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SEARCHES. “In the 1960’s and again in the late 1980s, two teams tried to understand whether a symmetric matter-antimatter universe could be consistent with observations.” https://lnkd.in/daA2SgMy View in LinkedIn

THE BEST CONCEPT EVER. “Dirac had shown that antimatter appears as the matter of negative energy going backwards in time.” https://lnkd.in/daA2SgMy View in LinkedIn

PARITY UNIVERSE. “The Dirac-Milne Universe is a universe that contains as much matter as antimatter.” https://lnkd.in/daA2SgMy View in LinkedIn

NEGATIVE ENERGY. “Since fermions always come in pairs, the vacuum breaks down with pair creation when a electron of mass me is confined in a potential well of depth larger than −2mec2 and not mec2, so that the electron has a negative total energy of −mec2 when the vacuum starts to break down.” https://lnkd.in/daA2SgMy View in LinkedIn

NOT EXTREME CONDITIONS. “Surprisingly, even at low fields, such a gravitational polarization will lead to observational consequences.” https://lnkd.in/daA2SgMy View in LinkedIn

THE POSSIBILITY OPENS. “In other words, if a negative energy solution is unstable in Minkowski (flat) spacetime, but is stable in an Einstein-de Sitter spacetime, while a few billion years are required to determine whether you live in one or the other of these two universes, it means that the instability of the negative mass solution has at most a characteristic timescale of a few billion years.” https://lnkd.in/daA2SgMy View in LinkedIn

BLACK HOLE HORIZON. “Indeed, under the diverging tension, the vacuum will eventually break down, and particle-antiparticle pairs will be created.” https://lnkd.in/daA2SgMy View in LinkedIn

NEGATIVE MASS. “The demonstration of the existence, in 2014, of perfectly respectable solutions of negative mass “bubbles” without instability as soon as they are placed in an expanding universe (here, the Einstein-de Sitter universe) finally demonstrated that instability does not constitute a sufficient argument to exclude a solution: it is indeed also necessary to calculate the characteristic time of instability, since cosmological solutions are themselves unstable, but with often enormous and therefore acceptable characteristic times.” https://lnkd.in/daA2SgMy View in LinkedIn

POSITIVITY OF ENERGY THEOREMS. “But whereas initially these theorems on the positivity of energy appeared as absolute no-go theorems, the increasing number of violations of the energy conditions, first through the quantum effects of the vacuum (for example in the Casimir effect), then from 1998 in an infinitely more significant way with the discovery of Dark Energy, led to question these theorems.” https://lnkd.in/daA2SgMy View in LinkedIn

Playing with geometric models can be a source of humbling puzzlement as you realize that childhood learnings have long faded! View in LinkedIn