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ALTERNATIVES. “There could be other expressions of the Equivalence Principle respecting the spirit of General Relativity but violating maximally its usual expression.” https://lnkd.in/daA2SgMy View in LinkedIn

PROBLEM OF NEGATIVE MASS. “Still we will see that General Relativity does predict gross violations of the Equivalence Principle as soon as negative mass components are allowed.” https://lnkd.in/daA2SgMy View in LinkedIn

TWEAKING RELATIVITY. “Truly enough, as soon as we express general relativity as a metric theory, with a single metric, it is difficult to see how gravity could distinguish matter from antimatter since according to the very formalism of a single metric, all particles must follow the same trajectory.” https://lnkd.in/daA2SgMy View in LinkedIn

VIOLATION OF EQUIVALENCE. “This will lead us to the Dirac-Milne universe, and a possible explanation of the repulsive gravity that we observe in cosmology, called Dark Energy for lack of better comprehension.” 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

TOXIC COMBINATION. “We have stone age emotions, medieval institutions and god-like technology.” (The late Professor EO Wilson, a giant among men). https://www.theguardian.com/environment/2021/dec/27/edward-o-wilson-naturalist-modern-day-darwin-dies?CMP=Share_iOSApp_Other View in LinkedIn