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What If Dark Gravity Is Just Entropy Winning?

  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_\...
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Is ΛCDM Holographic?

 $\Lambda$CDM and Holographic Dark Energy   Holographic dark energy (HDE) starts from a simple thought: the energy inside a region of size $L$ shouldn't exceed that of a black hole of the same size. Saturate that bound, up to a dimensionless number $c$ (not the speed of light), and $$\rho_{\rm DE}=3M_p^2\frac{c^2}{L^2}, \qquad\text{i.e.}\qquad c=HL\sqrt{\Omega_{\rm DE}}.$$ Units $\hbar=k=1$, $M_p^2=1/8\pi G$, prime $=d/d\ln a$, flat universe, $\Omega_X=\rho_X/3M_p^2H^2$. Li's Model In Li's 2004 model, $L$ is the future event horizon , the farthest a light ray sent today will ever get: $$L_e=a\int_t^\infty\frac{dt'}{a(t')}, \qquad \dot L_e=HL_e-1.$$ Li took $c$ constant, giving $w_{\rm DE}=-\frac13\left(1+\frac{2\sqrt{\Omega_{\rm DE}}}{c}\right)$. And this is where the problems begin. With $c=1$ and $\Omega_{\rm DE,0}=0.6889$, $w_0=-0.887$, about $5\sigma$ from Planck 2018 $w_0=-1.03\pm0.03$. Does not match observations! And any constant $c<1$ gives $w<...
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Blurring the horizon - the quantum width of the cosmic event horizon

A  paper by Zurek applied a random walk argument to a black hole horizon. Credit, Zurek, 2021 Zurek  ( Snowmass 2021 White Paper: Observational Signatures of Quantum Gravity )  called this a blurring of the horizon — a fuzzy, or uncertain horizon — and went through derivations supporting the idea that this length scale is the quantum uncertainty in the position of the black hole horizon: a dynamic quantum width of an event horizon. This is a concept which fundamentally applies to the Universe's own Cosmic Event Horizon (CEH). The Bekenstein-Hawking entropy gives the number of quantum degrees of freedom that can fluctuate. Below, we step out our own cosmic de Sitter derivation of the random walk argument. To do this, let $l_{\Lambda}$ represent the generalised de Sitter horizon scale. Due to the holographic UV/IR correspondence, this scale manifests dually: at the fundamental microscopic limit as $l_{UV} = 2L_p$ (the gravitational/casual limit, aka the Schwarzschild radi...
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The Cosmic Strange Metal

      Strange metals, quantum spin liquids, and SYK-like systems share a striking transport pattern: no quasiparticles, strong collective dynamics, Planckian relaxation, near-minimal viscosity, and maximal chaos. Their characteristic data are $$\frac{\eta}{s}=\frac{\hbar}{4\pi k_B}, \qquad \lambda_L=\frac{2\pi k_BT}{\hbar}, \qquad \tau_P=\frac{\hbar}{k_BT}.$$ The claim is not that the three-dimensional de Sitter bulk is literally a strange metal. The sharper claim is: $$\boxed{\text{The de Sitter stretched horizon belongs to the same transport universality class as a Planckian strange metal.}}$$ The correspondence applies to the horizon membrane, not to bulk spacetime. Membrane Paradigm and the KSS Value In the membrane paradigm, an event horizon behaves for exterior observers as a stretched viscous membrane with transport coefficients fixed by Einstein gravity. This does not require an assumed AdS/CFT dual. For de Sitter, $$\ell_\Lambda=\frac{c}{H}, \qquad T_{dS...
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Our cosmic event horizon on a string

A Cosmic Stringy Adventure ! As we previously discussed, our spacetime characterised by a positive cosmological constant $\Lambda$. The natural bounds are then a minimal  ultraviolet (UV) length $l_{UV} = 2L_P$ and an infrared (IR) cosmological horizon $l_{\Lambda}$.  This dual-boundary spacetime enforces a fundamental Compton–gravitational duality . Every geometric scale $r$ carries two natural mass definitions: $$m_C(r) = \frac{\hbar}{rc}, \qquad m_G(r) = \frac{c^2}{4G}\ r$$ The product of these masses, $m_C \ m_G = M_P^2/4$, is scale-independent. They intersect exclusively at the UV boundary $r = l_{UV}$, defining a maximal local force in GR: $F_{max} = c^4 / 4G$. At the opposite extreme, the Compton mass evaluated at the IR horizon yields the fundamental  spectral gap  (not a particle) of the universe: $m_s = \hbar / (l_{\Lambda} c)$.  In this post, to explore how energy propagates through this dual-scale geometry, we model the mass gap $m_s$ as a null-ener...
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