Space-time Variations Research Articles

The fine structure constant: a review of measurement results and possible space-time variations

A brief description of the main methods for determining the fine structure constant is given. It is shown that the exact value of the fine structure constant is important for the new International System of Units and for fundamental metrology. Recent measurement results and theoretical calculations of the fine structure constant, as well as its possible space-time variations, are presented. The results of laboratory experiments on the search for long-term variations of the fine structure constant are presented. The astrophysical and cosmological observational data on possible variability of the fine structure constant are presented. The possibility of slightly lower values of the fine structure constant in the remote past as compared to its modern value, as well as the existence of unresolved problems related to possible space-time variations of the fine structure constant and the spread of the results of its precise laboratory measurements, are noted. Despite the absence of experimentally confirmed long-term variations of the fine structure constant at a high level of accuracy, possible practical applications of the results are noted, namely, the construction of an optical frequency standard with high stability and frequency reproduction accuracy based on the ytterbium-171 ion and a laser frequency synthesizer which may replace the caesium frequency standard.

Disease mapping with individual level information; a case study of acute myocardial infarction mortality.

Disease mapping with individual level information; a case study of acute myocardial infarction mortality.

Colluding rhino poachers exploit space–time variation in opportunity and risk

ABSTRACTHuman behavior shapes both our impact on nature and the success of solutions to safeguard it. We used crime opportunity and deterrence theory, together with methods from epidemiology, to link space–time patterns in 560 rhino poaching incidents (2011–2021) to poacher and ranger behavior in a South African rhino stronghold. Poaching activity was significantly associated with proximity to ranger camps. Together with supplementary evidence we present from internal investigations, this suggests that criminal syndicates collude with some rangers to facilitate poaching. Poachers repeatedly targeted specific regions of the reserve for set periods before shifting, mirroring the “near‐repeat” behavior observed for other crimes. Poachers also avoided tourist activity and minimized time on the reserve. Results suggest poachers strategically leverage space–time variation in opportunity and risk. Solutions based on these behavioral insights include early response to space–time clusters of poaching, spatially targeted implementation of rhino dehorning, and bolstering ranger resilience to the corrupting influence of criminal syndicates.

Space and Time Dynamics of Honeybee (Apis mellifera L.)-Melliferous Resource Interactions Within a Foraging Area: A Case Study in the Banja Luka Region (Bosnia & Herzegovina).

Interactions between honeybees and the environment are often difficult to achieve, particularly when the purpose is to optimize beekeeping production. The present study proposed to monitor the space-time variations of melliferous resources potentially exploited by colonies within a foraging area in Bosnia & Herzegovina, characterized by contrasting landscapes. The combination of methods involving Geographical Information Systems, floristic monitoring, and modelling enabled honey production potential to be calculated for the entire foraging area. In particular, the location of taxa, their abundance, diversity, and phenology enabled us to determine the spatial distribution and temporal variation of production potential. Robinia pseudoacacia and Rubus sp. made a major contribution. This potential was highly contrasted, with distant areas from the apiary more attractive than closer ones, depending on the moment. Specific periods, such as June were particularly conducive to establishing a high potential. Forest and grassland played a major role in the temporal succession, mainly because of the area covered, but moments with lower potential were supported by specific land uses (orchards). Land uses with a small surface area, such as orchards, wasteland, and riparian zones had a high potential per unit area, and improving the production potential within a foraging area could involve increasing these specific surfaces.

Assessing the influence of model inputs on performance of the EMT + VS soil moisture downscaling model for a large foothills region in Northern Colorado

Assessing the influence of model inputs on performance of the EMT + VS soil moisture downscaling model for a large foothills region in Northern Colorado

Constraints on Evolutions of Fundamental Constants from Clustering of Fast Radio Burst Dispersion Measure

Abstract Constrained measurements of fundamental physical constants using astronomical observational data represent a powerful method for investigating potential new physics. In particular, the dispersion measure (DM) of fast radio bursts (FRBs), which probes the electron density along their propagation paths, may be influenced by the spacetime variation of the fine-structure constant α. In this study, we analyze the cross-correlation signal between foreground galaxies and the DM of background FRBs to constrain the evolution of α. Assuming large-scale structure galaxy surveys with the capabilities of the China Space Station Telescope at z = 0.15 and a mock FRB survey with N FRB = 105 at z = 0.4, we test how well α variation can be constrained, with a standard deviation of σ(Δα/α) = 0.0007 at z = 0.15. Furthermore, taking into account the nonminimal coupling between the scalar field and the electromagnetic field, the variation in α can lead to the nonconservation of the photon number along geodesics. This would result in a violation of the CDDR and affect the evolution of the cosmic microwave background (CMB) temperature. In this work, we obtain constraint results on the CDDR parameter η and the parameter β governing CMB temperature evolution at z = 0.15, yielding σ(η) = 0.0004 and σ(β) = 0.0006, respectively. Finally, we relate the variation in α to the time evolution of the proton-to-electron mass ratio, reporting a standard deviation of σ(Δμ/μ) = 0.002 at z = 0.15. Future FRB surveys hold significant potential for advancing our understanding of the evolution of fundamental physical constants.

Spatiotemporal Variations Affect DTPA-Extractable Heavy Metals in Coastal Salt-Affected Soils of Arid Regions

The concept of metal bioavailability in soils is increasingly becoming the key to addressing potential risks. Yet, space–time variations of heavy metal concentrations in salt-affected soils is still vague. The current work, therefore, is the first attempt to address spatial and seasonal analyses of heavy metals in a Mediterranean arid agroecosystem. This study was conducted in a coastal area in northeastern Egypt as an example. The DTPA-extractable concentrations of Cr, Co, Cu, Fe, Pb, Mn, Ni, and Zn in addition to the main properties of 70 georeferenced soil samples (0–30 cm) were determined during the wet (March) and dry (September) seasons. The results revealed that except for Cu, the concentrations of all the determined metals stood below the safe limits. On average, the concentrations of Cu were 4.1- and 5-fold the acceptable limit of 0.20 mg kg−1, respectively. The statistical analysis indicated that seasonal variations greatly affect the concentrations of Mn, Ni, and Zn. Compared with the wet season, significant increases of 1.25, 1.50, and 1.28-fold in the concentrations of these metals occurred during the dry season, respectively. The principal component analysis affirmed that the presence of Cr, Co, Fe, and Ni was closely related to geogenic factors; meanwhile, agronomic practices were likely the main inputs of Cu, Pb, and Zn. The geostatistical analysis illustrated that the geographic variability of Cr, Fe, Mn, and Zn was due to interactions of natural and stochastic processes. Farming practices controlled the spatial variability of Ni, Pb (in the wet period), and Co (in the dry period). The effect of natural processes during the wet period was evident for Cu, which showed strong spatial variability. The kriged maps showed that the concentrations of Co, Fe, and Ni tended to increase seaward and were found to be affected by pH, salt ions, and exchangeable Na+. Moreover, both silt and organic matter content had profound impacts on the spatial distribution of Cr, while the distributions of Cu, Pb, and Zn were linked to that of CaCO3 content. The suggested mechanisms governing metal bioavailability were sorption and complexation with ligands (for Co, Fe, and Ni), redox potential (for Cr), dissolution–precipitation (for Mn), and ion exchange (for Cu, Pb, and Zn). The results of this study affirm that drying–wetting cycles and spatial distribution affect the bioavailability of heavy metals in coastal salt-affected soils of arid regions. These findings imply that seasonality (wet and dry) and spatiality should be considered for monitoring and rehabilitation of degraded soils under similar ecological conditions.

Time-space characteristics of emergency medical service attendance and layperson naloxone administration during non-fatal opioid overdoses in Rhode Island: A retrospective, event-level analysis.

Time-space characteristics of emergency medical service attendance and layperson naloxone administration during non-fatal opioid overdoses in Rhode Island: A retrospective, event-level analysis.

Precision determination of an excited-state hyperfine splitting of cadmium ions

Precision determination of the hyperfine splitting (HFS) of cadmium ions is useful to study space-time variation of fundamental physical constants and isotope shifts. In this work, we present the precision frequency measurement of the excited-state 2P3/2 hyperfine splitting of 111,113Cd+ ions using the laser-induced fluorescence technique. By introducing the technology of sympathetic cooling and measuring the doublet line transition exploitation of an optical comb system, the uncertainties are improved to 16 and 12 kHz, respectively, two orders of magnitude higher precision than the reported results from the linear transformation of isotope shifts. The magnetic dipole constants AP3/2 of 111Cd+ and 113Cd+ are estimated to be 395 939(8) and 411 275(6) kHz, respectively. The difference between the measured and theoretical hyperfine structure constants indicates that more physical effects are required to be considered in the theoretical calculation and provides critical data for the examination of deviation from King-plot linearity in isotope shifts.

Unraveling the Depths: Serpentinite Distribution and Hydrogen Potential in the Subduction Zones of NW South America

Serpentine bodies, primarily formed through the hydration of mafic and ultramafic rocks, exhibit distinctive geophysical properties in the convergent margin of NW South America. This region features a complex subduction zone that includes a suture zone and a lithospheric tear, which control serpentinite outcrops' distribution and depth geometry. By analyzing gravity and magnetic anomalies, geothermal data, Vp/Vs ratio tomography, and magnetotelluric and gas measurements, we investigated the subsurface connections of serpentinite bodies, particularly within the Romeral Suture Zone (RSZ) and the Eastern Cordillera of Colombia. The main findings indicate that serpentinite occurrences are associated with specific geophysical anomalies and seismicity patterns, highlighting their role in subduction dynamics. Vp/Vs ratio tomography and space-time variations of apparent resistivity reveal deeper serpentinite diapirism on both sides of the volcanic arc, likely linked to buoyant advection from the subducted plates, affecting magmatism and earthquake distribution. The Caldas Tear could respond to the subduction geometry and the distribution of serpentinites, suggesting an interaction between tectonic processes and serpentinization. These insights enhance the understanding of subduction zone mechanics and the potential for natural hydrogen generation in serpentinized rocks, contributing to the broader knowledge of geotectonic evolution and renewable energy resource potential in subduction environments.

Constraints on the Variation of the Fine-structure Constant at 3 < z < 10 with JWST Emission-line Galaxies

Abstract We present constraints on the spacetime variation of the fine-structure constant α at redshifts 2.5 ≤ z &lt; 9.5 using JWST emission-line galaxies (ELGs). The galaxy sample consists of 621 high-quality spectra with strong and narrow [O iii] λλ4959,5007 doublet emission lines from 578 galaxies, including 232 spectra at z &gt; 5. The [O iii] doublet lines are arguably the best emission lines to probe the variation in α. We divide our sample into six subsamples based on redshift and calculate the relative variation Δα/α for the individual subsamples. The calculated Δα/α values are consistent with zero within 1σ at all redshifts, suggesting no time variation in α above a level of (1–2) × 10−4 (1σ) in the past 13.2 billion yr. When the whole sample is combined, the constraint is improved to be Δα/α = (0.2 ± 0.7) × 10−4. We further test the spatial variation in α using four subsamples of galaxies in four different directions on the sky. The measured Δα/α values are consistent with zero at a 1σ level of ∼2 × 10−4. While the constraints in this work are not as stringent as those from lower-redshift quasar absorption lines in previous studies, this work uses an independent tracer and provides the first constraints on Δα/α at the highest redshifts. With the growing number of ELGs from JWST, we expect to achieve stronger constraints in the future.

Vertical kinematics of the young Galactic clusters

ABSTRACT The young disc vertical phase is paramount in our understanding of Galaxy evolution. Analysing the vertical kinematics at different Galactic regions provides important information about the space–time variations of the Galactic potential. The vertical phase snail shell structure identified in Gaia Data Release 2 includes a wide age range. However, the structure of the $V_Z \ \mathrm{ versus} \ Z$ diagram appears linear when the analysis is limited to studying objects younger than 30 Ma. Based on the vertical velocity and height-over-disc maps obtained for a sample of young open clusters, this method also allows the matter density in the solar neighbourhood to be estimated using a completely different approach than previously found in the literature. We use two different catalogues of star clusters to confirm the previous result and study new age ranges. The linear pattern between $V_Z$ and Z shows different slopes, $\partial V_Z/\partial Z$, for various age groups. The results fit a simple model (harmonic oscillator) of in-plane decoupled vertical dynamics up to a certain age limit, corresponding to $\sim$30 Ma. This work also analyses the relationship between the local volumetric density of matter ($\rho _0$) and the disc vertical kinematics for different age ranges, all below 50 Ma. The best estimates of the effective volumetric mass density in the solar neighbourhood, 0.09–0.15 M$_\odot$ pc${}^{-3}$, agree with those given by other authors, assessing the reliability of the proposed dynamical model. These values are a minorant of the actual matter density in the region.

A search for the fine-structure constant evolution from fast radio bursts and type Ia supernovae data

The search for a space-time variation of the fundamental constants has been explored over the years to test our physical theories. In this paper, we use the dispersion measure (DM) of fast radio bursts (FRB) combined with type Ia supernovae (SNe) data to investigate a possible redshift evolution of the fine-structure constant (α), considering the runaway dilaton scenario, which predicts Δα/α = - γln(1+z), where γ is a constant proportional to the current value of the coupling between the dilaton field and hadronic matter. We derive all the relevant expressions for the DM dependence concerning the fine-structure constant and constrain the parameter γ from measurements of 17 well-localized FRBs and 1048 SNe data from the Pantheon compilation. We also use Monte Carlo simulations to forecast the constraining power of larger samples of FRB measurements for data sets with N = 500 and N = 1000 points. We found that the uncertainty on γ can be improved by one order of magnitude and that limits on Δα/α beyond σ ∼ 10-2 will depend crucially on better control of statistical and systematic uncertainties of upcoming FRB data.

Detection of infrasound sources using three-years array data in 2019-2021 deployed at the Lützow-Holm Bay region, Antarctica

Time-space variations of infrasound source locations for three years, 2019-2021, were studied byusing a combination of two local arrays in the Lützow-Holm Bay region (LHB), Antarctica. The local arrays deployed at two coastal outcrops clearly detected temporal variations in signal frequency content as well as propagating directions during the three years. A large number of infrasound sources were detected with many located to the north and north-west directions from the arrays. These events were generated within the Southern Indian Ocean and the northern part of LHB with frequency-content of a few seconds; these “microbaroms” are believed to originate from oceanic swells. From austral summer to fall additional infrasound sources are determined to be located to the north-east. These sources might be related to the effects of katabatic winds across the continental coastal area. Furthermore, several impulsive infrasound events during the winter had higher predominant frequencies of a few Hz, higher than the microbaroms. On the basis of a comparison of source locations with sea-ice and glacier distribution form MODIS satellite images, these high-frequency sporadic sources may be cryo-seismic signals associated with cryosphere dynamics near the local arrays. These results suggest that infrasound waves can be used to monitor surface environments in the coastal area of Antarctica.

Analysis on Spatial-temporal Characteristics and Driving Factors of PM2.5 in Heilongjiang Province in the Past 20 years

PM2.5 is an important indicator for measuring the degree of air pollution. Studying the space-time variation and the driving factors of spatial heterogeneity is important for controlling air pollution and improving regional air quality. Based on PM2.5 remote sensing data from 2000 to 2021, the Theil-Sen Median trend analysis, Mann-Kendall significant inspection, and spatial auto correlation were used to analyze the characteristics of space-time changes in PM2.5 concentration, and geographical detectors were combined with a multi-scale geographical weighted regression model to explore the key driver factor and its influence and direction of the impact and role of PM2.5 spatial differences. The results showed that： ① The average PM2.5 value of Heilongjiang Province was between 22.01 and 41 μg·m-3 from 2000 to 2021. From 2008 to 2015, the average PM2.5 value was higher than the secondary concentration limit （35 μg·m-3） of the "Environmental Air Quality Standard." The turning point of the PM2.5 concentration change that occurred in 2013 generally showed the trend of change and then a downward trend. Winter was the high incidence season for PM2.5 pollution. The PM2.5 concentration space was a distributed pattern in the south and north and the high-value zone was mainly based on Harbin, Daqing City, and the surrounding area. The low-value areas were distributed in the northern regions such as the Great Khingan Mountains Region and Heihe City. ② Factor detection results indicated that the average annual temperature was the most important driving factor that affected PM2.5 spatial differences. The remaining key driver factors were in turn： high-end, population density, average annual wind speed, land use, night lights, annual years precipitation, slope, annual relative humidity, and NDVI. Interactive detection showed that the interpretation of PM2.5 points after interaction was higher than a single factor after interaction, indicating that affecting PM2.5 spatial difference was the result of the common effect of each driver factor. The effect of natural factors was more obvious than that of social and economic factors. ③ The effect of different influence factors on PM2.5 had a significant spatial difference. The average annual temperature, average annual relative humidity, population density, and night lighting played a promotion effect on PM2.5 pollution and NDVI and land use played an inhibitory effect on PM2.5 pollution. PM2.5 was significantly different from the action role of various influencing factors and the average annual temperature, annual average wind speed, and NDVI impact scale were the smallest, with a variable bandwidth of 43； population density and land use impact scale were the largest, with a variable bandwidth of 140.

Modeling the Effects of Local Species Concentrations on the Selectivity of a Modified Cobalt Phthalocyanine Catalyst for CO2 Reduction to Produce Methanol

Methanol is a desirable end-product from CO2 reduction as it serves as a drop-in renewable fuel for the current fuel and transportation economy. Cobalt Phthalocyanine (CoPc) is an effective electrocatalyst to convert CO2 into methanol by preventing C-C coupling. In prior work with gas-fed CO2 electrolyzers, it has been shown that methanol production is suppressed when the relative concentration of CO2 to CO increases, as reaction sites for CO to methanol are blocked [1]. Therefore, having knowledge of the local concentrations of CO2 and CO can be significant to improve understanding and interpretation of experimental data. To probe these effects of mass-transfer in a gas-fed CO2 flow cell, we develop a three-dimensional computational model of the gas flow adjacent to the gas diffusion electrode. Different flow rates (1-30 ml/min) and partial pressure of the feed CO2 gas (0.02 - 1 atm) are modeled concurrently with inputs of experimentally measured partial current densities for methanol, carbon monoxide, and hydrogen formation. Model predictions determine space-time variations in the concentrations of all relevant reactant and product species. These are correlated with the relative concentrations of CO2 and CO on the measured reaction rates and selectivity. Results highlight that methanol production only occurs at sufficiently low mass flow rates or partial pressures of CO2 reactant gas, leading to low relative CO2 to CO concentrations. The value of the companion model developed is that it identifies the maximum value of the relative CO2 to CO concentration in the reactor that still yields methanol. Future predictive modeling studies can harness these local CO2:CO concentrations to relate to methanol productivity. Additionally, the modeling framework developed is applicable to probe and identify CO2 electrolyzer design/operating conditions that can enhance the relative concentration of CO as compared to CO2.[1] Yao et al. (2024) Electrochemical CO2 Reduction to Methanol by Cobalt Phthalocyanine: Quantifying CO2 and CO Binding Strengths and Their Influence on Methanol Production. ACS Catalysis DOI:10.1021/acscatal.3c04957

An assessment of the coverage of live-birth registration across space in Nigeria

ABSTRACT Birth registration is an important channel that allows children to be documented, providing them with legal identity and nationality early in life and protecting them against violence, abuse and exploitation. However, this privilege has been denied to millions of children, particularly in developing countries. Registration is limited in Nigeria with about three in every five births unregistered. Using data from three waves of the Nigeria Demographic and Health Survey, we adopt a geostatistical model to assess the space-time variations in registration coverage across Nigeria and compute the exceedance maps at different probabilities. The findings indicate a North-South divide in coverage but with improved coverage over time across the country. The probability of attaining about 60% coverage is low in the northern part of the country. The generated maps provide guiding tools to the Nigerian government to set priorities in order to scale up birth registration coverage in the country.

Automated position control of tunnel boring machine during excavation using deep reinforcement learning

Automated position control of tunnel boring machine during excavation using deep reinforcement learning

Constraints on the variation of physical constants, equivalence principle violation, and a fifth force from atomic experiments

The aim of this paper is to derive limits on various forms of “new physics” using atomic experimental data. Interactions with dark energy and dark matter fields can lead to space-time variations of fundamental constants, which can be detected through atomic spectroscopy. In this study, we examine the effects of a varying nuclear mass mN and nuclear radius rN on two transition ratios: the comparison of the two-photon transition in atomic hydrogen with the hyperfine transition in Cs133 based clocks, and the ratio of optical clock frequencies in Al+ and Hg+. The sensitivity of these frequency ratios to changes in mN and rN enables us to derive new limits on the variations of the proton mass, quark mass, and the QCD parameter θ. Additionally, we consider the scalar field generated by the Yukawa-type interaction of feebly interacting hypothetical scalar particles with Standard Model particles in the presence of massive bodies such as the Sun and Moon. Using the data from the Al+/Hg+, Yb+/Cs, and Yb+(E2)/Yb+(E3) transition frequency ratios, we place constraints on the interaction of the scalar field with photons, nucleons, and electrons for a range of scalar particle masses. We also investigate limits on the Einstein equivalence principle (EEP) violating term (c00) in the Standard Model extension (SME) Lagrangian and the dependence of fundamental constants on gravity. Published by the American Physical Society 2024

Constraints on the Spacetime Variation of the Fine-structure Constant Using DESI Emission-line Galaxies

We present strong constraints on the spacetime variation of the fine-structure constant α using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize ∼110,000 galaxies with strong and narrow [O iii] λ λ4959, 5007 emission lines to measure the relative variation Δα/α in space and time. The [O iii] doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our galaxy sample spans a redshift range of 0 < z < 0.95, covering half of all cosmic time. We divide the sample into subsamples in 10 redshift bins (Δz = 0.1), and calculate Δα/α for the individual subsamples. The uncertainties of the measured Δα/α are roughly between 2 × 10−6 and 2 × 10−5. We find an apparent α variation with redshift at a level of Δα/α = (2–3) × 10−5. This is highly likely to be caused by systematics associated with wavelength calibration, since such small systematics can be caused by a wavelength distortion of 0.002–0.003 Å, which is beyond the accuracy that the current DESI data can achieve. We refine the wavelength calibration using sky lines for a small fraction of the galaxies, but this does not change our main results. We further probe the spatial variation of α in small redshift ranges, and do not find obvious, large-scale structures in the spatial distribution of Δα/α. As DESI is ongoing, we will include more galaxies, and by improving the wavelength calibration, we expect to obtain a better constraint that is comparable to the strongest current constraint.