Classical unified field theories since antisymmetry seemed essential for electromagnetism, the symmetry requirement was relaxed for one or both fields. Einstein's proposed unified-field equations (fundamental laws of physics) were generally derived from a variational principle expressed in terms of the Riemann curvature tensor for the presumed space-time manifold. In field theories of this kind, particles appear as limited regions in space-time in which the field strength or the energy density are particularly high. Einstein and coworker Leopold Infeld managed to demonstrate that, in Einstein's final theory of the unified field, true singularities of the field did have trajectories resembling point particles. However, singularities are
Unified Theory (band) only. "Unified Theory" went on to sell over 16,000 albums by 2002. "California" and "Wither" were both released as singles. However, with the exception of Seattle, most major market radio stations avoided playing "California." Critically, the album received generally positive reviews. Reviewing for Allmusic, Greg Prato stated that "Unified Theory's self-titled debut shows that Shinn has brought a more modern rock sound to the proceedings, mixing Jeff Buckley and Radiohead with Smith and Thorn's retro rock stylings" and that the "12-track debut is a refreshing break from the norm." Lina Lecaro, of the "Los Angeles Times", describes the album as