Causarum Investigatio and the Two Bell's Theorems of John Bell

"Bell's theorem" can refer to two different theorems that John Bell proved, the first in 1964 and the second in 1976. His 1964 theorem is the incompatibility of quantum phenomena with the joint assumptions of Locality and Predetermination. His 1976 theorem is their incompatibility with the single property of Local Causality. This is contrary to Bell's own later assertions, that his 1964 theorem began with the assumption of Local Causality, even if not by that name. Although the two Bell's theorems are logically equivalent, their assumptions are not. Hence, the earlier and later theorems suggest quite different conclusions, embraced by operationalists and realists, respectively. The key issue is whether Locality or Local Causality is the appropriate notion emanating from Relativistic Causality, and this rests on one's basic notion of causation. For operationalists the appropriate notion is what is here called the Principle of Agent-Causation, while for realists it is Reichenbach's Principle of common cause. By breaking down the latter into even more basic Postulates, it is possible to obtain a version of Bell's theorem in which each camp could reject one assumption, happy that the remaining assumptions reflect its weltanschauung. Formulating Bell's theorem in terms of causation is fruitful not just for attempting to reconcile the two camps, but also for better describing the ontology of different quantum interpretations and for more deeply understanding the implications of Bell's marvellous work.Comment: 24 pages. Prepared for proceedings of the "Quantum [Un]speakables II" conference (Vienna, 2014), to be published by Springe

Complexity of coordinated beamforming and scheduling for OFDMA based heterogeneous networks

Coordination is foreseen to be an important component of future mobile radio networks. It is especially relevant in heterogeneous networks, where high power base stations produce strong interference to an underlying layer of low power base stations. This work investigates in detail the achievable performance gains for one coordination technique—coordinated beamforming. It reveals the main factors that influence the throughput of the mobile stations. These findings are combined with an analysis of the computational complexity. As a result, a heuristic algorithm is presented that achieves results close to an exhaustive search with significantly less calculations. Detailed simulation analysis is presented on a realistic network layout

Position certainty propagation: a location service for MANETs

International audienceLocalization in Mobile Ad-hoc Networks (MANETs) and Wireless Sensor Networks (WSNs) is an issue of great interest, especially in applications such as the IoT and VANETs. We propose a solution that overcomes two limiting characteristics of these types of networks. The first is the high cost of nodes with a location sensor (such as GPS) which we will refer to as anchor nodes. The second is the low computational capability of nodes in the network. The proposed algorithm addresses two issues; self-localization where each non-anchor node should discover its own position, and global localization where a node establishes knowledge of the position of all the nodes in the network. We address the problem as a graph where vertices are nodes in the network and edges indicate connectivity between nodes. The weights of edges represent the Euclidean distance between the nodes. Given a graph with at least three anchor nodes and knowing the maximum communication range for each node, we are able to localize nodes using fairly simple computations in a moderately dense graph

Ten years of a multidisciplinary diabetic foot team approach in Sao Paulo, Brazil

Diabetes mellitus can cause devastating foot problems including loss of protective sensation with subsequent ulcerations and amputations. The natural history and pathophysiology of diabetic foot ulcers is best understood and managed by a multiprofessional team approach. The main factors for prevention and treatment of these devastating diabetic foot conditions are shown, with special attention to education of the patient. This approach decreases the morbidity of the disease, besides its economical and social feasibility

Swedish social insurance officers' experiences of difficulties in assessing applications for disability pensions – an interview study

<p>Abstract</p> <p>Background</p> <p>In this study the focus is on social insurance officers judging applications for disability pensions. The number of applications for disability pension increased during the late 1990s, which has resulted in an increasing number of disability pensions in Sweden. A more restrictive attitude towards the clients has however evolved, as societal costs have increased and governmental guidelines now focus on reducing costs. As a consequence, the quantitative and qualitative demands on social insurance officers when handling applications for disability pensions may have increased. The aim of this study was therefore to describe the social insurance officers' experiences of assessing applications for disability pensions after the government's introduction of stricter regulations.</p> <p>Methods</p> <p>Qualitative methodology was employed and a total of ten social insurance officers representing different experiences and ages were chosen. Open-ended interviews were performed with the ten social insurance officers. Data was analysed with inductive content analysis.</p> <p>Results</p> <p>Three themes could be identified as problematic in the social insurance officers' descriptions of dealing with the applications in order to reach a decision on whether the issue qualified applicants for a disability pension or not: 1. Clients are heterogeneous. 2. Ineffective and time consuming waiting for medical certificates impede the decision process. 3. Perspectives on the issue of work capacity differed among different stakeholders. The backgrounds of the clients differ considerably, leading to variation in the quality and content of applications. Social insurance officers had to make rapid decisions within a limited time frame, based on limited information, mainly on the basis of medical certificates that were often insufficient to judge work capacity. The role as coordinating actor with other stakeholders in the welfare system was perceived as frustrating, since different stakeholders have different goals and demands. The social insurance officers experience lack of control over the decision process, as regulations and other stakeholders restrict their work.</p> <p>Conclusion</p> <p>A picture emerges of difficulties due to disharmonized systems, stakeholder-bound goals causing some clients to fall between two stools, or leading to unnecessary waiting times, which may limit the clients' ability to take an active part in a constructive process. Increased communication with physicians about how to elaborate the medical certificates might improve the quality of certificates and thereby reduce the clients waiting time.</p

Space-time code diversity by phase rotation in multi-carrier multi-user systems

Code diversity using space-time block codes was developed for single-carrier and single-receiver systems. In this paper, the extension of code diversity by phase rotation to multi-user and multi-carrier systems is proposed and analyzed. We show that code diversity with reduced feedback is possible in this new scenario and the coding gain has a mild logarithmic decrease with the number of users and the number of sub-carriers. In addition, we develop an analytical upper bound for the average error probability whose accuracy is verified by simulation

Testing foundations of quantum mechanics with photons

The foundational ideas of quantum mechanics continue to give rise to counterintuitive theories and physical effects that are in conflict with a classical description of Nature. Experiments with light at the single photon level have historically been at the forefront of tests of fundamental quantum theory and new developments in photonics engineering continue to enable new experiments. Here we review recent photonic experiments to test two foundational themes in quantum mechanics: wave-particle duality, central to recent complementarity and delayed-choice experiments; and Bell nonlocality where recent theoretical and technological advances have allowed all controversial loopholes to be separately addressed in different photonics experiments.Comment: 10 pages, 5 figures, published as a Nature Physics Insight review articl