620 research outputs found
Evidence of Strong Correlation between Instanton and QCD-monopole on SU(2) Lattice
The correlation between instantons and QCD-monopoles is studied both in the
lattice gauge theory and in the continuum theory. An analytical study in the
Polyakov-like gauge, where is diagonalized, shows that the
QCD-monopole trajectory penetrates the center of each instanton, and becomes
complicated in the multi-instanton system. Using the SU(2) lattice with ,
the instanton number is measured in the singular (monopole-dominating) and
regular (photon-dominating) parts, respectively. The monopole dominance for the
topological charge is found both in the maximally abelian gauge and in the
Polyakov gauge.Comment: 4 pages, Latex, 3 figures. Talk presented by H. Suganuma at
International Symposium on 'Lattice Field Theory', July 11 - 15, 1995,
Melbourne, Australi
Confinement Properties in the Multi-Instanton System
We investigate the confinement properties in the multi-instanton system,
where the size distribution is assumed to be for the large
instanton size . We find that the instanton vacuum gives the area law
behavior of the Wilson loop, which indicates existence of the linear confining
potential. In the multi-instanton system, the string tension increases
monotonously with the instanton density, and takes the standard value for the density . Thus, instantons
directly relate to color confinement properties.Comment: Talk presented by M. Fukushima at ``Lattice '97'', the International
Symposium on Lattice Field Theory, 22 - 26 July 1997, in Edinburgh, Scotland,
3 pages, Plain Late
Simulation of SU(2) Dynamical Fermion at Finite Chemical Potential and at Finite Temperature
SU(2) lattice gauge theory with dynamical fermion at non-zero chemical
potential and at finite temperature is studied. We focus on the influence of
chemical potential for quark condensate and mass of pseudoscalar meson at
finite temperature.
Hybrid Monte Carlo simulations with staggered fermions are carried
out on lattice. At and
0.05,0.07,0.1, we calculate the quark condensate and masses of
pseudoscalar meson consisting of light and heavier quarks for chemical
potential 0.0,0.02,0.05,0.1,0.2.Comment: Proceedings of the International Workshop on Nonperturbative Methods
and Lattice QCD, Guangzhou, Chin
Monopole Current Dynamics and Color Confinement
Color confinement can be understood by the dual Higgs theory, where monopole
condensation leads to the exclusion of the electric flux from the QCD vacuum.
We study the role of the monopole for color confinement by investigating the
monopole current system. When the self-energy of the monopole current is small
enough, long and complicated monopole world-lines appear, which is a signal of
monopole condensation. In the dense monopole system, the Wilson loop obeys the
area-law, and the string tension and the monopole density have similar behavior
as the function of the self-energy, which seems that monopole condensation
leads to color confinement. On the long-distance physics, the monopole current
system almost reproduces essential features of confinement properties in
lattice QCD. In the short-distance physics, however, the monopole-current
theory would become nonlocal and complicated due to the monopole size effect.
This monopole size would provide a critical scale of QCD in terms of the dual
Higgs mechanism.Comment: 6 pages LaTeX, 5 figures, uses espcrc1.sty, Talk presented at
International Conference on Quark Lepton Nuclear Physics, Osaka, May. 199
Responses of quark condensates to the chemical potential
The responses of quark condensates to the chemical potential, as a function
of temperature T and chemical potential \mu, are calculated within the
Nambu--Jona-Lasinio (NJL) model. We compare our results with those from the
recent lattice QCD simulations [QCD-TARO Collaboration, Nucl. Phys. B (Proc.
Suppl.) 106, 462 (2002)]. The NJL model and lattice calculations show
qualitatively similar behavior, and they will be complimentary ways to study
hadrons at finite density. The behavior above T_c requires more elaborated
analyses.Comment: 3 pages, 2 figs, based on a contribution to the Prof. Osamu Miyamura
memorial symposium, Hiroshima University, Nov. 16-17, 2001; slightly revised,
accepted for publication in Physical Review
Chiral symmetry breaking and stability of strangelets
We discuss the stability of strangelets by considering dynamical chiral
symmetry breaking and confinement. We use a
symmetric Nambu--Jona-Lasinio model for chiral symmetry breaking supplemented
by a boundary condition for confinement. It is shown that strangelets with
baryon number can stably exist. For the observables, we
obtain the masses and the charge-to-baryon number ratios of the strangelets.
These quantities are compared with the observed data of the exotic particles.Comment: 10 pages, 9 figures, submitted to Physical Review
The Role of Monopoles for Color Confinement
We study the role of the monopole for color confinement by using the monopole
current system. For the self-energy of the monopole current less than
ln, long and complicated monopole world-lines appear and the Wilson
loop obeys the area law, and therefore the monopole current system almost
reproduces essential features of confinement properties in the long-distance
physics. In the short-distance physics, however, the monopole-current theory
would become nonlocal due to the monopole size effect. This monopole size would
provide a critical scale of QCD in terms of the dual Higgs mechanism.Comment: 3 pages LaTeX, 3 figures, uses espcrc2.sty, Talk presented at
lattice97, Edinburgh, Scotland, July. 199
Real-time Loss Estimation for Instrumented Buildings
Motivation. A growing number of buildings have been instrumented to measure and record
earthquake motions and to transmit these records to seismic-network data centers to be archived and
disseminated for research purposes. At the same time, sensors are growing smaller, less expensive to
install, and capable of sensing and transmitting other environmental parameters in addition to
acceleration. Finally, recently developed performance-based earthquake engineering methodologies
employ structural-response information to estimate probabilistic repair costs, repair durations, and
other metrics of seismic performance. The opportunity presents itself therefore to combine these
developments into the capability to estimate automatically in near-real-time the probabilistic seismic
performance of an instrumented building, shortly after the cessation of strong motion. We refer to
this opportunity as (near-) real-time loss estimation (RTLE).
Methodology. This report presents a methodology for RTLE for instrumented buildings. Seismic
performance is to be measured in terms of probabilistic repair cost, precise location of likely physical
damage, operability, and life-safety. The methodology uses the instrument recordings and a Bayesian
state-estimation algorithm called a particle filter to estimate the probabilistic structural response of
the system, in terms of member forces and deformations. The structural response estimate is then
used as input to component fragility functions to estimate the probabilistic damage state of structural
and nonstructural components. The probabilistic damage state can be used to direct structural
engineers to likely locations of physical damage, even if they are concealed behind architectural
finishes. The damage state is used with construction cost-estimation principles to estimate
probabilistic repair cost. It is also used as input to a quantified, fuzzy-set version of the FEMA-356
performance-level descriptions to estimate probabilistic safety and operability levels.
CUREE demonstration building. The procedure for estimating damage locations, repair costs, and
post-earthquake safety and operability is illustrated in parallel demonstrations by CUREE and
Kajima research teams. The CUREE demonstration is performed using a real 1960s-era, 7-story, nonductile
reinforced-concrete moment-frame building located in Van Nuys, California. The building is
instrumented with 16 channels at five levels: ground level, floors 2, 3, 6, and the roof. We used the
records obtained after the 1994 Northridge earthquake to hindcast performance in that earthquake.
The building is analyzed in its condition prior to the 1994 Northridge Earthquake. It is found that,
while hindcasting of the overall system performance level was excellent, prediction of detailed damage
locations was poor, implying that either actual conditions differed substantially from those shown on
the structural drawings, or inappropriate fragility functions were employed, or both. We also found
that Bayesian updating of the structural model using observed structural response above the base of
the building adds little information to the performance prediction. The reason is probably that
Real-Time Loss Estimation for Instrumented Buildings
ii
structural uncertainties have only secondary effect on performance uncertainty, compared with the
uncertainty in assembly damageability as quantified by their fragility functions. The implication is
that real-time loss estimation is not sensitive to structural uncertainties (saving costly multiple
simulations of structural response), and that real-time loss estimation does not benefit significantly
from installing measuring instruments other than those at the base of the building.
Kajima demonstration building. The Kajima demonstration is performed using a real 1960s-era
office building in Kobe, Japan. The building, a 7-story reinforced-concrete shearwall building, was not
instrumented in the 1995 Kobe earthquake, so instrument recordings are simulated. The building is
analyzed in its condition prior to the earthquake. It is found that, while hindcasting of the overall
repair cost was excellent, prediction of detailed damage locations was poor, again implying either that
as-built conditions differ substantially from those shown on structural drawings, or that
inappropriate fragility functions were used, or both. We find that the parameters of the detailed
particle filter needed significant tuning, which would be impractical in actual application. Work is
needed to prescribe values of these parameters in general.
Opportunities for implementation and further research. Because much of the cost of applying
this RTLE algorithm results from the cost of instrumentation and the effort of setting up a structural
model, the readiest application would be to instrumented buildings whose structural models are
already available, and to apply the methodology to important facilities. It would be useful to study
under what conditions RTLE would be economically justified. Two other interesting possibilities for
further study are (1) to update performance using readily observable damage; and (2) to quantify the
value of information for expensive inspections, e.g., if one inspects a connection with a modeled 50%
failure probability and finds that the connect is undamaged, is it necessary to examine one with 10%
failure probability
- …