6,312 research outputs found
Ground-water resources of Collier County, Florida
The Biscayne Aquifer is the principal source of water for the heavily
populated area in the vicinity of West Palm Beach and Miami. The
publication of this data is timely and will assist in the intelligent development
of the water resources of the area.The report recognizes two major aquifers as the source of ground
water in Collier County. The lower aquifer is highly mineralized, but
contains usable water, and the more shallow aquifer is the source of
large supplies, which are utilized by municipalities and domestic users.
Adequate supplies of fresh water are present in the Naples area and by
proper planning, these can be developed in an orderly manner and salt
water encroachment can be prevented.
(PDF has 99 pages
Finite Temperature and Dynamical Properties of the Random Transverse-Field Ising Spin Chain
We study numerically the paramagnetic phase of the spin-1/2 random
transverse-field Ising chain, using a mapping to non-interacting fermions. We
extend our earlier work, Phys. Rev. 53, 8486 (1996), to finite temperatures and
to dynamical properties. Our results are consistent with the idea that there
are ``Griffiths-McCoy'' singularities in the paramagnetic phase described by a
continuously varying exponent , where measures the
deviation from criticality. There are some discrepancies between the values of
obtained from different quantities, but this may be due to
corrections to scaling. The average on-site time dependent correlation function
decays with a power law in the paramagnetic phase, namely
, where is imaginary time. However, the typical
value decays with a stretched exponential behavior, ,
where may be related to . We also obtain results for the full
probability distribution of time dependent correlation functions at different
points in the paramagnetic phase.Comment: 10 pages, 14 postscript files included. The discussion of the typical
time dependent correlation function has been greatly expanded. Other papers
of APY are available on-line at http://schubert.ucsc.edu/pete
Impurity spin relaxation in S=1/2 XX chains
Dynamic autocorrelations (\alpha=x,z) of an
isolated impurity spin in a S=1/2 XX chain are calculated. The impurity spin,
defined by a local change in the nearest-neighbor coupling, is either in the
bulk or at the boundary of the open-ended chain. The exact numerical
calculation of the correlations employs the Jordan-Wigner mapping from spin
operators to Fermi operators; effects of finite system size can be eliminated.
Two distinct temperature regimes are observed in the long-time asymptotic
behavior. At T=0 only power laws are present. At high T the x correlation
decays exponentially (except at short times) while the z correlation still
shows an asymptotic power law (different from the one at T=0) after an
intermediate exponential phase. The boundary impurity correlations follow power
laws at all T. The power laws for the z correlation and the boundary
correlations can be deduced from the impurity-induced changes in the properties
of the Jordan-Wigner fermion states.Comment: Final version to be published in Phys. Rev. B. Three references
added, extended discussion of relation to previous wor
Ising Dynamics with Damping
We show for the Ising model that is possible construct a discrete time
stochastic model analogous to the Langevin equation that incorporates an
arbitrary amount of damping. It is shown to give the correct equilibrium
statistics and is then used to investigate nonequilibrium phenomena, in
particular, magnetic avalanches. The value of damping can greatly alter the
shape of hysteresis loops, and for small damping and high disorder, the
morphology of large avalanches can be drastically effected. Small damping also
alters the size distribution of avalanches at criticality.Comment: 8 pages, 8 figures, 2 colum
An Evaluation Framework for Personalization Strategy Experiment Designs
Online Controlled Experiments (OCEs) are the gold standard in evaluating the
effectiveness of changes to websites. An important type of OCE evaluates
different personalization strategies, which present challenges in low test
power and lack of full control in group assignment. We argue that getting the
right experiment setup -- the allocation of users to treatment/analysis groups
-- should take precedence of post-hoc variance reduction techniques in order to
enable the scaling of the number of experiments. We present an evaluation
framework that, along with a few simple rule of thumbs, allow experimenters to
quickly compare which experiment setup will lead to the highest probability of
detecting a treatment effect under their particular circumstance.Comment: Presented in the AdKDD 2020 workshop, in conjunction with The 26th
ACM SIGKDD Conference on Knowledge Discovery and Data Mining, KDD 2020. Main
paper: 7 pages, 2 figures, 2 tables, Supplementary document: 6 page
Functional Forms for the Squeeze and the Time-Displacement Operators
Using Baker-Campbell-Hausdorff relations, the squeeze and harmonic-oscillator
time-displacement operators are given in the form , where ,
, , and are explicitly determined. Applications are
discussed.Comment: 10 pages, LaTe
Critical Behavior and Griffiths-McCoy Singularities in the Two-Dimensional Random Quantum Ising Ferromagnet
We study the quantum phase transition in the two-dimensional random Ising
model in a transverse field by Monte Carlo simulations. We find results similar
to those known analytically in one-dimension. At the critical point, the
dynamical exponent is infinite and the typical correlation function decays with
a stretched exponential dependence on distance. Away from the critical point
there are Griffiths-McCoy singularities, characterized by a single,
continuously varying exponent, z', which diverges at the critical point, as in
one-dimension. Consequently, the zero temperature susceptibility diverges for a
RANGE of parameters about the transition.Comment: 4 pages RevTeX, 3 eps-figures include
Zero--Temperature Quantum Phase Transition of a Two--Dimensional Ising Spin--Glass
We study the quantum transition at in the spin- Ising
spin--glass in a transverse field in two dimensions. The world line path
integral representation of this model corresponds to an effective classical
system in (2+1) dimensions, which we study by Monte Carlo simulations. Values
of the critical exponents are estimated by a finite-size scaling analysis. We
find that the dynamical exponent, , and the correlation length exponent,
, are given by and . Both the linear
and non-linear susceptibility are found to diverge at the critical point.Comment: RevTeX 10 pages + 4 figures (appended as uuencoded, compressed
tar-file), THP21-9
Correlation functions for the three state superintegrable chiral Potts spin chain of finite lengths
We compute the correlation functions of the three state superintegrable
chiral Potts spin chain for chains of length 3,4,5. From these results we
present conjectures for the form of the nearest neighbor correlation function.Comment: 10 pages; references update
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