Anomalous phonon dispersion in helium II |
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| Affiliation: | 1. Spectroscopy Department, Physics Division, National Research Centre, 33 El-Behouth St., Dokki, 12622 Cairo, Egypt;2. Photochemistry Department, National Research Centre, 33 El-Behouth St., Dokki, 12622 Cairo, Egypt;3. Organometallic and Organometalloid Chemistry Department, National Research Centre, 33 El-Behouth St., Dokki, 12622 Cairo, Egypt |
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| Abstract: | The present contribution reviews the experimental and theoretical developments to date in understanding the anomalous dispersion in the long-wavelength limit in superfluid 4He. Threshold energies for the occurrence of three-phonon processes are analysed in detail. Experimental studies are briefly outlined, their results compared and critically analysed. Besides giving details of phenomenological approaches, an attempt is made to sketch continuum models, some microscopic theories, studies based on sum rules and the polarization potential approach. |
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