English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We analyze the peculiar infrared instability that characterizes stationaryinhomogeneous flows when their velocity crosses the sound speed by decreasingvalues. For definiteness, we work in the context of one dimensional atomic Bosecondensates. These flows are unstable under ultra low real frequencyperturbations because of the unbounded mode amplification near the sonichorizon. This results in a condensation of low frequency phonons which producesa spatially structured flow in the supersonic domain. Numerical simulationsreveal that this zero-frequency undulation suppresses the instability when itsspatial extension is infinite, and when its phase is near that of a "shadowsoliton" solution attached to the sonic horizon. These phenomena are akin tothe condensation of rotons in flowing superfluid helium-4 when exceeding theLandau velocity. They also pertain to shallow water waves propagating ontranscritical flows.

Suppression of infrared instability in trans-sonic flows by condensation of zero-frequency short wave length phonons