A Halo-Scale Cutoff from Vortex-Mediated Mutual Friction in the SFV/dSB Model

In fuzzy/ultralight dark-matter (FDM) and related Bose--Einstein condensate (BEC) phenomenology, a kiloparsec-scale ``healing length'' (or wave-support scale) can set a minimum halo/core size. In the Superfluid False Vacuum / de~Sitter-Brane (SFV/dSB) framework, the calibrated bulk healing length is microscopic, so the standard BEC/FDM route to a kiloparsec cutoff does not apply. We construct an alternative halo-cutoff mechanism consistent with a two-fluid SFV picture in which the late-time normal component is a baryon-like off-brane LSP population produced during reheating via bounce-sourced distributed Landau--Zener (LZ) transport. We adopt the empirical dwarf-satellite inner scale $R\simeq 300\,\mathrm{pc}$ (the ``common mass'' scale) as a minimal observational anchor and derive the late-time coupling required for drag to become dynamically relevant at that scale. We show that the bounce-derived brane-wall surface tension cannot couple directly to kiloparsec curvature energetics without extreme suppression, motivating a late-time mechanism based on superfluid mutual friction rather than membrane curvature forces. Using Hall--Vinen--Bekharevich--Khalatnikov (HVBK) scaling for vortex-mediated mutual friction and a minimal bridge that relates the effective vortex-line momentum-transfer length $\sigma_L$ to the SFV healing length and the distributed LZ effective coupling, $\sigma_L=\lambda_{\rm eff}\xi$, we obtain\[R_{\min}\sim GM\left(\frac{\lambda_{\rm eff}\xi}{\kappa}\right)^2,\qquad \kappa\equiv \frac{h}{m},\]which evaluates to $R_{\min}\simeq 270\,\mathrm{pc}$ for $M\simeq 10^7M_\odot$, close to the adopted $300\,\mathrm{pc}$ anchor. We emphasize that this is not a blind prediction (because $\lambda_{\rm eff}$ is fixed by the abundance ratio and $M_{0.3}$ is observational input), but it is a nontrivial cross-domain internal-consistency result linking early-time wall transport to late-time dwarf-scale structure within the SFV/dSB ontology.