11,156 research outputs found
Mean-field calculation of critical parameters and log-periodic characterization of an aperiodic-modulated model
We employ a mean-field approximation to study the Ising model with aperiodic
modulation of its interactions in one spatial direction. Two different values
for the exchange constant, and , are present, according to the
Fibonacci sequence. We calculated the pseudo-critical temperatures for finite
systems and extrapolate them to the thermodynamic limit. We explicitly obtain
the exponents , , and and, from the usual scaling
relations for anisotropic models at the upper critical dimension (assumed to be
4 for the model we treat), we calculate , , , ,
and . Within the framework of a renormalization-group approach, the
Fibonacci sequence is a marginal one and we obtain exponents which depend on
the ratio , as expected. But the scaling relation is obeyed for all values of we studied. We characterize
some thermodynamic functions as log-periodic functions of their arguments, as
expected for aperiodic-modulated models, and obtain precise values for the
exponents from this characterization.Comment: 17 pages, including 9 figures, to appear in Phys. Rev.
Phase transition in a log-normal Markov functional model
We derive the exact solution of a one-dimensional Markov functional model
with log-normally distributed interest rates in discrete time. The model is
shown to have two distinct limiting states, corresponding to small and
asymptotically large volatilities, respectively. These volatility regimes are
separated by a phase transition at some critical value of the volatility. We
investigate the conditions under which this phase transition occurs, and show
that it is related to the position of the zeros of an appropriately defined
generating function in the complex plane, in analogy with the Lee-Yang theory
of the phase transitions in condensed matter physics.Comment: 9 pages, 5 figures. v2: Added asymptotic expressions for the
convexity-adjusted Libors in the small and large volatility limits. v3: Added
one reference. Final version to appear in Journal of Mathematical Physic
A Landslide Climate Indicator from Machine Learning
In order to create a Landslide Hazard Index, we accessed rain, snow, and a dozen other variables from the National Climate Assessment Land Data Assimilation System. These predictors were converted to probabilities of landslide occurrence with XGBoost, a major machine-learning tool. The model was fitted with thousands of historical landslides from the Pacific Northwest Landslide Inventory (PNLI)
Effects of Inventory Bias on Landslide Susceptibility Calculations
Many landslide inventories are known to be biased, especially inventories for large regions such as Oregon's SLIDO or NASA's Global Landslide Catalog. These biases must affect the results of empirically derived susceptibility models to some degree. We evaluated the strength of the susceptibility model distortion from postulated biases by truncating an unbiased inventory. We generated a synthetic inventory from an existing landslide susceptibility map of Oregon, then removed landslides from this inventory to simulate the effects of reporting biases likely to affect inventories in this region, namely population and infrastructure effects. Logistic regression models were fitted to the modified inventories. Then the process of biasing a susceptibility model was repeated with SLIDO data. We evaluated each susceptibility model with qualitative and quantitative methods. Results suggest that the effects of landslide inventory bias on empirical models should not be ignored, even if those models are, in some cases, useful. We suggest fitting models in well-documented areas and extrapolating across the study region as a possible approach to modeling landslide susceptibility with heavily biased inventories
Smooth Fano polytopes whose Ehrhart polynomial has a root with large real part
The symmetric edge polytopes of odd cycles (del Pezzo polytopes) are known as
smooth Fano polytopes. In this paper, we show that if the length of the cycle
is 127, then the Ehrhart polynomial has a root whose real part is greater than
the dimension. As a result, we have a smooth Fano polytope that is a
counterexample to the two conjectures on the roots of Ehrhart polynomials.Comment: 4 pages, We changed the order of the auhors and omitted a lot of
parts of the paper. (If you are interested in omitted parts, then please read
v1
Effective Invariant Theory of Permutation Groups using Representation Theory
Using the theory of representations of the symmetric group, we propose an
algorithm to compute the invariant ring of a permutation group. Our approach
have the goal to reduce the amount of linear algebra computations and exploit a
thinner combinatorial description of the invariant ring.Comment: Draft version, the corrected full version is available at
http://www.springer.com
Squeezing in the audio gravitational wave detection band
We demonstrate the generation of broad-band continuous-wave optical squeezing
down to 200Hz using a below threshold optical parametric oscillator (OPO). The
squeezed state phase was controlled using a noise locking technique. We show
that low frequency noise sources, such as seed noise, pump noise and detuning
fluctuations, present in optical parametric amplifiers have negligible effect
on squeezing produced by a below threshold OPO. This low frequency squeezing is
ideal for improving the sensitivity of audio frequency measuring devices such
as gravitational wave detectors.Comment: 5 pages, 6 figure
Changes in Extreme Precipitation and Landslides Over High Mountain Asia
High Mountain Asia is impacted by extreme monsoonal rainfall that triggers landslides in large proportions relative to global distributions, resulting in substantial human impacts and damage to infrastructure each year. Previous landslide research has qualitatively estimated how patterns in landslide activity may change based on climate change scenarios. We present the first quantitative view of potential modulation in future landslide activity over the High Mountain Asia region leveraging a new landslide hazard model and precipitation data from satellite and Global Climate Model sources. In doing so, we find that the rate of increase in landslide activity at the end of the century is expected to be greatest over areas covered by current glaciers and glacial lakes, potentially exacerbating the impacts of cascading hazards on populations downstream. This work demonstrates the potential of Global Climate Models and satellite-based precipitation estimates to characterize landslide hazards at time scales affected by climate change
Intellectual Property Management in Health and Agricultural Innovation: Executive Guide
Prepared by and for policy-makers, leaders of public sector research establishments, technology transfer professionals, licensing executives, and scientists, this online resource offers up-to-date information and strategies for utilizing the power of both intellectual property and the public domain. Emphasis is placed on advancing innovation in health and agriculture, though many of the principles outlined here are broadly applicable across technology fields. Eschewing ideological debates and general proclamations, the authors always keep their eye on the practical side of IP management. The site is based on a comprehensive Handbook and Executive Guide that provide substantive discussions and analysis of the opportunities awaiting anyone in the field who wants to put intellectual property to work. This multi-volume work contains 153 chapters on a full range of IP topics and over 50 case studies, composed by over 200 authors from North, South, East, and West. If you are a policymaker, a senior administrator, a technology transfer manager, or a scientist, we invite you to use the companion site guide available at http://www.iphandbook.org/index.html The site guide distills the key points of each IP topic covered by the Handbook into simple language and places it in the context of evolving best practices specific to your professional role within the overall picture of IP management
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