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

Aims. To validate the Einstein equivalence principle (local positioninvariance) by limiting the fractional changes in the electron-to-proton massratio, mu = m_e/m_p, measured in Galactic plane objects. Methods. Highresolution spectral observations of dark clouds in the inversion line ofNH3(1,1) and pure rotational lines of other molecules (the so-called ammoniamethod) were performed at the Medicina 32-m and the Effelsberg 100-m radiotelescopes to measure the radial velocity offsets, Delta RV = V_rot - V_inv,between the rotational and inversion transitions which have differentsensitivities to the value of mu. Results. In our previous observations(2008-2010), a mean offset of <Delta RV> = 0.027+/-0.010 km/s [3 sigmaconfidence level (C.L.)] was measured. To test for possible hidden errors, wecarried out additional observations of a sample of molecular cores in2010-2013. As a result, a systematic error in the radial velocities of anamplitude ~0.02 km/s was revealed. The averaged offset between the radialvelocities of the rotational transitions of HC3N(2-1), HC5N(9-8), HC7N(16-15),HC7N(21-20), and HC7N(23-22), and the inversion transition of NH3(1,1) <DeltaRV> = 0.003+/-0.018 km/s (3 sigma C.L.). This value, when interpreted in termsof Delta mu/mu= (mu_obs - mu_lab)/mu_lab, constraints the mu-variation at thelevel of Delta mu/mu < 2*10^{-8} (3 sigma C.L.), which is the most stringentlimit on the fractional changes in mu based on astronomical observations.

Limits on the spatial variations of the electron-to-proton mass ratio in the Galactic plane