Coherence macroscopic

Suppose we offset this motion by applying a Galilean transformation x = x +Pt ). In the new reference frame, the system will move just as it did in the old reference frame but, because a — /pqt = / i P )t/A, its diffusion is slowed down by a Lorentz-Fitzgerald-like time factor 1-/3. Intuitively, as some of the resources of the random walk computer are shifted toward producing coherent macroscopic motion (uniform motion of the center of mass), fewer resources will remain available for the task of producing incoherent motion (diffusion). [tofI89]... 

When the polymer chains are connected to each other by stable crosslinks, either chemical or physical ones, the whole system is stationary, although the chain elements between the crosslinks are in rapid motion. On a macroscopic scale, the systan is solid-like, whereas on a microscopic scale, it behaves as a liquid. Such a system is called a gel. Thus, a gel is a system in which colloidal particles are interconnected and form a coherent macroscopic structure that is permeable for the solvent... 

This is followed by two field actions which again create a vibrational coherence but, now, with opposite phase to the first coherence. Hence one obtains a partial rephasing, or echo, of the macroscopic polarization. The final field action creates the seventh order optical polarization which launches the signal field (the eighth field). Just as for the spin echo in NMR or the electronic echo in 4WM, the degree of rephasing (tlie... 

An alternative approach to obtaining microwave spectroscopy is Fourier transfonn microwave (FTMW) spectroscopy in a molecular beam [10], This may be considered as the microwave analogue of Fourier transfonn NMR spectroscopy. The molecular beam passes into a Fabry-Perot cavity, where it is subjected to a short microwave pulse (of a few milliseconds duration). This creates a macroscopic polarization of the molecules. After the microwave pulse, the time-domain signal due to coherent emission by the polarized molecules is detected and Fourier transfonned to obtain the microwave spectmm. 

The term collectivism has sometimes been used to distinguish this AL philosophy from the more traditional top down and bottom up philosophies. Collectivism embodies the belief that in order to properly understand complex systems, such systems must be viewed as coherent wholes whose open-ended evolution is continuously fueled by nonlinear feedback between their macroscopic states and microscopic constituents. It is neither completely reductionist (which seeks only to decompose a system into its primitive components), nor completely synthesist (which seeks to synthesize the system out of its constituent parts but neglects the feedback between emerging levels). 

The ability to create and observe coherent dynamics in heterostructures offers the intriguing possibility to control the dynamics of the charge carriers. Recent experiments have shown that control in such systems is indeed possible. For example, phase-locked laser pulses can be used to coherently amplify or suppress THz radiation in a coupled quantum well [5]. The direction of a photocurrent can be controlled by exciting a structure with a laser field and its second harmonic, and then varying the phase difference between the two fields [8,9]. Phase-locked pulses tuned to excitonic resonances allow population control and coherent destruction of heavy hole wave packets [10]. Complex filters can be designed to enhance specific characteristics of the THz emission [11,12]. These experiments are impressive demonstrations of the ability to control the microscopic and macroscopic dynamics of solid-state systems. 

If the electric dipole contribution dominates in the total SH response, the macroscopic response can be related to the presence of optically nonlinear active compounds at the interface. In this case, the susceptibility tensor is the sum of the contribution of each single molecule, all of them coherently radiating. For a collection of compounds, it yields ... 

Application to heterogeneous polymer solids, and elastic composites, is presented in the Section 7 (Gusev, Suter), which is followed by a summary and the outlook for the various methods reviewed here. It will be apparent to the reader that this review thus assembles several building blocks for the difficult task to bridge the gaps from the atomistic to the macroscopic scales in space and times for the simulation of polymeric materials. Integrating these building blocks into one coherent framework still is not fully solved and a matter of current research. 

Poisson distribution, multiparticle collision dynamics, macroscopic laws and transport coefficients, 102-104 Polyatomic molecules, coherence... 

For non-interacting, incompressible polymer systems the dynamic structure factors of Eq. (3) may be significantly simplified. The sums, which in Eq. (3) have to be carried out over all atoms or in the small Q limit over all monomers and solvent molecules in the sample, may be restricted to only one average chain yielding so-called form factors. With the exception of semi-dilute solutions in the following, we will always use this restriction. Thus, S(Q, t) and Sinc(Q, t) will be understood as dynamic structure factors of single chains. Under these circumstances the normalized, so-called macroscopic coherent cross section (scattering per unit volume) follows as... 

Nakamura, Y., Pashkin, Y.A. and Tsai, J.S. (1999) Coherent control of macroscopic quantum states in a single-Cooper-pair box. Nature, 398, 786-788. 

Summary. Coherent optical phonons are the lattice atoms vibrating in phase with each other over a macroscopic spatial region. With sub-10 fs laser pulses, one can impulsively excite the coherent phonons of a frequency up to 50THz, and detect them optically as a periodic modulation of electric susceptibility. The generation and relaxation processes depend critically on the coupling of the phonon mode to photoexcited electrons. Real-time observation of coherent phonons can thus offer crucial insight into the dynamic nature of the coupling, especially in extremely nonequilibrium conditions under intense photoexcitation. 

At the beginning of the analysis, the ensemble of frequencies is incoherent and has no measurable macroscopic effect on the cell. Ions with the same m/z ratio must be made coherent to conduct a frequency analysis. This is achieved by irradiating the cell with a short radiofrequency pulse (ca. 1 ms lifetime) that includes all the frequencies to be determined. During the irradiation pulse, ions will increase their... 

B. A. Hess The reason that macroscopic motions display coherence is that they are in most cases at the classical limit of quantum dynamics. In this case, a suitable occupation of quantum states ensures that quantum mechanical expectation values equal the classical value of an observable. In particular, the classical state of an electromagnetic field (the coherent state) is one in which the expectation value of the operator of the electromagnetic field equals the classical field strengths. 

P. W. Brumer Several of the speakers (namely Profs. B. A. Hess, M. Quack, and M. S. Child), responding to my question, have suggested that something different happens in the classical limit. However, if we accept the idea that quantum mechanics is a generally applicable theory, then it is applicable to macroscopic systems in the classical limit. As such, dynamics and coherences are, as I said, synonymous in both the quantum and the classical limits. I favor the view of Martin Quack that the closeness of the level spacings in large systems simplifies the preparation of a superposition. Hence experiments on larger molecules seem desirable. 

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