171 research outputs found
Dirac spectral density and mass anomalous dimension in 2+1 flavor QCD
We compute the Dirac spectral density of QCD in a wide range of eigenvalues
by using a stochastic method. We use 2+1 flavor lattice ensembles generated
with Mobius domain-wall fermion at three lattice spacings ( fm) to estimate the continuum limit. The discretization effect can be
minimized by a generalization of the valence domain-wall fermion. The spectral
density at relatively high eigenvalues can be matched with perturbation theory.
We compare the lattice results with the perturbative expansion available to
.Comment: 8 pages, 4 figures. Proceedings of the 35th International Symposium
on Lattice Field Theory, 18-24 June 2017, Granada, Spai
D meson semileptonic form factors in Nf=3 QCD with M\"obius domain-wall quarks
We present our calculation of D \to pi and D \to K semileptonic form factors
in Nf = 2+1 lattice QCD. We simulate three lattice cutoffs 1/a \sim 2.5, 3.6
and 4.5 GeV with pion masses as low as 230 MeV. The M\"obius domain-wall action
is employed for both light and charm quarks. We present our results for the
vector and scalar form factors and discuss their dependence on the lattice
spacing, light quark masses and momentum transfer.Comment: 8 pages, 5 figures, talk presented at the 35th International
Symposium on Lattice Field Theory (Lattice 2017), 18-24 June 2017, Granada,
Spai
Visual servoing with nonlinear observer
Visual servo system is a robot control system which incorporates the vision sensor in the feedback loop. Since the robot controller is also in the visual servo loop, compensation of the robot dynamics is important for high speed tasks. Moreover estimation of the object motion is necessary for real time tracking because the visual information includes considerable delay. This paper proposes a nonlinear model-based controller and a nonlinear observer for visual servoing. The observer estimates the object motion and the nonlinear controller makes the closed loop system asymptotically stable based on the estimated object motion. The effectiveness of the observer-based controller is verified by simulations and experiments on a two link planar direct drive robot</p
Topological susceptibility in 2+1-flavor QCD with chiral fermions
We compute the topological susceptibility of 2+1-flavor lattice QCD
with dynamical M\"obius domain-wall fermions, whose residual mass is kept at 1
MeV or smaller. In our analysis, we focus on the fluctuation of the topological
charge density in a "slab" sub-volume of the simulated lattice, as proposed by
Bietenholz et al. The quark mass dependence of our results agrees well with the
prediction of the chiral perturbation theory, from which the chiral condensate
is extracted. Combining the results for the pion mass and decay
constant , we obtain = 0.227(02)(11) at the
physical point, where the first error is statistical and the second is
systematic.Comment: 8 pages, 3 figures, talk given at the 35th International Symposium on
Lattice Field Theory, 18-24 June 2017, Granada, Spai
Axial U(1) symmetry and Dirac spectra in high-temperature phase of lattice QCD
The axial symmetry in the high-temperature phase is investigated with
lattice QCD simulations. The gauge ensembles are generated with
M\"obius domain-wall fermions, and the overlap/domain-wall reweighting is
applied. We find that the susceptibility evaluated from the spectrum
of overlap-Dirac eigenvalues is strongly suppressed in the chiral limit. We
also study its volume dependence.Comment: 7 pages, 2 figures, talk presented at the 36th International
Symposium on Lattice Field Theory (Lattice 2018), 22-28 July, 2018, Michigan,
US
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