Eigenstructure Assignment Based Controllers Applied to Flexible Spacecraft

The objective of this paper is to evaluate the behaviour of a controller designed using a parametric Eigenstructure Assignment method and to evaluate its suitability for use in flexible spacecraft. The challenge of this objective lies in obtaining a suitable controller that is specifically designated to alleviate the deflections and vibrations suffered by external appendages in flexible spacecraft while performing attitude manoeuvres. One of the main problems in these vehicles is the mechanical cross-coupling that exists between the rigid and flexible parts of the spacecraft. Spacecraft with fine attitude pointing requirements need precise control of the mechanical coupling to avoid undesired attitude misalignment. In designing an attitude controller, it is necessary to consider the possible vibration of the solar panels and how it may influence the performance of the rest of the vehicle. The nonlinear mathematical model of a flexible spacecraft is considered a close approximation to the real system. During the process of controller evaluation, the design process has also been taken into account as a factor in assessing the robustness of the system

Gauge-Higgs unification with brane kinetic terms

By identifying the Higgs field as an internal component of a higher dimensional gauge field it is possible to solve the little hierarchy problem. The construction of a realistic model that incorporates such a gauge-Higgs unification is an important problem that demands attention. In fact, several attempts in this direction have already been put forward. In this letter we single out one such attempt, a 6D SU(3) extended electroweak theory, where it is possible to obtain a Higgs mass prediction in accord with global fits. One shortcoming of the model is its prediction for the Weinberg angle, it is too large. We slightly modify the model by including brane kinetic terms in a way motivated by the orbifold action on the 6D fields. We show that in this way it is possible to obtain the correct Weinberg angle while keeping the desired results in the Higgs sector.Comment: 11 pages, 2 figures. References added. Version to appear in Phys. Lett.

CP violating phase from charged-lepton mixing

A model independent analysis of the leptonic Dirac CP-violating phase ({\delta}) is presented. The analysis uses the experimentally determined values of the mixing angles in the lepton mixing matrix in order to explore the allowed values for {\delta} and possible general forms for the charged lepton mixing matrix. This is done under two general assumptions: 1) that the mixing matrix in the neutrino sector is the so-called tribimaximal matrix and hence the non zero value for {\theta}13 arises due to the mixing matrix in the charged lepton sector and 2) the charged lepton mixing matrix is parametrized in terms of three angles and one phase. It is found that any value of {\delta} is still consistent with the data and that, considering the assumptions above, regardless of the value for {\delta}, the 1-3 mixing angle in the charged lepton sector is small but non zero and the 2-3 mixing angle can take values in only two possible small ranges around 0 and {\pi}/2 respectively.Comment: References adde

Electroweak scale neutrinos and decaying dark matter

We explore the scalar phenomenology of a model of electroweak scale neutrinos that incorporates the presence of a lepton number violating singlet scalar. An analysis of the pseudoscalar-Majoron field associated to this singlet field is carried out in order to verify the viability of the model and to restrict its parameter space. In particular we study the Majoron decay $J \to \nu \nu$ and use the bounds on the Majoron mass and width obtained in a modified Majoron Decaying Dark Matter scenario.Comment: 8 pages, 6 figures. A discussion on the invisible Higgs decay mode present in the model and some references were added . Version to appear in PL

A Model of Neutrino and Higgs Physics at the Electroweak Scale

We present and explore the Higgs physics of a model that in addition to the Standard Model fields includes a lepton number violating singlet scalar field. Based on the fact that the only experimental data we have so far for physics beyond the Standard Model is that of neutrino physics, we impose a constraint for any addition not to introduce new higher scales. As such, we introduce right-handed neutrinos with an Electroweak Scale mass. We study the Higgs decay $H \to \nu \nu$ and show that it leads to different signatures compared to those in the Standard Model, making it possible to detect them and to probe the nature of their couplings.Comment: 11 pages, 4 figures, 1 table. Corrected factor on eq. 17 and data table I. Added references. Version to appear in Physics Letters