5,243 research outputs found
Optimal generation of entanglement under local control
We study the optimal generation of entanglement between two qubits subject to
local unitary control. With the only assumptions of linear control and unitary
dynamics, by means of a numerical protocol based on the variational approach
(Pontryagin's Minimum Principle), we evaluate the optimal control strategy
leading to the maximal achievable entanglement in an arbitrary interaction
time, taking into account the energy cost associated to the controls. In our
model we can arbitrarily choose the relative weight between a large
entanglement and a small energy cost.Comment: 4 page
Geometry for the accelerating universe
The Lorentzian spacetime metric is replaced by an area metric which naturally
emerges as a generalized geometry in quantum string and gauge theory. Employing
the area metric curvature scalar, the gravitational Einstein-Hilbert action is
re-interpreted as dynamics for an area metric. Without the need for dark energy
or fine-tuning, area metric cosmology explains the observed small acceleration
of the late Universe.Comment: 4 pages, 1 figur
Effect of Pseudotsuga menziesii Plantations on Vascular Plants Diversity in Northwest Patagonia, Argentina
Mechanical-physical experimental tests on lime mortars and bricks reinforced with hemp
Hemp is an agricultural product used for various applications. In the Civil Engineering field, only a limited use of this natural material, called the “green pig” since exploitation of all its constituent parts is allowed, has been done. For this reason, in the paper an experimental activity on lime mortars and bricks reinforced with hemp components has been performed. Compression and bending tests have been carried out on specimens manufactured with hemp shives and fibres, respectively. The achieved results have shown that hemp products change the failure modes from brittle to ductile, leaving basically unaltered the strength capacity of reinforced specimens with respect to unreinforced ones
Miglioramento dell'efficienza tecnica e ambientale degli adesivi utilizzati nel settore del mobile
The response of precipitation characteristics to global warming from climate projections
Abstract. We revisit the issue of the response of precipitation characteristics to
global warming based on analyses of global and regional climate model
projections for the 21st century. The prevailing response we identify can be
summarized as follows: increase in the intensity of precipitation events and
extremes, with the occurrence of events of "unprecedented" magnitude, i.e.,
a magnitude not found in the present-day climate; decrease in the number of light
precipitation events and in wet spell lengths; and increase in the number of dry
days and dry spell lengths. This response, which is mostly consistent across
the models we analyzed, is tied to the difference between precipitation
intensity responding to increases in local humidity conditions and
circulations, especially for heavy and extreme events, and mean precipitation
responding to slower increases in global evaporation. These changes in
hydroclimatic characteristics have multiple and important impacts on the
Earth's hydrologic cycle and on a variety of sectors. As examples we
investigate effects on potential stress due to increases in dry and wet
extremes, changes in precipitation interannual variability, and changes in
the potential predictability of precipitation events. We also stress how the
understanding of the hydroclimatic response to global warming can provide
important insights into the fundamental behavior of precipitation processes,
most noticeably tropical convection
A Bayesian framework for describing and predicting the stochastic demand of home care patients
Home care providers are complex structures which include medical,
paramedical and social services delivered to patients at their domicile. High randomness affects the service delivery, mainly in terms of unplanned changes in
patients’ conditions, which make the amount of required visits highly uncertain.
Hence, each reliable and robust resource planning should include the estimation of
the future demand for visits from the assisted patients. In this paper, we propose a
Bayesian framework to represent the patients’ demand evolution along with the time
and to predict it in future periods. Patients’ demand evolution is described by means
of a generalized linear mixed model, whose posterior densities of parameters are
obtained through Markov chain Monte Carlo simulation. Moreover, prediction of
patients’ demands is given in terms of their posterior predictive probabilities. In the
literature, the stochastic description of home care patients’ demand is only marginally addressed and no Bayesian approaches exist to the best of our knowledge.
Results from the application to a relevant real case show the applicability of the
proposed model in the practice and validate the approach, since parameter densities
in accordance to clinical evidences and low prediction errors are found
Inductive Reasoning Games as Influenza Vaccination Models: Mean Field Analysis
We define and analyze an inductive reasoning game of voluntary yearly
vaccination in order to establish whether or not a population of individuals
acting in their own self-interest would be able to prevent influenza epidemics.
We find that epidemics are rarely prevented. We also find that severe epidemics
may occur without the introduction of pandemic strains. We further address the
situation where market incentives are introduced to help ameliorating
epidemics. Surprisingly, we find that vaccinating families exacerbates
epidemics. However, a public health program requesting prepayment of
vaccinations may significantly ameliorate influenza epidemics.Comment: 20 pages, 7 figure
A Composite Index for Measuring Stock Market Inefficiency
Market inefficiency is a latent concept, and it is difficult to be measured by means of a single indicator. In this paper, following both the adaptive market hypothesis (AMH) and the fractal market hypothesis (FMH), we develop a new time-varying measure of stock market inefficiency. The proposed measure, called composite efficiency index (CEI), is estimated as the synthesis of the most common efficiency measures such as the returns' autocorrelation, liquidity, volatility, and a new measure based on the Hurst exponent, called the Hurst efficiency index (HEI). To empirically validate the indicator, we compare different European stock markets in terms of efficiency over time
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