Article Abstract:
An analysis of the excitation spectrum of superfluid helium confined in porous aerogel glass explains the microscopic origin of the macroscopic fluid behavior. Neutron inelastic scattering estimations of the spectrum show that the elementary excitations, rotons, influence the system's behavior near the superfluid transition temperature. The effective mass of the rotons increases and their lifetime decreases in the system as compared to an unconfined disordered system. There are no theoretical explanations regarding the changes in the system.
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Article Abstract:
It is possible to directly observe the phase-space trajectories of fluctuations in a dynamical system by using analogue electronic circuits. This approach can play a valuable role in identifying a key difference between fluctational motion, in which the system is removed from a stable state, and relaxational motion, in which the system returns to this state. This technique has made it possible to identify new dynamical features of large fluctuations, and will be important for future experiments on natural systems.
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Article Abstract:
Quantized vortices in superfluid 3He surrounding a smooth wire can slowly unwind themselves, precessing as they unwind, a finding derived from an experiment measurement of the quantum value of circulation. R.E. Packard and colleagues achieved this startling result by determining the quantum of circulation kappa in superfluid 3He. The experiment used a thin wire pulled taught along the axis of a 2.96 millimeter diameter brass cylinder filled with superfluid 3He.
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