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We consider all bursts with known redshift and $\nu F_\nu$ peak energy, $E^{obs}_{peak}$. For a good fraction of them an estimate of the jet opening angle is available from the achromatic break of their afterglow light curve. This allows…

Astrophysics · Physics 2009-11-10 G. Ghirlanda , G. Ghisellini , D. Lazzati

Graph matching aims at finding the vertex correspondence between two unlabeled graphs that maximizes the total edge weight correlation. This amounts to solving a computationally intractable quadratic assignment problem. In this paper we…

Machine Learning · Statistics 2019-07-23 Zhou Fan , Cheng Mao , Yihong Wu , Jiaming Xu

Let $M$ be a mixed graph and $H(M)$ be its Hermitian-adjacency matrix. If we add every edge and arc in $M$ a Randi\'c weight, then we can get a new weighted Hermitian-adjacency matrix. What are the properties of this new matrix? Motivated…

Combinatorics · Mathematics 2016-11-01 Yong Lu , Ligong Wang , Qiannan Zhou

We study the logical properties of infinite geometric random graphs, introduced by Bonato and Janssen. These are graphs whose vertex set is a dense ``generic'' subset of a metric space, where two vertices are adjacent with probability $p>0$…

Logic · Mathematics 2023-04-24 Omer Ben-Neria , Itay Kaplan , Tingxiang Zou

A celebrated theorem of Pippenger states that any almost regular hypergraph with small codegrees has an almost perfect matching. We show that one can find such an almost perfect matching which is `pseudorandom', meaning that, for instance,…

Combinatorics · Mathematics 2020-11-18 Stefan Ehard , Stefan Glock , Felix Joos

Energy randomness is a notion of partial randomness introduced by Diamondstone and Kjos-Hanssen to characterize the sequences that can be elements of a Martin-L\"of random closed set (in the sense of Barmpalias, Brodhead, Cenzer, Dashti,…

Logic · Mathematics 2015-09-03 Joseph S. Miller , Jason Rute

We prove two conjectures in spectral extremal graph theory involving the linear combinations of graph eigenvalues. Let $\lambda_1(G)$ be the largest eigenvalue of the adjacency matrix of a graph $G$, and $\bar{G}$ be the complement of $G$.…

Combinatorics · Mathematics 2022-06-09 Lele Liu

The maximum-weight matching problem and the behavior of its energy landscape is numerically investigated. We apply a perturbation method adapted from the analysis of spin glasses. This gives inside into the complexity of the energy…

Disordered Systems and Neural Networks · Physics 2023-04-04 Till Kahlke , Alexander K. Hartmann

We study a variant of the Erd\H{o}s Matching Problem in random hypergraphs. Let $\mathcal{K}_p(n,k)$ denote the Erd\H{o}s-R\'enyi random $k$-uniform hypergraph on $n$ vertices where each possible edge is included with probability $p$. We…

Combinatorics · Mathematics 2025-09-24 Peter Frankl , Jiaxi Nie , Jian Wang

Let $G$ be a simple graph with vertex set $V(G) = \{v_1, v_2,\ldots, v_n\}$. The elliptic Sombor matrix of $G$, denoted by $A_{ESO}(G)$, is defined as the $n\times n$ matrix whose $(i,j)$-entry is $(d_i+d_j)\sqrt{d_i^2+d_j^2}$ if $v_i$ and…

Combinatorics · Mathematics 2024-04-30 Saeid Alikhani , Nima Ghanbari , Mohammad Ali Dehghanizadeh

It was conjectured by Mkrtchyan, Petrosyan, and Vardanyan that every graph $G$ with $\Delta(G)-\delta(G) \le 1$ has a maximum matching $M$ such that any two $M$-unsaturated vertices do not share a neighbor. In this note, we confirm the…

Combinatorics · Mathematics 2016-11-22 Dong Ye

Let $G$ be a graph on $n$ vertices and $m$ edges. For $\alpha \in [0,1]$, the $A_{\alpha}$-matrix of $G$ is defined as $A_{\alpha}(G) = \alpha D(G) + (1- \alpha) A(G)$, where $A(G)$ is the adjacency matrix and $D(G)$ is the degree diagonal…

Combinatorics · Mathematics 2026-03-26 Mainak Basunia , Pratima Panigrahi

Let $ G $ be a simple graph with the vertex cover number $ \tau $. The energy $ \mathcal{E}(G) $ of $ G $ is the sum of the absolute values of all the adjacency eigenvalues of $ G $. In this article, we establish $ \mathcal{E}(G)\geq 2\tau…

Combinatorics · Mathematics 2025-07-02 Aniruddha Samanta

A maximal $\varepsilon$-near perfect matching is a maximal matching which covers at least $(1-\varepsilon)|V(G)|$ vertices. In this paper, we study the number of maximal near perfect matchings in generalized quasirandom and dense graphs. We…

Combinatorics · Mathematics 2019-02-07 Yifan Jing , Akbar Rafiey

In this paper we extend the concept of energy to signed digraphs. We obtain Coulson's integral formula for energy of signed digraphs. Formulae for energies of signed directed cycles are computed and it is shown that energy of non cycle…

Combinatorics · Mathematics 2013-09-25 S. Pirzada , Mushtaq A. Bhat

Let $x_1, x_2, \dots, x_n$ be the eigenvalues of a signed graph $\Gamma$ of order $n$. The energy of $\Gamma$ is defined as $E(\Gamma)=\sum^{n}_{j=1}|x_j|.$ Let $\mathcal{P}_n^4$ be obtained by connecting a vertex of the negative circle…

Combinatorics · Mathematics 2018-09-18 Dijian Wang , Yaoping Hou

We study robust versions of properties of $(n,d,\lambda)$-graphs, namely, the property of a random sparsification of an $(n,d,\lambda)$-graph, where each edge is retained with probability $p$ independently. We prove such results for the…

Combinatorics · Mathematics 2025-11-04 Yaobin Chen , Yu Chen , Jie Han , Jingwen Zhao

The perfectly matchable subgraph polytope of a graph is a (0,1)-polytope associated with the vertex sets of matchings in the graph. In this paper, we study algebraic properties (compressedness, Gorensteinness) of the toric rings of…

Combinatorics · Mathematics 2023-07-18 Kenta Mori

The burning number of a graph $G$ is the smallest positive integer $k$ such that the vertex set of $G$ can be covered with balls of radii $0, 1, \dots, k-1$. A well-known conjecture by Bonato, Janssen and Roshabin states that any connected…

Combinatorics · Mathematics 2023-03-27 Anders Martinsson

A connected graph $G$ with at least $2m + 2n + 2$ vertices which contains a perfect matching is $E(m, n)$-{\it extendable}, if for any two sets of disjoint independent edges $M$ and $N$ with $|M| = m$ and $|N|= n$, there is a perfect…

Combinatorics · Mathematics 2023-06-22 Hongliang Lu , Qinglin Yu
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