Collective Motion of Particles at Finite Temperatures
A quantum statisticai theory of frequency spectra and damping constants of the coliective motion of interacting particles at finite temperatures is presented and used to clarify several problems. The formulation is based on the explicit recognition of the fact that a set of collective variables properly chosen describes the collective motion in such a way that the average values of the collective variables at a time determine their average values thereafter. The frequency distribution of the density fluctuations in fluids is thus analyzed, and molecular expressions for the intensities and widths of the spectral lines are obtained. The widths are written in terms of generalized transport coefficients which depend upon the wavelength of the collective oscillation or the frequency spectrum. The expressions are valid even in the case in which the hydrodynamical description is inapplicable, and turn out to be useful for describing the sound attenuation in iiquid helium II at low temperatures and the inelastic scattering of neutrons by liquids. The transport coefficients of fluids are formulated in terms of equilibrium fluctuations from a new point of view without the use of the local equiiibrium ensemble. The results for the shear viscosity and thermal conductivity agree with those obtained previously. A new term, however, is found to be added to the dynamical flux determining the buik viscosity. This term arises as a result of subtracting a pressure fiuctuation associated with the fluctuation of the mass and energy densities to define a random force. (auth)
- Research Organization:
- Kyoto Univ.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-011414
- OSTI ID:
- 4714771
- Journal Information:
- Progress of Theoretical Physics (Kyoto), Vol. 28, Issue 5; Other Information: Orig. Receipt Date: 31-DEC-63; ISSN 0033-068X
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ALLOTROPY
DENSITY
DISTRIBUTION
ELEMENTARY PARTICLES
ENERGY
FLUIDS
FREQUENCY
HELIUM
HELIUM 4
HELIUM II
INELASTIC SCATTERING
INTERACTIONS
LIQUIDS
LOSSES
LOW TEMPERATURE
MASS
MOLECULES
MOTION
NEUTRONS
OSCILLATIONS
PRESSURE
QUANTUM MECHANICS
SCATTERING
SOUND
SPECTRA
STATISTICS
TEMPERATURE
THERMAL CONDUCTIVITY
TRANSPORT THEORY
VARIATIONS
VISCOSITY