Decoherence of spin echoes

We define a quantity, the so-called purity fidelity, which measures the rate of dynamical irreversibility due to decoherence, observed e.g in echo experiments, in the presence of an arbitrary small perturbation of the total (system + environment) Hamiltonian. We derive a linear response formula for the purity fidelity in terms of integrated time correlation functions of the perturbation. Our relation predicts, similarly to the case of fidelity decay, faster decay of purity fidelity the slower decay of time correlations is. In particular, we find exponential decay in quantum mixing regime and faster, initially quadratic and later typically gaussian decay in the regime of non-ergodic, e.g. integrable quantum dynamics. We illustrate our approach by an analytical calculation and numerical experiments in the Ising spin 1/2 chain kicked with tilted homogeneous magnetic field where part of the chain is interpreted as a system under observation and part as an environment.Comment: 22 pages, 10 figure

Current optical technologies for wireless access

The objective of this paper is to describe recent activities and investigations on free-space optics (FSO) or optical wireless and the excellent results achieved within SatNEx an EU-framework 6th programme and IC 0802 a COST action. In a first part, the FSO technology is briefly discussed. In a second part, we mention some performance evaluation criterions for the FSO. In third part, we briefly discuss some optical signal propagation experiments through the atmosphere by mentioning network architectures for FSO and then discuss the recent investigations in airborne and satellite application experiments for FSO. In part four, we mention some recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented

Parametric statistics of zeros of Husimi representations of quantum chaotic eigenstates and random polynomials

Local parametric statistics of zeros of Husimi representations of quantum eigenstates are introduced. It is conjectured that for a classically fully chaotic systems one should use the model of parametric statistics of complex roots of Gaussian random polynomials which is exactly solvable as demonstrated below. For example, the velocities (derivatives of zeros of Husimi function with respect to an external parameter) are predicted to obey a universal (non-Maxwellian) distribution ${d P(v)}/{dv^2} = 2/(\pi\sigma^2)(1 + |v|^2/\sigma^2)^{-3},$ where $\sigma^2$ is the mean square velocity. The conjecture is demonstrated numerically in a generic chaotic system with two degrees of freedom. Dynamical formulation of the ``zero-flow'' in terms of an integrable many-body dynamical system is given as well.Comment: 13 pages in plain Latex (1 figure available upon request

Coworking in Lisbon: Experiences of collaboration and sharing on changing urban contexts

As innovative and creative ecosystems, Coworking Spaces (CWS) show high adaptability and recovery capacity in facing global event disruptions. This article is an exploratory study that aims to approach the development of coworking spaces in the city of Lisbon. It investigates the location patterns and adaptation of such ecosystems in Lisbon, by mapping the phenomenon and examining its spatio-temporal dynamics that was influenced by the urbanisation phases of the city, as well as the development and planning policies designed over the years. Starting from a broader view of CWS location in the city, this article moves on to present two particular cases, implemented in a different time and socio-economic circumstances in different parts of the city: LxFactory and The Creative Hub. This study is part of a broader contribution to COST Action (CA)18214 "The geography of the new workspaces and the impact on the periphery".info:eu-repo/semantics/publishedVersio

CULTURE.IMPACTS.DIY: A self-assessment toolkit unveiling the multidimensionality of value creation in cultural activities

The question of value and its measurability has always been central in the study of social and economic practices, including cultural activities. However, contemporary structural changes related to the emergence of cognitive-cultural capitalism bring new forms of cultural production, consumption and mediation that challenge the analysis of cultural activities’ value(s). Despite the recognition of multidimensionality of its value, impacts of cultural activities are still often underestimated, and evaluation exercises have difficulties in including the diversity of dimensions of value created by these activities, in economic, social, cultural, environmental or participatory terms. Combining work developed by a DINAMIA’CET iscte team in different research projects (CREATOUR, RESHAPE, IMPACTS-AR, ARTSBANK and STRONGER PERIPHERIES), this presentation addresses value creation processes in culture, based on work developed with artists, cultural promoters, creative tourism agents and public authorities, in recent years, in several territorial contexts, both Portuguese and European, assessing the impact of their activities in their communities. A new conceptual and analytical approach to assess the impact of cultural activities in a given territory is proposed. A multidimensional impact assessment method, (co)developed with actors in creative fields, is proposed, provided through a toolkit for (self)evaluation of value(s) generated by cultural institutions.info:eu-repo/semantics/publishedVersio

Arthropods biodiversity in a landscape mosaic dominated by organic olive groves in Alentejo (Portugal).

In olive groves, arthropods represent an important part of the biodiversity, where they can provide multiple ecosystem services, such as the biological control of crop pests. This service helps maintaining agricultural productivity and reduces the need of pesticide inputs. The objective of this work was to study the abundance and diversity of arthropods in a landscape mosaic dominated by organic olive groves in Alentejo, Portugal. In total, 7809 specimens were collected, belonging to 10 orders. Diptera was the most abundant ones representing 33.55%, followed by Thysanoptera with 23.83 % and Coleoptera with 20.69%. The abundance of Coccinellidae and Staphylinidae families was higher in the olive groves compared with the holm oak, that could be an indicator of their functions in olive grove agroecosystems

Environmental bioindicators: ants as a tool for monitoring urban green in the south of Portugal.

Ants contribute to the regulation and survival of many organisms as a result of being involved in numerous interactions through herbivory, predation and/or mutualism with other organisms, such as bacteria, plants, fungi, arthropods and vertebrates. Until recently, it was thought that urban areas were not interesting for biodiversity studies. However, there is much research on ant diversity in green areas within urban landscapes worldwide. In fact, urban ecosystems can ensure a high diversity of native ant species and contribute to their preservation. The present study was aimed at providing a baseline data on ant species diversity in Polytechnic Institute of Beja Campus and evaluating the disturbance level of habitats exposed to different anthropogenic pressure, using ants as bio-indicators of ecosystem health. Each species was classified according the functional groups used for Iberian Peninsula. Sampling was carried out from May to August, by installing 12 pitfall traps in three different habitats. In total, 17 ant species were identified. The results showed that although all the plots are disturbed, since they are ecosystems strongly managed by man; the average value of disturbance index is 53%, but the Disturbance index in each plot ranged from 60 to 75

An impact self-assessment tool for creative tourism with insights from its application to the CREATOUR ® project

Considering the small scale of creative tourism, the limited resources in any specific case, and the high engagement level of stakeholders, a self-assessment exercise (i.e. carried out by the organizers/promoters of creative tourism activities) is most appropriate in order to monitor activities and results. Thus, within the CREATOUR ® project, a self-assessment process for creative tourism initiatives was developed, beginning with an initial diagnosis and proceeding to an assessment of outcomes and impacts. The process and tools were co-developed between researchers and practitioners to help various types of creative tourism organizers to measure, monitor, and evaluate the course of their activities in order to improve management and decisionmaking processes. The main objective was to assist practitioners and stakeholder organizations to become more aware of the intentional and unintentional effects generated by creative tourism activities, highlighting the potential benefits of artistic, cultural, and creative experiences for territorial development. This article is divided into three parts: part I outlines the development of the self-assessment process and tools; part II presents a synthesis of overall findings from the CREATOUR ® project resulting from this self-assessment process; and part III lists take-aways for practitioners.info:eu-repo/semantics/acceptedVersio

Going against mass tourism: Creative tourism as an alternative, creatour as an example

In recent years, tourism statistics in Portugal have been showing a growth that is already beginning to cause some concern in the two major cities - Lisbon and Porto - while the rest of the country still expects to grow and benefit from this wave of tourist attractiveness that have been projecting the country in several international rankings. However, there is the notion that this growth should be done with some caution and in an adjusted manner, regarding the different territorial realities and in order to value the tangible and intangible assets that constitute tourism resources.For peripheral territories, such as rural areas or small sized cities, investing on creative tourism as a wide process of co-creation and exchange of cultural and symbolic experiences can be a good opportunity, not only to retain population and revitalize their cultural and social heritage, but also to enhance creative milieus and foster organic territorial dynamics, reflecting the “sense of place” and the unique characteristics of local communities.This communication will focus on cultural and creative tourism as a more sustainable and adapted alternative for low-density territories, giving the CREATOUR project as an example. This national multidisciplinary research project is being currently developed in the four NUTS II regions of Portugal. Simultaneously, CREATOUR works as an incubator of ideas and actions, aimed at providing the visitor-tourist co-production and knowledge experiences. Alongside with this creative tourism project and its conceptual bases, some of the results already obtained in the four regions of the country will also be presented and explored.info:eu-repo/semantics/publishedVersio