Classical Analog Research Articles

A comparison of the bremsstrahlung cross section in two frameworks: classical Lorentz–Abraham–Dirac dynamics and quantum field theory

In classical electromagnetic theory, the Lorentz–Abraham–Dirac (LAD) equation describes the dynamics of a charged particle, including radiation reaction. Though the LAD equation is derived from Maxwell’s equations, consistent with the conservation of energy and momentum, it admits unphysical solutions for point-like charged particles. By assuming small radiative effects, Landau and Lifshitz (LL) develop an approximation of the LAD equation that has no pathological solutions. Though the LL approximation is dynamically sound, it is the LAD equation that has firm theoretical underpinning. As such, the difficulties encountered in LAD dynamics suggest, in part, that an electrodynamic treatment of point-like particles lies outside the classical domain. Herein, we compute the cross section of a charged particle scattered by an attractive Coulombic potential using classical LAD and LL dynamics. We then compare this with the analogous cross section in quantum field theory (QFT). In particular, we compute the cross section for a charged scalar particle incident upon another extremely massive charged scalar with a single photon in the final state. We include the following -radiative corrections: scalar-photon vertex correction, infrared photon emission, vacuum polarization, and two-photon exchange. We find that the classical and quantum frameworks do not produce similar cross sections. Relative to the elastic cross section, the classical bremsstrahlung cross section vastly overestimates the relative QFT cross section; this is, in part, due to the fact that the additional radiative corrections in QFT do not have a classical analog in either the LAD or LL framework.

Explaining Rainfall Accumulations over Several Days in the French Alps Using Low-Dimensional Atmospheric Predictors Based on Analogy

AbstractWe propose a new approach to explain multiday rainfall accumulation over a French Alpine watershed using large-scale atmospheric predictors based on analogy. The classical analogy framework associates a rainfall cumulative distribution function (CDF) with a given atmospheric situation from the precipitation accumulations yielded by the closest situations. The analogy may apply to single-day or multiday sequences of pressure fields. The proposed approach represents a paradigm shift in analogy. It relies on the similarity of the local topology mapping the pressure field sequences, somehow forgetting the pressure fields per se. This topology is summarized by the way the sequences of pressure fields resemble their neighbors (dimensional predictors) and how fast they evolve in time (dynamical predictors). Although some information—and hence predictability—is expected to be lost when compared with classical analogy, this approach provides new insight on the atmospheric features generating rainfall CDFs. We apply both approaches to geopotential heights over western Europe in view of assessing 3-day rainfall accumulations over the Isère River catchment at Grenoble, France. Results show that dimensional predictors are the most skillful features for predicting 3-day rainfall—bringing alone 60% of the predictability of the classical analogy approach—whereas the dynamical predictors are less explicative. These results open new directions of research that the classical analogy approach cannot handle. They show, for instance, that both dry sequences and strong rainfall sequences are associated with singular 500-hPa geopotential shapes acting as local attractors—a way of explaining the change in rainfall CDFs in a changing climate.

Topological thermal Hall effect of magnetic monopoles in the pyrochlore U(1) spin liquid

"Magnetic monopole" is an exotic quantum excitation in pyrochlore U(1) spin liquid, and its emergence is purely of quantum origin and has no classical analogue. We predict topological thermal Hall effect (TTHE) of "magnetic monopoles" and present this prediction through non-Kramers doublets. We observe that, when the external magnetic field polarizes the Ising component of the local moment, internally this corresponds to the induction of emergent dual U(1) gauge flux for the "magnetic monopoles". The motion of "magnetic monopoles" is then twisted by the induced dual gauge flux. This emergent Lorentz force on "magnetic monopoles" is the fundamental origin of TTHE. Therefore, TTHE would be a direct evidence of the "monopole"-gauge coupling and the emergent U(1) gauge structure in pyrochlore U(1) spin liquid. Our result does not depend strongly on our choice of non-Kramers doublets for our presentation, and can be well extended to Kramers doublets. Our prediction can be readily tested among the pyrochlore spin liquid candidate materials. We give a detailed discussion about the expectation for different pyrochlore magnets.

Revival of water table experiment in fluid mechanics courses, part II

In an effort to find a simple and efficient method for observing and predicting compressible flows in an instructional environment, we revisit the classical hydraulic analogy. The focus is made on using a water table apparatus to visualize the formation of oblique surface waves in a flow around a wedge. These waves are analogous to the oblique shock waves seen in a compressible flow. A mathematical derivation of this analogy is presented together with water table experiment data collected by graduate students. The comparison between the predicted values and measured values is made and shows a remarkable correlation between the two for simulated Mach numbers.

ДОСЛІДЖЕННЯ ВПЛИВУ ЗАВАНТАЖЕНОСТІ МЕРЕЖІ НА ЯКІСТЬ ПЕРЕДАВАННЯ VoIP

The emergence of new technologies and protocols for data transmission in telecommunications networks leads to the emergence of new approaches to qualitative and efficient information transmission. The transmission of voice messages is one of the most common types of data being transmitted. In classical analogue systems, speech was transmitted by channel switching. But with the emergence of a packet switching approach, a new ideology for voice messaging has emerged. IP telephony, with which you can deploy telephone corporate networks, is among the most effective ones, in terms of utilizing the available bandwidth and adaptive quality settings. Today, there is a large number of protocols for building IP networks, or its segments, but it is not a simple task to choose the right protocol under specific network conditions. The purpose of the article is to investigate the effect of telecommunication network congestion on VoIP transmission quality, to choose the optimal protocol for specific transmission conditions, such as preset quality parameters (QoS) and transmission speed. The article discusses the problem of determining the admissible level of telecommunication network congestion for the optimal operation of VoIP communication. A model of a telecommunication network, in which there is a load of voice and videoconferencing, a comparison of characteristics of voice traffic for voice codecs, comparative analysis of characteristics at different load, is proposed. The optimum network connection type and usage criterion are determined. The article deals with the simulation of telecommunication network segment in order to model and analyze the characteristics of the most common codecs used in IP networks. MOS voice quality metrics have been also introduced for all network congestion scenarios considered. Based on the research, recommendations regarding the use of different codecs for different network congestion to provide the set parameters of MOS factor have been made.

“Silken Dalliance”: Fashion and Rhetoric in Byron’s Dramas and the Letter to Murray

ABSTRACTThis essay traces Byron’s inconsistent efforts to reinstate the civilizing “laws” of literature in the realm of English letters. Straddling the antique and the Romantic, Byron rebelled against Wordsworth by resorting to older models of social and literary decorum, which he identified as the “dress” that made language and society legible. While Wordsworth renounced the classical analogy of language as the “dress” of thought, Byron attempted to distinguish between rooted customary dress and arbitrary modern fashion as models for literary language. However the distinction between the figures that form the world into an orderly kosmos, or harmonious arrangement, and those that throw it into chaos crumbles under the pressure of Byron’s philosophy that the universe is caught in a cycle of destruction and re-creation. By reading the Letter to Murray alongside three of Byron’s dramas—Cain, The Deformed Transformed, and Sardanapalus—this essay maps how Byron’s polarizing view of history informed a poetics in which chaos and kosmos are locked in perpetual struggle. Furthermore, it argues that in Sardanapalus Byron brings the material conditions of life at the turn of the nineteenth century to bear on the long-standing polarity between chaos and kosmos in debates about poetic language.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ЦИКЛІЧНИХ КОДІВ МЕТОДАМИ КОМБІНАТОРНОЇ ОПТИМІЗАЦІЇ

The methods of improving the cyclic codes efficiency constructed on the basis of combinatorial configurations of the type "ideal ring bundles" (IRB) s by three factors – correction ability, power of coding method and complexity of the decoding procedure are considered. The method is based on the principle of combinatorial optimization, grounded on the algebraic theory of ordered integer sequences with a circular structure, all the numbers, as well as all sums of consecutive numbers exhaust the value sofnatural row numbers. Two theoretically grounded approaches to increase of noise immunity of cyclic codes are offered: implementation of optimized IRB-code, as well as monolithic and group one. Optimized cyclic IRB-code favorably differs from the rest of the codes of this class by the highest correction capacity at the same length of code words. Optimized IRB-codes constitute a large group of cyclic codes designed on a combinatorial models with selection of corresponding relationships between the parameters of the code to achieve its specified technical characteristics. Noise protected monolithic and group codes belong to the group of self-correcting codes with a ring structure and probabilistic assessment of the level of noise protection. This property allow so instant lydetect a particular part or all invalid characters in the code word by the majority principle. Mathematical calculations have been performed to calculate the optimized ratios between the parameters of cyclic IRB-codes, under which they reach maximum correction capacity. The algorithm of constructing and increasing the power of coding methods of optimized noise-resistant IRB-codes is examined and analyzed. The concrete examples of increase efficiency of combinatorial optimization cyclic codes methods with appropriate calculations and tables are given. The comparative analysis of the IRB-codes with the Golay codes and Bose – Chaudhuri – Hocquenghe (BCH) codes with respect to correction ability, power encoding method and computational complexity of decoding procedures is carried out. The advantages and disadvantages of cyclic, and ringmonolithic and group IRB-codes in comparison with classical analogues are determined. The prospect so fusing the research results in the problems of information and communication technologies are outlined.

Confinement-induced resonance (CIR) in classical vs. quantum scattering under 2D harmonic confinement

Using complex analysis, we have investigated classical quasi-one-dimensional atom–atom scattering under 2D harmonic confinement with two different interaction potentials (Yukawa and Lennard-Jones) and found that the confinement-induced resonance (CIR) that occurs in the quantum system seems to have a classical analogue. We observed CIR in our classical results in the sense that a clear minimum appeared in the transmission coefficient for the different interaction potentials. We also investigated the changes in the value and position of this minimum by varying the characteristic parameters of the system including the angular momentum $$L_z$$ along the longitudinal axis. In the quantum case, it has already been shown that for the zero range Huang potential, CIR occurs only for $$L_z = 0$$. Our results indicate that classical CIR can also occur for $$L_z \ne 0$$ using finite range potentials. We have endeavoured to provide extensive physical arguments to explain the observed results and to support the proposed analogy between the classical and quantum regimes where applicable.

Synthesis and Optical Properties of the New Kaede Chromophore Analog

A novel derivative of Kaede protein chromophore was synthesized. The compound showed the shift of absorption and emission maxima to the longwave region in comparison with the classical Kaede chromophore analog due to an increase in the conjugated π-system in the imidazolone fragment.

Anthropology, Comparative Studies, and the Classics: Receptions of the ‘Savage’ in the Metropole and the Periphery

That comparative studies, anthropology, and the Classics have been uneasy bedfellows in the study of the Classics in South Africa is well known. At the height of the British Empire, as more and more ethnographies of conquered peoples flooded into the metropole, and more Classically educated administrators and missionaries ventured forth into the colonies equipped with perceptions of the ‘savage other’, dissonances in the discourses generated by receptions of the ‘other’ in metropole and periphery appear. One such dissonance is how Classical scholarship in the metropole used ‘savage analogies’ to illuminate the dark origins of ancient Greek religion, whereas scholarly missionaries in the periphery used Classical analogies to redeem indigenous religions from the kind of ‘othering’ engendered by academic discourses in the metropole. To explore this dissonance, I use the research on Zulu religion of a British missionary in the former colony of Natal, Henry Callaway, to represent the periphery, and Jane Harrison’s work on ancient Greek religion as representative of the metropole.

Analog IC Design Using Precomputed Lookup Tables: Challenges and Solutions

Design productivity remains an important aspect in the analog integrated circuit design industry, as growing competition and shorter design cycles pressure the traditional flow that involves time-consuming manual iterations in a circuit simulator. This paper describes innovations within an alternative framework that uses precomputed look-up tables (LUTs) to enable fast and accurate evaluation of circuit sizing scenarios without a simulator in the loop. It lets the designer explore and understand the design space boundaries in a systematic setting, thus supporting informed decision making and architectural innovation that is difficult to attain with fully automated, black-box sizing tools. Our discussion begins with an overview of the LUT-based design paradigm and its two primary variants: inverse design (finding design parameters that meet the specifications) and forward evaluation (sweeping design parameters to search the design space). In support of the latter, the core of our work focuses on improving the accuracy and speed of LUT access, enabling millions of queries within seconds on a standard computer. Large improvements over prior art are enabled using enhanced interpolation methods, which allow for a relatively large LUT grid spacing (hence small memory footprint) and yet accurate parameter lookup. We evaluate the efficacy of the proposed methods using two classical analog circuits, a bandgap reference and a folded cascode amplifier. In the bandgap example, we observe less than 1 ppm error between the LUT-predicted temperature coefficient and circuit simulation. In the folded-cascode example, one million design points are generated in only 4 seconds, providing the designer with useful maps that delineate the reachability of certain target specifications.

Newman on Natural and Revealed Religion

This essay reflects on Newman’s famous analyses of natural and revealed religion and their relation in the tenth and final chapter of the Grammar of Assent. There are two lines of reflection, the first internalist, the second externalist. On the first front, the essay draws attention to how conscience plays a foundational role in Newman’s discussion of natural religion and how it helps to distinguish it from the “religion of civilization,” which Newman considers to be a rationalist substitute for the real religion. If natural religion is structurally grounded in conscience, it is historically illustrated in paganism and primitive religions to the extent to which these come to light in the modern age. Crucially, natural religion has significant content that is endorsed and recalibrated in revealed religion. It uncovers God as Judge and discloses humanity both to be under judgment and hoping for reconciliation through a mediator. The second and more externalist line of reflection draws attention to how Bishop Joseph Butler’s classic Analogy of Religion (1736) provides the basic frame for Newman’s reflection on natural and revealed religion and their relation.

Current carried by evanescent modes and possible device application

Quantum tunneling of an electron through a classically forbidden regime has no classical analogue and several aspects of it are still not well understood. In this work we analyze electronic currents under the barrier. For this we consider a multichannel Aharonov-Bohm ring and developed a correct formalism to calculate the currents inside the ring when the states are evanescent. We also show unlike other proposed quantum devices that such currents and associated conductance are not very sensitive to changes in material parameters and thus the system can be used to build stable devices that work on magnetic and transport properties. We also study the current magnification property of the ring in presence of both propagating and evanescent states.

Predicting quantum advantage by quantum walk with convolutional neural networks

Quantum walks are at the heart of modern quantum technologies. They allow to deal with quantum transport phenomena and are an advanced tool for constructing novel quantum algorithms. Quantum walks on graphs are fundamentally different from classical random walks analogs, in particular, they walk faster than classical ones on certain graphs, enabling in these cases quantum algorithmic applications and quantum-enhanced energy transfer. However, little is known about the possible advantages on arbitrary graphs not having explicit symmetries. For these graphs one would need to perform simulations of classical and quantum walk dynamics to check if the speedup occurs, which could take a long computational time. Here we present a new approach for the solution of the quantum speedup problem, which is based on a machine learning algorithm that predicts the quantum advantage by just ‘looking’ at a graph. The convolutional neural network, which we designed specifically to learn from graphs, observes simulated examples and learns complex features of graphs that lead to a quantum advantage, allowing to identify graphs that exhibit quantum advantage without performing any quantum walk or random walk simulations. The performance of our approach is evaluated for line and random graphs, where classification was always better than random guess even for the most challenging cases. Our findings pave the way to an automated elaboration of novel large-scale quantum circuits utilizing quantum walk based algorithms, and to simulating high-efficiency energy transfer in biophotonics and material science.

Experimental interference of uncorrelated photons

The distinguishing of the multiphoton quantum interference effect from the classical one forms one of the most important issues in modern quantum mechanics and experimental quantum optics. For a long time, the two-photon interference (TPI) of correlated photons has been recognized as a pure quantum effect that cannot be simulated with classical lights. In the meantime, experiments have been carried out to investigate the classical analogues of the TPI. In this study, we conduct TPI experiments with uncorrelated photons with different center frequencies from a luminescent light source, and we compare our results with the previous ones of correlated photons. The observed TPI fringe can be expressed in the form of three phase terms related to the individual single-photon and two-photon states, and the fringe pattern is strongly affected by the two single-photon-interference fringes and also by their visibilities. With the exception of essential differences such as valid and accidental coincidence events within a given resolving time and the two-photon spectral bandwidth, the interference phenomenon itself exhibits the same features for both correlated and uncorrelated photons in the single-photon counting regime.

Topoelectrical circuit octupole insulator with topologically protected corner states

Recent theoretical studies have extended the Berry phase framework to account for higher electric multipole moments, quadrupole and octupole topological phases have been proposed. Although the two-dimensional quantized quadrupole insulators have been demonstrated experimentally, octupole topological phases have not previously been observed experimentally. Here we report on the experimental realization of classical analog of octupole topological insulator in the electric circuit system. Three-dimensional topolectrical circuits for realizing such topological phases are constructed experimentally. We observe octupole topological states protected by the topology of the bulk, which are localized at the corners. Our results provide conclusive evidence of a form of robustness against disorder and deformation, which is characteristic of octupole topological insulators. Our study opens a new route toward higher-order topological phenomena in three-dimensions and paves the way for employing topolectrical circuitry to study complex topological phenomena.

How a moving passive observer can perceive its environment ? The Unruh effect revisited

We consider a point-like observer that moves in a medium illuminated by noise sources with Lorentz-invariant spectrum. We show that the autocorrelation function of the signal recorded by the observer allows it to perceive its environment. More precisely, we consider an observer with constant acceleration (along a Rindler trajectory) and we exploit the recent work on the emergence of the Green’s function from the cross correlation of signals transmitted by noise sources. First we recover the result that the signal recorded by the observer has a constant Wigner transform, i.e. a constant local spectrum, when the medium is homogeneous (this is the classical analogue of the Unruh effect). We complete that result by showing that the Rindler trajectory is the only straight-line trajectory that satisfies this property. We also show that, in the presence of an obstacle in the form of an infinite perfect mirror, the Wigner transform is perturbed when the observer comes into the neighborhood of the obstacle. The perturbation makes it possible for the observer to determine its position relative to the obstacle once the entire trajectory has been traversed.

Light propagation in inhomogeneous media, coupled quantum harmonic oscillators and phase transitions

This contribution has two main purposes. First, using classical optics we show how to model two coupled quantum harmonic oscillators and two interacting quantized fields. Second, we present classical analogs of coupled harmonic oscillators that correspond to anisotropic quadratic graded indexed media in a rotated reference frame, and we use operator techniques, common to quantum mechanics, to solve the propagation of light through a particular type of graded indexed medium. Additionally, we show that the system presents phase transitions.

Thresholded Quantum LIDAR: Exploiting Photon-Number-Resolving Detection.

We present a technique that improves the signal-to-noise-ratio (SNR) of range-finding, sensing, and other light-detection applications. The technique filters out low photon numbers using photon-number-resolving detectors. This technique has no classical analog and cannot be done with classical detectors. We investigate the properties of our technique and show under what conditions the scheme surpasses the classical SNR. Finally, we simulate the operation of a rangefinder, showing improvement with a low number of signal samplings and confirming the theory with a high number of signal samplings.

The acoustic analogy in four dimensions

The classical acoustic analogy theory is incomplete in the sense that the original research on the subject focused only on the prediction of acoustic pressure. There were no provisions for predicting the three components of acoustic velocity which are needed as input for aeroacoustic scattering applications. This is because the scalar wave equations of Lighthill and Ffowcs Williams and Hawkings were derived from the fluid conservation equations by eliminating three of the four governing differential equations from which the acoustic velocity could have been obtained. Recently developed acoustic analogy methods for predicting the acoustic velocity lead to complex formulations whose numerical evaluation can be problematic when providing input for large-scale scattering problems. Their calculation can overwhelm the numerical scattering process when the incident sound has high-frequency content, such as that produced by the rotating blades of various propulsion devices. To obtain improved acoustic analogy formulations for scattering and other applications, the three discarded differential equations are returned to the analysis in this paper and the historical acoustic analogy equations are derived anew using four-dimensional tensor methods. The 4-D formulation is an application of the electromagnetic analogy (EMA), a concept based on the equivalence of Maxwell’s equations and the fluid conservation equations of mass and momentum. The scalar equations of Lighthill, Ffowcs Williams and Hawkings, Farassat, and Kirchhoff are extended to four equations – one equation for the acoustic pressure (or acoustic density) and three equations for the acoustic velocity. The 4-D tensor representation provides significant theoretical and computational simplification relative to the classical approach. For each of the original acoustic analogy results, a single, concise formulation in 4D is derived that enables the simultaneous prediction of acoustic pressure and the three components of acoustic velocity.