ترغب بنشر مسار تعليمي؟ اضغط هنا

Stationary Phase and the Theory of Measurement -- 1/N expansion --

66   0   0.0 ( 0 )
 نشر من قبل Reijirou Fukuda
 تاريخ النشر 2008
  مجال البحث فيزياء
والبحث باللغة English
 تأليف R. Fukuda




اسأل ChatGPT حول البحث

The measuring process is studied, where a macroscopic number N of particles in the detector interact with the object. The macrovariable accompanies the stationary phase in the path-integral form, which is in one-to-one correspondence with the eigen-value of the object operator O to be measured. When N goes to infinity, the fluctuation of the object between different eigenvalues of O is suppressed, frozen to one the same state while the detector is on. A model is studied which produces the ideal result when N is infinite, and the correction terms are calculated in powers of 1/N. It is identical to the expansion including the fluctuation of the object successively.

قيم البحث

اقرأ أيضاً

We investigate theoretically the combination of first-order quadrupole-quadrupole and second-order dipole-dipole effects on the long-range electrostatic interactions between a ground-state homonuclear alkali-metal dimer and an excited alkali-metal at om. As the electrostatic energy is comparable to the dimer rotational structure, we develop a general description of the long-range interactions which allows for couplings between the dimer rotational levels. The resulting adiabatic potential energy curves, which exhibit avoided crossings, cannot be expanded on the usual $1/R^{n}$ series. We study in details the breakdown of this approximation in the particular case Cs$_{2}+$Cs. Our results are found promising in the prospect of accomplishing the photoassociation of ultracold trimers.
Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corre sponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained.
We consider the fate of $1/N$ expansions in unstable many-body quantum systems, as realized by a quench across criticality, and show the emergence of ${rm e}^{2lambda t}/N$ as a renormalized parameter ruling the quantum-classical transition and accou nting nonperturbatively for the local divergence rate $lambda$ of mean-field solutions. In terms of ${rm e}^{2lambda t}/N$, quasiclassical expansions of paradigmatic examples of criticality, like the self-trapping transition in an integrable Bose-Hubbard dimer and the generic instability of attractive bosonic systems toward soliton formation, are pushed to arbitrarily high orders. The agreement with numerical simulations supports the general nature of our results in the appropriately combined long-time $lambda tto infty$ quasiclassical $Nto infty$ regime, out of reach of expansions in the bare parameter $1/N$. For scrambling in many-body hyperbolic systems, our results provide formal grounds to a conjectured multiexponential form of out-of-time-ordered correlators.
We discuss the necessary, albeit not sufficient, conditions for tetraquark poles to occur in the 1/N expansion of QCD and find the minimum order at which such poles may appear. Assuming tetraquark poles, we find a new non-planar solution with the min imal number of topologies and tetraquark species. The solution implies narrow states. Mixing with quarkonium states is allowed so that P-wave tetraquarks with J^PC=1^-- would couple to e^+e^-.
A novel theory of hybrid quantum-classical systems is developed, utilizing the mathematical framework of constrained dynamical systems on the quantum-classical phase space. Both, the quantum and the classical descriptions of the respective parts of t he hybrid system are treated as fundamental. Therefore, the description of the quantum-classical interaction has to be postulated, and includes the effects of neglected degrees of freedom. Dynamical law of the theory is given in terms of nonlinear stochastic differential equations with Hamiltonian and gradient terms. The theory provides a successful dynamical description of the collapse during quantum measurement.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا