Fresnel-like Spatial Lens Hypothesis in D-LEM Cosmology

This paper proposes a phenomenological reinterpretation of gravitational lensing within the D-LEM framework. Insteadof treating lensing solely as a smooth convex-lens-like curvature generated by mass distribution, the model introduces aneffective-medium response of space governed by density gradients, filamentary environments, and history-dependentresidual responses. The standard general-relativistic theory of gravitational lensing is not rejected; it remains the baselineframework for multiple images, Einstein rings, arcs, magnification, and time delays. However, high-resolutionobservations by JWST and forthcoming wide-field surveys by Euclid and Roman increasingly emphasize asymmetricarcs, flux-ratio anomalies, substructure-sensitive residuals, and environmental dependence. The present model introducesan effective refractive index n_eff composed of a standard gravitational term n_GR plus D-LEM response termsassociated with density gradients, memory/history, and phase or wavelength dependence. In this interpretation,gravitational lensing is not a single smooth lens but a cumulative Fresnel-like response generated by local spatialresponse layers. The proposed observational predictions include filament-aligned deflection enhancement, environmentdependentEinstein radii for lenses of similar mass, asymmetric rings, time-delay residuals, weak multi-wavelength phasedifferences, and possible post-gravitational-wave residual image perturbations. The aim is not to establish D-LEM as acomplete replacement for general relativity, but to define a testable effective-medium hypothesis that can be comparedwith conventional dark-matter substructure interpretations in the JWST, Euclid, Roman, and SKA era.