Table 1 Sparse balance theory conditions: definitions of sparse structural balance theory that generalize existing definitions of balance.

From: The 1995-2018 global evolution of the network of amicable and hostile relations among nation-states

Balance model

Heider axioms

Structural equation (condition)

  

∀ ijk ∈ V, for every combination:

Classical9

A1, A2, A3, A4

if 7D2 ei k â‰  0 and ek j â‰  0

  

then ei j = ei kek j should be valid

  

∀ ijk ∈ V, for every combination:

Clustering18

A1, A2, A3

if ei k â‰  0 and ek j â‰  0

  

and (ei k > 0 or ek j > 0)

  

then ei j = ei kek j should be valid

  

∀ ijk ∈ V, for every combination:

Transitivity19

A1

and ei k > 0 and ek j > 0

  

then ei j = ei kek j should be valid

  1. Transitivity is the most general model that only requires the first axiom. V represents list of nodes in the network and eij represents the directed edge from node i to node j. For every three nodes of i, j, and k and any combinations of which in the network, the condition should hold to be considered structurally balanced. Supplementary Fig. 2 shows all 138 triads and if each triad is considered balance under any of these definitions.