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We consider continuous-time quantum walks on distance-regular graphs of small diameter. Using results about the existence of complex Hadamard matrices in association schemes, we determine which of these graphs have quantum walks that admit…

Combinatorics · Mathematics 2014-03-12 Chris Godsil , Natalie Mullin , Aidan Roy

The topological (or graph) structures of real-world networks are known to be predictive of multiple dynamic properties of the networks. Conventionally, a graph structure is represented using an adjacency matrix or a set of hand-crafted…

Social and Information Networks · Computer Science 2016-10-21 Cheng Li , Xiaoxiao Guo , Qiaozhu Mei

This paper represents a significant leap forward in the problem of enumerating vertex-transitive graphs. Recent breakthroughs on symmetry of Cayley (di)graphs show that almost all finite Cayley (di)graphs have the smallest possible…

Combinatorics · Mathematics 2025-11-25 Yunsong Gan , Pablo Spiga , Binzhou Xia

This paper considers *-graphs in which all vertices have degree 4 or 6, and studies the question of calculating the genus of orientable 2-surfaces into which such graphs may be embedded. A *-graph is a graph endowed with a formal adjacency…

Combinatorics · Mathematics 2012-12-27 Tyler Friesen , Vassily Manturov

Graphical models are commonly used to represent conditional dependence relationships between variables. There are multiple methods available for exploring them from high-dimensional data, but almost all of them rely on the assumption that…

Machine Learning · Statistics 2020-04-22 Tianxi Li , Cheng Qian , Elizaveta Levina , Ji Zhu

The low energy expansion of Type II superstring amplitudes at genus one is organized in terms of modular graph functions associated with Feynman graphs of a conformal scalar field on the torus. In earlier work, surprising identities between…

High Energy Physics - Theory · Physics 2017-10-16 Eric D'Hoker , Justin Kaidi

For any positive integer $m$, the complete graph on $2^{2m}(2^m+2)$ vertices is decomposed into $2^m+1$ commuting strongly regular graphs, which give rise to a symmetric association scheme of class $2^{m+2}-2$. Furthermore, the…

Combinatorics · Mathematics 2017-01-23 Hadi Kharaghani , Sara Sasani , Sho Suda

We generalize the concept of strong walk-regularity to directed graphs. We call a digraph strongly $\ell$-walk-regular with $\ell >1$ if the number of walks of length $\ell$ from a vertex to another vertex depends only on whether the two…

Combinatorics · Mathematics 2017-09-13 Edwin R. van Dam , Gholamreza Omidi

In 2015, Bogdanowicz gave a necessary and sufficient condition for a 4-regular circulant graph to be isomorphic to the Cartesian product of two cycles. Accordion graphs, denoted by $A[n,k]$, are 4-regular graphs on two parameters $n$ and…

Combinatorics · Mathematics 2021-11-11 John Baptist Gauci , Jean Paul Zerafa

We compare three transitivity properties of finite graphs, namely, for a positive integer $s$, $s$-distance transitivity, $s$-geodesic transitivity and $s$-arc transitivity. It is known that if a finite graph is $s$-arc transitive but not…

Combinatorics · Mathematics 2011-10-12 Alice Devillers , Wei Jin , Cai Heng Li , Cheryl E. Praeger

Large continuous-time Markov chains with exponentially small transition rates arise in modeling complex systems in physics, chemistry and biology. We propose a constructive graph-algorithmic approach to determine the sequence of critical…

Probability · Mathematics 2017-02-01 Tingyue Gan , Maria Cameron

Despite several advances in recent years, learning causal structures represented by directed acyclic graphs (DAGs) remains a challenging task in high dimensional settings when the graphs to be learned are not sparse. In this paper, we…

Machine Learning · Computer Science 2023-05-16 Zhuangyan Fang , Shengyu Zhu , Jiji Zhang , Yue Liu , Zhitang Chen , Yangbo He

The authors studied in [Ann. Inst. Henri Poincar\'e D 9, 367-433, (2022)], a complex multi-matrix model with $\mathrm{U}(N)^2 \times \mathrm{O}(D)$ symmetry, and whose double scaling limit where simultaneously the large-$N$ and large-$D$…

Mathematical Physics · Physics 2024-11-28 Rémi Cocou Avohou , Reiko Toriumi , Matthias Vancraeynest

As an extension of the Four-Color Theorem it is conjectured that every planar graph of odd-girth at least $2k+1$ admits a homomorphism to $PC_{2k}=(\mathbb{Z}_2^{2k}, \{e_1, e_2, ...,e_{2k}, J\})$ where $e_i$'s are standard basis and $J$ is…

Combinatorics · Mathematics 2015-01-22 Reza Naserasr , Sagnik Sen , Qiang Sun

The field of two-dimensional (2D) materials has expanded to multilayered systems where electronic, optical, and mechanical properties change-often dramatically-with stacking order, thickness, twist, and interlayer spacing [1-5]. For…

Materials Science · Physics 2019-06-27 Suk Hyun Sung , Noah Schnitzer , Lola Brown , Jiwoong Park , Robert Hovden

A mixed dihedral group is a group $H$ with two disjoint subgroups $X$ and $Y$, each elementary abelian of order $2^n$, such that $H$ is generated by $X\cup Y$, and $H/H'\cong X\times Y$. In this paper, for each $n\geq 2$, we construct a…

Combinatorics · Mathematics 2023-03-02 Daniel R. Hawtin , Jin-Xin Zhou , Cheryl E. Praeger

In this paper, some results concerning the colorings of graph powers are presented. The notion of helical graphs is introduced. We show that such graphs are hom-universal with respect to high odd-girth graphs whose $(2t+1)$st power is…

Combinatorics · Mathematics 2008-03-31 Hossein Hajiabolhassan

Building upon [1], this study aims to introduce fractal geometry into graph theory, and to establish a potential theoretical foundation for complex networks. Specifically, we employ the method of substitution to create and explore…

Dynamical Systems · Mathematics 2024-05-29 Nero Ziyu Li

The concept of domination in graphs plays a central role in understanding structural properties and applications in network theory. In this study, we focus on the paired disjunctive domination number in the context of middle graphs, a…

Discrete Mathematics · Computer Science 2025-12-19 Hande Tuncel Golpek , Zeliha Kartal Yildiz , Aysun Aytac

A vertex subset S of a graph G is said to 2-dominate the graph if each vertex not in S has at least two neighbors in it. As usual, the associated parameter is the minimum cardinal of a 2-dominating set, which is called the 2-domination…

Combinatorics · Mathematics 2024-09-26 José Antonio Martínez , Ana Belén Castaño-Fernández , María Luz Puertas