Searcharxiv⌕ Search

arXiv subjects

Mikio Namiki

Publications and source records attributed to Mikio Namiki.

8 recordsLinked to original sources
arXiv2004

Stochastic quantization of Born-Infeld field

We stochastically quantize the Born-Infeld field which can hardly be dealtwith by means of the standard canonical and/or path-integral quantization methods. We set a hypothetical Langevin equation in order to quantize the Born-Infeld field, following the basic idea of stochastic quantization method. Numerically solving this nonlinear Langevin equation, we obtain a sort of "particle mass" associated with the gauge-invariant Born-Infeld field as a function of the so-called universal length. This is a revised version of which original non-electronic one was published in 1995 by RISE in Waseda Univ.

hep-th↗
arXiv1997

Transverse Photon Spectrum from QGP Fluid

We calculate the thermal photon distribution from the hot QCD matter produced by high energy nuclear collisions based on a hydrodynamical model, and compare it with the recent experimental data obtained by CERN WA80. Through the asymptotic value of the slope parameter of the transverse momentum distribution, we investigate the characteristic temperature of the QCD fluid.

nucl-th↗
arXiv1996

Emergence of a Wiener process as a result of the quantum mechanical interaction with a macroscopic medium

We analyze a modified version of the Coleman-Hepp model, that is able to take into account energy-exchange processes between the incoming particle and the linear array made up of $N$ spin-1/2 systems. We bring to light the presence of a Wiener dissipative process in the weak-coupling, macroscopic ($N \rightarrow \infty$) limit. In such a limit and in a restricted portion of the total Hilbert space, the particle undergoes a sort of Brownian motion, while the free Hamiltonian of the spin array serves as a Wiener process. No assumptions are made on the spectrum of the Hamiltonian of the spin system, and no partial trace is computed over its states. The mechanism of appearance of the stochastic process is discussed and contrasted to other noteworthy examples in the literature. The links with van Hove's ``$λ^2 T$ limits are emphasized.

quant-ph↗
arXiv1996

Quantum dephasing by chaos

We examine whether the chaotic behavior of classical systems with a limited number of degrees of freedom can produce quantum dephasing, against the conventional idea that dephasing takes place only in large systems with a huge number of constituents and complicated internal interactions. On the basis of this analysis, we briefly discuss the possibility of defining quantum chaos and of inventing a ``chaos detector".

quant-ph↗
arXiv1996

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.

quant-ph↗
arXiv1995

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 ``$λ^2T$" 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.

quant-ph↗
arXiv1995

Numerical Analyses of CERN 200GeV/A Heavy-Ion Collisions Based on a Hydrodynamical Model with Phase Transition

We numerically analyze recent high energy heavy-ion collision experiments based on a hydrodynamical model with phase transition and discuss a systematic change of initial state of QGP-fluid depending on colliding-nuclei's mass. In a previous paper, we formulated a (3+1)-dimensional hydrodynamical model for quark-gluon plasma with phase transition and discussed numerically the space-time evolution in detail. We here compare the numerical solution with the hadronic distributions given by CERN WA80 and NA35. Systematic analyses of the experiments with various colliding nuclei enable us to discuss the dependences of the initial parameters of the hydrodynamical model on colliding nuclei's mass. Furthermore, extrapolating the present experiments, we derive the possible hadronic distributions for lead-lead 150GeV/A collision.

nucl-th↗