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quarta-feira, setembro 17, 2008

A constante G varia com a orientação espacial? E o princípio Antrópico?


OK, OK. Uma idéia que me ocorreu agora: usando raciocínio antrópico fraco (veja também na wiki inglesa) acho que seria possível determinar uma variação máxima Delta G compatível com vida inteligente no Universo. Necessariamente, a variação experimental precisa ficar dentro desse bound (1% segundo Freeman Dyson). Os dados da CODATA fornecem incerteza relativa de 0.15% (isso equivale a um desvio padrão?).
Ou seja, supondo três desvios padrões para termos 99% de segurança, temos que a incerteza experimental (que poderia refletir uma verdadeira variação cosmológica) seria de 0.45%. Isso se novas medidas não aumentarem essa incerteza...
Se o cálculo de Dyson for aprimorado, acho que a faixa antrópica diminuirá para menos de 1% (Alguém se dispõe a fazer essa conta?)
Assim, aposto uma cerveja de que Delta G (antropico) = Delta G observacional, ou seja, vivemos num Universo que permite a máxima variaçao de G compatível com a emergência de seres inteligentes.

Experimental evidence that the gravitational constant varies with orientation
Mikhail L. Gershteyn (1 and 2), Lev I. Gershteyn (2), Arkady Gershteyn (2), Oleg V. Karagioz (3) ((1) Massachusetts Institute of Technology, Cambridge, MA, U.S., (2) Insight Product Co., Brighton, MA, U.S., (3) Tribotech division of National Institute of Aviation Technology, Moscow, Russia)
In 1687, Isaac Newton published the universal law of gravitation stating that two bodies attract each other with a force proportional to the product of their masses and the inverse square of the distance. The constant of proportionality, G, is one of the fundamental constants of nature. As the precision of measurements increased the disparity between the values of G, gathered by different groups, surprisingly increased. This unique situation was reflected by the 1998 CODATA decision to increase the relative G uncertainty from 0.013% to 0.15 %. Our repetitive measurements of the gravitational constant (G) show that G varies significantly with the orientation of the test masses relative to the system of fixed stars, as was predicted by the Attractive Universe Theory. The distances between the test masses were in the decimeter range. We have observed that G changes with the orientation by at least 0.054%.
Comments:6 pages, pdf format, accepted by "Gravitation & Cosmology", to be published in volume 8, issue 3, 2002
Subjects:Classical Physics (physics.class-ph); General Physics (physics.gen-ph); Instrumentation and Detectors (physics.ins-det)
Report number:IP P-02-JF-12/1
Cite as:arXiv:physics/0202058v2 [physics.class-ph]

Time variation of $G$ and $\Lambda$, acceleration of the universe, coincidence problem and Mach's cosmological coincidence
We study a gravitational model in which {\it scale transformations} play the key role in obtaining dynamical $G$ and $\Lambda$. We take a non-scale invariant gravitational action with a cosmological constant and a gravitational coupling constant. Then, by a scale transformation, through a dilaton field, we obtain a new action containing cosmological and gravitational coupling terms which are dynamically dependent on the dilaton field with Higgs type potential. The vacuum expectation value of this dilaton field, through spontaneous symmetry breaking on the basis of {\it anthropic principle}, determines the time variations of $G$ and $\Lambda$. The relevance of these time variations to the current acceleration of the universe, coincidence problem, Mach's cosmological coincidence and those problems of standard cosmology addressed by inflationary models, are discussed. The current acceleration of the universe is shown to be a result of phase transition from radiation toward matter dominated eras. No real coincidence problem between matter and vacuum energy densities exists in this model and this apparent coincidence together with Mach's cosmological coincidence are shown to be simple consequences of a new kind of scale factor dependence of the energy momentum density as $\rho \sim a^{-4}$. This model also provides the possibility for a super fast expansion of the scale factor at very early universe by introducing exotic type matter like cosmic strings.
Comments:19 pages, context revised, new proposals for acceleration of the universe, coincidence problem and Mach's cosmological coincidence suggested
Subjects:General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
Cite as:arXiv:0802.0028v2 [gr-qc]

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