Frasi di Jacob Bekenstein (6 frasi) | Citazioni e frasi celebri

Jacob Bekenstein: 6 citazioni0 Mi piace

Jacob Bekenstein: Frasi in inglese

“In a previous paper we showed that a static (nonrotating) black hole cannot be endowed with exterior scalar-meson or massive vector-meson fields. Here we show that the same is true for massive spin-2 meson fields. We also extend the above results to the case of a rotating stationary black hole. We conclude from our results that a black hole in its final (static or stationary) state cannot interact with the exterior world via the strong interactions which are mediated by meson fields such as the π (scalar), ρ (vector), and ƒ (spin-2). A direct consequence of this is the impossibility of determining the baryon number of the black hole by means of exterior measurements alone. This results in the transcendence of the law of baryon-number conservation as originally predicted by Wheeler.”

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Jacob Bekenstein

[Nonexistence of baryon number for black holes. II, Physical Review D, 5, 10, 15 May 1972, 2403–2412, 10.1103/PhysRevD.5.2403]

“Within the DM paradigm the Tully-Fisher law must arise from galaxy formation since it connects luminosity of baryonic matter with a dynamical property, rotation, which is seen as dominated by the DM halo. But it has not been easy to derive Tully-Fisher from any natural connection between the two components. And as R. H. Sanders has pointed out, the messiness of galaxy formation is hardly the natural backdrop for such a sharp correlation between galaxy properties. The sharpness needs a dynamical reason as opposed to an evolutionary one.”

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Jacob Bekenstein

[Alternatives to dark matter: Modified gravity as an alternative to dark matter, arXiv preprint arXiv:1001.3876, 21 January 2010, https://arxiv.org/abs/1001.3876]

“Black holes set a limitation on the number of species of elementary particles—quarks, leptons, neutrinos—which may exist. And black holes lead to a fundamental limitation on the rate at which information can be transferred for given message energy by any communication system.”

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Jacob Bekenstein

[Black holes and everyday physics, General relativity and gravitation, 14, 4, April 1982, 355–359, 10.1007/BF00756269]

“We show that it is natural to introduce the concept of black-hole entropy as the measure of information about a black-hole interior which is inaccessible to an exterior observer. Considerations of simplicity and consistency, and dimensional arguments indicate that the black-hole entropy is equal to the ratio of the black-hole area to the square of the Planck length times a dimensionless constant of order unity. A different approach making use of the specific properties of Kerr black holes and of concepts from information theory leads to the same conclusion, and suggests a definite value for the constant.”

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Jacob Bekenstein

[Black Holes and Entropy, Phys. Rev. D, 7, 8, 2333–2346, 15 April 1973, 10.1103/PhysRevD.7.2333]

“The DM halo hypothesis is evidently an attempt to resolve the acceleration discrepancy within orthodox gravitation theory. But in coming to terms with this discrepancy, suspicion fell on Newtonian gravity already early in the game. Zwicky, who had exposed the acceleration discrepancy in clusters of galaxies …, opined much later that the discrepancy may reflect a failure of conventional physics …”

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Jacob Bekenstein

[The modified Newtonian dynamics—MOND and its implications for new physics, arXiv preprint astro-ph/0701848, 27 March 2007, https://arxiv.org/abs/astro-ph/0701848] (p. 2)

“There is a prescription that works well, MOND, but the reason it works so well is not known. You may say that MOND tells us how the real theory of gravity should look.”

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Jacob Bekenstein

as quoted in: [Milgrom, Mordehai, MOND from a brane-world picture, arXiv preprint arXiv:1804.05840, 2018, https://arxiv.org/abs/1804.05840] (p. 2)