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Showing posts from March, 2020

One Dark Scale, One Galactic Law

      We previously  discussed Verlinde's connection of the MOND acceleration scale to the entropy of de Sitter space. A different route appears in superfluid dark matter (a 2026 review is here ), where baryons interact with a phonon field whose nonlinear dynamics generate a MOND-like force. The superfluid theory introduces a characteristic scale $\Lambda_{\rm SF}$, which must be of order meV to reproduce the MOND scale. This is also the order of the vacuum-energy scale, $\rho_{\rm DE}^{1/4}\sim{\rm meV}$.  So, we postulate $\Lambda_{\rm SF}^4=\rho_{\rm DE}$.  To be clear, the idea of a unified dark sector is not new , e.g. a 2019 Unified Superfluid Dark Sector , 2026 A solid unification of the dark sector , and 2026 Unified dark sector approach to cosmological tensions among many others. What we do here is identify the MOND phonon scale exactly with vacuum energy, plus postulate a dimensionless infrared response coefficient.    So, let $\...
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Is there a Maximum Power Limit in General Relativity?

Yes! Also, it is not the 'Planck Power'   (despite what you might have read in   Misner, Thorne and Wheeler, P.980).  The existence of black hole horizons implies a maximum luminosity (power) limit in General Relativity. Not even gravitational waves can escape a black hole . Consider an (almost) black hole made of light (this is called a  Kugelblitz )  sphere of radius \begin{equation} \notag R \geq \frac{2Gp}{c^3} \end{equation}  which is filled with photons with a total mass-energy of momentum $p$ times speed of light $c$ \begin{equation} \notag E=p \ c \end{equation}  the shortest time which the entire sphere can release its energy is its light-crossing time:   \begin{equation} \notag t=R/c \end{equation}  with average power (luminosity)  $$ P = \frac{E}{t} \leq \frac{p \ c^2}{R}$$ So $$P_{max}=\frac{c^5}{2G}\approx 1.8\times10^{52} \ W$$   This is maximum power in GR , for a compact, casually connected emitter.  ...
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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 !   Requiring the reduced Compton wavelength to fit within a cosmic event horizon results in a "minimum mass" (this is not a minimum particle mass) $m_s = \frac{\hbar}{c l_{\Lambda}}$.   In this post  we interpret $m_s$ as a horizon energy gap and model the associated gravitational scale as a  lightlike energy flow along an effective classical string.   McDormand with a cosmic light-like energy flow $m_{s}$ along a string of minimal  radius $2L_p$, giving a centripetal force $F_{max}=c^4/4G$.    Mass-Energy Flux Along the String   Let's think about that string for a bit. In fact, a great number of physicists have spent their entire careers tied up  unravelling  string theory . For a classical string associated with Nambu-Goto action, the the string tension $T_G$ is a local force, or energy per unit length (dimensions $MLT^{-2}$): \begin{equation} \notag T_G = \frac{1}{2\pi \alpha_G \prime} \e...
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