Hopf insulators are characterized by a topological invariant called the Hopf index which classifies maps from three-sphere to two-sphere, instead of a Chern number or a Chern parity. In contrast to a topological insulator, the Hopf insulator is not protected by any kind of symmetry. By dimensional reduction, we argue that there exists a new type of Z(2) index for 2D Hamiltonian with a vanishing...

Let G be a simple connected graph with n vertices and m edges and let d(e1) > d(e2) > · · · > d(em) be edge degree sequence of graph G. Denote by EF = ∑m i=1 d(ei) 3 reformulated forgotten index of G. Lower and upper bounds for the invariant EF are obtained.

Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. In this paper we introduce four Z 2 topological indices ␨ k =0,1 at k = ͑0,0͒, ͑0,␲͒, ͑␲ ,0͒, and ͑␲ , ␲͒ characterizing 16...

We discuss the Witten index in terms of Krein's spectral shift function, and prove invariance of the Witten index under suitable relative trace class hypotheses.

During the last two decades a large number of numerical graph invariants (topological indices) have been defined and used for correlation analysis in theoretical chemisty, pharmacology, toxicology, and environmental chemistry. However, no systematic study has been undertaken to determine to what extent these indices are correlated with each other. In the present paper we have carried out a prin...

The rst Zagreb index of a graph is equal to the sum of the square of the vertex degrees of the graph and the forgotten topological index (Findex) of a graph is de ned as the sum of cubes of the vertex degrees of the graph. These parameters have applications in chemistry and drug structures. For any xed integer d ≥ 2, the d-ary tree is a rooted tree in which each node has no more than d children...

The intercorrelation between a series of physicochemical parameters and topological indices for a set of beta-blockers is investigated. Partition coefficients are calculated using the ClogP program, and the results are compared with previous data, both experimental and theoretical. These data are complemented by hydrophilicity and solubility calculations, together with the determination of mole...

Motivated by the recent experimental success in realizing synthetic spin-orbit coupling in ultracold atomic systems, we consider N -component atoms coupled to a non-Abelian SU(N) gauge field. More specifically, we focus on the case, referred to here as “SU(3) spin-orbit-coupling,” where the internal states of three-component atoms are coupled to their momenta via a matrix structure that involve...

The generalized Mycielskians are the generalization of the Mycielski graphs, which were introduced by Mycielski in 1955. A topological index is a numeric parameter mathematically derived from a graph and is invariant under automorphism of graphs. Topological indices are widely used for establishing correlations between the structure of a molecular compound and its different physico-chemical pro...

A procedure allowing for the construction of Lorentz invariant integrable models living in d+1 dimensional space-time and with an n dimensional target space is provided. Here, integrability is understood as the existence of the generalized zero-curvature formulation and infinitely many conserved quantities. A close relation between the Lagrange density of the integrable models and the pullback ...