Testing the weak equivalence principle by differential measurements of fundamental constants in the Magellanic Clouds

Abstract

Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of the elementary particles, thereby violating the Weak Equivalence Principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, µ, and/or the fine structure constant, α, measured in different environment conditions can be used as probes for this coupling. Here we perform differential measurements of F = µα 2 to test a non-standard coupling in the Magellanic Clouds -dwarf galaxies where the overall mass budget is dominated by dark matter. The analysis is based on [C i] and CO lines observed with the Herschel Space Observatory. Since these lines have different sensitivities to changes in µ and α, the combined α and µ variations can be evaluated through the radial velocity offsets, ∆V , between the CO and [C i] lines. Averaging over nine positions in the Magellanic Clouds, we obtain ∆V = −0.02 ± 0.07 km s −1 , leading to |∆F/F | < 2 × 10 −7 (1σ), where ∆F/F = (F obs − F lab )/F lab . However, for one position observed with five times higher spectral resolution we find ∆V = −0.05 ± 0.02 km s −1 , resulting in ∆F/F = (−1.7 ± 0.7) × 10 −7 . Whether this offset is due to changes in the fundamental constants, due to chemical segregation in the emitting gas or merely due to Doppler noise requires further investigations.

Constraints on the electron-to-proton mass ratio variation at the epoch of reionization

“…for an object in the Large Magellanic Cloud located at the galactocentric distance where ρ b /ρDM < 1 we deduced ∆µ/µ = (1.7 ± 0.7) × 10 −7 (Levshakov et al 2019). Similarly, a value of ∆µ/µ = (3.5 ± 1.2) × 10 −7 was reported by Kanekar (2011) for a faint dwarf galaxy at z = 0.69 where the dark matter may prevail.…”

“…Magellanic Clouds (z = 0). Analyzing data of 9 molecular clouds in the Large and Small Magellanic Clouds, we obtained for a highest resolution spectrum of a target PDR3-NE (LMC) an offset ∆V = −0.05 ± 0.02 km s −1 between the CO(7-6) and [C i] lines (Levshakov et al, 2019). Being interpreted in terms of α 2 /µ variations, this gives ∆F/F = (−1.7 ± 0.7) × 10 −7 , or ∆µ/µ = (1.7 ± 0.7) × 10 Gravitational lens system B0218+357 (z = 0.69).…”

“…A combination of [C i]/[C ii]/CO lines, -the so-called Fine Structure Method (FSM), -has already been used in differential measurements of the fundamental physical constants in a wide redshift range -from z 0 up to z 7 (Levshakov et al 2008(Levshakov et al , 2010(Levshakov et al , 2012(Levshakov et al , 2017(Levshakov et al , 2019Curran et al 2011;Weiß et al 2012). To note is also that the FSM provides, at least, a factor of 30 more sensitive probe of the variability of physical constants than traditionally used UV and optical resonance lines of atoms and ions Kozlov et al 2008).…”

Probing the electron-to-proton mass ratio gradient in the Milky Way with class I methanol masers

“…The radial velocities VLSR in Eq. 3 are calculated as described in Levshakov et al (2019). VLSR is attributed to the line centre which is defined as a point where the first order derivative of the line profile is equal to zero.…”

Fundamental physical constants: results in search for and description of variations

“…Let us therefore present the latest experimental constraints on the quantities α/α, μp /µ p , Ġ/G. The upper laboratory constraints on α/α, obtained by comparison of optical clocks, give [21,22] | α/α| ≤ 2 • 10 −17 yr −1 , and astrophysical observations of extragalactic sources give practically the same constraint [23]. At the same time, a number of studies based on a comparative analysis of the absorption spectra of quasars located in different directions on the celestial sphere have claimed the detection of not only temporal but also spatial variations of α (the so-called Australian dipole [24]).…”