Physics Perspective Research Articles

Guest Editorial: Scientific and Physics-Informed Machine Learning for Industrial Applications

Deep learning technology has become one of the core driving forces to promote the in-depth development of industrial automation. In [A1], Wang et al. interpreted the decision process of the convolutional neural network (CNN) by constructing a percolation model from a statistical physics perspective. In this perspective, the decision-making basis of CNN is difficult to understand, because CNN is usually used as a black box model. Furthermore, a novel concept of the differentiation degree and summarized an empirical formula for quantifying the differentiation degree is presented and discussed.

Confined Brownian suspensions: Equilibrium diffusion, thermodynamics, and rheology

We examine the impact of confinement on the structure, dynamics, and rheology of spherically confined macromolecular suspensions, with a focus on the role played by entropic forces, by comparing the limits of strong hydrodynamics and no hydrodynamics. We present novel measurements of the osmotic pressure, intrinsic viscosity, and long-time self-diffusivity in spherical confinement and find confinement induces strong structural correlations and restrictions on configurational entropy that drive up osmotic pressure and viscosity and drive down self-diffusion. Even in the absence of hydrodynamics, confinement produces distinct short-time and long-time self-diffusion regimes. This finding revises the previous understanding that short-time self-diffusion is a purely hydrodynamic quantity. The entropic short-time self-diffusion is proportional to an entropic mobility, a direct analog to the hydrodynamic mobility. A caging plateau following the short-time regime is stronger and more durable without hydrodynamics, and entropic drift—a gradient in volume fraction—drives particles out of their cages. The distinct long-time regime emerges when an entropic mobility gradient arising from heterogeneous distribution of particle volume drives particles out of local cages. We conclude that entropic mobility gradients produce a distinct long-time dynamical regime in confinement and that hydrodynamic interactions weaken this effect. From a statistical physics perspective, confinement restricts configurational entropy, driving up confined osmotic pressure, viscosity, and (inverse) long-time dynamics as confinement tightens. We support this claim by rescaling the volume fraction as the distance from confinement-dependent maximum packing, which collapses the data for each rheological measure onto a single curve.

Conjugated Polymers in Solution: A Physical Perspective.

Excellent progress has been made in the optoelectronic properties of conjugated polymers by controlling solution-state aggregation. However, due to the wide variety and complex structures of conjugated polymers, it is still challenging to fully understand the complex aggregation process and microstructures both in solution and in the solid state. This Perspective focuses on the chain conformations and the aggregation of conjugated polymers in solution. We discuss the factors in detail which affect solution-state aggregation and microstructures from the perspective of polymer physics in solutions, including chemical structures and environmental conditions. Based on the understanding of multiple interactions of conjugated polymers in solution, strategies to regulate solid-state microstructures and obtain high-performance polymer-based devices from solution-state aggregation are summarized.

Lorentz-covariant sampling theory for fields

Sampling theory is a discipline in communications engineering involved with the exact reconstruction of continuous signals from discrete sets of sample points. From a physics perspective, this is interesting in relation to the question of whether spacetime is continuous or discrete at the Planck scale, since in sampling theory we have functions which can be viewed as equivalently residing on a continuous or discrete space. Further, it is possible to formulate analogues of sampling which yield discreteness without disturbing underlying spacetime symmetries. In particular, there is a proposal for how this can be adapted for Minkowski spacetime. Here we will provide a detailed examination of the extension of sampling theory to this context. We will also discuss generally how spacetime symmetries manifest themselves in sampling theory, which at the surface seems in conflict with the fact that the discreteness of the sampling is not manifestly covariant. Specifically, we will show how the symmetry of a function space with a sampling property is equivalent to the existence of a family of possible sampling lattices related by the symmetry transformations.

The spread of infectious diseases from a physics perspective.

This article deals with the spread of infectious diseases from a physics perspective. It considers a population as a network of nodes representing the population members, linked by network edges representing the (social) contacts of the individual population members. Infections spread along these edges from one node (member) to another. This article presents a novel, modified version of the SIR compartmental model, able to account for typical network effects and percolation phenomena. The model is successfully tested against the results of simulations based on Monte-Carlo methods. Expressions for the (basic) reproduction numbers in terms of the model parameters are presented, and justify some mild criticisms on the widely spread interpretation of reproduction numbers as being the number of secondary infections due to a single active infection. Throughout the article, special emphasis is laid on understanding, and on the interpretation of phenomena in terms of concepts borrowed from condensed-matter and statistical physics, which reveals some interesting analogies. Percolation effects are of particular interest in this respect and they are the subject of a detailed investigation. The concept of herd immunity (its definition and nature) is intensively dealt with as well, also in the context of large-scale vaccination campaigns and waning immunity. This article elucidates how the onset of herd-immunity can be considered as a second-order phase transition in which percolation effects play a crucial role, thus corroborating, in a more pictorial/intuitive way, earlier viewpoints on this matter. An exact criterium for the most relevant form of herd-immunity to occur can be derived in terms of the model parameters. The analyses presented in this article provide insight in how various measures to prevent an epidemic spread of an infection work, how they can be optimized and what potentially deceptive issues have to be considered when such measures are either implemented or scaled down.

Construction of a digital twin system for the blended-wing-body underwater glider

The complexity of the marine environment adds unpredictable difficulties to researchers’ exploration. To study the application prospects of high-fidelity digital models to the maritime field, this study adopts the blended-wing-body underwater glider (BWBUG) as an example. A novel construction approach of an underwater simulation platform is proposed based on digital twin (DT) technology. The building process is described from the perspectives of geometry, physics, environment and behavior. Based on the Gazebo simulation platform, the proposed approach includes the construction of a high-fidelity model for underwater scenarios and is equipped with a vehicle body containing various sensors. Under the influence of ocean currents, the twin sensor data are integrated in the proportional–integral–derivative (PID) control algorithm, combined with a robot operating system (ROS), to achieve its pitch attitude control. The overshoot was reduced to at most 0.06% and the settling time is reduced to 29.5 s compared with the traditional PID. The results demonstrate that the proposed framework not only validates the implementability of control algorithms for unmanned systems in actual marine environment, but also has the potential for performance prediction, design improvement, and safety assessment in the next generation vehicle design process.

Breakthrough Infection and Death after COVID-19 Vaccination: A Physics Perspective

Breakthrough Infection and Death after COVID-19 Vaccination: A Physics Perspective

Космология между физикой и философией

It is shown that the canonical cosmological model of the Universe – Big Bang Theory (BBT) contains unacceptably many unsolvable contradictions either to facts, or logic, or, finally, to physics. They can be categorized into several groups: 1) unacceptable, 2) unsubstantiated, and 3) multivalued. To the unac­ceptable fragments of the concept of BBT it is reasonable to include ideas about: a) “singularity”; b) “cosmological inflation”; c) “infinite death of Nature”. Un­reasonable include: a) hypothesis about materiality of space-time, b) recognition of the possibility of their birth and death. Among the interpretations admitting other ones with high probability are: a) the principle of equivalence of the iner­tial and gravitational masses, b) the gravitational redshift, c) the effect of deflec­tion of light near large masses. Among the interpretations, which do not cause doubts, it is possible to note an explanation of the black hole nature, following from Newton’s classical theory of gravitation. The source of insoluble contradic­tions of the BBT was Einstein’s General Theory of Relativity (GTR), which was created on the basis of strictly deterministic classical mechanics. The underde­velopment of quantum mechanics at the beginning of the twentieth century mis­led the author of the GTR about the equivalence of inertial and gravitational masses. A consequence of this delusion was the erroneous recognition of space-time as material substances. It, in turn, led to a lot of unexplained events in the past of the Universe, and fantastic predictions about its future. But the most striking thing that distinguishes GTR is its violation of the fundamental law of conservation of energy, which cosmological theorists turn a blind eye to. This allows us to consider it a legacy of classical physics of the nineteenth century, unsatisfactory from the perspective of probabilistic physics of the twenty-first century.

On Quantum Causality

For Kant causality is an a priori category of the understanding, a necessary condition for the possibility of any experience. Later Wittgenstein’s philosophy rejects transcendentalism. We can only speak of causes and effects if in some basic situations, or ‘language games’, we already treat some things as causes of what happens. Since the notion of cause becomes meaningful only within a language game, it is not unambiguous. Quantum causal language games presuppose the use of quantum theory. We treat the latter as Wittgenstein’s grammar of a quantum form of life’, or rule (norm), anchored in its applications — quantum phenomena as language games. Quantum correlations are often interpreted as a manifestation of the nonlocality of quantum mechanics. This is a view of quantum phenomena from the perspective of classical physics. Our contextual point of view rejects the nonlocality of quantum theory in the sense of instantaneous causal influence at a distance. But it does not admit its locality in the sense of classical causality either. We introduce the notion of quantum causality which allows us to treat quantum correlations as local, but context-dependent. Their formal cause is an entangled wave function. Any particular quantum correlation, identifiable in a context of its observation as a result of the wave function reduction, post factum can be treated as a classical causal correlation. From the point of view of the proposed contextual quantum realism, epistemology is secondary, and ontology is sensitive to context. Quantum correlations exist (are real) before application of the theory, independently of their identification (description, measurement), but have no identity, which appears only as a result of application of the theory and their identification in the context. In other words, they are real, but not pre-determined, not autonomous.

Emerging Perspectives in Mathematical Physics: Interdisciplinary Approaches and Connections

Emerging Perspectives in Mathematical Physics: Interdisciplinary Approaches and Connections

On the impact of compact binary merger ejecta opacity on Kilonova transient signals

Returns of gravitational wave astronomy will largely benefit from the detection and identification of electromagnetic (EM) signatures to gravitationalwave sources. Kilonovae (KNe) are promising EM counterparts to compact binary mergers, offering to astronomers and nuclear astrophysicists a unique window to advance knowledge on the heavy-element nucleosynthesis and mergerdriven mass ejection. However, extremely heterogeneous post-merging ejecta composition of both light- and heavy-r process nuclei, implies strong effects on the KNe light-curve identification due to the varying opacity of the system. Hence, large uncertainties on the r-process final abundance via spectroscopic analysis of KNe signals are still present, hardly fixed by theoretical models. Here we will present some peculiar features of KNe studies, focusing on the opacity issue, from the atomic and plasma physics perspectives. In this view, efforts have been made recently at INFN-LNS, trying to put constraints on plasma opacity of interest for early-stage KNe emission. We will present the experimental progress on the problem, including instruments and methods which could open an interdisciplinary approach to tackle astrophysical problems in laboratory plasmas.

On-chip SRR and CSRR for millimeter-wave integrated systems: Review and applications

On-chip metadevices have been developed in progress aiming to generate extraordinary performance over conventional components in millimeter-wave (mmW) realms, and their full integration with advanced complementary-metal-oxide-semiconductor (CMOS) circuits pave a new way toward miniature and high-performance integrated systems. This article aims to provide a general overview of split-ring resonators (SRRs) and complementary split-ring resonators (CSRR), from the perspective of fundamental physics, recent progress of on-chip implementations, and their impacts on the development of mmW integrated circuits and systems. SRR/CSRR-based metadevices are discussed in terms of their design challenges, methods, implementation, and testing results. In particular, their applications to CMOS oscillators, modulator and signal source are highlighted. Finally, using the SRR/CSRR, a number of examples are provided to showcase the recent advances of integrated systems toward mmW communication and imaging. Future directions enabled by SRR and CSRR will be envisioned.

Spatial‐temporal modulation in radiation therapy

Spatial‐temporal modulation in radiation therapy

PHSOR09 Presentation Time: 1:10 PM: Establishing a Cs-131 Intraoperative Mesh Brachytherapy Program: Physics Perspective

<h3>Purpose</h3> Cs-131 has shown promise for the treatment of many cancers with its shorter half-life and more intense energy deposition compared to I-125. Cs-131 mesh has seeds embedded within a vicryl mesh, which keeps the seeds in place for about 30-35 days. Mesh applications have been limited to a few premier institutions. We present our process for the Intraoperative mesh brachytherapy program as a foundation for other new users to build upon. <h3>Methods and Materials</h3> A patient was selected after multidisciplinary tumor board discussion. Radiation Oncologist (RO) provided a written directive with the treatment site and prescription dose (60 Gy). TPS commissioning was carried out for Cs-131 (Cs-1, rev 2, IsoRay Medical Inc., Richland WA) utilizing half-life, source geometry, active source dimensions, dose rate constant, radial dose function, anisotropy function, air-kerma to activity conversion factor, etc. per TG43U1. Treatment planning CT with 1 mm slices was acquired. Target volume and nearby OARs were contoured. Pre-treatment plan was created in Varian Brachytherapy TPS v.15.6. Hand calculations and RadCalc were used to independently verify the TPS dose calculation. Planning CT was reconstructed with 1 cm slice thickness to match the mesh seed spacing. Seeds were modeled as line sources and placed within the target volume while modifying seed strength to achieve target coverage with the prescribed dose while sparing OARs. RO approved pre-plan. Mesh with optimal seed strength and number was ordered. 10% extra loose seeds plus 1 calibrated seed (same activity as determined per pre-plan) were ordered for strength verification. The mesh is received in sterile packaging. After a wipe test of the mesh container to ensure no radiation contamination, source strength for the loose seeds were verified using a well chamber (IVB1000 HO32871) calibrated for Cs-131.Vendor provided radiographs confirmed total seed number. A second independent physicist verified seed strength. Radiation safety training was completed with all personnel involved with the procedure. On implant day, MP and RO were both present. Mesh was taken to the OR after confirming the need for IORT per pathology. MP surveyed radiation levels throughout the procedure. RO and surgeon determined the mesh size to be implanted based on the at risk area. Once the implant was complete, the MP surveyed the OR room and accounted for total seed count. Numbers were verified by residual mesh radiography. Unused seeds were inventoried and stored in a lead container in the hot lab for decay. Post implant, radiation levels at 1 m were monitored periodically by the MP during the patient's hospital stay. Safety information was delivered to patient specific personnel by daily rounds, patient alerts and written instructions placed in the patient chart. MP provided verbal and written radiation safety recommendations to the patient and family members prior to discharge. A postoperative CT scan was acquired within 24 hours of the implant to review final implant dosimetry. <h3>Results</h3> The seed strength required per the pre-plan was 3.0 U. All loose seed strengths were within 2.3% of the vendor specified value. Post implant plan confirmed target coverage. Follow-up images acquired at 2 months confirmed nonsignificant seed migration. The exposure reading at 1 m from the patient was 1.0 mR/h immediately following the implant, and 0.5 mR/h at the day of discharge. The ring and collar badge readings for those directly handling the seed mesh were under regulatory limits. <h3>Conclusions</h3> An intraoperative mesh brachytherapy program has been safely established within our institution with the first patient successfully treated using the process described here.

A physical study of the LLL algorithm

This paper presents a study of the LLL algorithm from the perspective of statistical physics. Based on our experimental and theoretical results, we suggest that interpreting LLL as a sandpile model may help understand much of its mysterious behavior. In the language of physics, our work presents evidence that LLL and certain 1-d sandpile models with simpler toppling rules belong to the same universality class.This paper consists of three parts. First, we introduce sandpile models whose statistics imitate those of LLL with compelling accuracy, which leads to the idea that there must exist a meaningful connection between the two. Indeed, on those sandpile models, we are able to prove the analogues of some of the most desired statements for LLL, such as the existence of the gap between the theoretical and the experimental RHF bounds. Furthermore, we test the formulas from finite-size scaling theory (FSS) against the LLL algorithm itself, and find that they are in excellent agreement. This in particular explains and refines the geometric series assumption (GSA), and allows one to extrapolate various quantities of interest to the dimension limit. In particular, we obtain the estimate that the empirical average RHF converges to ≈1.02265 as the dimension goes to infinity.

Phenomenology of a flavored multiscalar Branco-Grimus-Lavoura-like model with three generations of massive neutrinos

In this paper, we present several possible anomaly free implementations of the Branco-Grimus-Lavoura (BGL) model with two Higgs doublets and one singlet scalar. The model also includes three generations of massive neutrinos that get their mass via a type-I seesaw mechanism. A particular anomaly free realization, which we dub $\ensuremath{\nu}\mathrm{BGL}$-1 scenario, is subjected to an extensive phenomenological analysis, from the perspective of flavor physics and collider phenomenology.

Coherent elastic neutrino-nucleus scattering (CEνNS) event rates for Ge, Zn and Si detector materials

Realistic nuclear structure calculations are presented for the event rates due to coherent elastic neutrino-nucleus scattering (CEνNS), assuming neutrinos from pion-decay at-rest, from nuclear reactors and from Earth’s interior. We focus on the currently interesting Germanium isotopes, 70,73,76Ge, which constitute detector materials of the recently planned CEνNS experiments. We study in addition the potential use of 64,70Zn and 28Si isotopes as promising CEνNS detectors. From nuclear physics perspectives, recently, calculations have been carried out within the framework of the deformed shell-model (DSM), based on realistic nuclear forces, and assessed on the reproducibility of spectroscopic nuclear properties. The high confidence level acquired by their agreement with experimental results and by their comparison with other mostly phenomenological calculations encouraged the use of DSM to extract predictions for the CEνNS event rates of the above isotopes. Our detailed estimation of the nuclear physics aspects of the recently observed neutral current coherent neutrino-nucleus scattering may shed light on unravelling the still remaining uncertainties for the CEνNS process within and beyond the Standard Model.

Hybrid Detection of Breast Abnormalities Based on Contrast Agents: Introducing a Proof of Concept from a Physics Perspective.

This manuscript attempts to present a proof of concept from a physics perspective of a hybrid detective system based on the utilization of contrast agents with the purpose of indicating breast tissue abnormalities. In the present concept, the photon-counting module of the detector is set up to the K-characteristic radiation emitted by the contrast agent. Τwo X-ray spectra were used: 40 kV- W/Al (1.6 mm) and 50 kV- W/Al (1.6 mm) with additional filtration of 0.3 mm Gd. Iodine (I) contrast agent was studied as a ‘‘fingerprint’’ for tissue abnormality indication. A computational Monte Carlo model, based on previously published validated tabulated data and tissue experimental measurements, was developed with the purpose of showing that the present concept has practical potential; however, with a weakness of not being accompanied by experimental validation. The study considered two types of internal tissue layers (fibrous/tumor with thickness values of 0.2–2.5 mm) within an external layer of fat tissue (4 and 8 cm). Quantitative (number of encountered K-photons) and qualitative (tumor–fibrous ratio) advantages of using X-ray spectra of a higher tube voltage (50 kV) and of counting the Κα photons were found. In addition, the quantitative and qualitative benefits were correspondingly more dominant at high (2.5 mm) and low (0.2 mm) tissue thickness values. In conclusion, by utilizing suitable contrast agents as ‘‘fingerprint’’ tissue abnormalities, the acquisition of combined morphological and functional imaging features (through the counting of K-X-rays) could enhance breast imaging in its present form and lead to advanced prognostic capabilities of breast abnormalities.

Non-extensive entropy and fragment–asperity interaction model for earthquakes

In this study, we developed a fragment–asperity interaction model for earthquakes. Based on Tsallis entropy, this model can provide mathematical expression for the non-extensive entropy of fragments and asperities in the gouge area. From a statistical physics perspective, we hypothesized that non-extensive entropy decreases with energy relaxation after crustal rupture (i.e., following an earthquake). By using a windowing process, the non-extensive entropy value was monitored for three relatively recent earthquakes: the 2009 M6.1 L’Aquila (Italy) earthquake, 2011 M9.0 Tohoku (Japan) megathrust earthquake, and 2016 M7.8 Kaikoura (New Zealand) earthquake. The results support our hypothesis and suggest that the non-extensive entropy formula obtained in this study can provide a good characterization of seismicity for a given area.

An Introduction to Machine Learning: a perspective from Statistical Physics

The recent progresses in Machine Learning opened the door to actual applications of learning algorithms but also to new research directions both in the field of Machine Learning directly and, at the edges with other disciplines. The case that interests us is the interface with physics, and more specifically Statistical Physics. In this short lecture, I will try to present first a brief introduction to Machine Learning from the angle of neural networks. After explaining quickly some fundamental models and global aspects of the training procedure, I will discuss into more detail two examples illustrate what can be done from the Statistical Physics perspective.