Contemporary Physics Research Articles

Effects of differences between neutron and proton density distributions onα-decay half-lives

The neutron skin of heavy nuclei is one of the hot topics in contemporary nuclear physics. In this article, effects of differences between neutron and proton density distributions on $\ensuremath{\alpha}$ decay are investigated. $\ensuremath{\alpha}$-decay calculations are performed within the generalized density-dependent cluster model, where the $\ensuremath{\alpha}$-core potential is determined in the double-folding model using the neutron and proton density distributions of daughter nuclei. The proton and neutron density distributions, assumed to be of two-parameter Fermi form, are constrained by the experimental nuclear charge radii as well as the neutron skin thickness of heavy nuclei. The resulting distribution of daughter nuclei results in an improved $\ensuremath{\alpha}$-core potential which is important for $\ensuremath{\alpha}$-decay calculations. It is found that the neutron skin thickness plays an important role in reducing the calculated $\ensuremath{\alpha}$-decay half-lives, implying a smaller $\ensuremath{\alpha}$ preformation factor. The calculations with neutron skin thickness show good agreement with the available experimental data for even-even nuclei including the known heaviest nuclei.

Sobre as pesquisas relacionadas ao ensino do efeito fotoelétrico

The number of researches and different aspects involved in teaching topics of Modern and Contemporary Physics (MCF) in high school have grown quite considerably in recent years, often requiring the survey and categorization of published works. In this sense, our work aims to present the results of a literature review related exclusively to the teaching of the photoelectric effect, preferably in high school, from national and international journals in the area of Teaching and Education. We have taken the work of Ostermann and Moreira (2000) as a starting point and followed it until the end of 2014. According to our selection criteria, we have identified 41 articles and classified them into eight categories, namely: (A) Theoretical and conceptual basis of the photoelectric effect; (B) Description of analogies and situations of contextualization of the photoelectric effect; (C) HFC aspects regarding the photoelectric effect; (D) Proposals or teaching reports of the photoelectric effect mediated by computer simulation; (E) Proposals or teaching reports of the photoelectric effect mediated by HFC; (F) proposals or teaching reports of the photoelectric effect mediated by experimentation and (G) Analysis of textbooks or manual regarding the photoelectric effect approach. The results indicate that most published studies report proposals to be used in the classroom by using computer simulation, experimentation or aspects of History and Philosophy of Science (HPS), however, few researchers have effectively investigated the construction process of the physical concepts present in the corpuscular model of light.

Performance of the AGATA γ-ray spectrometer in the PreSPEC set-up at GSI

In contemporary nuclear physics, the European Advanced GAmma Tracking Array (AGATA) represents a crucial detection system for cutting-edge nuclear structure studies. AGATA consists of highly segmented high-purity germanium crystals and uses the pulse-shape analysis technique to determine both the position and the energy of the γ-ray interaction points in the crystals. It is the tracking algorithms that deploy this information and enable insight into the sequence of interactions, providing information on the full or partial absorption of the γ ray. A series of dedicated performance measurements for an AGATA set-up comprising 21 crystals is described. This set-up was used within the recent PreSPEC–AGATA experimental campaign at the GSI Helmholtzzentrum für Schwerionenforschung. Using the radioactive sources 56Co, 60Co and 152Eu, absolute and normalized efficiencies and the peak-to-total of the array were measured. These quantities are discussed using different data analysis procedures. The quality of the pulse-shape analysis and the tracking algorithm are evaluated. The agreement between the experimental data and the Geant4 simulations is also investigated.

Formal and physical equivalence in two cases in contemporary quantum physics

The application of analytic continuation in quantum field theory (QFT) is juxtaposed to T-duality and mirror symmetry in string theory. Analytic continuation—a mathematical transformation that takes the time variable t to negative imaginary time—it—was initially used as a mathematical technique for solving perturbative Feynman diagrams, and was subsequently the basis for the Euclidean approaches within mainstream QFT (e.g., Wilsonian renormalization group methods, lattice gauge theories) and the Euclidean field theory program for rigorously constructing non-perturbative models of interacting QFTs. A crucial difference between theories related by duality transformations and those related by analytic continuation is that the former are judged to be physically equivalent while the latter are regarded as physically inequivalent. There are other similarities between the two cases that make comparing and contrasting them a useful exercise for clarifying the type of argument that is needed to support the conclusion that dual theories are physically equivalent. In particular, T-duality and analytic continuation in QFT share the criterion for predictive equivalence that two theories agree on the complete set of expectation values and the mass spectra and the criterion for formal equivalence that there is a “translation manual” between the physically significant algebras of observables and sets of states in the two theories. The analytic continuation case study illustrates how predictive and formal equivalence are compatible with physical inequivalence, but not in the manner of standard underdetermination cases. Arguments for the physical equivalence of dual theories must cite considerations beyond predictive and formal equivalence. The analytic continuation case study is an instance of the strategy of developing a physical theory by extending the formal or mathematical equivalence with another physical theory as far as possible. That this strategy has resulted in developments in pure mathematics as well as theoretical physics is another feature that this case study has in common with dualities in string theory.

Physics, philosophy, and the nature of reality.

Both science and philosophy have been characterized as seeking to understand the nature of reality. They are sometimes even pitted against each other, suggesting that the success of science undermines the relevance of philosophy. But attending to the sort of understanding or explanation being sought offers a different picture: contemporary physics as practiced sometimes fails to provide a clear physical account of the world. This lies at the root of the dissatisfaction with standard quantum theory expressed by Einstein, Schrödinger, and John Bell. As an example, close consideration of Schrödinger's famous cat example suggests that physicists often have missed his point. What a philosophical disposition can contribute is not alternative physics, but rather the sort of careful attention to argument needed to extract a physical picture from a mathematical formalism.

Neuroscience, Space and Time

The aim of the present article is to propose possible intersections between contemporary physics and neurosciences, in matters related to space-time. Such scope is of great significance both in “normal” and pathologic situations. In the latter, states like hypermnesia (enhanced capacity to evoke memories, with distortion of information stored in neural circuits) are described, which can be thought of – in a parallel with physics – as space-time scenarios with more than one time-type direction. Dimensions of such category – called Ataiyah-Ward space-time – have been considered in connection with systems of interest in the study of fundamental interactions, and, in macroscopic scale, in association with the issue of gravitational collapse. One has sought to understand physical phenomena in the presence of extra time to then use these studies to propose an attempt to modelling hypermnesia, through the concept that, in certain situations, neuronal system behaves as if immerse in a scenario with two time-type directions.

Ensino de matéria e radiação no ensino médio com o auxílio de simuladores interativos

The Modern and Contemporary Physics as a subject of knowledge in the high school education level has been defended by many authors. However, despite the technological and scientific advances, only few studies have been done regarding the use of computers and other media in teaching some topics in this area. In this work, which was performed in two High School classes from a public school, we applied a few ways to make use of computers and interactive simulators for a better understanding of some physical phenomena in this area. We conducted our analysis from the Vygotsky’s social-interactive perspective. We explored the topics of Spectroscopy, Radioactivity and Nuclear Physics by using interactive simulations developed by the project Physics Education Technology (PhET) at the University of Colorado. We concluded that the use of this interactive simulators collaborates with the teaching of this topics, enhancing the student's understanding and awakening their interest on the subject.

On the Matter of Time

Drawing on several disciplinary areas, this article considers diverse cultural concepts of time, space, and materiality. It explores historical shifts in ideas about time, observing that these have gone full circle, from visions in which time and space were conflated, through increasingly divergent linear understandings of the relationship between them, to their reunion in contemporary notions of space-time.Making use of long-term ethnographic research and explorations of the topic of Time at Durham University’s Institute of Advanced Study (2012–13), the article considers Aboriginal Australian ideas about relationality and the movement of matter through space and time. It asks why these earliest explanations of the cosmos, though couched in a wholly different idiom, seem to have more in common with the theories proposed by contemporary physicists than with the ideas that dominated the period between the Holocene and the Anthropocene. The analysis suggests that such unexpected resonance between these oldest and newest ideas about time and space may spring from the fact that they share an intense observational focus on material events. Comparing these vastly different but intriguingly compatible worldviews meets interdisciplinary aims in providing a fresh perspective on both of them.

The numerical relativity breakthrough for binary black holes

The evolution of black-hole (BH) binaries in vacuum spacetimes constitutes the two-body problem in general relativity. The solution of this problem in the framework of the Einstein field equations is a substantially more complex exercise than that of the dynamics of two point masses in Newtonian gravity, but it also presents us with a wealth of new exciting physics. Numerical methods are likely to be the only way to compute the dynamics of BH systems in the fully nonlinear regime and have been pursued since the 1960s, culminating in dramatic breakthroughs in 2005. Here we review the methodology and the developments that finally gave us a solution of this fundamental problem of Einstein's theory and discuss the breakthroughs' implications for the wide range of contemporary BH physics.

Steven Weinberg, To Explain the World: The Discovery of Modern Science. HarperCollins, 2015, xiv + 416 pages, $28.99

Steven Weinberg occupies a remarkable place in contemporary physics as well as being one of its most prominent public voices. He cofounded and named the Standard Model of particle physics, which synthesized the strong, weak, and electromagnetic interactions into a powerful theory amply confirmed by experiment. He is also a skillful and prolific writer not only of magisterial (and innovative) texts on general relativity and field theory but also of a number of very successful popular books. A regular contributor to the New York Review of Books, he is one of the most visible and widely respected physicists of the late twentieth and early twenty-first centuries, both among his peers and the general public; in these respects, one might compare him to Freeman Dyson. An eminent professor at the University of Texas (and many other places before that), Weinberg has in recent years given a course on the history of physics and astronomy, from which grew his new book, To Explain the World: The Discovery of Modern Science. Normally, this journal does not review essentially popular accounts, but Weinberg’s seems a special case because of its author’s eminence and influence and because his book raises important questions about the history of physics, how it is told by physicists and historians, how it is understood by the general public. Weinberg considers that, as a physicist, he can address history with the same vividness that he would bring to a physical problem, starting from first principles to give an account of some complex phenomenon. Indeed, this spirit served him well as he put together the theory that won him fame; he applied the same intellectual independence and freshness to his books on field theory and gravitation, which offered clear and sometimes new syntheses that have taught many physicists a great deal. He applied the same independent judgment to various conceptual issues that emerge from physics. For instance, in a number of writings for the general public he famously championed reductionism over the seductive charms of holism. Blunt and frank, he revels in polemic where he can bring to bear his formidable knowledge of physics, a certain love of contrarian positions, and his skill with words. Thus, his presentation of the history of physics is an event that merits close attention because it presumably will be taken by his peers and the general public as the considered judgment of this eminent physicist about the history of science. Indeed, his interest in history is long-standing; readers of his earlier books will notice how often and how keenly he devotes close attention to the history of the point in question, at times delving into the primary sources and wishing to go beyond often-recounted stories or summary accounts. In that sense, there is much to admire in To Explain the World. Weinberg sets out to explain in some detail the salient history and controversies that formed physics as we now know it, indeed the whole of science. By comparison with many works that stint or even

Music and the making of modern science

Music played a significant role in the making of modern science. In ancient Greek natural philosophy, music formed the earthly meeting place between numbers and perception. For the next two millennia, music remained a central part of higher education, united with arithmetic, geometry, and astronomy in the quadrivium. Accordingly, innovations reverberated between all these fields. This book presents the “scientific revolution” more as a phase in the restoration and augmentation of the ancient project of musicalizing the world than a change in the basic project of natural philosophy. After discussing the original Pythagorean synthesis of music, mathematics, and sense-experiment, the book presents cases in which prior developments in music led to some new direction in science from the fourteenth century to the twentieth. These include encounters between harmony and fifteenth-century cosmological controversies, between musical initiatives and irrational numbers, between vibrating bodies and emergent electromagnetism. The book presents new accounts of Johannes Kepler’s use of music, of René Descartes’s and Marin Mersenne’s interweaving of music and natural philosophy, of Isaac Newton’s imposition of the musical scale on color, of Leonhard Euler’s musical work in relation to his mathematics and optical theory, of Thomas Young’s musical optics, of Hermann von Helmholtz’s and Bernhard Riemann’s development of new concepts of space from studies of seeing and hearing, of atomic spectra as overtones, of Max Planck’s experiments with harmoniums and choruses in relation to his subsequent quantum theory, and of the continuing quest for cosmic harmonies in contemporary physics.

Początkowa osobliwość jako stworzenie świata. Niebezpieczeństwo powrotu do argumentu „God of the gaps”

The man desires to understand the surrounding world. One of the crucial question asked by mankind concerns the beginning of the universe. In this article have been shown the consequences of meeting Christian doctrine which is about creating the world with the idea of contemporary physics which explains space revolution as the beginning of the world. The Christian metaphysics provides satisfactory answers for two essential questions: about the beginning of the world and about the source of order and harmony inside the world. As far as the first issue is concerned, we can say both about the time of the creating the world and about perennial existence of the world. In the second issue the rationality of God the Creator justifies the rationality of creating the world. So this Christian doctrine of the creating the world faces with mathematical and empirical method of study the world, which this method tries to describe the examined episode of the world using suitable mathematical structures. The problem of initial singularity that appeared at the beginning of the 20th century in cosmology it became the source of lively discussion among scientists and philosophers and theologians. The question how can we link cosmological data with the theological concept of creation was the crucial background in this discussion. Another word, the debate began with the question whether the initial singularity prove the creation of the world and existing God as well or on the contrary, it may constitutes argument for His non-existence. This way of thinking caused to back to English scientists (called themselves “natural philosophers” or “virtuosi”) arguments from the 17th century. They desired to prove that God exists according to the lack of human’s nature knowledge, that was later called „God of the gaps”. As has been shown the issue of initial singularity is as area of unfinished research. The problem of initial singularity is neutral with regard to the doctrine of creation the world because singularity is a factor of some mathematics structure, where solutions of equations that describe cosmological model lose meaning. In connection with that we can claim that identification initial singularity with theological concept of creating the world became like kind of material used for building the argument: „God of the gaps” that according to theologians and scientists it is judged negative.

Non-relativistic high-energy physics: top production and dark matter annihilation

Non-relativistic physics is often associated with atomic physics and low-energy phenomena of the strong interactions between nuclei and quarks. In this review we cover three topics in contemporary high-energy physics at or close to the TeV scale, where non-relativistic dynamics plays an important if not defining role. We first discuss in detail the third-order corrections to top-quark pair production in electron-positron collisions in the threshold region, which plays a major role at a future high-energy e+e− collider. Threshold effects are also relevant in the production of heavy particles in hadronic collisions, where in addition to the Coulomb force soft gluon radiation contributes to enhanced quantum corrections. We review the joint resummation of non-relativistic and soft gluon effects for pair production of top quarks and supersymmetric particles to next-to-next-to-leading logarithmic accuracy. The third topic deals with pair annihilation of dark matter particles within the framework of the Minimal Supersymmetric Standard Model. Here the electroweak Yukawa force generated by the exchange of gauge and Higgs bosons can cause large “Sommerfeld” enhancements of the annihilation cross section in some parameter regions.

The isospin dependence of the nuclear force and its impact on the many-body system

A major goal of contemporary nuclear physics is to improve our knowledge of the nuclear matter equation of state. In particular, the equation of state of isospin- asymmetric matter (that is, with unequal concentrations of protons and neutrons), is not well understood, mostly due to our limited knowledge of the symmetry energy. The latter reduces the binding energy in a nucleus with unequal number of protons and neutrons, and is crucial for understanding nuclear stability. We review experimental, phenomenological, and theoretical facts about the symmetry energy. We emphasize the importance of adopting a microscopic approach towards a better understanding of this important quantity.

Bridging a gap between continuum-QCD and ab initio predictions of hadron observables

Within contemporary hadron physics there are two common methods for determining the momentum-dependence of the interaction between quarks: the top-down approach, which works toward an ab initio computation of the interaction via direct analysis of the gauge-sector gap equations; and the bottom-up scheme, which aims to infer the interaction by fitting data within a well-defined truncation of those equations in the matter sector that are relevant to bound-state properties. We unite these two approaches by demonstrating that the renormalisation-group-invariant running-interaction predicted by contemporary analyses of QCD's gauge sector coincides with that required in order to describe ground-state hadron observables using a nonperturbative truncation of QCD's Dyson–Schwinger equations in the matter sector. This bridges a gap that had lain between nonperturbative continuum-QCD and the ab initio prediction of bound-state properties.

Is the principle of least action a must?

The least action principle occupies a central part in contemporary physics. Yet, as far as classical field theory is concerned, it may not be as essential as generally thought. We show with three detailed examples of classical interacting field theories that it is possible, in cases of physical interest, to derive the correct field equations for all fields from the action (which we regard as defining the theory), some of its symmetries, and the conservation law of energy–momentum (this last regarded as ultimately coming from experiment).

Revising Whitehead’s Notion of Society in the Light of Contemporary Physics

AbstractThis article argues that Joseph A. Bracken’s revisions of Alfred North Whitehead’s derivative notion of “society” are plausible in view of developments in physics since Whitehead. In particular, Bracken argues that Whitehead’s derivative notion of “society” should rather be a category of existence equiprimordial with “actual entity,” and that contemporary actual entities in concrescence do influence each other as they directly prehend the society as a nexus. The article begins with Whitehead’s view of the metaphysical project as empirical, tentative, and subject to ongoing revision. Next, the essay explains Whitehead’s view of societies and contemporary actual entities. Following this is a survey of developments in physics since Whitehead that are relevant to his understanding of “society” and contemporary actual entities. The article then explains how Bracken differs from Whitehead on these points and argues that the physics developments corroborate Bracken’s proposed revisions to Whitehead. The essay ends with a restatement of Whitehead’s view of metaphysics as provisional and in need of ongoing revision.

Fluid Mechanics in Sommerfeld's School

Sommerfeld's affiliation with fluid mechanics started when he began his career as an assistant of the mathematician Felix Klein at Göttingen. He always regarded fluid mechanics as a particular challenge. In 1904, he published a theory of hydrodynamic lubrication. Four years later, he conceived an approach for the analysis of flow instability (the Orr-Sommerfeld approach) as an attempt to account for the transition from laminar to turbulent flow. The onset of turbulence also became a major challenge for some of his pupils, in particular Ludwig Hopf and Fritz Noether. Both contributed considerably to elaborate the Orr-Sommerfeld theory. Heisenberg's doctoral work was another attempt in this quest. When Sommerfeld published his lectures on theoretical physics during World War II, he dedicated one of the six volumes to the mechanics of continuous media. With chapters on boundary layer theory and turbulence, it exceeded the scope of contemporary theoretical physics—revealing Sommerfeld's persistent appreciation of fluid mechanics. He resorted to Prandtl's Göttingen school of fluid mechanics in order to stay abreast of the rapid development of these specialties.

Analogies in High School Classes on Quantum Physics

This paper presents preliminary findings of research on using analogies in high school classes on quantum physics. Use of analogies in teaching activities has been proposed in science education research as a method to construct appropriate meanings from and through science representations. We can find in the literature several articles where using such analogies requires some care in order to help in the learning process of concepts presented. However, we contend that in Modern and Contemporary Physics (MCP) we find some epistemological and/or ontological obstacles when trying to represent quantum entities, for example. Our purpose is, based on data gathered through the recording of classes on quantum physics at high school, and using categories from Curtis & Reigeluth (1984), to search for the common analogies that are used. We obtained transcriptions from the classes of teachers from different public schools in São Paulo. The identification of some features of a possible classification might help in the teacher training as well as in teaching of quantum physics. We highlight that it is essential that the teacher be aware of his/her actions. The recognition of some characteristics of the different representations may contribute to make the teacher's actions less and less alienating and enable sharing of the meaning with students.

Fundamental Physical Basis for Maxwell-Heaviside Gravitomagnetism

Gravitomagnetism is universally and formally recognised in contemporary physics as being the linear first-order approximation of Einstein’s field equations emerging from the General Theory of Relativity (GTR). Herein, we argue that, as has been done by others in the past, gravitomagnetism can be viewed as a fully-fledged independent theory of gravitomagnetism that can be divorced from Professor Einstein’s GTR. The gravitomagnetic theory whose exposition we give herein is exactly envisioned by Professor Maxwell and Dr. Heaviside. The once speculative Maxwell-Heaviside Gravitomagnetic theory now finds full justification as a fully fledged theory from Professor Jose Hera’s Existence Theorem which states that all that is needed for there to exist the four Max-well-type field equations is that a mass-current conservation law be obeyed. Our contribution in the present work, if any, is that we demonstrate conclusively that like electromagnetism, the gravitomagnetic phenomenon leads to the prediction of gravitomagnetic waves that travel at the speed of light. Further, we argue that for the gravitational phenomenon, apart from the Newtonian gravitational potential, there are four more potentials and these operate concurrently with the Newtonian potential. At the end of it, it is seen that the present work sets the stage for a very interesting investigation of several gravitational anomalies such as the ponderous Pioneer Anomaly, the vexing Flyby Anomalies, the mysterious Anomalous Rotation Curves of Spiral Galaxies and as well, the possibility of the generation of stellar magnetic fields by rotating gravitational masses.