HD60532, a planetary system in a 3:1 mean motion resonance

In a recent paper it was reported a planetary system around the star HD60532, composed by two giant planets in a possible 3:1 mean motion resonance, that should be confirmed within the next decade. Here we show that the analysis of the global dynamics of the system allows to confirm this resonance. The present best fit to data already corresponds to this resonant configuration and the system is stable for at least 5Gry. The 3:1 resonance is so robust that stability is still possible for a wide variety of orbital parameters around the best fit solution and also if the inclination of the system orbital plane with respect to the plane of the sky is as small as 15 deg. Moreover, if the inclination is taken as a free parameter in the adjustment to the observations, we find an inclination ~ 20 deg, which corresponds to M_b =3.1 M_Jup and M_c = 7.4 M_Jup for the planetary companions.Comment: 4 Pages, 4 Figures, accepted by A&

La2010: A new orbital solution for the long term motion of the Earth

We present here a new solution for the astronomical computation of the orbital motion of the Earth spanning from 0 to -250 Myr. The main improvement with respect to the previous numerical solution La2004 (Laskar et al. 2004) is an improved adjustment of the parameters and initial conditions through a fit over 1 Myr to a special version of the high accurate numerical ephemeris INPOP08 (Fienga et al. 2009). The precession equations have also been entirely revised and are no longer averaged over the orbital motion of the Earth and Moon. This new orbital solution is now valid over more than 50 Myr in the past or in the future with proper phases of the eccentricity variations. Due to chaotic behavior, the precision of the solution decreases rapidly beyond this time span, and we discuss the behavior of various solutions beyond 50 Myr. For paleoclimate calibrations, we provide several different solutions that are all compatible with the most precise planetary ephemeris. We have thus reached the time where geological data are now required to discriminate among planetary orbital solutions beyond 50 Myr.Comment: 17 pages, 14 figure

Statistics and Universality in Simplified Models of Planetary Formation

In this paper, we modify Laskar's simplified model of planetary evolution and accretion [J. Laskar, Phys. Rev. Lett, vol 84, p 3240 (2000)] to account for the full conservation of the total angular momentum of the system, and extend it to incorporate an accretion probability that depends on the mass and relative velocity of the colliding particles. We present statistical results for the mass and eccentricity of the planets formed, in terms of their semi-major axes, for a large number of realisations of different versions of the model. In particular, we find that by combining the mass-dependent accretion probability and the velocity-selection mechanism, the planets formed display a systematic occurrence at specific locations. By introducing properly scaled variables, our results are universal with respect to the total angular momentum of the system, the mass of the planetesimal disc, and the mass of the central star.Comment: 13 pages, 21 figures, some in colour. Accepted in MNRA

Frequency map analysis and quasiperiodic decompositions

Frequency Map Analysis is a numerical method based on refined Fourier techniques which provides a clear representation of the global dynamics of many multi-dimensional systems, and which is particularly adapted for systems of 3-degrees of freedom and more. This method relies heavily on the possibility of making accurate quasiperiodic approximations of of quasiperiodic signal given in a numerical way. In the present paper, we will describe the basis of the frequency analysis method, focussing on the quasi periodic approximation techniques. Application of these methods for the study of the global dynamics and chaotic diffusion of Hamiltonian systems and symplectic maps in different domains can be found in (Laskar, 1988, 1990, Laskar and Robutel, 1993, Robutel and Laskar, 2001, Nesvorny and Ferraz-Mello, 1997) for solar system dynamics, and in (Papaphilippou and Laskar, 1996, 1998, Laskar, 2000, Wachlin and Ferraz-Mello, 1998, Valluri and Merritt, 1998, Merritt and Valluri, 1999) for galactic dynamics. The method has been particularly successful for its application in particle accelerators (Dumas and Laskar, 1993, Laskar and Robin, 1996, Robin et al., 2000, Comunian et al., 2001, Papaphilippou and Zimmermann, 2002, Steier et al., 2002), and was also used for the understanding of atomic physics (Milczewski et al., 1997), or more general dynamical system issues (Laskar et al., 1992, Laskar, 1993, 1999, Chandre et al., 2001).Comment: 13 march 200

Andoyer construction for Hill and Delaunay variables

Andoyer variables are well known for the study of rotational dynamics. These variables were derived by Andoyer through a procedure that can be also used to obtain the Hill variables of the Kepler problem. Andoyer construction can also forecast the Delaunay variables which canonicity is then obtained without the use of a generating function.Comment: 8 pages, 2 figures, revised versio

Imprecision of Central Bank Announcements and Credibility

We consider a model where the central bank faces a credibility problem in its announcements, but also cares about its credibility and, therefore, wants to make truthful announcements. We show that, although the central bank would be able to perfectly transmit its information to the private sector through precise announcements, the central bank may nonetheless prefer to make imprecise announcements. This choice of the central bank would be suboptimal from the point of view of society. However, if the central bank gives enough weight to making truthful announcements, this suboptimality disappears, because the central bank would then prefer precise announcements to imprecise announcements.central bank transparency; central bank announcements; imprecise announcements; credibility

Stability analysis of the Martian obliquity during the Noachian era

We performed numerical simulations of the obliquity evolution of Mars during the Noachian era, at which time the giant planets were on drastically different orbits than today. For the preferred primordial configuration of the planets we find that there are two large zones where the Martian obliquity is stable and oscillates with an amplitude lower than 20$^\circ$. These zones occur at obliquities below 30$^\circ$ and above 60$^\circ$; intermediate values show either resonant or chaotic behaviour depending on the primordial orbits of the terrestrial planets

Determination of the threshold of the break-up of invariant tori in a class of three frequency Hamiltonian systems

We consider a class of Hamiltonians with three degrees of freedom that can be mapped into quasi-periodically driven pendulums. The purpose of this paper is to determine the threshold of the break-up of invariant tori with a specific frequency vector. We apply two techniques: the frequency map analysis and renormalization-group methods. The renormalization transformation acting on a Hamiltonian is a canonical change of coordinates which is a combination of a partial elimination of the irrelevant modes of the Hamiltonian and a rescaling of phase space around the considered torus. We give numerical evidence that the critical coupling at which the renormalization transformation starts to diverge is the same as the value given by the frequency map analysis for the break-up of invariant tori. Furthermore, we obtain by these methods numerical values of the threshold of the break-up of the last invariant torus.Comment: 18 pages, 4 figure

Central Bank Transparency and Shocks

According to the literature, in an expectations-augmented Phillips curve model, opacity is always preferred to transparency on central bank forecasts. By modelling the private sector's behavior explicitly, we show that transparency reduces the shocks. Consequently, transparency can be preferred.central bank, transparency, Phillips curve, shocks.