Total restrained coalitions in graphs

Abstract A vertex set in a graph without isolated vertices is a total restrained dominating set (TRD-set) if it is dominating, induces a subgraph without isolated vertices, and the vertices not in the set also induce a subgraph without isolated vertices. Two vertex sets, which are not TRD-sets, form a total restrained coalition if their union is a TRD-set. A total restrained coalition partition is a partition where none of its elements are TRD-sets, but each forms a total restrained coalition with another element. The goal is to maximize the cardinality of such a partition, denoted $$C_{tr}(G)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>C</mml:mi> <mml:mrow> <mml:mi>tr</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>G</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> . We initiate the study of this concept by proving certain properties, extremal values, general bounds, and its relation to known structural parameters. Exact values for specific graph families are also provided.