448 research outputs found
Reconstruction and actual trends of landslide activities in BruustâHaltiwald, Horw, canton of Lucerne, Switzerland
A spatiotemporal reconstruction of slope movements on the
edge of Lake Lucerne near the municipality of Horw, canton of Lucerne, is
presented. The reconstruction was realized by analyzing growth reactions of
beech (Fagus sylvatica L.) and fir (Abies alba Mill.) trees growing on this slope. Before
dendrochronological sampling, a detailed geomorphological mapping of the
landslide was conducted with the aim to determine the spatial extent of the
sliding area. For tree-ring analyses, 124Â increment cores from 62Â trees were
analyzed following standard techniques of dendrogeomorphology. In addition,
long micro-sections were prepared from the entire cores to extend the common
eccentricity analyses by microscopic determination of the onset of reaction
wood in fir and beech. Results clearly show that the area is moving at
least since 1948. A significant concentration of events was observed between
the years 1990 and 2000 as well as after 2006. The definition of a threshold
to define events using an eccentricity index alone is problematic and needs
to be adapted to specific site conditions. For this reason, we recommend always combining the application of an eccentricity index with a detailed
visual (anatomical) inspection to check for the occurrence of reaction wood.</p
Perfect topological charge for asymptotically free theories
The classical equations of motion of the perfect lattice action in
asymptotically free spin and gauge models possess scale invariant
instanton solutions. This property allows the definition of a topological
charge on the lattice which is perfect in the sense that no topological defects
exist. The basic construction is illustrated in the O(3) non--linear
--model and the topological susceptibility is measured to high
precision in the range of correlation lengths . Our results
strongly suggest that the topological susceptibility is not a physical quantity
in this model.Comment: Contribution to Lattice'94, 3 pages PostScript, uuencoded compresse
Hadron masses and decay constants in quenched QCD
We present results for the mass spectrum and decay constants using
non-perturbatively O(a) improved Wilson fermions. Three values of and
30 different quark masses are used to obtain the chiral and continuum limits.
Special emphasis will be given to the question of taking the chiral limit and
the existence of non-analytic behavior predicted by quenched chiral
perturbation theory.Comment: LATTICE99(spectrum), 3 pages, 6 figure
Prospects for perfect actions
The fixed-point (FP) action in QCD, although it is local and determined by
classical equations, is difficult to parametrize well and is expensive to
simulate. But the stake is high: the FP action has scale invariant instanton
solutions, has no topological artifacts, satisfies the index theorem on the
lattice, does not allow exceptional configurations, requires no tuning to get
the pion massless and is expected to reduce the cut-off effects significantly.
An overview is given including a discussion on tests in Yang-Mills theory, QCD
and spin and gauge models.Comment: 6 pages, Late
Full QCD light hadron spectrum from the CP-PACS
We report on an on-going two-flavor full QCD study on CP-PACS using an
RG-improved gauge action and a tadpole-improved SW quark action. Runs are made
for three lattice spacings , 1.3, and 2.5 GeV on
, , and lattices. Four sea quark
masses having --0.6 are simulated, for each
of which hadron masses are evaluated for valence quark masses corresponding to
--0.5. Results for hadron and light quark
masses are presented and compared with those obtained in quenched QCD.Comment: LATTICE98(spectrum), 3 pages, 3 figure
The static quark potential in full QCD
We report results on the static quark potential in two-flavor full QCD. The
calculation is performed for three values of lattice spacing and 2.5 GeV on and
lattices respectively, at sea quark masses corresponding to . An RG-improved gauge action and a tadpole-improved SW clover
quark action are employed. We discuss scaling of and
effects of dynamical quarks on the potential.Comment: LATTICE98(spectrum), 3 pages, 4 figure
Fixed Point Action and Topology in the CP^3 Model
We define a fixed point action in two-dimensional lattice
models. The fixed point action is a classical perfect lattice action, which is
expected to show strongly reduced cutoff effects in numerical simulations.
Furthermore, the action has scale-invariant instanton solutions, which enables
us to define a correct topological charge without topological defects. Using a
parametrization of the fixed point action for the model in a
Monte Carlo simulation, we study the topological susceptibility.Comment: 27 pages, 5 figures, typeset using REVTEX, Sec. 6 rewritten
(additional numerical results), to be published in Phys.Rev.
Heavy-light spectrum and decay constant from NRQCD with two flavors of dynamical quarks
We report on a study of B mesons on N_f = 2 full QCD configurations using an
RG-improved gauge action, NRQCD heavy quark action and tadpole-improved clover
light quark action. Results on the heavy-light spectrum and the decay constants
from 16^3x32 lattices at a^{-1} ~ 1.5 GeV are presented, and compared with
quenched results obtained with the same action combination at matching lattice
spacings.Comment: 3 pages, LaTeX, 2 PS figures, talk presented at LATTICE`99 (heavy
quarks
Topological Lattice Actions
We consider lattice field theories with topological actions, which are
invariant against small deformations of the fields. Some of these actions have
infinite barriers separating different topological sectors. Topological actions
do not have the correct classical continuum limit and they cannot be treated
using perturbation theory, but they still yield the correct quantum continuum
limit. To show this, we present analytic studies of the 1-d O(2) and O(3)
model, as well as Monte Carlo simulations of the 2-d O(3) model using
topological lattice actions. Some topological actions obey and others violate a
lattice Schwarz inequality between the action and the topological charge Q.
Irrespective of this, in the 2-d O(3) model the topological susceptibility
\chi_t = \l/V is logarithmically divergent in the continuum limit.
Still, at non-zero distance the correlator of the topological charge density
has a finite continuum limit which is consistent with analytic predictions. Our
study shows explicitly that some classically important features of an action
are irrelevant for reaching the correct quantum continuum limit.Comment: 38 pages, 12 figure
Eigenvalues of the hermitian Wilson-Dirac operator and chiral properties of the domain-wall fermion
Chiral properties of QCD formulated with the domain-wall fermion (DWQCD) are
studied using the anomalous quark mass m_{5q} and the spectrum of the
4-dimensional Wilson-Dirac operator. Numerical simulations are made with the
standard plaquette gauge action and a renormalization-group improved gauge
action. Results are reported on the density of zero eigenvalue obtained with
the accumulation method, and a comparison is made with the results for m_{5q}.Comment: Lattice 2000(Chiral Fermions), 4 pages, 6 eps figures,
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