7,080 research outputs found
Many-body approach to the nonlinear interaction of charged particles with an interacting free electron gas
We report various many-body theoretical approaches to the nonlinear decay
rate and energy loss of charged particles moving in an interacting free
electron gas. These include perturbative formulations of the scattering matrix,
the self-energy, and the induced electron density. Explicit expressions for
these quantities are obtained, with inclusion of exchange and correlation
effects.Comment: 11 pages, 5 figures. To appear in Journal of Physics
Screened Interaction and Self-Energy in an Infinitesimally Polarized Electron Gas via the Kukkonen-Overhauser Method
The screened electron-electron interaction and the
electron self-energy in an infinitesimally polarized electron gas are derived
by extending the approach of Kukkonen and Overhauser. Various quantities in the
expression for are identified in terms of the relevant
response functions of the electron gas. The self-energy is obtained from
by making use of the GW method which in this case
represents a consistent approximation. Contact with previous calculations is
made.Comment: 7 page
On Quantum Groups in the Hubbard Model with Phonons
The correct Hamiltonian for an extended Hubbard model with quantum group
symmetry as introduced by A. Montorsi and M. Rasetti is derived for a
D-dimensional lattice. It is shown that the superconducting SUq(2) holds as a
true quantum symmetry only for D = 1 and that terms of higher order in the
fermionic operators in addition to phonons are required for a quantum symmetric
hamiltonian. The condition for quantum symmetry is "half filling" and there is
no local electron-phonon coupling. A discussion of Quantum symmetries in
general is given in a formalism that should be readily accessible to non
Hopf-algebraists.Comment: latex, 17 page
Report of the Terrestrial Bodies Science Working Group. Volume 4: The moon
A rationale for furture exploration of the moon is given. Topics discussed include the objectives of the lunar polar orbiter mission, the mission profile, and general characteristics of the spacraft to be used
Benchmarking a semiclassical impurity solver for dynamical-mean-field theory: self-energies and magnetic transitions of the single-orbital Hubbard model
An investigation is presented of the utility of semiclassical approximations
for solving the quantum-impurity problems arising in the dynamical-mean-field
approach to the correlated-electron models. The method is based on performing a
exact numerical integral over the zero-Matsubara-frequency component of the
spin part of a continuous Hubbard-Stratonovich field, along with a
spin-field-dependent steepest descents treatment of the charge part. We test
this method by applying it to one or two site approximations to the single band
Hubbard model with different band structures, and comparing the results to
quantum Monte-Carlo and simplified exact diagonalization calculations. The
resulting electron self-energies, densities of states and magnetic transition
temperatures show reasonable agreement with the quantum Monte-Carlo simulation
over wide parameter ranges, suggesting that the semiclassical method is useful
for obtaining a reasonable picture of the physics in situations where other
techniques are too expensive.Comment: 14 pages, 15 figure
Reports on the Walnut Creek Watershed monitoring project, Jasper County, Iowa : water years 1995-2000
https://ir.uiowa.edu/igs_tis/1045/thumbnail.jp
Superconductivity in the quasi-two-dimensional Hubbard model
On the basis of spin and pairing fluctuation-exchange approximation, we study
the superconductivity in quasi-two-dimensional Hubbard model. The integral
equations for the Green's function are self-consistently solved by numerical
calculation. Solutions for the order parameter, London penetration depth,
density of states, and transition temperature are obtained. Some of the results
are compared with the experiments for the cuprate high-temperature
superconductors. Numerical techniques are presented in details. With these
techniques, the amount of numerical computation can be greatly reduced.Comment: 17 pages, 13 figure
All Coronal Loops are the Same: Evidence to the Contrary
The 1998 April 20 spectral line data from the Coronal Diagnostics
Spectrometer (CDS) on the {\it Solar and Heliospheric Observatory} (\SOHO)
shows a coronal loop on the solar limb. Our original analysis of these data
showed that the plasma was multi-thermal, both along the length of the loop and
along the line of sight. However, more recent results by other authors indicate
that background subtraction might change these conclusions, so we consider the
effect of background subtraction on our analysis. We show Emission Measure (EM)
Loci plots of three representative pixels: loop apex, upper leg, and lower leg.
Comparisons of the original and background-subtracted intensities show that the
EM Loci are more tightly clustered after background subtraction, but that the
plasma is still not well represented by an isothermal model. Our results taken
together with those of other authors indicate that a variety of temperature
structures may be present within loops.Comment: Accepted for publication in ApJ Letter
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