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Abstract

We investigate the Casimir effect for a massless scalar field confined between two parallel semitransparent mirrors in a vacuum modified by spontaneous Lorentz symmetry breaking. Using Green's function techniques and a point-splitting evaluation of the stress-energy tensor, we compute the vacuum expectation value of the energy density $T_{00}$. After a suitable renormalization, the Casimir energy is obtained as the difference between the vacuum configurations with and without the mirrors. We derive closed-form expressions that generalize the conventional result by simultaneously incorporating the mirror transparency and the Lorentz-violating background. Our analysis shows that the effect of transparency and Lorentz violation consists of a multiplicative correction and an effective rescaling of the plate separation, thereby modifying the functional dependence of the energy on the distance. Beyond the formal derivation, we discuss possible physical realizations of this framework, emphasizing anisotropic media such as nematic liquid crystals (e.g., 5CB), where uniaxial dielectric properties could emulate the Lorentz-violating background. Numerical estimates for such systems illustrate the phenomenological impact of our results and open the possibility of constraining Lorentz-violating coefficients through precision Casimir measurements.