1,780 research outputs found
Global design of an active integrated antenna for millimeter wave
An active integrated antenna working in the millimeter wave has been realized in a monolithic process. The concept of active integrated antenna is first introduced, then the design of the integrated circuit based on a global approach, following electromagnetic and circuit simulations, is presented. The obtained performances of the active antenna are discussed and compared to a passive one
On Dirac Zero Modes in Hyperdiamond Model
Using the SU(5) symmetry of the 4D hyperdiamond and results on the study of
4D graphene given in "Four Dimensional Graphene" (L.B Drissi, E.H Saidi, M.
Bousmina, CPM-11-01, Phys. Rev. D (2011)), we engineer a class of 4D lattice
QCD fermions whose Dirac operators have two zero modes. We show that generally
the zero modes of the Dirac operator in hyperdiamond fermions are captured by a
tensor {\Omega}_{{\mu}}^{l} with 4\times5 complex components linking the
Euclidean SO(4) vector {\mu}; and the 5-dimensional representation of SU(5).
The Bori\c{c}i-Creutz (BC) and the Karsten-Wilzeck (KW) models as well as their
Dirac zero modes are rederived as particular realizations of
{\Omega}_{{\mu}}^{l}. Other features are also given. Keywords: Lattice QCD,
Bori\c{c}i-Creutz and Karsten-Wilzeck models, 4D hyperdiamond, 4D graphene,
SU(5) Symmetry.Comment: LaTex, 28 pages, To appear in Phys Rev
Maximum Likelihood Approach to Vote Aggregation with Variable Probabilities
Condorcet (1785) initiated the statistical approach to vote aggregation. Two centuries later, Young (1988) showed that a correct application of the maximum likelihood principle leads to the selection of rankings called Kemeny orders, which have the minimal total number of disagreements with those of the voters. The Condorcet-Kemeny-Yoiung approach is based on the assumption that the voters have the same probability of comparing correctly two alternatives and that this probability is the same for any pair of alternatives. We relax the second part of this assumption by letting the probability of comparing correctly two alternatives be increasing with the distance between two alternatives in the allegedly true ranking. This leads to a rule in which the majority in favor of one alternative against another one is given a larger weight the larger the distance between the two alternatives in the true ranking, i.e. the larger the probability that the voters compare them correctly. This rule is not Condorcet consistent. Thus, it may be different from the Kemeny rule. Yet, it is anonymous, neutral, and paretian. However, contrary to the Kemeny rule, it does not satisfy Young and Levenglick (1978)'s local independence of irrelevant alternatives. Condorcet also hinted that the Condorcet winner or the top alternative in the Condorcet ranking is not necessarily most likely to be the best. Young confirms that indeed with a constant probability close to 1/2, this alternative is the Borda winner while it is the alternative whose smallest majority is the largest when the probability is close to 1. We extend his analysis to the case of variable probabilities. Young's result implies that the Kemeny rule does not necessarily select the alternative most likely to be the best. A natural question that comes to mind is whether the rule obtained with variable probabilities does better than the Kemeny rule in this respect. It appears that this performance imporves with the rate at which the probability increases.Vote Aggregation, Kemeny Rule, Maximum Likelihood, Variable Probabilities
Topological String on Toric CY3s in Large Complex Structure Limit
We develop a non planar topological vertex formalism and we use it to study
the A-model partition function of topological string on the
class of toric Calabi-Yau threefolds (CY3) in large complex structure limit. To
that purpose, we first consider the special Lagrangian
fibration of generic CY3-folds and we give the realization of the class of
large toric CY3-folds in terms of supersymmetric gauged linear sigma
model with \emph{non zero} gauge invariant superpotentials . Then, we focus on a one complex parameter supersymmetric gauged
model involving six chiral superfields with and we use it to compute the function
for the case of the local elliptic curve in the limit .Comment: Latex, 38 pages, 12 figures. To appear in Nucl Phys
Four Dimensional Graphene
Mimicking pristine 2D graphene, we revisit the BBTW model for 4D lattice QCD
given in ref.[5] by using the hidden SU(5) symmetry of the 4D hyperdiamond
lattice H_4. We first study the link between the H_4 and SU(5); then we refine
the BBTW 4D lattice action by using the weight vectors \lambda_1, \lambda_2,
\lambda_3, \lambda_4, \lambda_5 of the 5-dimensional representation of SU(5)
satisfying {\Sigma}_i\lambda_i=0. After that we study explicitly the solutions
of the zeros of the Dirac operator D in terms of the SU(5) simple roots
\alpha_1, \alpha_2, \alpha_3, \alpha_4 generating H_4; and its fundamental
weights \omega_1, \omega_2, \omega_3, \omega_4 which generate the reciprocal
lattice H_4^\ast. It is shown, amongst others, that these zeros live at the
sites of H_4^\ast; and the continuous limit D is given by ((id\surd5)/2)
\gamma^\muk_\mu with d, \gamma^\mu and k_\mu standing respectively for the
lattice parameter of H_4, the usual 4 Dirac matrices and the 4D wave vector.
Other features such as differences with BBTW model as well as the link between
the Dirac operator following from our construction and the one suggested by
Creutz using quaternions, are also given.
Keywords: Graphene, Lattice QCD, 4D hyperdiamond, BBTW model, SU(5) Symmetry.Comment: LaTex, 26 pages, 1 figure, To appear in Phys Rev
Halogenation of SiC for band-gap engineering and excitonic functionalization
The optical excitation spectra and excitonic resonances are investigated in
systematically functionalized SiC with Fluorine and/or Chlorine utilizing
density functional theory in combination with many-body perturbation theory.
The latter is required for a realistic description of the energy band-gaps as
well as for the theoretical realization of excitons. Structural, electronic and
optical properties are scrutinized and show the high stability of the predicted
two-dimensional materials. Their realization in laboratory is thus possible.
Huge band-gaps of the order of 4 eV are found in the so-called GW
approximation, with the occurrence of bright excitons, optically active in the
four investigated materials. Their binding energies vary from 0.9 eV to 1.75 eV
depending on the decoration choice and in one case, a dark exciton is foreseen
to exist in the fully chlorinated SiC. The wide variety of opto-electronic
properties suggest halogenated SiC as interesting materials with potential not
only for solar cell applications, anti-reflection coatings or high-reflective
systems but also for a possible realization of excitonic Bose-Einstein
condensation
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