Swampland Conjecture and Inflation Model from Brane Perspective

Over the past few decades, inflation models have been studied by researchers from different perspectives and conditions in order to introduce a model for the expanding universe. In this paper, we introduce a modified f(R) gravitational model as (R + γRp ) in order to examine a new condition for inflation models. Given that our studies are related to a modified f(R) gravitational model on the brane, therefore we will encounter modified cosmological parameters. So, we first introduce these modified cosmological parameters such as spectral index, a number of e-folds and etc. Then, we apply these conditions to our modified f(R) gravitational model in order to adapt to the swampland criteria. Finally, we determine the range of each of these parameters by plotting some figures and with respect to observable data such as Planck 2018.

Spatial effect of port service coordination of Yangtze River Delta in China based on fuzzy clustering and gravitational model

With the prevalence of international trade protectionism and transformation and upgrading of domestic market structure, the contradiction between demand and competitive development port market of the Yangtze River Delta in China has become increasingly prominent. Nineteen major ports of Yangtze River Delta in China were selected, using the methods of factor analysis, fuzzy clustering, gravitational model, the spatial effects in the hinterland were calculated from three dimensions: central potential, spatial gravity and distribution convenience, and the regional coordination of port services was analyzed. The results show that the potential of Shanghai Port and Ningbo-Zhoushan Port in China is stronger, and the distribution difference is quite obvious. The spatial gravity of each port city superimposes to form an obvious dense semi-circular zone, and the participation ability of the marginal ports is weak. The distribution convenience in hinterland changes from location-dependent to traffic-dependent. The service gap in the hinterland of the port system is more significant, but the expansions of spatial effects make regional coordination gradually improve.

Quantitative evidence for leapfrogging in urban growth

Urban growth can take different forms, such as infill, expansion and leapfrog development. Here we focus on leapfrogging, which is characterised as new urban development bypassing vacant land. Analysing a sample of 100 global locations, we study the probability that land cover is converted from non-urban to urban as a function of the minimum distance to existing urban cells. The probability decreases with the distance but in many of the considered real-world samples it increases again just before the maximum possible distance. Comparing these empirical findings with numerical ones from a gravitational model, we discover that the characteristic increase can be found in both. Our results indicate that the conversion probability as a function of the distance to urban land cover includes three urban growth domains. (i) Expansion of existing settlements, (ii) discontinuous development of coincidental new settlements rather close to existing ones and (iii) leapfrogging of new settlements far away from existing ones. We conclude that gravitational effects can explain discontinuous development but leapfrogging can be attributed to a scarcity of developable land at long distances to settlements.

A study on causality in f(R,ϕ,X) theory

The [Formula: see text]-essence modified [Formula: see text] gravity model, i.e. [Formula: see text] theory is studied. The question of violation of causality, in the framework of Gödel-type universes, is investigated in this gravitational model. Causal and noncausal solutions are allowed. A critical radius for noncausal solution is calculated. It is shown that the violation of causality depends on the content of matter.

A gravitational model extended by institutional and cultural factors for Colombian foreign trade

Gravitational models are currently a commonly used methodology to analyze the behavior of countries' trade flows. These studies typically seek to measure the impact of distance and the size of economies as factors that increase or decrease the propensity to trade between countries. Instead of using the traditional model, this paper introduces two distance variables which are built as modernity factors of culture and productive and institutional apparatus that give some evidence the importance of the economic and institutional stability of the countries to favor trade flows. The new model is tested using historical data of Colombia foreign trade between 1995 and 2015 (which is the most updated year publicly available).

Evaluation of the correspondence matrix by the Poisson method based on data from the online service for searching for car companions

For effective functioning of transport systems, information on spatial distribution of transport flows is necessary both at the current moment and for future periods. Traditional methods of obtaining observation results require very high costs, In addition, there is a high probability of obtaining low-quality data due to the strong influence of the human factor. The disadvantage of automated methods of traffic flow inspection is the high cost of equipment. The paper proposes a method for obtaining data on spatial distribution of passenger flows using constant monitoring of the online service of joint trips. To illustrate the possibilities of this approach, the online service for searching for car companions was used on the example of Sverdlovsk region. The correspondence matrix is constructed using a gravitational model applying the Poisson method. The Gauss - Seidlitz iterative method is used to find unknown parameters of the model. The assessment of quality and adequacy of the constructed model values of correspondence was carried out. It is shown that the spatial distribution of traffic flows obtained on the basis of data from online services for searching for car companions is well described by a gravitational model with a piecewise constant gravity function. Based on the analysis of the observed correspondence matrix, it was found that traffic flows between Yekaterinburg and all other cities of the Sverdlovsk region significantly exceed traffic flows between these cities.