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We know that $DS$ graphs are such connected graphs that determinable by their adjacency spectrum. Suppose $DS(n)$ and $G(n)$ show the number of $DS$ graphs and all graphs with $n$ vertices,respective …

Let $\mathcal{G}$ be the set of all finite connected simple graphs minus the complete graphs. For any $G\in \mathcal{G}$, let $\lambda_{\geq0}(G)$ denotes the smallest positive adjacency eigenvalue of …

We have the spectrum and the degree sequence of one graph. Can we uniquely determine the graph with these given information?

There are some facts that can be found by the spectrum of adjacency matrix of graph.For example, the number of edges and vertices, is bipartite or not, is complete multipartite or not and so on. Can w …

Suppose $G$ and $H$ are two isospectral connected graphs. Can we say anything about isospectrality of graphs that are obtained by applying a binary operation to $G$ and $H$? For example, to take one s …

Can somebody help me to construct two family of finite simple connected graph $G_i$ and $H_i$, $i=1, 2, \cdots,n$ ($n$ possibly large), such that: $1)$ $G_i‎\ncong H_i$ for $i=1, 2, \cdots, n$ $2)$ …

Let $G$ be a simple graph. We say this graph is self-index complementary ($SIC$) if $\lambda_1 (G)=\lambda_1 (\overline{G})$, where $\lambda_1(G)$ denotes the index of the adjacency matrix of the grap …

The simple connected graph $G$ has $n$ vertices and we have: 1) $|E(G)|‎\geq‎ \frac{n(n-1)}{3}$ 2) we have the spectrum and degree sequence of $G$ 3) $Spectrum(G)=Spectrum(H)$ Is $G \cong ‎H$?

Firstly, I apologize if the question is long. I appreciate any helpful answers and ideas. In the following all graphs are simple and connected. Let $G$ be graph with vertex set $V=\left\{v_1,v_2,\ld …

I am looking for a large family (infinite pairs) of cospectral graphs with these condtions: The graphs are non-regular, Minimum degree is greater than $1$, The degree sequences of these cospectral …

In spectral graph theory, there is a conjecture that claims: Almost every graph is determined by its adjacency spectrum ($DS$). This conjecture belongs to professor Willem Haemers. Also, we have a res …