ISSN:0002-9505    

DOI:10.1119/1.18898

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18826

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.19042

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

This Resource Letter provides a guide to the literature on the theory of solitons and its relevance in physics. Journal articles and books are cited for the following topics: the history of solitons, construction of soliton equations and of soliton solutions, solitons and mathematics, quantum solitons, solitons in physics and near-integrable equations.

ISSN:0002-9505    

DOI:10.1119/1.18889

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

A linear chain of point masses coupled by harmonic springs is a standard model used to introduce concepts of solid state physics. The well-ordered chain has sinusoidal standing wave normal modes (if the ends are fixed) or traveling wave normal modes (if the ends are connected in a ring). Ballistically propagating wave packets can be built from these normal modes, and illustrate the mechanism of heat propagation in insulating crystals. When the chain is disordered, new effects arise. Ballistic propagation is replaced by diffusive propagation on length scales larger than the mean free path for ballistic motion. However, a new length scale, the localization length, also enters. On length scales longer than the localization length, neither ballistic nor diffusive propagation occurs, and energy is trapped unless there are anharmonic forces. These ideas are illustrated by a computer experiment.

ISSN:0002-9505    

DOI:10.1119/1.18890

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

Klein’s paradox is shown to be resolved by a careful consideration of Feynman’s picture of antiparticles as negative energy solutions traveling backward in time. Implications associated with the spin-statistics theorem are pointed out.

ISSN:0002-9505    

DOI:10.1119/1.18891

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We consider the density functional theory from the point of view of one-dimensional two-particle systems, where the particles are either spin-1/2fermions or spin-0 bosons. The basic equations are derived and applied to the system of two coupled harmonic oscillators. An exact density functional solution is constructed from the exactly known single-particle density for this system. We demonstrate how this solution may be applied to other two-particle systems to calculate the exact single-particle density and energy.

ISSN:0002-9505    

DOI:10.1119/1.18892

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

Theoretical relations for such recession parameters as the Earth–galaxy(L)and Earth–photon(Lp)separation distances, Hubble parameter(H),universe density ratio (Ω), scale factor(R),and expansion factor distance(A)are given as functions of cosmic time(t).These relations are based on the standard flat, closed, and open models of the universe with the Einstein cosmological constantΛ=0.Comparisons are made of these models using selected values ofHoandΩo,which for each model indicate an age of the universe that is consistent with ages reported for the oldest stars.

ISSN:0002-9505    

DOI:10.1119/1.18893

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

We show how to use Schwinger’s method to evaluate determinants of differential operators that appear quite often in ordinary quantum mechanics. Although this method was introduced by Schwinger in the early fifties to compute effective actions for quantum electrodynamics and was recently applied by him in the Casimir effect, it has never been used in nonrelativistic problems. As explicit examples we compute the partition functions for both the bosonic and the fermionic harmonic oscillator.

ISSN:0002-9505    

DOI:10.1119/1.18894

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP

摘要:

When a long thin bar of a material is subject to periodic heating, a temperature wave propagates along the sample, and its propagation properties can be used to determine the thermal diffusivity of the material. In this paper, we present a simple experiment that can be used by undergraduate students to better understand thermal waves and their propagation and to measure thermal diffusivity. In spite of its simplicity, the experiment provides acceptable results for a copper sample.

ISSN:0002-9505    

DOI:10.1119/1.18899

出版商:American Association of Physics Teachers    

年代:1998

数据来源: AIP