Gravity Model Research Articles

A new look at the CO2 haven hypothesis using gravity model European Union and China

The pollution haven hypothesis (PHH) is defined as follows: a reduction in trade costs results in production of pollution-intensive goods shifting towards countries with easier environmental laws. The previous studies examined this hypothesis in the form of Kuznets' environmental hypothesis. In this way, they test the effect of foreign direct investment (FDI) on carbon emissions. However, this study investigates PHH from a new perspective. I will use Newton's gravity model to test this hypothesis. The basis of PHH is the difference in the environmental standards of the two business partners. One of the indicators used to measure the severity of a country's environmental laws is carbon emission intensity. The stricter the country's laws are, the lower the index value will be. In order to test the hypothesis, experimental data from China and OECD countries are used. China was as the pollution haven for the countries of the Organization for Economic Cooperation and Development. I found that environmental laws of host and guest countries have different effects on FDI. In addition, transportation costs have a negative effect on the FDI flow. Finally, the research results confirm the hypothesis on gravity model.

Late times ΛCDM f(T) gravity model with parameterized q(z)

According to a number of astronomical studies, the universe is currently undergoing an accelerated expansion phase. We employed the recently proposed gravity, which holds that the current accelerated expansion phase of the universe is caused by a torsion scalar. The investigation is carried out using a parameterization of [Formula: see text] (where [Formula: see text] and [Formula: see text] are the model parameters) and the [Formula: see text] using [Formula: see text] is obtained. The model shows good agreement with recent observations, such as the LCDM model at late times. Finally, we examined how the cosmological parameters behaved in for constrained values.

A multi-task stations cooperative air quality prediction system for sustainable development

In recent years, A series of environmental problems caused by air pollution have attracted widespread attention. Air quality forecasting has become an indispensable part of people’s daily life. However, the traditional air quality prediction (AQP) model WRF-CMAQ simulation system faces several challenges: (1) the fuzziness of pollutant formation mechanism; (2) the hardness of integrating the features of meteorological conditions; (3) the difficulty of cooperating among monitoring stations. To deal with these challenges, we propose a multi-task station cooperative air quality prediction (MTSC-AQP) system for sustainable development. The MTSC-AQP system contains three modules: air quality analysis, a WRF-LSTM module for initial pollutant prediction, and multi-station cooperative AQP. Through air quality analysis, it can calculate the air quality index (AQI) and analyze the correlation between pollutants and meteorological conditions. Then, the WRF-LSTM module integrates spatio-temporal multi-source data to forecast the initial concentration of pollutants. Finally, the system incorporates the gravity model to predict the final AQI. Extensive experiments conducted on real-world datasets show the effectiveness of forecasting the AQI by using the MTSC-AQP system.

The impact of international logistics performance on import and export trade: an empirical case of the “Belt and Road” initiative countries

As an important foundation of cargo transportation, logistics plays a vital role in developing international trade. Based on the international logistics performance index (LPI) and the sample data of the “Belt and Road” initiative countries from 2011 to 2022, this paper uses the extended trade gravity model to explore the impact of the logistics performance of the “Belt and Road” initiative countries on China’s import and export trade. The empirical results show that the improvement of the logistics performance level of the countries along the “Belt and Road” Initiative has a certain role in promoting the growth of China’s trade volume to the country, and the improvement of LPI has a more significant positive impact on China’s import and export to large-scale countries along the route. Finally, according to the analysis of empirical results, this paper puts forward specific suggestions to promote the development of logistics performance and import and export trade, which provides some reference value for implementing the “Belt and Road” initiative and improving national logistics and trade level.

Holographic fluids from 5D dilaton gravity

We study a solvable class of five-dimensional dilaton gravity models that continuously interpolate between anti-de Sitter (AdS5), linear dilaton (LD5) and positively curved spacetimes as a function of a continuous parameter ν. The dilaton vacuum expectation value is set by a potential localized on a flat brane. We chart the elementary properties of these backgrounds for any admissible ν, and determine stability conditions of the brane-dilaton system. We find that the spectrum of metric fluctuations can be either continuous or discrete. It features a massless graviton mode confined between the brane and the curvature singularity, and a massive radion mode tied to brane-dilaton stability. We show that, in the presence of a bulk black hole, the holographic theory living on the brane features a perfect fluid. The equation of state of the holographic fluid interpolates between radiation, pressureless matter and vacuum energy as a function of ν. This extends earlier findings on holographic fluids. Our results suggest that the thermodynamics of the fluid mirrors precisely the thermodynamics of the bulk black hole.

Inflation scenario in a non-minimal f(Q) gravity model

In the context of f(Q) gravity, cosmological inflation takes a different turn. f(Q) gravity is a modified theory of gravity, where the Lagrangian is a function of the non-metricity scalar Q. f(Q) gravity theory is part of an extensive class of modified gravity theories designed to explain the accelerated expansion of the universe without the requirement for dark energy. In this paper, we study the modified gravity f(Q) in which the scalar field is non-minimally coupled with the matter (it has a new interaction term αQ(1+ϕ2) with the inflaton scalar field (ϕ) and non-metricity scalar (Q)). In pursuit, an inflationary model is extended and investigated by determining the slow-roll parameters and obtaining the model's linear perturbations after calculating the field equation. By comparing the model parameters with the CMB observational data, the model is adapted to observational data through the constraint of the parameters. After some numerical calculations, we show our model is consistent with observational data and free of the phantom if 1<α<1.5 and 1.42<γ2<1.75.

Analysis of the spatial association network structure of China’s green innovation efficiency

Improving the green innovation efficiency (GIE) is the main approach to high-quality development in China. Identifying the spatial distribution and influencing factors of GIE is conducive to sustainable and balanced regional development. In this research, the slack based measure-data envelopment analysis model (SBM-DEA) is used to measure the GIE of 30 provinces in China from 2013 to 2023. The gravity model and social network analysis methods are used to explore the spatial correlation of GIE in the provinces. The influencing factors of GIE are analyzed by the Tobit model. The results show that: (1) During the study period, the GIE of China’s provinces presented a high level, the spatial accumulation characteristics were obvious and the spatial correlation showed a complex network structure; (2) The association network is still in the primary stage, and the network strength and network association degree are low; (3) Provinces with strong innovation ability do not affect the green innovation of other provinces. In addition, these regions have obtained higher innovation linkage benefits from other provinces; (4) The amount of patent, education and government support have a significant positive impact on GIE, while total energy consumption and the secondary industry’s share of the gross domestic product have a significant negative impact on GIE. This study will reveal the characteristics of green innovation behavior of China from a new perspective, and provide a scientific basis for the formulation of green innovation behavior and related policies of China.

A new view on estimating China's capital flight through the travel channel

AbstractThis paper proposes a novel approach to quantitatively estimating the magnitude of China's capital flight through the travel channel from 2014 to 2019. We set 2014 as the break point to account for a change in the methodology of compiling outbound travel expenditure and adopt a counterfactual method to calculate the magnitude of China's capital flight through the travel channel. Our results show that, from 2014 to 2019, China's capital flight through the travel channel reached a total of US$602 billion, with a quarterly average of about US$25 billion, accounting for about 40% of the total Chinese outbound travel expenditure. We further construct a gravity model using data from the United Nations' World Tourism Organisation to empirically show that China's capital flight tends to flow to economies with a high degree of financial development and often appears when the RMB depreciates against the US dollar.

Urban Green Infrastructure Connectivity: The Role of Private Semi-Natural Areas

Green spaces and blue spaces in cities provide a wealth of benefits to the urban social–ecological system. Unfortunately, urban development fragments natural habitats, reducing connectivity and biodiversity. Urban green–blue infrastructure (UGI) networks can mitigate these effects by providing ecological corridors that enhance habitat connectivity. This study examined UGI connectivity for two indicator species in a rapidly developing city in the southern United States. We mapped and analyzed UGI at a high resolution (0.6 m) across the entire city, with a focus on semi-natural areas in private land and residential neighborhoods. Integrating graph theory and a gravity model, we assessed structural UGI networks and ranked them based on their ability to support functional connectivity. Most of the potential habitat corridors we mapped in this project traversed private lands, including 58% of the priority habitat for the Golden-cheeked Warbler and 69% of the priority habitat for the Rio Grande Wild Turkey. Riparian zones and other areas with dense tree cover were critical linkages in these habitat corridors. Our findings illustrate the important role that private semi-natural areas play in UGI, habitat connectivity, and essential ecosystem services.

Comparing geophysical inversion and petrophysical measurements for northern Victoria Land, Antarctica

Summary Bedrock geology from Antarctica remains largely unknown since it is hidden beneath thick ice sheets. Geophysical methods such as gravity and magnetic inverse modelling provide a framework to infer crustal rock properties indirectly in Antarctica. However, due to limited availability of rock samples, validation against direct geological information is challenging. We present a new rock property catalogue containing density and susceptibility measurements on 320 rock samples from northern Victoria Land. This catalogue is used to assess the reliability of local and regional scale inverse results, including a new local high resolution magnetic inversion in the Mesa Range region and a previously published regional scale joint inversion of gravity and magnetic data in northern Victoria Land and the Wilkes Subglacial Basin. We compare our density and susceptibility measurements to global and local measurements from the literature to access the correlation to rock types and geological units. Furthermore, the measured values are compared against inverted values. The close correspondence between inverted and measured rock properties allows us to predict locations of rock types where currently such information is missing. The utility of measured susceptibility and density relationships for interpreting inversion output provides a strong incentive to incorporate local rock samples into geophysical studies of subglacial geology across Antarctica.

Environmental, Geographical, and Economic Impacts of Inbound Tourism in China: A Mixed-Effects Gravity Model Approach

This study examines the dynamics of inbound tourism in China, utilizing a mixed-effects gravity model to analyze data from urban clusters around China’s three major airports. The research methodology of the study includes applying advanced econometric techniques, such as the Poisson pseudo-maximum likelihood estimation, to ensure robust and accurate results. The study focuses on international tourist arrivals and foreign exchange earnings, identifying key drivers such as tourism resources, transportation safety, and service quality. Our findings indicate a 10% increase in per capita GDP correlates with a 0.88% rise in inbound tourist numbers. Additionally, proximity to major urban centers like Beijing, Shanghai, and Guangzhou significantly influences tourist arrivals, with every 100 km increase in distance resulting in a 5.56% decrease in tourist numbers. The study also explores the impact of environmental factors on tourism, suggesting that improvements in green coverage and reductions in industrial waste and traffic fatalities could enhance tourist arrivals. Conversely, environmental protection measures can both positively and negatively impact tourism. This research provides a strategic blueprint for policymakers and professionals in tourism and environmental sustainability, emphasizing the importance of integrated environmental sustainability in tourism development strategies. The model accounts for up to 79% of the variability in inbound tourism flows, offering robust evidence that economic and policy dimensions impact tourism.

Multidimensional Evaluation of Altimetry Marine Gravity Models with Shipborne Gravity Data from a New Platform Marine Gravimeter

With the development of satellite altimetry technology and the application of new altimetry satellites, the accuracy and resolution of altimeter-derived gravity field models have improved over the last decades. Nowadays, they are close enough to shipborne gravimetry. In this paper, multi-source shipborne gravity data in the South China Sea were taken to evaluate the accuracies of two high-precision altimeter-derived marine gravity field models (SS V30.1, DTU17). In these shipborne gravity data, there are dozens of routes’ ship gravimetry data, obtained from the National Geophysical Data Center (NGDC); data were tracked from a marine survey with a commercial marine gravimeter (type KSS31M), and data were tracked from a marine gravimetry campaign that was conducted with a newly developed platform gravimeter (type JMG) in the South China Sea in September 2020. After various data filtering, processing, and calibrations, the shipborne gravity data were validated with crossover points analysis. Then, the processed shipborne data were employed to evaluate the accuracy of the altimeter-derived marine gravity field models. During this procedure, the quality of JMG shipborne gravity data was compared with the results of KSS31M and NGDC data. Analysis and evaluation results show that the crossover points verification accuracies of KSS31M and JMG are 0.70 mGal and 1.61 mGal, which are much better than the accuracy of NGDC, which is larger than 8.0 mGal. In the area where the bathymetry changes slowly, the root mean square error values between altimetry gravity models and KSS31M data are respectively 3.28 mGal and 4.54 mGal, and those of the JMG data are respectively 2.94 mGal and 2.60 mGal. According to the above results, we can conclude that the JMG has the same 1–2 mGal accuracy level as KSS31M and can meet the measurement requirements of marine gravity.

Energy flow of λ in Hořava-Lifshitz cosmology

Hořava-Lifshitz gravity has been proposed as a renormalizable and ghost-free quantum gravity model candidate with an anisotropic UV-scaling between space and time. We present here a cosmological background analysis of two different formulations of the theory, with particular focus on the running of the parameter λ. Using a large dataset consisting of cosmic microwave background data from , Pantheon+supernovae catalog, SH0ES Cepheid variable stars, baryon acoustic oscillations (BAO), cosmic chronometers, and gamma-ray bursts (GRB), we arrive at new bounds on the cosmological parameters, in particular λ, which runs logarithmically with energy and describes deviation from general relativity, which corresponds to λ=1 For the detailed balance scenario we arrive at the bound λ=1.0406±0.0023, and for beyond detailed balance the limit reads λ=1.0064±0.0002. We also study the influence of different datasets and priors, and we find that removing low-redshift data generally moves λ closer toward UV values, while simultaneously widening the error bars. In the detailed balance scenario, this effect is more noticeable, and without prior λ≥1 it takes on values that are significantly below unity. Published by the American Physical Society 2024

Nonparametric estimation of the gravity model of migration: application of partitioning Poisson estimates to Japanese inter-municipal migration by age–sex group

Nonparametric estimation of the gravity model of migration: application of partitioning Poisson estimates to Japanese inter-municipal migration by age–sex group

Coupling coordination analysis on digital economy-tourism development-ecological environment

Growth-oriented tourism has caused global environmental degradation. The digital economy is widely regarded as a strategic engine of sustainable tourism, creating new potential for eco-environmental improvement by increasing innovation and efficiency, optimizing tourism sustainability management, and promoting sustainable tourist behavior. To reveal the coordination associations of the digital economy, tourism development, and ecological environment (DTE) and achieve sustainability in tourist destinations, this study aims to explore the DTE coupling coordination. We used the coupling coordination model to explore the coupling coordination degree of the DTE in 30 provinces in China from 2011 to 2021. Using Markov and modified gravity model, the dynamic evolution and spatial correlation intensity of the coupling coordination were examined, and influencing factors were determined by applying the GTWR model. The evaluation indices of the digital economy, tourism, and environment steadily increased but with significant spatial disequilibrium. The dominant trend was shifting from a lagging digital economy to lagging tourism development. Temporally, the coupling coordination state experienced a mild imbalance transformation to a near imbalance and a large gap with excellent coordination. Spatially, the coupling coordination is characterized by decreasing steps in the eastern, central, and western regions. The coupling coordination has regional diffusion and spatial correlation phenomena. Third, economic development, opening up, and government support positively affected the coupling coordination. Industrial structure had a fluctuating impact on the coupling coordination, and urbanization and transportation accessibility had a negative effect. Our study emphasizes the importance of DTE coordination development. Policymakers should consider these dynamics when promoting sustainable tourism practices in the digital age.

Cosmological constraints on f(Q) gravity models in the non-coincident formalism

The article investigates cosmological applications of f(Q) theories in a non-coincident formalism. We explore a new f(Q) theory dynamics utilizing a non-vanishing affine connection involving a non-constant function γ(t)=−a−1H˙, resulting in Friedmann equations that are entirely distinct from those of f(T) theory. In addition, we propose a new parameterization of the Hubble function that can consistently depicts the present deceleration parameter value, transition redshift, and the late time de-Sitter limit. We evaluate the predictions of the assumed Hubble function by imposing constraints on the free parameters utilizing Bayesian statistical analysis to estimate the posterior probability by employing the CC, Pantheon+SH0ES, and the BAO samples. Moreover, we conduct the AIC and BIC statistical evaluations to determine the reliability of MCMC analysis. Further, we consider some well-known corrections to the STEGR case such as an exponentital f(Q) correction, logarithmic f(Q) correction, and a power-law f(Q) correction and then we find the constraints on the parameters of these models via energy conditions. Finally, to test the physical plausibility of the assumed f(Q) models we conduct the thermodynamical stability analysis via the sound speed parameter.

Identification of composite ecological corridors and spatial planning guidance in built-up areas under the concept of park city: Taking Shenyang City Center as an example.

The concept of park city provides a new model for the integrated utilization of multiple elements in built-up areas. Ecological corridors, as key components of urban ecosystem, play a major role in facilitating information flow and material exchange between various ecological spaces within built-up area. We identified ecological (mixed) spaces in Shenyang using points of interest data on the ArcGIS 10.2 platform and considered them as sources. Using the least-cost model and gravity model, we identified potential ecological corridors with high, medium, and low resistance on the resistance surface, and proposed the spatial planning guidance strategy based on the distribution characteristics of potential corridors. The results showed that the number of ecological (mixed) spaces in the study area significantly increased during 2017-2022. The ecological resistance surface showed an outward expansion trend with continuous accumulation of resistance in the core area. There was an increase of one high-resistance and one medium-resistance potential corridor, and an increase of nine low-resistance potential corridors. However, there were problems, such as a single corridor network structure, the exacerbation of ecological isolation, and continuous accumulation of resistance. Based on the concept of park city and the spatial distribution characteristics of potential corridors, we put forward a spatial planning guidance strategy to strengthen the support system of composite space corridors.

FREmu: Power Spectrum Emulator for f(R) Gravity

To investigate gravity in the nonlinear regime of cosmic structure using measurements from stage IV surveys, it is imperative to accurately compute large-scale structure observables, such as nonlinear matter power spectra, for gravity models that extend beyond general relativity. However, the theoretical predictions of nonlinear observables are typically derived from N-body simulations, which demand substantial computational resources. In this study, we introduce a novel public emulator, termed FREmu, designed to provide rapid and precise forecasts of nonlinear power spectra specifically for the Hu–Sawicki f(R) gravity model across scales 0.0089h Mpc−1 < k < 0.5h Mpc−1 and redshifts 0 < z < 3. FREmu leverages principal component analysis and artificial neural networks to establish a mapping from parameters to power spectra, utilizing training data derived from the Quijote-MG simulation suite. With a parameter space encompassing seven dimensions, including Ω m , Ω b , h, n s , σ 8, M ν , and fR0 , the emulator achieves an accuracy exceeding 95% for the majority of cases, thus proving to be highly efficient for constraining parameters.

Response of the Northeast China grain market to climate change based on the gravity model approach

Scientific evidence has revealed that climate change negatively affects agricultural crop production both regionally and globally. Previous studies have indicated that the role of climate change is significant in some parts of China. Thus, assessing the impact of the future climate on the grain market is vital for ensuring regional and national food security. In this study, regional climate model (RCM 4.5 and 8.5) simulations were employed to investigate the role of future climate change on a major grain-producing market in China (Northeast China). For this purpose, historical (2004–2017) and future (2020–2076) data were applied in the gravity model to examine the effects of climate change on the Northeast China grain market. The results revealed that the maximum temperature is a crucial climate factor that significantly affects the grain market. The analysis revealed that precipitation was positively related and that the temperature was significantly negatively related to domestic consumption and exports of rice, maize, and soybean. Moreover, the analysis of the RCM (4.5 and 8.5) simulations revealed a negative contribution of the maximum temperature to domestic consumption and export levels. Overall, the analysis enhances our understanding of the impacts of climate change on the Northeast China grain market.

Fuzzy Gravity: Four‐Dimensional Gravity on a Covariant Noncommutative Space and Unification with Internal Interactions

AbstractIn the present work, an extended description of the covariant noncommutative space is presented, which accommodates the Fuzzy Gravity model constructed previously. It is based on the historical lesson that the use of larger algebras containing all generators of the isometry of the continuous one helped in formulating a fuzzy covariant noncommutative space. Specifically a further enlargement of the isometry group leads the authors, in addition to the construction of the covariant noncommutative space, also to the suggestion of the group that should be gauged on such a space in order to construct a Fuzzy Gravity theory. As a result, two Fuzzy Gravity models are obtained, one in de Sitter and one in anti‐de Sitter space, depending on the extension of the isometry group, and their spontaneous symmetry breaking leading to fuzzy versions of the noncommutative gravity are discussed. In addition, how to introduce fermions in the fuzzy gravity is discussed for the first time, and even more importantly, how to unify the constructed noncommutative‐fuzzy gravity with internal interactions based on or as grand unified theories.