscription   (Followers: 1)
Edited Series on Advances in Nonlinear Science and Complexity     Full-text available via subscription  
Electronic Journal of Graph Theory and Applications     Open Access   (Followers: 2)
Electronic Notes in Discrete Mathematics     Full-text available via subscription   (Followers: 2)
Elemente der Mathematik     Full-text available via subscription   (Followers: 3)
Energy for Sustainable Development     Hybrid Journal   (Followers: 9)
Enseñanza de las Ciencias : Revista de Investigación y Experiencias Didácticas     Open Access  
Ensino da Matemática em Debate     Open Access  
Entropy     Open Access   (Followers: 5)
ESAIM: Control Optimisation and Calculus of Variations     Full-text available via subscription   (Followers: 1)
European Journal of Combinatorics     Full-text available via subscription   (Followers: 4)
European Journal of Mathematics     Hybrid Journal   (Followers: 1)
European Scientific Journal     Open Access   (Followers: 2)
Experimental Mathematics     Hybrid Journal   (Followers: 3)
Expositiones Mathematicae     Hybrid Journal   (Followers: 2)
Facta Universitatis, Series : Mathematics and Informatics     Open Access  
Fasciculi Mathematici     Open Access  
Finite Fields and Their Applications     Full-text available via subscription   (Followers: 4)
Fixed Point Theory and Applications     Open Access   (Followers: 1)
Formalized Mathematics     Open Access   (Followers: 2)
Foundations and Trends® in Econometrics     Full-text available via subscription   (Followers: 4)

        1 2 3 4 | Last

Journal Cover European Journal of Combinatorics
  [SJR: 1.233]   [H-I: 35]   [4 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0195-6698 - ISSN (Online) 1095-9971
   Published by Elsevier Homepage  [3042 journals]
  • The average number of spanning trees in sparse graphs with given degrees
    • Abstract: Publication date: June 2017
      Source:European Journal of Combinatorics, Volume 63
      Author(s): Catherine Greenhill, Mikhail Isaev, Matthew Kwan, Brendan D. McKay
      We give an asymptotic expression for the expected number of spanning trees in a random graph with a given degree sequence d = ( d 1 , … , d n ) , provided that the number of edges is at least n + 1 2 d max 4 , where d max is the maximum degree. A key part of our argument involves establishing a concentration result for a certain family of functions over random trees with given degrees, using Prüfer codes.

      PubDate: 2017-03-13T02:50:09Z
       
  • Waiter–Client and Client–Waiter Hamiltonicity games on random
           graphs
    • Abstract: Publication date: June 2017
      Source:European Journal of Combinatorics, Volume 63
      Author(s): Dan Hefetz, Michael Krivelevich, Wei En Tan
      We study two types of two player, perfect information games with no chance moves, played on the edge set of the binomial random graph G ( n , p ) . In each round of the ( 1 : q ) Waiter–Client Hamiltonicity game, the first player, called Waiter, offers the second player, called Client, q + 1 edges of G ( n , p ) which have not been offered previously. Client then chooses one of these edges, which he claims, and the remaining q edges go back to Waiter. Waiter wins this game if by the time every edge of G ( n , p ) has been claimed by some player, the graph consisting of Client’s edges is Hamiltonian; otherwise Client is the winner. Client–Waiter games are defined analogously, the main difference being that Client wins the game if his graph is Hamiltonian and Waiter wins otherwise. In this paper we determine a sharp threshold for both games. Namely, for every fixed positive integer q , we prove that the smallest edge probability p for which a.a.s. Waiter has a winning strategy for the ( 1 : q ) Waiter–Client Hamiltonicity game is ( 1 + o ( 1 ) ) log n / n , and the smallest p for which a.a.s. Client has a winning strategy for the ( 1 : q ) Client–Waiter Hamiltonicity game is ( q + 1 + o ( 1 ) ) log n / n .

      PubDate: 2017-03-13T02:50:09Z
       
  • Announcement from the Editors
    • Abstract: Publication date: Available online 3 March 2017
      Source:European Journal of Combinatorics
      Author(s): Patrice Ossona de Mendez, Pierre Rosenstiehl


      PubDate: 2017-03-05T02:21:45Z
       
  • Nonexistence of perfect 2-error-correcting Lee codes in certain dimensions
    • Abstract: Publication date: June 2017
      Source:European Journal of Combinatorics, Volume 63
      Author(s): Dongryul Kim
      The Golomb–Welch conjecture states that there are no perfect e -error-correcting codes in Z n for n ≥ 3 and e ≥ 2 . In this note, we prove the nonexistence of perfect 2 -error-correcting codes for a certain class of n , which is expected to be infinite. This result further substantiates the Golomb–Welch conjecture.

      PubDate: 2017-02-26T01:09:35Z
       
  • A classification of primer hypermaps with a product of two primes number
           of hyperfaces
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Shaofei Du, Xinyuan Hu
      A hypermap is a cellular embedding of a connected bipartite graph G into a compact and connected surface S without border. The vertices of G lie in distinct partitions, colored black and white, and are called respectively the hypervertices and hyperedges of the hypermap, while the connected regions of G ∖ S are the hyperfaces. A hypermap H is called orientable if the underlying surface S is orientable. An orientable hypermap is called regular if its orientation preserving automorphism group G acts regularly on the flags (hypervertex, hyperedge and hyperface incident triples), and further, it is called (face-)primer if G induces a faithful action on their hyperfaces. In Breda d’Azevedo and Fernandes (2011), a classification of the primer hypermap with a prime number of hyperfaces is given. In this paper, a classification will be given, for all primer hypermaps with a product of two primes hyperfaces, see Theorem 5.1.

      PubDate: 2017-02-07T15:18:31Z
       
  • A size-sensitive inequality for cross-intersecting families
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Peter Frankl, Andrey Kupavskii
      Two families A and B of k -subsets of an n -set are called cross-intersecting if A ∩ B ≠ 0̸ for all A ∈ A , B ∈ B . Strengthening the classical Erdős–Ko–Rado theorem, Pyber proved that A B ≤ n − 1 k − 1 2 holds for n ≥ 2 k . In the present paper we sharpen this inequality. We prove that assuming B ≥ n − 1 k − 1 + n − i k − i + 1 for some 3 ≤ i ≤ k + 1 the stronger inequality A B ≤ ( n − 1 k − 1 + n − i k − i + 1 ) ( n − 1 k − 1 − n − i k − 1 ) holds. These inequalities are best possible. We also present a new short proof of Pyber’s inequality and a short computation-free proof of an inequality due to Frankl and Tokushige (1992).

      PubDate: 2017-02-07T15:18:31Z
       
  • W-associahedra have the non-leaving-face property
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Nathan Williams
      We use a projection argument to uniformly prove that W -permutahedra and W -associahedra have the property that if v , v ′ are two vertices on the same face f , then any geodesic between v and v ′ does not leave f . In type A , we show that our geometric projection recovers a slight modification of the combinatorial projection in Sleator et al. (1988).

      PubDate: 2017-02-07T15:18:31Z
       
  • Laminar matroids
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Tara Fife, James Oxley
      A laminar family is a collection A of subsets of a set E such that, for any two intersecting sets, one is contained in the other. For a capacity function c on A , let I be { I : I ∩ A ≤ c ( A )  for all  A ∈ A } . Then I is the collection of independent sets of a (laminar) matroid on E . We present a method of compacting laminar presentations, characterize the class of laminar matroids by their excluded minors, present a way to construct all laminar matroids using basic operations, and compare the class of laminar matroids to other well-known classes of matroids.

      PubDate: 2017-01-31T14:06:29Z
       
  • Exchange of three intervals: Substitutions and palindromicity
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Zuzana Masáková, Edita Pelantová, Štěpán Starosta
      We study purely morphic words coding symmetric non-degenerate three interval exchange transformation which are known to be palindromic, i.e., they contain infinitely many palindromes. We prove that such words are fixed by a conjugate to a morphism of class P , that is, a morphism such that each letter a is mapped to p p a where p and p a are both palindromes. We thus provide a new family of palindromic infinite words satisfying the conjecture of Hof, Knill and Simon. Given a morphism fixing such word, we give a formula to determine the parameters of the underlying three interval exchange and the intercept of the word.

      PubDate: 2017-01-31T14:06:29Z
       
  • Max-cut and extendability of matchings in distance-regular graphs
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Sebastian M. Cioabă, Jack Koolen, Weiqiang Li
      A connected graph G of even order v is called t -extendable if it contains a perfect matching, t < v / 2 and any matching of t edges is contained in some perfect matching. The extendability of G is the maximum t such that G is t -extendable. Since its introduction by Plummer in the 1980s, this combinatorial parameter has been studied for many classes of interesting graphs. In 2005, Brouwer and Haemers proved that every distance-regular graph of even order is 1 -extendable and in 2014, Cioabă and Li showed that any connected strongly regular graph of even order is 3-extendable except for a small number of exceptions. In this paper, we extend and generalize these results. We prove that all distance-regular graphs with diameter D ≥ 3 are 2-extendable and we also obtain several better lower bounds for the extendability of distance-regular graphs of valency k ≥ 3 that depend on k , λ and μ , where λ is the number of common neighbors of any two adjacent vertices and μ is the number of common neighbors of any two vertices in distance two. In many situations, we show that the extendability of a distance-regular graph with valency k grows linearly in k . We conjecture that the extendability of a distance-regular graph of even order and valency k is at least ⌈ k / 2 ⌉ − 1 and we prove this fact for bipartite distance-regular graphs. In course of this investigation, we obtain some new bounds for the max-cut and the independence number of distance-regular graphs in terms of their size and odd girth and we prove that our inequalities are incomparable with known eigenvalue bounds for these combinatorial parameters.

      PubDate: 2017-01-31T14:06:29Z
       
  • Hardness of computing clique number and chromatic number for Cayley graphs
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Chris Godsil, Brendan Rooney
      Computing the clique number and chromatic number of a general graph are well-known NP-Hard problems. Codenotti et al., (1998) showed that computing clique number and chromatic number are both NP-Hard problems for the class of circulant graphs. We show that computing clique number is NP-Hard for the class of Cayley graphs for the groups G n , where G is any fixed finite group (e.g., cubelike graphs). We also show that computing chromatic number cannot be done in polynomial time (under the assumption NP ≠ ZPP ) for the same class of graphs. Our presentation uses free Cayley graphs. The proof combines free Cayley graphs with quotient graphs and Goppa codes.

      PubDate: 2017-01-18T12:25:43Z
       
  • Enumeration of 4-regular one-face maps
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Evgeniy Krasko, Alexander Omelchenko
      We obtain explicit formulas for enumerating rooted and unrooted 4 -regular one-face maps on genus g surfaces. For rooted maps the result is combinatorially derived from Chapuy’s vertex cutting bijection and has a simple sum-free form similar to analogous formulas for general and cubic one-face maps. To enumerate unrooted maps we apply the approach of Liskovets, Mednykh and Nedela of reducing the problem to counting rooted maps on orbifolds. We show that for 4 -regular one-face maps the set of orbifolds to be considered has a simple description, which allows us to obtain the final formula in an explicit form of a sum over 3 integer indices.

      PubDate: 2017-01-18T12:25:43Z
       
  • The Smith normal form of a specialized Jacobi–Trudi matrix
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Richard P. Stanley
      Let JT λ be the Jacobi–Trudi matrix corresponding to the partition λ , so det JT λ is the Schur function s λ in the variables x 1 , x 2 , … . Set x 1 = ⋯ = x n = 1 and all other x i = 0 . Then the entries of JT λ become polynomials in n of the form ( n + j − 1 j ) . We determine the Smith normal form over the ring Q [ n ] of this specialization of JT λ . The proof carries over to the specialization x i = q i − 1 for 1 ≤ i ≤ n and x i = 0 for i > n , where we set q n = y and work over the ring Q ( q ) [ y ] .

      PubDate: 2017-01-18T12:25:43Z
       
  • Set families with a forbidden pattern
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Ilan Karpas, Eoin Long
      A balanced pattern of order 2 d is an element P ∈ { + , − } 2 d , where both signs appear d times. Two sets A , B ⊂ [ n ] form a P -pattern, which we denote by pat ( A , B ) = P , if A △ B = { j 1 , … , j 2 d } with 1 ≤ j 1 < ⋯ < j 2 d ≤ n and { i ∈ [ 2 d ] : P i = + } = { i ∈ [ 2 d ] : j i ∈ A ∖ B } . We say A ⊂ P [ n ] is P -free if pat ( A , B ) ≠ P for all A , B ∈ A . We consider the following extremal question: how large can a family A ⊂ P [ n ] be if A is P -free? We prove a number of results on the sizes of such families. In particular, we show that for some fixed c > 0 , if P is a d -balanced pattern with d < c log log n then ∣ A ∣ = o ( 2 n ) . We then give stronger bounds in the cases when (i) P consists of d + signs, followed by d − signs and (ii) P consists of alternating signs. In both cases, if d = o ( n ) then ∣ A ∣ = o ( 2 n ) . In the case of (i), this is tight.

      PubDate: 2017-01-18T12:25:43Z
       
  • Variants of the Erdős–Szekeres and Erdős–Hajnal
           Ramsey problems
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Dhruv Mubayi
      Given integers ℓ , n , the ℓ th power of the path P n is the ordered graph P n ℓ with vertex set v 1 < v 2 < ⋯ < v n and all edges of the form v i v j where i − j ≤ ℓ . The Ramsey number r ( P n ℓ , P n ℓ ) is the minimum N such that every 2-coloring of [ N ] 2 results in a monochromatic copy of P n ℓ . It is well-known that r ( P n 1 , P n 1 ) = ( n − 1 ) 2 + 1 . For ℓ > 1 , Balko–Cibulka–Král–Kynčl proved that r ( P n ℓ , P n ℓ ) < c ℓ n 128 ℓ and asked for the growth rate for fixed ℓ . When ℓ = 2 , we improve this upper bound substantially by proving r ( P n 2 , P n 2 ) < c n 19.5 . Using this result, we determine the correct tower growth rate of the k -uniform hypergraph Ramsey number of a ( k + 1 ) -clique versus an ordered tight path. Finally, we consider an ordered version of the classical Erdős–Hajnal hypergraph Ramsey problem, improve the tower height given by the trivial upper bound, and conjecture that this tower height is optimal.

      PubDate: 2017-01-18T12:25:43Z
       
  • On generalized hexagons of order (3,t) and (4,t) containing a subhexagon
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Anurag Bishnoi, Bart De Bruyn
      We prove that there are no semi-finite generalized hexagons with q + 1 points on each line containing the known generalized hexagons of order q as full subgeometries when q is equal to 3 or 4 , thus contributing to the existence problem of semi-finite generalized polygons posed by Tits. The case when q is equal to 2 was treated by us in an earlier work, for which we give an alternate proof. For the split Cayley hexagon of order 4 we obtain the stronger result that it cannot be contained as a proper full subgeometry in any generalized hexagon.

      PubDate: 2017-01-11T11:54:39Z
       
  • Cycles in graphs of fixed girth with large size
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): József Solymosi, Ching Wong
      Consider a family of graphs having a fixed girth and a large size. We give an optimal lower asymptotic bound on the number of even cycles of any constant length, as the order of the graphs tends to infinity.

      PubDate: 2017-01-11T11:54:39Z
       
  • On the Zero Defect Conjecture
    • Abstract: Publication date: May 2017
      Source:European Journal of Combinatorics, Volume 62
      Author(s): Sébastien Labbé, Edita Pelantová, Štěpán Starosta
      Brlek et al., conjectured in 2008 that any fixed point of a primitive morphism with finite palindromic defect is either periodic or its palindromic defect is zero. Bucci and Vaslet disproved this conjecture in 2012 by a counterexample over ternary alphabet. We prove that the conjecture is valid on binary alphabet. We also describe a class of morphisms over multiliteral alphabet for which the conjecture still holds. The proof is based on properties of extension graphs.

      PubDate: 2017-01-11T11:54:39Z
       
 
 
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