A Method for Theoretical Innovation in Economics

How can more theoretical innovation in economics be stimulated? Clues to the answer can be derived from the work of theorists who have been recognised for their innovative contributions to economic theory and from the philosophy of scientific progress. This paper takes the view that scientific progress is propelled by the need to address unsolved problems. From problem theory it is derived that these unsolved problems are generated by inconsistent assumptions and slows down theoretical progress for as long as such problems remain unsolved. Gifted economic theorists intuitively recognise logical inconsistencies, and employ various abductive reasoning strategies to find assumptions that remove these inconsistencies. Their research often produces new inconsistencies, and so triggers further theoretical innovation by others. A rational reconstruction of the seminal work of Nobel Prize winners Kydland and Prescott (1977) provides a running illustration, and shows that an understanding of the structure of economic problems can allow more economists to deliver innovative theoretical work.

Integrating authoritative disciplinary voices in postgraduate writing

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Die rol van ekonomiese integrasie in die ekonomiese ontwikkeling van Suider-Afrika met spesifiek verwysing na Suid-Afrika, Zambië, Zimbabwe en Malawi

M.Com. (Economics)The main purpose of the study was to investigate the role of economic integration in the economic development of the member states of an envisaged economically integrated Southern African bloc, that would include South Africa. The study contends that economic development will be aided, if economic integration were implemented correctly. Economic integration will influence both the allocation and distribution elements of the involved countries' wealth. Since economic development is inextricably entwined with the distribution of wealth, economic integration would have to give special attention to its effect on the distribution of wealth between countries. The mainstream theory of economic integration, however, places much more emphasis on the allocation aspect of integration than the distribution aspect. This imbalance means that economic integration, implemented according to the guidelines of the mainstream theory, will be detrimental to the economic development of especially the less developed countries. The orthodox approach to economic integration should therefore be adapted to the circumstances of developing countries. A suitable economic integration approach should comprise two steps. The first step involves the identification of areas for profitable specialisation, and the second the formulation of an economic integration strategy within the framework of a dirigiste approach to economic development. Porter's theory of the competitive advantage of nations served as the foundation for the formulation of the approaches to both economic development and economic integration in Southern Africa. Industry segments in which profitable specialisation could take place, were identified for South Africa, Malawi, Zambia and Zimbabwe by means of Porter's statistical method, and afterwards classified in clusters. The development and integration approaches will be centred around the various identified clusters with competitive advantage

Small Specialty Coffee Farmers’ Decision-Making Factors in an Asymmetric Information Market Environment

The global “Specialty Coffee” (SC) market is expected to grow from USD 53.67 Billion in 2021 to USD 152.69 Billion by 2030, at a CAGR of 12.32% during the forecast period 2022-2030. This growth mainly depends on prices coordinating the SC supply chain through information exchange. However, the current coffee price crisis threatens the sustainability of the coffee industry and the livelihoods of millions of coffee-growing families due the information asymmetries. This study investigates the determinants of SC prices that influence the optimal selling decision of small SC farmers, then as main contribution of this study we hypothesised that seven factors determine SC prices, factors which have been studied by different researchers but in an isolated manner, taking into account these factors at the same time, small specialty coffee farmers could make optimal selling decisions by choosing the best coffee price. The study used: IBM software chi-squared statistic and thematic analysis to determine the mean selling decisions factors which stablish the price of coffee. Primarily data was collected from 52 small SC farmers from Planadas Tolima involved in the local business adopting a purposive sampling technique. Research findings revealed a positive correlation between price and the seven independent variables object of this study with a significance of 95%. We concluded that there is a need to consider the variables being studied to solve the information asymmetries in the small SC industry so farmers can make optimal selling decisions. As knowledge of the availability of market information factors examined along the coffee supply chain is deeply understood, we might be able to provide the measurement of information asymmetry in the SC industry and propose a solution in order to solve the SC market disparities to benefit small farmers

The Boltzmann Equation from Quantum Field Theory

We show from first principles the emergence of classical Boltzmann equations from relativistic nonequilibrium quantum field theory as described by the Kadanoff-Baym equations. Our method applies to a generic quantum field, coupled to a collection of background fields and sources, in a homogeneous and isotropic spacetime. The analysis is based on analytical solutions to the full Kadanoff-Baym equations, using the WKB approximation. This is in contrast to previous derivations of kinetic equations that rely on similar physical assumptions, but obtain approximate equations of motion from a gradient expansion in momentum space. We show that the system follows a generalized Boltzmann equation whenever the WKB approximation holds. The generalized Boltzmann equation, which includes off-shell transport, is valid far from equilibrium and in a time dependent background, such as the expanding universe.Comment: title changed, discussion extended and example added, references adde

Quantum Field Theory in the Large N Limit: a review

We review the solutions of O(N) and U(N) quantum field theories in the large $N$ limit and as 1/N expansions, in the case of vector representations. Since invariant composite fields have small fluctuations for large $N$, the method relies on constructing effective field theories for composite fields after integration over the original degrees of freedom. We first solve a general scalar U(\phib^2) field theory for $N$ large and discuss various non-perturbative physical issues such as critical behaviour. We show how large $N$ results can also be obtained from variational calculations.We illustrate these ideas by showing that the large $N$ expansion allows to relate the (\phib^2)^2 theory and the non-linear $\sigma$-model, models which are renormalizable in different dimensions. Similarly, a relation between $CP(N-1)$ and abelian Higgs models is exhibited. Large $N$ techniques also allow solving self-interacting fermion models. A relation between the Gross--Neveu, a theory with a four-fermi self-interaction, and a Yukawa-type theory renormalizable in four dimensions then follows. We discuss dissipative dynamics, which is relevant to the approach to equilibrium, and which in some formulation exhibits quantum mechanics supersymmetry. This also serves as an introduction to the study of the 3D supersymmetric quantum field theory. Large $N$ methods are useful in problems that involve a crossover between different dimensions. We thus briefly discuss finite size effects, finite temperature scalar and supersymmetric field theories. We also use large $N$ methods to investigate the weakly interacting Bose gas. The solution of the general scalar U(\phib^2) field theory is then applied to other issues like tricritical behaviour and double scaling limit.Comment: Review paper: 200 pages, 13 figure

Conserving Gapless Mean-Field Theory for Weakly Interacting Bose Gases

This paper presents a conserving gapless mean-field theory for weakly interacting Bose gases. We first construct a mean-field Luttinger-Ward thermodynamic functional in terms of the condensate wave function $\Psi$ and the Nambu Green's function $\hat{G}$ for the quasiparticle field. Imposing its stationarity respect to $\Psi$ and $\hat{G}$ yields a set of equations to determine the equilibrium for general non-uniform systems. They have a plausible property of satisfying the Hugenholtz-Pines theorem to provide a gapless excitation spectrum. Also, the corresponding dynamical equations of motion obey various conservation laws. Thus, the present mean-field theory shares two important properties with the exact theory: ``conserving'' and ``gapless.'' The theory is then applied to a homogeneous weakly interacting Bose gas with s-wave scattering length $a$ and particle mass $m$ to clarify its basic thermodynamic properties under two complementary conditions of constant density $n$ and constant pressure $p$. The superfluid transition is predicted to be first-order because of the non-analytic nature of the order-parameter expansion near $T_{c}$ inherent in Bose systems, i.e., the Landau-Ginzburg expansion is not possible here. The transition temperature $T_{c}$ shows quite a different interaction dependence between the $n$-fixed and $p$-fixed cases. In the former case $T_{c}$ increases from the ideal gas value $T_{0}$ as $T_{c}/T_{0}= 1+ 2.33 an^{1/3}$, whereas it decreases in the latter as $T_{c}/T_{0}= 1- 3.84a(mp/2\pi\hbar^{2})^{1/5}$. Temperature dependences of basic thermodynamic quantities are clarified explicitly.Comment: 19 pages, 8 figure

Heart rate reduction with ivabradine promotes shear stress-dependent anti-inflammatory mechanisms in arteries

Blood flow generates wall shear stress (WSS) which alters endothelial cell (EC) function. Low WSS promotes vascular inflammation and atherosclerosis whereas high uniform WSS is protective. Ivabradine decreases heart rate leading to altered haemodynamics. Besides its cardio-protective effects, ivabradine protects arteries from inflammation and atherosclerosis via unknown mechanisms. We hypothesised that ivabradine protects arteries by increasing WSS to reduce vascular inflammation. Hypercholesterolaemic mice were treated with ivabradine for seven weeks in drinking water or remained untreated as a control. En face immunostaining demonstrated that treatment with ivabradine reduced the expression of pro-inflammatory VCAM-1 (p<0.01) and enhanced the expression of anti-inflammatory eNOS (p<0.01) at the inner curvature of the aorta. We concluded that ivabradine alters EC physiology indirectly via modulation of flow because treatment with ivabradine had no effect in ligated carotid arteries in vivo, and did not influence the basal or TNFα-induced expression of inflammatory (VCAM-1, MCP-1) or protective (eNOS, HMOX1, KLF2, KLF4) genes in cultured EC. We therefore considered whether ivabradine can alter WSS which is a regulator of EC inflammatory activation. Computational fluid dynamics demonstrated that ivabradine treatment reduced heart rate by 20 % and enhanced WSS in the aorta. In conclusion, ivabradine treatment altered haemodynamics in the murine aorta by increasing the magnitude of shear stress. This was accompanied by induction of eNOS and suppression of VCAM-1, whereas ivabradine did not alter EC that could not respond to flow. Thus ivabradine protects arteries by altering local mechanical conditions to trigger an anti-inflammatory response

Wall shear stress as measured in vivo: consequences for the design of the arterial system

Based upon theory, wall shear stress (WSS), an important determinant of endothelial function and gene expression, has been assumed to be constant along the arterial tree and the same in a particular artery across species. In vivo measurements of WSS, however, have shown that these assumptions are far from valid. In this survey we will discuss the assessment of WSS in the arterial system in vivo and present the results obtained in large arteries and arterioles. In vivo WSS can be estimated from wall shear rate, as derived from non-invasively recorded velocity profiles, and whole blood viscosity in large arteries and plasma viscosity in arterioles, avoiding theoretical assumptions. In large arteries velocity profiles can be recorded by means of a specially designed ultrasound system and in arterioles via optical techniques using fluorescent flow velocity tracers. It is shown that in humans mean WSS is substantially higher in the carotid artery (1.1–1.3 Pa) than in the brachial (0.4–0.5 Pa) and femoral (0.3–0.5 Pa) arteries. Also in animals mean WSS varies substantially along the arterial tree. Mean WSS in arterioles varies between about 1.0 and 5.0 Pa in the various studies and is dependent on the site of measurement in these vessels. Across species mean WSS in a particular artery decreases linearly with body mass, e.g., in the infra-renal aorta from 8.8 Pa in mice to 0.5 Pa in humans. The observation that mean WSS is far from constant along the arterial tree implies that Murray’s cube law on flow-diameter relations cannot be applied to the whole arterial system. Because blood flow velocity is not constant along the arterial tree either, a square law also does not hold. The exponent in the power law likely varies along the arterial system, probably from 2 in large arteries near the heart to 3 in arterioles. The in vivo findings also imply that in in vitro studies no average shear stress value can be taken to study effects on endothelial cells derived from different vascular areas or from the same artery in different species. The cells have to be studied under the shear stress conditions they are exposed to in real life

Towards a model of contemporary parenting: The parenting behaviours and dimensions questionnaire

The assessment of parenting has been problematic due to theoretical disagreement, concerns over generalisability, and problems with the psychometric properties of current parenting measures. The aim of this study was to develop a comprehensive, psychometrically sound self-report parenting measure for use with parents of preadolescent children, and to use this empirical scale development process to identify the core dimensions of contemporary parenting behaviour. Following item generation and parent review, 846 parents completed an online survey comprising 116 parenting items. Exploratory and confirmatory factor analyses supported a six factor parenting model, comprising Emotional Warmth, Punitive Discipline, Anxious Intrusiveness, Autonomy Support, Permissive Discipline and Democratic Discipline. This measure will allow for the comprehensive and consistent assessment of parenting in future research and practice