Exact Hausdorff and packing measures for random self-similar code-trees with necks
Random code-trees with necks were introduced recently to generalise the notion of $V$-variable and random homogeneous sets. While it is known that the Hausdorff and packing dimensions coincide irrespective of overlaps, their exact Hausdorff and packing measures have so far been largely ignored. In this article we consider the general question of an appropriate gauge function for positive and finite Hausdorff and packing measures. We first survey the current state of knowledge and establish some bounds on these gauge functions. We then show that self-similar code-trees do not admit gauge functions that simultaneously give positive and finite Hausdorff measure almost surely. This surprising result is in stark contrast to the random recursive model and sheds some light on the question of whether $V$-variable sets interpolate between random homogeneous and random recursive sets. We conclude by discussing implications of our results.