Green operators for low regularity spacetimes

In this paper we define and construct advanced and retarded Green operators for the wave operator on spacetimes with low regularity. In order to do so we require that the spacetime satisfies the condition of generalised hyperbolicity which is equivalent to well- posedness of the classical inhomogeneous problem with zero initial data where weak solutions are properly supported. Moreover, we provide an explicit formula for the kernel of the Green operators in terms of an arbitrary eigenbasis of H 1 and a suitable Green matrix that solves a system of second order ODEs

Generalised hyperbolicity in spacetimes with string-like singularities

In this paper we present well-posedness results of the wave equation in $H^{1}$ for spacetimes that contain string-like singularities. These results extend a framework able to characterise gravitational singularities as obstruction to the dynamics of test fields rather than point particles. In particular, we discuss spacetimes with cosmic strings and the relation of our results to the Strong Cosmic Censorship Conjecture.Comment: Accepted for publication in Classical and Quantum Gravit

Competitive pressure and labor productivity: world iron ore markets in the 1980s

Does the extent of competitive pressure industries face influence their productivity? We study a natural experiment conducted in the iron ore industry as a result of the collapse in world steel production in the early 1980s. For iron ore producers, whose only market is the steel industry, this collapse was an exogenous shock. The drop in steel production differed dramatically by region: it fell by about a third in the Atlantic Basin but only very little in the Pacific Basin. Given that the cost of transporting iron ore is very high relative to its mine value, Atlantic iron ore producers faced a much greater increase in competitive pressure than did Pacific iron ore producers. In response to the crisis, most Atlantic iron ore producers doubled their labor productivity; Pacific iron ore producers experienced few productivity gains. ; This article originally appeared in the American Economic Review. (c) American Economic Association.Labor productivity ; Steel industry and trade

Breathers in FPU systems, near and far from the phonon band

There exists a recent mathematical proof on the existence of small amplitude breathers in FPU systems near the phonon band, which includes a prediction of their amplitude and width. In this work we obtain numerically these breathers, and calculate the range of validity of the predictions, which extends relatively far from the phonon band. There exist also large amplitude breathers with the same frequency, with the consequence that there is an energy gap for breather creation in these systems.Comment: 3 pages, 2 figures, proceeding of the conference on Localization and to and Energy Transfer in Nonlinear Systems, June 17-21, 2002, San Lorenzo de El Escorial, Madrid, Spain. To be published by World Scientifi

Comparing aerobic adaptations with a running based high intensity interval training (HIIT) and a continuous endurance training (CET) protocol in relatively healthy adults

The purpose of this study was to compare a running based High Intensity Interval Training (HIIT) protocol to a Continuous Endurance Training (CET) and their aerobic adaptations, such as increased VO₂[subscritp max] and improved body composition. Recruitment of participant\u27s occured by flyers on campus. After indicating interest, volunteers answered no, to all questions on the PAR-Q to be eligible. Pre and post testing included a submaximal VO₂[subscritp max] test, using the 12 min cooper run test, and body composition using the BOD POD GS (COSMED USA Inc., Concord, California). After testing, the participants were randomly stratified based on matched aerobic capacity scores to either the HIIT, CET or control group. The CET and HIlT group completed 6 weeks of 3 days/week of the training protocol. The HIlT group did 10 X 60 s workload intervals with 60 s of rest in between each interval. The CET group did 40 to 60 min moderate intensity running. Pre to post test values were compared using a student t test with p \u3c̲ .05, and significance between were measured us a one-way ANOVA with a Tukey post-hoc when necessary. The HIlT and CET group found significance in regards to VO₂[subscritp max] with no difference between groups. The HIlT and CET respectively showed a 5.33 (± 4.48) ml̈kg⁻¹min⁻¹ (t = 4.30, p = .001) and a 2.95 (± 1.82) ml̈kg⁻¹min⁻¹ (t = -5.367, p \u3c .000) improvement. In regards to body composition HIlT also gained significant results with % Body Fat(% BF), Body Mass (BM), and Fat Free Mass (FFM) --Document