Hitesh Kumar

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20242026

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math.CO2024

A Linear Lower Bound for the Square Energy of Graphs

Saieed Akbari, Hitesh Kumar, Bojan Mohar +1

Let $G$ be a graph of order $n$ with eigenvalues $λ_{1} \geq \dots \geq λ_{n}$ . Let \[s^+(G)=\sum_{λ_i>0} λ_i^2, \qquad s^-(G)=\sum_{λ_i<0} λ_i^2.\] The smaller value, $s(G)=\min\{s^+(…

math.CO2024

On the second largest adjacency eigenvalue of trees with given diameter

Hitesh Kumar, Bojan Mohar, Shivaramakrishna Pragada +1

For a graph $G$ , let $λ_{2} (G)$ denote the second largest eigenvalue of the adjacency matrix of $G$ . We determine the extremal trees with maximum/minimum adjacency eigenvalue $λ_{2}$ i…

math.CO2024

Bollobás-Nikiforov Conjecture for graphs with not so many triangles

Hitesh Kumar, Shivaramakrishna Pragada

Bollobás and Nikiforov conjectured that for any graph $G \neq = K_{n}$ with $m$ edges \[ λ_1^2+λ_2^2\le \bigg( 1-\frac{1}{ω(G)}\bigg)2m\] where $λ_{1}$ and $λ_{2}$ denote the two largest e…