Matej Pavšič

In 1974 Pavšič considered a theory according to which nature is exactly symmetric with respect to space inversion, provided that one postulates the existence of mirror particles and mirror interactions among them.[7] The idea of mirror particles was introduced in 1956 by Lee and Yang in their paper on parity non conservation, and was in 1966 further elaborated by Yu. Kobzarev, L.B. Okun and I.Ya. Pomeranchuk within the context of a CP invariant theory. Nowadays, the so-called exact parity models are considered in many works as an explanation of dark matter.[8][9]

Pavšič also investigated the idea that spacetime is a 4-dimensional membrane embedded in a higher dimensional space. He first explained this idea in its rough contours in 1981,[10] and later in more elaborated works[11][12][13] and the book.[14]

Since 1992 Pavšič became interested in Clifford algebras as a useful tool for geometry and physics. Among other things, he showed[15] that the geometric calculus based on Clifford algebras resolves the ordering ambiguity of operators in curved spaces. Pavšič also found that under space inversion a geometric spinor (an element of a Clifford algebra) becomes a mirror particle experiencing mirror gauge interactions.

Following the important insights of several authors, Pavšič has found that in the presence of physically realistic interaction potentials, bounded from below and from above, the systems with negative energies are stable. As an example, he studied the Pais-Uhlenbeck oscillator in the presence of a bounded interaction term. The Pais-Uhlenbeck oscillator is a prototype of a higher derivative theory, and the demonstration of its stability indicates that higher derivative gravity is a physically viable theory[16]