Chiral plasmons without magnetic field.
Song, Justin C W; Rudner, Mark S
2016-04-26
Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons-chiral Berry plasmons (CBPs)-for a wide range of 2D metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron-electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically pumped 2D Dirac materials. Realization of CBPs will offer a powerful paradigm for magnetic field-free, subwavelength optical nonreciprocity, in the mid-IR to terahertz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands. PMID:27071090
Chiral plasmons without magnetic field
NASA Astrophysics Data System (ADS)
Song, Justin C. W.
2016-04-01
Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons—chiral Berry plasmons (CBPs)—for a wide range of 2D metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron–electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically pumped 2D Dirac materials. Realization of CBPs will offer a powerful paradigm for magnetic field-free, subwavelength optical nonreciprocity, in the mid-IR to terahertz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands.
Field induced spin chirality and chirality switching in magnetic multilayers
NASA Astrophysics Data System (ADS)
Tartakovskaya, Elena V.
2015-05-01
The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.
DH(*) in chiral smectics under electric field.
Meyer, C; Rabette, C; Gisse, P; Antonova, K; Dozov, I
2016-07-01
The behavior of double helices (DH(*) formed in the temperature interval N(*) -SmA(*) in compounds of non-chiral liquid crystals doped with chiral molecules was investigated. Two different systems presenting left-handed and right-handed chirality were studied. A statistics of the handedness of the DH(*) revealed a correlation with the mixture chirality, as predicted theoretically in C. Meyer, Yu. A. Nastishin, M. Kleman, Phys. Rev. E 82, 031704 (2010). By applying a gradually increasing AC electric field, one can observe the shrinking of the cylinder circumscribing the DH(*) . This shrink is accompanied by a reduction of the DH(*) 's pitch. This effect was similar to the one produced by the decrease of temperature in the absence of the field. PMID:27465656
Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures.
Tian, Xiaorui; Fang, Yurui; Sun, Mengtao
2015-01-01
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule. PMID:26621558
Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures
Tian, Xiaorui; Fang, Yurui; Sun, Mengtao
2015-01-01
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule. PMID:26621558
Chiral symmetry and effective field theories for hadronic, nuclear and stellar matter
NASA Astrophysics Data System (ADS)
Holt, Jeremy W.; Rho, Mannque; Weise, Wolfram
2016-03-01
Chiral symmetry, first entering in nuclear physics in the 1970s for which Gerry Brown played a seminal role, has led to a stunningly successful framework for describing strongly-correlated nuclear dynamics both in finite and infinite systems. We review how the early, germinal idea conceived with the soft-pion theorems in the pre-QCD era has evolved into a highly predictive theoretical framework for nuclear physics, aptly assessed by Steven Weinberg: "it (chiral effective field theory) allows one to show in a fairly convincing way that what they (nuclear physicists) have been doing all along... is the correct first step in a consistent approximation scheme". Our review recounts both how the theory presently fares in confronting Nature and how one can understand its extremely intricate workings in terms of the multifaceted aspects of chiral symmetry, namely, chiral perturbation theory, skyrmions, Landau Fermi-liquid theory, the Cheshire cat phenomenon, and hidden local and mended symmetries.
Surface chirality induced by rotational electrodeposition in magnetic fields
Mogi, Iwao; Morimoto, Ryoichi; Aogaki, Ryoichi; Watanabe, Kazuo
2013-01-01
The surfaces of minerals could serve important catalytic roles in the prebiotic syntheses of organic molecules, such as amino acids. Thus, the surface chirality is responsible for the asymmetric syntheses of biomolecules. Here, we show induction of the surface chirality of copper metal film by electrodeposition via electrochemical cell rotation in magnetic fields. Such copper film electrodes exhibit chiral behaviour in the electrochemical reaction of alanine enantiomers, and the rotating direction allows control of the chiral sign. These findings are discussed in connection with the asymmetric influence of the system rotation on the magnetohydrodynamic micro-vortices around the electrode surfaces. PMID:23999254
Chiral pumping effect induced by rotating electric fields
NASA Astrophysics Data System (ADS)
Ebihara, Shu; Fukushima, Kenji; Oka, Takashi
2016-04-01
We propose an experimental setup using 3D Dirac semimetals to access a novel phenomenon induced by the chiral anomaly. We show that the combination of a magnetic field and a circularly polarized laser induces a finite charge density with an accompanying axial current. This is because the circularly polarized laser breaks time-reversal symmetry and the Dirac point splits into two Weyl points, which results in an axial-vector field. We elucidate the appearance of the axial-vector field with the help of the Floquet theory by deriving an effective Hamiltonian for high-frequency electric fields. This anomalous charge density, i.e., the chiral pumping effect, is a phenomenon reminiscent of the chiral magnetic effect with a chiral chemical potential. We explicitly compute the pumped density and the axial-current expectation value. We also take account of coupling to the chiral magnetic effect to calculate a balanced distribution of charge and chirality in a material that behaves as a chiral battery.
Helical polyacetylene synthesized with a chiral nematic reaction field
Akagi; Piao; Kaneko; Sakamaki; Shirakawa; Kyotani
1998-11-27
Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications. PMID:9831554
Chiral Effective Field Theory in the $\\Delta$-resonance region
Vladimir Pascalutsa
2006-09-18
I discuss the problem of constructing an effective low-energy theory in the vicinity of a resonance or a bound state. The focus is on the example of the $\\Delta(1232)$, the lightest resonance in the nucleon sector. Recent developments of the chiral effective-field theory in the $\\Delta$-resonance region are briefly reviewed. I conclude with a comment on the merits of the manifestly covariant formulation of chiral EFT in the baryon sector.
Axial current generation from electric field: chiral electric separation effect.
Huang, Xu-Guang; Liao, Jinfeng
2013-06-01
We study a relativistic plasma containing charged chiral fermions in an external electric field. We show that with the presence of both vector and axial charge densities, the electric field can induce an axial current along its direction and thus cause chirality separation. We call it the chiral electric separation effect (CESE). On a very general basis, we argue that the strength of CESE is proportional to μ(V)μ(A) with μ(V) and μ(A) the chemical potentials for vector charge and axial charge. We then explicitly calculate this CESE conductivity coefficient in thermal QED at leading-log order. The CESE can manifest a new gapless wave mode propagating along the electric field. Potential observable effects of CESE in heavy-ion collisions are also discussed. PMID:25167486
Li, Bing-Wei; Cai, Mei-Chun; Zhang, Hong; Panfilov, Alexander V; Dierckx, Hans
2014-05-14
Chirality is one of the most fundamental properties of many physical, chemical, and biological systems. However, the mechanisms underlying the onset and control of chiral symmetry are largely understudied. We investigate possibility of chirality control in a chemical excitable system (the Belousov-Zhabotinsky reaction) by application of a chiral (rotating) electric field using the Oregonator model. We find that unlike previous findings, we can achieve the chirality control not only in the field rotation direction, but also opposite to it, depending on the field rotation frequency. To unravel the mechanism, we further develop a comprehensive theory of frequency synchronization based on the response function approach. We find that this problem can be described by the Adler equation and show phase-locking phenomena, known as the Arnold tongue. Our theoretical predictions are in good quantitative agreement with the numerical simulations and provide a solid basis for chirality control in excitable media. PMID:24832300
NASA Astrophysics Data System (ADS)
Li, Bing-Wei; Cai, Mei-Chun; Zhang, Hong; Panfilov, Alexander V.; Dierckx, Hans
2014-05-01
Chirality is one of the most fundamental properties of many physical, chemical, and biological systems. However, the mechanisms underlying the onset and control of chiral symmetry are largely understudied. We investigate possibility of chirality control in a chemical excitable system (the Belousov-Zhabotinsky reaction) by application of a chiral (rotating) electric field using the Oregonator model. We find that unlike previous findings, we can achieve the chirality control not only in the field rotation direction, but also opposite to it, depending on the field rotation frequency. To unravel the mechanism, we further develop a comprehensive theory of frequency synchronization based on the response function approach. We find that this problem can be described by the Adler equation and show phase-locking phenomena, known as the Arnold tongue. Our theoretical predictions are in good quantitative agreement with the numerical simulations and provide a solid basis for chirality control in excitable media.
Quark matter under strong magnetic fields in chiral models
Rabhi, Aziz; Providencia, Constanca
2011-05-15
The chiral model is used to describe quark matter under strong magnetic fields and is compared to other models, the MIT bag model and the two-flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic-field vacuum corrections are not taken into account explicitly, the parameters of the models should be fitted to low-density meson properties in the presence of the magnetic field.
Nuclear axial currents in chiral effective field theory
Baroni, Alessandro; Girlanda, Luca; Pastore, Saori; Schiavilla, Rocco; Viviani, Michele
2016-01-11
Two-nucleon axial charge and current operators are derived in chiral effective field theory up to one loop. The derivation is based on time-ordered perturbation theory and accounts for cancellations between the contributions of irreducible diagrams and the contributions owing to nonstatic corrections from energy denominators of reducible diagrams. Ultraviolet divergencies associated with the loop corrections are isolated in dimensional regularization. The resulting axial current is finite and conserved in the chiral limit, while the axial charge requires renormalization. As a result, a complete set of contact terms for the axial charge up to the relevant order in the power countingmore » is constructed.« less
Microscopically constrained mean-field models from chiral nuclear thermodynamics
NASA Astrophysics Data System (ADS)
Rrapaj, Ermal; Roggero, Alessandro; Holt, Jeremy W.
2016-06-01
We explore the use of mean-field models to approximate microscopic nuclear equations of state derived from chiral effective field theory across the densities and temperatures relevant for simulating astrophysical phenomena such as core-collapse supernovae and binary neutron star mergers. We consider both relativistic mean-field theory with scalar and vector meson exchange as well as energy density functionals based on Skyrme phenomenology and compare to thermodynamic equations of state derived from chiral two- and three-nucleon forces in many-body perturbation theory. Quantum Monte Carlo simulations of symmetric nuclear matter and pure neutron matter are used to determine the density regimes in which perturbation theory with chiral nuclear forces is valid. Within the theoretical uncertainties associated with the many-body methods, we find that select mean-field models describe well microscopic nuclear thermodynamics. As an additional consistency requirement, we study as well the single-particle properties of nucleons in a hot/dense environment, which affect e.g., charged-current weak reactions in neutron-rich matter. The identified mean-field models can be used across a larger range of densities and temperatures in astrophysical simulations than more computationally expensive microscopic models.
A sensitivity-enhanced field-effect chiral sensor
NASA Astrophysics Data System (ADS)
Torsi, Luisa; Farinola, Gianluca M.; Marinelli, Francesco; Tanese, M. Cristina; Omar, Omar Hassan; Valli, Ludovico; Babudri, Francesco; Palmisano, Francesco; Zambonin, P. Giorgio; Naso, Francesco
2008-05-01
Organic thin-film transistor sensors have been recently attracting the attention of the plastic electronics community for their potential exploitation in novel sensing platforms. Specificity and sensitivity are however still open issues: in this respect chiral discrimination-being a scientific and technological achievement in itself-is indeed one of the most challenging sensor bench-tests. So far, conducting-polymer solid-state chiral detection has been carried out at part-per-thousand concentration levels. Here, a novel chiral bilayer organic thin-film transistor gas sensor-comprising an outermost layer with built-in enantioselective properties-is demonstrated to show field-effect amplified sensitivity that enables differential detection of optical isomers in the tens-of-parts-per-million concentration range. The ad-hoc-designed organic semiconductor endowed with chiral side groups, the bilayer structure and the thin-film transistor transducer provide a significant step forward in the development of a high-performance and versatile sensing platform compatible with flexible organic electronic technologies.
NASA Astrophysics Data System (ADS)
Ruggieri, M.; Peng, G. X.
2016-05-01
In this article, we study spontaneous chiral symmetry breaking for quark matter in the background of static and homogeneous parallel electric field E and magnetic field B . We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at a finite temperature for a wide range of E and B . We study the effect of this background on the inverse catalysis of chiral symmetry breaking for E and B of the same order of magnitude. We then focus on the effect of the equilibration of chiral density n5 , produced dynamically by an axial anomaly on the critical temperature. The equilibration of n5 , a consequence of chirality-flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential μ5, which is computed self-consistently as a function of the temperature and field strength by coupling the number equation to the gap equation and solving the two within an expansion in E /T2 , B /T2 , and μ52/T2 . We find that even if chirality is produced and equilibrates within a relaxation time τM , it does not change drastically the thermodynamics, with particular reference to the inverse catalysis induced by the external fields, as long as the average μ5 at equilibrium is not too large.
Extended Chiral ({sigma},{pi},{omega}) Mean-Field Model with Vacuum Fluctuation Corrections
Uechi, Schun T.; Uechi, Hiroshi
2011-10-21
Density-dependent relations among saturation properties of symmetric nuclear matter and properties of hadronic stars are discussed by applying the conserving chiral nonlinear ({sigma},{pi},{omega}) mean-field theory. The chiral nonlinear ({sigma},{pi},{omega}) mean-field theory is an extension of the conserving nonlinear (nonchiral){sigma}-{omega} mean-field theory, which is thermodynamically consistent, relativistic and Lorentz-covariant. In the extended chiral ({sigma},{pi},{omega}) mean-field model, all the masses of hadrons are produced by the spontaneous chiral symmetry breaking, which is different from conventional chiral partner models. By comparing both nonchiral and chiral mean-field approximations, the effects of the chiral symmetry breaking mechanism on the mass of {sigma}-meson, coefficients of nonlinear interactions and Fermi-liquid properties are investigated in nuclear matter and neutron stars.
ERIC Educational Resources Information Center
Fennell, Francis (Skip); And Others
1982-01-01
A variety of ideas for working with money are presented. Activities provide experience in counting nickels and dimes, counting money and making change, determining sale prices by computing the percentage off a base or regular price, and keeping a record of current balances in checking and savings accounts. (MP)
ERIC Educational Resources Information Center
Immerzeel, George; Wiederanders, Don
1974-01-01
Four ideas are presented, each a variation of the tic-tac-toe game. Recognizing three addends is the goal of the primary level game; experiences with basic facts and fractions are objectives for upper levels. Each worksheet includes objectives, directions, and comments. (LS)
Spin of the proton in chiral effective field theory
NASA Astrophysics Data System (ADS)
Li, Hongna; Wang, P.; Leinweber, D. B.; Thomas, A. W.
2016-04-01
Proton spin is investigated in chiral effective field theory through an examination of the singlet axial charge, a0, and the two nonsinglet axial charges, a3 and a8. Finite-range regularization is considered as it provides an effective model for estimating the role of disconnected sea-quark loop contributions to baryon observables. Baryon octet and decuplet intermediate states are included to enrich the spin and flavor structure of the nucleon, redistributing spin under the constraints of chiral symmetry. In this context, the proton spin puzzle is well understood with the calculation describing all three of the axial charges reasonably well. The strange quark contribution to the proton spin is negative with magnitude 0.01. With appropriate Q2 evolution, we find the singlet axial charge at the experimental scale to be â0=0 .31-0.05+0.04 , consistent with the range of current experimental values.
Dynamic domain wall chirality rectification by rotating magnetic fields
NASA Astrophysics Data System (ADS)
Bisig, Andre; Mawass, Mohamad-Assaad; Stärk, Martin; Moutafis, Christoforos; Rhensius, Jan; Heidler, Jakoba; Gliga, Sebastian; Weigand, Markus; Tyliszczak, Tolek; Van Waeyenberge, Bartel; Stoll, Hermann; Schütz, Gisela; Kläui, Mathias
2015-03-01
We report on the observation of magnetic vortex domain wall chirality reversal in ferromagnetic rings that is controlled by the sense of rotation of a magnetic field. We use time-resolved X-ray microscopy to dynamically image the chirality-switching process and perform micromagnetic simulations to deduce the switching details from time-resolved snapshots. We find experimentally that the switching occurs within less than 4 ns and is observed in all samples with ring widths ranging from 0.5 μm to 2 μm, ring diameters between 2 μm and 5 μm, and a thickness of 30 nm, where a vortex domain wall is present in the magnetic onion state of the ring. From the magnetic contrast in the time-resolved images, we can identify effects of thermal activation, which plays a role for the switching process. Moreover, we find that the process is highly reproducible so that the domain wall chirality can be set with high fidelity.
Power counting regime of chiral effective field theory and beyond.
Hall, J. M.M.; Leinweber, D. B.; Young, R. D.; Physics; Univ. of Adelaide
2010-08-10
Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.
Power counting regime of chiral effective field theory and beyond
Hall, J. M. M.; Leinweber, D. B.; Young, R. D.
2010-08-01
Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.
Chirality of electrodeposits grown in a magnetic field
NASA Astrophysics Data System (ADS)
Mhíocháin, T. R.; Coey, J. M.
2004-06-01
Electrodeposits grown around a point cathode in a flat, horizontal electrochemical cell have fractal form. When grown in the presence of a perpendicular applied magnetic field, the deposits develop a spiral structure with chirality which reverses on switching the field direction. These structures are modeled numerically using biased variants of the diffusion limited aggregation (DLA) model. The effects of electric and magnetic fields are modeled successfully by varying the probabilities that a random walker will move in a given direction as a result of a Coulomb force and the Lorentz force-induced flow of electrolyte past the deposit surface. By contrast, a numerical model which considers only the effect of the Lorentz force on individual ions, without reference to the surface of the growing deposit, produces spiral structures with incorrect chirality. The modified DLA model is related to the differential equations for diffusion, migration, and convection. Length scales in the problem are understood by associating the step length of the random walker with the diffusion layer thickness, the lookup radius with the hydrodynamic boundary layer thickness and a point on the numerical deposit with a nucleation center for growth of a crystallite.
Chirality of electrodeposits grown in a magnetic field.
Mhíocháin, T R Ní; Coey, J M D
2004-06-01
Electrodeposits grown around a point cathode in a flat, horizontal electrochemical cell have fractal form. When grown in the presence of a perpendicular applied magnetic field, the deposits develop a spiral structure with chirality which reverses on switching the field direction. These structures are modeled numerically using biased variants of the diffusion limited aggregation (DLA) model. The effects of electric and magnetic fields are modeled successfully by varying the probabilities that a random walker will move in a given direction as a result of a Coulomb force and the Lorentz force-induced flow of electrolyte past the deposit surface. By contrast, a numerical model which considers only the effect of the Lorentz force on individual ions, without reference to the surface of the growing deposit, produces spiral structures with incorrect chirality. The modified DLA model is related to the differential equations for diffusion, migration, and convection. Length scales in the problem are understood by associating the step length of the random walker with the diffusion layer thickness, the lookup radius with the hydrodynamic boundary layer thickness and a point on the numerical deposit with a nucleation center for growth of a crystallite. PMID:15244565
Flavor Asymmetry in the Proton in Chiral Effective Field Theory
NASA Astrophysics Data System (ADS)
Salamu, Y.; Ji, C.-R.; Melnitchouk, W.; Wang, P.
2015-09-01
The flavor asymmetry in the proton arising from pion loops is computed using chiral effective field theory. The calculation includes both nucleon and Δ intermediate states, and uses both the fully relativistic and heavy baryon frameworks. The x dependence of extracted from the Fermilab E866 Drell-Yan data can be well reproduced in terms of a single transverse momentum cutoff parameter regulating the ultraviolet behavior of the loop integrals. In addition to the distribution at x > 0, corrections to the integrated asymmetry from zero momentum contributions are computed, which arise from pion rainbow and bubble diagrams at x = 0. These have not been accounted for in previous analyses, and can make important contributions to the lowest moment of.
Electric fields and chiral magnetic effect in Cu + Au collisions
NASA Astrophysics Data System (ADS)
Deng, Wei-Tian; Huang, Xu-Guang
2015-03-01
The non-central Cu + Au collisions can create strong out-of-plane magnetic fields and in-plane electric fields. By using the HIJING model, we study the general properties of the electromagnetic fields in Cu + Au collisions at 200 GeV and their impacts on the charge-dependent two-particle correlator γq1q2 = < cos (ϕ1 +ϕ2 - 2ψRP) > (see main text for definition) which was used for the detection of the chiral magnetic effect (CME). Compared with Au + Au collisions, we find that the in-plane electric fields in Cu + Au collisions can strongly suppress the two-particle correlator or even reverse its sign if the lifetime of the electric fields is long. Combining with the expectation that if γq1q2 is induced by elliptic-flow driven effects we would not see such strong suppression or reversion, our results suggest to use Cu + Au collisions to test CME and understand the mechanisms that underlie γq1q2.
Detecting Chirality in Molecules by Linearly Polarized Laser Fields.
Yachmenev, Andrey; Yurchenko, Sergei N
2016-07-15
A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a π phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic nonrigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states. PMID:27472111
Detecting Chirality in Molecules by Linearly Polarized Laser Fields
NASA Astrophysics Data System (ADS)
Yachmenev, Andrey; Yurchenko, Sergei N.
2016-07-01
A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a π phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic nonrigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states.
Electron-deuteron scattering based on the Chiral Effective Field Theory
NASA Astrophysics Data System (ADS)
Rozpȩdzik, Dagmara
2014-06-01
Based on the Chiral Effective Field Theory (ChEFT) dynamical picture of the two-pion exchange (TPE) contributions to the nuclear current operator which appear at higher order chiral expansions were considered. Their role in the electron-deuteron scattering reactions was studied and chiral predictions were compared with those obtained in the conventional framework. Results for cross section and various polarization observables are presented. The bound and scattering states were calculated with five different chiral nucleon-nucleon (NN) potentials which leads to the so-called theoretical uncertainty bands for the predicted results.
Quaternionic Analysis and Formulation of Generalized Electromagnetic fields in Chiral Media
Bisht, P. S.; Negi, O. P. S.; Singh, Jivan
2007-10-03
The time dependent Dirac-Maxwell's Equations in presence of electric and magnetic sources are written in chiral media and the solutions for the classical problem are obtained in unique simple and consistent manner. The quaternion reformulation of generalized electromagnetic fields in chiral media has also been developed in compact, simple and consistent manner.
Power counting for nuclear forces in chiral effective field theory
NASA Astrophysics Data System (ADS)
Long, Bingwei
2016-02-01
The present note summarizes the discourse on power counting issues of chiral nuclear forces, with an emphasis on renormalization-group invariance. Given its introductory nature, I will lean toward narrating a coherent point of view on the concepts, rather than covering comprehensively the development of chiral nuclear forces in different approaches.
Nucleon electromagnetic form factors on the lattice and in chiral effective field theory
Goeckeler, M.; Hemmert, T.R.; Horsley, R.; Pleiter, D.; Rakow, P.E.L.; Schaefer, A.; Schierholz, G.
2005-02-01
We compute the electromagnetic form factors of the nucleon in quenched lattice QCD, using nonperturbatively improved Wilson fermions, and compare the results with phenomenology and chiral effective field theory.
Tritium β decay in chiral effective field theory
Baroni, A.; Girlanda, L.; Kievsky, A.; Marcucci, L. E.; Schiavilla, R.; Viviani, M.
2016-08-18
We evaluate the Fermi and Gamow-Teller (GT) matrix elements in tritiummore » $$\\beta$$-decay by including in the charge-changing weak current the corrections up to one loop recently derived in nuclear chiral effective field theory ($$\\chi$$ EFT). The trinucleon wave functions are obtained from hyperspherical-harmonics solutions of the Schroedinger equation with two- and three-nucleon potentials corresponding to either $$\\chi$$ EFT (the N3LO/N2LO combination) or meson-exchange phenomenology (the AV18/UIX combination). We find that contributions due to loop corrections in the axial current are, in relative terms, as large as (and in some cases, dominate) those from one-pion exchange, which nominally occur at lower order in the power counting. Furthermore, we also provide values for the low-energy constants multiplying the contact axial current and three-nucleon potential, required to reproduce the experimental GT matrix element and trinucleon binding energies in the N3LO/N2LO and AV18/UIX calculations.« less
Numerical study of chiral plasma instability within the classical statistical field theory approach
NASA Astrophysics Data System (ADS)
Buividovich, P. V.; Ulybyshev, M. V.
2016-07-01
We report on a numerical study of real-time dynamics of electromagnetically interacting chirally imbalanced lattice Dirac fermions within the classical statistical field theory approach. Namely, we perform exact simulations of the real-time quantum evolution of fermionic fields coupled to classical electromagnetic fields, which are in turn coupled to the vacuum expectation value of the fermionic electric current. We use Wilson-Dirac Hamiltonian for fermions, and noncompact action for the gauge field. In general, we observe that the backreaction of fermions on the electromagnetic field prevents the system from acquiring chirality imbalance. In the case of chirality pumping in parallel electric and magnetic fields, the electric field is screened by the produced on-shell fermions and the accumulation of chirality is hence stopped. In the case of evolution with initially present chirality imbalance, axial charge tends to transform to helicity of the electromagnetic field. By performing simulations on large lattices we show that in most cases this decay process is accompanied by the inverse cascade phenomenon, which transfers energy from short-wavelength to long-wavelength electromagnetic fields. In some simulations, however, we observe a very clear signature of inverse cascade for the helical magnetic fields that is not accompanied by the axial charge decay. This suggests that the relation between the inverse cascade and axial charge decay is not as straightforward as predicted by the simplest form of anomalous Maxwell equations.
Opportunities for chiral discrimination using high harmonic generation in tailored laser fields
NASA Astrophysics Data System (ADS)
Smirnova, Olga; Mairesse, Yann; Patchkovskii, Serguei
2015-12-01
Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R Cireasa et al (2015 Nat. Phys. 11 654-8). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule CH3CHCH2O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independent measurement of the enatiomeric excess in a mixture of randomly oriented left-handed and right-handed molecules. Finally, for arbitrary configurations of laser fields, we connect the observables of the cHHG method to the amplitude and phase of chiral response, providing a basis for reconstructing wide range of chiral dynamics from cHHG measurements, with femtosecond to sub-femtosecond temporal resolution.
The nucleon and Delta-resonance masses in relativistic chiral effective-field theory
V. Pascalutsa; M. Vanderhaeghen
2005-11-28
We study the chiral behavior of the nucleon and De-isobar masses within a manifestly covariant chiral effective-field theory, consistent with the analyticity principle. We compute the {pi} N and {pi}{Delta} one-loop contributions to the mass and field-normalization constant, and find that they can be described in terms of universal relativistic loop functions, multiplied by appropriate spin, isospin and coupling constants. We show that these relativistic one-loop corrections, when properly renormalized, obey the chiral power-counting and vanish in the chiral limit. The results including only the {pi} N-loop corrections compare favorably with the lattice QCD data for the pion-mass dependence of the nucleon and De masses, while inclusion of the {pi}/De loops tends to spoil this agreement.
Multiple chiral doublet candidate nucleus {sup 105}Rh in a relativistic mean-field approach
Li Jian; Zhang, S. Q.; Meng, J.
2011-03-15
Following the reports of two pairs of chiral doublet bands observed in {sup 105}Rh, the adiabatic and configuration-fixed constrained triaxial relativistic mean-field calculations are performed to investigate their triaxial deformations with the corresponding configuration and the possible multiple chiral doublet (M{chi}D) phenomenon. The existence of the M{chi}D phenomenon in {sup 105}Rh is highly expected.
Baryons as solitons in effective chiral field theories
NASA Astrophysics Data System (ADS)
Holzwarth, G.
This lecture comprises some recent developments concerning the description of baryons as topological solitons in effective chiral meson theories. In the first part one-loop corrections to the classical tree approximation are discussed. This involves renormalization of low-energy coupling constants and evaluation of the finite next-to-leading-order terms in the {1}/{N c} expansion. In contrast to the corresponding procedure in the meson sector the magnitude of the chiral gradients involved in the soliton profile requires that counter terms and finite loop contributions be calculated to all chiral orders. Recent results for various nucleon observables are presented. They show that the {1}/{N c} expansion essentially works as expected. In the second part electro-magnetic nucleon form factors (FFs) with relativistic corrections are evaluated in a chiral soliton model including vector mesons. The magnetic FF GMp is shown to agree well with new SLAC data for spacelike Q2 up to 30 (GeV/c) 2 if superconvergence is enforced. The electric FF GEp is dominated by a zero in the few (GeV/c) 2 region due to a low-lying zero in the non-relativistic electric FF in tree approximation. The third part describes how to extract the strong πNN form factor from chiral soliton models, taking due care of the local metric created by the presence of the soliton. When used in a one-boson-exchange model for the nucleon-nucleon (NN) interaction, deuteron properties and phase parameters of NN scattering are reproduced as well as in conventional NN models that apply a hard monopole form factor at the πNN vertex.
Schnell, M; Sarriugarte, P; Neuman, T; Khanikaev, A B; Shvets, G; Aizpurua, J; Hillenbrand, R
2016-01-13
Chiral antennas and metasurfaces can be designed to react differently to left- and right-handed circularly polarized light, which enables novel optical properties such as giant optical activity and negative refraction. Here, we demonstrate that the underlying chiral near-field distributions can be directly mapped with scattering-type scanning near-field optical microscopy employing circularly polarized illumination. We apply our technique to visualize, for the first time, the circular-polarization selective nanofocusing of infrared light in Archimedean spiral antennas, and explain this chiral optical effect by directional launching of traveling waves in analogy to antenna theory. Moreover, we near-field image single-layer rosette and asymmetric dipole-monopole metasurfaces and find negligible and strong chiral optical near-field contrast, respectively. Our technique paves the way for near-field characterization of optical chirality in metal nanostructures, which will be essential for the future development of chiral antennas and metasurfaces and their applications. PMID:26666399
Emergent universe supported by chiral cosmological fields in 5D Einstein-Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Chervon, S. V.; Maharaj, S. D.; Beesham, Aroonkumar; Kubasov, A. S.
2014-07-01
We propose the application of the chiral cosmological model (CCM) for the Einstein--Gauss--Bonnet (EGB) theory of gravitation with the aim of finding new models of the Emergent Universe (EmU) scenario. We analysed the EmU supported by two chiral cosmological fields for a spatially flat universe, while we have used three chiral fields when we investigated open and closed universes. To prove the validity of the EmU scenario we fixed the scale factor and found the exact solution by decomposition of EGB equations and solving the chiral field dynamics equation. To this end, we suggested the decomposition of the EGB equations in such a way that the first chiral field is responsible for the Einstein part of the model, while the second field, together with kinetic interaction term, is connected with the Gauss--Bonnet part of the theory. We proved that both fields are phantom ones under this decomposition, and that the model has a solution if the kinetic interaction between the fields equals a constant. We have presented the exact solution in terms of cosmic time. This was done for a spatially flat universe. In the case of open and closed universes we introduced the third chiral field (canonical for closed and phantom for open universe) which is responsible for the EGB and curvature parts. The solution of the third field equation is obtained in quadratures. Thus we have proved that the CCM is able to support EmU scenario in EGB gravity for spatially flat, open and closed universes.
Strong superchiral field in hot spots and its interaction with chiral molecules
NASA Astrophysics Data System (ADS)
Liu, Yineng
We have found that strong superchiral fields created by surface plasmon resonance exist in hot spots of nonchiral plasmonic structure, which showed a chiral density greater than that of circularly polarized light by hundreds of times. We have demonstrated a direct correlation between the chirality of the local field and the circular dichroism (CD) response at the plasmon resonance bands induced by chiral molecules in the hot spots. Our results reveal that the wavelength-dependent superchiral fields in the hot spots can play a crucial role in the determination of the plasmonic CD effect. This finding is in contrast to the currently accepted physical model in which the electromagnetic field intensity in hot spots is a key factor to determine the peak intensity of the plasmonic CD spectrum. Some related experimental phenomena have been explained by using our theoretical analysis. The work was supported by the China National Natural Science Foundation (Grant No. 11504306).
Measuring chirality in NMR in the presence of a time-dependent electric field
Walls, Jamie D.; Harris, Robert A.
2014-06-21
Traditional nuclear magnetic resonance (NMR) experiments are “blind” to chirality since the spectra for left and right handed enantiomers are identical in an achiral medium. However, theoretical arguments have suggested that the effective Hamiltonian for spin-1/2 nuclei in the presence of electric and magnetic fields can be different for left and right handed enantiomers, thereby enabling NMR to be used to spectroscopically detect chirality even in an achiral medium. However, most proposals to detect the chiral NMR signature require measuring signals that are equivalent to picomolar concentrations for {sup 1}H nuclei, which are outside current NMR detection limits. In this work, we propose to use an AC electric field that is resonantly modulated at the Larmor frequency, thereby enhancing the effect of the chiral term by four to six orders of magnitude. We predict that a steady-state transverse magnetization, whose direction will be opposite for different enantiomers, will build up during application of an AC electric field. We also propose an experimental setup that uses a solenoid coil with an AC current to generate the necessary periodic electric fields that can be used to generate chiral signals which are equivalent to the signal from a {sup 1}H submicromolar concentration.
Electric-field-induced assembly and propulsion of chiral colloidal clusters.
Ma, Fuduo; Wang, Sijia; Wu, David T; Wu, Ning
2015-05-19
Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right- and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas out-of-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport. PMID:25941383
Electromagnetic fields in dispersive chiral media generated by modulated nonuniformly moving sources
NASA Astrophysics Data System (ADS)
Kravchenko, V. V.; Oviedo-Galdeano, H.; Rabinovich, V. S.
2013-03-01
A representation for the fields generated by moving sources in chiral media in the form of double time-frequency oscillating integrals is obtained by using quaternionic analysis methods. Some additional assumptions concerning the source allow us to introduce a large dimensionless parameter λ > 0 which characterizes simultaneously the slowness of variations of the amplitude and of the velocity of the source. Application of the two-dimensional stationary phase method to the integral representation of the field leads to asymptotic formulas for the electromagnetic field for large λ > 0, and efficient formulas for the frequency and the time Doppler effects in dispersive chiral media. As an application of the proposed method, we consider the Vavilov-Cherenkov radiation in chiral dispersive media.
Mobility inhibition of 1-phenylethanol chiral molecules in strong magnetic fields
NASA Astrophysics Data System (ADS)
Kozlova, Svetlana G.; Kompankov, Nikolay B.; Ryzhikov, Maxim R.; Slepkov, Vladimir A.
2015-12-01
Experimental evidences are first obtained to demonstrate the effect of external magnetic field on the mobility of 1-phenylethanol molecules characterized by conjugated ring bonds. Enantiomers of these molecules are shown to have different mobilities in chiral polarized mediums composed of these enantiomers taken in various proportions. The difference diminishes when the external magnetic field increases.
Mean field theory of the linear sigma-model: chiral solitons
Kahana, S.; Ripka, G.
1983-01-01
The mean field theory of the chiral invariant sigma-model is outlined. bound states (solitons) of valence quarks are obtained self-consistently using a hedgehog shape for the pion field. A schematic model for the coupled fermion-boson fields is presented. Renormalization is worked out for the fermion one-loop corrections and numerical results presented for the purely scalar-field case. The interpretation of the baryon number of the perturbed vacuum is considered.
Quark Number Fluctuations in a Chiral Model with a Magnetic Field
NASA Astrophysics Data System (ADS)
Cheng, Lidens; Incera, Vivian
2013-04-01
An important consequence of quantum chromodynamics (QCD) is the existence of a phase transition between the hadronic and quark-gluon phases. The hadronic phase exhibits confinement and broken chiral symmetry. The quark-gluon phase exhibits deconfinement and chiral symmetry. The phase boundary can be seen in the temperature-quark chemical potential plane. For large chemical potential, there is a first order chiral transition. For small chemical potential and 2 massless quarks flavors, there is a second order chiral transition. Thus, a critical end point (CEP) is expected where the first order phase transitions end. In the chiral limit or for finite quark masses, the net quark number susceptibility diverges at the CEP. However, when clear from the CEP, it is finite. Hence, the net quark number susceptibility is non-monotonic along the phase boundary if there is a CEP. In this case, the Nambu--Jona-Lasinio model is composed at finite temperature and quark and isospin chemical potentials. The addition of a strong magnetic field in the model is significant because strong magnetic fields are produced in off-central heavy-ion collisions and are present at the core of neutron stars.
Reversible "triple-Q" elastic field structures in a chiral magnet.
Hu, Yangfan; Wang, Biao
2016-01-01
The analytical solution of the periodic elastic fields in chiral magnets caused by presence of periodically distributed eigenstrains is obtained. For the skyrmion phase, both the periodic displacement field and the stress field are composed of three "triple-Q" structures with different wave numbers. The periodic displacement field, obtained by combining the three "triple-Q" displacement structures, is found to have the same lattice vectors with the magnetic skyrmion lattice. We find that for increasing external magnetic field, one type of "triple-Q" displacement structure and stress structure undergo a "configurational reversal", where the initial and the final field configuration share similar pattern but with opposite direction of all the field vectors. The solution obtained is of fundamental significance for understanding the emergent mechanical properties of skyrmions in chiral magnets. PMID:27457629
Reversible “triple-Q” elastic field structures in a chiral magnet
Hu, Yangfan; Wang, Biao
2016-01-01
The analytical solution of the periodic elastic fields in chiral magnets caused by presence of periodically distributed eigenstrains is obtained. For the skyrmion phase, both the periodic displacement field and the stress field are composed of three “triple-Q” structures with different wave numbers. The periodic displacement field, obtained by combining the three “triple-Q” displacement structures, is found to have the same lattice vectors with the magnetic skyrmion lattice. We find that for increasing external magnetic field, one type of “triple-Q” displacement structure and stress structure undergo a “configurational reversal”, where the initial and the final field configuration share similar pattern but with opposite direction of all the field vectors. The solution obtained is of fundamental significance for understanding the emergent mechanical properties of skyrmions in chiral magnets. PMID:27457629
Chiral restoration at finite T under the magnetic field with the meson-loop corrections
NASA Astrophysics Data System (ADS)
Nam, Seung-Il; Kao, Chung-Wen
2011-05-01
We investigate the (partial) chiral restoration at finite temperature (T) under the strong external magnetic field B=B0z^ of the SU(2) light-flavor QCD matter. To this end, we employ the instanton-liquid QCD vacuum configuration accompanied with the linear Schwinger method for inducing the magnetic field. The Harrington-Shepard caloron solution is used to modify the instanton parameters, i.e. the average instanton size (ρ¯) and interinstanton distance (R¯), as functions of T. In addition, we include the meson-loop corrections as the large-Nc corrections because they are critical for reproducing the universal chiral-restoration pattern. We present the numerical results for the constituent-quark mass as well as chiral condensate, which signal the spontaneous breakdown of chiral-symmetry (SBχS), as functions of T and B0. From our results we observe that the strengths of those chiral order parameters are enhanced with respect to B0 due to the magnetic-catalysis effect. We also find that there appears a region where the u and d-quark constituent masses coincide with each other at eB0≈(7-9)mπ2, even in the presence of the explicit isospin breaking (mu≠md). The critical T for the chiral restoration Tc tends to shift to the higher temperature in the presence of the B0 for the chiral limit but keeps almost stationary for the physical quark mass case. The strength of the isospin breaking between the quark condensates is also explored in detail by defining the ratio R≡(⟨iu†u⟩-⟨id†d⟩)/(⟨iu†u⟩+⟨id†d⟩), which indicates the competition between the explicitly isospin-breaking effect and magnetic-catalysis effect. We also compute the pion weak-decay constant Fπ and pion mass mπ below Tc, varying the strength of the magnetic field, showing correct partial chiral-restoration behaviors. Besides we find that the changes for the Fπ and mπ due to the magnetic field is relatively small, in comparison to those caused by the finite T effect.
Chiral restoration at finite T under the magnetic field with the meson-loop corrections
Nam, Seung-il; Kao, Chung-Wen
2011-05-01
We investigate the (partial) chiral restoration at finite temperature (T) under the strong external magnetic field B=B{sub 0}z-circumflex of the SU(2) light-flavor QCD matter. To this end, we employ the instanton-liquid QCD vacuum configuration accompanied with the linear Schwinger method for inducing the magnetic field. The Harrington-Shepard caloron solution is used to modify the instanton parameters, i.e. the average instanton size ({rho}) and interinstanton distance (R), as functions of T. In addition, we include the meson-loop corrections as the large-N{sub c} corrections because they are critical for reproducing the universal chiral-restoration pattern. We present the numerical results for the constituent-quark mass as well as chiral condensate, which signal the spontaneous breakdown of chiral-symmetry (SB{chi}S), as functions of T and B{sub 0}. From our results we observe that the strengths of those chiral order parameters are enhanced with respect to B{sub 0} due to the magnetic-catalysis effect. We also find that there appears a region where the u and d-quark constituent masses coincide with each other at eB{sub 0{approx_equal}}(7-9)m{sub {pi}}{sup 2}, even in the presence of the explicit isospin breaking (m{sub u{ne}}m{sub d}). The critical T for the chiral restoration T{sub c} tends to shift to the higher temperature in the presence of the B{sub 0} for the chiral limit but keeps almost stationary for the physical quark mass case. The strength of the isospin breaking between the quark condensates is also explored in detail by defining the ratio R{identical_to}(
The gamma N ---> Delta transition in chiral effective-field theory.
Vladimir Pascalutsa; Marc Vanderhaeghen
2006-04-27
We describe the pion electroproduction processes in the {Delta}(1232)-resonance region within the framework of chiral effective-field theory. By studying the observables of pion electroproduction in a next-to-leading order calculation we are able to make predictions and draw conclusions on the properties of the N {yields} {Delta} electromagnetic form factors.
The $\\gamma N\\to \\De$ transition in chiral effective-field theory
Vladimir Pascalutsa; Marc Vanderhaeghen
2006-04-27
We describe the pion electroproduction processes in the {Delta}(1232)-resonance region within the framework of chiral effective-field theory. By studying the observables of pion electroproduction in a next-to-leading order calculation we are able to make predictions and draw conclusions on the properties of the N {yields} {Delta} electromagnetic form factors.
Chiral Effective Field Theory Beyond the Power-Counting Regime
Hall, Jonathan M. M.; Leinweber, Derek B.; Young, Ross D.
2011-05-24
Novel techniques are presented, which identify the chiral power-counting regime (PCR), and realize the existence of an intrinsic energy scale embedded in lattice QCD results that extend outside the PCR. The nucleon mass is considered as a benchmark for illustrating this new approach. Using finite-range regularization, an optimal regularization scale can be extracted from lattice simulation results by analyzing the renormalization of the low energy coefficients. The optimal scale allows a description of lattice simulation results that extend beyond the PCR by quantifying and thus handling any scheme-dependence. Preliminary results for the nucleon magnetic moment are also examined, and a consistent optimal regularization scale is obtained. This indicates the existence of an intrinsic scale corresponding to the finite size of the source of the pion cloud.
Mondal, Prakash Chandra; Fontanesi, Claudio; Waldeck, David H; Naaman, Ron
2015-03-24
This work examines whether electrochemical redox reactions are sensitive to the electron spin orientation by examining the effects of magnetic field and molecular chirality on the charge transfer process. The working electrode is either a ferromagnetic nickel film or a nickel film that is coated with an ultrathin (5-30 nm) gold overlayer. The electrode is coated with a self-assembled monolayer that immobilizes a redox couple containing chiral molecular units, either the redox active dye toluidine blue O with a chiral cysteine linking unit or cytochrome c. By varying the direction of magnetization of the nickel, toward or away from the adsorbed layer, we demonstrate that the electrochemical current depends on the orientation of the electrons' spin. In the case of cytochrome c, the spin selectivity of the reduction is extremely high, namely, the reduction occurs mainly with electrons having their spin-aligned antiparallel to their velocity. PMID:25752750
Introduction to chiral symmetry
Koch, V.
1996-01-08
These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented.
Inerton Fields: Very New Ideas on Fundamental Physics
NASA Astrophysics Data System (ADS)
Krasnoholovets, Volodymyr
2010-12-01
Modern theories of everything, or theories of the grand unification of all physical interactions, try to describe the whole world starting from the first principles of quantum theory. However, the first principles operate with undetermined notions, such as the wave ψ-function, particle, lepton and quark, de Broglie and Compton wavelengths, mass, electric charge, spin, electromagnetic field, photon, gravitation, physical vacuum, space, etc. From a logical point of view this means that such modern approach to the theory of everything is condemned to failure… Thus, what should we suggest to improve the situation? It seems quite reasonable to develop initially a theory of something, which will be able to clarify the major fundamental notions (listed above) that physics operates with every day. What would be a starting point in such approach? Of course a theory of space as such, because particles and all physical fields emerge just from space. After that, when a particle and fields (and hence the fields' carriers) are well defined and introduced in the well defined physical space, different kinds of interactions can be proposed and investigated. Moreover, we must also allow for a possible interaction of a created particle with the space that generated the appearance of the particle. The mathematical studies of Michel Bounias and the author have shown what the real physical space is, how the space is constituted, how it is arranged and what its elements are. Having constructed the real physical space we can then derive whatever we wish, in particular, such basic notions as mass, particle and charge. How are mechanics of such objects (a massive particle, a charged massive particle) organised? The appropriate theory of motion has been called a sub microscopic mechanics of particles, which is developed in the real physical space, not an abstract phase space, as conventional quantum mechanics does. A series of questions arise: can these two mechanics (submicroscopic and
Field-driven sense elements for chirality-dependent domain wall detection and storage
Bowden, S. R.; Unguris, J.
2013-12-14
A method for locally sensing and storing data of transverse domain wall chirality in planar nanowire logic and memory systems is presented. Patterned elements, in close proximity to the nanowires, respond to the asymmetry in the stray field from the domain wall to produce a chirality-dependent response. When a bias field is applied, a stray field-assisted reversal of the element magnetization results in a reversed remanent state, measurable by scanning electron microscopy with polarization analysis (SEMPA). The elements are designed as triangles with tips pointing toward the nanowire, allowing the shape anisotropy to be dominated by the base but having a portion with lower volume and lower energy barrier closest to the domain wall. Micromagnetic modeling assists in the design of the nanowire-triangle systems and experiments using SEMPA confirm the importance of aspect ratio and spacing given a constant bias field magnitude.
Electric-field-driven alignment of chiral conductive polymer thin films.
Tassinari, Francesco; Mathew, Shinto P; Fontanesi, Claudio; Schenetti, Luisa; Naaman, Ron
2014-04-29
We investigated the effect of an electric field on the alignment and structural properties of thin films of a chiral polybithiophene-based conductive polymer, functionalized with a protected l-cysteine amino acid. Thin films were obtained by exploiting both drop-casting and spin-coating procedures. The electric properties, the polarized Raman spectrum, the UV-vis spectrum, and the CD spectra were measured as a function of the electric field intensity applied during film formation. It was found that beyond the enhancement of the conductivity observed when the electric field aligns the polymer, the electric field significantly affects the chiral properties and the effect depends on the method of deposition. PMID:24731141
USING CORONAL CELLS TO INFER THE MAGNETIC FIELD STRUCTURE AND CHIRALITY OF FILAMENT CHANNELS
Sheeley, N. R. Jr.; Warren, H. P.; Martin, S. F.; Panasenco, O.
2013-08-01
Coronal cells are visible at temperatures of {approx}1.2 MK in Fe XII coronal images obtained from the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory spacecraft. We show that near a filament channel, the plumelike tails of these cells bend horizontally in opposite directions on the two sides of the channel like fibrils in the chromosphere. Because the cells are rooted in magnetic flux concentrations of majority polarity, these observations can be used with photospheric magnetograms to infer the direction of the horizontal field in filament channels and the chirality of the associated magnetic field. This method is similar to the procedure for inferring the direction of the magnetic field and the chirality of the fibril pattern in filament channels from H{alpha} observations. However, the coronal cell observations are easier to use and provide clear inferences of the horizontal field direction for heights up to {approx}50 Mm into the corona.
Education in the Field Influences Children's Ideas and Interest toward Science
ERIC Educational Resources Information Center
Zoldosova, Kristina; Prokop, Pavol
2006-01-01
This paper explores the idea of informal science education in scientific field laboratory (The Science Field Centre). The experimental group of pupils (N = 153) was experienced with approximately 5-day lasting field trips and experiments in the Field Centre in Slovakia. After finishing the course, two different research methods were used to…
Phase diagram of 4D field theories with chiral anomaly from holography
NASA Astrophysics Data System (ADS)
Ammon, Martin; Leiber, Julian; Macedo, Rodrigo P.
2016-03-01
Within gauge/gravity duality, we study the class of four dimensional CFTs with chiral anomaly described by Einstein-Maxwell-Chern-Simons theory in five dimensions. In particular we determine the phase diagram at finite temperature, chemical potential and magnetic field. At high temperatures the solution is given by an electrically and magnetically charged AdS Reissner-Nordstroem black brane. For sufficiently large Chern-Simons coupling and at sufficiently low temperatures and small magnetic fields, we find a new phase with helical order, breaking translational invariance spontaneously. For the Chern-Simons couplings studied, the phase transition is second order with mean field exponents. Since the entropy density vanishes in the limit of zero temperature we are confident that this is the true ground state which is the holographic version of a chiral magnetic spiral.
Equilibrium instability of chiral mesons in external electromagnetic field via AdS/CFT
NASA Astrophysics Data System (ADS)
Taghavi, Seyed Farid; Vahedi, Ali
2016-06-01
We study the equilibrium instability of chiral quarkonia in a plasma in the presence of constant magnetic and electric field and at finite axial chemical potential using AdS/CFT duality. The model in use is a supersymmetric QCD at large 't Hooft coupling and number of colors. We show that the presence of the magnetic field and the axial chemical potential even in the absence of the electric field make the system unstable. In a gapped system, a stable/unstable equilibrium state phase transition is observed and the initial transition amplitude of the equilibrium state to the non-equilibrium state is investigated. We demonstrate that at zero temperature and large magnetic field the instability grows linearly by increasing the quarkonium binding energy. In the constant electric and magnetic field, the system is in a equilibrium state if the Ohm's law and the chiral magnetic effect cancel their effects. This happens in a sub-space of ( E, B, T, μ 5) space with constraint equation σ B B = - σE, where σ and σ B are electric and chiral magnetic conductivity, respectively. We analyze the decay rate of a gapless system when this constraint is slightly violated.
Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits
Jiang Weizhou; Li Baoan; Chen Liewen
2007-11-15
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 {sup 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 {rho} meson required by the partial restoration of chiral symmetry.
Zero-field Dissipationless Chiral Edge Current in Quantum Anomalous Hall State
NASA Astrophysics Data System (ADS)
Chang, Cui-Zu; Zhao, Weiwei; Kim, Duk Y.; Wei, Peng; Jain, J. K.; Liu, Chaoxing; Chan, Moses H. W.; Moodera, Jagadeesh S.
The quantum anomalous Hall (QAH) state is predicted to possess, at zero magnetic field, chiral edge channels that conduct spin polarized current without dissipation, and thus holds great promise for future high-performance information processing. In this talk, we will discuss our transport experiments that probe the QAH state with gate bias and temperature dependences, by local and nonlocal magnetoresistance measurements. This allows us to unambiguously distinguish the dissipationless edge transport from transport via other dissipative channels in the QAH system. Our experiments confirm a fundamental feature of the QAH state, namely the dissipationless transport by edge channels in zero applied fields, which will be crucial for future chiral interconnected electric and spintronic applications. This research is supported by the NSF Grants (DMR-1420620, Penn State MRSEC; in MIT by DMR-1207469 and the STC Center for Integrated Quantum Materials under NSF Grant DMR-1231319) and by ONR Grant N00014-13-1-0301.
Chiral magnetism and spin liquid Mott insulators induced by synthetic gauge fields
NASA Astrophysics Data System (ADS)
Paramekanti, Arun; Hickey, Ciaran; Cincio, Lukasz; Papic, Zlatko; Vellat-Sadashivan, Arun; Sohal, Ramanjit
2016-05-01
Recent experiments using Raman-assisted tunneling or lattice-shaking have realized synthetic gauge fields and optical lattice bands with nontrivial band topology. Here we examine the effect of particle interactions in such bands, focussing on two-component fermions with local Hubbard repulsion. We show that interactions can drive the integer quantum Hall insulator into Mott insulating states which possess noncoplanar chiral magnetic textures and even chiral spin liquids with many-body topological order. We establish our results using a combination of mean field theory, strong coupling expansions, numerical exact diagonalization and DMRG methods. We also discuss possible signatures of such non-coplanar orders in Bragg scattering and noise measurements.
Disoriented chiral condensate formation from a state with collective pion fields
Biro, T.S.; Molnar, D.; Feng, Z.; Csernai, L.P.
1997-06-01
At high temperatures it is believed that one can create a highly excited state, the starting point of disoriented chiral condensate (DCC) formation, which is sitting at the top of a potential barrier. We study here instead the evolution of a state where energy is stored initially in the collective motion too, in particular, in chiral rotations representing collective pion fields. We simulate the creation of such an initial state by letting the hot system evolve in time without cooling. It covers the microcanonically allowed phase space if the classical dynamics of the system is chaotic. We find the collective field dynamics chaotic in the linear {sigma} model coupled to quarks with explicit symmetry breaking. A rapid linear expansion from such initial states leads eventually to DCC formation. {copyright} {ital 1997} {ital The American Physical Society}
Uechi, Schun T.; Uechi, Hiroshi
2011-05-06
Density-dependent relations among saturation properties of symmetric nuclear matter and properties of hadronic stars are discussed by applying the conserving chiral nonlinear ({sigma},{pi},{omega}) hadronic mean-field theory. The chiral nonlinear ({sigma},{pi},{omega}) mean-field theory is an extension of the conserving nonlinear (nonchiral) {sigma}-{omega} hadronic mean-field theory which is thermodynamically consistent, relativistic and is a Lorentz-covariant mean-field theory of hadrons. In the extended chiral ({sigma},{pi},{omega}) mean-field model, all the masses of hadrons are produced by the breaking of chiral symmetry, which is different from other conventional chiral partner models. By comparing both nonchiral and chiral mean-field approximations, the effects of the chiral symmetry breaking mechanism on the mass of {sigma}-meson, coefficients of nonlinear interactions and Fermi-liquid properties are investigated in nuclear matter and neutron stars.
Cooper, F.
1997-09-22
This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.
NASA Astrophysics Data System (ADS)
Chen, Hong-Bo; Li, You-Quan
2016-07-01
We theoretically study the dynamics of a magnetic domain wall controlled by an electric field in the presence of the spin flexoelectric interaction. We reveal that this interaction generates an effective spin torque and results in significant changes in the current-driven domain wall motion. In particular, the electric field can stabilize the domain wall motion, leading to strong suppression of the current-induced Walker breakdown and thus allowing a higher maximum wall velocity. We can furthermore use this electric-field control to efficiently switch the chirality of a moving domain wall in the steady regime.
Kallin, Catherine; Berlinsky, John
2016-05-01
Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed. PMID:27088452
NASA Astrophysics Data System (ADS)
Kallin, Catherine; Berlinsky, John
2016-05-01
Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.
Chiral field theories as models for hadron substructure
Kahana, S.H.
1987-03-01
A model for the nucleon as soliton of quarks interacting with classical meson fields is described. The theory, based on the linear sigma model, is renormalizable and capable of including sea quarks straightforwardly. Application to nuclear matter is made in a Wigner-Seitz approximation.
Chiral effective-field theory in the Delta(1232) region : II. radiative pion photoproduction
Vladimir Pascalutsa; Marc Vanderhaeghen
2007-10-12
We present a theoretical study of the radiative pion photoproduction on the nucleon ($\\gamma N \\rightarrow \\pi N \\gamma'$) in the $\\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\\Delta^+(1232)$. The study is done within the framework of chiral effective-field theory where the expansion is performed (to next-to-leading order) in the $\\delta$ power-counting scheme which is an extension of chiral perturbation theory to the $\\Delta$-resonance energy region. We present in detail the results for the absorptive part of the $\\Delta$ MDM, as well as a sensitivity study for the radiative pion photoproduction observables on the real part of the $\\Delta$ MDM. We find that an asymmetry for circular polarization of the photon beam may provide a model-independent way to measure the $\\Delta$ MDM.
Chirality changes in carbon nanotubes studied with near-field Raman spectroscopy.
Anderson, Neil; Hartschuh, Achim; Novotny, Lukas
2007-03-01
We report on the direct visualization of chirality changes in carbon nanotubes by mapping local changes in resonant RBM phonon frequencies with an optical resolution of 40 nm using near-field Raman spectroscopy. We observe the transition from semiconducting-to-metal and metal-to-metal chiralities at the single nanotube level. Our experimental findings, based on detecting changes in resonant RBM frequencies, are complemented by measuring changes in the G-band frequency and line shape. In addition, we observe increased Raman scattering due to local defects associated with the structural transition. From our results, we determine the spatial extent of the transition region to be Ltrans approximately 40-100 nm. PMID:17324000
Chiral and magnetic rotation in atomic nuclei studied within self-consistent mean-field methods
NASA Astrophysics Data System (ADS)
Olbratowski, P.
2004-07-01
Currently, one application of the mean-field methods in nuclear physics is the investigation of exotic nuclear symmetries. This is related, in particular, to the study of nuclear rotation about an axis tilted with respect to the principal axes of the mass distribution in the Tilted-Axis Cranking (TAC) model. The present work presents one of the first TAC calculations performed within fully self-consistent methods. The Hartree-Fock method with the Skyrme effective two-body interaction has been used. A computer code has been developed that allows for the breaking of all spatial symmetries of the solution. As a first application, calculations for the magnetic bands in 142Gd and for the chiral bands in 130Cs, 132La, 134Pr, and 136Pm have been carried out. The appearance of those bands is due to a new mechanism of breaking the spherical symmetry and to the spontaneous breaking of the chiral symmetry, respectively. The self-consistent solutions for 142Gd confirm the important role of the shears mechanism in generating the total angular momentum. However, the agreement with experimental data is not satisfactory, probably due to the lack of the pairing correlations in the calculations or to the possibly overestimated deformation. The results obtained for 132La constitute the first fully self-consistent proof that the nuclear rotation can attain a chiral character. It has been shown that the chiral rotation can only exist above a certain critical angular frequency. It has also been checked that the terms of the Skyrme mean field odd under the time reversal have no qualitative influence on the results.
NASA Astrophysics Data System (ADS)
Li, Wenshan; Hennrich, Frank; Flavel, Benjamin S.; Kappes, Manfred M.; Krupke, Ralph
2016-09-01
The length of single-walled carbon nanotubes (SWCNTs) is an important metric for the integration of SWCNTs into devices and for the performance of SWCNT-based electronic or optoelectronic applications. In this work we propose a rather simple method based on electric-field induced differential absorption spectroscopy to measure the chiral-index-resolved average length of SWCNTs in dispersions. The method takes advantage of the electric-field induced length-dependent dipole moment of nanotubes and has been verified and calibrated by atomic force microscopy. This method not only provides a low cost, in situ approach for length measurements of SWCNTs in dispersion, but due to the sensitivity of the method to the SWCNT chiral index, the chiral index dependent average length of fractions obtained by chromatographic sorting can also be derived. Also, the determination of the chiral-index resolved length distribution seems to be possible using this method.
Constraints on Neutron Star Radii Based on Chiral Effective Field Theory Interactions
Hebeler, K.; Lattimer, J. M.; Pethick, C. J.; Schwenk, A.
2010-10-15
We show that microscopic calculations based on chiral effective field theory interactions constrain the properties of neutron-rich matter below nuclear densities to a much higher degree than is reflected in commonly used equations of state. Combined with observed neutron star masses, our results lead to a radius R=9.7-13.9 km for a 1.4M{sub {center_dot}} star, where the theoretical range is due, in about equal amounts, to uncertainties in many-body forces and to the extrapolation to high densities.
Spin dynamics under local gauge fields in chiral spin-orbit coupling systems
NASA Astrophysics Data System (ADS)
Tan, S. G.; Jalil, M. B. A.; Fujita, T.; Liu, X. J.
2011-02-01
We present a theoretical description of local spin dynamics in magnetic systems with a chiral spin texture and finite spin-orbit coupling (SOC). Spin precession about the relativistic effective magnetic field in a SOC system gives rise to a non-Abelian SU(2) gauge field reminiscent of the Yang-Mills field. In addition, the adiabatic relaxation of electron spin along the local spin yields an U(1) ⊗ U(1) topological gauge (Berry) field. We derive the corresponding equation of motion i.e. modified Landau-Lifshitz-Gilbert (LLG) equation, for the local spin under the influence of these effects. Focusing on the SU(2) gauge, we obtain the spin torque magnitude, and the amplitude and frequency of spin oscillations in this system. Our theoretical estimates indicate significant spin torque and oscillations in systems with large spin-orbit coupling, which may be utilized in technological applications such as current-induced magnetization-switching and tunable microwave oscillators.
NASA Astrophysics Data System (ADS)
Dvornikov, Maxim; Semikoz, Victor B.
2015-03-01
We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons (the e N interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field provides its growth up to ≳1 015 G during a time comparable with the ages of young magnetars ˜1 04 yr . The magnetic field instability originates from the parity violation in the e N interaction entering the generalized Dirac equation for right and left massless electrons in an external uniform magnetic field. We calculate the average electric current given by the solution of the modified Dirac equation containing an extra current for right and left electrons (positrons), which turns out to be directed along the magnetic field. Such a current includes both a changing chiral imbalance of electrons and the e N potential given by a constant neutron density in a NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic helicity which accounts for the e N interaction. By solving this system, we show that a sizable chiral imbalance arising in a neutron protostar due to the Urca process eL-+p →N +νeL diminishes very rapidly because of a huge chirality-flip rate. Thus the e N term prevails over the chiral effect, providing a huge growth of the magnetic helicity and the helical magnetic field.
NASA Astrophysics Data System (ADS)
Heo, Changhoon; Kiselev, Nikolai S.; Nandy, Ashis Kumar; Blügel, Stefan; Rasing, Theo
2016-06-01
Magnetic chiral skyrmions are vortex like spin structures that appear as stable or meta-stable states in magnetic materials due to the interplay between the symmetric and antisymmetric exchange interactions, applied magnetic field and/or uniaxial anisotropy. Their small size and internal stability make them prospective objects for data storage but for this, the controlled switching between skyrmion states of opposite polarity and topological charge is essential. Here we present a study of magnetic skyrmion switching by an applied magnetic field pulse based on a discrete model of classical spins and atomistic spin dynamics. We found a finite range of coupling parameters corresponding to the coexistence of two degenerate isolated skyrmions characterized by mutually inverted spin structures with opposite polarity and topological charge. We demonstrate how for a wide range of material parameters a short inclined magnetic field pulse can initiate the reliable switching between these states at GHz rates. Detailed analysis of the switching mechanism revealed the complex path of the system accompanied with the excitation of a chiral-achiral meron pair and the formation of an achiral skyrmion.
Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials.
Udagawa, M; Bergholtz, E J
2016-08-19
Three-dimensional condensed matter incarnations of Weyl fermions generically have a tilted dispersion-in sharp contrast to their elusive high-energy relatives where a tilt is forbidden by Lorentz invariance, and with the low-energy excitations of two-dimensional graphene sheets where a tilt is forbidden by either crystalline or particle-hole symmetry. Very recently, a number of materials (MoTe_{2}, LaAlGe, and WTe_{2}) have been identified as hosts of so-called type-II Weyl fermions whose dispersion is so strongly tilted that a Fermi surface is formed, whereby the Weyl node becomes a singular point connecting electron and hole pockets. We here predict that these systems have remarkable properties in the presence of magnetic fields. Most saliently, we show that the nature of the chiral anomaly depends crucially on the relative angle between the applied field and the tilt, and that an inversion-asymmetric overtilting creates an imbalance in the number of chiral modes with positive and negative slopes. The field-selective anomaly gives a novel magneto-optical resonance, providing an experimental way to detect concealed Weyl nodes. PMID:27588869
Heo, Changhoon; Kiselev, Nikolai S.; Nandy, Ashis Kumar; Blügel, Stefan; Rasing, Theo
2016-01-01
Magnetic chiral skyrmions are vortex like spin structures that appear as stable or meta-stable states in magnetic materials due to the interplay between the symmetric and antisymmetric exchange interactions, applied magnetic field and/or uniaxial anisotropy. Their small size and internal stability make them prospective objects for data storage but for this, the controlled switching between skyrmion states of opposite polarity and topological charge is essential. Here we present a study of magnetic skyrmion switching by an applied magnetic field pulse based on a discrete model of classical spins and atomistic spin dynamics. We found a finite range of coupling parameters corresponding to the coexistence of two degenerate isolated skyrmions characterized by mutually inverted spin structures with opposite polarity and topological charge. We demonstrate how for a wide range of material parameters a short inclined magnetic field pulse can initiate the reliable switching between these states at GHz rates. Detailed analysis of the switching mechanism revealed the complex path of the system accompanied with the excitation of a chiral-achiral meron pair and the formation of an achiral skyrmion. PMID:27273157
Heo, Changhoon; Kiselev, Nikolai S; Nandy, Ashis Kumar; Blügel, Stefan; Rasing, Theo
2016-01-01
Magnetic chiral skyrmions are vortex like spin structures that appear as stable or meta-stable states in magnetic materials due to the interplay between the symmetric and antisymmetric exchange interactions, applied magnetic field and/or uniaxial anisotropy. Their small size and internal stability make them prospective objects for data storage but for this, the controlled switching between skyrmion states of opposite polarity and topological charge is essential. Here we present a study of magnetic skyrmion switching by an applied magnetic field pulse based on a discrete model of classical spins and atomistic spin dynamics. We found a finite range of coupling parameters corresponding to the coexistence of two degenerate isolated skyrmions characterized by mutually inverted spin structures with opposite polarity and topological charge. We demonstrate how for a wide range of material parameters a short inclined magnetic field pulse can initiate the reliable switching between these states at GHz rates. Detailed analysis of the switching mechanism revealed the complex path of the system accompanied with the excitation of a chiral-achiral meron pair and the formation of an achiral skyrmion. PMID:27273157
Education in the Field Influences Children's Ideas and Interest toward Science
NASA Astrophysics Data System (ADS)
Zoldosova, Kristina; Prokop, Pavol
2006-10-01
This paper explores the idea of informal science education in scientific field laboratory (The Science Field Centre). The experimental group of pupils ( N = 153) was experienced with approximately 5-day lasting field trips and experiments in the Field Centre in Slovakia. After finishing the course, two different research methods were used to discover their interest and ideas toward science. Pupils from the experimental group showed significant differences from those that did not experience education in the Field Centre (control group, N = 365). In comparison to the control group, pupils of the experimental group highly preferred book titles that were related to their program in the Field Centre. There were differences between the drawings of ideal school environment from both pupils groups. In the drawings of the experimental group, we found significantly more items connected with the educational environment of the Field Centre (e.g. laboratory equipment, live animals). We suppose field science education would be one of the most effective ways to increase interest of pupils to study science and to invaluable intrinsic motivation at the expense extrinsic motivation.
Artificial gauge fields and chiral edge states for ultracold fermions in synthetic dimensions
NASA Astrophysics Data System (ADS)
Fallani, Leonardo
2015-05-01
I will report on very recent experiments performed at LENS with ultracold 173Yb Fermi gases in artificial gauge fields. We have engineered Raman transitions between different 173Yb nuclear spin states to synthesize an effective lattice dynamics in a finite-sized ``extra dimension,'' which is encoded in the internal degree of freedom of the atoms. By using this innovative approach, we have realized synthetic magnetic fields for effectively-charged fermions in ladder geometries with a variable number of legs. Direct imaging of the individual legs allowed us to demonstrate the emergence of chiral edge currents and to observe edge-cyclotron orbits propagating along the edges of the system, thus providing a direct evidence of a fundamental feature of quantum Hall physics in condensed-matter systems.
Chiral effective field theory predictions for muon capture on deuteron and $^3$He
Laura E. Marcucci, A. Kievsky, S. Rosati, R. Schiavilla, M. Viviani
2012-01-01
The muon-capture reactions {sup 2}H({mu}{sup -}, {nu}{sub {mu}})nn and {sup 3}He({mu}{sup -},{nu}{sub {mu}}){sup 3}H are studied with nuclear strong-interaction potentials and charge-changing weak currents, derived in chiral effective field theory. The low-energy constants (LEC's) c{sub D} and c{sub E}, present in the three-nucleon potential and (c{sub D}) axial-vector current, are constrained to reproduce the A=3 binding energies and the triton Gamow-Teller matrix element. The vector weak current is related to the isovector component of the electromagnetic current via the conserved-vector-current constraint, and the two LEC's entering the contact terms in the latter are constrained to reproduce the A=3 magnetic moments. The muon capture rates on deuteron and {sup 3}He are predicted to be 399 {+-} 3 sec{sup -1} and 1494 {+-} 21 sec{sup -1}, respectively, where the spread accounts for the cutoff sensitivity as well as uncertainties in the LEC's and electroweak radiative corrections. By comparing the calculated and precisely measured rates on {sup 3}He, a value for the induced pseudoscalar form factor is obtained in good agreement with the chiral perturbation theory prediction.
NASA Astrophysics Data System (ADS)
Lynn, J. E.
2016-03-01
I discuss our recent work on Green's function Monte Carlo (GFMC) calculations of light nuclei using local nucleon-nucleon interactions derived from chiral effective field theory (EFT) up to next-to-next-to-leading order (N2LO). I present the natural extension of this work to include the consistent three-nucleon (3N) forces at the same order in the chiral expansion. I discuss our choice of observables to fit the two low-energy constants which enter in the 3N sector at N2LO and present some results for light nuclei.
Koelling, S.; Epelbaum, E.; Krebs, H.; Meissner, U.-G.
2009-10-15
We derive the leading two-pion-exchange contributions to the two-nucleon electromagnetic current operator in the framework of chiral effective field theory using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.
Electromagnetic Nucleon-to-Delta Transition in Chiral Effective-Field Theory
Vladimir Pascalutsa; Marc Vanderhaeghen
2005-08-01
We perform a relativistic chiral effective-field theory calculation of the pion electroproduction off the nucleon (e{sup -} N {yields} e{sup -} N {pi}) in the {Delta}(1232)-resonance region. After fixing the three low-energy constants, corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) {gamma} N {Delta} couplings, our calculation provides a prediction for the momentum-transfer and pion-mass dependence of the {gamma} N {Delta} form factors. The prediction for the pion-mass dependence resolves the discrepancy between the recent lattice QCD results and the experimental value for the ''C2/M1 ratio'' at low Q{sup 2}.
${{\\bar{d}} - {\\bar{u}}}$ Flavor Asymmetry in the Proton in Chiral Effective Field Theory
Salamu, Y.; Ji, Cheung-Ryong; Melnitchouk, Wally; Wang, P.
2015-09-01
The ${\\bar d - \\bar u}$ flavor asymmetry in the proton arising from pion loops is computed using chiral effective field theory. The calculation includes both nucleon and Δ intermediate states, and uses both the fully relativistic and heavy baryon frameworks. The x dependence of ${\\bar d - \\bar u}$ extracted from the Fermilab E866 Drell–Yan data can be well reproduced in terms of a single transverse momentum cutoff parameter regulating the ultraviolet behavior of the loop integrals. In addition to the distribution at x > 0, corrections to the integrated asymmetry from zero momentum contributions are computed, which arise from pion rainbow and bubble diagrams at x = 0. These have not been accounted for in previous analyses, and can make important contributions to the lowest moment of ${\\bar d-\\bar u}$ .
NASA Astrophysics Data System (ADS)
Kao, Chung Wen; Nam, Seung-il
2013-03-01
We investigate the chiral restoration at finite temperature ( T) under the strong external magnetic field {{B}=B0hat{z}} of the SU(2) light-flavor QCD matter. We employ the instanton-liquid QCD vacuum configuration accompanied with the linear Schwinger method for inducing the magnetic field. The Harrington-Shepard caloron solution is used to modify the instanton parameters, i.e. the average instanton size {(bar{ρ})} and inter-instanton distance {(bar{R})}, as functions of T. In addition, we include the meson-loop corrections as the large- N c corrections because they are critical for reproducing the universal chiral restoration pattern. We present the numerical results for the constituent-quark mass as well as chiral condensate which signal the spontaneous breakdown of chiral-symmetry (SBχS), as functions of T and B. Besides we find that the changes for the F π and m π due to the magnetic field is relatively small, in comparison to those caused by the finite T effect.
Spin dynamics under local gauge fields in chiral spin-orbit coupling systems
Tan, S.G.; Jalil, M.B.A.; Fujita, T.; Liu, X.J.
2011-02-15
Research Highlights: > We derive a modified LLG equation in magnetic systems with spin-orbit coupling (SOC). > Our results are applied to magnetic multilayers, and DMS and magnetic Rashba systems. > SOC mediated magnetization switching is predicted in rare earth metals (large SOC). > The magnetization trajectory and frequency can be modulated by applied voltage. > This facilitates potential application as tunable microwave oscillators. - Abstract: We present a theoretical description of local spin dynamics in magnetic systems with a chiral spin texture and finite spin-orbit coupling (SOC). Spin precession about the relativistic effective magnetic field in a SOC system gives rise to a non-Abelian SU(2) gauge field reminiscent of the Yang-Mills field. In addition, the adiabatic relaxation of electron spin along the local spin yields an U(1) x U(1) topological gauge (Berry) field. We derive the corresponding equation of motion i.e. modified Landau-Lifshitz-Gilbert (LLG) equation, for the local spin under the influence of these effects. Focusing on the SU(2) gauge, we obtain the spin torque magnitude, and the amplitude and frequency of spin oscillations in this system. Our theoretical estimates indicate significant spin torque and oscillations in systems with large spin-orbit coupling, which may be utilized in technological applications such as current-induced magnetization-switching and tunable microwave oscillators.
Wang, L. C.
1980-01-01
Bäecklund Transformations (BT) and the derivation of local conservation laws are first reviewed in the classic case of the Sine-Gordon equation. The BT, conservation laws (local and nonlocal), and the inverse-scattering formulation are discussed for the chiral and the self-dual Yang-Mills fields. Their possible applications to the loop formulation for the Yang-Mills fields are mentioned. 55 references, 1 figure.
Chiral transport equation from the quantum Dirac Hamiltonian and the on-shell effective field theory
NASA Astrophysics Data System (ADS)
Manuel, Cristina; Torres-Rincon, Juan M.
2014-10-01
We derive the relativistic chiral transport equation for massless fermions and antifermions by performing a semiclassical Foldy-Wouthuysen diagonalization of the quantum Dirac Hamiltonian. The Berry connection naturally emerges in the diagonalization process to modify the classical equations of motion of a fermion in an electromagnetic field. We also see that the fermion and antifermion dispersion relations are corrected at first order in the Planck constant by the Berry curvature, as previously derived by Son and Yamamoto for the particular case of vanishing temperature. Our approach does not require knowledge of the state of the system, and thus it can also be applied at high temperature. We provide support for our result by an alternative computation using an effective field theory for fermions and antifermions: the on-shell effective field theory. In this formalism, the off-shell fermionic modes are integrated out to generate an effective Lagrangian for the quasi-on-shell fermions/antifermions. The dispersion relation at leading order exactly matches the result from the semiclassical diagonalization. From the transport equation, we explicitly show how the axial and gauge anomalies are not modified at finite temperature and density despite the incorporation of the new dispersion relation into the distribution function.
NASA Astrophysics Data System (ADS)
Laliena, Victor; Campo, Javier; Kishine, Jun-Ichiro; Ovchinnikov, Alexander S.; Togawa, Yoshihiko; Kousaka, Yusuke; Inoue, Katsuya
2016-04-01
The zero-temperature phase diagram of the monoaxial chiral helimagnet in the magnetic-field plane formed by the components parallel and perpendicular to the helical axis is thoroughly analyzed. The nature of the transition to the commensurate state depends on the angle between the field and the helical axis. For field directions close to the directions parallel or perpendicular to the helical axis the transition is continuous, while for intermediate angles the transition is discontinuous and the incommensurate and commensurate states coexist on the transition line. The continuous and discontinuous transition lines are separated by two tricritical points with specific singular behavior. The location of the continuous and discontinuous lines and of the tricritical points depend strongly on the easy-plane anisotropy, the effect of which is analyzed. For high anisotropy the conical approximation locates the transition line very accurately, although it does not predict the continuous transitions and the tricritical behavior. It is shown that for high anisotropy, as in CrNb3S6 , the form of the transition line is universal, that is, independent of the sample, and obeys a simple equation. The position of the tricritical points, which is not universal, is theoretically estimated for a sample of CrNb3S6 .
Incoherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei
NASA Astrophysics Data System (ADS)
Zhang, Xilin; Serot, Brian D.
2012-09-01
We study the incoherent neutrinoproduction of photons and pions with neutrino energy Eν⩽0.5GeV. These processes are relevant to the background analysis in neutrino-oscillation experiments [for example, MiniBooNE; A. A. Aquilar-Arevalo (MiniBooNE Collaboration), Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. The calculations are carried out using a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Delta (1232) (Δ), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and has SU(2)L⊗SU(2)R chiral symmetry realized nonlinearly. The contributions of one-body currents are studied in the local Fermi gas approximation. The current form factors are generated by meson dominance in the EFT Lagrangian. The conservation of the vector current and the partial conservation of the axial current are satisfied automatically, which is crucial for photon production. The Δ dynamics in nuclei, as a key component in the study, is explored. Introduced Δ-meson couplings explain the Δ spin-orbit coupling in nuclei, and this leads to interesting constraints on the theory. Meanwhile, a phenomenological approach is applied to parametrize the Δ width. To benchmark our approximations, we calculate the differential cross sections for quasielastic scattering and incoherent electroproduction of pions without a final-state interaction (FSI). The FSI can be ignored for photon production.
Neutrinoproduction of photons and pions from nucleons in a chiral effective field theory for nuclei
NASA Astrophysics Data System (ADS)
Serot, Brian D.; Zhang, Xilin
2012-07-01
Neutrino-induced production (neutrinoproduction) of photons and pions from nucleons and nuclei is important for the interpretation of neutrino-oscillation experiments, as these photons and pions are potential backgrounds in the MiniBooNE experiment [A. A. Aquilar-Arevalo (MiniBooNE Collaboration), Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. These processes are studied at intermediate energies, where the Δ(1232) resonance becomes important. The Lorentz-covariant effective field theory, which is the framework used in this series of studies, contains nucleons, pions, Δs, isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields. The Lagrangian exhibits a nonlinear realization of (approximate) SU(2)L⊗SU(2)R chiral symmetry and incorporates vector meson dominance. In this paper, we focus on setting up the framework. Power counting for vertices and Feynman diagrams is explained. Because of the built-in symmetries, the vector current is automatically conserved, and the axial-vector current is partially conserved. To calibrate the axial-vector transition current (N↔Δ), pion production from the nucleon is used as a benchmark and compared to bubble-chamber data from Argonne and Brookhaven National Laboratories. At low energies, the convergence of our power-counting scheme is investigated, and next-to-leading-order tree-level corrections are found to be small.
Weak Pion and Photon Production from Nuclei in a Chiral Effective Field Theory (Update)
NASA Astrophysics Data System (ADS)
Zhang, Xilin; Serot, Brian D.
2011-04-01
Neutrino-induced pion and photon production from nucleons and nuclei are important for the interpretation of neutrino-oscillation experiments. [A. A. Aquilar-Arevalo et al. (MiniBooNE Collaboration), Phys. Rev. Lett. 100, 032301 (2008)]. We have been working on these problems in a Lorentz-covariant effective field theory (known as QHD EFT), which contains nucleons, pions, Deltas (Δ), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields and has nonlinear chiral symmetry built in. Here we update our results on weak pion and photon production from nuclei, including both incoherent and coherent scattering. Connections between our results and the background analysis from MiniBooNE will be presented. In particular, coherent production of photons will be emphasized, and the possible relevance to the low-energy excess events at MiniBooNE will be explored. To justify our approximation scheme, we compare our results with data for inclusive electron scattering off nuclei up to the Δ peak and with coherent photoproduction of pions. Finally, we focus on the approximation scheme used and discuss the important Δ dynamics in the medium. An interesting mechanism to generate the Δ's spin-orbit coupling in the nucleus will be introduced, together with its possible consequences. Supported in part by the Department of Energy under Contract No. DE-FG02-87ER40365.
Synthetic-gauge-field stabilization of the chiral-spin-liquid phase
NASA Astrophysics Data System (ADS)
Chen, Gang; Hazzard, Kaden R. A.; Rey, Ana Maria; Hermele, Michael
2016-06-01
We explore the phase diagram of the SU (N ) Hubbard models describing fermionic alkaline-earth-metal atoms in a square optical lattice with, on average, one atom per site, using a slave rotor mean-field approach. We find that the chiral spin liquid (CSL) predicted for N ≥5 and large interactions passes through a fractionalized state with a spinon Fermi surface as interactions are decreased before transitioning to a weakly interacting metal. We show that by adding a uniform artificial gauge field with 2 π /N flux per plaquette, the CSL becomes the ground state for all N ≥3 at intermediate interactions, persists to weaker interactions, and exhibits a larger spin gap. For N ≥5 we find the CSL is the ground state everywhere the system is a Mott insulator. The gauge field stabilization of the CSL at lower interactions, and thus at weaker lattice depths, together with the increased spin gap, can relax the temperature constraints required for its experimental realization in ultracold atom systems.
NASA Astrophysics Data System (ADS)
Xia, Lifang
In the first part of this thesis, we use the generalized Landau-level represen- tation to study the effect of screening on the properties of the graphene quantum Hall states with integer filling factors. The analysis is performed in the low-energy Dirac model in the mean-field approximation, in which the long-range Coulomb in- teraction is modified by the one-loop static screening effects. The solutions demon- strate that static screening leads to a substantial suppression of the gap parameters in the quantum Hall states with a broken U (4) flavor symmetry. The results of the temperature dependence of the energy gaps mimic well the temperature dependence of the activation energies measured in experiment. The Landau-level running of the quasiparticle dynamical parameters could be tested via optical studies of the integer quantum Hall states. In the second part, by using the generalized Landau-level representation, we study the interaction induced chiral asymmetry in cold QED plasma beyond the weak-field approximation. The chiral shift and the parity-even chiral chemical potential function are obtained numerically and are found peaking near the Fermi surface and increases and decreases with the Landau level index, respectively. The results are used to quantify the chiral asymmetry of the Fermi surface in dense QED matter. The chiral asymmetry appears to be rather small even in the strongest mag- netic fields and at the highest stellar densities. However, the analogous asymmetry can be substantial in the case of dense quark matter.
ERIC Educational Resources Information Center
Herlocker, Helen; And Others
1988-01-01
Provides information on motivational activities, demonstrations, experiments, software, lessons, field trips, and a game as ideas for instructional use. Includes topics on digestion in paramecium, diffusion, cells, interactive displays, slime molds, and the construction of an underwater viewing device. (RT)
Field transformations and the classical equation of motion in chiral perturbation theory
Scherer, S.; Fearing, H.W.
1995-12-01
The construction of effective Lagrangians commonly involves the application of the ``classical equation of motion`` to eliminate redundant structures and thus generate the minimal number of independent terms. We investigate this procedure in the framework of chiral perturbation theory with particular emphasis on the new features which appear at {ital O}({ital p}{sup 6}). The use of the ``classical equation of motion`` is interpreted in terms of field transformations. Such an interpretation is crucial if one wants to bring a given Lagrangian into a canonical form with a minimal number of terms. We emphasize that the application of field transformations leads to a modification of the coefficients of higher-order terms as well as eliminating structures, or what is equivalent, expressing certain structures in terms of already known different structures. This will become relevant once one considers the problem of expressing in canonical form a model effective interaction containing terms beyond next-to-leading order, i.e., beyond {ital O}({ital p}{sup 4}). In such circumstances the naive application of the clasical equation of motion to simply drop terms, as is commonly done at lowest order, leads to subtle errors, which we discuss.
NASA Astrophysics Data System (ADS)
Wendt, Kyle
2016-03-01
How large is the 48Ca nucleus? While the electric charge distribution of this nucleus was accurately measured decades ago, both experimental and ab initio descriptions of the neutron distribution are deficient. We address this question using ab initio calculations of the electric charge, neutron, and weak distributions of 48Ca based on chiral effective field theory. Historically, chiral effective field theory calculations of systems larger than 4 nucleons have been plagued by strong systematic errors which result in theoretical descriptions that are too dense and over bound. We address these errors using a novel approach that permits us to accurately reproduce binding energy and charge radius of 48Ca, and to constrain electroweak observables such as the neutron radius, electric dipole polarizability, and the weak form factor. For a full list of contributors to this work, please see ``Neutron and weak-charge distributions of the 48Ca nucleus,'' Nature Physics (2015) doi:10.1038/nphys3529.
Chiral effective field theory analysis of hadronic parity violation in few-nucleon systems
Viviani, Michele; Baroni, Alessandro; Girlanda, Luca; Kievsky, Alejandro; Marcucci, Laura E.; Schiavilla, Rocco
2014-06-01
Background: Weak interactions between quarks induce a parity-violating (PV) component in the nucleonnucleon potential, whose effects are currently being studied in a number of experiments involving few-nucleon systems. In the present work, we reconsider the derivation of this PV component within a chiral effective field theory (chiEFT) framework. Purpose: The objectives of the present work are twofold. The first is to perform a detailed analysis of the PV nucleon-nucleon potential up to next-to-next-to-leading (N2LO) order in the chiral expansion, in particular, by determining the number of independent low-energy constants (LECs) at N2LO. The second objective is to investigate PV effects in a number of few-nucleon observables, including the p-p longitudinal asymmetry, the neutron spin rotation in n-p and n-d scattering, and the longitudinal asymmetry in the {sup 3}He( {vector n},p){sup 3}H chargeexchange reaction. Methods: The chiEFT PV potential includes one-pion-exchange, two-pion-exchange, and contact terms as well as 1/M (M being the nucleon mass) nonstatic corrections. Dimensional regularization is used to renormalize pion loops. The wave functions for the A = 2-4 nuclei are obtained by using strong two- and three-body potentials also derived, for consistency, from chiEFT. In the case of the A = 3-4 systems, the wave functions are computed by expanding on a hyperspherical harmonics functions basis. Results: We find that the PV potential at N2LO depends on six LECs: the pion-nucleon PV coupling constant h^1_pi and five parameters multiplying contact interactions. An estimate for the range of values of the various LECs is provided by using available experimental data, and these values are used to obtain predictions for the other PV observables. Conclusions: The chiEFT approach provides a very satisfactory framework to analyze PV effects in few-nucleon systems.
Uncertainty quantification for proton-proton fusion in chiral effective field theory
NASA Astrophysics Data System (ADS)
Acharya, B.; Carlsson, B. D.; Ekström, A.; Forssén, C.; Platter, L.
2016-09-01
We compute the S-factor of the proton-proton (pp) fusion reaction using chiral effective field theory (χEFT) up to next-to-next-to-leading order (NNLO) and perform a rigorous uncertainty analysis of the results. We quantify the uncertainties due to (i) the computational method used to compute the pp cross section in momentum space, (ii) the statistical uncertainties in the low-energy coupling constants of χEFT, (iii) the systematic uncertainty due to the χEFT cutoff, and (iv) systematic variations in the database used to calibrate the nucleon-nucleon interaction. We also examine the robustness of the polynomial extrapolation procedure, which is commonly used to extract the threshold S-factor and its energy-derivatives. By performing a statistical analysis of the polynomial fit of the energy-dependent S-factor at several different energy intervals, we eliminate a systematic uncertainty that can arise from the choice of the fit interval in our calculations. In addition, we explore the statistical correlations between the S-factor and few-nucleon observables such as the binding energies and point-proton radii of 2,3H and 3He as well as the D-state probability and quadrupole moment of 2H, and the β-decay of 3H. We find that, with the state-of-the-art optimization of the nuclear Hamiltonian, the statistical uncertainty in the threshold S-factor cannot be reduced beyond 0.7%.
Anomalous hysteresis as evidence for a magnetic-field-induced chiral superconducting state in LiFeAs
NASA Astrophysics Data System (ADS)
Li, G.; Urbano, R. R.; Goswami, P.; Tarantini, C.; Lv, B.; Kuhns, P.; Reyes, A. P.; Chu, C. W.; Balicas, L.
2013-01-01
Magnetometry measurements in high-quality LiFeAs single crystals reveal a change in the sign of the magnetic hysteresis in the vicinity of the upper critical field Hc2, from a clear diamagnetic response dominated by the pinning of vortices to a considerably smaller net hysteretic response of opposite sign, which disappears at Hc2. If the diamagnetic response at high fields results from pinned vortices and associated screening supercurrents, this sign change must result from currents circulating in the opposite sense, which give rise to a small field-dependent magnetic moment below Hc2. This behavior seems to be extremely sensitive to the sample quality or stoichiometry, as we have observed it only in a few fresh crystals, which also display the de Haas van Alphen effect. We provide arguments against the surface superconductivity, the flux compression, and the random π junction scenarios, which have been previously put forward to explain a paramagnetic Meissner effect, below the lower critical field Hc1. The observed anomalous hysteresis at high fields will be compatible with the existence of chiral gap wave functions, which possess a field-dependent magnetic moment. Within a Landau-Ginzburg framework, we demonstrate how a (dx2-y2+idxy) or a (px+ipy) chiral superconducting component can be stabilized in the mixed state of s± superconductor, due to the combined effects of the magnetic field and the presence of competing pairing channels. The realization of a particular chiral pairing depends on the microscopic details of the strengths of the competing pairing channels.
Gazit, Doron; Quaglioni, Sofia; Navratil, Petr
2009-09-04
The chiral low-energy constants c{sub D} and c{sub E} are constrained by means of accurate ab initio calculations of the A=3 binding energies and, for the first time, of the triton {beta} decay. We demonstrate that these low-energy observables allow a robust determination of the two undetermined constants, a result of the surprising fact that the determination of c{sub D} depends weakly on the short-range correlations in the wave functions. These two- plus three-nucleon interactions, originating in chiral effective field theory and constrained by properties of the A=2 system and the present determination of c{sub D} and c{sub E}, are successful in predicting properties of the A=3 and 4 systems.
Planar plasmonic chiral nanostructures.
Zu, Shuai; Bao, Yanjun; Fang, Zheyu
2016-02-21
A strong chiral optical response induced at a plasmonic Fano resonance in a planar Au heptamer nanostructure was experimentally and theoretically demonstrated. The scattering spectra show the characteristic narrow-band feature of Fano resonances for both left and right circular polarized lights, with a chiral response reaching 30% at the Fano resonance. Specifically, we systematically investigate the chiral response of planar heptamers with gradually changing the inter-particle rotation angles and separation distance. The chiral spectral characteristics clearly depend on the strength of Fano resonances and the associated near-field optical distributions. Finite element method simulations together with a multipole expansion method demonstrate that the enhanced chirality is caused by the excitation of magnetic quadrupolar and electric toroidal dipolar modes. Our work provides an effective method for the design of 2D nanostructures with a strong chiral response. PMID:26818746
Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya
2015-10-15
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
NASA Astrophysics Data System (ADS)
Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya Ken
2015-10-01
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
Coherent neutrinoproduction of photons and pions in a chiral effective field theory for nuclei
NASA Astrophysics Data System (ADS)
Zhang, Xilin; Serot, Brian D.
2012-09-01
Background: The neutrinoproduction of photons and pions from nucleons and nuclei is relevant to the background analysis in neutrino-oscillation experiments [for example, the MiniBooNE; MiniBooNE Collaboration, A. A. Aquilar-Arevalo , Phys. Rev. Lett.0031-900710.1103/PhysRevLett.100.032301 100, 032301 (2008)]. The production from nucleons and incoherent production with Eν⩽0.5GeV have been studied in B. D. Serot and X. Zhang, Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.86.015501 86, 015501 (2012); and X. Zhang and B. D. Serot, Phys. Rev. C1110-865710.1103/PhysRevC.86.035502 86, 035502 (2012).Purpose: Study coherent productions with Eν⩽0.5GeV. Also address the contributions of two contact terms in neutral current (NC) photon production that are partially related to the proposed anomalous ω(ρ), Z boson, and photon interactions.Methods: We work in the framework of a Lorentz-covariant effective field theory (EFT), which contains nucleons, pions, the Δ (1232) (Δs), isoscalar scalar (σ) and vector (ω) fields, and isovector vector (ρ) fields, and incorporates a nonlinear realization of (approximate) SU(2)L⊗SU(2)R chiral symmetry. A revised version of the so-called “optimal approximation” is applied, where one-nucleon interaction amplitude is factorized out and the medium-modifications and pion wave function distortion are included. The calculation is tested against the coherent pion photoproduction data.Results: The computation shows an agreement with the pion photoproduction data, although precisely determining the Δ modification is entangled with one mentioned contact term. The uncertainty in the Δ modification leads to uncertainties in both pion and photon neutrinoproductions. In addition, the contact term plays a significant role in NC photon production.Conclusions: First, the contact term increases NC photon production by ˜10% assuming a reasonable range of the contact coupling, which however seems not significant enough to explain the Mini
NASA Astrophysics Data System (ADS)
Sekine, Akihiko; Chiba, Takahiro
2016-06-01
We propose a realization of the electric-field-induced antiferromagnetic resonance. We consider three-dimensional antiferromagnetic insulators with spin-orbit coupling characterized by the existence of a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that, in contrast to conventional methods using ac magnetic fields, the antiferromagnetic resonance state is realized by ac electric fields along with static magnetic fields. This mechanism can be understood as the inverse process of the dynamical chiral magnetic effect, an alternating current generation by magnetic fields. In other words, we propose a way to electrically induce the dynamical axion field in condensed matter. We discuss a possible experiment to observe our proposal, which utilizes the spin pumping from the antiferromagnetic insulator into a heavy metal contact.
NASA Astrophysics Data System (ADS)
Zhong, Yang; Yang, Chun-Bin; Cai, Xu; Feng, Sheng-Qin
2016-08-01
It has been proposed that electric fields may lead to chiral separation in quark-gluon plasma (QGP). This is called the chiral electric separation effect. The strong electromagnetic field and the QCD vacuum can both be completely produced in off-central nuclear-nuclear collision. We use the Woods-Saxon nucleon distribution to calculate the electric field distributions of off-central collisions. The chiral electric field spatial distribution at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energy regions are systematically studied in this paper. The dependence of the electric field produced by the thermal quark in the central position with different impact parameters on the proper time with different collision energies in the RHIC and LHC energy regions are studied in this paper. Supported by National Natural Science Foundation of China (11375069, 11435054, 11075061, 11221504) and Key Laboratory Foundation of Quark and Lepton Physics (Hua-Zhong Normal University)(QLPL2014P01)
Ayala, Alejandro; Bashir, Adnan; Gutierrez, Enif; Raya, Alfredo; Sanchez, Angel
2010-09-01
We study chiral symmetry breaking for relativistic fermions, described by a parity-violating Lagrangian in 2+1-dimensions, in the presence of a heat bath and a uniform external magnetic field. Working within their four-component formalism allows for the inclusion of both parity-even and -odd mass terms. Therefore, we can define two types of fermion antifermion condensates. For a given value of the magnetic field, there exist two different critical temperatures which would render one of these condensates identically zero, while the other would survive. Our analysis is completely general: it requires no particular simplifying hierarchy among the energy scales involved, namely, bare masses, field strength, and temperature. However, we do reproduce some earlier results, obtained or anticipated in literature, corresponding to special kinematical regimes for the parity conserving case. Relating the chiral condensate to the one-loop effective Lagrangian, we also obtain the magnetization and the pair production rate for different fermion species in a uniform electric field through the replacement B{yields}-iE.
Chiral symmetry and chiral-symmetry breaking
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)
Chiral symmetry breaking in a microring optical cavity by engineered dissipation
NASA Astrophysics Data System (ADS)
Shu, Fang-Jie; Zou, Chang-Ling; Zou, Xu-Bo; Yang, Lan
2016-07-01
We propose a method to break the chiral symmetry of light in traveling wave resonators by coupling the optical modes to a lossy channel. Through the engineered dissipation, an indirect dissipative coupling between two oppositely propagating modes can be realized. Combined with reactive coupling, it can break the chiral symmetry of the resonator, allowing light propagating only in one direction. The chiral symmetry breaking is numerically verified by the simulation of an electromagnetic field in a microring cavity, with proper refractive index distributions. This work provokes us to emphasize the dissipation engineering in photonics, and that the generalized idea can also be applied to other systems.
ERIC Educational Resources Information Center
Matsumoto, Mitsuko
2015-01-01
Some argue that the field of study of "education and conflict" has yet to be solidified since its emergence in the 1990s, partly due to the weak theory base. This article reviews the literature on the "contribution" of schooling in contemporary violent conflict, via three strands of theoretical ideas, to demonstrate the…
Inflation in supergravity with a single chiral superfield
NASA Astrophysics Data System (ADS)
Ketov, Sergei V.; Terada, Takahiro
2014-09-01
We propose new supergravity models describing chaotic Linde- and Starobinsky-like inflation in terms of a single chiral superfield. The key ideas to obtain a positive vacuum energy during large field inflation are (i) stabilization of the real or imaginary partner of the inflaton by modifying a Kähler potential, and (ii) use of the crossing terms in the scalar potential originating from a polynomial superpotential. Our inflationary models are constructed by starting from the minimal Kähler potential with a shift symmetry, and are extended to the no-scale case. Our methods can be applied to more general inflationary models in supergravity with only one chiral superfield.
NASA Astrophysics Data System (ADS)
Dreissigacker, Ingo; Lein, Manfred
2014-05-01
Motivated by recent experiments on circular dichroism in the photoelectron momentum distributions from strong-field ionization of chiral molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012), 10.1002/anie.201109035; C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013), 10.1063/1.4844295], we investigate the origin of this effect theoretically. We show that it is not possible to describe photoelectron circular dichroism with the commonly used strong-field approximation due to its plane-wave nature. We therefore apply the Born approximation to the scattering state and use this as a continuum-state correction in the strong-field approximation. We obtain electron distributions for the molecules camphor and fenchone. In order to gain physical insight into the process, we study the contributions of individual molecular orientations.
Lin, Shi-Zeng; Saxena, Avadh
2015-11-03
Here we study the equilibrium and dynamical properties of skyrmions in thin films of chiral magnets with oblique magnetic field. The shape of an individual skyrmion is non-circular and the skyrmion density decreases with the tilt angle from the normal of films. As a result, the interaction between two skyrmions depends on the relative angle between them in addition to their separation. The triangular lattice of skyrmions under a perpendicular magnetic field is distorted into a centered rectangular lattice for a tilted magnetic field. For a low skyrmion density, skyrmions form a chain like structure. Lastly, the dynamical response of the non-circular skyrmions depends on the direction of external currents.
Lin, Shi-Zeng; Saxena, Avadh
2015-11-03
Here we study the equilibrium and dynamical properties of skyrmions in thin films of chiral magnets with oblique magnetic field. The shape of an individual skyrmion is non-circular and the skyrmion density decreases with the tilt angle from the normal of films. As a result, the interaction between two skyrmions depends on the relative angle between them in addition to their separation. The triangular lattice of skyrmions under a perpendicular magnetic field is distorted into a centered rectangular lattice for a tilted magnetic field. For a low skyrmion density, skyrmions form a chain like structure. Lastly, the dynamical response ofmore » the non-circular skyrmions depends on the direction of external currents.« less
Strangeness S =-1 hyperon-nucleon scattering in covariant chiral effective field theory
NASA Astrophysics Data System (ADS)
Li, Kai-Wen; Ren, Xiu-Lei; Geng, Li-Sheng; Long, Bingwei
2016-07-01
Motivated by the successes of covariant baryon chiral perturbation theory in one-baryon systems and in heavy-light systems, we study relevance of relativistic effects in hyperon-nucleon interactions with strangeness S =-1 . In this exploratory work, we follow the covariant framework developed by Epelbaum and Gegelia to calculate the Y N scattering amplitude at leading order. By fitting the five low-energy constants to the experimental data, we find that the cutoff dependence is mitigated, compared with the heavy-baryon approach. Nevertheless, the description of the experimental data remains quantitatively similar at leading order.
NASA Astrophysics Data System (ADS)
Adam, J.; Tater, M.; Truhlík, E.; Epelbaum, E.; Machleidt, R.; Ricci, P.
2012-03-01
The doublet capture rate Λ1 / 2 of the negative muon capture in deuterium is calculated employing the nuclear wave functions generated from accurate nucleon-nucleon (NN) potentials constructed at next-to-next-to-next-to-leading order of heavy-baryon chiral perturbation theory and the weak meson exchange current operator derived within the same formalism. All but one of the low-energy constants that enter the calculation were fixed from pion-nucleon and nucleon-nucleon scattering data. The low-energy constant dˆR (cD), which cannot be determined from the purely two-nucleon data, was extracted recently from the triton β-decay and the binding energies of the three-nucleon systems. The calculated values of Λ1 / 2 show a rather large spread for the used values of the dˆR. Precise measurement of Λ1 / 2 in the future will not only help to constrain the value of dˆR, but also provide a highly nontrivial test of the nuclear chiral EFT framework. Besides, the precise knowledge of the constant dˆR will allow for consistent calculations of other two-nucleon weak processes, such as proton-proton fusion and solar neutrino scattering on deuterons, which are important for astrophysics.
NASA Astrophysics Data System (ADS)
Bourget, Antoine; Troost, Jan
2016-03-01
We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.
Nonlinear chiral transport phenomena
NASA Astrophysics Data System (ADS)
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.
Han, Tian; Leng, Ji-Dong; Ding, You-Song; Wang, Yanyan; Zheng, Zhiping; Zheng, Yan-Zhen
2015-08-14
A one-dimensional dysprosium(iii)-carboxylate chain in which the Dy(III) ions sit in a pseudo D(2d)-symmetry environment is synthesized and shows different slow magnetic relaxation behaviours depending on the field and dilution effects. Besides, the chiral ligand introduces the additional functions of the Cotton effect and polarization for this compound. PMID:26159885
Microscopic optical potential for exotic isotopes from chiral effective field theory
NASA Astrophysics Data System (ADS)
Holt, J. W.; Kaiser, N.; Miller, G. A.
2016-06-01
We compute the isospin-asymmetry dependence of microscopic optical model potentials from realistic chiral two- and three-body interactions over a range of resolution scales Λ ≃400 -500 MeV. We show that at moderate projectile energies, E =110 -200 MeV, the real isovector part of the optical potential changes sign, a phenomenon referred to as isospin inversion. We also extract the strength and energy dependence of the imaginary isovector optical potential and find no evidence for an analogous phenomenon over the range of energies, E ≤200 MeV, considered in the present work. Finally, we compute for the first time the leading (quadratic) corrections to the Lane parametrization for the isospin-asymmetry dependence of the optical potential and observe an enhanced importance at low scattering energies.
2016-01-01
The combination of photonics and spintronics opens new ways to transfer and process information. It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena. We report on light induced and spin-dependent charge transfer process through helical oligopeptide–CdSe nanoparticles’ (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100–200 Oe). The spin control is achieved by the application of the chirality-induced spin-dependent electron transfer effect and is probed by two different methods: spin-controlled electrochemichemistry and photoluminescence (PL) at room temperature. The injected spin could be controlled by excitation of the nanoparticles. By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated. PMID:27027885
Mondal, Prakash Chandra; Roy, Partha; Kim, Dokyun; Fullerton, Eric E; Cohen, Hagai; Naaman, Ron
2016-04-13
The combination of photonics and spintronics opens new ways to transfer and process information. It is shown here that in systems in which organic molecules and semiconductor nanoparticles are combined, matching these technologies results in interesting new phenomena. We report on light induced and spin-dependent charge transfer process through helical oligopeptide-CdSe nanoparticles' (NPs) architectures deposited on ferromagnetic substrates with small coercive force (∼100-200 Oe). The spin control is achieved by the application of the chirality-induced spin-dependent electron transfer effect and is probed by two different methods: spin-controlled electrochemichemistry and photoluminescence (PL) at room temperature. The injected spin could be controlled by excitation of the nanoparticles. By switching the direction of the magnetic field of the substrate, the PL intensity could be alternated. PMID:27027885
Feng, Jian-Shen; Ren, Min; Cai, Zhong-Sheng; Fan, Kun; Bao, Song-Song; Zheng, Li-Min
2016-05-25
This Communication reports, for the first time, that enantiopure phosphonic acids can serve as chirality-inducing agents towards homochiral coordination polymers. Hence homochiral chain compounds (M)- or (P)-Co(SO4)(1,3-bbix)(H2O)3 (1M or 1P) are obtained successfully using an achiral precursor of 1,3-bis((1H-benzo[d]imidazol-1-yl)methyl)benzene (1,3-bbix) in the presence of a catalytic amount of (S)- or (R)-3-phenyl-2-((phosphonomethyl)amino)propanoic acid [(S)- or (R)-2-ppapH3]. Furthermore, compound 1M provides the first example of homochiral cobalt compounds showing field-induced single ion magnet behavior. PMID:27108929
Lin, Shuang-Yan; Wang, Chao; Zhao, Lang; Wu, Jianfeng; Tang, Jinkui
2015-01-01
Three pairs of homochiral mononuclear lanthanide complexes, with the general formula [LnH4LRRRRRR/SSSSSS(SCN)2](SCN)2·xCH3OH·yH2O(Ln = Dy (R/S-Dy1), Ho (R/S-Ho1) and Er (R/S-Er1)), have been obtained via self-assembly between chiral macrocyclic ligands and the respective thiocyanates, all of which show a saddle-type conformation with seven-coordinated metal ions. Magnetic measurements revealed that the Dy complex shows field-induced single-ion magnet behaviour, which is rarely reported in a seven-coordinated lanthanide-based SIM encapsulated in a macrocyclic ligand. The absolute configuration of all enantiomers was determined by single crystal X-ray crystallography and confirmed by electronic CD and VCD spectra. PMID:25369972
S. Pastore,L. Girlanda,R. Schiavilla,M. Viviani,S. Pastore,L. Girlanda,R. Schiavilla,M. Viviani
2011-08-01
The electromagnetic charge operator in a two-nucleon system is derived in chiral effective field theory ($\\chi$EFT) up to order $e\\, Q$ (or N4LO), where $Q$ denotes the low-momentum scale and $e$ is the electric charge. The specific form of the N3LO and N4LO corrections from, respectively, one-pion-exchange and two-pion-exchange depends on the off-the-energy-shell prescriptions adopted for the non-static terms in the corresponding potentials. We show that different prescriptions lead to unitarily equivalent potentials and accompanying charge operators. Thus, provided a consistent set is adopted, predictions for physical observables will remain unaffected by the non-uniqueness associated with these off-the-energy-shell effects.
NASA Astrophysics Data System (ADS)
Hiraoka, Y.; Tanaka, Y.; Oura, M.; Wakabayashi, Y.; Kimura, T.
2015-06-01
Spin-chiral domain structures near a cleaved crystal face of a magnetoelectric helimagnet, Ba0.5Sr1.5Zn2Fe12O22, were examined after various magnetic and electric field-cooling procedures by means of the scanning resonant X-ray microdiffraction technique using circularly polarized X-rays. We have found that the application of a magnetic field (1-2 k Oe) during the field-cooling procedure stabilizes one of the handedness among the two spin-chiral states (left- or right-handed screw structure) and makes nearly a single spin-chiral domain in the vicinity of the cleaved crystal face. However, it makes the degree of the spin chirality spatially inhomogeneous even within a domain. We discuss the observed field-cooling effect in terms of possible formation of spin-chiral domains with "stripe-type" domain walls accompanied by randomly-distributed ferromagnetic islands.
NASA Astrophysics Data System (ADS)
Kaul, S. N.; Messala, Umasankar
2016-03-01
Weak itinerant-electron ferromagnet Ni3Al is driven to magnetic instability (quantum critical point, QCP, where the long-range ferromagnetic order of the bulk ceases to exist) by reducing the average crystallite size to d=50 nm. 'Zero-field' (H=0) linear and nonlinear ac-susceptibilities, measured on Ni3Al nanoparticle aggregates, with d=50 nm (S1) and d=5 nm (S2), provide strong evidence for two spin glass (SG)-like thermodynamic phase transitions: one at Ti(H = 0) ≃ 30 K (Ti† (H = 0) ≃ 230 K) and the other at a lower temperature Tp(H = 0) ≃ 8 K (Th(H = 0) ≃ 52 K) in S1 (S2). 'In-field' (H ≠ 0) linear ac-susceptibility and dc magnetization demonstrate that the thermodynamic nature of these transitions is preserved in finite fields. The presently determined H-T phase diagrams for the samples S1 and S2 are compared with those predicted by the Kotliar-Sompolinsky and Gabay-Toulouse mean-field models and Monte Carlo simulations, based on the chirality-driven spin glass (SG) ordering scenario, for a three-dimensional nearest-neighbor Heisenberg SG system with or without weak random anisotropy. Such a detailed comparison permits us to unambiguously identify various 'zero-field' and 'in-field' SG phase transitions as: (i) the simultaneous paramagnetic (PM)-chiral glass (CG) and PM-SG phase transitions at Ti(H), (ii) the PM-CG transition at Ti† (H), (iii) the replica symmetry-breaking SG transition at Tp(H), and (iv) the continuous spin-rotation symmetry-breaking SG transition at Th(H). In the presence of random anisotropy, magnetization fails to saturate even at 90 kOe in S1 whereas negligibly small anisotropy allows even fields as weak as 1 kOe to saturate magnetization and induce ferromagnetism in S2. Due to the proximity to CG/SG-QCP, magnetization and susceptibility both exhibit non-Fermi liquid behavior over a wide range at low temperatures.
Lectures on Chiral Symmetries and Soft Pion Processes
DOE R&D Accomplishments Database
Nambu, Y.
1966-08-01
At the Istanbul Summer School in 1962 I gave lectures on "Chiral Symmetries in Weak and Strong Interactions." It is only recently, however, that the basic ideas that were started several years ago have begun to bear fruit. We will cover in the present lectures more or less the same general field, but certainly there will be a lot more results to be discussed now than four years ago.
Significant Ideas and Progressive Change
ERIC Educational Resources Information Center
Morgan, Gwen; Mitchell, Anne
2012-01-01
Ideas are not one-time "Eureka" moments, but are parts of concepts progressing forward. Sometimes years pass before ideas are implemented. They then resurface, connect with other ideas, and move policies ahead. Meanwhile, the idea remains alive in the field, influencing decisions and goals. Ideas build on one another when implemented. The field of…
Phase diagram of the chiral magnet Cr1 /3NbS2 in a magnetic field
NASA Astrophysics Data System (ADS)
Tsuruta, K.; Mito, M.; Deguchi, H.; Kishine, J.; Kousaka, Y.; Akimitsu, J.; Inoue, K.
2016-03-01
We construct the phase diagram of the chiral magnet Cr1 /3NbS2 in a dc magnetic field (Hdc) using ac magnetic susceptibility measurements. At Hdc=0 , the ac response at the transition from the helical magnetic (HM) state to the paramagnetic (PM) state consists of a giant third-order harmonic component (M3 ω) and a first-order harmonic component (M1 ω). By applying Hdc perpendicular to the c axis, the HM state is transformed to the chiral soliton lattice (CSL) state, which is a superlattice tuned by Hdc. The above giant M3 ω is markedly suppressed at small Hdc. The CSL state is found to consist of CSL-1, with dominant helical texture and a poor ferromagnetic array, and CSL-2, with a large ferromagnetic array. The transition between CSL-1 and the PM state causes a linear magnetic response, the dominant component of which is the in-phase M1 ω. With increasing temperature, CSL-2 is transformed into the forced ferromagnetic (FFM) state, and ultimately the PM state is reached. The transition between CSL-2 and the FFM state consists of a large M3 ω and large out-of-phase M1 ω as well as in-phase M1 ω. The transition between the FMM and PM states also yields a linear magnetic response, like the CSL-1-PM-state transition. Five typical magnetic dynamics in the transitions among the HM state, CSL-1, CSL-2, FFM state, and PM state were identified according to the equivalent dynamical motion equation of a nonlinear spring model.
Thermodynamics for a hadronic gas of fireballs with internal color structures and chiral fields
Zakout, Ismail; Greiner, Carsten
2008-09-15
The thermodynamic partition function for a gas of color-singlet bags consisting of fundamental and adjoint particles in both U(N{sub c}) and SU(N{sub c}) group representations is reviewed in detail. The constituent particle species are assumed to satisfy various thermodynamic statistics. The gas of bags is probed to study the phase transition for nuclear matter in extreme conditions. These bags are interpreted as the Hagedorn states, and they are the highly excited hadronic states produced below the phase transition point to the quark-gluon plasma (QGP). The hadronic density of states has the Gross-Witten critical point and exhibits a third-order phase transition from a hadronic phase dominated by the discrete low-lying hadronic mass spectrum particles to another hadronic phase dominated by the continuous Hagedorn states. The Hagedorn threshold production is found just above the highest known experimental discrete low-lying hadronic mass spectrum. The subsequent Hagedorn phase undergoes a first-order deconfinement phase transition to an explosive QGP. The role of the chiral phase transition in the phases of the discrete low-lying mass spectrum and the continuous Hagedorn mass spectrum is also considered. It is found to be crucial in the phase transition diagram. Alternative scenarios are briefly discussed for the Hagedorn gas undergoing a higher order phase transition through multiple processes of internal color-flavor structure modification.
Vladimir Pascalutsa; Marc Vanderhaeghen
2006-01-20
We develop an extension of chiral perturbation theory to the {Delta}(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon (e{sup -} N {yields} e{sup -} N {pi}). We present a complete calculation of this process, in the {Delta}-resonance region, up to next-to-leading order in the {delta}-expansion. At this order, the only free parameters are the three low-energy constants corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) {gamma} N {yields} {Delta} transition strength. After fitting these parameters to a few well-known data, our calculation provides a prediction for observables and multipole amplitudes of pion electroproduction. These results compare favorably with the phenomenological multipole solutions and recent experimental results from MIT-Bates and MAMI. Our prediction for the pion-mass dependence of the {gamma}N{Delta} form factors offers an explanation for the discrepancy between the recent lattice-QCD results and the experimental value for the ''C2/M1 ratio'' at low Q{sup 2}.
ERIC Educational Resources Information Center
Israel, Susan E., Ed.; Monaghan, E. Jennifer, Ed.
2007-01-01
Only by exploring the past of the reading field can the literacy leaders of today make informed decisions about reading education in the future. This indispensable resource offers new insight into the development of reading education by examining the groundbreaking contributions of the "early reading pioneers"--16 reading researchers, reading…
NASA Astrophysics Data System (ADS)
Nagy, S.
2016-07-01
We construct the states and symmetries of N = 4 super-Yang-Mills by tensoring two N = 1 chiral multiplets and introducing two extra SUSY generators. This allows us to write the maximal N = 8 supergravity as four copies of the chiral multiplet. We extend this to higher dimensions and discuss applications to scattering amplitudes.
Chiral Bosonization of Superconformal Ghosts
NASA Technical Reports Server (NTRS)
Shi, Deheng; Shen, Yang; Liu, Jinling; Xiong, Yongjian
1996-01-01
We explain the difference of the Hilbert space of the superconformal ghosts (beta,gamma) system from that of its bosonized fields phi and chi. We calculate the chiral correlation functions of phi, chi fields by inserting appropriate projectors.
NASA Astrophysics Data System (ADS)
Changlani, Hitesh; Kumar, Krishna; Clark, Bryan; Fradkin, Eduardo
Frustrated spin systems in two dimensions provide a fertile ground for discovering exotic states of matter, often with topologically non-trivial properties. In this work, we investigate the possible existence of a chiral spin liquid state in the spin 1/2 XXZ model on the frustrated kagome lattice in the presence of a magnetic field. This model is equivalent to a hard-core bosonic one with density-density interactions at finite filling fraction. Motivated by previous field theoretic predictions utilizing a Chern-Simons theory adapted for this lattice, we focus our attention to understanding the XY limit for the 2/3 magnetization plateau (equivalent to a system of hard-core bosons at 1/6 filling with weak nearest-neighbor repulsive interactions). Performing exact or accurate numerical computations, and based on energetics and construction of minimally entangled states and associated modular matrices, we provide evidence for such a spin liquid. We study the nature of this phase and examine its stability to additional interactions. We acknowledge support from the SciDAC program under Award Number DE-FG02-12ER46875.
Chiral imprint of a cosmic gauge field on primordial gravitational waves
NASA Astrophysics Data System (ADS)
Bielefeld, Jannis; Caldwell, Robert R.
2015-06-01
A cosmological gauge field with isotropic stress-energy introduces parity violation into the behavior of gravitational waves. We show that a primordial spectrum of inflationary gravitational waves develops a preferred handedness, left or right circularly polarized, depending on the abundance and coupling of the gauge field during the radiation era. A modest abundance of the gauge field would induce parity-violating correlations of the cosmic microwave background temperature and polarization patterns that could be detected by current and future experiments.
ERIC Educational Resources Information Center
Science Teacher, 1993
1993-01-01
Presents three teaching ideas entitled (1) Rearview Mirrors; (2) Chills and Fevers; and (3) Science Activities and the Learner. The second idea presents a poem to help students with the relationship between Centigrade and Fahrenheit. The third idea presents activities on evaporation. (PR)
NASA Astrophysics Data System (ADS)
English, Niall J.; Kusalik, Peter G.; Woods, Sarah A.
2012-03-01
Non-equilibrium molecular dynamics simulations of R and S enantiomers of 1,1-chlorofluoroethane, both for pure liquids and racemic mixtures, have been performed at 298 K in the absence and presence of both electromagnetic (e/m) and circularly polarised electric (CP) fields of varying frequency (100-2200 GHz) and intensity (0.025-0.2 V Å-1rms). Significant non-thermal field effects were noted in the coupling of rotational and translational motion; for instance, in microwave and far-infrared (MW/IR) e/m fields, marked increases in rotational and translational diffusion vis-à-vis the zero-field case took place at 0.025-0.1 V Å-1rms, with a reduction in translational diffusion vis-à-vis the zero-field case above 0.1 V Å-1rms above 100 GHz. This was due to enhanced direct coupling of rotational motion with the more intense e/m field at the ideal intrinsic rotational coupling frequency (approximately 700 GHz) leading to such rapidly oscillating rotational motion that extent of translational motion was effectively reduced. In the case of CP fields, rotational and translational diffusion was also enhanced for all intensities, particularly at approximately 700 GHz. For both MW/IR and CP fields, non-linear field effects were evident above around 0.1 V Å-1rms intensity, in terms of enhancements in translational and rotational motion. Simulation of 90-10 mol. % liquid mixtures of a Lennard-Jones solvent with R and S enantiomer-solutes in MW/IR and CP fields led to more limited promotion of rotational and translational diffusion, due primarily to increased frictional effects. For both e/m and CP fields, examination of the laboratory- and inertial-frame auto- and cross-correlation functions of velocity and angular velocity demonstrated the development of explicit coupling with the external fields at the applied frequencies, especially so in the more intense fields where nonlinear effects come into play. For racemic mixtures, elements of the laboratory- and inertial
The effect of magnetic field on chiral transmission in p-n-p graphene junctions
Li, Yuan; Wan, Qi; Peng, Yingzi; Wang, Guanqing; Qian, Zhenghong; Zhou, Guanghui; Jalil, Mansoor B. A.
2015-01-01
We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green’s function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a “constriction region” of low transmission when is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy. PMID:26679991
The effect of magnetic field on chiral transmission in p-n-p graphene junctions.
Li, Yuan; Wan, Qi; Peng, Yingzi; Wang, Guanqing; Qian, Zhenghong; Zhou, Guanghui; Jalil, Mansoor B A
2015-01-01
We investigate Klein tunneling in graphene heterojunctions under the influence of a perpendicular magnetic field via the non-equilibrium Green's function method. We find that the angular dependence of electron transmission is deflected sideways, resulting in the suppression of normally incident electrons and overall decrease in conductance. The off-normal symmetry axis of the transmission profile was analytically derived. Overall tunneling conductance decreases to almost zero regardless of the potential barrier height V0 when the magnetic field (B-field) exceeds a critical value, thus achieving effective confinement of Dirac fermions. The critical field occurs when the width of the magnetic field region matches the diameter of the cyclotron orbit. The potential barrier also induces distinct Fabry-Pérot fringe patterns, with a "constriction region" of low transmission when V0 is close to the Fermi energy. Application of B-field deflects the Fabry-Pérot interference pattern to an off-normal angle. Thus, the conductance of the graphene heterojunctions can be sharply modulated by adjusting the B-field strength and the potential barrier height relative to the Fermi energy. PMID:26679991
NASA Astrophysics Data System (ADS)
Thacker, H. B.; Xiong, Chi; Kamat, Ajinkya S.
2011-11-01
The Witten-Sakai-Sugimoto construction of holographic QCD in terms of D4 color branes and D8 flavor branes in type IIA string theory is used to investigate the role of topological charge in the chiral dynamics of quarks in QCD. The QCD theta term arises from a compactified five-dimensional Chern-Simons term on the D4 branes. This term couples the QCD topological charge to the Ramond-Ramond (RR) U(1) gauge field of type IIA string theory. For large Nc the contribution of instantons (D0 branes) is suppressed, and the nonzero topological susceptibility of pure-glue QCD is attributed to the presence of D6 branes, which constitute magnetic sources of the RR gauge field. The topological charge of QCD is required, by an anomaly inflow argument, to coincide in space-time with the intersection of the D6 branes and the D4 color branes. This clarifies the relation between D6 branes and the coherent, codimension-one topological charge membranes observed in QCD Monte Carlo calculations. Using open-string/closed-string duality, we interpret a quark loop (represented by a D4-D8 open-string loop) in terms of closed-string exchange between color and flavor branes. The role of the RR gauge field in quark-antiquark annihilation processes is discussed. RR exchange in the s-channel generates a 4-quark contact term which produces an η' mass insertion and provides an explanation for the observed spin-parity structure of the Okubo-Zweig-Iizuka rule. The (logDetU)2 form of the U(1) anomaly emerges naturally. RR exchange in the t-channel of the qq¯ scattering amplitude produces a Nambu-Jona-Lasinio interaction which may provide a mechanism for spontaneous breaking of SU(Nf)×SU(Nf).
Zhang, B.; Brooks, J.; Wang, Z.; Simmons, J.; Reno, J.; Lumpkin, N.; OBrien, J.; Clark, R.
1999-09-01
The transport properties of a quasi-three-dimensional, 200-layer quantum-well structure are investigated at integer filling in the quantum Hall state, concomitant with the chiral edge state condition. We find that the transverse magnetoresistance R{sub xx}, the Hall resistance R{sub xy}, and the vertical resistance R{sub zz} all follow a similar behavior with {ital both} temperature and in-plane magnetic field. A general characteristic of the influence of increasing in-plane field B{sub in} is that the quantization condition first improves, but above a critical value B{sub in}{sup C}, the quantization is systematically removed. We consider the interplay of the chiral edge state transport and the bulk (quantum Hall) transport properties. This mechanism may arise from the competition of the cyclotron energy with the superlattice band-structure energies. A comparison of the results with existing theories of the chiral edge state transport with in-plane field is also discussed. {copyright} {ital 1999} {ital The American Physical Society}
Poynting Robertson Battery and the Chiral Magnetic Fields of AGN Jets
NASA Technical Reports Server (NTRS)
Kazanas, Demosthenes
2010-01-01
We propose that the magnetic fields in the accretion disks of active galactic nuclei (AGNs) are generated by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with the AGN photons (the Poynting Robertson battery). This process provides a unique relation between the polarity of the poloidal B field to the angular velocity Omega of the accretion disk (B is parallel to Omega), a relation absent in the more popular dynamo B-field generation. This then leads to a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry comes about by chance being approx.0.06 %. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.
Chirality effect in disordered graphene ribbon junctions
NASA Astrophysics Data System (ADS)
Long, Wen
2012-05-01
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.
Floss, H.G.
1994-12-01
This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.
Suzuki, Nozomu; Wang, Yichun; Elvati, Paolo; Qu, Zhi-Bei; Kim, Kyoungwon; Jiang, Shuang; Baumeister, Elizabeth; Lee, Jaewook; Yeom, Bongjun; Bahng, Joong Hwan; Lee, Jaebeom; Violi, Angela; Kotov, Nicholas A
2016-02-23
Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of l/d-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the "crowded" edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210-220 and 250-265 nm that changed their signs for different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210-220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250-265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to L/D-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that d-GQDs have a stronger tendency to accumulate within the cellular membrane than L-GQDs. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials. PMID:26743467
NASA Astrophysics Data System (ADS)
H, Dhaouadi; R, Zgueb; O, Riahi; F, Trabelsi; T, Othman
2016-05-01
In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the (E,T) phase diagram of the studied product can be obtained. In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.
Baryon chiral perturbation theory
NASA Astrophysics Data System (ADS)
Scherer, S.
2012-03-01
We provide a short introduction to the one-nucleon sector of chiral perturbation theory and address the issue of power counting and renormalization. We discuss the infrared regularization and the extended on-mass-shell scheme. Both allow for the inclusion of further degrees of freedom beyond pions and nucleons and the application to higher-loop calculations. As applications we consider the chiral expansion of the nucleon mass to order Script O(q6) and the inclusion of vector and axial-vector mesons in the calculation of nucleon form factors. Finally, we address the complex-mass scheme for describing unstable particles in effective field theory.
NASA Astrophysics Data System (ADS)
Liu, Zhaosen; Ian, Hou
2016-04-01
We employed a quantum simulation approach to investigate the magnetic properties of monolayer square nanodisks with Dzyaloshinsky-Moriya (DM) interaction. The computational program converged very quickly, and generated chiral spin structures on the disk planes with good symmetry. When the DM interaction is sufficiently strong, multi-domain structures appears, their sizes or average distance between each pair of domains can be approximately described by a modified grid theory. We further found that the external magnetic field and uniaxial magnetic anisotropy both normal to the disk plane lead to reductions of the total free energy and total energy of the nanosystems, thus are able to stabilize and/or induce the vortical structures, however, the chirality of the vortex is still determined by the sign of the DM interaction parameter. Moreover, the geometric shape of the nanodisk affects the spin configuration on the disk plane as well.
ERIC Educational Resources Information Center
Instructor, 1979
1979-01-01
Presents ideas for teaching techniques and learning activities in areas such as: New Year's resolutions, bird feeding, typing to spell, using thermometers, and activities utilizing old calendars. (JMB)
Attosecond strong-field interferometry in graphene: Chirality, singularity, and Berry phase
NASA Astrophysics Data System (ADS)
Kelardeh, Hamed Koochaki; Apalkov, Vadym; Stockman, Mark I.
2016-04-01
We propose an interferometry in graphene's reciprocal space without a magnetic field, employing strong ultrafast circularly polarized optical pulses. The reciprocal space interferograms contain information on the electronic spectra and topological properties of graphene and on the waveform and circular polarization of the excitation optical pulses. These can be measured using angle-resolved photoemission spectroscopy (ARPES) with attosecond ultraviolet pulses. The predicted effects provide unique opportunities in fundamental studies of two-dimensional topological materials and in applications to future petahertz light-wave-driven electronics.
Sigarev, A A; Vij, J K; Lewis, R A; Hird, M; Goodby, J W
2003-09-01
The molecular orientation and the dichroic behavior of the vibrational bands of a homogeneously aligned helical cell containing chiral smectic liquid crystal (R)-(-)-1-methylheptyl 4-(4(')-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate are studied at various temperatures as a function of the bias field. These temperatures correspond to the various phase states of the sample at zero field. For those bands that exhibit significant dichroism, the field dependencies of the dichroic parameters (the dichroic ratio and the polarization angle of maximum absorbance) are found to be dependent on temperature, phase state, and helical unwinding. For the SmA* and SmC(*)(alpha) phases, the phenyl band dichroic ratio and the corresponding orientational order parameter are found to be almost independent of the bias field. The temperature dependence of the orientational order for zero field is discussed by taking into account the structures of the phases and the molecular tilt angles. The field dependencies of the phenyl band dichroic parameters for the SmC(*)(A) and SmC(*)(gamma) phases yield results about the distribution of directors in the layers of their unit cells and the state of helical unwinding. The azimuthal orientational distribution function of the carbonyl transition moments with respect to the long molecular axis has been determined. It is found that the degrees of the polar and quadrupolar biasing increase with decrease in temperature and the azimuthal biasing angle for the chiral carbonyl group increases significantly with a reduction in temperature. PMID:14524788
Chiral Alfvén Wave in Anomalous Hydrodynamics.
Yamamoto, Naoki
2015-10-01
We study the hydrodynamic regime of chiral plasmas at high temperature. We find a new type of gapless collective excitation induced by chiral effects in an external magnetic field. This is a transverse wave, and it is present even in incompressible fluids, unlike the chiral magnetic and chiral vortical waves. The velocity is proportional to the coefficient of the gravitational anomaly. We briefly discuss the possible relevance of this "chiral Alfvén wave" in physical systems. PMID:26551804
ERIC Educational Resources Information Center
Talesnick, Irwin, Ed.
1984-01-01
Provides innovative ideas in biology, chemistry, and physics on the following topics: enzyme decomposition; chemical waste; time measurement; acid-base color magic; ball bouncing properties; heat; cell theory; and specimen boxes. Materials and procedures are listed when appropriate along with hints for expanding these ideas and investigations. (JM)
NASA Astrophysics Data System (ADS)
Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari
2008-12-01
Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life’s homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average.
Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari
2008-12-01
Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average. PMID:18841492
NASA Astrophysics Data System (ADS)
Mekki-Berrada, Ali
Bringing closer phospholipids each other on a bilayer of liposome, causes their rotation around their fatty acids axis, generating a force which brings closer the two sheets of the bilayer. In this theoretical study I show that for getting the greater cohesion of the liposome, by these forces, the serine in the hydrophilic head must have a L chirality. In the case where the hydrophilic head is absent amino acids with L chirality could contribute to this cohesion by taking the place of L-serine. Some coenzymes having a configuration similar to ethanolamine may also contribute. This is the case of pyridoxamine, thiamine and tetrahydrofolic acid. The grouping of amino acids of L chirality and pyridoxamine on the wall could initialize the prebiotic metabolism of these L amino acids only. This would explain the origin of the homo-chirality of amino acids in living world. Furthermore I show that in the hydrophilic head, the esterification of glycerol-phosphate by two fatty acids go through the positioning of dihydroxyacetone-phosphate and L-glyceraldehyde-3-phosphate, but not of D-glyceraldehyde-3-phosphate, prior their hydrogenation to glycerol-3- phosphate. The accumulation of D-glyceraldehyde-3-phosphate in the cytoplasm displace the thermodynamic equilibria towards the synthesis of D-dATP from D-glyceraldehyde-3-phosphate, acetaldehyde and prebiotic adenine, a reaction which does not require a coenzyme in the biotic metabolism. D-dATP and thiamine, more prebiotic metabolism of L-amino acids on the wall, would initialize D-pentoses phosphate and D-nucleotides pathways from the reaction of D-glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate + prebiotic nucleic bases. The exhaustion of the prebiotic glyceraldehyde (racemic) and the nascent biotic metabolism dominated by D-glyceraldehyde-3-phosphate, would explain the origin of homo-chirality of sugars in living world. References: http://en.wikiversity.org/wiki/Prebiotic_chirality
ERIC Educational Resources Information Center
Kagan, Jerome
Noting that a reluctance to question some assumptions of social and behavior sciences is one reason for the halting progress in these fields, this book examines three potentially misleading ideas and reasons for their continued popularity. Chapter 1 critiques the idea that all behavior is influenced by one's psychological construction of the…
On the tensorial nature of chirality
NASA Astrophysics Data System (ADS)
Efrati, Efi; Irvine, William
2013-03-01
Chirality occupies a central role in fields ranging from biological self assembly to the design of optical meta-materials. The definition of chirality, as given by lord Kelvin in 1893, associates handedness with the lack of mirror symmetry. However, the quantification of chirality based on this definition has proven to be an elusive task. The difficulty in quantifying chirality is contrasted by the ease with which one determines the handedness of objects with a well defined axis such as screws and helices. In this talk I will present table-top demonstrations that show that a single object can simultaneously be left handed and right handed when considered from different directions. The orientation dependence of handedness motivates a tensorial quantification of chirality relating directions to rotations. I will give an explicit example of such a tensorial measure of chirality for embedded surfaces, and show how the tensorial nature of chirality can be probed in experiments and exploited as a design principle.
Meng, Qingwei; Sun, Xiao-Hua; Lu, Zhengyu; Xia, Ping-Fang; Shi, Zehua; Chen, Dongzhong; Wong, Man Shing; Wakim, Salem; Lu, Jianping; Baribeau, Jean-Marc; Tao, Ye
2009-01-01
A novel series of asymmetrically end-capped mesogenic oligothiophenes, with various oligothiophene core lengths, alkoxy tail lengths, and molecular polarities through introducing alkylsulfanyl or alkylsulfonyl functionalities as the terminal group, have been synthesized by palladium-catalyzed Suzuki cross-coupling and Kumada cross-coupling reactions as key steps. For the single end-capped oligothiophenes, C(m)O-Ar-OT(4)-H in which m=10, 12, 14, 16, and 18, all of these oligomers exhibited a broad temperature range of highly ordered smectic E and enantiotropic nematic phases, apart from the one with the longest octadecyloxy tail. For the double end-capped series C(10)O-Ar-OT(n)-R, R=Ph-SC(6) or Ph-SO(2)C(6) in which n=1, 2, 3, and 4, oligomers with more than one thiophene ring exhibited smectic A and smectic C phases, various crystal polymorphs and/or unusual low-temperature condensed phases. In the nonpolar, alkylsulfanylphenyl-substituted oligothiophene series, both the crystal/solid melting point and mesogenic clear point increased significantly with an increasing oligothiophene conjugation length. In the polar, alkylsulfonylphenyl-substituted oligothiophene series, all the oligomers showed increased melting points, but decreased mesogenic temperature intervals than those of their corresponding alkylsulfanyl counterparts. Remarkably, two different helical structures showing distinct striated textures or striped patterns were observed with a pitch of several to tens of micrometers under a polarized optical microscope upon cooling from their preceding fluidic smectic phases. The unusual twisted smectic layer structures in the thin solid films exhibiting distinct supramolecular chirality of both handednesses, revealed by circular dichroism measurements, were further confirmed by XRD analyses characterized by a sharp layer reflection together with its higher orders and diffuse wide-angle scatterings. In addition, initial studies showed that the highly ordered smectic
Pasti, Paolo; Tonin, Mario; Samsonov, Igor; Sorokin, Dmitri
2009-10-15
We reveal nonmanifest gauge and SO(1,5) Lorentz symmetries in the Lagrangian description of a six-dimensional free chiral field derived from the Bagger-Lambert-Gustavsson model in [P.-M. Ho and Y. Matsuo, J. High Energy Phys. 06 (2008) 105.] and make this formulation covariant with the use of a triplet of auxiliary scalar fields. We consider the coupling of this self-dual construction to gravity and its supersymmetrization. In the case of the nonlinear model of [P.-M. Ho, Y. Imamura, Y. Matsuo, and S. Shiba, J. High Energy Phys. 08 (2008) 014.] we solve the equations of motion of the gauge field, prove that its nonlinear field strength is self-dual and find a gauge-covariant form of the nonlinear action. Issues of the relation of this model to the known formulations of the M5-brane worldvolume theory are discussed.
Chiral perturbation theory with nucleons
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.
Li, Jing; Zhang, Yuting; Cheng, Youpu; Yuan, Shankui; Liu, Lei; Shao, Hui; Li, Hui; Li, Na; Zhao, Pengyue; Guo, Yongze
2016-03-20
A novel and sensitive ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous enantioselective determination of flufiprole and its hydrolysis metabolite in paddy field ecosystem. The separation and determination were performed using reversed-phase chromatography on a novel cellulose chiral stationary phase, a Lux Cellulose-4 (150 mm × 2.0 mm) column, under isocratic conditions at 0.25 mL/min flow rate. The effects of other four different polysaccharide-based chiral stationary phases (CSPs) on the separation and simultaneous enantioseparation of the two target compounds were also evaluated. The elution orders of the eluting enantiomers were identified by an optical rotation detector. Modified QuEChERS (acronym for Quick, Easy, Cheap, Effective, Rugged and Safe) method and solid-phase extraction (SPE) were used for the enrichment and cleanup of paddy water, rice straw, brown rice and paddy soil samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were evaluated. Under the optimal conditions, the mean recoveries for all enantiomers from the above four sample matrix were ranged from 83.6% to 107%, with relative standard deviations (RSD) in the range of 1.0-5.8%. Coefficients of determination R(2)≥0.998 were achieved for each enantiomer in paddy water, rice straw, brown rice and paddy soil matrix calibration curves within the range of 5-500 μg/kg. The limits of quantification (LOQ) for all stereoisomers in the above four matrices were all below 2.0 μg/kg. The methodology was successfully applied for simultaneously enantioselective analysis of flufiprole enantiomers and their chiral metabolite in the real samples, indicating its efficacy in investigating the environmental stereochemistry of flufiprole in paddy field ecosystem. PMID:26809615
Chiral Magnetic Effect in Hydrodynamic Approximation
NASA Astrophysics Data System (ADS)
Zakharov, Valentin I.
We review derivations of the chiral magnetic effect (ChME) in hydrodynamic approximation. The reader is assumed to be familiar with the basics of the effect. The main challenge now is to account for the strong interactions between the constituents of the fluid. The main result is that the ChME is not renormalized: in the hydrodynamic approximation it remains the same as for non-interacting chiral fermions moving in an external magnetic field. The key ingredients in the proof are general laws of thermodynamics and the Adler-Bardeen theorem for the chiral anomaly in external electromagnetic fields. The chiral magnetic effect in hydrodynamics represents a macroscopic manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue that the current induced by the magnetic field is dissipation free and talk about a kind of "chiral superconductivity". More precise description is a quantum ballistic transport along magnetic field taking place in equilibrium and in absence of a driving force. The basic limitation is the exact chiral limit while temperature—excitingly enough—does not seemingly matter. What is still lacking, is a detailed quantum microscopic picture for the ChME in hydrodynamics. Probably, the chiral currents propagate through lower-dimensional defects, like vortices in superfluid. In case of superfluid, the prediction for the chiral magnetic effect remains unmodified although the emerging dynamical picture differs from the standard one.
ERIC Educational Resources Information Center
Science Teacher, 1986
1986-01-01
Provides descriptions of activities and programs that have been successful with secondary science students. Includes ideas related to repairing radio-controlled cars, cooperative science-library center, observation exercises, recordkeeping skills and peer grading, DC power supply, chemistry of poison ivy, spore science, and a tic-tac-toe review…
ERIC Educational Resources Information Center
American School & University, 1996
1996-01-01
Describes innovative strategies that schools and universities are using to save money and reshape operations. Focuses on ideas in energy efficiency and facilities improvement, direct purchasing, energy management, retrofitting buildings, ceiling insulation upgrades, automation systems, electric demand programs, facilities programs, warranty…
ERIC Educational Resources Information Center
Science Teacher, 1993
1993-01-01
Presents a series of science teaching ideas with the following titles: When Demonstrations Are Misleading, Lasers and Refraction, An Improved Stair-Step Model, Correcting Your Compass, Seeing Is Not Believing, Food Coloring: From the Kitchen to the Lab, Punny Business, Portfolios in Science, Feathers or Gold: A Case for Using the Metric System,…
ERIC Educational Resources Information Center
Middleton, Kathleen, Ed.
1979-01-01
Ideas to aid the classroom teacher include integration of emphasis on reading into health education; definitions pertinent to contemporary health education; teaching students to read food labels; identification of implications of scientific advances such as test tube reproduction; and a card game to teach food groups to middle school children.…
ERIC Educational Resources Information Center
Armstrong, Phil
1999-01-01
Discusses how to upgrade lighting technology in schools to reduce energy consumption and cut operating costs. Explores fixture efficiency using ballast and lamp upgrades and compact fluorescent lights. Other ideas include changing exit signs to ones that use less wattage, improving luminary efficiency through use of reflectors and shielding…
NASA Astrophysics Data System (ADS)
Carlowicz, Michael
A century before the federal government established a council for “sustainable development,” John Wesley Powell was touting the idea as way to tame the American West. Powell's quiver of intellectual tools included one that modern environmentalists swear by: integrated assessment.
Lateral chirality-sorting optical forces
Hayat, Amaury; Mueller, J. P. Balthasar; Capasso, Federico
2015-01-01
The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. Because their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces. PMID:26453555
NASA Astrophysics Data System (ADS)
Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry
2007-10-01
pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4
A lattice formulation of chiral gauge theories
Bodwin, G.T.
1996-08-01
We present a method for implementing gauge theories of chiral fermions on the lattice. Discussed topics include: the lattice as a UV regulator, a chiral QED model, modification of the fermion determinant, large gauge-field momenta, and a non-perturbative problem.
De Klerck, Katrijn; Vander Heyden, Yvan; Mangelings, Debby
2014-02-01
Since their introduction on the market the applicability of immobilized polysaccharide-based chiral stationary phases in high-performance liquid chromatography has been thoroughly investigated. These immobilized phases have the benefit to be applicable with a wide range of modifiers, potentially extending the application range of the polysaccharide-based stationary phases. Because an increasing number of stationary phases are being introduced in the field of chiral chromatography it is important to evaluate their enantioselectivity in different techniques in order to get an idea about their applicability. In this study, three immobilized chiral polysaccharide-based stationary phases (Chiralpak IA, IB, and IC) are evaluated in supercritical fluid chromatography (SFC) with a test set of pharmaceutical racemates. This is done in a three-fold manner: their performance is evaluated (1) using traditional modifiers, (2) using mixtures of atypical modifiers, and (3) the results were compared to those on coated stationary phases with an equivalent chiral selector. To get a visual overview of the enantioselective patterns of the different chromatographic systems (mobile and stationary phase combinations), a Principal Component Analysis is performed, which allows determining the (dis)similarity between individual systems. To assess the complementarity cumulative success rates are determined. The immobilized chiral stationary phases prove to yield high cumulative success rates. PMID:24438871
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
NASA Astrophysics Data System (ADS)
Hayata, Tomoya; Yamamoto, Arata
2015-05-01
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Saori Pastore, S.C. Pieper, Rocco Schiavilla, Robert Wiringa
2013-03-01
Quantum Monte Carlo calculations of electromagnetic moments and transitions are reported for A{<=}9 nuclei. The realistic Argonne v{sub 18} two-nucleon and Illinois-7 three-nucleon potentials are used to generate the nuclear wave functions. Contributions of two-body meson-exchange current (MEC) operators are included for magnetic moments and M1 transitions. The MEC operators have been derived in both a standard nuclear physics approach and a chiral effective field theory formulation with pions and nucleons including up to one-loop corrections. The two-body MEC contributions provide significant corrections and lead to very good agreement with experiment. Their effect is particularly pronounced in the A=9, T=3/2 systems, in which they provide up to ~20% (~40%) of the total predicted value for the {sup 9}Li ({sup 9}C) magnetic moment.
NASA Astrophysics Data System (ADS)
Kohno, M.
2015-12-01
The nuclear saturation mechanism is discussed in terms of two-nucleon and three-nucleon interactions in chiral effective field theory (Ch-EFT), using the framework of lowest-order Brueckner theory. After the Coester band, which is observed in calculating saturation points with various nucleon-nucleon (NN) forces, is revisited using modern NN potentials and their low-momentum equivalent interactions, a detailed account of the saturation curve of the Ch-EFT interaction is presented. The three-nucleon force (3NF) is treated by reducing it to an effective two-body interaction by folding the third nucleon degrees of freedom. Uncertainties due to the choice of the 3NF low-energy constants c_D and c_E are discussed. The reduction of the cutoff-energy dependence of the NN potential is explained by demonstrating the effect of the 3NF in the ^1S_0 and ^3S_1 states.
Plum, Eric; Zheludev, Nikolay I.
2015-06-01
Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.
Macroscopic chirality of a liquid crystal from nonchiral molecules
NASA Astrophysics Data System (ADS)
Jákli, A.; Nair, G. G.; Lee, C. K.; Sun, R.; Chien, L. C.
2001-06-01
The transfer of chirality from nonchiral polymer networks to the racemic B2 phase of nonchiral banana-shaped molecules is demonstrated. This corresponds to the transfer of chirality from an achiral material to another achiral material. There are two levels of chirality transfers. (a) On a microscopic level the presence of a polymer network (chiral or nonchiral) favors a chiral state over a thermodynamically stable racemic state due to the inversion symmetry breaking at the polymer-liquid crystal interfaces. (b) A macroscopically chiral (enantimerically enriched) sample can be produced if the polymer network has a helical structure, and/or contains chemically chiral groups. The chirality transfer can be locally suppressed by exposing the liquid crystal to a strong electric field treatment.
NASA Astrophysics Data System (ADS)
Rajagopal, Krishna; Sadofyev, Andrey V.
2015-10-01
We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and
Tactoids of chiral liquid crystals
NASA Astrophysics Data System (ADS)
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.
NASA Astrophysics Data System (ADS)
Kittaka, Shunichiro; Shimizu, Yusei; Sakakibara, Toshiro; Haga, Yoshinori; Yamamoto, Etsuji; Ōnuki, Yoshichika; Tsutsumi, Yasumasa; Nomoto, Takuya; Ikeda, Hiroaki; Machida, Kazushige
2016-03-01
Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URu2Si2 were investigated by specific-heat C(T,H,φ ,θ ) measurements of a high-quality single crystal. The occurrence of QP excitations due to the Doppler-shift effect was detected regardless of the field direction in C(H) of the present clean sample, which is in sharp contrast to a previous report. Furthermore, the polar-angle-dependent C(θ) measured under a rotating magnetic field within the ac plane exhibits a shoulder-like anomaly at θ ˜ 45° and a sharp dip at θ = 90° (H || a) in the moderate-field region. These features are supported by theoretical analyses based on microscopic calculations assuming the gap symmetry of kz(kx + iky), whose gap structure is characterized by a combination of a horizontal line node at the equator and point nodes at the poles. The present results have settled the previous controversy over the gap structure of URu2Si2 and have authenticated its chiral d-wave superconductivity.
Dispersion relations for electromagnetic wave propagation in chiral plasmas
Gao, M. X.; Guo, B. Peng, L.; Cai, X.
2014-11-15
The dispersion relations for electromagnetic wave propagation in chiral plasmas are derived using a simplified method and investigated in detail. With the help of the dispersion relations for each eignwave, we explore how the chiral plasmas exhibit negative refraction and investigate the frequency region for negative refraction. The results show that chirality can induce negative refraction in plasmas. Moreover, both the degree of chirality and the external magnetic field have a significant effect on the critical frequency and the bandwidth of the frequency for negative refraction in chiral plasmas. The parameter dependence of the effects is calculated and discussed.
Orientation-Dependent Handedness and Chiral Design
NASA Astrophysics Data System (ADS)
Efrati, Efi; Irvine, William T. M.
2014-01-01
Chirality occupies a central role in fields ranging from biological self-assembly to the design of optical metamaterials. The definition of chirality, as given by Lord Kelvin, associates chirality with the lack of mirror symmetry: the inability to superpose an object on its mirror image. While this definition has guided the classification of chiral objects for over a century, the quantification of handed phenomena based on this definition has proven elusive, if not impossible, as manifest in the paradox of chiral connectedness. In this work, we put forward a quantification scheme in which the handedness of an object depends on the direction in which it is viewed. While consistent with familiar chiral notions, such as the right-hand rule, this framework allows objects to be simultaneously right and left handed. We demonstrate this orientation dependence in three different systems—a biomimetic elastic bilayer, a chiral propeller, and optical metamaterial—and find quantitative agreement with chirality pseudotensors whose form we explicitly compute. The use of this approach resolves the existing paradoxes and naturally enables the design of handed metamaterials from symmetry principles.
Chiral gravity, log gravity, and extremal CFT
Maloney, Alexander; Song Wei; Strominger, Andrew
2010-03-15
We show that the linearization of all exact solutions of classical chiral gravity around the AdS{sub 3} vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.
Chiral THz metamaterial with tunable optical activity
Zhou, Jiangfeng; Taylor, Antoinette; O' Hara, John; Chowdhury, Roy; Zhao, Rongkuo; Soukoullis, Costas M
2010-01-01
Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation
NASA Astrophysics Data System (ADS)
Dharmavaram, Sanjay; Xie, Fangming; Bruinsma, Robijn; Klug, William; Rudnick, Joseph
Most icosahedral viruses are classified by their T-number which identifies their capsid in terms of the number of capsomers and their relative arrangement. Certain T-numbers (T = 7 for instance) are inherently chiral (with no reflection planes) while others (e.g. T = 1) are achiral. We present a Landau-Brazovskii (LB) theory for weak crystallization in which a scalar order parameter that measures density of capsid proteins successfully predicts the various observed T-numbers and their respective chiralities. We find that chiral capsids gain stability by spontaneously breaking symmetry from an unstable chiral state. The inherently achiral LB-free energy does not preferentially select a particular chiral state from its mirror reflection. Based on the physical observation that proteins are inherently chiral molecules with directional interactions, we propose a new chiral term to the LB energy as a possible selection mechanism for chirality.
NASA Astrophysics Data System (ADS)
Milošević, D. B.
2015-10-01
S -matrix theory of high-order harmonic generation (HHG) is generalized to multielectron atoms. In the multielectron case the harmonic power is expressed via a coherent sum of the time-dependent dipoles, while for the one-electron models a corresponding incoherent sum appears. This difference is important for the inert atomic gases having a p ground state as used in a recent HHG experiment with a bicircular field [Nat. Photonics 9, 99 (2015), 10.1038/nphoton.2014.293]. We investigate HHG by such a bicircular field, which consists of two coplanar counter-rotating circularly polarized fields of frequency r ω and s ω . Selection rules for HHG by a bicircular field are analyzed from the aspects of dynamical symmetry of the system, conservation of the projection of the angular momentum on a fixed quantization axis, and the quantum number of the initial and final atomic ground states. A distinction is made between the selection rules for atoms with closed [J. Phys. B 48, 171001 (2015), 10.1088/0953-4075/48/17/171001] and nonclosed shells. An asymmetry in emission of the left- and right-circularly polarized harmonics is found and explained by using a semiclassical model and the electron probability currents which are related to a nonzero magnetic quantum number. This asymmetry can be important for the application of such harmonics to the exploration of chirality-sensitive processes and for generation of elliptic or even circular attosecond pulse trains. Such attosecond pulse trains are analyzed for longer wavelengths than in Opt. Lett. 40, 2381 (2015), 10.1364/OL.40.002381, and for various field-component intensities.
Intelligent Chiral Sensing Based on Supramolecular and Interfacial Concepts
Ariga, Katsuhiko; Richards, Gary J.; Ishihara, Shinsuke; Izawa, Hironori; Hill, Jonathan P.
2010-01-01
Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized. PMID:22163577
Disoriented chiral condensate: Theory and phenomenology
Bjorken, J.D.
1997-12-01
These notes are an abbreviated version of lectures given at the 1997 Zakopane School. They contain two topics. The first is a description in elementary terms of the basic ideas underlying the speculative hypothesis that pieces of strong-interaction vacuum with a rotated chiral order parameter, disoriented chiral condensate or DCC, might be produced in high energy elementary particle collisions. The second topic is a discussion of the phenomenological techniques which may be applied to data in order to experimentally search for the existence of DCC.
Elastic waves in structurally chiral composites
Yang, Shiuhkuang.
1990-01-01
Elastic wave propagation through structurally chiral (handed) media was studied. The primary objectives are to construct structurally chiral composites and to characterize their properties. Structurally chiral composites are constructed by stacking identical uniaxial plates, whose consecutive symmetric axes describe either a right- or a left-handed spiral. A matrix representation method is used to solve the elastic wave propagation in such layered composites. Numerical computation of the plane wave reflection and transmission characteristics for chiral arrangements are compared with those for the non-chiral one. It is concluded that the co-polarized characteristics are unaffected by the structural chirality, while the cross-polarized reflected and transmitted fields are greatly influenced by it. Numerical modeling is also applied for the real samples. The polarization ellipse of the transmitted field of each sample is calculated. To verify the form chirality, four glass-reinforced chiral and non-chiral composite samples are made from helix tape, molded, debulked, and cured individually under identical temperature and pressure histories. The spiral composites are characterized using shear and longitudinal wave transducers in ultrasonic experiments. Both the material properties and the polarization ellipse of the transmitted field of each sample are measured. It is proved conclusively that left and right handedness in the microstructures of a material rotates the plane of polarization of a propagating shear wave in the opposite directions. Thus it is now possible to say that by reducing the length scale of the handed microstructures tone more appropriate to its propagating wavelength, a medium is obtained that gives rise to effects similar to optical radar and optical dichroism.
Sharma, Anshul; Mori, Taizo; Lee, Huey-Charn; Worden, Matthew; Bidwell, Eric; Hegmann, Torsten
2014-12-23
Chirality at the nanoscale, or more precisely, the chirality or chiroptical effects of chiral ligand-capped metal nanoparticles (NPs) is an intriguing and rapidly evolving field in nanomaterial research with promising applications in catalysis, metamaterials, and chiral sensing. The aim of this work was to seek out a system that not only allows the detection and understanding of NP chirality but also permits visualization of the extent of chirality transfer to a surrounding medium. The nematic liquid crystal phase is an ideal candidate, displaying characteristic defect texture changes upon doping with chiral additives. To test this, we synthesized chiral cholesterol-capped gold NPs and prepared well-dispersed mixtures in two nematic liquid crystal hosts. Induced circular dichroism spectropolarimetry and polarized light optical microscopy revealed that all three gold NPs induce chiral nematic phases, and that those synthesized in the presence of a chiral bias (disulfide) are more powerful chiral inducers than those where the NP was formed in the absence of a chiral bias (prepared by conjugation of a chiral silane to preformed NPs). Helical pitch data here visually show a clear dependence on the NP size and the number of chiral ligands bound to the NP surface, thereby supporting earlier experimental and theoretical data that smaller metal NPs made in the presence of a chiral bias are stronger chiral inducers. PMID:25383947
Chirality in nonlinear optics.
Haupert, Levi M; Simpson, Garth J
2009-01-01
The past decade has witnessed the emergence of new measurement approaches and applications for chiral thin films and materials enabled by the observations of the high sensitivity of second-order nonlinear optical measurements to chirality. In thin films, the chiral response to second harmonic generation and sum frequency generation (SFG) from a single molecular monolayer is often comparable with the achiral response. The chiral specificity also allows for symmetry-allowed SFG in isotropic chiral media, confirming predictions made approximately 50 years ago. With these experimental demonstrations in hand, an important challenge is the construction of intuitive predictive models that allow the measured chiral response to be meaningfully related back to molecular and macromolecular structure. This review defines and considers three distinct mechanisms for chiral effects in uniaxially oriented assemblies: orientational chirality, intrinsic chirality, and isotropic chirality. The role of each is discussed in experimental and computational studies of bacteriorhodopsin films, binaphthol, and collagen. Collectively, these three model systems support a remarkably simple framework for quantitatively recovering the measured chiral-specific activity. PMID:19046125
NASA Astrophysics Data System (ADS)
Haupert, Levi M.; Simpson, Garth J.
2009-05-01
The past decade has witnessed the emergence of new measurement approaches and applications for chiral thin films and materials enabled by the observations of the high sensitivity of second-order nonlinear optical measurements to chirality. In thin films, the chiral response to second harmonic generation and sum frequency generation (SFG) from a single molecular monolayer is often comparable with the achiral response. The chiral specificity also allows for symmetry-allowed SFG in isotropic chiral media, confirming predictions made ˜50 years ago. With these experimental demonstrations in hand, an important challenge is the construction of intuitive predictive models that allow the measured chiral response to be meaningfully related back to molecular and macromolecular structure. This review defines and considers three distinct mechanisms for chiral effects in uniaxially oriented assemblies: orientational chirality, intrinsic chirality, and isotropic chirality. The role of each is discussed in experimental and computational studies of bacteriorhodopsin films, binaphthol, and collagen. Collectively, these three model systems support a remarkably simple framework for quantitatively recovering the measured chiral-specific activity.
NASA Astrophysics Data System (ADS)
Kopp, Victor I.; Zhang, Guoyin; Zhang, Sheng; Genack, Azriel Z.; Neugroschl, Dan
2009-02-01
We propose an in-fiber chiral optical isolator based on chiral fiber polarizer technology and calculate its performance by incorporating the magnetic field into the scattering matrix. The design will be implemented in a special preform, which is passed through a miniature heat zone as it is drawn and twisted. The birefringence of the fiber is controlled by adjusted the diameter of a dual-core optical fiber. By adjusting the twist, the fiber can convert linear to circular polarization and reject one component of circular polarization. In the novel central portion of the isolator, the fiber diameter is large. The effective birefringence of the circular central core with high Verdet constant embedded in an outer core of slightly smaller index of refraction is small. The central potion is a non-reciprocal polarization converter which passes forward traveling left circularly polarized (LCP) light as LCP, while converting backward propagating LCP to right circularly polarized (RCP) light. Both polarizations of light traveling backwards are scattered out of the isolator. Since it is an all-glass structure, we anticipate that the isolator will be able to handle several watts of power and will be environmentally robust.
A molecular propeller effect for chiral separation and analysis.
Clemens, Jonathon B; Kibar, Osman; Chachisvilis, Mirianas
2015-01-01
Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219
A molecular propeller effect for chiral separation and analysis
Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas
2015-01-01
Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219
A molecular propeller effect for chiral separation and analysis
NASA Astrophysics Data System (ADS)
Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas
2015-07-01
Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.
Pastore, S.; Wiringa, Robert B.; Pieper, Steven C.; Schiavilla, Rocco
2014-08-01
We report quantum Monte Carlo calculations of electromagnetic transitions in $^8$Be. The realistic Argonne $v_{18}$ two-nucleon and Illinois-7 three-nucleon potentials are used to generate the ground state and nine excited states, with energies that are in excellent agreement with experiment. A dozen $M1$ and eight $E2$ transition matrix elements between these states are then evaluated. The $E2$ matrix elements are computed only in impulse approximation, with those transitions from broad resonant states requiring special treatment. The $M1$ matrix elements include two-body meson-exchange currents derived from chiral effective field theory, which typically contribute 20--30\\% of the total expectation value. Many of the transitions are between isospin-mixed states; the calculations are performed for isospin-pure states and then combined with the empirical mixing coefficients to compare to experiment. In general, we find that transitions between states that have the same dominant spatial symmetry are in decent agreement with experiment, but those transitions between different spatial symmetries are often significantly underpredicted.
Ayala, Alejandro; Bashir, Adnan; Raya, Alfredo; Sanchez, Angel
2009-08-01
Working in the linear sigma model with quarks, we compute the finite-temperature effective potential in the presence of a weak magnetic field, including the contribution of the pion ring diagrams and considering the sigma as a classical field. In the approximation where the pion self-energy is computed perturbatively, we show that there is a region of the parameter space where the effect of the ring diagrams is to preclude the phase transition from happening. Inclusion of the magnetic field has small effects that however become more important as the system evolves to the lowest temperatures allowed in the analysis.
Drag suppression in anomalous chiral media
NASA Astrophysics Data System (ADS)
Sadofyev, Andrey V.; Yin, Yi
2016-06-01
We study a heavy impurity moving longitudinal with the direction of an external magnetic field in an anomalous chiral medium. Such system would carry a nondissipative current of chiral magnetic effect associated with the anomaly. We show, by generalizing Landau's criterion for superfluidity, that the "anomalous component" which gives rise to the anomalous transport will not contribute to the drag experienced by an impurity. We argue on a very general basis that those systems with a strong magnetic field would exhibit an interesting transport phenomenon—the motion of the heavy impurity is frictionless, in analogy to the case of a superfluid. We demonstrate and confirm our general results with two complementary examples: weakly coupled chiral fermion gases and strongly interacting chiral liquids.
Optical chiral metamaterials: a review of the fundamentals, fabrication methods and applications.
Wang, Zuojia; Cheng, Feng; Winsor, Thomas; Liu, Yongmin
2016-10-14
Optical chiral metamaterials have recently attracted considerable attention because they offer new and exciting opportunities for fundamental research and practical applications. Through pragmatic designs, the chiroptical response of chiral metamaterials can be several orders of magnitude higher than that of natural chiral materials. Meanwhile, the local chiral fields can be enhanced by plasmonic resonances to drive a wide range of physical and chemical processes in both linear and nonlinear regimes. In this review, we will discuss the fundamental principles of chiral metamaterials, various optical chiral metamaterials realized by different nanofabrication approaches, and the applications and future prospects of this emerging field. PMID:27606801
Control of normal chirality at hexagonal interfaces
Haraldsen, Jason T; Fishman, Randy Scott
2010-01-01
We study the net chirality created by the Dzyaloshinkii-Moriya interaction (DMI) at the boundary between hexagonal layers of magnetic and non-magnetic materials. It is shown that another mechanism besides elastic torsion is required to understand the change in chirality observed in Dy/Y multilayers during field-cooling. The paper shows that due to the overlap between magnetic and non-magnetic atoms, interfacial steps may produce a DMI normal to the interface in magnetic heterostructures.
Interference and isospin of disoriented chiral condensates
Suzuki, M.
1995-09-01
If coherent states describe the disoriented chiral condensates (DCC`s), many states of different chiral orientations should equally contribute to a given hadronic process. However, in the classical field description, we ignore the interference between the different DCC amplitudes. It results in a disregard of isospin invariance. We examine quantitatively how good this approximation is for the DCC`s of a typical size.
NASA Astrophysics Data System (ADS)
Dayi, Ömer F.; Elbistan, Mahmut
2016-05-01
In terms of the matrix valued Berry gauge field strength for the Weyl Hamiltonian in any even space-time dimensions a symplectic form whose elements are matrices in spin indices is introduced. Definition of the volume form is modified appropriately. A simple method of finding the path integral measure and the chiral current in the presence of external electromagnetic fields is presented. It is shown that within this new approach the chiral magnetic effect as well as the chiral anomaly in even d + 1 dimensions are accomplished straightforwardly.
NASA Astrophysics Data System (ADS)
Costa, Pedro
2016-06-01
The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2 +1 ) Nambu-Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultrarelativistic heavy ion collisions, and β equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen.
Theory of Chirality Transfer in Block Copolymer Melts
NASA Astrophysics Data System (ADS)
Prasad, Ishan; Grason, Gregory
Block copolymers assemble into a rich spectrum of ordered phases, with complexity driven by asymmetry in copolymer architecture. Despite decades of study, influence of intrinsic chirality on equilibrium mesophase assembly of block copolymers is not well understood and largely unexplored. Self-consistent field theory has been largely instrumental in prediction of physical properties of polymeric systems. Recently, a polar orientational self-consistent field (oSCF) theory was adopted to model chiral block copolymers having a thermodynamic preference for cholesteric ordering in chiral segments, and which confirmed the equilibrium stability of a helical cylinder morphology observed for chiral diblocks. Here, I describe a newly developed oSCF theory for chiral nematic copolymers, where segment orientations are characterized by quadrupolar interactions, and focus our study on intra-domain nematic ordering in flexible block copolymer assemblies, and in particular, mechanisms of transfer of segment chirality to mesochiral symmetries of self-assembled bicontinuous network morphologies.
On lattice chiral gauge theories
NASA Technical Reports Server (NTRS)
Maiani, L.; Rossi, G. C.; Testa, M.
1991-01-01
The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations.
Bootstrapping N=2 chiral correlators
NASA Astrophysics Data System (ADS)
Lemos, Madalena; Liendo, Pedro
2016-01-01
We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.
Chiral magnetic effect in ZrTe5
NASA Astrophysics Data System (ADS)
Li, Qiang; Zhang, Cheng; Gu, Genda; Valla, T.; Kharzeev, Dmitri; Pletikosic, I.
The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. Here we report on the measurement of magneto-transport in zirconium pentatelluride, ZrTe5 that provides a strong evidence for the chiral magnetic effect. Our angle-resolved photoemission spectroscopy experiments show that this material's electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. The observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background. We expect that chiral magnetic effect may emerge in a wide class of materials that are near the transition between the trivial and topological insulators.
Nuclear chiral dynamics and thermodynamics
NASA Astrophysics Data System (ADS)
Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram
2013-11-01
This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.
Regular Scanning Tunneling Microscope Tips can be Intrinsically Chiral
Tierney, Heather L.; Murphy, Colin J.; Sykes, E. Charles H.
2011-01-07
We report our discovery that regular scanning tunneling microscope tips can themselves be chiral. This chirality leads to differences in electron tunneling efficiencies through left- and right-handed molecules, and, when using the tip to electrically excite molecular rotation, large differences in rotation rate were observed which correlated with molecular chirality. As scanning tunneling microscopy is a widely used technique, this result may have unforeseen consequences for the measurement of asymmetric surface phenomena in a variety of important fields.
Magnetotransport phenomena related to the chiral anomaly in Weyl semimetals
NASA Astrophysics Data System (ADS)
Spivak, B. Z.; Andreev, A. V.
2016-02-01
We present a theory of magnetotransport phenomena related to the chiral anomaly in Weyl semimetals. We show that conductivity, thermal conductivity, thermoelectric, and the sound absorption coefficients exhibit strong and anisotropic magnetic field dependencies. We also discuss properties of magnetoplasmons and magnetopolaritons, whose existences are entirely determined by the chiral anomaly. Finally, we discuss the conditions of applicability of the quasiclassical description of electron transport phenomena related to the chiral anomaly.
Lerrick, Reinner I; Winstanley, Thomas P L; Haggerty, Karen; Wills, Corinne; Clegg, William; Harrington, Ross W; Bultinck, Patrick; Herrebout, Wouter; Benniston, Andrew C; Hall, Michael J
2014-05-11
The synthesis and resolution of a class of chiral organic fluorophores, axially chiral 4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (Ax*-BODIPY), is described. Ax*-BODIPYs were prepared through a modular synthesis combined with a late stage Heck functionalisation. Resolution was achieved by preparative chiral HPLC. Absolute stereochemical assignment was performed by comparison of experimental ECD spectra with TD-DFT calculations. PMID:24676233
Controlling and imaging chiral spin textures
NASA Astrophysics Data System (ADS)
Chen, Gong
Chirality in magnetic materials is fundamentally interesting and holds potential for logic and memory applications. Using spin-polarized low-energy electron microscopy at National Center for Electron Microscopy, we recently observed chiral domain walls in thin films. We developed ways to tailor the Dzyaloshinskii-Moriya interaction, which drives the chirality, by interface engineering and by forming ternary superlattices. We find that spin-textures can be switched between left-handed, right-handed, cycloidal, helical and mixed domain wall structures by controlling uniaxial strain in magnetic films. We also demonstrate an experimental approach to stabilize skyrmions in magnetic multilayers without external magnetic field. These results exemplify the rich physics of chirality associated with interfaces of magnetic materials
Optically active particles of chiral polymers.
Song, Ci; Liu, Xuan; Liu, Dong; Ren, Chonglei; Yang, Wantai; Deng, Jianping
2013-09-01
Particles constructed by chiral polymers (defined as PCPs) have emerged as a rapidly expanding research field in recent years because of their potentially wide-ranging applications in asymmetric catalysis, enantioselective crystallization, enantioselective release, amongst many others. The particles show considerable optical activity, due to the chirality of the corresponding polymers from which the particles are derived. This review article presents an overview on PCPs with emphasis on our group's recent achievements in the preparation of PCPs derived from optically active helical polymers and their applications. PCPs can be prepared via emulsion polymerization, precipitation polymerization, and suspension polymerization by starting from monomers. Emulsification of preformed chiral polymers and self-assembly approaches also can lead to PCPs. Chiral polymer-based core/shell particles, hollow particles, and magnetic particles are also covered because of their remarkable properties and significant potential applications. PMID:24030962
ERIC Educational Resources Information Center
Macia, Laura
2012-01-01
This paper examines the decisions and motivations of graduate students in cultural anthropology when defining the field sites and topics of their final projects. The decisions among students at the Universidad de los Andes in Colombia are contrasted with those at the University of Pittsburgh in the United States. A review of recent final projects…
NASA Astrophysics Data System (ADS)
Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong
2016-06-01
Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm–1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.
Kim, Cheol-Joo; Sánchez-Castillo, A; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong
2016-06-01
Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm(-1)) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra. PMID:26900756
Chiral route to pulling optical forces and left-handed optical torques
NASA Astrophysics Data System (ADS)
Canaguier-Durand, Antoine; Genet, Cyriaque
2015-10-01
We analyze how chirality can generate pulling optical forces and left-handed torques by cross-coupling linear-to-angular momenta between the light field and the chiral object. In the dipolar regime, we reveal that such effects can emerge from a competition between nonchiral and chiral contributions to dissipative optical forces and torques, a competition balanced by the strength of chirality of the object. We extend the analysis to large chiral spheres where the interplay between chirality and multipolar resonances can give rise to a break of symmetry that flips the signs of both optical forces and torques.
Magnetohydrodynamics of chiral relativistic fluids
NASA Astrophysics Data System (ADS)
Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg
2015-08-01
We study the dynamics of a plasma of charged relativistic fermions at very high temperature T ≫m , where m is the fermion mass, coupled to the electromagnetic field. In particular, we derive a magnetohydrodynamical description of the evolution of such a plasma. We show that, compared to conventional magnetohydronamics (MHD) for a plasma of nonrelativistic particles, the hydrodynamical description of the relativistic plasma involves new degrees of freedom described by a pseudoscalar field originating in a local asymmetry in the densities of left-handed and right-handed fermions. This field can be interpreted as an effective axion field. Taking into account the chiral anomaly we present dynamical equations for the evolution of this field, as well as of other fields appearing in the MHD description of the plasma. Due to its nonlinear coupling to helical magnetic fields, the axion field significantly affects the dynamics of a magnetized plasma and can give rise to a novel type of inverse cascade.
Exact chiral spin liquids and mean-field perturbations of gamma matrix models on the ruby lattice
NASA Astrophysics Data System (ADS)
Whitsitt, Seth; Chua, Victor; Fiete, Gregory A.
2012-11-01
We theoretically studied an exactly solvable gamma matrix generalization of the Kitaev spin model on the ruby lattice, which is a honeycomb lattice with ‘expanded’ vertices and links. We find that this model displays an exceptionally rich phase diagram that includes (i) gapless phases with stable spin Fermi surfaces, (ii) gapless phases with low-energy Dirac cones and quadratic band touching points and (iii) gapped phases with finite Chern numbers possessing the values ±4,±3,±2 and ±1. The model is then generalized to include Ising-like interactions that break the exact solvability of the model in a controlled manner. When these terms are dominant, they lead to a trivial Ising ordered phase which is shown to be adiabatically connected to a large coupling limit of the exactly solvable phase. In the limit where these interactions are weak, we treat them within mean-field theory and present the resulting phase diagrams. We discuss the nature of the transitions between various phases. Our results show the richness of possible ground states in closely related magnetic systems.
Chiral geometry in multiple chiral doublet bands
NASA Astrophysics Data System (ADS)
Zhang, Hao; Chen, Qibo
2016-02-01
The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with . The energy spectra, electromagnetic transition probabilities B(M1) and B(E2), angular momenta, and K-distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when γ deviates from 30°. The chiral geometry relies significantly on γ, and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands. Supported by Plan Project of Beijing College Students’ Scientific Research and Entrepreneurial Action, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206), Research Fund for Doctoral Program of Higher Education (20110001110087) and China Postdoctoral Science Foundation (2015M580007)
Generation of chiral spin state by quantum simulation
NASA Astrophysics Data System (ADS)
Tanamoto, Tetsufumi
2016-06-01
Chirality of materials in nature appears when there are asymmetries in their lattice structures or interactions in a certain environment. Recent development of quantum simulation technology has enabled the manipulation of qubits. Accordingly, chirality can be realized intentionally rather than passively observed. Here we theoretically provide simple methods to create a chiral spin state in a spin-1/2 qubit system on a square lattice. First, we show that switching on and off the Heisenberg and X Y interactions produces the chiral interaction directly in the effective Hamiltonian without controlling local fields. Moreover, when initial states of spin qubits are appropriately prepared, we prove that the chirality with desirable phase is dynamically obtained. Finally, even for the case where switching on and off the interactions is infeasible and the interactions are always on, we show that, by preparing an asymmetric initial qubit state, the chirality whose phase is π /2 is dynamically generated.
On consistency of hydrodynamic approximation for chiral media
NASA Astrophysics Data System (ADS)
Avdoshkin, A.; Kirilin, V. P.; Sadofyev, A. V.; Zakharov, V. I.
2016-04-01
We consider chiral liquids, that is liquids consisting of massless fermions and right-left asymmetric. In such media, one expects existence of electromagnetic current flowing along an external magnetic field, associated with the chiral anomaly. The current is predicted to be dissipation-free. We consider dynamics of chiral liquids, concentrating on the issues of possible instabilities and infrared sensitivity. Instabilities arise, generally speaking, already in the limit of vanishing electromagnetic constant, αel → 0. In particular, liquids with non-vanishing chiral chemical potential might decay into right-left asymmetric states containing vortices.
Influence of Chirality in Ordered Block Copolymer Phases
NASA Astrophysics Data System (ADS)
Prasad, Ishan; Grason, Gregory
2015-03-01
Block copolymers are known to assemble into rich spectrum of ordered phases, with many complex phases driven by asymmetry in copolymer architecture. Despite decades of study, the influence of intrinsic chirality on equilibrium mesophase assembly of block copolymers is not well understood and largely unexplored. Self-consistent field theory has played a major role in prediction of physical properties of polymeric systems. Only recently, a polar orientational self-consistent field (oSCF) approach was adopted to model chiral BCP having a thermodynamic preference for cholesteric ordering in chiral segments. We implement oSCF theory for chiral nematic copolymers, where segment orientations are characterized by quadrupolar chiral interactions, and focus our study on the thermodynamic stability of bi-continuous network morphologies, and the transfer of molecular chirality to mesoscale chirality of networks. Unique photonic properties observed in butterfly wings have been attributed to presence of chiral single-gyroid networks, this has made it an attractive target for chiral metamaterial design.
Axially symmetric multi-baryon solutions and their quantization in the chiral quark soliton model
NASA Astrophysics Data System (ADS)
Komori, S.; Sawado, N.; Shiiki, N.
2004-05-01
We study axially symmetric solutions with B=2-5 in the chiral quark soliton model. In the background of axially symmetric chiral fields, the quark eigenstates and profile functions of the chiral fields are computed self-consistently. The resultant quark bound spectrum are doubly degenerate due to the symmetry of the chiral field. Upon quantization, various observable spectra of the chiral solitons are obtained. Taking account of the Finkelstein-Rubinstein constraints, we show that the quantum numbers of our solitons coincide with the physical observations for B=2 and 4 while B=3 and 5 do not.
Nguyen, Lien Ai; He, Hua; Pham-Huy, Chuong
2006-01-01
About more than half of the drugs currently in use are chiral compounds and near 90% of the last ones are marketed as racemates consisting of an equimolar mixture of two enantiomers. Although they have the same chemical structure, most isomers of chiral drugs exhibit marked differences in biological activities such as pharmacology, toxicology, pharmacokinetics, metabolism etc. Some mechanisms of these properties are also explained. Therefore, it is important to promote the chiral separation and analysis of racemic drugs in pharmaceutical industry as well as in clinic in order to eliminate the unwanted isomer from the preparation and to find an optimal treatment and a right therapeutic control for the patient. In this article, we review the nomenclature, pharmacology, toxicology, pharmacokinetics, metabolism etc of some usual chiral drugs as well as their mechanisms. Different techniques used for the chiral separation in pharmaceutical industry as well as in clinical analyses are also examined. PMID:23674971
NASA Astrophysics Data System (ADS)
Ronci, F.; Gatti, R.; Caponi, G.; Colonna, S.; Galeotti, G.; Catone, D.; Turchini, S.; Prosperi, T.; Zema, N.; Palma, A.; Gori, P.; Contini, G.
2014-11-01
Chiral self-assembled molecular networks (SAMNs) are important for technological and fundamental reasons. In spite of the large number of works in this field, the mechanism of chirality transfer from single molecules to large-scale two-dimensional (2D) networks is not fully understood yet. This work reports on the self-assembly of simple amino alcohols with different chirality measures on Cu(100). Ethanolamine (2-amino-1-ethanol), alaninol (2-amino-1-propanol) and butanolamine (2-amino-1-butanol) adsorbed on Cu(100) have been investigated with scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. This study addresses the role of the single-molecule handedness in the global chirality expression, showing how the chirality measure of the precursors plays an important role in the formation of globally chiral superstructures.
Caveman
2000-01-01
Do you feel scientifically isolated? Do you find yourself sitting on the side-line while others take the field by the nose and lead it? Are you unable to publish a model that summarizes your data and ideas because reviewers label it as being too speculative and unsupported? Can't get those experiments published in any regular journal? Do you find that nobody is citing your papers? Haven't published in your field for some time, but want to show that you are still a player? Well, no need to worry! There is a special category of publication for you, 'the invited review', and even specialized journals, the 'review journals', that cater to every part of your neurosis. The major difference between many invited reviews and regular articles in journals ? this journal being an exception ? is that the invited review is generally not critiqued by outside, independent referees. In those rare cases when a review is critiqued, the letter from the editorial staff that accompanies the manuscript usually contains a disclaimer: "While we are interested in your critical evaluation of this manuscript, you should know that this review was solicited by the Editorial Board, and, therefore, we allow some latitude in the content and opinion expressed." What's the point of reviewing it when the writer has been given some sort of carte blanche to say what they want? Are you surprised? I have critiqued reviews to no affect (but then that's true also for research papers!), suggested that the writing was too biased, that the appropriate references were not cited and that the proposed model must have been conjured up while the writer was inebriated. Of course, all the critiques for my reviews were taken seriously, and I made all the suggested changes ? right! So, what kinds of review are there? As a postdoc, I got introduced to two extremes in one conversation. I was asked to write a review by my mentor. Not being very opinionated (at the time), I read hundreds of papers and cited them, and
Chiral sensing by nonchiral tetrapyrroles.
Labuta, Jan; Hill, Jonathan P; Ishihara, Shinsuke; Hanyková, Lenka; Ariga, Katsuhiko
2015-03-17
Enantiomeric excess (ee) is a measure of the purity of an enantiomer of a chiral compound with respect to the presence of the complementary enantiomer. It is an important aspect of chemistry, especially in the fields of pharmaceuticals and asymmetric catalysis. Existing methods for determination of enantiomeric excesses using nuclear magnetic resonance (NMR) spectroscopy mostly rely on special chiral reagents (auxiliaries) that form two or more diastereomeric complexes with a chiral compound. As a result of this, the NMR spectrum of each enantiomer is different, allowing the determination of enantiomeric excess. In this Account, we describe a molecular design process that has allowed us to prepare prochiral solvating agents for NMR determination of ee of a wide variety of analyte types. At the outset of this work, we initially encountered the phenomenon of NMR peak splitting in the oxoporphyrinogen (OxP) host component of a supramolecular host-guest complex, where the extent of the splitting is apparently proportional to the guests' ee. Upon closer examination of the mechanism of action, it was found that several complicating factors, including prototropic tautomerism, macrocyclic inversion (ring-flipping), and 1:2 host-guest stoichiometry, obstruct potential applications of OxP as a chiral solvating agent. By considering the molecular conformation of the OxP host, a saddle-shaped calix[4]pyrrole, we moved to study the tetraphenylporphyrin (TPP) dication since it has a similar form, and it was found that it could also be used to probe ee. However, although TPP does not suffer from disadvantageous tautomeric processes, it is still subject to macrocyclic inversion and has the additional serious disadvantage of operating for ee sensing only at depressed temperatures. The intrinsic disadvantages of the OxP and TPP systems were finally overcome by covalently modifying the OxP chromophore by regioselective N-alkylation at one face of the molecule. This procedure yields a
Chirality-induced negative refraction in magnetized plasma
Guo, B.
2013-09-15
Characteristic equations in magnetized plasma with chirality are derived in simple formulations and the dispersion relations for propagation parallel and perpendicular to the external magnetic field are studied in detail. With the help of the dispersion relations of each eigenwave, the author explores chirality-induced negative refraction in magnetized plasma and investigates the effects of parameters (i.e., chirality degree, external magnetic field, etc.) on the negative refraction. The results show that the chirality is the necessary and only one factor which leads to negative refraction without manipulating electrical permittivity and magnetic permeability. Both increasing the degree of chirality and reducing the external magnetic field can result in greater range negative refraction. Parameter dependence of the effects is calculated and discussed.
Chiral Langrangian with confinement from the QCD Langrangian
Yu A. Simonov
2002-01-01
An effective Langrangian for the light quark in the field of a static source is derived systematically using the exact field correlator expansion. The lowest Gaussian term is bosonized using nonlocal colorless bosonic fields and a general structure of effective chiral Langrangian is obtained containing all set of fields. The new and crucial result is that the condensation of scalar isoscalar field which is a usual onset of chiral symmetry breaking and is constant in space-time, assumes here the form of the confining string and contributes to the confining potential while the rest bosonic fields describe mesons with the q{rvec q} quark structure and pseudoscalars play the role of Nambu-Goldstone fields. Using derivative expansion the effective chiral Langrangian is deduced containing both confinement and chiral effects for heavy-light mesons. The pseudovector quark coupling constant is computed to be exactly unity in the local limit in agreement with earlier large N{sub c} arguments.
Objects of Maximum Electromagnetic Chirality
NASA Astrophysics Data System (ADS)
Fernandez-Corbaton, Ivan; Fruhnert, Martin; Rockstuhl, Carsten
2016-07-01
We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. Reciprocal objects attain the upper bound if and only if they are transparent for all the fields of one polarization handedness (helicity). Additionally, electromagnetic duality symmetry, i.e., helicity preservation upon interaction, turns out to be a necessary condition for reciprocal objects to attain the upper bound. We use these results to provide requirements for the design of such extremal objects. The requirements can be formulated as constraints on the polarizability tensors for dipolar objects or on the material constitutive relations for continuous media. We also outline two applications for objects of maximum electromagnetic chirality: a twofold resonantly enhanced and background-free circular dichroism measurement setup, and angle-independent helicity filtering glasses. Finally, we use the theoretically obtained requirements to guide the design of a specific structure, which we then analyze numerically and discuss its performance with respect to maximal electromagnetic chirality.
NASA Astrophysics Data System (ADS)
Tiburzi, Brian C.
The era of high-precision lattice QCD has led to synergy between lattice computations and phenomenological input from chiral perturbation theory. We provide an introduction to chiral perturbation theory with a bent towards understanding properties of the nucleon and other low-lying baryons. Four main topics are the basis for this chapter. We begin with a discussion of broken symmetries and the procedure to construct the chiral Lagrangian. The second topic concerns specialized applications of chiral perturbation theory tailored to lattice QCD, such as partial quenching, lattice discretization, and finite-volume effects. We describe inclusion of the nucleon in chiral perturbation theory using a heavy-fermion Euclidean action. Issues of convergence are taken up as our final topic. We consider expansions in powers of the strange-quark mass, and the appearance of unphysical singularities in the heavy-particle formulation. Our aim is to guide lattice practitioners in understanding the predictions chiral perturbation theory makes for baryons, and show how the lattice will play a role in testing the rigor of the chiral expansion at physical values of the quark masses.
Applications of chiral symmetry
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{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. 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}quenched{close_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.
Chirality control in oligothiophene through chiral wrapping.
Sanji, Takanobu; Kato, Nobu; Tanaka, Masato
2006-01-19
[structure: see text] Mixing oligothiophenes and polysaccharides, such as amylose and schizophyllan, affords novel inclusion complexes, in which oligothiophene guests adopt twisted conformation in the chiral channel created by left- or right-handed helical wrapping with the polysaccharide host polymers, leading to optical activity. PMID:16408883