Quasar absorption lines provide a precise test of whether the fine-structure constant, α, is the same in different places and through cosmological time. We present a new analysis of a large sample of ...quasar absorption-line spectra obtained using the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) in Chile. We apply the many-multiplet method to derive values of Δα/α≡ (α
z
−α0)/α0 from 154 absorbers, and combine these values with 141 values from previous observations at the Keck Observatory in Hawaii. In the VLT sample, we find evidence that α increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample provided evidence for a smaller α in the distant absorption clouds. Upon combining the samples, an apparent variation of α across the sky emerges which is well represented by an angular dipole model pointing in the direction RA = 17.3 ± 1.0 h and Dec. =−61°± 10°, with amplitude
. The dipole model is required at the 4.1σ statistical significance level over a simple monopole model where α is the same across the sky (but possibly different from the current laboratory value). The data sets reveal remarkable consistencies: (i) the directions of dipoles fitted to the VLT and Keck samples separately agree; (ii) the directions of dipoles fitted to z < 1.6 and z > 1.6 cuts of the combined VLT+Keck samples agree; and (iii) in the equatorial region of the dipole, where both the Keck and VLT samples contribute a significant number of absorbers, there is no evidence for inconsistency between Keck and VLT. The amplitude of the dipole is clearly larger at higher redshift. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with 'lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 ± 0.2) × 10−6 GLyr−1 and the model is significant at the 4.2σ confidence level over the null model (Δα/α≡ 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in α. To the best of our knowledge, this result is not in conflict with any other observational or experimental result.
Observations of the redshift
= 7.085 quasar J1120+0641 are used to search for variations of the fine structure constant, a, over the redshift range 5:5 to 7:1. Observations at
= 7:1 probe the physics ...of the universe at only 0.8 billion years old. These are the most distant direct measurements of a to date and the first measurements using a near-IR spectrograph. A new AI analysis method is employed. Four measurements from the x-shooter spectrograph on the Very Large Telescope (VLT) constrain changes in a relative to the terrestrial value (α
). The weighted mean electromagnetic force in this location in the universe deviates from the terrestrial value by Δα/α = (α
- α
)/α
= (-2:18 ± 7:27) × 10
, consistent with no temporal change. Combining these measurements with existing data, we find a spatial variation is preferred over a no-variation model at the 3:9σ level.
We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of 0.4 ≤ z
abs ≤ 2.3 observed on the Very Large Telescope (VLT) using the Ultraviolet ...and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of Δα/α = (0.22 ± 0.23) × 10−5, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular, we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of Δα/α measurements, thus unnecessarily reducing the overall precision. We further show that fitting absorption systems with too few velocity components also results in a significant increase in the scatter of Δα/α measurements, and in addition causes Δα/α error estimates to be systematically underestimated. These results thus identify some of the potential pitfalls in analysis techniques and provide a guide for future analyses.
Fine-structure constant measurements 13 Ga ago, plus lower redshift data, test space-time variation of a fundamental constant.
Observations of the redshift
z
= 7.085 quasar J1120+0641 are used to ...search for variations of the fine structure constant, α, over the redshift range 5:5 to 7:1. Observations at
z
= 7:1 probe the physics of the universe at only 0.8 billion years old. These are the most distant direct measurements of α to date and the first measurements using a near-IR spectrograph. A new AI analysis method is employed. Four measurements from the
x
-
shooter
spectrograph on the Very Large Telescope (VLT) constrain changes in a relative to the terrestrial value (α
0
). The weighted mean electromagnetic force in this location in the universe deviates from the terrestrial value by Δα/α = (α
z
− α
0
)/α
0
= (−2:18 ± 7:27) × 10
−5
, consistent with no temporal change. Combining these measurements with existing data, we find a spatial variation is preferred over a no-variation model at the 3:9σ level.
Observations of the redshift z=7.085 quasar J1120+0641 have been used to search for variations of the fine structure constant, alpha, over the redshift range 5.5 to 7.1. Observations at z=7.1 probe ...the physics of the universe when it was only 0.8 billion years old. These are the most distant direct measurements of alpha to date and the first measurements made with a near-IR spectrograph. A new AI analysis method has been employed. Four measurements from the X-SHOOTER spectrograph on the European Southern Observatory's Very Large Telescope (VLT) directly constrain any changes in alpha relative to the value measured on Earth (alpha_0). The weighted mean strength of the electromagnetic force over this redshift range in this location in the universe is da/a = (alpha_z - alpha_0)/alpha_0 = (-2.18 +/- 7.27) X 10^{-5}, i.e. we find no evidence for a temporal change from the 4 new very high redshift measurements. When the 4 new measurements are combined with a large existing sample of lower redshift measurements, a new limit on possible spatial variation of da/a is marginally preferred over a no-variation model at the 3.7 sigma level.
We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of \(0.4 \leq z_{abs} \leq 2.3\) observed on the Very Large Telescope (VLT) using the ...Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of \(\Delta\alpha/\alpha=\left(0.22\pm0.23\right)\times10^{-5}\), consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of \(\Delta\alpha/\alpha\) measurements, thus unnecessarily reducing the overall precision. We further show that fitting absorption systems with too few velocity components also results in a significant increase in the scatter of \(\Delta\alpha/\alpha\) measurements, and in addition causes \(\Delta\alpha/\alpha\) error estimates to be systematically underestimated. These results thus identify some of the potential pitfalls in analysis techniques and provide a guide for future analyses.
Chimeras of the catalytic subunits of the gastric H,K-ATPase and Na,K-ATPase were constructed and expressed in LLC-PK 1 cells. The chimeras included the following: (i) a control, H85N (the first 85 ...residues comprising the cytoplasmic N terminus
of Na,K-ATPase replaced by the analogous region of H,K-ATPase); (ii) H85N/H356â519N (the N-terminal half of the cytoplasmic
M4âM5 loop also replaced); and (iii) H519N (the entire front half replaced). The latter two replacements confer a decrease
in apparent affinity for extracellular K + . The 356â519 domain and, to a greater extent, the H519N replacement confer increased apparent selectivity for protons relative
to Na + at cytoplasmic sites as shown by the persistence of K + influx when the proton concentration is increased and the Na + concentration decreased. The pH and K + dependence of ouabain-inhibitable ATPase of membranes derived from the transfected cells indicate that the H519N and, to
a lesser extent, the H356â519N substitution decrease the effectiveness of K + to compete for protons at putative cytoplasmic H + activation sites. Notable pH-independent behavior of H85N/H356â519N at low Na + suggests that as pH is decreased, Na + /K + exchange is replaced largely by (Na + + H + )/K + exchange. With H519N, the pH and Na + dependence of pump and ATPase activities suggest relatively active H + /K + exchange even at neutral pH. Overall, this study provides evidence for important roles in cation selectivity for both the
N-terminal half of the M4âM5 loop and the adjacent transmembrane helice(s).
(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in ...Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current laboratory value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model Delta alpha/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.
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