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Sagittarius A* is the source of near infrared, X-ray, radio, and(sub)millimeter emission associated with the supermassive black hole at theGalactic Center. In the submillimeter regime, Sgr A* exhibits time-variablelinear polarization on timescales corresponding to <10 Schwarzschild radii ofthe presumed 4 million solar mass black hole. In previous work, we demonstratedthe potential for total-intensity (sub)millimeter-wavelength VLBI to detecttime-variable -- and periodic -- source structure changes in the Sgr A* blackhole system using nonimaging analyses. Here we extend this work to include fullpolarimetric VLBI observations. We simulate full-polarization (sub)millimeterVLBI data of Sgr A* using a hot-spot model that is embedded within an accretiondisk, with emphasis on nonimaging polarimetric data products that are robustagainst calibration errors. Although the source-integrated linear polarizationfraction in the models is typically only a few percent, the linear polarizationfraction on small angular scales can be much higher, enabling the detection ofchanges in the polarimetric structure of Sgr A* on a wide variety of baselines.The shortest baselines track the source-integrated linear polarizationfraction, while longer baselines are sensitive to polarization substructuresthat are beam-diluted by connected-element interferometry. The detection ofperiodic variability in source polarization should not be significantlyaffected even if instrumental polarization terms cannot be calibrated out. Asmore antennas are included in the (sub)mm-VLBI array, observations with fullpolarization will provide important new diagnostics to help disentangleintrinsic source polarization from Faraday rotation effects in the accretionand outflow region close to the black hole event horizon.

Detecting Changing Polarization Structures in Sagittarius A* with High Frequency VLBI