ISSN:0002-9505    

DOI:10.1119/1.16213

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16214

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16216

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16217

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

This Resource Letter provides a guide to the literature on the integral and fractional quantum Hall effects. The letter E after an item indicates elementary level or material of general interest to persons becoming informed in the field. The letter I, for intermediate level, indicates material of somewhat more specialized nature; and the letter A indicates rather specialized or advanced material. An asterisk (*) indicates articles that are especially useful or interesting; a double asterisk (**) indicates those articles to be included in an accompanying reprint book.

ISSN:0002-9505    

DOI:10.1119/1.16218

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The variational methods of classical field theory may be applied to any theory with an action that is invariant under local gauge transformations. What is the significance of the resulting Noether current? This article examines such currents for both Abelian and non‐Abelian gauge theories and provides an explanation for their form and limited range of physical significance on a level accessible to those with a basic knowledge of classical field theory. Several of the more subtle aspects encountered in the application of the residual local gauge symmetry found by Becchi, Rouet, Stora, and Tyutin are also considered in detail in a self‐contained manner.

ISSN:0002-9505    

DOI:10.1119/1.16219

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The correction of an erroneous textbook derivation on electrical charge relaxation in conductors is discussed. The actual decay in a good conductor is damped oscillatory instead of the simple exponential decay that is often claimed, while short wavelength disturbances spread through the medium much like particles of massm=ℏωp/〈v2〉, where ωpis the plasmon frequency and 〈v2〉 is the mean‐square electron velocity.

ISSN:0002-9505    

DOI:10.1119/1.16220

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

What rate (Pd) of energy transfer is attainable by a Maxwell’s demon who sorts gas molecules serially; and how much time (td) does it take to achieve a designated temperature difference ΔTacross a partition? Two estimates are made, using (i) the energy–time form of Heisenberg’s uncertainty principle and (ii) classical kinetic theory. For a dilute gas, at ∼300 K, the uncertainty principle impliesPd103years. These bounds are loose, but are of interest because this is one of few elementary applications of the energy–time uncertainty principle. With similar assumptions, classical kinetic theory implies much tighter bounds:Pd4×106years. The kinetic theory approach allows an extension of Brillouin’s demonstration that the second law of thermodynamics cannot be violated by a Maxwell’s demon using light signals.

ISSN:0002-9505    

DOI:10.1119/1.16221

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

NMR‐absorption signals in a 2‐cm3sample of glycerol can be observed in a small permanent magnet producing a field of 50 mT. Observing the beat frequency between the marginal oscillator used as spin detector and the Larmor frequency of the spin system after excitation with 10‐ to 20‐ μs high‐frequency pulses, the free‐induction decay and spin echoes can be detected. The experiment is capable of demonstrating the principles of NMR tomography, e.g., the Carr–Purcell sequence, inversion recovery, and image formation in a field gradient.

ISSN:0002-9505    

DOI:10.1119/1.16222

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The sum of a one‐dimensional, truncated harmonic oscillator potential and square well of the same range, defined in the positive half‐space, serves as a convenient and instructive example for which the Schrödinger equation may have both bound‐state and continuum solutions. A superposition of these solutions is used in a study of barrier penetration by a wave packet representing a particle with an initial position in the region of the potential well. The presence or absence of a bound state in the superposition is shown to be the key factor determining the evolution of the wave packet. If no bound state exists, the probability of the particle having a position within the potential well is a monotonically decreasing function of time. If the superposition includes a bound state, however, this probability oscillates slightly because of an interference between the bound‐state and continuum components of the wavefunction.

ISSN:0002-9505    

DOI:10.1119/1.16223

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP