Coherent Formalism Research Articles

Neural Activity in Quarks Language: Lattice Field Theory for a Network of Real Neurons.

Brain-computer interfaces have seen extraordinary surges in developments in recent years, and a significant discrepancy now exists between the abundance of available data and the limited headway made in achieving a unified theoretical framework. This discrepancy becomes particularly pronounced when examining the collective neural activity at the micro and meso scale, where a coherent formalization that adequately describes neural interactions is still lacking. Here, we introduce a mathematical framework to analyze systems of natural neurons and interpret the related empirical observations in terms of lattice field theory, an established paradigm from theoretical particle physics and statistical mechanics. Our methods are tailored to interpret data from chronic neural interfaces, especially spike rasters from measurements of single neuron activity, and generalize the maximum entropy model for neural networks so that the time evolution of the system is also taken into account. This is obtained by bridging particle physics and neuroscience, paving the way for particle physics-inspired models of the neocortex.

Generating indistinguishability within identical particle systems: spatial deformations as quantum resource activators.

Identical quantum subsystems can possess a property which does not have any classical counterpart: indistinguishability. As a long-debated phenomenon, identical particles' indistinguishability has been shown to be at the heart of various fundamental physical results. When concerned with the spatial degree of freedom, identical constituents can be made indistinguishable by overlapping their spatial wave functions via appropriately defined spatial deformations. By the laws of quantum mechanics, any measurement designed to resolve a quantity which depends on the spatial degree of freedom only and performed on the regions of overlap is not able to assign the measured outcome to one specific particle within the system. The result is an entangled state where the measured property is shared between the identical constituents. In this work, we present a coherent formalization of the concept of deformation in a general [Formula: see text]-particle scenario, together with a suitable measure of the degree of indistinguishability. We highlight the basic differences with non-identical particles scenarios and discuss the inherent role of spatial deformations as entanglement activators within the spatially localized operations and classical communication operational framework. This article is part of the theme issue 'Identity, individuality and indistinguishability in physics and mathematics'.

Scaling at quantum phase transitions above the upper critical dimension

The hyperscaling relation and standard finite-size scaling (FSS) are known to break down above the upper critical dimension due to dangerous irrelevant variables. We establish a coherent formalism for FSS at quantum phase transitions above the upper critical dimension following the recently introduced Q-FSS formalism for thermal phase transitions. Contrary to long-standing belief, the correlation sector is affected by dangerous irrelevant variables. The presented formalism recovers a generalized hyperscaling relation and FSS form. Using this new FSS formalism, we determine the full set of critical exponents for the long-range transverse-field Ising chain in all criticality regimes ranging from the nearest-neighbor to the long-range mean-field regime. For the same model, we also explicitly confirm the effect of dangerous irrelevant variables on the characteristic length scale.

Lagrangian and Hamiltonian dynamics for probabilities on the statistical bundle

We provide an Information-Geometric formulation of accelerated natural gradient on the Riemannian manifold of probability distributions, which is an affine manifold endowed with a dually-flat connection. In a non-parametric formalism, we consider the full set of positive probability functions on a finite sample space, and we provide a specific expression for the tangent and cotangent spaces over the statistical manifold, in terms of a Hilbert bundle structure that we call the Statistical Bundle. In this setting, we compute velocities and accelerations of a one-dimensional statistical model using the canonical dual pair of parallel transports and define a coherent formalism for Lagrangian and Hamiltonian mechanics on the bundle. We show how our formalism provides a consistent framework for accelerated natural gradient dynamics on the probability simplex, paving the way for direct applications in optimization.

A New Developmentalist model of structural change, economic growth and middle-income traps

When a rapidly growing country stagnates at middle-income levels and fails to transition into a high-income economy, we say it has fallen into a middle-income trap. An original interpretation of the causes of this phenomenon was offered in recent years by the so-called Brazilian New Developmentalist School. It must be noted, however, that this approach lacks a coherent formalization of its main propositions. This article aims at filling this gap in the literature. We assess, analytically and through numerical simulations, whether the Dutch disease can be propelled by the discovery of natural resources and the adoption of an external savings growth strategy. In both cases, a class coalition between workers and rentiers leads to an overvaluation of the real exchange rate. As a consequence, inflation is kept under control while artificially increasing real wages and financial incomes. The model provides a bridge between classical development theory and demand-led growth theories, drawing on elements from both traditions.

Combinatorial Optimization of Graphical User Interface Designs

The graphical user interface (GUI) has become the prime means for interacting with computing systems. It leverages human perceptual and motor capabilities for elementary tasks such as command exploration and invocation, information search, and multitasking. For designing a GUI, numerous interconnected decisions must be made such that the outcome strikes a balance between human factors and technical objectives. Normally, design choices are specified manually and coded within the software by professional designers and developers. This article surveys combinatorial optimization as a flexible and powerful tool for computational generation and adaptation of GUIs. As recently as 15 years ago, applications were limited to keyboards and widget layouts. The obstacle has been the mathematical definition of design tasks, on the one hand, and the lack of objective functions that capture essential aspects of human behavior, on the other. This article presents definitions of layout design problems as integer programming tasks, a coherent formalism that permits identification of problem types, analysis of their complexity, and exploitation of known algorithmic solutions. It then surveys advances in formulating evaluative functions for common design-goal foci such as user performance and experience. The convergence of these two advances has expanded the range of solvable problems. Approaches to practical deployment are outlined with a wide spectrum of applications. This article concludes by discussing the position of this application area within optimization and human-computer interaction research and outlines challenges for future work.

Coherent Extension, Composition, and Merging Operators in Contract Models for System Design

Contract models have been proposed to promote and facilitate reuse and distributed development. In this paper, we cast contract models into a coherent formalism used to derive general results about the properties of their operators. We study several extensions of the basic model, including the distinction between weak and strong assumptions and maximality of the specification. We then analyze the disjunction and conjunction operators, and show how they can be broken up into a sequence of simpler operations. This leads to the definition of a new contract viewpoint merging operator, which better captures the design intent in contrast to the more traditional conjunction. The adjoint operation, which we call separation, can be used to re-partition the specification into different viewpoints. We show the symmetries of these operations with respect to composition and quotient.

From fuzzy regression to gradual regression: Interval-based analysis and extensions

This paper proposes an analysis of parametric interval-based regression methodologies according to ontic and epistemic visions of intervals. When assuming an epistemic point of view, a new interpretation of fuzzy regression through the notion of gradual intervals is developed, which leads to gradual regression. Gradual regression is viewed as an extension of the imprecise interval-based regression, which is obtained by integrating an uncertain dimension. Gradual intervals can yield improved specificity compared to conventional intervals and jointly consider the concepts of imprecision and uncertainty through a single and coherent formalism. The formulation of the gradual regression problem, its resolution and the propagation of the information through the obtained regressive models are carried out via gradual interval arithmetic. The proposed method allows not only the extension of the interval vision to the gradual case but also interesting interpretations according to non-additive confidence measure theories (possibility and belief functions).

Experimental evidence for partial spatial coherence in imaging Mueller polarimetry.

We demonstrate experimentally the validity of the partial spatial coherence formalism in Mueller polarimetry and show that, in a finite spatial resolution experiment, the measured response is obtained through convolving the theoretical one with the instrument function. The reported results are of primary importance for Mueller imaging systems.

Enhanced light trapping in dye-sensitized solar cell by coupling to 1D photonic crystal and accounting for finite coherence length

Theoretical analysis of dye-sensitized solar cell integrated with photonic crystals based on coupled coherent and geometrical optics formalism has presented. The effect of structural parameters, such as thickness of layer, number of unit cells and light incident angle on the optical properties and photo-current magnification for the proposed photonic crystal based dye-sensitized solar cell have studied. The angular response of the cell in terms of light harvesting efficiency and cumulative photo-generation rate has also analysed. A strategy has presented to enhance the performance of the cell under oblique incidence. The effect of number of photonic crystal unit cells has also analysed in view of percentage enhancement in cumulative photo-generation rate. This work provides new insight into the design and tailoring of the photonic crystals to enhance the light harvesting efficiency in the solar cells.

Structure space of Bayesian networks is dramatically reduced by subdividing it in sub-networks

Currently, Bayesian Networks (BNs) have become one of the most complete, self-sustained and coherent formalisms used for knowledge acquisition, representation and application through computer systems. However, learning of BNs structures from data has been shown to be an NP-hard problem. It has turned out to be one of the most exciting challenges in machine learning. In this context, the present work’s major objective lies in setting up a further solution conceived to be a remedy for the intricate algorithmic complexity imposed during the learning of BN-structure with a massively-huge data backlog.

Putting biomedical ontologies to work.

Biomedical ontologies exist to serve integration of clinical and experimental data, and it is critical to their success that they be put to widespread use in the annotation of data. How, then, can ontologies achieve the sort of user-friendliness, reliability, cost-effectiveness, and breadth of coverage that is necessary to ensure extensive usage? Our focus here is on two different sets of answers to these questions that have been proposed, on the one hand in medicine, by the SNOMED CT community, and on the other hand in biology, by the OBO Foundry. We address more specifically the issue as to how adherence to certain development principles can advance the usability and effectiveness of an ontology or terminology resource, for example by allowing more accurate maintenance, more reliable application, and more efficient interoperation with other ontologies and information resources. SNOMED CT and the OBO Foundry differ considerably in their general approach. Nevertheless, a general trend towards more formal rigor and cross-domain interoperability can be seen in both and we argue that this trend should be accepted by all similar initiatives in the future. Future efforts in ontology development have to address the need for harmonization and integration of ontologies across disciplinary borders, and for this, coherent formalization of ontologies is a pre-requisite.

A theoretical study on phase‐contrast mammography with Thomson‐scattering x‐ray sources

The x-ray transmitted beam from any material/tissue depends on the complex refractive index (n= 1-delta+ibeta), where delta is responsible for the phase shift and beta is for the beam attenuation. Although for human tissues, the delta cross section is about 1000 times greater than the beta ones in the x-ray energy range from 10 to 150 keV, the gain in breast tumor visualization of phase-contrast mammography (PCM) with respect to absorption contact imaging (AI) is limited by the maximum dose that can be delivered to the patient. Moreover, in-line PC imaging (PCI) is the simplest experimental mode among all available x-ray PCI techniques since no optics are needed. The latter is a fundamental requirement in order to transfer the results of laboratory research into hospitals. Alternative to synchrotron radiation sources, the implementation of relativistic Thomson-scattering (TS) x-ray sources is particularly suitable for hospital use because of their high peak brightness within a relatively compact and affordable system. In this work, the possibility to realize PCM using a TS source in a hospital environment is studied, accounting for the effect of a finite deliverable dose on the PC visibility enhancement with respect to AI. The contrast-to-noise ratio of tumor-tissue lesions in PCM has been studied on the bases of a recent theoretical model, describing image contrast formation by means of both wave-optical theory and the mutual coherence formalism. The latter is used to describe the evolution, during wave propagation, of the coherence of the wave field emitted by a TS source. The contrast-to-noise ratio for both PCI and AI has been analyzed in terms of tumor size, beam energy, detector, and source distances, studying optimal conditions for performing PCM. Regarding other relevant factors which could influence "tumor" visibility, the authors have assumed simplified conditions such as a spherical shape description of the tumor inclusion, a constant surrounding background, ideal conditions for the calculus of the contrast-to-noise ratio. The results show the possibility to enhance with PCI the signal-to-noise ratio for features in the submillimeter scale. This finding could give PCM a great advantage with respect to AI, opening the possibility to decrease the number of wrong diagnoses before histological exams. The results agree with experimental evidences obtained by Dreossi et al. [D. Dreossi et al., "The mammography project at the SYRMEP beamline," Eur. J. Radiol. 68, S58-S62 (2008)] with real PCM using synchrotron radiation. The challenging characteristics of TS sources, suitable for PCM, should be fluxes of at least 10(11) photons/s emitted by very small sources of about 10 microm, together with moderate energy spreads (less than 10%) in order to realize both sufficient spatial coherence and enough fluence on the patient, collecting images in reasonable exposure times. These fluxes will be achieved by next generation TS sources which are already under development.

Voice-supported Electronic Health Record for Temporomandibular Joint Disorders

Objective: Biomedical ontologies exist to serve integration of clinical and experimental data, and it is critical to their success that they be put to widespread use in the annotation of data. How, then, can ontologies achieve the sort of user- friendliness, reliability, cost-effectiveness, and breadth of coverage that is necessary to ensure extensive usage? Methods: Our focus here is on two different sets of answers to these questions that have been proposed, on the one hand in medicine, by the SNOMED CT community, and on the other hand in biology, by the OBO Foundry. We address more specifically the issue as to how adherence to certain development principles can advance the usability and effectiveness of an ontology or terminology resource, for example by allowing more accurate maintenance, more reliable application, and more efficient interoperation with other ontologies and information resources. Results: SNOMED CT and the OBO Foundry differ considerably in their general approach. Nevertheless, a general trend towards more formal rigor and cross-domain interoperability can be seen in both and we argue that this trend should be accepted by all similar initiatives in the future. Conclusions: Future efforts in ontology development have t o address t he need f or harmonization and integration of ontologies across disciplinary borders, and for this, coherent formalization of ontologies is a pre-requisite.

Putting Biomedical Ontologies to Work

Objectives Biomedical ontologies exist to serve integration of clinical and expe- rimental data, and it is critical to their success that they be put to widespread use in the annotation of data. How, then, can ontologies achieve the sort of user- friendliness, reliability, cost-effectiveness, and breadth of coverage that is necessary to ensure extensive usage? Methods Our focus here is on two different sets of answers to these questions that have been proposed, on the one hand in medicine, by the SNOMED CT community, and on the other hand in biology, by the OBO Foundry. We address more specifically the issue as to how adherence to certain development principles can advance the usability and effectiveness of an ontology or terminology resource, for example by allowing more accurate maintenance, more reliable application, and more e f f i c i ent interoperation with other ontologies and information resources. Results SNOMED CT and the OBO Foundry differ considerably in their general approach. Nevertheless, a general trend towards more formal rigor and cross-domain interoperability can be seen in both and we argue that this trend should be accepted by all similar initiatives in the future. Conclusions Future efforts in ontology development have t o address t he need f or harmonization and integration of ontologies across disciplinary borders, and for this, coherent formalization of ontologies is a pre-requisite.

The statistics of gravitational lenses in a clumpy Universe

We evaluate the effect of small-scale inhomogeneities on large-scale observations within the statistics of gravitationally lensed quasars. To this end, we consider a cosmological model whose large-scale properties (dynamics, matter distribution) are the same as in Friedmann–Lemaître models, but whose matter distribution is locally inhomogeneous. We use the well-known Dyer–Roder distances to allow a simple analytical expression of the optical depth τ, and pay particular attention to the different roles played by the different notions of distance (filled beam angular diameter distance and Dyer–Roder distances) when calculating this quantity, following the 1986 prescription of Ehlers & Schneider for a coherent formalism. We find that the expected number of gravitationally lensed quasars is a decreasing function of the clumpiness parameter α.

Spontaneous emergence of complex optimal networks through evolutionary adaptation

An important feature of many complex systems, both natural and artificial, is the structure and organization of their interaction networks with interesting properties. Such networks are found in a variety of applications such as in supply chain networks, computer and communication networks, metabolic networks, food webs, etc. Here, we present a theory of self-organization by evolutionary adaptation in which we show how the structure and organization of a network is related to the survival, or in general the performance, objectives of the system. We propose that a complex system optimizes its network structure in order to maximize its overall survival fitness which is composed of short- and long-term survival components. These in turn depend on three critical measures of the network, namely, efficiency, robustness and cost, and the environmental selection pressure. Fitness maximization by adaptation leads to the spontaneous emergence of optimal network structures, both power law and non-power law, of various topologies depending on the selection pressure. Using a graph theoretical case study, we show that when efficiency is paramount the “star” topology emerges and when robustness is important the “circle” topology is found. When efficiency and robustness requirements are both important to varying degrees, other classes of networks such as the “hub” emerge. This theory provides a general conceptual framework for integrating survival or performance objectives, environmental or selection pressure, evolutionary adaptation, optimization of performance measures and topological features in a single coherent formalism. Our assumptions and results are consistent with observations across a wide variety of applications. This framework lays the ground work for a novel approach to model, design and analyze complex networks, both natural and artificial, such as metabolic pathways, supply chains and communication networks.

The Rashba Effect Within the Coherent Scattering Formalism with Applications to Electron Quantum Optics

The influence of spin–orbit coupling in electron quantum optics experiments is investigated within the framework of the Landauer–Buttiker coherent scattering formalism. We begin with a brief review of our electron quantum optics toolbox: an electron intensity interferometer (Hanbury Brown and Twiss-type experiment), an electron collision analyzer (Hong–Ou–Mandel-type experiment), and a proposed Bell state analyzer. These experiments are performed or proposed in two-dimensional electron gas systems and, therefore, may be influenced by the Rashba spin–orbit coupling. To quantify this effect, we define the creation/annihilation operators for the stationary states of the Rashba spin–orbit coupling Hamiltonian and use them to derive the current operator within the Landauer–Buttiker formalism. The current is expressed as it is in the standard spin-independent case, but with the spin label replaced by a new label that we call the spin–orbit coupling label. The spin–orbit coupling effects can then be represented in a scattering matrix that relates the spin–orbit coupling stationary states in different leads. We apply this new formalism to the case of a four-port beamsplitter, and it is shown to mix states with different spin–orbit coupling labels in a manner that depends on the angle between the leads. A noise measurement after the collision of spin-polarized electrons at an electron beamsplitter provides a new experimental means to measure the Rashba parameter α. It is also shown that the degree of electron bunching in an entangled-electron collision experiment is reduced by the spin–orbit coupling according the beamsplitter lead angle.

Beyond thermoeconomics? The concept of Extended Exergy Accounting and its application to the analysis and design of thermal systems

This paper presents a novel approach to the evaluation of energy conversion processes and systems, based on an extended representation of their exergy flow diagram. This approach is a systematic attempt to integrate into a unified coherent formalism both Cumulative Exergy Consumption and Thermo-economic methods, and constitutes a generalisation of both, in that its framework allows for a direct quantitative comparison of non-energetic quantities like labour and environmental impact (hence the apposition ‘Extended’). A critical examination of the existing state-of-the-art of energy- and exergy analysis methods and paradigms indicates that an extension of the existing ‘Design and Optimisation’ procedures to include explicitly ‘non-energetic externalities’ is indeed feasible. It appears that it can indeed be successfully argued that some of the issues that are difficult to address with a purely monetary theory of value can be resolved by Extended Exergy Accounting (‘EEA’ in the following) methods without introducing arbitrary assumptions external to the theory. In this respect, EEA can be regarded as a natural development of the economic theory of production of commodities, which it extends by properly accounting for the unavoidable energy dissipation in the productive chain. While a systematic description of the EEA theory is discussed in previous work by the same author, the present paper aims at a more specific target, and presents a formal representation of the application of EEA to a cogenerating plant based on a gas turbine process. It is shown that the solution indeed leads to an ‘optimal’ design, and that its formalism embeds even extended Thermo-economic formulations.

Radiatively corrected semileptonic spectra in B meson decays

We show how radiative QCD corrections calculated in terms of quarks can be incorporated at the hadron level in inclusive semileptonic B-meson decays. The bound state effects are described by a momentum distribution function of the $b$ quark. The summation over the final states and the averaging over the momentum distribution of the decaying quark render the radiative corrections finite. With this coherent formalism we investigate the shape of the electron spectra for $b\to u$ and $b\to c$ decays as a function of the parameters of the theory. The resultant $b\to c$ electron energy spectrum is in agreement with the experimental data.