Full twists factorization formula for double number of strings

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A formula for factorizations of the full twist in the braid group Br₂ₘ depending on any four factorizations of the full twist in Brₘ is given. Applying this formula, a symplectic 4-manifold X and two isotopic generic coverings fᵢ:X→ CP², branched, respectively, along cuspidal Hurwitz curves Hᵢ⊂ CP² (without negative nodes) having different braid monodromy factorization types, are constructed. The class of the fundamental groups of the complements of the affine plane Hurwitz curves is described in terms of generators and defining relations.