1. H. Bondi:Rev. Mod. Phys.,29, 423 (1957).
2. A. Föppl:Sitzber. Math. Phys. Kl. Kongl. Bayrisch. Akad. Wiss. München,27, 97 (1890). WhileFöppl developed a logically consistent theory of positive and negative masses, the possibility of stars composed of negative mass was considered byK. Pearson:Am. Journ. Math.,13, 309 (1891). For a historical account on negative mass, seeM. Jammer:Concepts of Mass in Classical and Modern Physics, Ch. 10 (New York, 1964).
3. A. Schüster:Nature,58, 367, 618 (1898). Although our attention is focused on the coupling of negative matter, it is important to clarify the relationship between negative matter and antimatter. An interesting discussion on the gravitational properties of antimatter has been given byL. I. Schiff:Proc. Natl. Acad. Sci. U.S.,45, 69 (1959); see alsoS. Weinberg:Phys. Rev.,135, B 1049 (1964);K. Hiida andY. Yamaguchi:Progr. Theor. Phys. Suppl., Extra Number, 261 (1965).
4. B. Hoffmann: article inPerspective in Geometry and Relativity (Indiana, 1966), p. 176. See alsoY. P. Terletsky: article inQuasi-Steller Sources and Gravitational Collapse (Chicago, 1965), p. 466; andParadoksy Teorii Otnositel’nosti, Chap. 6 (Moscow, 1966).
5. This experimental indeterminacy may imply more generally the irrelevance of the phase of mass, and the corresponding automorphism is the chiral gauge transformation. SeeA. Inomata:Progr. Theor. Phys.,28, 569 (1962).