Analysis of the Jun Ishiwara's "The universal meaning of the quantum of action"

Here we present an analysis of the paper "Universelle Bedeutung des Wirkungsquantums" (The universal meaning of the quantum of action), published by Jun Ishiwara in German in the "Proceedings of Tokyo Mathematico-Physical Society 8 (1915) 106-116". In his work, Ishiwara, established in the Sendai University, Japan, proposed - simultaneously with Arnold Sommerfeld, William Wilson and Niels Bohr in Europe - the phase-space-integral quantization, a rule that would be incorporated into the old-quantum-theory formalism. The discussions and analysis render this paper fully accessible to undergraduate students of physics with elementary knowledge of quantum mechanics.Comment: 12 page

Understanding the Pointer States

In quantum mechanics, pointer states are eigenstates of the observable of the measurement apparatus that represent the possible positions of the display pointer of the equipment. The origin of this concept lies in attempts to fill the blanks in the Everett's relative-state interpretation, and to make it a fully valid description of physical reality. To achieve this, it was necessary to consider not only the main system interacting with the measurement apparatus (like von Neumann and Everett did) but also the role of the environment in eliminating correlations between different possible measurements when interacting with the measurement apparatus. The interaction of the environment with the main system (and the measurement apparatus) is the core of the decoherence theory, which followed Everett's thesis. In this article, we review the measurement process according to von Neumann, Everett's relative state interpretation, the purpose of decoherence and some of its follow-up until Wojciech Zurek's primordial paper that consolidated the concept of pointer state, previously presented by Heinz Dieter Zeh. Employing a simple physical model consisting of a pair of two-level systems -- one representing the main system, the other the measurement apparatus -- and a thermal bath -- representing the environment -- we show how pointer states emerge, explaining its contributions to the question of measurement in quantum mechanics, as well as its limitations. Finally, we briefly show some of its consequences. This paper is accessible to readers with elementary knowledge about quantum mechanics, on the level of graduate courses.Comment: 29 pages (20 for main text and references, 9 for appendices

Influência do manejo florestal e do desmatamento na oferta de madeiras tropicais na amazônia brasileira.

This work presents an analysis of the behaviour, performance, and impact of timber price, forest management and of deforestation on the supply of tropical timbers in the Amazon Region. As a methodological basis, it has used regression analysis to estimate the supply equation and the substitution elasticity model to verify competitiveness between the two sources of tropical timbers. The results suggest that the supply of tropical timbers in the domestic market is inelastic, in which deforestation and timber prices have significantly influenced the quantities supplied in the period under study. The production originated from managed forest areas does not yet contribute significantly to the global supply of timber. The work further reveals that the substitution elasticity between the distinct sources of timber is significant and positive. This demonstrates that sustainable forest management competes with deforestation in the supply of tropical timbers.Este trabalho apresenta uma análise do comportamento, do desempenho e do impacto do preço da madeira, do manejo florestal sustentável e do desmatamento na oferta de madeiras tropicais na região Amazônica. Como base metodológica, utilizou a análise de regressão para estimar a equação de oferta e o modelo de elasticidade substituição para verificar a competição entre as fontes de oferta da madeira tropical. Os resultados sugerem que a oferta de madeiras tropicais no mercado doméstico é inelástica, e que o preço da madeira e o desmatamento influenciam significativamente as quantidades ofertadas no período estudado. A produção oriunda de área de floresta manejada ainda não contribui de forma significativa para a oferta global de madeira. O trabalho revela também que a elasticidade de substituição entre as fontes de oferta de madeiras é significativa e positiva. Isto demonstra que o manejo florestal sustentável vem substituindo em uma magnitude modesta o desmatamento na oferta de madeiras tropicais

How much time does a measurement take?

We consider the problem of measurement using the Lindblad equation, which allows the introduction of time in the interaction between the measured system and the measurement apparatus. We use analytic results, valid for weak system-environment coupling, obtained for a two-level system in contact with a measurer (Markovian interaction) and a thermal bath (non-Markovian interaction), where the measured observable may or may not commute with the system-environment interaction. Analysing the behavior of the coherence, which tends to a value asymptotically close to zero, we obtain an expression for the time of measurement which depends only on the system-measurer coupling, and which does not depend on whether the observable commutes with the system-bath interaction. The behavior of the coherences in the case of strong system-environment coupling, found numerically, indicates that an increase in this coupling decreases the measurement time, thus allowing our expression to be considered the upper limit for the duration of the process.Comment: REVISED VERSION: 17 pages, 2 figure

Protecting a quantum state from environmental noise by an incompatible finite-time measurement

We show that measurements of finite duration performed on an open two-state system can protect the initial state from a phase-noisy environment, provided the measured observable does not commute with the perturbing interaction. When the measured observable commutes with the environmental interaction, the finite-duration measurement accelerates the rate of decoherence induced by the phase noise. For the description of the measurement of an observable that is incompatible with the interaction between system and environment, we have found an approximate analytical expression, valid at zero temperature and weak coupling with the measuring device. We have tested the validity of the analytical predictions against an exact numerical approach, based on the superoperator-splitting method, that confirms the protection of the initial state of the system. When the coupling between the system and the measuring apparatus increases beyond the range of validity of the analytical approximation, the initial state is still protected by the finite-time measurement, according with the exact numerical calculations.Comment: REVISED VERSION: 37 pages, 3 figure

DEMANDA DE EXPORTAÇÃO DE PAINÉIS DE MADEIRA DO BRASIL

Os painéis de madeira estão consolidando posições de destaque no setor florestal e na economia brasileira, em decorrência do grande crescimento da produção na última década. Os principais motivos desse crescimento foram a instalação de novas unidades produtoras, a busca de novas tecnologias e a modernização do pátio industrial. Conseqüentemente, no ano de 2000, o Brasil alcançou a 10a posição de maior produtor mundial e também a 10a posição de maior exportador mundial. É evidente que no período em análise (1960-2000), os fatores referentes à demanda internacional tiveram um papel importante sobre as exportações brasileiras de painéis de madeira. Os resultados empíricos mostram que as exportações brasileiras de painéis de madeira não são sensíveis ao preço, que as exportações brasileiras de painéis de fibra, painéis de partícula e laminados são complementares às exportações mundiais e que segundo a renda mundial, o compensado brasileiro, indica ser um bem superior, e os demais painéis bens normais. DEMAND FOR BRAZILIAN WOOD-BASED PANELS EXPORTS Abstract The wood-based panels are consolidating an important position in the Brazilian forest sector and economy, due to its industry growth in the last decade. The main reasons for its growth are the installation of new industrial unities, the search for new technologies, and the industrial modernization. Consequently, in the year 2000, Brazil has reach the 10th position of main world producer and also the 10th position of main world exporter. In the studied period (1960-2000), the international demand had an important role over the Brazilian wood-based panels exports. The empirical results show that the Brazilian wood-based panels are not sensitive to price, that the Brazilian exports of particleboard, fibreboard, and veneers are complementary to the world exports, and that, based in the world revenue, the Brazilian plywood is a superior good and that the other pnels are normal goods