Chiral model predictions for electromagnetic polarizabilities of the nucleon: A 'consumer report'
International Nuclear Information System (INIS)
Broniowski, W.
1992-01-01
This contribution has two parts: (1) The author critically discusses predictions for the electromagnetic polarizabilities of the nucleon obtained in two different approaches: (a) hedgehog models (HM), such as Skyrmions, chiral quark models, hybrid bags, NJL etc., and (b) chiral perturbation theory (χPT). (2) The author shows new results obtained in HM: N c -counting of polarizabilities, splitting of the neutron and proton polarizabilities (he argues that α n > α p in models with pionic clouds), relevance of dispersive terms in the magnetic polarizability β, important role of the Δ resonance in pionic loops, and the effects of non-minimal substitution terms in the effective lagrangian. 3 refs
Nuclear dipole polarizability from mean-field modeling constrained by chiral effective field theory
Zhang, Zhen; Lim, Yeunhwan; Holt, Jeremy W.; Ko, Che Ming
2018-02-01
We construct a new Skyrme interaction Skχm* by fitting the equation of state and nucleon effective masses in asymmetric nuclear matter from chiral two- and three-body forces as well as the binding energies of finite nuclei. Employing this interaction to study the electric dipole polarizabilities of 48Ca, 68Ni, 120Sn, and 208Pb in the random-phase approximation, we find that the theoretical predictions are in good agreement with experimentally measured values without additional fine tuning of the Skyrme interaction, thus confirming the usefulness of the new Skyrme interaction in studying the properties of nuclei. We further use this interaction to study the neutron skin thicknesses of 48Ca and 208Pb, and they are found to be consistent with the experimental data.
Thole's interacting polarizability model in computational chemistry practice
deVries, AH; vanDuijnen, PT; Zijlstra, RWJ; Swart, M
Thole's interacting polarizability model to calculate molecular polarizabilities from interacting atomic polarizabilities is reviewed and its major applications in computational chemistry are illustrated. The applications include prediction of molecular polarizabilities, use in classical expressions
Electromagnetic polarizabilities of hadrons
International Nuclear Information System (INIS)
Friar, J.L.
1988-01-01
Electromagnetic polarizabilities of hadrons are reviewed, after a discussion of classical analogues. Differences between relativistic and non-relativistic approaches can lead to conflicts with conventional nuclear physics sum rules and calculational techniques. The nucleon polarizabilities are discussed in the context of the non-relativistic valence quark model, which provides a good qualitative description. The recently measured pion polarizabilities are discussed in the context of chiral symmetry and quark-loop models. 58 refs., 5 figs
Quadrupole polarizabilities of the pion in the Nambu-Jona-Lasinio model
International Nuclear Information System (INIS)
Hiller, B.; Broniowski, W.; Osipov, A.A.; Blin, A.H.
2009-01-01
The electromagnetic dipole and quadrupole polarizabilities of the neutral and charged pions are calculated in the Nambu-Jona-Lasinio model. Our results agree with the recent experimental analysis of these quantities based on dispersion sum rules. Comparison is made with the results from the chiral perturbation theory.
Indian Academy of Sciences (India)
In this talk I review studies of hadron properties in bosonized chiral quark models for the quark ﬂavor dynamics. Mesons are constructed from Bethe–Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two-fold Pauli–Villars regularization scheme not only fully ...
Woo Kim, Hyun; Rhee, Young Min
2012-07-30
Recently, many polarizable force fields have been devised to describe induction effects between molecules. In popular polarizable models based on induced dipole moments, atomic polarizabilities are the essential parameters and should be derived carefully. Here, we present a parameterization scheme for atomic polarizabilities using a minimization target function containing both molecular and atomic information. The main idea is to adopt reference data only from quantum chemical calculations, to perform atomic polarizability parameterizations even when relevant experimental data are scarce as in the case of electronically excited molecules. Specifically, our scheme assigns the atomic polarizabilities of any given molecule in such a way that its molecular polarizability tensor is well reproduced. We show that our scheme successfully works for various molecules in mimicking dipole responses not only in ground states but also in valence excited states. The electrostatic potential around a molecule with an externally perturbing nearby charge also exhibits a near-quantitative agreement with the reference data from quantum chemical calculations. The limitation of the model with isotropic atoms is also discussed to examine the scope of its applicability. Copyright © 2012 Wiley Periodicals, Inc.
International Nuclear Information System (INIS)
Musakhanov, M.M.
1980-01-01
The chiral bag model is considered. It is suggested that pions interact only with the surface of a quark ''bag'' and do not penetrate inside. In the case of a large bag the pion field is rather weak and goes to the linearized chiral bag model. Within that model the baryon mass spectrum, β decay axial constant, magnetic moments of baryons, pion-baryon coupling constants and their form factors are calculated. It is shown that pion corrections to the calculations according to the chiral bag model is essential. The obtained results are found to be in a reasonable agreement with the experimental data
Pion polarizability in nonlocal quark model
International Nuclear Information System (INIS)
Efimov, G.V.; Okhlopkova, V.A.
1978-01-01
The γγ→ππ amplitude was calculated in nonlocal quark model in the fourth order on the perturbation theory. The coefficients of electric[a) and magnetic polarizability (β) determined are equal in magnitude and opposite in sign αsub(π+-)=βsub(π+-)=+0.014α/msub(π)sup(3), αsub(πsup(0))=-βsub(πsup(0))=-0.07α/msub(π)sup(3). The results have been compared with calculations in other models
New predictions for generalized spin polarizabilities from heavy baryon chiral perturbation theory
International Nuclear Information System (INIS)
Chung-Wen Kao; Barbara Pasquini; Marc Vanderhaeghen
2004-01-01
We extract the next-to-next-to-leading order results for spin-flip generalized polarizabilities (GPs) of the nucleon from the spin-dependent amplitudes for virtual Compton scattering (VCS) at Ο(p 4 ) in heavy baryon chiral perturbation theory. At this order, no unknown low energy constants enter the theory, allowing us to make absolute predictions for all spin-flip GPs. Furthermore, by using constraint equations between the GPs due to nucleon crossing combined with charge conjugation symmetry of the VCS amplitudes, we get a next-to-next-to-next-to-leading order prediction for one of the GPs. We provide estimates for forthcoming double polarization experiments which allow to access these spin-flip GPs of the nucleon
Model-independent effects of Δ excitation in nucleon polarizabilities
International Nuclear Information System (INIS)
Pascalutsa, Vladimir; Phillips, Daniel R.
2003-01-01
Model-independent effects of Δ(1232) excitation on nucleon polarizabilities are computed in a Lorentz-invariant fashion. We find a large effect of relative order (M Δ -M)/M in some of the spin polarizabilities, with the backward spin polarizability receiving the largest contribution. Similar subleading effects are found to be important in the fourth-order spin-independent polarizabilities α Eν , α E2 , β Mν , and β M2 . Combining our results with those for the model-independent effects of pion loops we obtain predictions for spin and fourth-order polarizabilities which compare favorably with the results of a recent dispersion-relation analysis of data
Event horizons in the Polarizable Vacuum Model
Desiato, J T
2003-01-01
The Polarizable Vacuum (PV) Model representation of General Relativity (GR) is used to show that an in-falling particle of matter will reach the central mass object in a finite amount of proper time, as measured along the world line of the particle, when using the PV Metric. It is shown that the in-falling particle passes through an event horizon, analogous to that found in the Schwarzschild solution of GR. Once it passes through this horizon, any light signal emitted outward by the in-falling particle will be moving slower than the in-falling particle, due to the reduced speed of light in this region. Therefore the signal can never escape this horizon. However, the light emitted by a stationary object below the horizon is exponentially red-shifted and can escape along the null geodesics, as was originally predicted by the PV Model. A static, non-rotating charge distribution is added to the central mass and the PV equivalent to the Reissner-Nordstrom metric is derived. It is illustrated that the dipole moment...
International Nuclear Information System (INIS)
Colanero, K.; Chu, M.-C.
2002-01-01
We study a dynamical chiral bag model, in which massless fermions are confined within an impenetrable but movable bag coupled to meson fields. The self-consistent motion of the bag is obtained by solving the equations of motion exactly assuming spherical symmetry. When the bag interacts with an external meson wave we find three different kinds of resonances: fermionic, geometric, and σ resonances. We discuss the phenomenological implications of our results
Derivation of Distributed Models of Atomic Polarizability for Molecular Simulations.
Soteras, Ignacio; Curutchet, Carles; Bidon-Chanal, Axel; Dehez, François; Ángyán, János G; Orozco, Modesto; Chipot, Christophe; Luque, F Javier
2007-11-01
The main thrust of this investigation is the development of models of distributed atomic polarizabilities for the treatment of induction effects in molecular mechanics simulations. The models are obtained within the framework of the induced dipole theory by fitting the induction energies computed via a fast but accurate MP2/Sadlej-adjusted perturbational approach in a grid of points surrounding the molecule. Particular care is paid in the examination of the atomic quantities obtained from models of implicitly and explicitly interacting polarizabilities. Appropriateness and accuracy of the distributed models are assessed by comparing the molecular polarizabilities recovered from the models and those obtained experimentally and from MP2/Sadlej calculations. The behavior of the models is further explored by computing the polarization energy for aromatic compounds in the context of cation-π interactions and for selected neutral compounds in a TIP3P aqueous environment. The present results suggest that the computational strategy described here constitutes a very effective tool for the development of distributed models of atomic polarizabilities and can be used in the generation of new polarizable force fields.
Gaussian-Charge Polarizable and Nonpolarizable Models for CO2.
Jiang, Hao; Moultos, Othonas A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z
2016-02-11
A polarizable intermolecular potential model using three classical Drude oscillators on the atomic sites has been developed for CO2. The model is rigid with bond lengths and molecular geometries set to their experimental values. Electrostatic interactions are represented by three Gaussian charges connected to the molecular frame by harmonic springs. Nonelectrostatic interactions are represented by the Buckingham exponential-6 potential, with potential parameters optimized to vapor-liquid equilibria (VLE) data. A nonpolarizable CO2 model that shares the other ingredients of the polarizable model was also developed and optimized to VLE data. Gibbs ensemble Monte Carlo and molecular dynamics simulations were used to evaluate the two models with respect to a variety of thermodynamic and transport properties, including the enthalpy of vaporization, second virial coefficient, density in the one-phase fluid region, isobaric and isochoric heat capacities, radial distribution functions, self-diffusion coefficient, and shear viscosity. Excellent agreement between model predictions and experimental data was found for all properties studied. The polarizable and nonpolarizable models provide a similar representation of CO2 properties, which indicates that the properties of pure CO2 fluid are not strongly affected by polarization. The polarizable model, which has an order of magnitude higher computational cost than the nonpolarizable model, will likely be useful for the study of a mixture of CO2 and polar components for which polarization is important.
Wang, Junmei; Cieplak, Piotr; Li, Jie; Hou, Tingjun; Luo, Ray; Duan, Yong
2011-03-31
In this work, four types of polarizable models have been developed for calculating interactions between atomic charges and induced point dipoles. These include the Applequist, Thole linear, Thole exponential model, and the Thole Tinker-like. The polarizability models have been optimized to reproduce the experimental static molecular polarizabilities obtained from the molecular refraction measurements on a set of 420 molecules reported by Bosque and Sales. We grouped the models into five sets depending on the interaction types, that is, whether the interactions of two atoms that form the bond, bond angle, and dihedral angle are turned off or scaled down. When 1-2 (bonded) and 1-3 (separated by two bonds) interactions are turned off, 1-4 (separated by three bonds) interactions are scaled down, or both, all models including the Applequist model achieved similar performance: the average percentage error (APE) ranges from 1.15 to 1.23%, and the average unsigned error (AUE) ranges from 0.143 to 0.158 Å(3). When the short-range 1-2, 1-3, and full 1-4 terms are taken into account (set D models), the APE ranges from 1.30 to 1.58% for the three Thole models, whereas the Applequist model (DA) has a significantly larger APE (3.82%). The AUE ranges from 0.166 to 0.196 Å(3) for the three Thole models, compared with 0.446 Å(3) for the Applequist model. Further assessment using the 70-molecule van Duijnen and Swart data set clearly showed that the developed models are both accurate and highly transferable and are in fact have smaller errors than the models developed using this particular data set (set E models). The fact that A, B, and C model sets are notably more accurate than both D and E model sets strongly suggests that the inclusion of 1-2 and 1-3 interactions reduces the transferability and accuracy.
United polarizable multipole water model for molecular mechanics simulation
Energy Technology Data Exchange (ETDEWEB)
Qi, Rui; Wang, Qiantao; Ren, Pengyu, E-mail: pren@mail.utexas.edu [Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Wang, Lee-Ping; Pande, Vijay S. [Department of Chemistry, Stanford University, Stanford, California 94305 (United States)
2015-07-07
We report the development of a united AMOEBA (uAMOEBA) polarizable water model, which is computationally 3–5 times more efficient than the three-site AMOEBA03 model in molecular dynamics simulations while providing comparable accuracy for gas-phase and liquid properties. In this coarse-grained polarizable water model, both electrostatic (permanent and induced) and van der Waals representations have been reduced to a single site located at the oxygen atom. The permanent charge distribution is described via the molecular dipole and quadrupole moments and the many-body polarization via an isotropic molecular polarizability, all located at the oxygen center. Similarly, a single van der Waals interaction site is used for each water molecule. Hydrogen atoms are retained only for the purpose of defining local frames for the molecular multipole moments and intramolecular vibrational modes. The parameters have been derived based on a combination of ab initio quantum mechanical and experimental data set containing gas-phase cluster structures and energies, and liquid thermodynamic properties. For validation, additional properties including dimer interaction energy, liquid structures, self-diffusion coefficient, and shear viscosity have been evaluated. The results demonstrate good transferability from the gas to the liquid phase over a wide range of temperatures, and from nonpolar to polar environments, due to the presence of molecular polarizability. The water coordination, hydrogen-bonding structure, and dynamic properties given by uAMOEBA are similar to those derived from the all-atom AMOEBA03 model and experiments. Thus, the current model is an accurate and efficient alternative for modeling water.
Huang, Lei; Roux, Benoît
2013-08-13
Classical molecular dynamics (MD) simulations based on atomistic models are increasingly used to study a wide range of biological systems. A prerequisite for meaningful results from such simulations is an accurate molecular mechanical force field. Most biomolecular simulations are currently based on the widely used AMBER and CHARMM force fields, which were parameterized and optimized to cover a small set of basic compounds corresponding to the natural amino acids and nucleic acid bases. Atomic models of additional compounds are commonly generated by analogy to the parameter set of a given force field. While this procedure yields models that are internally consistent, the accuracy of the resulting models can be limited. In this work, we propose a method, General Automated Atomic Model Parameterization (GAAMP), for generating automatically the parameters of atomic models of small molecules using the results from ab initio quantum mechanical (QM) calculations as target data. Force fields that were previously developed for a wide range of model compounds serve as initial guess, although any of the final parameter can be optimized. The electrostatic parameters (partial charges, polarizabilities and shielding) are optimized on the basis of QM electrostatic potential (ESP) and, if applicable, the interaction energies between the compound and water molecules. The soft dihedrals are automatically identified and parameterized by targeting QM dihedral scans as well as the energies of stable conformers. To validate the approach, the solvation free energy is calculated for more than 200 small molecules and MD simulations of 3 different proteins are carried out.
Modeling Electronic Circular Dichroism within the Polarizable Embedding Approach
DEFF Research Database (Denmark)
Nørby, Morten S; Olsen, Jógvan Magnus Haugaard; Steinmann, Casper
2017-01-01
We present a systematic investigation of the key components needed to model single chromophore electronic circular dichroism (ECD) within the polarizable embedding (PE) approach. By relying on accurate forms of the embedding potential, where especially the inclusion of local field effects...... are in focus, we show that qualitative agreement between rotatory strength parameters calculated by full quantum mechanical calculations and the more efficient embedding calculations can be obtained. An important aspect in the computation of reliable absorption parameters is the need for conformational...
Polarizability of π-mesons in the quark confinement model
International Nuclear Information System (INIS)
Avakyan, E.Z.; Avakyan, S.L.; Efimov, G.V.; Ivanov, M.A.
1988-01-01
The electric α π and magnetic β π polarizabilities are calculated in the Quark Confinement Model (QCM). The diagrams with vector, scalar and axial intermediate states are taken into account. It is found that intermediate scalar mesons give an essential contribution to electric and magnetic polarizabilities of pions. The following values for α π and β π are obtained: α π ± =4.06x10 -43 cm 3 ; β π ± =-3.84x10 -43 ; α π 0 =-0.18x10 -43 cm 3 ; β π 0 =1.92x10 -43 cm 3 . The widths of strong (α 0 (980) → πη, f 0 (975) → ππ, ε(730) → ππ) and radiative (α 0 (980), f 0 (980), ε(730) → γγ) decays are calculated. The results are obtained to be in satisfactory agreement with expermental data
Revised Parameters for the AMOEBA Polarizable Atomic Multipole Water Model.
Laury, Marie L; Wang, Lee-Ping; Pande, Vijay S; Head-Gordon, Teresa; Ponder, Jay W
2015-07-23
A set of improved parameters for the AMOEBA polarizable atomic multipole water model is developed. An automated procedure, ForceBalance, is used to adjust model parameters to enforce agreement with ab initio-derived results for water clusters and experimental data for a variety of liquid phase properties across a broad temperature range. The values reported here for the new AMOEBA14 water model represent a substantial improvement over the previous AMOEBA03 model. The AMOEBA14 model accurately predicts the temperature of maximum density and qualitatively matches the experimental density curve across temperatures from 249 to 373 K. Excellent agreement is observed for the AMOEBA14 model in comparison to experimental properties as a function of temperature, including the second virial coefficient, enthalpy of vaporization, isothermal compressibility, thermal expansion coefficient, and dielectric constant. The viscosity, self-diffusion constant, and surface tension are also well reproduced. In comparison to high-level ab initio results for clusters of 2-20 water molecules, the AMOEBA14 model yields results similar to AMOEBA03 and the direct polarization iAMOEBA models. With advances in computing power, calibration data, and optimization techniques, we recommend the use of the AMOEBA14 water model for future studies employing a polarizable water model.
Solutions of ward's modified chiral model
International Nuclear Information System (INIS)
Ioannidou, T.; Zakrzewski, W.J.
1997-01-01
We discuss the adaptation of Uhlenbeck's method of solving the chiral model in 2 Euclidean dimensions to Ward's modified chiral model in (2+1) dimensions. We show that the method reduces the problem of solving the second-order partial differential equations for the chiral field to solving a sequence of first-order partial differential equations for time dependent projector valued fields
Pion and kaon polarizabilities in the quark confinement model
International Nuclear Information System (INIS)
Ivanov, M.A.; Mizutani, T.
1992-01-01
The quark confinement model (QCM) which is based on quark confinement and the composite nature of hadrons, is applied to the study of electromagnetic polarizabilities of the π and K mesons. The Compton scattering amplitude for pseudoscalar meson in the QCM obtains contributions from the following processes (or diagrams): (1) the photon scattering by a point charge, (2) diagrams which involve only one quark loop, (3) the scalar, vector, and axial meson exchanges. The presence of quark loops in QCM diagrams introduces nontrivial momentum dependences which do not exist in the effective Lagrangian scheme with only meson degrees of freedom
Transferability of polarizable models for ion-water electrostatic interaction
International Nuclear Information System (INIS)
Masia, Marco
2009-01-01
Studies of ion-water systems at condensed phase and at interfaces have pointed out that molecular and ionic polarization plays an important role for many phenomena ranging from hydrogen bond dynamics to water interfaces' structure. Classical and ab initio Molecular Dynamics simulations reveal that induced dipole moments at interfaces (e.g. air-water and water-protein) are usually high, hinting that polarizable models to be implemented in classical force fields should be very accurate in reproducing the electrostatic properties of the system. In this paper the electrostatic properties of three classical polarizable models for ion-water interaction are compared with ab initio results both at gas and condensed phase. For Li + - water and Cl - -water dimers the reproducibility of total dipole moments obtained with high level quantum chemical calculations is studied; for the same ions in liquid water, Car-Parrinello Molecular Dynamics simulations are used to compute the time evolution of ionic and molecular dipole moments, which are compared with the classical models. The PD2-H2O model developed by the author and coworkers [Masia et al. J. Chem. Phys. 2004, 121, 7362] together with the gaussian intermolecular damping for ion-water interaction [Masia et al. J. Chem. Phys. 2005, 123, 164505] showed to be the fittest in reproducing the ab initio results from gas to condensed phase, allowing for force field transferability.
An averaged polarizable potential for multiscale modeling in phospholipid membranes
DEFF Research Database (Denmark)
Witzke, Sarah; List, Nanna Holmgaard; Olsen, Jógvan Magnus Haugaard
2017-01-01
is underlined for the description of larger assemblies of lipids, that is, membranes. In conclusion, we find that specially developed polarizable parameters are needed for embedding calculations in membranes, while common non-polarizable point-charge force fields usually perform well enough for structural...
Principal chiral model on superspheres
Energy Technology Data Exchange (ETDEWEB)
Mitev, V.; Schomerus, V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quella, T. [Amsterdam Univ. (Netherlands). Inst. for Theoretical Physics
2008-09-15
We investigate the spectrum of the principal chiral model (PCM) on odd-dimensional superspheres as a function of the curvature radius R. For volume-filling branes on S{sup 3} {sup vertical} {sup stroke} {sup 2}, we compute the exact boundary spectrum as a function of R. The extension to higher dimensional superspheres is discussed, but not carried out in detail. Our results provide very convincing evidence in favor of the strong-weak coupling duality between supersphere PCMs and OSP(2S+2 vertical stroke 2S) Gross-Neveu models that was recently conjectured by Candu and Saleur. (orig.)
Principal chiral model on superspheres
International Nuclear Information System (INIS)
Mitev, V.; Schomerus, V.; Quella, T.
2008-09-01
We investigate the spectrum of the principal chiral model (PCM) on odd-dimensional superspheres as a function of the curvature radius R. For volume-filling branes on S 3 vertical stroke 2 , we compute the exact boundary spectrum as a function of R. The extension to higher dimensional superspheres is discussed, but not carried out in detail. Our results provide very convincing evidence in favor of the strong-weak coupling duality between supersphere PCMs and OSP(2S+2 vertical stroke 2S) Gross-Neveu models that was recently conjectured by Candu and Saleur. (orig.)
Timoshenko beam model for chiral materials
Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.
2017-12-01
Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.
Pentaquarks in chiral color dielectric model
Indian Academy of Sciences (India)
Recent experiments indicate that a narrow baryonic state having strangeness +1 and mass of about 1540 MeV may be existing. Such a state was predicted in chiral model by Diakonov et al. In this work I compute the mass and width of this state in chiral color dielectric model. I show that the computed width is about 30 MeV.
Hadron properties in chiral sigma model
International Nuclear Information System (INIS)
Shen Hong
2005-01-01
The modification of hadron masses in nuclear medium is studied by using the chiral sigma model, which is extended to generate the omega meson mass by the sigma condensation in the vacuum in the same way as the nucleon mass. The chiral sigma model provides proper equilibrium properties of nuclear matter. It is shown that the effective masses of both nucleons and omega mesons decrease in nuclear medium, while the effective mass of sigma mesons increases oat finite density in the chiral sigma model. The results obtained in the chiral sigma model are compared with those obtained in the Walecka model, which includes sigma and omega mesons in a non-chiral fashion. (author)
The paradigm of Pseudodual Chiral Models
International Nuclear Information System (INIS)
Zachos, C.K.; Curtright, T.L.
1994-01-01
This is a synopsis and extension of Phys. Rev. D49 5408 (1994). The Pseudodual Chiral Model illustrates 2-dimensional field theories which possess an infinite number of conservation laws but also allow particle production, at variance with naive expectations-a folk theorem of integrable models. We monitor the symmetries of the pseudodual model, both local and nonlocal, as transmutations of the symmetries of the (very different) usual Chiral Model. We refine the conventional algorithm to more efficiently produce the nonlocal symmetries of the model. We further find the canonical transformation which connects the usual chiral model to its fully equivalent dual model, thus contradistinguishing the pseudodual theory
Polarizability extraction of complementary metamaterial elements in waveguides for aperture modeling
Pulido-Mancera, Laura; Bowen, Patrick T.; Imani, Mohammadreza F.; Kundtz, Nathan; Smith, David
2017-12-01
We consider the design and modeling of metasurfaces that couple energy from guided waves to propagating wave fronts. To this purpose, we develop a comprehensive, multiscale dipolar interpretation for large arrays of complementary metamaterial elements embedded in a waveguide structure. Within this modeling technique, the detailed electromagnetic response of each metamaterial element is replaced by a polarizable dipole, described by means of an effective polarizability. In this paper, we present two methods to extract this effective polarizability. The first method invokes surface equivalence principles, averaging over the effective surface currents and charges induced in the element's surface in order to obtain the effective dipole moments, from which the effective polarizability can be inferred. The second method is based in the coupled-mode theory, from which a direct relationship between the effective polarizability and the amplitude coefficients of the scattered waves can be deduced. We demonstrate these methods on several variants of waveguide-fed metasurface elements (both one- and two-dimensional waveguides), finding excellent agreement between the two, as well as with the analytical expressions derived for circular and elliptical irises. With the effective polarizabilities of the metamaterial elements accurately determined, the radiated fields generated by a waveguide-fed metasurface can be found self-consistently by including the interactions between polarizable dipoles. The dipole description provides an effective perspective and computational framework for engineering metasurface structures such as holograms, lenses, and beam-forming arrays, among others.
Recent status of the chiral bag model
International Nuclear Information System (INIS)
Hosaka, Atsushi; Toki, Hiroshi.
1995-01-01
In this note, recent status of the chiral bag model is presented. As it combines the MIT quark bag model and the Skyrme model, the chiral bag model interpolates the two models smoothly as a function of the chiral bag radius R. The correct limit of R → ∞ is reproduced by including the higher order terms in the Ω expansion of the cranking method. It resolves the so-called small g A problem in a class of models where the semiclassical method is used. (author)
Quantum chromodynamics, chiral symmetry and bag models
International Nuclear Information System (INIS)
Soyeur, M.
1983-08-01
This course deals with the following subjects: quarks; quantum chromodynamics (the classical Lagrangian of QCD, quark masses, the classical equations of motion of QCD, general properties, lattices); chiral symmetry (massless free Dirac theory, realizations, the σ-model); the M.I.T. bag model (basic assumptions and equations of motion, spherical cavity approximation, properties of hadrons); the chiral bag models (basic assumptions, the cloudy bag model, the little bag model); non-topological soliton bag models
Unified Chiral models of mesons and baryons
International Nuclear Information System (INIS)
Mendez-Galain, R.; Ripka, G.
1990-01-01
Unified Chiral models of mesons and baryons are presented. Emphasis is placed on the underlying quark structure of hadrons including the Skyrmion. The Nambu Jona-Lasinio model with vector mesons is discussed
Bag model with broken chiral symmetry
International Nuclear Information System (INIS)
Efrosinin, V.P.; Zaikin, D.A.
1986-01-01
A variant of the bag model in which chiral symmetry is broken and which provides a description of all the experimental data on the light hadrons, including the pion, is discussed. The pion and kaon decay constants are calculated in this model. The problem of taking into account the center-of-mass motion in bag models and the boundary conditions in the bag model with broken chiral symmetry are also discussed
Geometry Optimization in Polarizable QM/MM Models: The Induced Dipole Formulation.
Caprasecca, Stefano; Jurinovich, Sandro; Viani, Lucas; Curutchet, Carles; Mennucci, Benedetta
2014-04-08
We present the mathematical derivation and the computational implementation of the analytical geometry derivatives for a polarizable QM/MM model (QM/MMPol). In the adopted QM/MMPol model, the focused part is treated at QM level of theory, while the remaining part (the environment) is described classically as a set of fixed charges and induced dipoles. The implementation is performed within the ONIOM procedure, resulting in a polarizable embedding scheme, which can be applied to solvated and embedded systems and combined with different polarizable force fields available in the literature. Two test cases characterized by strong hydrogen-bond and dipole-dipole interactions, respectively, are used to validate the method with respect to the nonpolarizable one. Finally, an application to geometry optimization of the chromophore of Rhodopsin is presented to investigate the impact of including mutual polarization between the QM and the classical parts in conjugated systems.
Chiral algebras in Landau-Ginzburg models
Dedushenko, Mykola
2018-03-01
Chiral algebras in the cohomology of the {\\overline{Q}}+ supercharge of two-dimensional N=(0,2) theories on flat spacetime are discussed. Using the supercurrent multiplet, we show that the answer is renormalization group invariant for theories with an R-symmetry. For N=(0,2) Landau-Ginzburg models, the chiral algebra is determined by the operator equations of motion, which preserve their classical form, and quantum renormalization of composite operators. We study these theories and then specialize to the N=(2,2) models and consider some examples.
A model with charges and polarizability for CS₂ in an ionic liquid
Indian Academy of Sciences (India)
The environment of a solute molecule in an ionic liquid is likely to have large fluctuating electrostatic fields, and so the electrostatic properties of such a solute including its charge distribution and its polarizability may make a difference to both its static and dynamic properties. We have developed a new model forthe static ...
Circular Intensity Differential Scattering of chiral molecules
Energy Technology Data Exchange (ETDEWEB)
Bustamante, C.J.
1980-12-01
In this thesis a theory of the Circular Intensity Differential Scattering (CIDS) of chiral molecules as modelled by a helix oriented with respect to the direction of incidence of light is presented. It is shown that a necessary condition for the existence of CIDS is the presence of an asymmetric polarizability in the scatterer. The polarizability of the scatterer is assumed generally complex, so that both refractive and absorptive phenomena are taken into account.
About chiral models of dense matter and its magnetic properties
International Nuclear Information System (INIS)
Kutschera, M.
1990-12-01
The chiral models of dense nucleon matter are discussed. The quark matter with broken chiral symmetry is described. The magnetic properties of dense matter are presented and conclusions are given. 37 refs. (A.S.)
Pentaquarks in chiral color dielectric model
Indian Academy of Sciences (India)
12], computation of quark matter equation of state [13] etc. It may be noted here that, because of the chiral invariance which is incorporated in the model, one can generate the coupling between Θ baryon and NK system in a natural way and one.
Dihyperons in chiral color dielectric model
Indian Academy of Sciences (India)
The mass of the dibaryon having spin, parity =0+, isospin = 0 and strangeness -2 is computed using chiral color dielectric model. ... Color magnetic energy due to gluon exchange, meson self energy and energy correction due to center of mass motion are computed. ... Institute of Physics, Bhubaneswar 751 005, India ...
Pentaquarks in chiral color dielectric model
Indian Academy of Sciences (India)
In this work I compute the mass and width of this state in chiral color dielectric model. I show that ... I find that the mass of the state can be fitted to the experimentally observed mass by invoking a color neutral vector field and its interaction with the quarks. ... Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005, India ...
Characteristics of the chiral phase transition in nonlocal quark models
International Nuclear Information System (INIS)
Gomez Dumm, D. Gomez; Scoccola, N.N.
2005-01-01
The characteristics of the chiral phase transition are analyzed within the framework of chiral quark models with nonlocal interactions in the mean-field approximation. In the chiral limit, we develop a semianalytic framework that allows us to explicitly determine the phase transition curve, the position of the critical points, some relevant critical exponents, etc. For the case of finite current quark masses, we show the behavior of various thermodynamical and chiral response functions across the phase transition
GROMOS polarizable charge-on-spring models for liquid urea: COS/U and COS/U2.
Lin, Zhixiong; Bachmann, Stephan J; van Gunsteren, Wilfred F
2015-03-07
Two one-site polarizable urea models, COS/U and COS/U2, based on the charge-on-spring model are proposed. The models are parametrized against thermodynamic properties of urea-water mixtures in combination with the polarizable COS/G2 and COS/D2 models for liquid water, respectively, and have the same functional form of the inter-atomic interaction function and are based on the same parameter calibration procedure and type of experimental data as used to develop the GROMOS biomolecular force field. Thermodynamic, dielectric, and dynamic properties of urea-water mixtures simulated using the polarizable models are closer to experimental data than using the non-polarizable models. The COS/U and COS/U2 models may be used in biomolecular simulations of protein denaturation.
Structure functions in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Sanjose, V.; Vento, V.
1989-07-13
We calculate the structure functions of an isoscalar nuclear target for the deep inelastic scattering by leptons in an extended version of the chiral bag model which incorporates the qanti q structure of the pions in the cloud. Bjorken scaling and Regge behavior are satisfied. The model calculation reproduces the low-x behavior of the data but fails to explain the medium- to large-x behavior. Evolution of the quark structure functions seem inevitable to attempt a connection between the low-energy models and the high-energy behavior of quantum chromodynamics. (orig.).
Cammi, Roberto
2013-01-01
This Brief presents the main aspects of the response functions theory (RFT) for molecular solutes described within the framework of the Polarizable Continuum Model (PCM). PCM is a solvation model for a Quantum Mechanical molecular system in which the solvent is represented as a continuum distribution of matter. Particular attention is devoted to the description of the basic features of the PCM model, and to the problems characterizing the study of the response function theory for molecules in solution with respect to the analogous theory on isolated molecules.
International Nuclear Information System (INIS)
Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.
2015-01-01
The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed
Energy Technology Data Exchange (ETDEWEB)
Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)
2015-01-22
The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.
Self-consistent nonlinearly polarizable shell-model dynamics for ferroelectric materials
International Nuclear Information System (INIS)
Mkam Tchouobiap, S.E.; Kofane, T.C.; Ngabireng, C.M.
2002-11-01
We investigate the dynamical properties of the polarizable shellmodel with a symmetric double Morse-type electron-ion interaction in one ionic species. A variational calculation based on the Self-Consistent Einstein Model (SCEM) shows that a theoretical ferroelectric (FE) transition temperature can be derive which demonstrates the presence of a first-order phase transition for the potassium selenate (K 2 SeO 4 ) crystal around Tc 91.5 K. Comparison of the model calculation with the experimental critical temperature yields satisfactory agreement. (author)
Analysis of a classical chiral bag model
International Nuclear Information System (INIS)
Nadeau, H.
1985-01-01
The author studies a classical chiral bag model with a Mexican hat-type potential for the self-coupling of the pion fields. He assumes a static spherical bag of radius R, the hedgehog ansatz for the chiral fields and that the quarks are all in the lowest lying s state. The author has considered three classes of models, the cloudy or pantopionic bags, the little or exopionic bags and the endopionic bags, where the pions are allowed all through space, only outside the bag and only inside the bag respectively. In all cases, the quarks are confined in the interior. He calculates the bag radius R, the bag constant B and the total ground state energy R for wide ranges of the two free parameters of the theory, namely the coupling constant λ and the quark frequency omega. The author focuses the study on the endopionic bags, the least known class, and compares the results with the familiar ones of other classes
Nucleon described by the chiral soliton in the chiral quark soliton model
Watabe, T.; Goeke, K.
1998-02-01
We give a survey of recent development and applications of the chiral quark soliton model (also called the Nambu-Jona-Lasinio soliton model) with N f=2 and N f=3 quark flavors for the structure of baryons. The model is an effective chiral quark model obtained from the instanton liquid model of the quantum chromodynamics. Mesons appear as quark-antiquark excitations and baryons arise as non-topological solitons with three valence quarks and a polarized Dirac sea. In this model, a wide variety of observables of baryons is considered.
Nucleon described by the chiral soliton in the chiral quark soliton model
Energy Technology Data Exchange (ETDEWEB)
Watabe, T.; Goeke, K. [Ruhr-Univ., Bochum (Germany). Inst. fur Theor. Phys. II
1998-02-02
We give a survey of recent development and applications of the chiral quark soliton model (also called the Nambu-Jona-Lasinio soliton model) with N{sub f} = 2 and N{sub f} = 3 quark flavors for the structure of baryons. The model is an effective chiral quark model obtained from the instanton liquid model of the quantum chromodynamics. Mesons appear as quark-antiquark excitations and baryons arise as non-topological solitons with three valence quarks and a polarized Dirac sea. In this model, a wide variety of observables of baryons is considered. (orig.). 12 refs.
Lorentz Invariant Spectrum of Minimal Chiral Schwinger Model
Kim, Yong-Wan; Kim, Seung-Kook; Kim, Won-Tae; Park, Young-Jai; Kim, Kee Yong; Kim, Yongduk
We study the Lorentz transformation of the minimal chiral Schwinger model in terms of the alternative action. We automatically obtain a chiral constraint, which is equivalent to the frame constraint introduced by McCabe, in order to solve the frame problem in phase space. As a result we obtain the Lorentz invariant spectrum in any moving frame by choosing a frame parameter.
Currents, charges, and canonical structure of pseudodual chiral models
International Nuclear Information System (INIS)
Curtright, T.; Zachos, C.
1994-01-01
We discuss the pseudodual chiral model to illustrate a class of two-dimensional theories which have an infinite number of conservation laws but allow particle production, at variance with naive expectations. We describe the symmetries of the pseudodual model, both local and nonlocal, as transmutations of the symmetries of the usual chiral model. We refine the conventional algorithm to more efficiently produce the nonlocal symmetries of the model, and we discuss the complete local current algebra for the pseudodual theory. We also exhibit the canonical transformation which connects the usual chiral model to its fully equivalent dual, further distinguishing the pseudodual theory
Electroweak amplitudes in chiral quark models
International Nuclear Information System (INIS)
Fiolhais, Manuel
2004-01-01
After referring to some basic features of chiral models for baryons, with quarks and mesons, we describe how to construct model states representing physical baryons. We consider soliton models such as the Linear Sigma Model or the Chromodielectric Model, and bag models such as the Cloudy Bag Model. These models are solved approximately using variational approaches whose starting point is a mean-field description. We go beyond the mean-field description by introducing quantum fluctuations in the mesonic degrees of freedom. This is achieved, in a first step, by using a quantum state to represent meson clouds and, secondly, by performing an angular momentum and isospin projection from the mean-field state (actually a coherent state). Model states for baryons (nucleon, Delta, Roper) constructed in this way are used to determine several physical properties. I this seminar we paid a particular attention to the nucleon-delta electromagnetic and weak transition, presenting the model predictions for the electromagnetic and axial amplitudes
Polarizable water model for the coarse-grained MARTINI force field.
Directory of Open Access Journals (Sweden)
Semen O Yesylevskyy
2010-06-01
Full Text Available Coarse-grained (CG simulations have become an essential tool to study a large variety of biomolecular processes, exploring temporal and spatial scales inaccessible to traditional models of atomistic resolution. One of the major simplifications of CG models is the representation of the solvent, which is either implicit or modeled explicitly as a van der Waals particle. The effect of polarization, and thus a proper screening of interactions depending on the local environment, is absent. Given the important role of water as a ubiquitous solvent in biological systems, its treatment is crucial to the properties derived from simulation studies. Here, we parameterize a polarizable coarse-grained water model to be used in combination with the CG MARTINI force field. Using a three-bead model to represent four water molecules, we show that the orientational polarizability of real water can be effectively accounted for. This has the consequence that the dielectric screening of bulk water is reproduced. At the same time, we parameterized our new water model such that bulk water density and oil/water partitioning data remain at the same level of accuracy as for the standard MARTINI force field. We apply the new model to two cases for which current CG force fields are inadequate. First, we address the transport of ions across a lipid membrane. The computed potential of mean force shows that the ions now naturally feel the change in dielectric medium when moving from the high dielectric aqueous phase toward the low dielectric membrane interior. In the second application we consider the electroporation process of both an oil slab and a lipid bilayer. The electrostatic field drives the formation of water filled pores in both cases, following a similar mechanism as seen with atomistically detailed models.
International Nuclear Information System (INIS)
Lyubovitskij, V.E.; Gutsche, Th.; Faessler, Amand; Mau, R. Vinh
2002-01-01
We apply the perturbative chiral quark model to the study of the low-energy πN interaction. Using an effective chiral Lagrangian we reproduce the Weinberg-Tomozawa result for the S-wave πN scattering lengths. After inclusion of the photon field we give predictions for the electromagnetic O(p 2 ) low-energy couplings of the chiral perturbation theory effective Lagrangian that define the electromagnetic mass shifts of nucleons and first-order (e 2 ) radiative corrections to the πN scattering amplitude. Finally, we estimate the leading isospin-breaking correction to the strong energy shift of the π - p atom in the 1s state, which is relevant for the experiment 'pionic hydrogen' at PSI
BRST-BFV quantization of chiral Schwinger model
International Nuclear Information System (INIS)
Srivastava, P.P.
1989-01-01
The BRST-BFV procedure of quantization is applied to establish, in a gauge independent manner, the equivalence of the gauge noninvariant and gauge invariant formulations of the Chiral Schwinger model. (author). 14 refs
Pion Polarizability Status Report (2017)
Moinester, Murray
2017-01-01
The electric ${\\alpha}_{\\pi}$ and magnetic $\\beta_{\\pi}$ charged pion Compton polarizabilities are of fundamental interest in the low-energy sector of quantum chromodynamics (QCD).They are directly linked to the phenomenon of spontaneously broken chiral symmetry within QCD and to the dynamics of the pion-photon interaction.The combination (${\\alpha}_{\\pi}-\\beta_{\\pi}$) was measured by:(1) CERN COMPASS via radiative pion Primakoff scattering (Bremsstrahlung) in the nuclear Coulomb field, ${\\pi...
DEFF Research Database (Denmark)
Eriksen, Janus Juul; Solanko, Lukasz Michal; Nåbo, Lina J.
2014-01-01
We present an implementation of the Polarizable Continuum Model (PCM) in combination with the Second–Order Polarization Propagator Approximation (SOPPA) electronic structure method. In analogy with the most common way of designing ground state calculations based on a Second–Order Møller-Plesset (MP......2) wave function coupled to PCM, we introduce dynamical PCM solvent effects only in the Random Phase Approximation (RPA) part of the SOPPA response equations while the static solvent contribution is kept in both the RPA terms as well as in the higher order correlation matrix components of the SOPPA...... response equations. By dynamic terms, we refer to contributions that describe a change in environmental polarization which, in turn, reflects a change in the core molecular charge distribution upon an electronic excitation. This new combination of methods is termed PCM-SOPPA/RPA. We apply this newly...
Evaluating excited state atomic polarizabilities of chromophores.
Heid, Esther; Hunt, Patricia A; Schröder, Christian
2018-03-28
Ground and excited state dipoles and polarizabilities of the chromophores N-methyl-6-oxyquinolinium betaine (MQ) and coumarin 153 (C153) in solution have been evaluated using time-dependent density functional theory (TD-DFT). A method for determining the atomic polarizabilities has been developed; the molecular dipole has been decomposed into atomic charge transfer and polarizability terms, and variation in the presence of an electric field has been used to evaluate atomic polarizabilities. On excitation, MQ undergoes very site-specific changes in polarizability while C153 shows significantly less variation. We also conclude that MQ cannot be adequately described by standard atomic polarizabilities based on atomic number and hybridization state. Changes in the molecular polarizability of MQ (on excitation) are not representative of the local site-specific changes in atomic polarizability, thus the overall molecular polarizability ratio does not provide a good approximation for local atom-specific polarizability changes on excitation. Accurate excited state force fields are needed for computer simulation of solvation dynamics. The chromophores considered in this study are often used as molecular probes. The methods and data reported here can be used for the construction of polarizable ground and excited state force fields. Atomic and molecular polarizabilities (ground and excited states) have been evaluated over a range of functionals and basis sets. Different mechanisms for including solvation effects have been examined; using a polarizable continuum model, explicit solvation and via sampling of clusters extracted from a MD simulation. A range of different solvents have also been considered.
The extended chiral quark model confronts QCD
International Nuclear Information System (INIS)
Andrianov, A.A.; Espriu, D.; Tarrach, R.
2000-01-01
We discuss the truncation of low energy effective action of QCD below the chiral symmetry breaking (CSB) scale, including all operators of dimensionality less or equal to 6 which can be built with quark and chiral fields. We perform its bosonization in the scalar, pseudoscalar, vector and axial-vector channels in the large-Nc and leading-log approximation. Constraints on the coefficients of the effective lagrangian are derived from the requirement of Chiral Symmetry Restoration (CSR) at energies above the CSB scale in the scalar-pseudoscalar and vector-axial-vector channels, from matching to QCD at intermediate scales, and by fitting some hadronic observables. In this truncation two types of pseudoscalar states (massless pions and massive Π-mesons), as well as a scalar, vector and axial-vector one arise as a consequence of dynamical chiral symmetry breaking. Their masses and coupling constants as well as a number of chiral structural constants are derived. A reasonable fit of all parameters supports a relatively heavy scalar meson (quarkonium) with the mass ∼ 1 GeV and a small value of axial pion-quark coupling constant gA ≅= 0.55
Light hadrons in the bag model with broken chiral symmetry
International Nuclear Information System (INIS)
Efrosinin, V.P.; Zaikin, D.A.
1987-01-01
A version of the bag model with broken chiral symmetry is proposed. A satisfactory description of the experimental data on light hadrons including the pion is obtained. The estimate of the pion-nucleon σ term is given in the framework of this model. The pion and kaon decay constants are calculated. The centre-of-mass motion problem in bag models is discussed
Sakai-Sugimoto model, tachyon condensation and chiral symmetry breaking
International Nuclear Information System (INIS)
Dhar, Avinash; Nag, Partha
2008-01-01
We modify the Sakai-Sugimoto model of chiral symmetry breaking to take into account the open string tachyon which stretches between the flavour D8-branes and D8-bar-branes. There are several reasons of consistency for doing this: (i) Even if it might be reasonable to ignore the tachyon in the ultraviolet where the flavour branes and antibranes are well separated and the tachyon is small, it is likely to condense and acquire large values in the infrared where the branes meet. This takes the system far away from the perturbatively stable minimum of the Sakai-Sugimoto model; (ii) The bifundamental coupling of the tachyon to fermions of opposite chirality makes it a suitable candidate for the quark mass and chiral condensate parameters. We show that the modified Sakai-Sugimoto model with the tachyon present has a classical solution satisfying all the desired consistency properties. In this solution chiral symmetry breaking coincides with tachyon condensation. We identify the parameters corresponding to the quark mass and the chiral condensate and also briefly discuss the mesonic spectra
The cavity electromagnetic field within the polarizable continuum model of solvation
Energy Technology Data Exchange (ETDEWEB)
Pipolo, Silvio, E-mail: silvio.pipolo@nano.cnr.it [Center S3, CNR Institute of Nanoscience, Modena (Italy); Department of Physics, University of Modena and Reggio Emilia, Modena (Italy); Corni, Stefano, E-mail: stefano.corni@nano.cnr.it [Center S3, CNR Institute of Nanoscience, Modena (Italy); Cammi, Roberto, E-mail: roberto.cammi@unipr.it [Department of Chemistry, Università degli studi di Parma, Parma (Italy)
2014-04-28
Cavity field effects can be defined as the consequences of the solvent polarization induced by the probing electromagnetic field upon spectroscopies of molecules in solution, and enter in the definitions of solute response properties. The polarizable continuum model of solvation (PCM) has been extended in the past years to address the cavity-field issue through the definition of an effective dipole moment that couples to the external electromagnetic field. We present here a rigorous derivation of such cavity-field treatment within the PCM starting from the general radiation-matter Hamiltonian within inhomogeneous dielectrics and recasting the interaction term to a dipolar form within the long wavelength approximation. To this aim we generalize the Göppert-Mayer and Power-Zienau-Woolley gauge transformations, usually applied in vacuo, to the case of a cavity vector potential. Our derivation also allows extending the cavity-field correction in the long-wavelength limit to the velocity gauge through the definition of an effective linear momentum operator. Furthermore, this work sets the basis for the general PCM treatment of the electromagnetic cavity field, capable to describe the radiation-matter interaction in dielectric media beyond the long-wavelength limit, providing also a tool to investigate spectroscopic properties of more complex systems such as molecules close to large nanoparticles.
Minimal quantization of two-dimensional models with chiral anomalies
International Nuclear Information System (INIS)
Ilieva, N.
1987-01-01
Two-dimensional gauge models with chiral anomalies - ''left-handed'' QED and the chiral Schwinger model, are quantized consistently in the frames of the minimal quantization method. The choice of the cone time as a physical time for system of quantization is motivated. The well-known mass spectrum is found but with a fixed value of the regularization parameter a=2. Such a unique solution is obtained due to the strong requirement of consistency of the minimal quantization that reflects in the physically motivated choice of the time axis
Chiral soliton model vs. pentaquark structure for Θ (1540)
Indian Academy of Sciences (India)
The exotic baryon + (1540 MeV) is visualized as an expected (iso) rotational excitation in the chiral soliton model. It is also argued as a pentaquark baryon state in a constituent quark model with strong diquark correlations. I contrast these two points of view; observe the similarities and differences between the two pictures.
Chiral soliton model vs. pentaquark structure for Θ(1540)
Indian Academy of Sciences (India)
of representations in the wake of SU(3) breaking. In contrast, constituent quark models prefer near 'ideal' mixing, similar to ω − φ mixing. Keywords. Chiral soliton model; pentaquarks; QCD; large N. PACS Nos 12.39.-x; 12.39.Dc. 1. Introduction. An exotic baryon Θ+(1540 MeV) with the quantum numbers of K+n has been.
On the vacuum baryon number in the chiral bag model
International Nuclear Information System (INIS)
Jaroszewicz, T.
1984-01-01
We give a rederivation, generalization and interpretation of the result of Goldstone and Jaffe on the vacuum baryon number in the chiral bag model. Our results are based on considering the bag model as a theory of free quarks, massless inside and infinitely massive outside the bag. (orig.)
Hidden symmetries of the Principal Chiral Model unveiled
International Nuclear Information System (INIS)
Devchand, C.; Schiff, J.
1996-12-01
By relating the two-dimensional U(N) Principal Chiral Model to a Simple linear system we obtain a free-field parametrization of solutions. Obvious symmetry transformations on the free-field data give symmetries of the model. In this way all known 'hidden symmetries' and Baecklund transformations, as well as a host of new symmetries, arise. (author). 21 refs
Linker, Gerrit-Jan; van Duijnen, Piet Th; van Loosdrecht, Paul H M; Broer, Ria
2012-07-05
The geometry of ethylenedioxy-tetrathiafulvalene, EDO-TTF, plays an important role in the metal-insulator transition in the charge transfer salt (EDO-TTF)(2)PF(6). The planar and off-planar geometrical conformations of the EDO-TTF molecules are explained using an extended Debye polarizability model for the bond angle. The geometrical structure of EDO-TTF is dictated by its four sulfur bond angles and these are, in turn, determined by the polarizability of the sulfur atoms. With Hartree-Fock and second-order Møller-Plesset perturbation theory calculations on EDO-TTF, TTF, H(2)S, and their oxygen and selenium substituted counterparts we confirm this hypothesis. The Debye polarizability model for bond angles relates directly the optimum bond angle with the polarizability of the center atom. Considering the (EDO-TTF)(2)PF(6) material in this light proves to be very fruitful.
A model with charges and polarizability for CS2 in an ionic liquid
Indian Academy of Sciences (India)
RUTH M LYNDEN-BELL
: CS2(C) and ring C1; red-dashed: CS2(S) and ring C1: .... The red curve shows the probability distribution of induced dipoles on the C site (which is purely axial as the polarizability is axial). The values of the C site dipole follow a Gaussian.
Nucleon-antinucleon annihilation in chiral soliton model
International Nuclear Information System (INIS)
Musakhanov, M.M.; Tashkentskij Gosudarstvennyj Univ., Tashkent; Musatov, I.V.
1991-01-01
We investigate annihilation process of nucleons in the chiral soliton model by the path integral method. A soliton-antisoliton pair is shown to decay into mesons at range of about 1fm, defined by the S bar S potential. Contribution of the annihilation channel to the elastic scattering is discussed
Model for dynamical chiral symmetry breaking and quark condensate
International Nuclear Information System (INIS)
Nekrasov, M.L.; Rochev, V.E.
1986-01-01
In the framework of the model, proposed earlier to describe nonperturbative QCD, the singularity of the type 1/k 4 in the gluon propagator is shown to result in dynamical chiral symmetry breaking and appearance of quark condensate. The value, obtained for quark condensate, is close to the phenomenological one
Stationary solutions of multicomponent chiral and gauge models
International Nuclear Information System (INIS)
Chudnovsky, D.V.; Chudnovsky, G.V.
1979-01-01
The authors examine stationary solutions of completely integrable systems in (x, t) dimensions having infinitely many components. Among the cases under investigation are: (1) the infinite-component non-linear Schroedinger equation; (2) infinite component CPsup(Ω) or SU(N) sigma-models; (3) general gauge and chiral completely integrable systems. (Auth.)
Finiteness for the k-factor model and chirality varieties
J. Draisma (Jan)
2008-01-01
htmlabstractThis paper deals with two families of algebraic varieties arising from applications. First, the k-factor model in statistics, consisting of n-times-n covariance matrices of n observed Gaussian variables that are pairwise independent given k hidden Gaussian variables. Second, chirality
Electrochemical Solvent Reorganization Energies in the Framework of the Polarizable Continuum Model.
Ghosh, Soumya; Horvath, Samantha; Soudackov, Alexander V; Hammes-Schiffer, Sharon
2014-05-13
Electron transfer reactions at electrochemical interfaces play a critical role in a wide range of catalytic processes. A key parameter in the rate constant expressions for such processes is the reorganization energy, which reflects the energetic cost of the solute and solvent rearrangements upon electron transfer. In this paper, we present dielectric continuum methods for calculating the solvent reorganization energy for electrochemical processes. We develop a method for calculating the electrochemical solvent reorganization energies with molecular-shaped cavities within the framework of the polarizable continuum model (PCM). The electronic and inertial responses of the solvent are separated according to their respective time scales, and two limiting cases of the relation between the solute and solvent electrons are examined. The effects of the electrode are included with the integral equations formalism PCM (IEF-PCM), in which the molecule-solvent boundary is treated explicitly, but the effects of the electrode-solvent boundary are included through an external Green's function. This approach accounts for the effects of detailed molecular charge redistribution in a molecular-shaped cavity, as well as the electronic and inertial solvent responses and the effects of the electrode. The calculated total reorganization energies are in reasonable agreement with experimental measurements for a series of electrochemical systems. Inclusion of the effects of the electrode is found to be essential for obtaining even qualitatively accurate solvent reorganization energies. These approaches are applicable to a wide range of systems and can be extended to include other types of boundaries, such as a self-assembled monolayer or double layer separating the electrode and the molecule.
Ng, Albert H.
2011-01-24
To incorporate protein polarization effects within a protein combinatorial optimization framework, we decompose the polarizable force field AMOEBA into low order terms. Including terms up to the third-order provides a fair approximation to the full energy while maintaining tractability. We represent the polarizable packing problem for protein G as a hypergraph and solve for optimal rotamers with the FASTER combinatorial optimization algorithm. These approximate energy models can be improved to high accuracy [root mean square deviation (rmsd) < 1 kJ mol -1] via ridge regression. The resulting trained approximations are used to efficiently identify new, low-energy solutions. The approach is general and should allow combinatorial optimization of other many-body problems. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 Copyright © 2011 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Trullàs J.
2011-05-01
Full Text Available Molecular dynamics simulations of molten NaI at 995 K have been carried out using polarizable ion models based on rigid ion pair potentials to which the anion induced dipole polarization is added. The polarization is added in such a way that point dipoles are induced on the anions by both local electric field and deformation short-range damping interactions that oppose the electrically induced dipole moments. The structure and self-diffusion results are compared with those obtained by Galamba and Costa Cabral using first principles Hellmann-Feynman molecular dynamics simulations and using classical molecular dynamics of a shell model which allows only the iodide polarization
Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry
2007-10-01
.5 GeV with BABAR / A. Denig. The pion vector form-factor and (g-2)u / C. Smith. Partially quenched CHPT results to two loops / J. Bijnens. Pion-pion scattering with mixed action lattice QCD / P.F. Bedaque. Meson systems with Ginsparg-Wilson valence quarks / A. Walker-Loud. Low energy constants from the MILC collaboration / C. Bernard. Finite volume effects: lattice meets CHPT / G. Schierholz. Lattice QCD simulations with two light dynamical (Wilson) quarks / L. Giusti. Do we understand the low-energy constant L8? / M. Golterman. Quark mass dependence of LECs in the two-flavour sector / M. Schmid. Progress report on the [Pie symbol]0 Lifetime experiment (PRIMEX) at Jlab / D.E. McNulty. Determination of the charged pion polarizabilities / L.V. Fil'kov. Proposed measurement of electroproduction of [Pie symbol]0 near threshold using a large acceptance spectrometer / R.A. Lindgren. The [Pie symbol] meson in [Pie symbol]K scattering / B. Moussallam. Strangeness -1 Meson-Baryon scattering S-wave / J.A. Oller. Results on light mesons decays and dynamics at KLOE / M. Martini. Studies of decays of [symbol] and [symbol] mesons with WASA detector / A. Kupsc. Heavy Quark-Diquark symmetry and X PT for doubly heavy baryons / T. Mehen. HHChPT applied to the charmed-strange parity partners/ R.P. Springer. Study of pion structure through precise measurements of the [Pie symbol]+ --> e+[symbol] decay / D. Pocanic. Exceptional and non-exceptional contributions to the radiative [Pie symbol] decay / V. Mateu. Leading chiral logarithms from unitarity, analyticity and the Roy equations / A. Fuhrer. All orders symmetric subtraction of the nonlinear sigma model in D=4 / A. Quadri -- pt. C. Chiral dynamics in few-nucleon systems. Working group summary: chiral dynamics in few-nucleon systems / H.W Hammer, N. Kalantar-Nayestanaki, and D.R. Phillips. Power counting in nuclear chiral effective field theory / U. van Kolck. On the consistency of Weinberg's power counting / U-G Mei ner. Renormalization
Continuum model for chiral induced spin selectivity in helical molecules
Energy Technology Data Exchange (ETDEWEB)
Medina, Ernesto [Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, Université de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France); Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); González-Arraga, Luis A. [IMDEA Nanoscience, Cantoblanco, 28049 Madrid (Spain); Finkelstein-Shapiro, Daniel; Mujica, Vladimiro [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Berche, Bertrand [Centro de Física, Instituto Venezolano de Investigaciones Científicas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, Université de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France)
2015-05-21
A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p{sub z} type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective π{sub z} − π{sub z} coupling via interbase p{sub x,y} − p{sub z} hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.
K- nuclear potentials from in-medium chirally motivated models
International Nuclear Information System (INIS)
Cieply, A.; Gazda, D.; Mares, J.; Friedman, E.; Gal, A.
2011-01-01
A self-consistent scheme for constructing K - nuclear optical potentials from subthreshold in-medium KN s-wave scattering amplitudes is presented and applied to analysis of kaonic atoms data and to calculations of K - quasibound nuclear states. The amplitudes are taken from a chirally motivated meson-baryon coupled-channel model, both at the Tomozawa-Weinberg leading order and at the next to leading order. Typical kaonic atoms potentials are characterized by a real part -Re V K - chiral =85±5 MeV at nuclear matter density, in contrast to half this depth obtained in some derivations based on in-medium KN threshold amplitudes. The moderate agreement with data is much improved by adding complex ρ- and ρ 2 -dependent phenomenological terms, found to be dominated by ρ 2 contributions that could represent KNN→YN absorption and dispersion, outside the scope of meson-baryon chiral models. Depths of the real potentials are then near 180 MeV. The effects of p-wave interactions are studied and found secondary to those of the dominant s-wave contributions. The in-medium dynamics of the coupled-channel model is discussed and systematic studies of K - quasibound nuclear states are presented.
Lattice chiral symmetry and the Wess-Zumino model
International Nuclear Information System (INIS)
Fujikawa, Kazuo; Ishibashi, Masato
2002-01-01
A lattice regularization of the supersymmetric Wess-Zumino model is studied by using Ginsparg-Wilson operators. We recognize a certain conflict between the lattice chiral symmetry and the Majorana condition for Yukawa couplings, or in Weyl representation a conflict between the lattice chiral symmetry and Yukawa couplings. This conflict is also related, though not directly, to the fact that the kinetic (Kaehler) term and the superpotential term are clearly distinguished in the continuum Wess-Zumino model, whereas these two terms are mixed in the Ginsparg-Wilson operators. We illustrate a case where lattice chiral symmetry together with naive Bose-Fermi symmetry is imposed by preserving a SUSY-like symmetry in the free part of the Lagrangian; one-loop level non-renormalization of the superpotential is then maintained for finite lattice spacing, though the finite parts of wave function renormalization deviate from the supersymmetric value. All these properties hold for the general Ginsparg-Wilson algebra independently of the detailed construction of lattice Dirac operators
Electric dipole polarizability: from few- to many-body systems
Directory of Open Access Journals (Sweden)
Miorelli Mirko
2016-01-01
Full Text Available We review the Lorentz integral transform coupled-cluster method for the calculation of the electric dipole polarizability. We benchmark our results with exact hyperspherical harmonics calculations for 4He and then we move to a heavier nucleus studying 16O. We observe that the implemented chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order underestimates the electric dipole polarizability.
Deep inelastic structure functions in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Sanjose, V. (Valencia Univ. (Spain). Dept. de Didactica de las Ciencias Experimentales); Vento, V. (Valencia Univ. (Spain). Dept. de Fisica Teorica; Centro Mixto CSIC/Valencia Univ., Valencia (Spain). Inst. de Fisica Corpuscular)
1989-10-02
We calculate the structure functions for deep inelastic scattering on baryons in the cavity approximation to the chiral bag model. The behavior of these structure functions is analyzed in the Bjorken limit. We conclude that scaling is satisfied, but not Regge behavior. A trivial extension as a parton model can be achieved by introducing the structure function for the pion in a convolution picture. In this extended version of the model not only scaling but also Regge behavior is satisfied. Conclusions are drawn from the comparison of our results with experimental data. (orig.).
Hybrid stars within a covariant, nonlocal chiral quark model
International Nuclear Information System (INIS)
Blaschke, D. B.; Dumm, D. Gomez; Grunfeld, A. G.; Klaehn, T.; Scoccola, N. N.
2007-01-01
We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses (M∼2M · ) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm -3
Pion-nucleon scattering in the chiral bag model
International Nuclear Information System (INIS)
Israilov, Z.Z.; Musakhanov, M.M.
1981-01-01
Pion-nucleon scattering in the (3.3) resonance region in the framework of chiral bag model(CBM) is considered. The effective Hamiltonian of πNΔ-system in the framework of the CBM contains πNN, πNΔ, πΔΔ interaction terms with the formfactor which is essentially dependent on the size and shape of the quark bag. The iteration of the Born graphs of this model provides successful description of the (3.3) and (3.1) scattering where the values of the parameters agree with CBM [ru
On the chiral phase transition in the linear sigma model
International Nuclear Information System (INIS)
Tran Huu Phat; Nguyen Tuan Anh; Le Viet Hoa
2003-01-01
The Cornwall- Jackiw-Tomboulis (CJT) effective action for composite operators at finite temperature is used to investigate the chiral phase transition within the framework of the linear sigma model as the low-energy effective model of quantum chromodynamics (QCD). A new renormalization prescription for the CJT effective action in the Hartree-Fock (HF) approximation is proposed. A numerical study, which incorporates both thermal and quantum effect, shows that in this approximation the phase transition is of first order. However, taking into account the higher-loop diagrams contribution the order of phase transition is unchanged. (author)
The Baryon Number Two System in the Chiral Soliton Model
International Nuclear Information System (INIS)
Mantovani-Sarti, V.; Drago, A.; Vento, V.; Park, B.-Y.
2013-01-01
We study the interaction between two B = 1 states in a chiral soliton model where baryons are described as non-topological solitons. By using the hedgehog solution for the B = 1 states we construct three possible B = 2 configurations to analyze the role of the relative orientation of the hedgehog quills in the dynamics. The strong dependence of the inter soliton interaction on these relative orientations reveals that studies of dense hadronic matter using this model should take into account their implications. (author)
Radiative decays of vector mesons in the chiral bag model
International Nuclear Information System (INIS)
Tabachenko, A.N.
1988-01-01
A new model of radiative π-meson decays of vector mesons in the chiral bag model is proposed. The quark-π-meson interaction has the form of a pseudoscalar coupling and is located on the bag surface. The vector meson decay width depends on the quark masses, the π-meson decay constant, the radius of the bag, and the free parameter Z 2 , which specifies the disappearance of the bag during the decay. The obtained results for the omega- and p-decay widths are in satisfactory agreement with the experiment
Pion-nucleon scattering in the Chiral bag model
International Nuclear Information System (INIS)
Israilov, Z.Z.; Musakhanov, M.M.
1981-01-01
The effective hamiltonian of the πNΔ-system in the framework of the Chiral Bag Model (CBM) contains πNN-, πNΔ-, πΔΔ-interaction terms with a form factor which is esstentially dependent on the size and shape of the quark bag. The interation of the Born graphs of this model provides successful description of the (3,3) and (3,1) phase shifts [in the (3,3) resonance region] where the values of the paramters agree with the CBM. (orig.)
Dihyperons in chiral color dielectric model
Indian Academy of Sciences (India)
symmetry breaking [3], surface energy term in the bag model [4], coupling of pseudo- scalar meson octet [5] etc. ... parameters of the CCD model are quark masses (m and m0), the 'bag constant' (B), strong coupling constant (αs = g2 .... The projection technique is used to project the good momentum states and these states ...
Nucleon form factors in the projected linear chiral soliton model
International Nuclear Information System (INIS)
Alberto, P.; Coimbra Univ.; Coimbra Univ.; Ruiz Arriola, E.; Gruemmer, F.; Fiolhais, M.; Urbano, J.N.; Coimbra Univ.; Goeke, K.; Bochum Univ.
1988-01-01
Electromagnetic and axial form factors of the nucleon are evaluated using the lagrangian of the linear chiral soliton model. To this end angular momentum and isospin projected mean field solutions are determined variationally assuming valence quarks and pions in generalized hedgehog configurations. With the proper pion decay constant and after fitting the quark-meson coupling constant to the nucleon energy both proton and neutron charge form factors are reproduced as well as the slope of the magnetic ones. The axial form factor agrees less well with experiment. The pion form factor can be approximated by a monopole with a cut-off mass of 690 MeV. (orig.)
The exact mass-gaps of the principal chiral models
Hollowood, Timothy J
1994-01-01
An exact expression for the mass-gap, the ratio of the physical particle mass to the $\\Lambda$-parameter, is found for the principal chiral sigma models associated to all the classical Lie algebras. The calculation is based on a comparison of the free-energy in the presence of a source coupling to a conserved charge of the theory computed in two ways: via the thermodynamic Bethe Ansatz from the exact scattering matrix and directly in perturbation theory. The calculation provides a non-trivial test of the form of the exact scattering matrix.
Linker, Gerrit-Jan; van Duijnen, Piet Th.; van Loosdrecht, Paul H. M.; Broer-Braam, Henderika
2012-01-01
The geometry of ethylenedioxy-tetrathiafulvalene, EDO-TTF, plays an important role in the metal-insulator transition in the charge transfer salt (EDO-TTF)(2)PF6. The planar and off-planar geometrical conformations of the EDO-TTF molecules are explained using an extended Debye polarizability model
Chiral models of low energy QCD
International Nuclear Information System (INIS)
Ripka, G.
1993-01-01
Two processes may be distinguished when a hadron propagates in a dense baryonic medium. The polarization of the medium and the change in the quark structure of the hadron. The polarization of the medium is better described in terms of colorless mesons and nucleons while the intrinsic change of the hadron is better described by quark models. It is shown how to couple the two processes. The scaling of effective Lagrangians, is related to changes in the quark constituent masses, based on the QCD scale anomaly. (author) 62 refs
Duchemin, Ivan; Jacquemin, Denis; Blase, Xavier
2016-04-01
We have implemented the polarizable continuum model within the framework of the many-body Green's function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.
Energy Technology Data Exchange (ETDEWEB)
Duchemin, Ivan, E-mail: ivan.duchemin@cea.fr [INAC, SP2M/L-Sim, CEA/UJF Cedex 09, 38054 Grenoble (France); Jacquemin, Denis [Laboratoire CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3 (France); Institut Universitaire de France, 1 rue Descartes, 75005 Paris Cedex 5 (France); Blase, Xavier [CNRS, Inst. NÉEL, F-38000 Grenoble (France); Univ. Grenoble Alpes, Inst. NÉEL, F-38000 Grenoble (France)
2016-04-28
We have implemented the polarizable continuum model within the framework of the many-body Green’s function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.
An Effective Chiral Meson Lagrangian at O(p6) from the NJL Model
International Nuclear Information System (INIS)
Bel'kov, A.A.; Lanev, A.V.; Schaale, A.; Scherer, S.; Mainz Univ.
1994-01-01
In this work we present a strong chiral meson Lagrangian up to and including O(p 6 ) in the momentum expansion. It is derived from the Nambu-Jona-Lasinio (NJL) model using the heat-kernel method. Identities related to the properties of covariant derivatives of the chiral matrix U as well as field transformations have been used to predict the chiral coefficients of a minimal set of linearly independent terms. 16 refs
The ΔS=1 weak chiral lagrangian as the effective theory of the chiral quark model
International Nuclear Information System (INIS)
Antonelli, V.; Bertolini, S.; Eeg, J.O.; Lashin, E.I.
1996-01-01
We use the chiral quark model to construct the complete O(p 2 ) weak ΔS = 1 chiral lagrangian via the bosonization of the ten relevant operators of the effective quark lagrangian. The chiral coefficients are given in terms of f π , the quark and gluon condensates and the scale-dependent NLO Wilson coefficients of the corresponding operators; in addition, they depend on the constituent quark mass M, a parameter characteristic of the model. All contributions of order N c 2 as well as N c and α s N c are included. The γ 5 -scheme dependence of the chiral coefficients, computed via dimensional regularization, and the Fierz transformation properties of the operator basis are discussed in detail. We apply our results to the evaluation of the hadronic matrix elements for the decays K →2 π, consistently including the renormalization induced by the meson loops. The effect of this renormalization is sizable and introduces a long-distance scale dependence that matches in the physical amplitudes the short-distance scale dependence of the Wilson coefficients. (orig.)
Vector meson decays in the chiral bag model
International Nuclear Information System (INIS)
Maxwell, O.V.; Jennings, B.K.
1985-01-01
Vector meson decays are examined in a model where a confined quark and antiquark annihilate, producing a pair of elementary pseudoscalar mesons. Two versions of the pseudoscalar meson-quark interaction are employed, one where the coupling is restricted to the bag surface and one where it extends throughout the bag volume. Energy conservation is ensured in the model through insertion of exponential factors containing the bag energy at each interaction vertex. To guarantee momentum conservation, a wave-packet description is utilized in which the decay widths are normalized by a factor involving the overlap of the initial bag state with the confined qanti q state of zero momentum. With either interaction, the model yields a value for the p-width that exceeds the empirical width by a factor two. For the Ksup(*) and PHI mesons, the computed widths depend strongly on the interaction employed. Implications of these results for chiral bag models are discussed. (orig.)
Chiral Dynamics and Dubna-Mainz Dynamical Model for Pion Photoproduction Reaction
Yang, Shin Nan
We demonstrate that the Dubna-Mainz-Taipei (DMT) meson-exchange dynamical model, which starts from an effective chiral Lagrangian, for pion photoproduction provides an excellent and economic framework to describe both the π0 threshold production and the Δ deformation, two features dictated by chiral dynamics.
Chiral Dynamics and Dubna-Mainz-Taipei Dynamical Model for Pion-Photoproduction Reaction
Yang, Shin Nan
2010-01-01
We demonstrate that the Dubna-Mainz-Taipei (DMT) meson-exchange dynamical model, which starts from an effective chiral Lagrangian, for pion photoproduction provides an excellent and economic framework to describe both the pi^0 threshold production and the Delta deformation, two features dictated by chiral dynamics.
Excited States in Solution through Polarizable Embedding
DEFF Research Database (Denmark)
Olsen, Jógvan Magnus; Aidas, Kestutis; Kongsted, Jacob
2010-01-01
We present theory and implementation of an advanced quantum mechanics/molecular mechanics (QM/MM) approach using a fully self-consistent polarizable embedding (PE) scheme. It is a polarizable layered model designed for effective yet accurate inclusion of an anisotropic medium in a quantum...... a nonequilibrium formulation of the environmental response. In our formulation of polarizable embedding we explicitly take into account the full self-consistent many-body environmental response from both ground and excited states. The PE-DFT method can be applied to any molecular system, e.g., proteins...
Chiral quark soliton model with Pauli-Villars regularization
Kubota, T.; Wakamatsu, M.; Watabe, T.
1999-07-01
The Pauli-Villars regularization scheme is often used for evaluating parton distributions within the framework of the chiral quark soliton model with the inclusion of the vacuum polarization effects. Its simplest version with a single subtraction term should, however, be taken with some caution, since it does not fully get rid of divergences contained in scalar and psuedoscalar quark densities appearing in the soliton equation of motion. To remedy this shortcoming, we propose here its natural extension, i.e., the Pauli-Villars regularization scheme with multisubtraction terms. We also carry out a comparative analysis of the Pauli-Villars regularization scheme and more popular proper-time one. It turns out that some isovector observables such as the isovector magnetic moment of the nucleon are rather sensitive to the choice of the regularization schemes. In the process of tracing the origin of this sensitivity, a noticeable difference of the two regularization schemes is revealed.
Chiral bag model with constituent quarks: topological and nontopological decisions
International Nuclear Information System (INIS)
Malakhov, I.Yu.; Sveshnikov, K.A.; Fedorov, S.M.; Khalili, M.F.
2002-01-01
The three-phase modification of the hybrid chiral bag containing along with asymptotic freedom and hadronization phases and also intermediate phase of the constituent quarks is considered. The self-consistent solutions of the equations of the model in the (1 + 1)-dimensional case are determined with an account of the fermion vacuum polarization effects. The bag renormalized complete energy is studied as a function of the parameters characterizing the bag geometry and its topological (baryon) charge. It is shown that for nonzero topological charge there exists the whole series of configurations representing the local minima of the bag complete energy and containing all three phases, whereas the bag energy minimum in the nontopological case corresponds to zero dimensions of the area corresponding to asymptotic freedom phase [ru
Chiral correlators in Landau-Ginsburg theories and N=2 superconformal models
International Nuclear Information System (INIS)
Howe, P.S.; West, P.C.
1989-01-01
Chiral correlation functions are computed in N=2 Landau-Ginsburg models using the ε-expansion and the superconformal Ward identities for the Landau-Ginsburg effective action. They are also computed directly using superconformal model techniques. The same results are obtained yielding further confirmation of the identification of superconformal minimal models with Landau-Ginsburg models evaluated at their fixed points. The formulae for the chiral commutators that we compute are extremely simple when expressed in terms of effective actions. (orig.)
Chiral anomaly, fermionic determinant and two dimensional models
International Nuclear Information System (INIS)
Rego Monteiro, M.A. do.
1985-01-01
The chiral anomaly in random pair dimension is analysed. This anomaly is perturbatively calculated by dimensional regularization method. A new method for non-perturbative Jacobian calculation of a general chiral transformation, 1.e., finite and non-Abelian, is developed. This method is used for non-perturbative chiral anomaly calculation, as an alternative to bosonization of two-dimensional theories for massless fermions and to study the phenomenum of fermion number fractionalization. The fermionic determinant from two-dimensional quantum chromodynamics is also studied, and calculated, exactly, as in decoupling gauge as with out reference to a particular gauge. (M.C.K.) [pt
Lu, Shih-I.
2018-01-01
We use the discrete solvent reaction field model to evaluate the linear and second-order nonlinear optical susceptibilities of 3-methyl-4-nitropyridine-1-oxyde crystal. In this approach, crystal environment is created by supercell architecture. A self-consistent procedure is used to obtain charges and polarizabilities for environmental atoms. Impact of atomic polarizabilities on the properties of interest is highlighted. This approach is shown to give the second-order nonlinear optical susceptibilities within error bar of experiment as well as the linear optical susceptibilities in the same order as experiment. Similar quality of calculations are also applied to both 4-N,N-dimethylamino-3-acetamidonitrobenzene and 2-methyl-4-nitroaniline crystals.
Chiral condensate in the Schwinger model with matrix product operators
Energy Technology Data Exchange (ETDEWEB)
Banuls, Mari Carmen [Max-Planck-Institut fuer Quantenoptik (MPQ), Garching (Germany); Cichy, Krzysztof [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Poznan Univ. (Poland). Faculty of Physics; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Saito, Hana [Tsukuba Univ. (Japan). Center for Computational Sciences
2016-03-15
Tensor network (TN) methods, in particular the Matrix Product States (MPS) ansatz, have proven to be a useful tool in analyzing the properties of lattice gauge theories. They allow for a very good precision, much better than standard Monte Carlo (MC) techniques for the models that have been studied so far, due to the possibility of reaching much smaller lattice spacings. The real reason for the interest in the TN approach, however, is its ability, shown so far in several condensed matter models, to deal with theories which exhibit the notorious sign problem in MC simulations. This makes it prospective for dealing with the non-zero chemical potential in QCD and other lattice gauge theories, as well as with real-time simulations. In this paper, using matrix product operators, we extend our analysis of the Schwinger model at zero temperature to show the feasibility of this approach also at finite temperature. This is an important step on the way to deal with the sign problem of QCD. We analyze in detail the chiral symmetry breaking in the massless and massive cases and show that the method works very well and gives good control over a broad range of temperatures, essentially from zero to infinite temperature.
The Chiral Quark Soliton Model for the Nucleon
Watabe, T.; Toki, H.
1992-03-01
We study the chiral invariant quark model lagrangians under the Hartree approximation for construction of a hedgehog solution with the baryon number B = 1. We take into account the Dirac sea contributions to the energy and various densities in terms of the heat-kernel method. With the parameters of the Nambu-Jona-Lasinio model lagrangian fixed by the meson properties, we do not find any B = 1 hedgehog solutions except for one case, even which is, however, unstable against small perturbation. We study then the Diakonov-Petrov model lagrangian, which is introduced by investigating the properties of the quark field in the instanton background in QCD. We find in this case stable hedgehog solutions under the heat-kernel regularization method in some parameter region. We study also the isoscalar-vector type (omega-meson type) correlations among quarks for the nucleon properties. The hedgehog energy, the baryon root mean square radius and the axial vector coupling constant g_{A} are calculated as a function of the omega-quark coupling strength.
Martel, P P; Miskimen, R; Aguar-Bartolome, P; Ahrens, J; Akondi, C S; Annand, J R M; Arends, H J; Barnes, W; Beck, R; Bernstein, A; Borisov, N; Braghieri, A; Briscoe, W J; Cherepnya, S; Collicott, C; Costanza, S; Denig, A; Dieterle, M; Downie, E J; Fil'kov, L V; Garni, S; Glazier, D I; Gradl, W; Gurevich, G; Hall Barrientos, P; Hamilton, D; Hornidge, D; Howdle, D; Huber, G M; Jude, T C; Kaeser, A; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Krusche, B; Lazarev, A; Lisin, V; Livingston, K; MacGregor, I J D; Mancell, J; Manley, D M; Meyer, W; Middleton, D G; Mushkarenkov, A; Nefkens, B M K; Neganov, A; Nikolaev, A; Oberle, M; Ortega Spina, H; Ostrick, M; Ott, P; Otte, P B; Oussena, B; Pedroni, P; Polonski, A; Polyansky, V; Prakhov, S; Rajabi, A; Reicherz, G; Rostomyan, T; Sarty, A; Schrauf, S; Schumann, S; Sikora, M H; Starostin, A; Steffen, O; Strakovsky, I I; Strub, T; Supek, I; Thiel, M; Tiator, L; Thomas, A; Unverzagt, M; Usov, Y; Watts, D P; Witthauer, L; Werthmüller, D; Wolfes, M
2015-03-20
The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4) fm(4).
Chiral phase transition in the soft-wall model of AdS/QCD
Energy Technology Data Exchange (ETDEWEB)
Chelabi, Kaddour [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190 (China); University of Chinese Academy of Sciences (UCAS),Beijing 100049 (China); Laboratory of Particle Physics and Statistical Physics, Ecole Normale Superieure-Kouba,B.P. 92,16050, Vieux-Kouba, Algiers (Algeria); Fang, Zhen [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190 (China); University of Chinese Academy of Sciences (UCAS),Beijing 100049 (China); Huang, Mei [Institute of High Energy Physics, Chinese Academy of Sciences,Beijing 100049 (China); Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences,Beijing 100049 (China); Li, Danning [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190 (China); Wu, Yue-Liang [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190 (China); University of Chinese Academy of Sciences (UCAS),Beijing 100049 (China)
2016-04-06
We investigate the chiral phase transition in the soft-wall model of AdS/QCD at zero chemical potential for two-flavor and three-flavor cases, respectively. We show that there is no spontaneous chiral symmetry breaking in the original soft-wall model. After detailed analysis, we find that in order to realize chiral symmetry breaking and restoration, both profiles for the scalar potential and the dilaton field are essential. The scalar potential determines the possible solution structure of the chiral condensate, except the mass term, it takes another quartic term for the two-flavor case, and for the three-flavor case, one has to take into account an extra cubic term due to the t’Hooft determinant interaction. The profile of the dilaton field reflects the gluodynamics, which is negative at a certain ultraviolet scale and approaches positive quadratic behavior at far infrared region. With this set-up, the spontaneous chiral symmetry breaking in the vacuum and its restoration at finite temperature can be realized perfectly. In the two-flavor case, it gives a second order chiral phase transition in the chiral limit, while the transition turns to be a crossover for any finite quark mass. In the case of three-flavor, the phase transition becomes a first order one in the chiral limit, while above sufficient large quark mass it turns to be a crossover again. This scenario agrees exactly with the current understanding on chiral phase transition from lattice QCD and other effective model studies.
Degenerate and chiral states in the extended Heisenberg model on the kagome lattice
Gómez Albarracín, F. A.; Pujol, P.
2018-03-01
We present a study of the low-temperature phases of the antiferromagnetic extended classical Heisenberg model on the kagome lattice, up to third-nearest neighbors. First, we focus on the degenerate lines in the boundaries of the well-known staggered chiral phases. These boundaries have either semiextensive or extensive degeneracy, and we discuss the partial selection of states by thermal fluctuations. Then, we study the model under an external magnetic field on these lines and in the staggered chiral phases. We pay particular attention to the highly frustrated point, where the three exchange couplings are equal. We show that this point can be mapped to a model with spin-liquid behavior and nonzero chirality. Finally, we explore the effect of Dzyaloshinskii-Moriya (DM) interactions in two ways: a homogeneous and a staggered DM interaction. In both cases, there is a rich low-temperature phase diagram, with different spontaneously broken symmetries and nontrivial chiral phases.
Form factors in the projected linear chiral sigma model
International Nuclear Information System (INIS)
Alberto, P.; Coimbra Univ.; Bochum Univ.; Ruiz Arriola, E.; Fiolhais, M.; Urbano, J.N.; Coimbra Univ.; Goeke, K.; Gruemmer, F.; Bochum Univ.
1990-01-01
Several nucleon form factors are computed within the framework of the linear chiral soliton model. To this end variational means and projection techniques applied to generalized hedgehog quark-boson Fock states are used. In this procedure the Goldberger-Treiman relation and a virial theorem for the pion-nucleon form factor are well fulfilled demonstrating the consistency of the treatment. Both proton and neutron charge form factors are correctly reproduced, as well as the proton magnetic one. The shapes of the neutron magnetic and of the axial form factors are good but their absolute values at the origin are too large. The slopes of all the form factors at zero momentum transfer are in good agreement with the experimental data. The pion-nucleon form factor exhibits to great extent a monopole shape with a cut-off mass of Λ=690 MeV. Electromagnetic form factors for the vertex γNΔ and the nucleon spin distribution are also evaluated and discussed. (orig.)
Di Remigio, Roberto; Beerepoot, Maarten T P; Cornaton, Yann; Ringholm, Magnus; Steindal, Arnfinn Hykkerud; Ruud, Kenneth; Frediani, Luca
2016-12-21
The study of high-order absorption properties of molecules is a field of growing importance. Quantum-chemical studies can help design chromophores with desirable characteristics. Given that most experiments are performed in solution, it is important to devise a cost-effective strategy to include solvation effects in quantum-chemical studies of these properties. We here present an open-ended formulation of self-consistent field (SCF) response theory for a molecular solute coupled to a polarizable continuum model (PCM) description of the solvent. Our formulation relies on the open-ended, density matrix-based quasienergy formulation of SCF response theory of Thorvaldsen, et al., [J. Chem. Phys., 2008, 129, 214108] and the variational formulation of the PCM, as presented by Lipparini et al., [J. Chem. Phys., 2010, 133, 014106]. Within the PCM approach to solvation, the mutual solute-solvent polarization is represented by means of an apparent surface charge (ASC) spread over the molecular cavity defining the solute-solvent boundary. In the variational formulation, the ASC is an independent, variational degree of freedom. This allows us to formulate response theory for molecular solutes in the fixed-cavity approximation up to arbitrary order and with arbitrary perturbation operators. For electric dipole perturbations, pole and residue analyses of the response functions naturally lead to the identification of excitation energies and transition moments. We document the implementation of this approach in the Dalton program package using a recently developed open-ended response code and the PCMSolver libraries and present results for one-, two-, three-, four- and five-photon absorption processes of three small molecules in solution.
International Nuclear Information System (INIS)
Saito, H; Jansen, K.; Cichy, K.; Frankfurt Univ.; Poznan Univ.
2014-12-01
We present our recent results for the tensor network (TN) approach to lattice gauge theories. TN methods provide an efficient approximation for quantum many-body states. We employ TN for one dimensional systems, Matrix Product States, to investigate the 1-flavour Schwinger model. In this study, we compute the chiral condensate at finite temperature. From the continuum extrapolation, we obtain the chiral condensate in the high temperature region consistent with the analytical calculation by Sachs and Wipf.
Polarizable Water Model for the Coarse-Grained MARTINI Force Field
Yesylevskyy, Semen O.; Schafer, Lars V.; Sengupta, Durba; Marrink, Siewert J.
Coarse-grained (CG) simulations have become an essential tool to study a large variety of biomolecular processes, exploring temporal and spatial scales inaccessible to traditional models of atomistic resolution. One of the major simplifications of CG models is the representation of the solvent,
Chiral and color-superconducting phase transitions with vector interaction in a simple model
International Nuclear Information System (INIS)
Kitazawa, Masakiyo; Koide, Tomoi; Kunihiro, Teiji; Nemoto, Yukio
2002-01-01
We investigate effects of the vector interaction on chiral and color superconducting (CSC) phase transitions at finite density and temperature in a simple Nambu-Jona-Lasinio model. It is shown that the repulsive density-density interaction coming from the vector term, which is present in the effective chiral models but has been omitted, enhances the competition between the chiral symmetry breaking (χSB) and CSC phase transition, and thereby makes the thermodynamic potential have a shallow minimum over a wide range of values of the correlated chiral and CSC order parameters. We find that when the vector coupling is increased, the first order transition between the χSB and CSC phases becomes weaker, and the coexisting phase in which both the chiral and color-gauge symmetry are dynamically broken comes to exist over a wider range of the density and temperature. We also show that there can exist two endpoints, which are tricritical points in the chiral limit, along the critical line of the first order transition in some range of values of the vector coupling. Although our analysis is based on a simple model, the nontrivial interplay between the χSB and CSC phases induced by the vector interaction is expected to be a universal phenomenon and might give a clue to understanding results obtained with two-color QCD on the lattice. (author)
Jensen, L; Astrand, PO; Mikkelsen, KV
An atomic dipole interaction model has been used for calculating the second hyperpolarizability of carbon nanotubes on a length scale up to 75 nm. It is demonstrated that an atomistic representation of mesoscale systems such as nanotubes can be used to obtain a cubic response property up to a size
A model with charges and polarizability for CS2 in an ionic liquid
Indian Academy of Sciences (India)
RUTH M LYNDEN-BELL
Abstract. The environment of a solute molecule in an ionic liquid is likely to have large fluctuating electro- static fields, and so the electrostatic properties of such a solute including its charge distribution and its polar- izability may make a difference to both its static and dynamic properties. We have developed a new model for.
Liu, Fang; Luehr, Nathan; Kulik, Heather J; Martínez, Todd J
2015-07-14
The conductor-like polarization model (C-PCM) with switching/Gaussian smooth discretization is a widely used implicit solvation model in chemical simulations. However, its application in quantum mechanical calculations of large-scale biomolecular systems can be limited by computational expense of both the gas phase electronic structure and the solvation interaction. We have previously used graphical processing units (GPUs) to accelerate the first of these steps. Here, we extend the use of GPUs to accelerate electronic structure calculations including C-PCM solvation. Implementation on the GPU leads to significant acceleration of the generation of the required integrals for C-PCM. We further propose two strategies to improve the solution of the required linear equations: a dynamic convergence threshold and a randomized block-Jacobi preconditioner. These strategies are not specific to GPUs and are expected to be beneficial for both CPU and GPU implementations. We benchmark the performance of the new implementation using over 20 small proteins in solvent environment. Using a single GPU, our method evaluates the C-PCM related integrals and their derivatives more than 10× faster than that with a conventional CPU-based implementation. Our improvements to the linear solver provide a further 3× acceleration. The overall calculations including C-PCM solvation require, typically, 20-40% more effort than that for their gas phase counterparts for a moderate basis set and molecule surface discretization level. The relative cost of the C-PCM solvation correction decreases as the basis sets and/or cavity radii increase. Therefore, description of solvation with this model should be routine. We also discuss applications to the study of the conformational landscape of an amyloid fibril.
Out-of-equilibrium relaxation of the thermal Casimir effect in a model polarizable material.
Dean, David S; Démery, Vincent; Parsegian, V Adrian; Podgornik, Rudolf
2012-03-01
Relaxation of the thermal Casimir or van der Waals force (the high temperature limit of the Casimir force) for a model dielectric medium is investigated. We start with a model of interacting polarization fields with a dynamics that leads to a frequency dependent dielectric constant of the Debye form. In the static limit, the usual zero frequency Matsubara mode component of the Casimir force is recovered. We then consider the out-of-equilibrium relaxation of the van der Waals force to its equilibrium value when two initially uncorrelated dielectric bodies are brought into sudden proximity. For the interaction between dielectric slabs, it is found that the spatial dependence of the out-of-equilibrium force is the same as the equilibrium one, but it has a time dependent amplitude, or Hamaker coefficient, which increases in time to its equilibrium value. The final relaxation of the force to its equilibrium value is exponential in systems with a single or finite number of polarization field relaxation times. However, in systems, such as those described by the Havriliak-Negami dielectric constant with a broad distribution of relaxation times, we observe a much slower power law decay to the equilibrium value.
Naserifar, Saber; Brooks, Daniel J.; Goddard, William A.; Cvicek, Vaclav
2017-03-01
Electrostatic interactions play a critical role in determining the properties, structures, and dynamics of chemical, biochemical, and material systems. These interactions are described well at the level of quantum mechanics (QM) but not so well for the various models used in force field simulations of these systems. We propose and validate a new general methodology, denoted PQEq, to predict rapidly and dynamically the atomic charges and polarization underlying the electrostatic interactions. Here the polarization is described using an atomic sized Gaussian shaped electron density that can polarize away from the core in response to internal and external electric fields, while at the same time adjusting the charge on each core (described as a Gaussian function) so as to achieve a constant chemical potential across all atoms of the system. The parameters for PQEq are derived from experimental atomic properties of all elements up to Nobelium (atomic no. = 102). We validate PQEq by comparing to QM interaction energy as probe dipoles are brought along various directions up to 30 molecules containing H, C, N, O, F, Si, P, S, and Cl atoms. We find that PQEq predicts interaction energies in excellent agreement with QM, much better than other common charge models such as obtained from QM using Mulliken or ESP charges and those from standard force fields (OPLS and AMBER). Since PQEq increases the accuracy of electrostatic interactions and the response to external electric fields, we expect that PQEq will be useful for a large range of applications including ligand docking to proteins, catalytic reactions, electrocatalysis, ferroelectrics, and growth of ceramics and films, where it could be incorporated into standard force fields as OPLS, AMBER, CHARMM, Dreiding, ReaxFF, and UFF.
Introduction to Chiral Symmetry
Energy Technology Data Exchange (ETDEWEB)
Koch, Volker [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2017-05-09
These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. We will also discuss some effective chiral models such as the linear and nonlinear sigma model as well as the essential ideas of chiral perturbation theory. We will present some applications to the physics of ultrarelativistic heavy ion collisionsd.
Polarizable Density Embedding Coupled Cluster Method
DEFF Research Database (Denmark)
Hršak, Dalibor; Olsen, Jógvan Magnus Haugaard; Kongsted, Jacob
2018-01-01
by an embedding potential consisting of a set of fragment densities obtained from calculations on isolated fragments with a quantum-chemistry method such as Hartree-Fock (HF) or Kohn-Sham density functional theory (KS-DFT) and dressed with a set of atom-centered anisotropic dipole-dipole polarizabilities......). In the PDE-CC method, the smaller, but chemically important core region is described with a high-level CC method. The environment surrounding the core region can be separated into two levels of description: an inner and an outer region. The effect of the inner region on the core region is described......We present the theory and implementation of the polarizable density embedding (PDE) model in combination with coupled cluster (CC) theory (PDE-CC). This model has been implemented in the Dalton quantum chemistry program by adapting the CC code to the polarizable embedding library (PElib...
Electroweak chiral Lagrangian from a natural topcolor-assisted technicolor model
International Nuclear Information System (INIS)
Lang Junyi; Jiang Shaozhou; Wang Qing
2009-01-01
Based on previous studies on computing coefficients of the electroweak chiral Lagrangian from C. T. Hill's schematic topcolor-assisted technicolor model, we generalize the calculation to K. Lane's prototype natural topcolor-assisted technicolor model. We find that typical features of the model are qualitatively similar to those of Hill's, but Lane's model prefers a smaller technicolor group and the Z ' mass must be smaller than 400 GeV. Furthermore, the S parameter is around the order of +1, mainly due to the existence of three doublets of techniquarks. We obtain the values for all coefficients of the electroweak chiral Lagrangian up to the order p 4 . Apart from large negative four-fermion coupling values, the extended technicolor impacts on the electroweak chiral Lagrangian coefficients are small, since the techniquark self energy, which determines these coefficients, in general receives almost no influence from the extended technicolor induced four-fermion interactions except for its large momentum tail.
Chiral symmetry and chiral-symmetry breaking
International Nuclear Information System (INIS)
Peskin, M.E.
1982-12-01
These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed
Kovatcheva, A; Golbraikh, A; Oloff, S; Feng, J; Zheng, W; Tropsha, A
2005-01-01
Shape descriptors used in 3D QSAR studies naturally take into account chirality; however, for flexible and structurally diverse molecules such studies require extensive conformational searching and alignment. QSAR modeling studies of two datasets of fragrance compounds with complex stereochemistry using simple alignment-free chirality sensitive descriptors developed in our laboratories are presented. In the first investigation, 44 alpha-campholenic derivatives with sandalwood odor were represented as derivatives of several common structural templates with substituents numbered according to their relative spatial positions in the molecules. Both molecular and substituent descriptors were used as independent variables in MLR calculations, and the best model was characterized by the training set q2 of 0.79 and external test set r2 of 0.95. In the second study, several types of chirality descriptors were employed in combinatorial QSAR modeling of 98 ambergris fragrance compounds. Among 28 possible combinations of seven types of descriptors and four statistical modeling techniques, k nearest neighbor classification with CoMFA descriptors was initially found to generate the best models with the internal and external accuracies of 76 and 89%, respectively. The same dataset was then studied using novel atom pair chirality descriptors (cAP). The cAP are based on a modified definition of the atomic chirality, in which the seniority of the substituents is defined by their relative partial charge values: higher values correspond to higher seniorities. The resulting models were found to have higher predictive power than those developed with CoMFA descriptors; the best model was characterized by the internal and external accuracies of 82 and 94%, respectively. The success of modeling studies using simple alignment free chirality descriptors discussed in this paper suggests that they should be applied broadly to QSAR studies of many datasets when compound stereochemistry plays an
Investigation of the chiral antiferromagnetic Heisenberg model using projected entangled pair states
Poilblanc, Didier
2017-09-01
A simple spin-1/2 frustrated antiferromagnetic Heisenberg model (AFHM) on the square lattice—including chiral plaquette cyclic terms—was argued [A. E. B. Nielsen, G. Sierra, and J. I. Cirac, Nat. Commun. 4, 2864 (2013), 10.1038/ncomms3864] to host a bosonic Kalmeyer-Laughlin (KL) fractional quantum Hall ground state [V. Kalmeyer and R. B. Laughlin, Phys. Rev. Lett. 59, 2095 (1987), 10.1103/PhysRevLett.59.2095]. Here, we construct generic families of chiral projected entangled pair states (chiral PEPS) with low bond dimension (D =3 ,4 ,5 ) which, upon optimization, provide better variational energies than the KL Ansatz. The optimal D =3 PEPS exhibits chiral edge modes described by the Wess-Zumino-Witten SU(2) 1 model, as expected for the KL spin liquid. However, we find evidence that, in contrast to the KL state, the PEPS spin liquids have power-law dimer-dimer correlations and exhibit a gossamer long-range tail in the spin-spin correlations. We conjecture that these features are genuine to local chiral AFHM on bipartite lattices.
Chiral model for q-barq and qq-barqq mesons
International Nuclear Information System (INIS)
Napsuciale, Mauro; Rodriguez, Simon
2004-01-01
We point out that the spectrum of pseudoscalar and scalar mesons exhibits a quasidegenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum. Based on the empirical linear rising of the mass of a hadron with the number of constituent quarks which yields a mass around 1.4 GeV for tetraquarks, we conjecture that this quasichiral nonet arises from the mixing of a chiral nonet composed of tetraquarks with conventional q-barq states. We explore this possibility in the framework of a chiral model assuming a tetraquark chiral nonet around 1.4 GeV with chiral symmetry realized directly. We stress that U A (1) transformations can distinguish q-barq from tetraquark states, although it cannot distinguish specific dynamics in the later case. We find that the measured spectrum is consistent with this picture. In general, pseudoscalar states arise as mainly q-barq states but scalar states turn out to be strong admixtures of q-barq and tetraquark states. We work out also the model predictions for the most relevant couplings and calculate explicitly the strong decays of the a 0 (1450) and K 0 *(1430) mesons
Upper Higgs boson mass bounds from a chirally invariant lattice Higgs-Yukawa Model
Energy Technology Data Exchange (ETDEWEB)
Gerhold, P. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; John von Neumann-Institut fuer Computing NIC/DESY, Zeuthen (Germany); Jansen, K. [John von Neumann-Institut fuer Computing NIC/DESY, Zeuthen (Germany)
2010-02-15
We establish the cutoff-dependent upper Higgs boson mass bound by means of direct lattice computations in the framework of a chirally invariant lattice Higgs-Yukawa model emulating the same chiral Yukawa coupling structure as in the Higgs-fermion sector of the Standard Model. As expected from the triviality picture of the Higgs sector, we observe the upper mass bound to decrease with rising cutoff parameter {lambda}. Moreover, the strength of the fermionic contribution to the upper mass bound is explored by comparing to the corresponding analysis in the pure {phi}{sup 4}-theory. (orig.)
Correct Fujikawa regularization prescription in the chiral Schwinger model and the Wess-Zumino term
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J.; Farina de Souza, C.
1988-07-15
In the solutions for the chiral Schwinger model found in the literature, where path-integral methods were applied, the problem of Hermiticity of the regulator operator has been forgotten. We use two Hermitian prescriptions to solve this model exactly. We also include the Wess-Zumino term through the Faddeev-Popov procedure and study its behavior under both Hermitian prescriptions.
Directory of Open Access Journals (Sweden)
IVAN GUTMAN
1999-08-01
Full Text Available A simple explanation is offered for the recently discovered chiral amplification in the alkylation reaction of benzaldehyde by means of dialkylzinc, catalyzed by (dimethylaminoisoborneol. The model presentd is similar to, yet somewhat simpler than, the model put forward by Noyori et al.
Modeling finite-volume effects and chiral symmetry breaking in two-flavor QCD thermodynamics
Klein, Bertram
2017-11-01
Finite-volume effects in Quantum Chromodynamics (QCD) have been a subject of much theoretical interest for more than two decades. They are in particular important for the analysis and interpretation of QCD simulations on a finite, discrete space-time lattice. Most of these effects are closely related to the phenomenon of spontaneous breaking of the chiral flavor symmetry and the emergence of pions as light Goldstone bosons. These long-range fluctuations are strongly affected by putting the system into a finite box, and an analysis with different methods can be organized according to the interplay between pion mass and box size. The finite volume also affects critical behavior at the chiral phase transition in QCD. In the present review, I will be mainly concerned with modeling such finite volume effects as they affect the thermodynamics of the chiral phase transition for two quark flavors. I review recent work on the analysis of finite-volume effects which makes use of the quark-meson model for dynamical chiral symmetry breaking. To account for the effects of critical long-range fluctuations close to the phase transition, most of the calculations have been performed using non-perturbative Renormalization Group (RG) methods. I give an overview over the application of these methods to a finite volume. The method, the model and the results are put into the context of related work in random matrix theory for very small volumes, chiral perturbation theory for larger volumes, and related methods and approaches. They are applied towards the analysis of finite-volume effects in lattice QCD simulations and their interpretation, mainly in the context of the chiral phase transition for two quark flavors.
Efficient modeling of chiral media using SCN-TLM method
Directory of Open Access Journals (Sweden)
Yaich M.I.
2004-01-01
Full Text Available An efficient approach allowing to include linear bi-isotropic chiral materials in time-domain transmission line matrix (TLM calculations by employing recursive evaluation of the convolution of the electric and magnetic fields and susceptibility functions is presented. The new technique consists to add both voltage and current sources in supplementary stubs of the symmetrical condensed node (SCN of the TLM method. In this article, the details and the complete description of this approach are given. A comparison of the obtained numerical results with those of the literature reflects its validity and efficiency.
Directory of Open Access Journals (Sweden)
Yizhuang Liu
2016-08-01
Full Text Available We derive an exact formula for the stochastic evolution of the characteristic determinant of a class of deformed Wishart matrices following from a chiral random matrix model of QCD at finite chemical potential. In the WKB approximation, the characteristic determinant describes a sharp droplet of eigenvalues that deforms and expands at large stochastic times. Beyond the WKB limit, the edges of the droplet are fuzzy and described by universal edge functions. At the chiral point, the characteristic determinant in the microscopic limit is universal. Remarkably, the physical chiral condensate at finite chemical potential may be extracted from current and quenched lattice Dirac spectra using the universal edge scaling laws, without having to solve the QCD sign problem.
Tabulated Neutron Star Equations of State Modelled within the Chiral Mean Field Model
Dexheimer, V.
2017-12-01
In this special issue article, I review some of the accomplishments of the chiral mean field (CMF) model, which contains nucleon, hyperon, and quark degrees of freedom, and its applications to proto-neutron and neutron stars. I also present a set of equation of state and particle population tables built using the CMF model subject to physical constraints necessary to reproduce different environments, such as those present in cold neutron stars, core-collapse supernova explosions, and different stages of compact star mergers.
Random matrix theory and higher genus integrability: the quantum chiral Potts model
International Nuclear Information System (INIS)
Angles d'Auriac, J.Ch.; Maillard, J.M.; Viallet, C.M.
2002-01-01
We perform a random matrix theory (RMT) analysis of the quantum four-state chiral Potts chain for different sizes of the chain up to size L 8. Our analysis gives clear evidence of a Gaussian orthogonal ensemble (GOE) statistics, suggesting the existence of a generalized time-reversal invariance. Furthermore, a change from the (generic) GOE distribution to a Poisson distribution occurs when the integrability conditions are met. The chiral Potts model is known to correspond to a (star-triangle) integrability associated with curves of genus higher than zero or one. Therefore, the RMT analysis can also be seen as a detector of 'higher genus integrability'. (author)
Directory of Open Access Journals (Sweden)
IVAN GUTMAN
1999-11-01
Full Text Available The Noyori model of chiral amplification in the alkylation of aldehydes by means of dialkylzinc, catalyzed by chiral aminoalcohols, is further elaborated. A direct, but approximate, relation is obtained between the enantiomeric excess of the catalyst added and the enantiomeric excess of the product.
Kac-Moody algebra is not hidden symmetry of chiral models
International Nuclear Information System (INIS)
Devchand, C.; Schiff, J.
1997-01-01
A detailed examination of the infinite dimensional loop algebra of hidden symmetry transformations of the Principal Chiral Model reveals it to have a structure differing from a standard centreless Kac-Moody algebra. A new infinite dimensional Abelian symmetry algebra is shown to preserve a symplectic form on the space of solutions. (author). 15 refs
Chiral symmetry restoration and pion properties in a q-deformed NJL model
International Nuclear Information System (INIS)
Timoteo, V.S.; Lima, C.L.
2006-01-01
We review the implementation of a q-deformed fermionic algebra in the Nambu-Jona-Lasinio model (NJL). The gap equations obtained from a deformed condensate as well as from the deformation of the NJL Hamiltonian are discussed. The effect of both temperature and deformation in the chiral symmetry restoration process as well as in the pion properties is studied. (author)
Energy Technology Data Exchange (ETDEWEB)
Sato, K.; Koide, Tomoi; Maruyama, Masahiro [Tohoku Univ., Faculty of Science, Sendai, Miyagi (Japan)
1999-08-01
There are various approaches to nonequilibrium system. We use the projection operator method investigated by F. Shibata and N. Hashitsume on the linear sigma model at finite temperature and density. We derive a differential equation of the time evolution for the order parameter and pion number density in chiral phase transition. (author)
International Nuclear Information System (INIS)
Toru, Kojo; Hidaka, Y.; Pisarski, R.; McLerran, L.
2010-01-01
We argue the properties of confining dense quark matter, 'quarkyonic' matter, from the viewpoint of both bulk properties and excitation modes. After a brief review of confining aspects, the chiral breaking/restoration will be discussed. We argue that the strong infrared correlations induce the chiral spiral, i.e., the spatial modulation of the chiral condensate which breaks the chiral symmetry locally but restore it globally. The effective dimensional reduction takes place, allowing us to analyzing the system as 2D model in which several exact results can be explicitly derived. We also discuss the excitation spectra, both mesonic and baryonic ones, on the chiral spiral. (author)
Chirality invariance and 'chiral' fields
International Nuclear Information System (INIS)
Ziino, G.
1978-01-01
The new field model derived in the present paper actually gives a definite answer to three fundamental questions concerning elementary-particle physics: 1) The phenomenological dualism between parity and chirality invariance: it would be only an apparent display of a general 'duality' principle underlying the intrinsic nature itself of (spin 1/2) fermions and expressed by the anticommutativity property between scalar and pseudoscalar charges. 2) The real physical meaning of V - A current structure: it would exclusively be connected to the one (just pointed out) of chiral fields themselves. 3) The unjustified apparent oddness shown by Nature in weak interactions, for the fact of picking out only one of the two (left- and right-handed) fermion 'chiral' projections: the key to such a 'mystery' would just be provided by the consequences of the dual and partial character of the two fermion-antifermion field bases. (Auth.)
Sun, Haitao
2016-05-16
We propose a new methodology for the first-principles description of the electronic properties relevant for charge transport in organic molecular crystals. This methodology, which is based on the combination of a non-empirical, optimally tuned range-separated hybrid functional with the polarizable continuum model, is applied to a series of eight representative molecular semiconductor crystals. We show that it provides ionization energies, electron affinities, and transport gaps in very good agreement with experimental values as well as with the results of many-body perturbation theory within the GW approximation at a fraction of the computational costs. Hence, this approach represents an easily applicable and computationally efficient tool to estimate the gas-to-crystal-phase shifts of the frontier-orbital quasiparticle energies in organic electronic materials.
Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits
International Nuclear Information System (INIS)
Jiang Weizhou; Li Baoan; Chen Liewen
2007-01-01
We study several structure properties of finite nuclei using relativistic mean-field Lagrangians constructed according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities. The models are consistent with current experimental constraints for the equations of state of symmetric matter at both normal and supranormal densities and of asymmetric matter at subsaturation densities. It is shown that these models can successfully describe the binding energies and charge radii of finite nuclei. Compared to calculations with usual relativistic mean-field models, these models give a reduced thickness of neutron skin in 208 Pb between 0.17 fm and 0.21 fm. The reduction of the predicted neutron skin thickness is found to be due to not only the softening of the symmetry energy but also the scaling property of ρ meson required by the partial restoration of chiral symmetry
Bahrami, M; Donadi, S; Ferialdi, L; Bassi, A; Curceanu, C; Di Domenico, A; Hiesmayr, B C
2013-01-01
Collapse models provide a theoretical framework for understanding how classical world emerges from quantum mechanics. Their dynamics preserves (practically) quantum linearity for microscopic systems, while it becomes strongly nonlinear when moving towards macroscopic scale. The conventional approach to test collapse models is to create spatial superpositions of mesoscopic systems and then examine the loss of interference, while environmental noises are engineered carefully. Here we investigate a different approach: We study systems that naturally oscillate-creating quantum superpositions-and thus represent a natural case-study for testing quantum linearity: neutrinos, neutral mesons, and chiral molecules. We will show how spontaneous collapses affect their oscillatory behavior, and will compare them with environmental decoherence effects. We will show that, contrary to what previously predicted, collapse models cannot be tested with neutrinos. The effect is stronger for neutral mesons, but still beyond experimental reach. Instead, chiral molecules can offer promising candidates for testing collapse models.
Dynamic polarizabilities for the low lying states of Ca+
International Nuclear Information System (INIS)
Tang, Yong-Bo; Shi, Ting-Yun; Qiao, Hao-Xue; Mitroy, J
2014-01-01
The dynamic polarizabilities of the 4s, 3d and 4p states of Ca + are calculated using a relativistic structure model. The wavelengths at which the Stark shifts between different pairs of transitions are zero are calculated. Experimental determination of the magic wavelengths could prove useful in developing better atomic structure models and in particular lead to improved values of the polarizabilities for the Ca + (3d) states
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Energy Technology Data Exchange (ETDEWEB)
Biernat, Elmer P. [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Pena, Maria Teresa [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Departamento de FÃsica, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Ribiero, Jose' Emilio F. [CeFEMA, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Stadler, Alfred [Departamento de FÃsica, Universidade de Ãvora, 7000-671 Ãvora, Portugal; Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.
Higgs-Yukawa model in chirally-invariant lattice field theory
Bulava, John; Jansen, Karl; Kallarackal, Jim; Knippschild, Bastian; Lin, C.-J.David; Nagai, Kei-Ichi; Nagy, Attila; Ogawa, Kenji
2013-01-01
Non-perturbative numerical lattice studies of the Higgs-Yukawa sector of the standard model with exact chiral symmetry are reviewed. In particular, we discuss bounds on the Higgs boson mass at the standard model top quark mass, and in the presence of heavy fermions. We present a comprehensive study of the phase structure of the theory at weak and very strong values of the Yukawa coupling as well as at non-zero temperature.
Weak ωNN coupling in the non-linear chiral model
International Nuclear Information System (INIS)
Shmatikov, M.
1988-01-01
In the non-linear chiral model with the soliton solution stabilized by the ω-meson field the weak ωNN coupling constants are calculated. Applying the vector dominance model for the isoscalar current the constant of the isoscalar P-odd ωNN interaction h ω (0) =0 is obtained while the constant of the isovector (of the Lagrangian of the ωNN interaction proves to be h ω (1) ≅ 1.0x10 -7
Higgs-Yukawa model in chirally-invariant lattice field theory
Energy Technology Data Exchange (ETDEWEB)
Bulava, John [CERN, Geneva (Switzerland). Physics Department; Gerhold, Philipp; Kallarackal, Jim; Nagy, Attila [Humboldt Univ. Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Knippschild, Bastian [National Taiwan Univ., Taipei (China). Dept. of Physics; Lin, C.J. David [National Chiao-Tung Univ., Hsinchu (China). Inst. of Physics; National Centre for Theoretical Sciences, Hsinchu (China). Div. of Physics; Nagai, Kei-Ichi [Nagoya Univ., Nagoya, Aichi (Japan). Kobayashi-Maskawa Institute; Ogawa, Kenji [Chung-Yuan Christian Univ., Chung-Li (China). Dept. of Physics
2012-10-15
Non-perturbative numerical lattice studies of the Higgs-Yukawa sector of the standard model with exact chiral symmetry are reviewed. In particular, we discuss bounds on the Higgs boson mass at the standard model top quark mass, and in the presence of heavy fermions. We present a comprehensive study of the phase structure of the theory at weak and very strong values of the Yukawa coupling as well as at non-zero temperature.
Higgs mass bounds from a chirally invariant lattice Higgs-Yukawa model with overlap fermions
Energy Technology Data Exchange (ETDEWEB)
Gerhold, Philipp; Kallarackal, Jim [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2008-10-15
We study the parameter dependence of the Higgs mass in a chirally invariant lattice Higgs-Yukawa model emulating the same Higgs-fermion coupling structure as in the Higgs sector of the electroweak Standard Model. Eventually, the aim is to establish upper and lower Higgs mass bounds. Here we present our preliminary results on the lower Higgs mass bound at several selected values for the cutoff and give a brief outlook towards the upper Higgs mass bound. (orig.)
Symplectic structures in the chirally gauged Wess-Zumino-Witten model
International Nuclear Information System (INIS)
Inamoto, T.
1992-01-01
The algebraic structure of the chirally gauged Wess-Zumino-Witten model is studied from the Hamiltonian point of view. The consistent chiral anomaly, which is reproduced at the tree level in this model, is related to the Schwinger term of the Gauss-law algebra through descent equations constructed with phase-space differential forms. The descent equations express the effects of the consistent anomaly upon the symplectic structure of the theory, and provide the Hamiltonian analogue of the Wess-Zumino consistency condition in the Weyl gauge. We also clarify the canonical structure of the ungauged Wess-Zumino-Witten model, and the algebra associated with the global Noether symmetry is derived
Parity nonconservation and nuclear polarizabilities
International Nuclear Information System (INIS)
Haxton, W.
1990-01-01
The hadronic weak interaction contributes to parity nonconserving observables in semileptonic interactions. Weak nuclear polarizabilities are frequently important in such interactions. Some of the interesting physics is illustrated by 18 F, a nucleus that provides an important constraint on the neutral weak hadronic current. One observable where the nuclear polarizability is expected to dominate is the nuclear anapole moment. The long-range pion contribution to this weak radiative correction is explored for both nucleons and nuclei. Similar polarizabilities that arise for time-reversal-odd hadronic interactions that conserve or violate parity are discussed in connection with atomic electric dipole moments. 20 refs., 4 figs
Measurement of the charged pion polarizability at COMPASS
International Nuclear Information System (INIS)
Nagel, Thiemo Christian Ingo
2012-01-01
The reaction π - +Z→π - +γ+Z in which a photon is produced by a beam pion scattering off a quasi-real photon of the Coulomb field of the target nucleus is identified experimentally by the tiny magnitude of the momentum transfer to the nucleus. This process gives access to the charged pion polarizabilities α π and β π whose experimental determination constitutes an important test of Chiral Perturbation Theory. In this work, the pion polarizability is obtained as α π =(1.9±0.7 stat. ±0.8 syst. ) x 10 -4 fm 3 from data taken with 190 GeV/c hadron beam provided by SPS to the COMPASS experiment at CERN in November 2009 and under the assumption of α π +β π =0.
Measurement of the charged pion polarizability at COMPASS
Energy Technology Data Exchange (ETDEWEB)
Nagel, Thiemo Christian Ingo
2012-09-26
The reaction {pi}{sup -}+Z{yields}{pi}{sup -}+{gamma}+Z in which a photon is produced by a beam pion scattering off a quasi-real photon of the Coulomb field of the target nucleus is identified experimentally by the tiny magnitude of the momentum transfer to the nucleus. This process gives access to the charged pion polarizabilities {alpha}{sub {pi}} and {beta}{sub {pi}} whose experimental determination constitutes an important test of Chiral Perturbation Theory. In this work, the pion polarizability is obtained as {alpha}{sub {pi}}=(1.9{+-}0.7{sub stat.}{+-}0.8{sub syst.}) x 10{sup -4} fm{sup 3} from data taken with 190 GeV/c hadron beam provided by SPS to the COMPASS experiment at CERN in November 2009 and under the assumption of {alpha}{sub {pi}}+{beta}{sub {pi}}=0.
Chiral Light Design and Detection Inspired by Optical Antenna Theory.
Poulikakos, Lisa V; Thureja, Prachi; Stollmann, Alexia; De Leo, Eva; Norris, David J
2018-03-23
Chiral metallic nanostructures can generate evanescent fields which are more highly twisted than circularly polarized light. However, it remains unclear how best to exploit this phenomenon, hindering the optimal utilization of chiral electromagnetic fields. Here, inspired by optical antenna theory, we address this challenge by introducing chiral antenna parameters: the chirality flux efficiency and the chiral antenna aperture. These quantities, which are based on chirality conservation, quantify the generation and dissipation of chiral light. We then present a label-free experimental technique, chirality flux spectroscopy, which measures the chirality flux efficiency, providing valuable information on chiral near fields in the far field. This principle is verified theoretically and experimentally with two-dimensionally chiral coupled nanorod antennas, for which we show that chiral near and far fields are linearly dependent on the magnetoelectric polarizability. This elementary system confirms our concept to quantify chiral electromagnetic fields and paves the way toward broadly tunable chiral optical applications including ultrasensitive detection of molecular chirality or optical information storage and transfer.
Neutral meson properties under an external magnetic field in nonlocal chiral quark models
Gómez Dumm, D.; Izzo Villafañe, M. F.; Scoccola, N. N.
2018-02-01
We study the behavior of neutral meson properties in the presence of a static uniform external magnetic field in the context of nonlocal chiral quark models. The formalism is worked out introducing Ritus transforms of Dirac fields, which allow to obtain closed analytical expressions for π0 and σ meson masses and for the π0 decay constant. Numerical results for these observables are quoted for various parametrizations. In particular, the behavior of the π0 meson mass with the magnetic field is found to be in good agreement with lattice QCD results. It is also seen that the Goldberger-Treiman and Gell-Mann-Oakes-Renner chiral relations remain valid within these models in the presence of the external magnetic field.
Chiral family classification of fermionic Z2xZ2 heterotic orbifold models
International Nuclear Information System (INIS)
Faraggi, Alon E.; Kounnas, Costas; Rizos, John
2007-01-01
Free fermionic construction of four-dimensional string vacua, are related to the Z 2 xZ 2 orbifolds at special points in the moduli space, and yielded the most realistic three family string models to date. Using free fermionic construction techniques we are able to classify more than 10 10 string vacua by the net family and anti-family number. Using a Monte Carlo technique we find a bell shaped distribution that peaks at vanishing net number of chiral families. We also observe that ∼15% of the models have three net chiral families. In addition to mirror symmetry we find that the distribution exhibits a symmetry under the exchange of (spinor plus anti-spinor) representations with vectorial representations
International Nuclear Information System (INIS)
Alkofer, R.; Reinhardt, H.
1995-01-01
This book is an introduction to chiral quark dynamics. In the first chapter the reduction of low-energy QCD to QFD with the derivation of effective low-energy quark interactions and invariance properties is described. Then the effective meson theory is introduced. In this connection the functional integral bosonization of the quark-antiquark interaction, the small amplitude expansion of the action, the dynamical breaking of chiral symmetry, the Bethe-Salpeter equation for pseudoscalar mesons, the gauged linear σ model, the Skyrme model, and the chiral anomaly are considered. Then baryons are described as chiral solitons. Finally baryons are considered as bound states of diquarks and quarks. (HSI)
E M form factors of the nucleon in a chiral model with momentum projection
International Nuclear Information System (INIS)
Drago, A.; Tambini, U.; Fiolhais, M.
1997-01-01
The chiral chromo dielectric model with a quadratic potential for the confining field is used to compute electromagnetic form factors of the nucleon. A variational approach based on the hedgehog Ansatz and on angular momentum-isospin and linear momentum projection formalism is applied to describe the nucleon. The form factors are computed using momentum eigenstates, therefore taking into account recoil effects. With the exception of the magnetic form factor of the proton, the others are well reproduced. (author)
Study of baryon octet charge form factors in perturbative chiral quark model
International Nuclear Information System (INIS)
Liu, X.Y.; Khosonthongkee, K.; Limphirat, A.; Yan, Y.
2014-01-01
The charge form factors of baryon octet are studied in the perturbative chiral quark model (PCQM). The relativistic quark wave function is extracted by fitting the theoretical results of the nucleon charge form factors to the experimental data and the predetermined quark wave function is applied to study the charge form factors of other octet baryons. The PCQM results are found, based on the predetermined quark wave function, in good agreement with the experimental data. (author)
Chiral symmetry restoration and quark deconfinement beyond mean field in a magnetized PNJL model
Mao, Shijun
2018-01-01
We study chiral symmetry restoration and quark deconfinement beyond the mean field approximation in a magnetized PNJL model. The feedback from mesons to quarks modifies the quark coupling constant and Polyakov potential. As a result, the separate critical temperatures for the two phase transitions at the mean field level coincide, and the magnetic catalysis becomes an inverse magnetic catalysis when the meson contribution is included.
Pion polarizabilities measurement at COMPASS
Guskov, Alexey
2008-01-01
The electromagnetic structure of pions is probed in $\\pi^{−}+(A,Z) \\rightarrow\\pi^{−}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric ($\\bar{\\alpha_{\\pi}}$) and the magnetic ($\\bar{\\beta_{\\pi}}$) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with a $\\pi^{-}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction.
Molecular Properties through Polarizable Embedding
DEFF Research Database (Denmark)
Olsen, Jógvan Magnus Haugaard; Kongsted, Jacob
2011-01-01
We review the theory related to the calculation of electric and magnetic molecular properties through polarizable embedding. In particular, we derive the expressions for the response functions up to the level of cubic response within the density functional theory-based polarizable embedding (PE......-DFT) formalism. In addition, we discuss some illustrative applications related to the calculation of nuclear magnetic resonance parameters, nonlinear optical properties, and electronic excited states in solution....
Chiral effective potential in N = {1/2} non-commutative Wess-Zumino model
International Nuclear Information System (INIS)
Banin, A.T.; Buchbinder, I.L.; Pletnev, N.G.
2004-01-01
We study a structure of holomorphic quantum contributions to the effective action for N = {1/2} noncommutative Wess-Zumino model. Using the symbol operator techniques we present the one-loop chiral effective potential in a form of integral over proper time of the appropriate heat kernel. We prove that this kernel can be exactly found. As a result we obtain the exact integral representation of the one-loop effective potential. Also we study the expansion of the effective potential in a series in powers of the chiral superfield φ and derivative D 2 φ and construct a procedure for systematic calculation of the coefficients in the series. We show that all terms in the series without derivatives can be summed up in an explicit form. (author)
The half-skyrmion phase in a chiral-quark model
International Nuclear Information System (INIS)
Mantovani Sarti, Valentina; Vento, Vicente
2014-01-01
The Chiral Dilaton Model, where baryons arise as non-topological solitons built from the interaction of quarks and chiral mesons, shows in the high density low temperature regime a two phase scenario in the nuclear matter phase diagram. Dense soliton matter described by the Wigner–Seitz approximation generates a periodic potential in terms of the sigma and pion fields that leads to the formation of a band structure. The analysis up to three times nuclear matter density shows that soliton matter undergoes two separate phase transitions: a delocalization of the baryon number density leading to B=1/2 structures, as in skyrmion matter, at moderate densities, and quark deconfinement at larger densities. This description fits well into the so-called quarkyonic phase where, before deconfinement, nuclear matter should undergo structural changes involving the restoration of fundamental symmetries of QCD
Finite-size effects on the chiral phase diagram of four-fermion models in four dimensions
International Nuclear Information System (INIS)
Abreu, L.M.; Malbouisson, A.P.C.; Malbouisson, J.M.C.; Santana, A.E.
2009-01-01
We study the size dependence of the dynamical symmetry breaking in the four-dimensional Nambu-Jona-Lasinio model. We show that the presence of boundaries reduces the chiral breaking region, and this effect is strengthened for a larger number of compactified dimensions. A critical value for the length of the compactified dimensions exists, below which the dynamical symmetry breaking is not possible. Considering finite temperature and chemical potential, the chiral phase structure for the system with compactified dimensions is obtained. A gradual decreasing of the chiral breaking region with increasing of chemical potential is found. Also, at fixed chemical potential, the decreasing of the size of the system changes the order of the chiral phase transition.
Three-flavor chiral effective model with four baryonic multiplets within the mirror assignment
Olbrich, Lisa; Zétényi, Miklós; Giacosa, Francesco; Rischke, Dirk H.
2016-02-01
In the case of three quark flavors, (pseudo)scalar diquarks transform as antiquarks under chiral transformations. We construct four spin-1 /2 baryonic multiplets from left- and right-handed quarks as well as left- and right-handed diquarks. The fact that two of these multiplets transform in a "mirror" way allows for chirally invariant mass terms. We then embed these baryonic multiplets into the Lagrangian of the so-called extended linear sigma model, which features (pseudo)scalar and (axial-)vector mesons, as well as glueballs. Reducing the Lagrangian to the two-flavor case, we obtain four doublets of nucleonic states. These mix to produce four experimentally observed states with definite parity: the positive-parity nucleon N (939 ) and Roper resonance N (1440 ), as well as the negative-parity resonances N (1535 ) and N (1650 ). We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of the aforementioned states. Studying the limit of vanishing quark condensate, we conclude that N (939 ) and N (1535 ), as well as N (1440 ) and N (1650 ), form pairs of chiral partners.
Thermal evolution of massive strange compact objects in a SU(3) chiral Quark Meson model
Energy Technology Data Exchange (ETDEWEB)
Zacchi, Andreas
2017-07-04
In this work, thermodynamical properties of strongly interacting matter within a chiral SU(2)- and SU(3) chiral Quark Meson model have been analysed. Both effective models describe the development of the quark masses in media via the corresponding fields through chiral symmetry, which is expected to be restored at high temperatures and/or high densities, and spontaneously broken at low temperatures and/or densities. Spontaneous and explicit chiral symmetry breaking patterns give rise to massive Goldstone bosons, which are associated with the pions. Their chiral partners, the sigma mesons, are expected to be degenerate in mass, which was what we studied and observed at large temperatures/densities. The derivation and computation of thermodynamical quantities and properties in both cases can for instance be used to study relativistic and hydrodynamic Heavy Ion Collisions and the early universe for vanishing baryon number (SU(2)-case). They are also interesting for extreme astrophysical scenarios, such as Supernova explosions and the thermal evolution of their remnants, which has been among the topics of this thesis (SU(3)-case). Inclusion of the zero point energy in the SU(2) model has been carried out separately for the meson sector and for the quark sector as well as in a combined approach, where we learned, that the quark sector is quite dominant and that the vacuum fluctuations of the meson fields have little influence on the order parameter, but affect the relativistic degrees of freedom. In the SU(3) case, the inclusion of the zero point energy in the quark sector is much more computationally complex, but, as in the SU(2) case, is also not negliable, as its influence also changes the thermodynamical quantities at finite temperatures in a nontrivial manner. Here some features of the Supernova equation of state have been studied, which look promising for further investigations for Supernovae (proto neutron stars) and also for compact star mergers. The final
Zheng, Zilong
2016-06-24
Density functional theory (DFT) approaches based on range-separated hybrid functionals are currently methods of choice for the description of the charge-transfer (CT) states in organic donor/acceptor solar cells. However, these calculations are usually performed on small-size donor/acceptor complexes and as result do not account for electronic polarization effects. Here, using a pentacene/C60 complex as a model system, we discuss the ability of long-range corrected (LCR) hybrid functionals in combination with the polarizable continuum model (PCM) to determine the impact of the solid-state environment on the CT states. The CT energies are found to be insensitive to the interactions with the dielectric medium when a conventional time-dependent DFT/PCM (TDDFT/PCM) approach is used. However, a decrease in the energy of the CT state in the framework of LRC functionals can be obtained by using a smaller range-separated parameter when going from an isolated donor/acceptor complex to the solid-state case.
Chiral symmetry and chiral-symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Peskin, M.E.
1982-12-01
These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)
Pion polarizabilities measurement at COMPASS
Guskov, Alexey
2008-01-01
The electromagnetic structure of pions is probed in $\\pi^{−} + (A,Z)\\rightarrow\\pi^{−} + (A,Z) +\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\bar{\\alpha_{\\pi}})$ and the magnetic $(\\bar{\\beta_{\\pi}})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with $a \\pi^{−}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction. The preliminary result for pion polarizabilities under the assumption of $\\bar{\\alpha_{\\pi}} + \\bar{\\beta_{\\pi}} =$ 0 is $\\ba...
The Role of Stochastic Models in Interpreting the Origins of Biological Chirality
Directory of Open Access Journals (Sweden)
Gábor Lente
2010-04-01
Full Text Available This review summarizes recent stochastic modeling efforts in the theoretical research aimed at interpreting the origins of biological chirality. Stochastic kinetic models, especially those based on the continuous time discrete state approach, have great potential in modeling absolute asymmetric reactions, experimental examples of which have been reported in the past decade. An overview of the relevant mathematical background is given and several examples are presented to show how the significant numerical problems characteristic of the use of stochastic models can be overcome by non-trivial, but elementary algebra. In these stochastic models, a particulate view of matter is used rather than the concentration-based view of traditional chemical kinetics using continuous functions to describe the properties system. This has the advantage of giving adequate description of single-molecule events, which were probably important in the origin of biological chirality. The presented models can interpret and predict the random distribution of enantiomeric excess among repetitive experiments, which is the most striking feature of absolute asymmetric reactions. It is argued that the use of the stochastic kinetic approach should be much more widespread in the relevant literature.
SIMP model at NNLO in chiral perturbation theory
DEFF Research Database (Denmark)
Hansen, Martin Rasmus Lundquist; Langaeble, K.; Sannino, F.
2015-01-01
We investigate the phenomenological viability of a recently proposed class of composite dark matter models where the relic density is determined by 3 to 2 number-changing processes in the dark sector. Here the pions of the strongly interacting field theory constitute the dark matter particles...
K- nuclear potentials from in-medium chirally motivated models
Czech Academy of Sciences Publication Activity Database
Cieplý, Aleš; Friedman, E.; Gal, A.; Gazda, Daniel; Mareš, Jiří
2011-01-01
Roč. 84, č. 4 (2011), 045206/1-045206/11 ISSN 0556-2813 R&D Projects: GA ČR GA202/09/1441 Institutional research plan: CEZ:AV0Z10480505 Keywords : p-wave interactions * coupled-channel model Subject RIV: BE - Theoretical Physics Impact factor: 3.308, year: 2011
Chiral mixed phase in disordered 3d Heisenberg models
Bekhechi, S.; Southern, B. W.
2004-01-01
Using Monte Carlo simulations, we compute the spin stiffness of a site-random 3d Heisenberg model with competing ferromagnetic and antiferromagnetic interactions. Our results for the pure limit yield values of the the critical temperature and the critical exponent $\
Baryon number fluctuations in chiral effective models and their phenomenological implications
Almási, Gábor András; Friman, Bengt; Redlich, Krzysztof
2017-07-01
We study the critical properties of net-baryon-number fluctuations at the chiral restoration transition in a medium at finite temperature and net baryon density. The chiral dynamics of quantum chromodynamics (QCD) is modeled by the Polyakov-loop extended quark-meson Lagrangian that includes the coupling of quarks to vector meson and temporal gauge fields. The functional renormalization group is employed to properly account for the O (4 ) criticality at the phase boundary. We focus on the properties and systematics of ratios of the net-baryon-number cumulants χBn, for 1 ≤n ≤6 , near the phase boundary. The results are presented in the context of the recent experimental data of the STAR Collaboration on fluctuations of the net proton number in heavy-ion collisions at RHIC. We show that the model results for the energy dependence of the cumulant ratios are in good overall agreement with the data, with one exception. At center-of-mass energies below 19.6 GeV, we find that the measured fourth-order cumulant deviates considerably from the model results, which incorporate the expected O (4 ) and Z (2 ) criticality. We assess the influence of model assumptions and in particular of repulsive vector-interactions, which are used to modify the location of the critical end point in the model, on the cumulants ratios. Finally, we discuss a possibility to test to what extent the fluctuations are affected by nonequilibrium dynamics by comparing certain ratios of cumulants.
Gravitational polarizability of black holes
International Nuclear Information System (INIS)
Damour, Thibault; Lecian, Orchidea Maria
2009-01-01
The gravitational polarizability properties of black holes are compared and contrasted with their electromagnetic polarizability properties. The 'shape' or 'height' multipolar Love numbers h l of a black hole are defined and computed. They are then compared to their electromagnetic analogs h l EM . The Love numbers h l give the height of the lth multipolar 'tidal bulge' raised on the horizon of a black hole by faraway masses. We also discuss the shape of the tidal bulge raised by a test-mass m, in the limit where m gets very close to the horizon.
Anomaly cancellation in a class of chiral flavor gauge models
International Nuclear Information System (INIS)
Pisano, F.; Tran Anh Tuan.
1993-07-01
We show typical features on anomaly cancellation in the 3 - n - 1 extensions of the 3 - 2 - 1 standard model, with n = 3,4 which has been proposed recently. We point out that in this class of theories a natural explanation for the fundamental question of fermion family replication arises from the theoretical requirements of renormalizability and self-consistency, which constrains the number of the QFD families to the QCD color degrees of freedom. (author). 10 refs
$Z_b(10650)$ and $Z_b(10610)$ states in a chiral quark model
Li, M. T.; Wang, W. L.; Dong, Y. B.; Zhang, Z. Y.
2012-01-01
We perform a systematic study of $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ systems by using effective interaction in our chiral quark model. Our results show that the interactions of $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ states are attractive, which consequently result in $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ bound states. The recent observed exotic-like hadrons of $Z_b(10610)$ and $Z_b(10650)$ are, therefore in our approach,...
The electroproduction of the /Δ(1232) in the chiral quark-soliton model
Silva, A.; Urbano, D.; Watabe, T.; Fiolhais, M.; Goeke, K.
2000-08-01
We calculate the ratios E2 / M1 and C2 / M1 for the electroproduction of the Δ(1232) in the region of photon virtuality 0<- q2<1 GeV 2 . The magnetic dipole amplitude M1 is also presented. The theory used is the chiral quark-soliton model, which is based on the instanton vacuum of the QCD. The calculations are performed in flavours SU(2) and SU(3) taking rotational ( 1/ Nc ) corrections into account. The results for the ratios agree qualitatively with the available data, although the magnitude of both ratios seems to underestimate the latest experimental results.
The electroproduction of the Δ(1232) in the chiral quark-soliton model
International Nuclear Information System (INIS)
Silva, A.; Urbano, D.; Watabe, T.; Fiolhais, M.; Goeke, K.
2000-01-01
We calculate the ratios E2/M1 and C2/M1 for the electroproduction of the Δ(1232) in the region of photon virtuality 0 2 2 . The magnetic dipole amplitude M1 is also presented. The theory used is the chiral quark-soliton model, which is based on the instanton vacuum of the QCD. The calculations are performed in flavours SU(2) and SU(3) taking rotational (1/N c ) corrections into account. The results for the ratios agree qualitatively with the available data, although the magnitude of both ratios seems to underestimate the latest experimental results
The electroproduction of the {delta}(1232) in the chiral quark-soliton model
Energy Technology Data Exchange (ETDEWEB)
Silva, A. E-mail: ajsilva@tp2.ruhr-uni-bochum.de; Urbano, D. E-mail: dianau@tp2.ruhr-uni-bochum.de; Watabe, T. E-mail: watabe@rcnp.osaka-u.ac.jp; Fiolhais, M. E-mail: tmanuel@teor.fis.uc.pt; Goeke, K. E-mail: klaus.goeke@tp2.ruhr-uni-bochum.de
2000-08-14
We calculate the ratios E2/M1 and C2/M1 for the electroproduction of the {delta}(1232) in the region of photon virtuality 0<-q{sup 2}<1 GeV {sup 2} . The magnetic dipole amplitude M1 is also presented. The theory used is the chiral quark-soliton model, which is based on the instanton vacuum of the QCD. The calculations are performed in flavours SU(2) and SU(3) taking rotational (1/N{sub c}) corrections into account. The results for the ratios agree qualitatively with the available data, although the magnitude of both ratios seems to underestimate the latest experimental results.
Hybrid stars with color superconductivity within a nonlocal chiral quark model
International Nuclear Information System (INIS)
Grigorian, H.; Blaschke, D.; Aguilera, D.N.
2004-01-01
The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state. We present a fit formula for the Bag pressure, which is density dependent in the case when the quark matter is color superconducting. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and demonstrate the effects of diquark condensation on the stability of hybrid stars for different form factors of the quark interaction
Directory of Open Access Journals (Sweden)
Yifeng Chai
2012-01-01
Full Text Available Chiral separations of five β-adrenergic antagonists (propranolol, esmolol, atenolol, metoprolol, and bisoprolol were studied by capillary electrophoresis using six cyclodextrins (CDs as the chiral selectors. Carboxymethylated-β-cyclodextrin (CM-β-CD exhibited a higher enantioselectivity power compared to the other tested CDs. The influences of the concentration of CM-β-CD, buffer pH, buffer concentration, temperature, and applied voltage were investigated. The good chiral separation of five β-adrenergic antagonists was achieved using 50 mM Tris buffer at pH 4.0 containing 8 mM CM-β-CD with an applied voltage of 24 kV at 20 °C. In order to understand possible chiral recognition mechanisms of these racemates with CM-β-CD, host-guest binding procedures of CM-β-CD and these racemates were studied using the molecular docking software Autodock. The binding free energy was calculated using the Autodock semi-empirical binding free energy function. The results showed that the phenyl or naphthyl ring inserted in the hydrophobic cavity of CM-β-CD and the side chain was found to point out of the cyclodextrin rim. Hydrogen bonding between CM-β-CD and these racemates played an important role in the process of enantionseparation and a model of the hydrogen bonding interaction positions was constructed. The difference in hydrogen bonding formed with the –OH next to the chiral center of the analytes may help to increase chiral discrimination and gave rise to a bigger separation factor. In addition, the longer side chain in the hydrophobic phenyl ring of the enantiomer was not beneficial for enantioseparation and the chiral selectivity factor was found to correspond to the difference in binding free energy.
Gómez Nicola, A.; Rivers, R. J.; Steer, D. A.
2000-03-01
We show that in certain limits the (1+1)-dimensional massive Thirring model at finite temperature T is equivalent to a one-dimensional Coulomb gas of charged particles at the same T. This equivalence is then used to explore the phase structure of the massive Thirring model. For strong coupling and T ≫ m (the fermion mass), the system is shown to behave as a free gas of "molecules" (charge pairs in the Coulomb gas terminology) made of pairs of chiral condensates. This binding of chiral condensates is responsible for the restoration of chiral symmetry as T→∞. In addition, when a fermion chemical potential μ≠0 is included, the analogy with a Coulomb gas still holds with μ playing the rôle of a purely imaginary external electric field. For small T and μ we find a typical massive Fermi gas behaviour for the fermion density, whereas for large μ it shows chiral restoration by means of a vanishing effective fermion mass. Some similarities with the chiral properties of low-energy QCD at finite T and baryon chemical potential are discussed.
Energy Technology Data Exchange (ETDEWEB)
McCloy, John S.; Riley, Brian J.; Johnson, Bradley R.; Schweiger, Michael J.; Qiao, Hong (Amy); Carlie, Nathan
2010-06-01
Four compositions of high density (~8 g/cm3) heavy metal oxide glasses composed of PbO, Bi2O3, and Ga2O3 were produced and refractivity parameters (refractive index and density) were computed and measured. Optical basicity was computed using three different models – average electronegativity, ionic-covalent parameter, and energy gap – and the basicity results were used to compute oxygen polarizability and subsequently refractive index. Refractive indices were measured in the visible and infrared at 0.633 μm, 1.55 μm, 3.39 μm, 5.35 μm, 9.29 μm, and 10.59 μm using a unique prism coupler setup, and data were fitted to the Sellmeier expression to obtain an equation of the dispersion of refractive index with wavelength. Using this dispersion relation, single oscillator energy, dispersion energy, and lattice energy were determined. Oscillator parameters were also calculated for the various glasses from their oxide values as an additional means of predicting index. Calculated dispersion parameters from oxides underestimate the index by 3 to 4%. Predicted glass index from optical basicity, based on component oxide energy gaps, underpredicts the index at 0.633 μm by only 2%, while other basicity scales are less accurate. The predicted energy gap of the glasses based on this optical basicity overpredicts the Tauc optical gap as determined by transmission measurements by 6 to 10%. These results show that for this system, density, refractive index in the visible, and energy gap can be reasonably predicted using only composition, optical basicity values for the constituent oxides, and partial molar volume coefficients. Calculations such as these are useful for a priori prediction of optical properties of glasses.
Blanco, Celia; Ribó, Josep M; Hochberg, David
2015-02-01
We derive the class of population balance equations (PBE), recently applied to model the Viedma deracemization experiment, from an underlying microreversible kinetic reaction scheme. The continuum limit establishing the relationship between the micro- and macroscopic processes and the associated particle fluxes erases the microreversible nature of the molecular interactions in the population growth rate functions and limits the scope of such PBE models to strict kinetic control. The irreversible binary agglomeration processes modeled in those PBEs contribute an additional source of kinetic control. These limitations are crucial regarding the question of the origin of biological homochirality, where the interest in any model lies precisely in its ability for absolute asymmetric synthesis and the amplification of the tiny inherent statistical chiral fluctuations about the ideal racemic composition up to observable enantiometric excess levels.
Chiral recognition in separation science: an overview.
Scriba, Gerhard K E
2013-01-01
Chiral recognition phenomena play an important role in nature as well as analytical separation sciences. In separation sciences such as chromatography and capillary electrophoresis, enantiospecific interactions between the enantiomers of an analyte and the chiral selector are required in order to observe enantioseparations. Due to the large structural variety of chiral selectors applied, different mechanisms and structural features contribute to the chiral recognition process. This chapter briefly illustrates the current models of the enantiospecific recognition on the structural basics of various chiral selectors.
The polarizable embedding coupled cluster method
DEFF Research Database (Denmark)
Sneskov, Kristian; Schwabe, Tobias; Kongsted, Jacob
2011-01-01
We formulate a new combined quantum mechanics/molecular mechanics (QM/MM) method based on a self-consistent polarizable embedding (PE) scheme. For the description of the QM region, we apply the popular coupled cluster (CC) method detailing the inclusion of electrostatic and polarization effects......-called PE-CCSDR(3) model. Finally, we utilize the presented method in the description of a full protein by investigating the shift of the intense electronic excitation energy of the photoactive yellow protein due to the surrounding amino acids....
Fukuda, Ryoichi; Ehara, Masahiro; Cammi, Roberto
2015-05-12
Novel molecular photochemistry can be developed by combining high pressure and laser irradiation. For studying such high-pressure effects on the confined electronic ground and excited states, we extend the PCM (polarizable continuum model) SAC (symmetry-adapted cluster) and SAC-CI (SAC-configuration interaction) methods to the PCM-XP (extreme pressure) framework. By using the PCM-XP SAC/SAC-CI method, molecular systems in various electronic states can be confined by polarizable media in a smooth and flexible way. The PCM-XP SAC/SAC-CI method is applied to a furan (C4H4O) molecule in cyclohexane at high pressure (1-60 GPa). The relationship between the calculated free-energy and cavity volume can be approximately represented with the Murnaghan equation of state. The excitation energies of furan in cyclohexane show blueshifts with increasing pressure, and the extents of the blueshifts significantly depend on the character of the excitations. Particularly large confinement effects are found in the Rydberg states. The energy ordering of the lowest Rydberg and valence states alters under high-pressure. The pressure effects on the electronic structure may be classified into two contributions: a confinement of the molecular orbital and a suppression of the mixing between the valence and Rydberg configurations. The valence or Rydberg character in an excited state is, therefore, enhanced under high pressure.
Applications of chiral symmetry
International Nuclear Information System (INIS)
Pisarski, R.D.
1995-03-01
The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T χ implies that the ρ and a 1 vector mesons are degenerate in mass. In a gauged linear sigma model the ρ mass increases with temperature, m ρ (T χ ) > m ρ (0). The author conjectures that at T χ the thermal ρ - a 1 , peak is relatively high, at about ∼1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The ω meson also increases in mass, nearly degenerate with the ρ, but its width grows dramatically with temperature, increasing to at least ∼100 MeV by T χ . The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from open-quotes quenchedclose quotes heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates
Chiral forces and molecular dissymmetry
International Nuclear Information System (INIS)
Mohan, R.
1992-01-01
Chiral molecules leading to helical macromolecules seem to preserve information and extend it better. In the biological world RNA is the very paradigm for self-replication, elongation and autocatalytic editing. The nucleic acid itself is not chiral. It acquires its chirality by association with D-sugars. Although the chiral information or selectivity put in by the unit monomer is no longer of much interest to the biologists - they tend to leave it to the Darwinian selection principle to take care of it as illustrated by Frank's model - it is vital to understand the origin of chirality. There are three different approaches for the chiral origin of life: (1) Phenomenological, (2) Electromagnetic molecular and Coriolis forces and (3) Atomic or nuclear force, the neutral weak current. The phenomenological approach involves spontaneous symmetry breaking fluctuations in far for equilibrium systems or nucleation and crystallization. Chance plays a major role in the chiral molecule selected
The Higgs boson resonance width from a chiral Higgs-Yukawa model on the lattice
International Nuclear Information System (INIS)
Gerhold, Philipp; Kallarackal, Jim; Humboldt-Universitaet, Berlin; Jansen, Karl
2011-11-01
The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for quarks, leptons and the weak gauge bosons. We use a 4-dimensional Euclidean lattice formulation of the Higgs-Yukawa sector of the electroweak model to compute physical quantities in the path integral approach which is evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. The chiral symmetry of the model is incorporated by using the Neuberger overlap Dirac operator. The here considered Higgs-Yukawa model does not involve the weak gauge bosons and furthermore, only a degenerate doublet of top- and bottom quarks are incorporated. The goal of this work is to study the resonance properties of the Higgs boson and its sensitivity to the strength of the quartic self coupling. (orig.)
Masses of the light hadrons in the chiral and cloudy bag models
International Nuclear Information System (INIS)
Saito, Koichi.
1983-10-01
The masses of the light hadrons except for the pion are calculated in the stable chiral and cloudy bag models with the massless or massive u, d quark and pion. Two difficulties in these models, i.e. the lack of stability and the divergence of the quark self-energy, are removed by taking account of a simple non-local quark-pion interaction. The effects of the finite size of the qq-bar pion and the behavior of the quark self-energy are discussed in detail. In our calculation the bag self-energy due to the pion has an important role in the origin of the N-Δ and the Σ-Λ mass differences. The baryon octet and decuplet masses are well reproduced by the present model. (author)
Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals
Directory of Open Access Journals (Sweden)
Yogesh K. Murugesan
2010-12-01
Full Text Available Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications.
Sengupta, Bidisha; Mukherjee, Chirantan Sen; Chakraborty, Sandipan; Muhammad, Maria Jones; Gladney, William; Armstrong, George
2017-12-01
Aniline, heterocyclic aromatic amines, and arylamines are known carcinogens. Recently aniline mustard has come into prominence as a novel anticancer agent. In this project, microwave irradiation has been used to synthesize an optically active alkylated aniline namely 2,6-dimethyl-4-(1-(p-tolyl)ethyl)aniline (abbreviated DMPA). The presence of quartet and doublet peaks in NMR and a single chromatogram in HPLC verified that the final product DMPA, prepared from the synthesis reactions, had no major impurities. By using a Lux chiral column in HPLC, two peaks have been detected in the chromatogram, which correspond to two enantiomers of the chiral aniline derivative. Fluorescence spectroscopic measurements on DMPA indicated conspicuous dependence of its emission behavior on the polarity (in terms of the empirical polarity parameter ET(30)) of the homogeneous solvents used, a property important for an optical sensor. The nature of the emission profiles, along with the relevant parameter namely wavelength at emission maximum (λemmax) is used to infer the distribution, binding and microenvironment of the DMPA molecules in human serum albumin protein (HSA). DMPA is weakly fluorescent in aqueous buffer medium, with a dramatic enhancement in the fluorescence emission in the presence of HSA. Molecular modeling studies have been carried out on the two enantiomers (R and S) of DMPA with HSA. The implications of these findings are examined in relation to the potentialities of DMPA as a novel fluorescence sensor for biological systems.
DEFF Research Database (Denmark)
Svendsen, Casper Steinmann; Blædel, Kristoffer L.; Christensen, Anders Steen
2013-01-01
An interface between semi-empirical methods and the polarized continuum model (PCM) of solvation successfully implemented into GAMESS following the approach by Chudinov et al (Chem. Phys. 1992, 160, 41). The interface includes energy gradients and is parallelized. For large molecules...
DEFF Research Database (Denmark)
Svendsen, Casper Steinmann; Blædel, Kristoffer; Christensen, Anders S
2013-01-01
An interface between semi-empirical methods and the polarized continuum model (PCM) of solvation successfully implemented into GAMESS following the approach by Chudinov et al (Chem. Phys. 1992, 160, 41). The interface includes energy gradients and is parallelized. For large molecules such as ubiq......An interface between semi-empirical methods and the polarized continuum model (PCM) of solvation successfully implemented into GAMESS following the approach by Chudinov et al (Chem. Phys. 1992, 160, 41). The interface includes energy gradients and is parallelized. For large molecules...... such as ubiquitin a reasonable speedup (up to a factor of six) is observed for up to 16 cores. The SCF convergence is greatly improved by PCM for proteins compared to the gas phase....
DEFF Research Database (Denmark)
Reinholdt, Peter; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard
2017-01-01
and diffuse basis sets that are otherwise questionable-due to electron spill-out effects-in standard embedding models. Based on our analysis, we find the PDE model to be robust and much more systematic than less sophisticated focused embedding models, and thus outline the PDE model as a very efficient...
Inoue, Yoshihisa
2004-01-01
Direct Asymmetric Photochemistry with Circularly Polarized Light, H. RauCoherent Laser Control of the Handedness of Chiral Molecules, P. Brumer and M. ShapiroMagnetochiral Anisotropy in Asymmetric Photochemistry, G.L.J.A.RikkenEnantiodifferentiating Photosensitized Reactions, Y. InoueDiastereodifferentiating Photoreactions, N. Hoffmann and J.-P. PeteChirality in Photochromism, Y. Yokoyama and M. SaitoChiral Photochemistry with Transition Metal Complexes, S. Sakaki and T. HamadaTemplate-Induced Enantioselective Photochemical Reactions in S
Chiral spin liquids at finite temperature in a three-dimensional Kitaev model
Kato, Yasuyuki; Kamiya, Yoshitomo; Nasu, Joji; Motome, Yukitoshi
2017-11-01
Chiral spin liquids (CSLs) in three dimensions and thermal phase transitions to paramagnet are studied by unbiased Monte Carlo simulations. For an extension of the Kitaev model to a three-dimensional tricoordinate network dubbed the hypernonagon lattice, we derive low-energy effective models in two different anisotropic limits. We show that the effective interactions between the emergent Z2 degrees of freedom called fluxes are unfrustrated in one limit, while highly frustrated in the other. In both cases, we find a first-order phase transition to the CSL, where both time-reversal and parity symmetries are spontaneously broken. In the frustrated case, however, the CSL state is highly exotic—the flux configuration is subextensively degenerate while showing a directional order with broken C3 rotational symmetry. Our results provide two contrasting archetypes of CSLs in three dimensions, both of which allow approximation-free simulation for investigating the thermodynamics.
Kramers-Wannier duality and worldline representation for the SU(2) principal chiral model
Gattringer, Christof; Göschl, Daniel; Marchis, Carlotta
2018-03-01
In this letter we explore different representations of the SU(2) principal chiral model on the lattice. We couple chemical potentials to two of the conserved charges to induce finite density. This leads to a complex action such that the conventional field representation cannot be used for a Monte Carlo simulation. Using the recently developed Abelian color flux approach we derive a new worldline representation where the partition sum has only real and positive weights, such that a Monte Carlo simulation is possible. In a second step we transform the model to new dual variables in the Kramers-Wannier (KW) sense, such that the constraints are automatically fulfilled, and we obtain a second representation free of the complex action problem. We implement exploratory Monte Carlo simulations for both, the worldline, as well as the KW-dual form, for cross-checking the two dualizations and a first assessment of their potential for dual simulations.
Analysis of η,KL→π+π-γ using chiral models
International Nuclear Information System (INIS)
Picciotto, C.
1992-01-01
The decay η→π + π - γ is analyzed using two different approaches that incorporate vector mesons in the chiral Lagrangian, one which treats vector mesons as massive Yang-Mills bosons and one which treats them as dynamical gauge bosons of a hidden symmetry. From these approaches a common way of adding vector mesons to that decay emerges. A rate and photon spectrum are generated which compare reasonably to the experimental data. The procedure is then adapted into a simple pole model and used to calculate the more complicated decay K L →π + π - γ. Notwithstanding some uncertainties in the model, a rate that matches the experimental one is obtained with reasonable values of SU(3)-breaking parameters
One-dimensional model of chiral fermions with Feshbach resonant interactions
Prem, Abhinav; Gurarie, Victor
2018-02-01
We study a model of two species of 1D linearly dispersing fermions interacting via an s-wave Feshbach resonance at zero temperature. While this model is known to be integrable, it possesses novel features that have not previously been investigated. Here, we present an exact solution based on the coordinate Bethe Ansatz. In the limit of infinite resonance strength, which we term the strongly interacting limit, the two species of fermions behave as free Fermi gases. In the limit of infinitely weak resonance, or the weakly interacting limit, the gases can be in different phases depending on the detuning, the relative velocities of the particles, and the particle densities. When the molecule moves faster or slower than both species of atoms, the atomic velocities get renormalized and the atoms may even become non-chiral. On the other hand, when the molecular velocity is between that of the atoms, the system may behave like a weakly interacting Lieb–Liniger gas.
The phase structure of a chirally invariant lattice Higgs-Yukawa model
Energy Technology Data Exchange (ETDEWEB)
Gerhold, P. [Humboldt-Universitaet, Berlin (Germany); Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2007-12-15
We consider a chirally invariant lattice Higgs-Yukawa model based on the Neuberger overlap operator D{sup (ov)}. As a first step towards the eventual determination of Higgs mass bounds we present the phase structure of the model analytically in the large N{sub f}-limit in the physically interesting region of the Yukawa coupling constant. We confront the analytically obtained phase diagram with corresponding HMC-simulations and find an excellent agreement at large values of N{sub f}. In the opposite case the large N{sub f} computation still gives a good qualitative description of the phase diagram. We also present first and very preliminary results on the Higgs upper bound at one selected cut-off {lambda}. (orig.)
Beilinson, Alexander
2004-01-01
Chiral algebras form the primary algebraic structure of modern conformal field theory. Each chiral algebra lives on an algebraic curve, and in the special case where this curve is the affine line, chiral algebras invariant under translations are the same as well-known and widely used vertex algebras. The exposition of this book covers the following topics: the "classical" counterpart of the theory, which is an algebraic theory of non-linear differential equations and their symmetries; the local aspects of the theory of chiral algebras, including the study of some basic examples, such as the ch
The Ice-Vapor Interface and the Melting Point of Ice I-h for the Polarizable POL3 Water Model
Czech Academy of Sciences Publication Activity Database
Muchová, E.; Gladich, Ivan; Picaud, S.; Hoang, P. N. M.; Roeselová, Martina
2011-01-01
Roč. 115, č. 23 (2011), s. 5973-5982 ISSN 1089-5639 R&D Projects: GA ČR(CZ) GAP208/10/1724; GA MŠk LC512; GA MŠk MEB020919; GA MŠk MEB020715 Institutional research plan: CEZ:AV0Z40550506 Keywords : polarizable water force field * ice surface * melting point * ice slab Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.946, year: 2011
Czech Academy of Sciences Publication Activity Database
Zalesny, R.; Bartkowiak, W.; Toman, Petr; Leszczynski, J.
2007-01-01
Roč. 337, 1-3 (2007), s. 77-80 ISSN 0301-0104 Grant - others:Polish Committee for Scientific Research and the Ministry of Education, Youth, and Sports of the Czech Republic(PL) CZ25 Institutional research plan: CEZ:AV0Z40500505 Keywords : polarizability * first hyperpolarizability * second hyperpolarizability * nonlinear optical properties Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.805, year: 2007
Polarizability effects on the structure and dynamics of ionic liquids
Energy Technology Data Exchange (ETDEWEB)
Cavalcante, Ary de Oliveira, E-mail: arycavalcante@ufam.edu.br [Institute of Chemistry, University of Campinas – UNICAMP, Cx. P. 6154, Campinas, SP 13084-862 (Brazil); Departamento de Química, Universidade Federal do Amazonas, Av. Rodrigo Octávio, 6200, Coroado, Manaus, AM (Brazil); Ribeiro, Mauro C. C. [Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, São Paulo, SP C.P. 26077, 05513 970 São Paulo, SP (Brazil); Skaf, Munir S. [Institute of Chemistry, University of Campinas – UNICAMP, Cx. P. 6154, Campinas, SP 13084-862 (Brazil)
2014-04-14
Polarization effects on the structure and dynamics of ionic liquids are investigated using molecular dynamics simulations. Four different ionic liquids were simulated, formed by the anions Cl{sup −} and PF{sub 6}{sup −}, treated as single fixed charge sites, and the 1-n-alkyl-3-methylimidazolium cations (1-ethyl and 1-butyl-), which are polarizable. The partial charge fluctuation of the cations is provided by the electronegativity equalization model (EEM) and a complete parameter set for the cations electronegativity (χ) and hardness (J) is presented. Results obtained from a non-polarizable model for the cations are also reported for comparison. Relative to the fixed charged model, the equilibrium structure of the first solvation shell around the imidazolium cations shows that inclusion of EEM polarization forces brings cations closer to each other and that anions are preferentially distributed above and below the plane of the imidazolium ring. The polarizable model yields faster translational and reorientational dynamics than the fixed charges model in the rotational-diffusion regime. In this sense, the polarizable model dynamics is in better agreement with the experimental data.
DEFF Research Database (Denmark)
Hršak, Dalibor; Nørby, Morten Steen; Coriani, Sonia
2018-01-01
We present a formulation of the polarizable density embedding (PDE) method in combination with the complex polarization propagator (CPP) method for the calculation of absorption spectra of molecules in solutions. The method is particularly useful for the calculation of near-edge X-ray absorption...... fine structure (NEXAFS) spectra. We compare the performance of PDE-CPP with the previously formulated polarizable embedding (PE)-CPP model for the calculation of the NEXAFS spectra of adenine, formamide, glycine, and adenosine triphosphate (ATP) in water at the carbon and nitrogen K-edges, as well...
Dimensional reduction of the chiral-continuous Gross-Neveu model
Energy Technology Data Exchange (ETDEWEB)
Ananos, G.N.J.; Malbouisson, A.P.C.; Silva Neto, M.B.; Svaiter, N.F
1997-11-01
We study the finite-temperature phase transition of the generalized Gross-Neveu model with continuous chiral symmetry in 2< d{<=} 4 euclidean dimensions. The critical exponents are computed to the leading order in the 1/N expansion at both zero and finite temperatures. A dimensionally reduced theory is obtained after the introduction of thermal counterterms necessary to cancel thermal divergences that arise in the limit of high temperature. Although at zero temperature we have an infinitely and continuously degenerate vacuum state, we show that at finite temperature this degeneracy is discrete and, depending on the values of the bare parameters, we may have either total or partial restoration of symmetry. Finally we determine the universality class of the reduced theory by a simple analysis of the infrared structure of thermodynamic quantities computed using the reduced action as starting point. (author) 18 refs.
The phase structure of a chirally invariant lattice Higgs-Yukawa model. Numerical simulations
Energy Technology Data Exchange (ETDEWEB)
Gerhold, P. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2007-07-15
The phase diagram of a chirally invariant lattice Higgs-Yukawa model is explored by means of numerical simulations. The results revealing a rich phase structure are compared to analytical large N{sub f} calculations which we performed earlier. The analytical and numerical results are in excellent agreement at large values of N{sub f}. In the opposite case the large N{sub f} computation still gives a good qualitative description of the phase diagram. In particular we find numerical evidence for the predicted ferrimagnetic phase at intermediate values of the Yukawa coupling constant and for the symmetric phase at strong Yukawa couplings. Emphasis is put on the finite size effects which can hide the existence of the latter symmetric phase. (orig.)
Chiral discrimination in nuclear magnetic resonance spectroscopy
Lazzeretti, Paolo
2017-11-01
Chirality is a fundamental property of molecules whose spatial symmetry is characterized by the absence of improper rotations, making them not superimposable to their mirror image. Chiral molecules constitute the elementary building blocks of living species and one enantiomer is favoured in general (e.g. L-aminoacids and D-sugars pervade terrestrial homochiral biochemistry) because most chemical reactions producing natural substances are enantioselective. Since the effect of chiral chemicals and drugs on living beings can be markedly different between enantiomers, the quest for practical spectroscopical methods to scrutinize chirality is an issue of great importance and interest. Nuclear magnetic resonance (NMR) is a topmost analytical technique, but spectrometers currently used are ‘blind’ to chirality, i.e. unable to discriminate the two mirror-image forms of a chiral molecule, because, in the absence of a chiral solvent, the spectral parameters, chemical shifts and spin-spin coupling constants are identical for enantiomers. Therefore, the development of new procedures for routine chiral recognition would offer basic support to scientists. However, in the presence of magnetic fields, a distinction between true and false chirality is mandatory. The former epitomizes natural optical activity, which is rationalized by a time-even pseudoscalar, i.e. the trace of a second-rank tensor, the mixed electric dipole/magnetic dipole polarizability. The Faraday effect, magnetic circular dichroism and magnetic optical activity are instead related to a time-odd axial vector. The present review summarizes recent theoretical and experimental efforts to discriminate enantiomers via NMR spectroscopy, with the focus on the deep connection between chirality and symmetry properties under the combined set of fundamental discrete operations, namely charge conjugation, parity (space inversion) and time (motion) reversal.
International Nuclear Information System (INIS)
Ge Fengjun; Jiang Shaozhou; Wang Qing
2011-01-01
The electroweak chiral Lagrangian for the topcolor-assisted technicolor model proposed by K. Lane, which uses nontrivial patterns of techniquark condensation and walking, was investigated in this study. We found that the features of the model are qualitatively similar to those of Lane's previous natural topcolor-assisted technicolor prototype model, but there is no limit on the upper bound of the Z ' mass. We discuss the phase structure and possible walking behavior of the model. We obtained the values of all coefficients of the electroweak chiral Lagrangian up to an order of p 4 . We show that although the walking effect reduces the S parameter to half its original value, it maintains an order of 2. Moreover, a special hypercharge arrangement is needed to achieve further reductions in its value.
Sensitivity to properties of the phi-meson in the nucleon structure in the chiral soliton model
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, N.C.; Zhang, L. [Rensselaer Polytechnic Inst., Troy, NY (United States)
1994-04-01
The influence of the {phi}-meson on the nucleon properties in the chiral soliton model is discussed. Properties of the {phi}-meson and its photo- and electroproduction are of fundamental interest to CEBAF and its possible future extension. The quark model assigns {phi} an s{bar s} structure, thus forbidding the radiative decay {phi}{yields}{pi}{sup 0}{gamma}. Experimentally it is also found to be suppressed, yielding a branching fraction of 1.3{times}10{sup {minus}3}. However, {phi}{yields}{rho}{pi} and {phi}{yields}{pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} are not suppressed at all. Thus, it is possible to incorporate the widths of these decays into the framework of the chiral soliton model, by making use of a specific model for the compliance with OZI rule. Such a model is for example, the {omega}-{phi} mixing model. Consequence of this in the context of a chiral soliton model, which builds on the {pi}{rho}{omega}a{sub 1}(f{sub 1}) meson effective Lagrangian, is the context of this report.
Electronic Energy Transfer in Polarizable Heterogeneous Environments
DEFF Research Database (Denmark)
Svendsen, Casper Steinmann; Kongsted, Jacob
2015-01-01
such couplings provide important insight into the strength of interaction between photo-active pigments in protein-pigment complexes. Recently, attention has been payed to how the environment modifies or even controls the electronic couplings. To enable such theoretical predictions, a fully polarizable embedding......-order multipole moments. We use this extended model to systematically examine three different ways of obtaining EET couplings in a heterogeneous medium ranging from use of the exact transition density to a point-dipole approximation. Several interesting observations are made including that explicit use...... of transition densities in the calculation of the electronic couplings - also when including the explicit environment contribution - can be replaced by a much simpler transition point charge description without comprising the quality of the model predictions....
Accounting for electronic polarization in non-polarizable force fields.
Leontyev, Igor; Stuchebrukhov, Alexei
2011-02-21
The issues of electronic polarizability in molecular dynamics simulations are discussed. We argue that the charges of ionized groups in proteins, and charges of ions in conventional non-polarizable force fields such as CHARMM, AMBER, GROMOS, etc should be scaled by a factor about 0.7. Our model explains why a neglect of electronic solvation energy, which typically amounts to about a half of total solvation energy, in non-polarizable simulations with un-scaled charges can produce a correct result; however, the correct solvation energy of ions does not guarantee the correctness of ion-ion pair interactions in many non-polarizable simulations. The inclusion of electronic screening for charged moieties is shown to result in significant changes in protein dynamics and can give rise to new qualitative results compared with the traditional non-polarizable force field simulations. The model also explains the striking difference between the value of water dipole μ∼ 3D reported in recent ab initio and experimental studies with the value μ(eff)∼ 2.3D typically used in the empirical potentials, such as TIP3P or SPC/E. It is shown that the effective dipole of water can be understood as a scaled value μ(eff) = μ/√ε(el), where ε(el) = 1.78 is the electronic (high-frequency) dielectric constant of water. This simple theoretical framework provides important insights into the nature of the effective parameters, which is crucial when the computational models of liquid water are used for simulations in different environments, such as proteins, or for interaction with solutes.
Computational analysis of electronic polarizabilities in Thomas ...
African Journals Online (AJOL)
The electric polarizability,α, of a molecule is a measure of its ability to respond to an electric field and acquire an electric dipole moment, μ. The electric polarizability, α has been calculated for several ions and atoms by obtaining the perturbation of wave functions by an external field from a numerical solution of differential ...
Nonlinear optical properties of chiral polyesters: a joint experimental and theoretical study
Biju, Philip; Sreekumar, K.
2003-10-01
A series of polyesters containing donor-acceptor π-conjugated polar segments (4,4'-azobenzene dicarbonyl chloride) and chiral building units [L(+)-diethyl tartrate] in the main chain were synthesized and characterized by spectroscopic (IR, UV-Vis, 1H NMR, 13C NMR), thermal (TG/DTG, DSC), and optical (refractive index, optical rotation techniques). Chiral order was induced with a preferred helical sense to attain noncentrosymmetric ordering of dipoles (polar order) in macroscopic dimensions by chemical synthesis (chemical poling). A comprehensive attempt has been made to correlate the polar order of the polymer chains with the chiral order arising out of a preferred helical sense of the chains. This has been achieved by adopting four different theoretical models and comparing the results with the experimentally observed values of the second order polarizability tensor β. The models used are (1) Logarithmic Law of Mixing (LLM), (2) the Extended Boundary Condition Method (EBCM), (3) The Random Field Ising Model (RFIM) and (4) Semiempirical Computational Model (SCM). The results of the theoretical predictions are compared with the experimentally determined values of β.
Chiral U(1) flavor models and flavored Higgs doublets: the top FB asymmetry and the W jj
Energy Technology Data Exchange (ETDEWEB)
Ko, P.; Omura, Yuji; Yu, Chaehyun
2012-01-01
We present U(1) flavor models for leptophobic Z' with flavor dependent couplings to the right-handed up-type quarks in the Standard Model (SM), which can accommodate the recent data on the top forward-backward (FB) asymmetry and the dijet resonance associated with a W boson reported by CDF Collaboration. Such flavor-dependent leptophobic charge assignments generally require extra chiral fermions for anomaly cancellation. Also the chiral nature of U(1)' flavor symmetry calls for new U(1)'-charged Higgs doublets in order for the SM fermions to have realistic renormalizable Yukawa couplings. The stringent constraints from the top FB asymmetry at the Tevatron and the same sign top pair production at the LHC can be evaded due to contributions of the extra Higgs doublets. We also show that the extension could realize cold dark matter candidates.
Explicit de Sitter flux vacua for global string models with chiral matter
Cicoli, Michele; Klevers, Denis; Krippendorf, Sven; Mayrhofer, Christoph; Quevedo, Fernando; Valandro, Roberto
2014-05-01
We address the open question of performing an explicit stabilisation of all closed string moduli (including dilaton, complex structure and Kähler moduli) in fluxed type IIB Calabi-Yau compactifications with chiral matter. Using toric geometry we construct Calabi-Yau manifolds with del Pezzo singularities. D-branes located at such singularities can support the Standard Model gauge group and matter content or some close extensions. In order to control complex structure moduli stabilisation we consider Calabi-Yau manifolds which exhibit a discrete symmetry that reduces the effective number of complex structure moduli. We calculate the corresponding periods in the symplectic basis of invariant three-cycles and find explicit flux vacua for concrete examples. We compute the values of the flux superpotential and the string coupling at these vacua. Starting from these explicit complex structure solutions, we obtain AdS and dS minima where the Kähler moduli are stabilised by a mixture of D-terms, non-perturbative and perturbative α ' corrections as in the LARGE Volume Scenario. In the considered example the visible sector lives at a dP6 singularity which can be higgsed to the phenomenologically interesting class of models at the dP3 singularity.
Explicit de Sitter flux vacua for global string models with chiral matter
Energy Technology Data Exchange (ETDEWEB)
Cicoli, Michele [Dipartimento di Fisica e Astronomia, Università di Bologna, via Irnerio 46, 40126 Bologna (Italy); INFN, Sezione di Bologna, via Irnerio 46, 40126 Bologna (Italy); ICTP, Strada Costiera 11, 34014 Trieste (Italy); Klevers, Denis [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396 (United States); Krippendorf, Sven [Bethe Center for Theoretical Physics and Physikalisches Institut der Universität Bonn, Nussallee 12, 53115 Bonn (Germany); Mayrhofer, Christoph [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany); Quevedo, Fernando [ICTP, Strada Costiera 11, 34014 Trieste (Italy); DAMTP, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Valandro, Roberto [ICTP, Strada Costiera 11, 34014 Trieste (Italy); INFN, Sezione di Trieste, Trieste (Italy)
2014-05-05
We address the open question of performing an explicit stabilisation of all closed string moduli (including dilaton, complex structure and Kähler moduli) in fluxed type IIB Calabi-Yau compactifications with chiral matter. Using toric geometry we construct Calabi-Yau manifolds with del Pezzo singularities. D-branes located at such singularities can support the Standard Model gauge group and matter content or some close extensions. In order to control complex structure moduli stabilisation we consider Calabi-Yau manifolds which exhibit a discrete symmetry that reduces the effective number of complex structure moduli. We calculate the corresponding periods in the symplectic basis of invariant three-cycles and find explicit flux vacua for concrete examples. We compute the values of the flux superpotential and the string coupling at these vacua. Starting from these explicit complex structure solutions, we obtain AdS and dS minima where the Kähler moduli are stabilised by a mixture of D-terms, non-perturbative and perturbative α{sup ′} corrections as in the LARGE Volume Scenario. In the considered example the visible sector lives at a dP{sub 6} singularity which can be higgsed to the phenomenologically interesting class of models at the dP{sub 3} singularity.
Particle model for skyrmions in metallic chiral magnets: Dynamics, pinning, and creep
Lin, Shi-Zeng; Reichhardt, Charles; Batista, Cristian D.; Saxena, Avadh
2013-06-01
Recently spin textures called skyrmions have been discovered in certain chiral magnetic materials without spatial inversion symmetry, and they have attracted enormous attention due to their promising application in spintronics since only a low applied current is necessary to drive their motion. When a conduction electron moves around the skyrmion, its spin is fully polarized by the spin texture and acquires a quantized phase; thus, the skyrmion yields an emergent electrodynamics that in turn determines skyrmion motion and gives rise to a finite Hall angle. As topological excitations, skyrmions behave as particles. In this paper we derive the equation of motion for skyrmions as rigid point particles from a microscopic continuum model and obtain the short-range interaction between skyrmions and the interaction between skyrmions and defects. Skyrmions also experience a Magnus force perpendicular to their velocity due to the underlying emergent electromagnetic field. We validate the equation of motion by studying the depinning transition using both the particle and the continuum models. By using the particle description, we explain the recent experimental observations of the rotation of a skyrmion lattice in the presence of a temperature gradient. We also predict quantum and thermal creep motion of skyrmions in the pinning potential.
International Nuclear Information System (INIS)
Masili, Mauro; Groote, J.J. de
2004-01-01
Using a model potential representation combined with a variationally stable method, we present a precise calculation of the electric dipole polarizabilities of the sodium negative ion (Na - ). The effective two-electron eigensolutions for Na - are obtained from a hyperspherical coupled-channel calculation. This approach allows efficient error control and insight into the system's properties through one-dimensional potential curves. Our result of 1018.3 a.u. for the static dipole polarizability is in agreement with previous calculations and supports our results for the dynamic polarizability, which has scarcely been investigated hitherto
What's wrong with anomalous chiral gauge theory?
International Nuclear Information System (INIS)
Kieu, T.D.
1994-05-01
It is argued on general ground and demonstrated in the particular example of the Chiral Schwinger Model that there is nothing wrong with apparently anomalous chiral gauge theory. If quantised correctly, there should be no gauge anomaly and chiral gauge theory should be renormalisable and unitary, even in higher dimensions and with non-Abelian gauge groups. Furthermore, it is claimed that mass terms for gauge bosons and chiral fermions can be generated without spoiling the gauge invariance. 19 refs
Covariant perturbation theory and chiral superpropagators
Ecker, G
1972-01-01
The authors use a covariant formulation of perturbation theory for the non-linear chiral invariant pion model to define chiral superpropagators leading to S-matrix elements which are independent of the choice of the pion field coordinates. The relation to the standard definition of chiral superpropagators is discussed. (11 refs).
Quark structure of chiral solitons
Energy Technology Data Exchange (ETDEWEB)
Dmitri Diakonov
2004-05-01
There is a prejudice that the chiral soliton model of baryons is something orthogonal to the good old constituent quark models. In fact, it is the opposite: the spontaneous chiral symmetry breaking in strong interactions explains the appearance of massive constituent quarks of small size thus justifying the constituent quark models, in the first place. Chiral symmetry ensures that constituent quarks interact very strongly with the pseudoscalar fields. The ''chiral soliton'' is another word for the chiral field binding constituent quarks. We show how the old SU(6) quark wave functions follow from the ''soliton'', however, with computable relativistic corrections and additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.
Chirality in adsorption on solid surfaces.
Zaera, Francisco
2017-12-07
In the present review we survey the main advances made in recent years on the understanding of chemical chirality at solid surfaces. Chirality is an important topic, made particularly relevant by the homochiral nature of the biochemistry of life on Earth, and many chiral chemical reactions involve solid surfaces. Here we start our discussion with a description of surface chirality and of the different ways that chirality can be bestowed on solid surfaces. We then expand on the studies carried out to date to understand the adsorption of chiral compounds at a molecular level. We summarize the work published on the adsorption of pure enantiomers, of enantiomeric mixtures, and of prochiral molecules on chiral and achiral model surfaces, especially on well-defined metal single crystals but also on other flat substrates such as highly ordered pyrolytic graphite. Several phenomena are identified, including surface reconstruction and chiral imprinting upon adsorption of chiral agents, and the enhancement or suppression of enantioselectivity seen in some cases upon adsorption of enantiomixtures of chiral compounds. The possibility of enhancing the enantiopurity of adsorbed layers upon the addition of chiral seeds and the so-called "sergeants and soldiers" phenomenon are presented. Examples are provided where the chiral behavior has been associated with either thermodynamic or kinetic driving forces. Two main approaches to the creation of enantioselective surface sites are discussed, namely, via the formation of supramolecular chiral ensembles made out of small chiral adsorbates, and by adsorption of more complex chiral molecules capable of providing suitable chiral environments for reactants by themselves, via the formation of individual adsorbate:modifier adducts on the surface. Finally, a discussion is offered on the additional effects generated by the presence of the liquid phase often required in practical applications such as enantioselective crystallization, chiral
Dynamical study of Ωc0 in the chiral quark model
Yang, Gang; Ping, Jialun
2018-02-01
Recently, the experimental results of the LHCb Collaboration suggested the existence of five new excited states of Ωc0 : Ωc(3000 )0 , Ωc(3050 )0 , Ωc(3066 )0 , Ωc(3090 )0 , and Ωc(3119 )0 ; however, the quantum numbers of these new particles are not determined now. To understand the nature of these states, a dynamical calculation of Ωc0 both in five-quark configuration with quantum numbers I JP=0 (1/2 )- , 0 (3/2 )- , 0 (5/2 )- and in three-quark configuration with positive parity and negative parity was performed in the framework of the chiral quark model with the help of the Gaussian expansion method. The results show the masses both of the 1 P and the 2 S states in s s c systems are comparable to experimental data; Besides, Ξ D ¯ , ΞcK ¯ , and Ξc*K ¯ are also possible candidates of these new particles if the parity is negative. The distances between quark pairs suggest a compact structure nature.
Exact scattering in the SU(n) supersymmetric principal chiral model
Evans, J M; Evans, Jonathan M; Hollowood, Timothy J
1997-01-01
The complete spectrum of states in the supersymmetric principal chiral model based on SU(n) is conjectured, and an exact factorizable S-matrix is proposed to describe scattering amongst these states. The SU(n)_L*SU(n)_R symmetry of the lagrangian is manifest in the S-matrix construction. The supersymmetries, on the other hand, are incorporated in the guise of spin-1/2 charges acting on a set of RSOS kinks associated with su(n) at level n. To test the proposed S-matrix, calculations of the change in the ground-state energy in the presence of a coupling to a background charge are carried out. The results derived from the lagrangian using perturbation theory and from the S-matrix using the TBA are found to be in complete agreement for a variety of background charges which pick out, in turn, the highest weight states in each of the fundamental representations of SU(n). In particular, these methods rule out the possibility of additional CDD factors in the S-matrix. Comparison of the expressions found for the free-...
Description of a nucleon in nuclear matter using the chiral bag model
International Nuclear Information System (INIS)
Bunatyan, G.G.
1990-01-01
The chiral bag (cloudy bag) model, which contains an essentially nonlinear interaction of quarks with both the classical and quantum pion field, is extended for description of a nucleon in nuclear matter. The dependence on the density and temperature of the medium is studied. The pion field in nuclear matter differs considerably from the free field, and this leads to a modification of the nucleon bag. Increase of the density ρ and temperature T causes strengthening of the pion field and growth of its thermodynamic fluctuations. At sufficiently high densities ρ approx-gt ρ CB and temperatures T≥T cr this leads to instability of the three-quark nucleon bag. Under such conditions nuclear matter cannot be composed only of nucleons, and one should expect the appearance of a different, non-nucleon, phase. Estimates of the critical density and temperature are obtained: ρ CB ∼ (1.5-2)ρ 0 and T cr ∼ 200 MeV (where ρ 0 is the conventional nuclear density)
Classification of Simple Oxides: A Polarizability Approach
Dimitrov, Vesselin; Komatsu, Takayuki
2002-01-01
A simple oxide classification has been proposed on the basis of correlation between electronic polarizabilities of the ions and their binding energies determined by XPS. Three groups of oxides have been considered taking into account the values obtained on refractive-index- or energy-gap-based oxide ion polarizability, cation polarizability, optical basicity, O 1s binding energy, metal (or nonmetal) binding energy, and Yamashita-Kurosawa's interaction parameter of the oxides. The group of semicovalent predominantly acidic oxides includes BeO, B2O3, P2O5, SiO2, Al2O3, GeO2, and Ga2O3 with low oxide ion polarizability, high O 1s binding energy, low cation polarizability, high metal (or nonmetal) outermost binding energy, comparatively low optical basicity, and strong interionic interaction, leading to the formation of strong covalent bonds. Some main group oxides so-called ionic or basic such as CaO, In2O3, SnO2, and TeO2 and most transition metal oxides show relatively high oxide ion polarizability, O 1s binding energy in a very narrow medium range, high cation polarizability, and low metal (or nonmetal) binding energy. Their optical basicity varies in a narrow range and it is close to that of CaO. The group of very ionic or very basic oxides includes CdO, SrO, and BaO as well as PbO, Sb2O3, and Bi2O3, which possess very high oxide ion polarizability, low O 1s binding energy, very high cation polarizability, and very low metal (or nonmetal) binding energy. Their optical basicity is higher than that of CaO and the interionic interaction is very weak, giving rise to the formation of very ionic chemical bonds.
Two-chiral component microemulsion EKC - chiral surfactant and chiral oil. Part 2: diethyl tartrate.
Kahle, Kimberly A; Foley, Joe P
2007-08-01
In this second study on dual-chirality microemulsions containing a chiral surfactant and a chiral oil, a less hydrophobic and lower interfacial tension chiral oil, diethyl tartrate, is employed (Part 1, Foley, J. P. et al.., Electrophoresis, DOI: 10.1002/elps.200600551). Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and diethyl tartrate (D, L, or racemic, 0.88% v/v) were examined as pseudostationary phases (PSPs) for the enantioseparation of six chiral pharmaceutical compounds: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Average efficiencies increased with the addition of a chiral oil to R-DDCV PSP formulations. Modest improvements in resolution and enantioselectivity (alpha(enant)) were achieved with two-chiral-component systems over the one-chiral-component microemulsion. Slight enantioselective synergies were confirmed using a thermodynamic model. Results obtained in this study are compared to those obtained in Part 1 as well as those obtained with chiral MEEKC using an achiral, low-interfacial-tension oil (ethyl acetate). Dual-chirality microemulsions with the more hydrophobic oil dibutyl tartrate yielded, relative to diethyl tartrate, higher efficiencies (100,000-134,000 vs. 80,800-94,300), but lower resolution (1.64-1.91 vs. 2.08-2.21) due to lower enantioselectivities (1.060-1.067 vs. 1.078-1.081). Atenolol enantiomers could not be separated with the dibutyl tartrate-based microemulsions but were partially resolved using diethyl tartrate microemulsions. A comparable single-chirality microemulsion based on the achiral oil ethyl acetate yielded, relative to diethyl tartrate, lower efficiency (78 300 vs. 91 600), higher resolution (1.99 vs. 1.83), and similar enantioselectivities.
The electric polarizability of a particle bound by a one-dimensional ionic crystal
International Nuclear Information System (INIS)
Balderas, Daniel; González, Gabriel
2013-01-01
We consider the problem of a particle confined to a one-dimensional ionic crystal of finite length modeled by repulsive and attractive delta functions and subject to the application of an external constant electric field. Exact expressions for the electric polarizability of the system via the Dalgarno–Lewis technique are obtained in second order perturbation theory. The study uncovers the behavior of the electric polarizability as a function of the number of ions in the system. (paper)
International Nuclear Information System (INIS)
Ecker, G.
1996-06-01
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering. (author)
Quarks, baryons and chiral symmetry
Hosaka, Atsushi
2001-01-01
This book describes baryon models constructed from quarks, mesons and chiral symmetry. The role of chiral symmetry and of quark model structure with SU(6) spin-flavor symmetry are discussed in detail, starting from a pedagogic introduction. Emphasis is placed on symmetry aspects of the theories. As an application, the chiral bag model is studied for nucleon structure, where important methods of theoretical physics, mostly related to the semiclassical approach for a system of strong interactions, are demonstrated. The text is more practical than formal; tools and ideas are explained in detail w
Coupled-channels study of Lambda K and Sigma K states in the chiral SU(3) quark model
Huang, F.; Zhang, D.; Zhang, Z. Y.; Yu, Y. W.
2005-01-01
The $S$-wave $\\Lambda K$ and $\\Sigma K$ states with isospin $I=1/2$ are dynamically investigated within the framework of the chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a good description of the energies of the baryon ground states, the binding energy of the deuteron, and the experimental data of the nucleon-nucleon ($NN$) and nucleon-hyperon ($NY$) scattering. Assumed not to give important con...
A Conformational Model for MTPA Esters of Chiral N-(2-Hydroxyalkylacrylamides
Directory of Open Access Journals (Sweden)
Eduardo M. Rustoy
2014-01-01
Full Text Available The absolute stereochemistry of novel chiral N-(2-hydroxylalkylacrylamides prepared by a lipase-catalyzed resolution was successfully determined by 1H NMR of their MTPA esters. The method was validated for this particular case by computational experiments.
Variation of the electronic dipole polarizability on the reaction path.
Jędrzejewski, Mateusz; Ordon, Piotr; Komorowski, Ludwik
2013-10-01
The reaction force and the electronic flux, first proposed by Toro-Labbé et al. (J Phys Chem A 103:4398, 1999) have been expressed by the existing conceptual DFT apparatus. The critical points (extremes) of the chemical potential, global hardness and softness have been identified by means of the existing and computable energy derivatives: the Hellman-Feynman force, nuclear reactivity and nuclear stiffness. Specific role of atoms at the reaction center has been unveiled by indicating an alternative method of calculation of the reaction force and the reaction electronic flux. The electron dipole polarizability on the IRC has been analyzed for the model reaction HF + CO→HCOF. The electron polarizability determined on the IRC α e (ξ) was found to be reasonably parallel to the global softness curve S(ξ). The softest state on the IRC (not TS) coincides with zero electronic flux.
Chirality effect in disordered graphene ribbon junctions
International Nuclear Information System (INIS)
Long Wen
2012-01-01
We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon. (paper)
Two-loop coupling constant renormalization in lattice SU(N)xSU(N) 2D chiral models
Energy Technology Data Exchange (ETDEWEB)
Magnoli, N.; Ravanini, F.
1986-08-01
For the most general link action of lattice SU(N)xSU(N) two dimensional chiral models, the two loop coupling constant renormalization is discussed in the context of the background field method. A non-linear reparametrization of the fields, necessary to keep the invariance of the theory, introduces unpleasant extra-terms. However some of the non-universal contributions are unaffected by these extra-terms and can be easily calculated. This allows to compute the difference between the first non-universal coefficients of the Callan-Symanzik beta functions for two actions having the same scale ..lambda...
{E2}/{M1} ratio for the γN → Δ transition in the chiral quark soliton model
Watabe, T.; Christov, Chr. V.; Goeke, K.
1995-02-01
We calculate the electric quadrupole to magnetic dipole transition ratio {E2}/{M1} for the reaction γN → Δ (1232) in the chiral quark soliton model. The calculated {E2}/{M1} ratio is in a good agreement with the very new experimental data. We obtain non-zero negative value for the electric quadrupole N - Δ transition moment, which suggests an oblate deformed charge structure of the nucleon or/and the delta isobar. Other observables related to this quantity, namely the N - Δ mass splitting, the isovector charge radius, and isovector magnetic moment, are properly reproduced as well.
International Nuclear Information System (INIS)
Dorokhov, A.E.; Kanokov, Z.; Musakhanov, M.M.; Rakhimov, A.M.
1989-01-01
Pion production on a nucleon is studied in the chiral bag model (CBM). A CBM version is investigated in which the pions get into the bag and interact with quarks in a pseudovector way in the entire volume. Charged pion photoproduction amplitudes are found taking into account the recoil nucleon motion effects. Angular and energy distributions of charged pions, polarization of the recoil nucleon, multipoles are calculated. The recoil effects are shon to give an additional contribution to the static approximation of order of 10-20%. At bag radius value R=1 in the calculations are consistent with the experimental data
Chiral pinwheel clusters lacking local point chirality.
Sun, Kai; Shao, Ting-Na; Xie, Jia-Le; Lan, Meng; Yuan, Hong-Kuan; Xiong, Zu-Hong; Wang, Jun-Zhong; Liu, Ying; Xue, Qi-Kun
2012-07-09
The supramolecular pinwheel cluster is a unique chiral structure with evident handedness. Previous studies reveal that the chiral pinwheels are composed of chiral or achiral molecules with polar groups, which result in strong intermolecular interactions such as hydrogen-bonding or dipole interactions. Herein, it is shown that the simple linear aromatic molecule, pentacene, can be self-assembled into large chiral pinwheel clusters on the semimetal Bi(111) surface, due to enhanced intermolecular interactions. The pentacene pinwheels reveal two levels of organizational chirality: the chiral hexamers resulting from asymmetric shifting along the long molecular axis, and chiral arrangement of six hexamers with a rotor motif. Furthermore, a new relation between the local point chirality and organizational chirality is identified from the pinwheels: the former is not essential for the latter in 2D pinwheel clusters of the pentacene molecule. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Description of meson strong and electromagnetic interactions in quantum chiral theory
International Nuclear Information System (INIS)
Volkov, M.K.; Pervushin, V.N.
1978-01-01
Strong and electromagnetic interactions of mesons in the framework of the chiral theory are considered. The pion-pion scattering phases, the pion electromagnetic form factor, the mean squared radius of a K-meson, and the electric and magnetic polarizabilities of pions are calculated using the superpropagator method. The rho-meson mass, Msub(rho)=800 MeV, is calculated too
Time reversal violating nuclear polarizability and atomic electric dipole moment
International Nuclear Information System (INIS)
Ginges, J.S.M.; Flambaum, V.V.; Mititelu, G.
2000-01-01
Full text: We propose a nuclear mechanism which can induce an atomic electric dipole moment (EDM). The interaction of external electric E and magnetic H fields with nuclear electric and magnetic dipole moments, d and ,u, gives rise to an energy shift, U= -β ik E i H k , where β ik is the nuclear polarizability. Parity and time invariance violating (P,T-odd) nuclear forces generate a mixed P,T-odd nuclear polarizability, whereψ 0 and ψ n are P,T-odd perturbed ground and excited nuclear states, respectively. In the case of a heavy spherical nucleus with a single unpaired nucleon, the perturbed wavefunctions are U = -β ik E i H k , where ξis a constant proportional to the strength of the nuclear P,T-odd interaction, σ is the nuclear spin operator, and ψ n is an unperturbed wavefunction. There are both scalar and tensor contributions to the nuclear P,T-odd polarizability. An atomic EDM is induced by the interaction of the fields of an unpaired electron in an atom with the P,T-odd perturbed atomic nucleus. An estimate for the value of this EDM has been made. The measurements of atomic EDMs can provide information about P,T-odd nuclear forces and test models of CP-violation
Kahle, Kimberly A; Foley, Joe P
2007-08-01
Novel microemulsion formulations containing all chiral components are described for the enantioseparation of six pairs of pharmaceutical enantiomers (atenolol, ephedrine, metoprolol, N-methyl ephedrine, pseudoephedrine, and synephrine). The chiral surfactant dodecoxycarbonylvaline (DDCV, R- and S-), the chiral cosurfactant S-2-hexanol, and the chiral oil diethyl tartrate (R- and S-) were combined to create four different chiral microemulsions, three of which were stable. Results obtained for enantioselectivity, efficiency, and resolution were compared for the triple-chirality systems and the single-chirality system that contained chiral surfactant only. Improvements in enantioselectivity and resolution were achieved by simultaneously incorporating three chiral components into the aggregate. The one-chiral-component microemulsion provided better efficiencies. Enantioselective synergies were identified for the three-chiral-component nanodroplets using a thermodynamic model. Additionally, two types of dual-chirality systems, chiral surfactant/chiral cosurfactant and chiral surfactant/chiral oil, were examined in terms of chromatographic figures of merit, with the former providing much better resolution. The two varieties of two-chiral-component microemulsions gave similar values for enantioselectivity and efficiency. Lastly, the microemulsion formulations were divided into categories based on the number of chiral microemulsion reagents and the average results for each pair of enantiomers were analyzed for trends. In general, enantioselectivity and resolution were enhanced while efficiency was decreased as more chiral components were used to create the pseudostationary phase (PSP).
Quark spin-flavor layered structure with condensed π/sup 0/ field in Chiral bag model
International Nuclear Information System (INIS)
Tamagaki, R.; Tatsumi, T.
1984-01-01
In order to understand predispositions of high density matter, a new phase possibly arising from the neutron matter under π/sup 0/ condensation is studied in chiral bag model, as a facet in which both quark and pion degrees of freedom are incorporated in a well-developed situation of π/sup 0/ condensation. The aspects of this phase are characterized by the periodic layered structure of the two-dimensional quark matter with a specific spin-flavor order the π/sup 0/ field existent as the Nambu-Goldstone mode between the adjacent layers. Such quark configuration is caused due to the pion-quark coupling at the layer (bag) surface which drastically lowers quark energy. Energy properties of the system are examined, and it is shown that the one-gluon-exchange contribution provides the repulsive effect to prevent the layered structure from collapsing. This model provides an example which can be solved nonperturbatively in the chiral bag model and suggests the possibility of an intermediate stage which may appear prior to the phase transition to uniform quark matter
Polarizability expressions for predicting resonances in plasmonic and Mie scatterers
Colom, Rémi; Devilez, Alexis; Enoch, Stefan; Stout, Brian; Bonod, Nicolas
2017-06-01
Polarizability expressions are commonly used in optics and photonics to model light scattering by small particles. Models based on Taylor series of the scattering coefficients of the particles fail to predict the morphologic resonances hosted by dielectric particles. Here we propose to use the factorization of the special functions appearing in the expression of the Mie scattering coefficients to derive pointlike models. These models can be applied to reproduce both Mie resonances of dielectric particles and plasmonic resonances of metallic particles. They provide simple but robust tools to predict accurately the electric and magnetic Mie resonances in dielectric particles.
The Higgs boson resonance from a chiral Higgs-Yukawa model on the lattice
Energy Technology Data Exchange (ETDEWEB)
Kallarackal, Jim
2011-04-28
Despite the fact that the standard model of particle physics has been confirmed in many high energy experiments, the existence of the Higgs boson is not assured. The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for fermions and the weak gauge bosons. The goal of this work is to set limits on the mass and the decay width of the Higgs boson. The basis to compute the physical quantities is the path integral which is here evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. A polynomial hybrid Monte Carlo algorithm is used to incorporate dynamical fermions. The chiral symmetry of the electroweak model is incorporated by using the Neuberger overlap operator. Here, the standard model is considered in the limit of a Higgs-Yukawa sector which does not contain the weak gauge bosons and only a degenerate doublet of top- and bottom quarks are incorporated. Results from lattice perturbation theory up to one loop of the Higgs boson propagator are compared with those obtained from Monte Carlo simulations at three different values of the Yukawa coupling. At all values of the investigated couplings, the perturbative results agree very well with the Monte Carlo data. A main focus of this work is the investigation of the resonance parameters of the Higgs boson. The resonance width and the resonance mass are investigated at weak and at large quartic couplings. The parameters of the model are chosen such that the Higgs boson can decay into any even number of Goldstone bosons. Thus, the Higgs boson does not appear as an asymptotic stable state but as a resonance. In all considered cases the Higgs boson resonance width lies below 10% of the resonance mass. The obtained resonance mass is compared with the mass obtained from the Higgs boson propagator. The results agree perfectly at all values of the quartic coupling considered. Finally, the effect of a heavy fourth generation of fermions on the
Charged pions polarizability measurement at COMPASS
Guskov, A
2010-01-01
The pion electromagnetic structure can be probed in $\\pi^{−}+(A,Z)\\rightarrow\\pi^{-}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\alpha_{\\pi})$ and the magnetic $(\\beta_{\\pi})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of point-like pions with the measured cross section. The opportunity to measure pion polarizability via the Primakoff reaction at the COMPASS experiment was studied with $a$ $\\pi^{-}$ beam of 190 GeV during pilot run 2004. The obtained results were used for preparation of the new data taking which was performed in 2009.
Measurement of the pion polarizabilities at COMPASS
Guskov, A V
2006-01-01
The electromagnetic structure of pions is probed in $\\pi\\gamma$ Compton scattering in inverse kinematics (Primakoff effect) and described by the electric ($\\alpha_{\\pi}$) and magnetic ($\\beta_{\\pi}$) polarizabilities, that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the theoretically predicted (under approximation of unstructured pion) cross section of Primakoff scattering and the measured cross section. The high beam intensity, good spectrometer resolution, the high rate capability, the high acceptance and possibility to use pion and muon beams, that are unique to the COMPASS experiment provide the tools to measure precisely the pion polarizabilities in the $\\pi^{-} + (A,Z)\\rightarrow\\pi^{-} + (A,Z) + \\gamma$ Primakoff reaction. This cross section is related to the cross section of Compton scattering on pion. A precise tracking system, electromagnetic and hadron calorimeters provide good conditions for...
International Nuclear Information System (INIS)
Jiang Weizhou; Li Baozn; Chen Liewen
2007-01-01
Using in-medium hadron properties according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities and considering naturalness of the coupling constants, we have newly constructed several relativistic mean-field Lagrangians with chiral limits. The model parameters are adjusted such that the symmetric part of the resulting equation of state at supra-normal densities is consistent with that required by the collective flow data from high energy heavy-ion reactions, while the resulting density dependence of the symmetry energy at sub-saturation densities agrees with that extracted from the recent isospin diffusion data from intermediate energy heavy-ion reactions. The resulting equations of state have the special feature of being soft at intermediate densities but stiff at high densities naturally. With these constrained equations of state, it is found that the radius of a 1.4M o canonical neutron star is in the range of 11.9 km≤R≤13.1 km, and the maximum neutron star mass is around 2.0M o close to the recent observations
Open-ended response theory with polarizable embedding
DEFF Research Database (Denmark)
Steindal, Arnfinn Hykkerud; Beerepoot, Maarten T P; Ringholm, Magnus
2016-01-01
We present the theory and implementation of an open-ended framework for electric response properties at the level of Hartree-Fock and Kohn-Sham density functional theory that includes effects from the molecular environment modeled by the polarizable embedding (PE) model. With this new state......) properties can be studied by evaluating single residues of the response functions. The PE approach includes mutual polarization effects between the quantum and classical parts of the system through induced dipoles that are determined self-consistently with respect to the electronic density. The applicability...
Enantioselective Biotransformation of Chiral Persistent Organic Pollutants.
Zhang, Ying; Ye, Jing; Liu, Min
2017-01-01
Enantiomers of chiral compounds commonly undergo enantioselective transformation in most biologically mediated processes. As chiral persistent organic pollutants (POPs) are extensively distributed in the environment, differences between enantiomers in biotransformation should be carefully considered to obtain exact enrichment and specific health risks. This review provides an overview of in vivo biotransformation of chiral POPs currently indicated in the Stockholm Convention and their chiral metabolites. Peer-reviewed journal articles focused on the research question were thoroughly searched. A set of inclusion and exclusion criteria were developed to identify relevant studies. We mainly compared the results from different animal models under controlled laboratory conditions to show the difference between enantiomers in terms of distinct transformation potential. Interactions with enzymes involved in enantioselective biotransformation, especially cytochrome P450 (CYP), were discussed. Further research areas regarding this issue were proposed. Limited evidence for a few POPs has been found in 30 studies. Enantioselective biotransformation of α-hexachlorocyclohexane (α-HCH), chlordane, dichlorodiphenyltrichloroethane (DDT), heptachlor, hexabromocyclododecane (HBCD), polychlorinated biphenyls (PCBs), and toxaphene, has been investigated using laboratory mammal, fish, bird, and worm models. Tissue and excreta distributions, as well as bioaccumulation and elimination kinetics after administration of racemate and pure enantiomers, have been analyzed in these studies. Changes in enantiomeric fractions have been considered as an indicator of enantioselective biotransformation of chiral POPs in most studies. Results of different laboratory animal models revealed that chiral POP biotransformation is seriously affected by chirality. Pronounced results of species-, tissue-, gender-, and individual-dependent differences are observed in in vivo biotransformation of chiral POPs
Energy Technology Data Exchange (ETDEWEB)
Gerhold, P. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2009-02-15
We study the coupling parameter dependence of the Higgs boson mass in a chirally invariant lattice Higgs-Yukawa model emulating the same Yukawa coupling structure as in the Higgs-fermion sector of the Standard Model. Eventually, the aim is to establish non-perturbative upper and lower Higgs boson mass bounds derived from first principles, in particular not relying on vacuum stability considerations for the latter case. Here, we present our lattice results for the lower Higgs boson mass bound at several values of the cutoff {lambda} and compare them to corresponding analytical calculations based on the effective potential as obtained from lattice perturbation theory. Furthermore, we give a brief outlook towards the calculation of the upper Higgs boson mass bound. (orig.)
K$_{-}$ and K$_{-}$ polarizability from kaonic atoms
Backenstoss, Gerhard; Bergström, I; Bunaciu, T; Egger, J; Hagelberg, R; Hultberg, S; Koch, H; Lynen, Y; Ritter, H G; Schwitter, A; Tauscher, L
1973-01-01
The K/sup -/ mass was determined from kaonic atomic X-rays from Au and Ba to be 493.691+or-0.040 MeV. An upper limit for the polarizability of the K/sup -/ was found to be 0.020 fm/sup 3/ at 90% confidence. (18 refs).
The axial polarizability of nucleons and nuclei
International Nuclear Information System (INIS)
Ericson, M.; Figureau, A.
1981-02-01
The part of the static nuclear axial polarizability arising from the nucleonic excitations is derived from the low energy expansion of the πN amplitude. It is shown that the contribution of the Δ intermediate state, though dominant, does not saturate the nucleonic response. A similar effect, though more pronounced, is known to occur for the magnetic susceptibility
International Nuclear Information System (INIS)
Santos, R.P. dos.
1986-12-01
The superfield method is applied to the effective potential calculation in supersymmetric models. The Weinberg and Jackiw methods are discussed in the context of supersymmetric field theories, highlighting the greater simplicity obtained when the Feynman super diagrams are used. The chiral superfield propagators are derived and their relations with components field are commented. (L.C.J.A.)
Steensma, M.; Kuipers, N.J.M.; de Haan, A.B.; Kwant, Gerard
2007-01-01
This paper reports on determination of the intrinsic reaction kinetics in reactive extraction of chiral compounds. It is important to know the mass transfer rates and reaction kinetics separately for a reliable scale-up. A kinetic model is developed to interpret the experimental data from the
Energy Technology Data Exchange (ETDEWEB)
Popov, Alexander P., E-mail: APPopov@mephi.ru [Department of Molecular Physics, National Research Nuclear University MEPhI, Kashirskoe shosse 31, 115409 Moscow (Russian Federation); Gloria Pini, Maria, E-mail: mariagloria.pini@isc.cnr.it [Istituto dei Sistemi Complessi del CNR (CNR-ISC), Unità di Firenze, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Rettori, Angelo [Dipartimento di Fisica ed Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto Fiorentino (Italy)
2016-03-15
The metastable states of a finite-size chain of N classical spins described by the chiral XY-model on a discrete one-dimensional lattice are calculated by means of a general theoretical method recently developed by one of us. This method allows one to determine all the possible equilibrium magnetic states in an accurate and systematic way. The ground state of a chain consisting of N classical XY spins is calculated in the presence of (i) a symmetric ferromagnetic exchange interaction, favoring parallel alignment of nearest neighbor spins, (ii) a uniaxial anisotropy, favoring a given direction in the film plane, and (iii) an antisymmetric Dzyaloshinskii–Moriya interaction (DMI), favoring perpendicular alignment of nearest neighbor spins. In addition to the ground state with a non-uniform helical spin arrangement, which originates from the energy competition in the finite-size chain with open boundary conditions, we have found a considerable number of higher-energy equilibrium states. In the investigated case of a chain with N=10 spins and a DMI much smaller than the in-plane uniaxial anisotropy, it turns out that a metastable (unstable) state of the finite chain is characterized by a configuration where none (at least one) of the inner spins is nearly parallel to the hard axis. The role of the DMI is to establish a unique rotational sense for the helical ground state. Moreover, the number of both metastable and unstable equilibrium states is doubled with respect to the case of zero DMI. This produces modifications in the Peierls–Nabarro potential encountered by a domain wall during its displacement along the discrete spin chain. - Highlights: • A finite-size chain of N classical spins within the XY-chiral model is investigated. • Using a systematic theoretical method, all equilibrium states are calculated for N=10. • The ground state has a non-uniform helical order with unique rotational sense. • Metastable states contain a domain wall whose energy
Silva, António; Urbano, Diana; Kim, Hyun-Chul
2018-02-01
We investigate the flavor decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model (χQSM) with symmetry-conserving quantization. We consider the rotational 1/N_c and linear strange-quark mass (ms) corrections. We discuss the results of the flavor-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). Finally, we discuss the transverse charge densities for both unpolarized and polarized nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the center within the SU(3) χQSM, which can be explained by the contribution of the strange quark.
Statistical field theory description of inhomogeneous polarizable soft matter.
Martin, Jonathan M; Li, Wei; Delaney, Kris T; Fredrickson, Glenn H
2016-10-21
We present a new molecularly informed statistical field theory model of inhomogeneous polarizable soft matter. The model is based on fluid elements, referred to as beads, that can carry a net monopole of charge at their center of mass and a fixed or induced dipole through a Drude-type distributed charge approach. The beads are thus polarizable and naturally manifest attractive van der Waals interactions. Beyond electrostatic interactions, beads can be given soft repulsions to sustain fluid phases at arbitrary densities. Beads of different types can be mixed or linked into polymers with arbitrary chain models and sequences of charged and uncharged beads. By such an approach, it is possible to construct models suitable for describing a vast range of soft-matter systems including electrolyte and polyelectrolyte solutions, ionic liquids, polymerized ionic liquids, polymer blends, ionomers, and block copolymers, among others. These bead models can be constructed in virtually any ensemble and converted to complex-valued statistical field theories by Hubbard-Stratonovich transforms. One of the fields entering the resulting theories is a fluctuating electrostatic potential; other fields are necessary to decouple non-electrostatic interactions. We elucidate the structure of these field theories, their consistency with macroscopic electrostatic theory in the absence and presence of external electric fields, and the way in which they embed van der Waals interactions and non-uniform dielectric properties. Their suitability as a framework for computational studies of heterogeneous soft matter systems using field-theoretic simulation techniques is discussed.
Piras, Patrick; Sheridan, Robert; Sherer, Edward C; Schafer, Wes; Welch, Christopher J; Roussel, Christian
2018-03-01
Predicting whether a chiral column will be effective is a daily task for many analysts. Moreover, finding the best chiral column for separating a particular racemic compound is mostly a matter of trial and error that may take up to a week in some cases. In this study we have developed a novel prediction approach based on combining a random forest classifier and an optimized discretization method for dealing with enantioselectivity as a continuous variable. Using the optimization results, models were trained on data sets divided into four enantioselectivity classes. The best model performances were achieved by over-sampling the minority classes (α ≤ 1.10 and α ≥ 2.00), down-sampling the majority class (1.2 ≤ α < 2.0), and aggregating multicategory predictions into binary classifications. We tested our method on 41 chiral stationary phases using layered fingerprints as descriptors. Experimental results show that this learning methodology was successful in terms of average area under the Receiver Operating Characteristic curve, Kappa indices and F-measure for structure-based prediction of the enantioselective behavior of 34 chiral columns. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Biguet, Alexandre; Hansen, Hubert; Brugiere, Timothee; Costa, Pedro; Borgnat, Pierre
2015-01-01
The measurement of the position of the chiral critical end point (CEP) in the QCD phase diagram is under debate. While it is possible to predict its position by using effective models specifically built to reproduce some of the features of the underlying theory (QCD), the quality of the predictions (e.g., the CEP position) obtained by such effective models, depends on whether solving the model equations constitute a well- or ill-posed inverse problem. Considering these predictions as being inverse problems provides tools to evaluate if the problem is ill-conditioned, meaning that infinitesimal variations of the inputs of the model can cause comparatively large variations of the predictions. If it is ill-conditioned, it has major consequences because of finite variations that could come from experimental and/or theoretical errors. In the following, we shall apply such a reasoning on the predictions of a particular Nambu-Jona-Lasinio model within the mean field + ring approximations, with special attention to the prediction of the chiral CEP position in the (T-μ) plane. We find that the problem is ill-conditioned (i.e. very sensitive to input variations) for the T-coordinate of the CEP, whereas, it is well-posed for the μ-coordinate of the CEP. As a consequence, when the chiral condensate varies in a 10MeV range, μ CEP varies far less. As an illustration to understand how problematic this could be, we show that the main consequence when taking into account finite variation of the inputs, is that the existence of the CEP itself cannot be predicted anymore: for a deviation as low as 0.6% with respect to vacuum phenomenology (well within the estimation of the first correction to the ring approximation) the CEP may or may not exist. (orig.)
Laser Writing of Multiscale Chiral Polymer Metamaterials
Directory of Open Access Journals (Sweden)
E. P. Furlani
2012-01-01
Full Text Available A new approach to metamaterials is presented that involves laser-based patterning of novel chiral polymer media, wherein chirality is realized at two distinct length scales, intrinsically at the molecular level and geometrically at a length scale on the order of the wavelength of the incident field. In this approach, femtosecond-pulsed laser-induced two-photon lithography (TPL is used to pattern a photoresist-chiral polymer mixture into planar chiral shapes. Enhanced bulk chirality can be realized by tuning the wavelength-dependent chiral response at both the molecular and geometric level to ensure an overlap of their respective spectra. The approach is demonstrated via the fabrication of a metamaterial consisting of a two-dimensional array of chiral polymer-based L-structures. The fabrication process is described and modeling is performed to demonstrate the distinction between molecular and planar geometric-based chirality and the effects of the enhanced multiscale chirality on the optical response of such media. This new approach to metamaterials holds promise for the development of tunable, polymer-based optical metamaterials with low loss.
Chiral unitary theory: Application to nuclear problems
Indian Academy of Sciences (India)
Sept. 2001 physics pp. 417–431. Chiral unitary theory: Application to nuclear problems ... parameters which are adjusted to the data or alternatively derived in some models. Chiral perturbation theory up ..... consistent with a large broadening of the and more experimental studies are under way at GSI (HADES collaboration) ...
Chiralities of spiral waves and their transitions
Pan, Jun-ting; Cai, Mei-chun; Li, Bing-wei; Zhang, Hong
2013-06-01
The chiralities of spiral waves usually refer to their rotation directions (the turning orientations of the spiral temporal movements as time elapses) and their curl directions (the winding orientations of the spiral spatial geometrical structures themselves). Traditionally, they are the same as each other. Namely, they are both clockwise or both counterclockwise. Moreover, the chiralities are determined by the topological charges of spiral waves, and thus they are conserved quantities. After the inwardly propagating spirals were experimentally observed, the relationship between the chiralities and the one between the chiralities and the topological charges are no longer preserved. The chiralities thus become more complex than ever before. As a result, there is now a desire to further study them. In this paper, the chiralities and their transition properties for all kinds of spiral waves are systemically studied in the framework of the complex Ginzburg-Landau equation, and the general relationships both between the chiralities and between the chiralities and the topological charges are obtained. The investigation of some other models, such as the FitzHugh-Nagumo model, the nonuniform Oregonator model, the modified standard model, etc., is also discussed for comparison.
Polarizabilities of the beryllium clock transition
International Nuclear Information System (INIS)
Mitroy, J.
2010-01-01
The polarizabilities of the three lowest states of the beryllium atom are determined from a large basis configuration interaction calculation. The polarizabilities of the 2s 2 1 S e ground state (37.73a 0 3 ) and the 2s2p 3 P 0 o metastable state (39.04a 0 3 ) are found to be very similar in size and magnitude. This leads to an anomalously small blackbody radiation shift at 300 K of -0.018(4) Hz for the 2s 2 1 S e -2s2p 3 P 0 o clock transition. Magic wavelengths for simultaneous trapping of the ground and metastable states are also computed.
Induction of Chirality in Two-Dimensional Nanomaterials: Chiral 2D MoS2 Nanostructures.
Purcell-Milton, Finn; McKenna, Robert; Brennan, Lorcan J; Cullen, Conor P; Guillemeney, Lilian; Tepliakov, Nikita V; Baimuratov, Anvar S; Rukhlenko, Ivan D; Perova, Tatiana S; Duesberg, Georg S; Baranov, Alexander V; Fedorov, Anatoly V; Gun'ko, Yurii K
2018-02-27
Two-dimensional (2D) nanomaterials have been intensively investigated due to their interesting properties and range of potential applications. Although most research has focused on graphene, atomic layered transition metal dichalcogenides (TMDs) and particularly MoS 2 have gathered much deserved attention recently. Here, we report the induction of chirality into 2D chiral nanomaterials by carrying out liquid exfoliation of MoS 2 in the presence of chiral ligands (cysteine and penicillamine) in water. This processing resulted in exfoliated chiral 2D MoS 2 nanosheets showing strong circular dichroism signals, which were far past the onset of the original chiral ligand signals. Using theoretical modeling, we demonstrated that the chiral nature of MoS 2 nanosheets is related to the presence of chiral ligands causing preferential folding of the MoS 2 sheets. There was an excellent match between the theoretically calculated and experimental spectra. We believe that, due to their high aspect ratio planar morphology, chiral 2D nanomaterials could offer great opportunities for the development of chiroptical sensors, materials, and devices for valleytronics and other potential applications. In addition, chirality plays a key role in many chemical and biological systems, with chiral molecules and materials critical for the further development of biopharmaceuticals and fine chemicals, and this research therefore should have a strong impact on relevant areas of science and technology such as nanobiotechnology, nanomedicine, and nanotoxicology.
International Nuclear Information System (INIS)
Zeeb, G.
2006-01-01
In this thesis the thermodynamical properties of strongly interacting hadronic matter and the microscopic in-medium properties of hadrons are investigated at high temperatures and high baryonic densities within a chiral flavor-SU(3) model. The applied model is a generalized σ-ω model in mean-field approximation with baryons and mesons as effective degrees of freedom. It is built on spontaneously broken chiral symmetry and scale invariance. The phase transition behavior is systematically analyzed and is thus shown to depend significantly on the couplings of additional heavier hadronic degrees of freedom. A phase diagram in qualitative agreement with current lattice QCD (lQCD) calculations can result from an according coupling of the lowest lying baryonic decuplet to the model. Alternatively, the coupling of a heavy baryonic test-resonance is investigated, which effectively represents the spectrum of the heavy hadronic states. For a certain range of parameters one can even obtain a phase diagram in quantitative agreement with the lQCD calculations and, simultaneously, a successful description of the ground state properties of nuclear matter. It is shown that (within the model assumptions) the phase transition region is experimentally accessible for the CBM experiment at the upcoming FAIR facility at GSI Darmstadt. The chiral model is further applied to particle yield ratios measured in heavy-ion collisions from AGS, SPS and RHIC. For these investigations parameter sets with strongly differing phase diagrams due to different couplings of the baryon decuplet are used and in addition an ideal hadron gas. At the lower and mid collision energies the chiral parameter sets show an improved description as compared to the ideal hadron gas, especially for parameter sets with phase diagrams similar to the lQCD predictions. The interaction within the chiral model leads to in-medium modifications of the chemical potentials and the hadron masses. Therefore the resulting freeze
Quantum Gravitational Force Between Polarizable Objects
Ford, L. H.; Hertzberg, Mark P.; Karouby, J.
2016-04-01
Since general relativity is a consistent low energy effective field theory, it is possible to compute quantum corrections to classical forces. Here we compute a quantum correction to the gravitational potential between a pair of polarizable objects. We study two distant bodies and compute a quantum force from their induced quadrupole moments due to two-graviton exchange. The effect is in close analogy to the Casimir-Polder and London-van der Waals forces between a pair of atoms from their induced dipole moments due to two photon exchange. The new effect is computed from the shift in vacuum energy of metric fluctuations due to the polarizability of the objects. We compute the potential energy at arbitrary distances compared to the wavelengths in the system, including the far and near regimes. In the far distance, or retarded, regime, the potential energy takes on a particularly simple form: V (r )=-3987 ℏc G2α1 Sα2 S/(4 π r11) , where α1 S , α2 S are the static gravitational quadrupole polarizabilities of each object. We provide estimates of this effect.
Axial polarizability and weak currents in nuclei
International Nuclear Information System (INIS)
Ericson, M.
1977-01-01
The weak interaction nucleonic coupling constants in nuclei are modified by the presence of the neighbouring nucleons. One type of modification is due to the virtual excitation of the isobars through meson exchange. The influence of the isobars is described by means of the nuclear axial polarizability coefficient. This polarizability is known; it is linked to the p-wave πN scattering volume. A relation is derived between the axial nuclear current and the pion field which incorporates the polarizability effects. This relation has an electromagnetic analogue. It is then possible to derive the axial and pseudoscalar coupling constants from a knowledge of the pion field. This field in turn obeys a Klein-Gordon equation which has to include the isobaric excitations. The propagation of the pion field is similar to that of an electromagnetic wave in a dielectric medium. The strong interaction coupling constant is shown to be renormalized in nuclei by the effect of the various types of correlations. (author)
Lin, Fang-Yu; MacKerell, Alexander D
2018-02-13
The quality of the force field is crucial to ensure the accuracy of simulations used in molecular modeling, including computer-aided drug design (CADD). To perform more accurate modeling and simulations of halogenated molecules, in this study the polarizable force field based on the classical Drude oscillator model was extended to both aliphatic and aromatic systems using halogenated ethane and benzene model compounds for the halogens F, Cl, Br, and I. The force field parameters were optimized targeting quantum mechanical dipole moments, water interactions, and molecular polarizabilities as well as experimental observables, including enthalpies of vaporization, molecular volumes, hydration free energies, and dielectric constants. The developed halogenated polarizable force field is capable of reproducing QM relative energies and geometries of both halogen bonds and halogen-hydrogen bond donor interactions at an unprecedented level due to the inclusion of a virtual particle and anisotropic atomic polarizability on the halogen and, notably, the inclusion of Lennard-Jones parameters on the halogen Drude particle. The model was validated on the basis of its ability to accurately reproduce pure solvent properties for halogenated naphthalenes and alkanes, including species analogous to those used as refrigerants. Accordingly, it is anticipated that the model will be applicable for the study of halogenated derivatives in CADD as well as in other chemical and biophysical studies.
Kahle, Kimberly A; Foley, Joe P
2007-06-01
The first simultaneous use of a chiral surfactant and a chiral oil for microemulsion EKC (MEEKC) is reported. Six stereochemical combinations of dodecoxycarbonylvaline (DDCV: R, S, or racemic, 2.00% w/v), racemic 2-hexanol (1.65% v/v), and dibutyl tartrate (D, L, or racemic, 1.23% v/v) were examined as chiral pseudostationary phases (PSPs) for the separation of six pairs of pharmaceutical enantiomers: pseudoephedrine, ephedrine, N-methyl ephedrine, metoprolol, synephrine, and atenolol. Subtle differences were observed for three chromatographic figures of merit (alpha(enant), alpha(meth), k) among the chiral microemulsions; a moderate difference was observed for efficiency (N) and elution range. Dual-chirality microemulsions provided both the largest and smallest enantioselectivities, due to small positive and negative synergies between the chiral microemulsion components. For the ephedrine family of compounds, dual-chiral microemulsions with surfactant and oil in opposite stereochemical configurations provided higher enantioselectivities than the single-chiral component microemulsion (RXX), whereas dual-chiral microemulsions with surfactant and oil in the same stereochemical configurations provided lower enantioselectivities than RXX. Slight to moderate enantioselective synergies were confirmed using a thermodynamic model. Efficiencies observed with microemulsions comprised of racemic dibutyl tartrate or dibutyl-D-tartrate were significantly higher than those obtained with dibutyl-L-tartrate, with an average difference in plate count of about 25 000. Finally, one two-chiral-component microemulsion (RXS) provided significantly better resolution than the remaining one- and two-chiral-component microemulsions for the ephedrine-based compounds, but only slightly better or equivalent resolution for non-ephedrine compounds.
Small, Meagan C.; Aytenfisu, Asaminew H.; Lin, Fang-Yu; He, Xibing; MacKerell, Alexander D.
2017-04-01
The majority of computer simulations exploring biomolecular function employ Class I additive force fields (FF), which do not treat polarization explicitly. Accordingly, much effort has been made into developing models that go beyond the additive approximation. Development and optimization of the Drude polarizable FF has yielded parameters for selected lipids, proteins, DNA and a limited number of carbohydrates. The work presented here details parametrization of aliphatic aldehydes and ketones (viz. acetaldehyde, propionaldehyde, butaryaldehyde, isobutaryaldehyde, acetone, and butanone) as well as their associated acyclic sugars ( d-allose and d-psicose). LJ parameters are optimized targeting experimental heats of vaporization and molecular volumes, while the electrostatic parameters are optimized targeting QM water interactions, dipole moments, and molecular polarizabilities. Bonded parameters are targeted to both QM and crystal survey values, with the models for ketones and aldehydes shown to be in good agreement with QM and experimental target data. The reported heats of vaporization and molecular volumes represent a compromise between the studied model compounds. Simulations of the model compounds show an increase in the magnitude and the fluctuations of the dipole moments in moving from gas phase to condensed phases, which is a phenomenon that the additive FF is intrinsically unable to reproduce. The result is a polarizable model for aliphatic ketones and aldehydes including the acyclic sugars d-allose and d-psicose, thereby extending the available biomolecules in the Drude polarizable FF.
Chiral Inorganic Nanostructures.
Ma, Wei; Xu, Liguang; de Moura, André F; Wu, Xiaoling; Kuang, Hua; Xu, Chuanlai; Kotov, Nicholas A
2017-06-28
The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of individual nanoparticles (NPs) and their assemblies and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others. Multiple chiral geometries were observed with characteristic scales from ångströms to microns. Uniquely high values of chiral anisotropy factors that spurred the development of the field and differentiate it from chiral structures studied before, are now well understood; they originate from strong resonances of incident electromagnetic waves with plasmonic and excitonic states typical for metals and semiconductors. At the same time, distinct similarities with chiral supramolecular and biological systems also emerged. They can be seen in the synthesis and separation methods, chemical properties of individual NPs, geometries of the nanoparticle assemblies, and interactions with biological membranes. Their analysis can help us understand in greater depth the role of chiral asymmetry in nature inclusive of both earth and space. Consideration of both differences and similarities between chiral inorganic, organic, and biological nanostructures will also accelerate the development of technologies based on chiroplasmonic and chiroexcitonic effects. This review will cover both experiment and theory of chiral nanostructures starting with the origin and multiple components of mirror asymmetry of individual NPs and their assemblies. We shall consider four different types of chirality in nanostructures and related physical, chemical, and
The static polarizability and second hyperpolarizability of fullerenes and carbon nanotubes
Jensen, L; Astrand, PO; Mikkelsen, KV
2004-01-01
Utilizing a point-dipole interaction model, we present an investigation of the static polarizability and second hyperpolarizability of fullerenes and carbon nanotubes by varying their structure. The following effects are investigated: (1) the length dependence of the components of the static
Fusion rules of chiral algebras
International Nuclear Information System (INIS)
Gaberdiel, M.
1994-01-01
Recently we showed that for the case of the WZW and the minimal models fusion can be understood as a certain ring-like tensor product of the symmetry algebra. In this paper we generalize this analysis to arbitrary chiral algebras. We define the tensor product of conformal field theory in the general case and prove that it is associative and symmetric up to equivalence. We also determine explicitly the action of the chiral algebra on this tensor product. In the second part of the paper we demonstrate that this framework provides a powerful tool for calculating restrictions for the fusion rules of chiral algebras. We exhibit this for the case of the W 3 algebra and the N=1 and N=2 NS superconformal algebras. (orig.)
Chirally motivated K- nuclear potentials
International Nuclear Information System (INIS)
Cieply, A.; Friedman, E.; Gal, A.; Gazda, D.; Mares, J.
2011-01-01
In-medium subthreshold K-bar N scattering amplitudes calculated within a chirally motivated meson-baryon coupled-channel model are used self consistently to confront K - atom data across the periodic table. Substantially deeper K - nuclear potentials are obtained compared to the shallow potentials derived in some approaches from threshold K-bar N amplitudes, with ReV K chiral =-(85±5) MeV at nuclear matter density. When K-bar NN contributions are incorporated phenomenologically, a very deep K - nuclear potential results, ReV K c hiral+phen. =-(180±5) MeV, in agreement with density dependent potentials obtained in purely phenomenological fits to the data. Self consistent dynamical calculations of K - -nuclear quasibound states generated by V K chiral are reported and discussed.
Chiral symmetry on the lattice
Energy Technology Data Exchange (ETDEWEB)
Creutz, M.
1994-11-01
The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model.
Chiral symmetry on the lattice
International Nuclear Information System (INIS)
Creutz, M.
1994-11-01
The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model
Communication: Permanent dipoles contribute to electric polarization in chiral NMR spectra
International Nuclear Information System (INIS)
Buckingham, A. David
2014-01-01
Nuclear magnetic resonance spectroscopy is blind to chirality because the spectra of a molecule and its mirror image are identical unless the environment is chiral. However, precessing nuclear magnetic moments in chiral molecules in a strong magnetic field induce an electric polarization through the nuclear magnetic shielding polarizability. This effect is equal and opposite for a molecule and its mirror image but is small and has not yet been observed. It is shown that the permanent electric dipole moment of a chiral molecule is partially oriented through the antisymmetric part of the nuclear magnetic shielding tensor, causing the electric dipole to precess with the nuclear magnetic moment and producing a much larger temperature-dependent electric polarization with better prospects of detection
On chiral and non chiral 1D supermultiplets
International Nuclear Information System (INIS)
Toppan, Francesco
2011-01-01
In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)
On chiral and non chiral 1D supermultiplets
Energy Technology Data Exchange (ETDEWEB)
Toppan, Francesco, E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (TEO/CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Fisica Teorica
2011-07-01
In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)
Radiation damping of a polarizable particle
Novotny, Lukas
2017-09-01
A polarizable body moving in an external electromagnetic field will slow down. This effect is referred to as radiation damping and is analogous to Doppler cooling in atomic physics. Using the principles of special relativity we derive an expression for the radiation damping force and find that it solely depends on the scattered power. The cooling of the particle's center-of-mass motion is balanced by heating due to radiation pressure shot noise, giving rise to an equilibrium that depends on the ratio of the field's frequency and the particle's mass. While damping is of relativistic nature, heating has its roots in quantum mechanics.
Radiative corrections for pion polarizability experiments
International Nuclear Information System (INIS)
Akhundov, A.A.; Gerzon, S.; Kananov, S.; Moinester, M.A.
1994-08-01
We use the semi-analytical program RCFORGV to evaluate radiative corrections to one-photon radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic number Z. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect is α rc π =-β rc π =(0.20±0.05) x 10 -43 cm 3 , for pion energies 40-600 GeV. We also study the range of applicability of the equivalent photon approximation in describing one-photon radiative emission. (author). 21 refs, 6 figs, 1 tab
Relativistic corrections to molecular dynamic dipole polarizabilities
DEFF Research Database (Denmark)
Kirpekar, Sheela; Oddershede, Jens; Jensen, Hans Jørgen Aagaard
1995-01-01
in the correlated calculations, as has also been observed for other properties. For SnH4 the correlation contribution and the pure relativistic correction are of the same order of magnitude, whereas for PbH 4 the relativistic correction becomes more important than the correlation contribution. We report estimated...... Cauchy moments, obtained from fitting the dispersion of the calculated corrections as a function of ω2. The frequency dependence of the nonrelativistic polarizability is most pronounced at the correlated level, mainly due to lower excitation energies in the multiconfigurational calculations than those...
Directory of Open Access Journals (Sweden)
Gustavo Cabrera
2017-11-01
Full Text Available The procedure for the synthesis of 3-cyano-4-hydroxycoumarin is presented along with the results from the analysis of its tautomeric equilibrium using Density Functional Theory (DFT and Polarizable Continuum Model (PCM. The geometry of the compounds was optimized with Gaussian 03 and from the resulting structures, a group of thermodynamic and kinetic parameters were determined. It was found that 3-cyano-4-hydroxycoumarin was the most stable tautomer, as was also shown by spectroscopic techniques. Other parameters, such as: transition state energy, equlibrium constant, kinetic constant, bond orders and bond angles, were also calculated.
Nuclear magnetic resonance J coupling constant polarizabilities of hydrogen peroxide
DEFF Research Database (Denmark)
Kjær, Hanna; Nielsen, Monia R.; Pagola, Gabriel I.
2012-01-01
In this paper we present the so far most extended investigation of the calculation of the coupling constant polarizability of a molecule. The components of the coupling constant polarizability are derivatives of the NMR indirect nuclear spin-spin coupling constant with respect to an external elec...
Towards Molecular Dynamics Simulations of Chiral Room-Temperature Ionic Liquids
Czech Academy of Sciences Publication Activity Database
Lísal, Martin; Chval, Z.; Storch, Jan; Izák, Pavel
2014-01-01
Roč. 189, SI (2014), s. 85-94 ISSN 0167-7322 R&D Projects: GA ČR(CZ) GAP106/12/0569; GA MŠk LH12020 Institutional support: RVO:67985858 Keywords : chiral room-temperature ionic liquid * molecular dynamics simulation * non-polarizable fully flexible all-atom force field Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.515, year: 2014
Zschiesche, D; Greiner, W; Schramm, S; 10.1103/PhysRevC.65.064902
2002-01-01
The space-time dynamics and pion-Hanbury Brown-Twiss (HBT) radii in central heavy ion collisions at CERN-SPS and BNL-RHIC are investigated within a hydrodynamic simulation. The dependence of the dynamics and the HBT parameters on the equation of state (EOS) is studied with different parametrizations of a chiral SU(3) sigma - omega model. The self-consistent collective expansion includes the effects of effective hadron masses, generated by the nonstrange and strange scalar condensates. Different chiral EOS show different types of phase transitions and even a crossover. The influence of the order of the phase transition and of the latent heat on the space-time dynamics and pion-HBT radii is studied. A small latent heat, i.e., a weak first-order chiral phase transition, or a smooth crossover lead to distinctly different HBT predictions than a strong first order phase transition. A quantitative description of the data, both at SPS energies as well as at RHIC energies, appears difficult to achieve within the ideal...
Size-scaling behaviour of the electronic polarizability of one-dimensional interacting systems
Chiappe, G.; Louis, E.; Vergés, J. A.
2018-05-01
Electronic polarizability of finite chains is accurately calculated from the total energy variation of the system produced by small but finite static electric fields applied along the chain direction. Normalized polarizability, that is, polarizability divided by chain length, diverges as the second power of length for metallic systems but approaches a constant value for insulating systems. This behaviour provides a very convenient way to characterize the wave-function malleability of finite systems as it avoids the need of attaching infinite contacts to the chain ends. Hubbard model calculations at half filling show that the method works for a small U = 1 interaction value that corresponds to a really small spectral gap of 0.005 (hopping t = ‑1 is assumed). Once successfully checked, the method has been applied to the long-range hopping model of Gebhard and Ruckenstein showing 1/r hopping decay (Gebhard and Ruckenstein 1992 Phys. Rev. Lett. 68 244; Gebhard et al 1994 Phys. Rev. B 49 10926). Metallicity for U values below the reported metal-insulator transition is obtained but the surprise comes for U values larger than the critical one (when a gap appears in the spectral density of states) because a steady increase of the normalized polarizability with size is obtained. This critical size-scaling behaviour can be understood as corresponding to a molecule which polarizability is unbounded. We have checked that a real transfer of charge from one chain end to the opposite occurs as a response to very small electric fields in spite of the existence of a large gap of the order of U for one-particle excitations. Finally, ab initio quantum chemistry calculations of realistic poly-acetylene chains prove that the occurrence of such critical behaviour in real systems is unlikely.
Fürthauer, S; Strempel, M; Grill, S W; Jülicher, F
2012-09-01
Active processes in biological systems often exhibit chiral asymmetries. Examples are the chirality of cytoskeletal filaments which interact with motor proteins, the chirality of the beat of cilia and flagella as well as the helical trajectories of many biological microswimmers. Here, we derive constitutive material equations for active fluids which account for the effects of active chiral processes. We identify active contributions to the antisymmetric part of the stress as well as active angular momentum fluxes. We discuss four types of elementary chiral motors and their effects on a surrounding fluid. We show that large-scale chiral flows can result from the collective behavior of such motors even in cases where isolated motors do not create a hydrodynamic far field.
On the theory of electric double layer with explicit account of a polarizable co-solvent
International Nuclear Information System (INIS)
Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.
2016-01-01
We present a continuation of our theoretical research into the influence of co-solvent polarizability on a differential capacitance of the electric double layer. We formulate a modified Poisson-Boltzmann theory, using the formalism of density functional approach on the level of local density approximation taking into account the electrostatic interactions of ions and co-solvent molecules as well as their excluded volume. We derive the modified Poisson-Boltzmann equation, considering the three-component symmetric lattice gas model as a reference system and minimizing the grand thermodynamic potential with respect to the electrostatic potential. We apply present modified Poisson-Boltzmann equation to the electric double layer theory, showing that accounting for the excluded volume of co-solvent molecules and ions slightly changes the main result of our previous simplified theory. Namely, in the case of small co-solvent polarizability with its increase under the enough small surface potentials of electrode, the differential capacitance undergoes the significant growth. Oppositely, when the surface potential exceeds some threshold value (which is slightly smaller than the saturation potential), the increase in the co-solvent polarizability results in a differential capacitance decrease. However, when the co-solvent polarizability exceeds some threshold value, its increase generates a considerable enhancement of the differential capacitance in a wide range of surface potentials. We demonstrate that two qualitatively different behaviors of the differential capacitance are related to the depletion and adsorption of co-solvent molecules at the charged electrode. We show that an additive of the strongly polarizable co-solvent to an electrolyte solution can shift significantly the saturation potential in two qualitatively different manners. Namely, a small additive of strongly polarizable co-solvent results in a shift of saturation potential to higher surface potentials. On
On the theory of electric double layer with explicit account of a polarizable co-solvent.
Budkov, Yu A; Kolesnikov, A L; Kiselev, M G
2016-05-14
We present a continuation of our theoretical research into the influence of co-solvent polarizability on a differential capacitance of the electric double layer. We formulate a modified Poisson-Boltzmann theory, using the formalism of density functional approach on the level of local density approximation taking into account the electrostatic interactions of ions and co-solvent molecules as well as their excluded volume. We derive the modified Poisson-Boltzmann equation, considering the three-component symmetric lattice gas model as a reference system and minimizing the grand thermodynamic potential with respect to the electrostatic potential. We apply present modified Poisson-Boltzmann equation to the electric double layer theory, showing that accounting for the excluded volume of co-solvent molecules and ions slightly changes the main result of our previous simplified theory. Namely, in the case of small co-solvent polarizability with its increase under the enough small surface potentials of electrode, the differential capacitance undergoes the significant growth. Oppositely, when the surface potential exceeds some threshold value (which is slightly smaller than the saturation potential), the increase in the co-solvent polarizability results in a differential capacitance decrease. However, when the co-solvent polarizability exceeds some threshold value, its increase generates a considerable enhancement of the differential capacitance in a wide range of surface potentials. We demonstrate that two qualitatively different behaviors of the differential capacitance are related to the depletion and adsorption of co-solvent molecules at the charged electrode. We show that an additive of the strongly polarizable co-solvent to an electrolyte solution can shift significantly the saturation potential in two qualitatively different manners. Namely, a small additive of strongly polarizable co-solvent results in a shift of saturation potential to higher surface potentials. On
Kesselgruber, Martin
2001-01-01
The element of planar chirality turned out to be of special importance to achieve high enantioselectivities in various asymmetric processes. In the course of this PhD thesis, the sulfoximine unit was established as a new chiral ortho-directing group for ferrocenes. By variation of the metal fragment and other structural properties of a published chiral ligand, a cyclopentadienylrhenium(I)tricarbonyl complex was identified as more selective than the original ferrocene system in the asymmetric ...
8th International Workshop on Chiral Dynamics
2016-01-01
The International Workshop on Chiral Dynamics 2015, the eighth in a series which started in 1994 at MIT, and was later held in Mainz (1997), Jefferson Lab (2000 and 2012), Bonn (2003), Duke (2006) and Bern (2009), will take place in Pisa, from June 29 to July 3 2015, and will be jointly hosted by the Department of Physics of the University of Pisa and the Pisa branch of the Istituto Nazionale di Fisica Nucleare. The purpose of this workshop series is to bring physicists together who are active in this field, as well as those who are interested, to discuss and debate the most recent achievements and future developments. The workshop will have a near equal contribution from theorists and experimentalists and, as in the latest editions, a strong synergy with the lattice community will be present. Topics: Hadron structure Isospin breaking in hadronic systems Meson-meson and meson-baryon interaction Effective field theory and chiral perturbation theory Few-body physics Compton scattering and the polarizabilities o...
{E2}/{M1} and {C2}/{M1} for the electroproduction of the Δ(1232) in the chiral quark-soliton model
Urbano, D.; Silva, A.; Fiolhais, M.; Watabe, T.; Goeke, K.
2000-04-01
We present the ratios {E2}/{M1} and {C2}/{M1} for the electroproduction of the Δ(1232) in the interval of photon virtuality 0 < - q2 < 1 GeV 2. The model used is the chiral quark-soliton model, which is treated in the framework of large number of colours ( Nc). The results presented refer to flavours SU(2) and SU(3) and are found to underestimate the most recent experimental results, however showing a good agreement regarding the dependence with - q2.
DEFF Research Database (Denmark)
Esparza-Isunza, T.; González-Brambila, M.; Gani, Rafiqul
2015-01-01
In this study we consider the theoretical coupling of an otherwise thermodynamically limited ω-transaminase reaction to an Oppenauer oxidation, in order to shift the equilibria of both reactions, with the aim of achieving a significant (and important) increase in the yield of the desired chiral...... sequentially in fed batch–batch mode. Both reactors are interconnected through a semi-permeable membrane, where multicomponent intra-membrane transport takes place by diffusion and viscous flow. The kinetic modeling of both reactions has been carried out and model simulations show that in this way...
Out of equilibrium phase transitions and a toy model for disoriented chiral condensates
International Nuclear Information System (INIS)
Bedaque, P.F.; Das, A.
1993-07-01
We study the dynamics of a second order phase transition in a situation that mimics a sudden quench to a temperature below the critical temperature in a model with dynamical symmetry breaking. In particular we show that the domains of correlated values of the condensate grow as √t and that this result seems to be largely model independent. (author). 9 refs
Doped Chiral Polymer Metamaterials Project
National Aeronautics and Space Administration — Doped Chiral Polymer Metamaterials (DCPM) with tunable resonance frequencies have been developed by adding plasmonic inclusions into chiral polymers with variable...
Energy Technology Data Exchange (ETDEWEB)
Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459 (Singapore); Du Yu, E-mail: du_yu@jlu.edu.cn, E-mail: yhyang@ntu.edu.sg [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)
2010-04-23
Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.
A chiral quark model for meson electroproduction in the S11 partial wave
International Nuclear Information System (INIS)
Golli, B.; Sirca, S.
2011-01-01
We calculate the meson scattering and electroproduction amplitudes in the S11 partial wave in a coupled-channel approach that incorporates quasi-bound quark-model states. Using the quark wave functions and the quark-meson interaction from the Cloudy Bag Model, we obtain a good overall agreement with the available experimental results for the partial widths of the N(1535) and the N(1650) resonances as well as for the pion, eta and kaon electroproduction amplitudes. Our model is consistent with the N(1535) resonance being dominantly a genuine three-quark state rather than a quasi-bound state of mesons and baryons. (orig.)
A quantitative analysis of instabilities in the linear chiral sigma model
International Nuclear Information System (INIS)
Nemes, M.C.; Nielsen, M.; Oliveira, M.M. de; Providencia, J. da
1990-08-01
We present a method to construct a complete set of stationary states corresponding to small amplitude motion which naturally includes the continuum solution. The energy wheighted sum rule (EWSR) is shown to provide for a quantitative criterium on the importance of instabilities which is known to occur in nonasymptotically free theories. Out results for the linear σ model showed be valid for a large class of models. A unified description of baryon and meson properties in terms of the linear σ model is also given. (author)
Green-Schwarz superstring as an asymmetric chiral field sigma model
International Nuclear Information System (INIS)
Isaev, A.P.; Ivanov, E.A.
1988-01-01
A new class of two-dimensional σ-models of the Wess-Zumino-Witten type is constructed. The target manifold of these models is coset space GxG/G - , where supergroup G is obtained by contraction from an arbitrary semisimple Lie supergroup and G - is some abelian supergroup of translations in GxG. It is shown that the equations of motion following from the Wess-Zumino-Witten type action of these models admit a zero-curvature representation. 16 refs
Density and polarizability of liquid 4He
International Nuclear Information System (INIS)
Kempin'ski, V.; Zhuk, T.; Stankovski, Ya.; Sitarzh, S.
1988-01-01
The temperature changes in the density of liquid helium are measured in the temperature range of 1.63 to 4.2 K.; Unlike the conventional pycnometric technique, the changes in the hydrostatic displacement of the liquid were determined. The cirrectness of the method chosen and the appropriate equipment for its realization are substantiated. The results obtained are in good agreement with those of other authors. On the basis of temperature measurements of the dependence of density ρ and permittivity ε, the dependence of polarizability A of liquid 4 He on temperature and density was calculated. The results obtained show an alternating character of the dependences A(T) and A(ρ). These dependences are found to correlate
An epistemological note on chirality
International Nuclear Information System (INIS)
Mislow, K.; Bickart, P.
1976-01-01
The terms ''chiral'' and ''achiral'' are sharply defined when applied to geometric figures or models. The same terms are also commonly used to refer to the real systems to which these models have been adjoined. e.g., molecules, solvents, or reagents. Here, the terms are not sharply defined but depend upon conditions or measurement. The contrast between the geometric and operational usages is discussed in detail
Heavy–light mesons in chiral AdS/QCD
Energy Technology Data Exchange (ETDEWEB)
Liu, Yizhuang, E-mail: yizhuang.liu@stonybrook.edu; Zahed, Ismail, E-mail: ismail.zahed@stonybrook.edu
2017-06-10
We discuss a minimal holographic model for the description of heavy–light and light mesons with chiral symmetry, defined in a slab of AdS space. The model consists of a pair of chiral Yang–Mills and tachyon fields with specific boundary conditions that break spontaneously chiral symmetry in the infrared. The heavy–light spectrum and decay constants are evaluated explicitly. In the heavy mass limit the model exhibits both heavy-quark and chiral symmetry and allows for the explicit derivation of the one-pion axial couplings to the heavy–light mesons.
Chiral bags, skyrmions and quarks in nuclei
International Nuclear Information System (INIS)
Rho, M.
1984-09-01
Recent developments on an intriguing connection between the quark-bag description of the baryons (nucleons in particular) and the Skyrmion model are discussed in terms of the constraints coming from chiral anomalies. Topics treated are the leaking baryon charge, axial charge and energy density; the role of chiral anomalies; the role of Skyrme's quartic term and the connection to the meson degrees of freedom; and finally some qualitative implications in nuclei. The presentation is purposely descriptive and intuitive instead of mathematically precise
Chen, Ting; Li, Shu-Ying; Wang, Dong; Wan, Li-Jun
2017-11-01
Noncovalently introducing stereogenic information is a promising approach to embed chirality in achiral molecular systems. However, the interplay of the noncovalently introduced chirality with the intrinsic chirality of molecules or molecular aggregations has rarely been addressed. We report a competitive chiral expression of the noncovalent interaction-mediated chirality induction and the intrinsic stereogenic center-controlled chirality induction in a two-dimensional (2D) molecular assembly at the liquid/solid interface. Two enantiomorphous honeycomb networks are formed by the coassembly of an achiral 5-(benzyloxy)isophthalic acid (BIC) derivative and 1-octanol at the liquid/solid interface. The preferential formation of the globally homochiral assembly can be achieved either by using the chiral analog of 1-octanol, ( S )-6-methyl-1-octanol, as a chiral coadsorber to induce chirality to the BIC assembly via noncovalent hydrogen bonding or by covalently linking a chiral center in the side chain of BIC. Both the chiral coadsorber and the intrinsically chiral BIC derivative can act as a chiral seeds to induce a preferred handedness in the assembly of the achiral BIC derivatives. Furthermore, the noncovalent interaction-mediated chirality induction can restrain or even overrule the manifestation of the intrinsic chirality of the BIC molecule and dominate the handedness of the 2D molecular coassembly. This study provides insight into the interplay of intrinsically chiral centers and external chiral coadsorbers in the chiral induction, transfer, and amplification processes of 2D molecular assembly.
Interfacial Structural Transition in Hydration Shells of a Polarizable Solute.
Dinpajooh, Mohammadhasan; Matyushov, Dmitry V
2015-05-22
Electrostatics of polar solvation is typically described by harmonic free energy functionals. Polarizability contributes a negative polarization term that can make the harmonic free energy negative. The harmonic truncation fails in this regime. Simulations of polarizable ideal dipoles in water show that water's susceptibility passes through a maximum in the range of polarizabilities zeroing the harmonic term out. The microscopic origin of the nonmonotonic behavior is an interfacial structural transition involving the density collapse of the first hydration layer and enhanced number of dangling OH bonds.
Kolesnikov, A L; Budkov, Yu A; Basharova, E A; Kiselev, M G
2017-06-21
The paper presents a theoretical approach for describing the influence of an electric field on the conformation of an electrically neutral dielectric polymer chain dissolved in a dielectric solvent with an admixture of a target compound. Each monomer and each molecule of the target compound carries positive excess polarizability and the solvent is described as a continuous dielectric medium. The model is based on the Flory-type mean-field theory. We demonstrate non-monotonic dependences of the expansion factor and the concentration of the target compound on the strength of the electric field and molecular polarizability. Namely, the target compound concentration in the internal polymer volume as a function of electric field strength has pronounced maxima if the molecules are polarizable. In addition, the expansion factor of the non-polarizable polymer chain can be controlled by the electric field. The dependences of the expansion factor and target compound concentration on the monomer polarizability exhibit minima and intersection points. The intersection points correspond to the equality of dielectric permittivities in the bulk solution and in the internal polymer volume.
Zhu, Hanyu
2018-02-01
Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing.
Investigation of the phase structure of a chirally-invariant Higgs-Yukawa model
Bulava, John; Hou, George W.-S.; Jansen, Karl; Knippschild, Bastian; Lin, C.-J.David; Nagai, Kei-Ichi; Nagy, Attila; Ogawa, Kenji
2012-01-01
We present new data on our ongoing project on the investigation of the phase structure of the Higgs-Yukawa model at large bare Yukawa couplings. The data presented last year are extended in terms of statistics, the number of bare Yukawa couplings at existing, and new larger volumes. In addition, this study is extended by a finite temperature project at the physical top quark mass m_t =175 GeV and a hypothetical fourth generation top quark with a mass of m_t' =700 GeV .
Polarizabilities and hyperpolarizabilities of the alkali metal atoms
Energy Technology Data Exchange (ETDEWEB)
Fuentealba, P. (Chile Univ., Santiago (Chile). Departamento de Fisica and Centro de Mecanica Cuantica Aplicada (CMCA)); Reyes, O. (Chile Univ., Santiago (Chile). Dept. de Fisica)
1993-08-14
The electric static dipole polarizability [alpha], quadrupole polarizability C, dipole-quadrupole polarizability B, and the second dipole hyperpolarizability [gamma] have been calculated for the alkali metal atoms in the ground state. The results are based on a pseudopotential which is able to incorporate the very important core-valence correlation effect through a core polarization potential, and, in an empirical way, the main relativistic effects. The calculated properties compare very well with more elaborated calculations for the Li atom, excepting the second hyperpolarizability [gamma]. For the other atoms, there is neither theoretical nor experimental information about most of the higher polarizabilities. Hence, the results of this paper should be seen as a first attempt to give a complete account of the series expansion of the interaction energy of an alkali metal atom and a static electric field. (author).
International Nuclear Information System (INIS)
Jacobson, Orit; Laky, Desideriu; Carlson, Kathryn E.; Elgavish, Sharona; Gozin, Michael; Even-Sapir, Einat; Leibovitc, Ilan; Gutman, Mordechai; Chisin, Roland; Katzenellenbogen, John A.; Mishani, Eyal
2006-01-01
Most prostate cancers are androgen dependent upon initial diagnosis. On the other hand, some very aggressive forms of prostate cancer were shown to have lost the expression of the androgen receptor (AR). Although the AR is routinely targeted in endocrine treatment, the clinical outcome remains suboptimal. Therefore, it is crucial to demonstrate the presence and activity of the AR in each case of prostate cancer, before and after treatment. While noninvasive positron emission tomography (PET) has the potential to determine AR expression of tumor cells in vivo, fully optimized PET imaging agents are not yet available. Based on molecular modeling, three novel derivatives of hydroxyflutamide (Compounds 1-3) were designed and synthesized. They contain an electron-rich group (dimethylamine) located on the methyl moiety, which may confer a better stability to the molecule in vivo. Compounds 1-3 have AR binding that is similar or higher than that of the currently used commercial drugs. An automated carbon-11 radiolabeling route was developed, and the compounds were successfully labeled with a 10-15% decay-corrected radiochemical yield, 99% radiochemical purity and a specific activity of 4Ci/μmol end of bombardment (n=15). These labeled biomarkers may facilitate the future quantitative molecular imaging of AR-positive prostate cancer using PET and may also allow for image-guided treatment of prostate cancer
On the use of pseudostates to calculate molecular polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Jones, Marc; Tennyson, Jonathan [Department of Physics and Astronomy, University College London, Gower St, London WC1E 6BT (United Kingdom)
2010-02-28
The polarizability of a molecule is an intrinsic property which is important for a large variety of problems. However, determining reliable values for these polarizabilities is not straightforward: for instance the standard sum over states formulation of the problem does not converge because of the need to include not only many excited states but also to allow for contributions from the continuum. Here a formulation of this technique is given which uses pseudostates to allow for physical and continuum states otherwise omitted from the expansion. The pseudostates are represented by even-tempered expansions of Gaussian-type orbitals at the molecular centre-of-mass. The method is tested for LiH, Li{sub 2}, water and CO molecules. For LiH and CO, calculations for the polarizability of low-lying excited states are presented including that for the A {sup 3}PI state of CO, whose polarizability appears not to have been previously determined. It is suggested that the use of pseudostates provides a straightforward method of calculating static polarizabilities of molecules in both ground and excited electronic states. The extension of the method to the calculation of dynamic polarizabilities is discussed.
Induced-Charge Enhancement of the Diffusion Potential in Membranes with Polarizable Nanopores.
Ryzhkov, I I; Lebedev, D V; Solodovnichenko, V S; Shiverskiy, A V; Simunin, M M
2017-12-01
When a charged membrane separates two salt solutions of different concentrations, a potential difference appears due to interfacial Donnan equilibrium and the diffusion junction. Here, we report a new mechanism for the generation of a membrane potential in polarizable conductive membranes via an induced surface charge. It results from an electric field generated by the diffusion of ions with different mobilities. For uncharged membranes, this effect strongly enhances the diffusion potential and makes it highly sensitive to the ion mobilities ratio, electrolyte concentration, and pore size. Theoretical predictions on the basis of the space-charge model extended to polarizable nanopores fully agree with experimental measurements in KCl and NaCl aqueous solutions.
Isotensor Axial Polarizability and Lattice QCD Input for Nuclear Double-β Decay Phenomenology
Shanahan, Phiala E.; Tiburzi, Brian C.; Wagman, Michael L.; Winter, Frank; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas; Savage, Martin J.; Nplqcd Collaboration
2017-08-01
The potential importance of short-distance nuclear effects in double-β decay is assessed using a lattice QCD calculation of the n n →p p transition and effective field theory methods. At the unphysical quark masses used in the numerical computation, these effects, encoded in the isotensor axial polarizability, are found to be of similar magnitude to the nuclear modification of the single axial current, which phenomenologically is the quenching of the axial charge used in nuclear many-body calculations. This finding suggests that nuclear models for neutrinoful and neutrinoless double-β decays should incorporate this previously neglected contribution if they are to provide reliable guidance for next-generation neutrinoless double-β decay searches. The prospects of constraining the isotensor axial polarizabilities of nuclei using lattice QCD input into nuclear many-body calculations are discussed.
Polarizability of Kr6+ from high-L Kr5+ fine-structure measurements
International Nuclear Information System (INIS)
Lundeen, S. R.; Fehrenbach, C. W.
2007-01-01
The transition between n=55 and n=109 Rydberg levels of Kr 5+ has been studied at high resolution using the resonant excitation stark ionization spectroscopy method. Resolved excitation of L=6, 7, 8, and 9 levels in n=55 lead to a determination of the fine-structure energies of these levels. Interpreted with the long-range polarization model, this leads to a measurement of the dipole polarizabilities of Zn-like Kr 6+ , α d =2.69(4)a 0 3 . Obtaining a value of the quadrupole polarizability from the data will require additional theoretical input. Factors contributing to the signal and noise levels in measurements of this type are discussed
Spectral signatures of chirality
DEFF Research Database (Denmark)
Pedersen, Jesper Goor; Mortensen, Asger
2009-01-01
We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...
Sadofyev, Andrey; Sen, Srimoyee
2018-02-01
The linearized Einstein equation describing graviton propagation through a chiral medium appears to be helicity dependent. We analyze features of the corresponding spectrum in a collision-less regime above a flat background. In the long wave-length limit, circularly polarized metric perturbations travel with a helicity dependent group velocity that can turn negative giving rise to a new type of an anomalous dispersion. We further show that this chiral anomalous dispersion is a general feature of polarized modes propagating through chiral plasmas extending our result to the electromagnetic sector.
Characterization of chiral mesoporous materials by transmission electron microscopy.
Ohsuna, Tetsu; Liu, Zheng; Che, Shunai; Terasaki, Osamu
2005-02-01
By using transmission electron microscopy (TEM), the chirality of novel mesoporous materials has been studied. In addition, a computer simulation that uses a simple structural model was employed. The existence of chiral channels inside a tubelike material was confirmed by the observation of fringes along the length of the tubes. The chiral pitch of the channels was measured from the intermittent period, the chirality (right- or left-handed) was determined from the tilt direction of a tube compared with the direction of incident electrons and the curvature direction of the curved intermitted fringes as viewed in the TEM images.
Chiral nucleon-nucleon forces in nuclear structure calculations
Directory of Open Access Journals (Sweden)
Coraggio L.
2016-01-01
Full Text Available Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.
Energy Technology Data Exchange (ETDEWEB)
Gerhold, P. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)
2007-05-15
We consider a chirally invariant lattice Higgs-Yukawa model based on the Neuberger overlap operator D{sup (ov)}. As a first step towards the eventual determination of Higgs mass bounds we study the phase diagram of the model analytically in the large N{sub f}-limit. We present an expression for the effective potential at tree-level in the regime of small Yukawa and quartic coupling constants and determine the order of the phase transitions. In the case of strong Yukawa couplings the model effectively becomes an O(4)-symmetric non-linear {sigma}-model for all values of the quartic coupling constant. This leads to the existence of a symmetric phase also in the regime of large values of the Yukawa coupling constant. On finite and small lattices, however, strong finite volume effects prevent the expectation value of the Higgs field from vanishing thus obscuring the existence of the symmetric phase at strong Yukawa couplings. (orig.)
Indian Academy of Sciences (India)
to those articles for a more expatiated presentation of numerical results. In addition, I re- fer to the .... The soliton profile F(r) is then obtained from extremizing E self-consistently [3]. States possessing good .... 95% or more by their valence quark (18) contributions once the self-consistent soliton is substituted. This provides ...
Molecular-Level Design of Heterogeneous Chiral Catalysis
International Nuclear Information System (INIS)
Zaera, Francisco
2012-01-01
The following is a proposal to continue our multi-institutional research on heterogeneous chiral catalysis. Our team combines the use of surface-sensitive analytical techniques for the characterization of model systems with quantum and statistical mechanical calculations to interpret experimental data and guide the design of future research. Our investigation focuses on the interrelation among the three main mechanisms by which enantioselectivity can be bestowed to heterogeneous catalysts, namely: (1) by templating chirality via the adsorption of chiral supramolecular assemblies, (2) by using chiral modifiers capable of forming chiral complexes with the reactant and force enantioselective surface reactions, and (3) by forming naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration
Molecular-Level Design of Heterogeneous Chiral Catalysis
Energy Technology Data Exchange (ETDEWEB)
Francisco Zaera
2012-03-21
The following is a proposal to continue our multi-institutional research on heterogeneous chiral catalysis. Our team combines the use of surface-sensitive analytical techniques for the characterization of model systems with quantum and statistical mechanical calculations to interpret experimental data and guide the design of future research. Our investigation focuses on the interrelation among the three main mechanisms by which enantioselectivity can be bestowed to heterogeneous catalysts, namely: (1) by templating chirality via the adsorption of chiral supramolecular assemblies, (2) by using chiral modifiers capable of forming chiral complexes with the reactant and force enantioselective surface reactions, and (3) by forming naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration
The multi-configuration self-consistent field method within a polarizable embedded framework
Hedegârd, Erik Donovan; List, Nanna H.; Jensen, Hans Jørgen Aagaard; Kongsted, Jacob
2013-07-01
We present a detailed derivation of Multi-Configuration Self-Consistent Field (MCSCF) optimization and linear response equations within the polarizable embedding scheme: PE-MCSCF. The MCSCF model enables a proper description of multiconfigurational effects in reaction paths, spin systems, excited states, and other properties which cannot be described adequately with current implementations of polarizable embedding in density functional or coupled cluster theories. In the PE-MCSCF scheme the environment surrounding the central quantum mechanical system is represented by distributed multipole moments and anisotropic dipole-dipole polarizabilities. The PE-MCSCF model has been implemented in DALTON. As a preliminary application, the low lying valence states of acetone and uracil in water has been calculated using Complete Active Space Self-Consistent Field (CASSCF) wave functions. The dynamics of the water environment have been simulated using a series of snapshots generated from classical Molecular Dynamics. The calculated shifts from gas-phase to water display between good and excellent correlation with experiment and previous calculations. As an illustration of another area of potential applications we present calculations of electronic transitions in the transition metal complex, [Fe(NO)(CN)5]2 - in a micro-solvated environment. This system is highly multiconfigurational and the influence of solvation is significant.
Chu, Huiying; Peng, Xiangda; Li, Yan; Zhang, Yuebin; Li, Guohui
2017-12-31
In all of the classical force fields, electrostatic interaction is simply treated and explicit electronic polarizability is neglected. The condensed-phase polarization, relative to the gas-phase charge distributions, is commonly accounted for in an average way by increasing the atomic charges, which remain fixed throughout simulations. Based on the lipid polarizable force field DMPC and following the same framework as Atomic Multipole Optimized Energetics for BiomoleculAr (AMOEBA) simulation, the present effort expands the force field to new anionic lipid models, in which the new lipids contain DMPG and POPS. The parameters are compatible with the AMOEBA force field, which includes water, ions, proteins, etc. The charge distribution of each atom is represented by the permanent atomic monopole, dipole and quadrupole moments, which are derived from the ab initio gas phase calculations. Many-body polarization including the inter- and intramolecular polarization is modeled in a consistent manner with distributed atomic polarizabilities. Molecular dynamics simulations of the two aqueous DMPG and POPS membrane bilayer systems, consisting of 72 lipids with water molecules, were then carried out to validate the force field parameters. Membrane width, area per lipid, volume per lipid, deuterium order parameters, electron density profile, electrostatic potential difference between the center of the bilayer and water are all calculated, and compared with limited experimental data.
Energy Technology Data Exchange (ETDEWEB)
Becher,
2002-08-08
After contrasting the low energy effective theory for the baryon sector with one for the Goldstone sector, I use the example of pion nucleon scattering to discuss some of the progress and open issues in baryon chiral perturbation theory.
Wang, Jian-Bo; Reetz, Manfred T.
2015-12-01
Racemic or enantiomerically pure alcohols can be converted with high yield into enantiopure chiral amines in a one-pot redox-neutral cascade process by the clever combination of an alcohol dehydrogenase and an appropriate amine dehydrogenase.
Nonlinear chiral transport phenomena
Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki
2016-06-01
We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.
Communication: Polarizable polymer chain under external electric field in a dilute polymer solution
International Nuclear Information System (INIS)
Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.
2015-01-01
We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such “field-induced” globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification
Chiral Boson Theory on the Light-Front
Energy Technology Data Exchange (ETDEWEB)
Srivastava, Prem P.
1999-09-16
The framework for describing the quantized theory of chiral boson is discussed. It avoids the conflict with the requirement of the principle of microcausality as is found in the conventional treatment. The discussion of the Floreanini-Jackiw model and its modified version for describing the chiral boson becomes very transparent on the light-front.
Two photon decay of neutral scalars below 1.5 GeV in a chiral model for qq and qqqq states
International Nuclear Information System (INIS)
Rodriguez, Simon; Napsuciale, Mauro
2005-01-01
We study the two photon decay of neutral scalars below 1.5 GeV in the context of a recently proposed chiral model for qq and qqqq states. We find good agreement with experimental results for the a 0 (980)→γγ decay. Our calculations for f 0 (980)→γγ shows that further work is necessary in order to understand the structure of this meson. The model predicts Γ(a 0 (1450)→γγ)=0.16±0.10 KeV, Γ(σ→γγ)=(0-1.13) KeV, Γ(f 0 (1370)→γγ)=(0-0.22) KeV, Γ(f 0 (1500)→γγ)=(0-1.51) KeV
Chiral quarks and proton decay
International Nuclear Information System (INIS)
Chadha, S.; Daniel, M.; Gounaris, G.J.; Murphy, A.J.
1984-04-01
The authors calculate the hadronic matrix elements of baryon decay operators using a chiral effective Lagrangian with quarks, gluons and Goldstone boson fields. The cases where the ΔB=1 operators arise from supersymmetric SU(5) GUT as well as the minimal SU(5) GUT model are studied. In each model the results depend on two parameters. In particular there is a range of values for the two parameters, where the dominant decay modes in the minimal SU(5) GUT are: p→etae + and n→π - e + . (author)
The possibility for a pion polarizability measurement at COMPASS
Guskov, A
2010-01-01
The pion electromagnetic structure can be probed in $\\pi^{−}+(A,Z)\\rightarrow\\pi^{-}+(A,Z) + \\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\alpha_{\\pi})$ and the magnetic $(\\beta_{\\pi})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of point-like pions with the measured cross section. The opportunity to measure pion polarizability via the Primakoff reaction at the COMPASS experiment was studied with a $\\pi^{−}$ beam of 190 GeV. The obtained results are used for preparation of the new measurement.
Dipole (hyper)polarizabilities of neutral silver clusters
Jorge, Francisco E.; de Macedo, Luiz G. M.
2016-12-01
At the Douglas-Kroll-Hess (DKH) level, the B3PW91 functional along with the all-electron relativistic basis sets of valence triple and quadruple zeta qualities are used to determine the structure, stability, and electronic properties of the small silver clusters (Agn, n ⩽ 7). The results presented in this study are in good agreement with the experimental data and theoretical values obtained at a higher level of theory from the literature. Static polarizability and hyperpolarizability are also reported. It is verified that the mean dipole polarizability per atom exhibits an odd-even oscillation and that the polarizability anisotropy is directly related to the cluster shape. In this article, the first study of hyperpolarizabilities of small silver clusters is presented. Except for the monomer, the second hyperpolarizabilities of the silver clusters are significantly larger than those of the copper clusters. Project supported by CNPq, CAPES, and FAPES (Brazilian Agencies).
Chiral anomalies and differential geometry
Energy Technology Data Exchange (ETDEWEB)
Zumino, B.
1983-10-01
Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)
Quantization of massive chiral electrodynamics reexamined
Energy Technology Data Exchange (ETDEWEB)
Fosco, C.; Montemayor, R. (Centro Atomico Bariloche, Comision Nacional de Energia Atomica and Instituto Balseiro, Universidad Nacional de Cuyo, 8400 San Carlos de Bariloche, Rio Negro (Argentina))
1993-05-15
We show that the models considered by Andrianov [ital et] [ital al]. [Phys. Rev. Lett. 63, 1554 (1989); and Phys. Rev. D 44, 2602 (1991)] are equivalent to other models where it is easily proved that the anomaly decouples and consequently the value of the chiral triangles amplitude is irrelvant for the unitarity of the [ital S] matrix.
QM/MM based fitting of atomic polarizabilities for use in condensed-phase biomolecular simulation
Vosmeer, C.R.; Rustenburg, A.S.; Rice, J.E.; Horn, H.W.; Swope, W.C.; Geerke, D.P.
2012-01-01
Accounting for electronic polarization effects in biomolecular simulation (by using a polarizable force field) can increase the accuracy of simulation results. However, the use of gas-phase estimates of atomic polarizabilities α
International Nuclear Information System (INIS)
Garron, Nicolas; Hudspith, Renwick J.; Lytle, Andrew T.
2016-01-01
We compute the hadronic matrix elements of the four-quark operators relevant for K 0 −K̄ 0 mixing beyond the Standard Model. Our results are from lattice QCD simulations with n f =2+1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing (a∼0.08 and a∼0.11 fm) and with lightest unitary pion mass ∼300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼5% or better.
Gan, Lin; Camacho-Alanis, Fernanda; Ros, Alexandra
2015-12-15
DNA nanoassemblies, such as DNA origamis, hold promise in biosensing, drug delivery, nanoelectronic circuits, and biological computing, which require suitable methods for migration and precision positioning. Insulator-based dielectrophoresis (iDEP) has been demonstrated as a powerful migration and trapping tool for μm- and nm-sized colloids as well as DNA origamis. However, little is known about the polarizability of origami species, which is responsible for their dielectrophoretic migration. Here, we report the experimentally determined polarizabilities of the six-helix bundle origami (6HxB) and triangle origami by measuring the migration times through a potential landscape exhibiting dielectrophoretic barriers. The resulting migration times correlate to the depth of the dielectrophoretic potential barrier and the escape characteristics of the origami according to an adapted Kramer's rate model, allowing their polarizabilities to be determined. We found that the 6HxB polarizability is larger than that of the triangle origami, which correlates with the variations in charge density of both origamis. Further, we discuss the orientation of both origami species in the dielectrophoretic trap and discuss the influence of diffusion during the escape process. Our study provides detailed insight into the factors contributing to the migration through dielectrophoretic potential landscapes, which can be exploited for applications with DNA and other nanoassemblies based on dielectrophoresis.
Molecular-level Design of Heterogeneous Chiral Catalysts
Energy Technology Data Exchange (ETDEWEB)
Gellman, Andrew John [Carnegie Mellon University; Sholl, David S. [Georgia Institute of Technology; Tysoe, Wilfred T. [University of Wisconsin - Milwaukee; Zaera, Francisco [University of California at Riverside
2013-04-28
Understanding and controlling selectivity is one of the key challenges in heterogeneous catalysis. Among problems in catalytic selectivity enantioselectivity is perhaps the most the most challenging. The primary goal of the project on “Molecular-level Design of Heterogeneous Chiral Catalysts” is to understand the origins of enantioselectivity on chiral heterogeneous surfaces and catalysts. The efforts of the project team include preparation of chiral surfaces, characterization of chiral surfaces, experimental detection of enantioselectivity on such surfaces and computational modeling of the interactions of chiral probe molecules with chiral surfaces. Over the course of the project period the team of PI’s has made some of the most detailed and insightful studies of enantioselective chemistry on chiral surfaces. This includes the measurement of fundamental interactions and reaction mechanisms of chiral molecules on chiral surfaces and leads all the way to rationale design and synthesis of chiral surfaces and materials for enantioselective surface chemistry. The PI’s have designed and prepared new materials for enantioselective adsorption and catalysis. Naturally Chiral Surfaces • Completion of a systematic study of the enantiospecific desorption kinetics of R-3-methylcyclohexanone (R-3-MCHO) on 9 achiral and 7 enantiomeric pairs of chiral Cu surfaces with orientations that span the stereographic triangle. • Discovery of super-enantioselective tartaric acid (TA) and aspartic acid (Asp) decomposition as a result of a surface explosion mechanism on Cu(643)R&S. Systematic study of super-enantiospecific TA and Asp decomposition on five enantiomeric pairs of chiral Cu surfaces. • Initial observation of the enantiospecific desorption of R- and S-propylene oxide (PO) from Cu(100) imprinted with {3,1,17} facets by L-lysine adsorption. Templated Chiral Surfaces • Initial observation of the enantiospecific desorption of R- and S-PO from Pt(111) and Pd(111
Shape Selection in Self-Assembled Chiral Membranes: New Mechanism Based on the Flexoelectric Effect
Lu, Zhao; Selinger, Robin; Selinger, Jonathan
2006-03-01
Many biological materials self-assemble into chiral microstructures such as cylindrical tubules and helical ribbons. A chiral elastic theory proposed by Selinger et al., based on the elastic properties and chirality of amphiphilic lipid molecules, has been successful in explaining the formation of tubules and helical ribbons. Recently, an experiment has shown that achiral lipid molecules can also form chiral microstructures. This challenges the previous theory based on molecular chirality. Toward understanding this problem, we develop a new model for membrane shape selection based on the flexoelectric effect. We investigate this model through both analytical calculations and dissipative particle dynamic simulations on tethered membranes.
Thorne, Ben; Fujita, Tomohiro; Hazumi, Masashi; Katayama, Nobuhiko; Komatsu, Eiichiro; Shiraishi, Maresuke
2018-02-01
A detection of B-mode polarization of the cosmic microwave background (CMB) anisotropies would confirm the presence of a primordial gravitational wave background (GWB). In the inflation paradigm, this would be an unprecedented probe of the energy scale of inflation as it is directly proportional to the power spectrum of the GWB. However, similar tensor perturbations can be produced by the matter fields present during inflation, breaking the simple relationship between energy scale and the tensor-to-scalar ratio r . It is therefore important to find ways of distinguishing between the generation mechanisms of the GWB. Without doing a full model selection, we analyze the detectability of a new axion-S U (2 ) gauge field model by calculating the signal-to-noise ratio of future CMB and interferometer observations sensitive to the chirality of the tensor spectrum. We forecast the detectability of the resulting CMB temperature and B-mode (TB) or E-mode and B-mode (EB) cross-correlation by the LiteBIRD satellite, considering the effects of residual foregrounds, gravitational lensing, and assess the ability of such an experiment to jointly detect primordial TB and EB spectra and self-calibrate its polarimeter. We find that LiteBIRD will be able to detect the chiral signal for r*>0.03 , with r* denoting the tensor-to-scalar ratio at the peak scale, and that the maximum signal-to-noise ratio for r*small scales inaccessible to the CMB, a highly significant detection could be made using space-based laser interferometers.
Doped Chiral Polymer Metamaterials
Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Gordon, Keith L. (Inventor); Sauti, Godfrey (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert G. (Inventor)
2017-01-01
Some implementations provide a composite material that includes a first material and a second material. In some implementations, the composite material is a metamaterial. The first material includes a chiral polymer (e.g., crystalline chiral helical polymer, poly-.gamma.-benzyl-L-glutamate (PBLG), poly-L-lactic acid (PLA), polypeptide, and/or polyacetylene). The second material is within the chiral polymer. The first material and the second material are configured to provide an effective index of refraction value for the composite material of 1 or less. In some implementations, the effective index of refraction value for the composite material is negative. In some implementations, the effective index of refraction value for the composite material of 1 or less is at least in a wavelength of one of at least a visible spectrum, an infrared spectrum, a microwave spectrum, and/or an ultraviolet spectrum.
Hidden QCD in Chiral Gauge Theories
DEFF Research Database (Denmark)
Ryttov, Thomas; Sannino, Francesco
2005-01-01
The 't Hooft and Corrigan-Ramond limits of massless one-flavor QCD consider the two Weyl fermions to be respectively in the fundamental representation or the two index antisymmetric representation of the gauge group. We introduce a limit in which one of the two Weyl fermions is in the fundamental...... representation and the other in the two index antisymmetric representation of a generic SU(N) gauge group. This theory is chiral and to avoid gauge anomalies a more complicated chiral theory is needed. This is the generalized Georgi-Glashow model with one vector like fermion. We show that there is an interesting...... phase in which the considered chiral gauge theory, for any N, Higgses via a bilinear condensate: The gauge interactions break spontaneously to ordinary massless one-flavor SU(3) QCD. The additional elementary fermionic matter is uncharged under this SU(3) gauge theory. It is also seen that when...
A chiral q-bar q-bar qq nonet?
International Nuclear Information System (INIS)
Napsuciale, Mauro; Rodriguez, Simon
2004-01-01
We point out that meson spectrum indicates the existence of a degenerate chiral nonet in the energy region around 1.4 GeV with a slightly inverted spectrum with respect to a q-bar q nonet. Based on this observation and the approximately linear rising of the mass of a hadron with the number of constituent quarks we conjecture the existence of a tetraquark chiral nonet in this energy region with chiral symmetry implemented directly. We realize this idea in a chiral model and take into account the mixing of the tetraquark chiral nonet with a conventional q-bar q nonet. We find that the mass spectrum of mesons below 1.5 GeV is consistent with this picture. In general, pseudoscalar states arise as mainly q-bar q states but scalar states turn out to be strong admixtures of q-bar q and tetraquark states
Scalar spin chirality and quantum hall effect on triangular lattices
Energy Technology Data Exchange (ETDEWEB)
Martin, Ivar [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory
2008-01-01
We study the Kondo Lattice and Hubbard models on a triangular lattice for band filling factor 3/4. We show that a simple non-coplanar chiral spin ordering (scalar spin chirality) is naturally realized in both models due to perfect nesting of the fermi surface. The resulting triple-Q magnetic ordering is a natural counterpart of the collinear Neel ordering of the half-filled square lattice Hubbard model. We show that the obtained chiral phase exhibits a spontaneous quantum Hall-effect with {sigma}{sub xy} = e{sup 2}/h.
Chiral algebras for trinion theories
International Nuclear Information System (INIS)
Lemos, Madalena; Peelaers, Wolfger
2015-01-01
It was recently understood that one can identify a chiral algebra in any four-dimensional N=2 superconformal theory. In this note, we conjecture the full set of generators of the chiral algebras associated with the T n theories. The conjecture is motivated by making manifest the critical affine module structure in the graded partition function of the chiral algebras, which is computed by the Schur limit of the superconformal index for T n theories. We also explicitly construct the chiral algebra arising from the T 4 theory. Its null relations give rise to new T 4 Higgs branch chiral ring relations.
Substituent effects of the alkyl groups: Polarity vs. polarizability
Czech Academy of Sciences Publication Activity Database
Exner, Otto; Böhm, S.
-, č. 17 (2007), s. 2870-2876 ISSN 1434-193X Institutional research plan: CEZ:AV0Z40550506 Keywords : density functional calculations * hyperconjugation * inductive effect * polarizability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.914, year: 2007
Neutron polarizability. Possibilities of its determination in neutron experiments
Aleksandrov, Y A
2001-01-01
The history of question of neutron polarizability is discussed. Most of the neutron physical experiments conducted at neutron energies below 14 MeV to discover the electric polarizability of the neutron are reviewed.The existence of additional scattering after all known long range-related phenomena are taken into account are emphasized. In the keV neutron energy region, the effect of neutron polarizability on the angular distribution of scattering (over a wide range of angles) and the energy behavior of the total cross section of neutron interaction is studied. Finally, in the region of low energies (below 1 keV) the focus is on the influence of polarizability on the energy dependence of total neutron cross sections. It is emphasized that measurements at energies below several hundreds keV have not given any positive results yet due to the smallness of the experimental effect. Possible existence of an additional potential of neutron scattering on nuclei with a longer range than that of the usual nuclear poten...
Theory and applications of atomic and ionic polarizabilities
International Nuclear Information System (INIS)
Mitroy, J; Safronova, M S; Clark, Charles W
2010-01-01
Atomic polarization phenomena impinge upon a number of areas and processes in physics. The dielectric constant and refractive index of any gas are examples of macroscopic properties that are largely determined by the dipole polarizability. When it comes to microscopic phenomena, the existence of alkaline-earth anions and the recently discovered ability of positrons to bind to many atoms are predominantly due to the polarization interaction. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. Accurate polarizabilities for the group I and II atoms and ions of the periodic table have recently become available by a variety of techniques. These include refined many-body perturbation theory and coupled-cluster calculations sometimes combined with precise experimental data for selected transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index measurements in microwave cavities, ab initio calculations of atomic structures using explicitly correlated wavefunctions, interferometry with atom beams and velocity changes of laser cooled atoms induced by an electric field. This review examines existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on cold-atom physics and the metrology of atomic frequency standards. (topical review)
Partial Molar Volume of Methanol in Water: Effect of Polarizability
Czech Academy of Sciences Publication Activity Database
Moučka, F.; Nezbeda, Ivo
2009-01-01
Roč. 74, č. 4 (2009), s. 559-563 ISSN 0010-0765 R&D Projects: GA AV ČR IAA400720802 Institutional research plan: CEZ:AV0Z40720504 Keywords : water–methanol mixtures * partial molar volume * polarizability Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.856, year: 2009
Theory and applications of atomic and ionic polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Mitroy, J [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Safronova, M S [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Clark, Charles W, E-mail: jxm107@rsphysse.anu.edu.a, E-mail: msafrono@udel.ed, E-mail: charles.clark@nist.go [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, MD 20899-8410 (United States)
2010-10-28
Atomic polarization phenomena impinge upon a number of areas and processes in physics. The dielectric constant and refractive index of any gas are examples of macroscopic properties that are largely determined by the dipole polarizability. When it comes to microscopic phenomena, the existence of alkaline-earth anions and the recently discovered ability of positrons to bind to many atoms are predominantly due to the polarization interaction. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. Accurate polarizabilities for the group I and II atoms and ions of the periodic table have recently become available by a variety of techniques. These include refined many-body perturbation theory and coupled-cluster calculations sometimes combined with precise experimental data for selected transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index measurements in microwave cavities, ab initio calculations of atomic structures using explicitly correlated wavefunctions, interferometry with atom beams and velocity changes of laser cooled atoms induced by an electric field. This review examines existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on cold-atom physics and the metrology of atomic frequency standards. (topical review)
Transport properties of chiral fermions
Energy Technology Data Exchange (ETDEWEB)
Puhr, Matthias
2017-04-26
Anomalous transport phenomena have their origin in the chiral anomaly, the anomalous non-conservation of the axial charge, and can arise in systems with chiral fermions. The anomalous transport properties of free fermions are well understood, but little is known about possible corrections to the anomalous transport coefficients that can occur if the fermions are strongly interacting. The main goal of this thesis is to study anomalous transport effects in media with strongly interacting fermions. In particular, we investigate the Chiral Magnetic Effect (CME) in a Weyl Semimetal (WSM) and the Chiral Separation Effect (CSE) in finite-density Quantum Chromodynamics (QCD). The recently discovered WSMs are solid state crystals with low-energy excitations that behave like Weyl fermions. The inter-electron interaction in WSMs is typically very strong and non-perturbative calculations are needed to connect theory and experiment. To realistically model an interacting, parity-breaking WSM we use a tight-binding lattice Hamiltonian with Wilson-Dirac fermions. This model features a non-trivial phase diagram and has a phase (Aoki phase/axionic insulator phase) with spontaneously broken CP symmetry, corresponding to the phase with spontaneously broken chiral symmetry for interacting continuum Dirac fermions. We use a mean-field ansatz to study the CME in spatially modulated magnetic fields and find that it vanishes in the Aoki phase. Moreover, our calculations show that outside of the Aoki phase the electron interaction has only a minor influence on the CME. We observe no enhancement of the magnitude of the CME current. For our non-perturbative study of the CSE in QCD we use the framework of lattice QCD with overlap fermions. We work in the quenched approximation to avoid the sign problem that comes with introducing a finite chemical potential on the lattice. The overlap operator calls for the evaluation of the sign function of a matrix with a dimension proportional to the volume
Chirality in molecular collision dynamics
Lombardi, Andrea; Palazzetti, Federico
2018-02-01
Chirality is a phenomenon that permeates the natural world, with implications for atomic and molecular physics, for fundamental forces and for the mechanisms at the origin of the early evolution of life and biomolecular homochirality. The manifestations of chirality in chemistry and biochemistry are numerous, the striking ones being chiral recognition and asymmetric synthesis with important applications in molecular sciences and in industrial and pharmaceutical chemistry. Chiral discrimination phenomena, due to the existence of two enantiomeric forms, very well known in the case of interaction with light, but still nearly disregarded in molecular collision studies. Here we review some ideas and recent advances about the role of chirality in molecular collisions, designing and illustrating molecular beam experiments for the demonstration of chiral effects and suggesting a scenario for a stereo-directional origin of chiral selection.
Domain nucleation in the contact layer at an interface of water and a polarizable substrate
Shevkunov, S. V.
2013-10-01
The growth of a molecular water film on the basic plane of a silver iodide monocrystal is studied through computer simulation. Decomposition into domains with spontaneous polarization is observed in the contact layer of the film at the interface with the substrate. The formation of domains is found to be sharply enhanced on a model substrate with the double polarizability of iodine ions; heteropolarization interactions caused by the formation of domain structures increase the film's coupling with the substrate. It is demonstrated that the vapor pressure needed for molecular film growth is reduced appreciably via heteropolarization interactions.
Energy Technology Data Exchange (ETDEWEB)
Rachet, Florent; Chrysos, Michael, E-mail: michel.chrysos@univ-angers.fr [LUNAM Université, Université d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 Bd Lavoisier, 49045 Angers (France); Dixneuf, Sophie [Forschungszentrum Jülich GmbH IEK-8, Troposphere, 52425 Jülich (Germany)
2015-05-07
We report the room-temperature isotropic collision-induced light scattering spectrum of Ne–Ne over a wide interval of Raman shifts, and we compare it with the only available experimental spectrum for that system as well as with spectra calculated quantum-mechanically with the employ of advanced ab initio-computed data for the incremental mean polarizability. The spectral range previously limited to 170 cm{sup −1} is now extended to 485 cm{sup −1} allowing us to successfully solve the inverse-scattering problem toward an analytic model for the mean polarizability that perfectly matches our measurements. We also report the depolarization ratio of the scattering process, lingering over the usefulness of this property for more stringent checks between the various polarizability models.
Rachet, Florent; Dixneuf, Sophie; Chrysos, Michael
2015-05-07
We report the room-temperature isotropic collision-induced light scattering spectrum of Ne-Ne over a wide interval of Raman shifts, and we compare it with the only available experimental spectrum for that system as well as with spectra calculated quantum-mechanically with the employ of advanced ab initio-computed data for the incremental mean polarizability. The spectral range previously limited to 170 cm(-1) is now extended to 485 cm(-1) allowing us to successfully solve the inverse-scattering problem toward an analytic model for the mean polarizability that perfectly matches our measurements. We also report the depolarization ratio of the scattering process, lingering over the usefulness of this property for more stringent checks between the various polarizability models.
Optofluidic sorting of material chirality by chiral light
Tkachenko, Georgiy; Brasselet, Etienne
2014-04-01
The lack of mirror symmetry, chirality, plays a fundamental role in physics, chemistry and life sciences. The passive separation of entities that only differ by their handedness without need of a chiral material environment remains a challenging task with attractive scientific and industrial benefits. To date, only a few experimental attempts have been reported and remained limited down to the micron scale, most of them relying on hydrodynamical forces associated with the chiral shape of the micro-objects to be sorted. Here we experimentally demonstrate that material chirality can be passively sorted in a fluidic environment by chiral light owing to spin-dependent optical forces without chiral morphology prerequisite. This brings a new twist to the state-of-the-art optofluidic toolbox and the development of a novel kind of passive integrated optofluidic sorters able to deal with molecular scale entities is envisioned.
Sum-Frequency Generation from Chiral Media and Interfaces
International Nuclear Information System (INIS)
Ji, Na
2006-01-01
Sum frequency generation (SFG), a second-order nonlinear optical process, is electric-dipole forbidden in systems with inversion symmetry. As a result, it has been used to study chiral media and interfaces, systems intrinsically lacking inversion symmetry. This thesis describes recent progresses in the applications of and new insights into SFG from chiral media and interfaces. SFG from solutions of chiral amino acids is investigated, and a theoretical model explaining the origin and the strength of the chiral signal in electronic-resonance SFG spectroscopy is discussed. An interference scheme that allows us to distinguish enantiomers by measuring both the magnitude and the phase of the chiral SFG response is described, as well as a chiral SFG microscope producing chirality-sensitive images with sub-micron resolution. Exploiting atomic and molecular parity nonconservation, the SFG process is also used to solve the Ozma problems. Sum frequency vibrational spectroscopy is used to obtain the adsorption behavior of leucine molecules at air-water interfaces. With poly(tetrafluoroethylene) as a model system, we extend the application of this surface-sensitive vibrational spectroscopy to fluorine-containing polymers
Sum-Frequency Generation from Chiral Media and Interfaces
Energy Technology Data Exchange (ETDEWEB)
Ji, Na [Univ. of California, Berkeley, CA (United States)
2006-02-13
Sum frequency generation (SFG), a second-order nonlinear optical process, is electric-dipole forbidden in systems with inversion symmetry. As a result, it has been used to study chiral media and interfaces, systems intrinsically lacking inversion symmetry. This thesis describes recent progresses in the applications of and new insights into SFG from chiral media and interfaces. SFG from solutions of chiral amino acids is investigated, and a theoretical model explaining the origin and the strength of the chiral signal in electronic-resonance SFG spectroscopy is discussed. An interference scheme that allows us to distinguish enantiomers by measuring both the magnitude and the phase of the chiral SFG response is described, as well as a chiral SFG microscope producing chirality-sensitive images with sub-micron resolution. Exploiting atomic and molecular parity nonconservation, the SFG process is also used to solve the Ozma problems. Sum frequency vibrational spectroscopy is used to obtain the adsorption behavior of leucine molecules at air-water interfaces. With poly(tetrafluoroethylene) as a model system, we extend the application of this surface-sensitive vibrational spectroscopy to fluorine-containing polymers.
Přibyl, Michal; Slouka, Zdeněk
2015-11-01
Recent progress in material chemistry and surface engineering has led to emergence of new electrode materials with unique physical and electrochemical properties. Here, we introduce a physical model describing charging of ideal polarizable electrode-electrolyte interface where the electrode is characterized by a limited capacity to store charge. The analytical model treats the electrode and electrolyte phases as independent nonlinear capacitors that are eventually coupled through the condition of equality of the total stored electrical charge opposite in sign. Gouy-Chapman and condensed layer theories applied to a general 1:n valent electrolyte are used to predict dependencies of differential capacitance of the electrolyte phase and surface concentration of the electrical charge on the applied potential. The model of the nonlinear capacitor for the electrode phase is described by a theory of electron donors and acceptors present in conductive solids as a result of thermal fluctuations. Both the differential capacitance and the surface concentration of the electrical charge in the electrode are evaluated as functions of the applied potential and related to the capacity of the electrode phase to accumulate charge and its ability to form electron donors and acceptors. The knowledge of capacitive properties of both phases allows to predict electrochemical characteristics of ideal polarizable interfaces, e.g., current responses in linear sweep voltammetry. The coupled model also shows significant potential drops in the electrode comparable to those in the electrolyte phase for materials with low charge carrier concentrations.
International Nuclear Information System (INIS)
Adler, S.L.
1999-01-01
We construct extensions of the standard model based on the hypothesis that Higgs bosons also exhibit a family structure and that the flavor weak eigenstates in the three families are distinguished by a discrete Z 6 chiral symmetry that is spontaneously broken by the Higgs sector. We study in detail at the tree level models with three Higgs doublets and with six Higgs doublets comprising two weakly coupled sets of three. In a leading approximation of S 3 cyclic permutation symmetry the three-Higgs-doublet model gives a open-quotes democraticclose quotes mass matrix of rank 1, while the six-Higgs-doublet model gives either a rank-1 mass matrix or, in the case when it spontaneously violates CP, a rank-2 mass matrix corresponding to nonzero second family masses. In both models, the CKM matrix is exactly unity in the leading approximation. Allowing small explicit violations of cyclic permutation symmetry generates small first family masses in the six-Higgs-doublet model, and first and second family masses in the three-Higgs-doublet model, and gives a nontrivial CKM matrix in which the mixings of the first and second family quarks are naturally larger than mixings involving the third family. Complete numerical fits are given for both models, flavor-changing neutral current constraints are discussed in detail, and the issues of unification of couplings and neutrino masses are addressed. On a technical level, our analysis uses the theory of circulant and retrocirculant matrices, the relevant parts of which are reviewed. copyright 1998 The American Physical Society
Kashid, Vikas; Schena, Timo; Zimmermann, Bernd; Mokrousov, Yuriy; Blügel, Stefan; Shah, Vaishali; Salunke, H. G.
2014-08-01
We investigate the chiral magnetic order in freestanding planar 3d-5d biatomic metallic chains (3d: Fe, Co; 5d: Ir, Pt, Au) using first-principles calculations based on density functional theory. We find that the antisymmetric exchange interaction, commonly known as the Dzyaloshinskii-Moriya interaction (DMI), contributes significantly to the energetics of the magnetic structure. For the Fe-Pt and Co-Pt chains, the DMI can compete with the isotropic Heisenberg-type exchange interaction and the magnetocrystalline anisotropy energy, and for both cases a homogeneous left-rotating cycloidal chiral spin-spiral with a wavelength of 51 Å and 36 Å, respectively, was found. The sign of the DMI, which determines the handedness of the magnetic structure, changes in the sequence of the 5d atoms Ir(+), Pt(-), Au(+). We use the full-potential linearized augmented plane wave method and perform self-consistent calculations of homogeneous spin spirals, calculating the DMI by treating the effect of spin-orbit interaction in the basis of the spin-spiral states in first-order perturbation theory. To gain insight into the DMI results of our ab initio calculations, we develop a minimal tight-binding model of three atoms and four orbitals that contains all essential features: the spin canting between the magnetic 3d atoms, the spin-orbit interaction at the 5d atoms, and the structure inversion asymmetry facilitated by the triangular geometry. We find that spin canting can lead to spin-orbit active eigenstates that split in energy due to the spin-orbit interaction at the 5d atom. We show that the sign and strength of the hybridization, the bonding or antibonding character between d orbitals of the magnetic and nonmagnetic sites, the bandwidth, and the energy difference between occupied and unoccupied states of different spin projection determine the sign and strength of the DMI. The key features observed in the trimer model are also found in the first-principles results.
Chiral symmetry restoration and the critical end point in QCD
Directory of Open Access Journals (Sweden)
Morones-Ibarra Jose Rubén
2017-12-01
Full Text Available In a system of quark matter we study the chiral phase transition, the behavior of the chiral and quark number susceptibility and the CEP at finite temperature and chemical potential. This is done within the framework of two-flavor Nambu and Jona-Lasinio model. We have calculated the chiral quark condensate and the quark number density and, with this, we have found the phase transition type. With these quantities we have determined the phase diagram for QCD and the CEP.
Non-perturbative chiral corrections for lattice QCD
International Nuclear Information System (INIS)
Thomas, A.W.; Leinweber, D.B.; Lu, D.H.
2002-01-01
We explore the chiral aspects of extrapolation of observables calculated within lattice QCD, using the nucleon magnetic moments as an example. Our analysis shows that the biggest effects of chiral dynamics occur for quark masses corresponding to a pion mass below 600 MeV. In this limited range chiral perturbation theory is not rapidly convergent, but we can develop some understanding of the behaviour through chiral quark models. This model dependent analysis leads us to a simple Pade approximant which builds in both the limits m π → 0 and m π → ∞ correctly and permits a consistent, model independent extrapolation to the physical pion mass which should be extremely reliable. (author)
Energy Technology Data Exchange (ETDEWEB)
Albaladejo, M.; Fernandez-Soler, P.; Nieves, J.; Ortega, P.G. [Centro Mixto CSIC-Universidad de Valencia, Instituto de Fisica Corpuscular (IFIC), Institutos de Investigacion de Paterna, Aptd. 22085, Valencia (Spain)
2017-03-15
The discovery of the D{sup *}{sub s0}(2317) and D{sub s1}(2460) resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between Q anti q and (Q anti q)(q anti q) Fock components. In contrast to the c anti s sector, there is no experimental evidence of J{sup P} = 0{sup +}, 1{sup +} bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the D{sub s0}{sup *}(2317) and D{sub s1}(2460) states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark-model P-wave anti B{sub s} scalar and axial mesons and the anti B{sup (*)}K channels is incorporated employing an effective interaction, consistent with heavy-quark spin symmetry, constrained by the lattice energy levels. (orig.)
Grajewski, J; Piotrowska, K; Zgorzelak, M; Janiak, A; Biniek-Antosiak, K; Rychlewska, U; Gawronski, J
2018-02-07
Novel chiral macrocyclic polyimines with spiro carbon atoms are described. The key feature of the synthesis is the formation of an axially chiral quaternary carbon atom having four constitutionally identical substituents. This is possible either by the freezing of the labile conformation of a spiro-diboronate moiety or by the diastereomeric fitting of a conformationally stable spiro-acetal moiety into a chiral framework. A general model for the description of this type of axial chirality is proposed.
Polarizability of deformed nuclei and energy shifts in muonic atoms
International Nuclear Information System (INIS)
Nali, P.F.; Quarati, P.
1980-01-01
The polarizability and nuclear-polarization energy shifts of nuclei composed of closed shells plus valence nucleons in muonic atoms have been calculated: the harmonic-oscillator results of the El polarizability and the energy shifts have been corrected by means of a perturbative approach, which takes into account the effects introduced by the deformation Nilsson potential. Furthermore, to take into account the core polarization effect, different harmonic-oscillator parameters for the core and the valence nucleons have been assumed. The energy shifts of a sequence of states occupied by the muon during its atomic electromagnetic cascade for the nuclei 17 O and 17 F, 41 Ca and 41 Sc have been calculated. (author)
Dynamic polarizability of a complex atom in strong laser fields
International Nuclear Information System (INIS)
Rapoport, L.P.; Klinskikh, A.F.; Mordvinov, V.V.
1997-01-01
An asymptotic expansion of the dynamic polarizability of a complex atom in a strong circularly polarized light field is found for the case of high frequencies. The self-consistent approximation of the Hartree-Fock type for the ''atom+field'' system is developed, within the framework of which a numerical calculation of the dynamic polarizability of Ne, Kr, and Ar atoms in a strong radiation field is performed. The strong field effect is shown to manifest itself not only in a change of the energy spectrum and the character of behavior of the wave functions of atomic electrons, but also in a modification of the one-electron self-consistent potential for the atom in the field
Chiral damping of magnetic domain walls
Jué, Emilie
2015-12-21
Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics1, current-induced spin–orbit torques2, 3, 4, 5, 6, 7 and some topological magnetic structures8, 9, 10, 11, 12. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii–Moriya interaction (DMI) exhibit identical spatial symmetry13, 14, 15, 16, 17, 18, 19. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. 20).
Realization of chiral symmetry in the ERG
International Nuclear Information System (INIS)
Echigo, Yoshio; Igarashi, Yuji
2011-01-01
We discuss within the framework of the ERG how chiral symmetry is realized in a linear σ model. A generalized Ginsparg-Wilson relation is obtained from the Ward-Takahashi identities for the Wilson action assumed to be bilinear in the Dirac fields. We construct a family of its non-perturbative solutions. The family generates the most general solutions to the Ward-Takahashi identities. Some special solutions are discussed. For each solution in this family, chiral symmetry is realized in such a way that a change in the Wilson action under non-linear symmetry transformation is canceled with a change in the functional measure. We discuss that the family of solutions reduces via a field redefinition to a family of the Wilson actions with some composite object of the scalar fields which has a simple transformation property. For this family, chiral symmetry is linearly realized with a continuum analog of the operator extension of γ 5 used on the lattice. We also show that there exist some appropriate Dirac fields which obey the standard chiral transformations with γ 5 in contrast to the lattice case. Their Yukawa interaction with scalars, however, becomes non-linear. (author)
International Nuclear Information System (INIS)
Safronova, M. S.; Safronova, U. I.
2011-01-01
A systematic study of Ca + atomic properties is carried out using a high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to n=7. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole scalar polarizabilities for the 5s, 6s, 7s, 8s, 4p j , 5p j , 3d j , and 4d j states and tensor polarizabilities for the 4p 3/2 , 5p 3/2 , 3d j , and 4d j states in Ca + are calculated. Methods are developed to accurately treat the contributions from highly excited states, resulting in significant (factor of 3) improvement in the accuracy of the 3d 5/2 static polarizability value, 31.8(3)a 0 3 , in comparison with the previous calculation [Arora et al., Phys. Rev. A 76, 064501 (2007).]. The blackbody radiation shift of the 4s-3d 5/2 clock transition in Ca + is calculated to be 0.381(4) Hz at room temperature, T=300 K. Electric-quadrupole 4s-nd and electric-octupole 4s-nf matrix elements are calculated to obtain the ground-state multipole E2 and E3 static polarizabilities. Excitation energies of the ns, np, nd, nf, and ng states with n≤ 7 in are evaluated and compared with experiment. Recommended values are provided for the 7p 1/2 , 7p 3/2 , 8p 1/2 , and 8p 3/2 removal energies for which experimental measurements are not available. The hyperfine constants A are determined for the low-lying levels up to n=7. The quadratic Stark effect on hyperfine structure levels of 43 Ca + ground state is investigated. These calculations provide recommended values critically evaluated for their accuracy for a number of Ca + atomic properties for use in planning and analysis of various experiments as well as theoretical modeling.
Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability.
Appelquist, T; Berkowitz, E; Brower, R C; Buchoff, M I; Fleming, G T; Jin, X-Y; Kiskis, J; Kribs, G D; Neil, E T; Osborn, J C; Rebbi, C; Rinaldi, E; Schaich, D; Schroeder, C; Syritsyn, S; Vranas, P; Weinberg, E; Witzel, O
2015-10-23
We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar "stealth baryon" dark matter candidate, arising from a dark SU(4) confining gauge theory-"stealth dark matter." In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest "baryon" states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m(B)(6), suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.
Experimental Constraints on Polarizability Corrections to Hydrogen Hyperfine Structure
International Nuclear Information System (INIS)
Nazaryan, Vahagn; Carlson, Carl E.; Griffioen, Keith A.
2006-01-01
We present a state-of-the-art evaluation of the polarizability corrections--the inelastic nucleon corrections--to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value Δ pol =1.3±0.3 ppm. This is 1-2 ppm smaller than the value of Δ pol deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits
Real and virtual Compton scattering: The nucleon polarizabilities
International Nuclear Information System (INIS)
Downie, E.J.; Fonvieille, H.
2011-01-01
We give an overview of low-energy Compton scattering γ (*) p → γp with a real or virtual incoming photon. These processes allow the investigation of one of the fundamental properties of the nucleon, i.e. how its internal structure deforms under an applied static electromagnetic field. Our knowledge of nucleon polarizabilities and their generalization to non-zero four-momentum transfer will be reviewed, including the presently ongoing experiments and future perspectives. (authors)
Directory of Open Access Journals (Sweden)
D. Gambacurta
2018-02-01
Full Text Available The second random–phase–approximation model corrected by a subtraction procedure designed to cure double counting, instabilities, and ultraviolet divergences, is employed for the first time to analyze the dipole strength and polarizability in 48Ca. All the terms of the residual interaction are included, leading to a fully self-consistent scheme. Results are illustrated with two Skyrme parametrizations, SGII and SLy4. Those obtained with the SGII interaction are particularly satisfactory. In this case, the low-lying strength below the neutron threshold is well reproduced and the giant dipole resonance is described in a very satisfactory way especially in its spreading and fragmentation. Spreading and fragmentation are produced in a natural way within such a theoretical model by the coupling of 1 particle-1 hole and 2 particle-2 hole configurations. Owing to this feature, we may provide for the electric polarizability as a function of the excitation energy a curve with a similar slope around the centroid energy of the giant resonance compared to the corresponding experimental results. This represents a considerable improvement with respect to previous theoretical predictions obtained with the random–phase approximation or with several ab-initio models. In such cases, the spreading width of the excitation cannot be reproduced and the polarizability as a function of the excitation energy displays a stiff increase around the predicted centroid energy of the giant resonance.
Gambacurta, D.; Grasso, M.; Vasseur, O.
2018-02-01
The second random-phase-approximation model corrected by a subtraction procedure designed to cure double counting, instabilities, and ultraviolet divergences, is employed for the first time to analyze the dipole strength and polarizability in 48Ca. All the terms of the residual interaction are included, leading to a fully self-consistent scheme. Results are illustrated with two Skyrme parametrizations, SGII and SLy4. Those obtained with the SGII interaction are particularly satisfactory. In this case, the low-lying strength below the neutron threshold is well reproduced and the giant dipole resonance is described in a very satisfactory way especially in its spreading and fragmentation. Spreading and fragmentation are produced in a natural way within such a theoretical model by the coupling of 1 particle-1 hole and 2 particle-2 hole configurations. Owing to this feature, we may provide for the electric polarizability as a function of the excitation energy a curve with a similar slope around the centroid energy of the giant resonance compared to the corresponding experimental results. This represents a considerable improvement with respect to previous theoretical predictions obtained with the random-phase approximation or with several ab-initio models. In such cases, the spreading width of the excitation cannot be reproduced and the polarizability as a function of the excitation energy displays a stiff increase around the predicted centroid energy of the giant resonance.
Density Functional Studies of Molecular Polarizabilities. 10. Fulvenes and Fulvalenes
Directory of Open Access Journals (Sweden)
Humberto J. SoscÃƒÂºn Machado
2000-09-01
Full Text Available We report accurate Ab Initio Hartree Fock (HF and Density Functional Theory (DFT studies of the static dipole polarizabilities and first hyperpolarizabilities of the [n] fulvene and the [n,m] fulvalene series of molecules (with n, m = 3,5,7. Calculations are also reported for the parent cycloalkenes: cyclopropene, cyclopentadiene and cycloheptatriene (1-3 respectively. Geometries were optimized at the HF/6-311G(3d,2p level of theory. All the fulvenes (4-6 and the smaller fulvalenes (7, 9 and 10 are found to be planar. Pentaheptafulvalene (11 is slightly non-planar whilst heptafulvalene (12 has a folded C2h structure. Calculated C-C bond lengths are consistently smaller than the experimental values. Dipole polarizabilities and non-zero hyperpolarizabilities were calculated at the HF/6-311++G(3d,2p and BLYP/6-311++G(3d,2p levels of theory, using HF/6-311G(3d,2p geometries. Dipole polarizabilities correlate well with those given on the basis of atom additivity. Molecules (8, (9 and (11 show very large dipole hyperpolarizabilities.
Steindal, Arnfinn Hykkerud; Beerepoot, Maarten T P; Ringholm, Magnus; List, Nanna Holmgaard; Ruud, Kenneth; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard
2016-10-12
We present the theory and implementation of an open-ended framework for electric response properties at the level of Hartree-Fock and Kohn-Sham density functional theory that includes effects from the molecular environment modeled by the polarizable embedding (PE) model. With this new state-of-the-art multiscale functionality, electric response properties to any order can be calculated for molecules embedded in polarizable atomistic molecular environments ranging from solvents to complex heterogeneous macromolecules such as proteins. In addition, environmental effects on multiphoton absorption (MPA) properties can be studied by evaluating single residues of the response functions. The PE approach includes mutual polarization effects between the quantum and classical parts of the system through induced dipoles that are determined self-consistently with respect to the electronic density. The applicability of our approach is demonstrated by calculating MPA strengths up to four-photon absorption for the green fluorescent protein. We show how the size of the quantum region, as well as the treatment of the border between the quantum and classical regions, is crucial in order to obtain reliable MPA predictions.
Energy Technology Data Exchange (ETDEWEB)
Garron, Nicolas [Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool,Brownlow Hill, Liverpool, L69 3BX (United Kingdom); Hudspith, Renwick J. [Department of Physics and Astronomy, York University,4700 Keele Street, Toronto, Ontario, M3J 1P3 (Canada); Lytle, Andrew T. [SUPA, School of Physics and Astronomy, University of Glasgow,University Avenue, Glasgow, G12 8QQ (United Kingdom); Collaboration: The RBC/UKQCD collaboration
2016-11-02
We compute the hadronic matrix elements of the four-quark operators relevant for K{sup 0}−K̄{sup 0} mixing beyond the Standard Model. Our results are from lattice QCD simulations with n{sub f}=2+1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing (a∼0.08 and a∼0.11 fm) and with lightest unitary pion mass ∼300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼5% or better.
International Nuclear Information System (INIS)
Dorenbos, P.; Andriessen, J.; Eijk, C.W.E. van
2003-01-01
Data collected on the centroid shift of the 5d-configuration of Ce 3+ in oxide and fluoride compounds were recently analyzed with a model involving the correlated motion between 5d-electron and ligand electrons. The correlation effects are proportional to the polarizability of the anion ligands and it leads, like covalency, to lowering of the 5d-orbital energies. By means of ab initio Hartree-Fock-LCAO calculations including configuration interaction the contribution from covalency and correlated motion to the centroid shift are determined separately for Ce 3+ in various compounds. It will be shown that in fluoride compounds, covalency provides an insignificant contribution. In oxides, polarizability appears to be of comparable importance as covalency
Simplified chiral superfield propagators for chiral constant mass superfields
International Nuclear Information System (INIS)
Srivastava, P.P.
1983-01-01
Unconstrained superfield potentials are introduced to derive Feynman rules for chiral superfields following conventional procedure which is easy and instructive. Propagators for the case when the mass parameters are constant chiral superfields are derived. The propagators reported here are very simple compared to those available in literature and allow a manageable calculation of higher loops. (Author) [pt
Some aspects of chirality: Fermion masses and chiral p-forms
International Nuclear Information System (INIS)
Kleppe, A.
1997-05-01
The properties of fermion mass matrices are investigated from different points of view, both within the minimal Standard Model and in extensions of the model. It is shown how mass matrix invariants are used to define the measurables of the quark mixing matrix as invariant functions of the mass matrices. One model is presented where the family pattern is suggested to originate from a kind of mass scaling. A Lagrangian density is defined for an entire charge sector, such that the existence of a Dirac field with mass m 0 implies the existence of other Dirac fields where the corresponding quanta have masses Rm 0 , R 2 m 0 , .. which are obtained by a discrete scale transformation. This suggests a certain type of democratic fermion mass matrices. Also extensions of the minimal Standard Model are investigated, obtained by including right-handed neutrinos in the model. The Standard Model extended by two right-handed neutrinos gives rise to a mass spectrum with two massive and three massless neutrinos. The phenomenological consequences of this model are discussed. The neutrino mass matrix in such a scheme has what is defined as a democratic texture. They are studied for the cases with two and three right-handed neutrinos, resp. The chiral fields that we find in the Standard Model have certain similarities with self-dual fields. Among other things, both chiral and self-dual fields suffer species doubling on the lattice. Chiral p-forms are self-dual fields that appear in twice odd dimensions. Chiral p-forms violate manifest covariance, in the same sense as manifest covariance is violated by non-covariant gauges in electrodynamics. It is shown that a covariant action can nevertheless be formulated for chiral p-forms, by introducing an infinite set of gauge fields in a carefully controlled way
Some aspects of chirality: Fermion masses and chiral p-forms
Energy Technology Data Exchange (ETDEWEB)
Kleppe, A.
1997-05-01
The properties of fermion mass matrices are investigated from different points of view, both within the minimal Standard Model and in extensions of the model. It is shown how mass matrix invariants are used to define the measurables of the quark mixing matrix as invariant functions of the mass matrices. One model is presented where the family pattern is suggested to originate from a kind of mass scaling. A Lagrangian density is defined for an entire charge sector, such that the existence of a Dirac field with mass m{sub 0} implies the existence of other Dirac fields where the corresponding quanta have masses Rm{sub 0}, R{sup 2}m{sub 0}, .. which are obtained by a discrete scale transformation. This suggests a certain type of democratic fermion mass matrices. Also extensions of the minimal Standard Model are investigated, obtained by including right-handed neutrinos in the model. The Standard Model extended by two right-handed neutrinos gives rise to a mass spectrum with two massive and three massless neutrinos. The phenomenological consequences of this model are discussed. The neutrino mass matrix in such a scheme has what is defined as a democratic texture. They are studied for the cases with two and three right-handed neutrinos, resp. The chiral fields that we find in the Standard Model have certain similarities with self-dual fields. Among other things, both chiral and self-dual fields suffer species doubling on the lattice. Chiral p-forms are self-dual fields that appear in twice odd dimensions. Chiral p-forms violate manifest covariance, in the same sense as manifest covariance is violated by non-covariant gauges in electrodynamics. It is shown that a covariant action can nevertheless be formulated for chiral p-forms, by introducing an infinite set of gauge fields in a carefully controlled way.
Chiral realization of the non-leptonic weak interactions
International Nuclear Information System (INIS)
Ecker, G.
1990-01-01
After a short introduction to chiral perturbation theory an attempt to relate the strong and the non-leptonic weak low-energy constants is reviewed. The weak deformation model is stimulated both by the geometrical structure of chiral perturbation theory and by phenomenological considerations. Applications to the radiative decays K → πγγ and K L → γe + e - are discussed. (Author) 38 refs., 4 figs
Baryons as non-topological chiral solitons
Christov, Chr. V.; Blotz, A.; Kim, H.-C.; Pobylitsa, P.; Watabe, T.; Meissner, Th.; Ruiz Arriola, E.; Goeke, K.
The present review gives a survey of recent developments and applications of the Nambu-Jona-Lasinio model with Nf = 2 and Nf = 3 quark flavors for the structure of baryons. The model is an effective chiral quark theory which incorporates the SU(N f) L⊗SU(N f) R⊗U(1) V approximate symmetry of Quantum chromodynamics. The approach describes the spontaneous chiral symmetry breaking and dynamical quark mass generation. Mesons appear as quark-antiquark excitations and baryons arise as non-topological solitons with three valence quarks and a polarized Dirac sea. For the evaluation of the baryon properties the present review concentrates on the non-linear Nambu-Jona-Lasinio model with quark and Goldstone degrees of freedom which is identical to the Chiral quark soliton model obtained from the instanton liquid model of the QCD vacuum. In this non-linear model, a wide variety of observables of baryons of the octet and decuplet is considered. These include, in particular, electromagnetic, axial, pseudoscalar and pion nucleon form factors and the related static properties like magnetic moments, radii and coupling constants of the nucleon as well as the mass splittings and electromagnetic form factors of hyperons. Predictions are given for the strange form factors, the scalar form factor and the tensor charge of the nucleon.
Energy Technology Data Exchange (ETDEWEB)
Labidi, N.S., E-mail: labidi2006@univ-usto.d [Department of chemistry, Faculty of sciences, University of the Sciences and Technology of Oran (U.S.T.O.MB), BP-1505 Oran El-M' naouer, 31000 (Algeria); Djebaili, A. [Faculte des Sciences, Universite de Batna, 05000 (Algeria)
2010-05-25
The static polarizabilities {alpha} for a series of substituted hexatriene molecules of the NO{sub 2}-(CH=CH){sub 3}-D and NO{sub 2}-(CH=CH){sub 3}-A types (D, A = N(Me){sub 2}, Br, OCH{sub 3},CH{sub 3}, NH{sub 2}, Cl, OH, F, COCN, C{sub 2}H, COF, NO, CHO, CN, CF{sub 3}) have been computed using DFT method at B3LYP/6-311 G(d,p) level of theory. Our results allowed to sort out the considered {Pi}-donor and {Pi}-acceptor substituents by decreasing static isotropic {alpha} value. An excellent agreement between the DFT and PM6 results, they give a correlation coefficient of 0.97. Miller QSAR-quality polarizability calculations give a correlation coefficient of 0.99 when compared with B3LYP/6-311G(d,p) values. Empirical models based on molecular volumes give unrealistic values for <{alpha}> but these values correlate well 0.97 with B3LYP/6-311G(d,p) results.
Buividovich, P. V.; Davody, A.
2017-12-01
We develop numerical tools for diagrammatic Monte Carlo simulations of non-Abelian lattice field theories in the t'Hooft large-N limit based on the weak-coupling expansion. First, we note that the path integral measure of such theories contributes a bare mass term in the effective action which is proportional to the bare coupling constant. This mass term renders the perturbative expansion infrared-finite and allows us to study it directly in the large-N and infinite-volume limits using the diagrammatic Monte Carlo approach. On the exactly solvable example of a large-N O (N ) sigma model in D =2 dimensions we show that this infrared-finite weak-coupling expansion contains, in addition to powers of bare coupling, also powers of its logarithm, reminiscent of resummed perturbation theory in thermal field theory and resurgent trans-series without exponential terms. We numerically demonstrate the convergence of these double series to the manifestly nonperturbative dynamical mass gap. We then develop a diagrammatic Monte Carlo algorithm for sampling planar diagrams in the large-N matrix field theory, and apply it to study this infrared-finite weak-coupling expansion for large-N U (N ) ×U (N ) nonlinear sigma model (principal chiral model) in D =2 . We sample up to 12 leading orders of the weak-coupling expansion, which is the practical limit set by the increasingly strong sign problem at high orders. Comparing diagrammatic Monte Carlo with conventional Monte Carlo simulations extrapolated to infinite N , we find a good agreement for the energy density as well as for the critical temperature of the "deconfinement" transition. Finally, we comment on the applicability of our approach to planar QCD at zero and finite density.
Biaxiality of chiral liquid crystals
International Nuclear Information System (INIS)
Longa, L.; Trebin, H.R.; Fink, W.
1993-10-01
Using extended deGennes-Ginzburg-Landau free energy expansion in terms of the anisotropic part of the dielectric tensor field Q αβ (χ) a connection between the phase biaxiality and the stability of various chiral liquid crystalline phases is studied. In particular the cholesteric phase, the cubic Blue Phases and the phases characterized by an icosahedral space group symmetry are analysed in detail. Also a general question concerning the applicability of the mean-field approximation in describing the chiral phases is addressed. By an extensive study of the model over a wide range of the parameters a new class of phenomena, not present in the original deGennes-Ginzburg-Landau model, has been found. These include: a) re-entrant phase transitions between the cholesteric and the cubic blue phases and b) the existence of distinct phases of the same symmetry but of different biaxialities. The phase biaxiality serves here as an extra scalar order parameter. Furthermore, it has been shown that due to the presence of the competing bulk terms in the free energy, the stable phases may acquire a large degree of biaxiality, also in liquid crystalline materials composed of effectively uniaxial molecules. A study of icosahedral space group symmetries gives a partial answer to the question as to whether an icosahedral quasicrystalline liquid could be stabilized in liquid crystals. Although, in general, the stability of icosahedral structures could be enhanced by the extra terms in the free energy no absolutely stable icosahedral phase has been found. (author). 16 refs, 3 figs, 1 tab
Review of chiral perturbation theory
Indian Academy of Sciences (India)
41] which will be measured to high accuracy at Jefferson Laboratory at the experiment PrimEx. 4. Baryon chiral perturbation theory. Baryon chiral perturbation theory in the modern era was first formulated in [6]. This was a relativistic formulation ...
Algebraic study of chiral anomalies
Indian Academy of Sciences (India)
2012-06-14
Jun 14, 2012 ... Abstract. The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles ... Editor's Note: †Reproduced with kind permission from Springer Science+Business Media: Algebraic study of chiral anoma- ..... We shall see in the sequel several examples in which this ambiguity helps.
Graphene chiral liquid crystals and macroscopic assembled fibres.
Xu, Zhen; Gao, Chao
2011-12-06
Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles.
Physical Principles of Development of the State Standard of Biological Cell Polarizability
Shuvalov, G. V.; Generalov, K. V.; Generalov, V. M.; Kruchinina, M. V.; Koptev, E. S.; Minin, O. V.; Minin, I. V.
2018-03-01
A new state standard of biological cell polarizability based on micron-size latex particles has been developed. As a standard material, it is suggested to use polystyrene. Values of the polarizability calculated for erythrocytes and values of the polarizability of micron-size spherical latex particles measured with measuring-computing complexes agree within the limits of satisfactory relative error. The Standard allows one the unit of polarizability measurements [m3] to be assigned to cells and erythrocytes for the needs of medicine.
Dynamic dipole polarizabilities of the Li atom and the Be+ ion
International Nuclear Information System (INIS)
Tang Liyan; Yan Zongchao; Shi Tingyun; Mitroy, J.
2010-01-01
The dynamic dipole polarizabilities for Li atoms and Be + ions in the 2 2 S and 2 2 P states are calculated using the variational method with a Hylleraas basis. The present polarizabilities represent the definitive values in the nonrelativistic limit. Corrections due to relativistic effects are also estimated. Analytic representations of the polarizabilities for frequency ranges encompassing the n=3 excitations are presented. The recommended polarizabilities for 7 Li and 9 Be + are 164.11±0.03 a 0 3 and 24.489±0.004 a 0 3 , respectively.
Chiral fermions in asymptotically safe quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Meibohm, J. [Gothenburg University, Department of Physics, Goeteborg (Sweden); Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); Pawlowski, J.M. [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung mbH, ExtreMe Matter Institute EMMI, Darmstadt (Germany)
2016-05-15
We study the consistency of dynamical fermionic matter with the asymptotic safety scenario of quantum gravity using the functional renormalisation group. Since this scenario suggests strongly coupled quantum gravity in the UV, one expects gravity-induced fermion self-interactions at energies of the Planck scale. These could lead to chiral symmetry breaking at very high energies and thus to large fermion masses in the IR. The present analysis which is based on the previous works (Christiansen et al., Phys Rev D 92:121501, 2015; Meibohm et al., Phys Rev D 93:084035, 2016), concludes that gravity-induced chiral symmetry breaking at the Planck scale is avoided for a general class of NJL-type models. We find strong evidence that this feature is independent of the number of fermion fields. This finding suggests that the phase diagram for these models is topologically stable under the influence of gravitational interactions. (orig.)
A Polarizable and Transferable PHAST CO 2 Potential for Materials Simulation
Mullen, Ashley L.
2013-12-10
Reliable PHAST (Potentials with High Accuracy Speed and Transferability) intermolecular potential energy functions for CO2 have been developed from first principles for use in heterogeneous systems, including one with explicit polarization. The intermolecular potentials have been expressed in a transferable form and parametrized from nearly exact electronic structure calculations. Models with and without explicit many-body polarization effects, known to be important in simulation of interfacial processes, are constructed. The models have been validated on pressure-density isotherms of bulk CO 2 and adsorption in three metal-organic framework (MOF) materials. The present models appear to offer advantages over high quality fluid/liquid state potentials in describing CO2 interactions in interfacial environments where sorbates adopt orientations not commonly explored in bulk fluids. Thus, the nonpolar CO2-PHAST and polarizable CO 2-PHAST* potentials are recommended for materials/interfacial simulations. © 2013 American Chemical Society.
Gluonic contributions in the chiral hyperbag
International Nuclear Information System (INIS)
Park, B.Y.; Vento, V.; Valencia Univ./CSIC, Valencia
1990-01-01
We incorporate into a non-perturbative chiral bag model scheme the gluons and the η' in a perturbative fashion. We analyze in this context the proton matrix element for the flavor singlet axial current, where due account is taken of the anomaly, and the delta-nucleon mass difference. Our results show that the contribution due to the gluons is significant for large bag radii and that they are crucial in order to establish the Cheshire cat principle. (orig.)
Lodahl, Peter; Mahmoodian, Sahand; Stobbe, Søren; Rauschenbeutel, Arno; Schneeweiss, Philipp; Volz, Jürgen; Pichler, Hannes; Zoller, Peter
2017-01-25
Advanced photonic nanostructures are currently revolutionizing the optics and photonics that underpin applications ranging from light technology to quantum-information processing. The strong light confinement in these structures can lock the local polarization of the light to its propagation direction, leading to propagation-direction-dependent emission, scattering and absorption of photons by quantum emitters. The possibility of such a propagation-direction-dependent, or chiral, light-matter interaction is not accounted for in standard quantum optics and its recent discovery brought about the research field of chiral quantum optics. The latter offers fundamentally new functionalities and applications: it enables the assembly of non-reciprocal single-photon devices that can be operated in a quantum superposition of two or more of their operational states and the realization of deterministic spin-photon interfaces. Moreover, engineered directional photonic reservoirs could lead to the development of complex quantum networks that, for example, could simulate novel classes of quantum many-body systems.
Chiral liquid crystals: the vestigial chiral phases of T, O, I matter
Nissinen, Jaakko; Liu, Ke; Slager, Robert-Jan; Wu, Kai; Zaanen, Jan
We show how chiral order develops in vestigial isotropic phases of T , O and I liquid crystalline systems in three dimensions. The liquid crystal phases are realized in a lattice model of orientational degrees of freedom with point group symmetries G ⊂ O (3) , represented as O (3) -rotors coupled to G gauge fields. The model incorporates also disclinations via the gauge fields, features an ordered nematic phase with unbroken G rotations at low temperatures and a high temperature isotropic liquid phase. We observe an intermediate phase with spontaneous chirality but isotropic SO (3) symmetry (a liquid) for the gauge groups T, O, and I, the proper symmetry groups of the tetrahedron, cube and icosahedron, respectively. For the other subgroups of SO (3) , Cn <= ∞ and Dn <= ∞, there is generically only a single phase transition from the nematic phase to the isotropic liquid. We discuss the nature of the phase transitions and conditions under which the chiral phase is stabilized by the nematic order parameter fluctuations. The nature of the vestigial chiral phase is reminiscent of the so-called Ising nematic phase in iron based superconductors. Research supported by the Netherlands foundation for Fundamental Research of Matter (FOM).
Chiral perturbation theory with nucleons
Energy Technology Data Exchange (ETDEWEB)
Meissner, U.G.
1991-09-01
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, {pi}N scattering and the {sigma}-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon.
Chiral perturbation theory with nucleons
International Nuclear Information System (INIS)
Meissner, U.G.
1991-09-01
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, πN scattering and the σ-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon
On the magnetic polarizability tensor of US coinage
Davidson, John L.; Abdel-Rehim, Omar A.; Hu, Peipei; Marsh, Liam A.; O’Toole, Michael D.; Peyton, Anthony J.
2018-03-01
The magnetic dipole polarizability tensor of a metallic object gives unique information about the size, shape and electromagnetic properties of the object. In this paper, we present a novel method of coin characterization based on the spectroscopic response of the absolute tensor. The experimental measurements are validated using a combination of tests with a small set of bespoke coin surrogates and simulated data. The method is applied to an uncirculated set of US coins. Measured and simulated spectroscopic tensor responses of the coins show significant differences between different coin denominations. The presented results are encouraging as they strongly demonstrate the ability to characterize coins using an absolute tensor approach.
Calculations of polarizabilities and hyperpolarizabilities for the Be+ ion
International Nuclear Information System (INIS)
Tang Liyan; Zhang Junyi; Mitroy, J.; Yan Zongchao; Shi Tingyun; Babb, James F.
2009-01-01
The polarizabilities and hyperpolarizabilities of the Be + ion in the 2 2 S state and the 2 2 P state are determined. Calculations are performed using two independent methods: (i) variationally determined wave functions using Hylleraas basis set expansions and (ii) single electron calculations utilizing a frozen-core Hamiltonian. The first few parameters in the long-range interaction potential between a Be + ion and a H, He, or Li atom, and the leading parameters of the effective potential for the high-L Rydberg states of beryllium were also computed. All the values reported are the results of calculations close to convergence. Comparisons are made with published results where available.
1/N perturbation theory and quantum conservation laws for supersymmetrical chiral field. 2
International Nuclear Information System (INIS)
Aref'eva, I.Ya.; Krivoshchekov, V.K.; Medvedev, P.B.; Gosudarstvennyj Komitet Standartov Soveta Ministrov SSSR, Moscow; Gosudarstvennyj Komitet po Ispol'zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Teoreticheskoj i Ehksperimental'noj Fiziki)
1980-01-01
The renormalizability of the supersymmetric chiral model (supersymmetric nonlinear σ-model) is proved in the framework of the 1/N perturbation theory expansion proposed in the previous paper. The renormalizability proof is essentially based on the quantum supersymmetric chirality condition. The supersymmetric formulation of equations of motion is given. The first non-trivial quantum conservation laws are derived
Pattern production through a chiral chasing mechanism
Woolley, Thomas E.
2017-09-01
Recent experiments on zebrafish pigmentation suggests that their typical black and white striped skin pattern is made up of a number of interacting chromatophore families. Specifically, two of these cell families have been shown to interact through a nonlocal chasing mechanism, which has previously been modeled using integro-differential equations. We extend this framework to include the experimentally observed fact that the cells often exhibit chiral movement, in that the cells chase, and run away, at angles different to the line connecting their centers. This framework is simplified through the use of multiple small limits leading to a coupled set of partial differential equations which are amenable to Fourier analysis. This analysis results in the production of dispersion relations and necessary conditions for a patterning instability to occur. Beyond the theoretical development and the production of new pattern planiforms we are able to corroborate the experimental hypothesis that the global pigmentation patterns can be dependent on the chirality of the chromatophores.
Geada, Isidro Lorenzo; Ramezani-Dakhel, Hadi; Jamil, Tariq; Sulpizi, Marialore; Heinz, Hendrik
2018-02-19
Metallic nanostructures have become popular for applications in therapeutics, catalysts, imaging, and gene delivery. Molecular dynamics simulations are gaining influence to predict nanostructure assembly and performance; however, instantaneous polarization effects due to induced charges in the free electron gas are not routinely included. Here we present a simple, compatible, and accurate polarizable potential for gold that consists of a Lennard-Jones potential and a harmonically coupled core-shell charge pair for every metal atom. The model reproduces the classical image potential of adsorbed ions as well as surface, bulk, and aqueous interfacial properties in excellent agreement with experiment. Induced charges affect the adsorption of ions onto gold surfaces in the gas phase at a strength similar to chemical bonds while ions and charged peptides in solution are influenced at a strength similar to intermolecular bonds. The proposed model can be applied to complex gold interfaces, electrode processes, and extended to other metals.
Chiral diamine-silver(I)-alkene complexes: a quantum chemical and NMR study
DEFF Research Database (Denmark)
Kieken, Elsa; Wiest, Olaf; Helquist, Paul
2005-01-01
The ability of chiral diamine silver complexes to bind chiral and prochiral alkenes has been analyzed in detail. The stereoselectivity in binding of alkenes to a chiral ethanediamine silver complex has been investigated by NMR. The low-energy conformations of several small model complexes have been...... calculation of stereoselectivities that match well the experimental results. For a chiral allylic alcohol substrate, the correct stereoselectivity was obtained only when the structures were optimized with a continuum representation of the solvent. The discrepancy between gas phase and solution data is found...
Amino-Acid-Based Polymerizable Surfactants for the Synthesis of Chiral Nanoparticles.
Preiss, Laura C; Wagner, Manfred; Mastai, Yitzhak; Landfester, Katharina; Muñoz-Espí, Rafael
2016-09-01
Amino-acid-based chiral surfactants with polymerizable moieties are synthesized, and a versatile approach to prepare particles thereof with a chiral surface functionality is presented. As an example of an application, the synthesized particles are tested for their ability as nucleating agents in the enantioselective crystallization of amino acid conglomerate systems, taking rac-asparagine as a model system. Particles resulting from chiral surfactants with different tail groups are compared and the results demonstrate that only the chiral nanoparticles made of the polymerizable surfactant are able to act efficiently as nucleation agent in enantioselective crystallization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Towards chiral diamines as chiral catalytic precursors for the borane ...
Indian Academy of Sciences (India)
2)-2-anilinomethylpiperidine (2) have been employed as chiral catalytic sources in the borane-mediated asymmetric reduction of prochiral ketones thus providing the resulting secondary alcohols in good enantiomeric purities (up to 81% ) ...
Out-of-equilibrium chiral magnetic effect from chiral kinetic theory
Huang, Anping; Jiang, Yin; Shi, Shuzhe; Liao, Jinfeng; Zhuang, Pengfei
2018-02-01
Recently there has been significant interest in the macroscopic manifestation of chiral anomaly in many-body systems of chiral fermions. A notable example is the Chiral Magnetic Effect (CME). Enthusiastic efforts have been made to search for the CME in the quark-gluon plasma created in heavy ion collisions. A crucial challenge is that the extremely strong magnetic field in such collisions may last only for a brief moment and the CME current may have to occur at so early a stage that the quark-gluon matter is still far from thermal equilibrium. This thus requires modeling of the CME in an out-of-equilibrium setting. With the recently developed theoretical tool of chiral kinetic theory, we make a first phenomenological study of the CME-induced charge separation during the pre-thermal stage in heavy ion collisions. The effect is found to be very sensitive to the time dependence of the magnetic field and also influenced by the initial quark momentum spectrum as well as the relaxation time of the system evolution toward thermal equilibrium. Within the present approach, such pre-thermal charge separation is found to be modest.
Weak-field Hall effect and static polarizability of Bloch electrons
Czech Academy of Sciences Publication Activity Database
Středa, Pavel; Jonckheere, T.
2009-01-01
Roč. 79, č. 11 (2009), 115115/1-115115/8 ISSN 1098-0121 R&D Projects: GA ČR GA202/08/0551 Institutional research plan: CEZ:AV0Z10100521 Keywords : Hall effect * magnetization * Bloch electrons electron polarizability * electron polarizability Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009
The electric double layer at high surface potentials: The influence of excess ion polarizability
Hatlo, M. M.|info:eu-repo/dai/nl/412640678; van Roij, R.H.H.G.|info:eu-repo/dai/nl/152978984; Lue, L.
2012-01-01
By including the excess ion polarizability into the Poisson-Boltzmann theory, we show that the decrease in differential capacitance with voltage, observed for metal electrodes above a threshold potential, can be understood in terms of thickening of the double layer due to ion-induced polarizability
Kwaadgras, B.W.; Verdult, M.; Dijkstra, M.; van Roij, R.H.H.G.
2011-01-01
We employ the coupled dipole method to calculate the polarizability tensor of various anisotropic dielectric clusters of polarizable atoms, such as cuboid-, bowl-, and dumbbell-shaped nanoparticles. Starting from a Hamiltonian of a many-atom system, we investigate how this tensor depends on the size
Enhancement of polarizabilities of cylinders with cylinder-slab resonances.
Xiao, Meng; Huang, Xueqin; Liu, H; Chan, C T
2015-02-02
If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much "brighter" is actually closely related to the reverse effect known in the literature as "cloaking by anomalous resonance" which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder.
Cook, Jamie E.
2012-01-01
Amino acids are among the most heavily studied organic compound class in carbonaceous chondrites. The abundance, distributions, enantiomeric compositions, and stable isotopic ratios of amino acids have been determined in carbonaceous chondrites fi'om a range of classes and petrographic types, with interesting correlations observed between these properties and the class and typc of the chondritcs. In particular, isomeric distributions appear to correlate with parent bodies (chondrite class). In addition, certain chiral amino acids are found in enantiomeric excess in some chondrites. The delivery of these enantiomeric excesses to the early Earth may have contributed to the origin of the homochirality that is central to life on Earth today. This talk will explore the amino acids in carbonaceous chondritcs and their relevance to the origin of life.
Krishnan, Chethan; Raju, Avinash
2017-06-01
We construct a candidate for the most general chiral higher spin theory with AdS3 boundary conditions. In the Chern-Simons language, on the left it has the Drinfeld-Sokolov reduced form, but on the right all charges and chemical potentials are turned on. Altogether (for the spin-3 case) these are 19 functions. Despite this, we show that the resulting metric has the form of the "most general" AdS3 boundary conditions discussed by Grumiller and Riegler. The asymptotic symmetry algebra is a product of a W3 algebra on the left and an affine s l (3 )k current algebra on the right, as desired. The metric and higher spin fields depend on all the 19 functions. We compare our work with previous results in the literature.
International Nuclear Information System (INIS)
Hollauer, E.; Nascimento, M.A.C.
1985-01-01
The photoionization cross-section and dynamic polarizability for lithium atom are calculated using a discrete basis set to represent both the bound and the continuum-states of the atom, to construct an approximation to the dynamic polarizability. From the imaginary part of the complex dynamic polarizability one extracts the photoionization cross-section and from its real part the dynamic polarizability. The results are in good agreement with the experiments and other more elaborate calculations (Author) [pt
Kwaadgras, Bas W; Verdult, Maarten; Dijkstra, Marjolein; van Roij, René
2011-10-07
We employ the coupled dipole method to calculate the polarizability tensor of various anisotropic dielectric clusters of polarizable atoms, such as cuboid-, bowl-, and dumbbell-shaped nanoparticles. Starting from a Hamiltonian of a many-atom system, we investigate how this tensor depends on the size and shape of the cluster. We use the polarizability tensor to calculate the energy difference associated with turning a nanocluster from its least to its most favorable orientation in a homogeneous static electric field, and we determine the cluster dimension for which this energy difference exceeds the thermal energy such that particle alignment by the field is possible. Finally, we study in detail the (local) polarizability of a cubic-shaped cluster and present results indicating that, when retardation is ignored, a bulk polarizability cannot be reached by scaling up the system. © 2011 American Institute of Physics
Continuous chiral separations in microreactors
Susanti, Susanti; Meinds, Tim G.; Pinxterhuis, Erik; Schuur, Boelo; de Vries, Johannes G.; Feringa, B.L.; Winkelman, Jozef; Yue, Jun; Heeres, Hero
2016-01-01
The potential of microreactors for enantioselective liquid-liquid extraction has been explored. The experiments were performed in capillary microreactors with combined reactive extraction and phase separation, for the chiral separation of a representative racemic amino acid derivative
Review of chiral perturbation theory
Indian Academy of Sciences (India)
Abstract. A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.
Chirality Quantum Phase Transition in Noncommutative Dirac Oscillator
International Nuclear Information System (INIS)
Wang Shao-Hua; Hou Yu-Long; Jing Jian; Wang Qing; Long Zheng-Wen
2014-01-01
The charged Dirac oscillator on a noncommutative plane coupling to a uniform perpendicular magnetic held is studied in this paper. We map the noncommutative plane to a commutative one by means of Bopp shift and study this problem on the commutative plane. We find that this model can be mapped onto a quantum optics model which contains Anti—Jaynes—Cummings (AJC) or Jaynes—Cummings (JC) interactions when a dimensionless parameter ζ (which is the function of the intensity of the magnetic held) takes values in different regimes. Furthermore, this model behaves as experiencing a chirality quantum phase transition when the dimensionless parameter ζ approaches the critical point. Several evidences of the chirality quantum phase transition are presented. We also study the non-relativistic limit of this model and find that a similar chirality quantum phase transition takes place in its non-relativistic limit. (physics of elementary particles and fields)
Spontaneous chiral symmetry breaking in early molecular networks
Directory of Open Access Journals (Sweden)
Markovitch Omer
2010-05-01
Full Text Available Abstract Background An important facet of early biological evolution is the selection of chiral enantiomers for molecules such as amino acids and sugars. The origin of this symmetry breaking is a long-standing question in molecular evolution. Previous models addressing this question include particular kinetic properties such as autocatalysis or negative cross catalysis. Results We propose here a more general kinetic formalism for early enantioselection, based on our previously described Graded Autocatalysis Replication Domain (GARD model for prebiotic evolution in molecular assemblies. This model is adapted here to the case of chiral molecules by applying symmetry constraints to mutual molecular recognition within the assembly. The ensuing dynamics shows spontaneous chiral symmetry breaking, with transitions towards stationary compositional states (composomes enriched with one of the two enantiomers for some of the constituent molecule types. Furthermore, one or the other of the two antipodal compositional states of the assembly also shows time-dependent selection. Conclusion It follows that chiral selection may be an emergent consequence of early catalytic molecular networks rather than a prerequisite for the initiation of primeval life processes. Elaborations of this model could help explain the prevalent chiral homogeneity in present-day living cells. Reviewers This article was reviewed by Boris Rubinstein (nominated by Arcady Mushegian, Arcady Mushegian, Meir Lahav (nominated by Yitzhak Pilpel and Sergei Maslov.
Chiral thermodynamics of nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Fiorilla, Salvatore
2012-10-23
The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.
Chiral thermodynamics of nuclear matter
International Nuclear Information System (INIS)
Fiorilla, Salvatore
2012-01-01
The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.
Chiral analysis of baryon form factors
Energy Technology Data Exchange (ETDEWEB)
Gail, T.A.
2007-11-08
This work presents an extensive theoretical investigation of the structure of the nucleon within the standard model of elementary particle physics. In particular, the long range contributions to a number of various form factors parametrizing the interactions of the nucleon with an electromagnetic probe are calculated. The theoretical framework for those calculations is chiral perturbation theory, the exact low energy limit of Quantum Chromo Dynamics, which describes such long range contributions in terms of a pion-cloud. In this theory, a nonrelativistic leading one loop order calculation of the form factors parametrizing the vector transition of a nucleon to its lowest lying resonance, the {delta}, a covariant calculation of the isovector and isoscalar vector form factors of the nucleon at next to leading one loop order and a covariant calculation of the isoscalar and isovector generalized vector form factors of the nucleon at leading one loop order are performed. In order to perform consistent loop calculations in the covariant formulation of chiral perturbation theory an appropriate renormalization scheme is defined in this work. All theoretical predictions are compared to phenomenology and results from lattice QCD simulations. These comparisons allow for a determination of the low energy constants of the theory. Furthermore, the possibility of chiral extrapolation, i.e. the extrapolation of lattice data from simulations at large pion masses down to the small physical pion mass is studied in detail. Statistical as well as systematic uncertainties are estimated for all results throughout this work. (orig.)
Macdonald index and chiral algebra
Song, Jaewon
2017-08-01
For any 4d N = 2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. We conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type ( A 1 , A 2 n ) and ( A 1 , D 2 n+1) where the chiral algebras are given by Virasoro and \\widehat{su}(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.
A polarizable QM/MM approach to the molecular dynamics of amide groups solvated in water
Energy Technology Data Exchange (ETDEWEB)
Schwörer, Magnus; Wichmann, Christoph; Tavan, Paul, E-mail: tavan@physik.uni-muenchen.de [Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians Universität München, Oettingenstr. 67, 80538 München (Germany)
2016-03-21
The infrared (IR) spectra of polypeptides are dominated by the so-called amide bands. Because they originate from the strongly polar and polarizable amide groups (AGs) making up the backbone, their spectral positions sensitively depend on the local electric fields. Aiming at accurate computations of these IR spectra by molecular dynamics (MD) simulations, which derive atomic forces from a hybrid quantum and molecular mechanics (QM/MM) Hamiltonian, here we consider the effects of solvation in bulk liquid water on the amide bands of the AG model compound N-methyl-acetamide (NMA). As QM approach to NMA we choose grid-based density functional theory (DFT). For the surrounding MM water, we develop, largely based on computations, a polarizable molecular mechanics (PMM) model potential called GP6P, which features six Gaussian electrostatic sources (one induced dipole, five static partial charge distributions) and, therefore, avoids spurious distortions of the DFT electron density in hybrid DFT/PMM simulations. Bulk liquid GP6P is shown to have favorable properties at the thermodynamic conditions of the parameterization and beyond. Lennard-Jones (LJ) parameters of the DFT fragment NMA are optimized by comparing radial distribution functions in the surrounding GP6P liquid with reference data obtained from a “first-principles” DFT-MD simulation. Finally, IR spectra of NMA in GP6P water are calculated from extended DFT/PMM-MD trajectories, in which the NMA is treated by three different DFT functionals (BP, BLYP, B3LYP). Method-specific frequency scaling factors are derived from DFT-MD simulations of isolated NMA. The DFT/PMM-MD simulations with GP6P and with the optimized LJ parameters then excellently predict the effects of aqueous solvation and deuteration observed in the IR spectra of NMA. As a result, the methods required to accurately compute such spectra by DFT/PMM-MD also for larger peptides in aqueous solution are now at hand.
A polarizable QM/MM approach to the molecular dynamics of amide groups solvated in water.
Schwörer, Magnus; Wichmann, Christoph; Tavan, Paul
2016-03-21
The infrared (IR) spectra of polypeptides are dominated by the so-called amide bands. Because they originate from the strongly polar and polarizable amide groups (AGs) making up the backbone, their spectral positions sensitively depend on the local electric fields. Aiming at accurate computations of these IR spectra by molecular dynamics (MD) simulations, which derive atomic forces from a hybrid quantum and molecular mechanics (QM/MM) Hamiltonian, here we consider the effects of solvation in bulk liquid water on the amide bands of the AG model compound N-methyl-acetamide (NMA). As QM approach to NMA we choose grid-based density functional theory (DFT). For the surrounding MM water, we develop, largely based on computations, a polarizable molecular mechanics (PMM) model potential called GP6P, which features six Gaussian electrostatic sources (one induced dipole, five static partial charge distributions) and, therefore, avoids spurious distortions of the DFT electron density in hybrid DFT/PMM simulations. Bulk liquid GP6P is shown to have favorable properties at the thermodynamic conditions of the parameterization and beyond. Lennard-Jones (LJ) parameters of the DFT fragment NMA are optimized by comparing radial distribution functions in the surrounding GP6P liquid with reference data obtained from a "first-principles" DFT-MD simulation. Finally, IR spectra of NMA in GP6P water are calculated from extended DFT/PMM-MD trajectories, in which the NMA is treated by three different DFT functionals (BP, BLYP, B3LYP). Method-specific frequency scaling factors are derived from DFT-MD simulations of isolated NMA. The DFT/PMM-MD simulations with GP6P and with the optimized LJ parameters then excellently predict the effects of aqueous solvation and deuteration observed in the IR spectra of NMA. As a result, the methods required to accurately compute such spectra by DFT/PMM-MD also for larger peptides in aqueous solution are now at hand.
Anomalous chiral lagrangians and e+e- annihilation into three pions
Bramon, A.; Pallante, E.; Petronzio, R.
1991-01-01
We investigate the reaction e+e-â†’3Ï€ that can be described by the anomalous part of an effective chiral lagrangian. We calculate the next-to-leading corrections to the process and make an estimate of all-order correction within a specific chiral model of pseudoscalars and vector resonances. Our
Heisenberg spin glass experiments and the chiral ordering scenario
International Nuclear Information System (INIS)
Campbell, Ian A.; Petit, Dorothee C.M.C.
2010-01-01
An overview is given of experimental data on Heisenberg spin glass materials so as to make detailed comparisons with numerical results on model Heisenberg spin glasses, with particular reference to the chiral driven ordering transition scenario due to Kawamura and collaborators. On weak anisotropy systems, experiments show critical exponents which are very similar to those estimated numerically for the model Heisenberg chiral ordering transition but which are quite different from those at Ising spin glass transitions. Again on weak anisotropy Heisenberg spin glasses, experimental torque data show well defined in-field transverse ordering transitions up to strong applied fields, in contrast to Ising spin glasses where fields destroy ordering. When samples with stronger anisotropies are studied, critical and in-field behavior tend progressively towards the Ising limit. It can be concluded that the essential physics of laboratory Heisenberg spin glasses mirrors that of model Heisenberg spin glasses, where chiral ordering has been demonstrated numerically. (author)
Chiral symmetry constraints on resonant amplitudes
Bruns, Peter C.; Mai, Maxim
2018-03-01
We discuss the impact of chiral symmetry constraints on the quark-mass dependence of meson resonance pole positions, which are encoded in non-perturbative parametrizations of meson scattering amplitudes. Model-independent conditions on such parametrizations are derived, which are shown to guarantee the correct functional form of the leading quark-mass corrections to the resonance pole positions. Some model amplitudes for ππ scattering, widely used for the determination of ρ and σ resonance properties from results of lattice simulations, are tested explicitly with respect to these conditions.
Non-leptonic hyperon decays and the chiral meson coupling to bags
International Nuclear Information System (INIS)
Horvat, D.; Tadic, D.
1986-01-01
Hyperon nonleptonic decays have been analyzed using a chiral-bag model instead of the MIT-bag model which was used in earlier analyses. The adopted theoretical formalism allows a step by step comparison between the new and the old approaches. The results are in agreement with the calculation which has used chiral model in its cloudy-bag variant. Chiral-bag model based theoretical predictions are not significantly different from the old MIT-bag model based results. Theory can account for overall gross features of the hyperon nonleptonic decays but not for the fine details like the exact, almost vanishing, value of the A(Σsub(+) + ) amplitude. (orig.)
Virtual Compton Scattering at MAMI and measurement of the proton generalized polarizabilities
International Nuclear Information System (INIS)
Roche, Julie
1998-01-01
We have measured the absolute unpolarized cross sections for photon electro-production of the proton with the Three-Spectrometer-Setup at MAMI at a momentum transfer q=600 MeV (or squared quadra-momentum of the virtual photon 0.33 GeV square) and a virtual photon polarization 0.62. The momentum for the outgoing real photon q' ranged from 33 to 111 MeV. We extracted two combinations of the generalized polarizabilities (GPs) of the proton. The reaction of interest is Virtual Compton Scattering off the proton. We can access to a measurement of the rigidity of the internal structure of the nucleon. Below pion production threshold but arbitrary squared quadra-momentum of the virtual photon, measured observables are the GPs. They generalize the concept of electric and magnetic polarizabilities already defined in Real Compton Scattering. Experimentally, the scattered electron was detected in coincidence with the recoiling proton in two high-resolution spectrometers. The photon emission process was selected by a cut on the missing mass squared distribution around zero. This PhD work describes the analysis work from raw data to absolute and precise cross sections (within a 3 pc statistical and 4 pc systematic accuracies). Our experiment at Mainz demonstrates that it is possible to measure two structure functions related to the GPs; extracted values are presented. These observables are compared with theoretical predictions and are very efficient to disentangle models of the non-perturbative structure of the nucleon. (author) [fr
Multipolar Polarizabilities and Hyperpolarizabilities in the Sr Optical Lattice Clock
Porsev, S. G.; Safronova, M. S.; Safronova, U. I.; Kozlov, M. G.
2018-02-01
We address the problem of the lattice Stark shifts in the Sr clock caused by the multipolar M 1 and E 2 atom-field interactions and by the term nonlinear in lattice intensity and determined by the hyperpolarizability. We develop an approach to calculate hyperpolarizabilities for atoms and ions based on a solution of the inhomogeneous equation which allows us to effectively and accurately carry out complete summations over intermediate states. We apply our method to the calculation of the hyperpolarizabilities for the clock states in Sr. We also carry out an accurate calculation of the multipolar polarizabilities for these states at the magic frequency. Understanding these Stark shifts in optical lattice clocks is crucial for further improvement of the clock accuracy.
Is chiral symmetry restored in the excited meson spectrum?
Segovia, J.; Entem, D. R.; Fernández, F.
2008-04-01
The large degeneracy observed in the excited meson spectrum by the Cristal Barrel Collaboration in the experimental data on proton-antiproton annihilation in flight into mesons in the range 1.9-2.4 GeV has been interpreted as a signal of chiral symmetry restoration. In this work we suggest that such degeneracy may be an indication of the confinement potential modification by color screening. The experimental data can be fairly well reproduced in a constituent quark model with a screened linear confinement potential without changing the dynamical quark mass. Observables that could discriminate our model from those which explicitly restore the chiral symmetry are proposed.
Dynamical chiral symmetry breaking and Bethe-Salpeter equation
Energy Technology Data Exchange (ETDEWEB)
Naito, Kenichi [Tokyo Inst. of Tech. (Japan)
1998-08-01
{pi} meson, (pseudo) Nambu-Goldstone particle caused by a spontaneous breaking of chiral symmetry, was studied by use of Bethe-Salpeter (BS) equation in the limits of effective model as a bound state of quark and antiquark. The effective model has nonlocal interaction and proved to satisfy the Gell-Mann-Oaks-Renner (GMOR) mass formula by treating correct Noether current in spite of loss of local chiral invariance of interaction term. GMOR mass formula: M{sub {pi}}{sup 2}f{sub {pi}}{sup 2}{approx_equal}-2m{sub 0}
e +e- modes and U(1) spontaneous chiral symmetry breaking
International Nuclear Information System (INIS)
Steininger, K.
1992-01-01
In this paper, motivated by evidence for a chiral phase transition in strong coupling lattice QED, the authors calculate the two-particle spectrum of the broken QED phase. This is done in the framework of a Nambu and Jona-Lasinio model with U(1) symmetry including chiral symmetry and symmetry breaking properties of QED. The second order chiral phase transition behavior in our model and in lattice QED are in excellent agreement. The authors then present a detailed analysis of the spectra of the e + e - modes in the broken phase. The authors examine whether these modes have any possible relationship to the narrow e + e - resonances found in soft heavy ion collisions at GSL. The authors' answer is negative
Amplification of chirality in liquid crystals
Eelkema, Rienk; Feringa, Ben L.
2006-01-01
The amplification of molecular chirality by liquid crystalline systems is widely applied in investigations towards enantioselective solvent - solute interactions, chiral supramolecular assemblies, smart materials, and the development of liquid crystal displays. Here we present an overview of recent
Doped Chiral Polymer Negative Index Materials (DCPNIM)
National Aeronautics and Space Administration — Doped Chiral Polymer-Negative Index Materials (DCP-NIM) with tunable resonance frequencies are developed by adding various plasmonic nanoinclusions into chiral...
Charge radii of octet and decuplet baryons in chiral constituent ...
Indian Academy of Sciences (India)
lated in the framework of chiral constituent quark model (χCQM) using a general parametrization method (GPM). Our results are not only comparable with the latest experimental studies but also agree with other phenomenological models. The effects of SU(3) symmetry breaking pertaining to the strangeness contribution ...
Theoretical studies of the global minima and polarizabilities of small lithium clusters
Energy Technology Data Exchange (ETDEWEB)
Hu, Hanshi; Zhao, Ya-Fan; Hammond, Jeffrey R.; Bylaska, Eric J.; Apra, Edoardo; van Dam, Hubertus JJ; Li, Jun; Govind, Niranjan; Kowalski, Karol
2016-01-16
Lithium clusters Lin (n=1-20) have been investigated with density functional theory (DFT) and coupled—cluster (CC) methods. The global-minimum structures are located via an improved basin---hopping algorithm and the lowest energy Lin isomers are confirmed with DFT geometry optimizations, CCSD(T) energy calculations, and by comparing simulated and experimental polarizabilities. The tetrahedral Li4 structure is found to be the basic building block of lithium clusters Lin (n=6-20). Simulated polarizabilities, including thermal effects at room temperature, are in good agreement with measured isotropic polarizabilities.
Tactoids of chiral liquid crystals
Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo
The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.
Optical activity via Kerr nonlinearity in a spinning chiral medium
Energy Technology Data Exchange (ETDEWEB)
Khan, Anwar Ali, E-mail: anwarali@uom.edu.pk [Department of Physics, University of Malakand at Chakdara Dir(L) (Pakistan); Bacha, Bakht Amin, E-mail: aminoptics@gmail.com [Department of Physics, University of Malakand at Chakdara Dir(L) (Pakistan); Khan, Rahmat Ali, E-mail: rahmat_alipk@yahoo.com [Department of Mathematics, University of Malakand (Pakistan)
2016-11-11
Optical activity is investigated in a chiral medium by employing the four level cascade atomic model, in which the optical responses of the atomic medium are studied with Kerr nonlinearity. Light entering into a chiral medium splits into circular birefringent beams. The angle of divergence between the circular birefringent beams and the polarization states of the two light beams is manipulated with Kerr nonlinearity. In the stationary chiral medium the angle of divergence between the circular birefringent beams is calculated to be 1.3 radian. Furthermore, circular birefringence is optically controlled in a spinning chiral medium, where the maximum rotary photon drag angle for left (right) circularly polarized beam is ±1.1 (±1.5) microradian. The change in the angle of divergence between circular birefringent beams by rotary photon drag is calculated to be 0.4 microradian. The numerical results may help to understand image designing, image coding, discovery of photonic crystals and optical sensing technology. - Highlights: • Coherent control of a circular birefringence in a chiral medium is studied. • Angle of divergence between birefringent beams is modified with Kerr nonlinearity. • Rotary photon drag is controlled for birefringent beams and enhanced with Kerr nonlinearity in a spinning medium. • Rotation of the angle of divergence is observed with mechanical rotation of the medium about an axis and modified with Kerr effect. • A change in the angle of divergence is calculated by about a microradian with rotary photon drag.
On the Mechanical Properties of Chiral Carbon Nanotubes
Directory of Open Access Journals (Sweden)
Mahnaz Zakeri
2013-12-01
Full Text Available Carbon nanotubes (CNTs are specific structures with valuable characteristics. In general, the structure of each nanotube is defined by a unique chiral vector. In this paper, different structures of short single-walled CNTs are simulated and their mechanical properties are determined using finite element method. For this aim, a simple algorithm is presented which is able to model the geometry of single-walled CNTs with any desired structure based on nano-scale continuum mechanics approach. By changing the chiral angle from 0 to 30 degree for constant length to radius ratio, the effect of nanotube chirality on its mechanical properties is evaluated. It is observed that the tensile modulus of CNTs changes between 0.93-1.02 TPa for different structures, and it can be higher for chiral structures than zigzag and armchair ones. Also, for different chiral angles, the bending modulus changes between 0.76-0.82 TPa, while the torsional modulus varies in the range of 0.283-0.301TPa.
Modeling magnetic circular dichroism within the polarizable embedding approach
DEFF Research Database (Denmark)
Nørby, Morten Steen; Coriani, Sonia; Kongsted, Jacob
2018-01-01
Magnetic circular dichroism (MCD) is defined as the differential absorption of left and right circularly polarized light in a sample subjected to an external magnetic field. In order to interpret the results of MCD measurements, theoretical predictions of key MCD parameters can be of utmost...... of the more conventional dielectric continuum approach. Results are presented for cytosine and hypoxanthine solvated in water....
Transition polarizability model of induced resonance Raman optical activity
Czech Academy of Sciences Publication Activity Database
Yamamoto, S.; Bouř, Petr
2013-01-01
Roč. 34, č. 25 (2013), s. 2152-2158 ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA13-03978S; GA MŠk(CZ) LH11033 Grant - others:AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : induced resonance Raman optical activity * europium complexes * density functional computations * light scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.601, year: 2013
Introduction to chiral symmetry in QCD
Directory of Open Access Journals (Sweden)
Sazdjian H.
2017-01-01
Full Text Available The main aspects of chiral symmetry in QCD are presented. The necessity of its spontaneous breakdown is explained. Some low-energy theorems are reviewed. The role of chiral effective Lagrangians in the formulation and realization of chiral perturbation theory is emphasized. The consequences of the presence of anomalies are sketched.
Developments of Chiral Metallocenes as Polymerization Catalysts
Directory of Open Access Journals (Sweden)
Takeshi Shiono
2005-07-01
Full Text Available This review article describes developments in chiral metallocenes as polymerization catalysts focusing on C2 symmetric ansa-zirconocene complexes. Selective synthesis of rac-isomers of ansa-zirconocenes are surveyed. Isospecific polymerizations of propylene catalyzed by chiral zirconocenes are summarized. Advanced series of polymerizations by chiral metallocenes such as asymmetric polymerization and polymerization of polar monomers are also introduced.
Chiral phase transition from string theory.
Parnachev, Andrei; Sahakyan, David A
2006-09-15
The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.
Conformation and chirality in liquid crystals
West, John L.; Zhao, Lei
2013-09-01
High helical twisting powerchiral additives are required for an expanding variety of liquid crystal displays and devices. Molecular conformation plays a critical role in determining the helical twisting power, HTP, of chiral additives. We studied additives based on an isosorbide benzoate ester core. Molecular modeling revealed two low energy states with very different conformations for this core The ultra-violet absorption and NMR spectra show two stable isosorbide conformers These spectra reveal how the relative populations of these two conformations change with temperature and how this is related to the helical twisting power. Conformation changes can explain many of the observed anomalous responses of HPT to temperature.
Anomalies in chiral W--gravity
International Nuclear Information System (INIS)
Carvalho, Marcelo; Vilar, Luiz Claudio Queiroz; Sorella, S.P.
1994-01-01
W-algebras are an extension of the Virasoro algebra. They describe the commutation relations between the components of the stress-energy tensor (T ++ ,T -- ) and the currents (W ++++... , W ----... ) of higher spin. Among the various W-algebras considered in the recent literature, the so-called W 3 -algebra plays a rather special role, due to the fact that it has a simple field theory realization. The corresponding field model, known as W 3 -gravity, yields a generalization of the usual bosonic string action. In this work, anomalies in chiral W--gravity are studied
Development and Investigation of NMR tools for chiral compound identification
Energy Technology Data Exchange (ETDEWEB)
Alam, Todd Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Electronic, Optical and Nano Materials; Lansdon, Rick [Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States)
2014-09-01
The goal behind the assigned summer project was to investigate the ability of nuclear magnetic resonance spectroscopy (NMR) to identify enantiomers of select chiral organo-fluorophosphates (OFPs) compounds which are analogs of chemical warfare agents (CWAs, e.g. Sarin). This involved investigations utilizing chiral solvating agents (CSAs) and characterizing the binding phenomena with cyclodextrins. The resolution of OFPs enantiomers using NMR would be useful for research into toxicodynamics and toxicokinetics in biological systems due to the widely differing properties of the CWA enantiomers [1]. The optimization of decontamination abilities in the case of a CWA events, with this method’s potential rapidity and robustness, as well as the development of models correlating chiral compounds with CSAs for optimal resolution are all rational benefits of this research.
Non-leptonic weak decay of hadrons and chiral symmetry
International Nuclear Information System (INIS)
Suzuki, Katsuhiko
2000-01-01
We review the non-leptonic weak decay of hyperons and ΔI=1/2 rule with a special emphasis on the role of chiral symmetry. The soft-pion theorem provides a powerful framework to understand the origin of ΔI=1/2 rule qualitatively. However, quantitative description is still incomplete in any model of the hadrons. Naive chiral perturbation theory cannot explain the parity-conserving and violating amplitudes simultaneously, and convergence of the chiral expansion seems to be worse. We demonstrate how the non-leptonic weak decay amplitudes are sensitive to the quark-pair correlation in the baryons, and show the importance of the strong quark correlation in the spin-0 channel to reproduce the experimental data. We finally remark several related topics. (author)
International Nuclear Information System (INIS)
Orimoto, Yuuichi; Aoki, Yuriko
2016-01-01
An automated property optimization method was developed based on the ab initio O(N) elongation (ELG) method and applied to the optimization of nonlinear optical (NLO) properties in DNA as a first test. The ELG method mimics a polymerization reaction on a computer, and the reaction terminal of a starting cluster is attacked by monomers sequentially to elongate the electronic structure of the system by solving in each step a limited space including the terminal (localized molecular orbitals at the terminal) and monomer. The ELG-finite field (ELG-FF) method for calculating (hyper-)polarizabilities was used as the engine program of the optimization method, and it was found to show linear scaling efficiency while maintaining high computational accuracy for a random sequenced DNA model. Furthermore, the self-consistent field convergence was significantly improved by using the ELG-FF method compared with a conventional method, and it can lead to more feasible NLO property values in the FF treatment. The automated optimization method successfully chose an appropriate base pair from four base pairs (A, T, G, and C) for each elongation step according to an evaluation function. From test optimizations for the first order hyper-polarizability (β) in DNA, a substantial difference was observed depending on optimization conditions between “choose-maximum” (choose a base pair giving the maximum β for each step) and “choose-minimum” (choose a base pair giving the minimum β). In contrast, there was an ambiguous difference between these conditions for optimizing the second order hyper-polarizability (γ) because of the small absolute value of γ and the limitation of numerical differential calculations in the FF method. It can be concluded that the ab initio level property optimization method introduced here can be an effective step towards an advanced computer aided material design method as long as the numerical limitation of the FF method is taken into account.
Spin flexoelectricity and chiral spin structures in magnetic films
Pyatakov, A. P.; Sergeev, A. S.; Mikailzade, F. A.; Zvezdin, A. K.
2015-06-01
In this short review a broad range of chiral phenomena observed in magnetic films (spin cycloid and skyrmion structures formation as well as chirality dependent domain wall motion) is considered under the perspective of spin flexoelectricity, i.e. the relation between bending of magnetization pattern and electric polarization. The similarity and the difference between the spin flexoelectricity and the newly emerged notion of spin flexomagnetism are discussed. The phenomenological arguments based on the geometrical idea of curvature-induced effects are supported by analysis of the microscopic mechanisms of spin flexoelectricity based on three-site ion indirect exchange and twisted RKKY interaction models.
Chiral symmetry breaking in a semilocalized magnetic field
Cao, Gaoqing
2018-03-01
In this work, we explore the pattern of chiral symmetry breaking and restoration in a solvable magnetic field configuration within the Nambu-Jona-Lasinio model. The special semilocalized static magnetic field can roughly mimic the realistic situation in peripheral heavy ion collisions; thus, the study is important for the dynamical evolution of quark matter. We find that the magnetic-field-dependent contribution from discrete spectra usually dominates over the contribution from continuum spectra and chiral symmetry breaking is locally catalyzed by both the magnitude and scale of the magnetic field. The study is finally extended to the case with finite temperature or chemical potential.
Chirality transfer across length-scales in nematic liquid crystals: fundamentals and applications.
Pieraccini, Silvia; Masiero, Stefano; Ferrarini, Alberta; Piero Spada, Gian
2011-01-01
When a chiral dopant is dissolved in an achiral liquid crystal medium, the whole sample organizes into a helical structure with a characteristic length-scale of the order of microns. The relation between chirality at these quite different length-scales can be rationalized by a relatively simple model, which retains the relevant factors coming into play: the molecular shape of the chiral dopant, which controls the chirality of short range intermolecular interactions, and the elastic properties of the nematic environment, which control the restoring torques opposing distortion of the director. In this tutorial review the relation between molecular and phase chirality will be reviewed and several applications of the chiral doping of nematic LCs will be discussed. These range from the exploitation of the amplified molecular chirality for stereochemical purposes (e.g., the determination of the absolute configuration or the enantiomeric excess), to newer applications in physico-chemical fields. The latter take advantage of the periodicity of the chiral field, with length-scales ranging from hundreds to thousands of nanometres, which characterise the cholesteric phase.
Conduction of molecular electronic devices: Qualitative insights through atom-atom polarizabilities
International Nuclear Information System (INIS)
Stuyver, T.; Fias, S.; De Proft, F.; Geerlings, P.; Fowler, P. W.
2015-01-01
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability
Conduction of molecular electronic devices: qualitative insights through atom-atom polarizabilities.
Stuyver, T; Fias, S; De Proft, F; Fowler, P W; Geerlings, P
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
Conduction of molecular electronic devices: Qualitative insights through atom-atom polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Stuyver, T.; Fias, S., E-mail: sfias@vub.ac.be; De Proft, F.; Geerlings, P. [ALGC, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel (Belgium); Fowler, P. W. [Department of Chemistry, University of Sheffield, Sheffield S3 7HF (United Kingdom)
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
Metal-organic materials (MOMs) for adsorption of polarizable gases and methods of using MOMs
Zaworotko, Michael; Mohamed, Mona H.; Elsaidi, Sameh
2017-06-14
Embodiments of the present disclosure provide for multi-component metal-organic materials (MOMs), systems including the MOM, systems for separating components in a gas, methods of separating polarizable gases from a gas mixture, and the like.
Carnimeo, Ivan; Cappelli, Chiara
2015-01-01
A polarizable quantum mechanics (QM)/ molecular mechanics (MM) approach recently developed for Hartree–Fock (HF) and Kohn–Sham (KS) methods has been extended to energies and analytical gradients for MP2, double hybrid functionals, and TD‐DFT models, thus allowing the computation of equilibrium structures for excited electronic states together with more accurate results for ground electronic states. After a detailed presentation of the theoretical background and of some implementation details, a number of test cases are analyzed to show that the polarizable embedding model based on fluctuating charges (FQ) is remarkably more accurate than the corresponding electronic embedding based on a fixed charge (FX) description. In particular, a set of electronegativities and hardnesses has been optimized for interactions between QM and FQ regions together with new repulsion–dispersion parameters. After validation of both the numerical implementation and of the new parameters, absorption electronic spectra have been computed for representative model systems including vibronic effects. The results show remarkable agreement with full QM computations and significant improvement with respect to the corresponding FX results. The last part of the article provides some hints about computation of solvatochromic effects on absorption spectra in aqueous solution as a function of the number of FQ water molecules and on the use of FX external shells to improve the convergence of the results. © 2015 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26399473
Towards chiral diamines as chiral catalytic precursors for the borane ...
Indian Academy of Sciences (India)
Administrator
anilinomethylpiperidine (2) have been employed as chiral catalytic sources in the borane-mediated asymmetric reduction of prochiral ketones ..... 7⋅86 min (S) and 8.53 min (R)]. 2.7c (S)-2-Bromo-1-(4-bromophenyl)ethanol [(S)– ... of (a) compound 8 and (b) compound 15-TFA salt (Hydrogen atoms were omitted for clarity).
Chiral trans-1,2-diaminocyclohexane derivatives as chiral solvating ...
Indian Academy of Sciences (India)
Administrator
pounds in biological and pharmaceutical chemistry,. 1–4 there is increasing requirement for fast and accurate methodologies for the determination of enantiomeric composition of these chiral compounds. Among the various available methods, NMR spectroscopy has the advantages of easy performance and accessibi- lity.
The reaction γγ → π0π0 in generalized chiral perturbation theory
International Nuclear Information System (INIS)
Knecht, M.; Moussallam, B.; Stern, J.
1994-01-01
The cross section for γγ → π 0 π 0 and the pion polarizabilities are computed, within generalized chiral perturbation theory, in the full one loop approximation, i.e. up to and including order O(p 5 ). The result depends on the parameter α ππ defining the tree level π-π scattering amplitude and on an additional low energy constant. The latter is shown to be related by an exact sum-rule to the e + e - data. The parameter α ππ is related to the quark mass ratio r=m s /m via the expansion of pseudoscalar meson masses. Higher order corrections are estimated comparing the calculation with the dispersive approach. (authors). 35 refs., 6 figs., 1 tab
Chiral xenobiotics bioaccumulations and environmental health prospectives.
Hussain, Iqbal; ALOthman, Zeid A; Alwarthan, Abdulrahman A; Sanagi, Mohd Marsin; Ali, Imran
2015-08-01
The chiral xenobiotics are very dangerous for all of us due to the different enantioselective toxicities of the enantiomers. Besides, these have different enantioselective bioaccumulations and behaviors in our body and other organisms. It is of urgent need to understand the enantioselective bioaccumulations, toxicities, and the health hazards of the chiral xenobiotics. The present article describes the classification, sources of contamination, distribution, enantioselective bioaccumulation, and the toxicities of the chiral xenobiotics. Besides, the efforts are also made to discuss the prevention and remedial measures of the havoc of the chiral xenobiotics. The challenges of the chiral xenobiotics have also been highlighted. Finally, future prospectives are also discussed.
Chiral structure of the nucleon
International Nuclear Information System (INIS)
Bernard, V.; Kaiser, N.; Kambor, J.; Meissner, U.G.
1992-01-01
We analyze the structure of QCD Green functions with on external nucleon, treated as a very massive field. We discuss the matching conditions and relations of various nucleon matrix elements of quark currents to the relativistic approach. Particular emphasis is put on the forward Compton amplitudes. Besides the nucleon electromagnetic polarizabilities we consider the spin-flip amplitude f 2 (ω 2 ) to one-loop order. We predict the slope parameter of f 2 (ω 2 ) which can be determined from the absorption cross sections of circularly polarized photons on polarized nucleon. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Ganguly, Jayanta [Department of Chemistry, Brahmankhanda Basapara High School, Basapara, Birbhum 731 215, West Bengal (India); Ghosh, Manas, E-mail: pcmg77@rediffmail.com [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)
2014-06-25
Highlights: • Linear polarizability of quantum dot has been studied. • Quantum dot is doped with a repulsive impurity. • The polarizabilities are frequency-dependent. • Influence of Gaussian white noise has been monitored. • Noise exploited is of additive and multiplicative nature. - Abstract: We investigate the profiles of diagonal components of frequency-dependent linear (α{sub xx} and α{sub yy}) optical response of repulsive impurity doped quantum dots. The dopant impurity potential chosen assumes Gaussian form. The study principally puts emphasis on investigating the role of noise on the polarizability components. In view of this we have exploited Gaussian white noise containing additive and multiplicative characteristics (in Stratonovich sense). The frequency-dependent polarizabilities are studied by exposing the doped dot to a periodically oscillating external electric field of given intensity. The oscillation frequency, confinement potentials, dopant location, and above all, the noise characteristics tune the linear polarizability components in a subtle manner. Whereas the additive noise fails to have any impact on the polarizabilities, the multiplicative noise influences them delicately and gives rise to additional interesting features.
Analytical transition-matrix treatment of electric multipole polarizabilities of hydrogen-like atoms
International Nuclear Information System (INIS)
Kharchenko, V.F.
2015-01-01
The direct transition-matrix approach to the description of the electric polarization of the quantum bound system of particles is used to determine the electric multipole polarizabilities of the hydrogen-like atoms. It is shown that in the case of the bound system formed by the Coulomb interaction the corresponding inhomogeneous integral equation determining an off-shell scattering function, which consistently describes virtual multiple scattering, can be solved exactly analytically for all electric multipole polarizabilities. Our method allows to reproduce the known Dalgarno–Lewis formula for electric multipole polarizabilities of the hydrogen atom in the ground state and can also be applied to determine the polarizability of the atom in excited bound states. - Highlights: • A new description for electric polarization of hydrogen-like atoms. • Expression for multipole polarizabilities in terms of off-shell scattering functions. • Derivation of integral equation determining the off-shell scattering function. • Rigorous analytic solving the integral equations both for ground and excited states. • Study of contributions of virtual multiple scattering to electric polarizabilities
International Nuclear Information System (INIS)
Ganguly, Jayanta; Ghosh, Manas
2014-01-01
Highlights: • Linear polarizability of quantum dot has been studied. • Quantum dot is doped with a repulsive impurity. • The polarizabilities are frequency-dependent. • Influence of Gaussian white noise has been monitored. • Noise exploited is of additive and multiplicative nature. - Abstract: We investigate the profiles of diagonal components of frequency-dependent linear (α xx and α yy ) optical response of repulsive impurity doped quantum dots. The dopant impurity potential chosen assumes Gaussian form. The study principally puts emphasis on investigating the role of noise on the polarizability components. In view of this we have exploited Gaussian white noise containing additive and multiplicative characteristics (in Stratonovich sense). The frequency-dependent polarizabilities are studied by exposing the doped dot to a periodically oscillating external electric field of given intensity. The oscillation frequency, confinement potentials, dopant location, and above all, the noise characteristics tune the linear polarizability components in a subtle manner. Whereas the additive noise fails to have any impact on the polarizabilities, the multiplicative noise influences them delicately and gives rise to additional interesting features
Chiral Symmetry Breaking in Peptide Systems During Formation of Life on Earth
Konstantinov, Konstantin K.; Konstantinova, Alisa F.
2018-03-01
Chiral symmetry breaking in complex chemical systems with a large number of amino acids and a large number of similar reactions was considered. It was shown that effective averaging over similar reaction channels may result in very weak effective enantioselectivity of forward reactions, which does not allow most of the known models to result in chiral symmetry breaking during formation of life on Earth. Models with simple and catalytic synthesis of a single amino acid, formation of peptides up to length five, and sedimentation of insoluble pair of substances were considered. It was shown that depending on the model and the values of the parameters, chiral symmetry breaking may occur in up to about 10% out of all possible unique insoluble pair combinations even in the absence of any catalytic synthesis and that minimum total number of amino acids in the pair is 5. If weak enantioselective forward catalytic synthesis of amino acids is present, then the number of possible variants, in which chiral symmetry breaking may occur, increases substantially. It was shown that that the most interesting catalysts have zero or one amino acid of "incorrect" chirality. If the parameters of the model are adjusted in such a way to result in an increase of concentration of longer peptides, then catalysts with two amino acids of incorrect chirality start to appear at peptides of length five. Models of chiral symmetry breaking in the presence of epimerization were considered for peptides up to length three. It was shown that the range of parameters in which chiral symmetry breaking could occur significantly shrinks in comparison to previously considered models with peptides up to length two. An experiment of chiral symmetry breaking was proposed. The experiment consists of a three-step cycle: reversible catalytic synthesis of amino acids, reversible synthesis of peptides, and irreversible sedimentation of insoluble substances.
Planar chiral metamaterials for biosensing applications
Murugkar, Sangeeta; De Leon, Israel; Horton, Matthew; Qassim, Hammam; Leach, Jonathan; Boyd, Robert W.
2013-02-01
There has been a considerable effort recently in the development of planar chiral metamaterials. Owing to the lack of inversion symmetry, these materials have been shown to display interesting physical properties such as negative index of refraction and giant optical activity. However, the biosensing capabilities of these chiral metamaterials have not been fully explored. Ultrasensitive detection and structural characterization of proteins adsorbed on chiral plasmonic substrates was demonstrated recently using UV-visible circular dichroism (CD) spectroscopy. Second harmonic generation microscopy is an extremely sensitive nonlinear optical probe to investigate the chirality of biomaterials. In this study, we characterize the chiral response of chiral plasmonic metamaterials using second harmonic generation microscopy and CD spectroscopy. These planar chiral metamaterials, fabricated by electron-beam lithography, consist of right-handed and left-handed gold gammadions of length 400 nm and thickness 100nm, deposited on a glass substrate and arranged in a square lattice with a periodicity of 800nm.
On the path integral quantization of chiral bosons
International Nuclear Information System (INIS)
Schaposnik, F.A.; Schaposnik, F.A.; Solomin, J.E.
1989-01-01
The authors show that, in the covariant Lagrangian formalism, a proper treatment of the gauge degree of freedom in a model of chiral bosons proposed by Siegel uncovers the presence of a Jacobian (a Wess-Zumino action): the group of gauge transformations gets quantized and the anomaly is absorbed
Chiral symmetry in the path-integral approach
International Nuclear Information System (INIS)
Schaposnik, F.A.
1987-01-01
The derivation of anomalous Ward-Takahashi identities related to chiral symmetries in the path-integral framework is presented. Some two-dimensional models in both abelian and non-abelian cases are discussed. The quantization of such theories using Weyl fermions is also presented. (L.C.) [pt
Chiral separation of amino-alcohols using extractant impregnated resins
Babic, K.; Driessen, G.H.M.; van der Ham, Aloysius G.J.; de Haan, A.B.
2007-01-01
The performance of extractant impregnated resin (EIR) technology for chiral separation of amino-alcohols has been investigated. Phenylglycinol was selected as an archetype model enantiomer and azophenolic crown ether was used as a versatile enantioselective extractant. 1-Phenyloctane was selected as
Single chirality through crystal grinding
Noorduin, W.L.
2010-01-01
The properties of chiral molecules in living organisms can be different for left- and right-handed molecules. Therefore, ways to produce molecules of single handedness are of paramount importance, especially for economical, high yielding processes to synthesize pharmaceutical compounds that must be
Principles of chiral perturbation theory
International Nuclear Information System (INIS)
Leutwyler, H.
1995-01-01
An elementary discussion of the main concepts used in chiral perturbation theory is given in textbooks and a more detailed picture of the applications may be obtained from the reviews. Concerning the foundations of the method, the literature is comparatively scarce. So, I will concentrate on the basic concepts and explain why the method works. (author)
The chiral condensate in matter
International Nuclear Information System (INIS)
Brockmann, R.; Weise, W.
1995-01-01
The change of the chiral condensate in dense matter is discussed. Especially the higher order terms in the density of nuclear matter are evaluated (in the relativistic Brueckner-Hartree-Fock approach). Implications for nuclear physics and relativistic heavy ion collisions are discussed, such as the strong Dirac scalar mean field that results from the density dependence of . (orig.)
Review of chiral perturbation theory
Indian Academy of Sciences (India)
A review of chiral perturbation theory and recent developments on the comparison of its predictions with .... terms of the effective Lagrangian at two-loop or O(p6) order is now available [12]. The formidable task of ... and straightforward manner for the system and are of great importance for the analysis of experimental ...
Descendants of the Chiral Anomaly
Jackiw, R.
2000-01-01
Chern-Simons terms are well-known descendants of chiral anomalies, when the latter are presented as total derivatives. Here I explain that also Chern-Simons terms, when defined on a 3-manifold, may be expressed as total derivatives.
Chiral phosphines in nucleophilic organocatalysis
Directory of Open Access Journals (Sweden)
Yumei Xiao
2014-09-01
Full Text Available This review discusses the tertiary phosphines possessing various chiral skeletons that have been used in asymmetric nucleophilic organocatalytic reactions, including annulations of allenes, alkynes, and Morita–Baylis–Hillman (MBH acetates, carbonates, and ketenes with activated alkenes and imines, allylic substitutions of MBH acetates and carbonates, Michael additions, γ-umpolung additions, and acylations of alcohols.
Effect of dipole polarizability on positron binding by strongly polar molecules
International Nuclear Information System (INIS)
Gribakin, G F; Swann, A R
2015-01-01
A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron–positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including the polarization potential via perturbation theory and non-perturbatively. The perturbative model makes reliable predictions of binding energies for a range of polar organic molecules and hydrogen cyanide. The model also agrees with the linear dependence of the binding energies on the polarizability inferred from the experimental data (Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203). The effective core radii, however, remain unphysically small for most molecules. Treating molecular polarization non-perturbatively leads to physically meaningful core radii for all of the molecules studied and enables even more accurate predictions of binding energies to be made for nearly all of the molecules considered. (paper)
Stark effect, polarizability, and electroabsorption in silicon nanocrystals
Bulutay, Ceyhun; Kulakci, Mustafa; Turan, Raşit
2010-03-01
Demonstrating the quantum-confined Stark effect (QCSE) in silicon nanocrystals (NCs) embedded in oxide has been rather elusive, unlike the other materials. Here, the recent experimental data from ion-implanted Si NCs is unambiguously explained within the context of QCSE using an atomistic pseudopotential theory. This further reveals that the majority of the Stark shift comes from the valence states which undergo a level crossing that leads to a nonmonotonic radiative recombination behavior with respect to the applied field. The polarizability of embedded Si NCs including the excitonic effects is extracted over a diameter range of 2.5-6.5 nm, which displays a cubic scaling, α=cDNC3 , with c=2.436×10-11C/(Vm) , where DNC is the NC diameter. Finally, based on intraband electroabsorption analysis, it is predicted that p -doped Si NCs will show substantial voltage tunability, whereas n -doped samples should be almost insensitive. Given the fact that bulk silicon lacks the linear electro-optic effect as being a centrosymmetric crystal, this may offer a viable alternative for electrical modulation using p -doped Si NCs.
Lemkul, Justin A; MacKerell, Alexander D
2017-05-09
Empirical force fields seek to relate the configuration of a set of atoms to its energy, thus yielding the forces governing its dynamics, using classical physics rather than more expensive quantum mechanical calculations that are computationally intractable for large systems. Most force fields used to simulate biomolecular systems use fixed atomic partial charges, neglecting the influence of electronic polarization, instead making use of a mean-field approximation that may not be transferable across environments. Recent hardware and software developments make polarizable simulations feasible, and to this end, polarizable force fields represent the next generation of molecular dynamics simulation technology. In this work, we describe the refinement of a polarizable force field for DNA based on the classical Drude oscillator model by targeting quantum mechanical interaction energies and conformational energy profiles of model compounds necessary to build a complete DNA force field. The parametrization strategy employed in the present work seeks to correct weak base stacking in A- and B-DNA and the unwinding of Z-DNA observed in the previous version of the force field, called Drude-2013. Refinement of base nonbonded terms and reparametrization of dihedral terms in the glycosidic linkage, deoxyribofuranose rings, and important backbone torsions resulted in improved agreement with quantum mechanical potential energy surfaces. Notably, we expand on previous efforts by explicitly including Z-DNA conformational energetics in the refinement.
Energy Technology Data Exchange (ETDEWEB)
Deprele, Sylvine; Kashemirov, Boris A.; Hogan, James M.; Ebetino, Frank H.; Barnett, Bobby L.; Evdokimov, Artem; McKenna, Charles E. (USC); (UCIN); (PG)
2008-08-19
The complex formed from crystallization of human farnesyl pyrophosphate synthase (hFPPS) from a solution of racemic [6,7-dihydro-5H-cyclopenta[c]pyridin-7-yl(hydroxy)methylene]bis(phosphonic acid) (NE-10501, 8), a chiral analog of the anti-osteoporotic drug risedronate, contained the R enantiomer in the enzyme active site. This enantiospecificity was assessed by computer modeling of inhibitor-active site interactions using Autodock 3, which was also evaluated for predictive ability in calculations of the known configurations of risedronate, zoledronate, and minodronate complexed in the active site of hFPPS. In comparison with these structures, the 8 complex exhibited certain differences, including the presence of only one Mg{sup 2+}, which could contribute to its 100-fold higher IC{sub 50}. An improved synthesis of 8 is described, which decreases the number of steps from 12 to 8 and increases the overall yield by 17-fold.
International Nuclear Information System (INIS)
Sjoeberg, Daniel
2009-01-01
We present four variational principles for the electric and magnetic polarizabilities for a structure consisting of anisotropic media with perfect electric conductor (PEC) inclusions. From these principles, we derive monotonicity results and upper and lower bounds on the electric and magnetic polarizabilities. When computing the polarizabilities numerically, the bounds can be used as error bounds. The variational principles demonstrate important differences between electrostatics and magnetostatics when PEC bodies are present.
International Nuclear Information System (INIS)
Vakulina, E.V.; Maksimenko, N.V.
2017-01-01
Using the relativistic-invariant effective tensor representation of the Lagrangians of the two-photon interaction with hadrons within the Duffin-Kemmer-Petiau formalism, the spin polarizabilities of the spin 1 particles that are characteristic of spin 1/2 hadrons have been determined. Along with this, new spin polarizabilities of spin 1 particles have been determined, that are related to the presence of the tensor polarizabilities.
Lock-in of a Chiral Soliton Lattice by Itinerant Electrons
Okumura, Shun; Kato, Yasuyuki; Motome, Yukitoshi
2018-03-01
Chiral magnets often show intriguing magnetic and transport properties associated with their peculiar spin textures. A typical example is a chiral soliton lattice, which is found in monoaxial chiral magnets, such as CrNb3S6 and Yb(Ni1-xCux)3Al9 in an external magnetic field perpendicular to the chiral axis. Here, we theoretically investigate the electronic and magnetic properties in the chiral soliton lattice by a minimal itinerant electron model. Using variational calculations, we find that the period of the chiral soliton lattice can be locked at particular values dictated by the Fermi wave number, in stark contrast to spin-only models. We discuss this behavior caused by the spin-charge coupling as a possible mechanism for the lock-in discovered in Yb(Ni1-xCux)3Al9 [T. Matsumura et al., https://doi.org/10.7566/JPSJ.86.124702" xlink:type="simple">J. Phys. Soc. Jpn. 86, 124702 (2017)]. We also show that the same mechanism leads to the spontaneous formation of the chiral soliton lattice even in the absence of the magnetic field.