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As humans, we are fundamentally social creatures. From birth we orient to other people, and as we develop we acquire abilities for interacting with one another, ranging from expression and gesture through spoken and written language. As adults we are exquisitely sensitive to the actions and interactions of those around us. Every day we make countless decisions that are shaped by our social context. Whether it is wrapping up a talk when the audience starts fidgeting, or deciding to forgo the grocery shopping because the parking lot is jammed, social information provides a basis for inferences, planning and coordinating activity.

The collective interaction of atoms with light is a topic of fundamental interest. In particular, the phenomena of superradiance and superfluorescence have received much attention since Dicke published his original paper on the topic [1]. Most work has focused either on the overall geometry dependent coupling between the atoms and the field to establish a preferred direction of emission, or it has assumed a preferred direction and then focused on the time evolution of the emission, often using a semiclassical approximation which neglects fluctuations in the atomic state (see references in [2]).

We study theoretically selected aspects of the collective interaction between two coupled quantum dots (QDs) forming a quantum dot molecule (QDM) and the modes of the electromagnetic field, as manifested in the optical response of QDMs under various experimental conditions. Unlike atomic systems, the artificial QD structures show shape and size inhomogeneity, which has to be included in the theoretical description. Moreover, for tightly spaced QDMs, coupling between the QDs cannot be neglected.

Using the language of quantum field theory, we present a concise derivation for the electromagnetic vector potential ${A}_{\ensuremath{\mu}},$ which is valid for an anisotropic superstrong magnetoactive electron plasma. It is shown that the expression for the vector potential ${A}_{\ensuremath{\mu}}$ can be reduced to various known limits. Applications to important problems in astrophysics are briefly discussed. The relevance of our result to the recent development of the collective interaction between intense neutrino fluxes and stellar plasmas is briefly stressed.

A phenomenological diagram is presented to explain the interaction between a fundamental wave and its sub-harmonic wave in 2D shear layers based on linear stability theory. These diagrams indicate that there are only four classes of subharmonic interactions, which are symmetric collective interaction, the first class of asymmetric collective interaction, the second class of collective interaction and tearing. Each of them can be determined uniquely by a couple of parameters m and p, where m is the ratio of wavenumber and p is a parameter of phase difference between the fundamental wave and its subharmonic wave. For each class of subharmonic interactions, a couple of parameters m and p have been deduced from the phenomenological diagram. We think that they are significant for accurate flow control of shear layers.

Artificial neural networks have been introduced as a novel computing paradigm (Kohenen 1988). Processing (or retrieving) in neural networks requires a collective interaction of a number of neurons. Output of neurons are computed based on the inputs from other neurons, weights associated with such inputs, and a non-linear activation function. Specifically, most artificial neurons follow a mathematical model that is expressed as: $$ {Y_i}(t + 1) = F(\sum\limits_{j = 1}^N {{W_{ij}}{Y_j}(t)} ) $$ (1) where Wij is the weight, Yj(t) is the neuron input, N is the number of neurons connected to neuron 1, and F is a non linear function which is usually a sigmoid (Hopfield 1984) as shown below.

The vaporization of a droplet, interacting with its neighbors in a non-dilute spray environment is examined and a vaporization scaling law established. The interacting droplet is modeled with a centrally located droplet and its vapor bubble which is surrounded by a cloud of droplets. The distribution of the droplets and the size of cloud are characterized by a pair-distribution function. The analysis reveals that the vaporization of a droplet is retarded by the collective thermal quenching, vapor concentration accumulated in the outer sphere, and by the limited percolative passages for mass, momentum and energy fluxes. The retardation is scaled by the local collective interaction parameters group combustion number of a droplet cloud, droplet spacing, renormalization number and the local ambient conditions. The numerical results of a selected case study reveal that the vaporization correction factor falls from unity monotonically as the group combustion number increases, and saturation is likely to occur when the group combustion number reaches 35–40 with interdroplet spacing of 7.5 diameters and the environment temperature of 500 K. The scaling law suggests that dense sprays can be classified into: (1) a “Diffusively Dense” cloud characterized by uniform thermal quenching in the cloud, (2) a “ Stratified Dense” cloud characterized by a radial stratification in temperature by the differential thermal quenching of the cloud, or (3) a “Sharply Dense” cloud marked by a dense cloud structure and the magnitude of the correction factor that depends on the collective parameters, pair-distribution function, group combustion number and stratification factor of the cloud.

A multidimensional fluid model of the DC elevated pressure glow discharge has been used to study the growth of the instability near an anode inside a parallel plane surface geometry. This model is based on a fluid description of electron and ion transport coupled with Poisson's equation. The numerical results of studies of the anode glow stratification, resulting in the formation of separate glowing regions extended along the gas flow, are presented. The electron diffusion, full current, and volume electron-ion recombination have a profound effect on the collective interaction of current structures.

This paper discusses how the degree of coherence of intense resonance radiation affects the evolution process of collective photoinduced luminescence, which determines the absorption-emission dynamics in concentrated molecular systems. It is shown that the partial breakdown of coherence reduces the radius of the volume in which effective collective interaction occurs in the field-matter system and in which the relative role of classical mechanisms in the absorption-emission cycle increases.

The paper presents the results of an experimental study of hysteresis losses in a transverse magnetic field by samples that represent small coils made of round wire of Nb-Ti alloy. The experimental results turned out to be considerably different from the values computed by the methods described in the literature. A theoretical analysis has been conducted of the effect of the demagnetization factors of the conductor and the field, associated with magnetization of other turns of the winding, and used as the basis for obtaining sufficiently general closed-form types of dependence which make it possible to compute the losses with a high degree of accuracy

Particle ratios K lireh and J5IJrch in proton-nucleus collisions at high energies are calculated within the framework of two classes of models, one of which (collective models) assumes that a collective interaction is responsible for multi-hadron production in the central region and another (non-collective models) does not assume such. The collective models predict that the particle ratios increase as the target mass number increases while the non-collective models predict that they decrease provided that both KIJreh and plJ[ch are dominated by the central component.

Physical grounds of the “gathering” model are discussed. It is shown that the “gathering” of nucleons in a collective interaction is a direct consequence of the behaviour of colour forces at large distances. An analytical variant of the model is presented which allows a large simplification of the calculation procedure. The results obtained are compared with the data onπ- andK-meson cumulative production. The model applicability for relativistic nucleus-nucleus collisions is discussed.

If two rarefied masses of gas collide at a sufficiently high speed, their relative motion will be stopped by a collective plasma instability, rather than by collisions of individual particles. This is true even if the gases are initially non-ionized. In the present note, the possible influence of magnetic fields is ignored for the most part, but a criterion is found to decide under what conditions the collective interaction remains dominant even when they cannot be ignored. It seems that the neglect of magnetic effects may be justified, for example, in the case of two galaxies in collision at a relative speed of 1000 km/sec. The magnetic energy density here is (1/8π)H2∼4X10−12 erg/cm3 (with H∼10−5 gauss), which is much less than the kinetic energy density 1/2NmU2∼8X10−9 erg/cm3 (with N∼1 particle per cm3).

Die Anwendbarkeit der Debye-Huckelschen Theorie auf das Plasma wird diskutiert. Zu der Onsager-Kirkwood-Bedingung tritt eine Forderung hinzu, deren Form davon abhangt, ob Mittelwertbildung moglich ist oder nicht. Die allgemeine Formulierung der Kraftwirkung auf neutrale und geladene Teilchen wird durch die Separation der individuellen und kollektiven Komponenten in auswertbare Form gebracht. Dies liefert die Begrundung des Polarisationsmodells, welches hier — wie in I — zur Erfassung der kollektiven Wechselwirkung verwendet wird. Es zeigt sich ferner, da\ von der gesamten individuellen Wechselwirkung nur der Bruchteil von Bedeutung ist, der zur Aufpunktfeldstarke in Korrelation steht. Diese Korrelation bedingt im Bereichδ}>1 Unterschiede zwischen neutralem und geladenem Aufpunkt nur bei extremen Feldstarken. Die maschinelle Auswertung unter voller Berucksichtigung des Debyeschen Feldverlaufes gelingt ohne Vernachlassigungen. Das Grenzverhaltenδ=0 wird untersucht. To begin with we discuss the applicability of Debye-Huckel-Theory to the plasma. In addition to the well known Onsager-Kirkwood-condition we find another limitation which depends on whether averaging is possible or not. The general formulation of the force on a neutral or charged particle can be simplified by making use of the separation in individual and collective components. The result justifies the polarisation-approximation used here and in I to account for the collective interaction of the system. Moreover we find that only that fraction of the individual interaction energy is of importance which shows correlation to the field at the origin. This correlation causes differences in the results for neutral and charged particles. As long asδ>0 holds this difference is restricted to large fields. In contrast to I we were able to carry through the evaluation without using the cutoff-approximation. Furthermore we investigate the relations near the limit δ=0.

Delinquent activities are viewed from the perspective of con verging research findings on the nature of groups and their impact on the behavior of members. Theory and research show the importance of group processes for adolescent behavior whether socially desirable or undesirable. Their examination helps to resolve some paradoxes and predict "unexpected events" that currently plague formulations on delinquency. As part of the effort to achieve generally applicable concepts for theory and research, the advantage is noted of using non-pejorative terms as research tools without the stereotyped connotations of labels such as "gang" or "delinquent subculture." Based on accumulating experimental and empirical findings, a summary account is given of (a) the circumstances and motives conducive to group forma tion and (b) the step-by-step formation of the group. The socially harmful and socially desirable impact of reference groups on the identified membership is sketched and the func tion and importance of adolescent reference groups in modern societies are examined. With reference to research findings on group formation, on adolescence, and on collective interaction, implications are drawn for research methods in the study of group processes.

It is shown that theory of the Penning discharge essentially involves taking into account the collective interaction of the electrons in the near-anode region. Following investigations of the Penning discharge in a strong magnetic field (density up to 12 kOe) empirical formulae are proposed for calculating the pumping speed and the minimum operating pressures of getter-ion pumps. Methods of calculation for built-in getter-ion pump parameters and design peculiarities are considered.

Time dependent renormalized droplet theory is used to examine the dynamic saturation of a test droplet under the effects of the short range collective interaction of neighboring droplets in a non-dilute spray environment. The dynamic saturation behavior of the renormalized droplet during a transient heating is caused by the vapor accumulation and the cooling of the vapor atmosphere of a droplet. The permanent saturation or slow vaporization due to the collective interactions is found to be dependent on the group combustion number, the renormalization number and the characteristics of the environmental spray.

It is shown that the collective interaction of an ordered beam of particles with matter can give rise to coherent resonance effects (excitation, stimulated emission, ionization, etc.) if one of the eigenfrequencies of the beam, associated with its periodic structure, is equal to the frequency of a quantum transition in matter. The energy transferred to matter by one particle in the beam may be much less than the energy of this quantum transition.