151,576 research outputs found
Vibrating the QCD string
The large distance behaviour of the adiabatic hybrid potentials is studied in
the framework of the QCD string model. The calculated spectra are shown to be
the result of interplay between potential-type longitudinal and string-type
transverse vibrations.Comment: LaTeX2e, 9 pages, 2 Postscript figures, final version to appear in
Yad.Fi
Elliptic operators in even subspaces
In the paper we consider the theory of elliptic operators acting in subspaces
defined by pseudodifferential projections. This theory on closed manifolds is
connected with the theory of boundary value problems for operators violating
Atiyah-Bott condition. We prove an index formula for elliptic operators in
subspaces defined by even projections on odd-dimensional manifolds and for
boundary value problems, generalizing the classical result of Atiyah-Bott.
Besides a topological contribution of Atiyah-Singer type, the index formulas
contain an invariant of subspaces defined by even projections. This homotopy
invariant can be expressed in terms of the eta-invariant. The results also shed
new light on P.Gilkey's work on eta-invariants of even-order operators.Comment: 39 pages, 2 figure
Design and Construction of the 3.2 Mev High Voltage Column for Darht II
A 3.2 MeV injector has been designed and built for the Darht II Project at
Los Alamos Lab. The installation of the complete injector system is nearing
completion at this time. The requirements for the injector are to produce a 3.2
MeV, 2000 ampere electron pulse with a flattop width of at least 2-microseconds
and emittance of less than 0.15 p cm-rad normalized. A large high voltage
column has been built and installed. The column is vertically oriented, is 4.4
meters long, 1.2 meters in diameter, and weights 5700 kilograms. A novel method
of construction has been employed which utilizes bonded mycalex insulating
rings. This paper will describe the design, construction, and testing completed
during construction. Mechanical aspects of the design will be emphasized.Comment: 3 pages, 4 figures, Linac 200
Double-exciton component of the cyclotron spin-flip mode in a quantum Hall ferromagnet
We report on the calculation of the cyclotron spin-flip excitation (CSFE) in
a spin-polarized quantum Hall system at unit filling. This mode has a
double-exciton component which contributes to the CSFE correlation energy but
can not be found by means of a mean field approach. The result is compared with
available experimental data.Comment: 9 pages, 2 figure
Screening effects in the electron-optical phonon interaction
We show that recently reported unusual hardening of optical phonons
renormalized by the electron-phonon interaction is due to the neglect of
screening effects. When the electron-ion interaction is properly screened
optical phonons soften in three dimension. It is important that for
short-wavelength optical phonons screening is static while for long-wavelength
optical phonons screening is dynamic. In two-dimensional and one-dimensional
cases due to crossing of the nonperturbed optical mode with gapless plasmons
the spectrum of renormalized optical phonon-plasmon mode shows split momentum
dependence.Comment: 7 page
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