Large Cycles in Graphs Around Conjectures of Bondy and Jung -- Modifications and Sharpness

A number of new sufficient conditions for generalized cycles (large cycles including Hamilton and dominating cycles as special cases) in an arbitrary $k$-connected graph $(k=1,2,\mathrm{.}\mathrm{.}\mathrm{.})$ and new lower bounds for the circumference (the length of a longest cycle) are derived, inspiring a number of modifications of famous conjectures of Bondy (1980) and Jung (2001). All results (both old and new) are shown to be best possible in a sense based on three types of sharpness indicating the intervals in which the result is sharp and the intervals in which the result can be further improved. In addition, the presented modifications cannot be derived directly from Bondy’s and Jung’s conjectures as special cases.