8,832 research outputs found
Mirror-orientation noise in a Fabry-Perot interferometer gravitational wave detector
The influence of angular mirror-orientation errors on the length of a Fabry-Perot resonator is analyzed geometrically. Under conditions in which dominant errors are static or vary slowly over time, the analysis permits a simple prediction of the spectrum of short-term cavity length fluctuations resulting from mirror-orientation noise. The resulting model is applicable to the design of mirror control systems for the Laser Interferometer Gravitational-Wave Observatory, which will monitor separations between mirrored surfaces of suspended inertial test bodies as a way to measure astrophysical gravitational radiation. The analysis is verified by measuring the response of the Laser Interferometer Gravitational- Wave Observatory's 40-m interferometer test-bed to the rotation of its mirrors
Numerical study of the ordering of the +-J XY spin-glass ladder
The properties of the domain-wall energy and of the correlation length are
studied numerically for the one-dimensional +-J XY spin glass on the two-leg
ladder lattice, focusing on both the spin and the chirality degrees of freedom.
Analytic results obtained by Ney-Niftle et al for the same model were confirmed
for asymptotically large lattices, while the approach to the asymptotic limit
is slow and sometimes even non-monotonic. Attention is called to the occurrence
of the SO(2)-Z_2 decoupling and its masking in spin correlations, the latter
reflecting the inequality between the SO(2) and Z_2 exponents. Discussion is
given concerning the behaviors of the higher-dimensional models.Comment: 14 pages, 10 figure
Ordering of the three-dimensional Heisenberg spin glass in magnetic fields
Spin and chirality orderings of the three-dimensional Heisenberg spin glass
are studied under magnetic fields in light of the recently developed
spin-chirality decoupling-recoupling scenario. It is found by Monte Carlo
simulations that the chiral-glass transition and the chiral-glass ordered
state, which are essentially of the same character as their zero-field
counterparts, occur under magnetic fields. Implication to experimental phase
diagram is discussed.Comment: 5 pages, 3 figure
Creep rupture of materials: insights from a fiber bundle model with relaxation
I adapted a model recently introduced in the context of seismic phenomena, to
study creep rupture of materials. It consists of linear elastic fibers that
interact in an equal load sharing scheme, complemented with a local
viscoelastic relaxation mechanism. The model correctly describes the three
stages of the creep process, namely an initial Andrade regime of creep
relaxation, an intermediate regime of rather constant creep rate, and a
tertiary regime of accelerated creep towards final failure of the sample. In
the tertiary regime creep rate follows the experimentally observed one over
time-to-failure dependence. The time of minimum strain rate is systematically
observed to be about 60-65 % of the time to failure, in accordance with
experimental observations. In addition, burst size statistics of breaking
events display a -3/2 power law for events close to the time of failure, and a
steeper decay for the all-time distribution. Statistics of interevent times
shows a tendency of the events to cluster temporarily. This behavior should be
observable in acoustic emission experiments
Dynamical simulation of spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses
Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
glasses are studied with and without randaom magnetic anisotropy by dynamical
Monte Carlo simulations. In isotropic case, clear evidence of a
finite-temperature chiral-glass transition is presented. While the spin
autocorrelation exhibits only an interrupted aging, the chirality
autocorrelation persists to exhibit a pronounced aging effect reminisecnt of
the one observed in the mean-field model. In anisotropic case, asymptotic
mixing of the spin and the chirality is observed in the off-equilibrium
dynamics.Comment: 4 pages including 5 figures, LaTex, to appear in Phys. Rev. Let
Anomalous U(1) D-term Contribution in Type I String Models
We study the -term contribution for anomalous U(1) symmetries in type I
string models and derive general formula for the -term contribution,
assuming that the dominant source of SUSY breaking is given by -terms of the
dilaton, (overall) moduli or twisted moduli fields. On the basis of the
formula, we also point out that there are several different features from the
case in heterotic string models. The differences originate from the different
forms of K\"ahler potential between twisted moduli fields in type I string
models and the dilaton field in heterotic string models.Comment: 16 pages, latex, no figur
Monte Carlo Studies of the Ordering of the Three-Dimensional Isotropic Heisenberg Spin Glass in Magnetic Fields
Spin and chirality orderings of the three-dimensional Heisenberg spin glass
under magnetic fields are studied by large-scale equilibrium Monte Carlo
simulations. It is found that the chiral-glass transition and the chiral-glass
ordered state, which are essentially of the same character as their zero-field
counterparts, occur under magnetic fields. The chiral-glass ordered state
exhibits a one-step-like peculiar replica-symmetry breaking in the chiral
sector, while it does not accompany the spin-glass order perpendicular to the
applied field. Critical perperties of the chiral-glass transition are different
from those of the standard Ising spin glass. Magnetic phase diagram of the
model is constructed, which reveals that the chiral-glass state is quite robust
against magnetic fields. The chiral-glass transition line has a character of
the Gabay-Toulouse line of the mean-field model, yet its physical origin being
entirely different. These numerical results are discussed in light of the
recently developed spin-chirality decoupling-recoupling scenario. Implication
to experimental phase diagram is also discussed.Comment: 23 pages, 23 figure
Novel spin-liquid states in the frustrated Heisenberg antiferromagnet on the honeycomb lattice
Recent experiment on a honeycomb-lattice Heisenberg antiferromagnet (AF)
BiMnO(NO) revealed a novel spin-liquid-like behavior down to
low temperature, which was ascribed to the frustration effect due to the
competition between the AF nearest- and next-nearest-neighbor interactions
and . Motivated by the experiment, we study the ordering of the
- frustrated classical Heisenberg AF on a honeycomb lattice both by
a low-temperature expansion and a Monte Carlo simulation. The model has been
known to possess a massive degeneracy of the ground state, which, however,
might be lifted due to thermal fluctuations leading to a unique ordered state,
the effect known as 'order-by-disorder'. We find that the model exhibits an
intriguing ordering behavior, particularly near the AF phase boundary. The
energy scale of the order-by-disorder is suppressed there down to extremely low
temperatures, giving rise to exotic spin-liquid states like a "ring-liquid" or
a "pancake-liquid" state accompanied by the characteristic spin structure
factor and the field-induced antiferromagnetism. We argue that the recent
experimental data are explicable if the system is in such exotic spin-liquid
states
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