bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical analysis of Bose–Einstein condensation in a three-dimensional harmonic oscillator potential
Authors: Ligare Martin
Published: September 2005

Bose–Einstein condensation is the anomalous accumulation of particles in the ground state of a system of bosons, when compared with the population in a system of particles obeying classical statistics. I use undergraduate-level statistical mechanics and a symbolic algebra computer program to study the occupation numbers of the energy levels of a finite number of noninteracting particles confined in a three-dimensional harmonic oscillator potential. I also calculate the heat capacity of the gas. The harmonic oscillator potential simplifies the calculations and approximates the conditions of the recent experiments achieving Bose–Einstein condensation in laser-cooled alkali vapors.
Almost rolling motion: An investigation of rolling grooved cylinders
Authors: Mead Lawrence R. , Bentrem Frank W.
Published: September 2005

We examine the dynamics of cylinders that are grooved to form N teeth for rolling motion down an inclined plane. The grooved cylinders are experimentally found to reach a terminal velocity. This result can be explained by the inclusion of inelastic processes which occur whenever a tooth hits the surface. The fraction of the angular velocity that is lost during an inelastic collision is phenomenologically found to be proportional to 2 sin2 π/N−α sin3 π/N, and the method of least squares is used to find the constant α=0.98. The adjusted theoretical results for the time of rolling as well as for terminal velocity are found to be in good agreement with the experimental results.
Student expectations in introductory physics
Authors: Redish Edward F. , Saul Jeffery M. , Steinberg Richard N.
Published: September 2005

Students’ understanding of what science is about, how it is done, and their expectations as to what goes on in a science course, can play a powerful role in what they get out of introductory college physics. In this paper, we describe the Maryland Physics Expectations survey; a 34-item Likert-scale (agree–disagree) survey that probes student attitudes, beliefs, and assumptions about physics. We report on the results of pre- and post-instruction delivery of this survey to 1500 students in introductory calculus-based physics at six colleges and universities. We note a large gap between the expectations of experts and novices and observe a tendency for student expectations to deteriorate rather than improve as a result of the first term of introductory calculus-based physics.
Calorimetric determination of the work function
Authors: Kraftmakher Yaakov
Published: September 2005

A student experiment on the calorimetric determination of the work function is described. This approach clearly demonstrates the energy transfer by electrons leaving the cathode of a vacuum tube. The changes in the temperature due to the energy transfer are detectable by measurements of the resistance of the cathode or radiation from it. Oxide-coated cathodes are more suitable for such measurements than tungsten cathodes. The calorimetric determination of the work function may become a good addition to the traditional student experiments in the field.
Multipole expansion in magnetostatics
Authors: González H. , Juárez S. R. , Kielanowski P. , Loewe Mark
Published: September 2005

We derive the multipole expansions of the magnetostatic field and vector potential of an arbitrary steady current density. A simplifying parametrization of the (l+1)th-order tensor of lth-order moments of the current density in terms of an lth-order tensor bi1…il allows us to derive all orders in the multipole expansions using only Cartesian coordinates of tensors. We do not use a magnetic scalar potential or spherical harmonics. The field B(l)(r) of the lth-order magnetostatic multipole depends on only the 2l+1 independent components of the symmetric traceless part bi1…ils0 of bi1…il in exactly the same way as the field E(l)(r) of the lth-order electrostatic multipole depends on the lth-order symmetric traceless tensor ρi1…ils0 of multipole moments of the charge density. The vector potential that depends on only the symmetric traceless tensors bi1…ils0 differs from the vector potential in the Coulomb gauge. Our derivation shows that the fact that only the symmetric traceless part of bi1…il contributes to the magnetostatic field is a consequence of charge conservation and gauge invariance.
Evolving few-ion clusters of Na and Cl
Authors: Michaelian K.
Published: September 2005

The ground state configuration of a macroscopic quantity of Na and Cl ions is the well-known crystalline, face-centered cubic structure (table salt). However, when the number of ions is reduced to a handful, geometrically quite different and interesting ground state structures occur. Such configurations are realized in the early stages of crystal growth and are important in a growing number of physical applications. This article describes the application of a genetic algorithm to the difficult problem of the determination of the lowest-energy geometrical configurations of few-ion (⩽12) clusters of Na and Cl. The binding energy and the frequencies of vibration determined for these structures are compared to experimental data and to published results of other calculations. The advantages and limitations of the genetic algorithm as a tool for cluster physics are discussed.
Integral equations and the simple harmonic oscillator
Authors: Muñoz Gerardo
Published: September 2005

The energy eigenstates for the simple harmonic oscillator in quantum mechanics are found through the solution of an integral equation.
Axial intensity distribution of the diffractive image of a point object
Authors: Perkalskis Benjamin S. , Freeman J. Reuben
Published: September 2005

The axial intensity distribution for the image of an axial point object in an ideal circular lens is derived by vector addition of the Huygens wavelets (the vibration curve method).
A primer on electrical units in the Système International
Authors: Zimmerman Neil M.
Published: September 2005

I examine the dissemination of the electrical units, from basic physical laws to commercial calibrations. I discuss the important distinction between realization and representation of units, which refers back to the distinction between SI (Le Système International d’Unités) units and practical units. I then outline the current dissemination of electrical units, heavily based on the fundamental quantum standards (Josephson voltage and quantized Hall resistance standards), as well as on a classic metrology experiment, the calculable capacitor. We will see that this chain of unit realizations is one way physicists test the accuracy of the basic physical laws. As an example of the dissemination, I also outline the transfer chain from the primary voltage standard to the factory floor. Finally, I briefly discuss some areas of current research which have the potential to induce permanent changes in the definition of SI units (in particular the kilogram), and to close the “metrology triangle.”
Covariance of the total energy–momentum four-vector of a charge and current carrying macroscopic body
Authors: Hnizdo Vladimir
Published: September 2005

The relativistic covariance of the four-vector of the total energy–momentum of a macroscopic body that, in its rest frame, carries general stationary macroscopic charge and current distributions is demonstrated in explicit detail using the balancing of the forces in the body, the existence of hidden mechanical momentum, and the Lorentz-transformation properties of the energy-momentum four-tensors of the “mechanical” and “electromagnetic” parts of the system.
An approximate method for the direct calculation of radiation reaction
Authors: Templin Jacques D.
Published: September 2005

An approximate method for the direct or near-field calculation of radiation reaction is introduced. The usual technique for the direct calculation requires determining the effect of the field produced by an extended source at a retarded time acting on the same extended source at the current time. The approximation consists of replacing the retarded source by a point source whose properties are determined by the radiation field. This approximation is applied to three examples: the average power radiated by a circular current loop, the radiation reaction torque acting on a rotating magnetic dipole, and the radiation reaction force exerted on a charged particle.
Kinetic energy and the equivalence principle
Authors: Carlip S.
Published: September 2005

According to the general theory of relativity, kinetic energy contributes to gravitational mass. Surprisingly, the observational evidence for this prediction does not seem to be discussed in the literature. I reanalyze existing experimental data to test the equivalence principle for the kinetic energy of atomic electrons, and show that fairly strong limits on possible violations can be obtained. I discuss the relationship of this result to the occasional claim that “light falls with twice the acceleration of ordinary matter.”
Describing the state of a stochastic process
Authors: Gillespie Daniel T.
Published: September 2005

The conventional way of mathematically describing the state of a classical stochastic process is criticized. A different approach, which emphasizes the important role of conditioning, is recommended.
Path integral for the quantum harmonic oscillator using elementary methods
Authors: Cohen S. M.
Published: September 2005

We present a purely analytical method to calculate the propagator for the quantum harmonic oscillator using Feynman’s path integral. Though the details of the calculation are involved, the general approach uses only matrix diagonalization and well-known integrals, techniques which an advanced undergraduate should understand. The full propagator, including both the prefactor and the classical action, is obtained from a single calculation which involves the exact diagonalization of the discretized action for the system.
Neutrino mass and low-temperature calorimetry
Authors: Wang Sun-chong , Zhou Jun-wei , Redi O. , Stroke H. H. , Coron N. , Leblanc J.
Published: September 2005

We describe how the problem of measuring the neutrino mass led us to the development of low-temperature calorimetry. The search for a “17-keV neutrino” concluded with a negative result, but a wide range of applications are now carried on by us and other groups in the fields of x-ray astronomy, recoil measurements of dark matter particles, high precision particle spectrometry, specific heat determinations, neutron detection, and rare decay studies. The masses of the bolometers (calorimeters) extend from 1 mg to 1 kg, nearly as large as for quantum detectors. By lowering the temperature into the 10- 20-mK range, calorimetry is on its way to substantially surpassing the high precision of particle metrology obtainable with the quantum detectors. Calorimeter developments and perspectives are discussed.
The harmonic oscillator propagator
Authors: Holstein Barry R.
Published: September 2005

The Feynman propagator for the harmonic oscillator is evaluated by a variety of path-integral-based means.
Quantitative measurement of acoustic whistlers
Authors: Adler C. L. , Mita K. , Phipps D.
Published: September 2005

We present an experimental setup capable of quantitative examination of acoustic whistlers in tubes of varying lengths and diameters. It is simple enough to be used as an undergraduate lab or classroom demonstration. The setup can be used to show the transverse modes of a cavity, and the difference between the group and phase velocity of a wave. It can also be used to determine the velocity of sound to an accuracy of 3%. We present the results of several experiments used to determine the acoustic modes present in transient whistlers. Our results differ significantly from a “geometrical acoustics” derivation of the acoustic whistler made in an earlier paper.
Ultrafast phenomena: A laboratory experiment for undergraduates
Authors: Donnelly T. D. , Grossman Carl
Published: September 2005

We present a set of experiments that introduce students to ultrafast science. We discuss the relationship between the description of an ultrashort laser pulse in the frequency domain and the time domain. Using experimental results we demonstrate that this relationship is constrained by the lower limit of the Heisenberg uncertainty principle. Students carrying out the experiments will become familiar with ultrafast techniques, such as autocorrelation and laser cavity design, as well as various other concepts such as dispersion, Fourier transformation, interference, and nonlinear optics.
Hearing the shape of a rod by the sound of its collision
Authors: Mascarenhas Francesca M. F. , Spillmann C. M. , Lindner John F. , Jacobs D. T.
Published: September 2005

We collide rods of different lengths and infer the vibrational motion of the longer rod by a spectral analysis of the resulting sound. Collisions of rods of square and circular cross sections are audibly different. While longitudinal modes of vibration do not discriminate between different cross-sectional shapes, flexural modes do, and these enable us to hear the shapes of the rods. We use a microphone, an amplifier, and a spectrum analyzer to observe the longitudinal and flexural modes of the ringing rod. With an accessible mathematical model and a simple apparatus, we obtain good agreement between theory and experiment.
Particles in a gravitational field
Authors: Odagaki Takashi , Kawai Hidetoshi
Published: September 2005

The average number of classical particles at a given height in a gravitational field is studied. For one particle, the average number increases with height and diverges at the classical turning point. We explain how the average number changes to a decreasing function of height when two or more particles are present.
A simple method for controlling chaos
Authors: Flynn Cathal , Wilson Niall
Published: September 2005

A new method for the control of chaos is presented. The procedure is based on proportional feedback and is very simple to implement. The presentation is pedagogical, and in order to illustrate the method, we apply it to the Hénon map and to the Lorenz equations. Finally, we look at the stability of the control algorithm in the presence of noise.
Cubic acres
Authors: Brownstein K. R.
Published: September 2005

The triple scalar product of the three edge vectors of a parallelpiped is ±V, where V is its volume. We point out that the triple scalar product of its three area vectors is ±V2, which could be measured in cubic acres.
A rooftop radio observatory: An undergraduate telescope system at the University of California at Berkeley
Authors: Parthasarathy R. , Frank C. , Treffers R. , Cudaback D. , Heiles C. , Hancox C. , Millan R.
Published: September 2005

We describe the 1- to 2-GHz radio telescope built by undergraduates with faculty guidance at the University of California at Berkeley. The telescope is optimized to observe the 1420-MHz (21-cm) emission line of neutral atomic hydrogen and is used in the recently created advanced undergraduate radio astronomy laboratory course, as well as in part of a graduate course on astronomical observation. We discuss the design of the telescope and the structure of the course and also present astronomical observations made with the telescope.
The optical-mechanical analogy for stationary metrics in general relativity
Authors: Alsing Paul M.
Published: September 2005

The optical-mechanical analogy allows for a common description of the motion of particles in mechanics and for light in geometrical optics. In a recent series of articles in this journal, it has been shown that the optical-mechanical analogy can be extended to general relativity for the case of static metrics expressible in isotropic coordinates. In this paper, we extend the optical-mechanical analogy in general relativity to the case of stationary metrics. A variational principle for the trajectories of both photons and particles is derived which takes the form of Fermat’s principle or the principle of Maupertuis. When the (suitably defined) spatial portion of the metric is written as or restricted to an isotropic form, exact equations of motion for both massless and massive particles are obtained in the form of Newtonian mechanics, describing objects moving in a medium with a spatially varying index of refraction. Such restrictions of the metric commonly occur, for example, when orbital motion is considered in a plane perpendicular to the axis of rotation of a rotating black hole or spacetime. The Newtonian form of the equations of geodesic motion are illustrated by applications to a uniformly rotating reference system and a rotating black hole (the Kerr metric).
Who were Fabry and Pérot?
Authors: Mulligan Joseph F.
Published: September 2005

In 1897 Charles Fabry and Alfred Pérot published their most important article on what we now call the Fabry–Pérot interferometer. Despite the great importance of this instrument for present-day research in physics and astrophysics, its inventors are almost completely unknown to most physicists. This article presents brief accounts of the life and work of Fabry and Pérot, who at the beginning of the twentieth century were highly regarded by physicists throughout the world for their contributions to optics and spectroscopy. Later they also made many important contributions to astrophysics, including Fabry’s 1913 discovery (with Henri Buisson) of the ozone layer in the Earth’s atmosphere.
Energy conservation and chaos in the gravitationally driven Fermi oscillator
Authors: Lopac V. , Dananić V.
Published: September 2005

Chaotic dynamics of the two-body conservative system, which consists of a particle of mass m bouncing elastically on a horizontal plate of mass M supported by an elastic spring, is investigated. The system integrates the properties of coupled oscillators with those of the bouncing-ball and impact oscillator problems. Results obtained by varying the mass ratio M/m and the spring constant k in numerical computations are presented in the form of time-dependent diagrams and discrete maps. The rich variety of resulting chaotic behavior includes strange attractors with fractal structure, resonant islands, crisis, and intermittency route to chaos. The system has a remarkable didactic value as an example of chaotic behavior in simple systems close to everyday experience. The integrable limit M=0 is appropriate for introducing the phase portraits and discussing the interrelationship between the shape of the potential energy curves and the resulting oscillatory motion.
Using an E-mail tutorial and student seminars to improve an intermediate-level undergraduate physics course
Authors: Finch J. D. , Hand L. N.
Published: September 2005

The authors revised the junior-level classical mechanics course at Cornell University to incorporate asynchronous, autonomous, and group learning. We created an E-mail tutorial and a student seminar. We will first discuss the theoretical background for these changes and then describe the results of their implementation over a period of three years.
Meaning of counterfactual statements in quantum physics
Authors: Stapp Henry P.
Published: September 2005

David Mermin suggests that my recent proof pertaining to quantum nonlocality is undermined by an essential ambiguity pertaining to the meaning of counterfactual statements in quantum physics. The ambiguity he cites arises from his imposition of a certain criterion for the meaningfulness of such counterfactual statements. That criterion conflates the meaning of a counterfactual statement with the details of a proof of its validity in such a way as to make the meaning of such a statement dependent upon the context in which it occurs. That dependence violates the normal demand in logic that the meaning of a statement be defined by the words in the statement itself, not by the context in which the statement occurs. My proof conforms to that normal requirement. I describe the context-independent meaning within my proof of the counterfactual statements in question.
Nonlocal character of quantum theory?
Authors: Mermin N. David
Published: September 2005

In a recent article under the above title (but without the question mark) Henry Stapp has presented arguments which lead him to conclude that under suitable conditions “the truth of a statement that refers only to phenomena confined to an earlier time” must “depend on which measurement an experimenter freely chooses to perform at a later time.” I suggest that this conclusion contains an essential ambiguity as regards the meaning of the expression “statement referring only to phenomena confined to an earlier time,” when such a statement talks about the outcome of an experiment that was not actually performed. As a result Stapp’s argumentation does not imply that future choices can affect present facts. But it does provide a wonderful and instructively different opportunity to reexamine a central point of Bohr’s famous reply to Einstein, Podolsky, and Rosen.
Propagator for the simple harmonic oscillator
Authors: Thornber Nora S. , Taylor Edwin F.
Published: September 2005

Through direct simulation with a computer program, we have verified that the published formula for the propagator of the one-dimensional simple harmonic oscillator (1DSHO), when applied in the straightforward manner in which physicists might interpret it, predicts the wrong development of the wave function for half the future times. This note presents a new and simple derivation of the (known) explicit phase factors of the normalization of the 1DSHO propagator that yield the correct development of any initial wave function for all times.
Radiative energy shifts for a nonrelativistic atom
Authors: Ford G. W. , von Waldenfels W.
Published: September 2005

The radiative shift of the energy levels of a nonrelativistic electron in an arbitrary external potential is calculated including the effects of retardation. After mass renormalization a finite (cutoff free) expression is obtained. For the Coulomb potential the result is an expression for the Lamb shift that is as simple as that obtained by Bethe [Phys. Rev. 72, 1157 (1947)] and by Welton [Phys. Rev. 74, 1157 (1948)] with the neglect of retardation. As an application, a closed-form expression is given for the shift of the levels of the three-dimensional oscillator. This latter shift vanishes with the neglect of retardation.
Experimental investigation of the “effective potential” of an inverted pendulum
Authors: Fenn Julia G. , Bayne Derek A. , Sinclair Bruce D.
Published: September 2005

The range of stability of a vertically driven inverted pendulum is explored using simple experimental techniques. The results are found to compare well with those expected from “effective potential” theory. This vindicates the use of the theory in modeling this intriguing system.
Unicycles and bifurcations
Authors: Johnson R. C.
Published: September 2005

A model of balancing upright on a unicycle has pitchfork and Hopf bifurcations, and describes riders from novice to expert with both good and not-so-good reactions.
The trajectory of a ball in lawn bowls
Authors: Cross Rod
Published: September 2005

The main objective in lawn bowls is to bowl a ball along a curved trajectory on a smooth grass surface so that it stops closer to the jack (a small white ball) than the opponent’s ball. The curvature of the path is induced by shaping the ball so that one side is heavier than the other. Some of the properties of the trajectory are described to illustrate this interesting example of precessional motion.
An advanced laboratory in nuclear-isotope mass spectroscopy
Authors: Shaheen S. A. , Shapiro M. , Becchetti F. D.
Published: September 2005

We describe an experiment in nuclear-isotope mass spectroscopy, suitable for an advanced physics laboratory, which utilizes a relatively inexpensive commercial 60°-dipole residual gas analyzer. Students measure the terrestrial abundance of the isotope Ne22 relative to Ne20 and compare this with recent measurements of this ratio in meteorites. These ratios provide clues to the astrophysical sites, astrophysical processes, and nuclear reactions which formed these isotopes. The mass spectrometer is also used as a residual gas analyzer to examine the gas composition (O2, N2, H2O,…) at various pressures in a typical vacuum system. This gives students insight into the design of vacuum apparatus including the optimal selection of components such as vacuum pumps for particular applications.
Knots and physics: Old wine in new bottles
Authors: Hirshfeld Allen C.
Published: September 2005

The history of the interplay between physics and mathematics in the theory of knots is briefly reviewed. In particular, Gauss’ original definition of the linking number in the context of electromagnetism is presented, along with analytical, algebraical, and geometrical derivations. In a modern context, the linking number appears in the first-order term in the perturbation expansion of a Wilson loop in Chern–Simons quantum field theory. New knot invariants, the Vassiliev numbers, arise in higher-order terms of the expansion, and can be written in a form which shows them to be generalizations of the linking number.
An ideal quantum gas in a finite-sized container
Authors: Pathria R. K.
Published: September 2005

The role of finite-size effects in determining the thermodynamic behavior of an ideal gas is critically examined. While classical statistics do not produce any perceptible effects, quantum statistics do yield results that play a crucial role in determining the low-temperature behavior of the given system. For illustration, we carry out an exact analysis of the ideal Bose gas in one dimension and show that at least in this case (i) the bulk term (customarily obtained by replacing the summation-over-states by an integration) yields results that are, at best, misleading, whereas (ii) the correct behavior of the system is determined almost entirely by terms representing finite-size effects. The subtle, yet distinctive, role played by the boundary conditions imposed on the system is also explored.
Triaxial bifurcations of rapidly rotating spheroids
Authors: Dankova Ts. , Rosensteel G.
Published: September 2005

A rotating system, such as a star, liquid drop, or atomic nucleus, may rotate as an oblate spheroid about its symmetry axis or, if the angular velocity is greater than a critical value, as a triaxial ellipsoid about a principal axis. The oblate and triaxial equilibrium configurations minimize the total energy, the sum of the rotational kinetic energy plus the potential energy. For a star or galaxy the potential is the self-gravitating potential, for a liquid drop, the surface tension energy, and for a nucleus, the potential is the sum of the repulsive Coulomb energy plus the attractive surface energy. A simple, but accurate, Padé approximation to the potential function is used for the energy minimization problem that permits closed analytic expressions to be derived. In particular, the critical deformation and angular velocity for bifurcation from MacLaurin spheroids to Jacobi ellipsoids is determined analytically in the approximation.
Regularization and renormalization in scattering from Dirac delta potentials
Authors: Mitra Indrajit , DasGupta Ananda , Dutta-Roy Binayak
Published: September 2005

Various regularization schemes used in quantum field theory, including the widely used dimensional regularization scheme, and the concept of renormalization, are introduced through the study of scattering from an attractive Dirac delta potential in more than one dimension. This is expected to make such advanced concepts and techniques available to enthusiastic beginners within the realm of elementary quantum mechanics.
Attempt frequency in tunneling
Authors: Price Peter J.
Published: September 2005

The nature of the “attempt frequency,” in the rate of escape of a particle from a confining structure by quantum tunneling through its outer barrier, is elucidated. It is shown that even for a general internal potential the reciprocal of the attempt frequency is equal to the formal quantum propagation time that is given by the energy derivative of the “round trip” phase change for the wave function reflected from and returning to the barrier.
Physics in Burma Today
Authors: Rigden John S.
Published: September 2005

The laws of physics are invariant in all inertial frames of reference. They are also the same in all cultural frames of reference. But the way physicists are trained, the style in which physics is practiced, and the roles of physics and physicists in academia and society differ from one cultural setting to another. Burma is no exception. There is a domestic flavor to much of Burmese physics with the Irrawaddy River, Burmese bamboo, and the music of the pattalar all an integral part of the physics scenario. Perhaps “relevancy,” a demand heard so frequently these days in the United States, has already been achieved in this small nation sandwiched between the subcontinents of China and India. In Burma, three factors exert determining influences on the subject of physics: The physical sciences are not part of the long standing cultural tradition; the students must prepare for competitive and external exams; and the opportunities for pursuing a career as a physicist are extremely limited.
Was Giordano Bruno a Scientist?: A Scientist's View
Authors: Lerner Lawrence S. , Gosselin Edward A.
Published: September 2005

Giordano Bruno has been seen as a precursor of the scientific revolution and as a martyr for modern science. We examine the significance of his arguments from a strictly scientific viewpoint. In his cosmological dialog, The Supper of Ashes, he defends the Copernican theory and discusses optics and geological change, as well as the ship experiment later to be made famous by Galileo and Gassendi. But even when correct in their conclusions, Bruno's “scientific” arguments do not exhibit any understanding of scientific reasoning or purpose. Rather they serve the totally unrelated function of allegorical descriptions of a metaphysical relationship between Man and God as well as Catholic and Protestant. Bruno sees Nature as the signature of God, and he believes that this signature can best be perceived through the hieroglyph of the Copernican theory.
Propagation of a Disturbance in a Chain of Interacting Harmonic Oscillators
Authors: Wang Y. Y. , Lee K. H.
Published: September 2005

The exponential Fourier transform method is used to study the propagation of a general disturbance along a semi-infinite chain of interacting harmonic oscillators. In addition to the harmonic coupling between nearest neighbors in simple chains, each particle is bound to its equilibrium position by an ideal spring. In contrast with previous studies on simple chains, the initial conditions (at t=0) are not specified, and the motion of all the oscillators is expressed in terms of either the specified time-dependent displacement of the end particle or the specified time-dependent external force applied to it. The inverse transforms not readily available from tables are obtained by carrying out the inversion integrals explicitly in the complex frequency plane. By specializing some results of the present work, those of previous calculations on simple chains are recovered.
Gauge Invariant Vacuum Polarization
Authors: Ferrell Richard A.
Published: September 2005

Because of its highly singular nature, the current operator in relativistic quantum electrodynamics has to be defined by a limiting process. If gauge invariance is satisfied at every stage of this process, an additional quadratically divergent term appears in the polarizability tensor. As noted by Johnson, this new term is identical to the counter term invoked in less rigorous treatments, in order to keep the photon mass equal to zero and to satisfy gauge invariance. We present here an alternative derivation of Johnson's result which is based on Ward's identity and which employs notions generally familiar to students of relativistic quantum mechanics.
Resource Letter PCP-1: Pre-College Physics Curriculum Materials
Authors: Paldy Lester G. , Swartz Clifford E.
Published: September 2005

Prepared at the request of the AAPT Committee on Resource Letters. This is one of a series of Resource Letters on different topics, intended to guide college physicists to some of the literature and other teaching aids that may help them improve course contents in specified fields of physics. No Resource Letter is meant to be exhaustive and complete; in time there may be more than one letter on some of the main subjects of interest. Comments and suggestions concerning the content and arrangement of letters as well as suggestions for future topics will be welcomed. Please send such communications to Professor Arthur Quinton, Chairman, Resource Letter Committee, Department of Physics, University of Massachusetts, Amherst, Massachusetts 01002 (current address until Fall of 1978: Prof. Arthur Quinton, Department of Nuclear Physics, Australian National University, Box 4 P.O., Canberra ACT, Australia 2600).
Consortium for the Advancement of Physics Education: Three Years of Activity
Authors: Spangler John D. , Hathaway C. E.
Published: September 2005

In January 1969, Kansas State University joined with six non-Ph.D. granting institutions to form the Consortium for the Advancement of Physics Education (CAPE). CAPE has conducted a number of programs, supported mainly by an NSF COSIP-B grant. These programs include junior-senior student symposia, senior honors research projects, junior-senior summer research assistantships, faculty summer research fellowships, and a faculty symposium on physical science teaching. In this paper we criticize the various programs on the basis of our three years of experience with CAPE, indicating the activities that appear to have been successful and to he worthy of trial in other regions, and also indicating certain activities that were less successful than we had originally hoped. We attempt to give reasons for the latter disappointments.
Some Pitfalls in Special Relativity
Authors: Chai An-Ti
Published: September 2005

The problem of observing a collision between two spaceships is utilized to illustrate the misuse of time dilation and length contraction, and the incorrect description of space-time coordinates in special relativity. By emphasizing the equivalence of all inertial frames, students can be guided to correct descriptions of space-time coordinates and to proper applications of time dilation and length contraction.
A Simple MHD Power Generator for the Student Laboratory
Authors: Alexeff Igor , Pace Marshall , Hofer Leon D. , Lonngren Karl
Published: September 2005

A simple demonstration model MHD generator has been developed using readily available toy rocket motors as a power source. Both the open-circuit voltage (several volts) and the short-circuit current (several milliamperes) can be predicted, giving students an excellent insight into the properties of this new power system.
On the Demonstration and Interpretation of the Coriolis Effect
Authors: Thompson Owen E.
Published: September 2005

The Coriolis effect, the tendency for rightward, normal acceleration of a body moving relative to a reference system rotating counterclockwise, is considered. A simple logical derivation of equations of motion in a rotating, noninertial coordinate system which contain the Coriolis and other terms is presented and analyzed. A new device is described that should have certain advantages for laboratory instruction and experimentation. A careful interpretation of the Coriolis effect is given which hopefully appeals to the most basic physical intuition. Finally, the implication of the effect for atmospheric and oceanic motion is discussed, and four provocative problems dealing with the Coriolis effect are posed for the interested reader.
Diffusion with Stochastic Jump Times
Authors: Mullins W. W.
Published: September 2005

The consequence of a randomized jump time in the random walk derivation of the diffusion coefficient D is calculated from a theorem specifying the way in which the spatial and time variances add. If the elapsed time between consecutive jumps has a mean μ = 1/v and a variance k2, then in one dimension one finds D = 12v[〈x2〉−(1−α)〈x〉2] where α = k2/μ2, and where 〈x〉 and 〈x2〉 are the first and second moment of the probability density function per jump. The ratio α is zero when the number of jumps is a definite function of the time and unity for Poisson statistics. Analogous results are obtained for three dimensions.
What's Next?—Careers for Physics Students
Authors: Listerman Thomas W.
Published: September 2005

Students attending a recent regional Society of Physics Students meeting suggested the need for special regional meetings to be held each fall to assist physics students, particularly graduating seniors, in planning their careers. Such a meeting, based on the specific agenda items suggested by these students, was held at Wright State University on 4 November 1972. The meeting was successful and might serve as a model for similar meetings in other regions. This paper gives many details regarding the agenda, arrangements, and costs of such a meeting.
Nonlinear Acoustics
Authors: Beyer Robert T.
Published: September 2005

The treatment of acoustical problems by linear equations is only a first approximation. There are nonlinear terms in the “wave equation,” in the relation equation of state of the medium, and sometimes in the boundary conditions. The effect of these nonlinearities on sound propagation in gases, liquids, and solids is reviewed and some traditional problems examined.
The Rod Contraction-Clock Retardation Ether Theory and the Special Theory of Relativity
Authors: Erlichson Herman
Published: September 2005

This paper is a historical and critical review of an ether theory which starts with rod contraction and clock retardation, and a comparison between this ether theory and the special theory of relativity. The two theories are generally equivalent since they both lead to the Lorentz transformation equations. The possibility of an experimental difference between the two theories may lie in a one-way experiment, and this subject is briefly explored with the tentative conclusion that so far it seems that no one has made a specific proposal for such a crucial one-way experiment nor has anyone conclusively demonstrated the impossibility of such a test.
A Simple Variational Formula in Quantum
Authors: Park David
Published: September 2005

If one assumes that the change in a ground-state wave function produced by a perturbing potential V is proportional to V, a general and very simple formula for the perturbation in energy results. The formula is illustrated with two examples.
Microwave Spectroscopy and Molecular Structure: Some Undergraduate Laboratory Projects
Authors: Kukolich Stephen G.
Published: September 2005

Experiments on determination of the structure of some small molecules by microwave spectroscopy are reported. These experiments are suggested for undergraduate laboratories. The apparatus is relatively simple and inexpensive and demonstrates principles of spectroscopy and electronics. The observation of rotational absorption lines demonstrates basic principles of quantum mechanics. Electric dipole moments or nuclear quadrupole coupling may be obtained from further analysis of the data. Apparatus and specific experiments on OCS, BrCN, HDO, HDS, and NH2D are described.
A Simple Variational Formula in Quantum
Authors: Mott David L.
Published: September 2005

The equations of the αβ digital filter, a computer procedure used in real-time data processing, are derived, and an appropriate transfer function is obtained using Laplace Transforms. It is then shown how α and β can be chosen to yield prescribed values of damping ratio and bandwidth.
Focal depth shifting of a time reversal mirror in a range-independent waveguide
Authors: Walker S. C. , Roux Philippe , Kuperman W. A.
Published: September 2005

A time-reversal mirror refocuses back at the original probe source position. A goal has been to refocus at different positions without model based calculations. A method to refocus at different ranges has already been developed using frequency shifting. Here we present a technique to refocus at different depths than the original probe source in a shallow ocean range-independent waveguide. The requirement is to collect data from various ranges at a single depth, as from a moving broadband radiator, over a distance sufficient to construct the relevant frequency-wave-number (f-k) structure of the waveguide. With this information, it is then possible to focus at arbitrary depth at any of the ranges that the probe source data were taken. Experimental results confirm the theory.
Symmetry and Snell’s law
Authors: Bergman David R.
Published: September 2005

A connection between the acoustic rays in a moving fluid medium (with a sound speed and subsonic flow each depending arbitrarily on position and time) and the null geodesics of a pseudo-Riemannian manifold allows one to derive several well-known results used in underwater and atmospheric acoustic ray theory from one single underlying symmetry principle, isometry. These results being well known in cases with Cartesian symmetry generalize to any system of curvilinear coordinates and three-dimensional fluid flows. Snell’s law, range, and travel time integrals for Cartesian and cylindrically symmetry systems are derived and an illustrative example presented.
The influence of spectral distinctiveness on acoustic cue weighting in children’s and adults’ speech perception
Authors: Mayo Catherine , Turk Alice
Published: September 2005

Children and adults appear to weight some acoustic cues differently in perceiving certain speech contrasts. One possible explanation for this difference is that children and adults make use of different strategies in the way that they process speech. An alternative explanation is that adult-child cue weighting differences are due to more general sensory (auditory) processing differences between the two groups. It has been proposed that children may be less able to deal with incomplete or insufficient acoustic information than are adults, and thus may require cues that are longer, louder, or more spectrally distinct to identify or discriminate between auditory stimuli. The current study tested this hypothesis by examining adults’ and 3- to 7-year-old children’s cue weighting for contrasts in which vowel-onset formant transitions varied from spectrally distinct (/no/-/mo/, /do/-/bo/, and /ta/-/da/) to spectrally similar (/ni/-/mi/, /de/-/be/, and /ti/-/di/). Spectrally distinct cues were more likely to yield different consonantal responses than were spectrally similar cues, for all listeners. Furthermore, as predicted by a sensory hypothesis, children were less likely to give different consonantal responses to stimuli distinguished by spectrally similar transitional cues than were adults. However, this pattern of behavior did not hold for all contrasts. Implications for theories of adult-child cue weighting differences are discussed.
Contextual variation in the acoustic and perceptual similarity of North German and American English vowels
Authors: Strange Winifred , Bohn Ocke-Schwen , Nishi Kanae , Trent Sonja A.
Published: September 2005

Strange et al. [J. Acoust. Soc. Am. 115, 1791–1807 (2004)] reported that North German (NG) front-rounded vowels in hVp syllables were acoustically intermediate between front and back American English (AE) vowels. However, AE listeners perceptually assimilated them as poor exemplars of back AE vowels. In this study, speaker- and context-independent cross-language discriminant analyses of NG and AE vowels produced in CVC syllables (C=labial, alveolar, velar stops) in sentences showed that NG front-rounded vowels fell within AE back-vowel distributions, due to the “fronting” of AE back vowels in alveolar/velar contexts. NG [ɪ, e, ε, ɔ] were located relatively “higher” in acoustic vowel space than their AE counterparts and varied in cross-language similarity across consonantal contexts. In a perceptual assimilation task, naive listeners classified NG vowels in terms of native AE categories and rated their goodness on a 7-point scale (very foreign to very English sounding). Both front- and back-rounded NG vowels were perceptually assimilated overwhelmingly to back AE categories and judged equally good exemplars. Perceptual assimilation patterns did not vary with context, and were not always predictable from acoustic similarity. These findings suggest that listeners adopt a context-independent strategy when judging the cross-language similarity of vowels produced and presented in continuous speech contexts.
A theoretical and numerical analysis of vibration-controlled modules for use in active segmented partitions
Authors: Leishman Timothy W. , Tichy Jiri
Published: September 2005

Many applications of active sound transmission control (ASTC) require lightweight partitions, high transmission loss over a broad frequency range, simple control strategies, and consistent performance for various source and receiving space conditions. In recent years, researchers have begun to investigate active segmented partitions (ASPs) because of their potential to meet such requirements. This paper provides a theoretical and numerical analysis of four ASP module configurations that are candidates for these applications. Analogous circuit methods are used to provide normal-incidence transmission loss and reflection coefficient estimates for their passive and active states. The active control objective for each configuration is to induce global vibration control of various transmitting surfaces through direct vibration control of a principal transmitting surface. Two characteristic single-composite-leaf (SCL) configurations are unable to use the strategy effectively. However, design adjustments are investigated to improve their performances. Two double-composite-leaf (DCL) configurations use the strategy much more effectively to produce efficient global control of transmitting surface vibrations and achieve high transmission loss over a broad frequency range. This is achieved through a minimum volume velocity condition on the source side of each module. One DCL configuration enhances module isolation in full ASP arrays while satisfying other design and performance criteria.
Speed of sound in nitrogen as a function of temperature and pressure
Authors: Hagermann Axel , Zarnecki John C.
Published: September 2005

Speed of sound measurements in nitrogen by Younglove and McCarty [J. Chem. Thermodynam. 12, 1121–1128 (1980)] are revisited and an empirical polynomial equation for the speed of sound is derived. The polynomial coefficients differ from those given by Wong and Wu [J. Acoust. Soc. Am. 102, 650–651 (1997)] with the result that discrepancies between predicted and measured values at low temperatures are reduced. The maximal error over the complete temperature and pressure range from 80 to 350 K and 0.031 to 0.709 MPa is reduced from 5.38% to 0.78%.