Unbounded randomness certification using sequences of measurements

Unpredictability, or randomness, of the outcomes of measurements made on an entangled state can be certified provided that the statistics violate a Bell inequality. In the standard Bell scenario where each party performs a single measurement on its share of the system, only a finite amount of randomness, of at most $4 log_2 d$ bits, can be certified from a pair of entangled particles of dimension $d$. Our work shows that this fundamental limitation can be overcome using sequences of (nonprojective) measurements on the same system. More precisely, we prove that one can certify any amount of random bits from a pair of qubits in a pure state as the resource, even if it is arbitrarily weakly entangled. In addition, this certification is achieved by near-maximal violation of a particular Bell inequality for each measurement in the sequence.Comment: 4 + 5 pages (1 + 3 images), published versio

The Lifelines Cohort Study:a data source available for studying informal caregivers’ experiences and the outcomes of informal caregiving

Background Informal care is taking an increasingly important role in our health care system, and an improvement in our understanding of caregiving experiences and outcomes has become more relevant. The Lifelines informal care add-on study (Lifelines ICAS) was initiated within the Lifelines Cohort Study to cover the large heterogeneity in the caregiver population and to investigate the complex interplay among the characteristics of the caregiver, care recipient, and care situation and positive and negative caregiver outcomes. In this paper, we discuss the study design and data collection procedures of Lifelines ICAS, provide a detailed overview of its measures, and describe the caregiver study population. Methods Lifelines participants who participated in the 2nd Lifelines follow-up questionnaire were asked whether they provided informal care. Subsequently, they were invited to participate in Lifelines ICAS. Descriptive statistics were used to describe all informal caregivers in the 2nd Lifelines follow-up questionnaire and to describe the subsample of informal caregivers participating in Lifelines ICAS. Results A total of 11,651 Lifelines participants were self-identified as an informal caregiver and provided basic information about their care situation. A subsample of 965 informal caregivers participated in Lifelines ICAS and completed a comprehensive questionnaire about their care situation. In this subsample, the average age of caregivers was 53 years (SD 9.8), 75% were female, and 56% cared for a parent (in-law). Care recipients were on average 68 years old (SD 23.5), and 64% were female. Discussion Considering that informal caregivers are a huge resource for our health care system, Lifelines ICAS enables the study of differences among caregivers, care recipients, and care situations, as well as the study of common characteristics and features across caregiver groups. Notably, data from the Lifelines Cohort Study and Lifelines ICAS are available to all researchers on a fee-for-service basis, and Lifelines ICAS data may be enhanced by one or more follow-up measurements or linkages with other data sources

Networks of reliable reputations and cooperation: a review

Reputation has been shown to provide an informal solution to the problem of cooperation in human societies. After reviewing models that connect reputations and cooperation, we address how reputation results from information exchange embedded in a social network that changes endogenously itself. Theoretical studies highlight that network topologies have different effects on the extent of cooperation, since they can foster or hinder the flow of reputational information. Subsequently, we review models and empirical studies that intend to grasp the coevolution of reputations, cooperation and social networks. We identify open questions in the literature concerning how networks affect the accuracy of reputations, the honesty of shared information and the spread of reputational information. Certain network topologies may facilitate biased beliefs and intergroup competition or in-group identity formation that could lead to high cooperation within but conflicts between different subgroups of a network. Our review covers theoretical, experimental and field studies across various disciplines that target these questions and could explain how the dynamics of interactions and reputations help or prevent the establishment and sustainability of cooperation in small- and large-scale societies

Population ageing research: a family of disciplines

To study life course trajectories and ageing, scientific expertise is needed beyond epidemiology. More specifically, appropriate models of life course require a theoretical micro-foundation, need to incorporate multi-level context conditions and the interplay between them. It also requires the application of additional social scientific research methods that go beyond the application of statistical methods based on the multi-stage life table. These research theories and methods are available in disciplines like sociology, cultural anthropology, psychology, demography and economics. To effectively study healthy ageing of populations the individual approach of epidemiology has to be extended with the macro-population and socio-cultural approach of (social) demography and the institutional and network approaches of sociology

Topology of energy surfaces and existence of transversal Poincar\'e sections

Two questions on the topology of compact energy surfaces of natural two degrees of freedom Hamiltonian systems in a magnetic field are discussed. We show that the topology of this 3-manifold (if it is not a unit tangent bundle) is uniquely determined by the Euler characteristic of the accessible region in configuration space. In this class of 3-manifolds for most cases there does not exist a transverse and complete Poincar\'e section. We show that there are topological obstacles for its existence such that only in the cases of $S^1\times S^2$ and $T^3$ such a Poincar\'e section can exist.Comment: 10 pages, LaTe