8,065 research outputs found
Density functional theory for fermions close to the unitary regime
We consider interacting Fermi systems close to the unitary regime and compute
the corrections to the energy density that are due to a large scattering length
and a small effective range. Our approach exploits the universality of the
density functional and determines the corrections from the analyical results
for the harmonically trapped two-body system. The corrections due to the finite
scattering length compare well with the result of Monte Carlo simulations. We
also apply our results to symmetric neutron matter.Comment: 4 pages, 2 figure
Double beta decay and the extra-dimensional seesaw mechanism
We study the model-building conditions under which an observable 0vBB decay
signal is predicted due to Kaluza-Klein singlet neutrinos in theories with
large extra dimensions. Our analysis is based on 5-dimensional singlet-neutrino
models compactified on an S^1/Z_2 orbifold, where the Standard-Model fields are
localized on a 3-brane. We show that sizeable 0vBB rates within the above
minimal 5-dimensional framework would require a non-vanishing shift of the
3-brane from the orbifold fixed points by an amount smaller than the typical
scale 100 inverse MeV characterizing the Fermi nuclear momentum. The resulting
5-dimensional models predict a sizeable effective Majorana-neutrino mass that
could be several orders of magnitude larger than the light neutrino masses.Comment: 12 pages, 2 figures, talk presented by H. Paes at AHEP-2003,
Valencia, Spai
Stability margins for multilinear interval systems by way of phase conditions: A unified approach
A simple way of checking the stability with respect to an arbitrary stability region of a family of polynomials containing a vector of parameters varying within prescribed intervals is discussed. It is assumed that the parameters appear affine multilinearly in the characteristic polynomial coefficients. The condition proposed is simply to check the phase difference of the vertex polynomials. This test based on the mapping theorem significantly reduces computational complexity. Mathematical proofs are omitted. The results can be used to determine various stability margins of control systems containing interconnected interval subsystems. These include the gain, phase, time-delay, H(sup infinity), and nonlinear sector bounded stability margins of multilinear interval systems
Parametric stability margin for multilinear interval control systems
Recently, a necessary and sufficient condition to determine the robust stability of a multilinear interval control system has been reported as an extension of the well-known Box theorem which deals with the linear affine case. A simple but computationally efficient algorithm, based on the above result, to check the robust stability of such systems is introduced. The method is also extended to find the parametric stability margin of such a system
Neutrino mass and magnetic moment in supersymmetry without R-parity in the light of recent data
We consider the generation of neutrino Majorana mass and transition magnetic
moment by the lepton-number violating and/or couplings in
R-parity-violating supersymmetric models. We update (and improve) the existing
upper limits on the relevant couplings using the most recent data on neutrino
masses and mixings, indicating also the possible improvement by the GENIUS
project. We study the implication of this update on the induced neutrino
magnetic moment.Comment: 7 pages, Latex, uses axodraw.sty; refs updated, to appear in PL
The 32nd CDC: Robust stabilizer synthesis for interval plants using Nevanlina-pick theory
The synthesis of robustly stabilizing compensators for interval plants, i.e., plants whose parameters vary within prescribed ranges is discussed. Well-known H(sup infinity) methods are used to establish robust stabilizability conditions for a family of plants and also to synthesize controllers that would stabilize the whole family. Though conservative, these methods give a very simple way to come up with a family of robust stabilizers for an interval plant
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