1,370 research outputs found
Tsallis' deformation parameter q quantifies the classical-quantum transition
We investigate the classical limit of a type of semiclassical evolution, the
pertinent system representing the interaction between matter and a given field.
On using as a quantifier of the ensuing dynamics Tsallis q-entropy, we
encounter that it not only appropriately describes the quantum-classical
transition, but that the associated deformation-parameter q itself
characterizes the different regimes involved in the process, detecting the most
salient fine details of the changeover.Comment: 19 pages, 7 figure
Honesty by typing
We propose a type system for a calculus of contracting processes. Processes may stipulate contracts, and then either behave honestly, by keeping the promises made, or not. Type safety guarantees that a typeable process is honest - that is, the process abides by the contract it has stipulated in all possible contexts, even those containing dishonest adversaries
Model checking usage policies
We study usage automata, a formal model for specifying policies on the usage of resources. Usage automata extend finite state automata with some additional features, parameters and guards, that improve their expressivity. We show that usage automata are expressive enough to model policies of real-world applications. We discuss their expressive power, and we prove that the problem of telling whether a computation complies with a usage policy is decidable. The main contribution of this paper is a model checking technique for usage automata. The model is that of usages, i.e. basic processes that describe the possible patterns of resource access and creation. In spite of the model having infinite states, because of recursion and resource creation, we devise a polynomial-time model checking technique for deciding when a usage complies with a usage policy
Wavelet entropy and fractional Brownian motion time series
We study the functional link between the Hurst parameter and the Normalized
Total Wavelet Entropy when analyzing fractional Brownian motion (fBm) time
series--these series are synthetically generated. Both quantifiers are mainly
used to identify fractional Brownian motion processes (Fractals 12 (2004) 223).
The aim of this work is understand the differences in the information obtained
from them, if any.Comment: 10 pages, 2 figures, submitted to Physica A for considering its
publicatio
Formal Models of Bitcoin Contracts: A Survey
Although Bitcoin is mostly used as a decentralized application to transfer cryptocurrency, over the last 10 years there have been several studies on how to exploit Bitcoin to execute smart contracts. These are computer protocols which allow users to exchange bitcoins according to complex pre-agreed rules. Some of these studies introduce formal models of Bitcoin contracts, which specify their behavior in non-ambiguous terms, in some cases providing tools to automatically verify relevant contract properties. In this paper, we survey the formal models proposed in the scientific literature, comparing their expressiveness and applicability in the wild
Characterization of laser propagation through turbulent media by quantifiers based on the wavelet transform: dynamic study
We analyze, within the wavelet theory framework, the wandering over a screen
of the centroid of a laser beam after it has propagated through a time-changing
laboratory-generated turbulence. Following a previous work (Fractals 12 (2004)
223) two quantifiers are used, the Hurst parameter, , and the Normalized
Total Wavelet Entropy, . The temporal evolution of both
quantifiers, obtained from the laser spot data stream is studied and compared.
This allows us to extract information of the stochastic process associated to
the turbulence dynamics.Comment: 11 pages, 3 figures, accepted to be published in Physica
Wavelet entropy of stochastic processes
We compare two different definitions for the wavelet entropy associated to
stochastic processes. The first one, the Normalized Total Wavelet Entropy
(NTWS) family [Phys. Rev. E 57 (1998) 932; J. Neuroscience Method 105 (2001)
65; Physica A (2005) in press] and a second introduced by Tavares and Lucena
[Physica A 357 (2005)~71]. In order to understand their advantages and
disadvantages, exact results obtained for fractional Gaussian noise (-1<alpha<
1) and the fractional Brownian motion (1 < alpha < 3) are assessed. We find out
that NTWS family performs better as a characterization method for these
stochastic processes.Comment: 12 pages, 4 figures, submitted to Physica
Modelling and verifying contract-oriented systems in Maude
We address the problem of modelling and verifying contractoriented systems, wherein distributed agents may advertise and stipulate contracts, but — differently from most other approaches to distributed agents — are not assumed to always behave “honestly”. We describe an executable specification in Maude of the semantics of CO2, a calculus for contract-oriented systems [6]. The honesty property [5] characterises those agents which always respect their contracts, in all possible execution contexts. Since there is an infinite number of such contexts, honesty cannot be directly verified by model-checking the state space of an agent (indeed, honesty is an undecidable property in general [5]). The main contribution of this paper is a sound verification technique for honesty. To do that, we safely over-approximate the honesty property by abstracting from the actual contexts a process may be engaged with. Then, we develop a model-checking technique for this abstraction, we describe an implementation in Maude, and we discuss some experiments with it
Non-binary Language Forms in Spanish: Consciously Using it Facilitates Processing during Comprehension?
Several grammatical studies have focused on the study of morphological innovations used as non-binary forms in Spanish (-x; -e). However, there are no experimental studies that analyze their psycholinguistic processing or the multiple and complex relationships between production and comprehension in non- binary language. To analyze this phenomenon, we performed a sentence reading and comprehension task. We recorded reading times, response times, and accuracy. We considered morphology, stereotypicality and frequency of use of non-binary forms in the participants as predictors. The results show specialization of the non-binary forms as generic morphological variants, as opposed to the generic masculine. The non- binary forms consistently elicited a reference to mixed groups and response times showed that these morphological variants do not carry a higher processing cost than the generic masculine. Moreover, it is possible to see that the conscious use of non-binary forms influences the comprehension processes of the different variants of gender morphology: as the voluntary use of non-binary forms increases, the generic masculine seems to concentrate its reference to groups of men exclusively. Thus, in addition to showing general evidence regarding the processing costs and comprehension of gender morphology in Spanish, our data allow us to observe a potential reciprocal link between production and comprehension processes that deserves further study
A fractional Brownian motion model for the turbulent refractive index in lightwave propagation
It is discussed the limitations of the widely used markovian approximation
applied to model the turbulent refractive index in lightwave propagation.
It is well-known the index is a passive scalar field. Thus, the actual
knowledge about these quantities is used to propose an alternative stochastic
process to the markovian approximation: the fractional Brownian motion. This
generalizes the former introducing memory; that is, there is correlation along
the propagation path.Comment: 11 pages, no figures. Submitted and revised for Optics Communication
- …