# Casimir stress in materials: hard divergency at soft walls

## TL;DR

This paper predicts a specific power-law behavior of Casimir stress inside soft walls with discontinuous derivatives in refractive index, revealing that edges are incompatible with liquid aggregation at surfaces.

## Contribution

It introduces a new theoretical prediction of Casimir stress behavior in materials with soft walls and discontinuous refractive index derivatives.

## Key findings

- Power-law divergence of Casimir stress near edges
- Edges prevent liquid aggregation at surfaces
- Stress behavior depends on refractive index discontinuity

## Abstract

The Casimir force between macroscopic bodies is well understood, but not the Casimir stress inside bodies. Suppose empty space or a uniform medium meets a soft wall where the refractive index is continuous but its derivative jumps. For this situation we predict a characteristic power law for the stress inside the soft wall and close to its edges. Our result shows that such edges are not tolerated in the aggregation of liquids at surfaces, regardless whether the liquid is attracted or repelled.