Cauchy sequence F-contraction Hadamard spaces Hilbert space Matemáticas Mathematics & science Research & information: general S-type tricyclic contraction T-contraction T-transitivity almost Rg-Geraghty type contraction b-metric space b-metric-like spaces b2-metric space binary relation binary relations bv(s)-metric space common coupled fixed point common fixed point common fixed points compatible maps convex metric spaces convex minimization problem coupled fixed points cyclic maps demicontractive mappings directed graph end-point equilibrium error estimate