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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

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

REMAINING OBSTACLES. “Very strong theorems seemed to exclude any possibility of negative mass particles or objects, or more generally violating the positivity of energy.” https://lnkd.in/daA2SgMy View in LinkedIn

NEW BRIDGES. “By the 1950s, Bondi had built negative mass solutions that respected the equivalence principle.” https://lnkd.in/daA2SgMy View in LinkedIn

LATER CONCLUSIONS. “But rather obviously, these studies had assumed that matter and antimatter had both a positive gravitational mass. Today, the discovery of a repulsive gravity through observations of SN1a supernovae luminosity distance, called Dark Energy, leads us to be more cautious: indeed, what seemed previously impossible, repulsive gravity, is the major topic of interest in cosmology.” https://lnkd.in/daA2SgMy View in LinkedIn