Temporal behavior of quantum mechanical systems

The temporal behavior of quantum mechanical systems is reviewed. We study the so-called quantum Zeno effect, that arises from the quadratic short-time behavior, and the analytic properties of the ``survival" amplitude. It is shown that the exponential behavior is due to the presence of a simple pole in the second Riemannian sheet, while the contribution of the branch point yields a power behavior for the amplitude. The exponential decay form is cancelled at short times and dominated at very long times by the branch-point contributions, which give a Gaussian behavior for the former and a power behavior for the latter. In order to realize the exponential law in quantum theory, it is essential to take into account a certain kind of macroscopic nature of the total system. Some attempts at extracting the exponential decay law from quantum theory, aiming at the master equation, are briefly reviewed, including van Hove's pioneering work and his well-known ``$\lambda^2T$" limit. We clarify these general arguments by introducing and studying a solvable dynamical model. Some implications for the quantum measurement problem are also discussed, in particular in connection with dissipation.Comment: 48 pages, LaTeX, uuencoded file with 7 figures include

Understanding the quantum Zeno effect

The quantum Zeno effect consists in the hindrance of the evolution of a quantum system that is very frequently monitored and found to be in its initial state at every single measurement. On the basis of the correct formula for the survival probability, i.e. the probability of finding the system in its initial state at every single measurement, we critically analyze a recent proposal and experimental test, that make use of an oscillating system.Comment: 9 pages, LaTeX, including 1 epsfigure, tar+gzip+uuencoded to appear in Phys. Lett.

On the Stochastic Quantization Method: Characteristics and Applications to Singular Systems

Introducing the generalized Langevin equation, we extend the stochastic quantization method so as to deal with singular dynamical systems beyond the ordinary territory of quantum mechanics. We also show how the uncertainty relation is built up to the quantum mechanical limit with respect to fictitious time, irrespective of its initial value, within the framework of the usual stochastic quantization method

Quantum Zeno Effect in the Measurement Problem

Critically analyzing the so-called quantum Zeno effect in the measurement problem, we show that observation of this effect does not necessarily mean experimental evidence for the naive notion of wave-function collapse by measurement (the simple projection rule). We also examine what kind of limitation the uncertainty relation and others impose on the observation of the quantum Zeno effect

Decoherence and dephasing in a quantum measurement process

We numerically simulate the quantum measurement process by modeling the measuring apparatus as a one-dimensional Dirac comb that interacts with an incoming object particle. The global effect of the apparatus can be well schematized in terms of the total transmission probability and the decoherence parameter, which quantitatively characterizes the loss of quantum-mechanical coherence and the wave-function collapse by measurement. These two quantities alone enable one to judge whether the apparatus works well or not as a detection system. We derive simple theoretical formulas that are in excellent agreement with the numerical results, and can be very useful in order to make a ``design theory'' of a measuring system (detector). We also discuss some important characteristics of the wave-function collapse. \textcopyright{} 1996 The American Physical Society

Reconsideration of progression to CRPC during androgen deprivation therapy

Androgen blockade-naïve prostate cancer (PCa) develops into CRPC during androgen deprivation therapy (ADT) by various genetic actions. The androgen-AR signaling axis plays a key role in this development. PCa cells mainly adapt themselves to the environment of lower androgen concentrations and change into androgen-hypersensitive cells or androgen-independent cells. Androgens of adrenal origin and their metabolites synthesized in the microenvironment in an intracrine/paracrine fashion act on surviving PCa cells and secrete prostate specific antigen (PSA). Total androgen deprivation (TAD) (castration, antiandrogen, and CYP17A1 inhibitor) can become an effective therapeutic strategy concerning the androgen signaling axis-related pathway. However, it is important to ascertain whether elevation of serum PSA results from AR activation or from an androgen-independent tumor volume effect. Then, clinicians can judge it adequately using the imaging studies such as CT or bone scan as well as PSA and bone metabolic markers, an approach which is necessary to judge which treatment is most suitable for the CRPC patients. This article is part of a Special Issue entitled \u27Essential role of DHEA\u27

Optimal treatment for castration-resistant prostate cancer

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