Pub Date : 2025-02-19DOI: 10.1016/j.dam.2025.02.007
Mareike Fischer , Michael Hendriksen
In a recent study, Bryant, Francis and Steel investigated the concept of “future-proofing” consensus methods in phylogenetics. That is, they investigated if such methods can be robust against the introduction of additional data like added trees or new species. In the present manuscript, we analyze consensus methods under a different aspect of introducing new data, namely concerning the discovery of new clades. In evolutionary biology, often formerly unresolved clades get resolved by refined reconstruction methods or new genetic data analyses. In our manuscript we investigate which properties of consensus methods can guarantee that such new insights do not disagree with previously found consensus trees, but merely refine them, a property termed monotonicity. Along the lines of analyzing monotonicity, we also study two established supertree methods, namely Matrix Representation with Parsimony (MRP) and Matrix Representation with Compatibility (MRC), which have also been suggested as consensus methods in the literature. While we (just like Bryant, Francis and Steel in their recent study) unfortunately have to conclude some negative answers concerning general consensus methods, we also state some relevant and positive results concerning the majority rule () and strict consensus methods, which are amongst the most frequently used consensus methods. Moreover, we show that there exist infinitely many consensus methods which are monotonic and have some other desirable properties.
{"title":"A survey of the monotonicity and non-contradiction of consensus methods and supertree methods","authors":"Mareike Fischer , Michael Hendriksen","doi":"10.1016/j.dam.2025.02.007","DOIUrl":"10.1016/j.dam.2025.02.007","url":null,"abstract":"<div><div>In a recent study, Bryant, Francis and Steel investigated the concept of “future-proofing” consensus methods in phylogenetics. That is, they investigated if such methods can be robust against the introduction of additional data like added trees or new species. In the present manuscript, we analyze consensus methods under a different aspect of introducing new data, namely concerning the discovery of new clades. In evolutionary biology, often formerly unresolved clades get resolved by refined reconstruction methods or new genetic data analyses. In our manuscript we investigate which properties of consensus methods can guarantee that such new insights do not disagree with previously found consensus trees, but merely refine them, a property termed <em>monotonicity</em>. Along the lines of analyzing monotonicity, we also study two established supertree methods, namely Matrix Representation with Parsimony (MRP) and Matrix Representation with Compatibility (MRC), which have also been suggested as consensus methods in the literature. While we (just like Bryant, Francis and Steel in their recent study) unfortunately have to conclude some negative answers concerning general consensus methods, we also state some relevant and positive results concerning the majority rule (<span><math><mstyle><mi>M</mi><mi>R</mi></mstyle></math></span>) and strict consensus methods, which are amongst the most frequently used consensus methods. Moreover, we show that there exist infinitely many consensus methods which are monotonic and have some other desirable properties.</div></div>","PeriodicalId":50573,"journal":{"name":"Discrete Applied Mathematics","volume":"368 ","pages":"Pages 1-17"},"PeriodicalIF":1.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-17DOI: 10.1016/j.dam.2025.02.013
Hengzhe Li , Menghan Ma , Shuli Zhao , Xiao Zhao , Xiaohui Hua , Yingbin Ma , Hong-Jian Lai
<div><div>Let <span><math><mi>H</mi></math></span> be a connected subgraph of a connected graph <span><math><mi>G</mi></math></span>. The <span><math><mi>H</mi></math></span>-structure connectivity of the graph <span><math><mi>G</mi></math></span>, denoted by <span><math><mrow><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><mi>H</mi><mo>)</mo></mrow></mrow></math></span>, is the minimum cardinality of a set of disjoint subgraphs <span><math><mrow><mi>F</mi><mo>=</mo><mrow><mo>{</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span> in <span><math><mi>G</mi></math></span>, such that every <span><math><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>F</mi></mrow></math></span> is isomorphic to <span><math><mi>H</mi></math></span> and <span><math><mrow><mi>G</mi><mo>−</mo><msub><mrow><mo>∪</mo></mrow><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>F</mi></mrow></msub><mi>V</mi><mrow><mo>(</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> is disconnected or trivial. By definition, the vertex connectivity of a graph <span><math><mi>G</mi></math></span> equals its <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>-structure connectivity, that is, <span><math><mrow><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo></mrow><mo>=</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span>. Define <span><math><mrow><msub><mrow><mi>κ</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>=</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></mrow></mrow></math></span>, known as the <em>matching-connectivity</em> of <span><math><mi>G</mi></math></span>.</div><div>In this paper, we prove that <span><math><mrow><msub><mrow><mi>κ</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> is well-defined if and only if <span><math><mrow><mi>G</mi><mo>∉</mo><mrow><mo>{</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>,</mo><mi>n</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span>. For a connected graph <span><math><mrow><mi>G</mi><mo>∉</mo><mrow><mo>{</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>,</mo><mi>n</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span>, we prove <span><math><mrow><mrow><mo>⌈</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>/</mo><mn>2</mn><mo>⌉</mo></mrow><mo>≤</mo><msub><mrow><mi
{"title":"The matching-connectivity of a graph","authors":"Hengzhe Li , Menghan Ma , Shuli Zhao , Xiao Zhao , Xiaohui Hua , Yingbin Ma , Hong-Jian Lai","doi":"10.1016/j.dam.2025.02.013","DOIUrl":"10.1016/j.dam.2025.02.013","url":null,"abstract":"<div><div>Let <span><math><mi>H</mi></math></span> be a connected subgraph of a connected graph <span><math><mi>G</mi></math></span>. The <span><math><mi>H</mi></math></span>-structure connectivity of the graph <span><math><mi>G</mi></math></span>, denoted by <span><math><mrow><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><mi>H</mi><mo>)</mo></mrow></mrow></math></span>, is the minimum cardinality of a set of disjoint subgraphs <span><math><mrow><mi>F</mi><mo>=</mo><mrow><mo>{</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><mo>…</mo><mo>,</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span> in <span><math><mi>G</mi></math></span>, such that every <span><math><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>F</mi></mrow></math></span> is isomorphic to <span><math><mi>H</mi></math></span> and <span><math><mrow><mi>G</mi><mo>−</mo><msub><mrow><mo>∪</mo></mrow><mrow><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>F</mi></mrow></msub><mi>V</mi><mrow><mo>(</mo><msub><mrow><mi>F</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> is disconnected or trivial. By definition, the vertex connectivity of a graph <span><math><mi>G</mi></math></span> equals its <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>-structure connectivity, that is, <span><math><mrow><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>)</mo></mrow><mo>=</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span>. Define <span><math><mrow><msub><mrow><mi>κ</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>=</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>;</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></mrow></mrow></math></span>, known as the <em>matching-connectivity</em> of <span><math><mi>G</mi></math></span>.</div><div>In this paper, we prove that <span><math><mrow><msub><mrow><mi>κ</mi></mrow><mrow><mi>M</mi></mrow></msub><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> is well-defined if and only if <span><math><mrow><mi>G</mi><mo>∉</mo><mrow><mo>{</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>,</mo><mi>n</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span>. For a connected graph <span><math><mrow><mi>G</mi><mo>∉</mo><mrow><mo>{</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn><mi>n</mi></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mi>n</mi><mo>,</mo><mi>n</mi></mrow></msub><mo>}</mo></mrow></mrow></math></span>, we prove <span><math><mrow><mrow><mo>⌈</mo><mi>κ</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>/</mo><mn>2</mn><mo>⌉</mo></mrow><mo>≤</mo><msub><mrow><mi","PeriodicalId":50573,"journal":{"name":"Discrete Applied Mathematics","volume":"367 ","pages":"Pages 210-217"},"PeriodicalIF":1.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-17DOI: 10.1016/j.dam.2025.02.016
Ping Li
An edge-coloring of graph is called closed-neighborhood (resp. open-neighborhood) conflict-free edge-coloring if for every edge , there is a color assigned to exactly one edge among (resp. ). The smallest number of colors needed in any possible closed-neighborhood (resp. open-neighborhood) conflict-free edge-coloring of , denoted (resp. ), is called the closed-neighborhood (resp. open-neighborhood) conflict-free index of . In this paper, we prove that decide whether or is NP-complete, even if is a bipartite graph.
{"title":"Complexity results for two kinds of conflict-free edge-coloring of graphs","authors":"Ping Li","doi":"10.1016/j.dam.2025.02.016","DOIUrl":"10.1016/j.dam.2025.02.016","url":null,"abstract":"<div><div>An edge-coloring of graph <span><math><mi>G</mi></math></span> is called <em>closed-neighborhood</em> (resp. <em>open-neighborhood</em>) <em>conflict-free edge-coloring</em> if for every edge <span><math><mrow><mi>u</mi><mi>v</mi><mo>∈</mo><mi>E</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span>, there is a color assigned to exactly one edge among <span><math><mrow><mi>E</mi><mrow><mo>(</mo><mi>u</mi><mo>)</mo></mrow><mo>∪</mo><mi>E</mi><mrow><mo>(</mo><mi>v</mi><mo>)</mo></mrow></mrow></math></span> (resp. <span><math><mrow><mi>E</mi><mrow><mo>(</mo><mi>u</mi><mo>)</mo></mrow><mo>∪</mo><mi>E</mi><mrow><mo>(</mo><mi>v</mi><mo>)</mo></mrow><mo>−</mo><mrow><mo>{</mo><mi>u</mi><mi>v</mi><mo>}</mo></mrow></mrow></math></span>). The smallest number of colors needed in any possible closed-neighborhood (resp. open-neighborhood) conflict-free edge-coloring of <span><math><mi>G</mi></math></span>, denoted <span><math><mrow><msubsup><mrow><mi>χ</mi></mrow><mrow><mi>C</mi><mi>F</mi></mrow><mrow><mo>′</mo></mrow></msubsup><mrow><mo>[</mo><mi>G</mi><mo>]</mo></mrow></mrow></math></span> (resp. <span><math><mrow><msubsup><mrow><mi>χ</mi></mrow><mrow><mi>C</mi><mi>F</mi></mrow><mrow><mo>′</mo></mrow></msubsup><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span>), is called the <em>closed-neighborhood</em> (resp. <em>open-neighborhood</em>) <em>conflict-free index</em> of <span><math><mi>G</mi></math></span>. In this paper, we prove that decide whether <span><math><mrow><msubsup><mrow><mi>χ</mi></mrow><mrow><mi>C</mi><mi>F</mi></mrow><mrow><mo>′</mo></mrow></msubsup><mrow><mo>[</mo><mi>G</mi><mo>]</mo></mrow><mo>=</mo><mn>2</mn></mrow></math></span> or <span><math><mrow><msubsup><mrow><mi>χ</mi></mrow><mrow><mi>C</mi><mi>F</mi></mrow><mrow><mo>′</mo></mrow></msubsup><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>=</mo><mn>2</mn></mrow></math></span> is NP-complete, even if <span><math><mi>G</mi></math></span> is a bipartite graph.</div></div>","PeriodicalId":50573,"journal":{"name":"Discrete Applied Mathematics","volume":"367 ","pages":"Pages 218-225"},"PeriodicalIF":1.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-16DOI: 10.1016/j.dam.2025.02.011
Zhenzhen Li, Baoyindureng Wu
An edge-colored graph is called properly connected if every pair of distinct vertices of is connected by a proper path. For a connected graph , the proper connection number of , denoted by , is defined as the smallest number of colors that are needed in order to make properly connected. Guan, Xue, Cheng and Yang (Guan et al., 2019) conjectured that if is a connected graph of order , and , then , where takes the value 1 if and 0 if . We confirm the validity of the conjecture.
{"title":"Minimum degree and size conditions for the graphs of proper connection number 2","authors":"Zhenzhen Li, Baoyindureng Wu","doi":"10.1016/j.dam.2025.02.011","DOIUrl":"10.1016/j.dam.2025.02.011","url":null,"abstract":"<div><div>An edge-colored graph <span><math><mi>G</mi></math></span> is called properly connected if every pair of distinct vertices of <span><math><mi>G</mi></math></span> is connected by a proper path. For a connected graph <span><math><mi>G</mi></math></span>, the proper connection number of <span><math><mi>G</mi></math></span>, denoted by <span><math><mrow><mi>p</mi><mi>c</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span>, is defined as the smallest number of colors that are needed in order to make <span><math><mi>G</mi></math></span> properly connected. Guan, Xue, Cheng and Yang (Guan et al., 2019) conjectured that if <span><math><mi>G</mi></math></span> is a connected graph of order <span><math><mi>n</mi></math></span>, <span><math><mrow><mi>δ</mi><mo>≥</mo><mn>3</mn></mrow></math></span> and <span><math><mrow><mrow><mo>|</mo><mi>E</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>|</mo></mrow><mo>≥</mo><mfenced><mfrac><mrow><mi>n</mi><mo>−</mo><mi>p</mi><mo>−</mo><mrow><mo>(</mo><mn>3</mn><mo>−</mo><mi>p</mi><mo>)</mo></mrow><mrow><mo>(</mo><mi>δ</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow></mrow><mrow><mn>2</mn></mrow></mfrac></mfenced><mo>+</mo><mrow><mo>(</mo><mn>3</mn><mo>−</mo><mi>p</mi><mo>)</mo></mrow><mfenced><mfrac><mrow><mi>δ</mi><mo>+</mo><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac></mfenced><mo>+</mo><mn>4</mn></mrow></math></span>, then <span><math><mrow><mi>p</mi><mi>c</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow><mo>≤</mo><mn>2</mn></mrow></math></span>, where <span><math><mi>p</mi></math></span> takes the value 1 if <span><math><mrow><mi>δ</mi><mo>=</mo><mn>3</mn></mrow></math></span> and 0 if <span><math><mrow><mi>δ</mi><mo>≥</mo><mn>4</mn></mrow></math></span>. We confirm the validity of the conjecture.</div></div>","PeriodicalId":50573,"journal":{"name":"Discrete Applied Mathematics","volume":"367 ","pages":"Pages 179-194"},"PeriodicalIF":1.0,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-14DOI: 10.1016/j.dam.2025.02.015
Weidong Li , Yaru Yang , Man Xiao , Xin Chen , Małgorzata Sterna , Jacek Błażewicz
In this paper, we introduce a novel scheduling criterion named as a discounted profit (to be maximized), which could be considered as a generalization of early work (also to be maximized). The goals of such scheduling models are to maximize , where