Vacuum birefringence from Lorentz and CPT violation in the Standard-Model Extension can be constrained using ground-based optical polarimetry of extragalactic sources .
We describe results from a pilot program with an automated system that can perform simultaneous optical polarimetry in multiple passbands on different telescopes with an effective 0.45 m aperture . [ 1 ] Despite the limited collecting area , our polarization measurements of AGN using a wider effective optical passband than previous studies yielded individual line-of-sight constraints for Standard-Model Extension mass dimension d = 5 operators within a factor of about one to ten of comparable broadband polarimetric bounds obtained using data from a 3.6 m telescope with roughly 64 times the collecting area . [ 2 ] Constraining more general anisotropic Standard-Model Extension coefficients at higher d would require more AGN along different lines of sight .
This motivates a future dedicated ground-based , multi-band , optical polarimetry AGN survey with { \gtrsim } { 1 } m-class telescopes , to obtain state-of-the-art anisotropic Standard-Model Extension d { = } 4 , 5 , 6 constraints , while also using complementary archival polarimetry .
This could happen more quickly and cost-effectively than via spectropolarimetry and long before more competitive constraints from space- or balloon-based x-ray/ \gamma -ray polarization measurements .