A Planck Time Window Entropy Solution to the Vacuum Catastrophe in Haug Tatum RH = ctCosmology

We present a likely solution to the vacuum catastrophe within the Haug--Tatum black-hole $R_H=ct$ cosmology. The Bekenstein--Hawking entropy of the Hubble sphere is interpreted as the total entropy accumulated from the beginning of the universe to cosmic time $t$. The entropy associated with the current Planck-time window is consequently $S_{t_p}=S_{BH,H}t_p/t_H$. We show that multiplication of this Planck-window entropy by the Hawking--Planck temperature gives exactly the critical Friedmann energy inside the Hubble sphere. Division by the Hubble volume then gives $\rho_\Lambda=3H^2/(8\pi G)$. Since $\Omega_\Lambda=1$ in the Haug--Tatum model, this is the vacuum density required by the cosmology. The result connects the Planck and Hubble scales without inserting the observed vacuum density as a free parameter and indicates that horizon-entropy scaling is a likely solution to the vacuum catastrophe within this specific $R_H=ct$ framework.