156 research outputs found
Renormalization of the electron-phonon interaction: a reformulation of the BCS-gap equation
A recently developed renormalization approach is used to study the
electron-phonon coupling in many-electron systems. By starting from an
Hamiltonian which includes a small gauge symmetry breaking field, we directly
derive a BCS-like equation for the energy gap from the renormalization
approach. The effective electron-electron interaction for Cooper pairs does not
contain any singularities. Furthermore, it is found that phonon-induced
particle-hole excitations only contribute to the attractive electron-electron
interaction if their energy difference is smaller than the phonon energy.Comment: 8 pages, version to appear in Eur. Phys. J.
Preparation of high density heavy metal fluoride glasses with extended ultraviolet and infra red ranges, and such high density heavy metal fluoride glasses
A heavy metal fluoride glass composition range (in mol percent) consisting essentially of: (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24)InF.sub.3 or GaF.sub.3.(4-16)CdF.sub.2.(6-24)YbF.sub.3.(4-22)ZnF.sub.2. In an alternative embodiment, a heavy metal fluoride glass composition range (in mol percent) comprises (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24) of (0-24)InF.sub.3, (0-24)GaF.sub.3 and (0-19)AlF.sub.3.(1-16)CdF.sub.2.(6-24)YbF.sub.3.(4-26)ZnF.sub.2. A preferred heavy metal fluoride glass produced in accordance with the present invention comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.7InF.sub.3.5GaF.sub.3.10CdF.sub.2.18YbF.sub.3. 16ZnF.sub.2. A preferred heavy metal fluoride glass has maximum thickness of most preferably about 3 mm. Another preferred heavy metal fluoride glass comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.12AlF.sub.3.10CdF.sub.2.18YbF.sub.3.16ZnF.sub.2
Stimulus Responsive Nanoparticles
Disclosed are various embodiments of methods and systems related to stimulus responsive nanoparticles. In one embodiment includes a stimulus responsive nanoparticle system, the system includes a first electrode, a second electrode, and a plurality of elongated electro-responsive nanoparticles dispersed between the first and second electrodes, the plurality of electro-responsive nanorods configured to respond to an electric field established between the first and second electrodes
G-actions with close orbit spaces
The classification of G-spaces by Palais is refined for the case where the
orbit space satisfies certain mild topological hypotheses.
It is shown that when a sequence of such orbit spaces is "close" to a limit
orbit space, in some suitable sense, within a larger ambient orbit space, the
G-spaces in the tail of the sequence are strongly equivalent to the limit
G-space.Comment: 12 pages, 1 figure. The result as previously stated in v1 was
incorrect; the hypotheses were insufficien
Renormalisation and fixed points in Hilbert Space
The energies of low-lying bound states of a microscopic quantum many-body
system of particles can be worked out in a reduced Hilbert space. We present
here and test a specific non-perturbative truncation procedure. We also show
that real exceptional points which may be present in the spectrum can be
identified as fixed points of coupling constants in the truncation procedure.Comment: 4 pages, 1 tabl
Representations of the Weyl Algebra in Quantum Geometry
The Weyl algebra A of continuous functions and exponentiated fluxes,
introduced by Ashtekar, Lewandowski and others, in quantum geometry is studied.
It is shown that, in the piecewise analytic category, every regular
representation of A having a cyclic and diffeomorphism invariant vector, is
already unitarily equivalent to the fundamental representation. Additional
assumptions concern the dimension of the underlying analytic manifold (at least
three), the finite wide triangulizability of surfaces in it to be used for the
fluxes and the naturality of the action of diffeomorphisms -- but neither any
domain properties of the represented Weyl operators nor the requirement that
the diffeomorphisms act by pull-backs. For this, the general behaviour of
C*-algebras generated by continuous functions and pull-backs of homeomorphisms,
as well as the properties of stratified analytic diffeomorphisms are studied.
Additionally, the paper includes also a short and direct proof of the
irreducibility of A.Comment: 71 pages, 1 figure, LaTeX. Changes v2 to v3: previous results
unchanged; some addings: inclusion of gauge transforms, several comments,
Subsects. 1.5, 3.7, 3.8; comparison with LOST paper moved to Introduction;
Def. 2.5 modified; some typos corrected; Refs. updated. Article now as
accepted by Commun. Math. Phy
The state of peer-to-peer network simulators
Networking research often relies on simulation in order to test and evaluate new ideas. An important requirement of this process is that results must be reproducible so that other researchers can replicate, validate and extend existing work. We look at the landscape of simulators for research in peer-to-peer (P2P) networks by conducting a survey of a combined total of over 280 papers from before and after 2007 (the year of the last survey in this area), and comment on the large quantity of research using bespoke, closed-source simulators. We propose a set of criteria that P2P simulators should meet, and poll the P2P research community for their agreement. We aim to drive the community towards performing their experiments on simulators that allow for others to validate their results
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