21,368 research outputs found
Phonon Linewidths and Electron Phonon Coupling in Nanotubes
We prove that Electron-phonon coupling (EPC) is the major source of
broadening for the Raman G and G- peaks in graphite and metallic nanotubes.
This allows us to directly measure the optical-phonon EPCs from the G and G-
linewidths. The experimental EPCs compare extremely well with those from
density functional theory. We show that the EPC explains the difference in the
Raman spectra of metallic and semiconducting nanotubes and their dependence on
tube diameter. We dismiss the common assignment of the G- peak in metallic
nanotubes to a Fano resonance between phonons and plasmons. We assign the G+
and G- peaks to TO (tangential) and LO (axial) modes.Comment: 5 pages, 4 figures (correction in label of fig 3
Bistability of persistent currents in mesoscopic rings
We study the persistent currents flowing in a mesoscopic ring threaded by a
magnetic flux and connected to a stub of finite length. Multistability
processes and Coulomb blockade are demonstrated to be present in this system.
These properties are functions of the magnetic flux crossing the ring which
plays the role that the external applied potential fulfills in the
multistability behaviour of the standard mesoscopic heterostructures.Comment: 13 pages (Revtex), 4 PostScript figures. Send e-mail to:
[email protected]
The C-metric as a colliding plane wave space-time
It is explicitly shown that part of the C-metric space-time inside the black
hole horizon may be interpreted as the interaction region of two colliding
plane waves with aligned linear polarization, provided the rotational
coordinate is replaced by a linear one. This is a one-parameter generalization
of the degenerate Ferrari-Ibanez solution in which the focussing singularity is
a Cauchy horizon rather than a curvature singularity.Comment: 6 pages. To appear in Classical and Quantum Gravit
Off-shell renormalization in the presence of dimension 6 derivative operators. II. UV coefficients
The full off-shell one loop renormalization for all divergent amplitudes up
to dimension 6 in the Abelian Higgs-Kibble model, supplemented with a maximally
power counting violating higher-dimensional gauge-invariant derivative
interaction , is
presented. This allows one to perform the complete renormalization of
radiatively generated dimension 6 operators in the model at hand. We describe
in details the technical tools required in order to disentangle the
contribution to UV divergences parameterized by (generalized) non-polynomial
field redefinitions. We also discuss how to extract the dependence of the
-function coefficients on the non-renormalizable coupling in one
loop approximation, as well as the cohomological techniques (contractible
pairs) required to efficiently separate the mixing of contributions associated
to different higher-dimensional operators in a spontaneously broken effective
field theory.Comment: 33 pages; revised version including the derivation of the one-loop
beta function
Community Involvement - Outreach / Development
Tonya Aiken: Horse Program Success. Kyle Cecil: Natural Resources and the Extension Educator. Karol Dyson: Building Strong Communities through Empowerment. Lisa Dennis: Food Smart . Theresa M. Ferrari: Community Service Experiences & 4-H Teens. t. Stacey Harper: Connecting the Youth with the Community. Joseph G. Hiller: Extension Work in Indian Country. Alice P. Kersey: Outreach to the NR Community. Carla M. Sousa: Learning from Latino Community Efforts
Does Magnetic Charge Imply a Massive Photon ?
In Abelian theories of monopoles the magnetic charge is required to be
enormous. Using the electric-magnetic duality of electromagnetism it is argued
that the existence of such a large, non-perturbative magnetic coupling should
lead to a phase transition where magnetic charge is permanently confined and
the photon becomes massive. The apparent masslessness of the photon could then
be used as an argument against the existence of such a large, non-perturbative
magnetic charge. Finally it is shown that even in the presence of this
dynamical mass generation the Cabbibo-Ferrari formulation of magnetic charge
gives a consistent theory.Comment: 10 pages LaTe
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