The theory of real closed fields can be decided in exponential space or parallel exponential time. In fixed dimension, the theory can be decided in NC. © 1986.
Ben-Or, M., Kozen, D., & Reif, J. (1986). The complexity of elementary algebra and geometry. Journal of Computer and System Sciences, 32(2), 251–264. https://doi.org/10.1016/0022-0000(86)90029-2