Studies Of Long-range Interactions Research Articles

Quantum simulation of ultracold atoms in optical lattice based on dynamical mean-field theory

With the development of atomic cooling technology and optical lattice technology, the quantum system composed of optical lattice and ultracold atomic gas has become a powerful tool for quantum simulation. The purity and highly controllable nature of the optical lattice give it a strong regulatory capability. Therefore, more complex and interesting physical phenomena can be simulated, which deepens the understanding of quantum many-body physics. In recent years, we have studied different Bose systems with strong correlations in optical lattice based on the bosonic dynamical mean-field theory, including multi-component system, high- orbit bosonic system, and long-range interaction system. In this review, we introduce the research progress of the above mentioned. Through the calculation by using bosonic dynamical mean-field theory which has been generalized to multi-component and real space versions, a variety of physical phenomena of optical crystal lattice Bose system in weak interaction intervals to strong interaction intervals can be simulated. The phase diagram of spin-1 ultracold bosons in a cubic optical lattice at zero temperature and finite temperature are drawn. A spin-singlet condensate phase is found, and it is observed that the superfluid can be heated into a Mott insulator with even (odd) filling through the first (second) phase transition. In the presence of a magnetic field, the ground state degeneracy is broken, and there are very rich quantum phases in the system, such as nematic phase, ferromagnetic phase, spin-singlet insulating phase, polar superfluid, and broken-axisymmetry superfluid. In addition, multistep condensations are also observed. Further, we calculate the zero-temperature phase diagram of the mixed system of spin-1 alkali metal atoms and spin-0 alkali earth metal atoms, and find that the system exhibits a non-zero magnetic ordering, which shows a second-order Mott insulation-superfluid phase transition when the filling number is <inline-formula><tex-math id="M1">\begin{document}$n=1$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230701_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230701_M1.png"/></alternatives></inline-formula>, and a first-order Mott insulation-superfluid phase transition when the filling number is <inline-formula><tex-math id="M2">\begin{document}$n=2$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230701_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230701_M2.png"/></alternatives></inline-formula>. The two-step Mott-insulating-superfluid phase transition due to mass imbalance is also observed. In the study of long-range interactions, we first use Rydberg atoms to find two distinctive types of supersolids, and then realize the superradiant phase coupled to different orbits by controlling the reflection of the pump laser in the system coupled to the high-finesse cavity. Finally, we study the high-orbit Bose system. We propose a new mechanism of spin angular-momentum coupling with spinor atomic Bosons based on many-body correlation and spontaneous symmetry breaking in a two-dimensional optical lattice, and then study the orbital frustration in a hexagonal lattice. We find that the interaction between orbital frustration and the strong interaction results in exotic Mott and superfluid phases with spin-orbital intertwined orders.

Two-dipole and three-dipole interaction coefficients of group XII elements

Study of long-range interactions is increasingly becoming essential due to its various applications in cold atomic physics. These interactions can be conveniently expressed in terms of various dispersion coefficients. In the present work, theoretical calculations have been carried out for the two-dipole (C6), and three-dipole (C9) dispersion coefficients among the group XII atoms and their ions, viz. Zn, Cd, Hg, Zn+, Cd+, and Hg+. To obtain these coefficients, the dynamic dipole polarizabilities and reduced matrix elements required are evaluated using the relativistic methods. Further, using the calculated matrix elements, the oscillator strengths corresponding to leading transitions and static dipole polarizabilities of these atoms and ions are determined for the comparison purposes.

A computational framework for identifying the transcription factors involved in enhancer-promoter loop formation

The pairwise interaction between transcription factors (TFs) plays an important role in enhancer-promoter loop formation. Although thousands of TFs in the human genome have been found, only a few TF pairs have been demonstrated to be related to loop formation. It is still a challenge to determine which TF pairs could be involved in the enhancer-promoter regulation network. This work describes a computational framework to identify TF pairs in enhancer-promoter regulation. By integrating different levels of data derived from Promoter Capture Hi-C, chromatin immunoprecipitation sequencing (ChIP-seq) of histone marks, RNA-seq, protein-protein interaction (PPI), and TF motif, we identified 361 significant TF pairs and constructed a TF interaction network. From the network, we found several hub-TFs, which may have important roles in the regulation of long-range interactions. Our studies extended TF pairs identified in other experimental and computational approaches. These findings will help the further study of long-range interactions between enhancers and promoters.

Long-Range Ordered Water Correlations between A–T/C–G Nucleotides

Summary The interactions between complementary base pairs are crucial to the helical duplex structure of DNA. Although base-base interactions have been widely reported, the study of long-range interactions in the base-pairing processes is still a major challenge in this field. Here, we first study the long-range interactions between the base pairs by atomic force microscopy-based single-molecule force spectroscopy (SMFS). The SMFS results of A–T/C–G imply that there are weak long-range interactions between them, which have a range of 15–25 nm. Raman spectroscopy results imply that these weak interactions can be attributed to multiplex hydrogen bond interaction of ordered water structure between A–T/C–G nucleotides. In addition, the theoretical calculations deduce that the ideal structure of these water molecules exhibits a specific helical structure. Our findings might open up a new understanding of biological assembly processes and provide helpful strategies for bio-nanotechnology.

Analysis tools for the interplay between genome layout and regulation.

BackgroundGenome layout and gene regulation appear to be interdependent. Understanding this interdependence is key to exploring the dynamic nature of chromosome conformation and to engineering functional genomes. Evidence for non-random genome layout, defined as the relative positioning of either co-functional or co-regulated genes, stems from two main approaches. Firstly, the analysis of contiguous genome segments across species, has highlighted the conservation of gene arrangement (synteny) along chromosomal regions. Secondly, the study of long-range interactions along a chromosome has emphasised regularities in the positioning of microbial genes that are co-regulated, co-expressed or evolutionarily correlated. While one-dimensional pattern analysis is a mature field, it is often powerless on biological datasets which tend to be incomplete, and partly incorrect. Moreover, there is a lack of comprehensive, user-friendly tools to systematically analyse, visualise, integrate and exploit regularities along genomes.ResultsHere we present the Genome REgulatory and Architecture Tools SCAN (GREAT:SCAN) software for the systematic study of the interplay between genome layout and gene expression regulation. GREAT:SCAN is a collection of related and interconnected applications currently able to perform systematic analyses of genome regularities as well as to improve transcription factor binding sites (TFBS) and gene regulatory network predictions based on gene positional information.ConclusionsWe demonstrate the capabilities of these tools by studying on one hand the regular patterns of genome layout in the major regulons of the bacterium Escherichia coli. On the other hand, we demonstrate the capabilities to improve TFBS prediction in microbes. Finally, we highlight, by visualisation of multivariate techniques, the interplay between position and sequence information for effective transcription regulation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-016-1047-0) contains supplementary material, which is available to authorized users.

Monte Carlo Study of Long-Range Interactions of a Ferroelectric Bilayer with Antiferroelectric Interfacial Coupling

By the use of Monte Carlo simulation, we have studied the critical behavior of a ferroelectric bilayer with antiferroelectric interfacial coupling using the transverse spin- $\frac{1}{2}$ Ising model. We discuss the effects of long-range interactions for the internal energy, specific heat, free energy, dielectric susceptibility, and polarization. The dependence of the Curie temperature on the thickness of the bilayer, long-range interactions, and the transverse field was also investigated. It is assumed that the long-range interaction decays with the distance between the pseudo-spins as a power law.

Numerical study of long-range interaction between two beams in (1+2)-dimensional thermal nonlocal media

According to the nonlinear Schrödinger equation and Poisson equation of thermal diffusion, we investigate the interaction of double beams in (1+2)-dimension thermal nonlocal medium, using the slip-step Fourier algorithm and multi-grid method. The results show that the two beams intertwine with each other during propagation. If the power and the tilt parameter are appropriate, the projections of the trajectories of the beams in (X, Y) plane are approximately circle, even if the incident distance between the beams is changed. Because of the strongly nonlocal property of thermal medium, the influences of boundaries and initial transverse momentum can be felt when beams are far from the boundaries; there will be an oscillatory propagation when the mass center of the input field deviates from sample center or the initial transverse momentum is unequal to zero.

Long-term earthquake triggering in the Southern and Northern Apennines

We argue that the study of long-range interaction between seismic sources in the peri-Adriatic regions may significantly contribute to estimating seismic hazard in Italy. This hypothesis is supported by the reconstruction of the geodynamic and tectonic settings in the Central Mediterranean region, the space–time distribution of major past earthquakes, and the quantification of post-seismic relaxation. The most significant evidence of long-distance interaction is recognized for the Southern Apennines, whose major earthquakes have almost regularly followed within a few years the largest events in the Montenegro-Albania zone since 1850. Statistical analyses of the post-1850 earthquake catalogues give a probability of about 10% that a major event in the Southern Apennines is not preceded by the occurrence of a strong event in the Southern Dinarides–Albanides within 3–5 years. Conversely, the probability of false alarms is relevant (50% within 3 years, 33% within 5 years). Northward, the tectonic setting and some patterns of regularity seen in major events suggest that the seismic activation of the main transtensional decoupling shear zones in the Central Apennines should influence the probability of major earthquakes in the Northern Apennines.

Spherical tensor theory of long‐range interactions between two molecules

AbstractThe Rayleigh–Schrödinger perturbation treatment can be applied in the quantum mechanical study of long‐range interactions between molecules, when we can assume that the molecular charge distributions do not overlap. In these cases the multipole expansion is a good approximation of real interaction potential and can be treated as a perturbation. In this paper we obtain closed expressions for the anisotropic long‐range interaction energy between two molecules in all orders of the perturbation, using spherical tensor formalism. Then we show how spherical multipoles and polarizabilities of the isolated molecules can be inserted into general formulas for interaction energy.

Ab initio Studies of long range interactions between ethylene molecules in the multipole expansion

The multipole moments and multipole polarizabilities of ethylene and the long range coefficients for the interactions between two ethylene molecules have been calculated using LCAO-SCF wave functions. Subjecting different AO basis sets to a completeness test, we have shown that the inclusion of polarization functions slightly more diffuse than the valence orbitals is required for an appropriate description of the second order quantities. The (theoretical) Unsöld procedure which is introduced to approximate the second order interaction energy, appears to be rather accurate and is preferable for small basis sets.

Theory of the chemical bond. IV. Long range interatomic interactions and their relationship to internal kinetic and potential energy variations

Implicit perturbation theory is applied to the study of long range interactions. It is shown that internal kinetic and potential energy changes effect the interaction energy in the third order.

Ab initio Studies of long range interactions between ethylene molecules in the multipole expansion

The multipole moments and multipole polarizabilities of ethylene and the long range coefficients for the interactions between two ethylene molecules have been calculated using LCAO-SCF wave functions. Subjecting different AO basis sets to a completeness test, we have shown that the inclusion of polarization functions slightly more diffuse than the valence orbitals is required for an appropriate description of the second order quantities. The (theoretical) Unsold procedure which is introduced to approximate the second order interaction energy, appears to be rather accurate and is preferable for small basis sets.

“Hydrophobic Bonds”? A Study of Long-Range Interactions in Polymers

Abstract Inelastic neutron scattering spectroscopy offers a unique method of studying the intermolecular forces binding molecular crystals and polymers. The results from incoherent and coherent neutron spectroscopy are here related. For polyethylene they lead to the conclusion that the interchain forces are nearly two orders of magnitude weaker than the valence forces in a chain.