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Heisenberg and interaction representations in thermo field dynamics (1992)

Evans, T. S. ; Hardman, I. ; Umezawa, H. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

Journal of Mathematical Physics 33 (1992), S. 370-378

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ISSN: 1089-7658

Source: AIP Digital Archive

Topics: Mathematics , Physics

Notes: In this paper the so-called α degree of freedom appearing in thermal quantum field theory is discussed, using thermo field dynamics (TFD). This paper is confined to stationary thermal situations, both nonequilibrium and equilibrium. The main result is that when the stationary number distribution differs from the equilibrium one the use of time ordered and antitime ordered formalisms picks up α=1 and α=0, in contrast to the general belief that the Feynman diagram method is usable for any other α as well. This situation in TFD will be compared with the other approaches. The reason why the Feynman diagram method becomes available for any α in the case of the equilibrium distributions is also studied.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.529915

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Effects of presence of a circumpolar region on buoyancy-driven circulation (1994)

Ishikawa, I. ; Yamanaka, Y. ; Suginohara, N.

Springer

Journal of oceanography 50 (1994), S. 247-263

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ISSN: 1573-868X

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract Effects of the presence of a circumpolar region on buoyancy-driven circulation are investigated by using an idealized numerical ocean model. Comparison of circulation and meridional density (heat) transport is made between a closed ocean and an ocean with a cyclic gap near its southern boundary. The presence of the circumpolar region leads to disconnection of the meridional overturning across the circumpolar region. And the circumpolar eastward flow reaches the bottom of the ocean. It is essential for this that the pycnocline is deeper than the bottom of the gap. Since the amount of the mass transported northward must return southward at the levels deeper than the bottom of the cyclic gap, the weak stratification, hence weak vertical geostrophic shear, at the deeper levels leads to inactive communication across the circumpolar region. Meridional heat transport across the circumpolar region is made mainly by horizontal diffusion for the ocean with the cyclic gap, while the contribution of the advection is dominant for the closed ocean. Sensitivity of meridional heat transport to change in horizontal diffusivity is studied. The meridional heat transport for the ocean with the cyclic gap is more sensitive than for the closed ocean. The change in heat transport occurs not only in the circumpolar region but also in the rest of the ocean. It is suggested that subgrid scale phenomena, especially mesoscale eddies, in the circumpolar region controls the whole ocean to a great extent.