22,424 research outputs found
The noncommutative harmonic oscillator in more than one dimensions
The noncommutative harmonic oscillator in arbitrary dimension is examined. It
is shown that the -genvalue problem can be decomposed into separate
harmonic oscillator equations for each dimension. The noncommutative plane is
investigated in greater detail. The constraints for rotationally symmetric
solutions and the corresponding two-dimensional harmonic oscillator are solved.
The angular momentum operator is derived and its -genvalue problem is
shown to be equivalent to the usual eigenvalue problem. The -genvalues
for the angular momentum are found to depend on the energy difference of the
oscillations in each dimension. Furthermore two examples of assymetric
noncommutative harmonic oscillator are analysed. The first is the
noncommutative two-dimensional Landau problem and the second is the
three-dimensional harmonic oscillator with symmetrically noncommuting
coordinates and momenta.Comment: 12 page
A finite difference solution to a mixed boundary value problem for Laplace's equation
Finite difference solution to mixed boundary value problem for Laplace equatio
Evidence for the Role of Instantons in Hadron Structure from Lattice QCD
Cooling is used as a filter on a set of gluon fields sampling the Wilson
action to selectively remove essentially all fluctuations of the gluon field
except for the instantons. The close agreement between quenched lattice QCD
results with cooled and uncooled configurations for vacuum correlation
functions of hadronic currents and for density-density correlation functions in
hadronic bound states provides strong evidence for the dominant role of
instantons in determining light hadron structure and quark propagation in the
QCD vacuum.Comment: 26 pages in REVTeX, plus 10 figures, uuencoded. Submitted to Physical
Review D. MIT-CTP-226
Theoretical studies on tone noise from a ducted fan rotor
The method of computing radiated noise from a ducted rotor due to inflow distortion and turbulence are examined. Analytical investigations include an appropriate description of sources, the cut-off conditions imposed on the modal propagation of the pressure waves in the annular duct, and reflections at the upstream end of the duct. Far field sound pressure levels at blade passing frequency due to acoustic radiation from a small scale low speed fan are computed. Theoretical predictions are in reasonable agreement with experimental measurements
BMN operators with vector impurities, Z_2 symmetry and pp-waves
We calculate the coefficients of three-point functions of BMN operators with
two vector impurities. We find that these coefficients can be obtained from
those of the three-point functions of scalar BMN operators by interchanging the
coefficient for the symmetric-traceless representation with the coefficient for
the singlet. We conclude that the Z_2 symmetry of the pp-wave string theory is
not manifest at the level of field theory three-point correlators.Comment: 25 pages, 7 figures. v1: A reference and a footnote added; v2: New
contributions found, Z_2 symmetry lost in 3-point function
Correlation Functions of Hadron Currents in the QCD Vacuum Calculated in Lattice QCD
Point-to-point vacuum correlation functions for spatially separated hadron
currents are calculated in quenched lattice QCD on a lattice
with . The lattice data are analyzed in terms of dispersion
relations, which enable us to extract physical information from small distances
where asymptotic freedom is apparent to large distances where the hadronic
resonances dominate. In the pseudoscalar, vector, and axial vector channels
where experimental data or phenomenological information are available,
semi-quantitative agreement is obtained. In the nucleon and delta channels,
where no experimental data exist, our lattice data complement experiments.
Comparison with approximations based on sum rules and interacting instantons
are made, and technical details of the lattice calculation are described.Comment: 31 pages in REVTeX (with 10 figures to be added using figures
command), MIT CTP #214
Resolution-dependent quark masses from meson correlators
We explore the impact of a resolution-dependent constituent quark mass, as
recently applied to diffractive meson production, in QCD correlation functions
of several spin-0 and spin-1 meson channels. We compare the resulting
correlators with experimental and lattice data, analyze the virtues and
limitations of the approach, and discuss the channel dependence of the obtained
effective quark masses.Comment: 15 pages, 5 figures, to be published in Phys. Rev. C, reference adde
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