A theoretical preprint posted to arXiv introduces a mathematical framework for understanding how different quantum reference frames lead to observer-dependent entropy assignments. The work, which has not undergone peer review, is purely theoretical and relies on mathematical derivations rather than laboratory experiments; it involves no empirical data, sample sizes, or statistical analysis. Authors show that while observers may assign different entropy values to the same quantum system, these differences are quantitatively constrained. They identify a family of frame-independent diagonal Rényi entropies that apply to arbitrary subsystems and establish a generalized tradeoff between multipartite coherence and entanglement. For ideal reference frames, the observer-dependence of subsystem entropy can be exactly decomposed into single-frame coherences plus inter-frame correlations. For non-ideal frames, the discrepancy is bounded by the dimension of an effective relational Hilbert space dictated by the frames' representation structure. The study notes limitations including idealized assumptions about frame representations and does not address practical implementation challenges. The authors suggest the results could inform discussions of observer-dependent entropy in quantum gravity settings. Source: https://arxiv.org/abs/2603.23598