745 research outputs found
Perturbative Construction of Models of Algebraic Quantum Field Theory
We review the construction of models of algebraic quantum field theory by
renormalized perturbation theory.Comment: 38 page
Analysis, classification and comparison of scheduling techniques for software transactional memories
Transactional Memory (TM) is a practical programming paradigm for developing concurrent applications. Performance is a critical factor for TM implementations, and various studies demonstrated that specialised transaction/thread scheduling support is essential for implementing performance-effective TM systems. After one decade of research, this article reviews the wide variety of scheduling techniques proposed for Software Transactional Memories. Based on peculiarities and differences of the adopted scheduling strategies, we propose a classification of the existing techniques, and we discuss the specific characteristics of each technique. Also, we analyse the results of previous evaluation and comparison studies, and we present the results of a new experimental study encompassing techniques based on different scheduling strategies. Finally, we identify potential strengths and weaknesses of the different techniques, as well as the issues that require to be further investigated
Functional renormalization group for the - tensorial group field theory with closure constraint
This paper is focused on the functional renormalization group applied to the
tensor model on the Abelian group with closure constraint. For
the first time, we derive the flow equations for the couplings and mass
parameters in a suitable truncation around the marginal interactions with
respect to the perturbative power counting. For the second time, we study the
behavior around the Gaussian fixed point, and show that the theory is
nonasymptotically free. Finally, we discuss the UV completion of the theory. We
show the existence of several nontrivial fixed points, study the behavior of
the renormalization group flow around them, and point out evidence in favor of
an asymptotically safe theory.Comment: 24 pages, 9 figure
Reason Maintenance - State of the Art
This paper describes state of the art in reason maintenance with a focus on its future usage in the KiWi project. To give a bigger picture of the field, it also mentions closely related issues such as non-monotonic logic and paraconsistency. The paper is organized as follows: first, two motivating scenarios referring to semantic wikis are presented which are then used to introduce the different reason maintenance techniques
Coherent Imaging through Multicore Fibres with Applications in Endoscopy
Imaging through optical fibres has recently emerged
as a promising method of micro-scale optical imaging within
a hair-thin form factor. This has significant applications in
endoscopy and may enable minimally invasive imaging deep
within live tissue for improved diagnosis of disease. Multi-mode
fibres (MMF) are the most common choice because of their high
resolution but multicore fibres (MCF) offer a number of advantages
such as widespread clinical use, ability to form approximate
images without correction and an inherently sparse transmission
matrix (TM) enabling simple and fast characterisation. We
present a novel experimental investigation into properties of MCF
important for imaging, specifically: a new method to upsample
and downsample measured TMs with minimal information loss,
the first experimental measurement of MCF spatial eigenmodes,
a novel statistical treatment of behaviour under bending based
on a wireless fading model, and an experimental observation
of TM drift due to self-heating effects and discussion of how
to compensate this. We next present practical techniques for
imaging through MCFs, including alignment, how to parallelise
TM characterisation measurements to improve speed and how
to use non-interferometric phase and polarisation recovery for
improved stability. Finally, we present two recent applications
of MCF imaging: polarimetric imaging using a robust Bayesian
inference approach, and entropic imaging for imaging early-stage
tumours
Context-Aware Group Communication in Mobile Ad-Hoc Networks
Abstract. The widespread availability of both fixed and wireless network con-nectivity and the growing market of portable devices are enabling anytime and anywhere impromptu collaboration. The emergence of Mobile Ad-Hoc Net-works (MANET) further opens up new possibilities for the provisioning of ad-vanced collaborative services, such as civil protection, e-care, and troop car management. However, the design and the deployment of collaborative appli-cations in MANET scenarios raises new group management challenges. In par-ticular, MANET characteristics, e.g., unpredictable and frequent mobility of us-ers/devices, intermittent device connectivity, continuous variations of network topology, make it impossible any a-priori knowledge about group members availability and ask for novel solutions to handle properly the communication about group members. The paper proposes a context-aware communication model to govern communication on the basis of the characteristics of the com-municating parties, such as their location and their profiling information. The model provides communication patterns with different semantics to address both point-to-point and point-to-multipoint communication needs. The paper shows the implementation of the proposed model in the AGAPE framework for the design, deployment, and support of collaborative applications in MANET environments and presents the functioning of the AGAPE communication sup-port in the context of a civil protection application scenario.
Dimensional Regularization in Position Space, and a Forest Formula for Epstein-Glaser Renormalization
We reformulate dimensional regularization as a regularization method in
position space and show that it can be used to give a closed expression for the
renormalized time-ordered products as solutions to the induction scheme of
Epstein-Glaser. For scalar fields the resulting renormalization method is
always applicable, we compute several examples. We also analyze the Hopf
algebraic aspects of the combinatorics. Our starting point is the Main Theorem
of Renormalization of Stora and Popineau and the arising renormalization group
as originally defined by Stueckelberg and Petermann.Comment: 51 pages, to be published in Journal of Mathematical Physic
On chip interconnects for multiprocessor turbo decoding architectures
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