8,365 research outputs found
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 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
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
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