24,544 research outputs found
Bosonic Operator Methods for the Quark Model
Quark model matrix elements can be computed using bosonic operators and the
holomorphic representation for the harmonic oscillator. The technique is
illustrated for normal and exotic baryons for an arbitrary number of colors.
The computations are much simpler than those using conventional quark model
wavefunctions
Recent Load Calibrations Experience with the YF-12 Airplane
The use of calibrated strain gages to measure wing loads on the YF-12A airplane is discussed as well as structural configurations relative to the thermal environment and resulting thermal stresses. A thermal calibration of the YF-12A is described to illustrate how contaminating thermal effects can be removed from loads equations. The relationship between ground load calibrations and flight measurements is examined for possible errors, and an analytical approach to accommodate such errors is presented
A study of the effect of radical load distributions on calibrated strain gage load equations
For several decades, calibrated strain gages have been used to measure loads on airplanes. The accuracy of the equations used to relate the strain gage measurements to the applied loads has been based primarily on the results of the load calibration. An approach is presented for studying the effect of widely varying load distributions on strain gage load equations. The computational procedure provides a link between the load calibration and the load to be measured in flight. A matrix approach to equation selection is presented, which is based on equation standard error, load distribution, and influence coefficient plots of the strain gage equations, and is applied to a complex, delta-wing structure
Aspects of Nucleon Chiral Perturbation Theory
I review recent progress made in the calculation of nucleon properties in the
framework of heavy baryon CHPT. Topics include: Compton scattering,
scattering, the anatomy of a low-energy constant and the induced pseudoscalar
form factor.Comment: plain TeX (macro included), 12pp, lecture delivered at the workshop
on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199
Analysis of General Power Counting Rules in Effective Field Theory
We derive the general counting rules for a quantum effective field theory
(EFT) in dimensions. The rules are valid for strongly and weakly
coupled theories, and predict that all kinetic energy terms are canonically
normalized. They determine the energy dependence of scattering cross sections
in the range of validity of the EFT expansion. We show that the size of cross
sections is controlled by the power counting of EFT, not by chiral
counting, even for chiral perturbation theory (PT). The relation between
and is generalized to dimensions. We show that the
naive dimensional analysis counting is related to counting. The
EFT counting rules are applied to PT, low-energy weak interactions,
Standard Model EFT and the non-trivial case of Higgs EFT.Comment: V2: more details and examples added; version published in journal. 17
pages, 4 figures, 2 table
On the structure of large N cancellations in baryon chiral perturbation theory
We show how to compute loop graphs in heavy baryon chiral perturbation theory
including the full functional dependence on the ratio of the Delta--nucleon
mass difference to the pion mass, while at the same time automatically
incorporating the 1/N cancellations that follow from the large-N spin-flavor
symmetry of baryons in QCD. The one-loop renormalization of the baryon axial
vector current is studied to demonstrate the procedure. A new cancellation is
identified in the one-loop contribution to the baryon axial vector current. We
show that loop corrections to the axial vector currents are exceptionally
sensitive to deviations of the ratios of baryon-pion axial couplings from SU(6)
values
The use of a simplified structural model as an aid in the strain gage calibration of a complex wing
The use of a relatively simple structural model to characterize the load responses of strain gages located on various spars of a delta wing is examined. Strains measured during a laboratory load calibration of a wing structure are compared with calculations obtained from a simplified structural analysis model. Calculated and measured influence coefficient plots that show the shear, bending, and torsion characteristics of typical strain gage bridges are presented. Typical influence coefficient plots are shown for several load equations to illustrate the derivation of the equations from the component strain gage bridges. A relatively simple structural model was found to be effective in predicting the general nature of strain distributions and influence coefficient plots. The analytical processes are shown to be an aid in obtaining a good load calibration. The analytical processes cannot, however, be used in lieu of an actual load calibration of an aircraft wing
Hilbert Series for Flavor Invariants of the Standard Model
The Hilbert series is computed for the lepton flavor invariants of the
Standard Model with three generations including the right-handed neutrino
sector needed to generate light neutrino masses via the see-saw mechanism. We
also compute the Hilbert series of the quark flavor invariants for the case of
four generations.Comment: 6 page
1/N_c Expansion of the Heavy Baryon Isgur-Wise Functions
The 1/N_c expansion of the heavy baryon Isgur-Wise functions is discussed.
Because of the contracted SU(2N_f) light quark spin-flavor symmetry, the
universality relations among the Isgur-Wise functions of \Lambda_b to \Lambda_c
and \Sigma_b^{(*)} to \Sigma_c^{(*)} are valid up to the order of 1/N_c^2.Comment: 7 pages, latex, no figures, to appear in Phys. Rev.
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