Dynamic dipole–dipole induction of coherence among a quantum dot ensemble

The quantum mechanical dynamic resonance due to dipole–dipole interaction is shown possibly to induce coherent modes of electrons within an ensemble of two-level systems or quantum dots. The physical origin of this coherence would naturally be postulated as the parity inheritance into a site being excited from another site being de-excited. An experimental spectrum suggestive of this dipole–dipole mode is also shown. This coherence is expected to be useful for quantum computing.     

Critique of generalised purity as an entanglement measure: Explicit failure in simple separable Bose–Hubbard models

The SU(2) and SU(3) Lie algebras lend themselves naturally to studies of two- and three-well Bose–Einstein condensates, with the group operators being expressed in terms of bosonic annihilation and creation operators at each site. The success of these representations has led to the purities associated with these algebras to be promoted as a measure of entanglement in these systems. In this work, we show that these purities do not provide an unambiguous measure of entanglement between wells, but instead give results which depend on the quantum statistical states of the atomic ensembles in each well. Using the example of totally uncoupled wells where the atoms in one have never interacted with the atoms in the other, we quantify these purities for different states and show that completely separable states can give values which have been claimed to indicate the presence of entanglement. We also consider claims that the generalised purities measure particle rather than mode entanglement, with emphasis on the case of indistinguishable bosons, as found in these systems.     

Effect of anomalous tbW vertex on decay-lepton distributions in e + e − → tt and CP-violating asymmetries

We obtain analytic expressions for the energy and polar-angle double differential distributions of a secondary lepton l ⁺ (l ⁻) arising from the decay of t(t) in e ⁺ e ⁻ → tt with an anomalous tbW decay vertex. We also obtain analytic expressions for the various differential cross-sections with the lepton energy integrated over. In this case, we find that the angular distributions of the secondary lepton do not depend on the anomalous coupling in the decay, regardless of possible anomalous couplings occurring in the production amplitude for e ⁺ e ⁻ → tt. Our study includes the effect of longitudinal e ⁻ and e ⁺ beam polarization. We also study the lepton energy and beam polarization dependence of certain CP-violating lepton angular asymmetries arising from an anomalous tbW decay vertex and compare them with the asymmetries arising due to CP-violation in the production process due to the top electric or weak dipole moment.     

Control of excitons in a bent bunch of molecular aggregates by dipole–dipole interaction with quantum dots

The nonlocal dipole–dipole interaction is studied between excitations in chromophores forming a bunch or a tube of J-aggregates and closely spaced quantum dots (QDs). Equations describing the evolution of exciton pulses in a quasi-one-dimensional medium are derived taking into account the interaction with the transition resonant to nanoparticles. It is shown that the efficient controllable resonance energy transfer can occur in the system between QDs and an exciton pulse. The efficiency of this process significantly increases if the bunch of aggregates is deformed to bend nanoparticles round. It is shown that the interaction of permanent dipole moments of QDs and chromophores leads to the formation of a potential barrier or a well. It is found that the combined influence of these factors can be used to efficiently control the dynamics of pulses in aggregates.     

Demonstration of a quasi-scalar angular Goos-Hänchen effect

We show experimentally that the angular Goos-H?nchen (GH) effect can be easily observed, also without employing its resonant enhancement at Brewster incidence. An s-polarized beam was used to decouple the polarization from the propagation dynamics of the beam. We found that, in this case, the angular GH effect can be strongly enhanced by increasing the angular aperture of the Gaussian beam. Our experiments suggest a route toward observing the angular GH effect for true scalar waves, such as acoustic waves and quantum matter waves.     

Microscopic theory of dipole–dipole interaction in ensembles of impurity atoms in a Fabry–Perot cavity

We develop a consistent quantum theory of the collective effects that take place when electromagnetic radiation interacts with a dense ensemble of impurity centers embedded in a transparent dielectric and placed in a Fabry–Perot cavity. We have calculated the spontaneous decay dynamics of an excited impurity atom as a specific example of applying the developed general theory. We analyze the dependence of the decay rate on the density of impurity centers and the sample sizes as well as on the characteristic level shifts of impurity atoms caused by the internal fields of the dielectric. We show that a cavity can affect significantly the pattern of collective processes, in particular, the lifetimes of collective states.     

Improvement of spectral resolution by using the excitation dependence of dipole–dipole interaction in a dense atomic gas

We have studied the selective reflection from the interface between a dense rubidium (Rb) atomic vapor and a transparent dielectric. A remarkable narrowing of the spectrum, which can be used to improve the resolution of spectroscopy of dense media, has been demonstrated. This narrowing results from the reduction of the dipole–dipole interaction between atoms when the Rb vapor is excited by a strong pump laser. By using this technique, we have resolved the hyperfine structure of the Rb D₂ line, which is hidden by collisional broadening. PACS 32.70.Jz; 42.50.Ct; 34.80.Dp     

Asymmetry of π− meson emission in nucleus-nucleus collisions as a measure of the target-to-projectile ratio of the numbers of interacting nucleons

Experimental data on the forward-backward asymmetry of π^- emission in (d,⁴He,¹²C)¹⁸¹Ta interactions atp/A=4.2 GeV/c are presented. The absolute value of the asymmetry coefficient of the inclusive π^- production in the nucleon-nucleonCMS decreases asA _p ^?0.35 with increasing atomic mass of projectile nucleus. A method of obtaining the target-to-projectile ratio of the numbers of participant nucleonsN _t /N _p through measuring the velocity of the symmetric pion emission system is proposed. It has been found that N_t/N_p～A _p ^?0.73 .     

States of one-dimensional Coulomb systems as simple examples of θ vacua and confinement

The one-dimensional Coulomb system is known to have equilibrium states with nonvanishing electric field. These states are shown here to be analogous, and related, to the vacua which have been discussed for gauge theories in two or more space-time dimensions. The system exhibits confinement of fractional charges, which we dicuss with the purpose of offering a simple example of the-vacua phenomenology. Precise relations and connections between one-dimensional Coulomb gases and two-dimensional Abelian gauge theories, and quantum-mechanical matter systems, are discussed.Supported in part by National Science Foundation Grant PHY-2825390 A01.     

Scattering of a surface plasmon polariton beam by chains of dipole nanoparticles

Scattering and splitting of surface plasmon polaritons (SPPs) by a chain of strongly interacting nanoparticles located near a metal surface are numerically studied. The applied numerical model is based on the Green’s function formalism and point–dipole approximation for scattering by nanoparticles. Dependencies of the splitting efficiency on the inter-particle distance in the chain and on the angle of incidence of the SPP Gaussian beam are considered. It is found that the splitting efficiency depends on the inter-particle distances especially when the angle between the SPP beam and the chain is relatively small. The role of multiple scattering in the SPP splitting by the chains of nanoparticles is also discussed.     

A simple geometric representative for μ of a point

ForSU(2) (orSO(3)) Donaldson theory on a 4-manifoldX, we construct a simple geometric representative for of a point. Letp be a generic point inX. Then the set {[A]F _A ^– (p) is reducible}, with coefficient –1/4 and appropriate orientation, is our desired geometric representative. The construction is an exercise in real algebraic geometry in the style of Ehresmann and Pontryagin.This work is partially supported by an NSF Mathematical Sciences Postdoctoral Fellowship and Texas Advanced Research Project grant ARP-037.     

The dipole moment function of CO(a 3Π)

The dipole moment function of the a ³Π state of CO is calculated using the multi-configuration self-consistent-field method of Wahl and Das. Only the dominant valence charge-transfer correlation configurations are mixed with the Hartree-Fock configuration since only the region between the classical turning points of the v = 1 vibrational level is considered. The calculated function does not agree with the shape of the fitted dipole moment function of Wicke et al. Configurations chosen on the basis of the model of optimized valence configurations do not determine an accurate dipole moment function for an open shell system.     

Normalized entropy of rank distribution： a novel measure of heterogeneity of complex networks

Many unique properties of complex networks result from heterogeneity. The measure and analysis of heterogeneity are important and desirable to the research of the properties and functions of complex networks. In this paper, the rank distribution is proposed as a new statistic feature of complex networks. Based on the rank distribution, a novel measure of the heterogeneity called a normalized entropy of rank distribution (NERD) is proposed. The NERD accords with the normal meaning of heterogeneity within the context of complex networks compared with conventional measures. The heterogeneity of scale-free networks is studied using the NERD. It is shown that scale-free networks become more heterogeneous as the scaling exponent decreases and the NERD of scale-free networks is independent of the number of vertices, which indicates that the NERD is a suitable and effective measure of heterogeneity for networks with different sizes.     

Quantum-electrodynamic modification of atomic dipole matrix element in a strong converging laser field

In this paper we report at the first time a quantum-electrodynamic modificationresult to the dipole transition matrix elements related to the bound levels of an atom in a strongconverging laser field.When the laser intensity increases,the dipole matrix elements increaseat first.However,further intensity increase will bring about the matrix elements decrease.That means the dipole transition probability is suppressed.     

Preparation of CeO2 by a simple microwave–hydrothermal method

Cerium carbonate hydroxide (orthorhombic Ce(OH)CO₃) hexagonal-shaped microplates were synthesized by a simple and fast microwave–hydrothermal method at 150 °C for 30 min. Cerium nitrate, urea and cetyltrimethylammonium bromide were used as precursors. Ceria (cubic CeO₂) rhombus-shape was obtained by a thermal decomposition oxidation process at 500 °C for 1 h using as- synthesized Ce(OH)CO₃. The products were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, thermogravimetric analysis and Fourier transformed infrared spectroscopy. The use of microwave–hydrothermal method allowed to obtain cerium compounds at low temperature and shorter time compared to other synthesis methods.     

Additional Z′-boson and polarization asymmetries in annihilationary creation of a scalar quark pair

The possibility is studied of using the longitudinal and transverse polarization asymmetries as principle variables for detecting creation of scalar quark states in e⁺e^–-annihilation, taking into account the contribution of the superstring Z-boson.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 101–106, April, 1991.The authors thank A. A. Iogansen and I. S. Satsunkevich for stimulating discussion and their interest to this work.     

Resonance Conversion as a Catalyzer of Nuclear Reactions

It is shown that resonance internal conversion offers a feasible tool for mastering nuclear processes with laser or synchrotron radiation. The physics of the process is discussed in detail in a historical aspect. Possible experimental application is shown in the case of the M1 70.6-keV transition in nuclei of 169 Yb. The nuclear transition rate in hydrogen-like ions of this nuclide can be enhanced by up to four orders of magnitude.     

Phase diagram of a simple model of Eu p Sr1−p S

A random site Ising model on the checkerboard square lattice with first neighbor interactionsJ in all first neighbor bonds and second neighbor interactionsJ in red squares is considered as a simple model of the dilute spin glass of Eu _p Sr_1–p S. The phase boundary between the paramagnetic and ferromagnetic phases, and that between the paramagnetic and spin glass phases are calculated. The obtained phase diagram is qualitatively similar to the experimental result by Maletta and Convert.