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Quantum theory

J S Rojas-Arias, B A Rodríguez, H Vinck-Posada
Dipolaritons are quasiparticles that arise in coupled quantum wells embedded in a microcavity, they are a superposition of a photon, a direct exciton and an indirect exciton. We propose the existence of dipolaritons in a system of two coupled quantum dots inside a microcavity in direct analogy with the quantum well case and find that, despite some similarities, dipolaritons in quantum dots have different properties and can lead to true dark polariton states. We use a finite system theory to study the effects of the magnetic field on the system, including the emission, and find that it can be used as a control parameter of the properties of excitons and dipolaritons, and the overall magnetic behaviour of the structure...
October 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Matthias Kleinmann, Adán Cabello
We show that, for any n, there are m-outcome quantum correlations, with m>n, which are stronger than any nonsignaling correlation produced from selecting among n-outcome measurements. As a consequence, for any n, there are m-outcome quantum measurements that cannot be constructed by selecting locally from the set of n-outcome measurements. This is a property of the set of measurements in quantum theory that is not mandatory for general probabilistic theories. We also show that this prediction can be tested through high-precision Bell-type experiments and identify past experiments providing evidence that some of these strong correlations exist in nature...
October 7, 2016: Physical Review Letters
Tobias Dornheim, Simon Groth, Travis Sjostrom, Fionn D Malone, W M C Foulkes, Michael Bonitz
We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with the linear response theory, we are able to remove finite-size errors from the potential energy over the substantial parts of the warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)]. Extensive new QMC results for up to N=1000 electrons enable us to compute the potential energy V and the exchange-correlation free energy F_{xc} of the macroscopic electron gas with an unprecedented accuracy of |ΔV|/|V|,|ΔF_{xc}|/|F|_{xc}∼10^{-3}...
October 7, 2016: Physical Review Letters
Diogo Boito, Matthias Jamin, Ramon Miravitllas
The quantum chromodynamics (QCD) coupling α_{s} is not a physical observable of the theory, since it depends on conventions related to the renormalization procedure. We introduce a definition of the QCD coupling, denoted by α[over ^]_{s}, whose running is explicitly renormalization scheme invariant. The scheme dependence of the new coupling α[over ^]_{s} is parametrized by a single parameter C, related to transformations of the QCD scale Λ. It is demonstrated that appropriate choices of C can lead to substantial improvements in the perturbative prediction of physical observables...
October 7, 2016: Physical Review Letters
Koichi Hattori, Yi Yin
We investigate novel transport phenomena in a chiral fluid originated from an interplay between a vorticity and strong magnetic field, which induces a redistribution of vector charges in the system and an axial current along the magnetic field. The corresponding transport coefficients are obtained from an energy-shift argument for the chiral fermions in the lowest Landau level due to a spin-vorticity coupling and also from diagrammatic computations on the basis of the linear response theory. Based on consistent results from both methods, we observe that the transport coefficients are proportional to the anomaly coefficient and are independent of temperature and chemical potential...
October 7, 2016: Physical Review Letters
David A Mazziotti
A central challenge of physics is the computation of strongly correlated quantum systems. The past ten years have witnessed the development and application of the variational calculation of the two-electron reduced density matrix (2-RDM) without the wave function. In this Letter we present an orders-of-magnitude improvement in the accuracy of 2-RDM calculations without an increase in their computational cost. The advance is based on a low-rank, dual formulation of an important constraint on the 2-RDM, the T2 condition...
October 7, 2016: Physical Review Letters
Y Tang, A G Sykes, N Q Burdick, J M DiSciacca, D S Petrov, B L Lev
We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the postexpansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases...
October 7, 2016: Physical Review Letters
Junki Yoshitake, Joji Nasu, Yukitoshi Motome
Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid...
October 7, 2016: Physical Review Letters
Giuseppe Lanza, Maria A Chiacchio
Exploration of interfacial hydration networks of zwitterion and non-ionized trialanine has been performed using DFT-M062X quantum chemical computations explicitly considering up to 41 water molecules. The step-by-step water molecules peptide surrounding, carried out for unfolded extended (β), polyproline II (PPII) conformations reveals the crucial importance of explicit solvent effects in stabilizing the zwitterion form and the left-handed PPII-helix ubiquitously found at room temperature for short polyalanines...
October 21, 2016: Journal of Physical Chemistry. B
Martin Leder, Christopher Grossert, Lukas Sitta, Maximilian Genske, Achim Rosch, Martin Weitz
To describe a mobile defect in polyacetylene chains, Su, Schrieffer and Heeger formulated a model assuming two degenerate energy configurations that are characterized by two different topological phases. An immediate consequence was the emergence of a soliton-type edge state located at the boundary between two regions of different configurations. Besides giving first insights in the electrical properties of polyacetylene materials, interest in this effect also stems from its close connection to states with fractional charge from relativistic field theory...
October 21, 2016: Nature Communications
Erfan Dashtimoghadam, Ghasem Bahlakeh, Hamed Salimi-Kenari, Mohammad Mahdi Hasani-Sadrabadi, Hamid Mirzadeh, Bo Nyström
The temperature-induced gelation of chitosan/glycerophosphate (Chs/GP) systems through physical interactions has shown great potential for various biomedical applications. In the present work, hydroxyethyl cellulose (HEC) was added to the thermosensitive Chs/GP solution to improve the mechanical strength and gel properties of the incipient Chs/HEC/GP gel in comparison with the Chs/GP hydrogel at body temperature. The physical features of the macromolecular complexes formed by the synergistic interaction between chitosan and hydroxyethyl cellulose in the presence of β-glycerophosphate disodium salt solution have been studied essentially from a rheological point of view...
October 21, 2016: Biomacromolecules
Olujide O Olubiyi, Birgit Strodel
In this article we provide a data package containing the topology files and parameters compatible with the CHARMM22 force field for thirteen non-natural amino acids. The force field parameters were derived based on quantum mechanical (QM) calculations involving geometry optimization and potential energy surface scanning at the HF 6-31G(d) and HF 6-311G(d,p) levels of theory. The resulting energy data points were fitted to mathematical functions representing each component of the CHARMM22 force field. Further fine-tuning of the parameters utilized molecular mechanics energies, which were iteratively calculated and compared to the corresponding QM values until the latter were satisfactorily reproduced...
December 2016: Data in Brief
Tao Jiang, Menghua Wang, Li Li, Jinguang Si, Bo Song, Cao Zhou, Meng Yu, Xuewei Wang, Yonggang Zhang, Gang Ding, Zhongmei Zou
Overexpression of laeA in Chaetomium globosum CBS148.51 up-regulated expression of the chaetoglobosin gene cluster and resulted in the isolation of a new cytochalasan, chaetoglobosin Z (1), together with six known analogues, chaetoglobosins A (2), B (3), D (4), E (5), O (6), and V (7). RT-PCR analysis confirmed that the key genes in the chaetoglobosin gene cluster were significantly up-regulated. The structure of the new compound chaetoglobosin Z (1) was elucidated using NMR data. The relative and absolute configurations were determined by NOESY and electronic circular dichroism combined with quantum-chemical calculations adopting time-dependent density functional theory methods, respectively...
October 19, 2016: Journal of Natural Products
Mukul R Gupta, Alok Kumar, Naveen K Khare
Two new compounds 1 (Methyl 26-di-deoxy-6-methyl-β-D-allohexopyranoside) and 3 (3, 11, 12, 20 tetra-O-acetyl-pregn-5-ene-14β-ol) have been isolated from the chloroform-soluble extract of the whole plant of Marsdenia roylei (family: Asclepiadaceae) and their structures were determined by 1D, 2D NMR and ESI-MS as well as by chemical modification. We have calculated the molecular geometries, local reactivity descriptors by the density functional theory with B3LYP functional with basis set 6-311G+(d,2p) of 1, 3 and 4 (deacylated 3)...
October 18, 2016: Natural Product Research
William W Parson
The rates of nonadiabatic electron-transfer reactions depend on four main factors: the probability of finding the system in a conformation in which the reactant and product states have the same energy, the electronic coupling that drives oscillations between the two diabatic states, the dephasing that damps these oscillations, and the vibrational or electronic relaxations that trap the product state by transferring energy to the surroundings. This paper develops a simple expression that combines these factors in a relatively realistic manner...
October 18, 2016: Journal of Physical Chemistry. B
Teng-Fei Lu, Wei Li, Jie Chen, Fu-Quan Bai, Jian Wang, Ling-Jun He, Hong-Xing Zhang
In this work, we designed three dyes (Ru1, Ru2, and Ru3) by modifying the square-planar quadridentate ligand of the experimental Ru(ii) complex K1, [RuL(trans-NCS)2] with L = dimethyl-6,60-bis(methyl-2-pyridylamino)-2,20-bipyridine-4,40-dicarboxylate, from a theoretical viewpoint. As is known, K1 shows obvious advantages over the famous dye N749 in light absorption ability because of its highly conjugated ancillary ligands. Density functional theory and time-dependent density functional theory methods were used to determine the geometrical structures, electronic structures and absorption spectra of the dye complexes...
October 18, 2016: Physical Chemistry Chemical Physics: PCCP
Lucjan Jerzykiewicz, Adam Sroka, Irena Majerz
The crystal structure of fenamic acid-acridine complex is determined by X-ray diffraction. The strong OHN hydrogen bond linking the complex components and other interactions responsible for packing of the molecules into a crystal are investigated within the Quantum Theory of Atom in Molecule theory. The crystal structure is compared with the structure optimized at B3LYP/6-311++G** level and with the theoretical structures optimized under systematically changed pressure. Analysis of the lattice constants, hydrogen bond lengths, and angles of the inter- and intramolecular hydrogen bond under compression is performed...
October 14, 2016: Journal of Pharmaceutical Sciences
Gertrud Zwicknagl
This article attempts to review how band structure calculations can help to better understand the intriguing behavior of materials with strongly correlated electrons. Prominent examples are heavy-fermion systems whose highly anomalous low-temperature properties result from quantum correlations not captured by standard methods of electronic structure calculations. It is shown how the band approach can be modified to incorporate the typical many-body effects which characterize the low-energy excitations. Examples underlining the predictive power of this ansatz are discussed...
October 17, 2016: Reports on Progress in Physics
David Williams-Young, Joshua J Goings, Xiaosong Li
Solutions of the real-time time-dependent density functional theory (RT-TDDFT) equations provide an affordable route to understanding the electronic dynamics that underpins many spectroscopic techniques. From the solutions of the RT-TDDFT equations it is possible to extract optical absorption and circular dichroism spectra, as well as descriptions of charge transfer and charge transport dynamics. In order to apply RT-TDDFT to increasingly large systems, it is necessary to develop methods to overcome computational bottlenecks...
October 17, 2016: Journal of Chemical Theory and Computation
Shibing Chu, Emanuele Coccia, Matteo Barborini, Leonardo Guidoni
Electron correlation plays a crucial role in the energetics of reactions catalyzed by transition metal complexes, such as water splitting. In the present work we exploit the performance of various methods to describe the thermodynamics of a simple but representative model of water splitting reaction, based on a single cobalt ion as catalyst. Density Functional Theory (DFT) calculations show a significant dependance on the the adopted functional and not negligible differences with respect to CSSD(T) findings are found along the reaction cycle...
October 17, 2016: Journal of Chemical Theory and Computation
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