Dissipation at the core-mantle boundary on a small-scale topography

International audienceThe parameters of the nutations are now known with a good accuracy, and the theory accounts for most of their values. Dissipative friction at the core-mantle boundary (CMB) and at the inner core boundary is an important ingredient of the theory. Up to now, viscous coupling at a smooth interface and electromagnetic coupling have been considered. In some cases they appear hardly strong enough to account for the observations. We advocate here that the CMB has a small-scale roughness and estimate the dissipation resulting from the interaction of the fluid core motion with this topography. We conclude that it might be significant

A description of the neutralino observables in terms of projectors

Applying Jarlskog's treatment of the CKM matrix, to the neutralino mass matrix in MSSM for real soft gaugino SUSY breaking and $\mu$-parameters, we construct explicit analytical expressions for the four projectors which acting on any neutralino state project out the mass eigenstates. Analytical expressions for the neutralino mass eigenvalues in terms of the various SUSY parameters, are also given. It is shown that these projectors and mass eigenvalues are sufficient to describe any physical observable involving neutralinos, to any order of perturbation theory. As an example, the $e^-e^+ \to \tilde \chi^0_i \tilde \chi^0_j$ cross section at tree level is given in terms of these projectors. The expected magnitude of their various matrix elements in plausible SUSY scenarios is also discussed.Comment: 14 pages, no figures. Version to appear in Phys. Rev. D. e-mail: [email protected]

On the external forcing of global eruptive activity in the past 300 years

The decryption of the temporal sequence of volcanic eruptions is a key step in better anticipating future events. Volcanic activity is the result of a complex interaction between internal and external processes, with time scales spanning multiple orders of magnitude. We review periodicities that have been detected or correlated with volcanic eruptions/phenomena and interpreted as resulting from external forces. Taking a global perspective and longer time scales than a few years, we approach this interaction by analyzing three time series using singular spectral analysis: the global number of volcanic eruptions (NVE) between 1700 and 2022, the number of sunspots (ISSN), a proxy for solar activity, the polar motion (PM) and length of day (lod), two proxies for gravitational force. Several pseudo-periodicities are common to NVE and ISSN, in addition to the 11-year Schwabe cycle that has been reported in previous work, but NVE shares even more periodicities with PM. These quasi-periodic components range from ~5 to ~130 years. We interpret our analytical results in light of the Laplace's paradigm and propose that, similarly to the movement of Earth's rotation axis, global eruptive activity is modulated by commensurable orbital moments of the Jovian planets, whose influence is also detected in solar activity

The neutralino projector formalism for complex SUSY parameters

We present a new formalism describing the neutralino physics in the context of the minimal supersymmetric model (MSSM), where CP violation induced by complex $M_1$ and $\mu$ parameters is allowed. The formalism is based on the construction of neutralino projectors, and can be directly generalized to non-minimal SUSY models involving any number of neutralinos. It extends a previous work applied to the real SUSY parameter case. In MSSM, the method allows to describe all physical observables related to a specific neutralino, in terms of its CP eigenphase and three complex numbers called its "reduced projector elements". As the experimental knowledge on the neutralino-chargino sectors will be being accumulated, the problem of extracting the various SUSY parameters will arise. Motivated by this, we consider various scenarios concerning the quantities that could be first measured. Analytical disentangled expressions determining the related SUSY parameters from them, are then derived, which also emphasize the efficiency of the formalism.Comment: Version accepted in Phys. Rev. D. e-mail: [email protected]

Optimal Charge and Color Breaking conditions in the MSSM

In the MSSM, we make a careful tree-level study of Charge and Color Breaking conditions in the plane $(H_2, \tilde{u}_L, \tilde{u}_R)$, focusing on the top quark scalar case. A simple and fast procedure to compute the VEVs of the dangerous vacuum is presented and used to derive a model-independent optimal CCB bound on $A_t$. This bound takes into account all possible deviations of the CCB vacuum from the D-flat directions. For large $\tan \beta$, it provides a CCB maximal mixing for the stop scalar fields $\tilde{t}_1,\tilde{t}_2$, which automatically rules out the Higgs maximal mixing $|A_t|=\sqrt{6} m_{\tilde{t}}$. As a result, strong limits on the stop mass spectrum and a reduction, in some cases substantial, of the one-loop upper bound on the CP-even lightest Higgs boson mass, $m_h$, are obtained. To incorporate one-loop leading corrections, this tree-level CCB condition should be evaluated at an appropriate renormalization scale which proves to be the SUSY scale.Comment: 41 pages, 7 eps figures, minor corrections, references added, to appear in Nucl. Phys.