Quantum stochastic differential equations and continuous measurements: unbounded coefficients

A natural formulation of the theory of quantum measurements in continuous time is based on quantum stochastic differential equations (Hudson-Parthasarathy equations). However, such a theory was developed only in the case of Hudson-Parthasarathy equations with bounded coefficients. By using some results on Hudson-Parthasarathy equations with unbounded coefficients, we are able to extend the theory of quantum continuous measurements to cases in which unbounded operators on the system space are involved. A significant example of a quantum optical system (the degenerate parametric oscillator) is shown to fulfill the hypotheses introduced in the general theory.Comment: 28 page

Soil solarization for weed control in carrot.

Soil solarization is a technique used for weed and plant disease control in regions with high levels of solar radiation. The effect of solarization (0, 3, 6, and 9 weeks) upon weed populations,carrot (Daucus carota L. cv. Brasília) yield and nematode infestation in carrot roots was studied in São Luís (2o35' S; 44o10' W), MA, Brazil, using transparent polyethylene films (100 and 150 mm of thickness). The maximum temperature at 5 cm of depth was about 10oC warmer in solarized soil than in control plots. In the study 20 weed types were recorded. Solarization reduced weed biomass and density in about 50% of weed species, including Cyperus spp., Chamaecrista nictans var. paraguariensis(Chod & Hassl.) Irwin & Barneby,Marsypianthes chamaedrys (Vahl) O. Kuntze, Mitracarpus sp.,Mollugo verticillata L., Sebastiania corniculata M. Arg., and Spigelia anthelmia L. Approximately 40% of species in the weed flora were not affected by soil mulching. Furthermore, seed germination of Commelina benghalensis L. was increased by soil solarization. Marketable yield of carrots was greater in solarized soil than in the unsolarized one. It was concluded that solarization for nine weeks increases carrot yield and is effective for controlling more than half of the weed species recorded. Mulching was not effective for controlling root-knot nematodes in carrot

How Do Central Banks React to Wealth Composition and Asset Prices?

We assess the response of monetary policy to developments in asset markets in the Euro Area, the US and the UK. We estimate the reaction of monetary policy to wealth composition and asset prices using: (i) a linear framework based on a fully simultaneous system approach in a Bayesian environment; and (ii) a nonlinear specification that relies on a smooth transition regression model. The linear framework suggests that wealth composition is indeed important in the formulation of monetary policy. However, the attempts of central banks to mitigate undesirable fluctuations in say, financial wealth, may disrupt housing wealth. A similar result can be found when we assess the reaction of monetary authority to asset prices, although concerns about "price" effects are smaller. The nonlinear model confirms these findings. However, the concerns over wealth and its components are stronger once inflation is under control, i.e. below a certain target. Some disruptions between financial and housing wealth effects are still present. They can also be found in the reaction to asset prices, despite being less intense.monetary policy rules, wealth composition, asset prices.

Finite BRST Mapping in Higher Derivative Models

We continue the study of finite field dependent BRST (FFBRST) symmetry in the quantum theory of gauge fields. An expression for the Jacobian of path integral measure is presented, depending on a finite field-dependent parameter, and the FFBRST symmetry is then applied to a number of well-established quantum gauge theories in a form which includes higher-derivative terms. Specifically, we examine the corresponding versions of the Maxwell theory, non-Abelian vector field theory, and gravitation theory. We present a systematic mapping between different forms of gauge-fixing, including those with higher-derivative terms, for which these theories have better renormalization properties. In doing so, we also provide the independence of the S-matrix from a particular gauge-fixing with higher derivatives. Following this method, a higher-derivative quantum action can be constructed for any gauge theory in the FFBRST framework.Comment: 9 pages, published in Braz. J. Phy

Valse Melancolique

https://digitalcommons.library.umaine.edu/mmb-ps/2707/thumbnail.jp

How Does Fiscal Policy React to Wealth Composition and Asset Prices?

We assess the response of fical policy to developments in asset markets in the US and the UK. We estimate fical polyce rules augmented with aggregate wealth, wealth composition (i.e. financial and housing wealth) and asset prices (i.e. stock and housing prices) using: (i) a linear framework based on a fully simultaneous system approach; and (ii) two nonlinear specifications that rely on a smooth transition regression (STR) and a Markov-switching (MS) model. The linear framework suggests that, while primary spending does not seem to react to wealth composition or asset prices, taxes and primary surplus are significantly: (i) cut when financial wealth or stock prices rise, and (ii) raised when housing wealth or housing prices increase. The smooth transition regression model shows that primary spending and fiscal balance are adjusted in a nonlinear fashion to both wealth and price effects, while the Markov-switching framework highlights the importance of tax cuts (in the US) and spending hikes (in the UK) to offset the decline in wealth suring major recessions and financial crises. Overall, our results provide evidence of a non-stabilizing effect of government debt, a countercyclical policy and a vigilant track of wealth developments by fiscal authorities.fiscal policy, wealth composition, asset prices

How Does Fiscal Policy React to Wealth Composition and Asset Prices?

We assess the response of fiscal policy to developments in asset markets in the US and the UK. We estimate fiscal policy rules augmented with aggregate wealth, wealth composition (i.e. financial and housing wealth) and asset prices (i.e. stock and housing prices) using: (i) a linear framework based on a fully simultaneous system approach; and (ii) two nonlinear specifications that rely on a smooth transition regression (STR) and a Markov-switching (MS) model. The linear framework suggests that, while primary spending does not seem to react to wealth composition or asset prices, taxes and primary surplus are significantly: (i) cut when financial wealth or stock prices rise; and (ii) raised when housing wealth or housing prices increase. The smooth transition regression model shows that primary spending and fiscal balance are adjusted in a nonlinear fashion to both wealth and price effects, while the Markov-switching framework highlights the importance of tax cuts (in the US) and spending hikes (in the UK) to offset the decline in wealth during major recessions and financial crises. Overall, our results provide evidence of a non-stabilizing effect of government debt, a countercyclical policy and a vigilant track of wealth developments by fiscal authorities.fiscal policy, wealth composition, asset prices.