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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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A First Quantum Horizon and Cosmic Information

  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...

Minimum and Maximum Mass from the Cosmic Horizon

  A positive cosmological constant sets the future cosmic event-horizon radius of an expanding FLRW universe: $$l_\Lambda=\sqrt{\frac{3}{\Lambda}}.$$ Associate two lengths with a positive mass $m$: $$\bar\lambda_C=\frac{\hbar}{mc} \qquad r_g=\frac{2Gm}{c^2}$$ where $\bar\lambda_C$ is the reduced Compton wavelength and $r_g$ is the gravitational radius. Requiring both lengths not to exceed the cosmic horizon, $$\bar\lambda_C\le l_\Lambda \qquad r_g\le l_\Lambda,$$ gives $$\boxed{ m_{\min}= m_s=\frac{\hbar}{cl_\Lambda} =\frac{\hbar}{c}\sqrt{\frac{\Lambda}{3}} }$$ $m_s$ is the minimum mass first pointed out by Wesson , 2003. This was also adopted by  Bohmer and Harko , 2005 to derive a  minimum density for static bodies  using the cosmological Buchdahl inequality. and $$\boxed{ m_{\max}=\frac{c^2l_\Lambda}{2G} =\frac{c^2}{2G}\sqrt{\frac{3}{\Lambda}} \equiv m_{\rm CEH}. }$$ Wesson also conjectured a maximum mass, but was off by a factor of 2, as well ...

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<...

Zeta Zeros as Logarithmic Spiral Waves

Zeta Zeros as Logarithmic Spiral Waves Matthew R. Watkins gives a striking geometric interpretation of the nontrivial zeros of the Riemann zeta function as generating "spiral wave" contributions whose superposition encodes fluctuations in Chebyshev's prime-counting function $\psi(x)$. Watkins observes that $x^\rho$ maps the positive real axis onto a logarithmic spiral, while conjugate zeros combine to produce real logarithmically rescaled waveforms. See: Matthew R. Watkins, " Encoding the Zeta Zeros "    The algebra below is elementary complex exponentiation; Watkins's contribution is the geometric spiral-wave interpretation. Let $\rho=\beta+i\gamma$ and $t=\ln x$. Then $$x^\rho=e^{\rho\ln x} = e^{\beta t}e^{i\gamma t} = e^{\beta t}\left(\cos(\gamma t)+i\sin(\gamma t)\right).$$ So $\beta$ is the amplitude growth rate in logarithmic time, and $\gamma$ is the angular frequency in logarithmic time. The frequency in cycles per unit $t$ is $f=|\gamma|/(2\...

De Sitter Horizon: Surface Tension, Laplace Pressure, and What They Actually Mean

  In the static patch of de Sitter spacetime , the cosmological horizon behaves thermodynamically in ways closely analogous to a physical interface. One can assign it entropy, temperature, and even an effective surface tension . Remarkably, the familiar Young–Laplace pressure relation from surface physics appears naturally at the horizon.      In the static patch of de Sitter spacetime, the cosmological horizon admits a useful surface-thermodynamic description. It has an effective surface tension and pressure satisfying a Young–Laplace-like relation. Use $G=c=\hbar=k_B=1$. The metric is $$ds^2=-f(r),dt^2+\frac{dr^2}{f(r)}+r^2d\Omega^2, \qquad f(r)=1-\frac{r^2}{L^2}, \qquad L=\sqrt{\frac3\Lambda}.$$ The horizon is at $r=L$. 1. Horizon Data The area, entropy, and temperature are $$A=4\pi L^2, \qquad S=\frac A4=\pi L^2, \qquad T=\frac{1}{2\pi L}.$$ The Misner–Sharp energy is $M(r)=\frac r2(1-f)=\frac{r^3}{2L^2}$, so at the horizon $M(L)=L/2$. This equals both th...

Riemann Zeros from the Edge of Spacetime

This not a proof of the Riemann Hypothesis (RH) .  Its purpose is to isolate a precise mathematical problem whose solution would imply RH. Let $\xi(s)$ be the completed Riemann $\xi$-function, and let $Q_W$ denote the Weil quadratic form. Weil's criterion states, for the standard admissible test-function class, $$\mathrm{RH}\iff Q_W(f)\ge0\quad\text{for all }f.$$ The program is to obtain this positivity from horizon modular/reflection positivity.   1. Horizon Modular Flow is Logarithmic Translation For a non-extremal horizon, the local modular flow is Rindler/boost flow. On a horizon half-line $x>0$, $$(U_u\psi)(x)=e^{u/2}\psi(e^u x).$$ The half-density factor makes $U_u$ unitary on $L^2(\mathbb R_+,dx)$. Its generator is $$K_{\rm sc} =-i\left(x\frac{d}{dx}+\frac12\right).$$ Introduce $q=\ln x$ and $\phi(q)=e^{q/2}\psi(e^q)$. Then $$U_u\phi(q)=\phi(q+u), \qquad K_0=-i\frac{d}{dq}.$$ Thus the geometric horizon Hamiltonian is simply translation in logarithmic coo...

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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...

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...

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...