Productivity and Economic Growth: the Case of Chile

After a decade and a half of economic growth above 7% per year, the Chilean economy has been growing at rates below 3% during the last five years. In this article we suggest that in order to produce a new surge in economic growth, Chile needs a productivity shock arising from economic policy initiatives aimed at improving economic efficiency and institutions. Although Chile has a good record in both, it is still possible to have an upgrade. We run a cross section regression in which the dependent variable is total factor productivity. We conclude that modest changes in the country’s policies and institutions may increase Chile’s rate of growth in 1.5 percent points.

Axion-like-particle decay in strong electromagnetic backgrounds

The decay of a massive pseudoscalar, scalar and U(1) boson into an electron-positron pair in the presence of strong electromagnetic backgrounds is calculated. Of particular interest is the constant-crossed-field limit, relevant for experiments that aim to measure high-energy axion-like-particle conversion into electron-positron pairs in a magnetic field. The total probability depends on the quantum nonlinearity parameter - a product of field and lightfront momentum invariants. Depending on the seed particle mass, different decay regimes are identified. In the below-threshold case, we find the probability depends on a non-perturbative tunnelling exponent depending on the quantum parameter and the particle mass. In the above-threshold case, we find that when the quantum parameter is varied linearly, the probability oscillates nonlinearly around the spontaneous decay probability. A strong-field limit is identified in which the threshold is found to disappear. In modelling the fall-off of a quasi-constant-crossed magnetic field, we calculate probabilities beyond the constant limit and investigate when the decay probability can be regarded as locally constant.Comment: 22 pages, 7 figure

Early environmental field research career exploration: An analysis of impacts on precollege apprentices

Research apprenticeships offer opportunities for deep understanding of scientific practice, transparency about research careers, and possible transformational effects on precollege youth. We examined two consecutive field-based environmental biology apprenticeship programs designed to deliver realistic career exploration and connections to research scientists. The Shaw Institute for Field Training (SIFT) program combines introductory field-skills training with research assistance opportunities, and the subsequent Tyson Environmental Research Fellowships (TERF) program provides immersive internships on university field station–based research teams. In a longitudinal mixed-methods study grounded in social cognitive career theory, changes in youth perspectives were measured during program progression from 10th grade through college, evaluating the efficacy of encouraging career path entry. Results indicate SIFT provided self-knowledge and career perspectives more aligned with reality. During SIFT, differences were found between SIFT-only participants compared with those who progressed to TERF. Transition from educational activities to fieldwork with scientists was a pivotal moment at which data showed decreased or increased interest and confidence. Continuation to TERF provided deeper relationships with role models who gave essential early-career support. Our study indicates the two-stage apprenticeship structure influenced persistence in pursuit of an environmental research career pathway. Recommendations for other precollege environmental career–exploration programs are presented

Feynman versus Bakamjian-Thomas in Light Front Dynamics

We compare the Bakamjian-Thomas (BT) formulation of relativistic few-body systems with light front field theories that maintain closer contact with Feynman diagrams. We find that Feynman diagrams distinguish Melosh rotations and other kinematical quantities belonging to various composite subsystem frames that correspond to different loop integrals. The BT formalism knows only the rest frame of the whole composite system, where everything is evaluated.Comment: 5 page

Medium corrections in the formation of light charged particles in heavy ion reactions

Within a microscopic statistical description of heavy ion collisions, we investigate the effect of the medium on the formation of light clusters. The dominant medium effects are self-energy corrections and Pauli blocking that produce the Mott effect for composite particles and enhanced reaction rates in the collision integrals. Microscopic description of composites in the medium follows the Dyson equation approach combined with the cluster mean-field expansion. The resulting effective few-body problem is solved within a properly modified Alt-Grassberger-Sandhas formalism. The results are incorporated in a Boltzmann-Uehling-Uhlenbeck simulation for heavy ion collisions. The number and spectra of light charged particles emerging from a heavy ion collision changes in a significant manner in effect of the medium modification of production and absorption processes.Comment: 16 pages, 6 figure

Neutron Charge Radius: Relativistic Effects and the Foldy Term

The neutron charge radius is studied within a light-front model with different spin coupling schemes and wave functions. The cancellation of the contributions from the Foldy term and Dirac form factor to the neutron charge form factor is verified for large nucleon sizes and it is independent of the detailed form of quark spin coupling and wave function. For the physical nucleon our results for the contribution of the Dirac form factor to the neutron radius are insensitive to the form of the wave function while they strongly depend on the quark spin coupling scheme.Comment: 12 pages, 5 figures, Latex, Int. J. Mod. Phys.

One-dimensional infinite component vector spin glass with long-range interactions

We investigate zero and finite temperature properties of the one-dimensional spin-glass model for vector spins in the limit of an infinite number m of spin components where the interactions decay with a power, \sigma, of the distance. A diluted version of this model is also studied, but found to deviate significantly from the fully connected model. At zero temperature, defect energies are determined from the difference in ground-state energies between systems with periodic and antiperiodic boundary conditions to determine the dependence of the defect-energy exponent \theta on \sigma. A good fit to this dependence is \theta =3/4-\sigma. This implies that the upper critical value of \sigma is 3/4, corresponding to the lower critical dimension in the d-dimensional short-range version of the model. For finite temperatures the large m saddle-point equations are solved self-consistently which gives access to the correlation function, the order parameter and the spin-glass susceptibility. Special attention is paid to the different forms of finite-size scaling effects below and above the lower critical value, \sigma =5/8, which corresponds to the upper critical dimension 8 of the hypercubic short-range model.Comment: 27 pages, 27 figures, 4 table

Relative Age Effects in Elite Olympic Weightlifters

PURPOSE: To determine if RAEs exist in elite Olympic weightlifters from the past five Olympic Games. METHODS: Using retrospective competition data from the International Weightlifting Federation database a total of 953 Olympic Weightlifters (595 males and 358 females) who competed in the Olympic Games between 2000 and 2016 were included in this study. Weightlifters who competed in multiple Olympic Games were only counted once and duplicates were removed from this investigation. The weightlifters were divided into subset weight classes; men lightweight (56kg, 62kg, and 69kg), men middleweight (77kg, 85kg, and 94kg), men heavyweight (105kg and 105kg+), women lightweight (48kg, 53kg, and 58kg), women middleweight (63kg and 69kg), and women heavyweight (75kg and 75kg+). Using the subset weight classes, the observed date of birth distribution vs. the expected worldwide date of birth distribution were compared using multiple chi square (χ2) goodness of fit tests with the alpha level set at (p≤0.05). Following up the χ2 test, standardized residuals were calculated for each month with values of ±2 denoting significant over-and under-representation. RESULTS: RAEs were present overall for Olympic weightlifters (χ2 = 189.428, p\u3c0.001), with significant over-representation in January (z= +12.6, 20.9%) and under-representation in June (z= -2.1, 6.3%), September (z= -3.2, 5.7%), and November (z= -3.0, 5.1%). RAEs were also present in all three male classes; men lightweight (χ2 = 74.773, p\u3c0.001), men middleweight (χ2 = 41.786, p\u3c0.001), and men heavyweight (χ2 = 39.395, p\u3c0.001) and women lightweight (χ2 = 37.251, p\u3c0.001). Significant over-representation was noted in January for men lightweight (24.1%), men middleweight (20.0%), men heavyweight (22.2%), and women lightweight (21.2%), and there was a significant under-representation for the month of November in men lightweight (z= -2.7, 2.8%). However, RAEs were not present in the women’s middleweight (χ2 = 18.632, p=0.068) or heavyweight (χ2 = 16.692, p= 0.117) classes. CONCLUSION: In males significant RAEs are present in Olympic weightlifters regardless of weight class. However, for females RAEs only exist for lightweight Olympic weightlifters. Indicating that RAEs are present in Olympic weightlifting is important because it will help maintain the amount of opportunity for all athletes regardless of when they were born in the year. PRACTICAL APPLICATIONS: Coaches should be aware of the possible advantages of training age and the effect of physical maturation as a result of these RAEs. Coaches may use this information for athlete selection but the presence of RAEs should not discourage athletes from participating in the sport of weightlifting

B-T phase diagram of CoCr2O4 in magnetic fields up to 14 T

We have measured the magnetization and specific heat of multiferroic CoCr2O4 in magnetic fields up to 14 T. The high-field magnetization measurements indicate a new phase transition at T* = 5 - 6 K. The phase between T* and the lock-in transition at 15 K is characterized by magnetic irreversibility. At higher magnetic fields, the irreversibility increases. Specific-heat measurements confirm the transition at T*, and also show irreversible behavior. We construct a field-temperature phase diagram of CoCr2O4.Comment: 4 page