The expansion of polynomial invariants for $2$-decompositions of   generalized graphs
  The $2$-decomposition for ribbon graphs was introduced in [Annals of Combinatorics 15 (2011), pp 675-706]. We extend this result to half-edged ribbon graphs and to rank $D$-weakly colored graphs [SIGMA 12 (2016), 030], generalizing therefore the $2$-sums and tensor products of these graphs. Using this extension for the $2$-decompositions, we provide new expansion formulas for the Bollob\'as Riordan polynomial for half-edged ribbon graphs and also for the polynomial invariant for weakly colored stranded graphs. 
Remi Cocou Avohou
math.CO