Biblioteca Digital

The quantitative aspirations of economists and financial analysts have for many years been based on the belief that it should be possible to build models of economic systems - and financial markets in particular - that are as predictive as those in physics. While this perspective has led to a number of important breakthroughs in economics, "physics envy" has also created a false sense of mathematical precision in some cases. We speculate on the origins of physics envy, and then describe an alternate perspective of economic behavior based on a new taxonomy of uncertainty. We illustrate the relevance of this taxonomy with two concrete examples: the classical harmonic oscillator with some new twists that make physics look more like economics, and a quantitative equity market-neutral strategy. We conclude by offering a new interpretation of tail events, proposing an "uncertainty checklist" with which our taxonomy can be implemented, and considering the role that quants played in the current financial crisis.; Comment: v3 adds 2 references

The paper discusses fundamental problems in mathematical description of social systems based on physical concepts, with so-called statistical social systems being the main subject of consideration. Basic properties of human beings and human societies that distinguish social and natural systems from each other are listed to make it clear that individual mathematical formalism and physical notions should be developed to describe such objects rather then can be directly inherited from classical mechanics and statistical physics. As a particular example systems with motivation are considered. Their characteristic features are analyzed individually and the appropriate mathematical description is proposed. Finally the paper concludes that the basic elements necessary for describing statistical social systems or, more rigorously, systems with motivation are available or partly developed in modern physics and applied mathematics.; Comment: 25 pages, 4 pictures

The paradoxes of thermodynamics and statistical physics are unavoidable in the study of physical paradoxes because of their importance at the time they came to be as well as the frequency of their appearance in historical studies of physics. In this work paradoxes are presented together with the historical studies of their creation, their solutions are given and they are analysed according to a number of characteristics: is it an exparadox, is it of theoretic or experimental nature, is it a thought experiment and the type of paradox it belongs to.; Comment: 15 pages, 1 figure, 5 tables, 3 graphics

This article describes five common student misconceptions about succeeding in college-level Physics courses: the miracle finish, the soft hearted professor, an extension of high school, weak areas won't be tested, and passing is more important than learning. These fantasies are unique to neither Physics nor freshman, but the challenge of learning Physics brings more certain negative consequences to students retaining these attitudes. Ascribing these student misconceptions to freshmen acknowledges that they diminish with increasing academic maturity.; Comment: 3 pages, submitted to The Physics Teacher

This is a completely reformulated presentation of a previous paper with the same title; this time with a much stronger emphasis on conceptual aspects of string theory and a detailed review of its already more than four decades lasting history within a broader context, including some little-known details. Although there have been several books and essays on the sociological impact and its philosophical implications, there is yet no serious attempt to scrutinize its claims about particle physics using the powerful conceptual arsenal of contemporary local quantum physics. I decided to leave the previous first version on the arXiv because it may be interesting to the reader to notice the change of viewpoint and the reason behind it. Other reasons for preventing my first version to go into print and to rewrite it in such a way that its content complies with my different actual viewpoint can be found at the end of the article. The central message, contained in sections 5 and 6, is that string theory is not what string theorists think and claim it is. The widespread acceptance of a theory whose interpretation has been obtained by metaphoric reasoning had a corroding influence on the rest of particle physics theory as will be illustrated in several concrete cases. The work is dedicated to the memory of Juergen Ehlers with whom I shared many critical ideas...

Five physics mechanisms of interaction leading to the binding of the ${\rm H}_3^+$ molecular ion are identified. They are realized in a form of variational trial functions and their respective total energies are calculated. Each of them provides subsequently the most accurate approximation for the Born-Oppenheimer (BO) ground state energy among (two-three-seven)-parametric trial functions being correspondingly, H$_2$-molecule plus proton (two variational parameters), H$_2^+$-ion plus H-atom (three variational parameters) and generalized Guillemin-Zener (seven variational parameters). These trial functions are chosen following a criterion of physical adequacy. They include the electronic correlation in the exponential form $\sim\exp{(\gamma r_{12})}$, where $\gamma$ is a variational parameter. Superpositions of two different mechanisms of binding are investigated and a particular one, which is a generalized Guillemin-Zener plus H$_2$-molecule plus proton (ten variational parameters), provides the total energy at the equilibrium of $E=-1.3432$\ a.u. The superposition of three mechanisms: generalized Guillemin-Zener plus (H$_2$ -molecule plus proton) plus (H$_2^+$ -ion plus H) (fourteen parameters) leads to the total energy which deviates from the best known BO energy to $\sim 0.0004$\ a.u....

Just as expert physicists vary in their personal stances on interpretation in quantum mechanics, instructors vary on whether and how to teach interpretations of quantum phenomena in introductory modern physics courses. In this paper, we document variations in instructional approaches with respect to interpretation in two similar modern physics courses recently taught at the University of Colorado, and examine associated impacts on student perspectives regarding quantum physics. We find students are more likely to prefer realist interpretations of quantum-mechanical systems when instructors are less explicit in addressing student ontologies. We also observe contextual variations in student beliefs about quantum systems, indicating that instructors who choose to address questions of ontology in quantum mechanics should do so explicitly across a range of topics.; Comment: 18 pages, references, plus 2 pages supplemental materials. 8 figures. PACS: 01.40.Fk, 03.65.-w

This is a report of a course on modern physics designed and taught to undergraduate science and engineering students in the Spring of 2013. The course, meant for freshmen, attempts to integrate statistical mechanics into non-classical physics and introduces some novel teaching ideas such as the field approach in contrast to typical wave and particle viewpoints traditionally covered in usual textbooks. The various modern applications of quantum theory in realizing practical devices are recounted in a way that is amenable to beginners. Especially, we describe the inclusion of visually appealing and carefully designed robust experiments inside the formal classroom environment. This collection of applications and demonstrations serves as a useful collection of teaching aids and can be easily transformed into active learning exercises. The impact of this teaching strategy on student learning and its role in exciting an interest in physics is assessed.; Comment: 11 pages, 11 figures, submitted to The Physics Teacher

This study investigates how an urban, high school physics class responded to the inclusion of a classroom set of iPads and associated applications, such as screencasting. The participatory roles of students and the expressions of their relationships to physics were examined. Findings suggest that iPad technology altered classroom norms and student relationships to include increased student agency and use of evidence. Findings also suggest that the iPad provided a connection between physics, social status, and play. Videos, observations, interviews, and survey responses were analyzed to provide insight into the nature of these changes.; Comment: 4 pages, 6 figures, Physics Education Research Conference Proceedings

Since 2010, the Yale physics department has offered a novel calculus-based introductory physics for the life science (IPLS) sequence, that re-imagines the IPLS syllabus to include a selection of biologically and medically relevant topics, that are highly meaningful to its audience of biological science and premedical undergraduates. The first semester, in particular, differs considerably from traditional first-semester introductory physics. Here, we highlight the novel aspects of Yale's first-semester course, and describe student feedback about the course, including a comparison between how students evaluate the course and how they evaluate courses with a traditional syllabus, and how students' perceptions of the relevance of physics to biology and medicine are affected by having taken the course.; Comment: 9 pages, 5 figures

Commercial video games are increasingly using sophisticated physics simulations to create a more immersive experience for players. This also makes them a powerful tool for engaging students in learning physics. We provide some examples to show how commercial off-the-shelf games can be used to teach specific topics in introductory undergraduate physics. The examples are selected from a course taught predominantly through the medium of commercial video games.; Comment: Accepted to Physics Education, Fig1 does not render properly in this version

We review the development of random-matrix theory (RMT) during the last decade. We emphasize both the theoretical aspects, and the application of the theory to a number of fields. These comprise chaotic and disordered systems, the localization problem, many-body quantum systems, the Calogero-Sutherland model, chiral symmetry breaking in QCD, and quantum gravity in two dimensions. The review is preceded by a brief historical survey of the developments of RMT and of localization theory since their inception. We emphasize the concepts common to the above-mentioned fields as well as the great diversity of RMT. In view of the universality of RMT, we suggest that the current development signals the emergence of a new "statistical mechanics": Stochasticity and general symmetry requirements lead to universal laws not based on dynamical principles.; Comment: 178 pages, Revtex, 45 figures, submitted to Physics Reports

The activities carried out by Italian physicists in the field of semiconductor physics during the period spanning from 1945 to the foundation of the National Group of Structure of the Matter (GNSM, 1965) are reviewed within their historical context. Until the fifties, the Italian research was only marginally involved, if at all, in the main streams of advancement in solid state physics. Starting from the early fifties, an interest for technical applications of the newly introduced semiconductor devices began to grow in the electronic engineering community. In the following years, the birth of a few experimental and theoretical groups lead by highly motivated scientists (some of them with international experience) allowed to deal with the main topics related to condensed matter and semiconductor phenomena. The work developed by these "pioneers", discussed in this paper, represented an invaluable contribution for the new generations of physicists in this research field.; Comment: 26 pages

It is known that Einstein's conceptual base for his theory of relativity was the philosophy formulated by Immanuel Kant. Things appear differently to observers in different frames. However, Kant's Ding-an-Sich leads to the existence of the absolute reference frame which is not acceptable in Einstein's theory. It is possible to avoid this conflict using the ancient Chinese philosophy of Taoism where two different views can co-exist in harmony. This is not enough to explain Einstein's discovery of the mass-energy relation. The energy-momentum relations for slow and ultra-fast particles take different forms. Einstein was able to synthesize these two formulas to create his energy-mass relation. Indeed, this is what Hegelianism is about in physics. Isaac Newton synthesized open orbits for comets and closed orbits for planets to create his second law of motion. Maxwell combined electricity and magnetism to create his four equations to the present-day wireless world. In order to synthesize wave and particle views of matter, Heisenberg formulated his uncertainty principle. Relativity and quantum mechanics are the two greatest theories formulated in the 20th Century. Efforts to synthesize these two theories are discussed in detail.; Comment: Latex 10 pages with 6 figures...

We demonstrate the implementation of a simple time-of-flight (ToF) mass spectrometer with medium-mass resolution ($m/\Delta m\sim50$) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from a linear quadrupole trap, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. Here we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.; Comment: 7 pages, 7 figures

In active engagement physics classrooms, students get opportunities to make sense of physics together through discussion. They do not always take up these opportunities, in part because of the risk of sharing their ideas and having them rejected by their classmates or the instructors. In this case study, I analyze videotaped discourse of a tutorial group's early discussions to investigate how students manage these risks in creating a safe space to sensemake. I find that the students and instructors alike rely on a common discursive resource - epistemic distancing - to share their ideas while protecting themselves affectively if others disagree. Epistemic distancing includes hedging, joking, deferring, and other discourse moves used to soften one's stance in conversation. I use video analysis to illustrate the effects of these moves on tutorial groups' sensemaking discussions, and discuss implications for instructors wishing to encourage sensemaking discussions in their physics classrooms.; Comment: preprint of a paper submitted to the Physics Education Research Conference 2015, 4 pages, 1 figure

The basic ingredients of the discovery creativity is presented. Understanding, problem solving, heuristics, computer thinking, technology and physics, and so on. We present some discoveries from the viewpoint of creativity. The Dirac equation, the Riccati equation, the nonlinear Schroedinger equation, the quantum navier Sokes equation, the equation of the quantum magnetohydrodynamics and so on. We discuss nonlinear Lorentz transformation involving the maximal acceleration which we relate to the Hagedorn temperature, and possible dependence of mass on acceleration. We consider the relation between physics and technology and so on.; Comment: 37 pages

We discuss and analyze the fact that physics is generally losing its ability to captivate students who may possess the potential to enhance the quality of our future in this age of technology. We have tried to investigate the reasons behind this low enrollment in the light of the results of a few surveys with the undergraduate students in different physics courses and in current relevant college programs. It is not an exclusively descriptive issue, so our analysis is a way to delineate the details of the matter leading to the suggestions for future improvements.; Comment: 22 pages

The videos posted on YouTube can be very helpful to teach any subject in the classroom. In Physics, there is a wealth of material just waiting for the teachers to know what to do with them. In this study, we present a report on how we used videos of magic performances as a teaching aid to supplement Physics classes. Since the goal of magic is to challenge a principle or a natural law, it is interesting to use it in order to try to unravel its secret in a scientific way. To illustrate the application of this strategy, we used a performance of the magician Dynamo, held in London, where he quietly walks on the water of the River Thames. Having overcome the surprise of illusion, students are led by the teacher to try to get a physically plausible explanation for the secret of the magic. To carry out this task, we followed the paths of so-called scientific method in their traditionally defined form in schoolbooks. The results are very positive as and clearly point out the engagement of students in the search for the correct explanation. This strategy is recommended for use in high school Physics classes and in the initial semesters in College courses.; http://dx.doi.org/10.5007/2175-7941.2015v32n2p483Os vídeos postados no YouTube podem ser muito úteis em sala de aula...

This paper describes how was implemented a computer simulation of an ionizing radiation detection system similar to those found in traditional modern physics laboratories. The simulation models a system with radioactive “sources” of photons with well-defined energies and a “detector” that behaves like a photon spectrometer (scintillator + photomultiplier tube + multichannel analyzer). As with the real system, besides choosing the source, it is possible to adjust the high voltage applied at the photomultiplier tube, the gain of the analog amplifier and the conversion gain of the multichannel analyzer, observing the corresponding changes in the acquired “data”. There are presented and discussed results obtained with the simulator for some experimental set-ups (energy calibration, identification of unknown energies, system energy resolution, etc.). The simulation was used with two groups of undergraduate students from a distance learning physics course at UFSC in 2011 and 2014, along with the execution of the real experiment. Throughout the text there are comments on the motivations and problems of using simulations in this context. Finally, it is discussed how this work relates to the main goals of introductory physics laboratories...