202 research outputs found
Momentum dependent relaxation rate and pseudogap in doped magnetic insulators
The spectral functions and corresponding self energies are calculated within
the planar t-t'-J model as relevant to hole-doped cuprates using the exact
diagonalization method at finite temperatures, combined with the averaging over
twisted boundary conditions. Results show truncated Fermi surface at low doping
and t'<0 in the antinodal region while the self energy reveals weakly k- and
doping dependent anomalous relaxation rate |\Sigma''(k,\omega)|~ a+b|\omega|
for \omega<0, consistent with recent ARPES results, and a pseudogap-generating
component of Lorentzian form. The latter is well pronounced at low doping and
strongly depends on k and t'.Comment: 5 pages, 5 figure
scattering in the Roper channel
We present results from our recent lattice QCD study of scattering in
the positive-parity nucleon channel, where the puzzling Roper resonance
resides in experiment. Using a variety of hadron operators, that
include -like, in -wave and in -wave, we
systematically extract the excited lattice spectrum in the nucleon channel up
to 1.65 GeV. Our lattice results indicate that N scattering in the elastic
approximation alone does not describe a low-lying Roper. Coupled channel
effects between and seem to be crucial to render a low-lying
Roper in experiment, reinforcing the notion that this state could be a
dynamically generated resonance. After giving a brief motivation for studying
the Roper channel and the relevant technical details to this study, we will
discuss the results and the conclusions based on our lattice investigation and
in comparison with other lattice calculations.Comment: 8 pages, 5 figures, presented at the 35th International Symposium on
Lattice Field Theory, 18-24 June 2017, Granada, Spai
Predicting positive parity mesons from lattice QCD
We determine the spectrum of 1P states using lattice QCD. For the
and mesons, the results are in good agreement
with the experimental values. Two further mesons are expected in the quantum
channels and near the and thresholds. A
combination of quark-antiquark and meson-Kaon interpolating fields
are used to determine the mass of two QCD bound states below the
threshold, with the assumption that mixing with and
isospin-violating decays to are negligible. We predict a
bound state with mass GeV. With
further assumptions motivated theoretically by the heavy quark limit, a bound
state with GeV is predicted in the
channel. The results from our first principles calculation are compared to
previous model-based estimates.Comment: 5 pages, 2 figures; Final versio
The pion-pion Interaction in the rho Channel in Finite Volume
The aim of this paper is to investigate an efficient strategy that allows to
obtain pi-pi phase shifts and rho meson properties from QCD lattice data with
high precision. For this purpose we evaluate the levels of the pi-pi system in
the rho channel in finite volume using chiral unitary theory. We investigate
the dependence on the pi mass and compare with other approaches which use QCD
lattice calculations and effective theories. We also illustrate the errors
induced by using the conventional Luscher approach instead of a more accurate
one recently developed that takes into account exactly the relativistic two
meson propagators. Finally we make use of this latter approach to solve the
inverse problem, getting pi-pi phase shifts from "synthetic" lattice data,
providing an optimal strategy and showing which accuracy is needed in these
data to obtain the properties with a desired accuracy.Comment: 16 pages, 13 figures, 1 table, substantially modified with practical
examples of use to lattice researchers, new comments and references adde
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