95 research outputs found
A First Assessment of the Corrections for the Consistency of the IAU2000 and IAU2006 Precession-Nutation Models
The Earth precession-nutation model endorsed by resolutions of each the International Astronomical Union and the International Union of Geodesy and Geophysics is composed of two theories developed independently, namely IAU2006 precession and IAU2000A nutation. The IAU2006 precession was adopted to supersede the precession part of the IAU 2000A precession-nutation model and tried to get the new precession theory dynamically consistent with the IAU2000A nutation. However, full consistency was not reached, and slight adjustments of the IAU2000A nutation amplitudes at the micro arcsecond level were required to ensure consistency. The first set of formulae for these corrections derived by Capitaine et al. (Astrophys 432(1):355–367, 2005), which was not included in IAU2006 but provided in some standards and software for computing nutations. Later, Escapa et al. showed that a few additional terms of the same order of magnitude have to be added to the 2005 expressions to get complete dynamical consistency between the official precession and nutation models. In 2018 Escapa and Capitaine made a joint review of the problem and proposed three alternative ways of nutation model and its parameters to achieve consistency to certain different extents, although no estimation of their respective effects could be worked out to illustrate the proposals. Here we present some preliminary results on the assessment of the effects of each of the three sets of corrections suggested by Escapa and Capitaine (Proceedings of the Journées, des Systémes de Référence et de la Rotation Terrestre: Furthering our Knowledge of Earth Rotation, Alicante, 2018) by testing them in conjunction with the conventional celestial pole offsets given in the IERS EOP14C04 time series.The four first authors were partially supported by Spanish Project AYA2016-79775-P (AEI/FEDER, UE)
Reconsidering the galactic coordinate system
Initially defined by the IAU in 1958, the galactic coordinate system was
thereafter in 1984 transformed from the B1950.0 FK4-based system to the J2000.0
FK5-based system. In 1994, the IAU recommended that the dynamical reference
system FK5 be replaced by the ICRS, which is a kinematical non-rotating system
defined by a set of remote radio sources. However the definition of the
galactic coordinate system was not updated. We consider that the present
galactic coordinates may be problematic due to the unrigorous transformation
method from the FK4 to the FK5, and due to the non-inertiality of the FK5
system with respect to the ICRS. This has led to some confusions in
applications of the galactic coordinates. We tried to find the transformation
matrix in the framework of the ICRS after carefully investigating the
definition of the galactic coordinate system and transformation procedures,
however we could not find a satisfactory galactic coordinate system that is
connected steadily to the ICRS. To avoid unnecessary misunderstandings, we
suggest to re-consider the definition of the galactic coordinate system which
should be directly connected with the ICRS for high precise observation at
micro-arcsecond level.Comment: 10 pages, 3 figures, accepted for publication in A&
Lifespan extension and the doctrine of double effect
Recent developments in biogerontology—the study of the biology of ageing—suggest that it may eventually be possible to intervene in the human ageing process. This, in turn, offers the prospect of significantly postponing the onset of age-related diseases. The biogerontological project, however, has met with strong resistance, especially by deontologists. They consider the act of intervening in the ageing process impermissible on the grounds that it would (most probably) bring about an extended maximum lifespan—a state of affairs that they deem intrinsically bad. In a bid to convince their deontological opponents of the permissibility of this act, proponents of biogerontology invoke an argument which is grounded in the doctrine of double effect. Surprisingly, their argument, which we refer to as the ‘double effect argument’, has gone unnoticed. This article exposes and critically evaluates this ‘double effect argument’. To this end, we first review a series of excerpts from the ethical debate on biogerontology in order to substantiate the presence of double effect reasoning. Next, we attempt to determine the role that the ‘double effect argument’ is meant to fulfil within this debate. Finally, we assess whether the act of intervening in ageing actually can be justified using double effect reasoning
Time separation as a hidden variable to the Copenhagen school of quantum mechanics
The Bohr radius is a space-like separation between the proton and electron in
the hydrogen atom. According to the Copenhagen school of quantum mechanics, the
proton is sitting in the absolute Lorentz frame. If this hydrogen atom is
observed from a different Lorentz frame, there is a time-like separation
linearly mixed with the Bohr radius. Indeed, the time-separation is one of the
essential variables in high-energy hadronic physics where the hadron is a bound
state of the quarks, while thoroughly hidden in the present form of quantum
mechanics. It will be concluded that this variable is hidden in Feynman's rest
of the universe. It is noted first that Feynman's Lorentz-invariant
differential equation for the bound-state quarks has a set of solutions which
describe all essential features of hadronic physics. These solutions explicitly
depend on the time separation between the quarks. This set also forms the
mathematical basis for two-mode squeezed states in quantum optics, where both
photons are observable, but one of them can be treated a variable hidden in the
rest of the universe. The physics of this two-mode state can then be translated
into the time-separation variable in the quark model. As in the case of the
un-observed photon, the hidden time-separation variable manifests itself as an
increase in entropy and uncertainty.Comment: LaTex 10 pages with 5 figure. Invited paper presented at the
Conference on Advances in Quantum Theory (Vaxjo, Sweden, June 2010), to be
published in one of the AIP Conference Proceedings serie
Potent inhibitory effect of alcoholic beverages upon gastrointestinal passage of food and gallbladder emptying
Observational constraints on spatial anisotropy of G from orbital motions
A phenomenological anisotropic variation \Delta G/G of the Newtonian
gravitational coupling parameter G, if real, would affect the orbital dynamics
of a two-body gravitationally bound system in a specific way. We analytically
work out the long-term effects that such a putative modification of the usual
Newtonian inverse-square law would induce on the trajectory of a test particle
orbiting a central mass. Without making any a-priori simplifying assumptions
concerning the orbital configuration of the test particle, it turns out that
its osculating semi-major axis a, eccentricity e, pericenter \varpi and mean
anomaly M undergo long-term temporal variations, while the inclination I and
the node \Omega are left unaffected. Moreover, the radial and the transverse
components of the position and the velocity vectors r and v of the test
particle experience non-vanishing changes per orbit, contrary to the
out-of-plane ones. Then, we compute our theoretical predictions for some of the
major bodies of the solar system by orienting the gradient of G(r) towards the
Galactic Center and keeping it fixed over the characteristic timescales
involved. By comparing our calculation to the latest observational
determinations for the same bodies, we infer \Delta G/G <= 10^-17 over about 1
au. Finally, we consider also the Supermassive Black Hole hosted by the
Galactic Center in Sgr A^* and the main sequence star S2 orbiting it in about
16 yr, obtaining just \Delta G/G <= 10^-2 over 1 kau.Comment: LaTex2e, 18 pages, no figures, 4 tables. Accepted by Classical and
Quantum Gravity (CQG). Typo fixed. Reference update
Conseils pratiques aux jeunes officiers pour la préparation du fantassin au service en campagne, par le capitaine Perizonius, trad. de l'allemand par A. C.,...
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