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

The polarization of Cosmic Microwave Background (CMB) photons is rotated asthey pass through (ultralight-) axion string loops. Studying this birefringencecan reveal valuable information about the axion-photon coupling and thestructure of the string network. We develop an approximate analytic formalismand identify a kernel function that can be used to calculate the two-pointcorrelation function for CMB birefringence induced by an arbitrary axion stringnetwork. Using this formalism, we evaluate the birefringence signal for somesimple loop distributions (including scaling and network collapse). We findthat the angular correlation function has a characteristic angular scale set by$\theta_\mathrm{min}$, which corresponds to the angular extent of the loops atthe time of recombination. This results in a peak in the birefringence powerspectrum around $\ell_p \sim 1/\theta_\mathrm{min}$. An additional scale,controlled by the axion's mass, is introduced if the network collapses beforetoday.

CMB birefringence from ultra-light axion string networks