Stochastic gravity and turbulence

We study the ensemble average of the thermal expectation value of an energy momentum tensor in the presence of a random external metric. In a holographic setup this quantity can be read off of the near boundary behavior of the metric in a stochastic theory of gravity. By numerically solving the associated Einstein equations and mapping the result to the dual boundary theory, we find that the non relativistic energy power spectrum exhibits a power law behavior as expected by the theory of Kolmogorov and Kraichnan.

Determinants efficiency of Vietnam’s footwear export: A stochastic gravity analysis

This study was conducted to estimate the determinants as well as the efficiency of Vietnam’s footwear export to 50 trading partners by applying stochastic fronter gravity approach for the period 2001-2018. We found that Vietnam’s footwear export is positively affected by income measured by gross domestic product (GDP), border and landlock situation. The income elasticity of footwear export of Vietnam was about 1.2%. We also showed that the export efficiency of Vietnam’s footwear was not very high with the average ranges from 50.8% to 63.1%. The 10 most efficient countries were Cambodia, Panama, Slovakia, Belgium, Myanmar, Hongkong, Korea, Chile, the US and the Netherlands. We also found that 10 countries with the largest export potential were the US, China, Germany, Japan, Belgium, the UK, Netherlands, Korea, France, Canada. Regarding the determinants of export efficiency, the study provides evidence that trade freedom, financial freedom and importers’ population density positively contributed to efficiency. Our findings also support further integration of Vietnam since membership to many FTA enhances Vietnam’s footwear export efficiency. These FTAs include AFTA, Vietnam-Chile FTA, ASEAN-India FTA, ASEAN-Korean FTA, ASEAN-Japan FTA, ASEAN-China FTA, ASEAN-Australia-New Zealand FTA. Finally, the study recommends a relevant market policy for Vietnam’s footwear export in the coming years. We have provided 4 types of markets with different levels of priorities that Vietnam’s footwear exporters should focus on. The top footwear market priority should be countries with high potential yet low efficiency such as China, Russia, Brazil, Thailand, Sweden, Singapore and Australia.

A hybrid gravity and route choice model to assess vector traffic in large-scale road networks

Human traffic along roads can be a major vector for infectious diseases and invasive species. Though most road traffic is local, a small number of long-distance trips can suffice to move an invasion or disease front forward. Therefore, understanding how many agents travel over long distances and which routes they choose is key to successful management of diseases and invasions. Stochastic gravity models have been used to estimate the distribution of trips between origins and destinations of agents. However, in large-scale systems, it is hard to collect the data required to fit these models, as the number of long-distance travellers is small, and origins and destinations can have multiple access points. Therefore, gravity models often provide only relative measures of the agent flow. Furthermore, gravity models yield no insights into which roads agents use. We resolve these issues by combining a stochastic gravity model with a stochastic route choice model. Our hybrid model can be fitted to survey data collected at roads that are used by many long-distance travellers. This decreases the sampling effort, allows us to obtain absolute predictions of both vector pressure and pathways, and permits rigorous model validation. After introducing our approach in general terms, we demonstrate its benefits by applying it to the potential invasion of zebra and quagga mussels ( Dreissena spp.) to the Canadian province British Columbia. The model yields an R 2 -value of 0.73 for variance-corrected agent counts at survey locations.

Stochastic Gravity and Ontological Quantum Mechanics

Some physicists surmise that gravity lies outside of quantum mechanics. Thus theories like the standard semiclassical theory of quantum to gravity coupling (that of Rosenfeld and Møller) are possible real models of interaction, rather than a mere approximation of a theory of quantum gravity. Unfortunately, semiclassical gravity creates inconsistencies such as superluminal communication. Alternatives by authors such as Diósi, Martin, Penrose, and Wang often use the term 'stochastic' to set themselves apart from the standard semiclassical theory. These theories couple to fluctuations caused by for instance continuous spontaneous localization, hence the term 'stochastic'. This paper looks at stochastic gravity in the framework of a class of emergent or ontological quantum theories, such as those by Bohm, Cetto, and de Broglie. It is found that much or all of the trouble in connecting gravity with a microscopic system falls away, as Einstein's general relativity is free to react directly with the microscopic beables. The resulting continuous gravitational wave radiation by atomic and nuclear systems does not, in contrast to Einstein's speculation, cause catastrophic problems. The small amount of energy exchanged by gravitational waves may have measurable experimental consequences. A very recent experiment by Vinante et al. performed on a small cantilever at mK temperatures shows a surprising non-thermal noise component, the magnitude of which is consistent with the stochastic gravity coupling explored here.

Efficiency of India’s Agricultural Exports

This article is an empirical study employing various time-invariant and time-varying specifications of a stochastic gravity model of trade. It enumerates the inefficiency component among the determinants of Indian agricultural export flows to 112 partner countries, over the years 2000–2013. The panel study finds empirical support for high yet decreasing home country inefficiency or ‘behind-the-border’ constraints to trade. Also significance of regional groups ASEAN, SAFTA and Africa shows that trade policy concentrating on developing countries have been successful export policies. Thus, the export efficiency scores help in articulating future policy initiatives for diversification of the country’s exports according to the significance and level of efficiency of partners. Nevertheless, literal interpretations of the efficiency scores are sensitive to the nature of modelling and their specifications.