5,158 research outputs found
Estimation of the Tropical Cyclone Diurnal Cycle Using Simulated Observations from the NASA TROPICS Earth Venture Mission
No abstract availabl
Surface-State Localization at Adatoms
Low-temperature scanning tunneling spectroscopy of magnetic and non-magnetic
metal atoms on Ag(111) and on Cu(111) surfaces reveals the existence of a
common electronic resonance at an energy below the binding energies of the
surface states. Using an extended Newns-Anderson model, we assign this
resonance to an adsorbate-induced bound state, split off from the bottom of the
surface-state band, and broadened by the interaction with bulk states. A
lineshape analysis of the bound state indicates that native adatoms decrease
the surface-state lifetime, while a cobalt adatom causes no significant change.Comment: 4 pages, 4 figure
Theoretical analysis of STM-derived lifetimes of excitations in the Shockley surface state band of Ag(111)
We present a quantitative many-body analysis using the GW approximation of
the decay rate due to electron-electron scattering of excitations in
the Shockley surface state band of Ag(111), as measured using the scanning
tunnelling microscope (STM). The calculations include the perturbing influence
of the STM, which causes a Stark-shift of the surface state energy and
concomitant increase in . We find varies more rapidly with
than recently found for image potential states, where the STM has been shown to
significantly affect measured lifetimes. For the Shockley states, the
Stark-shifts that occur under normal tunnelling conditions are relatively small
and previous STM-derived lifetimes need not be corrected.Comment: 4 pages, 3 figure
Ramanujan and Extensions and Contractions of Continued Fractions
If a continued fraction is known to converge
but its limit is not easy to determine, it may be easier to use an extension of
to find the limit. By an extension of
we mean a continued fraction whose odd or even part is . One can
then possibly find the limit in one of three ways:
(i) Prove the extension converges and find its limit;
(ii) Prove the extension converges and find the limit of the other
contraction (for example, the odd part, if is the
even part);
(ii) Find the limit of the other contraction and show that the odd and even
parts of the extension tend to the same limit.
We apply these ideas to derive new proofs of certain continued fraction
identities of Ramanujan and to prove a generalization of an identity involving
the Rogers-Ramanujan continued fraction, which was conjectured by Blecksmith
and Brillhart.Comment: 16 page
Controlled Contact to a C60 Molecule
The conductance of C60 on Cu(100) is investigated with a low-temperature
scanning tunneling microscope. At the transition from tunneling to the contact
regime the conductance of C60 adsorbed with a pentagon-hexagon bond rises
rapidly to 0.25 conductance quanta G0. An abrupt conductance jump to G0 is
observed upon further decreasing the distance between the instrument's tip and
the surface. Ab-initio calculations within density functional theory and
non-equilibrium Green's function techniques explain the experimental data in
terms of the conductance of an essentially undeformed C60. From a detailed
analysis of the crossover from tunneling to contact we conclude that the
conductance in this region is strongly affected by structural fluctuations
which modulate the tip-molecule distance.Comment: 4 pages, 3 figure
Harmonic and minimal unit vector fields on Riemannian symmetric spaces
We present new examples of harmonic and minimal unit vector fields on Riemannian symmetric spaces. These examples are constructed from cohomogeneity one actions with a reflective singular orbit. The radial unit vector field associated to such a reflective submanifold is harmonic and minimal
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