arXiv subjects

Stamatis Vokos

Publications and source records attributed to Stamatis Vokos.

9 recordsLinked to original sources

arXiv2016

Development of Habits Through Apprenticeship in a Community: Conceptual Model of Physics Teacher Preparation

We propose the DHAC conceptual model of teacher preparation (Development of Habits through Apprenticeship in a Community), which builds on the contemporary literature on teacher preparation in physics and other disciplines and strives to provide a better understanding of the process of teacher formation. Extant literature on teacher preparation suggests that pre-service teachers learn best when they are immersed in a community that allows them to develop dispositions, knowledge, and practical skills and share with the community a strong vision of what good teaching entails. However, despite having developed the requisite dispositions, knowledge, and skills in pursuing the shared vision of good teaching, the professional demands on a teacher's time are so great out of and so complex during class time that if every decision requires multiple considerations and deliberations with oneself, the productive decisions might not materialize. We therefore argue that the missing link between intentional decision-making and actual teaching practice are the teacher's habits (spontaneous responses to situational cues). Teachers unavoidably develop habits with practical experience and under the influence of knowledge and belief structures that in many ways condition the responses of teachers in their practical work. To steer new teachers away from developing unproductive habits directed towards "survival" instead of student learning, we argue that any teacher preparation program (e.g., physics) should strive to develop in pre-service teachers strong habits of mind and practice that will serve as an underlying support structure for beginning teachers. These habits form the core of the conceptual model described in the paper. We provide examples of habits, which physics teachers need to develop before starting teaching and propose mechanisms for the development of such habits.

physics.ed-ph↗

arXiv2014

Energy conservation in dissipative processes: Teacher expectations and strategies associated with imperceptible thermal energy

Research has demonstrated that many students and some teachers do not consistently apply the conservation of energy principle when analyzing mechanical scenarios. In observing elementary and secondary teachers engaged in learning activities that require tracking and conserving energy, we find that challenges to energy conservation often arise in dissipative scenarios in which kinetic energy transforms into thermal energy (e.g., a ball rolls to a stop). We find that teachers expect that when they can see the motion associated with kinetic energy, they should be able to perceive the warmth associated with thermal energy. Their expectations are violated when the warmth produced is imperceptible. In these cases, teachers reject the idea that the kinetic energy transforms to thermal energy. Our observations suggest that apparent difficulties with energy conservation may have their roots in a strong and productive association between forms of energy and their perceptible indicators. We see teachers resolve these challenges by relating the original scenario to an exaggerated version in which the dissipated thermal energy is associated with perceptible warmth. Using these exaggerations, teachers infer that thermal energy is present to a lesser degree in the original scenario. They use this exaggeration strategy to productively track and conserve energy in dissipative scenarios.

physics.ed-ph↗

arXiv2014

Goals for teacher learning about energy degradation and usefulness

The Next Generation Science Standards (NGSS) require teachers to understand aspects of energy degradation and the second law of thermodynamics, including energy's availability and usefulness, changes in energy concentration, and the tendency of energy to spread uniformly. In an effort to develop learning goals that support teachers in building robust understandings of energy from their existing knowledge, we studied teachers' impromptu conversations about these topics during professional development courses about energy. Many of these teachers' ideas appear to align with statements from the NGSS, including the intuition that energy can be present but inaccessible, that energy can change in its usefulness as it transforms within a system, and that energy can lose its usefulness as it disperses, often ending up as thermal energy. Some teachers' ideas about energy degradation go beyond what is articulated in the NGSS, including the idea that thermal energy can be useful in some situations and the idea that energy's usefulness depends on the objects included in a scenario. Based on these observations, we introduce learning goals for energy degradation and the second law of thermodynamics that (1) represent a sophisticated physics understanding of these concepts, (2) originate in ideas that teachers already use, and (3) align with the NGSS.

physics.ed-ph↗

arXiv2002

Student understanding of time in special relativity: simultaneity and reference frames

This article reports on an investigation of student understanding of the concept of time in special relativity. A series of research tasks are discussed that illustrate, step-by-step, how student reasoning of fundamental concepts of relativity was probed. The results indicate that after standard instruction students at all academic levels have serious difficulties with the relativity of simultaneity and with the role of observers in inertial reference frames. Evidence is presented that suggests many students construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity harmoniously co-exist.

physics.ed-ph↗

arXiv2002

The challenge of changing deeply-held student beliefs about the relativity of simultaneity

Previous research indicates that after standard instruction students at all academic levels often construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity co-exist. This article describes the development and assessment of instructional materials intended to improve student understanding of the concept of time in special relativity, the relativity of simultaneity, and the role of observers in inertial reference frames. Results from pretests and post-tests are presented to demonstrate the effect of the curriculum in helping students deepen their understanding of these topics. Excerpts from taped interviews and classroom interactions help illustrate the intense cognitive conflict that students encounter as they are led to confront the incompatibility of their deeply-held beliefs about simultaneity with the results of special relativity.

physics.ed-ph↗

arXiv1995

Long Range Forces in Quantum Gravity

We calculate the leading quantum and semi-classical corrections to the Newtonian potential energy of two widely separated static masses. In this large-distance, static limit, the quantum behaviour of the sources does not contribute to the quantum corrections of the potential. These arise exclusively from the propagation of massless degrees of freedom. Our one-loop result is based on Modanese's formulation and is in disagreement with Donoghue's recent calculation. Also, we compare and contrast the structural similarities of our approach to scattering at ultra-high energy and large impact parameter. We connect our approach to results from string perturbation theory.

hep-th↗

arXiv1994

Motion of Spin-1/2 Particles in External Gravitational and Electromagnetic Fields

(Talk presented at the 7th Marcel Grossmann Meeting on General Relativity, Stanford, CA, July 24-30, 1994) We study the semi-classical limit of the solution of the Dirac equation in a background electromagnetic/gravitational plane wave. We show that the exact solution corresponding to an asymptotically fixed incoming momentum satisfies constraints consistent with the classical notion of a spinning particle. In order to further analyze the motion of a spinning particle in this external inhomogeneous field one has to consider wave-packet superpositions of these exact solutions. We are currently investigating the existence of a classical theory of a phenomenological spin tensor which reproduces our quantum-mechanical results.

hep-th↗

arXiv1993

Thermal Self-Energies Near Zero Four-Momentum

(Talk presented at the 3rd Workshop on Thermal Field Theories and Their Applications, Banff, Canada, August 1993. This is a review of work done with Peter Arnold, Paulo Bedaque, and Ashok Das.) We demonstrate that one-loop self-energies at finite temperature have a unique limit as the external four-momentum goes to zero, as long as the particles propagating in the loop have distinct masses. We show that in spontaneously broken theories, this result nonetheless does not affect the difference between screening and propagating modes and hence the usual resummed perturbation expansion remains unaltered.

hep-ph↗

arXiv1993

Is Geodetic Precession of Massive Neutrinos the solution to the Solar Neutrino Problem?

We examine a recent suggestion by Milburn that slightly massive electron neutrinos, produced left-handed at the core of the sun, suffer geodetic precession adequate to render them right-handed (and therefore sterile) in sufficient numbers to solve the solar neutrino problem. In that light, we perform a complete, general-relativistic calculation of the geodetic spin precession of an ultrarelativistic particle in the Schwartzschild metric. We conclude that the effect is negligible, in disagreement with Milburn's analysis.

hep-ph↗