676 research outputs found
Feedback laws for fuel minimization for transport aircraft
The Theoretical Mechanics Branch has as one of its long-range goals to work toward solving real-time trajectory optimization problems on board an aircraft. This is a generic problem that has application to all aspects of aviation from general aviation through commercial to military. Overall interest is in the generic problem, but specific problems to achieve concrete results are examined. The problem is to develop control laws that generate approximately optimal trajectories with respect to some criteria such as minimum time, minimum fuel, or some combination of the two. These laws must be simple enough to be implemented on a computer that is flown on board an aircraft, which implies a major simplification from the two point boundary value problem generated by a standard trajectory optimization problem. In addition, the control laws allow for changes in end conditions during the flight, and changes in weather along a planned flight path. Therefore, a feedback control law that generates commands based on the current state rather than a precomputed open-loop control law is desired. This requirement, along with the need for order reduction, argues for the application of singular perturbation techniques
Natural solution in the refined Gribov-Zwanziger theory
We analyse the one loop effective action of the Gribov-Zwanziger Lagrangian
and use the local composite operator formalism to include the most general
Becchi-Rouet-Stora-Tyutin (BRST) dimension two mass operator for the localizing
ghost fields. We show that the energetically favourable colour channel
corresponds to what is known as the R direction.Comment: 9 latex page
Renormalization properties of the mass operator A^2 in three dimensional Yang-Mills theories in the Landau gauge
Massive renormalizable Yang-Mills theories in three dimensions are analysed
within the algebraic renormalization in the Landau gauge. In analogy with the
four dimensional case, the renormalization of the mass operator A^2 turns out
to be expressed in terms of the fields and coupling constant renormalization
factors. We verify the relation we obtain for the operator anomalous dimension
by explicit calculations in the large N_f. The generalization to other gauges
such as the nonlinear Curci-Ferrari gauge is briefly outlined.Comment: 15 pages, 3 figure
Nonperturbative ghost dynamics in the maximal Abelian gauge
We construct the effective potential for the ghost condensate
in the maximal Abelian gauge. This condensate is an
order parameter for a global continuous symmetry, which is spontaneously broken
since a nonvanishing value of lowers the vacuum energy.
The associated Goldstone mode turns out to be unphysical.Comment: 16 pages. v2: version accepted for publication in JHE
Evaluation of a closed-circuit television display in landing operations with a helicopter
Evaluating closed circuit television display in helicopter landing operation
O(1/N_f) Corrections to the Thirring Model in 2<d<4
The Thirring model, that is, a relativistic field theory of fermions with a
contact interaction between vector currents, is studied for dimensionalities
2<d<4 using the 1/N_f expansion, where N_f is the number of fermion species.
The model is found to have no ultraviolet divergences at leading order provided
a regularization respecting current conservation is used. Explicit O(1/N_f)
corrections are computed, and the model shown to be renormalizable at this
order in the massless limit; renormalizability appears to hold to all orders
due to a special case of Weinberg's theorem. This implies there is a universal
amplitude for four particle scattering in the asymptotic regime. Comparisons
are made with both the Gross-Neveu model and QED.Comment: 22 pages in plain TeX, with 7 figs included using psfig.tex (Minor
conceptual changes - algebra unaffected
The asymmetry of the dimension 2 gluon condensate: the zero temperature case
We provide an algebraic study of the local composite operators A_\mu
A_\nu-\delta_{\mu\nu}/d A^2 and A^2, with d=4 the spacetime dimension. We prove
that these are separately renormalizable to all orders in the Landau gauge.
This corresponds to a renormalizable decomposition of the operator A_\mu A_\nu
into its trace and traceless part. We present explicit results for the relevant
renormalization group functions to three loop order, accompanied with various
tests of these results. We then develop a formalism to determine the zero
temperature effective potential for the corresponding condensates, and recover
the already known result for \neq 0, together with <A_\mu
A_\nu-\delta_{\mu\nu}/d A^2>=0, a nontrivial check that the approach is
consistent with Lorentz symmetry. The formalism is such that it is readily
generalizable to the finite temperature case, which shall allow a future
analytical study of the electric-magnetic symmetry of the condensate,
which received strong evidence from recent lattice simulations by Chernodub and
Ilgenfritz, who related their results to 3 regions in the Yang-Mills phase
diagram.Comment: 25 page
UV finiteness of 3D Yang-Mills theories with a regulating mass in the Landau gauge
We prove that three-dimensional Yang-Mills theories in the Landau gauge
supplemented with a infrared regulating, parity preserving mass term are
ultraviolet finite to all orders. We also extend this result to the
Curci-Ferrari gauge.Comment: 6 page
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