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We extend the standard solid-state quantum mechanical Hamiltonian containing only Coulomb interactions between the charged particles by inclusion of the (transverse) current-current diamagnetic interaction starting from the non-relativistic QED restricted to the states without photons and neglecting the retardation in the photon propagator. This derivation is supplemented with a derivation of an analogous result along the non-rigorous old classical Darwin-Landau-Lifshitz argumentation within the physical Coulomb gauge. [ABSTRACT FROM AUTHOR]

In the present work, the cooperativity effect on the NLO response of clusters aggregated with bifurcated metal bonds is reported by DFT calculations at the CAM-B3LYP/6-311++G(d,p) level. Linear clusters of (LiN(CHO)) and (NaN(CHO)) which are connected with bifurcated metal bonds have been selected as model systems. Stabilization energies, polarizability, first hyperpolarizability, energy gap of HOMO and LUMO, and charge transfer (CT) were obtained at the same level of optimization. In the studied clusters, first hyperpolarizability is increased by cluster size and its values were obtained in ranges of 606.1-1327.4 and 1239.4-2071.1 a.u. for (LiN(CHO)) and (NaN(CHO)) clusters, respectively. The many-body analysis was carried out to determine two-body and many-body contributions in total interaction-induced properties. TD-DFT calculations were performed to compute the crucial electronic transitions of the related clusters. UV-vis spectra exhibit red shift due to cooperativity effects. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method to describe the many-body problem of electrons in honeycomb materials via the introduction of random fields which are coupled to the electrons and have a Gaussian distribution. From a one-body approach to the problem, after integrating exactly the contribution of the random fields, one builds a non-hermitian and dissipative effective Hamiltonian with two-body interactions. Our approach introduces besides the usual average over the electron field a second average over the random fields. The interplay of two averages enables the definition of various types of Green's functions which allow the investigation of fluctuation-dissipation characteristics of the interactions that are a manifestation of the many-body problem. In the current work, we study only the dissipative term, through the perturbative analysis of the dynamics associated the effective Hamiltonian generated by two different kinds of couplings. For the cases analyzed, the eigenstates of the effective Hamiltonian are complex and, therefore, some of the states have a finite life time. Moreover, we also investigate, in the mean field approximation, the most general parity conserving coupling to the random fields and compute the width of charge carriers Γ as a function of the Fermi energy E . The theoretical prediction for Γ( E ) is compared to the available experimental data for graphene. The good agreement between Γ and Γ suggests that description of the many-body problem associated to the electrons in honeycomb materials can indeed be done via the introduction of random fields. [ABSTRACT FROM AUTHOR]

This paper reports the explorations on the particle dynamics, ion distribution, energy spectra and temperature in a new-designed inertial electrostatic confinement fusion device in case of low azimuthal magnetic field. The proposed design has six bar-sized cathodes at the vicinity of the central region and a central DC current-carrying bar injects a homogeneous azimuthal magnetic flux on the particles. The cylindrical device is simulated in the fully ionized Deuterium media. Following the 3D design of the chamber, the real-time simulations have been performed by the time integration of the electrical and magnetic forces. The model uses the many-body approach with the particle-particle and particle-chamber interactions. To implement the particle-chamber interaction, the finite difference method has been applied. Besides, the model includes reflection effects of particles from the electrically grounded chamber wall. According to the simulations, the particle trajectories exhibit complex fluctuations in the central region and nearby the chamber walls. The ion temperature has been calculated around T = 35 keV for the source potential V = −150 kV. In addition, the ion distribution indicates that 68 % of ions can be collected in the central region. According to the velocity distribution, there exists a double Gaussian distribution with a low velocity peak. In addition, nearly 61 % of ions stay in the energy scale between 2 keV ≤ E ≤ 39 keV. The averaged neutron rate is estimated as 5.96 × 10 n/s. [ABSTRACT FROM AUTHOR]

Quantum vortex reconnections can be considered as a fundamental unit of interaction in complex turbulent quantum gases. Understanding the dynamics of single vortex reconnections as elementary events is an essential precursor to the explanation of the emergent properties of turbulent quantum gases. It is thought that a lone pair of quantum vortex lines will inevitably interact given a sufficiently long time. This paper investigates aspects of reconnections of quantum vortex pairs imprinted in a Bose-Einstein condensate with 101 bosons held in an anisotropic three-dimensional trap using an exact many-body treatment. In particular, the impact of the interaction strength and the trap anisotropy in the reconnection time is studied. It is found that interaction strength has no effect on reconnection time over short time scales and that the trap anisotropy can cause the edge of the condensate to interfere with the reconnection process. It is also found that the initially coherent system fragments very slowly, even for a relatively large interaction strength, and therefore the system tends to stay condensed during the reconnections. [ABSTRACT FROM AUTHOR]

Despite the myriad complexities inherent in human conflict, a common pattern has been identified across a wide range of modern insurgencies and terrorist campaigns involving the severity of individual events-namely an approximate power-law x with exponent α≈2.5. We recently proposed a simple toy model to explain this finding, built around the reported loose and transient nature of operational cells of insurgents or terrorists. Although it reproduces the 2.5 power-law, this toy model assumes every actor is identical. Here we generalize this toy model to incorporate individual heterogeneity while retaining the model's analytic solvability. In the case of kinship or team rules guiding the cell dynamics, we find that this 2.5 analytic result persists-however an interesting new phase transition emerges whereby this cell distribution undergoes a transition to a phase in which the individuals become isolated and hence all the cells have spontaneously disintegrated. Apart from extending our understanding of the empirical 2.5 result for insurgencies and terrorism, this work illustrates how other statistical physics models of human grouping might usefully be generalized in order to explore the effect of diverse human social, cultural or behavioral traits. [ABSTRACT FROM AUTHOR]

Non-additivity of base-base interactions in all ten possible model dinucleotide steps were analyzed on MP2/aug-cc-pvDZ quantum chemistry level. Conformations of four nucleobases exactly matched to ones occurring in B-DNA crystals. In most of thw 162 analyzed tetramers both three- and four-body contributions are negligible except for d(GpG) steps. However, in these dinucleotides both contributions are always of opposite signs and in all cases the sum of all non-additive part of intermolecular interactions do not exceed 2.6 kcal mol. This stands for less than 5% of the overall binding energy of dinucleotide steps. Also replacements of guanine with 8-oxoguanine in d(GpG) systems introduces non-additivity of the same magnitude as for canonical dinucleotides. It is observed linear relationships between values of total binding energy obtained in the tetramer basis set and estimated energy exclusively in dimers basis sets with assumption of pairwise additivities. For all analyzed dinucleotides steps there are also linear correlations between amount of non-additive contributions and magnitude of pairs interactions. Based on differences in electrostatic contribution to the total binding energy of four nucleobases and polarity of dinucleotide steps three distinct classes of dinucleotide steps were identified. [ABSTRACT FROM AUTHOR]

Transient regime relaxation in nanostructures is governed by the two-way information exchange between the active region and the contacts. In this paper, we introduce a second order quantum master equation for the active region’s many-body reduced density matrix, which includes the information exchange between the active region and the contacts, while eliminating the contacts explicitly from the simulation. For the case of a resonant-tunneling diode, the master equation is solved numerically. Proper injection from/into the contacts is obtained, and natural oscillations of the current and the number of particles in the well are observed, with a frequency in the mid-terahertz regime. [ABSTRACT FROM AUTHOR]