Early Mass-varying Neutrino Dark Energy: Nugget Formation and Hubble Anomaly

We present a novel scenario, in which light ($\sim$ few \rm{eV}) dark fermions (sterile neutrinos) interact with scalar field like mass varying neutrino energy theories. As the $\rm{eV}$ sterile states naturally become non-relativistic before Matter Radiation Equality (MRE), we show that neutrino-scalar fluid develops strong perturbative instability followed by formation of neutrino-nuggets and early behaviour disappears around MRE. The stability nugget is achieved when Fermi pressure balances attractive force numerically find radius heavy cold nuggets solving for static configuration field. case DM density sub-dominant most DE goes into dynamics, it can principle relax Hubble anomaly. Especially kinetic dominated phase appears after transition, dilutes faster than radiation satisfy requirements $H_0$ In our unlike originally proposed theory, controlled ($\rm{eV}$) does not require fine tuned EDE scale. perform MCMC analysis confront model Planck + SHOES BAO data an evidence non-zero during Our shows this agreement nearly 1.3$\sigma$ measurement $H_0 = 74.03 \pm 1.42$ km/s/Mpc.