As per the usual tradition, the mass of a classical object is taken as a "positive quantity". It can, however, be known to be "negative" as well in reality. My query is of a basic type. What are the different significances of "negative mass" of a classical object or classical particle in accordance with the latest investigations? Can anyone provide any reference or link for the answer?
General relativity distinguishes qualitatively between positive and negative masses. Take the Schwarzschild solution as an example. It follows that a positive mass black hole is covered with an event horizon while a negative mass black hole is not covered with such a horizon.
There is no evidence of negative mass. Evidence would be if gravity repelled one object and not others. Inertial evidence would be acceleration of an object in the opposite direction than the applied force.
Dirac found energy squared and mass squared. From these he guessed at antimatter with negative energy and negative mass as one of the possible roots of his equation. Antimatter was found, but it has positive energy.
CERN is experimenting to discover the mass of antimatter. Projects ATHENA, ALPGA, AGEIS, and GBAR have promised to discover the mass of antimatter, but have not yet done so.
Dear Karmakar,
The only place where it was found what could be called "negative mass" is in a Bose-Einstein condensate with great electronic spin-orbit interaction.
See https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.155301
Dear Karmakar: We know that Dirac has transformed the Klein Gordon square operator as a product of two linear operators. It is evident that the square operator work for positive or negative charge associated to positive energy or negative energy. With Dirac it has been supposed that one of the linear operator is for the negative charge and the other for the positive. It is surprising that the same operator is use for two different particles. Well, but at this time the variation of the mass giving two flux of matter between the proton and the electron was not considered. In “The symmetry of the motion, the mass and the quantum state”, I explain that: “The hypothesis of exchanges of matter divided into two fluxes of opposite directions brings a simple answer. Indeed each flux is characterized with a direction of the speed of propagation of the grains, they determine the masses active and inert, thus the energy must be considered as positive or negative according to the flux. The classical equation corresponds to the positive flux and the other equation to the negative flux.”
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