460 research outputs found
How universal is the one-particle Green's function of a Luttinger liquid?
The one-particle Green's function of the Tomonaga-Luttinger model for
one-dimensional interacting Fermions is discussed. Far away from the origin of
the plane of space-time coordinates the function falls off like a power law.
The exponent depends on the direction within the plane. For a certain form of
the interaction potential or within an approximated cut-off procedure the
different exponents only depend on the strength of the interaction at zero
momentum and can be expressed in terms of the Luttinger liquid parameters
and of the model at hand. For a more general
interaction and directions which are determined by the charge velocity
and spin velocity the exponents also depend on the
smoothness of the interaction at zero momentum and the asymptotic behavior of
the Green's function is not given by the Luttinger liquid parameters alone.
This shows that the physics of large space-time distances in Luttinger liquids
is less universal than is widely believed.Comment: 5 pages with 2 figure
Boundary Effects on Spectral Properties of Interacting Electrons in One Dimension
The single electron Green's function of the one-dimensional
Tomonaga-Luttinger model in the presence of open boundaries is calculated with
bosonization methods. We show that the critical exponents of the local spectral
density and of the momentum distribution change in the presence of a boundary.
The well understood universal bulk behavior always crosses over to a boundary
dominated regime for small energies or small momenta. We show this crossover
explicitly for the large-U Hubbard model in the low-temperature limit.
Consequences for photoemission experiments are discussed.Comment: revised and reformatted paper to appear in Phys. Rev. Lett. (Feb.
1996). 5 pages (revtex) and 3 embedded figures (macro included). A complete
postscript file is available from http://FY.CHALMERS.SE/~eggert/luttinger.ps
or by request from [email protected]
Interpretation of Photoemission Spectra of (TaSe4)2I as Evidence of Charge Density Wave Fluctuations
The competition between different and unusual effects in
quasi-one-dimensional conductors makes the direct interpretation of
experimental measurements of these materials both difficult and interesting. We
consider evidence for the existence of large charge-density-wave fluctuations
in the conducting phase of the Peierls insulator (TaSe4)2I, by comparing the
predictions of a simple Lee, Rice and Anderson theory for such a system with
recent angle-resolved photoemission spectra. The agreement obtained suggests
that many of the unusual features of these spectra may be explained in this
way. This view of the system is contrasted with the behaviour expected of a
Luttinger liquid.Comment: Archive copy of published paper. 19 pages, 12 figures, uses IOP
macro
Imaging of ανβ3 integrin expression in rheumatoid arthritis with [68Ga]Ga-NODAGA-RGDyk PET/CT in comparison to [18F]FDG PET/CT
[Ga-68] Ga-NODAGA-RGDyk PET/CT and [F-18] FDG PET/CT were performed in a 65-year-old woman during the work-up of a squamous cell carcinoma of the tongue within a clinical study protocol. Images revealed both tracers' uptake in the primary tumor and cervical lymph nodes, but also bilaterally in the shoulders, elbows, wrists, metacarpophalangeal, interphalangeal, and hip joints. The patient had been diagnosed with rheumatoid arthritis 8 years prior to the examination. Images showed a significantly higher [F-18] FDG than [Ga-68] Ga-NODAGA-RGDyk uptake in primary tumor and cervical lymph nodes. However, the patient with moderately active rheumatoid arthritis had similar levels of [Ga-68]Ga-NODAGA-RGDyk and [F-18] FDG uptake in the involved joints, but with no [Ga-68] Ga-NODAGA-RGDyk uptake in the surrounding muscles, unlike with [F-18]FDG. Our case suggests that [Ga-68]Ga-NODAGA-RGDyk PET/CT allows imaging of integrins expression in rheumatoid arthritis, including integrins expressed in synovial angiogenesis, with potentially a better signal-to-noise ratio than on [F-18]FDG PET/CT. (C) 2021 The Author(s). Published by Elsevier Masson SAS
Phase diagram of the one-dimensional extended Hubbard model with attractive and/or repulsive interactions at quarter filling
We study the phase diagram of the one dimensional (1D) model at quarter
filling in the most general case where the on-site and first-neighbour
interactions and can be both attractive and repulsive. The results have
been obtained using exact diagonalization of small clusters and variational
techniques, as well as exact results in various limits. We have analyzed four
properties of the groundstate: i)~whether it is insulating or metallic;
\hbox{ii)~whether} it is homogenous or phase separated; iii)~whether it has a
spin gap; iv)~whether it has dominant superconducting fluctuations. With eight
phases, the resulting phase diagram is unexpectedly rich. The four phases not
found in the weak coupling limit are: i) an insulating phase when and
are large enough; ii) a region of phase separation when is attractive; iii)
another region of phase separation when is large enough and small; iv)
a region with dominant superconducting fluctuations when is intermediate
and small. The actual nature of this last phase, which has pairs but no
spin gap, is not fully clear yet.Comment: 24 pages, RevTeX (4 postscript figures attached to the end
Spectral function of the 1D Hubbard model in the limit
We show that the one-particle spectral functions of the one-dimensional
Hubbard model diverge at the Fermi energy like
in the limit. The Luttinger liquid behaviour
, where as ,
should be limited to (for large but
finite), which shrinks to a single point, ,in that limit.
The consequences for the observation of the Luttinger liquid behaviour in
photoemission and inverse photoemission experiments are discussed.Comment: 4 pages, RevTeX, 2 figures on reques
Crack Detection of Timoshenko Beams Using Vibration Behavior and Neural Network
ABSTRACT In this research, at first, natural frequencies of a cracked beam are obtained analytically. Also, the location and the depth of a crack in the beam are identified by neural network method, in this study. This research is applied on a beam with an open edge crack for three different boundary conditions. For this purpose, firstly, the natural frequencies of the cracked beam are analytically obtained to get the examples for training the neural network. Then, inversely, the trained neural network is used for obtaining the location and depth of the crack. The effect of the numbers of the natural frequencies as input of the network was evaluated on the prediction accuracy. Results and measure of errors show that the neural network is a powerful method to determine the location and depth of crack. Also, increasing the numbers of the natural frequencies causes the prediction accuracy to be increased
Remnant Fermi surface in the presence of an underlying instability in layered 1T-TaS_2
We report high resolution angle-scanned photoemission and Fermi surface (FS)
mapping experiments on the layered transition-metal dichalcogenide 1T-TaS_2 in
the quasi commensurate (QC) and the commensurate (C) charge-density-wave (CDW)
phase. Instead of a nesting induced partially removed FS in the CDW phase we
find a pseudogap over large portions of the FS. This remnant FS exhibits the
symmetry of the one-particle normal state FS even when passing from the
QC-phase to the C-phase. Possibly, this Mott localization induced transition
represents the underlying instability responsible for the pseudogapped FS
Insulator-Metal Transition in One Dimension Induced by Long-Range Electronic Interactions
The effects of a long range electronic potential on a one dimensional
commensurate Charge Density Wave (CDW) state are investigated. Using numerical
techniques it is shown that a transition to a metallic ground state is reached
as the range of the electron-electron repulsion increases. In this metallic
state, the optical conductivity exhibits a large Drude weight. Possible
interpretations of our results are discussed.Comment: 5 pages, Revtex, minor misprints corrected and a reference to earlier
work by V. Emery and C. Noguera adde
Non-fermi-liquid single particle lineshape of the quasi-one-dimensional non-CDW metal Li_{0.9}Mo_{6}O_{17} : comparison to the Luttinger liquid
We report the detailed non-Fermi liquid (NFL) lineshape of the dispersing
excitation which defines the Fermi surface (FS) for quasi-one-dimensional
Li_{0.9}Mo_{6}O_{17}. The properties of Li_{0.9}Mo_{6}O_{17} strongly suggest
that the NFL behavior has a purely electronic origin. Relative to the
theoretical Luttinger liquid lineshape, we identify significant similarities,
but also important differences.Comment: 5 pages, 3 eps figure
- …