Characteristic box dimension of unit-time map near nilpotent singularity   of planar vector field and applications
  This article shows how box dimension of the unit-time map can be used in studying the multiplicity of nilpotent singularities of planar vector fields. Using unit-time map on the characteristic curve of nilpotent singularity we define characteristic map and characteristic box dimension of the unit-time map. We study connection between the box dimension of discrete orbits generated by the unit-time map of planar vector fields on the characteristic or invariant curves, and the multiplicity of singularities. Nilpotent singularities which are studied are nilpotent node, focus and cusp. Also, we show how box dimension of the Poincar\' e map near the nilpotent focus on the characteristic curve reveals the upper bound for cyclicity. Moreover, we study the characteristic box dimension of nilpotent cusp at infinity which is connected to the order of cusp. At the end, we applied the results of box dimension of unit-time map to the Bogdanov-Takens bifurcation. 
Lana Horvat Dmitrovi\'c and Vesna \v{Z}upanovi\'c
math.DS