A Minimal Entropic Derivation of MOND-like Gravity Motivation Verlinde (2016) proposed that de Sitter space contains a volume-scaling entropy associated with dark energy. Matter removes part of this entropy. Beyond a critical scale, the remaining volume entropy dominates and produces an apparent dark gravitational component. Peach (2019) reformulated the idea using an entropic-screen construction. The argument below combines these ideas and fixes the force normalisation using Verlinde's spherical response coefficient. Competing Entropies For a sphere of radius $r$, the de Sitter entropy is $$S_{\rm DE}(r) = \frac{r}{L}\frac{A(r)c^3}{4G\hbar}, \qquad A(r)=4\pi r^2,$$ while a central mass $M$ removes $$S_M(r)=\frac{2\pi Mc}{\hbar}r.$$ Thus $S_{\rm DE}\propto r^3$ and $S_M\propto r$. Define $a_\Lambda=c^2/L$. Their ratio is $$\frac{S_{\rm DE}}{S_M} = \frac{a_\Lambda r^2}{2GM} = \left(\frac{r}{r_c}\right)^2,$$ where $$\boxed{r_c=\sqrt{\frac{2GM}{a_\...
Consider a spherical Schwarzschild horizon of radius $R$. Its energy, temperature, and entropy are $$E=\frac{c^{4}R}{2G},\qquad k_BT_H=\frac{\hbar c}{4\pi R},\qquad S=\frac{k_BA}{4L_P^2},$$ where $A=4\pi R^2$ and $L_P^2=\hbar G/c^3$. 1. Quantized Horizon The horizon's thermal period defines an angular frequency $$\omega_H=\frac{2\pi k_BT_H}{\hbar}=\frac{c}{2R}.$$ Treat the Euclidean horizon cycle as a periodic quantum motion and define its action by $dI=dE/\omega_H$. Since $dE=c^4dR/2G$, we obtain $dI=c^3RdR/G$, and therefore $$I=\frac{c^3R^2}{2G} =\frac{\hbar R^2}{2L_P^2} =\frac{\hbar A}{8\pi L_P^2}.$$ Equivalently, using $dE=T_HdS$, $$I=\frac{\hbar S}{2\pi k_B}.$$ Quantizing this periodic motion gives $$I_n=\left(n+\frac12\right)\hbar, \qquad n=0,1,2,\ldots$$ where the half-unit is the ground-state contribution associated with the regular centre of the Euclidean horizon geometry. Hence $$A_n=4\pi(2n+1)L_P^2, \qquad R_n=\sqrt{2n+1},L_P.$$ Thus the first nonzero hor...