“Dark matter and dark energy, supposed to represent about 95% of the universe energy density, but which have remarkably resisted to experimental identification so far.” https://t.co/a9WFh6XRxW
“Another major drawback of the Standard Model is the fact that it uses two predominant components, dark matter and dark energy.” https://t.co/a9WFh6XRxW
RT @TenFleming: “The fact that in several respects our universe appears very similar to a coasting or empty universe is a motivation to rec…
“Whatever the experimental results, they will have important repercussions on our understanding of the evolution of our universe.” (The end of this exciting paper). https://t.co/a9WFh6XRxW
The ALPHA collaboration, “which made the first spectroscopic measurements on antihydrogen, achieved in 2013 the first constraints on antimatter gravity, though still a factor ≈ 65 larger than the sensitivity necessary to test antigravity.” https://t.co/a9W
“Gbar is preparing a precision measurement with antihydrogen ions cooled to a few tens of microkelvin.” https://t.co/a9WFh6XRxW
“Importantly, a key test of the Dirac-Milne cosmology will soon be realized in the laboratory with cold antihydrogen atoms: the AEgIS, ALPHA-g and Gbar experiments at CERN are expected to provide tests of the antigravity hypothesis.” (2018). https://t.co/
The Dirac-Milne universe, “a symmetric matter-antimatter universe, where antimatter is endowed with negative mass, an analog of the electron-hole system in a semi-conductor, providing a cosmology impressively concordant with our universe.” https://t.co/a9W
“This led us to the study of the properties of the Dirac-Milne universe, a symmetric matter-antimatter universe.” https://t.co/a9WFh6XRxW
“The fact that in several respects our universe appears very similar to a coasting or empty universe is a motivation to reconsider the impossibility arguments against the existence of negative mass, on the one hand, and antigravity, on the other.” https://
The unwinding. “The standard cosmological model finds itself in the unpalatable situation of explaining most observations using concepts that are little, or not at all, understood.” https://t.co/a9WFh6XRxW
The unwinding. “Another “dark” component, namely Dark Matter, is supposed to represent roughly 25% of the universe.” https://t.co/a9WFh6XRxW
Dogma cracking. “The situation has changed rather dramatically since the discovery in 1998 of what we call, by lack of better understanding, Dark Energy, representing about two thirds of the universe energy density.” https://t.co/a9WFh6XRxW
Dogma cracking. “Most physicists would still bet against antigravity for antimatter.” https://t.co/a9WFh6XRxW
The Dirac-Milne cosmology may also explain “the same amount of antimatter surviving in clouds of cold gas occupying the vast majority of the intergalactic space in our universe.” https://t.co/a9WFh6XRxW
“As a hypothesis that remains to be confirmed, the Dirac-Milne cosmology may also explain why there remains approximately only one billionth of matter following the primordial annihilation.” https://t.co/a9WFh6XRxW
Extraordinary analogy. “This violation of the equivalence principle has a physical motivation as it corresponds to the electron-hole system in a semiconductor.” (Macro = micro). https://t.co/a9WFh6XRxW
“Dubinski et al. the evolution of underdense regions, which expand and lead to large “voids” that occupy the largest fraction of our universe, could be described as the evolution of negative mass particles violating “maximally” the equivalence principle.”
“Motivated by the fact that our universe shares several aspects with a coasting universe, we have studied structure formation in universes involving equal amounts of negative and positive mass, with a particular emphasis on the Dirac-Milne cosmology.” http
Helium-3. “The authors themselves note that (their) “result for 3He is exactly the opposite of what one would expect (...).” https://t.co/a9WFh6XRxW
Helium-3. “As a result, it has sparked little enthusiasm from experimentalists, and the measurements, clearly below the prediction of the Dirac-Milne universe, are probably inconclusive.” https://t.co/a9WFh6XRxW
“But helium-3 is a bad probe of the primordial universe since it can be both destroyed and produced after the initial phases of the universe.” https://t.co/a9WFh6XRxW
1st problem. “Taken at face value, there are two observational problems facing the Dirac-Milne universe. The first problem is related to an overproduction, by nearly a factor 10, of helium-3.” https://t.co/a9WFh6XRxW
A solution. “On this basis, Benoit-Levy and Chardin proposed the so-called “Dirac-Milne” universe, a universe containing the same amount of matter and anti-matter (hence Dirac’s name), endowed respectively with positive and negative mass.” https://t.co/a9W
“Several authors have noted that our universe is very similar to a gravitationally empty or coasting universe (neither accelerating or decelerating).” https://t.co/a9WFh6XRxW
Never forget this. Dark matter and dark energy “have remarkably resisted to experimental identification so far.” https://t.co/a9WFh6XRxW
Never forget this. “Another major drawback of the Standard Model is the fact that it uses two predominant components, dark matter and dark energy, supposed to represent about 95% of the universe energy density.” https://t.co/a9WFh6XRxW
Dark Energy dominance “leading to a universe of accelerated expansion, where galaxies will find themselves isolated from each other in a (relatively) near future.” https://t.co/a9WFh6XRxW
“And it is only at the age of a few billion years that the Dark Energy component, a name hiding our ignorance of its true nature, becomes dominant.” https://t.co/a9WFh6XRxW
“Leading about 10(5) years later (virtually an eternity), to a period where matter, until then mostly irrelevant, manages eventually to become the majority component while radiation as well as dark energy are then totally negligible.” https://t.co/a9WFh6XR
Flawed dogma. “At the end of inflation, when the universe is not even 10(−30) seconds old, a new phase of very violent deceleration is supposed to start…” https://t.co/a9WFh6XRxW
Standard model failings. “A time slightly too long will lead to a virtually empty universe, whereas a time slightly too short will lead to the re-collapse of the universe in a few Planck times (10(−44 0) s).” https://t.co/a9WFh6XRxW
Standard model failings. “In particular, there does not exist any precise fundamental theory allowing to understand how one can not only enter but also leave this phase of inflation.” https://t.co/a9WFh6XRxW
Standard Model “featuring an extremely brief initial phase of very brutal deceleration, followed by a rather mysterious and very brief repulsive phase of inflation…justified by the need to solve the enigma of the homogeneity of the primordial universe.” ht
“It also underlined the improbability of the Standard Model of Cosmology.” https://t.co/a9WFh6XRxW
Key observation. “The discovery in 1998 of a mysterious repulsive energy, dubbed Dark Energy, and representing more than two thirds of the energy content of the universe, provided the first massive evidence for repulsive gravity.” https://t.co/a9WFh6XRxW
Hoyle and Narlikar proposal. “But today, with the knowledge that negative mass solutions are allowed, and the observation of repulsive gravity…the initial Machian perspective of Einstein could effectively be realized in the Dirac-Milne universe.” https://t
Hoyle and Narlikar proposal. “For Hawking, it clearly meant that the theory was wrong.” https://t.co/a9WFh6XRxW
A symmetrical universe. “Hawking had noted that the Machian formulation of general relativity proposed by Hoyle and Narlikar only works if there exists equal amounts of negative mass and positive mass particles in the universe.” https://t.co/a9WFh6XRxW
“It is therefore natural to test whether antimatter is not by any chance such an “exotic” material.” https://t.co/a9WFh6XRxW
“And we also know since the early 1990s that building a time machine in general relativity —for example using a wormhole as a time machine— requires violating the positivity of energy.” https://t.co/a9WFh6XRxW
The best concept ever. “Dirac had shown that antimatter appears as the matter of negative energy going backwards in time.” https://t.co/a9WFh6XRxW
Fermions: “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
“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” gave options. https
Solutions of negative mass: “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://t.co/a9WFh6X
Solutions of negative mass “bubbles” without instability “finally demonstrated that instability does not constitute a sufficient argument to exclude a solution.” https://t.co/a9WFh6XRxW
“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).” https://t.co/a9WFh6XRxW
“The increasing number of violations of the energy conditions, first through the quantum effects of the vacuum (Casimir effect), then from 1998 in an infinitely more significant way with the discovery of Dark Energy, led to question these theorems.” https:
“Initially these theorems on the positivity of energy appeared as absolute no-go theorems.” https://t.co/a9WFh6XRxW
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://t.co/a9WFh6XRxW
New bridges. “By the 1950s, Bondi had built negative mass solutions that respected the equivalence principle.” https://t.co/a9WFh6XRxW
Later conclusions. “What seemed previously impossible, repulsive gravity, is the major topic of interest in cosmology.” https://t.co/a9WFh6XRxW
Later conclusions. “Today, the discovery of a repulsive gravity through observations of SN1a supernovae luminosity distance, called Dark Energy, leads us to be more cautious.” https://t.co/a9WFh6Ypnu
Later conclusions. “But rather obviously, these studies had assumed that matter and antimatter had both a positive gravitational mass.“ https://t.co/a9WFh6XRxW
Early conclusions. “An annihilation between matter and antimatter in conflict with observational limits, unless the domains of matter and antimatter had a size exceeding several billion light-years, which seems unrealistic.” https://t.co/a9WFh6XRxW
Early conclusions. “Even if the primordial universe had succeeded in creating a symmetrical world between matter and antimatter, diffusion of matter and antimatter at their domain boundaries would lead…to an annihilation between matter and antimatter.” htt
If matter and antimatter have positive gravitational masses “already difficult to justify in the early 1970s, at the epoch of the SAS-2 satellite, and clearly inconsistent with the much more sensitive contemporary satellites, such as the Fermi satellite.”
“If matter and antimatter have both positive gravitational masses and respect the equivalence principle, matter-antimatter annihilation continues to occur after the Universe has become transparent, leading to a diffuse high energy gamma-ray background.” ht
Symmetrical universe. “The conclusion of their study…was that the primordial Universe…does not provide enough time for a matter-antimatter universe to create structures large enough to evade the constraints of the diffuse gamma-ray flux.” https://t.co/a9WF
“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://t.co/a9WFh6XRxW
Parity universe. “The Dirac-Milne Universe is a universe that contains as much matter as antimatter.” https://t.co/a9WFh6XRxW
“Surprisingly, even at low fields, such a gravitational polarization will lead to observational consequences.” https://t.co/a9WFh6XRxW
Black hole horizon. “Indeed, under the diverging tension, the vacuum will eventually break down, and particle-antiparticle pairs will be created.” https://t.co/a9WFh6XRxW
“While this polarization will go completely unnoticed in weak gravitational fields, such as the Earth, in the strong field regime, for example near the horizon of a black hole, the behaviour predicted by general relativity will change dramatically.” https:
“Price also demonstrates that, as soon as negative masses exist, the vacuum will become polarized.“ https://t.co/a9WFh6XRxW
Slight antigravity. “Schiff’s argument that in case of antigravity, bodies should, according to their composition, undergo (slightly) different accelerations in a gravitational field.” https://t.co/a9WFh6XRxW
Negative mass. “So, in complete contradiction with intuition, there are only two possible behaviors: a 100% violation of the principle of equivalence, or no violation at all!” https://t.co/a9WFh6XRxW
The Price observation: “although the overall (inertial) mass of the system has decreased —it is equal to the algebraic sum of the two masses of the bound system—the trajectory of the composite system remains the same.” https://t.co/a9WFh6XRxW
The Price observation. “But as soon as the negative and positive masses differ even slightly in absolute value, the composite system always falls with exactly the same acceleration, respecting again the principle of equivalence.” https://t.co/a9WFh6XRxW
Levitating antimass: “the bound system composed of a mass +m and a mass −m, equal and opposite, levitates and polarizes itself (Fig. 2), the negative mass lying slightly above the positive mass in the levitating system.” https://t.co/a9WFh6XRxW
Levitating antimass: “a negative mass falls exactly like a positive mass when it is without interactions.” https://t.co/a9WFh6XRxW
Levitating antimass. “Richard Price noticed an extremely surprising property.” https://t.co/a9WFh6XRxW
“If antimatter antigravitates, then “two elements with rather different binding energies, these bodies should follow different trajectories in gravitational fields.” https://t.co/a9WFh6XRxW
“Some authors have argued, notably in supersymmetric theories, that antigravity, meaning here a slightly different acceleration of antimatter with respect to matter in a gravitational field, is possible without implying any dissipation or instability.” htt
Black hole evaporation. “As we will see, it is mostly in strong fields, such as those occurring near the horizon of black holes, that this antigravity will lead to significant effects.” https://t.co/a9WFh6XRxW
“For a black hole of the mass of our Sun, the evaporation timescale is of the order of 2 × 10(66) years.“ https://t.co/a9WFh7fspu
“There could be other expressions of the Equivalence Principle respecting the spirit of General Relativity but violating maximally its usual expression.” https://t.co/a9WFh7fspu
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://t.co/a9WFh6XRxW
When general relativity is 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:/
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://t.co/a9WFh6XRxW
“General relativity violates maximally the usual expression of the Equivalence Principle as soon as the existence of negative mass, possibly as virtual constituents of the quantum vacuum, is allowed.” https://t.co/a9WFh6XRxW
“Could it be that antigravity, in the sense of antimatter “falling up”, is actually a prediction, which seems at first antinomic, of general relativity?” https://t.co/a9WFh6XRxW
Negative mass. “Why then these three experiments?” https://t.co/a9WFh6XRxW
“Few consider possible an antigravity where antihydrogen would “fall up”, as the CERN presents the three current experiments testing the equivalence principle by the ELENA antiproton decelerator.” https://t.co/a9WFh6XRxW
“The vast majority of theoretical physicists believe that, if a difference in acceleration between matter and antimatter exists, it can only be extremely small.” https://t.co/a9WFh6XRxW
Extraordinary patallel. “We study the Dirac-Milne cosmology, a symmetric matter-antimatter cosmology where antiparticles have the same gravitational properties as holes in a semiconductor.” (Macro to micro). https://t.co/a9WFh6XRxW
The Equivalence Principle is violated by General Relativity by negative mass “which may provide a fundamental explanation of MOND phenomenology, obviating the need for Dark Matter.” https://t.co/a9WFh6XRxW
“We show that, very surprisingly, the usual expression of the Equivalence Principle is violated by General Relativity when particles of negative mass are supposed to exist.” https://t.co/a9WFh6XRxW
“We review the main arguments against antigravity, a different acceleration of antimatter relative to matter in a gravitational field.” https://t.co/a9WFh6XRxW
[1807.11198] Gravity, antimatter and the Dirac-Milne universe https://t.co/zzFy4bbm2Z
https://t.co/gF9ESJnSkD possibly significant?
RT @qraal: Gravity, antimatter and the Dirac-Milne universe https://t.co/zzFy4aTKEp
RT @qraal: Gravity, antimatter and the Dirac-Milne universe https://t.co/zzFy4aTKEp
RT @qraal: Gravity, antimatter and the Dirac-Milne universe https://t.co/zzFy4aTKEp
Gravity, antimatter and the Dirac-Milne universe. https://t.co/ylhDR4LvRR
Gravity, antimatter and the Dirac-Milne universe https://t.co/zzFy4aTKEp
Gravity, antimatter and the Dirac-Milne universe. (arXiv:1807.11198v1 [gr-qc]) https://t.co/tGcoxseN7s