Subfields Of Physics Research Articles

Automatedly Distilling Canonical Equations From Random State Data

Abstract Canonical equations play a pivotal role in various sub-fields of physics and mathematics. However, for complex systems and systems without first principles, deriving canonical equations analytically is quite laborious or might even be impossible. This work is devoted to automatedly distilling the canonical equations solely from random state data. The random state data are collected from stochastically excited, dissipative dynamical systems either experimentally or numerically, while other information, such as the system characterization itself and the excitations, is not needed. The identification procedure comes down to a nested optimization problem, and the explicit expressions of the momentum (density) functions and energy (density) functions are identified simultaneously. Three representative examples are investigated to illustrate its high accuracy of identification, the small requirement for data amount, and high robustness to excitations and dissipation. The identification procedure serves as a filter, filtering out nonconservative information while retaining conservative information, which is especially suitable for systems with unobtainable excitations.

Generalization of Young-Laplace, Kelvin, and Gibbs-Thomson equations for arbitrarily curved surfaces

The Young-Laplace, Kelvin, and Gibbs-Thomson equations form a cornerstone of colloidal and surface sciences and have found successful applications in many subfields of physics, chemistry, and biology. The Gibbs-Thomson effect, for example, predicts that small crystals are in equilibrium with their liquid melt at a lower temperature than large crystals and the positive interfacial energy increases the energy required to form small particles with a high curvature interface. In cases of liquids contained within porous media (confined geometry), the effect indicates decreasing the freezing/melting temperatures and the increment of the temperature is inversely proportional to the pore size. These phenomena can be reformulated for Gaussian maps of macromolecules and can be asked the following question: can one use the equations for predicting the melting temperature and shape of polymer chains in confined geometries? The answer is no, mainly because macromolecules form highly curved surfaces (Gaussian maps), and the equations hold only for simple geometries (sphere, plane, or cylinder). Here, we present general Young-Laplace, Kelvin, and Gibbs-Thomson equations for arbitrarily curved surfaces and apply them to predict temperature distribution on a few protein surfaces. Also, after increased interest toward liquid/liquid phase separation in biology, we derive generic Ostwald ripening and show that for shape-changing condensates, instead of a monotonic growing mechanism, a variety of processes are possible. Due to the generality of equations, we clarify that at appropriate internal/external pressure conditions systems, bounded by surfaces, may adopt any shape and thermal stability is strongly influenced by the geometries of confined spaces.

Annalen der Physik – Wiley's Physics Forum and Center of Excellence

<i>Annalen der Physik</i> – Wiley's Physics Forum and Center of Excellence

National Academies Report and Biophysics Education

National Academies Report and Biophysics Education

Electron Tractor Beam: Deterministic Manipulation of Liquid Droplets on Solid Surfaces

AbstractThe motion of liquid droplets is studied across many physics subfields and manipulation of nanoscale droplets on demand holds great promise in, e.g., nanotechnology. In this study, AuGe droplets on a germanium substrate are manipulated by an electron beam in a scanning electron microscope. The electron beam exposure creates a local temperature gradient in a substrate and induces a directional thermomigration of droplets nearby. To quantitatively analyse this phenomenon and to reveal the mechanism behind it, experimental observations under different conditions (beam current, sample temperature, scanning strategy) and simulations are combined. The obtained insights suggest that the droplet motion is limited by the dissolution of the substrate below the droplet. In addition, it is shown that the electron tractor beam is not only able to control the droplet motion but can also be used to split the droplets, thus opening new possibilities for droplet manipulation inside an SEM.

The influence of Chinese scholars on global research

The rise of China as a scientific research superpower has been frequently discussed in media and literature. However, past analyses are usually based on the geographical database and they ignore how the millions of emigrated Chinese students, who are now being considered the major research workforce in many countries, affect their academic outputs. Here we quantitatively analyze the contribution of Chinese scholars in physical science around the globe by their publications in a country’s papers from 2010 to 2021 as well as their citations. Contrary to common perception, we find that increasing the number of Chinese scholars does not correlate with the net publication growth or decline in their host countries before the Chinese population exceeds a critical value. On the other hand, increasing Chinese authors in a paper improves its citations. The phenomena, though anomalous, are observed in many subfields of physics across the globe. Our analysis suggests that although Chinese scholars do not change the perceived publication capabilities of many countries but may have reshaped their research culture as well as workforce distributions. The results would be valuable for R&D, higher education, and immigration policymakers.

Physicists, non physical topics, and interdisciplinarity

Defining interdisciplinary physics today requires first a reformulation of what is physics today, which in turn calls for clarifying what makes a physicist. This assessment results from my 40-year journey arguing and fighting to build sociophysics. My view on interdisciplinary physics has thus evolved jumping repeatedly to opposite directions before settling down to the following claim: today physics is what is done by physicists who handle a problem the “physicist’s way”. However the training of physicists should stay restricted to inert matter. Yet adding a focus on the universality of the physicist approach as a generic path to investigate a topic. Consequently, interdisciplinary physics should become a cabinet of curiosities including an incubator. The cabinet of curiosities would welcome all one shots papers related to any kind of object provided it is co-authored at least by one physicist. Otherwise the paper should uses explicitly technics from physics. In case a topic gets many papers, it would be moved to the incubator to foster the potential emergence of a new appropriate subfield of physics. A process illustrated by the subsection social physics in Frontiers in physics.

Geometry-induced wave-function collapse

When a quantum particle moves in a curved space, a geometric potential can arise. In spite of a long history of extensive theoretical studies, to experimentally observe the geometric potential remains a challenge. What are the physically observable consequences of such a geometric potential? Solving the Schr\"odinger equation on a truncated conic surface, we uncover a class of quantum scattering states that bear a strong resemblance to the quasiresonant states associated with atomic collapse about a Coulomb impurity, a remarkable quantum phenomenon in which an infinite number of quasiresonant states emerge. A characteristic defining feature of such collapse states is the infinite oscillations of the local density of states (LDOS) about the zero energy point separating the scattering from the bound states. The emergence of such states in the curved (Riemannian) space requires neither a relativistic quantum mechanism nor any Coulomb impurity: they have zero angular momentum and their origin is purely geometrical, hence the term ``geometry-induced wave-function collapse.'' We establish the collapsing nature of these states through a detailed comparative analysis of the behavior of the LDOS for both the zero and finite angular momentum states as well as the corresponding classical picture. Potential experimental schemes to realize the geometry-induced collapse states are articulated. Not only does our paper uncover an intrinsic connection between the geometric potential and atomic collapse, it also provides a method to experimentally observe and characterize geometric potentials arising from different subfields of physics. For example, in nanoscience and nanotechnology, curved geometry has become increasingly common. Our finding suggests that wave-function collapse should be an important factor of consideration in designing and developing nanodevices.

Strategies In Learning Fluid Mechanics: A literature Review

One of the broad and intricate subfields of physics is fluid mechanics. Learning techniques for students are an essential component of learning fluid mechanics because they increase their motivation to learn, enhance learning outcomes, and encourage active participation in class. An overview of the prior research was highlighted in this publication, and several fluid mechanics learning methodologies were looked at in this review. The study found that the majority of students performed well in group settings, particularly when fluid mechanics principles are used in practical settings, which is the most successful teaching method. The studies that were reviewed in this literature review demonstrated that offering students team-based experiential learning is the best way to inspire them to learn fluid mechanics and to recognize the value of doing so. Therefore, by developing ideas and putting them into practice through active exploration, students learn more.

Linear growth of quantum circuit complexity

The complexity of quantum states has become a key quantity of interest across various subfields of physics, from quantum computing to the theory of black holes. The evolution of generic quantum systems can be modelled by considering a collection of qubits subjected to sequences of random unitary gates. Here we investigate how the complexity of these random quantum circuits increases by considering how to construct a unitary operation from Haar-random two-qubit quantum gates. Implementing the unitary operation exactly requires a minimal number of gates—this is the operation’s exact circuit complexity. We prove a conjecture that this complexity grows linearly, before saturating when the number of applied gates reaches a threshold that grows exponentially with the number of qubits. Our proof overcomes difficulties in establishing lower bounds for the exact circuit complexity by combining differential topology and elementary algebraic geometry with an inductive construction of Clifford circuits.

Quantum harmonic oscillators with nonlinear effective masses in the weak density approximation

We study the eigen-energy and eigen-function of a quantum particle acquiring the probability density-dependent effective mass (DDEM) in harmonic oscillators. Instead of discrete eigen-energies, continuous energy spectra are revealed due to the introduction of a nonlinear effective mass. Analytically, we map this problem into an infinite discrete dynamical system and obtain the stationary solutions in the weak density approximation, along with the proof on the monotonicity in the perturbed eigen-energies. Numerical results not only give agreement to the asymptotic solutions stemmed from the expansion of Hermite-Gaussian functions, but also unveil a family of peakon-like solutions without linear counterparts. As nonlinear Schrödinger wave equation has served as an important model equation in various sub-fields in physics, our proposed generalized quantum harmonic oscillator opens an unexplored area for quantum particles with nonlinear effective masses.

Steady-state thermodynamics for population dynamics in fluctuating environments with side information

Steady-state thermodynamics (SST) is a relatively newly emerging subfield of physics, which deals with transitions between steady states. In this paper, we find an SST-like structure in population dynamics of organisms that can sense their fluctuating environments. As heat is divided into two parts in SST, we decompose population growth into two parts: housekeeping growth and excess growth. Then, we derive the Clausius equality and inequality for excess growth. Using numerical simulations, we demonstrate how the Clausius inequality behaves depending on the magnitude of noise and strategies that organisms employ. Finally, we discuss the novelty of our findings and compare them with a previous study.

Ideal-Gas Approach to Hydrodynamics

Transport is one of the most important physical processes in all energy and length scales. Ideal gases and hydrodynamics are, respectively, two opposite limits of transport. Here, we present an unexpected mathematical connection between these two limits; that is, there exist situations that the solution to a class of interacting hydrodynamic equations with certain initial conditions can be exactly constructed from the dynamics of noninteracting ideal gases. We analytically provide three such examples. The first two examples focus on scale-invariant systems, which generalize fermionization to the hydrodynamics of strongly interacting systems, and determine specific initial conditions for perfect density oscillations in a harmonic trap. The third example recovers the dark soliton solution in a one-dimensional Bose condensate. The results can explain a recent puzzling experimental observation in ultracold atomic gases by the Paris group and make further predictions for future experiments. We envision that extensive examples of such an ideal-gas approach to hydrodynamics can be found by systematical numerical search, which can find broad applications in different problems in various subfields of physics.

How to Unify All Schools of Thought in Social Science and Humanities into One Scientific School of Thought

There are hundreds and thousands of schools of thought in social science and humanities, while there is only one school of thought in natural science. This paper investigates the question how to unify all schools of thought in social science and humanities into one scientific school of thought by transforming social science and humanities into subfields of physics. By being parts of physics, the scientific version of social science and humanities should allow only one school of thought logically and naturally. This paper will discuss what this scientific version of social science and humanities will look like and how it can be uniquely defined in terms of physics of human society, mathematics, methodology, history, facts, forecasting models, equilibrium values systems, and equilibrium solutions to normative problems. This paper should be useful for reconciling the current extremely polarized policy debates between the left and right around the world.

Effective theories and infinite idealizations: a challenge for scientific realism

Williams and J. Fraser have recently argued that effective field theory methods enable scientific realists to make more reliable ontological commitments in quantum field theory (QFT) than those commonly made. In this paper, I show that the interpretative relevance of these methods extends beyond the specific context of QFT by identifying common structural features shared by effective theories across physics. In particular, I argue that effective theories are best characterized by the fact that they contain intrinsic empirical limitations, and I extract from their structure one central interpretative constraint for making more reliable ontological commitments in different subfields of physics. While this is in principle good news, this constraint still raises a challenge for scientific realists in some contexts, and I bring the point home by focusing on Williams’s and J. Fraser’s defense of selective realism in QFT.

Hands-on Curriculum in Optics of Microscopy

ABSTRACT Optics is an important subfield of physics required for instrument design and used in a variety of other disciplines, especially subjects that intersect the life sciences. Students from a variety of disciplines and backgrounds should be educated in the basics of optics to train the next generation of interdisciplinary researchers and instrumentalists who will push the boundaries of discovery or create inexpensive optical-based diagnostics. We present an experimental curriculum developed to teach students the basics of geometric optics, including ray and wave optics. The students learn these concepts in an active, hands-on manner through designing, building, and testing a homebuilt light microscope made from component parts. We describe the experimental equipment and basic measurements students can perform to learn these basic optical principles focusing on good optical design techniques, testing, troubleshooting, and iterative design. Students are also exposed to fundamental concepts of measurement uncertainty inherent in all experimental systems. The project students build is open and versatile to allow advanced projects, such as epifluorescence. We also describe how the equipment and curriculum can be flexibly used for an undergraduate level optics course, an advanced laboratory course, and graduate-level training modules or short courses.

Are Contributions from Chinese Physicists Undercited?

Abstract Purpose In this work, we want to examine whether or not there are some scientific fields to which contributions from Chinese scholars have been under or over cited. Design/methodology/approach We do so by comparing the number of received citations and the IOF of publications in each scientific field from each country. The IOF is calculated from applying the modified closed system input–output analysis (MCSIOA) to the citation network. MCSIOA is a PageRank-like algorithm which means here that citations from the more influential subfields are weighted more towards the IOF. Findings About 40% of subfields in physics in China are undercited, meaning that their net influence ranks are higher (better) than the direct rank, while about 75% of subfields in the USA and German are undercited. Research limitations Only APS data is analyzed in this work. The expected citation influence is assumed to be represented by the IOF, and this can be wrong. Practical implications MCSIOA provides a measure of net influences and according to that measure. Overall, Chinese physicists’ publications are more likely overcited rather than being undercited. Originality/value The issue of under or over cited has been analyzed in this work using MCSIOA.

Scientific journals still matter in the era of academic search engines and preprint archives

AbstractJournals play a critical role in the scientific process because they evaluate the quality of incoming papers and offer an organizing filter for search. However, the role of journals has been called into question because new preprint archives and academic search engines make it easier to find articles independent of the journals that publish them. Research on this issue is complicated by the deeply confounded relationship between article quality and journal reputation. We present an innovative proxy for individual article quality that is divorced from the journal's reputation or impact factor: the number of citations to preprints posted on arXiv.org. Using this measure to study three subfields of physics that were early adopters of arXiv, we show that prior estimates of the effect of journal reputation on an individual article's impact (measured by citations) are likely inflated. While we find that higher‐quality preprints in these subfields are now less likely to be published in journals compared to prior years, we find little systematic evidence that the role of journal reputation on article performance has declined.

Quantum control of molecular rotation

The angular momentum of molecules, or, equivalently, their rotation in three-dimensional space, is ideally suited for quantum control. Molecular angular momentum is naturally quantized, time evolution is governed by a well-known Hamiltonian with only a few accurately known parameters, and transitions between rotational levels can be driven by external fields from various parts of the electromagnetic spectrum. Control over the rotational motion can be exerted in one-, two- and many-body scenarios, thereby allowing to probe Anderson localization, target stereoselectivity of bimolecular reactions, or encode quantum information, to name just a few examples. The corresponding approaches to quantum control are pursued within separate, and typically disjoint, subfields of physics, including ultrafast science, cold collisions, ultracold gases, quantum information science, and condensed matter physics. It is the purpose of this review to present the various control phenomena, which all rely on the same underlying physics, within a unified framework. To this end, we recall the Hamiltonian for free rotations, assuming the rigid rotor approximation to be valid, and summarize the different ways for a rotor to interact with external electromagnetic fields. These interactions can be exploited for control --- from achieving alignment, orientation, or laser cooling in a one-body framework, steering bimolecular collisions, or realizing a quantum computer or quantum simulator in the many-body setting.

Structure and evolution of Indian physics co-authorship networks

We trace the evolution of Indian physics community from 1919 to 2013 by analyzing the co-authorship network constructed from papers published by authors in India in American Physical Society (APS) journals. We make inferences on India’s contribution to different branches of Physics and identify the most influential Indian physicists at different time periods. The relative contribution of India to global physics publication (research) and its variation across subfields of physics is assessed. We extract the changing collaboration pattern of authors between Indian physicists through various network measures. We study the evolution of Indian physics communities and trace the mean life and stationarity of communities by size in different APS journals. We map the transition of authors between communities of different sizes from 1970 to 2013, capturing their birth, growth, merger and collapse. We find that Indian–Foreign collaborations are increasing at a faster pace compared to the Indian–Indian. We observe that the degree distribution of Indian collaboration networks follows the power law, with distinct patterns between Physical Review A, B and E, and high energy physics journals Physical Review C and D, and Physical Review Letters. In almost every measure, we observe strong structural differences between low-energy and high-energy physics journals.