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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Motivated by tension between the predictions of ordinary cold dark matter(CDM) and observations at galactic scales, ultralight axionlike particles(ULALPs) with mass of the order $10^{-22}~{\rm eV}$ have been proposed as analternative CDM candidate. We consider cold and collisionless ULALPs producedin the early Universe by the vacuum realignment mechanism and constituting mostof CDM. The ULALP fluid is commonly described by classical field equations.However, we show that, like QCD axions, the ULALPs thermalize by gravitationalself-interactions and form a Bose-Einstein condensate, a quantum phenomenon.ULALPs, like QCD axions, explain the observational evidence for caustic ringsof dark matter because they thermalize and go to the lowest energy stateavailable to them. This is one of rigid rotation on the turnaround sphere. Bystudying the heating effect of infalling ULALPs on galactic disk stars and thethickness of the nearby caustic ring as observed from a triangular feature inthe IRAS map of our galactic disk, we obtain lower-mass bounds on the ULALPmass of order $10^{-23}$ and $10^{-20}~{\rm eV}$, respectively.

New astrophysical bounds on ultralight axionlike particles