From MOND entropy to extended uncertainty principles: A unified framework

Abstract: In this study, we explore the relation between generalised entropies and the extended uncertainty principle (EUP) models. Starting from the higher-order extended uncertainty principle (HOEUP), we obtain the modified entropy-area relation. Then, we derive the modified Friedmann equations through three different approaches: the first law of thermodynamics at the apparent horizon, the entropic gravity case, and the emergence of cosmic space. Furthermore, we check the validity of the generalised second law (GSL). Notably, HOEUP modified Friedmann equations are the limiting cases of those obtained from a recently proposed novel entropy, which is derived from Modified Newtonian Dynamics (MOND) [{\it Phys. Dark Universe} {\bf 49} (2025) 101967]. Motivated by this connection, we derive a novel EUP, referred to as MOND EUP, from a reverse procedure. This novel EUP reproduces to EUP relations associated with Rényi and dual Kaniadakis entropies in the limiting cases. Moreover, we show that HOEUP corresponds to perturbative limit of MOND entropy. The main new result of this paper is a reverse procedure beginning from a recently proposed novel MOND entropy to construct a unified EUP. This reverse procedure is not limited with the present case. In principle, the method can be applied to other generalised entropy formalisms, suggesting that our findings may establish a unified framework that bridges the generalised entropies, cutoff mechanisms, and EUP models. In particular, the corresponding modified uncertainty principles may have effective cutoff mechanisms for the entropy forms, which do not explicitly display cutoff mechanisms. Thus, these entropies may have cutoff mechanism due to their corresponding modified uncertainty principles.