Space Group Symmetry Fractionalization in a Chiral Kagome Heisenberg Antiferromagnet.
Zaletel, Michael P; Zhu, Zhenyue; Lu, Yuan-Ming; Vishwanath, Ashvin; White, Steven R
2016-05-13
The anyonic excitations of a spin liquid can feature fractional quantum numbers under space group symmetries. Detecting these fractional quantum numbers, which are analogs of the fractional charge of Laughlin quasiparticles, may prove easier than the direct observation of anyonic braiding and statistics. Motivated by the recent numerical discovery of spin-liquid phases in the kagome Heisenberg antiferromagnet, we theoretically predict the pattern of space group symmetry fractionalization in the kagome lattice SO(3)-symmetric chiral spin liquid. We provide a method to detect these fractional quantum numbers in finite-size numerics which is simple to implement in the density matrix renormalization group. Applying these developments to the chiral spin liquid phase of a kagome Heisenberg model, we find perfect agreement between our theoretical prediction and numerical observations.
Generation of symmetry coordinates for crystals using multiplier representations of the space groups
DEFF Research Database (Denmark)
Hansen, Flemming Yssing
1978-01-01
Symmetry coordinates play an important role in the normal-mode calculations of crystals. It is therefore of great importance to have a general method, which may be applied for any crystal at any wave vector, to generate these. The multiplier representations of the space groups as given by Kovalev...... and the projection-operator technique provide a basis for such a method. The method is illustrated for the nonsymmorphic D36 space group, and the theoretical background for the representations of space groups in general is reviewed and illustrated on the example above. It is desirable to perform the projection...... of symmetry coordinates in such a way that they may be used for as many wave vectors as possible. We discuss how to achieve this goal. The detailed illustrations should make it simple to apply the theory in any other case....
Flack, H D; Wondratschek, H; Hahn, T; Abrahams, S C
2000-01-01
The definition of 'symmetry element' given in the Report of the IUCr Ad-Hoc Committee on the Nomenclature of Symmetry by de Wolff et al. [Acta Cryst. (1989). A45, 494-499] is shown to contain an ambiguity in the case of space groups P6/m, P6/mmm, P6/mcc and point groups 6/m and 6/mmm. The ambiguity is removed by redefining the 'geometric element' as a labelled geometric item in which the label is related to the rotation angle of the rotation or rotoinversion symmetry operation. The complete set of different types of glide plane is shown to contain three more than the 15 that are illustrated in the 1992 Report by de Wolff et al. [Acta Cryst. (1992). A48, 727-732].
Ruf, Armin; Tetaz, Tim; Schott, Brigitte; Joseph, Catherine; Rudolph, Markus G
2016-11-01
Fructose-1,6-bisphosphatase (FBPase) is a key regulator of gluconeogenesis and a potential drug target for type 2 diabetes. FBPase is a homotetramer of 222 symmetry with a major and a minor dimer interface. The dimers connected via the minor interface can rotate with respect to each other, leading to the inactive T-state and active R-state conformations of FBPase. Here, the first crystal structure of human liver FBPase in the R-state conformation is presented, determined at a resolution of 2.2 Å in a tetragonal setting that exhibits an unusual arrangement of noncrystallographic symmetry (NCS) elements. Self-Patterson function analysis and various intensity statistics revealed the presence of pseudo-translation and the absence of twinning. The space group is P41212, but structure determination was also possible in space groups P43212, P4122 and P4322. All solutions have the same arrangement of three C2-symmetric dimers spaced by 1/3 along an NCS axis parallel to the c axis located at (1/4, 1/4, z), which is therefore invisible in a self-rotation function analysis. The solutions in the four space groups are related to one another and emulate a body-centred lattice. If all NCS elements were crystallographic, the space group would be I4122 with a c axis three times shorter and a single FBPase subunit in the asymmetric unit. I4122 is a minimal, non-isomorphic supergroup of the four primitive tetragonal space groups, explaining the space-group ambiguity for this crystal.
A Phase Transformation with no Change in Space Group Symmetry: Octafluoronaphtalene
DEFF Research Database (Denmark)
Pawley, G. S.; Dietrich, O. W.
1975-01-01
, the shear movement being equal to one carbon-carbon bond of the naphthalene skeleton. In this process the molecules reorient, but are still related by the same symmetry operations. This transformation, although not unique, is probably the first of its kind to be discovered in molecular systems....
Isaak, D. G.; Ohno, I.
2001-12-01
In past years, the rectangular parallelepiped resonance (RPR) method has been used to measure single-crystal elastic moduli, and their temperature dependences, of several materials important to geophysics. The high-temperature elastic properties of cubic, orthorhombic, tetragonal, and trigonal crystals, in addition to polycrystals, have all been studied with the RPR method. One feature of the RPR method is that, in principle, all the single-crystal elastic moduli (Cij) can be obtained from a single spectral sweep. However, no materials with crystal symmetry lower than orthorhombic symmetry have been reported in RPR studies. We extend the RPR theory to monoclinic and triclinic crystal symmetries. With these developments, we are able to compute single-crystal resonant spectra using a set of assumed Cij for right-rectangular parallelepiped monoclinic specimens cut along the b and c axes, or monoclinic specimens cut along known, but arbitrary, axes. We present initial results showing the comparison of calculated and measured resonance modes for single-crystal monoclinic diopside. Our measured resonance spectrum on chrome diopside is markedly more consistent with the spectrum calculated from the elasticity data of Collins and Brown (PCM, 26, 7-13, 1998) using a specimen that is 72% diopside than the end-member diopside elasticity data reported by Levien et al. (PCM, 4, 105-113, 1979).
Mörschel, Philipp; Schmidt, Martin U
2015-01-01
A crystallographic quantum-mechanical/molecular-mechanical model (c-QM/MM model) with full space-group symmetry has been developed for molecular crystals. The lattice energy was calculated by quantum-mechanical methods for short-range interactions and force-field methods for long-range interactions. The quantum-mechanical calculations covered the interactions within the molecule and the interactions of a reference molecule with each of the surrounding 12-15 molecules. The interactions with all other molecules were treated by force-field methods. In each optimization step the energies in the QM and MM shells were calculated separately as single-point energies; after adding both energy contributions, the crystal structure (including the lattice parameters) was optimized accordingly. The space-group symmetry was maintained throughout. Crystal structures with more than one molecule per asymmetric unit, e.g. structures with Z' = 2, hydrates and solvates, have been optimized as well. Test calculations with different quantum-mechanical methods on nine small organic molecules revealed that the density functional theory methods with dispersion correction using the B97-D functional with 6-31G* basis set in combination with the DREIDING force field reproduced the experimental crystal structures with good accuracy. Subsequently the c-QM/MM method was applied to nine compounds from the CCDC blind tests resulting in good energy rankings and excellent geometric accuracies.
Ochi, Masayuki; Akashi, Ryosuke; Kuroki, Kazuhiko
2016-09-01
We perform first-principles band structure calculations for the tetragonal and monoclinic structures of LaO0.5F0.5BiS2. We find that the Bi 6px,y bands on two BiS2 layers exhibit a sizable splitting at the X = (π ,0,0) and several other k-points for the monoclinic structure. We show that this feature originates from the inter-BiS2 layer coupling strongly enhanced by the symmetry breaking of the crystal structure. The Fermi surface also shows a large splitting and becomes anisotropic with respect to the kx- and ky-directions in the monoclinic structure, whereas it remains almost flat with respect to the kz-direction.
Nomoto, Takuya; Ikeda, Hiroaki
2017-02-01
We present the group-theoretical classification of gap functions in superconductors coexisting with some magnetic order in non-symmorphic magnetic space groups. On the basis of the weak-coupling BCS theory, we show that UCoGe-type ferromagnetic superconductors must have horizontal line nodes on either the kz = 0 or ±π/c plane. Moreover, it is likely that additional Weyl point nodes exist at the axial point. On the other hand, in UPd2Al3-type antiferromagnetic superconductors, gap functions with Ag symmetry possess horizontal line nodes in the antiferromagnetic Brillouin zone boundary perpendicular to the c-axis. In other words, the conventional fully gapped s-wave superconductivity is forbidden in this type of antiferromagnetic superconductor, regardless of the pairing mechanism, as long as the Fermi surface crosses a zone boundary. UCoGe and UPd2Al3 are candidate unconventional superconductors possessing hidden symmetry-protected line nodes, peculiar to non-symmorphic magnetic space groups.
1-Nitro-4-(4-nitrophenoxybenzene: a second monoclinic polymorph
Directory of Open Access Journals (Sweden)
Arif Nadeem
2013-12-01
Full Text Available In the title compound, C12H8N2O5, the aromatic rings are inclined to one another by 56.14 (7°. The nitro groups are inclined by to the benzene rings to which they are attached by 3.86 (17 and 9.65 (15°. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming a three-dimensional structure. The title compound is a new monoclinic polymorph, crystallizing in space group P21/c. The first polymorph crystallized in space group C2/c and the molecule possesses twofold rotation symmetry. Two low-temperature structures of this polymorph (150 K and 100 K, respectively have been reported [Meciarova et al. (2004. Private Communication (refcode IXOGAD. CCDC, Cambridge, England, and Dey & Desiraju (2005. Chem. Commun. pp. 2486–2488].
Space groups for solid state scientists
Glazer, Michael; Glazer, Alexander N
2014-01-01
This Second Edition provides solid state scientists, who are not necessarily experts in crystallography, with an understandable and comprehensive guide to the new International Tables for Crystallography. The basic ideas of symmetry, lattices, point groups, and space groups are explained in a clear and detailed manner. Notation is introduced in a step-by-step way so that the reader is supplied with the tools necessary to derive and apply space group information. Of particular interest in this second edition are the discussions of space groups application to such timely topics as high-te
A monoclinic polymorph of (1E,5E-1,5-bis(2-hydroxybenzylidenethiocarbonohydrazide
Directory of Open Access Journals (Sweden)
Bonell Schmitt
2011-08-01
Full Text Available The title compound, C15H14N4O2S, is a derivative of thioureadihydrazide. In contrast to the previously reported polymorph (orthorhombic, space group Pbca, Z = 8, the current study revealed monoclinic symmetry (space group P21/n, Z = 4. The molecule shows non-crystallographic C2 as well as approximate Cs symmetry. Intramolecular bifurcated O—H...(N,S hydrogen bonds, are present. In the crystal, intermolecular N—H...S hydrogen bonds and C—H...π contacts connect the molecules into undulating chains along the b axis. The shortest centroid–centroid distance between two aromatic systems is 4.5285 (12 Å.
1-Nitro-4-(4-nitro-phen-oxy)benzene: a second monoclinic polymorph.
Naz, Mehwish; Akhter, Zareen; McKee, Vickie; Nadeem, Arif
2013-11-01
In the title compound, C12H8N2O5, the aromatic rings are inclined to one another by 56.14 (7)°. The nitro groups are inclined by to the benzene rings to which they are attached by 3.86 (17) and 9.65 (15)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming a three-dimensional structure. The title compound is a new monoclinic polymorph, crystallizing in space group P21/c. The first polymorph crystallized in space group C2/c and the mol-ecule possesses twofold rotation symmetry. Two low-temperature structures of this polymorph (150 K and 100 K, respectively) have been reported [Meciarova et al. (2004). Private Communication (refcode IXOGAD). CCDC, Cambridge, England, and Dey & Desiraju (2005). Chem. Commun. pp. 2486-2488].
Space Group of Aquaimidazolemaleatozinc, [(H2O)(C3H4N2)(O2CCH=CHCO2Zn)]n
Institute of Scientific and Technical Information of China (English)
NG Seik Weng
2005-01-01
The space group of [(H2O)(C3H4N2)(O2CCH=CHCO2Zn)]n, which was originally described in the acentric Pc space group (Liu et al., Chin. J. Struct. Chem. 2004, 23, 160～163), is re-described in the centric P21/c space group.The crystal structure of (H2O)(C3H4N2)O2C-CH=CHCO2Zn was refined in the acentric Pc space group on 266 variables to R = 0.037 for the 1926 of the 2067 obeying the I > 2σ criterion[1]. The structure is better described in the centric P21/c space group (Table 1) as the two indepen-dent formula units are related by a center of symmetry. The 21 screw axis is must be pre-sent, as noted from the systematically absent 0k0 (k = 2n + 1) reflections in the 3302 reflections that were simulated[2, 3] from the published cell dimensions and atomic coordinates. Crystallo-graphica[4] estimates the hemisphere of reflections to be 3302, so that only a little more than the minimum monoclinic data must have been collec-ted in the study. A revision from Pc to P21/c is not particularly common[5] as the P21/c space group is uniquely determined from systematic absences. The polymeric chain propagates linearly along the c-axis of the unit cell (Fig. 1).
Monoclinic deformation of calcite crystals at ambient conditions
Przeniosło, R.; Fabrykiewicz, P.; Sosnowska, I.
2016-09-01
High resolution synchrotron radiation powder diffraction shows that the average crystal structure of calcite at ambient conditions is described with the trigonal space group R 3 bar c but there is a systematic hkl-dependent Bragg peak broadening. A modelling of this anisotropic peak broadening with the microstrain model from Stephens (1999) [15] is presented. The observed lattice parameters' correlations can be described by assuming a monoclinic-type deformation of calcite crystallites. A quantitative model of this monoclinic deformation observed at ambient conditions is described with the space group C 2 / c . The monoclinic unit cell suggested at ambient conditions is related with the monoclinic unit cell reported in calcite at high pressure (Merrill and Bassett (1975) [10]).
Space group constraints on weak indices in topological insulators
Varjas, Dániel; de Juan, Fernando; Lu, Yuan-Ming
2017-07-01
Lattice translation symmetry gives rise to a large class of "weak" topological insulators (TIs), characterized by translation-protected gapless surface states and dislocation bound states. In this work we show that space group symmetries lead to constraints on the weak topological indices that define these phases. In particular, we show that screw rotation symmetry enforces the Hall conductivity in planes perpendicular to the screw axis to be quantized in multiples of the screw rank, which generally applies to interacting systems. We further show that certain 3D weak indices associated with quantum spin Hall effects (class AII) are forbidden by the Bravais lattice and by glide or even-fold screw symmetries. These results put strong constraints on weak TI candidates in the experimental and numerical search for topological materials, based on the crystal structure alone.
Unexpected origin of magnetism in monoclinic Nb12O29 from first-principles calculations
Fang, C. M.; Van Huis, M. A.; Xu, Q.; Cava, R. J.; Zandbergen, H. W.
2015-01-01
Nb12O29 is a 4d transition metal oxide that occurs in two forms with different symmetries, monoclinic (m) and orthorhombic (o). The monoclinic form has unusual magnetic properties; below a temperature of 12 K, it exhibits both metallic conductivity and antiferromagnetic ordering. Here, first-princip
Symmetry and group theory in chemistry
Ladd, M
1998-01-01
A comprehensive discussion of group theory in the context of molecular and crystal symmetry, this book covers both point-group and space-group symmetries.Provides a comprehensive discussion of group theory in the context of molecular and crystal symmetryCovers both point-group and space-group symmetriesIncludes tutorial solutions
A novel monoclinic phase of impurity-doped CaGa2S4 as a phosphor with high emission intensity
Directory of Open Access Journals (Sweden)
Akihiro Suzuki
2012-06-01
Full Text Available In the solid-state synthesis of impurity-doped CaGa2S4, calcium tetrathiodigallate(III, a novel phosphor material (denominated as the X-phase, with monoclinic symmetry in the space group P21/a, has been discovered. Its emission intensity is higher than that of the known orthorhombic polymorph of CaGa2S4 crystallizing in the space group Fddd. The asymmetric unit of the monoclinic phase consists of two Ca, four Ga and eight S sites. Each of the Ca and Ga atoms is surrounded by seven and four sulfide ions, respectively, thereby sharing each of the sulfur sites with the nearest neighbours. In contrast, the corresponding sites in the orthorhombic phase are surrounded by eight and four S atoms, respectively. The photoluminescence peaks from Mn2+ and Ce3+ in the doped X-phase, both of which are supposed to replace Ca2+ ions, have been observed to shift towards the high energy side in comparison with those in the orthorhombic phase. This suggests that the crystal field around the Mn2+ and Ce3+ ions in the X-phase is weaker than that in the orthorhombic phase.
Structural, microstructural and vibrational analyses of the monoclinic tungstate BiLuWO{sub 6}
Energy Technology Data Exchange (ETDEWEB)
Ait Ahsaine, H. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Taoufyq, A. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Patout, L. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Ezahri, M.; Benlhachemi, A.; Bakiz, B. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106 Cité Dakhla, Agadir (Morocco); Villain, S.; Guinneton, F. [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France); Gavarri, J.-R., E-mail: gavarri.jr@univ-tln.fr [Institut Matériaux Microélectronique et Nanosciences de Provence, IM2NP, UMR CNRS 7334, Université de Toulon, BP 20132, 83957 La Garde Cedex (France)
2014-10-15
The bismuth lutetium tungstate phase BiLuWO{sub 6} has been prepared using a solid state route with stoichiometric mixtures of oxide precursors. The obtained polycrystalline phase has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. In the first step, the crystal structure has been refined using Rietveld method: the crystal cell was resolved using monoclinic system (parameters a, b, c, β) with space group A2/m. SEM images showed the presence of large crystallites with a constant local nominal composition (BiLuW). TEM analyses showed that the actual local structure could be better represented by a superlattice (a, 2b, c, β) associated with space groups P2 or P2/m. The Raman spectroscopy showed the presence of vibrational bands similar to those observed in the compounds BiREWO{sub 6} with RE=Y, Gd, Nd. However, these vibrational bands were characterized by large full width at half maximum, probably resulting from the long range Bi/Lu disorder and local WO{sub 6} octahedron distortions in the structure. - Graphical abstract: The average structure of BiLuWO{sub 6} determined from X-ray diffraction data can be represented by A2/m space group. Experimental Electron Diffraction patterns along the [0vw] zone axes of the monoclinic structure and associated simulated patterns show the existence of a monoclinic superstructure with space group P2 or P2/m. - Highlights: • A new monoclinic BiLuWO{sub 6} phase has been elaborated from solid-state reaction. • The space group of the monoclinic disordered average structure should be A2/m. • Transmission electron microscopy leads to a superlattice with P2/m space group. • Raman spectroscopy suggests existence of local disorder.
On Chiral Space Groups and Chiral Molecules
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations). For a chiral molecule, which must crystallize in a chiral space group, the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.
On Chiral Space Groups and Chiral Molecules
Institute of Scientific and Technical Information of China (English)
NgSeikWng; HUSheng－Zhi
2003-01-01
This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations).For a chiral molecule,which must crystallize in a chiral space group,the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.
DEFF Research Database (Denmark)
Faldt, André; Krebs, Frederik C; Thorup, Niels
1997-01-01
determined, The crystal structure of4,8,12-trioxa-12c-oxophospha-4,8,12,12c-tetrahydrodibenzo[cd,mn] pyrene (13) has also been determined for comparison, Compounds 3 and 11 crystallise in non-centrosymmetric space groups, Compound 12 also crystallises in a centrosymmetric :space group but molecules...... of opposite chirality are present within the unit cell, Finally compound 13 crystallises in a centrosymmetric space group. The room temperature pyroelectric coefficient of 3 has been determined, The spatial extent of the trioxatriangulene ground system has been perturbed by chemical substitution...
Symmetry and Condensed Matter Physics
El-Batanouny, M.; Wooten, F.
2008-03-01
Preface; 1. Symmetry and physics; 2. Symmetry and group theory; 3. Group representations: concepts; 4. Group representations: formalism and methodology; 5. Dixon's method for computing group characters; 6. Group action and symmetry projection operators; 7. Construction of the irreducible representations; 8. Product groups and product representations; 9. Induced representations; 10. Crystallographic symmetry and space-groups; 11. Space groups: Irreps; 12. Time-reversal symmetry: color groups and the Onsager relations; 13. Tensors and tensor fields; 14. Electronic properties of solids; 15. Dynamical properties of molecules, solids and surfaces; 16. Experimental measurements and selection rules; 17. Landau's theory of phase transitions; 18. Incommensurate systems and quasi-crystals; References; Bibliography; Index.
Bera, Ganesh; Reddy, V. R.; Rambabu, P.; Mal, P.; Das, Pradip; Mohapatra, N.; Padmaja, G.; Turpu, G. R.
2017-09-01
Phase diagram of FeVO4-CrVO4 solid solutions pertinent with structural and magnetic phases is presented with unambiguous experimental evidences. Solid solutions Fe1-xCrxVO4 (0 ≤ x ≤ 1.0) were synthesized through the standard solid state route and studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectra of X-rays, Raman spectroscopy, d.c. magnetization, and 57Fe Mössbauer spectroscopic studies. FeVO4 and CrVO4 were found to be in triclinic (P-1 space group) and orthorhombic structures (Cmcm space group), respectively. Cr incorporation into the FeVO4 lattice leads to the emergence of a new monoclinic phase dissimilar to the both end members of the solid solutions. In Fe1-xCrxVO4 up to x = 0.10, no discernible changes in the triclinic structure were found. A new structural monoclinic phase (C2/m space group) emerges within the triclinic phase at x = 0.125, and with the increase in Cr content, it gets stabilized with clear single phase signatures in the range of x = 0.175-0.25 as evidenced by the Rietveld analysis of the structures. Beyond x = 0.33, orthorhombic phase similar to CrVO4 (Cmcm space group) emerges and coexists with a monoclinic structure up to x = 0.85, which finally tends to stabilize in the range of x = 0.90-1.00. The Raman spectroscopic studies also confirm the structural transition. FeVO4 Raman spectra show the modes related to three nonequivalent V ions in the triclinic structure, where up to 42 Raman modes are observed in the present study. With the stabilization of structures having higher symmetry, the number of Raman modes decreases and the modes related to symmetry inequivalent sites collate into singular modes from the doublet structure. A systematic crossover from two magnetic transitions in FeVO4, at 21.5 K and 15.4 K to single magnetic transition in CrVO4, at 71 K (antiferromagnetic transition), is observed in magnetization studies. The intermediate solid solution with x = 0.15 shows two magnetic transitions
A second monoclinic polymorph of 2-(diformylmethylidene-3,3-dimethyl-2,3-dihydro-1H-indole
Directory of Open Access Journals (Sweden)
Hamid Khaledi
2009-10-01
Full Text Available The crystal structure of the title compound, C13H13NO2, is a polymorph of the structure first reported by Helliwell et al. [Acta Cryst. (2006, E62, o737-o738]. It is also monoclinic (space group P21/c, but with completely different cell constants. The molecular conformations of these polymorphs differ by a 180° rotation of one formyl group. The present molecule is planar [maximum deviation 0.089 (2 Å] with the exception of the two methyl groups which lie on either side of the plane. There are strong intra- and intermolecular N—H...O hydrogen bonds. The latter link pairs of molecules across crystallographic centers of symmetry. Two aldehyde O atoms are brought close together [2.896 (4 Å in this arrangement but are not hydrogen bonded. In the earlier polymorph, one formyl group is rotated by 180° to yield intermolecular hydrogen bonding and an infinite polymeric chain. The other formyl group is involved in the same intramolecular hydrogen bonding as has been found here.
Symmetries, Symmetry Breaking, Gauge Symmetries
Strocchi, Franco
2015-01-01
The concepts of symmetry, symmetry breaking and gauge symmetries are discussed, their operational meaning being displayed by the observables {\\em and} the (physical) states. For infinitely extended systems the states fall into physically disjoint {\\em phases} characterized by their behavior at infinity or boundary conditions, encoded in the ground state, which provide the cause of symmetry breaking without contradicting Curie Principle. Global gauge symmetries, not seen by the observables, are nevertheless displayed by detectable properties of the states (superselected quantum numbers and parastatistics). Local gauge symmetries are not seen also by the physical states; they appear only in non-positive representations of field algebras. Their role at the Lagrangian level is merely to ensure the validity on the physical states of local Gauss laws, obeyed by the currents which generate the corresponding global gauge symmetries; they are responsible for most distinctive physical properties of gauge quantum field ...
Bis[2-(hydroxyiminomethylphenolato]nickel(II: a second monoclinic polymorph
Directory of Open Access Journals (Sweden)
Julia A. Rusanova
2011-02-01
Full Text Available The title compound, [Ni(C7H6NO22], (I, is a second monoclinic polymorph of the compound, (II, reported by Srivastava et al. [Acta Cryst. (1967, 22, 922] and Mereiter [Private communication (2002 CCDC refcode NISALO01]. The bond lengths and angles are similar in both structures. The molecule in both structures lies on a crystallographic inversion center and both have an internal hydrogen bond. The title compound crystallizes in the space group P21/c (Z = 2, whereas compound (II is in the space group P21/n (Z = 2 with a similar cell volume but different cell parameters. In both polymorphs, molecules are arranged in the layers but in contrast to the previously published compound (II where the dihedral angle between the layers is 86.3°, in the title polymorph the same dihedral angle is 29.4°. The structure of (I is stabilized by strong intramolecular O—H...O hydrogen bonding between the O—H group and the phenolate O atom.
Crystal field analysis of Nd{sup 3+} energy levels in monoclinic NdAl{sub 3}(BO{sub 3}){sub 4} laser
Energy Technology Data Exchange (ETDEWEB)
Cascales, C.; Zaldo, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, Madrid (Spain); Caldino, U. [Departamento de Fisica, Universidad Autonoma Metropolitana, Iztapalapa, Mexico DF (Mexico); Garcia Sole, J. [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, Madrid (Spain); Luo, Z.D. [Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian (China)
2001-09-03
The energies of 135 Kramers doublets extending up to the {sup 2}H1{sub 11/2} multiplet for Nd{sup 3+} in a monoclinic C2/c space group (No 15) NdAl{sub 3}(BO{sub 3}){sub 4} (NAB) single crystal laser have been determined from polarized optical absorption and photoluminescence measurements at 7 K. The strongly polarized character of the Nd spectra has been discussed under the assumption of a local D{sub 3} symmetry, higher than the C{sub 2} symmetry of NAB, and the observed energy levels have been labelled with the adequate crystal quantum numbers and irreducible representations. A detailed Hamiltonian of 21 parameters has been used in the simulation of the energy levels and associated wavefunctions of the 4f{sup 3} configuration of Nd{sup 3+}. The diagonalized complete energy matrix combines simultaneously the free-ion and single-particle crystal field interactions. Starting B{sup k}{sub q} CF parameters were calculated from the semi-empirical simple overlap model SOM. A comparative simulation considering the C{sub 2} symmetry of NAB is provided. Moreover, two-electron CF interactions as well as an empirical correction have been tested in calculating the anomalous splitting of the {sup 2}H2{sub 11/2} levels. A final fit in D{sub 3} symmetry produces a very good adjustment with a low rms deviation {sigma}=15.3 cm{sup -1} between observed and calculated energy levels. (author)
Giera, Alicja; Manecki, Maciej; Borkiewicz, Olaf; Zelek, Sylwia; Rakovan, John; Bajda, Tomasz; Marchlewski, Tomasz
2016-04-01
Seven samples of hydroxyl analogues of pyromorphite-mimetite solid solutions series were synthesized from aqueous solutions at 80° C in a computer-controlled chemistate: 200 mL aqueous solutions of 0.05M Pb(NO3)2 and 0.03M KH2AsO4 and/or KH2PO4 were dosed with a 0.25 mL/min rate to a glass beaker, which initially contained 100 mL of distilled water. Constant pH of 8 was maintained using 2M KOH. The syntheses yielded homogeneous fine-grained white precipitates composition of which was close to theoretical Pb10[(PO4)6-x(AsO4)x](OH)2, where x = 0, 1, 2, 3, 4, 5, 6. High-resolution powder X-ray diffraction data were obtained in transmission geometry at the beamline 11-BM at the Advanced Photon Source (Argonne National Laboratory in Illinois, USA). The structure Rietveld refinements based on starting parameters of either hexagonal hydroxylpyromorphite or monoclinic mimetite-M were performed using GSAS+EXPGUI software. Apatite usually crystallizes in the hexagonal crystal system with the space group P63/m. For the first time, however, the lowering of the hexagonal to monoclinic crystal symmetry was observed in the hydroxyl variety of pyromorphite-mimetite solid solution series. This is indicated by better fitting of the modeled monoclinic structure to the experimental data. The same is not the case for analogous calcium hydroxylapatite series Ca5(PO4)3OH - Ca5(AsO4)3OH (Lee et al. 2009). Systematical linear increase of unit cell parameters is observed with As substitution from a=9.88, b=19.75, and c=7.43 for Pb10(PO4)6(OH)2 to a=10.23, b=20.32, and c=7.51 for Pb10(AsO4)6(OH)2. A strong pseudohexagonal character (γ ≈ 120° and b ≈ 2a) of the analyzed monoclinic phases was established. This work is partially funded by AGH research grant no 11.11.140.319 and partially by Polish NCN grant No 2011/01/M/ST10/06999. Lee Y.J., Stephens P.W., Tang Y., Li W., Philips B.L., Parise J.B., Reeder R.J., 2009. Arsenate substitution in hydroxylapatite: Structural characterization
Synthesis of monoclinic zinc diphosphide single crystals
Energy Technology Data Exchange (ETDEWEB)
Mowles, T.A.
1978-05-01
Monoclinic zinc diphosphide is a cheap, plentiful, direct-gap semiconductor with an optimum transition energy for solar absorption. Single crystals were grown from the vapor to be evaluated as a new photovoltaic material. Monoclinic and tetragonal crystal formed within evacuated quartz ampules that were charged with zinc and excess phosphorous and heated in a temperature gradient to give phosphorous pressures from 0.07 to 8.5 atmospheres. The monoclinic form melts incongruently near 990/sup 0/C. The tetragonal form is metastable; its growth is enhanced by impurities but retarded by high phosphorous pressures. The mechanism of the synthesis indicates that a tightly-controlled vapor deposition is possible and that high-quality thin films should form at temperatures from 950 to 990/sup 0/C at pressures below 10 atmospheres. By a modification of the technique, sesquizinc phosphide single crystals were grown for comparison.
Monoclinic polymorph of poly[aqua(μ4-hydrogen tartratosodium
Directory of Open Access Journals (Sweden)
Mohammad T. M. Al-Dajani
2010-02-01
Full Text Available A monoclinic polymorph of the title compound, [Na(C4H5O6(H2O]n, is reported and complements an orthorhombic form [Kubozono, Hirano, Nagasawa, Maeda & Kashino (1993. Bull. Chem. Soc. Jpn, 66, 2166–2173]. The asymmetric unit contains a hydrogen tartrate anion, an Na+ cation and a water molecule. The Na+ ion is surrounded by seven O atoms derived from one independent and three symmetry-related hydrogen tartrate anions, and a water molecule, forming a distorted pentagonal–bipyramidal geometry. Independent units are linked via a pair of intermolecular bifurcated O—H...O acceptor bonds, generating an R21(6 ring motif to form polymeric two-dimensional arrays parallel to the (100 plane. In the crystal packing, the arrays are linked by adjacent ring motifs, together with additional intermolecular O—H...O interactions, into a three-dimensional network.
Reflection of and SV waves at the free surface of a monoclinic elastic half-space
Indian Academy of Sciences (India)
Sarva Jit Singh; Sandhya Khurana
2002-12-01
The propagation of plane waves in an anisotropic elastic medium possessing monoclinic symmetry is discussed. The expressions for the phase velocity of qP and qSV waves propagating in the plane of elastic symmetry are obtained in terms of the direction cosines of the propagation vector. It is shown that, in general, qP waves are not longitudinal and qSV waves are not transverse. Pure longitudinal and pure transverse waves can propagate only in certain specific directions. Closed-form expressions for the reflection coefficients of qP and qSV waves incident at the free surface of a homogeneous monoclinic elastic half-space are obtained. These expressions are used for studying numerically the variation of the reflection coefficients with the angle of incidence. The present analysis corrects some fundamental errors appearing in recent papers on the subject.
Evidence for photo-induced monoclinic metallic VO{sub 2} under high pressure
Energy Technology Data Exchange (ETDEWEB)
Hsieh, Wen-Pin, E-mail: wphsieh@stanford.edu; Mao, Wendy L. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305 (United States); Trigo, Mariano [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Reis, David A. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Photon Science and Applied Physics, Stanford University, Stanford, California 94305 (United States); Andrea Artioli, Gianluca; Malavasi, Lorenzo [Dipartimento di Chimica, Sezione di Chimica Fisica, INSTM (UdR Pavia), Università di Pavia, Viale Taramelli 16, 27100 Pavia (Italy)
2014-01-13
We combine ultrafast pump-probe spectroscopy with a diamond-anvil cell to decouple the insulator-metal electronic transition from the lattice symmetry changing structural transition in the archetypal strongly correlated material vanadium dioxide. Coherent phonon spectroscopy enables tracking of the photo-excited phonon vibrational frequencies of the low temperature, monoclinic (M{sub 1})-insulating phase that transforms into the metallic, tetragonal rutile structured phase at high temperature or via non-thermal photo-excitations. We find that in contrast with ambient pressure experiments where strong photo-excitation promptly induces the electronic transition along with changes in the lattice symmetry, at high pressure, the coherent phonons of the monoclinic (M{sub 1}) phase are still clearly observed upon the photo-driven phase transition to a metallic state. These results demonstrate the possibility of synthesizing and studying transient phases under extreme conditions.
Three-dimensional organic Dirac-line materials due to nonsymmorphic symmetry: A data mining approach
Geilhufe, R. Matthias; Bouhon, Adrien; Borysov, Stanislav S.; Balatsky, Alexander V.
2017-01-01
A data mining study of electronic Kohn-Sham band structures was performed to identify Dirac materials within the Organic Materials Database. Out of that, the three-dimensional organic crystal 5,6-bis(trifluoromethyl)-2-methoxy-1 H -1,3-diazepine was found to host different Dirac-line nodes within the band structure. From a group theoretical analysis, it is possible to distinguish between Dirac-line nodes occurring due to twofold degenerate energy levels protected by the monoclinic crystalline symmetry and twofold degenerate accidental crossings protected by the topology of the electronic band structure. The obtained results can be generalized to all materials having the space group P 21/c (No. 14, C2h 5) by introducing three distinct topological classes.
Bayesian probability theory applied to the space group problem in powder diffraction
Markvardsen, A. J.
2004-11-01
Crystal structure determination from powder diffraction data has become a viable option for molecules with less than 50 non-hydrogen atoms in the asymmetric unit and this includes the majority of compounds of pharmaceutical interest. The solution of crystal structures, including space group determination, is more challenging from powder diffraction data than from single crystal diffraction data. Here, it will be demonstrated how a Bayesian probability analysis of this problem has helped to provide a new algorithm for the determination of the space group symmetry of a crystal from powder diffraction data. Specifically, the relative probabilities of different extinction symbols are accessed within a particular crystal system. Examples will be presented to illustrate this approach.
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The space groups of [ (CH3CH2)4N]3 { [(SCH2CH2S)MoS3]2Fe} and [ (CH3CH2)4N]2 { [S2CN(C2H5)2 ]4Fe4S4 } are revised from Cc to C2/c by solving the C2/c structure from the structure factorsthat are calculated from the Cc structure. The structures are both disordered in one of the tetraethylammonium cations. The space P21/c; because of the severe disorder in the cations that was not addressed in the original refinements, only the atomic coordinates of the metal-cluster anions could be re(originally described in P1) is re-assigned to C2/c. The general descriptions of the structures are unchanged in the higher-symmetry settings. The revised coordinates are given.
3-dimensional organic Dirac-line material due to non-symmorphic symmetry: a data mining approach
Geilhufe, R Matthias; Borysov, Stanislav S; Balatsky, Alexander V
2016-01-01
A data mining study of electronic Kohn-Sham band structures was performed to identify Dirac materials within the Organic Materials Database (OMDB). Out of that, the 3-dimensional organic crystal 5,6-Bis(trifluoromethyl)-2-methoxy-1H-1,3-diazepine was found to host different Dirac line-nodes within the band structure. From a group theoretical analysis, it is possible to distinguish between Dirac line-nodes occurring due to 2-fold degenerate energy levels protected by the monoclinic crystalline symmetry and 2-fold degenerate accidental crossings protected by the topology of the electronic band structure. The obtained results can be generalized to all materials having the space group $P2_1/c$ ($\\#14$, $C^5_{2h}$) by introducing three distinct topological classes.
Peculiarities of Crystal Structure of the Cubic System Compounds with T 4 and T 5 Space Groups
Zolotarev, M. L.; Poplavnoi, A. S.
2016-09-01
We study symmetry peculiarities of crystalline compounds of a cubic system with the space groups T 4 and T 5 caused by the absence of point Wyckoff-sets in the unit cells of these groups. Due to the high multiplicity of the available Wyckoff positions, such compounds possess unit cells of complex composition. In these compounds, pseudosymmetry is realized with high probability when some group of atoms is located in positions close to the positions of higher-symmetry groups. We provide examples of crystalline compounds showing predicted specific structural features.
Space Group Debris Imaging Based on Sparse Sample
Directory of Open Access Journals (Sweden)
Zhu Jiang
2016-02-01
Full Text Available Space group debris imaging is difficult with sparse data in low Pulse Repetition Frequency (PRF spaceborne radar. To solve this problem in the narrow band system, we propose a method for space group debris imaging based on sparse samples. Due to the diversity of mass, density, and other factors, space group debris typically rotates at a high speed in different ways. We can obtain angular velocity through the autocorrelation function based on the diversity in the angular velocity. The scattering field usually presents strong sparsity, so we can utilize the corresponding measurement matrix to extract the data of different debris and then combine it using the sparse method to reconstruct the image. Furthermore, we can solve the Doppler ambiguity with the measurement matrix in low PRF systems and suppress some energy of other debris. Theoretical analysis confirms the validity of this methodology. Our simulation results demonstrate that the proposed method can achieve high-resolution Inverse Synthetic Aperture Radar (ISAR images of space group debris in low PRF systems.
2-(4-Fluorobenzylidenepropanedinitrile: monoclinic polymorph
Directory of Open Access Journals (Sweden)
Ahmed M. El-Agrody
2013-04-01
Full Text Available The title compound, C10H5FN2, is a monoclinic (P21/c polymorph of the previously reported triclinic (P-1 form [Antipin et al. (2003. J. Mol. Struct. 650, 1–20]. The 13 non-H atoms in the title polymorph are almost coplanar (r.m.s. deviation = 0.020 Å; a small twist between the fluorobenzene and dinitrile groups [C—C—C—C torsion angle = 175.49 (16°] is evident in the triclinic polymorph. In the crystal, C—H...N interactions lead to supramolecular layers parallel to (-101; these are connected by C—F...π interactions.
Monoclinic zirconia distributions in plasma-sprayed thermal barrier coatings
Lance, M. J.; Haynes, J. A.; Ferber, M. K.; Cannon, W. R.
2000-03-01
Phase composition in an air plasma-sprayed Y2O3-stabilized ZrO2 (YSZ) top coating of a thermal barrier coating (TBC) system was characterized. Both the bulk phase content and localized pockets of monoclinic zirconia were measured with Raman spectroscopy. The starting powder consisted of ˜15 vol.% monoclinic zirconia, which decreased to ˜2 vol.% in the as-sprayed coating. Monoclinic zirconia was concentrated in porous pockets that were evenly distributed throughout the TBC. The pockets resulted from the presence of unmelted granules in the starting powder. The potential effect of the distributed monoclinic pockets on TBC performance is discussed.
What causes the Besnus transition in monoclinic pyrrhotite?
Gehring, A. U.; Koulialias, D.; Löffler, J. F.; Charilaou, M.
2016-12-01
Monoclinic 4C pyrrhotite (ideal formula Fe7S8) is a major magnetic remanence carrier in the Earth's crust and in extraterrestrial materials. Because of its low-temperature magnetic transition around 30 K also known as Besnus transition, this mineral phase is easily detectable in rock samples. An intrinsic origin of the Besnus transition due to a crystallographic change similar to that in the Verwey transition has generally been postulated (1). Although the physical properties of pyrrhotite have intensively been studied, the physics behind the pronounced change in magnetization at the low-temperature transition is still unresolved. To address this question we performed structural and magnetic analyses on a natural pyrrhotite single crystal (Fe6.6S8) from Auerbach, Germany (2,3). Chemical analysis, X-ray diffractometry and transmission electron microscopy show that this pyrrhotite consists of an intergrowth of 4C and an incommensurate 5C* superstructure that are polymorphs with different vacancy distributions. The occurrence of two superstructures is magnetically confirmed by symmetric inflection points in the hysteresis measurements above the transition at about 30 K. The disappearance of the inflection points and the associated change of the hysteresis parameters indicate that the two superstructures become embedded to form a unitary magnetic anisotropy system at the transition. This embedding of the 5C* into the 4C pyrrhotite at about 30 K is directly visible by the occurrence of additional 4-fold and 12-fold symmetry terms in magnetic anisotropy and anisotropic magnetic resistivity mesarurements, respectively. From this it follows that the Besnus transition in monoclinic pyrrhotite is an extrinsic magnetic phenomenon with respect to the 4C superstructure, i.e., a coupling effect, and therefore the physics behind it is in fact different from that of the well-known Verwey transition. (1) Rochette et al., The IRM Quarterly, 21, 1 (2011); (2) Charilaou et al., J
Systematic prediction of new ferroelectrics in space group P3.
Abrahams, S C
2000-10-01
The current release of the Inorganic Crystal Structure Database contains a total of 57 entries under space group P3 that correspond to 50 different materials. There are 21 structures reported with this space group that satisfy the criteria for ferroelectricity, at a confidence level that depends on the reliability of the underlying structural determination. One ferroelectric discovered earlier is also listed. In addition, the database contains 19 entries that probably should be assigned to a centrosymmetric space group, seven that are polar but probably not ferroelectric and two that are without atomic coordinates. Seven entries are either duplicates or present additional structural studies of the same material. Structures in space group P3 identified as potentially new ferroelectrics include LiAsCu(0.93), Na(2)UF(6), BiTeI, BaGe(4)O(9), alpha-UMo(2)O(8), Cu(2)SiS(3), Co(IO(3))(2), Sr(7)Al(12)O(25), KSn(2)F(5), YbIn(2)S(4), Na(5)CrF(2)(PO(4))(2), Sn(ClO(2))(2)(ClO(4))(6), Eu(3)BWO(9), Li(H(2)O)(4)B(OH)(4).2H(2)O, Mn(3)V(1/2)(SiO(4))O(OH)(2), Ca(6)(Si(2)O(7))(OH)(6), Na(6. 9(2))[Al(5.6(1))Si(6.4(1))O(24)](S(2)O(3))(1.0(1)).2H(2)O, BaCa(2)In(6)O(12), Ni(H(2)O)(6)[Sb(OH)(6)](2), Sr(4)Cr(3)O(9) and Cu(5)O(2)(VO(4))(2).CuCl(2).
Kisi, E H; Forrester, J S; Howard, C J
2003-01-01
Lead zinc niobate-lead titanate (PZN-PT) single crystals show very large piezoelectric strains for electric fields applied along the unit cell edges e.g. [001] sub R. It has been widely reported that this effect is caused by an electric field induced phase transition from rhombohedral (R3m) to monoclinic (Cm or Pm) symmetry in an essentially continuous manner. Group theoretical analysis using the computer program ISOTROPY indicates phase transitions between R3m and Cm (or Pm) must be discontinuous under Landau theory. An analysis of the symmetry of a strained unit cell in R3m and a simple expansion of the piezoelectric strain equation indicate that the piezoelectric distortion due to an electric field along a cell edge in rhombohedral perovskite-based ferroelectrics is intrinsically monoclinic (Cm), even for infinitesimal electric fields. PZN-PT crystals have up to nine times the elastic compliance of other piezoelectric perovskites and it might be expected that the piezoelectric strains are also very large. ...
Energy Technology Data Exchange (ETDEWEB)
Ackermann, Matthias; Andersen, Lionel; Becker, Petra; Bohaty Ladislav [Koeln Univ. (Germany). Inst. fuer Kristallographie
2015-07-01
The pyroelectric effect of four isomorphic monoclinic (space group Cc), non-ferroelectric rare earth nitrates A{sub 2}Ln(NO{sub 3}){sub 5}.4H{sub 2}O (A = NH{sub 4}, Rb; Ln = La, Ce) was investigated in the temperature range between 100 K and 300 K, using a home-made continuous-flow cryostat for measurements of pyroelectric currents. The symmetry-allowed temperature-dependent change of orientation of the pyroelectric vector p within the mirror plane is unusually large, showing a rotation of p of 148 , 129 , 36 and 40 for (NH{sub 4}){sub 2}La(NO{sub 3}){sub 5}.4H{sub 2}O, (NH{sub 4}){sub 2}Ce(NO{sub 3}){sub 5}.4H{sub 2}O, Rb{sub 2}La(NO{sub 3}){sub 5}.4H{sub 2}O and Rb{sub 2}Ce(NO{sub 3}){sub 5}.4H{sub 2}O, respectively, while changing the temperature from 100 K to 300 K in each case. The pyroelectric coefficients are up to ten times larger than p{sub 3} of tourmaline. In addition, new data of the pyroelectric coefficients of Li{sub 2}SO{sub 4}.H{sub 2}O and BiB{sub 3}O{sub 6} and their temperature dependence are given.
Prediction of a novel monoclinic carbon allotrope
Amsler, Maximilian; Flores-Livas, José A.; Marques, Miguel A. L.; Botti, Silvana; Goedecker, Stefan
2013-09-01
A novel allotrope of carbon with P2/ m symmetry was identified during an ab initio minima-hopping structural search which we call M10-carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of s p 3 bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X-ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite.
Energy Technology Data Exchange (ETDEWEB)
Tan, K.B., E-mail: tankb@science.upm.my [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Chon, M.P. [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Khaw, C.C. [Department of Mechanical and Material Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Setapak, Kuala Lumpur (Malaysia); Zainal, Z.; Taufiq Yap, Y.H.; Tan, P.Y. [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)
2014-04-01
Highlights: • Novel BCT monoclinic zirconolite phase was prepared through solid state reaction. • Comprehensive study of reaction mechanism was performed by careful firing control. • Qualitative structural and phase analyses were conducted. • Electrical response in broad range of temperature and frequency was investigated. - Abstract: Synthesis of novel monoclinic zirconolite, Bi{sub 1.92}Cu{sub 0.08}(Cu{sub 0.3}Ta{sub 0.7}){sub 2}O{sub 7.06} (β-BCT) using solid state reaction had been finalised at the firing temperature of 900 °C over 24 h. The X–ray diffraction pattern of β-BCT was fully indexed on a monoclinic symmetry, space group, C2/c with lattice constants, a = 13.1052 (8), b = 7.6749 (5), c = 12.162 (6), α = γ = 90° and β = 101.32° (1), respectively. The reaction mechanism study indicated phase formation was greatly influenced by the reaction between intermediate bismuth tantalate binary phases and CuO at elevated temperatures. β-BCT was thermally stable up to a temperature of 900 °C and contained spherulite grains with sizes ranging from 1 to 14 μm. Electrical properties of this material were characterised over a broad temperature range covering temperatures from 10 K to 874 K. At the temperature of 304 K, two semicircles were discernible in complex Cole–Cole plot showing an insulating grain boundary with C{sub gb} = 6.63 × 10{sup −9} F cm{sup −1} and a bulk response capacitance, C{sub b} = 6.74 × 10{sup −12} F cm{sup −1}. The Power law frequency-dependent ac conductivity of β-BCT was apparent in three frequency regimes; a low–frequency plateau regime, a high-frequency plateau regime and a dispersive regime taking place in the temperature range of 220–576 K. The frequency-dependent ac conductivity of β-BCT with increasing temperature was attributed to the thermal activated electrical conduction mechanism within the structure.
Bis[2-(hy-droxy-imino-meth-yl)phenolato]nickel(II): a second monoclinic polymorph.
Rusanova, Julia A; Buvaylo, Elena A; Rusanov, Eduard B
2011-01-15
The title compound, [Ni(C(7)H(6)NO(2))(2)], (I), is a second monoclinic polymorph of the compound, (II), reported by Srivastava et al. [Acta Cryst. (1967), 22, 922] and Mereiter [Private communication (2002) CCDC refcode NISALO01]. The bond lengths and angles are similar in both structures. The mol-ecule in both structures lies on a crystallographic inversion center and both have an inter-nal hydrogen bond. The title compound crystallizes in the space group P2(1)/c (Z = 2), whereas compound (II) is in the space group P2(1)/n (Z = 2) with a similar cell volume but different cell parameters. In both polymorphs, mol-ecules are arranged in the layers but in contrast to the previously published compound (II) where the dihedral angle between the layers is 86.3°, in the title polymorph the same dihedral angle is 29.4°. The structure of (I) is stabilized by strong intra-molecular O-H⋯O hydrogen bonding between the O-H group and the phenolate O atom.
Nucci, M. C.
2016-09-01
We review some of our recent work devoted to the problem of quantization with preservation of Noether symmetries, finding hidden linearity in superintegrable systems, and showing that nonlocal symmetries are in fact local. In particular, we derive the Schrödinger equation for the isochronous Calogero goldfish model using its relation to Darwin equation. We prove the linearity of a classical superintegrable system on a plane of nonconstant curvature. We find the Lie point symmetries that correspond to the nonlocal symmetries (also reinterpreted as λ-symmetries) of the Riccati chain.
Volk, Michael W. R.; Gilder, Stuart A.; Feinberg, Joshua M.
2016-12-01
Monoclinic pyrrhotite (Fe7S8) owes its ferrimagnetism to an ordered array of Fe vacancies. Its magnetic properties change markedly around 30 K, in what is known as the Besnus transition. Plausible explanations for the Besnus transition are either due to changes in crystalline anisotropy from a transformation in crystal symmetry or from the establishment of a two-phase system with magnetic interaction between the two phases. To help resolve this discrepancy, we measured hysteresis loops every 5° and backfield curves every 10° in the basal plane of an oriented single crystal of monoclinic pyrrhotite at 300 K and every 2 K from 50 K through the Besnus transition until 20 K. Between 50 and 30 K, hysteresis loops possess double inflections between crystallographic a-axes and only a single inflection parallel to the a-axes. Magnetization energy calculations and relative differences of the loops show a sixfold symmetry in this temperature range. We propose that the inflections stem from magnetic axis switching, which is both field and temperature dependent, in a manner somewhat analogous to an isotropic point where magnetocrystalline constants change their sign. The Besnus transition is best characterized by changes in magnetic remanence and coercivity over a 6° temperature span (28-34 K) with a maximum rate of change at 30 K. A surprising yet puzzling finding is that the coercivity ratio becomes less than unity below the transition when fourfold symmetry arises. Because the changes in magnetic parameters are linked to the crystal structure, we conclude the Besnus transition owes its origin to a distortion of the crystallographic axes below 30 K rather than an apparition of a two-phase system. An isothermal magnetization of natural pyrrhotite cycled from room temperature to successively lower temperatures through the Besnus transition decreases 2-4 times less than equivalent grain sizes of magnetite, with less than a 10 per cent loss in remanence between 300 and 150 K
Four-dimensional space groups for pedestrians: composite structures.
Sun, Junliang; Lee, Stephen; Lin, Jianhua
2007-10-01
Higher-dimensional crystals have been studied for the last thirty years. However, most practicing chemists, materials scientists, and crystallographers continue to eschew the use of higher-dimensional crystallography in their work. Yet it has become increasingly clear in recent years that the number of higher-dimensional systems continues to grow from hundreds to as many as a thousand different compounds. Part of the problem has to do with the somewhat opaque language that has developed over the past decades to describe higher-dimensional systems. This language, while well-suited to the specialist, is too sophisticated for the neophyte wishing to enter the field, and as such can be an impediment. This Focus Review hopes to address this issue. The goal of this article is to show the regular chemist or materials scientist that knowledge of regular 3D crystallography is all that is really necessary to understand 4D crystal systems. To this end, we have couched higher-dimensional composite structures in the language of ordinary 3D crystals. In particular, we developed the principle of complementarity, which allows one to identify correctly 4D space groups solely from examination of the two 3D components that make up a typical 4D composite structure.
The Possible Topologic structure Types of Orthopyroxene with Space Group P21ca
Institute of Scientific and Technical Information of China (English)
罗谷风; 林承毅; 等
1990-01-01
The possible topologic structure types of orthopyroxene with space group P21ca comprise four kinds of tetrahedral chains and four kinds of octahedral sites.all of which are non-equivalent in symmetry,In these structure types,the skew of the octahedral layers has a sequence of ++--,There are sixteen possible combination forms for the rotation type of tetradral chain.Twelve of them violate Thompson 's sparity rule and the remainder constitutes two pairs.In each pair,the two polar forms show a relationship of anti-orientation for their polar a-axes.Thus,there are only two possible different topologic structure types for P21ca-orthopyroxene.The ratios of O-rotated and S-rotated tetrahedral chains for these two structure types are 3:1 and 1:3,respectively,In the view S-rotated tetrahedral chains for these two structure types are 3:1 and 1:3,respectively,In the view of crystallochemical principle,the most likely form is the one with a ratio of 3:1,and its constitutions of two stacks of I-beam,which are non-equivalent both in symmetry and in topology,are and the configurations of the two types of M2 sites are P.P and P.N,respectively,A complementary twinning on(100) would be formed between the anti-oriented structure pairs,and their twin boundary is exactly equivalent to the inversion boundary,Moreover,it is possible that the ordered structure would appear when the atom ratio of Mg:Fe is equal to 3:1 as well as to 1：1。
High-symmetry organic scintillator systems
Energy Technology Data Exchange (ETDEWEB)
Feng, Patrick L.
2017-07-18
An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.
High-symmetry organic scintillator systems
Energy Technology Data Exchange (ETDEWEB)
Feng, Patrick L.
2017-09-05
An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.
Directory of Open Access Journals (Sweden)
Ahmed M. Orlando
2010-08-01
Full Text Available A new monoclinic form of the title compound, C14H17N3O3S, has been found upon slow crystallization from water. Another monoclinic form of the compound was obtained previously from a mixture of dichloromethane and diethyl ether [Clerici et al. (2002. Tetrahedron, 58, 5173–5178]. Both phases crystallize in space group P21/n with one molecule in the asymmetric unit. The formally single exocyclic C—N bond that connects the –NEt2 unit with the thiazete ring is considerably shorter than the adjacent, formally double, endocyclic C=N bond. This is likely to be due to the extended conjugated system between the electron-donor diethylammine fragment and the electron-withdrawing sulfonyl group. In the newly discovered polymorph, the methoxy group is rotated by almost 180° around the phenyl–OCH3 bond, resulting in a different molecular conformation.
Energy Technology Data Exchange (ETDEWEB)
Weisinger-Lewin, Y.; Frolow, F.; Lahav, M.; Leiserowitz, L. (Weizmann Institute of Science, Rehovot (Israel)); McMullan, R.K.; Koetzle, T.F. (Brookhaven National Lab., Upton, NY (USA))
1989-02-01
It has been demonstrated, for the first time by diffraction methods, that a solid solution composed of host and guest molecules can exhibit a crystal symmetry lower than that of the host. The study proves that the symmetry of a solid solution is dependent not only upon the host crystal structure and the guest molecular structure but also upon the surface structure and symmetry of the host crystal. The crystal structures of (S)-asparagine monohydrate (D{sub 2}NCOCH{sub 2}CH(ND{sub 3})CO{sub 2} {times} D{sub 2}O) and of the solid solution (0.848:0.152) (S)-asparagine/(S)-aspartic acid (DO{sub 2}CCD{sub 2}CD(ND{sub 3})CO{sub 2}) monohydrate were refined by using neutron diffraction data obtained at 15 K. The space group of the pure host crystal is P2{sub 1}2{sub 1}2{sub 1} (Z = 4), whereas that of the host/guest crystal is monoclinic P12{sub 1}1 with two molecular sites per asymmetric unit. The ratios of guest/host occupancies of the two independent sites are 0.173:0.827 and 0.132:0.868. The reduction in symmetry is in accordance with the preferred adsorption of guest aspartic acid on the (010) crystal face at half of the orthorhombic, symmetry-related surface sites. Aspartic acid mimics, at the preferred (010) surface sites, molecular asparagine, participating in all hydrogen bonds. At the less-favored (010) surface sites a normal N-H{hor ellipsis}O(host) hydrogen bond is replaced by O(hydroxyl){hor ellipsis}O(host) repulsion between lone-pair electrons. 21 refs., 5 figs., 6 tabs.
Voisin, Claire
1999-01-01
This is the English translation of Professor Voisin's book reflecting the discovery of the mirror symmetry phenomenon. The first chapter is devoted to the geometry of Calabi-Yau manifolds, and the second describes, as motivation, the ideas from quantum field theory that led to the discovery of mirror symmetry. The other chapters deal with more specialized aspects of the subject: the work of Candelas, de la Ossa, Greene, and Parkes, based on the fact that under the mirror symmetry hypothesis, the variation of Hodge structure of a Calabi-Yau threefold determines the Gromov-Witten invariants of its mirror; Batyrev's construction, which exhibits the mirror symmetry phenomenon between hypersurfaces of toric Fano varieties, after a combinatorial classification of the latter; the mathematical construction of the Gromov-Witten potential, and the proof of its crucial property (that it satisfies the WDVV equation), which makes it possible to construct a flat connection underlying a variation of Hodge structure in the ...
Häring, Reto Andreas
1993-01-01
The representations of the observable algebra of a low dimensional quantum field theory form the objects of a braided tensor category. The search for gauge symmetry in the theory amounts to finding an algebra which has the same representation category. In this paper we try to establish that every quantum field theory satisfying some basic axioms posseses a weak quasi Hopf algebra as gauge symmetry. The first step is to construct a functor from the representation category to the category of finite dimensional vector spaces. Given such a functor we can use a generalized reconstruction theorem to find the symmetry algebra. It is shown how this symmetry algebra is used to build a gauge covariant field algebra and we investigate the question why this generality is necessary.
Hoki, T.; Senju, T.; Mizuguchi, Jin
2005-01-01
The title compound, C(20)H(10)Cl(2)N(2)S(2)(.)2C(4)H(9)NO, is a dimethylacetamide (DMA) disolvate of DTQ-Cl, which is a thionated derivative of a 2,9-dichloroquinacridone pigment. The compound shows polymorphism and this paper reports the monoclinic form ( space group P2(1)/c, Z = 4). Two DMA molecules are hydrogen bonded via their O atoms to the NH group of DTQ-Cl. The molecular planes of the two DMA molecules are asymmetrically twisted with respect to the DTQ-Cl skeleton by 11.65 (8) and 31...
A second monoclinic polymorph of 2-[2-(4-methoxyphenylhydrazinylidene]-1,3-diphenylpropane-1,3-dione
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Carlos Bustos
2011-07-01
Full Text Available The title compound, C22H18N2O3 is the second monoclinic polymorph (P21/c of the compound, the first being reported in space group P21 [Bertolasi et al. (1993. J. Chem. Soc. Perkin Trans. 2, pp. 2223–2228]. In the molecular structure of the title compound, the interplanar angle between the benzoyl units is 80.04 (5°, while the corresponding angles between the phenylhydrazinylidene and benzoyl groups are 36.11 (5 and 55.77 (2°. A strong resonance-assisted intramolecular N—H...O hydrogen bond is found. In the crystal, the entire supramolecular structure is constructed by weak intermolecular C—H...O interactions and an inter-ring π–π interaction [centroid–centroid distance = 3.6088 (8 Å].
Monoclinic high-pressure polymorph of AlOOH predicted from first principles
Zhong, Xin; Hermann, Andreas; Wang, Yanchao; Ma, Yanming
2016-12-01
Aluminum oxide hydroxide, AlOOH, is a prototypical hydrous mineral in the geonomy. The study of the high-pressure phase evolution of AlOOH is of fundamental importance in helping to understand the role of hydrous minerals in the water storage and transport in Earth, as in other planets. Here, we have systematically investigated the high-pressure phase diagram of AlOOH up to 550 GPa using the efficient crystal structure analysis by particle swarm optimization (CALYPSO) algorithm in conjunction with first principles calculations. We predict a peculiar monoclinic phase (space group P 21/c , 16 atoms/cell, Z =4 ) as the most stable phase for AlOOH above 340 GPa. The occurrence of this new phase results in the breakup of symmetric linear O-H-O hydrogen bonds into asymmetric, bent O-H-O linkages and in sevenfold coordinated metal cations. The new P 21/c phase turns out to be a universal high-pressure phase in group 13 oxide hydroxides, and stable for both compressed GaOOH and InOOH. The formation of the new phase in all compounds is favored by volume reduction due to denser packing.
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A. Concha-Balderrama
2016-12-01
Full Text Available La0.7Sr0.3Cr0.4Mn0.6O3-δ perovskite nanoparticles have been synthetized using an ethylene glycol modified sol-gel method and impregnated by Cu0.75Ni0.25 nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. Findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size <26 nm start through nuclei formation of La0.7Sr0.3Cr0.4Mn0.6O3-δ and SrCrO4 solid solutions with Pm3¯m cubic and P21/n monoclinic symmetry respectively in the range of 600–650 °C. Symmetry reduction from the Pm3¯m⟶R3¯c space group had been obtained at a lower temperature (750 °C than those reported in the literature in oxygen atmosphere and it was confirmed by an octahedral distortion, which takes place in the crystallographic direction[22̅1]/(12̅2. The Johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D3d6 point group symmetry.
Non-laminate Microstructures in Monoclinic-I Martensite
Chenchiah, Isaac Vikram
2012-01-01
We study the symmetrised rank-one convex hull of monoclinic-I martensite (a twelve-variant material) in the context of geometrically-linear elasticity. We show that this hull is strictly larger than the symmetrised lamination convex hull by constructing sets of T3s, which are (non-trivial) symmetrised rank-one convex hulls of 3-tuples of pairwise incompatible strains. Moreover we construct a five-dimensional continuum of T3s and show that its intersection with the boundary of the symmetrised rank-one convex hull is four-dimensional. Along the way we show that there is another kind of monoclinic-I martensite with qualitatively different semi-convex hulls which, so far as we know, has not been experimentally observed. Our strategy is to combine understanding of the algebraic structure of symmetrised rank-one convex cones with knowledge of the faceting structure of the convex polytope formed by the strains.
Non-Laminate Microstructures in Monoclinic-I Martensite
Chenchiah, Isaac Vikram; Schlömerkemper, Anja
2013-01-01
We study the symmetrised rank-one convex hull of monoclinic-I martensite (a twelve-variant material) in the context of geometrically-linear elasticity. We construct sets of T 3s, which are (non-trivial) symmetrised rank-one convex hulls of three-tuples of pairwise incompatible strains. In addition, we construct a fivedimensional continuum of T 3s and show that its intersection with the boundary of the symmetrised rank-one convex hull is four-dimensional.We also show that there is another kind of monoclinic-I martensite with qualitatively different semi-convex hulls which, as far as we know, has not been experimentally observed. Our strategy is to combine understanding of the algebraic structure of symmetrised rank-one convex cones with knowledge of the faceting structure of the convex polytope formed by the strains.
Observation of spin glass behavior in monoclinic Li{sub 0.33}MnO{sub 2}
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Bie, Xiaofei; Wei, Yingjin; Liu, Lina [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Nikolowski, Kristian; Ehrenberg, Helmut [Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Chen, Hong [College of Physics, Beihua University, Jilin 132013 (China); Wang, Chunzhong; Chen, Gang [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Du, Fei, E-mail: dufei@jlu.edu.cn [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China)
2013-02-25
Highlights: Black-Right-Pointing-Pointer The structure of Li{sub 0.33}MnO{sub 2} has been refined with monoclinic phase (space group C2/m). Black-Right-Pointing-Pointer Spin glass has been confirmed by analyzing dc, ac, and time-dependence remanence. Black-Right-Pointing-Pointer Geometrical frustration combined random competition was suggested to be the main cause for spin glass formation. Black-Right-Pointing-Pointer In order to distinguish the spin glass from the superparamagnetism, ac susceptibility under different frequencies is studied. - Abstract: The structure and magnetic properties of Li{sub 0.33}MnO{sub 2} were studied by X-ray diffraction, dc and ac susceptibilities. Li{sub 0.33}MnO{sub 2} belongs to the monoclinic structure with two different Mn sites. The irreversibility and spin freezing behaviors are observed in the dc magnetization curves. The peaks of ac susceptibility display the dependences on the frequency. Both the magnetic relaxation effect and the corresponding analysis confirm a spin glass (SG) transition at low temperature. By evaluating the geometrical frustration parameter, we suggest the spin glass in Li{sub 0.33}MnO{sub 2} originate from the frustration effect combined with the competition among the Mn{sup 3+/4+}-O{sup 2-}-Mn{sup 3+/4+} exchange interaction.
Solid State Synthesis and Properties of Monoclinic Celsian
Bansal, Narottam P.
1996-01-01
Monoclinic celsian of Ba(0.75)Sr(0.25)Al2Si2O8 (BSAS-1) and B(0.85)Sr(O.15)Al2Si2O8 (BSAS-2) compositions have been synthesized from metal carbonates and oxides by solid state reaction. A mixture of BaCO3, SrCO3, Al2O3, and SiO2 powders was precalcined at approx. 900-940 C to decompose the carbonates followed by hot pressing at approx. 1300 C. The hot pressed BSAS-1 material was almost fully dense and contained the monoclinic celsian phase, with complete absence of the undesirable hexacelsian as indicated by x-ray diffraction. In contrast, a small fraction of hexacelsian was still present in hot pressed BSAS-2. However, on further heat treatment at 1200 C for 24 h, the hexacelsian phase was completely eliminated. The average linear thermal expansion coefficients of BSAS-1 and BSAS-2 compositions, having the monoclinic celsian phase, were measured to be 5.28 x 10(exp -6)/deg C and 5.15 x 10(exp -6)/deg C, respectively from room temperature to 1200 C. The hot pressed BSAS-1 celsian showed room temperature flexural strength of 131 MPa, elastic modulus of 96 GPa and was stable in air up to temperatures as high as approx. 1500 C.
Form, symmetry and packing of biomacromolecules. II. Serotypes of human rhinovirus
Janner, A.
2010-05-01
The differentiation of the human rhinovirus into serotypes, all having very similar structures and the same architecture, is shown to be related to the packing of the viruses in the crystal and to its space-group symmetry.
Attanucci, Frank J.; Losse, John
2008-01-01
In a first calculus course, it is not unusual for students to encounter the theorems which state: If f is an even (odd) differentiable function, then its derivative is odd (even). In our paper, we prove some theorems which show how the symmetry of a continuous function f with respect to (i) the vertical line: x = a or (ii) with respect to the…
Bis(1,3-dimethyl-1H-imidazolium hexafluorosilicate: the second monoclinic polymorph
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Maxim V. Borzov
2013-08-01
Full Text Available The title compound, 2C5H9N2+·SiF62−, (I, crystallized as a new polymorph, different from the previously reported one (Ia [Light et al. (2007 private communication (refcode: NIQFAV. CCDC, Cambridge, England]. The symmetry [space groups P21/n for (I and C2/c for(Ia] and crystal packing patterns are markedly different for this pair of polymorphs. In (I, all imidazolium cations in the lattice are nearly parallel to each other, whereas a herringbone arrangement can be found in (Ia. In (I, each SiF62– dianion forms four short C—H...F contacts with adjacent C5H9N2+ cations, resulting in the formation of layers parallel to the ac plane. In (Ia, the C—H...F contacts are generally longer and result in the formation of layers along the bc plane.
Development of Symmetry Concepts for Aperiodic Crystals
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Ted Janssen
2014-03-01
Full Text Available An overview is given of the use of symmetry considerations for aperiodic crystals. Superspace groups were introduced in the seventies for the description of incommensurate modulated phases with one modulation vector. Later, these groups were also used for quasi-periodic crystals of arbitrary rank. Further extensions use time reversal and time translation operations on magnetic and electrodynamic systems. An alternative description of magnetic structures to that with symmetry groups, the Shubnikov groups, is using representations of space groups. The same can be done for aperiodic crystals. A discussion of the relation between the two approaches is given. Representations of space groups and superspace groups play a role in the study of physical properties. These, and generalizations of them, are discussed for aperiodic crystals. They are used, in particular, for the characterization of phase transitions between aperiodic crystal phases.
Symmetry, Symmetry Breaking and Topology
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Siddhartha Sen
2010-07-01
Full Text Available The ground state of a system with symmetry can be described by a group G. This symmetry group G can be discrete or continuous. Thus for a crystal G is a finite group while for the vacuum state of a grand unified theory G is a continuous Lie group. The ground state symmetry described by G can change spontaneously from G to one of its subgroups H as the external parameters of the system are modified. Such a macroscopic change of the ground state symmetry of a system from G to H correspond to a “phase transition”. Such phase transitions have been extensively studied within a framework due to Landau. A vast range of systems can be described using Landau’s approach, however there are also systems where the framework does not work. Recently there has been growing interest in looking at such non-Landau type of phase transitions. For instance there are several “quantum phase transitions” that are not of the Landau type. In this short review we first describe a refined version of Landau’s approach in which topological ideas are used together with group theory. The combined use of group theory and topological arguments allows us to determine selection rule which forbid transitions from G to certain of its subgroups. We end by making a few brief remarks about non-Landau type of phase transition.
Zakaria, Choudhury M; Ferguson, George; Lough, Alan J; Glidewell, Christopher
2003-07-01
Hexamethylenetetramine, C(6)H(12)N(4), and ferrocenecarboxylic acid, C(11)H(10)FeO(2), form a 1:2 adduct, (I), which is a salt, viz. hexamethylenetetraminium(2+) bis(ferrocenecarboxylate), (C(6)H(14)N(4))[Fe(C(5)H(5))(C(6)H(4)O(2))](2). The dication in (I) is disordered with two orientations at a site of mm2 symmetry in space group Fmm2, while the anion lies across a mirror plane with its unsubstituted cyclopentadienyl ring disordered over two sets of sites. With ferrocene-1,1'-dicarboxylic acid, C(12)H(10)FeO(4), hexamethylenetetramine forms a 1:1 adduct, (II), in which both components are neutral, viz. hexamethylenetetramine-ferrocene-1,1'-dicarboxylic acid (1/1), [Fe(C(6)H(5)O(2))(2)].C(6)H(12)N(4). The amine component in (II) is disordered with two orientations at a site of mm2 symmetry in space group Cmcm, while the acid component is disordered with two orientations at a site of 2/m symmetry. The components in (I) are linked into a finite three-ion aggregate by a single N-H.O hydrogen bond, while the components of (II) are linked into continuous chains by a single O-H.N hydrogen bond.
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Xin Gui
2017-07-01
Full Text Available A new 122-type phase, monoclinic BaIr2Ge2 is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr2Ge2 adopts a clathrate-like channel framework structure of the monoclinic BaRh2Si2-type, with space group P21/c. Structural comparisons of clathrate, ThCr2Si2, CaBe2Ge2, and BaRh2Si2 structure types indicate that BaIr2Ge2 can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr2Ge2 displays a metallic resistivity. Electronic structure calculations performed for BaIr2Ge2 support its observed structural stability and physical properties.
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Kirstin Peters
2010-11-01
Full Text Available A well-known result by Palamidessi tells us that πmix (the π-calculus with mixed choice is more expressive than πsep (its subset with only separate choice. The proof of this result argues with their different expressive power concerning leader election in symmetric networks. Later on, Gorla offered an arguably simpler proof that, instead of leader election in symmetric networks, employed the reducibility of incestual processes (mixed choices that include both enabled senders and receivers for the same channel when running two copies in parallel. In both proofs, the role of breaking (initial symmetries is more or less apparent. In this paper, we shed more light on this role by re-proving the above result - based on a proper formalization of what it means to break symmetries without referring to another layer of the distinguishing problem domain of leader election. Both Palamidessi and Gorla rephrased their results by stating that there is no uniform and reasonable encoding from πmix into πsep. We indicate how the respective proofs can be adapted and exhibit the consequences of varying notions of uniformity and reasonableness. In each case, the ability to break initial symmetries turns out to be essential.
The structure of the linear anisotropic elastic symmetries
Cowin, S. C.; Mehrabadi, M. M.
1992-10-01
AN INSIGHTFUL, STRUCTURALLY appealing and potentially utilitarian formulation of the anisotropic form of the linear Hooke's law due to Lord Kelvin was independently rediscovered by R YCHLEWSKI (1984, Prikl. Mat. Mekh.48, 303) and M EHRABADI and C OWIN (1990, Q. J. Mech. appl. Math.43, 14). The eigenvectors of the three-dimensional fourth-rank anisotropic elasticity tensor, considered as a second-rank tensor in six-dimensional space, are called eigentensors when projected back into three-dimensional space. The maximum number of eigentensors for any elastic symmetry is therefore six. The concept of an eigentensor was introduced by K ELVIN (1856, Phil. Trans. R. Soc.166, 481) who called eigentensors "the principal types of stress or of strain". Kelvin determined the eigentensors for many elastic symmetries and gave a concise summary of his results in the 9th edition of the Encyclopaedia Britannica (1878). The eigentensors for a linear isotropic elastic material are familiar. They are the deviatoric second-rank tensor and a tensor proportional to the unit tensor, the spherical, hydrostatic or dilatational part of the tensor. M EHRABADI and C OWIN (1990, Q. J. Mech. appl. Math.43, 14) give explicit forms of the eigentensors for all of the linear elastic symmetries except monoclinic and triclinic symmetry. We discuss two approaches for the determination of eigentensors and illustrate these approaches by partially determining the eigentensors for monoclinic symmetry. With the nature of the eigentensors for monoclinic symmetry known, a rather complete table of the structural properties of all linear elastic symmetries can be constructed. The purpose of this communication is to give the most specifically detailed presentation of the eigenvalues and eigentensors of the Kelvin formulation to date.
Synthesis and characterization of monoclinic TiO2 nanosheets
Institute of Scientific and Technical Information of China (English)
WU Yu; XU Boqing
2005-01-01
A novel two-step method for the synthesis of monoclinic titanium oxide (i.e. TiO2(B)) nanosheets is presented in this report. The method is featured by two steps: 1) synthesis of hydrogen titanate nanosheets, followed by 2) calcination of the titanate nanosheets at elevated temperatures. The hydrogen titanate nanosheets were prepared first by autoclaving anatase TiO2 powders, obtained by air calcining an ethanol-gel of Ti(OH)4 at 500℃, in aqueous NaOH (10 mol/L) at 150―200℃, and then by washing with hydrochloric acid under supersonic irradiation. While sizes of the nanosheets were found to increase with increasing the temperature of the hydrothermal treatment, the calcination at 400―500℃ of the hydrogen titanate nanosheets that were synthesized at higher autoclaving temperatures (180―200℃) produced monoclinic TiO2 nanosheets with a uniform morphology. By contrast, the same calcination of the titanate nanosheets synthesized at the autoclaving temperature 180℃ led to anatase TiO2 nanoparticles.
2,3-Dibromo-3-phenylpropanoic acid: a monoclinic polymorph
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Trent R. Howard
2016-11-01
Full Text Available Bromination of trans-cinnamic acid resulted in the formation of 2,3-dibromo-3-phenylpropanoic acid, C9H8Br2O2. Crystallization from ethanol–water (1:1 gave crystals of different shapes. One is in the form of rods, that crystallized as the orthorhombic polymorph (Pnma, and whose structure has been described [Thong et al. (2008. Acta Cryst. E64, o1946]. The other are thin plate-like crystals which are the monoclinic polymorph (P21/n. The structure of this monoclinic polymorph is similar to that of the orthorhombic polymorph; here the aliphatic C atoms are disordered over three sets of sites (occupancy ratio 0.5:0.25:0.25. In the crystal, molecules are linked by pairs of O—H...O hydrogen bonds, forming inversion dimers with an R22(8 ring motif. The dimers are linked by weak C—H...Br hydrogen bonds, forming chains propagating along the a-axis direction.
Dynamic Heterogeneity In The Monoclinic Phase Of CCl$_4$
Caballero, Nirvana B; Carignano, Marcelo; Serra, Pablo
2016-01-01
Carbon tetrachloride (CCl$_4$) is one of the simplest compounds having a translationally stable monoclinic phase while exhibiting a rich rotational dynamics below 226 K. Recent nuclear quadrupolar resonance (NQR) experiments revealed that the dynamics of CCl$_4$ is similar to that of the other members of the isostructural series CBr$_{n}$Cl$_{4-n}$, suggesting that the universal relaxation features of canonical glasses such as $\\alpha$- and $\\beta$-relaxation are also present in non-glass formers. Using molecular dynamics (MD) simulations we studied the rotational dynamics in the monoclinic phase of CCl$_4$. The molecules undergo $C3$ type jump-like rotations around each one of the four C-Cl bonds. The rotational dynamics is very well described with a master equation using as the only input the rotational rates measured from the simulated trajectories. It is found that the heterogeneous dynamics emerges from faster and slower modes associated with different rotational axes, which have fixed orientations relat...
Crystallographic interpretation of Galois symmetries for magnetic pentagonal ring
Milewski, J.; Lulek, T.; Łabuz, M.
2017-03-01
Galois symmetry of exact Bethe Ansatz eigenstates for the magnetic pentagonal ring within the XXX model are investigated by a comparison with crystallographic constructions of space groups. It follows that the arithmetic symmetry of Bethe parameters for the interior of the Brillouin zone admits crystallographic interpretation, in terms of the periodic square Z2 ×Z2 , that is the two-dimensional crystal lattice with Born-Karman period two in both directions.
On the finite-dimensional PUA representations of the Shubnikov space groups
Broek, van den P.M.
1977-01-01
The finite-dimensional PUA epresentations of the Shubnikov space groups are discussed using the method of generalised induction given by Shaw and Lever. In particular we derive expressions for the calculation of the little groups.
Elastic and vibrational properties of monoclinic HfO2 from first-principles study
Wu, Rui; Zhou, Bo; Li, Qian; Jiang, ZhenYi; Wang, WenBo; Ma, WenYan; Zhang, XiaoDong
2012-03-01
The elastic and vibrational properties of crystalline monoclinic HfO2 have been investigated using density functional perturbation theory. Using the Voigt and Reuss theory, we estimate the bulk, shear and Young's modulus for polycrystalline HfO2, which agree very well with the available experimental and theoretical data. Additionally, we present a systematic analysis of the elastic properties of HfO2 polymorphs and find the trends in the elastic parameters for the HfO2 structures are consistent with those for the ZrO2 structures. The choice of exchange-correlation functional has an important effect on the results of elastic and vibrational properties. The utilization of Hartwigzen-Goedecker-Hutter type functional is a great improvement on calculation of the zone-centre phonon frequencies, and shows the root-mean-square absolute deviation of 7 cm-1 with experiments. A rigorous assignment of all the Raman modes is achieved by combining symmetry analysis with the first-principles calculations, which helps us to identify the main peak and some other features of Raman spectra. Furthermore, the Raman spectrum of HfO2 powder has been simulated for the first time, providing a theoretical benchmark for the interpretation of the unresolved problems in experimental studies.
Peters, Kirstin
2010-01-01
A well-known result by Palamidessi tells us that {\\pi}mix (the {\\pi}-calculus with mixed choice) is more expressive than {\\pi}sep (its subset with only separate choice). The proof of this result argues with their different expressive power concerning leader election in symmetric networks. Later on, Gorla of- fered an arguably simpler proof that, instead of leader election in symmetric networks, employed the reducibility of "incestual" processes (mixed choices that include both enabled senders and receivers for the same channel) when running two copies in parallel. In both proofs, the role of breaking (ini- tial) symmetries is more or less apparent. In this paper, we shed more light on this role by re-proving the above result-based on a proper formalization of what it means to break symmetries-without referring to another layer of the distinguishing problem domain of leader election. Both Palamidessi and Gorla rephrased their results by stating that there is no uniform and reason- able encoding from {\\pi}mix i...
Peters, Kirstin; 10.4204/EPTCS.41.10
2010-01-01
A well-known result by Palamidessi tells us that \\pimix (the \\pi-calculus with mixed choice) is more expressive than \\pisep (its subset with only separate choice). The proof of this result argues with their different expressive power concerning leader election in symmetric networks. Later on, Gorla offered an arguably simpler proof that, instead of leader election in symmetric networks, employed the reducibility of incestual processes (mixed choices that include both enabled senders and receivers for the same channel) when running two copies in parallel. In both proofs, the role of breaking (initial) symmetries is more or less apparent. In this paper, we shed more light on this role by re-proving the above result - based on a proper formalization of what it means to break symmetries without referring to another layer of the distinguishing problem domain of leader election. Both Palamidessi and Gorla rephrased their results by stating that there is no uniform and reasonable encoding from \\pimix into \\pisep. We...
Energy Technology Data Exchange (ETDEWEB)
Iturbe-Zabalo, E., E-mail: iturbe@ill.fr [Institut Laue-Langevin (ILL), 6 rue Jules Horowitz, BP156, 38042 Grenoble Cedex 9 (France); Fisika Aplikatua II Saila, Zientzia eta Teknologia Fakultatea, UPV/EHU, P.O. Box 644, 48080 Bilbao (Spain); Igartua, J.M. [Fisika Aplikatua II Saila, Zientzia eta Teknologia Fakultatea, UPV/EHU, P.O. Box 644, 48080 Bilbao (Spain); Faik, A. [CICEnergigune, Parque Tecnologico, Albert Einstein 48, 01510 Minano, Alava (Spain); Larranaga, A. [X-Izpien Zerbitzu Orokorra, SGIKer, UPV/EHU, P.O. Box 644, 48080 Bilbao (Spain); Hoelzel, M. [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TUM, 85747 Garching (Germany); Cuello, G.J. [Institut Laue-Langevin (ILL), 6 rue Jules Horowitz, BP156, 38042 Grenoble Cedex 9 (France)
2013-02-15
Crystal structures of SrNdZnRuO{sub 6}, SrNdCoRuO{sub 6}, SrNdMgRuO{sub 6} and SrNdNiRuO{sub 6} double perovskites have been studied by X-ray, synchrotron radiation and neutron powder diffraction method, at different temperatures, and using the symmetry-mode analysis. All compounds adopt the monoclinic space group P2{sub 1}/n at room-temperature, and contain a completely ordered array of the tilted MO{sub 6} and RuO{sub 6} octahedra, whereas Sr/Nd cations are completely disordered. The analysis of the structures in terms of symmetry-adapted modes of the parent phase allows the identification of the modes responsible for the phase-transition. The high-temperature study (300-1250 K) has shown that the compounds present a temperature induced structural phase-transition: P2{sub 1}/n{yields}P4{sub 2}/n{yields}Fm3{sup Macron }m. - Graphical abstract: Representation of the dominant distortion modes of the symmetry mode decomposition of the room-temperature (P2{sub 1}/n), intermediate (P4{sub 2}/n) and cubic (Fm-3m) phase SrNdMRuO{sub 6} (M=Zn,Co,Mg,Ni), with respect to the parent phase Fm-3m. The dominant distortion modes are: in the monoclinic phase-GM{sub 4}{sup +} (blue arrow), X{sub 3}{sup +} (green arrow) and X{sub 5}{sup +} acting on A-site cations (red arrow); in the tetragonal phase-GM{sub 4}{sup +} (pink arrow), X{sub 3}{sup +} (light blue arrow) and X{sub 5}{sup +} acting on A-site cations (brown arrow). Highlights: Black-Right-Pointing-Pointer Structural study of four ruthenate double perovskites. Black-Right-Pointing-Pointer Room-temperature structural determination using symmetry-mode procedure. Black-Right-Pointing-Pointer Determination of temperature induced structural phase-transitions. Black-Right-Pointing-Pointer Symmetry adapted-mode analysis.
A monoclinic polymorph of 1,2-bis[(1-methyl-1H-tetrazol-5-ylsulfanyl]ethane (BMTTE
Directory of Open Access Journals (Sweden)
Saray Argibay-Otero
2017-10-01
Full Text Available The synthesis and crystal structure of a monoclinic (P21/c polymorph of the title compound, C6H10S2N8, are reported. The molecule has pseudo-twofold rotational symmetry, with the tetrazole rings being inclined to one another by 5.50 (6°. In the crystal, molecules are linked by C—H...N hydrogen bonds, forming chains propagating along [101] and enclosing R22(20 ring motifs. The chains are linked by offset π–π interactions involving the tetrazole rings [intercentroid distances vary from 3.3567 (7 to 3.4227 (7 Å], forming layers parallel to the ac plane. The crystal structure of the triclinic polymorph (P\\overline{1} has been described previously [Li et al. (2011. Acta Cryst. E67, o1669].
A monoclinic polymorph of 2-(4-nitrophenylacetic acid
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Alan R. Kennedy
2016-12-01
Full Text Available A new monoclinic form of 4-nitrophenylacetic acid, C8H7NO4, (I, differs from the known orthorhombic form both in its molecular conformation and in its intermolecular contacts. The conformation is different as the plane of the carboxylic acid group in (I is more nearly perpendicular to the plane of the aromatic ring [dihedral angle = 86.9 (3°] than in the previous form (74.5°. Both polymorphs display hydrogen-bonded R22(8 carboxylic acid dimeric pairs, but in (I, neighbouring dimers interact through nitro–nitro N...O dipole–dipole contacts rather than the nitro–carbonyl contacts found in the orthorhombic form.
A Simple Approach for Synthesis of TAPO-11 Molecular Sieve with Controllable Space Group
Institute of Scientific and Technical Information of China (English)
Yue Ming LIU; Huan Yan ZHANG; Hai Jiao ZHANG; Hai Hong WU; Peng WU; Ming Yuan HE
2006-01-01
A TAPO-11 molecular sieve with the space group Icm2 was synthesized successfully.The samples with different space group were controlled simply only by adjusting the crystallization temperature (CT) in the hydrothermal system. In the system of gel with a molar composition of 0.7R: xTiO2: P2O5: Al2O3: 30H2O, where x is 0.01-0.10 and the R is a mixture of di-n-propylamine and diisopropylamine as templates. When CT was between 150-160℃, the calcined sample showed the space group of Icm2, while it showed Pna21 at CTlarger than 190℃.The characterizations of UV-Vis and FT-IR confirmed that Ti was incorporated into the AEL framework successfully.
CP and other Symmetries of Symmetries
Trautner, Andreas
2016-01-01
Outer automorphisms of symmetries ("symmetries of symmetries") in relativistic quantum field theories are studied, including charge conjugation (C), space-reflection (P) , and time-reversal (T) transformations. The group theory of outer automorphisms is pedagogically introduced and it is shown that CP transformations are special outer automorphisms of the global, local, and space-time symmetries of a theory. It is shown that certain discrete groups allow for a group theoretical prediction of parameter independent CP violating complex phases with fixed geometrical values. The remainder of this thesis pioneers the study of outer automorphisms which are not related to C, P, or T. It is shown how outer automorphisms, in general, relate symmetry invariants and, in theories with spontaneous symmetry breaking, imply relations between different vacuum expectation values. Thereby, outer automorphisms can give rise to emergent symmetries. An example model with a discrete symmetry and three copies of the Standard Model ...
Energy Technology Data Exchange (ETDEWEB)
Henley, E.M.
1981-09-01
Internal and space-time symmetries are discussed in this group of lectures. The first of the lectures deals with an internal symmetry, or rather two related symmetries called charge independence and charge symmetry. The next two discuss space-time symmetries which also hold approximately, but are broken only by the weak forces; that is, these symmetries hold for both the hadronic and electromagnetic forces. (GHT)
Symmetry and symmetry breaking in particle physics
Tsou, ST
1998-01-01
Symmetry, in particular gauge symmetry, is a fundamental principle in theoretical physics. It is intimately connected to the geometry of fibre bundles. A refinement to the gauge principle, known as ``spontaneous symmetry breaking'', leads to one of the most successful theories in modern particle physics. In this short talk, I shall try to give a taste of this beautiful and exciting concept.
Dispersion of Love Waves in a Composite Layer Resting on Monoclinic Half-Space
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Sukumar Saha
2011-01-01
Full Text Available Dispersion of Love waves is studied in a fibre-reinforced layer resting on monoclinic half-space. The wave velocity equation has been obtained for a fiber-reinforced layer resting on monoclinic half space. Shear wave velocity ratio curve for Love waves has been shown graphically for fibre reinforced material layer resting on various monoclinic half-spaces. In a similar way, shear wave velocity ratio curve for Love waves has been plotted for an isotropic layer resting on various monoclinic half-spaces. From these curves, it has been observed that the curves are of similar type for a fibre reinforced layer resting on monoclinic half-spaces, and the shear wave velocity ratio ranges from 1.14 to 7.19, whereas for the case isotropic layer, this range varies from 1.0 to 2.19.
Phatak, Rohan; Gupta, Santosh K; Maheshwari, Priya; Das, Amitabh; Sali, Sanjay K
2017-01-31
A one-third lanthanum deficiency was created in Ba2LaM(5+)O6 compounds (LaM compounds) to form Ba2La2/3M(5+)O5.5 compounds (La2/3M compounds) for M = Nb, Sb, and Bi. The compounds were prepared by a gel-combustion method using citric acid as a fuel. All the compounds were characterized by powder X-ray diffraction (XRD). The XRD analysis showed that the space group of the La2/3M compounds remains the same for the Bi and Sb samples when compared to the reported LaM compounds, except for the Nb sample. La2/3Nb and La2/3Sb adopt a rhombohedral structure with the space group R3[combining macron], whereas La2/3Bi adopts a monoclinic structure with the space group I2/m. As the positron annihilation spectroscopy (PALS) technique is sensitive to cation deficiency, it was used to detect the presence of cation vacancies in the samples, which are formed due to the decrease in the lanthanum concentration. The PALS analyses indicated that the absence of cation deficiency in the La2/3M compounds is similar to that observed in the LaM compound. Thus, the crystal structure of the La2/3M compound was modeled, such that the cation deficiency at the La site is filled by Ba(2+) and M(5+) ions, and the crystal structure formula is given as Ba2(La0.727Ba0.182M0.091)MO6. This model was confirmed by Rietveld refinement of the XRD data. The emission spectra of Eu(3+) showed a strong dependence on its local site symmetry in the host material, in which it is being doped and this can be used as a spectroscopic probe for detecting any differences in the symmetry. Comparison of the local symmetry around La(3+) cation was studied using photoluminescence (PL) by doping 2 atom% Eu(3+) in LaM and La2/3M compounds. Infrared spectroscopy (IRS) analyses were also carried out for LaM and La2/3M compounds. There was complete agreement between the PL and IRS results and they were also in concordance with the predicted crystal structure model. Interestingly in these La2/3M compounds, the equilibrium
Proton ordering in tetragonal and monoclinic H2O ice
Yen, Fei; Berlie, Adam; Liu, Xiaodi; Goncharov, Alexander F
2015-01-01
H2O ice remains one of the most enigmatic materials as its phase diagram reveals up to sixteen solid phases. While the crystal structure of these phases has been determined, the phase boundaries and mechanisms of formation of the proton-ordered phases remain unclear. From high precision measurements of the complex dielectric constant, we probe directly the degree of ordering of the protons in H2O tetragonal ice III and monoclinic ice V down to 80 K. A broadened first-order phase transition is found to occur near 202 K we attribute to a quenched disorder of the protons which causes a continuous disordering of the protons during cooling and metastable behavior. At 126 K the protons in ice III become fully ordered, and for the case of ice V becoming fully ordered at 113 K forming ice XIII. Two triple points are proposed to exist: one at 0.35 GPa and 126 K where ices III, IX and V coexist; and another at 0.35 GPa and 113 K where ices V, IX and XIII coexist. Our findings unravel the underlying mechanism driving th...
Growth of orthorhombic and tetragonal modifications of TlInS{sub 2} from its monoclinic phase
Energy Technology Data Exchange (ETDEWEB)
Alekperov, O.Z.; Ibragimov, G.B.; Axundov, I.A.; Nadjafov, A.I.; Fakix, A.R. [Institute of Physics, Azerbaijan National Academy of Sciences, Baku (Azerbaijan)
2009-05-15
Orthorhombic (O) and tetragonal (T) modifications of TlInS{sub 2} were grown by sulfur vapor annealing of monoclinic (M) crystals. Lattice parameters and syngony of the grown crystals were determined from X-ray investigations (Laue, Weissenberg, rocking crystal and powder diffractions). The lattice parameters a =6.88 A, b=14.04 A, c=4.02 A, Z=4 and a=b=7.76 A, c=26.6 A, Z=20 as well as space groups (SG), P2{sub 1}2{sub 1}2{sub 1} and P4{sub 1}2{sub 1}2 were ascribed to O and T modifications, correspondingly. The transition of M-crystals to O- or T-phase takes place through the intermediate disordered state of M-phase in which the unit packets with c{approx}15 A are randomly positioned along the c-axis. From photoconductivity (PC) edge it was found that the band gap of O-TlInS{sub 2} (E{sub g}=2.52{+-}0.01 eV) is slightly higher whereas that of T-TlInS{sub 2} (E{sub g}=1.87{+-}0.01 eV) is noticeably lower than the band gap of M-TlInS{sub 2}. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Jaffé, Hans H
1977-01-01
This book, devoted exclusively to symmetry in chemistry and developed in an essentially nonmathematical way, is a must for students and researchers. Topics include symmetry elements and operations, multiple symmetry operations, multiplication tables and point groups, group theory applications, and crystal symmetry. Extensive appendices provide useful tables.
Lattice Regularization and Symmetries
Hasenfratz, Peter; Von Allmen, R; Allmen, Reto von; Hasenfratz, Peter; Niedermayer, Ferenc
2006-01-01
Finding the relation between the symmetry transformations in the continuum and on the lattice might be a nontrivial task as illustrated by the history of chiral symmetry. Lattice actions induced by a renormalization group procedure inherit all symmetries of the continuum theory. We give a general procedure which gives the corresponding symmetry transformations on the lattice.
Deriving diffeomorphism symmetry
Kleppe, Astri
2014-01-01
In an earlier article, we have "derived" space, as a part of the Random Dynamics project. In order to get locality we need to obtain reparametrization symmetry, or equivalently, diffeomorphism symmetry. There we sketched a procedure for how to get locality by first obtaining reparametrization symmetry, or equivalently, diffeomorphism symmetry. This is the object of the present article.
Energy Technology Data Exchange (ETDEWEB)
Hering, Stefanie A. [Dept. Chemie und Biochemie, Ludwig-Maximilians-Univ. Muenchen (Germany); Huppertz, Hubert [Inst. fuer Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Univ. Innsbruck (Austria)
2009-09-15
Monoclinic holmium sesquioxide B-Ho{sub 2}O{sub 3} and orthorhombic holmium orthogallate HoGaO{sub 3} were synthesized in a Walker-type multianvil apparatus under high-pressure / high-temperature conditions of 11.5 GPa / 1250 C and 7.5 GPa / 1250 C, respectively. Both crystal structures could be determined by single-crystal X-ray diffraction data, collected at r.t. The monoclinic holmium oxide crystallizes in the space group C2/m (Z = 6) with the parameters a = 1394.7(3), b = 350.83(7), c = 865.6(2) pm, {beta} = 100.23(3) . R1 = 0.0517, wR2 = 0.1130 (all data), and the orthorhombic compound HoGaO{sub 3} in Pnma (Z = 4) with the parameters a = 553.0(2), b = 753.6(2), c = 525.4(2) pm. R1 = 0.0222, and wR2 = 0.0303 (all data). (orig.)
Van Isacker, P
2010-01-01
The use of dynamical symmetries or spectrum generating algebras for the solution of the nuclear many-body problem is reviewed. General notions of symmetry and dynamical symmetry in quantum mechanics are introduced and illustrated with simple examples such as the SO(4) symmetry of the hydrogen atom and the isospin symmetry in nuclei. Two nuclear models, the shell model and the interacting boson model, are reviewed with particular emphasis on their use of group-theoretical techniques.
Identification of monoclinic θ-phase dispersoids in a 6061 aluminium alloy
Buchanan, Karl; Ribis, Joël; Garnier, Jérôme; Colas, Kimberly
2016-04-01
Intermetallic dispersoids play an important role in controlling the 6xxx alloy series' grain distribution and increasing the alloy's toughness. The dispersoid distribution in a 6061 aluminium alloy (Al-Mg-Si) was analysed by transmission electron microscopy, selected area diffraction and energy-dispersive X-ray spectroscopy. The dispersoids had three unique crystal structures: simple cubic ?, body-centred cubic ? and monoclinic (C2/m). While the SC and BCC dispersoids have been well characterized in the literature, a detailed analysis of monoclinic dispersoids has not been presented. Therefore, the current work discusses the chemical composition, crystal structure and morphology of the monoclinic dispersoids.
Directory of Open Access Journals (Sweden)
Xiaoyan Lu
2016-10-01
Full Text Available Phase morphology and corresponding piezoelectricity in ferroelectric solid solutions were studied by using a phenomenological theory with the consideration of phase coexistence. Results have shown that phases with similar energy potentials can coexist, thus induce interfacial stresses which lead to the formation of adaptive monoclinic phases. A new tetragonal-like monoclinic to rhombohedral-like monoclinic phase transition was predicted in a shear stress state. Enhanced piezoelectricity can be achieved by manipulating the stress state close to a critical stress field. Phase coexistence is universal in ferroelectric solid solutions and may provide a way to optimize ultra-fine structures and proper stress states to achieve ultrahigh piezoelectricity.
Valset, K; Tafto, J
2011-06-01
We classify the point symmetries at the different points in the Brillouin zone for the 17 two-dimensional space groups and the symmetries of the Bloch waves for the 10 two-dimensional crystallographic point groups. Simple examples involving breakdown of Friedels law, Gjonnes-Moodie lines, and reflection and refraction at interfaces are presented.
Ermolenko, Alexander E; Perepada, Elena A
2007-01-01
The paper contains a description of basic regularities in the manifestation of symmetry of human structural organization and its ontogenetic and phylogenetic development. A concept of macrobiocrystalloid with inherent complex symmetry is proposed for the description of the human organism in its integrity. The symmetry can be characterized as two-plane radial (quadrilateral), where the planar symmetry is predominant while the layout of organs of radial symmetry is subordinated to it. Out of the two planes of symmetry (sagittal and horizontal), the sagittal plane is predominant. The symmetry of the chromosome, of the embrio at the early stages of cell cleavage as well as of some organs and systems in their phylogenetic development is described. An hypothesis is postulated that the two-plane symmetry is formed by two mechanisms: a) the impact of morphogenetic fields of the whole crystalloid organism during embriogenesis and, b) genetic mechanisms of the development of chromosomes having two-plane symmetry.
Bis(1,3-dimethyl-1H-imidazolium) hexa-fluoro-silicate: the second monoclinic polymorph.
Tian, Chong; Nie, Wanli; Borzov, Maxim V
2013-01-01
The title compound, 2C5H9N2 (+)·SiF6 (2-), (I), crystallized as a new polymorph, different from the previously reported one (Ia) [Light et al. (2007 ▶) private communication (refcode: NIQFAV). CCDC, Cambridge, England]. The symmetry [space groups P21/n for (I) and C2/c for(Ia)] and crystal packing patterns are markedly different for this pair of polymorphs. In (I), all imidazolium cations in the lattice are nearly parallel to each other, whereas a herringbone arrangement can be found in (Ia). In (I), each SiF6 (2-) dianion forms four short C-H⋯F contacts with adjacent C5H9N2 (+) cations, resulting in the formation of layers parallel to the ac plane. In (Ia), the C-H⋯F contacts are generally longer and result in the formation of layers along the bc plane.
Shmueli, U; Rabinovich, S; Weiss, G H
1989-06-01
An exact expression is derived for the conditional probability density function of a three-phase invariant and the general result is applied to the space group P1. The expression for the conditional density is given in terms of a sixfold Fourier series. A straightforward numerical evaluation of this series, without further analysis, is extremely time consuming. Much of the present paper is therefore devoted to an exposition of symmetries hidden in the various summations. The computational effort required for the evaluation of the above expression is thereby reduced to manageable proportions in a number of interesting cases. Results of numerical computations of the exact conditional density are given in the second paper in this series. It is also shown that the exact expression for the conditional probability reduces to that given by Cochran [Acta Cryst. (1955), 8, 473-478].
Phase field modeling of tetragonal to monoclinic phase transformation in zirconia
Mamivand, Mahmood
Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for
Energy Technology Data Exchange (ETDEWEB)
Upadhyay, Ashutosh; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)
2015-04-14
Results of the room temperature structural studies on (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} ceramics using Rietveld analysis of the powder x-ray diffraction data in the composition range 0.28 ≤ x ≤ 0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4 mm) phases in the composition range 0.33 ≤ x ≤ 0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28 ≤ x ≤ 0.32. The structure for the compositions with x ≥ 0.45 is found to be predominantly tetragonal with space group P4 mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x = .35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size.
Brading, Katherine; Castellani, Elena
2010-01-01
Preface; Copyright acknowledgements; List of contributors; 1. Introduction; Part I. Continuous Symmetries: 2. Classic texts: extracts from Weyl and Wigner; 3. Review paper: On the significance of continuous symmetry to the foundations of physics C. Martin; 4. The philosophical roots of the gauge principle: Weyl and transcendental phenomenological idealism T. Ryckman; 5. Symmetries and Noether's theorems K. A. Brading and H. R. Brown; 6. General covariance, gauge theories, and the Kretschmann objection J. Norton; 7. The interpretation of gauge symmetry M. Redhead; 8. Tracking down gauge: an ode to the constrained Hamiltonian formalism J. Earman; 9. Time-dependent symmetries: the link between gauge symmetries and indeterminism D. Wallace; 10. A fourth way to the Aharanov-Bohm effect A. Nounou; Part II. Discrete Symmetries: 11. Classic texts: extracts from Lebniz, Kant and Black; 12. Review paper: Understanding permutation symmetry S. French and D. Rickles; 13. Quarticles and the identity of discernibles N. Hugget; 14. Review paper: Handedness, parity violation, and the reality of space O. Pooley; 15. Mirror symmetry: what is it for a relational space to be orientable? N. Huggett; 16. Physics and Leibniz's principles S. Saunders; Part III. Symmetry Breaking: 17: Classic texts: extracts from Curie and Weyl; 18. Extract from G. Jona-Lasinio: Cross-fertilization in theoretical physics: the case of condensed matter and particle physics G. Jona-Lasinio; 19. Review paper: On the meaning of symmetry breaking E. Castellani; 20. Rough guide to spontaneous symmetry breaking J. Earman; 21. Spontaneous symmetry breaking: theoretical arguments and philosophical problems M. Morrison; Part IV. General Interpretative Issues: 22. Classic texts: extracts from Wigner; 23. Symmetry as a guide to superfluous theoretical structure J. Ismael and B. van Fraassen; 24. Notes on symmetries G. Belot; 25. Symmetry, objectivity, and design P. Kosso; 26. Symmetry and equivalence E. Castellani.
Rašin, Andrija
1994-01-01
We discuss the idea of approximate flavor symmetries. Relations between approximate flavor symmetries and natural flavor conservation and democracy models is explored. Implications for neutrino physics are also discussed.
Directory of Open Access Journals (Sweden)
Joe Rosen
2005-12-01
Full Text Available Abstract: The symmetry principle is described in this paper. The full details are given in the book: J. Rosen, Symmetry in Science: An Introduction to the General Theory (Springer-Verlag, New York, 1995.
Energy Technology Data Exchange (ETDEWEB)
Nilles, Hans Peter [Bonn Univ. (Germany). Bethe Center for Theoretical Physics; Bonn Univ. (Germany). Physikalisches Inst.; Ratz, Michael [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-04-15
Discrete (family) symmetries might play an important role in models of elementary particle physics. We discuss the origin of such symmetries in the framework of consistent ultraviolet completions of the standard model in field and string theory. The symmetries can arise due to special geometrical properties of extra compact dimensions and the localization of fields in this geometrical landscape. We also comment on anomaly constraints for discrete symmetries.
Neutrinos and flavor symmetries
Tanimoto, Morimitsu
2015-07-01
We discuss the recent progress of flavor models with the non-Abelian discrete symmetry in the lepton sector focusing on the θ13 and CP violating phase. In both direct approach and indirect approach of the flavor symmetry, the non-vanishing θ13 is predictable. The flavor symmetry with the generalised CP symmetry can also predicts the CP violating phase. We show the phenomenological analyses of neutrino mixing for the typical flavor models.
Neutrinos and flavor symmetries
Energy Technology Data Exchange (ETDEWEB)
Tanimoto, Morimitsu
2015-07-15
We discuss the recent progress of flavor models with the non-Abelian discrete symmetry in the lepton sector focusing on the θ{sub 13} and CP violating phase. In both direct approach and indirect approach of the flavor symmetry, the non-vanishing θ{sub 13} is predictable. The flavor symmetry with the generalised CP symmetry can also predicts the CP violating phase. We show the phenomenological analyses of neutrino mixing for the typical flavor models.
Symmetry and physical properties of crystals
Malgrange, Cécile; Schlenker, Michel
2014-01-01
Crystals are everywhere, from natural crystals (minerals) through the semiconductors and magnetic materials in electronic devices and computers or piezoelectric resonators at the heart of our quartz watches to electro-optical devices. Understanding them in depth is essential both for pure research and for their applications. This book provides a clear, thorough presentation of their symmetry, both at the microscopic space-group level and the macroscopic point-group level. The implications of the symmetry of crystals for their physical properties are then presented, together with their mathematical description in terms of tensors. The conditions on the symmetry of a crystal for a given property to exist then become clear, as does the symmetry of the property. The geometrical representation of tensor quantities or properties is presented, and its use in determining important relationships emphasized. An original feature of this book is that most chapters include exercises with complete solutions. This all...
Polynomial Graphs and Symmetry
Goehle, Geoff; Kobayashi, Mitsuo
2013-01-01
Most quadratic functions are not even, but every parabola has symmetry with respect to some vertical line. Similarly, every cubic has rotational symmetry with respect to some point, though most cubics are not odd. We show that every polynomial has at most one point of symmetry and give conditions under which the polynomial has rotational or…
Polynomial Graphs and Symmetry
Goehle, Geoff; Kobayashi, Mitsuo
2013-01-01
Most quadratic functions are not even, but every parabola has symmetry with respect to some vertical line. Similarly, every cubic has rotational symmetry with respect to some point, though most cubics are not odd. We show that every polynomial has at most one point of symmetry and give conditions under which the polynomial has rotational or…
Chiral symmetry and chiral-symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Peskin, M.E.
1982-12-01
These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)
Bouwknegt, P G
1995-01-01
W-symmetry is an extension of conformal symmetry in two dimensions. Since its introduction in 1985, W-symmetry has become one of the central notions in the study of two-dimensional conformal field theory. The mathematical structures that underlie W-symmetry are so-called W-algebras, which are higher-spin extensions of the Virasoro algebra. This book contains a collection of papers on W-symmetry, covering the period from 1985 through 1993. Its main focus is the construction of W-algebras and their representation theory. A recurrent theme is the intimate connection between W-algebras and affine
Post-patterning of an electronic homojunction in atomically thin monoclinic MoTe2
Kim, Sera; Kim, Jung Ho; Kim, Dohyun; Hwang, Geunwoo; Baik, Jaeyoon; Yang, Heejun; Cho, Suyeon
2017-06-01
Monoclinic group 6 transition metal dichalcogenides (TMDs) have been extensively studied for their intriguing 2D physics (e.g. spin Hall insulator) as well as for ohmic homojunction contacts in 2D device applications. A critical prerequisite for those applications is thickness control of the monoclinic 2D materials, which allows subtle engineering of the topological states or electronic bandgaps. Local thickness control enables the realization of clean homojunctions between different electronic states, and novel device operation in a single material. However, conventional fabrication processes, including chemical methods, typically produce non-homogeneous and relatively thick monoclinic TMDs, due to their distorted octahedral structures. Here, we report on a post-patterning technique using laser-irradiation to fabricate homojunctions between two different thickness areas in monoclinic MoTe2. A thickness-dependent electronic change from a metallic to semiconducting state, resulting in an electronic homojunction, was realized by the optical patterning of pristine MoTe2 flakes, and a pre-patterned device channel of monoclinic MoTe2 with a thickness-resolution of 5 nm. Our work provides insight on an optical post-process method for controlling thickness, as a promising approach for fabricating impurity-free 2D TMDs homojunction devices.
ON THE NOETHER SYMMETRY AND LIE SYMMETRY OF MECHANICAL SYSTEMS
Institute of Scientific and Technical Information of China (English)
梅凤翔; 郑改华
2002-01-01
The Noether symmetry is an invariance of Hamilton action under infinitesimal transformations of time and the coordinates. The Lie symmetry is an invariance of the differential equations of motion under the transformations. In this paper, the relation between these two symmetries is proved definitely and firstly for mechanical systems. The results indicate that all the Noether symmetries are Lie symmetries for Lagrangian systems meanwhile a Noether symmetry is a Lie symmetry for the general holonomic or nonholonomic systems provided that some conditions hold.
From physical symmetries to emergent gauge symmetries
Energy Technology Data Exchange (ETDEWEB)
Barceló, Carlos [Instituto de Astrofísica de Andalucía (IAA-CSIC),Glorieta de la Astronomía, 18008 Granada (Spain); Carballo-Rubio, Raúl [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Laboratory for Quantum Gravity & Strings,Department of Mathematics & Applied Mathematics, University of Cape Town,Private Bag, Rondebosch 7701 (South Africa); Di Filippo, Francesco [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Dipartamento di Scienze Fisiche “E.R. Caianiello”, Università di Salerno,I-84081 Fisciano (Italy); Garay, Luis J. [Departamento de Física Teórica II, Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Estructura de la Materia (IEM-CSIC), Serrano 121, 28006 Madrid (Spain)
2016-10-17
Gauge symmetries indicate redundancies in the description of the relevant degrees of freedom of a given field theory and restrict the nature of observable quantities. One of the problems faced by emergent theories of relativistic fields is to understand how gauge symmetries can show up in systems that contain no trace of these symmetries at a more fundamental level. In this paper we start a systematic study aimed to establish a satisfactory mathematical and physical picture of this issue, dealing first with abelian field theories. We discuss how the trivialization, due to the decoupling and lack of excitation of some degrees of freedom, of the Noether currents associated with physical symmetries leads to emergent gauge symmetries in specific situations. An example of a relativistic field theory of a vector field is worked out in detail in order to make explicit how this mechanism works and to clarify the physics behind it. The interplay of these ideas with well-known results of importance to the emergent gravity program, such as the Weinberg-Witten theorem, are discussed.
From physical symmetries to emergent gauge symmetries
Barceló, Carlos; Carballo-Rubio, Raúl; Di Filippo, Francesco; Garay, Luis J.
2016-10-01
Gauge symmetries indicate redundancies in the description of the relevant degrees of freedom of a given field theory and restrict the nature of observable quantities. One of the problems faced by emergent theories of relativistic fields is to understand how gauge symmetries can show up in systems that contain no trace of these symmetries at a more fundamental level. In this paper we start a systematic study aimed to establish a satisfactory mathematical and physical picture of this issue, dealing first with abelian field theories. We discuss how the trivialization, due to the decoupling and lack of excitation of some degrees of freedom, of the Noether currents associated with physical symmetries leads to emergent gauge symmetries in specific situations. An example of a relativistic field theory of a vector field is worked out in detail in order to make explicit how this mechanism works and to clarify the physics behind it. The interplay of these ideas with well-known results of importance to the emergent gravity program, such as the Weinberg-Witten theorem, are discussed.
From physical symmetries to emergent gauge symmetries
Barceló, Carlos; Di Filippo, Francesco; Garay, Luis J
2016-01-01
Gauge symmetries indicate redundancies in the description of the relevant degrees of freedom of a given field theory and restrict the nature of observable quantities. One of the problems faced by emergent theories of relativistic fields is to understand how gauge symmetries can show up in systems that contain no trace of these symmetries at a more fundamental level. In this paper we start a systematic study aimed to establish a satisfactory mathematical and physical picture of this issue, dealing first with abelian field theories. We discuss how the trivialization, due to the decoupling and lack of excitation of some degrees of freedom, of the Noether currents associated with physical symmetries leads to emergent gauge symmetries in specific situations. An example of a relativistic field theory of a vector field is worked out in detail in order to make explicit how this mechanism works and to clarify the physics behind it. The interplay of these ideas with well-known results of importance to the emergent grav...
Optimization leads to symmetry
Institute of Scientific and Technical Information of China (English)
Chenghong WANG; Yuqian GUO; Daizhan CHENG
2004-01-01
The science of complexity studies the behavior and properties of complex systems in nature and human society.Particular interest has been put on their certain simple common properties.Symmetry is one of such properties.Symmetric phenomena can be found in many complex systems.The purpose of this paper is to reveal the internal reason of the symmetry.Using some physical systems and geometric objects,the paper shows that many symmetries are caused by optimization under certain criteria.It has also been revealed that an evolutional process may lead to symmetry.
Approximate and renormgroup symmetries
Energy Technology Data Exchange (ETDEWEB)
Ibragimov, Nail H. [Blekinge Institute of Technology, Karlskrona (Sweden). Dept. of Mathematics Science; Kovalev, Vladimir F. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Mathematical Modeling
2009-07-01
''Approximate and Renormgroup Symmetries'' deals with approximate transformation groups, symmetries of integro-differential equations and renormgroup symmetries. It includes a concise and self-contained introduction to basic concepts and methods of Lie group analysis, and provides an easy-to-follow introduction to the theory of approximate transformation groups and symmetries of integro-differential equations. The book is designed for specialists in nonlinear physics - mathematicians and non-mathematicians - interested in methods of applied group analysis for investigating nonlinear problems in physical science and engineering. (orig.)
Symmetries in atmospheric sciences
Bihlo, Alexander
2009-01-01
Selected applications of symmetry methods in the atmospheric sciences are reviewed briefly. In particular, focus is put on the utilisation of the classical Lie symmetry approach to derive classes of exact solutions from atmospheric models. This is illustrated with the barotropic vorticity equation. Moreover, the possibility for construction of partially-invariant solutions is discussed for this model. A further point is a discussion of using symmetries for relating different classes of differential equations. This is illustrated with the spherical and the potential vorticity equation. Finally, discrete symmetries are used to derive the minimal finite-mode version of the vorticity equation first discussed by E. Lorenz (1960) in a sound mathematical fashion.
Complete theory of symmetry-based indicators of band topology.
Po, Hoi Chun; Vishwanath, Ashvin; Watanabe, Haruki
2017-06-30
The interplay between symmetry and topology leads to a rich variety of electronic topological phases, protecting states such as the topological insulators and Dirac semimetals. Previous results, like the Fu-Kane parity criterion for inversion-symmetric topological insulators, demonstrate that symmetry labels can sometimes unambiguously indicate underlying band topology. Here we develop a systematic approach to expose all such symmetry-based indicators of band topology in all the 230 space groups. This is achieved by first developing an efficient way to represent band structures in terms of elementary basis states, and then isolating the topological ones by removing the subset of atomic insulators, defined by the existence of localized symmetric Wannier functions. Aside from encompassing all earlier results on such indicators, including in particular the notion of filling-enforced quantum band insulators, our theory identifies symmetry settings with previously hidden forms of band topology, and can be applied to the search for topological materials.Understanding the role of topology in determining electronic structure can lead to the discovery, or appreciation, of materials with exotic properties such as protected surface states. Here, the authors present a framework for identifying topologically distinct band-structures for all 3D space groups.
Energy Technology Data Exchange (ETDEWEB)
Duffort, V.; Sarkar, T. [CRISMAT, CNRS-ENSICAEN, 6 Bd Marechal Juin, 14050 Caen (France); Caignaert, V., E-mail: vincent.caignaert@ensicaen.fr [CRISMAT, CNRS-ENSICAEN, 6 Bd Marechal Juin, 14050 Caen (France); Pralong, V.; Raveau, B. [CRISMAT, CNRS-ENSICAEN, 6 Bd Marechal Juin, 14050 Caen (France); Avdeev, M. [Bragg Institute, Australian Nuclear Science and Technology Organization, PMB 1, Menai, NSW 2234 (Australia); Cervellino, A. [Paul Scherrer Institute, Swiss Light Source, CH-5232 Villigen (Switzerland); Waerenborgh, J.C.; Tsipis, E.V. [UCQR, IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, CFMC-UL, 2686-953 Sacavém (Portugal)
2013-09-15
The possibility to lift the geometric frustration in the “114” stoichiomeric tetragonal oxide YBaFe{sub 4}O{sub 7.0} by decreasing the temperature has been investigated using neutron and synchrotron powder diffraction techniques. Besides the structural transition from tetragonal to monoclinic symmetry that appears at T{sub S}=180 K, a magnetic transition is observed below T{sub N}=95 K. The latter corresponds to a lifting of the 3D geometric frustration toward an antiferromagnetic long range ordering, never observed to date in a cubic based “114’” oxide. The magnetic structure, characterized by the propagation vector k{sub 1}=(0,0,½), shows that one iron Fe2 exhibits a larger magnetic moment than the three others, suggesting a possible charge ordering according to the formula YBaFe{sup 3+}Fe{sub 3}{sup 2+}O{sub 7.0}. The magnetic M(T) and χ′(T) curves, in agreement with neutron data, confirm the structural and magnetic transitions and evidence the coexistence of residual magnetic frustration. Moreover, the transport measurements show a resistive transition from a thermally activated conduction mechanism to a variable range hopping mechanism at T{sub S}=180 K, with a significant increase of the dependence of the resistivity vs. temperature. Mössbauer spectroscopy clearly evidences a change in the electronic configuration of the iron framework at the structural transition as well as coexistence of several oxidation states. The role of barium underbonding in these transitions is discussed. - Graphical abstract: Atomic displacements at the tetragonal-monoclinic transition in YBaFe{sub 4}O{sub 7}. Display Omitted - Highlights: • The structural and magnetic phase transitions of YBaFe{sub 4}O{sub 7} were studied below room temperature. • The tetragonal to monoclinic transition, characterized by NPD and SXRD, was studied using mode crystallography approach. • Monoclinic distortion allows the lifting of the geometrical frustration on the iron sublattice
Energy Technology Data Exchange (ETDEWEB)
Kohlmann, Holger [Leipzig Univ. (Germany). Inst. of Inorganic Chemistry; Hein, Christina; Kautenburger, Ralf [Saarland Univ., Saarbruecken (Germany). Inorganic Solid State Chemistry; Hansen, Thomas C.; Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Doyle, Stephen [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Synchrotron Radiation (ISS)
2016-11-01
The crystal structures of monoclinic samarium and cubic europium sesquioxide, Sm{sub 2}O{sub 3} and Eu{sub 2}O{sub 3}, were reinvestigated by powder diffraction methods (laboratory X-ray, synchrotron, neutron). Rietveld analysis yields more precise structural parameters than previously known, especially for oxygen atoms. Interatomic distances d(Sm-O) in Sm{sub 2}O{sub 3} range from 226.3(4) to 275.9(2) pm [average 241.6(3) pm] for the monoclinic B type Sm{sub 2}O{sub 3} [space group C2/m, a = 1418.04(3) pm, b = 362.660(7) pm, c = 885.48(2) pm, β = 100.028(1) ], d(Eu-O) in Eu{sub 2}O{sub 3} from 229.9(2) to 238.8(2) pm for the cubic bixbyite (C) type [space group Ia anti 3, a = 1086.87(1) pm]. Neutron diffraction at 50 K and 2 K did not show any sign for magnetic ordering in Sm{sub 2}O{sub 3}. Isotopically enriched {sup 154}Sm{sub 2}O{sub 3} and {sup 153}Eu{sub 2}O{sub 3} were used for the neutron diffraction work because of the enormous absorption cross section of the natural isotopic mixtures for thermal neutrons. The isotopic purity was determined by inductively coupled plasma - mass spectrometry to be 98.9% for {sup 154}Sm and 99.8% for {sup 153}Eu. Advanced analysis of the neutron diffraction data suggest that the bound coherent scattering lengths of {sup 154}Sm and {sup 153}Eu need to be revised. We tentatively propose b{sub c}({sup 154}Sm) = 8.97(6) fm and b{sub c}({sup 153}Eu) = 8.85(3) fm for a neutron wavelength of 186.6 pm to be better values for these isotopes, showing up to 8% deviation from accepted literature values. It is shown that inaccurate scattering lengths may result in severe problems in crystal structure refinements causing erroneous structural details such as occupation parameters, which might be critically linked to physical properties like superconductivity in multinary oxides.
Wang, Guocheng; Meng, Fanhao; Ding, Chuanxian; Chu, Paul K; Liu, Xuanyong
2010-03-01
A monoclinic zirconia coating with a nanostructural surface was prepared on the Ti-6Al-4V substrate by an atmospheric plasma-spraying technique, and its microstructure and composition, as well as mechanical and biological properties, were investigated to explore potential application as a bioactive coating on bone implants. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and Raman spectroscopy revealed that the zirconia coating was composed of monoclinic zirconia which was stable at low temperature, and its surface consists of nano-size grains 30-50 nm in size. The bond strength between the coating and the Ti-6Al-4V substrate was 48.4 + or - 6.1 MPa, which is higher than that of plasma-sprayed HA coatings. Hydrothermal experiments indicated that the coating was stable in a water environment and the phase composition and Vickers hardness were independent of the hydrothermal treatment time. Bone-like apatite is observed to precipitate on the surface of the coating after soaking in simulated body fluid for 6 days, indicating excellent bioactivity in vitro. The nanostructured surface composed of monoclinic zirconia is believed to be crucial to its bioactivity. Morphological observation and the cell proliferation test demonstrated that osteoblast-like MG63 cells could attach to, adhere to and proliferate well on the surface of the monoclinic zirconia coating, suggesting possible applications in hard tissue replacements.
van Dalfsen, Koop; van Wolferen, Hendricus A.G.M.; Dijkstra, Mindert; Aravazhi, S.; Bernhardi, Edward; García Blanco, Sonia Maria; Pollnau, Markus
2012-01-01
By varying the thulium concentration in the range of 1.5 – 8.0 at.% in thulium- gadolinium-lutetium-yttrium-co-doped monoclinic double tungstate channel waveguides, a maximum laser slope efficiency of 70% with respect to the absorbed pump power was obtained. Further integration of these channel
Marchis, Iuliana
2009-01-01
Symmetry is one of the fundamental concepts in Geometry. It is a Mathematical concept, which can be very well connected with Art and Ethnography. The aim of the article is to show how to link the geometrical concept symmetry with interculturality. For this mosaics from different countries are used.
2016-01-01
The Symmetry Festival is a science and art program series, the most important periodic event (see its history) to bring together scientists, artists, educators and practitioners interested in symmetry (its roots, what is behind, applications, etc.), or in the consequences of its absence.
Schaft, A.J. van der
1987-01-01
It is argued that the existence of symmetries may simplify, as in classical mechanics, the solution of optimal control problems. A procedure for obtaining symmetries for the optimal Hamiltonian resulting from the Maximum Principle is given; this avoids the actual calculation of the optimal
Loebbert, Florian
2016-01-01
In these introductory lectures we discuss the topic of Yangian symmetry from various perspectives. Forming the classical counterpart of the Yangian and an extension of ordinary Noether symmetries, first the concept of nonlocal charges in classical, two-dimensional field theory is reviewed. We then define the Yangian algebra following Drinfeld's original motivation to construct solutions to the quantum Yang-Baxter equation. Different realizations of the Yangian and its mathematical role as a Hopf algebra and quantum group are discussed. We demonstrate how the Yangian algebra is implemented in quantum, two-dimensional field theories and how its generators are renormalized. Implications of Yangian symmetry on the two-dimensional scattering matrix are investigated. We furthermore consider the important case of discrete Yangian symmetry realized on integrable spin chains. Finally we give a brief introduction to Yangian symmetry in planar, four-dimensional super Yang-Mills theory and indicate its impact on the dila...
Nicolis, Alberto
2011-01-01
For relativistic quantum field theories, we consider Lorentz breaking, spatially homogeneous field configurations or states that evolve in time along a symmetry direction. We dub this situation "spontaneous symmetry probing" (SSP). We mainly focus on internal symmetries, i.e. on symmetries that commute with the Poincare group. We prove that the fluctuations around SSP states have a Lagrangian that is explicitly time independent, and we provide the field space parameterization that makes this manifest. We show that there is always a gapless Goldstone excitation that perturbs the system in the direction of motion in field space. Perhaps more interestingly, we show that if such a direction is part of a non-Abelian group of symmetries, the Goldstone bosons associated with spontaneously broken generators that do not commute with the SSP one acquire a gap, proportional to the SSP state's "speed". We outline possible applications of this formalism to inflationary cosmology.
Partial Dynamical Symmetry as an Intermediate Symmetry Structure
Leviatan, A
2003-01-01
We introduce the notion of a partial dynamical symmetry for which a prescribed symmetry is neither exact nor completely broken. We survey the different types of partial dynamical symmetries and present empirical examples in each category.
Sikora, W
2011-01-01
The evacuation of football stadium scenarios are discussed as model realizing ordered states, described as movements of individuals according to fields of displacements, calculated correspondingly to given scenario. The symmetry of the evacuation space is taken into account in calculation of displacements field - the displacements related to every point of this space are presented in the coordinate frame in the best way adapted to given symmetry space group, which the set of basic vectors of irreducible representation of given group is. The speeds of individuals at every point in the presented model have the same quantity. As the results the times of evacuation and average forces acting on individuals during the evacuation are given. Both parameters are compared with the same parameters got without symmetry considerations. They are calculated in the simulation procedure. The new program (using modified Helbing model) has been elaborated and presented in this work for realization the simulation tasks the.
Mei Symmetry and Lie Symmetry of Relativistic Hamiltonian System
Institute of Scientific and Technical Information of China (English)
FANG Jian-Hui; YAN Xiang-Hong; LI Hong; CHEN Pei-Sheng
2004-01-01
The Mei symmetry and the Lie symmetry of the relativistic Hamiltonian system are studied. The definition and criterion of the Mei symmetry and the Lie symmetry of the relativistic Hamiltonian system are given. The relationship between them is found. The conserved quantities which the Mei symmetry and the Lie symmetry lead to are obtained.An example is given to illustrate the application of the result.
Crystal structure of low-symmetry rondorfite
Rastsvetaeva, R. K.; Zadov, A. E.; Chukanov, N. V.
2008-03-01
The crystal structure of an aluminum-rich variety of the mineral rondorfite with the composition Ca16[Mg2(Si7Al)(O31OH)]Cl4 from the skarns of the Verkhne-Chegemskoe plateau (the Kabardino-Balkarian Republic, the Northern Caucasus Region, Russia) was solved in the triclinic space group with the unit-cell parameters a = 15.100(2) Å, b = 15.110(2) Å, c = 15.092(2) Å, α = 90.06(1)°, β = 90.01(1)°, γ = 89.93(1)°, Z = 4, sp. gr. P1. The structural model consisting of 248 independent atoms was determined by the phase-correction method and refined to R = 3.8% with anisotropic displacement parameters based on all 7156 independent reflections with 7156 F > 3σ( F). The crystal structure is based on pentamers consisting of four Si tetrahedra linked by the central Mg tetrahedron. The structure can formally be refined in the cubic space group ( a = 15.105 Å, sp. gr. Fd overline 3 , seven independent positions) with anisotropic displacement parameters to R = 2.74% based on 579 reflections with F > 3σ( F) without accounting for more than 1000 observed reflections, which are inconsistent with the cubic symmetry of the crystal structure.
Institute of Scientific and Technical Information of China (English)
伍锡荣; 谢兆雄
2003-01-01
The structure factors of any crystal structure can be simulated from its atomic coordinates (and temperature factors) in a SHELXL-97 run on a dummy hkl in which only the scale factor is refined. The squares of the structure factors are retrieved from the fcf, and such simulated data are used in the revision of the space groups of several incorrectly-refined crystal structures. Two cases, a P1 to P revision and a chemically-incorrect structure that is refined in a correct space group, are discussed.
Leviatan, A
2010-01-01
This overview focuses on the notion of partial dynamical symmetry (PDS), for which a prescribed symmetry is obeyed by a subset of solvable eigenstates, but is not shared by the Hamiltonian. General algorithms are presented to identify interactions, of a given order, with such intermediate-symmetry structure. Explicit bosonic and fermionic Hamiltonians with PDS are constructed in the framework of models based on spectrum generating algebras. PDSs of various types are shown to be relevant to nuclear spectroscopy, quantum phase transitions and systems with mixed chaotic and regular dynamics.
Schwichtenberg, Jakob
2015-01-01
This is a textbook that derives the fundamental theories of physics from symmetry. It starts by introducing, in a completely self-contained way, all mathematical tools needed to use symmetry ideas in physics. Thereafter, these tools are put into action and by using symmetry constraints, the fundamental equations of Quantum Mechanics, Quantum Field Theory, Electromagnetism, and Classical Mechanics are derived. As a result, the reader is able to understand the basic assumptions behind, and the connections between the modern theories of physics. The book concludes with first applications of the previously derived equations.
Institute of Scientific and Technical Information of China (English)
龚(龙天); 王文清; 刘虹雯; 杜世萱; 郭海明; 王业亮; 高鸿钧
2005-01-01
利用原子力显微镜(AFM)成像技术来观察DL-缬氨酸晶体表面分子的规则排列,研究表明对映体分子在DL-缬氨酸晶体中相互配对排列,每个晶胞单元中包含两个对映体分子,属于具有中心对称结构P1群,整个晶体是消旋的.通过原子力显微镜对DL-缬氨酸晶体表面重复单元的测量结果与X衍射数据对比,发现用AFM观察到的DL-缬氨酸晶体中分子表面形貌的规整排列的距离,同X衍射得出的三斜晶系晶胞参数数据基本一致,由此判定该晶体属于三斜晶系而不是单斜晶系.探讨了利用纳米技术的研究手段在分子水平研究生命起源中的手性问题,在确定的晶面上通过分子周期性结构排列规律,对DL-缬氨酸晶体表面分子进行手性识别.%Atomic force microscopy(AFM) has been used to image arrays of molecules at the surface of DL-valine crystals. AFM images of DL-valine show that D- and L- molecular pairs formed from a DL-racemic mixture are exclusively homochiral. There are two different conclusions about the crystal structure of DL-valine with the data of X-ray crystallography. First, the structure of DL-valine was solved in the monoclinic space group P21/c. Second, the crystal structure of DL-valine has been refined in the centrosymmetric space group P1 and indicated a triclinic rather than a monoclinic space group. The present work emphasizes to solve the contradicting observations of space group and to provide direct evidence for chiral recognition at molecular level. DL-valine molecules {001 } are all in zwitterionic form with the isopropyl groups close to the surface and methyl groups on the top site, showing an ordered molecular morphology of triclinic unit cells, which are in fair agreement with the X-ray diffraction data. The application of AFM to the investigation of protein' s origins and a molecular-level illustration of chiral recognition at a periodic 2D surface structure ofracemic crystals is discussed.
Thangaraju, D.; Moorthy Babu, S.; Durairajan, A.; Balaji, D.; Samuel, P.; Hayakawa, Y.
2013-01-01
Growth of pure KGW, 0.5, 2 and 5 wt% Pr3+ doped KGd(WO4)2 single crystals were carried out using top seeded solution growth (TSSG) method with K2WO4 as flux. Growth parameters that include the cooling rate and pulling rate were modified to achieve transparent doped crystals to that of pure crystals. Optically polished samples were used for optical and structural studies. Structure of grown crystals was confirmed and lattice parameter values were calculated using single crystal X-ray diffractometer. Both pure and doped crystals belong to the monoclinic phase with C2/c space group. When compared to pure matrix of KGW, some notable changes were observed in the lattice parameter values of doped crystals. It may be due to the ionic radii mismatch of replacing praseodymium ion in the place of gadolinium ion. Absorption and emission measurements were carried out for the 2 mm thick polished samples. The doped samples show a very good transparency with an intense absorption band around the blue region of the spectrum with additional absorption peaks in the IR region as well. Strong red emission was observed in the emission spectrum. The energy levels and their corresponding transitions were figured out in Pr3+ ions inside the matrix. Emission characteristics were compared for different dopant concentration. Raman spectra reveal the intense tungstate vibrational modes in the higher frequency region. Comparison of pure and doped samples reveal that there is no significant change in vibrational modes at higher doping concentration.
Golubitsky, Martin
2012-04-01
Many gaits of four-legged animals are described by symmetry. For example, when a horse paces it moves both left legs in unison and then both right legs and so on. The motion is described by two symmetries: Interchange front and back legs, and swap left and right legs with a half-period phase shift. Biologists postulate the existence of a central pattern generator (CPG) in the neuronal system that sends periodic signals to the legs. CPGs can be thought of as electrical circuits that produce periodic signals and can be modeled by systems with symmetry. In this lecture we discuss animal gaits; use gait symmetries to construct a simplest CPG architecture that naturally produces quadrupedal gait rhythms; and make several testable predictions about gaits.
Lovelady, Benjamin C
2015-01-01
According to the Coleman-Mandula theorem, any gauge theory of gravity combined with an internal symmetry based on a Lie group must take the form of a direct product in order to be consistent with basic assumptions of quantum field theory. However, we show that an alternative gauging of a simple group can lead dynamically to a spacetime with compact internal symmetry. The biconformal gauging of the conformal symmetry of n-dim Euclidean space doubles the dimension to give a symplectic manifold. Examining one of the Lagrangian submanifolds in the flat case, we find that in addition to the expected SO(n) connection and curvature, the solder form necessarily becomes Lorentzian. General coordinate invariance gives rise to an SO(n-1,1) connection on the spacetime. The principal fiber bundle character of the original SO(n) guarantees that the two symmetries enter as a direct product, in agreement with the Coleman-Mandula theorem.
Gauge symmetry from decoupling
Energy Technology Data Exchange (ETDEWEB)
Wetterich, C., E-mail: c.wetterich@thphys.uni-heidelberg.de
2017-02-15
Gauge symmetries emerge from a redundant description of the effective action for light degrees of freedom after the decoupling of heavy modes. This redundant description avoids the use of explicit constraints in configuration space. For non-linear constraints the gauge symmetries are non-linear. In a quantum field theory setting the gauge symmetries are local and can describe Yang–Mills theories or quantum gravity. We formulate gauge invariant fields that correspond to the non-linear light degrees of freedom. In the context of functional renormalization gauge symmetries can emerge if the flow generates or preserves large mass-like terms for the heavy degrees of freedom. They correspond to a particular form of gauge fixing terms in quantum field theories.
Gauge symmetry from decoupling
Directory of Open Access Journals (Sweden)
C. Wetterich
2017-02-01
Full Text Available Gauge symmetries emerge from a redundant description of the effective action for light degrees of freedom after the decoupling of heavy modes. This redundant description avoids the use of explicit constraints in configuration space. For non-linear constraints the gauge symmetries are non-linear. In a quantum field theory setting the gauge symmetries are local and can describe Yang–Mills theories or quantum gravity. We formulate gauge invariant fields that correspond to the non-linear light degrees of freedom. In the context of functional renormalization gauge symmetries can emerge if the flow generates or preserves large mass-like terms for the heavy degrees of freedom. They correspond to a particular form of gauge fixing terms in quantum field theories.
CPT Symmetry Without Hermiticity
Mannheim, Philip D
2016-01-01
In the literature the $CPT$ theorem has only been established for Hamiltonians that are Hermitian. Here we extend the $CPT$ theorem to quantum field theories with non-Hermitian Hamiltonians. Our derivation is a quite minimal one as it requires only the time independent evolution of scalar products and invariance under complex Lorentz transformations. The first of these requirements does not force the Hamiltonian to be Hermitian. Rather, it forces its eigenvalues to either be real or to appear in complex conjugate pairs, forces the eigenvectors of such conjugate pairs to be conjugates of each other, and forces the Hamiltonian to admit of an antilinear symmetry. The latter requirement then forces this antilinear symmetry to be $CPT$, with Hermiticity of a Hamiltonian thus only being a sufficient condition for $CPT$ symmetry and not a necessary one. $CPT$ symmetry thus has primacy over Hermiticity, and it rather than Hermiticity should be taken as a guiding principle for constructing quantum theories. With confo...
Gauge symmetry from decoupling
Wetterich, C.
2017-02-01
Gauge symmetries emerge from a redundant description of the effective action for light degrees of freedom after the decoupling of heavy modes. This redundant description avoids the use of explicit constraints in configuration space. For non-linear constraints the gauge symmetries are non-linear. In a quantum field theory setting the gauge symmetries are local and can describe Yang-Mills theories or quantum gravity. We formulate gauge invariant fields that correspond to the non-linear light degrees of freedom. In the context of functional renormalization gauge symmetries can emerge if the flow generates or preserves large mass-like terms for the heavy degrees of freedom. They correspond to a particular form of gauge fixing terms in quantum field theories.
Lovelady, Benjamin C.; Wheeler, James T.
2016-04-01
According to the Coleman-Mandula theorem, any gauge theory of gravity combined with an internal symmetry based on a Lie group must take the form of a direct product in order to be consistent with basic assumptions of quantum field theory. However, we show that an alternative gauging of a simple group can lead dynamically to a spacetime with compact internal symmetry. The biconformal gauging of the conformal symmetry of n-dimensional Euclidean space doubles the dimension to give a symplectic manifold. Examining one of the Lagrangian submanifolds in the flat case, we find that in addition to the expected S O (n ) connection and curvature, the solder form necessarily becomes Lorentzian. General coordinate invariance gives rise to an S O (n -1 ,1 ) connection on the spacetime. The principal fiber bundle character of the original S O (n ) guarantees that the two symmetries enter as a direct product, in agreement with the Coleman-Mandula theorem.
Superconductivity and symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Sarasua, L.G., E-mail: sarasua@fisica.edu.uy [Instituto de Fisica, Facultad de Ciencias, Universidad de la Republica, Montevideo (Uruguay)
2012-02-15
In the present work we consider the relation between superconductivity and spontaneous gauge symmetry breaking (SGBS). We show that ODLRO does not require in principle SBGS, even in the presence of particle number fluctuations, by examining exact solutions of a fermionic pairing model. The criteria become equivalent if a symmetry breaking field is allowed, which can be attributed to the interaction with the environment. However, superconducting states without SBGS are not forbidden.
Hamhalter, Jan; Turilova, Ekaterina
2017-02-01
Quantum symmetries of spectral lattices are studied. Basic properties of spectral order on A W ∗-algebras are summarized. Connection between projection and spectral automorphisms is clarified by showing that, under mild conditions, any spectral automorphism is a composition of function calculus and Jordan ∗-automorphism. Complete description of quantum spectral symmetries on Type I and Type II A W ∗-factors are completely described.
Necessary N-representability Constraints from Time-reversal Symmetry for Periodic Systems
Rubin, Nicholas C
2016-01-01
The variational calculation of the two-electron reduced density matrix (2-RDM) is extended to periodic molecular systems. If the 2-RDM theory is extended to the periodic case without consideration of time-reversal symmetry, however, it can yields energies that are significantly lower than the correct energies. We derive and implement linear constraints that enforce time-reversal symmetry on the 2-RDM without destroying its computationally favorable block-diagonal structure from translational invariance. Time-reversal symmetry is distinct from space-group or spin (SU(2)) symmetries which can be expressed by unitary transformations. The time-reversal symmetry constraints are demonstrated through calculations of the metallic hydrogen chain and the one-dimensional lithium hydride crystal.
Energy Technology Data Exchange (ETDEWEB)
Blum, Alexander Simon
2009-06-10
This thesis deals with the possibility of describing the flavor sector of the Standard Model of Particle Physics (with neutrino masses), that is the fermion masses and mixing matrices, with a discrete, non-abelian flavor symmetry. In particular, mass independent textures are considered, where one or several of the mixing angles are determined by group theory alone and are independent of the fermion masses. To this end a systematic analysis of a large class of discrete symmetries, the dihedral groups, is analyzed. Mass independent textures originating from such symmetries are described and it is shown that such structures arise naturally from the minimization of scalar potentials, where the scalars are gauge singlet flavons transforming non-trivially only under the flavor group. Two models are constructed from this input, one describing leptons, based on the group D{sub 4}, the other describing quarks and employing the symmetry D{sub 14}. In the latter model it is the quark mixing matrix element V{sub ud} - basically the Cabibbo angle - which is at leading order predicted from group theory. Finally, discrete flavor groups are discussed as subgroups of a continuous gauge symmetry and it is shown that this implies that the original gauge symmetry is broken by fairly large representations. (orig.)
Baldo, M.; Burgio, G. F.
2016-11-01
The nuclear symmetry energy characterizes the variation of the binding energy as the neutron to proton ratio of a nuclear system is varied. This is one of the most important features of nuclear physics in general, since it is just related to the two component nature of the nuclear systems. As such it is one of the most relevant physical parameters that affect the physics of many phenomena and nuclear processes. This review paper presents a survey of the role and relevance of the nuclear symmetry energy in different fields of research and of the accuracy of its determination from the phenomenology and from the microscopic many-body theory. In recent years, a great interest was devoted not only to the Nuclear Matter symmetry energy at saturation density but also to its whole density dependence, which is an essential ingredient for our understanding of many phenomena. We analyze the nuclear symmetry energy in different realms of nuclear physics and astrophysics. In particular we consider the nuclear symmetry energy in relation to nuclear structure, astrophysics of Neutron Stars and supernovae, and heavy ion collision experiments, trying to elucidate the connections of these different fields on the basis of the symmetry energy peculiarities. The interplay between experimental and observational data and theoretical developments is stressed. The expected future developments and improvements are schematically addressed, together with most demanded experimental and theoretical advances for the next few years.
Zhou, Bin; Qu, Jiuhui; Zhao, Xu; Liu, Huijuan
2011-01-01
Monoclinic bismuth vanadate (BiVO4) thin film was fabricated on indium-tin oxide glass from an amorphous heteronuclear complex via dip-coating. After annealation at 400, 500, and 600 degrees C, the thin films were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The BiVO4 particles on the ITO glass surface had a monoclinic structure. The UV-Visible diffuse reflection spectra showed the BiVO4 thin film had photoabsorption properties, with a band gap around 2.5 eV. In addition, the thin film showed high visible photocatalytic activities towards 2,4-dichlorophenol and Bisphenol A degradation under visible light irradiation (lambda > 420 nm). Over 90% of the two organic pollutants were removed in 5 hr. A possible degradation mechanism of 2,4-dichlorophenol were also studied.
Institute of Scientific and Technical Information of China (English)
Bin Zhou; Jiuhui Qu; Xu Zhao; Huijuan Liu
2011-01-01
Monoclinic bismuth vanadate (BiVO4) thin film was fabricated on indium-tin oxide glass from an amorphous heteronuclear complex via dip-coating.After annealation at 400, 500, and 600℃, the thin films were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry.The BiVO4 particles on the ITO glass surface had a monoclinic structure.The UV-Visible diffuse reflection spectra showed the BiVO4 thin film had photoabsorption properties, with a band gap around 2.5 eV.In addition, the thin film showed high visible photocatalytic activities towards 2,4-dichiorophenol and Bisphenol A degradation under visible light irradiation (λ.＞ 420 nm).Over 90％ of the two organic pollutants were removed in 5 hr.A possible degradation mechanism of 2,4-dichlorophenol were also studied.
Seismic Data Interpretation: A Case Study of Southern Sindh Monocline, Lower Indus Basin, Pakistan
Directory of Open Access Journals (Sweden)
Shabeer Ahmed Abbasi
2015-04-01
Full Text Available The Sindh monocline in Lower Indus Basin is an important oil and gas producing area of Pakistan where a large number of oil, gas and condensate fields have been discovered from structural traps. This research involves the interpretation of stratigraphic and structural styles of Sindh Monocline using 2D (Two-Dimensional seismic reflection and well log. Four reflectors of different formations have been marked and were named as Reflector-1 as of Khadro Formation, Reflector-2 as Upper Goru Member, Reflector-3 as Lower Goru Formation and Reflector-4 as Chiltan Limestone. The average depth of Khadro Formation was marked at 449.0m, Upper Goru Member at 968m, Lower Goru Formation at 1938m and Chiltan Limestone at 2943m. Faults were marked on seismic sections which collectively form horsts and grabens which is the evidence of extensional tectonic in the area. Seismic interpretation was carried out through window based Kingdom Software
Crystalline and magnetic ordering in the monoclinic phase of the layered perovskite PAMC
DEFF Research Database (Denmark)
Harris, P.; Lebech, B.; Achiwa, N.
1994-01-01
of 1/3b*, and below 39 K PAMC is an antiferromagnet with a small ferromagnetic component. The temperature dependence of the monoclinic angle alpha depends on the mosaicity of the crystal which increases with the number of 'cooling cycles'. The satellite reflections do not have any contribution from...... the magnetic ordering, but their intensity has abrupt changes that coincide with changes in either the nuclear or the magnetic ordering parameter. Magnetoelastic effects seem to influence the ordering of the crystal....
Energy Technology Data Exchange (ETDEWEB)
Sanz, Alejandro, E-mail: alejandro.sanz@csic.es; Nogales, Aurora; Ezquerra, Tiberio A. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain); Puente-Orench, Inés [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France); Instituto de Ciencia de Materiales de Aragón, ICMA-CSIC, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Jiménez-Ruiz, Mónica [Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9 (France)
2014-02-07
Transformation of deuterated ethanol from the plastic crystal phase into the monoclinic one is investigated by means of a singular setup combining simultaneously dielectric spectroscopy with neutron diffraction. We postulate that a dynamic transition from plastic crystal to supercooled liquid-like configuration through a deep reorganization of the hydrogen-bonding network must take place as a previous step of the crystallization process. Once these precursor regions are formed, subsequent crystalline nucleation and growth develop with time.
Lv, Li; Tong, Wenming; Zhang, Yanbing; Su, Yiguo; Wang, Xiaojing
2011-11-01
Metastable monoclinic ZnMoO4 was successfully synthesized via a hydrothermal route with variation of reaction temperatures and time at pH value of 5.7. Systematic sample characterizations were carried out, including X-ray powder diffraction, scanning electron microscopy, Fourier transformed infrared spectra, UV-visible diffuse reflectance spectra, and photoluminescence spectra. The results show that all as-prepared ZnMoO4 samples were demonstrated to crystallize in a pure-phase of monoclinic wolframite structure. All samples were formed in plate-like morphology. Six IR active vibrational bands were observed in the wave number range of 400-900 cm(-1). The band gap of as-prepared ZnMoO4 was estimated to be 2.86 eV by Tauc equation. Photoluminescence measurement indicates that as-prepared ZnMoO4 exhibits a broad blue-green emission under excitation wavelength of 280 nm at room temperature. Photocatalytic activity of as-prepared ZnMoO4 was examined by monitoring the degradation of methyl orange dye in an aqueous solution under UV radiation of 365 nm. The as-prepared ZnMoO4 obtained at 180 degrees C for 40 h showed the best photocatalytic activity with completing degradation of MO in irradiation time of 120 min. Consequently, monoclinic ZnMoO4 proved to be an efficient near visible light photocatalyst.
Cui, Yuanyuan; Liu, Bin; Chen, Lanli; Luo, Hongjie; Gao, Yanfeng
2016-10-01
VO2 is an attractive candidate for intelligent windows and thermal sensors. There are challenges for developing VO2-based devices, since the properties of monoclinic VO2 are very sensitive to its intrinsic point defects. In this work, the formation energies of the intrinsic point defects in monoclinic VO2 were studied through the first-principles calculations. Vacancies, interstitials, as well as antisites at various charge states were taken into consideration, and the finite-size supercell correction scheme was adopted as the charge correction scheme. Our calculation results show that the oxygen interstitial and oxygen vacancy are the most abundant intrinsic defects in the oxygen rich and oxygen deficient condition, respectively, indicating a consistency with the experimental results. The calculation results suggest that the oxygen interstitial or oxygen vacancy is correlated with the charge localization, which can introduce holes or electrons as free carriers and subsequently narrow the band gap of monoclinic VO2. These calculations and interpretations concerning the intrinsic point defects would be helpful for developing VO2-based devices through defect modifications.
Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K. V.; Rödel, Jürgen; Xing, Xianran
2017-07-01
High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic MA structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic MB , rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.
Energy Technology Data Exchange (ETDEWEB)
Roy Choudhury, Samrat, E-mail: samratroychoudhury@gmail.com [Indian Statistical Institute, Biological Sciences Division (India); Mandal, Amrita; Chakravorty, Dipankar [Indian Association for the Cultivation of Science (India); Gopal, Madhuban [Indian Agricultural Research Institute, Divisions of Agricultural Chemicals (India); Goswami, Arunava [Indian Statistical Institute, Biological Sciences Division (India)
2013-04-15
Stable nanocolloids of monoclinic sulfur ({beta}-SNPs) were prepared through 'water-in-oil microemulsion technique' at room temperature after suitable modifications of the surface. The morphology (rod shaped; {approx}50 nm in diameter) and allotropic nature (monoclinic) of the SNPs were investigated with Transmission Electron Microscopy and X-ray Diffraction technique. The surface modification, colloidal stability, and surface topology of {beta}-SNPs were evaluated with Fourier Transform Infrared Spectroscopy, zeta potential analysis, and Atomic Force Microscopy. Thermal decomposition pattern of these nanosized particles was determined by Thermo Gravimetric Analysis (TGA). {beta}-SNPs-colloids expressed excellent antimicrobial activities against a series of fungal and bacterial isolates with prominent deformities at their surface. In contrast, insignificant cytotoxicity was achieved against the human derived hepatoma (HepG2) cell line upon treatment with {beta}-SNPs. A simultaneous study was performed to determine the stock concentration of {beta}-SNP-colloids using a novel high phase liquid chromatographic method. Cumulative results of this study hence, elucidate the stabilization of nanosized monoclinic sulfur at room temperature and their potential antimicrobial efficacy over micron-sized sulfur.
Kawamura, Yoshiharu
2015-01-01
We study the quantization of systems with local particle-ghost symmetries. The systems contain ordinary particles including gauge bosons and their counterparts obeying different statistics. The particle-ghost symmetry is a kind of fermionic symmetry, different from the space-time supersymmetry and the BRST symmetry. Subsidiary conditions on states guarantee the unitarity of systems.
Invariants of broken discrete symmetries
Kalozoumis, P; Diakonos, F K; Schmelcher, P
2014-01-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying in particular to acoustic, optical and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
Jubilite: A 4-,8-connected Cubic Structural Pattern in Space Group Pm3
Directory of Open Access Journals (Sweden)
Eduardo A. Castro
2005-05-01
Full Text Available Abstract: In the course of investigating structural modifications of the 3-,4-connected net known as the Pt3O4 structure-type (waserite, a novel 4-,8-connected structure-type was discovered. This lattice is generated by replacing the 3-connected trigonal planar vertices of the Pt3O4 structure-type with 4-connected tetrahedral vertices, to achieve a structure which possesses a generic empirical formula of JK6L8. In such a topological modification, the four 3-fold axes of the parent cubic, Pm3n, Pt3O4 structure-type are retained. Thus the 4-connected tetrahedral vertices are oriented so as to preserve cubic symmetry in the resulting Pm3, JK6L8 (jubilite lattice. The unit cell contains a single 8-connected cubecentered vertex, six 4-connected distorted square planar vertices and eight 4-connected distorted tetrahedral vertices. It is a Wellsean structure with a Wells point symbol given by (4166484(42826(43838 and a SchlÃƒÂ¤fli symbol of (53/4, 4.2667. This latter index reveals a decrease in the latticeÃ¢Â€Â™s polygonality and concomitant increase in the connectivity through the transformation from waserite to jubilite. The topology of the parent waserite lattice (Pt3O4 corresponds to that of the Catalan structures with the Wells point symbol (843(834, which has the SchlÃƒÂ¤fli symbol (8, 3.4285. Finally, it can be seen that a sequence of structure-types starting with waserite (Pt3O4 and moving to jubilite (JK6L8 and finally to fluorite (CaF2 represents a continuous crystallographic structural transformation in which the symmetry and topology undergo concomitant changes from one structure-type (waserite to the other structure-types. The topology of the fluorite lattice, represented by the Wells point symbol (424(462, and the SchlÃƒÂ¤fli symbol (4, 51/3, indicates a discontinuous topological transformation from the intermediate jubilite lattice; like the discontinuous topological transformation from Pt3O4 to JK6L8; in which the
Symmetry-imposed shape of linear response tensors
Seemann, M.; Ködderitzsch, D.; Wimmer, S.; Ebert, H.
2015-10-01
A scheme suggested in the literature to determine the symmetry-imposed shape of linear response tensors is revised and extended to allow for the treatment of more complex situations. The extended scheme is applied to discuss the shape of the spin conductivity tensor for all magnetic space groups. This allows in particular investigating the character of longitudinal as well as transverse spin transport for arbitrary crystal structure and magnetic order that give rise, e.g., to the spin Hall, Nernst, and the spin-dependent Seebeck effects.
Baldo, M
2016-01-01
The nuclear symmetry energy characterizes the variation of the binding energy as the neutron to proton ratio of a nuclear system is varied. This is one of the most important features of nuclear physics in general, since it is just related to the two component nature of the nuclear systems. As such it is one of the most relevant physical parameters that affect the physics of many phenomena and nuclear processes. This review paper presents a survey of the role and relevance of the nuclear symmetry energy in different fields of research and of the accuracy of its determination from the phenomenology and from the microscopic many-body theory. In recent years, a great interest was devoted not only to the Nuclear Matter symmetry energy at saturation density but also to its whole density dependence, which is an essential ingredient for our understanding of many phenomena. We analyze the nuclear symmetry energy in different realms of nuclear physics and astrophysics. In particular we consider the nuclear symmetry ene...
Loebbert, Florian
2016-08-01
In these introductory lectures we discuss the topic of Yangian symmetry from various perspectives. Forming the classical counterpart of the Yangian and an extension of ordinary Noether symmetries, first the concept of nonlocal charges in classical, two-dimensional field theory is reviewed. We then define the Yangian algebra following Drinfel’d's original motivation to construct solutions to the quantum Yang-Baxter equation. Different realizations of the Yangian and its mathematical role as a Hopf algebra and quantum group are discussed. We demonstrate how the Yangian algebra is implemented in quantum, two-dimensional field theories and how its generators are renormalized. Implications of Yangian symmetry on the two-dimensional scattering matrix are investigated. We furthermore consider the important case of discrete Yangian symmetry realized on integrable spin chains. Finally we give a brief introduction to Yangian symmetry in planar, four-dimensional super Yang-Mills theory and indicate its impact on the dilatation operator and tree-level scattering amplitudes. These lectures are illustrated by several examples, in particular the two-dimensional chiral Gross-Neveu model, the Heisenberg spin chain and { N }=4 superconformal Yang-Mills theory in four dimensions.
Energy Technology Data Exchange (ETDEWEB)
Joshipura, A.S. [Physical Research Laboratory, Navarangpura, Ahmedabad (India)
2008-01-15
The possible maximal mixing seen in the oscillations of atmospheric neutrinos has led to the postulate of {mu}-{tau} symmetry, which interchanges {nu}{sub {mu}} and {nu}{sub {tau}}. We argue that such a symmetry need not be special to neutrinos but can be extended to all fermions. The assumption that all fermion mass matrices are approximately invariant under the interchange of the second and the third generation fields is shown to be phenomenologically viable and has interesting consequences. In the quark sector, the smallness of V{sub ub} and V{sub cb} can be consequences of this approximate 2-3 symmetry. The same approximate symmetry can simultaneously lead to a large atmospheric mixing angle and can describe the leptonic mixing quite well. We identify two generic scenarios leading to this. One is based on the conventional type-I seesaw mechanism and the other follows from the type-II seesaw model. The latter requires a quasi-degenerate neutrino spectrum for obtaining large atmospheric neutrino mixing in the presence of an approximate {mu}-{tau} symmetry. (orig.)
Weiss, Asia; Whiteley, Walter
2014-01-01
This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme. Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology. The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...
Seeing Science through Symmetry
Gould, L. I.
Seeing Through Symmetry is a course that introduces non-science majors to the pervasive influence of symmetry in science. The concept of symmetry is usedboth as a link between subjects (such as physics, biology, mathematics, music, poetry, and art) and as a method within a subject. This is done through the development and use of interactive multimedia learning environments to stimulate learning. Computer-based labs enable the student to further explore the concept by being gently led from the arts to science. This talk is an update that includes some of the latest changes to the course. Explanations are given on methodology and how a variety of interactive multimedia tools contribute to both the lecture and lab portion of the course (created in 1991 and taught almost every semester since then, including one in Sweden).
Binary Tetrahedral Flavor Symmetry
Eby, David A
2013-01-01
A study of the T' Model and its variants utilizing Binary Tetrahedral Flavor Symmetry. We begin with a description of the historical context and motivations for this theory, together with some conceptual background for added clarity, and an account of our theory's inception in previous works. Our model endeavors to bridge two categories of particles, leptons and quarks, a unification made possible by the inclusion of additional Higgs particles, shared between the two fermion sectors and creating a single coherent system. This is achieved through the use of the Binary Tetrahedral symmetry group and an investigation of the Tribimaximal symmetry evidenced by neutrinos. Our work details perturbations and extensions of this T' Model as we apply our framework to neutrino mixing, quark mixing, unification, and dark matter. Where possible, we evaluate model predictions against experimental results and find excellent matching with the atmospheric and reactor neutrino mixing angles, an accurate prediction of the Cabibb...
Segmentation Using Symmetry Deviation
DEFF Research Database (Denmark)
Hollensen, Christian; Højgaard, L.; Specht, L.
2011-01-01
and evaluate the method. The method uses deformable registration on computed tomography(CT) to find anatomical symmetry deviations of Head & Neck squamous cell carcinoma and combining it with positron emission tomography (PET) images. The method allows the use anatomical and symmetrical information of CT scans...... to improve automatic delineations. Materials: PET/CT scans from 30 patients were used for this study, 20 without cancer in hypopharyngeal volume and 10 with hypharyngeal carcinoma. An head and neck atlas was created from the 20 normal patients. The atlas was created using affine and non-rigid registration...... of the CT-scans into a single atlas. Afterwards the standard deviation of anatomical symmetry for the 20 normal patients was evaluated using non-rigid registration and registered onto the atlas to create an atlas for normal anatomical symmetry deviation. The same non-rigid registration was used on the 10...
Leadership, power and symmetry
DEFF Research Database (Denmark)
Spaten, Ole Michael
2016-01-01
Research publications concerning managers who coach their own employees are barely visible despite its wide- spread use in enterprises (McCarthy & Milner, 2013; Gregory & Levy, 2011; Crabb, 2011). This article focuses on leadership, power and moments of symmetry in the coaching relationship...... session. Thereafter we executed qualitative interviews with both managers and employees. Subsequently, a Thematic Analysis resulted in several themes, including power and moments of symmetry in the coaching relationship. One main conclusion is that the most fruitful coaching was obtained when the coachee...... experienced moments of symmetry and that necessary and sufficient conditions to bring forth such moments include a strong working alliance and the coach being aware of the power at play....
Energy Technology Data Exchange (ETDEWEB)
Chanowitz, M.S.
1990-09-01
The Higgs mechanism is reviewed in its most general form, requiring the existence of a new symmetry-breaking force and associated particles, which need not however be Higgs bosons. The first lecture reviews the essential elements of the Higgs mechanism, which suffice to establish low energy theorems for the scattering of longitudinally polarized W and Z gauge bosons. An upper bound on the scale of the symmetry-breaking physics then follows from the low energy theorems and partial wave unitarity. The second lecture reviews particular models, with and without Higgs bosons, paying special attention to how the general features discussed in lecture 1 are realized in each model. The third lecture focuses on the experimental signals of strong WW scattering that can be observed at the SSC above 1 TeV in the WW subenergy, which will allow direct measurement of the strength of the symmetry-breaking force. 52 refs., 10 figs.
Trautmann, Wolfgang; Russotto, Paolo
2016-01-01
The nuclear equation-of-state is a topic of highest current interest in nuclear structure and reactions as well as in astrophysics. In particular, the equation-of-state of asymmetric matter and the symmetry energy representing the difference between the energy densities of neutron matter and of symmetric nuclear matter are not sufficiently well constrained at present. The density dependence of the symmetry energy is conventionally expressed in the form of the slope parameter L describing the derivative with respect to density of the symmetry energy at saturation. Results deduced from nuclear structure and heavy-ion reaction data are distributed around a mean value L=60 MeV. Recent studies have more thoroughly investigated the density range that a particular observable is predominantly sensitive to. Two thirds of the saturation density is a value typical for the information contained in nuclear-structure data. Higher values exceeding saturation have been shown to be probed with meson production and collective ...
Gravitation and Duality Symmetry
D'Andrade, V C; Pereira, J G
2005-01-01
By generalizing the Hodge dual operator to the case of soldered bundles, and working in the context of the teleparallel equivalent of general relativity, an analysis of the duality symmetry in gravitation is performed. Although the basic conclusion is that, at least in the general case, gravitation does not present duality symmetry, there is a particular theory in which this symmetry is present. This theory is a self dual (or anti-self dual) teleparallel gravity in which, owing to the fact that it does not contribute to the gravitational interaction of fermions, the purely tensor part of torsion is assumed to vanish. The corresponding fermionic gravitational interaction is found to be chiral. Since duality is intimately related to renormalizability, this theory will probably be much more amenable to renormalization than teleparallel gravity or general relativity. Although obtained in the context of teleparallel gravity, these results must also be true for general relativity.
Schubert, Mathias
2016-11-18
A coordinate-invariant generalization of the Lyddane-Sachs-Teller relation is presented for polar vibrations in materials with monoclinic and triclinic crystal systems. The generalization is derived from an eigendielectric displacement vector summation approach, which is equivalent to the microscopic Born-Huang description of polar lattice vibrations in the harmonic approximation. An expression for a general oscillator strength is also described for materials with monoclinic and triclinic crystal systems. A generalized factorized form of the dielectric response characteristic for monoclinic and triclinic materials is proposed. The generalized Lyddane-Sachs-Teller relation is found valid for monoclinic β-Ga_{2}O_{3}, where accurate experimental data became available recently from a comprehensive generalized ellipsometry investigation [Phys. Rev. B 93, 125209 (2016)]. Data for triclinic crystal systems can be measured by generalized ellipsometry as well, and are anticipated to become available soon and results can be compared with the generalized relations presented here.
Flavour from accidental symmetries
Energy Technology Data Exchange (ETDEWEB)
Ferretti, Luca [SISSA/ISAS and INFN, I-34013 Trieste (Italy); King, Stephen F. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Romanino, Andrea [SISSA/ISAS and INFN, I-34013 Trieste (Italy)
2006-11-15
We consider a new approach to fermion masses and mixings in which no special 'horizontal' dynamics is invoked to account for the hierarchical pattern of charged fermion masses and for the peculiar features of neutrino masses. The hierarchy follows from the vertical, family-independent structure of the model, in particular from the breaking pattern of the Pati-Salam group. The lightness of the first two fermion families can be related to two family symmetries emerging in this context as accidental symmetries.
Symmetry, structure, and spacetime
Rickles, Dean
2007-01-01
In this book Rickles considers several interpretative difficulties raised by gauge-type symmetries (those that correspond to no change in physical state). The ubiquity of such symmetries in modern physics renders them an urgent topic in philosophy of physics. Rickles focuses on spacetime physics, and in particular classical and quantum general relativity. Here the problems posed are at their most pathological, involving the apparent disappearance of spacetime! Rickles argues that both traditional ontological positions should be replaced by a structuralist account according to which relational
Weakly broken galileon symmetry
Energy Technology Data Exchange (ETDEWEB)
Pirtskhalava, David [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Santoni, Luca; Trincherini, Enrico [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); INFN, Sezione di Pisa, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Vernizzi, Filippo [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette cédex, F-91191 (France)
2015-09-01
Effective theories of a scalar ϕ invariant under the internal galileon symmetryϕ→ϕ+b{sub μ}x{sup μ} have been extensively studied due to their special theoretical and phenomenological properties. In this paper, we introduce the notion of weakly broken galileon invariance, which characterizes the unique class of couplings of such theories to gravity that maximally retain their defining symmetry. The curved-space remnant of the galileon’s quantum properties allows to construct (quasi) de Sitter backgrounds largely insensitive to loop corrections. We exploit this fact to build novel cosmological models with interesting phenomenology, relevant for both inflation and late-time acceleration of the universe.
Liu, Keh-Fei
2016-01-01
The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $\\pi N \\sigma$ term and strangeness. The third one is the role of chiral $U(1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.
Arzano, Michele; Kowalski-Glikman, Jerzy
2016-09-01
We construct discrete symmetry transformations for deformed relativistic kinematics based on group valued momenta. We focus on the specific example of κ-deformations of the Poincaré algebra with associated momenta living on (a sub-manifold of) de Sitter space. Our approach relies on the description of quantum states constructed from deformed kinematics and the observable charges associated with them. The results we present provide the first step towards the analysis of experimental bounds on the deformation parameter κ to be derived via precision measurements of discrete symmetries and CPT.
Kudoh, Y.; Kuribayashi, T.; Suzuki, A.; Ohtani, E.; Kamada, T.
2003-04-01
A single crystal of δ-AlOOH synthesized by Suzuki et al. (2000) at conditions of 1000^oC and 21 GPa was used in this study. A set of X-ray diffraction intensities up to sinθ/λ=0.80 Å-1 were measured with a single crystal of 83×35×24 μm using MoKα radiation (50 kV, 40 mA). Al:Mg:Si ratio 0.84:0.07:0.09 measured by EDS with the same crystal used in the X-ray diffraction intensity measurement yielded the chemical formula (Al0.84Mg0.07Si0.09)H0.98O_2. Suzuki et al. (2000) reported the space group P2_1nm from powder X-ray data but the systematic absence of reflections observed in this study indicated another space group Pnn2. The systematic absence of reflections observed in the present work were h+l odd for h0l and k+l odd for 0kl, indicating possible space group Pnn2 or Pnnm. The N(Z) test for a center of symmetry indicated an acentric space group. The non-centrosymmetric space group Pnn2 was therefore employed and was confirmed by the structural refinement. The agreement factors for 109 independent reflections (Io>= 3.0σ Io) were R=3.6% with anisotropic temperature factors. The difference Fourier synthesis was calculated and two significant Fourier peaks H1 and H2 for the possible hydrogen sites were found. The H1 site locates around two-fold rotation axis with H1-H1 distance of 0.55 Å. The H1 site is considered to be for symmetrical statistical distribution of hydrogen atoms. The H2-H2 are separated with H2-H2 distance 2.12 Å which is larger than the sum of van der Waals radii of hydrogen atoms. The partial occupancy of Mg and Si atoms at Al site suggests the possibility of limited solid solution among δ-AlOOH, stishovite SiO_2 and hypothetical rutile-structured Mg(OH)_2. The H1 site is considered to be for AlOOH and the H_2 site for Mg(OH)_2.
Dieperink, AEL; van Neck, D; Suzuki, T; Otsuka, T; Ichimura, M
2005-01-01
The role of isospin asymmetry in nuclei and neutron stars is discussed, with an emphasis on the density dependence of the nuclear symmetry energy. Results obtained with the self-consistent Green function method are presented and compared with various other theoretical predictions. Implications for t
Quantum entanglement and symmetry
Energy Technology Data Exchange (ETDEWEB)
Chruscinski, D; Kossakowski, A [Institute of Physics, Nicolaus Copernicus University, Grudziadzka 5/7, 87-100 Torun (Poland)
2007-11-15
One of the main problem in Quantum Information Theory is to test whether a given state of a composite quantum system is entangled or separable. It turns out that within a class of states invariant under the action of the symmetry group this problem considerably simplifies. We analyze multipartite invariant states and the corresponding symmetric quantum channels.
Quantum entanglement and symmetry
Chruściński, D.; Kossakowski, A.
2007-11-01
One of the main problem in Quantum Information Theory is to test whether a given state of a composite quantum system is entangled or separable. It turns out that within a class of states invariant under the action of the symmetry group this problem considerably simplifies. We analyze multipartite invariant states and the corresponding symmetric quantum channels.
Gray, P L
2003-01-01
"The subatomic pion particle breaks the charge symmetry rule that governs both fusion and decay. In experiments performed at the Indiana University Cyclotron Laboratory, physicists forced heavy hydrogen (1 proton + 1 neutron) to fuse into helium in a controlled, measurable environment" (1 paragraph).
Symmetries in fundamental physics
Sundermeyer, Kurt
2014-01-01
Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P.Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also underst...
Symmetries in fundamental physics
Sundermeyer, Kurt
2014-01-01
Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P. Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also unders...
Crumpecker, Cheryl
2003-01-01
Describes an art lesson used with children in the third grade to help them learn about symmetry, as well as encouraging them to draw larger than usual. Explains that students learn about the belief called "Horror Vacui" of the Northwest American Indian tribes and create their interpretation of this belief. (CMK)
Gauging without Initial Symmetry
Kotov, Alexei
2016-01-01
The gauge principle is at the heart of a good part of fundamental physics: Starting with a group G of so-called rigid symmetries of a functional defined over space-time Sigma, the original functional is extended appropriately by additional Lie(G)-valued 1-form gauge fields so as to lift the symmetry to Maps(Sigma,G). Physically relevant quantities are then to be obtained as the quotient of the solutions to the Euler-Lagrange equations by these gauge symmetries. In this article we show that one can construct a gauge theory for a standard sigma model in arbitrary space-time dimensions where the target metric is not invariant with respect to any rigid symmetry group, but satisfies a much weaker condition: It is sufficient to find a collection of vector fields v_a on the target M satisfying the extended Killing equation v_{a(i;j)}=0 for some connection acting on the index a. For regular foliations this is equivalent to merely requiring the distribution orthogonal to the leaves to be invariant with respect to leaf...
Pels, D.L.
1996-01-01
While symmetry and impartiality have become ruling principles in S&TS, defining its core ideal of a 'value-free relativism', their philosophical anchorage has attracted much less discussion than the issue or:how far their jurisdiction can be extended or generalized. This paper seeks to argue that sy
Applications of chiral symmetry
Pisarski, R D
1995-01-01
I discuss several topics in the applications of chiral symmetry at nonzero temperature, including: where the rho goes, disoriented chiral condensates, and the phase diagram for QCD with 2+1 flavors. (Based upon talks presented at the "Workshop on Finite Temperature QCD", Wuhan, P.R.C., April, 1994.)
Einmahl, John; Gan, Zhuojiong
2016-01-01
Omnibus tests for central symmetry of a bivariate probability distribution are proposed. The test statistics compare empirical measures of opposite regions. Under rather weak conditions, we establish the asymptotic distribution of the test statistics under the null hypothesis; it follows that they a
Symmetries of hadrons after unbreaking the chiral symmetry
Glozman, L Ya; Schröck, M
2012-01-01
We study hadron correlators upon artificial restoration of the spontaneously broken chiral symmetry. In a dynamical lattice simulation we remove the lowest lying eigenmodes of the Dirac operator from the valence quark propagators and study evolution of the hadron masses obtained. All mesons and baryons in our study, except for a pion, survive unbreaking the chiral symmetry and their exponential decay signals become essentially better. From the analysis of the observed spectroscopic patterns we conclude that confinement still persists while the chiral symmetry is restored. All hadrons fall into different chiral multiplets. The broken U(1)_A symmetry does not get restored upon unbreaking the chiral symmetry. We also observe signals of some higher symmetry that includes chiral symmetry as a subgroup. Finally, from comparison of the \\Delta - N splitting before and after unbreaking of the chiral symmetry we conclude that both the color-magnetic and the flavor-spin quark-quark interactions are of equal importance.
Pedrera, A.; Ruiz-Constán, A.; Marín-Lechado, C.; Galindo-Zaldívar, J.; González, A.; Peláez, J. A.
2013-12-01
We examine the late Tortonian to present-day deformation of an active seismic sector of the eastern Iberian foreland basement of the Betic Cordillera, in southern Spain. Transpressive faults affecting Paleozoic basement offset up to Triassic rocks. Late Triassic clays and evaporites constitute a décollement level decoupling the basement rocks and a ~100 m thick cover of Jurassic carbonates. Monoclines trending NE-SW to ENE-WSW deform the Jurassic cover driven by the propagation of high-angle transpressive right-lateral basement faults. They favor the migration of clays and evaporites toward the propagated fault tip, i.e., the core of the anticline, resulting in fluid overpressure, fluid flow, and precipitation of fibrous gypsum parallel to a vertical σ3. The overall geometry of the studied monoclines, as well as the intense deformation within the clays and evaporites, reproduces three-layer discrete element models entailing a weak middle unit sandwiched between strong layers. Late Tortonian syn-folding sediments recorded the initial stages of the fault-propagation folding. Equivalent unexposed transpressive structures and associated monoclines reactivated under the present-day NW-SE convergence are recognized and analyzed in the Sabiote-Torreperogil region, using seismic reflection, gravity, and borehole data. A seismic series of more than 2100 low-magnitude earthquakes was recorded within a very limited area of the basement of this sector from October 2012 to May 2013. Seismic activity within a major NE-SW trending transpressive basement fault plane stimulated rupture along a subsidiary E-W (~N95°E) strike-slip relay fault. The biggest event (mbLg 3.9, MW 3.7) occurred at the junction between them in a transpressive relay sector.
DEFF Research Database (Denmark)
Chen, Ko-Hua; Li, Mei-Jane; Cheng, Wen-Ting;
2009-01-01
Raman microspectroscopy was first used to determine the composition of a calcified plaque located at the pterygium-excision site of a 51-year-old female patient's left nasal sclera after surgery. It was unexpectedly found that the Raman spectrum of the calcified sample at 1149, 1108, 1049, 756, 517...... to the characteristic peak at 958/cm of hydroxyapatite (HA). This is the first study to report the spectral biodiagnosis of both monoclinic CPPD and HA co-deposited in the calcified plaque of a patient with sclera dystrophic calcification using Raman microspectroscopy....
On Symmetries in Optimal Control
van der Schaft, A. J.
1986-01-01
We discuss the use of symmetries in solving optimal control problems. In particular a procedure for obtaining symmetries is given which can be performed before the actual calculation of the optimal control and optimal Hamiltonian.
On Symmetries in Optimal Control
Schaft, A.J. van der
1986-01-01
We discuss the use of symmetries in solving optimal control problems. In particular a procedure for obtaining symmetries is given which can be performed before the actual calculation of the optimal control and optimal Hamiltonian.
A relativistic symmetry in nuclei
Energy Technology Data Exchange (ETDEWEB)
Ginocchio, J N [MS B283, Theoretical Division, Los Alamos National Laboratory Los Alamos, New Mexico 87545 (Mexico)
2007-11-15
We review some of the empirical and theoretical evidence supporting pseudospin symmetry in nuclei as a relativistic symmetry. We review the case that the eigenfunctions of realistic relativistic nuclear mean fields approximately conserve pseudospin symmetry in nuclei. We discuss the implications of pseudospin symmetry for magnetic dipole transitions and Gamow-Teller transitions between states in pseudospin doublets. We explore a more fundamental rationale for pseudospin symmetry in terms of quantum chromodynamics (QCD), the basic theory of the strong interactions. We show that pseudospin symmetry in nuclei implies spin symmetry for an anti-nucleon in a nuclear environment. We also discuss the future and what role pseudospin symmetry may be expected to play in an effective field theory of nucleons.
Invariants of broken discrete symmetries
Kalozoumis, P.; Morfonios, C.; Diakonos, F. K.; Schmelcher, P.
2014-01-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying in particular to acoustic, optical and matter waves. Nonvanishing values of the invariant currents provide a systematic ...
Vladan Nikolić; Ljiljana Radović; Biserka Marković
2015-01-01
The idea of construction of twin buildings is as old as architecture itself, and yet there is hardly any study emphasizing their specificity. Most frequently there are two objects or elements in an architectural composition of “twins” in which there may be various symmetry relations, mostly bilateral symmetries. The classification of “twins” symmetry in this paper is based on the existence of bilateral symmetry, in terms of the perception of an observer. The classification includes both, 2D a...
Symmetry analysis of the behavior of the family R6M23 compounds upon hydrogenation
Kuna, Agnieszka; Sikora, Wiesława
2011-06-01
Symmetry analysis was applied in this work to discuss the behavior of the family R6M23 compounds upon hydrogenation (deuteration), where different structural transformations and magnetic properties, depending on the type of R and M atoms and hydrogen (deuterium) concentrations, have been found. The crystallographic structure of these compounds is described by the Fm3m space group and contain 116 atoms per unit cell occupying the positions 24e(R), 4b, 24d, 32f1 and 32f2(M). Additionally in the elementary cell, there could be up to 100 atoms of hydrogen (or deuterium) occupying the interstitial positions 4a, 32f3, 96j1 and 96k1. The symmetry analysis in the frame of the theory of space groups and their representation gives the opportunity to find all possible transformations from high symmetry parent structure to the structures with symmetry belonging to one of its subgroups. For a given transformation it indicates possible displacements of atoms from initial positions in the parent structure, ordering of hydrogen over interstitial sites and also ordering of magnetic moments, described by the smallest possible number of free parameters. The analysis was carried out by means of the MODY computer program for vectors k = (0; 0; 0) and k = (0; 0; 1) describing the changes of translational symmetry and all positions occupied by the R, M and D atoms.
Dynamical Symmetries in Classical Mechanics
Boozer, A. D.
2012-01-01
We show how symmetries of a classical dynamical system can be described in terms of operators that act on the state space for the system. We illustrate our results by considering a number of possible symmetries that a classical dynamical system might have, and for each symmetry we give examples of dynamical systems that do and do not possess that…
Scattering matrices with block symmetries
Życzkowski, Karol
1997-01-01
Scattering matrices with block symmetry, which corresponds to scattering process on cavities with geometrical symmetry, are analyzed. The distribution of transmission coefficient is computed for different number of channels in the case of a system with or without the time reversal invariance. An interpolating formula for the case of gradual time reversal symmetry breaking is proposed.
Emergence of Symmetries from Entanglement
CERN. Geneva
2016-01-01
Maximal Entanglement appears to be a key ingredient for the emergence of symmetries. We first illustrate this phenomenon using two examples: the emergence of conformal symmetry in condensed matter systems and the relation of tensor networks to holography. We further present a Principle of Maximal Entanglement that seems to dictate to a large extend the structure of gauge symmetry.
Probing IrTe2 crystal symmetry by polarized Raman scattering
Lazarević, N.; Bozin, E. S.; Šćepanović, M.; Opačić, M.; Lei, Hechang; Petrovic, C.; Popović, Z. V.
2014-06-01
Polarized Raman scattering measurements on IrTe2 single crystals carried out over the 15-640 K temperature range, and across the structural phase transition, reveal different insights regarding the crystal symmetry. In the high temperature regime three Raman active modes are observed at all of the studied temperatures above the structural phase transition, rather than two as predicted by the factor group analysis for the assumed P3¯m1 symmetry. This indicates that the actual symmetry of the high temperature phase is lower than previously thought. The observation of an additional Eg mode at high temperature can be explained by doubling of the original trigonal unit cell along the c axis and within the P3¯c1 symmetry. In the low temperature regime (below 245 K) the other Raman modes appear as a consequence of the symmetry lowering phase transition and the corresponding increase of the primitive cell. All of the modes observed below the phase transition temperature can be assigned within the monoclinic crystal symmetry. The temperature dependence of the Raman active phonons in both phases is mainly driven by anharmonicity effects. The results call for reconsideration of the crystallographic phases of IrTe2.
Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO 2 Nanowires
Asayesh-Ardakani, Hasti
2015-10-12
There has been long-standing interest in tuning the metal-insulator phase transition in vanadium dioxide (VO) via the addition of chemical dopants. However, the underlying mechanisms by which doping elements regulate the phase transition in VO are poorly understood. Taking advantage of aberration-corrected scanning transmission electron microscopy, we reveal the atomistic origins by which tungsten (W) dopants influence the phase transition in single crystalline WVO nanowires. Our atomically resolved strain maps clearly show the localized strain normal to the (122¯) lattice planes of the low W-doped monoclinic structure (insulator). These strain maps demonstrate how anisotropic localized stress created by dopants in the monoclinic structure accelerates the phase transition and lead to relaxation of structure in tetragonal form. In contrast, the strain distribution in the high W-doped VO structure is relatively uniform as a result of transition to tetragonal (metallic) phase. The directional strain gradients are furthermore corroborated by density functional theory calculations that show the energetic consequences of distortions to the local structure. These findings pave the roadmap for lattice-stress engineering of the MIT behavior in strongly correlated materials for specific applications such as ultrafast electronic switches and electro-optical sensors.
Monoclinic tridymite in clast-rich impact melt rock from the Chesapeake Bay impact structure
Jackson, J.C.; Horton, J.W.; Chou, I.-Ming; Belkin, H.E.
2011-01-01
X-ray diffraction and Raman spectroscopy confirm a rare terrestrial occurrence of monoclinic tridymite in clast-rich impact melt rock from the Eyreville B drill core in the Chesapeake Bay impact structure. The monoclinic tridymite occurs with quartz paramorphs after tridymite and K-feldspar in a microcrystalline groundmass of devitrified glass and Fe-rich smectite. Electron-microprobe analyses revealed that the tridymite and quartz paramorphs after tridymite contain different amounts of chemical impurities. Inspection by SEM showed that the tridymite crystal surfaces are smooth, whereas the quartz paramorphs contain irregular tabular voids. These voids may represent microporosity formed by volume decrease in the presence of fluid during transformation from tridymite to quartz, or skeletal growth in the original tridymite. Cristobalite locally rims spherulites within the same drill core interval. The occurrences of tridymite and cristobalite appear to be restricted to the thickest clast-rich impact melt body in the core at 1402.02-1407.49 m depth. Their formation and preservation in an alkali-rich, high-silica melt rock suggest initially high temperatures followed by rapid cooling.
Ab initio velocity-field curves in monoclinic β-Ga2O3
Ghosh, Krishnendu; Singisetti, Uttam
2017-07-01
We investigate the high-field transport in monoclinic β-Ga2O3 using a combination of ab initio calculations and full band Monte Carlo (FBMC) simulation. Scattering rate calculation and the final state selection in the FBMC simulation use complete wave-vector (both electron and phonon) and crystal direction dependent electron phonon interaction (EPI) elements. We propose and implement a semi-coarse version of the Wannier-Fourier interpolation method [Giustino et al., Phys. Rev. B 76, 165108 (2007)] for short-range non-polar optical phonon (EPI) elements in order to ease the computational requirement in FBMC simulation. During the interpolation of the EPI, the inverse Fourier sum over the real-space electronic grids is done on a coarse mesh while the unitary rotations are done on a fine mesh. This paper reports the high field transport in monoclinic β-Ga2O3 with deep insight into the contribution of electron-phonon interactions and velocity-field characteristics for electric fields ranging up to 450 kV/cm in different crystal directions. A peak velocity of 2 × 107 cm/s is estimated at an electric field of 200 kV/cm.
Li, Zejun; Wu, Jiajing; Hu, Zhenpeng; Lin, Yue; Chen, Qi; Guo, Yuqiao; Liu, Yuhua; Zhao, Yingcheng; Peng, Jing; Chu, Wangsheng; Wu, Changzheng; Xie, Yi
2017-06-01
In correlated systems, intermediate states usually appear transiently across phase transitions even at the femtosecond scale. It therefore remains an open question how to determine these intermediate states--a critical issue for understanding the origin of their correlated behaviour. Here we report a surface coordination route to successfully stabilize and directly image an intermediate state in the metal-insulator transition of vanadium dioxide. As a prototype metal-insulator transition material, we capture an unusual metal-like monoclinic phase at room temperature that has long been predicted. Coordinate bonding of L-ascorbic acid molecules with vanadium dioxide nanobeams induces charge-carrier density reorganization and stabilizes metallic monoclinic vanadium dioxide, unravelling orbital-selective Mott correlation for gap opening of the vanadium dioxide metal-insulator transition. Our study contributes to completing phase-evolution pathways in the metal-insulator transition process, and we anticipate that coordination chemistry may be a powerful tool for engineering properties of low-dimensional correlated solids.
Koulialias, D.; Kind, J.; Charilaou, M.; Weidler, P. G.; Löffler, J. F.; Gehring, A. U.
2016-02-01
Non-stoichiometric monoclinic 4C pyrrhotite (Fe7S8) is a major magnetic remanence carrier in the Earth's crust and in extraterrestrial materials. Because of its low-temperature magnetic transition around 30 K also known as Besnus transition, which is considered to be an intrinsic property, this mineral phase is easily detectable in natural samples. Although the physical properties of pyrrhotite have intensively been studied, the mechanism behind the pronounced change in magnetization at the low-temperature transition is still debated. Here we report magnetization experiments on a pyrrhotite crystal (Fe6.6S8) that consists of a 4C and an incommensurate 5C* superstructure that are different in their defect structure. The occurrence of two superstructures is magnetically confirmed by symmetric inflection points in hysteresis measurements above the transition at about 30 K. The disappearance of the inflection points and the associated change of the hysteresis parameters indicate that the two superstructures become strongly coupled to form a unitary magnetic anisotropy system at the transition. From this it follows that the Besnus transition in monoclinic pyrrhotite is an extrinsic magnetic phenomenon with respect to the 4C superstructure and therefore the physics behind it is in fact different from that of the well-known Verwey transition.
Crystal structure of a new monoclinic polymorph of N-(4-methylphenyl-3-nitropyridin-2-amine
Directory of Open Access Journals (Sweden)
Aina Mardia Akhmad Aznan
2014-08-01
Full Text Available The title compound, C12H11N3O2, is a second monoclinic polymorph (P21, with Z′ = 4 of the previously reported monoclinic (P21/c, with Z′ = 2 form [Akhmad Aznan et al. (2010. Acta Cryst. E66, o2400]. Four independent molecules comprise the asymmetric unit, which have the common features of a syn disposition of the pyridine N atom and the toluene ring, and an intramolecular amine–nitro N—H...O hydrogen bond. The differences between molecules relate to the dihedral angles between the rings which range from 2.92 (19 to 26.24 (19°. The geometry-optimized structure [B3LYP level of theory and 6–311 g+(d,p basis set] has the same features except that the entire molecule is planar. In the crystal, the three-dimensional architecture is consolidated by a combination of C—H...O, C—H...π, nitro-N—O...π and π–π interactions [inter-centroid distances = 3.649 (2–3.916 (2 Å].
Symmetry versus Asymmetry in the Molecules of Life: Homomeric Protein Assemblies
Directory of Open Access Journals (Sweden)
Biserka Kojić-Prodić
2010-04-01
Full Text Available The essay is dedicated to the relation of symmetry and asymmetry-chirality in Nature. The Introduction defines symmetry and its impact on basic definitions in science and human activities. The following section Chirality of molecules reveals breifly development of notion of chirality and its significance in living organisms and science. Homochirality is a characteristic hallmark of life and its significance is presented in the section Homochirality of Life. Proteins, important constituents of living cells performing versatile functions are chiral macromolecules composed of L-amino acids. In particular, the protein assemblies are of a great importance in functions of a cell. Therefore, they have attracted researches to examine them from different points of view. Among proteins of known three-dimensional structures about 50–80% of them exist as homomeric protein complexes. Protein monomers lack any intrinsic, underlying symmetry, i.e. enantiomorphic protein molecules involve left-handed amino acids but their asymmetry does not appear to extend to the level of quaternary structures (homomeric complexes as observed by Chothia in 1991. In the section Homomeric assemblies we performed our analysis of very special cases of homomers revealing non-crystallographic symmetry in crystals. Homochiral proteins can crystallize only in enantiomorphic space groups. Among 230 existing space groups 65 are enantiomorphic containing limited symmetry elements that are rotation and screw-rotation axes. Any axis of rotation symmetry of a crystal lattice must be two-fold, three-fold, four-fold, or six-fold. Five-fold, seven-fold, and higher-fold rotation symmetry axes are incompatible with the symmetry under spatial displacement of the three-dimensional crystal lattice.
Leadership, power and symmetry
DEFF Research Database (Denmark)
Spaten, Ole Michael
2016-01-01
regarding managers coaching their employees and it is asked; what contributes to coaching of high quality when one reflects on the power aspect as being immanent? Fourteen middle managers coached five of their employees, and all members of each party wrote down cues and experiences immediately after each......Research publications concerning managers who coach their own employees are barely visible despite its wide- spread use in enterprises (McCarthy & Milner, 2013; Gregory & Levy, 2011; Crabb, 2011). This article focuses on leadership, power and moments of symmetry in the coaching relationship...... session. Thereafter we executed qualitative interviews with both managers and employees. Subsequently, a Thematic Analysis resulted in several themes, including power and moments of symmetry in the coaching relationship. One main conclusion is that the most fruitful coaching was obtained when the coachee...
Asymmetry, Symmetry and Beauty
Directory of Open Access Journals (Sweden)
Abbe R. Kopra
2010-07-01
Full Text Available Asymmetry and symmetry coexist in natural and human processes. The vital role of symmetry in art has been well demonstrated. This article highlights the complementary role of asymmetry. Further we show that the interaction of asymmetric action (recursion and symmetric opposition (sinusoidal waves are instrumental in generating creative features (relatively low entropy, temporal complexity, novelty (less recurrence in the data than in randomized copies and complex frequency composition. These features define Bios, a pattern found in musical compositions and in poetry, except for recurrence instead of novelty. Bios is a common pattern in many natural and human processes (quantum processes, the expansion of the universe, gravitational waves, cosmic microwave background radiation, DNA, physiological processes, animal and human populations, and economic time series. The reduction in entropy is significant, as it reveals creativity and contradicts the standard claim of unavoidable decay towards disorder. Artistic creations capture fundamental features of the world.
Symmetry rules How science and nature are founded on symmetry
Rosen, Joe
2008-01-01
When we use science to describe and understand the world around us, we are in essence grasping nature through symmetry. In fact, modern theoretical physics suggests that symmetry is a, if not the, foundational principle of nature. Emphasizing the concepts, this book leads the reader coherently and comprehensively into the fertile field of symmetry and its applications. Among the most important applications considered are the fundamental forces of nature and the Universe. It is shown that the Universe cannot possess exact symmetry, which is a principle of fundamental significance. Curie's principle - which states that the symmetry of the effect is at least that of the cause - features prominently. An introduction to group theory, the mathematical language of symmetry, is included. This book will convince all interested readers of the importance of symmetry in science. Furthermore, it will serve as valuable background reading for all students in the physical sciences.
1985-08-01
way to choose among them. Spirals can occur in natural figures, e.g. a spiralled tail or a coil of rope or vine tendril, and in line drawings. Since...generated and removes it and all regions similar to it from the list of regions. The end result is a pruned list of distinct optimal regions. 4.7...that, at least to a first approximation, the potential symmetry regions pruned by the locality restriction are not perceptually salient. For example
Symmetry and quantum mechanics
Corry, Scott
2016-01-01
This book offers an introduction to quantum mechanics for professionals, students, and others in the field of mathematics who have a minimal background in physics with an understanding of linear algebra and group theory. It covers such topics as Lie groups, algebras and their representations, and analysis (Hilbert space, distributions, the spectral Theorem, and the Stone-Von Neumann Theorem). The book emphasizes the role of symmetry and is useful to physicists as it provides a mathematical introduction to the topic.
Momeni, Davood
2014-01-01
The symmetry issue for Galileons has been studied. In particular we address scaling (conformal) and Noether symmetrized Galileons. We have been proven a series of theorems about the form of Noether conserved charge (current) for irregular (not quadratic) dynamical systems. Special attentions have been made on Galileons. We have been proven that for Galileons always is possible to find a way to "symmetrized" Galileo's field .
MOSTAFAZADEH, Ali
2013-01-01
PHYSICAL REVIEW A 87, 012103 (2013) Invisibility and PT symmetry Ali Mostafazadeh* Department of Mathematics, Koc¸ University, Sarıyer 34450, Istanbul, Turkey (Received 9 July 2012; published 3 January 2013) For a general complex scattering potential defined on a real line, we show that the equations governing invisibility of the potential are invariant under the combined action of parity and time-reversal (PT ) transformation. We determine the PT -symmetric as well as no...
Energy Technology Data Exchange (ETDEWEB)
Herrero, O F, E-mail: o.f.herrero@hotmail.co [Conservatorio Superior de Musica ' Eduardo Martinez Torner' Corrada del Obispo s/n 33003 - Oviedo - Asturias (Spain)
2010-06-01
Music and Physics are very close because of the symmetry that appears in music. A periodic wave is what music really is, and there is a field of Physics devoted to waves researching. The different musical scales are the base of all kind of music. This article tries to show how this musical scales are made, how the consonance is the base of many of them and how symmetric they are.
Invariants of Broken Discrete Symmetries
Kalozoumis, P. A.; Morfonios, C.; Diakonos, F. K.; Schmelcher, P.
2014-08-01
The parity and Bloch theorems are generalized to the case of broken global symmetry. Local inversion or translation symmetries in one dimension are shown to yield invariant currents that characterize wave propagation. These currents map the wave function from an arbitrary spatial domain to any symmetry-related domain. Our approach addresses any combination of local symmetries, thus applying, in particular, to acoustic, optical, and matter waves. Nonvanishing values of the invariant currents provide a systematic pathway to the breaking of discrete global symmetries.
Directory of Open Access Journals (Sweden)
Vladan Nikolić
2015-02-01
Full Text Available The idea of construction of twin buildings is as old as architecture itself, and yet there is hardly any study emphasizing their specificity. Most frequently there are two objects or elements in an architectural composition of “twins” in which there may be various symmetry relations, mostly bilateral symmetries. The classification of “twins” symmetry in this paper is based on the existence of bilateral symmetry, in terms of the perception of an observer. The classification includes both, 2D and 3D perception analyses. We start analyzing a pair of twin buildings with projection of the architectural composition elements in 2D picture plane (plane of the composition and we distinguish four 2D keyframe cases based on the relation between the bilateral symmetry of the twin composition and the bilateral symmetry of each element. In 3D perception for each 2D keyframe case there are two sub-variants, with and without a symmetry plane parallel to the picture plane. The bilateral symmetry is dominant if the corresponding symmetry plane is orthogonal to the picture plane. The essence of the complete classification is relation between the bilateral (dominant symmetry of the architectural composition and the bilateral symmetry of each element of that composition.
Directory of Open Access Journals (Sweden)
Mohammad Sadiq
2015-08-01
Full Text Available Zirconia was prepared by a precipitation method and calcined at 723 K, 1023 K, and 1253 K in order to obtain monoclinic zirconia. The prepared zirconia was characterized by XRD, SEM, EDX, surface area and pore size analyzer, and particle size analyzer. Monoclinic ZrO2 as a catalyst was used for the gas-phase oxidation of isopropanol to acetone in a Pyrex-glass-flow-type reactor with a temperature range of 443 K - 473 K. It was found that monoclinic ZrO2 shows remarkable catalytic activity (68% and selectivity (100% for the oxidation of isopropanol to acetone. This kinetic study reveals that the oxidation of isopropanol to acetone follows the L-H mechanism.
Cubic or monoclinic Y 2O 3:Eu 3+ nanoparticles by one step flame spray pyrolysis
Camenzind, Adrian; Strobel, Reto; Pratsinis, Sotiris E.
2005-11-01
Continuous, single-step synthesis of monocrystalline Y 2O 3:Eu 3+ nanophosphor particles (10-25 nm in diameter and 5 wt% Eu) was achieved by flame spray pyrolysis (FSP). The effect of FSP process parameters on materials properties was investigated by X-ray diffraction (XRD), nitrogen adsorption (BET) and transmission electron microscopy (TEM). Photoluminescence (PL) emission were measured as well as the time-resolved PL-intensity decay. Controlled synthesis of monoclinic or cubic Y 2O 3:Eu 3+ nanoparticles was achieved without post-treatment by controlling the high temperature residence time of these particles. The cubic nanoparticles exhibited longer decay times but lower maximum PL intensity than commercial micron-sized bulk Y 2O 3:Eu 3+ phosphor powder.
THE MONOCLINIC PHASE IN PZT: NEW LIGHT ON MORPHOTROPIC PHASE BOUNDARIES
Energy Technology Data Exchange (ETDEWEB)
NOHEDA,B.; GONZALO,J.A.; GUO,R.; PARK,S.E.; CROSS,L.E.; COX,D.E.; SHIRANE,G.
2000-03-09
A summary of the work recently carried out on the morphotropic phase boundary (MPB) of PZT is presented. By means of x-ray powder diffraction on ceramic samples of excellent quality, the MPB has been successfully characterized by changing temperature in a series of closely spaced compositions. As a result, an unexpected monoclinic phase has been found to exist in between the well-known tetragonal and rhombohedral PZT phases. A detailed structural analysis, together with the investigation of the field effect in this region of compositions, have led to an important advance in understanding the mechanisms responsible for the physical properties of PZT as well as other piezoelectric materials with similar morphotropic phase boundaries.
Electronic structure and optical properties of monoclinic clinobisvanite BiVO4.
Zhao, Zongyan; Li, Zhaosheng; Zou, Zhigang
2011-03-14
Monoclinic clinobisvanite bismuth vanadate is an important material with wide applications. However, its electronic structure and optical properties are still not thoroughly understood. Density functional theory calculations were adopted in the present work, to comprehend the band structure, density of states, and projected wave function of BiVO(4). In particular, we put more emphasis upon the intrinsic relationship between its structure and properties. Based on the calculated results, its molecular-orbital bonding structure was proposed. And a significant phenomenon of optical anisotropy was observed in the visible-light region. Furthermore, it was found that its slightly distorted crystal structure enhances the lone-pair impact of Bi 6s states, leading to the special optical properties and excellent photocatalytic activities.
Calculation of thermodynamic, electronic, and optical properties of monoclinic Mg2NiH4
Energy Technology Data Exchange (ETDEWEB)
Myers, W.R.; Richardson, T.J.; Rubin, M.D.; Wang, L-W.
2001-10-01
Ab initio total-energy density functional theory is used to investigate the low temperature (LT) monoclinic form of Mg2NiH4. The calculated minimum energy geometry of LT Mg2NiH4 is close to that determined from neutron diffraction data, and the NiH4 complex is close to a regular tetrahedron. The enthalpies of the phase change to high temperature (HT) pseudo-cubic Mg2NiH4 and of hydrogen absorption by Mg2Ni are calculated and compared with experimental values. LT Mg2NiH4 is found to be a semiconductor with an indirect band gap of 1.4 eV. The optical dielectric function of LT Mg2NiH4 differs somewhat from that of the HT phase. A calculated thin film transmittance spectrum is consistent with an experimental spectrum.
Farmer, David W
1995-01-01
In most mathematics textbooks, the most exciting part of mathematics-the process of invention and discovery-is completely hidden from the reader. The aim of Groups and Symmetry is to change all that. By means of a series of carefully selected tasks, this book leads readers to discover some real mathematics. There are no formulas to memorize; no procedures to follow. The book is a guide: Its job is to start you in the right direction and to bring you back if you stray too far. Discovery is left to you. Suitable for a one-semester course at the beginning undergraduate level, there are no prerequ
Renner, R
2007-01-01
Given a quantum system consisting of many parts, we show that symmetry of the system's state, i.e., invariance under swappings of the subsystems, implies that almost all of its parts are virtually identical and independent of each other. This result generalises de Finetti's classical representation theorem for infinitely exchangeable sequences of random variables as well as its quantum-mechanical analogue. It has applications in various areas of physics as well as information theory and cryptography. For example, in experimental physics, one typically collects data by running a certain experiment many times, assuming that the individual runs are mutually independent. Our result can be used to justify this assumption.
Yale, Paul B
2012-01-01
This book is an introduction to the geometry of Euclidean, affine, and projective spaces with special emphasis on the important groups of symmetries of these spaces. The two major objectives of the text are to introduce the main ideas of affine and projective spaces and to develop facility in handling transformations and groups of transformations. Since there are many good texts on affine and projective planes, the author has concentrated on the n-dimensional cases.Designed to be used in advanced undergraduate mathematics or physics courses, the book focuses on ""practical geometry,"" emphasi
Greene, Brian R
1997-01-01
Mirror symmetry has undergone dramatic progress during the last five years. Tremendous insight has been gained on a number of key issues. This volume surveys these results. Some of the contributions in this work have appeared elsewhere, while others were written specifically for this collection. The areas covered are organized into 4 sections, and each presents papers by both physicists and mathematicians. This volume collects the most important developments that have taken place in mathematical physics since 1991. It is an essential reference tool for both mathematics and physics libraries and for students of physics and mathematics.
Mota, Yasmine A; Cotes, Caroline; Carvalho, Rodrigo F; Machado, João P B; Leite, Fabíola P P; Souza, Rodrigo O A; Özcan, Mutlu
2017-10-01
This study evaluated the influence of two aging procedures on the biaxial flexural strength of yttria-stabilized tetragonal zirconia ceramics. Disc-shaped zirconia specimens and (ZE: E.max ZirCAD, Ivoclar; ZT: Zirkon Translucent, Zirkonzahn) (N = 80) (∅:12 mm; thickness:1.2 mm, ISO 6872) were prepared and randomly divided into four groups (n = 10 per group) according to the aging procedures: C: Control, no aging; M: mechanical cycling (2 × 10(6) cycles/3.8 Hz/200 N); AUT: Aging in autoclave at 134°C, 2 bar for 24 h; AUT + M: Autoclave aging followed by mechanical cycling. After aging, the transformed monoclinic zirconia (%) were evaluated using X-ray diffraction and surface roughness was measured using atomic force microscopy. The average grain size was measured by scanning electron microscopy and the specimens were submitted to biaxial flexural strength testing (1 mm/min, 1000 kgf in water). Data (MPa) were statistically analyzed using 2-way analysis of variance and Tukey's test (α = 0.05). Aging procedures significantly affected (p = 0.000) the flexural strength data but the effect of zirconia type was not significant (p = 0.657). AUTZT (936.4 ± 120.9(b) ) and AUT + MZE (867.2 ± 49.3(b) ) groups presented significantly higher values (p autoclave aging alone or with mechanical aging increased the flexure strength but also induced higher transformation from tetragonal to monoclinic phase in both zirconia materials tested. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1972-1977, 2017. © 2016 Wiley Periodicals, Inc.
Cerón, María Luisa; Herrera, Barbara; Araya, Paulo; Gracia, Francisco; Toro-Labbé, Alejandro
2013-07-01
We present a theoretical study of the water gas shift reaction taking place on zirconia surfaces modeled by monoclinic and tetragonal clusters. In order to understand the charge transfer between the active species, in this work we analyze the influence of the geometry of monoclinic and tetragonal zirconia using reactivity descriptors such as electronic chemical potential (μ), charge transfer (ΔN) and molecular hardness (η). We have found that the most preferred surface is tetragonal zirconia (tZrO2) indicating also that low charge transfer systems will generate less stable intermediates, that will allow to facilitate desorption process.
Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN2 and PtN2
Institute of Scientific and Technical Information of China (English)
Zhao Wen-Jie; Wang Yuan-Xu
2009-01-01
This paper studies the elastic and electronic structure properties of two new low-energy structures of PdN2 and PtN2 by first-principles calculations. It finds that tetragonal and monoclinic structures are more stable than a pyrite one. The always positive eigenvalues of the elastic constant matrix confirm that both the tetragonal and monoclinic structures are elastically stable. The origin of the low bulk modulus of the two structures is discussed. The results of the calculated density of states show that both of the two low-energy structures are metallic.
Bootstrap Dynamical Symmetry Breaking
Directory of Open Access Journals (Sweden)
Wei-Shu Hou
2013-01-01
Full Text Available Despite the emergence of a 125 GeV Higgs-like particle at the LHC, we explore the possibility of dynamical electroweak symmetry breaking by strong Yukawa coupling of very heavy new chiral quarks Q . Taking the 125 GeV object to be a dilaton with suppressed couplings, we note that the Goldstone bosons G exist as longitudinal modes V L of the weak bosons and would couple to Q with Yukawa coupling λ Q . With m Q ≳ 700 GeV from LHC, the strong λ Q ≳ 4 could lead to deeply bound Q Q ¯ states. We postulate that the leading “collapsed state,” the color-singlet (heavy isotriplet, pseudoscalar Q Q ¯ meson π 1 , is G itself, and a gap equation without Higgs is constructed. Dynamical symmetry breaking is affected via strong λ Q , generating m Q while self-consistently justifying treating G as massless in the loop, hence, “bootstrap,” Solving such a gap equation, we find that m Q should be several TeV, or λ Q ≳ 4 π , and would become much heavier if there is a light Higgs boson. For such heavy chiral quarks, we find analogy with the π − N system, by which we conjecture the possible annihilation phenomena of Q Q ¯ → n V L with high multiplicity, the search of which might be aided by Yukawa-bound Q Q ¯ resonances.
Rosensteel, George
1995-01-01
Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.
Applications of chiral symmetry
Energy Technology Data Exchange (ETDEWEB)
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.
Directory of Open Access Journals (Sweden)
Angel Garrido
2011-01-01
Full Text Available In this paper, we analyze a few interrelated concepts about graphs, such as their degree, entropy, or their symmetry/asymmetry levels. These concepts prove useful in the study of different types of Systems, and particularly, in the analysis of Complex Networks. A System can be defined as any set of components functioning together as a whole. A systemic point of view allows us to isolate a part of the world, and so, we can focus on those aspects that interact more closely than others. Network Science analyzes the interconnections among diverse networks from different domains: physics, engineering, biology, semantics, and so on. Current developments in the quantitative analysis of Complex Networks, based on graph theory, have been rapidly translated to studies of brain network organization. The brain's systems have complex network features—such as the small-world topology, highly connected hubs and modularity. These networks are not random. The topology of many different networks shows striking similarities, such as the scale-free structure, with the degree distribution following a Power Law. How can very different systems have the same underlying topological features? Modeling and characterizing these networks, looking for their governing laws, are the current lines of research. So, we will dedicate this Special Issue paper to show measures of symmetry in Complex Networks, and highlight their close relation with measures of information and entropy.
Energy Technology Data Exchange (ETDEWEB)
El Naschie, M.S. [King Abdul Aziz City of Science and Technology, Riyadh (Saudi Arabia)
2007-04-15
The notion of a particle-like state emerging from a symmetry breaking is given five corresponding pictures. We start from a geometrical picture in two dimensions involving a modular curve constructed using 336 triangles. The same number of building blocks is found again, this time as 336 contact points in the ten dimensional space of super string theory in the context of the largest kissing number of lattice sphere packing. The next corresponding representation is an abstract one pertinent to the order of the simple linear Lie group SL(2, n) in seven dimensions (n = 7) which leads to 336 symmetries. Subsequently a tensorial picture is given using the Riemannian tensor of relativity theory but this time in an eight dimensional space (n = 8) for which the number of independent components is again 336. Finally we use a physical string theory related picture in the 12 dimensions of F theory to find 336 moduli space dimensions representing the instanton cells of our theory. It is evident that the five preceding pictures are ten fold interconnected and exchangeable. This additional mental freedom does not only enhance the feeling of understanding, but also facilitates the easy recognition of complex mathematical relations and its connection to the physical concepts.
Chia, Tze Shyang; Quah, Ching Kheng
2016-12-01
As a function of temperature, the hexamethylenetetramine-2-methylbenzoic acid (1/2) cocrystal, C6H12N4·2C8H8O2, undergoes a reversible structural phase transition. The orthorhombic high-temperature phase in the space group Pccn has been studied in the temperature range between 165 and 300 K. At 164 K, a t2 phase transition to the monoclinic subgroup P21/c space group occurs; the resulting twinned low-temperature phase was investigated in the temperature range between 164 and 100 K. The domains in the pseudomerohedral twin are related by a twofold rotation corresponding to the matrix (100/0-10/00-1. Systematic absence violations represent a sensitive criterium for the decision about the correct space-group assignment at each temperature. The fractional volume contributions of the minor twin domain in the low-temperature phase increases in the order 0.259 (2) → 0.318 (2) → 0.336 (2) → 0.341 (3) as the temperature increases in the order 150 → 160 → 163 → 164 K. The transformation occurs between the nonpolar point group mmm and the nonpolar point group 2/m, and corresponds to a ferroelastic transition or to a t2 structural phase transition. The asymmetric unit of the low-temperature phase consists of two hexamethylenetetramine molecules and four molecules of 2-methylbenzoic acid; it is smaller by a factor of 2 in the high-temperature phase and contains two half molecules of hexamethylenetetramine, which sit across twofold axes, and two molecules of the organic acid. In both phases, the hexamethylenetetramine residue and two benzoic acid molecules form a three-molecule aggregate; the low-temperature phase contains two of these aggregates in general positions, whereas they are situated on a crystallographic twofold axis in the high-temperature phase. In both phases, one of these three-molecule aggregates is disordered. For this disordered unit, the ratio between the major and minor conformer increases upon cooling from
SYMMETRY IN WORLD TRADE NETWORK
Institute of Scientific and Technical Information of China (English)
Hui WANG; Guangle YAN; Yanghua XIAO
2009-01-01
Symmetry of the world trade network provides a novel perspective to understand the world-wide trading system. However, symmetry in the world trade network (WTN) has been rarely studied so far. In this paper, the authors systematically explore the symmetry in WTN. The authors construct WTN in 2005 and explore the size and structure of its automorphism group, through which the authors find that WTN is symmetric, particularly, locally symmetric to a certain degree. Furthermore, the authors work out the symmetric motifs of WTN and investigate the structure and function of the symmetric motifs, coming to the conclusion that local symmetry will have great effect on the stability of the WTN and that continuous symmetry-breakings will generate complexity and diversity of the trade network. Finally, utilizing the local symmetry of the network, the authors work out the quotient of WTN, which is the structural skeleton dominating stability and evolution of WTN.
Wilczek, Frank
2004-01-01
Powerful symmetry principles have guided physicists in their quest for nature's fundamental laws. The successful gauge theory of electroweak interactions postulates a more extensive symmetry for its equations than are manifest in the world (8 pages) Powerful symmetry principles have guided physicists in their quest for nature's fundamental laws. The successful gauge theory of electroweak interactions postulates a more extensive symmetry for its equations than are manifest in the world. The discrepancy is ascribed to a pervasive symmetry-breaking field, which fills all space uniformly, rendering the Universe a sort of exotic superconductor. So far, the evidence for these bold ideas is indirect. But soon the theory will undergo a critical test depending on whether the quanta of this symmetry-breaking field, the so-called Higgs particles, are produced at the Large Hadron Collider (due to begin operation in 2007).
Symmetry of crystals and molecules
Ladd, Mark
2014-01-01
This book successfully combines a thorough treatment of molecular and crystalline symmetry with a simple and informal writing style. By means of familiar examples the author helps to provide the reader with those conceptual tools necessary for the development of a clear understanding of what are often regarded as 'difficult' topics. Christopher Hammond, University of Leeds This book should tell you everything you need to know about crystal and molecular symmetry. Ladd adopts an integrated approach so that the relationships between crystal symmetry, molecular symmetry and features of chemical interest are maintained and reinforced. The theoretical aspects of bonding and symmetry are also well represented, as are symmetry-dependent physical properties and the applications of group theory. The comprehensive coverage will make this book a valuable resource for a broad range of readers.
Energy Technology Data Exchange (ETDEWEB)
Strocchi, F. [Scuola Normale Superiore, Classe di Scienze, Pisa (Italy)
2008-07-01
This new edition of Prof. Strocchi's well received primer on rigorous aspects of symmetry breaking presents a more detailed and thorough discussion of the mechanism of symmetry breaking in classical field theory in relation with the Noether theorem. Moreover, the link between symmetry breaking without massless Goldstone bosons in Coulomb systems and in gauge theories is made more explicit in terms of the delocalized Coulomb dynamics. Furthermore, the chapter on the Higgs mechanism has been significantly expanded with a non-perturbative treatment of the Higgs phenomenon, at the basis of the standard model of particle physics, in the local and in the Coulomb gauges. Last but not least, a subject index has been added and a number of misprints have been corrected. From the reviews of the first edition: The notion of spontaneous symmetry breaking has proven extremely valuable, the problem is that most derivations are perturbative and heuristic. Yet mathematically precise versions do exist, but are not widely known. It is precisely the aim of his book to correct this unbalance. - It is remarkable to see how much material can actually be presented in a rigorous way (incidentally, many of the results presented are due to Strocchi himself), yet this is largely ignored, the original heuristic derivations being, as a rule, more popular. - At each step he strongly emphasizes the physical meaning and motivation of the various notions introduced, a book that fills a conspicuous gap in the literature, and does it rather well. It could also be a good basis for a graduate course in mathematical physics. It can be recommended to physicists as well and, of course, for physics/mathematics libraries. J.-P. Antoine, Physicalia 28/2, 2006 Strocchi's main emphasis is on the fact that the loss of symmetric behaviour requires both the non-symmetric ground states and the infinite extension of the system. It is written in a pleasant style at a level suitable for graduate students in
Exact Dynamical and Partial Symmetries
Leviatan, A
2010-01-01
We discuss a hierarchy of broken symmetries with special emphasis on partial dynamical symmetries (PDS). The latter correspond to a situation in which a non-invariant Hamiltonian accommodates a subset of solvable eigenstates with good symmetry, while other eigenstates are mixed. We present an algorithm for constructing Hamiltonians with this property and demonstrate the relevance of the PDS notion to nuclear spectroscopy, to quantum phase transitions and to mixed systems with coexisting regularity and chaos.
Exact dynamical and partial symmetries
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A, E-mail: ami@phys.huji.ac.il [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
2011-03-01
We discuss a hierarchy of broken symmetries with special emphasis on partial dynamical symmetries (PDS). The latter correspond to a situation in which a non-invariant Hamiltonian accommodates a subset of solvable eigenstates with good symmetry, while other eigenstates are mixed. We present an algorithm for constructing Hamiltonians with this property and demonstrate the relevance of the PDS notion to nuclear spectroscopy, to quantum phase transitions and to mixed systems with coexisting regularity and chaos.
Physical Theories with Average Symmetry
Alamino, Roberto C.
2013-01-01
This Letter probes the existence of physical laws invariant only in average when subjected to some transformation. The concept of a symmetry transformation is broadened to include corruption by random noise and average symmetry is introduced by considering functions which are invariant only in average under these transformations. It is then shown that actions with average symmetry obey a modified version of Noether's Theorem with dissipative currents. The relation of this with possible violat...
Physical Theories with Average Symmetry
Alamino, Roberto C
2013-01-01
This Letter probes the existence of physical laws invariant only in average when subjected to some transformation. The concept of a symmetry transformation is broadened to include corruption by random noise and average symmetry is introduced by considering functions which are invariant only in average under these transformations. It is then shown that actions with average symmetry obey a modified version of Noether's Theorem with dissipative currents. The relation of this with possible violations of physical symmetries, as for instance Lorentz invariance in some quantum gravity theories, is briefly commented.
The conservation of orbital symmetry
Woodward, R B
2013-01-01
The Conservation of Orbital Symmetry examines the principle of conservation of orbital symmetry and its use. The central content of the principle was that reactions occur readily when there is congruence between orbital symmetry characteristics of reactants and products, and only with difficulty when that congruence does not obtain-or to put it more succinctly, orbital symmetry is conserved in concerted reaction. This principle is expected to endure, whatever the language in which it may be couched, or whatever greater precision may be developed in its application and extension. The book ope
Karp, Dagan; Riggins, Paul; Whitcher, Ursula
2011-01-01
We exhaustively analyze the toric symmetries of CP^3 and its toric blowups. Our motivation is to study toric symmetry as a computational technique in Gromov-Witten theory and Donaldson-Thomas theory. We identify all nontrivial toric symmetries. The induced nontrivial isomorphisms lift and provide new symmetries at the level of Gromov-Witten Theory and Donaldson-Thomas Theory. The polytopes of the toric varieties in question include the permutohedron, the cyclohedron, the associahedron, and in fact all graph associahedra, among others.
Givental graphs and inversion symmetry
Dunin-Barkowski, P; Spitz, L
2012-01-01
Inversion symmetry is a very non-trivial discrete symmetry of Frobenius manifolds. It was obtained by Dubrovin from one of the elementary Schlesinger transformations of a special ODE associated to Frobenius manifold. In this paper, we review the Givental group action on Frobenius manifolds in terms of Feynman graphs and then we obtain an interpretation of the inversion symmetry in terms of the action of the Givental group. We also consider the implication of this interpretation of the inversion symmetry for the Schlesinger transformations and for the Hamiltonians of the associated principle hierarchy.
Leptogenesis and residual CP symmetry
Energy Technology Data Exchange (ETDEWEB)
Chen, Peng; Ding, Gui-Jun [Department of Modern Physics, University of Science and Technology of China,Hefei, Anhui 230026 (China); King, Stephen F. [Physics and Astronomy, University of Southampton,Southampton, SO17 1BJ (United Kingdom)
2016-03-31
We discuss flavour dependent leptogenesis in the framework of lepton flavour models based on discrete flavour and CP symmetries applied to the type-I seesaw model. Working in the flavour basis, we analyse the case of two general residual CP symmetries in the neutrino sector, which corresponds to all possible semi-direct models based on a preserved Z{sub 2} in the neutrino sector, together with a CP symmetry, which constrains the PMNS matrix up to a single free parameter which may be fixed by the reactor angle. We systematically study and classify this case for all possible residual CP symmetries, and show that the R-matrix is tightly constrained up to a single free parameter, with only certain forms being consistent with successful leptogenesis, leading to possible connections between leptogenesis and PMNS parameters. The formalism is completely general in the sense that the two residual CP symmetries could result from any high energy discrete flavour theory which respects any CP symmetry. As a simple example, we apply the formalism to a high energy S{sub 4} flavour symmetry with a generalized CP symmetry, broken to two residual CP symmetries in the neutrino sector, recovering familiar results for PMNS predictions, together with new results for flavour dependent leptogenesis.
Symmetry fractionalization and twist defects
Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz
2016-03-01
Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.
Stability of the monoclinic phase in the ferroelectric perovskite PbZr1-xTixO3
Noheda, B.; Cox, D.E.; Shirane, G.; Guo, R.; Jones, B.; Cross, L.E.
2000-01-01
Recent structural studies of ferroelectric PbZr1-xTixO3 (PZT) with x=0.48, have revealed a monoclinic phase in the vicinity of the morphotropic phase boundary (MPB), previously regarded as the boundary separating the rhombohedral and tetragonal regions of the PZT phase diagram. In the present paper,
DEFF Research Database (Denmark)
Taylor, M.A.; Alonso, R.E.; Errico, L.A.
2010-01-01
A combination of experiments and ab initio quantum-mechanical calculations has been applied to examine hyperfine interactions in Ta-doped hafnium dioxide. Although the properties of monoclinic HfO2 have been the subject of several earlier studies, some aspects remain open. In particular, time dif...
Symmetry reduction related with nonlocal symmetry for Gardner equation
Ren, Bo
2017-01-01
Based on the truncated Painlevé method or the Möbious (conformal) invariant form, the nonlocal symmetry for the (1+1)-dimensional Gardner equation is derived. The nonlocal symmetry can be localized to the Lie point symmetry by introducing one new dependent variable. Thanks to the localization procedure, the finite symmetry transformations are obtained by solving the initial value problem of the prolonged systems. Furthermore, by using the symmetry reduction method to the enlarged systems, many explicit interaction solutions among different types of solutions such as solitary waves, rational solutions, Painlevé II solutions are given. Especially, some special concrete soliton-cnoidal interaction solutions are analyzed both in analytical and graphical ways.
Bosonization and Mirror Symmetry
Kachru, Shamit; Torroba, Gonzalo; Wang, Huajia
2016-01-01
We study bosonization in 2+1 dimensions using mirror symmetry, a duality that relates pairs of supersymmetric theories. Upon breaking supersymmetry in a controlled way, we dynamically obtain the bosonization duality that equates the theory of a free Dirac fermion to QED3 with a single scalar boson. This duality may be used to demonstrate the bosonization duality relating an $O(2)$-symmetric Wilson-Fisher fixed point to QED3 with a single Dirac fermion, Peskin-Dasgupta-Halperin duality, and the recently conjectured duality relating the theory of a free Dirac fermion to fermionic QED3 with a single flavor. Chern-Simons and BF couplings for both dynamical and background gauge fields play a central role in our approach. In the course of our study, we describe a chiral mirror pair that may be viewed as the minimal supersymmetric generalization of the two bosonization dualities.
Greiner, Walter
1989-01-01
"Quantum Dynamics" is a major survey of quantum theory based on Walter Greiner's long-running and highly successful courses at the University of Frankfurt. The key to understanding in quantum theory is to reinforce lecture attendance and textual study by working through plenty of representative and detailed examples. Firm belief in this principle led Greiner to develop his unique course and to transform it into a remarkable and comprehensive text. The text features a large number of examples and exercises involving many of the most advanced topics in quantum theory. These examples give practical and precise demonstrations of how to use the often subtle mathematics behind quantum theory. The text is divided into five volumes: Quantum Mechanics I - An Introduction, Quantum Mechanics II - Symmetries, Relativistic Quantum Mechanics, Quantum Electrodynamics, Gauge Theory of Weak Interactions. These five volumes take the reader from the fundamental postulates of quantum mechanics up to the latest research in partic...
Energy Technology Data Exchange (ETDEWEB)
Heeck, Julian
2013-04-15
Augmenting the Standard Model by three right-handed neutrinos allows for an anomaly-free gauge group extension G{sub max}=U(1){sub B−L}×U(1){sub L{sub e−L{sub μ}}}×U(1){sub L{sub μ−L{sub τ}}}. Simple U(1) subgroups of G{sub max} can be used to impose structure on the righthanded neutrino mass matrix, which then propagates to the active neutrino mass matrix via the seesaw mechanism. We show how this framework can be used to gauge the approximate lepton-number symmetries behind the normal, inverted, and quasidegenerate neutrino mass spectrum, and also how to generate texture-zeros and vanishing minors in the neutrino mass matrix, leading to testable relations among mixing parameters.
Bosonization and mirror symmetry
Kachru, Shamit; Mulligan, Michael; Torroba, Gonzalo; Wang, Huajia
2016-10-01
We study bosonization in 2 +1 dimensions using mirror symmetry, a duality that relates pairs of supersymmetric theories. Upon breaking supersymmetry in a controlled way, we dynamically obtain the bosonization duality that equates the theory of a free Dirac fermion to QED3 with a single scalar boson. This duality may be used to demonstrate the bosonization duality relating an O (2 )-symmetric Wilson-Fisher fixed point to QED3 with a single Dirac fermion, Peskin-Dasgupta-Halperin duality, and the recently conjectured duality relating the theory of a free Dirac fermion to fermionic QED3 with a single flavor. Chern-Simons and BF couplings for both dynamical and background gauge fields play a central role in our approach. In the course of our study, we describe a "chiral" mirror pair that may be viewed as the minimal supersymmetric generalization of the two bosonization dualities.
Symmetry Breaking by Nonstationay Optimisation
Prestwich, S.; Hnich, B.; Rossi, R.; Tarim, S.A.
2008-01-01
We describe a new partial symmetry breaking method that can be used to break arbitrary variable/value symmetries in combination with depth first search, static value ordering and dynamic variable ordering. The main novelty of the method is a new dominance detection technique based on local search in
Lie Symmetries of Ishimori Equation
Institute of Scientific and Technical Information of China (English)
SONG Xu-Xia
2013-01-01
The Ishimori equation is one of the most important (2+1)-dimensional integrable models,which is an integrable generalization of (1+1)-dimensional classical continuous Heisenberg ferromagnetic spin equations.Based on importance of Lie symmetries in analysis of differential equations,in this paper,we derive Lie symmetries for the Ishimori equation by Hirota's direct method.
Hole localization and symmetry breaking
Broer, R; Nieuwpoort, W.C.
1999-01-01
A brief overview is presented of some theoretical work on the symmetry breaking of electronic wavefunctions that followed the early work on Bagus and Schaefer who observed that a considerable lower SCF energy could be obtained for an ionized state of the O2 molecule with a 1s hole if the symmetry re
Symmetry Breaking by Nonstationay Optimisation
Prestwich, S.; Hnich, B.; Rossi, R.; Tarim, S.A.
2008-01-01
We describe a new partial symmetry breaking method that can be used to break arbitrary variable/value symmetries in combination with depth first search, static value ordering and dynamic variable ordering. The main novelty of the method is a new dominance detection technique based on local search in
Yang, Hexiong; Ghose, Subrata; Hatch, Dorian M.
1993-04-01
Cryolite, Na3AlF6[ = 2Na+(Na0.5 +Al0.5 3+)F3] is a mixed fluoride perovskite, in which the corner-sharing octahedral framework is formed by alternating [NaF6] and [AlF6] octahedra and the cavities are occupied by Na+ ions. At 295 K, it is monoclinic ( α phase), space group P2 1/ n with a = 5.4139 (7), b = 5.6012 (5) and c = 7.7769 (8) Å and β = 90.183 (3)∘, Z = 2. A high temperature single crystal X-ray diffraction study in the range 295 900 K indicates a fluctuation-induced first-order phase transition from monoclinic to orthorhombic symmetry at T 0 ˜ 885 K, in contrast to a previous report that it becomes cubic at ˜823 K. The space group of the high temperature β phase is Immm with a = 5.632 (4), b = 5.627 (3) and c = 7.958 (4) Å, Z = 2 at 890 K. Above T 0, the coordination number of the Na+ ion in the cavity increases from eight to twelve and the zigzag Na1 — Al octahedral chains parallel to c become straight with the Na1-F-Al angle = 180 °. The phase transition is driven by two coupled primary order parameters. The first corresponds to the rotation of the nearly rigid [AlF6] group and transforms according to the Γ 4 + irreducible representation of Immm. Coupled to the [AlF6] rotation is a second primary order parameter corresponding to the displacement of the Na2+ ion in the cavity from its equilibrium position. This order parameter transforms according to the X 3 + irreducible representation of Immm. Following Immm → P2 1 / n phase transition, four equivalent domains of P2 1/ n are determined relative to Immm, which are in an antiphase and/or twin relationship. The abrupt shortening of the octahedral Al-F and Na-F bonds and a sudden change in orientations of the atomic thermal vibration ellipsoids above T 0 indicate a crossover from displacive to an order-disorder mechanism near the transition temperature. The β phase is interpreted as a dynamic average of four micro-twin and -antiphase domains of the a phase. This view is consistent with the
Asymptotic Symmetries from finite boxes
Andrade, Tomas
2015-01-01
It is natural to regulate an infinite-sized system by imposing a boundary condition at finite distance, placing the system in a "box." This breaks symmetries, though the breaking is small when the box is large. One should thus be able to obtain the asymptotic symmetries of the infinite system by studying regulated systems. We provide concrete examples in the context of Einstein-Hilbert gravity (with negative or zero cosmological constant) by showing in 4 or more dimensions how the Anti-de Sitter and Poincar\\'e asymptotic symmetries can be extracted from gravity in a spherical box with Dirichlet boundary conditions. In 2+1 dimensions we obtain the full double-Virasoro algebra of asymptotic symmetries for AdS$_3$ and, correspondingly, the full Bondi-Metzner-Sachs (BMS) algebra for asymptotically flat space. In higher dimensions, a related approach may continue to be useful for constructing a good asymptotically flat phase space with BMS asymptotic symmetries.
UV completion without symmetry restoration
Endlich, Solomon; Penco, Riccardo
2013-01-01
We show that it is not possible to UV-complete certain low-energy effective theories with spontaneously broken space-time symmetries by embedding them into linear sigma models, that is, by adding "radial" modes and restoring the broken symmetries. When such a UV completion is not possible, one can still raise the cutoff up to arbitrarily higher energies by adding fields that transform non-linearly under the broken symmetries, that is, new Goldstone bosons. However, this (partial) UV completion does not necessarily restore any of the broken symmetries. We illustrate this point by considering a concrete example in which a combination of space-time and internal symmetries is broken down to a diagonal subgroup. Along the way, we clarify a recently proposed interpretation of inverse Higgs constraints as gauge-fixing conditions.
Discrete symmetries in the MSSM
Energy Technology Data Exchange (ETDEWEB)
Schieren, Roland
2010-12-02
The use of discrete symmetries, especially abelian ones, in physics beyond the standard model of particle physics is discussed. A method is developed how a general, abelian, discrete symmetry can be obtained via spontaneous symmetry breaking. In addition, anomalies are treated in the path integral approach with special attention to anomaly cancellation via the Green-Schwarz mechanism. All this is applied to the minimal supersymmetric standard model. A unique Z{sup R}{sub 4} symmetry is discovered which solves the {mu}-problem as well as problems with proton decay and allows to embed the standard model gauge group into a simple group, i.e. the Z{sup R}{sub 4} is compatible with grand unification. Also the flavor problem in the context of minimal flavor violation is addressed. Finally, a string theory model is presented which exhibits the mentioned Z{sup R}{sub 4} symmetry and other desirable features. (orig.)
Shape analysis with subspace symmetries
Berner, Alexander
2011-04-01
We address the problem of partial symmetry detection, i.e., the identification of building blocks a complex shape is composed of. Previous techniques identify parts that relate to each other by simple rigid mappings, similarity transforms, or, more recently, intrinsic isometries. Our approach generalizes the notion of partial symmetries to more general deformations. We introduce subspace symmetries whereby we characterize similarity by requiring the set of symmetric parts to form a low dimensional shape space. We present an algorithm to discover subspace symmetries based on detecting linearly correlated correspondences among graphs of invariant features. We evaluate our technique on various data sets. We show that for models with pronounced surface features, subspace symmetries can be found fully automatically. For complicated cases, a small amount of user input is used to resolve ambiguities. Our technique computes dense correspondences that can subsequently be used in various applications, such as model repair and denoising. © 2010 The Author(s).
He, Huabing; Gao, Heng; Wu, Wei; Cao, Shixun; Hong, Jiawang; Yu, Dehong; Deng, Guochu; Gao, Yanfeng; Zhang, Peihong; Luo, Hongjie; Ren, Wei
2016-11-01
Recent experiments have revealed an intriguing pressure-induced isostructural transition of the low temperature monoclinic V O2 and hinted to the existence of a new metallization mechanism in this system. The physics behind this isostructural phase transition and the metallization remains unresolved. In this work, we show that the isostructural transition is a result of pressure-induced instability of a phonon mode that relates to a CaC l2 -type of rotation of the oxygen octahedra, which alleviates, but does not completely remove, the dimerization and zigzagging arrangement of V atoms in the M1 phase. This phonon mode shows an increasing softening with pressure, ultimately leading to an isostructural phase transition characterized by the degree of the rotation of the oxygen octahedra. We also find that this phase transition is accompanied by an anisotropic compression, in excellent agreement with experiments. More interestingly, in addition to the experimentally identified M1' phase, we find a closely related M1 '' phase, which is nearly degenerate with the M1 ' phase. Unlike the M1 ' phase, which has a nearly pressure-independent electronic band gap, the gap of the M1 '' drops quickly at high pressures and vanishes at a theoretical pressure of about 40 GPa.
Energy Technology Data Exchange (ETDEWEB)
Li Haibin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)], E-mail: coastllee@hotmail.com; Liu Guocong [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Department of Chemistry, Yulin Normal University, Yulin 537000 (China); Duan Xuechen [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)
2009-05-15
Monoclinic bismuth vanadate (BiVO{sub 4}) samples with regular morphologies were prepared by a facile hydrothermal process with Bi{sub 2}O{sub 3} and NH{sub 4}VO{sub 3} as starting materials. The physical and photophysical properties of the as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR), and UV-vis diffuse reflectance spectroscopy (UV-vis). It was found that cuboid-like, square plate-like and flower-like BiVO{sub 4} could be readily obtained by tailoring the pH values of the reaction suspensions in the presence of CTAB. Both pH value and CTAB played crucial roles in the morphology evolution of the as-prepared samples. The bandgaps (E{sub g}) of cuboid-like, square plate-like and flower-like BiVO{sub 4} were 2.39 eV, 2.40 eV and 2.46 eV, respectively. The photocatalytic performance of the as-prepared BiVO{sub 4} was much better than that of P25 for photodegradation of methyl orange under sunlight irradiation. The photocatalytic activities of BiVO{sub 4} samples were highly related to their crystallinities and shapes.
Zhang, Li; Chen, Dairong; Jiao, Xiuling
2006-02-16
Bismuth vanadate (BiVO(4)) nanosheets have been hydrothermally synthesized in the presence of sodium dodecyl benzene sulfonate (SDBS) as a morphology-directing template. The nanosheets were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) equipped with an X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), IR spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM). The BiVO(4) nanosheets had a monoclinic structure, were ca. 10-40 nm thick, and showed a preferred (010) surface orientation. The formation mechanism and the effects of reaction temperature and time on the products were investigated. UV-visible diffuse reflection spectra indicated that the BiVO(4) nanosheets had outstanding spectral selectivity and improved color properties compared with the corresponding bulk materials. Furthermore, the nanosheets showed good visible photocatalytic activities as determined by degradation of N,N,N',N'-tetraethylated rhodamine (RB) under solar irradiation.
Silva, A M; Costa, S N; Sales, F A M; Freire, V N; Bezerra, E M; Santos, R P; Fulco, U L; Albuquerque, E L; Caetano, E W S
2015-12-10
The infrared absorption and Raman scattering spectra of the monoclinic P21 l-aspartic acid anhydrous crystal were recorded and interpreted with the help of density functional theory (DFT) calculations. The effect of dispersive forces was taken into account, and the optimized unit cells allowed us to obtain the vibrational normal modes. The computed data exhibits good agreement with the measurements for low wavenumbers, allowing for a very good assignment of the infrared and Raman spectral features. The vibrational spectra of the two lowest energy conformers of the l-aspartic molecule were also evaluated using the hybrid B3LYP functional for the sake of comparison, showing that the molecular calculations give a limited description of the measured IR and Raman spectra of the l-aspartic acid crystal for wavenumbers below 1000 cm(-1). The results obtained reinforce the need to use solid-state calculations to describe the vibrational properties of molecular crystals instead of calculations for a single isolated molecule picture even for wavenumbers beyond the range usually associated with lattice modes (200 cm(-1) < ω < 1000 cm(-1)).
Lin, Xianqing; Ni, Jun
2017-07-01
First-principles calculations have been performed to study the intrinsic spin Hall effect (SHE) and its behavior under vertical electric field in monoclinic transition metal dichalcogenide monolayers (1T‧-MX2 with M = Mo, W and X = S, Se, Te). We find that the pristine systems exhibit nonquantized intrinsic spin Hall conductivity (SHC) due to the unconserved spin around the direct band gaps though they have nontrivial band topology. The unconserved spin is attributed to the band crossings at Fermi levels for systems without spin-orbit coupling and the distinct composition of the band states around the crossings. Despite the nonquantization of SHC, calculations with the hybrid functional predict SHC approaching the quantized value in W based systems, especially 1T‧-WTe2, which has been realized in experiments. More interesting, a sharp drop of SHC to almost zero in semiconducting systems induced by vertical electric field is observed at the topological phase transition point, suggesting that such systems exhibit a strong switch effect of SHC. In contrast, the switch effect is weak in semi-metallic systems, where the SHC decreases almost continuously with increasing field strength for the chemical potential around the Fermi levels. Our findings suggest potential applications of the pristine 1T‧-MX2 and those under vertical electric field in spintronics devices by utilizing the intrinsic SHE of their bulk states.
Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure
Sinmyo, Ryosuke; Bykova, Elena; Ovsyannikov, Sergey V.; McCammon, Catherine; Kupenko, Ilya; Ismailova, Leyla; Dubrovinsky, Leonid
2016-09-01
Iron oxides are fundamentally important compounds for basic and applied sciences as well as in numerous industrial applications. In this work we report the synthesis and investigation of a new binary iron oxide with the hitherto unknown stoichiometry of Fe7O9. This new oxide was synthesized at high-pressure high-temperature (HP-HT) conditions, and its black single crystals were successfully recovered at ambient conditions. By means of single crystal X-ray diffraction we determined that Fe7O9 adopts a monoclinic C2/m lattice with the most distorted crystal structure among the binary iron oxides known to date. The synthesis of Fe7O9 opens a new portal to exotic iron-rich (M,Fe)7O9 oxides with unusual stoichiometry and distorted crystal structures. Moreover, the crystal structure and phase relations of such new iron oxide groups may provide new insight into the cycling of volatiles in the Earth’s interior.
Mei Symmetry and Lie Symmetry of the Rotational Relativistic Variable Mass System
Institute of Scientific and Technical Information of China (English)
FANGJian-Hui
2003-01-01
The Mei symmetry and the Lie symmetry of a rotational relativistic variable mass system are studied. The definitions and criteria of the Mei symmetry and the Lie symmetry of the rotational relativistic variable mass system are given. The relation between the Mei symmetry and the Lie symmetry is found. The conserved quantities which the Mei symmetry and the Lie symmetry lead to are obtained. An example is given to illustrate the application of the result.
Effects of Mg and Si ions on the symmetry of δ-AlOOH
Komatsu, K.; Sano-Furukawa, A.; Kagi, H.
2011-10-01
We conducted powder neutron diffraction for δ-AlOOH samples with and without Mg and Si ions under ambient conditions in order to investigate the long-standing problem of the symmetry of this phase. The observed reflection conditions clearly show that the space group of pure δ-AlOOH is P21 nm with ordered hydrogen bonds, whereas that of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm or Pnn2 with disordered hydrogen bonds. It is more likely that the space group of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm, because cation or hydrogen ordering that breaks the mirror plane perpendicular to c axis in the Pnnm structure would not occur. The previously reported inconsistency for the space group of this phase was caused by the substitution of Mg and Si ions to Al site, i.e., the disordered cations with different valences may fluctuate hydrogen positions, and the disordered hydrogen causes the symmetry change.
Saadatmand, S. N.; McCulloch, I. P.
2016-09-01
Using density-matrix renormalization-group calculations for infinite cylinders, we elucidate the properties of the spin-liquid phase of the spin-1/2 J1-J2 Heisenberg model on the triangular lattice. We find four distinct ground states characteristic of a nonchiral, Z2 topologically ordered state with vison and spinon excitations. We shed light on the interplay of topological ordering and global symmetries in the model by detecting fractionalization of time-reversal and space-group dihedral symmetries in the anyonic sectors, which leads to the coexistence of symmetry protected and intrinsic topological order. The anyonic sectors, and information on the particle statistics, can be characterized by degeneracy patterns and symmetries of the entanglement spectrum. We demonstrate the ground states on finite-width cylinders are short-range correlated and gapped; however, some features in the entanglement spectrum suggest that the system develops gapless spinonlike edge excitations in the large-width limit.
Spin-1 Dirac-Weyl fermions protected by bipartite symmetry
Energy Technology Data Exchange (ETDEWEB)
Lin, Zeren [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); School of Physics, Peking University, Beijing 100871 (China); Liu, Zhirong, E-mail: LiuZhiRong@pku.edu.cn [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), Peking University, Beijing 100871 (China)
2015-12-07
We propose that bipartite symmetry allows spin-1 Dirac-Weyl points, a generalization of the spin-1/2 Dirac points in graphene, to appear as topologically protected at the Fermi level. In this spirit, we provide methodology to construct spin-1 Dirac-Weyl points of this kind in a given 2D space group and get the classification of the known spin-1 systems in the literature. We also apply the workflow to predict two new systems, P3m1-9 and P31m-15, to possess spin-1 at K/K′ in the Brillouin zone of hexagonal lattice. Their stability under various strains is investigated and compared with that of T{sub 3}, an extensively studied model of ultracold atoms trapped in optical lattice with spin-1 also at K/K′.
Gravitation and Gauge Symmetries
Stewart, J
2002-01-01
The purpose of this book (I quote verbatim from the back cover) is to 'shed light upon the intrinsic structure of gravity and the principle of gauge invariance, which may lead to a consistent unified field theory', a very laudable aim. The content divides fairly clearly into four sections (and origins). After a brief introduction, chapters 2-6 review the 'Structure of gravity as a theory based on spacetime gauge symmetries'. This is fairly straightforward material, apparently based on a one-semester graduate course taught at the University of Belgrade for about two decades, and, by implication, this is a reasonably accurate description of its level and assumed knowledge. There follow two chapters of new material entitled 'Gravity in flat spacetime' and 'Nonlinear effects in gravity'. The final three chapters, entitled 'Supersymmetry and supergravity', 'Kaluza-Klein theory' and 'String theory' have been used for the basis of a one-semester graduate course on the unification of fundamental interactions. The boo...
Symmetries in nuclear structure
Allaart, K; Dieperink, A
1983-01-01
The 1982 summer school on nuclear physics, organized by the Nuclear Physics Division of the Netherlands' Physical Society, was the fifth in a series that started in 1963. The number of students attending has always been about one hundred, coming from about thirty countries. The theme of this year's school was symmetry in nuclear physics. This book covers the material presented by the enthusi astic speakers, who were invited to lecture on this subject. We think they have succeeded in presenting us with clear and thorough introductory talks at graduate or higher level. The time schedule of the school and the location allowed the participants to make many informal contacts during many social activities, ranging from billiards to surf board sailing. We hope and expect that the combination of a relaxed atmosphere during part of the time and hard work during most of the time, has furthered the interest in, and understanding of, nuclear physics. The organization of the summer school was made possible by substantia...
O'Hanlon actions by Noether symmetry
Darabi, F.
2015-01-01
By using the conformal symmetry between Brans-Dicke action with $\\omega=-\\frac{3}{2}$ and O'Hanlon action, we seek the O'Hanlon actions in Einstein frame respecting the Noether symmetry. Since the Noether symmetry is preserved under conformal transformations, the existence of Noether symmetry in the Brans-Dicke action asserts the Noether symmetry in O'Hanlon action in Einstein frame. Therefore, the potentials respecting Noether symmetry in Brans-Dicke action give the corresponding potentials ...
Spectral theorem and partial symmetries
Energy Technology Data Exchange (ETDEWEB)
Gozdz, A. [University of Maria Curie-Sklodowska, Department of Mathematical Physics, Institute of Physics (Poland); Gozdz, M. [University of Maria Curie-Sklodowska, Department of Complex Systems and Neurodynamics, Institute of Informatics (Poland)
2012-10-15
A novel method of the decompositon of a quantum system's Hamiltonian is presented. In this approach the criterion of the decomposition is determined by the symmetries possessed by the sub-Hamiltonians. This procedure is rather generic and independent of the actual global symmetry, or the lack of it, of the full Hamilton operator. A detailed investigation of the time evolution of the various sub-Hamiltonians, therefore the change in time of the symmetry of the physical object, is presented for the case of a vibrator-plus-rotor model. Analytical results are illustrated by direct numerical calculations.
Astroparticle tests of Lorentz symmetry
Energy Technology Data Exchange (ETDEWEB)
Diaz, Jorge [Karlsruhe Institute of Technology, Karlsruhe (Germany)
2016-07-01
Lorentz symmetry is a cornerstone of modern physics. As the spacetime symmetry of special relativity, Lorentz invariance is a basic component of the standard model of particle physics and general relativity, which to date constitute our most successful descriptions of nature. Deviations from exact symmetry would radically change our view of the universe and current experiments allow us to test the validity of this assumption. In this talk, I describe effects of Lorentz violation in cosmic rays and gamma rays that can be studied in current observatories.
Symmetry protected single photon subradiance
Cai, Han; Svidzinsky, Anatoly A; Zhu, Shi-Yao; Scully, Marlan O
2016-01-01
We study the protection of subradiant states by the symmetry of the atomic distributions in the Dicke limit, in which collective Lamb shift cannot be neglected. We find that anti-symmetric states are subradiant states for distribution with reflection symmetry. These states can be prepared by anti-symmetric optical modes and converted to superradiant states by properly tailored 2\\pipulses. Continuous symmetry can also be used to achieve subradiance. This study is relevant to the problem of robust quantum memory with long storage time and fast readout.
Gebremichael, W.; Petit, Y.; Rouzet, S.; Fargues, A.; Veber, P.; Velazquez, M.; Jubera, V.; Canioni, L.; Manek-Hönninger, I.
2017-02-01
In this contribution we detail the full characterization of the anisotropy of the absorption properties of two different Yb-doped monoclinic borate compounds under polarized light. The studied crystals are Li6(Gd)0.75Yb0.25(BO3)3 and Li6Y0.75Yb0.25(BO3)3, respectively, grown by the Czochralski method. We focused on the study of their absorption at the zero line transition as a function of the polarization direction of the incident light for two different crystal cuts of each compound. We discuss the different Eigen frames that must be considered in these materials due to their monoclinic character, as well as the optimal crystal orientation for the considered absorption and the potential influences when used as laser materials.
Kabalan, Ihab; Michelin, Laure; Rigolet, Séverinne; Marichal, Claire; Daou, T. Jean; Lebeau, Bénédicte; Paillaud, Jean-Louis
2016-08-01
The impact of crystal size on the transition orthorhombic ↔ monoclinic phase in MFI-type purely silica zeolites is investigated between 293 and 473 K using 29Si MAS NMR and powder X-ray diffraction. Three silicalite-1 zeolites are synthesized: a material constituted of micron-sized crystals, pseudospherical nanometer-sized crystals and hierarchical porous zeolites with a mesoporous network created by the use of a gemini-type diquaternary ammonium surfactant giving nanosheet zeolites. Our results show for the first time that the orthorhombic ↔ monoclinic phase transition already known for micron-sized particles also occurs in nanometer-sized zeolite crystals whereas our data suggest that the extreme downsizing of the zeolite crystal to one unit cell in thickness leads to an extinction of the phase transition.
Thermal Hydrolysis Synthesis and Characterization of Monoclinic Metahewettite CaV6O16•3H2O
Institute of Scientific and Technical Information of China (English)
LI Lanjie; ZHENG Shili; WANG Shaona; DU Hao; ZHANG Yi
2014-01-01
Monoclinic metahewettite CaV6O16•3H2O has been fabricated via thermal hydrolysis of calcium vanadate (Ca10V6O25). High purity calcium vanadate precipitate, featuring column structure with surface area of 8.61 m2/g, can be obtained by reacting sodium orthovanadate (Na3VO4) with calcium oxide at 90℃for 2 h. By acidification of calcium vanadate in hot water at pH of 1.0-3.0, the monoclinic metahewettite crystals with uniform particle distribution, layered structure and nonporous structure can be fabricated. With the well crystallized layered structure, CaV6O16•3H2O may be a potential cathode material for secondary batteries as well as super capacitor materials.
Parmar, Kanak Pal Singh; Kang, Hyun Joon; Bist, Amita; Dua, Piyush; Jang, Jum Suk; Lee, Jae Sung
2012-10-01
The visible-light-induced water oxidation ability of metal-ion-doped BiVO(4) was investigated and of 12 metal ion dopants tested, only W and Mo dramatically enhanced the water photo-oxidation activity of bare BiVO(4); Mo had the highest improvement by a factor of about six. Thus, BiVO(4) and W- or Mo-doped (2 atom %) BiVO(4) photoanodes about 1 μm thick were fabricated onto transparent conducting substrate by a metal-organic decomposition/spin-coating method. Under simulated one sun (air mass 1.5G, 100 mW cm(-2)) and at 1.23 V versus a reversible hydrogen electrode, the highest photocurrent density (J(PH)) of about 2.38 mA cm(-2) was achieved for Mo doping followed by W doping (J(PH) ≈ 1.98 mA cm(-2)), whereas undoped BiVO(4) gave a J(PH) value of about 0.42 mA cm(-2). The photoelectrochemical water oxidation activity of W- and Mo-doped BiVO(4) photoanodes corresponded to the incident photon to current conversion efficiency of about 35 and 40 % respectively. Electrochemical impedance spectroscopy and Mott-Schottky analysis indicated a positive flat band shift of about 30 mV, a carrier concentration 1.6-2 times higher, and a charge-transfer resistance reduced by 3-4-fold for W- or Mo-doped BiVO(4) relative to undoped BiVO(4). Electronic structure calculations revealed that both W and Mo were shallow donors and Mo doping generated superior conductivity to W doping. The photo-oxidation activity of water on BiVO(4) photoanodes (undopedphotocatalytic and photoelectrochemical water oxidation activity of monoclinic BiVO(4) by drastically reducing its charge-transfer resistance and thereby minimizing photoexcited electron-hole pair recombination.
The Limits of Custodial Symmetry
Chivukula, R Sekhar; Foadi, Roshan; Simmons, Elizabeth H
2010-01-01
We introduce a toy model implementing the proposal of using a custodial symmetry to protect the Z b_L bbar_L coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) x U(1)_X = SU(2)_L x SU(2)_R x P_LR x U(1)_X symmetry in the top-quark mass generating sector. This symmetry is softly broken to the gauged SU(2)_L x U(1)_Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M to 0) and standard-model-like (M to infinity) limits.
The Limits of Custodial Symmetry
Chivukula, R Sekhar; Foadi, Roshan; Simmons, Elizabeth H
2010-01-01
We introduce a toy model implementing the proposal of using a custodial symmetry to protect the Zbb coupling from large corrections. This "doublet-extended standard model" adds a weak doublet of fermions (including a heavy partner of the top quark) to the particle content of the standard model in order to implement an O(4) x U(1)_X = SU(2)_L x SU(2)_R x P_{LR} x U(1)_X symmetry that protects the Zbb coupling. This symmetry is softly broken to the gauged SU(2)_L x U(1)_Y electroweak symmetry by a Dirac mass M for the new doublet; adjusting the value of M allows us to explore the range of possibilities between the O(4)-symmetric (M to 0) and standard-model-like (M to infinity) limits.
Symmetries from the solution manifold
Aldaya, Víctor; Guerrero, Julio; Lopez-Ruiz, Francisco F.; Cossío, Francisco
2015-07-01
We face a revision of the role of symmetries of a physical system aiming at characterizing the corresponding Solution Manifold (SM) by means of Noether invariants as a preliminary step towards a proper, non-canonical, quantization. To this end, "point symmetries" of the Lagrangian are generally not enough, and we must resort to the more general concept of contact symmetries. They are defined in terms of the Poincaré-Cartan form, which allows us, in turn, to find the symplectic structure on the SM, through some sort of Hamilton-Jacobi (HJ) transformation. These basic symmetries are realized as Hamiltonian vector fields, associated with (coordinate) functions on the SM, lifted back to the Evolution Manifold through the inverse of this HJ mapping, that constitutes an inverse of the Noether Theorem. The specific examples of a particle moving on S3, at the mechanical level, and nonlinear SU(2)-sigma model in field theory are sketched.
External symmetry in general relativity
Cotaescu, I I
2000-01-01
We propose a generalization of the isometry transformations to the geometric context of the field theories with spin where the local frames are explicitly involved. We define the external symmetry transformations as isometries combined with suitable tetrad gauge transformations and we show that these form a group which is locally isomorphic with the isometry one. We point out that the symmetry transformations that leave invariant the equations of the fields with spin have generators with specific spin terms which represent new physical observables. The examples we present are the generators of the central symmetry and those of the maximal symmetries of the de Sitter and anti-de Sitter spacetimes derived in different tetrad gauge fixings. Pacs: 04.20.Cv, 04.62.+v, 11.30.-j
Lucas, Thomas J.
This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia. The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 mum from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist
Moon, San; Jung, Young Hwa; Jung, Wook Ki; Jung, Dae Soo; Choi, Jang Wook; Kim, Do Kyung
2013-12-03
On page 6547 Do Kyung Kim, Jang Wook Choi and co-workers describe a highly aligned and carbon-encapsulated sulfur cathode synthesized with an AAO template that exhibits a high and long cycle life, and the best rate capability based on the complete encapsulation of sulfur (physical) and implementation of the monoclinic sulfur phase (chemical). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Symmetry via Lie algebra cohomology
Eastwood, Michael
2010-01-01
The Killing operator on a Riemannian manifold is a linear differential operator on vector fields whose kernel provides the infinitesimal Riemannian symmetries. The Killing operator is best understood in terms of its prolongation, which entails some simple tensor identities. These simple identities can be viewed as arising from the identification of certain Lie algebra cohomologies. The point is that this case provides a model for more complicated operators similarly concerned with symmetry.
Dynamical (Super)Symmetry Breaking
Murayama, H
2001-01-01
Dynamical Symmetry Breaking (DSB) is a concept theorists rely on very often in the discussions of strong dynamics, model building, and hierarchy problems. In this talk, I will discuss why this is such a permeating concept among theorists and how they are used in understanding physics. I also briefly review recent progress in using dynamical symmetry breaking to construct models of supersymmetry breaking and fermion masses.
Discrete R Symmetries and Anomalies
Michael Dine(Santa Cruz Institute for Particle Physics and Department of Physics, Santa Cruz CA 95064, U.S.A.); Angelo Monteux(Santa Cruz Institute for Particle Physics, University of California Santa Cruz, 1156 High Street, Santa Cruz, U.S.A.)
2012-01-01
We comment on aspects of discrete anomaly conditions focussing particularly on $R$ symmetries. We review the Green-Schwarz cancellation of discrete anomalies, providing a heuristic explanation why, in the heterotic string, only the "model-independent dilaton" transforms non-linearly under discrete symmetries; this argument suggests that, in other theories, multiple fields might play a role in anomaly cancellations, further weakening any anomaly constraints at low energies. We provide examples...
Study of magnetic and magnetocaloric properties of monoclinic and triclinic spin chain CoV2O6
Nandi, Moumita; Mandal, Prabhat
We have investigated magnetic and magnetocaloric properties of both monoclinic and triclinic phases of CoV2O6 from magnetization and heat capacity measurements. Conventional and inverse magnetocaloric effects have been observed in both phases of CoV2O6. For a field change from 0 to 7 T, maximum values of magnetic entropy change and adiabatic temperature change reach 11.8 J kg-1 K-1 and 9.5 K respectively for monoclinic CoV2O6 while the corresponding values reach 12.1 J kg-1 K-1 and 13.1 K for triclinic CoVO6. Particularly for triclinic CoVO6, the magnetocaloric parameters are quite large in low or moderate field range. Apart from this, we have constructed magnetic phase diagram of monoclinic CoV2O6 where field-induced complex magnetic phases appear below a certain critical temperature 6 K when external magnetic field is applied along crystallographic easy axis.
Epifani, Mauro; Comini, Elisabetta; Díaz, Raül; Andreu, Teresa; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Faglia, Guido; Morante, Joan R
2014-10-01
We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 °C in oleic acid of W chloroalkoxide solutions was employed. It was shown that the bulk monoclinic crystallographic phase is the stable one even for the nanosized regime (mean size 4 nm). The nanocrystals were characterized by X-ray diffraction, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis, Fourier transform infrared and Raman spectroscopy. It was concluded that they were constituted by a core of monoclinic WO3, surface covered by unstable W(V) species, slowly oxidized upon standing in room conditions. The WO3 nanocrystals could be easily processed to prepare gas-sensing devices, without any phase transition up to at least 500 °C. The devices displayed remarkable response to both oxidizing (nitrogen dioxide) and reducing (ethanol) gases in concentrations ranging from 1 to 5 ppm and from 100 to 500 ppm, at low operating temperatures of 100 and 200 °C, respectively. The analysis of the electrical data showed that the nanocrystals were characterized by reduced surfaces, which enhanced both nitrogen dioxide adsorption and oxygen ionosorption, the latter resulting in enhanced ethanol decomposition kinetics.
Sensitive Probe for Symmetry Potential
Institute of Scientific and Technical Information of China (English)
LIU Jian-Ye; XIAO Guo-Qing; GUO Wen-Jun; REN ZhongZhou; ZUO Wei; LEE Xi-Guo
2007-01-01
Based on both very obvious isospin effect of the neutron-proton number ratio of nucleon emissions (n/p)nucl on symmetry potential and (n/p)nucl's sensitive dependence on symmetry potential in the nuclear reactions induced by halo-neutron projectiles, compared to the same mass stable projectile, probing symmetry potential is investigated within the isospin-dependent quantum molecular dynamics with isospin and momentum-dependent interactions for different symmetry potentials U1sym and U2sym. It is found that the neutron-halo projectile induces very obvious increase of (n/p)nucl and strengthens the dependence of (n/p)nucl on the symmetry potential for all the beam energies and impact parameters, compared to the same mass stable projectile under the same incident channel condition. Therefore (n/p)nucl induced by the neutron-halo projectile is a more favourable probe than the normal neutron-rich and neutron-poor projectiles for extracting the symmetry potential.
Leptogenesis and residual CP symmetry
Chen, Peng; King, Stephen F
2016-01-01
We discuss flavour dependent leptogenesis in the framework of lepton flavour models based on discrete flavour and CP symmetries applied to the type-I seesaw model. Working in the flavour basis, we analyse the case of two general residual CP symmetries in the neutrino sector, which corresponds to all possible semi-direct models based on a preserved $Z_2$ in the neutrino sector, together with a CP symmetry, which constrains the PMNS matrix up to a single free parameter which may be fixed by the reactor angle. We systematically study and classify this case for all possible residual CP symmetries, and show that the $R$-matrix is tightly constrained up to a single free parameter, with only certain forms being consistent with successful leptogenesis, leading to possible connections between leptogenesis and PMNS parameters. The formalism is completely general in the sense that the two residual CP symmetries could result from any high energy discrete flavour theory which respects any CP symmetry. As a simple example,...
Mei Symmetry and Lie Symmetry of the Rotational Relativistic Variable Mass System
Institute of Scientific and Technical Information of China (English)
FANG Jian-Hui
2003-01-01
The Mei symmetry and the Lie symmetry of a rotational relativistic variable masssystem are studied. Thedefinitions and criteria of the Mei symmetry and the Lie symmetry of the rotational relativistic variable mass system aregiven. The relation between the Mei symmetry and the Lie symmetry is found. The conserved quantities which the Meisymmetry and the Lie symmetry lead to are obtained. An example is given to illustrate the application of the result.
Molecular replacement study on form-B monoclinic crystal of insulin
Institute of Scientific and Technical Information of China (English)
定瑾晖; 万柱礼; 常文瑞; 梁栋材
1996-01-01
The form-B monodinic insulin crystal was obtained from the sodium citrate buffer with 1% zinc chloride, keeping phenolic content between 0.76% and 1.25%. Its space group is P21, cell constants are: a = 4.924nm, b=6.094nm, c=4.818nm, β=95.8°. There are 6 insulin molecules which form a hexamer. The initial phase was obtained by using rotation function program of X-PLOR program package and molecular packing program of our laboratory. The molecular model was chosen from 4 zinc bovine insulin hexamer. After the preliminary refinement by using the rnacromolecular rigid body refinement technique, the molecular model was further refined and adjusted by using the energy-minimizing stereochemically restrained least-squared refinement on the difference Fourier maps. The finial R-factor is 214% at 0.3nm resolution, the r.m.s. deviations from standard bond length and bond angle are 0.0022nm and 4.7°, respectively.
SASS: a symmetry adapted stochastic search algorithm exploiting site symmetry.
Wheeler, Steven E; Schleyer, Paul V R; Schaefer, Henry F
2007-03-14
A simple symmetry adapted search algorithm (SASS) exploiting point group symmetry increases the efficiency of systematic explorations of complex quantum mechanical potential energy surfaces. In contrast to previously described stochastic approaches, which do not employ symmetry, candidate structures are generated within simple point groups, such as C2, Cs, and C2v. This facilitates efficient sampling of the 3N-6 Pople's dimensional configuration space and increases the speed and effectiveness of quantum chemical geometry optimizations. Pople's concept of framework groups [J. Am. Chem. Soc. 102, 4615 (1980)] is used to partition the configuration space into structures spanning all possible distributions of sets of symmetry equivalent atoms. This provides an efficient means of computing all structures of a given symmetry with minimum redundancy. This approach also is advantageous for generating initial structures for global optimizations via genetic algorithm and other stochastic global search techniques. Application of the SASS method is illustrated by locating 14 low-lying stationary points on the cc-pwCVDZ ROCCSD(T) potential energy surface of Li5H2. The global minimum structure is identified, along with many unique, nonintuitive, energetically favorable isomers.
Test of Pseudospin Symmetry in Deformed Nuclei
Ginocchio, J N; Meng, J; Zhou, S G; Zhou, Shan-Gui
2004-01-01
Pseudospin symmetry is a relativistic symmetry of the Dirac Hamiltonian with scalar and vector mean fields equal and opposite in sign. This symmetry imposes constraints on the Dirac eigenfunctions. We examine extensively the Dirac eigenfunctions of realistic relativistic mean field calculations of deformed nuclei to determine if these eigenfunctions satisfy these pseudospin symmetry constraints.
Generalised CP and $\\Delta (96)$ Family Symmetry
Ding, Gui-Jun
2014-01-01
We perform a comprehensive study of the $\\Delta (96)$ family symmetry combined with the generalised CP symmetry $H_{\\rm{CP}}$. We investigate the lepton mixing parameters which can be obtained from the original symmetry $\\Delta (96)\\rtimes H_{\\rm{CP}}$ breaking to different remnant symmetries in the neutrino and charged lepton sectors, namely $G_{\
Comparing dualities and gauge symmetries
De Haro, Sebastian; Teh, Nicholas; Butterfield, Jeremy N.
2017-08-01
We discuss some aspects of the relation between dualities and gauge symmetries. Both of these ideas are of course multi-faceted, and we confine ourselves to making two points. Both points are about dualities in string theory, and both have the 'flavour' that two dual theories are 'closer in content' than you might think. For both points, we adopt a simple conception of a duality as an 'isomorphism' between theories: more precisely, as appropriate bijections between the two theories' sets of states and sets of quantities. The first point (Section 3) is that this conception of duality meshes with two dual theories being 'gauge related' in the general philosophical sense of being physically equivalent. For a string duality, such as T-duality and gauge/gravity duality, this means taking such features as the radius of a compact dimension, and the dimensionality of spacetime, to be 'gauge'. The second point (Sections 4-6) is much more specific. We give a result about gauge/gravity duality that shows its relation to gauge symmetries (in the physical sense of symmetry transformations that are spacetime-dependent) to be subtler than you might expect. For gauge theories, you might expect that the duality bijections relate only gauge-invariant quantities and states, in the sense that gauge symmetries in one theory will be unrelated to any symmetries in the other theory. This may be so in general; and indeed, it is suggested by discussions of Polchinski and Horowitz. But we show that in gauge/gravity duality, each of a certain class of gauge symmetries in the gravity/bulk theory, viz. diffeomorphisms, is related by the duality to a position-dependent symmetry of the gauge/boundary theory.
A reciprocal space approach for locating symmetry elements in Patterson superposition maps
Energy Technology Data Exchange (ETDEWEB)
Hendrixson, T.
1990-09-21
A method for determining the location and possible existence of symmetry elements in Patterson superposition maps has been developed. A comparison of the original superposition map and a superposition map operated on by the symmetry element gives possible translations to the location of the symmetry element. A reciprocal space approach using structure factor-like quantities obtained from the Fourier transform of the superposition function is then used to determine the best'' location of the symmetry element. Constraints based upon the space group requirements are also used as a check on the locations. The locations of the symmetry elements are used to modify the Fourier transform coefficients of the superposition function to give an approximation of the structure factors, which are then refined using the EG relation. The analysis of several compounds using this method is presented. Reciprocal space techniques for locating multiple images in the superposition function are also presented, along with methods to remove the effect of multiple images in the Fourier transform coefficients of the superposition map. In addition, crystallographic studies of the extended chain structure of (NHC{sub 5}H{sub 5})SbI{sub 4} and of the twinning method of the orthorhombic form of the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7-x} are presented. 54 refs.
Symmetry Breaking for Answer Set Programming
Drescher, Christian
2010-01-01
In the context of answer set programming, this work investigates symmetry detection and symmetry breaking to eliminate symmetric parts of the search space and, thereby, simplify the solution process. We contribute a reduction of symmetry detection to a graph automorphism problem which allows to extract symmetries of a logic program from the symmetries of the constructed coloured graph. We also propose an encoding of symmetry-breaking constraints in terms of permutation cycles and use only generators in this process which implicitly represent symmetries and always with exponential compression. These ideas are formulated as preprocessing and implemented in a completely automated flow that first detects symmetries from a given answer set program, adds symmetry-breaking constraints, and can be applied to any existing answer set solver. We demonstrate computational impact on benchmarks versus direct application of the solver. Furthermore, we explore symmetry breaking for answer set programming in two domains: firs...
Petrology of Karoo volcanic rocks in the southern Lebombo monocline, Mozambique
Melluso, Leone; Cucciniello, Ciro; Petrone, Chiara M.; Lustrino, Michele; Morra, Vincenzo; Tiepolo, Massimo; Vasconcelos, Lopo
2008-11-01
The Karoo volcanic sequence in the southern Lebombo monocline in Mozambique contains different silicic units in the form of pyroclastic rocks, and two different basalt types. The silicic units in the lower part of the Lebombo sequence are formed by a lower unit of dacites and rhyolites (67-80 wt.% SiO 2) with high Ba (990-2500 ppm), Zr (800-1100 ppm) and Y (130-240 ppm), which are part of the Jozini-Mbuluzi Formation, followed by a second unit, interlayered with the Movene basalts, of high-SiO 2 rhyolites (76-78 wt.%; the Sica Beds Formation), with low Sr (19-54 ppm), Zr (340-480 ppm) and Ba (330-850 ppm) plus rare quartz-trachytes (64-66 wt.% SiO 2), with high Nb and Rb contents (240-250 and 370-381 ppm, respectively), and relatively low Zr (450-460 ppm). The mafic rocks found at the top of the sequence are basalts and ferrobasalts belonging to the Movene Formation. The basalts have roughly flat mantle-normalized incompatible element patterns, with abundances of the most incompatible elements not higher than 25 times primitive mantle. The ferrobasalt has TiO 2 ˜ 4.7 wt.%, Fe 2O 3t = 16 wt.%, and high Y (100 ppm), Zr (420 ppm) and Ba (1000 ppm). The Movene basalts have initial (at 180 Ma) 87Sr/ 86Sr = 0.7052-0.7054 and 143Nd/ 144Nd = 0.51232, and the Movene ferrobasalt has even lower 87Sr/ 86Sr (0.70377) and higher 143Nd/ 144Nd (0.51259). The silicic rocks show a modest range of initial Sr-( 87Sr/ 86Sr = 0.70470-0.70648) and Nd-( 143Nd/ 144Nd = 0.51223-0.51243) isotope ratios. The less evolved dacites could have been formed after crystal fractionation of oxide-rich gabbroic cumulates from mafic parental magmas, whereas the most silica-rich rhyolites could have been formed after fractional crystallization of feldspars, pyroxenes, oxides, zircon and apatite from a parental dacite magma. The composition of the Movene basalts imply different feeding systems from those of the underlying Sabie River basalts.
Parity-time symmetry broken by point-group symmetry
Energy Technology Data Exchange (ETDEWEB)
Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar; Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Blvd. 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2014-04-15
We discuss a parity-time (PT) symmetric Hamiltonian with complex eigenvalues. It is based on the dimensionless Schrödinger equation for a particle in a square box with the PT-symmetric potential V(x, y) = iaxy. Perturbation theory clearly shows that some of the eigenvalues are complex for sufficiently small values of |a|. Point-group symmetry proves useful to guess if some of the eigenvalues may already be complex for all values of the coupling constant. We confirm those conclusions by means of an accurate numerical calculation based on the diagonalization method. On the other hand, the Schrödinger equation with the potential V(x, y) = iaxy{sup 2} exhibits real eigenvalues for sufficiently small values of |a|. Point group symmetry suggests that PT-symmetry may be broken in the former case and unbroken in the latter one.
Gauge symmetry enhancement in Hamiltonian formalism
Hong, S T; Lee, T H; Oh, P; Oh, Phillial
2003-01-01
We study the Hamiltonian structure of the gauge symmetry enhancement in the enlarged CP(N) model coupled with U(2) chern-Simons term, which contains a free parameter governing explicit symmetry breaking and symmetry enhancement. After giving a general discussion of the geometry of constrained phase space suitable for the symmetry enhancement, we explicitly perform the Dirac analysis of out model and compute the Dirac brackets for the symmetry enhanced and broken cases. We also discuss some related issues.
Localization of Nonlocal Symmetries and Symmetry Reductions of Burgers Equation
Wu, Jian-Wen; Lou, Sen-Yue; Yu, Jun
2017-05-01
The nonlocal symmetries of the Burgers equation are explicitly given by the truncated Painlevé method. The auto-Bäcklund transformation and group invariant solutions are obtained via the localization procedure for the nonlocal residual symmetries. Furthermore, the interaction solutions of the solition-Kummer waves and the solition-Airy waves are obtained. Supported by the Global Change Research Program China under Grant No. 2015CB953904, the National Natural Science Foundations of China under Grant Nos. 11435005, 11175092, and 11205092, Shanghai Knowledge Service Platform for Trustworthy Internet of Things under Grant No. ZF1213, and K. C. Wong Magna Fund in Ningbo University
Energy Technology Data Exchange (ETDEWEB)
Qi-Jun, Liu; Fu-Sheng, Liu, E-mail: qijunliu@home.swjtu.edu.cn [School of Physical Science and Technology, Southwest Jiaotong University, Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Chengdu (China); Bond and Band Engineering Group, Sichuan Provincial Key Laboratory (for Universities) of High Pressure Science and Technology, Southwest Jiaotong University, Chengdu (China); Zheng-Tang, Liu [State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi' an, (China)
2015-08-15
Structural, elastic, mechanical, and electronic properties of monoclinic N{sub 2}H{sub 5}N{sub 3} at zero and high pressure have been investigated using the plane-wave ultrasoft pseudopotential method within the density-functional theory (DFT). The pressure dependences of structural parameters, elastic constants, mechanical properties, band gaps, and density of states of monoclinic N{sub 2}H{sub 5}N{sub 3} have been calculated and discussed. The obtained results show that monoclinic N{sub 2}H{sub 5}N{sub 3} is unstable at pressures exceeding the value 126.1 GPa. The ratio of B/G and the Cauchy’s pressure indicate that monoclinic N{sub 2}H{sub 5}N{sub 3} behaves in ductile nature with pressure ranging from 0 to 200 GPa. (author)
Miller, G A
2003-01-01
Two new experiments have detected charge-symmetry breaking, the mechanism responsible for protons and neutrons having different masses. Symmetry is a crucial concept in the theories that describe the subatomic world because it has an intimate connection with the laws of conservation. The theory of the strong interaction between quarks - quantum chromodynamics - is approximately invariant under what is called charge symmetry. In other words, if we swap an up quark for a down quark, then the strong interaction will look almost the same. This symmetry is related to the concept of sup i sospin sup , and is not the same as charge conjugation (in which a particle is replaced by its antiparticle). Charge symmetry is broken by the competition between two different effects. The first is the small difference in mass between up and down quarks, which is about 200 times less than the mass of the proton. The second is their different electric charges. The up quark has a charge of +2/3 in units of the proton charge, while ...
Symmetry Guide to Ferroaxial Transitions
Hlinka, J.; Privratska, J.; Ondrejkovic, P.; Janovec, V.
2016-04-01
The 212 species of the structural phase transitions with a macroscopic symmetry breaking are inspected with respect to the occurrence of the ferroaxial order parameter, the electric toroidal moment. In total, 124 ferroaxial species are found, some of them being also fully ferroelectric (62) or fully ferroelastic ones (61). This ensures a possibility of electrical or mechanical switching of ferroaxial domains. Moreover, there are 12 ferroaxial species that are neither ferroelectric nor ferroelastic. For each species, we have also explicitly worked out a canonical form for a set of representative equilibrium property tensors of polar and axial nature in both high-symmetry and low-symmetry phases. This information was gathered into the set of 212 mutually different symbolic matrices, expressing graphically the presence of nonzero independent tensorial components and the symmetry-imposed links between them, for both phases simultaneously. Symmetry analysis reveals the ferroaxiality in several currently debated materials, such as VO2 , LuFe2 O4 , and URu2 Si2 .
Emergent low-symmetry phases with large property enhancement in ferroelectric KNbO3 bulk crystals
Energy Technology Data Exchange (ETDEWEB)
Lummen, Tom T. A.; Leung, J; Kumar, Amit; Wu, X; Ren, Y; Vanleeuwen, Brian K; Haislmaier, Ryan C.; Holt, Martin; Lai, Keji; Kalinin, Sergei V.; Gopalan, Venkatraman
2017-08-18
The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only approximate to 0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low-symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m(-1). This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.
Hydronium perchlorate–dibenzo-18-crown-6 (1/1: monoclinic polymorph
Directory of Open Access Journals (Sweden)
Michaela Pojarová
2010-12-01
Full Text Available The asymmetric unit of the title compound, H3O+·ClO4−·C20H24O6, contains two molecules/ions of each species. Both dibenzo-18-crown-6 molecules have a complexed hydronium ion inside their cavity with O—H...O and O—H...(O,O links between the two species. The associated perchlorate anions also accept O—H...O hydrogen bonds from the hydronium ion. Both crown ether molecules are present in a butterfly conformation with approximate C2v symmetry and their cavities are closed by the benzene ring of a neighbouring molecule. The packing is consolidated by C—H...O and C—H...π interactions.
Vujicic-Zagar, A.; Dijkstra, B. W.; Vujičić-Žagar, A.
Aspergillus niger alpha-amylase catalyses the hydrolysis of alpha-1,4-glucosidic bonds in starch. It shows 100% sequence identity to the A. oryzae homologue (also called TAKA-amylase), three crystal structures of which have been published to date. Two of them belong to the orthorhombic space group
Weyl semimetal from spontaneous inversion symmetry breaking in pyrochlore oxides
Bzdušek, Tomáš; Rüegg, Andreas; Sigrist, Manfred
2015-04-01
We study the electronic properties of strongly spin-orbit coupled electrons on the elastic pyrochlore lattice. Akin to the Peierls transition in one-dimensional systems, the coupling of the lattice to the electronic degrees of freedom can stabilize a spontaneous deformation of the crystal. This deformation corresponds to a breathing mode, which breaks the inversion symmetry. We find that for intermediate values of the staggered strain, the inversion-symmetry broken phase realizes a topological Weyl semimetal. In the temperature-elasticity phase diagram, the Weyl semimetal shows a reentrant phase behavior: it can be reached from a symmetric phase realized both at higher and at lower temperatures. The symmetric phase is a Dirac semimetal, which is protected by the nonsymmorphic space group of the pyrochlore lattice. Beyond a critical value of the staggered strain, the symmetry-broken phase is a fully gapped trivial insulator. The surface states of the Weyl semimetal form open Fermi arcs and we observe that their connectivity depends on the termination of the crystal. In particular, for the {111 } films, the semiclassical closed electronic orbits of the surface states in a magnetic field cross the bulk either twice, four, six, or twelve times. We demonstrate how one can tune the number of bulk crossings through a Lifshitz-like transition of the Fermi arcs, which we call Weyl-Lifshitz transition, by applying a surface potential. Our results offer a route to a topological Weyl semimetal in nonmagnetic materials and might be relevant for pyrochlore oxides with heavy transition-metal ions such as alloys of iridates.
Heisenberg symmetry and hypermultiplet manifolds
Antoniadis, Ignatios; Petropoulos, P Marios; Siampos, Konstantinos
2015-01-01
We study the emergence of Heisenberg (Bianchi II) algebra in hyper-K\\"ahler and quaternionic spaces. This is motivated by the r\\^ole these spaces with this symmetry play in $\\mathcal{N}=2$ hypermultiplet scalar manifolds. We show how to construct related pairs of hyper-K\\"ahler and quaternionic spaces under general symmetry assumptions, the former being a zooming-in limit of the latter at vanishing cosmological constant. We further apply this method for the two hyper-K\\"ahler spaces with Heisenberg algebra, which is reduced to $U(1)\\times U(1)$ at the quaternionic level. We also show that no quaternionic spaces exist with a strict Heisenberg symmetry -- as opposed to $\\text{Heisenberg} \\ltimes U(1)$. We finally discuss the realization of the latter by gauging appropriate $Sp(2,4)$ generators in $\\mathcal{N}=2$ conformal supergravity.
Symmetry and Asymmetry Level Measures
Directory of Open Access Journals (Sweden)
Angel Garrido
2010-04-01
Full Text Available Usually, Symmetry and Asymmetry are considered as two opposite sides of a coin: an object is either totally symmetric, or totally asymmetric, relative to pattern objects. Intermediate situations of partial symmetry or partial asymmetry are not considered. But this dichotomy on the classification lacks of a necessary and realistic gradation. For this reason, it is convenient to introduce "shade regions", modulating the degree of Symmetry (a fuzzy concept. Here, we will analyze the Asymmetry problem by successive attempts of description and by the introduction of the Asymmetry Level Function, as a new Normal Fuzzy Measure. Our results (both Theorems and Corollaries suppose to be some new and original contributions to such very active and interesting field of research. Previously, we proceed to the analysis of the state of art.
Gribov problem and BRST symmetry
Fujikawa, K
1995-01-01
After a brief historical comment on the study of BRS(or BRST) symmetry , we discuss the quantization of gauge theories with Gribov copies. A path integral with BRST symmetry can be formulated by summing the Gribov-type copies in a very specific way if the functional correspondence between \\tau and the gauge parameter \\omega defined by \\tau (x) = f( A_{\\mu}^{\\omega}(x)) is ``globally single valued'', where f( A_{\\mu}^{\\omega}(x)) = 0 specifies the gauge condition. As an example of the theory which satisfies this criterion, we comment on a soluble gauge model with Gribov-type copies recently analyzed by Friedberg, Lee, Pang and Ren. We also comment on a possible connection of the dynamical instability of BRST symmetry with the Gribov problem on the basis of an index notion.
Hidden Symmetries of Stochastic Models
Directory of Open Access Journals (Sweden)
Boyka Aneva
2007-05-01
Full Text Available In the matrix product states approach to $n$ species diffusion processes the stationary probability distribution is expressed as a matrix product state with respect to a quadratic algebra determined by the dynamics of the process. The quadratic algebra defines a noncommutative space with a $SU_q(n$ quantum group action as its symmetry. Boundary processes amount to the appearance of parameter dependent linear terms in the algebraic relations and lead to a reduction of the $SU_q(n$ symmetry. We argue that the boundary operators of the asymmetric simple exclusion process generate a tridiagonal algebra whose irriducible representations are expressed in terms of the Askey-Wilson polynomials. The Askey-Wilson algebra arises as a symmetry of the boundary problem and allows to solve the model exactly.
Heisenberg symmetry and hypermultiplet manifolds
Directory of Open Access Journals (Sweden)
Ignatios Antoniadis
2016-04-01
Full Text Available We study the emergence of Heisenberg (Bianchi II algebra in hyper-Kähler and quaternionic spaces. This is motivated by the rôle these spaces with this symmetry play in N=2 hypermultiplet scalar manifolds. We show how to construct related pairs of hyper-Kähler and quaternionic spaces under general symmetry assumptions, the former being a zooming-in limit of the latter at vanishing scalar curvature. We further apply this method for the two hyper-Kähler spaces with Heisenberg algebra, which is reduced to U(1×U(1 at the quaternionic level. We also show that no quaternionic spaces exist with a strict Heisenberg symmetry – as opposed to Heisenberg⋉U(1. We finally discuss the realization of the latter by gauging appropriate Sp(2,4 generators in N=2 conformal supergravity.
An Introduction to Emergent Symmetries
Gomes, Pedro R S
2015-01-01
These are intended to be introductory notes on emergent symmetries, i.e., symmetries which manifest themselves in specific sectors of energy in many systems. The emphasis is on the physical aspects rather than computation methods. We include some elementary background material and proceed to our discussion by examining several interesting problems in field theory, statistical mechanics and condensed matter. These problems illustrate how some important symmetries, such as Lorentz invariance and supersymmetry, usually believed to be fundamental, can arise naturally in low-energy regimes of systems involving a large number of degrees of freedom. The aim is to discuss how these examples could help us to face other complex and fundamental problems.
Yao, Mingming; Gan, Lihua; Liu, Mingxian; Tripathi, Pranav K.; Liu, Yafei; Hu, Zhonghua
2015-06-01
In this paper, carbon-doped monoclinic scheelite mesoporous bismuth vanadate was synthesized through template-engaged in situ method. The bismuth nitrate pentahydrate and ammonia metavanadate were used as bismuth and vanadium precursors, respectively, glucose as carbon source, and mesoporous SiO2 aerogel as a hard template. Carbon-doped monoclinic mesoporous BiVO4 were obtained by heat treatment of BiVO4/glucose/template to carbonize glucose and form monoclinic crystal, followed by etching with NaOH solution to remove the SiO2 template. The samples were characterized by x-ray diffraction, N2 adsorption and desorption, UV-visible spectroscopy, Energy dispersive spectrometry, Raman spectroscopy, and Transmission electron microscopy. It was found that the sample with a carbon content of 0.5 wt.% possesses a specific surface area of 10.2 m2/g and has mesoporous structure with the most probable pore size of 13.9 nm. The band gap of carbon-doped monoclinic mesoporous BiVO4 was estimated to be 2.33 eV, indicating the superior photocatalytic activity under visible light. The photocatalytic efficiency of carbon-doped monoclinic mesoporous BiVO4 for the degradation of Rhodamine B under visible light (λ > 400 nm) in 120 min reaches 98.7%, Besides, the carbon-doped monoclinic mesoporous BiVO4 photocatalyst still showed high stability: 85% for Rhodamine B degradation after ten recycles.
Mathieu Moonshine and Symmetry Surfing
Gaberdiel, Matthias R; Paul, Hynek
2016-01-01
Mathieu Moonshine, the observation that the Fourier coefficients of the elliptic genus on K3 can be interpreted as dimensions of representations of the Mathieu group M24, has been proven abstractly, but a conceptual understanding in terms of a representation of the Mathieu group on the BPS states, is missing. Some time ago, Taormina and Wendland showed that such an action can be naturally defined on the lowest non-trivial BPS states, using the idea of `symmetry surfing', i.e., by combining the symmetries of different K3 sigma models. In this paper we find non-trivial evidence that this construction can be generalized to all BPS states.
Cosmological Reflection of Particle Symmetry
Directory of Open Access Journals (Sweden)
Maxim Khlopov
2016-08-01
Full Text Available The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetry and the mechanisms of its breaking are the subject of the present review.
Symposium Symmetries in Science XIII
Gruber, Bruno J; Yoshinaga, Naotaka; Symmetries in Science XI
2005-01-01
This book is a collection of reviews and essays about the recent developments in the area of Symmetries and applications of Group Theory. Contributions have been written mostly at the graduate level but some are accessible to advanced undergraduates. The book is of interest to a wide audience and covers a broad range of topics with a strong degree of thematical unity. The book is part of a Series of books on Symmetries in Science and may be compared to the published Proceedings of the Colloquia on Group Theoretical Methods in Physics. Here, however, prevails a distinguished character for presenting extended reviews on present applications to Science, not restricted to Theoretical Physics.
Symmetry of intramolecular quantum dynamics
Burenin, Alexander V
2012-01-01
The main goal of this book is to give a systematic description of intramolecular quantum dynamics on the basis of only the symmetry principles. In this respect, the book has no analogs in the world literature. The obtained models lead to a simple, purely algebraic, scheme of calculation and are rigorous in the sense that their correctness is limited only to the correct choice of symmetry of the internal dynamics. The book is basically intended for scientists working in the field of molecular spectroscopy, quantum and structural chemistry.
Quantum Symmetries and Exceptional Collections
Karp, Robert L.
2011-01-01
We study the interplay between discrete quantum symmetries at certain points in the moduli space of Calabi-Yau compactifications, and the associated identities that the geometric realization of D-brane monodromies must satisfy. We show that in a wide class of examples, both local and compact, the monodromy identities in question always follow from a single mathematical statement. One of the simplest examples is the {{mathbb Z}_5} symmetry at the Gepner point of the quintic, and the associated D-brane monodromy identity.
Quantum symmetries and exceptional collections
Karp, Robert L
2008-01-01
We study the interplay between discrete quantum symmetries at certain points in the moduli space of Calabi-Yau compactifications, and the associated identities that the geometric realization of D-brane monodromies must satisfy. We show that in a wide class of examples, both local and compact, the monodromy identities in question always follow from a single mathematical statement. One of the simplest examples is the Z_5 symmetry at the Gepner point of the quintic, and the associated D-brane monodromy identity.
Theta functions and mirror symmetry
Gross, Mark
2012-01-01
This is a survey covering aspects of varied work of the authors with Mohammed Abouzaid, Paul Hacking, and Sean Keel. While theta functions are traditionally canonical sections of ample line bundles on abelian varieties, we motivate, using mirror symmetry, the idea that theta functions exist in much greater generality. This suggestion originates with the work of the late Andrei Tyurin. We outline how to construct theta functions on the degenerations of varieties constructed in previous work of the authors, and then explain applications of this construction to homological mirror symmetry and constructions of broad classes of mirror varieties.
Exact symmetries of electron states and optical selection rules in wurtzite-based nanostructures
Kitaev, Yu. E.; Tronc, P.
2001-11-01
The crystal structure of wurtzite-based (hexagonal) quantum wells (QW's), such as (GaN)m/AlN ones for example, is found to be described by the layer group P3m1 (DG69) and does not depend on the number of atomic monolayers constituting the QW whereas the symmetry of wurtzite-based superlattices (SL's), such as (GaN)m(AlN)n ones for example, has been previously shown to be described by the space groups C13v or C46v depending on m+n is even or odd. The P3m1 (DG69) group is a factor group of the C13v group, the latter being the product of the P3m1 group and the subgroup containing the translations along the z axis. Basing on these symmetries, we have determined the exact symmetries of Bloch states at the Γ and other symmetry points of the Brillouin zones of QW's and SL's and derived optical selection rules for carriers and excitons. The latters present large Rydberg values. We have shown that the built-in electric field, directed along the z axis due to the symmetry, breaks the translational invariance of the SL's along this direction reducing their symmetry to that of a single QW. We have established that when one (several) phonon(s) is (are) involved in a radiative process, it is always possible to connect any initial state to any final one. The energy of the emitted photon depends on the nature of the phonon(s) if several channels are allowed for the transition. The symmetry of electron states in very thin QW's and short-period SL's is shown to be determined by their exact symmetry rather than that implied in envelope function approximation (EFA). Within the domain of validity of the EFA, i.e., for not too thin layers, a detailed analysis of the Bloch-state symmetry is performed on imposing the invariance of the structure under the change of z to -z (the σz symmetry operation). The correspondence is established between the symmetry of a Bloch state and the parity with respect to σz of its associated envelope function. It is shown that EFA artificially induces a
Institute of Scientific and Technical Information of China (English)
HOU Ming-Xiu; HE Kai-Hua; ZHENG Guang; HOU Shu-En
2008-01-01
The structural, electronic and optical properties of the monoclinic ZrO2 were studied by ab initio calculations based on the density functional theory and pseudopotential method. The calculated lattice parameters and band gap are in agreement with the experimental and other theo- retical values. The evolution of lattice parameters and electronic properties were illustrated under high pressure. Meanwhile, the optical properties, such as adsorption coefficients, imaginary part of dielectric function, and energy loss function, were investigated under both ambient and high pressures.
Synthesis of Monoclinic Form of Gd2-xNaxCuO4 by Direct Precipitation from Molten Salt
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A new phase of Gd2-xNaxCuO4 was synthesized by direct precipitation from the mixture of Gd2O3 and CuO in the molten KOH/NaOH/KNO3 solution at temperature as low as 280° C. The resulting precipitate was characterized by using SEM, XRD, EDX, XPS and magnetic method. The XRD data indicate that the precipitated Gd2-xNaxCuO4 is monoclinic with lattice parameters a=8.6816(A), b=3.7233(A). C=6.0796(A), α =γ =90°, β =108.75° and V=186.1(A)3.
Indian Academy of Sciences (India)
Anil Kumar; Sarvajit Singh; Jagdish Singh
2002-06-01
Static deformation of two monoclinic elastic half-spaces in welded contact due to a long inclined strike-slip fault situated in one of the half-spaces is studied analytically and numerically. Closedform algebraic expressions for the displacement at any point of the medium are obtained. The variation of the displacement at the interface with the horizontal distance from the fault is studied. The effect of anisotropy on the displacement field is examined. It is found that while the anisotropy of the source half-space has a significant effect on the displacement at the interface, the anisotropy of the other half-space has only a marginal effect.
Charge symmetry at the partonic level
Energy Technology Data Exchange (ETDEWEB)
Londergan, J. T.; Peng, J. C.; Thomas, A. W.
2010-07-01
This review article discusses the experimental and theoretical status of partonic charge symmetry. It is shown how the partonic content of various structure functions gets redefined when the assumption of charge symmetry is relaxed. We review various theoretical and phenomenological models for charge symmetry violation in parton distribution functions. We summarize the current experimental upper limits on charge symmetry violation in parton distributions. A series of experiments are presented, which might reveal partonic charge symmetry violation, or alternatively might lower the current upper limits on parton charge symmetry violation.
Symmetry Non-restoration at High Temperature
Rius, N
1998-01-01
We discuss the (non)-restoration of global and local symmetries at high temperature. First, we analyze a two-scalar model with $Z_2 \\times Z_2$ symmetry using the exact renormalization group. We conclude that inverse symmetry breaking is possible in this kind of models within the perturbative regime. Regarding local symmetries, we consider the $SU(2) \\otimes U(1)$ gauge symmetry and focus on the case of a strongly interacting scalar sector. Employing a model-independent chiral Lagrangian we find indications of symmetry restoration.
A model of intrinsic symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Ge, Li [Research Center for Quantum Manipulation, Department of Physics, Fudan University, Shanghai 200433 (China); Li, Sheng [Department of Physics, Zhejiang Normal University, Zhejiang 310004 (China); George, Thomas F., E-mail: tfgeorge@umsl.edu [Office of the Chancellor and Center for Nanoscience, Department of Chemistry and Biochemistry, University of Missouri-St. Louis, St. Louis, MO 63121 (United States); Department of Physics and Astronomy, University of Missouri-St. Louis, St. Louis, MO 63121 (United States); Sun, Xin, E-mail: xin_sun@fudan.edu.cn [Research Center for Quantum Manipulation, Department of Physics, Fudan University, Shanghai 200433 (China)
2013-11-01
Different from the symmetry breaking associated with a phase transition, which occurs when the controlling parameter is manipulated across a critical point, the symmetry breaking presented in this Letter does not need parameter manipulation. Instead, the system itself suddenly undergoes symmetry breaking at a certain time during its evolution, which is intrinsic symmetry breaking. Through a polymer model, it is revealed that the origin of the intrinsic symmetry breaking is nonlinearity, which produces instability at the instance when the evolution crosses an inflexion point, where this instability breaks the original symmetry.
Monoclinic superstructure of Pr{sub 3}Rh{sub 4}Ge{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Vosswinkel, Daniel; Hoffmann, Rolf-Dieter; Greiwe, Magnus; Eul, Matthias; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie
2016-07-01
Pr{sub 3}Rh{sub 4}Ge{sub 4} was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr{sub 3}Rh{sub 4}Ge{sub 4} adopts the U{sub 3}Ni{sub 4}Si{sub 4} type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/m(α0γ)00; α=1/2, γ=1/2; (Z=2). This commensurately modulated structure could be refined with 1448 F{sup 2} values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1{sup st} order, [a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1) , 1448 F{sup 2} values, 69 variables and wR=0.0499. The relation of the U{sub 3}Ni{sub 4}Si{sub 4} type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μ{sub B}/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K.
Partial Dynamical Symmetries in Nuclei
Leviatan, A
2000-01-01
Partial dynamical symmetries (PDS) are shown to be relevant to the interpretation of the $K=0_2$ band and to the occurrence of F-spin multiplets of ground and scissors bands in deformed nuclei. Hamiltonians with bosonic and fermionic PDS are presented.
Symmetry-protected topological entanglement
Marvian, Iman
2017-01-01
We propose an order parameter for the symmetry-protected topological (SPT) phases which are protected by Abelian on-site symmetries. This order parameter, called the SPT entanglement, is defined as the entanglement between A and B , two distant regions of the system, given that the total charge (associated with the symmetry) in a third region C is measured and known, where C is a connected region surrounded by A , B , and the boundaries of the system. In the case of one-dimensional systems we prove that in the limit where A and B are large and far from each other compared to the correlation length, the SPT entanglement remains constant throughout a SPT phase, and furthermore, it is zero for the trivial phase while it is nonzero for all the nontrivial phases. Moreover, we show that the SPT entanglement is invariant under the low-depth quantum circuits which respect the symmetry, and hence it remains constant throughout a SPT phase in the higher dimensions as well. Also, we show that there is an intriguing connection between SPT entanglement and the Fourier transform of the string order parameters, which are the traditional tool for detecting SPT phases. This leads to an algorithm for extracting the relevant information about the SPT phase of the system from the string order parameters. Finally, we discuss implications of our results in the context of measurement-based quantum computation.
Symmetry structure and phase transitions
Indian Academy of Sciences (India)
Ashok Goyal; Meenu Dahiya; Deepak Chandra
2003-05-01
We study chiral symmetry structure at ﬁnite density and temperature in the presence of external magnetic ﬁeld and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and their survival.
Quantitative Analysis of Face Symmetry.
Tamir, Abraham
2015-06-01
The major objective of this article was to report quantitatively the degree of human face symmetry for reported images taken from the Internet. From the original image of a certain person that appears in the center of each triplet, 2 symmetric combinations were constructed that are based on the left part of the image and its mirror image (left-left) and on the right part of the image and its mirror image (right-right). By applying a computer software that enables to determine length, surface area, and perimeter of any geometric shape, the following measurements were obtained for each triplet: face perimeter and area; distance between the pupils; mouth length; its perimeter and area; nose length and face length, usually below the ears; as well as the area and perimeter of the pupils. Then, for each of the above measurements, the value C, which characterizes the degree of symmetry of the real image with respect to the combinations right-right and left-left, was calculated. C appears on the right-hand side below each image. A high value of C indicates a low symmetry, and as the value is decreasing, the symmetry is increasing. The magnitude on the left relates to the pupils and compares the difference between the area and perimeter of the 2 pupils. The major conclusion arrived at here is that the human face is asymmetric to some degree; the degree of asymmetry is reported quantitatively under each portrait.
Strong coupling electroweak symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Barklow, T.L. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Burdman, G. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics; Chivukula, R.S. [Boston Univ., MA (United States). Dept. of Physics
1997-04-01
The authors review models of electroweak symmetry breaking due to new strong interactions at the TeV energy scale and discuss the prospects for their experimental tests. They emphasize the direct observation of the new interactions through high-energy scattering of vector bosons. They also discuss indirect probes of the new interactions and exotic particles predicted by specific theoretical models.
(Hybrid) Baryons Symmetries and Masses
Page, P R
1999-01-01
We construct (hybrid) baryons in the flux-tube model of Isgur and Paton. In the limit of adiabatic quark motion, we build proper eigenstates of orbital angular momentum and construct the flavour, spin and J^P of hybrid baryons from the symmetries of the system. The lowest mass hybrid baryon is estimated at approximately 2 GeV.
Dark Energy and Spacetime Symmetry
Directory of Open Access Journals (Sweden)
Irina Dymnikova
2017-03-01
Full Text Available The Petrov classification of stress-energy tensors provides a model-independent definition of a vacuum by the algebraic structure of its stress-energy tensor and implies the existence of vacua whose symmetry is reduced as compared with the maximally symmetric de Sitter vacuum associated with the Einstein cosmological term. This allows to describe a vacuum in general setting by dynamical vacuum dark fluid, presented by a variable cosmological term with the reduced symmetry which makes vacuum fluid essentially anisotropic and allows it to be evolving and clustering. The relevant solutions to the Einstein equations describe regular cosmological models with time-evolving and spatially inhomogeneous vacuum dark energy, and compact vacuum objects generically related to a dark energy: regular black holes, their remnants and self-gravitating vacuum solitons with de Sitter vacuum interiors—which can be responsible for observational effects typically related to a dark matter. The mass of objects with de Sitter interior is generically related to vacuum dark energy and to breaking of space-time symmetry. In the cosmological context spacetime symmetry provides a mechanism for relaxing cosmological constant to a needed non-zero value.
Turning Students into Symmetry Detectives
Wilders, Richard; VanOyen, Lawrence
2011-01-01
Exploring mathematical symmetry is one way of increasing students' understanding of art. By asking students to search designs and become pattern detectives, teachers can potentially increase their appreciation of art while reinforcing their perception of the use of math in their day-to-day lives. This article shows teachers how they can interest…
Hidden Local Symmetry and Beyond
Yamawaki, Koichi
2016-01-01
Gerry Brown was a godfather of our hidden local symmetry (HLS) for the vector meson from the birth of the theory throughout his life. The HLS is originated from very nature of the nonlinear realization of the symmetry G based on the manifold G/H, and thus is universal to any physics based on the nonlinear realization. Here I focus on the Higgs Lagrangian of the Standard Model (SM), which is shown to be equivalent to the nonlinear sigma model based on G/H= SU(2)_L x SU(2)_R/SU(2)_V with additional symmetry, the nonlinearly realized scale symmetry. Then the SM does have a dynamical gauge boson of the SU(2)_V HLS, "SM rho meson", in addition to the Higgs as a pseudo dilaton as well as the NG bosons to be absorbed into the W and Z. Based on the recent work done with S. Matsuzaki and H. Ohki, I discuss a novel possibility that the SM rho meson acquires kinetic term by the SM dynamics itself, which then stabilizes the skyrmion dormant in the SM as a viable candidate for the dark matter, what we call "Dark SM skyrmi...
Symmetry violation in weak decays
Vos, Kimberley Keri
2016-01-01
Our current knowledge of particle physics is described by the Standard Model (SM). This model, however, leaves important observations unexplained. To answer these outstanding questions, as of yet, unknown physics is required. In the search for new physics, symmetries and their breaking play a guidin
Hidden local symmetry and beyond
Yamawaki, Koichi
Gerry Brown was a godfather of our hidden local symmetry (HLS) for the vector meson from the birth of the theory throughout his life. The HLS is originated from very nature of the nonlinear realization of the symmetry G based on the manifold G/H, and thus is universal to any physics based on the nonlinear realization. Here, I focus on the Higgs Lagrangian of the Standard Model (SM), which is shown to be equivalent to the nonlinear sigma model based on G/H = SU(2)L × SU(2)R/SU(2)V with additional symmetry, the nonlinearly-realized scale symmetry. Then, the SM does have a dynamical gauge boson of the SU(2)V HLS, "SM ρ meson", in addition to the Higgs as a pseudo-dilaton as well as the NG bosons to be absorbed in to the W and Z. Based on the recent work done with Matsuzaki and Ohki, I discuss a novel possibility that the SM ρ meson acquires kinetic term by the SM dynamics itself, which then stabilizes the skyrmion dormant in the SM as a viable candidate for the dark matter, what we call "dark SM skyrmion (DSMS)".
Symmetry of tetrahydroxycalix[4]arenes
Directory of Open Access Journals (Sweden)
M. GHORBANI
2006-10-01
Full Text Available Graph theory provides an elegant and natural representation of molecular symmetry and the resulting group expressed in terms of permutations is isomorphic to the permutation-inversion group of Longuet-Higgins. In this paper, using the group theory package GAP, the character table and the automorphism group of the Euclidean graph of tetrahydroxycalix[4]arenes were computed.
Nanoscale self-templating for oxide epitaxy with large symmetry mismatch
Gao, Xiang; Lee, Shinbuhm; Nichols, John; Meyer, Tricia L.; Ward, Thomas Z.; Chisholm, Matthew F.; Lee, Ho Nyung
2016-12-01
Direct observations using scanning transmission electron microscopy unveil an intriguing interfacial bi-layer that enables epitaxial growth of a strain-free, monoclinic, bronze-phase VO2(B) thin film on a perovskite SrTiO3 (STO) substrate. We observe an ultrathin (2-3 unit cells) interlayer best described as highly strained VO2(B) nanodomains combined with an extra (Ti,V)O2 layer on the TiO2 terminated STO (001) surface. By forming a fully coherent interface with the STO substrate and a semi-coherent interface with the strain-free epitaxial VO2(B) film above, the interfacial bi-layer enables the epitaxial connection of the two materials despite their large symmetry and lattice mismatch.
Ab initio calculation of electron-phonon coupling in monoclinic β-Ga2O3 crystal
Ghosh, Krishnendu; Singisetti, Uttam
2016-08-01
The interaction between electrons and vibrational modes in monoclinic β-Ga2O3 is theoretically investigated using ab-initio calculations. The large primitive cell of β-Ga2O3 gives rise to 30 phonon modes all of which are taken into account in transport calculation. The electron-phonon interaction is calculated under density functional perturbation theory and then interpolated using Wannier-Fourier interpolation. The long-range interaction elements between electrons and polar optical phonon (POP) modes are calculated separately using the Born effective charge tensor. The direction dependence of the long-range POP coupling in a monoclinic crystal is explored and is included in the transport calculations. Scattering rate calculations are done using the Fermi golden rule followed by solving the Boltzmann transport equation using the Rode's method to estimate low field mobility. A room temperature mobility of 115 cm2/V s is observed. Comparison with recent experimentally reported mobility is done for a wide range of temperatures (30 K-650 K). It is also found that the POP interaction dominates the electron mobility under low electric field conditions. The relative contribution of the different POP modes is analyzed and the mode 21 meV POP is found to have the highest impact on low field electron mobility at room temperature.
Energy Technology Data Exchange (ETDEWEB)
Dong, Fengqiang; Wu, Qingsheng; Ma, Jie; Chen, Yijun [Department of Chemistry, Tongji University, Shanghai (China)
2009-01-15
The monoclinic scheelite BiVO{sub 4} nanocrystals were easily prepared via an oxide-hydrothermal synthesis (OHS) method directly utilizing bulk-phase materials of V{sub 2}O{sub 5} and Bi{sub 2}O{sub 3} as precursor. In the presence of PEG 4000, the reactions were performed in the mild temperature range from 130 C to 200 C. The products were characterized with FTIR, XRD, TEM and UV-vis DRS. These data clearly demonstrated that monoclinic scheelite structure BiVO{sub 4} could be synthesized by the feasible OHS route. The aspect ratios of nanorods were increased with the synthesized temperature. The as-prepared BiVO{sub 4} showed high photocatalytic activity, which was demonstrated by degradation of methylene blue (MB) solution under visible-light irradiation ({lambda}>420 nm). A growth mechanism of bismuth vanadate was proposed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Pseudospin symmetry as an accidental symmetry in the relativistic framework
Energy Technology Data Exchange (ETDEWEB)
Marcos, S.; Niembro, R. [Universidad de Cantabria, Departamento de Fisica Moderna, Santander (Spain); Lopez-Quelle, M. [Universidad de Cantabria, Departamento de Fisica Aplicada, Santander (Spain); Savushkin, L.N. [St. Petersburg University for Telecommunications, Department of Physics, St. Petersburg (Russian Federation)
2008-08-15
We analyse the arguments used in the relativistic context to base the quasi-degeneracy of pseudospin doublets (PSDs) observed in atomic nuclei on the smallness of the single-particle central potential ({sigma}{sub S}+{sigma}{sub 0}), discussing, especially, the implications of the results obtained in the limit {sigma}{sub S}+{sigma}{sub 0}=0. We study also the transition from a relativistic model, where {sigma}{sub S}+{sigma}{sub 0} is a harmonic-oscillator potential and exhibits degenerate PSDs, to a more realistic one with broken pseudospin symmetry. We examine, in particular, the effect of the corresponding pseudospin symmetry-breaking term on the Dirac spinors of the PSDs. An extension of the Nilsson model to the relativistic case is also considered. (orig.)
Notes on generalized global symmetries in QFT
Sharpe, E
2015-01-01
It was recently argued that quantum field theories possess one-form and higher-form symmetries, labelled `generalized global symmetries.' In this paper, we describe how those higher-form symmetries can be understood mathematically as special cases of more general 2-groups and higher groups, and discuss examples of quantum field theories admitting actions of more general higher groups than merely one-form and higher-form symmetries. We discuss analogues of topological defects for some of these higher symmetry groups, relating some of them to ordinary topological defects. We also discuss topological defects in cases in which the moduli `space' (technically, a stack) admits an action of a higher symmetry group. Finally, we outline a proposal for how certain anomalies might potentially be understood as describing a transmutation of an ordinary group symmetry of the classical theory into a 2-group or higher group symmetry of the quantum theory, which we link to WZW models and bosonization.
Inflation, Symmetry, and B-Modes
Hertzberg, Mark P
2014-01-01
We examine the role of using symmetry and effective field theory in inflationary model building. We describe the standard formulation of starting with an approximate shift symmetry for a scalar field, and then introducing corrections systematically in order to maintain control over the inflationary potential. We find that this leads to models in good agreement with recent data. On the other hand, there are attempts in the literature to deviate from this paradigm by envoking other symmetries and corrections. In particular: in a suite of recent papers, several authors have made the claim that standard Einstein gravity with a cosmological constant and a massless scalar carries conformal symmetry. They further claim that such a theory carries another hidden symmetry; a global SO(1,1) symmetry. By deforming around the global SO(1,1) symmetry, they are able to produce a range of inflationary models with asymptotically flat potentials, whose flatness is claimed to be protected by these symmetries. These models tend ...
Noether gauge symmetry approach in quintom cosmology
Aslam, Adnan; Momeni, Davood; Myrzakulov, Ratbay; Rashid, Muneer Ahmad; Raza, Muhammad
2013-01-01
In literature usual point like symmetries of the Lagrangian have been introduced to study the symmetries and the structure of the fields. This kind of Noether symmetry is a subclass of a more general family of symmetries, called Noether Gauge Symmetries (NGS). Motivated by this mathematical tool, in this article, we discuss the generalized Noether symmetry of Quintom model of dark energy, which is a two component fluid model of quintessence and phantom fields. Our model is a generalization of the Noether symmetries of a single and multiple components which have been investigated in detail before. We found the general form of the quintom potential in which the whole dynamical system has a point like symmetry. We investigated different possible solutions of the system for diverse family of gauge function. Specially, we discovered two family of potentials, one corresponds to a free quintessence (phantom) and the second is in the form of quadratic interaction between two components. These two families of potentia...
Approximate Flavor Symmetry in Supersymmetric Model
Tao, Zhijian
1998-01-01
We investigate the maximal approximate flavor symmetry in the framework of generic minimal supersymmetric standard model. We consider the low energy effective theory of the flavor physics with all the possible operators included. Spontaneous flavor symmetry breaking leads to the approximate flavor symmetry in Yukawa sector and the supersymmetry breaking sector. Fermion mass and mixing hierachies are the results of the hierachy of the flavor symmetry breaking. It is found that in this theory i...
Horizontal Symmetry: Bottom Up and Top Down
Lam, C S
2011-01-01
A group-theoretical connection between horizontal symmetry $\\G$ and fermion mixing is established, and applied to neutrino mixing. The group-theoretical approach is consistent with a dynamical theory based on $U(1)\\times \\G$, but the dynamical theory can be used to pick out the most stable mixing that purely group-theoretical considerations cannot. A symmetry common to leptons and quarks is also discussed. This higher symmetry picks $A_4$ over $S_4$ to be the preferred symmetry for leptons.
Partial Dynamical Symmetry in Nuclear Systems
Energy Technology Data Exchange (ETDEWEB)
Escher, J E
2003-06-02
Partial dynamical symmetry (PDS) extends and complements the concepts of exact and dynamical symmetry. It allows one to remove undesired constraints from an algebraic theory, while preserving some of the useful aspects of a dynamical symmetry, and to study the effects of symmetry breaking in a controlled manner. An example of a PDS in an interacting fermion system is presented. The associated PDS Hamiltonians are closely related with a realistic quadrupole-quadrupole interaction and provide new insights into this important interaction.
Symmetry reduction due to gallium substitution in the garnet Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12
Lars Robben; Elena Merzlyakova; Paul Heitjans; Gesing, Thorsten M.
2016-01-01
Single-crystal structure refinements on lithium lanthanum zirconate (LLZO; Li7La3Zr2O12) substituted with gallium were successfully carried out in the cubic symmetry space group I\\overline{4}3d. Gallium was found on two lithium sites as well as on the lanthanum position. Due to the structural distortion of the resulting Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12 (Ga–LLZO) single crystals, a reduction of the LLZO cubic garnet symmetry from Ia\\overline{3}d to I\\overline{4}3d was necessary, which could h...
Symmetry reduction due to gallium substitution in the garnet Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12
Robben, Lars; Merzlyakova, Elena; Heitjans, Paul; Gesing, Thorsten M.
2016-01-01
Single-crystal structure refinements on lithium lanthanum zirconate (LLZO; Li7La3Zr2O12) substituted with gallium were successfully carried out in the cubic symmetry space group I [Formula: see text]3d. Gallium was found on two lithium sites as well as on the lanthanum position. Due to the structural distortion of the resulting Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12 (Ga-LLZO) single crystals, a reduction of the LLZO cubic garnet symmetry from Ia[Formula: see text] d to I [Formula: see text]3d was ...
Symmetries in multi-Higgs-doublet models
Ivanov, I P
2012-01-01
We report the recent progress in understanding of symmetries which can be implemented in the scalar sector of electroweak symmetry breaking models with several Higgs doublets. In particular we present the list of finite reparametrization symmetry groups which can appear in the three-Higgs-doublet models.
Generalized Partial Dynamical Symmetry in Nuclei
Leviatan, A
2002-01-01
We introduce the notion of a generalized partial dynamical symmetry for which part of the eigenstates have part of the dynamical symmetry. This general concept is illustrated with the example of Hamiltonians with a partial dynamical O(6) symmetry in the framework of the interacting boson model. The resulting spectrum and electromagnetic transitions are compared with empirical data in $^{162}$Dy.
Generalized partial dynamical symmetry in nuclei.
Leviatan, A; Isacker, P Van
2002-11-25
We introduce the notion of a generalized partial dynamical-symmetry for which part of the eigenstates have part of the dynamical symmetry. This general concept is illustrated with the example of Hamiltonians with a partial dynamical O(6) symmetry in the framework of the interacting boson model. The resulting spectrum and electromagnetic transitions are compared with empirical data in 162Dy.
Partial Dynamical Symmetry in Deformed Nuclei
Energy Technology Data Exchange (ETDEWEB)
Leviatan, A. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
1996-07-01
We discuss the notion of partial dynamical symmetry in relation to nuclear spectroscopy. Explicit forms of Hamiltonians with partial SU(3) symmetry are presented in the framework of the interacting boson model of nuclei. An analysis of the resulting spectrum and electromagnetic transitions demonstrates the relevance of such partial symmetry to the spectroscopy of axially deformed nuclei. {copyright} {ital 1996 The American Physical Society.}
Partial dynamical symmetry in deformed nuclei
Leviatan, A
1996-01-01
We discuss the notion of partial dynamical symmetry in relation to nuclear spectroscopy. Explicit forms of Hamiltonians with partial SU(3) symmetry are presented in the framework of the interacting boson model of nuclei. An analysis of the resulting spectrum and electromagnetic transitions demonstrates the relevance of such partial symmetry to the spectroscopy of axially deformed nuclei.
Simultaneous occurrence of distinct symmetries in nuclei
Leviatan, A
2015-01-01
We show that distinct emergent symmetries, such as partial dynamical symmetry and quasi dynamical symmetry, can occur simultaneously in the same or different eigenstates of the Hamiltonian. Implications for nuclear spectroscopy in the rare-earth region and for first-order quantum phase transitions between spherical and deformed shapes, are considered.
General Formalism for the BRST Symmetry
Institute of Scientific and Technical Information of China (English)
Suhail Ahmad
2013-01-01
In this paper we will discuss Faddeev-Popov method for gauge theories with a general form of gauge symmetry in an abstract way.We will then develope a general formalism for dealing with the BRST symmetry.This formalism will make it possible to analyse the BRST symmetry for any theory.
Parameter Symmetry of the Interacting Boson Model
Shirokov, A M; Smirnov, Yu F; Shirokov, Andrey M.; Smirnov, Yu. F.
1998-01-01
We discuss the symmetry of the parameter space of the interacting boson model (IBM). It is shown that for any set of the IBM Hamiltonian parameters (with the only exception of the U(5) dynamical symmetry limit) one can always find another set that generates the equivalent spectrum. We discuss the origin of the symmetry and its relevance for physical applications.
Noether symmetries and duality transformations in cosmology
Paliathanasis, Andronikos; Capozziello, Salvatore
2016-09-01
We discuss the relation between Noether (point) symmetries and discrete symmetries for a class of minisuperspace cosmological models. We show that when a Noether symmetry exists for the gravitational Lagrangian, then there exists a coordinate system in which a reversal symmetry exists. Moreover, as far as concerns, the scale-factor duality symmetry of the dilaton field, we show that it is related to the existence of a Noether symmetry for the field equations, and the reversal symmetry in the normal coordinates of the symmetry vector becomes scale-factor duality symmetry in the original coordinates. In particular, the same point symmetry as also the same reversal symmetry exists for the Brans-Dicke scalar field with linear potential while now the discrete symmetry in the original coordinates of the system depends on the Brans-Dicke parameter and it is a scale-factor duality when ωBD = 1. Furthermore, in the context of the O’Hanlon theory for f(R)-gravity, it is possible to show how a duality transformation in the minisuperspace can be used to relate different gravitational models.
Symmetries of the dissipative Hofstadter model
Freed, D E
1993-01-01
The dissipative Hofstadter model, which describes a particle in 2-D subject to a periodic potential, uniform magnetic field, and dissipation, is also related to open string boundary states. This model exhibits an SL(2,Z) duality symmetry and hidden reparametrization invariance symmetries. These symmetries are useful for finding exact solutions for correlation functions.
Symmetry and electromagnetism. Simetria y electromagnetismo
Energy Technology Data Exchange (ETDEWEB)
Fuentes Cobas, L.E.; Font Hernandez, R.
1993-01-01
An analytical treatment of electrostatic and magnetostatic field symmetry, as a function of charge and current distribution symmetry, is proposed. The Newmann Principle, related to the cause-effect symmetry relation, is presented and applied to the characterization of simple configurations. (Author) 5 refs.
Symmetry Breaking for Black-Scholes Equations
Institute of Scientific and Technical Information of China (English)
YANG Xuan-Liu; ZHANG Shun-Li; QU Chang-Zheng
2007-01-01
Black-Scholes equation is used to model stock option pricing. In this paper, optimal systems with one to four parameters of Lie point symmetries for Black-Scholes equation and its extension are obtained. Their symmetry breaking interaction associated with the optimal systems is also studied. As a result, symmetry reductions and corresponding solutions for the resulting equations are obtained.
Neutrino mass, mixing and discrete symmetries
Smirnov, Alexei Y
2013-01-01
Status of the discrete symmetry approach to explanation of the lepton masses and mixing is summarized in view of recent experimental results, in particular, establishing relatively large 1-3 mixing. The lepton mixing can originate from breaking of discrete flavor symmetry $G_f$ to different residual symmetries $G_{\\ell}$ and $G_\
Prediction of human eye fixations using symmetry
Kootstra, Gert; Schomaker, Lambert
2009-01-01
Humans are very sensitive to symmetry in visual patterns. Reaction time experiments show that symmetry is detected and recognized very rapidly. This suggests that symmetry is a highly salient feature. Existing computational models of saliency, however, have mainly focused on contrast as a measure of
Exact Chiral Symmetry on the Lattice
Neuberger, H
2001-01-01
Developments during the last eight years have refuted the folklore that chiral symmetries cannot be preserved on the lattice. The mechanism that permits chiral symmetry to coexist with the lattice is quite general and may work in Nature as well. The reconciliation between chiral symmetry and the lattice is likely to revolutionize the field of numerical QCD.
Gravitating fluids with Lie symmetries
Msomi, A M; Maharaj, S D
2010-01-01
We analyse the underlying nonlinear partial differential equation which arises in the study of gravitating flat fluid plates of embedding class one. Our interest in this equation lies in discussing new solutions that can be found by means of Lie point symmetries. The method utilised reduces the partial differential equation to an ordinary differential equation according to the Lie symmetry admitted. We show that a class of solutions found previously can be characterised by a particular Lie generator. Several new families of solutions are found explicitly. In particular we find the relevant ordinary differential equation for all one-dimensional optimal subgroups; in several cases the ordinary differential equation can be solved in general. We are in a position to characterise particular solutions with a linear barotropic equation of state.
Critical Point Symmetries in Nuclei
Bonatsos, D; Petrellis, D; Terziev, P A; Yigitoglu, I; Bonatsos, Dennis
2006-01-01
Critical Point Symmetries (CPS) appear in regions of the nuclear chart where a rapid change from one symmetry to another is observed. The first CPSs, introduced by F. Iachello, were E(5), which corresponds to the transition from vibrational [U(5)] to gamma-unstable [O(6)] behaviour, and X(5), which represents the change from vibrational [U(5)] to prolate axially deformed [SU(3)] shapes. These CPSs have been obtained as special solutions of the Bohr collective Hamiltonian. More recent special solutions of the same Hamiltonian, to be described here, include Z(5) and Z(4), which correspond to maximally triaxial shapes (the latter with ``frozen'' gamma=30 degrees), as well as X(3), which corresponds to prolate shapes with ``frozen'' gamma=0. CPSs have the advantage of providing predictions which are parameter free (up to overall scale factors) and compare well to experiment. However, their mathematical structure [with the exception of E(5)] needs to be clarified.
CP symmetry in optical systems
Dana, Brenda; Malomed, Boris A
2015-01-01
We introduce a model of a dual-core optical waveguide with opposite signs of the group-velocity-dispersion (GVD) in the two cores, and a phase-velocity mismatch between them. The coupler is embedded into an active host medium, which provides for the linear coupling of a gain-loss type between the two cores. The same system can be derived, without phenomenological assumptions, by considering the three-wave propagation in a medium with the quadratic nonlinearity, provided that the depletion of the second-harmonic pump is negligible. This linear system offers an optical realization of the charge-parity ($\\mathcal{CP}$) symmetry, while the addition of the intra-core cubic nonlinearity breaks the symmetry. By means of direct simulations and analytical approximations, it is demonstrated that the linear system generates expanding Gaussian states, while the nonlinear one gives rise to broad oscillating solitons, as well as a general family of stable stationary gap solitons.
Superconformal Symmetry, NMSSM, and Inflation
Ferrara, Sergio; Linde, Andrei; Marrani, Alessio; Van Proeyen, Antoine
2011-01-01
We identify a particularly simple class of supergravity models describing superconformal coupling of matter to supergravity. In these models, which we call the canonical superconformal supergravity (CSS) models, the kinetic terms in the Jordan frame are canonical, and the scalar potential is the same as in the global theory. The pure supergravity part of the total action has a local Poincare supersymmetry, whereas the chiral and vector multiplets coupled to supergravity have a larger local superconformal symmetry. The scale-free globally supersymmetric theories, such as the NMSSM with a scale-invariant superpotential, can be naturally embedded into this class of theories. After the supergravity embedding, the Jordan frame scalar potential of such theories remains scale free; it is quartic, it contains no mass terms, no nonrenormalizable terms, no cosmological constant. The local superconformal symmetry can be broken by additional terms, which, in the small field limit, are suppressed by the gravitational coup...
Symmetry breaking around a wormhole
Choudhury, A. L.
1996-11-01
We have modified the extended version Coule and Maeda's version (D. H. Coule and Kei-ichi Maeda, Class.Quant.Grav.7,995(1990)) of the Gidding-Strominger model (S. B. Giddings and A. Strominger, Nucl.Phys. B307, 854(l988)) of the euclidean gravitational field interacting with axion. The new model has R-symmetry in contrast to the previous model. At the lowest perturbation case the model retains a wormhole solution. We assume that the scalar expands adiabatically and satisfies ideal gas law in a crude first approximation. Under the Higg's mechanism the symmetry can be broken at the tree approximation. This mechanism, we hope, can be used to introduce the degeneracy of quark masses.
Flavor Symmetries in Extra Dimensions
Aranda, A; Aranda, Alfredo
2002-01-01
We present a model of flavor based on a discrete local symmetry that reproduces all fermion masses and mixing angles both in the quark and lepton sectors. The particle content of the model is that of the standard model plus an additional flavon field. All the fields propagate in a fifth universal extra dimension and the flavor scale is associated with the cutoff of the 5D theory which is $\\sim 10$ TeV. The Yukawa matrices as well as the Majorana mass matrix for the neutrinos are generated by higher dimension operators involving the flavon field. When the flavon field acquires a vacuum expectation value it breaks the flavor symmetry and thus generates the Yukawa couplings. The model is consistent with the nearly bimaximal solution to the solar and atmospheric neutrino deficits.
Symmetry realization of texture zeros
Energy Technology Data Exchange (ETDEWEB)
Grimus, W. [Institut fuer Theoretische Physik, Universitaet Wien, Boltzmanngasse 5, 1090, Wien (Austria); Joshipura, A.S. [Physical Research Laboratory, 380009, Ahmedabad (India); Lavoura, L. [Centro de Fisica das Interaccoes Fundamentais, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, 1049-001, Lisboa (Portugal); Tanimoto, M. [Department of Physics, Niigata University, Ikarashi 2-8050, 950-2181, Niigata (Japan)
2004-08-01
We show that it is possible to enforce texture zeros in arbitrary entries of the fermion mass matrices by means of Abelian symmetries; in this way, many popular mass-matrix textures find a symmetry justification. We propose two alternative methods which allow one to place zeros in any number of elements of the mass matrices that one wants. They are applicable simultaneously in the quark and lepton sectors. They are also applicable in grand unified theories. The number of scalar fields required by our methods may be large; still, in many interesting cases this number can be reduced considerably. The larger the desired number of texture zeros is, the simpler are the models which reproduce the texture. (orig.)
Symmetry realization of texture zeros
Grimus, Walter; Lavoura, L; Tanimoto, M
2004-01-01
We show that it is possible to enforce texture zeros in arbitrary entries of the fermion mass matrices by means of Abelian symmetries; in this way, many popular mass-matrix textures find a symmetry justification. We propose two alternative methods which allow to place zeros in any number of elements of the mass matrices that one wants. They are applicable simultaneously in the quark and lepton sectors. They are also applicable in Grand Unified Theories. The number of scalar fields required by our methods may be large; still, in many interesting cases this number can be reduced considerably. The larger the desired number of texture zeros is, the simpler are the models which reproduce the texture.
Dark Matter and Global Symmetries
Mambrini, Yann; Queiroz, Farinaldo S
2015-01-01
General considerations in general relativity and quantum mechanics rule out global symmetries in the context of any consistent theory of quantum gravity. Motivated by this, we derive stringent and robust bounds from gamma-ray, X-ray, cosmic ray, neutrino and CMB data on models that invoke global symmetries to stabilize the dark matter particle. Under realistic assumptions we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (keV-TeV), including the WIMP regime. We then specialize our analysis and apply our bounds to specific models such as the Two-Higgs-Doublet, Left-Right, Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. In the supplemental material we derive robust, updated model-independent limits on the dark matter lifetime.
Lepton mixing and discrete symmetries
Hernandez, D.; Smirnov, A. Yu.
2012-09-01
The pattern of lepton mixing can emerge from breaking a flavor symmetry in different ways in the neutrino and charged lepton Yukawa sectors. In this framework, we derive the model-independent conditions imposed on the mixing matrix by the structure of discrete groups of the von Dyck type which include A4, S4, and A5. We show that, in general, these conditions lead to at least two equations for the mixing parameters (angles and CP phase δ). These constraints, which correspond to unbroken residual symmetries, are consistent with nonzero 13 mixing and deviations from maximal 2-3 mixing. For the simplest case, which leads to an S4 model and reproduces the allowed values of the mixing angles, we predict δ=(90°-120°).
Cosmological Reflection of Particle Symmetry
Maxim Khlopov
2016-01-01
The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetr...
Explaining quantum spontaneous symmetry breaking
Liu, Chuang; Emch, Gérard G.
Two accounts of quantum symmetry breaking (SSB) in the algebraic approach are compared: the representational and the decompositional account. The latter account is argued to be superior for understanding quantum SSB. Two exactly solvable models are given as applications of our account: the Weiss-Heisenberg model for ferromagnetism and the BCS model for superconductivity. Finally, the decompositional account is shown to be more conducive to the causal explanation of quantum SSB.
Symmetries in Lagrangian Field Theory
Búa, Lucia; Bucataru, Ioan; León, Manuel de; Salgado, Modesto; Vilariño, Silvia
2015-06-01
By generalising the cosymplectic setting for time-dependent Lagrangian mechanics, we propose a geometric framework for the Lagrangian formulation of classical field theories with a Lagrangian depending on the independent variables. For that purpose we consider the first-order jet bundles J1π of a fiber bundle π : E → ℝk where ℝk is the space of independent variables. Generalized symmetries of the Lagrangian are introduced and the corresponding Noether theorem is proved.
Symmetries of partial differential equations
Gaussier, Hervé; Merker, Joël
2004-01-01
We establish a link between the study of completely integrable systems of partial differential equations and the study of generic submanifolds in C^n. Using the recent developments of Cauchy-Riemann geometry we provide the set of symmetries of such a system with a Lie group structure. Finally we determine the precise upper bound of the dimension of this Lie group for some specific systems of partial differential equations.
Models of electroweak symmetry breaking
Pomarol, Alex
2015-01-01
This chapter present models of electroweak symmetry breaking arising from strongly interacting sectors, including both Higgsless models and mechanisms involving a composite Higgs. These scenarios have also been investigated in the framework of five-dimensional warped models that, according to the AdS/CFT correspondence, have a four-dimensional holographic interpretation in terms of strongly coupled field theories. We explore the implications of these models at the LHC.
Dirac neutrinos from flavor symmetry
Aranda, Alfredo; Morisi, S; Peinado, E; Valle, J W F
2013-01-01
We present a model where Majorana neutrino mass terms are forbidden by the flavor symmetry group Delta(27). Neutrinos are Dirac fermions and their masses arise in the same way as that of the charged fermions, due to very small Yukawa couplings. The model fits current neutrino oscillation data and correlates the octant of the atmospheric angle with the magnitude of the lightest neutrino mass, with maximal mixing excluded for any neutrino mass
Geometric symmetries in light nuclei
Bijker, Roelof
2016-01-01
The algebraic cluster model is is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in terms of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle for 12C, and a regular tetrahedron for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles.
Measuring Complexity through Average Symmetry
Alamino, Roberto C.
2015-01-01
This work introduces a complexity measure which addresses some conflicting issues between existing ones by using a new principle - measuring the average amount of symmetry broken by an object. It attributes low (although different) complexity to either deterministic or random homogeneous densities and higher complexity to the intermediate cases. This new measure is easily computable, breaks the coarse graining paradigm and can be straightforwardly generalised, including to continuous cases an...
Painlevé property, symmetries and symmetry reductions of the coupled Burgers system
Institute of Scientific and Technical Information of China (English)
Lian Zeng-Ju; Chen Li-Li; Lou Sen-Yue
2005-01-01
The Painlevé property, inverse recursion operator, infinite number of symmetries and Lie symmetry reductions of the coupled Burgers equation are given explicitly. Three sets of infinitely many symmetries of the considered model are obtained by acting the recursion operator and the inverse recursion operator on the trivial symmetries such as the identity transformation, the space translation and the scaling transformation respectively. These symmetries constitute an infinite dimensional Lie algebra while its finite dimensional Lie point symmetry subalgebra is used to find possible symmetry reductions and then the group invariant solutions.
Dark matter and global symmetries
Mambrini, Yann; Profumo, Stefano; Queiroz, Farinaldo S.
2016-09-01
General considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. Assuming the validity of such considerations, we derive stringent bounds from gamma-ray, X-ray, cosmic-ray, neutrino, and CMB data on models that invoke global symmetries to stabilize the dark matter particle. We compute up-to-date, robust model-independent limits on the dark matter lifetime for a variety of Planck-scale suppressed dimension-five effective operators. We then specialize our analysis and apply our bounds to specific models including the Two-Higgs-Doublet, Left-Right, Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. Assuming that (i) global symmetries are broken at the Planck scale, that (ii) the non-renormalizable operators mediating dark matter decay have O (1) couplings, that (iii) the dark matter is a singlet field, and that (iv) the dark matter density distribution is well described by a NFW profile, we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (keV-TeV), including the WIMP regime.
Assessing symmetry of financial returns series
Coronel-Brizio, H F; Rodriguez-Achach, M
2007-01-01
Testing symmetry of a probability distribution is a common question arising from applications in several fields. Particularly, in the study of observables used in the analysis of stock market index variations, the question of symmetry has not been fully investigated by means of statistical procedures. In this work a distribution-free test statistic Tn for testing symmetry, derived by Einmahl and McKeague, based on the empirical likelihood approach, is used to address the study of symmetry of financial returns. The asymptotic points of the test statistic Tn are also calculated and a procedure for assessing symmetry for the analysis of the returns of stock market indices is presented.
Automatic CP invariance and flavor symmetry
Dutta, G; Dutta, Gautam; Joshipura, Anjan S
1996-01-01
The approximate conservation of CP can be naturally understood if it arises as an automatic symmetry of the renormalizable Lagrangian. We present a specific realistic example with this feature. In this example, the global Peccei-Quinn symmetry and gauge symmetries of the model make the renormalizable Lagrangian CP invariant but allow non zero hierarchical masses and mixing among the three generations. The left-right and a horizontal U(1)_H symmetry is imposed to achieve this. The non-renormalizable interactions invariant under these symmetries violate CP whose magnitude can be in the experimentally required range if U(1)_H is broken at very high, typically, near the grand unification scale.
Neutrino masses and spontaneously broken flavor symmetries
Energy Technology Data Exchange (ETDEWEB)
Staudt, Christian
2014-06-16
We study the phenomenology of supersymmetric flavor models. We show how the predictions of models based on spontaneously broken non-Abelian discrete flavor symmetries are altered when we include so-called Kaehler corrections. Furthermore, we discuss anomaly-free discrete R symmetries which are compatible with SU(5) unification. We find a set of symmetries compatible with suppressed Dirac neutrino masses and a unique symmetry consistent with the Weinberg operator. We also study a pseudo-anomalous U(1){sub R} symmetry which explains the fermion mass hierarchies and, when amended with additional singlet fields, ameliorates the fine-tuning problem.
Symmetries, Integrals and Solutions of Ordinary Differential Equations of Maximal Symmetry
Indian Academy of Sciences (India)
P G L Leach; R R Warne; N Caister; V Naicker; N Euler
2010-02-01
Second-and third-order scalar ordinary differential equations of maximal symmetry in the traditional sense of point, respectively contact, symmetry are examined for the mappings they produce in solutions and fundamental first integrals. The properties of the `exceptional symmetries’, i.e. those not considered to be generic to scalar equations of maximal symmetry, can be recast into a form which is applicable to all such equations of maximal symmetry. Some properties of these symmetries are demonstrated.
Mei Symmetry and Noether Symmetry of the Relativistic Variable Mass System
Institute of Scientific and Technical Information of China (English)
FANG Jian-Hui
2004-01-01
The definition and criterion of the Mei symmetry of a relativistic variable mass system are given. The relation between the Mei symmetry and the Noether symmetry of the system is found under infinitesimal transformations of groups. The conserved quantities to which the Mei symmetry and Noether symmetry of the system lead are obtained.An example is given to illustrate the application of the result.
The Symmetry of Optical Field in Photonic Crystal Fibre with Trigonal Symmetry
Directory of Open Access Journals (Sweden)
Ivan Turek
2006-01-01
Full Text Available Some photographs of intensity of optical field of a photonic crystal fibre are presented in the contribution. Presented photographs document that the symmetry of photonic crystal creating the cladding of fibre is manifested in the symmetry of distribution of the optical field intensity. In case when more modes are excited in the fibre the symmetry of the generated field can be different as the symmetry of the eventual modes. How the symmetry may be changed is illustrated by amodel example.
Generalization of Friedberg-Lee symmetry
Huang, Chao-Shang; Li, Tianjun; Liao, Wei; Zhu, Shou-Hua
2008-07-01
We study the possible origin of Friedberg-Lee symmetry. First, we propose the generalized Friedberg-Lee symmetry in the potential by including the scalar fields in the field transformations, which can be broken down to the Friedberg-Lee symmetry spontaneously. We show that the generalized Friedberg-Lee symmetry allows a typical form of Yukawa couplings, and the realistic neutrino masses and mixings can be generated via the seesaw mechanism. If the right-handed neutrinos transform nontrivially under the generalized Friedberg-Lee symmetry, we can have the testable TeV scale seesaw mechanism. Second, we present two models with the SO(3)×U(1) global flavor symmetry in the lepton sector. After the flavor symmetry breaking, we can obtain the charged lepton masses, and explain the neutrino masses and mixings via the seesaw mechanism. Interestingly, the complete neutrino mass matrices are similar to those of the above models with generalized Friedberg-Lee symmetry. So the Friedberg-Lee symmetry is the residual symmetry in the neutrino mass matrix after the SO(3)×U(1) flavor symmetry breaking.
Brain Activity in Response to Visual Symmetry
Directory of Open Access Journals (Sweden)
Marco Bertamini
2014-12-01
Full Text Available A number of studies have explored visual symmetry processing by measuring event related potentials and neural oscillatory activity. There is a sustained posterior negativity (SPN related to the presence of symmetry. There is also functional magnetic resonance imaging (MRI activity in extrastriate visual areas and in the lateral occipital complex. We summarise the evidence by answering six questions. (1 Is there an automatic and sustained response to symmetry in visual areas? Answer: Yes, and this suggests automatic processing of symmetry. (2 Which brain areas are involved in symmetry perception? Answer: There is an extended network from extrastriate areas to higher areas. (3 Is reflection special? Answer: Reflection is the optimal stimulus for a more general regularity-sensitive network. (4 Is the response to symmetry independent of view angle? Answer: When people classify patterns as symmetrical or random, the response to symmetry is view-invariant. When people attend to other dimensions, the network responds to residual regularity in the image. (5 How are brain rhythms in the two hemispheres altered during symmetry perception? Answer: Symmetry processing (rather than presence produces more alpha desynchronization in the right posterior regions. Finally, (6 does symmetry processing produce positive affect? Answer: Not in the strongest sense, but behavioural measures reveal implicit positive evaluation of abstract symmetry.
Axial symmetry and conformal Killing vectors
Mars, M; Mars, Marc; Senovilla, Jose M.M.
1993-01-01
Axisymmetric spacetimes with a conformal symmetry are studied and it is shown that, if there is no further conformal symmetry, the axial Killing vector and the conformal Killing vector must commute. As a direct consequence, in conformally stationary and axisymmetric spacetimes, no restriction is made by assuming that the axial symmetry and the conformal timelike symmetry commute. Furthermore, we prove that in axisymmetric spacetimes with another symmetry (such as stationary and axisymmetric or cylindrically symmetric spacetimes) and a conformal symmetry, the commutator of the axial Killing vector with the two others mush vanish or else the symmetry is larger than that originally considered. The results are completely general and do not depend on Einstein's equations or any particular matter content.
Symmetries of Ginsparg-Wilson Chiral Fermions
Mandula, Jeffrey E
2009-01-01
The group structure of the variant chiral symmetry discovered by Luscher in the Ginsparg-Wilson description of lattice chiral fermions is analyzed. It is shown that the group contains an infinite number of linearly independent symmetry generators, and the Lie algebra is given explicitly. CP is an automorphism of this extended chiral group, and the CP transformation properties of the symmetry generators are found. The group has an infinite-parameter subgroup, and the factor group whose elements are its cosets is isomorphic to the continuum chiral symmetry group. Features of the currents associated with these symmetries are discussed, including the fact that some different, non-commuting symmetry generators lead to the same Noether current. These are universal features of lattice chiral fermions based on the Ginsparg-Wilson relation; they occur in the overlap, domain-wall, and perfect-action formulations. In a solvable example - free overlap fermions - these non-canonical elements of lattice chiral symmetry are...
Symmetries of Massive and Massless Neutrinos
Kim, Y S
2016-01-01
Wigner's little groups are subgroups of the Lorentz group dictating the internal space-time symmetries of massive and massless particles. These little groups are like O(3) and E(2) for massive and massless particles respectively. While the geometry of the O(3) symmetry is familiar to us, the geometry of the flat plane cannot explain the E(2)-like symmetry for massless particles. However, the geometry of a circular cylinder can explain the symmetry with the helicity and gauge degrees of freedom. It is shown further that the symmetry of the massless particle can be obtained as a zero-mass limit of O(3)-like symmetry for massive particles. It is shown further that the polarization of massless neutrinos is a consequence of gauge invariance, while the symmetry of massive neutrinos is still like O(3).
Faddeev-Jackiw approach to hidden symmetries
Wotzasek, C
1994-01-01
The study of hidden symmetries within Dirac's formalism does not possess a systematic procedure due to the lack of first-class constraints to act as symmetry generators. On the other hand, in the Faddeev-Jackiw approach, gauge and reparametrization symmetries are generated by the null eigenvectors of the sympletic matrix and not by constraints, suggesting the possibility of dealing systematically with hidden symmetries through this formalism. It is shown in this paper that indeed hidden symmetries of noninvariant or gauge fixed systems are equally well described by null eigenvectors of the sympletic matrix, just as the explicit invariances. The Faddeev-Jackiw approach therefore provide a systematic algorithm for treating all sorts of symmetries in an unified way. This technique is illustrated here by the SL(2,R) Kac-Moody current algebra of the 2-D induced gravity proposed by Polyakov, which is a hidden symmetry in the canonical approach of constrained systems via Dirac's method, after conformal and reparamet...
Symmetry constraints on many-body localization
Potter, Andrew C.; Vasseur, Romain
2016-12-01
We derive general constraints on the existence of many-body localized (MBL) phases in the presence of global symmetries, and show that MBL is not possible with symmetry groups that protect multiplets (e.g., all non-Abelian symmetry groups). Based on simple representation theoretic considerations, we derive general Mermin-Wagner-type principles governing the possible alternative fates of nonequilibrium dynamics in isolated, strongly disordered quantum systems. Our results rule out the existence of MBL symmetry-protected topological phases with non-Abelian symmetry groups, as well as time-reversal symmetry-protected electronic topological insulators, and in fact all fermion topological insulators and superconductors in the 10-fold way classification. Moreover, extending our arguments to systems with intrinsic topological order, we rule out MBL phases with non-Abelian anyons as well as certain classes of symmetry-enriched topological orders.
Maharjan, N. B.; Paudyal, D. D.; Mishra, D. R.; Byahut, S.; Aryal, M. M.; Cho, Hwa-Suck; Scheicher, R. H.; Chow, Lee; Jeong, Junho; Das, T. P.
2006-03-01
The electron structures of Selenium chains and rings with Te impurities in hexagonal and monoclinic structures respectively and Se impurities in Te chains in hexagonal lattice have been studied using Hartree-Fock cluster model including many-body effects, including lattice relaxation effects. The calculated electronic wave-functions are utilized to obtain ^77Se and ^125Te nuclear quadrupole coupling constants e^2qQ and asymmetry parameters η and compared with available experimental data from Mossbauer and perturbed angular correlation measurements. From our results, the expected nature of nuclear quadrupole interactions associated with Sb impurities will be discussed. *Supported by NSF US-Nepal Program and UGC Nepal **Also at UCF, Orlando
Cao, Ziyi; Xiao, Xiudi; Lu, Xuanming; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang
2016-12-01
In this approach, the VO2 nanoparticles have been successfully fabricated via combusting the low-cost precursor solution consisted of NH4VO3, C2H6O2 and C2H5OH. By the XRD, TEM and XPS analysis, it can be found that the synthetic monoclinic VO2 is single crystal and no impurity is defined. After dispersing the VO2 nanoparticles into the polymer, the solar modulation of VO2-based composite film is up to 12.5% with luminous transmission and haze around 62.2% and 0.5%, respectively. In other words, the composite films show high performance of thermochromic properties. This could open an efficient way to fabricate low-cost and large-scale VO2 (M) nanoparticles and thermochromic films.
Börzsönyi, Tamás; Akamatsu, Silvère; Faivre, Gabriel
2009-11-01
We present an experimental study of thin-sample directional solidification (T-DS) in impure biphenyl. The platelike growth shape of the monoclinic biphenyl crystals includes two low-mobility (001) facets and four high-mobility {110} facets. Upon T-DS, biphenyl plates oriented with (001) facets parallel to the sample plane can exhibit either a strong growth-induced plastic deformation (GID), or deformation-free weakly faceted (WF) growth patterns. We determine the respective conditions of appearance of these phenomena. GID is shown to be a long-range thermal-stress effect, which disappears when the growth front has a cellular structure. An early triggering of the cellular instability allowed us to avoid GID and study the dynamics of WF patterns as a function of the orientation of the crystal.
Energy Technology Data Exchange (ETDEWEB)
Kisi, E.H. [Univ. of Newcastle, Callaghan, New South Wales (Australia). Dept. of Mechanical Engineering; Kennedy, S.J.; Howard, C.J. [Australian Nuclear Science and Technology Organisation, Menai, New South Wales (Australia). Neutron Scattering Group
1997-03-01
In-situ neutron diffraction has been used to study the plastic deformation of a tetragonal zirconia polycrystal stabilized with 12 mol% ceria under compressive loads up to 1.6 GPa. The development of significant plastic strain in the ceramic has been found to be due to a combination of ferroelastic switching and the tetragonal-to-monoclinic phase transformation, both beginning at {approximately}1.2 GPa. Evidence of a strong coupling between the two phenomena is present. Both transitions are partially reversed on removal of the load. The linear elastic response of the a and c crystal axes of the parent tetragonal phase suggests that the ferroelastic switching occurs directly by a shear mechanism rather than via a cubic intermediate state. Anisotropic distortion of the tetragonal unit cell, as the critical stress is approached, gives some insight into the shear transformation mechanisms.
Monoclinic β-Li2TiO3: Neutron diffraction study and estimation of Li diffusion pathways
Monchak, M.; Dolotko, O.; Mühlbauer, M. J.; Baran, V.; Senyshyn, A.; Ehrenberg, H.
2016-11-01
A neutron powder diffraction study on lithium titanate Li2TiO3 was performed at low temperatures. The monoclinic β-phase has been found to be stable over the whole investigated range of temperatures (4 K-300 K). A smooth and nonlinear increase of the lattice parameters has been observed upon heating and correlated to the behavior of interatomic distances. Lithium diffusion pathways in Li2TiO3 were estimated theoretically on the basis of the obtained structural data using bond-valence modeling. Experimentally diffusion pathways were evaluated by analysis of the negative nuclear scattering densities at 1073 K, which were reconstructed using a maximum entropy method. Although the bond-valence mismatch map indicated a possible Li diffusion either in ab plane or along c direction, analysis of the experimental data revealed that Li migration is thermodynamically less feasible in latter case.
Daramola, Damilola A; Muthuvel, Madhivanan; Botte, Gerardine G
2010-07-29
Geometry and vibration properties for monoclinic zirconium oxide were studied using Gaussian basis sets and LDA, GGA, and B3LYP functionals. Bond angles, bond lengths, lattice parameters, and Raman frequencies were calculated and compared to experimental values. Bond angles and lengths were found to agree within experimental standard deviations. The B3LYP gave the best performance of all three functionals with a percent error of 1.35% for the lattice parameters while the average difference between experimental and calculated Raman frequency values was -3 cm(-1). The B3LYP functional was then used to assign the atomic vibrations causing each frequency mode using isotopic substitution of (93.40)Zr for (91.22)Zr and (18.00)O for (16.00)O. This resulted in seven modes assigned to the Zr atom, ten modes to the O atom, and one mode being a mixture of both.
Generalization of Friedberg-Lee Symmetry
Huang, Chao-Shang; Liao, Wei; Zhu, Shou-Hua
2008-01-01
We study the possible origin of Friedberg-Lee symmetry. First, we propose the generalized Friedberg-Lee symmetry in the potential by including the scalar fields in the field transformations, which can be broken down to the FL symmetry spontaneously. We show that the generalized Friedberg-Lee symmetry allows a typical form of Yukawa couplings, and the realistic neutrino masses and mixings can be generated via see-saw mechanism. If the right-handed neutrinos transform non-trivially under the generalized Friedberg-Lee symmetry, we can have the testable TeV scale see-saw mechanism. Second, we present two models with the $SO(3)\\times U(1)$ global flavour symmetry in the lepton sector. After the flavour symmetry breaking, we can obtain the charged lepton masses, and explain the neutrino masses and mixings via see-saw mechanism. Interestingly, the complete neutrino mass matrices are similar to those of the above models with generalized Friedberg-Lee symmetry. So the Friedberg-Lee symmetry is the residual symmetry in...
Relativistic RPA in axial symmetry
Arteaga, D Pena; 10.1103/PhysRevC.77.034317
2009-01-01
Covariant density functional theory, in the framework of self-consistent Relativistic Mean Field (RMF) and Relativistic Random Phase approximation (RPA), is for the first time applied to axially deformed nuclei. The fully self-consistent RMF+RRPA equations are posed for the case of axial symmetry and non-linear energy functionals, and solved with the help of a new parallel code. Formal properties of RPA theory are studied and special care is taken in order to validate the proper decoupling of spurious modes and their influence on the physical response. Sample applications to the magnetic and electric dipole transitions in $^{20}$Ne are presented and analyzed.
Symmetry in the Basic Sciences
1989-04-01
that a nonprimitive, or centered, cell is obtained. In the triclinic system no symmetry restrictions occur, so a primitive cell can always be chosen. In...point (1/2, 1/2, 0) is a lattice point, and the unit cell defined by (1, 0, 0), (0, 1, 0), and (0, 0, 1) is not primitive. A primitive cell may be...in a primitive cell . The C centered unit cell has two lattice points in a plane shared by one other cell, in addition to the eight points at the
Geometric Baryogenesis from Shift Symmetry.
De Simone, Andrea; Kobayashi, Takeshi; Liberati, Stefano
2017-03-31
We present a new scenario for generating the baryon asymmetry of the Universe that is induced by a Nambu-Goldstone (NG) boson. The shift symmetry naturally controls the operators in the theory while allowing the NG boson to couple to the spacetime geometry as well as to the baryons. The cosmological background thus sources a coherent motion of the NG boson, which leads to baryogenesis. Good candidates of the baryon-generating NG boson are the QCD axion and axionlike fields. In these cases, the axion induces baryogenesis in the early Universe and can also serve as dark matter in the late Universe.
Symmetry properties of subdivision graphs
Daneshkhah, Ashraf; Devillers, Alice; Praeger, Cheryl E.
2010-01-01
The subdivision graph $S(\\Sigma)$ of a graph $\\Sigma$ is obtained from $\\Sigma$ by `adding a vertex' in the middle of every edge of $\\Si$. Various symmetry properties of $\\S(\\Sigma)$ are studied. We prove that, for a connected graph $\\Sigma$, $S(\\Sigma)$ is locally $s$-arc transitive if and only if $\\Sigma$ is $\\lceil\\frac{s+1}{2}\\rceil$-arc transitive. The diameter of $S(\\Sigma)$ is $2d+\\delta$, where $\\Sigma$ has diameter $d$ and $0\\leqslant \\delta\\leqslant 2$, and local $s$-distance transi...
Crossing symmetry in Alpha space
CERN. Geneva
2017-01-01
The conformal bootstrap program aims to catalog all conformal field theories (second-order phase transitions) in D dimensions. Despite its ambitious scope much progress has been made over the past decade, e.g. in computing critical exponents for the 3D O(N) models to high precision. At this stage, analytic methods to explore the CFT landscape are not as well developed. In this talk I will describe a new mathematical framework for the bootstrap known as "alpha space", which reduces crossing symmetry to a set of integral equations. Based on arXiv:1702.08471 (with Balt van Rees) and arXiv:1703.08159.
Killing Symmetry on Finsler Manifold
Ootsuka, Takayoshi; Ishida, Muneyuki
2016-01-01
Killing vector fields $K$ are defined on Finsler manifold. The Killing symmetry is reformulated simply as $\\delta K^\\flat =0$ by using the Killing non-linear 1-form $K^\\flat$ and the spray operator $\\delta$ with the Finsler non-linear connection. $K^\\flat$ is related to the generalization of Killing tensors on Finsler manifold, and the condition $\\delta K^\\flat =0$ gives an analytical method of finding higher derivative conserved quantities, which may be called hidden conserved quantities. We show two examples: the Carter constant on Kerr spacetime and the Runge-Lentz vectors in Newtonian gravity.
Hidden symmetries in jammed systems
Morse, Peter K.; Corwin, Eric I.
2016-07-01
There are deep, but hidden, geometric structures within jammed systems, associated with hidden symmetries. These can be revealed by repeated transformations under which these structures lead to fixed points. These geometric structures can be found in the Voronoi tesselation of space defined by the packing. In this paper we examine two iterative processes: maximum inscribed sphere (MIS) inversion and a real-space coarsening scheme. Under repeated iterations of the MIS inversion process we find invariant systems in which every particle is equal to the maximum inscribed sphere within its Voronoi cell. Using a real-space coarsening scheme we reveal behavior in geometric order parameters which is length-scale invariant.
History of electroweak symmetry breaking
Kibble, T W B
2015-01-01
In this talk, I recall the history of the development of the unified electroweak theory, incorporating the symmetry-breaking Higgs mechanism, as I saw it from my standpoint as a member of Abdus Salam's group at Imperial College. I start by describing the state of physics in the years after the Second World War, explain how the goal of a unified gauge theory of weak and electromagnetic interactions emerged, the obstacles encountered, in particular the Goldstone theorem, and how they were overcome, followed by a brief account of more recent history, culminating in the historic discovery of the Higgs boson in 2012.
Zhu, D.-W.; Han, Q.; Qiu, W.; Campbell, R. L.; Xie, B.-X.; Azzi, A.; Lin, S.-X.
1999-01-01
Human estrogenic 17β-hydroxysteroid dehydrogenase (17β-HSD1) is responsible for the synthesis of active estrogens that stimulate the proliferation of breast cancer cells. The enzyme has been crystallized using a Mg 2+/PEG (3500)/β-octyl glucoside system [Zhu et al., J. Mol. Biol. 234 (1993) 242]. The space group of these crystals is C2. Here we report that cations can affect 17β-HSD1 crystallization significantly. In the presence of Mn 2+ instead of Mg 2+, crystals have been obtained in the same space group with similar unit cell dimensions. In the presence of Li + and Na + instead of Mg 2+, the space group has been changed to P2 12 12 1. A whole data set for a crystal of 17ß-HSD1 complex with progesterone grown in the presence of Li + has been collected to 1.95 Å resolution with a synchrotron source. The cell dimensions are a=41.91 Å, b=108.21 Å, c=117.00 Å. The structure has been preliminarily determined by molecular replacement, yielding important information on crystal packing in the presence of different cations. In order to further understand the structure-function relationship of 17β-HSD1, enzyme complexes with several ligands have been crystallized. As the steroids have very low aqueous solubility, we used a combined method of seeding and co-crystallization to obtain crystals of 17β-HSD1 complexed with various ligands. This method provides ideal conditions for growing complex crystals, with ligands such as 20α-hydroxysteroid progesterone, testosterone and 17β-methyl-estradiol-NADP +. Several complex structures have been determined with reliable electronic density of the bound ligands.
Directory of Open Access Journals (Sweden)
Julian Heeck
2014-12-01
Full Text Available The difference between baryon number B and lepton number L is the only anomaly-free global symmetry of the Standard Model, easily promoted to a local symmetry by introducing three right-handed neutrinos, which automatically make neutrinos massive. The non-observation of any (B–L-violating processes leads us to scrutinize the case of unbroken gauged B–L; besides Dirac neutrinos, the model contains only three parameters, the gauge coupling strength g′, the Stückelberg mass MZ′, and the kinetic mixing angle χ. The new force could manifest itself at any scale, and we collect and derive bounds on g′ over the entire testable range MZ′=0–1013 eV, also of interest for the more popular case of spontaneously broken B–L or other new light forces. We show in particular that successful Big Bang nucleosynthesis provides strong bounds for masses 10 eV
Heeck, Julian
2014-01-01
The difference between baryon number B and lepton number L is the only anomaly-free global symmetry of the Standard Model, easily promoted to a local symmetry by introducing three right-handed neutrinos, which automatically make neutrinos massive. The non-observation of any (B-L)-violating processes leads us to scrutinize the case of unbroken gauged B-L; besides Dirac neutrinos, the model contains only three parameters, the gauge coupling strength g', the Stueckelberg mass $M_{Z'}$, and the kinetic mixing angle $\\chi$. The new force could manifest itself at any scale, and we collect and derive bounds on g' over the entire testable range $M_{Z'}$ = 0 - $10^{13}$ eV, also of interest for the more popular case of spontaneously broken B-L or other new light forces. We show in particular that successful Big Bang nucleosynthesis provides strong bounds for masses 10 eV < $M_{Z'}$ < 10 GeV due to resonant enhancement of the rate $\\overline{f} f \\leftrightarrow \\overline{\
Introduction to Electroweak Symmetry Breaking
Energy Technology Data Exchange (ETDEWEB)
Dawson,S.
2008-10-02
The Standard Model (SM) is the backbone of elementary particle physics-not only does it provide a consistent framework for studying the interactions of quark and leptons, but it also gives predictions which have been extensively tested experimentally. In these notes, I review the electroweak sector of the Standard Model, discuss the calculation of electroweak radiative corrections to observables, and summarize the status of SM Higgs boson searches. Despite the impressive experimental successes, however, the electroweak theory is not completely satisfactory and the mechanism of electroweak symmetry breaking is untested. I will discuss the logic behind the oft-repeated statement: 'There must be new physics at the TeV scale'. These lectures reflect my strongly held belief that upcoming results from the LHC will fundamentally change our understanding of electroweak symmetry breaking. In these lectures, I review the status of the electroweak sector of the Standard Model, with an emphasis on the importance of radiative corrections and searches for the Standard Model Higgs boson. A discussion of the special role of the TeV energy scale in electroweak physics is included.
Chiral symmetry breaking and monopoles
Di Giacomo, Adriano; Pucci, Fabrizio
2015-01-01
To understand the relation between the chiral symmetry breaking and monopoles, the chiral condensate which is the order parameter of the chiral symmetry breaking is calculated in the $\\overline{\\mbox{MS}}$ scheme at 2 [GeV]. First, we add one pair of monopoles, varying the monopole charges $m_{c}$ from zero to four, to SU(3) quenched configurations by a monopole creation operator. The low-lying eigenvalues of the Overlap Dirac operator are computed from the gauge links of the normal configurations and the configurations with additional monopoles. Next, we compare the distributions of the nearest-neighbor spacing of the low-lying eigenvalues with the prediction of the random matrix theory. The low-lying eigenvalues not depending on the scale parameter $\\Sigma$ are compared to the prediction of the random matrix theory. The results show the consistency with the random matrix theory. Thus, the additional monopoles do not affect the low-lying eigenvalues. Moreover, we discover that the additional monopoles increa...
Extreme lattices: symmetries and decorrelation
Andreanov, A.; Scardicchio, A.; Torquato, S.
2016-11-01
We study statistical and structural properties of extreme lattices, which are the local minima in the density landscape of lattice sphere packings in d-dimensional Euclidean space {{{R}}d} . Specifically, we ascertain statistics of the densities and kissing numbers as well as the numbers of distinct symmetries of the packings for dimensions 8 through 13 using the stochastic Voronoi algorithm. The extreme lattices in a fixed dimension of space d (d≥slant 8 ) are dominated by typical lattices that have similar packing properties, such as packing densities and kissing numbers, while the best and the worst packers are in the long tails of the distribution of the extreme lattices. We also study the validity of the recently proposed decorrelation principle, which has important implications for sphere packings in general. The degree to which extreme-lattice packings decorrelate as well as how decorrelation is related to the packing density and symmetry of the lattices as the space dimension increases is also investigated. We find that the extreme lattices decorrelate with increasing dimension, while the least symmetric lattices decorrelate faster.
Optical properties of GaAs 2D Archimedean photonic lattice tiling with the p4g symmetry
Directory of Open Access Journals (Sweden)
Jovanović Đ.
2008-01-01
Full Text Available In this paper we present our investigation of 2D Archimedean lattice photonic crystals with p4g space group symmetry. The structures are made of GaAs both as air holes and dielectric rods in air. In order to analyze the photonic crystal optical properties we performed calculations of the band structures, equi-frequency contours and electromagnetic propagation through the basic structures and waveguides. In addition, we investigated negative refraction and left-handedness in the p4g photonic crystal.
Symmetry energy of dilute warm nuclear matter.
Natowitz, J B; Röpke, G; Typel, S; Blaschke, D; Bonasera, A; Hagel, K; Klähn, T; Kowalski, S; Qin, L; Shlomo, S; Wada, R; Wolter, H H
2010-05-21
The symmetry energy of nuclear matter is a fundamental ingredient in the investigation of exotic nuclei, heavy-ion collisions, and astrophysical phenomena. New data from heavy-ion collisions can be used to extract the free symmetry energy and the internal symmetry energy at subsaturation densities and temperatures below 10 MeV. Conventional theoretical calculations of the symmetry energy based on mean-field approaches fail to give the correct low-temperature, low-density limit that is governed by correlations, in particular, by the appearance of bound states. A recently developed quantum-statistical approach that takes the formation of clusters into account predicts symmetry energies that are in very good agreement with the experimental data. A consistent description of the symmetry energy is given that joins the correct low-density limit with quasiparticle approaches valid near the saturation density.
Local discrete symmetries from superstring derived models
Energy Technology Data Exchange (ETDEWEB)
Faraggi, A.E.
1996-10-01
Discrete and global symmetries play an essential role in many extensions of the Standard Model, for example, to preserve the proton lifetime, to prevent flavor changing neutral currents, etc. An important question is how can such symmetries survive in a theory of quantum gravity, like superstring theory. In a specific string model the author illustrates how local discrete symmetries may arise in string models and play an important role in preventing fast proton decay and flavor changing neutral currents. The local discrete symmetry arises due to the breaking of the non-Abelian gauge symmetries by Wilson lines in the superstring models and forbids, for example dimension five operators which mediate rapid proton decay, to all orders of nonrenormalizable terms. In the context of models of unification of the gauge and gravitational interactions, it is precisely this type of local discrete symmetries that must be found in order to insure that a given model is not in conflict with experimental observations.
Dynamics-dependent symmetries in Newtonian mechanics
Holland, Peter
2014-01-01
We exhibit two symmetries of one-dimensional Newtonian mechanics whereby a solution is built from the history of another solution via a generally nonlinear and complex potential-dependent transformation of the time. One symmetry intertwines the square roots of the kinetic and potential energies and connects solutions of the same dynamical problem (the potential is an invariant function). The other symmetry connects solutions of different dynamical problems (the potential is a scalar function). The existence of corresponding conserved quantities is examined using Noethers theorem and it is shown that the invariant-potential symmetry is correlated with energy conservation. In the Hamilton-Jacobi picture the invariant-potential transformation provides an example of a field-dependent symmetry in point mechanics. It is shown that this transformation is not a symmetry of the Schroedinger equation.
Dynamical symmetries of the Kepler problem
Cariglia, Marco
2013-01-01
This work originates from a first year undergraduate research project on hidden symmetries of the dynamics for classical Hamiltonian systems, under the program 'Jovens talentos para a Ciencia' of Brazilian funding agency Capes. For pedagogical reasons the main subject chosen was Kepler's problem of motion under a central potential, since it is a completely solved system. It is well known that for this problem the group of dynamical symmetries is strictly larger than the isometry group O(3), the extra symmetries corresponding to hidden symmetries of the dynamics. By taking the point of view of examining the group action of the dynamical symmetries on the allowed trajectories, it is possible to teach in the same project basic elements of as many important subjects in physics as: Hamiltonian formalism, hidden symmetries, integrable systems, group theory, and the use of manifolds.
Local discrete symmetries from superstring derived models
Faraggi, Alon E.
1997-02-01
Discrete and global symmetries play an essential role in many extensions of the Standard Model, for example, to preserve the proton lifetime, to prevent flavor changing neutral currents, etc. An important question is how can such symmetries survive in a theory of quantum gravity, like superstring theory. In a specific string model I illustrate how local discrete symmetries may arise in string models and play an important role in preventing fast proton decay and flavor changing neutral currents. The local discrete symmetry arises due to the breaking of the non-Abelian gauge symmetries by Wilson lines in the superstring models and forbids, for example dimension five operators which mediate rapid proton decay, to all orders of nonrenormalizable terms. In the context of models of unification of the gauge and gravitational interactions, it is precisely this type of local discrete symmetries that must be found in order to insure that a given model is not in conflict with experimental observations.
Local discrete symmetries from superstring derived models
Faraggi, A E
1996-01-01
Discrete and global symmetries play an essential role in many extensions of the Standard Model, for example, to preserve the proton lifetime, to prevent flavor changing neutral currents, etc. An important question is how can such symmetries survive in a theory of quantum gravity, like superstring theory. In a specific string model I illustrate how local discrete symmetries may arise in string models and play an important role in preventing fast proton decay and flavor changing neutral currents. The local discrete symmetry arises due to the breaking of the non--Abelian gauge symmetries by Wilson lines in the superstring models and forbids, for example dimension five operators which mediate rapid proton decay, to all orders of nonrenormalizable terms. In the context of models of unification of the gauge and gravitational interactions, it is precisely this type of local discrete symmetries that must be found in order to insure that a given model is not in conflict with experimental observations.
Comments on the dual-BRST symmetry
Krishna, S; Malik, R P
2011-01-01
In view of a raging controversy on the topic of dual-Becchi-Rouet-Stora-Tyutin (dual-BRST/co-BRST) and anti-co-BRST symmetry transformations in the context of four (3+1)-dimensional (4D) Abelian 2-form and 2D (non-)Abelian 1-form gauge theories, we attempt, in our present short note, to settle the dust by taking the help of mathematics of differential geometry, connected with the Hodge theory, which was the original motivation for the nomenclature of dual-BRST symmetry in our earlier set of works. It has been claimed, in a recent set of papers, that the co-BRST symmetries are not independent of BRST symmetries. We show that the BRST and co-BRST symmetries are independent symmetries in the same fashion as the exterior and co-exterior derivatives are independent entities belonging to the set of de Rham cohomological operators of differential geometry.
On the origin of neutrino flavour symmetry
King, Stephen F
2009-01-01
We study classes of models which are based on some discrete family symmetry which is completely broken such that the observed neutrino flavour symmetry emerges indirectly as an accidental symmetry. For such "indirect" models we discuss the D-term flavon vacuum alignments which are required for such an accidental flavour symmetry consistent with tri-bimaximal lepton mixing to emerge. We identify large classes of suitable discrete family symmetries, namely the $\\Delta(3n^2)$ and $\\Delta(6n^2)$ groups, together with other examples such as $Z_7\\rtimes Z_3$. In such indirect models the implementation of the type I see-saw mechanism is straightforward using constrained sequential dominance. However the accidental neutrino flavour symmetry may be easily violated, for example leading to a large reactor angle, while maintaining accurately the tri-bimaximal solar and atmospheric predictions.
Beyond bilateral symmetry: geometric morphometric methods for any type of symmetry
Directory of Open Access Journals (Sweden)
Klingenberg Christian
2011-09-01
Full Text Available Abstract Background Studies of symmetric structures have made important contributions to evolutionary biology, for example, by using fluctuating asymmetry as a measure of developmental instability or for investigating the mechanisms of morphological integration. Most analyses of symmetry and asymmetry have focused on organisms or parts with bilateral symmetry. This is not the only type of symmetry in biological shapes, however, because a multitude of other types of symmetry exists in plants and animals. For instance, some organisms have two axes of reflection symmetry (biradial symmetry; e.g. many algae, corals and flowers or rotational symmetry (e.g. sea urchins and many flowers. So far, there is no general method for the shape analysis of these types of symmetry. Results We generalize the morphometric methods currently used for the shape analysis of bilaterally symmetric objects so that they can be used for analyzing any type of symmetry. Our framework uses a mathematical definition of symmetry based on the theory of symmetry groups. This approach can be used to divide shape variation into a component of symmetric variation among individuals and one or more components of asymmetry. We illustrate this approach with data from a colonial coral that has ambiguous symmetry and thus can be analyzed in multiple ways. Our results demonstrate that asymmetric variation predominates in this dataset and that its amount depends on the type of symmetry considered in the analysis. Conclusions The framework for analyzing symmetry and asymmetry is suitable for studying structures with any type of symmetry in two or three dimensions. Studies of complex symmetries are promising for many contexts in evolutionary biology, such as fluctuating asymmetry, because these structures can potentially provide more information than structures with bilateral symmetry.
Dynamical Flavor Origin of ZN Symmetries
Aristizabal Sierra, Diego; Vicente, Avelino; Fong, Sheng; Dhen, Mikael
2015-01-01
Discrete Abelian symmetries (ZN) are a common “artifact” of beyond the standard model physics models. They provide different avenues for constructing consistent scenarios for lepton and quark mixing patterns, radiative neutrino mass generation as well as dark matter stabilization. We argue that these symmetries can arise from the spontaneous breaking of the Abelian U(1) factors contained in the global flavor symmetry transformations of the gauge-invariant kinetic Lagrangian. This will be the ...
The near-symmetry of proteins.
Bonjack-Shterengartz, Maayan; Avnir, David
2015-04-01
The majority of protein oligomers form clusters which are nearly symmetric. Understanding of that imperfection, its origins, and perhaps also its advantages requires the conversion of the currently used vague qualitative descriptive language of the near-symmetry into an accurate quantitative measure that will allow to answer questions such as: "What is the degree of symmetry deviation of the protein?," "how do these deviations compare within a family of proteins?," and so on. We developed quantitative methods to answer this type of questions, which are capable of analyzing the whole protein, its backbone or selected portions of it, down to comparison of symmetry-related specific amino-acids, and which are capable of visualizing the various levels of symmetry deviations in the form of symmetry maps. We have applied these methods on an extensive list of homomers and heteromers and found that apparently all proteins never reach perfect symmetry. Strikingly, even homomeric protein clusters are never ideally symmetric. We also found that the main burden of symmetry distortion is on the amino-acids near the symmetry axis; that it is mainly the more hydrophilic amino-acids that take place in symmetry-distortive interactions; and more. The remarkable ability of heteromers to preserve near-symmetry, despite the different sequences, was also shown and analyzed. The comprehensive literature on the suggested advantages symmetric oligomerizations raises a yet-unsolved key question: If symmetry is so advantageous, why do proteins stop shy of perfect symmetry? Some tentative answers to be tested in further studies are suggested in a concluding outlook. © 2014 Wiley Periodicals, Inc.
Anomalous Mirror Symmetry Generated by Optical Illusion
Directory of Open Access Journals (Sweden)
Kokichi Sugihara
2016-04-01
Full Text Available This paper introduces a new concept of mirror symmetry, called “anomalous mirror symmetry”, which is physically impossible but can be perceived by human vision systems because of optical illusion. This symmetry is characterized geometrically and a method for creating cylindrical surfaces that create this symmetry is constructed. Examples of solid objects constructed by a 3D printer are also shown.
Dark matter reflection of particle symmetry
Khlopov, Maxim Yu.
2017-05-01
In the context of the relationship between physics of cosmological dark matter and symmetry of elementary particles, a wide list of dark matter candidates is possible. New symmetries provide stability of different new particles and their combination can lead to a multicomponent dark matter. The pattern of symmetry breaking involves phase transitions in the very early Universe, extending the list of candidates by topological defects and even primordial nonlinear structures.
Parameter counting in models with global symmetries
Energy Technology Data Exchange (ETDEWEB)
Berger, Joshua [Institute for High Energy Phenomenology, Newman Laboratory of Elementary Particle Physics, Cornell University, Ithaca, NY 14853 (United States)], E-mail: jb454@cornell.edu; Grossman, Yuval [Institute for High Energy Phenomenology, Newman Laboratory of Elementary Particle Physics, Cornell University, Ithaca, NY 14853 (United States)], E-mail: yuvalg@lepp.cornell.edu
2009-05-18
We present rules for determining the number of physical parameters in models with exact flavor symmetries. In such models the total number of parameters (physical and unphysical) needed to described a matrix is less than in a model without the symmetries. Several toy examples are studied in order to demonstrate the rules. The use of global symmetries in studying the minimally supersymmetric standard model (MSSM) is examined.
Inverse semigroups the theory of partial symmetries
Lawson, Mark V
1998-01-01
Symmetry is one of the most important organising principles in the natural sciences. The mathematical theory of symmetry has long been associated with group theory, but it is a basic premise of this book that there are aspects of symmetry which are more faithfully represented by a generalization of groups called inverse semigroups. The theory of inverse semigroups is described from its origins in the foundations of differential geometry through to its most recent applications in combinatorial group theory, and the theory tilings.
Master Symmetry for Holographic Wilson Loops
Klose, Thomas; Munkler, Hagen
2016-01-01
We identify the symmetry underlying the recently observed spectral-parameter transformations of holographic Wilson loops alias minimal surfaces in AdS/CFT. The generator of this nonlocal symmetry is shown to furnish a raising operator on the classical Yangian-type charges of symmetric coset models. We explicitly demonstrate how this master symmetry acts on strong-coupling Wilson loops and indicate a possible extension to arbitrary coupling.
Unified symmetry of Vacco dynamical systems
Institute of Scientific and Technical Information of China (English)
Li Yuan-Cheng; Jing Hong-Xing; Xia Li-Li; Wang Jing; Hou Qi-Bao
2007-01-01
Based on the total time derivative along the trajectory of the time, we study the unified symmetry of Vacco dynamical systems. The definition and the criterion of the unified symmetry for the system are given. Three kinds of conserved quantities, i.e. the Noether conserved quantity, the generalized Hojman conserved quantity and the Mei conserved quantity, are deduced from the unified symmetry. An example is presented to illustrate the results.
The pseudospin symmetry in atomic nuclei
Energy Technology Data Exchange (ETDEWEB)
Marcos, S [Departamento de Fisica Moderna, Universidad de Cantabria, E-39005 Santander (Spain); Lopez-Quelle, M [Departamento de Fisica Aplicada, Universidad de Cantabria, E-39005 Santander (Spain); Niembro, R [Departamento de Fisica Moderna, Universidad de Cantabria, E-39005 Santander (Spain); Savushkin, L N [Department of Physics, St Petersburg University for Telecommunications, 191186 St Petersburg (Russian Federation)
2005-10-01
The grounds on which the nuclear pseudospin symmetry (PSS) is supposed to be based are analysed within the relativistic mean-field framework. A comparative analysis of the mechanisms responsible for the breaking of the spin and pseudospin symmetries, which clarifies the different nature of these symmetries, is made. A non-relativistic explanation of the PSS, based on the effect of the spin-orbit interaction, is also sketched.
Energy Technology Data Exchange (ETDEWEB)
Fuh, Huei-Ru; Chang, Ching-Ray [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan (China); Weng, Ke-Chuan [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Wang, Yin-Kuo, E-mail: kant@ntnu.edu.tw [Center for General Education and Department of Physics, National Taiwan Normal University, Taipei 106, Taiwan (China)
2015-05-07
Double perovskite La{sub 2}FeCoO{sub 6} with monoclinic structure and rhombohedra structure show as ferromagnetic semiconductor based on density functional theory calculation. The ferromagnetic semiconductor state can be well explained by the superexchange interaction. Moreover, the ferromagnetic semiconductor state remains under the generalized gradient approximation (GGA) and GGA plus onsite Coulomb interaction calculation.
Sevvana, Madhumati; Hasselt, Kristin; Grau, Florian C; Burkovski, Andreas; Muller, Yves A
2017-03-01
AmtR belongs to the TetR family of transcription regulators and is a global nitrogen regulator that is induced under nitrogen-starvation conditions in Corynebacterium glutamicum. AmtR regulates the expression of transporters and enzymes for the assimilation of ammonium and alternative nitrogen sources, for example urea, amino acids etc. The recognition of operator DNA by homodimeric AmtR is not regulated by small-molecule effectors as in other TetR-family members but by a trimeric adenylylated PII-type signal transduction protein named GlnK. The crystal structure of ligand-free AmtR (AmtRorth) has been solved at a resolution of 2.1 Å in space group P21212. Comparison of its quaternary assembly with the previously solved native AmtR structure (PDB entry 5dy1) in a trigonal crystal system (AmtRtri) not only shows how a solvent-content reduction triggers a space-group switch but also suggests a model for how dimeric AmtR might stoichiometrically interact with trimeric adenylylated GlnK.
Partial Dynamical Symmetry and Mixed Dynamics
Leviatan, A
1996-01-01
Partial dynamical symmetry describes a situation in which some eigenstates have a symmetry which the quantum Hamiltonian does not share. This property is shown to have a classical analogue in which some tori in phase space are associated with a symmetry which the classical Hamiltonian does not share. A local analysis in the vicinity of these special tori reveals a neighbourhood of phase space foliated by tori. This clarifies the suppression of classical chaos associated with partial dynamical symmetry. The results are used to divide the states of a mixed system into ``chaotic'' and ``regular'' classes.
Fake Conformal Symmetry in Unimodular Gravity
Oda, Ichiro
2016-01-01
We study Weyl symmetry (local conformal symmetry) in unimodular gravity. It is shown that the Noether currents for both Weyl symmetry and global scale symmetry, identically vanish as in the conformally invariant scalar-tensor gravity. We clearly explain why in the class of conformally invariant gravitational theories, the Noether currents vanish by starting with the conformally invariant scalar-tensor gravity. Moreover, we comment on both classical and quantum-mechanical equivalences among Einstein's general relativity, the conformally invariant scalar-tensor gravity and the Weyl-transverse (WTDiff) gravity. Finally, we discuss the Weyl current in the conformally invariant scalar action and see that it is also vanishing.
Fake conformal symmetry in unimodular gravity
Oda, Ichiro
2016-08-01
We study Weyl symmetry (local conformal symmetry) in unimodular gravity. It is shown that the Noether currents for both Weyl symmetry and global scale symmetry vanish exactly as in conformally invariant scalar-tensor gravity. We clearly explain why in the class of conformally invariant gravitational theories, the Noether currents vanish by starting with conformally invariant scalar-tensor gravity. Moreover, we comment on both classical and quantum-mechanical equivalences in Einstein's general relativity, conformally invariant scalar-tensor gravity, and the Weyl-transverse gravity. Finally, we discuss the Weyl current in the conformally invariant scalar action and see that it is also vanishing.
Non-Crystallographic Symmetry in Packing Spaces
Directory of Open Access Journals (Sweden)
Valery G. Rau
2013-01-01
Full Text Available In the following, isomorphism of an arbitrary finite group of symmetry, non-crystallographic symmetry (quaternion groups, Pauli matrices groups, and other abstract subgroups, in addition to the permutation group, are considered. Application of finite groups of permutations to the packing space determines space tilings by policubes (polyominoes and forms a structure. Such an approach establishes the computer design of abstract groups of symmetry. Every finite discrete model of the real structure is an element of symmetry groups, including non-crystallographic ones. The set packing spaces of the same order N characterizes discrete deformation transformations of the structure.
Symmetries in Images on Ancient Seals
Sparavigna, Amelia
2008-01-01
In this paper, we discuss the presence of symmetries in images engraved on ancient seals, in particular on stamp seals. Mainly used to secure the containers from tampering and for owner's identification, these objects appeared during the 5th millennium BC in Mesopotamia. Usually the seals were engraved with simple images, suitable to communicate an immediate information. Rotational symmetries are already displayed by the most ancient stamp seals, whose images reach a quasi-perfect symmetry in their small circular or ovoid spaces. Bilateral symmetries are quite common in Egyptian scarab seals.
PREFACE: Symmetries in Science XV
Schuch, Dieter; Ramek, Michael
2012-08-01
Logo Bregenz, the peaceful monastery of Mehrerau and the Opera on the Floating Stage again provided the setting for the international symposium 'Symmetries in Science'. The series which has been running for more than 30 years brings together leading theoreticians whose area of research is, in one way or another, related to symmetry. Since 1992 the meeting took place biannually in Brengez until 2003. In 2009, with the endorsement of the founder, Professor Bruno Gruber, we succeeded in re-establishing the series without external funding. The resounding success of that meeting encouraged us to continue in 2011 and, following on the enthusiasm and positive feedback of the participants, we expect to continue in 2013. Yet again, our meeting in 2011 was very international in flavour and brought together some 30 participants representing 12 nationalities, half of them from countries outside the European Union (from New Zealand to Mexico, Russia to Israel). The broad spectrum, a mixture of experienced experts and highly-motivated newcomers, the intensive exchange of ideas in a harmonious and relaxed atmosphere and the resulting joint projects are probably the secrets of why this meeting is considered to be so special to its participants. At the resumption in 2009 some leading experts and younger scientists from economically weak countries were unable to attend due to the lack of financial resources. This time, with the very worthy and unbureaucratic support of the 'Vereinigung von Freunden und Förderern der J W Goethe-Universität Frankfurt am Main' (in short: 'Friends and Supporters of the Frankfurt University'), it was possible for all candidates to participate. In particular some young, inspired scientists had the chance of presenting their work to a very competent, but also friendly, audience. We wish to thank the 'Freunde und Förderer' for supporting Symmetries in Science XV. Almost all participants contributed to the publication of this Conference Proceedings. There
Electroweak symmetry breaking via QCD.
Kubo, Jisuke; Lim, Kher Sham; Lindner, Manfred
2014-08-29
We propose a new mechanism to generate the electroweak scale within the framework of QCD, which is extended to include conformally invariant scalar degrees of freedom belonging to a larger irreducible representation of SU(3)c. The electroweak symmetry breaking is triggered dynamically via the Higgs portal by the condensation of the colored scalar field around 1 TeV. The mass of the colored boson is restricted to be 350 GeV≲mS≲3 TeV, with the upper bound obtained from perturbative renormalization group evolution. This implies that the colored boson can be produced at the LHC. If the colored boson is electrically charged, the branching fraction of the Higgs boson decaying into two photons can slightly increase, and moreover, it can be produced at future linear colliders. Our idea of nonperturbative electroweak scale generation can serve as a new starting point for more realistic model building in solving the hierarchy problem.
Pitts, T
1998-01-01
This theory makes time symmetric by Weyl's definition; it hypothesizes that space, time and mass-energy expand outward from the Big Bang along the time axis equally in the (+-) and (-) directions. In the Feynman-Stueckelberg Interpretation, antimatter is identical to matter but moves backward in time. This essay argues that this interpretation is physically real via an analysis of the time-symmetry of the Schrodinger equation. As time expands from zero, in both directions in time away from the origin, quantum uncertainty allows a brief, decreasing leakage of mass between (+-) and (-) universes. Matter leaking from (-) to (+-) time moves forward in time, producing a preponderance of matter in (+-) time. Antimatter leakage from (+-) time to (-) time in the same way produces an antimatter preponderance in the (-) time universe. The remaining opposite particles left behind after the leakage, (antimatter and matter respectively) proceeding outward in antitime and time respectively, after many annihilations also in...
Supergravity backgrounds and symmetry superalgebras
Ertem, Ümit
2016-01-01
We consider the bosonic sectors of supergravity theories in ten and eleven dimensions which correspond to the low energy limits of string theories and M-theory. The solutions of supergravity field equations are known as supergravity backgrounds and the number of preserved supersymmetries in those backgrounds are determined by Killing spinors. We provide some examples of supergravity backgrounds which preserve different fractions of supersymmetry. An important invariant for the characterization of supergravity backgrounds is their Killing superalgebras which are constructed out of Killing vectors and Killing spinors of the background. After constructing Killing superalgebras of some special supergravity backgrounds, we discuss about the possibilities of the extensions of these superalgebras to include the higher degree hidden symmetries of the background.
Quantum measurements with prescribed symmetry
Bruzda, Wojciech; Goyeneche, Dardo; Życzkowski, Karol
2017-08-01
We introduce a method to determine whether a given generalized quantum measurement is isolated or if it belongs to a family of measurements having the same prescribed symmetry. The technique proposed reduces to solving a linear system of equations in some relevant cases. As a consequence, we provide a simple derivation of the maximal family of symmetric informationally complete positive operator-valued measure SIC-POVM in dimension 3. Furthermore, we show that the following remarkable geometrical structures are isolated, so that free parameters cannot be introduced: (a) maximal sets of mutually unbiased bases in prime power dimensions from 4 to 16, (b) SIC-POVM in dimensions from 4 to 16, and (c) contextual Kochen-Specker sets in dimension 3, 4, and 6, composed of 13, 18, and 21 vectors, respectively.
Coning, symmetry and spherical frameworks
Schulze, Bernd
2011-01-01
In this paper, we combine separate works on (a) the transfer of infinitesimal rigidity results from an Euclidean space to the next higher dimension by coning, (b) the further transfer of these results to spherical space via associated rigidity matrices, and (c) the prediction of finite motions from symmetric infinitesimal motions at regular points of the symmetry-derived orbit rigidity matrix. Each of these techniques is reworked and simplified to apply across several metrics, including the Minkowskian metric $\\M^{d}$ and the hyperbolic metric $\\H^{d}$. This leads to a set of new results transferring infinitesimal and finite motions associated with corresponding symmetric frameworks among $\\E^{d}$, cones in $E^{d+1}$, $\\SS^{d}$, $\\M^{d}$, and $\\H^{d}$. We also consider the further extensions associated with the other Cayley-Klein geometries overlaid on the shared underlying projective geometry.
Dileptons and Chiral Symmetry Restoration
Hohler, P M
2015-01-01
We report on recent work relating the medium effects observed in dilepton spectra in heavy-ion collisions to potential signals of chiral symmetry restoration. The key connection remains the approach to spectral function degeneracy between the vector-isovector channel with its chiral partner, the axialvector-isovector channel. Several approaches are discussed to elaborate this connection, namely QCD and Weinberg sum rules with input for chiral order parameters from lattice QCD, and chiral hadronic theory to directly evaluate the medium effects of the axialvector channel and the pertinent pion decay constant as function of temperature. A pattern emerges where the chiral mass splitting between rho and a_1 burns off and is accompanied by a strong broadening of the spectral distributions.
Spectral Theory and Mirror Symmetry
Marino, Marcos
2015-01-01
Recent developments in string theory have revealed a surprising connection between spectral theory and local mirror symmetry: it has been found that the quantization of mirror curves to toric Calabi-Yau threefolds leads to trace class operators, whose spectral properties are conjecturally encoded in the enumerative geometry of the Calabi-Yau. This leads to a new, infinite family of solvable spectral problems: the Fredholm determinants of these operators can be found explicitly in terms of Gromov-Witten invariants and their refinements; their spectrum is encoded in exact quantization conditions, and turns out to be determined by the vanishing of a quantum theta function. Conversely, the spectral theory of these operators provides a non-perturbative definition of topological string theory on toric Calabi-Yau threefolds. In particular, their integral kernels lead to matrix integral representations of the topological string partition function, which explain some number-theoretic properties of the periods. In this...
Renormalizable theories with symmetry breaking
Becchi, Carlo M
2016-01-01
The description of symmetry breaking proposed by K. Symanzik within the framework of renormalizable theories is generalized from the geometrical point of view. For an arbitrary compact Lie group, a soft breaking of arbitrary covariance, and an arbitrary field multiplet, the expected integrated Ward identities are shown to hold to all orders of renormalized perturbation theory provided the Lagrangian is suitably chosen. The corresponding local Ward identity which provides the Lagrangian version of current algebra through the coupling to an external, classical, Yang-Mills field, is then proved to hold up to the classical Adler-Bardeen anomaly whose general form is written down. The BPHZ renormalization scheme is used throughout in such a way that the algebraic structure analyzed in the present context may serve as an introduction to the study of fully quantized gauge theories.
Inflation, symmetry, and B-modes
Directory of Open Access Journals (Sweden)
Mark P. Hertzberg
2015-05-01
Full Text Available We examine the role of using symmetry and effective field theory in inflationary model building. We describe the standard formulation of starting with an approximate shift symmetry for a scalar field, and then introducing corrections systematically in order to maintain control over the inflationary potential. We find that this leads to models in good agreement with recent data. On the other hand, there are attempts in the literature to deviate from this paradigm by envoking other symmetries and corrections. In particular: in a suite of recent papers, several authors have made the claim that standard Einstein gravity with a cosmological constant and a massless scalar carries conformal symmetry. They claim this conformal symmetry is hidden when the action is written in the Einstein frame, and so has not been fully appreciated in the literature. They further claim that such a theory carries another hidden symmetry; a global SO(1,1 symmetry. By deforming around the global SO(1,1 symmetry, they are able to produce a range of inflationary models with asymptotically flat potentials, whose flatness is claimed to be protected by these symmetries. These models tend to give rise to B-modes with small amplitude. Here we explain that standard Einstein gravity does not in fact possess conformal symmetry. Instead these authors are merely introducing a redundancy into the description, not an actual conformal symmetry. Furthermore, we explain that the only real (global symmetry in these models is not at all hidden, but is completely manifest when expressed in the Einstein frame; it is in fact the shift symmetry of a scalar field. When analyzed systematically as an effective field theory, deformations do not generally produce asymptotically flat potentials and small B-modes as suggested in these recent papers. Instead, deforming around the shift symmetry systematically, tends to produce models of inflation with B-modes of appreciable amplitude. Such simple models
Nonlocalization of Nonlocal Symmetry and Symmetry Reductions of the Burgers Equation
Institute of Scientific and Technical Information of China (English)
金艳; 贾曼; 楼森岳
2012-01-01
Symmetry reduction method is one of the best ways to find exact solutions. In this paper, we study the possibility of symmetry reductions of the well known Burgers equation including the nonlocal symmetry. The related new group Jnvariant solutions are obtained. Especially, the interactions among solitons, Airy waves, and Kummer waves are explicitly given.
Flavor symmetries and fermion masses
Energy Technology Data Exchange (ETDEWEB)
Rasin, A.
1994-04-01
We introduce several ways in which approximate flavor symmetries act on fermions and which are consistent with observed fermion masses and mixings. Flavor changing interactions mediated by new scalars appear as a consequence of approximate flavor symmetries. We discuss the experimental limits on masses of the new scalars, and show that the masses can easily be of the order of weak scale. Some implications for neutrino physics are also discussed. Such flavor changing interactions would easily erase any primordial baryon asymmetry. We show that this situation can be saved by simply adding a new charged particle with its own asymmetry. The neutrality of the Universe, together with sphaleron processes, then ensures a survival of baryon asymmetry. Several topics on flavor structure of the supersymmetric grand unified theories are discussed. First, we show that the successful predictions for the Kobayashi-Maskawa mixing matrix elements, V{sub ub}/V{sub cb} = {radical}m{sub u}/m{sub c} and V{sub td}/V{sub ts} = {radical}m{sub d}/m{sub s}, are a consequence of a large class of models, rather than specific properties of a few models. Second, we discuss how the recent observation of the decay {beta} {yields} s{gamma} constrains the parameter space when the ratio of the vacuum expectation values of the two Higgs doublets, tan{Beta}, is large. Finally, we discuss the flavor structure of proton decay. We observe a surprising enhancement of the branching ratio for the muon mode in SO(10) models compared to the same mode in the SU(5) model.
Directory of Open Access Journals (Sweden)
METODIJA NAJDOSKI
2000-07-01
Full Text Available Fourier-transform infrared (FT-IR reflection spectra, asquired at nearnormal incidence, were recorded from single crystals belonging to six crystal systems: CsCr(SO42.12H2O (alum, cubic, K2CuCl2·2H2O (Mitscherlichite, tetragonal, CaCO3 (calcite, hexagonal, KHSO4 (mercallite, orthorhombic, CaSO4·2H2O (gypsum, monoclinic and CuSO4·5H2O (chalcantite, triclinic. The acquired IR reflection spectra were further transformed into absorption spectra, employing the Kramers-Kronig transformation. Except for the cubic alums, the spectra strongly depend on the crystal face from which they were recorded; this is a consequence of anisotropy. Phonons of a given symmetry (E-species, in tetragonal/hexagonal and B-species, in monoclinic crystals may be resolved without using a polariser. The spectrum may be simplified in the case of an orthorhombic crystal, as well. The longitudinal-optical (LO and transversal-optical (TO mode frequencies were calculated in the case of optically isotropic and the simplified spectra of optically uniaxial crystals.
Notes on generalized global symmetries in QFT
Energy Technology Data Exchange (ETDEWEB)
Sharpe, Eric [Department of Physics MC 0435, 850 West Campus Drive, Virginia Tech, Blacksburg, VA (United States)
2015-11-15
It was recently argued that quantum field theories possess one-form and higher-form symmetries, labelled 'generalized global symmetries.' In this paper, we describe how those higher-form symmetries can be understood mathematically as special cases of more general 2-groups and higher groups, and discuss examples of quantum field theories admitting actions of more general higher groups than merely one-form and higher-form symmetries. We discuss analogues of topological defects for some of these higher symmetry groups, relating some of them to ordinary topological defects. We also discuss topological defects in cases in which the moduli 'space' (technically, a stack) admits an action of a higher symmetry group. Finally, we outline a proposal for how certain anomalies might potentially be understood as describing a transmutation of an ordinary group symmetry of the classical theory into a 2-group or higher group symmetry of the quantum theory, which we link to WZW models and bosonization. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Hidden flavor symmetries of SO(10) GUT
Bajc, Borut
2016-01-01
The Yukawa interactions of the SO(10) GUT with fermions in 16-plets (as well as with singlets) have certain intrinsic ("built-in") symmetries which do not depend on the model parameters. Thus, the symmetric Yukawa interactions of the 10 and 126 dimensional Higgses have intrinsic discrete $Z_2\\times Z_2$ symmetries, while the antisymmetric Yukawa interactions of the 120 dimensional Higgs have a continuous SU(2) symmetry. The couplings of SO(10) singlet fermions with fermionic 16-plets have $U(1)^3$ symmetry. We consider a possibility that some elements of these intrinsic symmetries are the residual symmetries, which originate from the (spontaneous) breaking of a larger symmetry group $G_f$. Such an embedding leads to the determination of certain elements of the relative mixing matrix $U$ between the matrices of Yukawa couplings $Y_{10}$, $Y_{126}$, $Y_{120}$, and consequently, to restrictions of masses and mixings of quarks and leptons. We explore the consequences of such embedding using the symmetry group con...
Nuclear symmetry energy: An experimental overview
Indian Academy of Sciences (India)
D V Shetty; S J Yennello
2010-08-01
The nuclear symmetry energy is a fundamental quantity important for studying the structure of systems as diverse as the atomic nucleus and the neutron star. Considerable efforts are being made to experimentally extract the symmetry energy and its dependence on nuclear density and temperature. In this article, the experimental studies carried out up-to-date and their current status are reviewed.
Charge-symmetry-breaking nucleon form factors
Kubis, Bastian
2009-01-01
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for Helium-4.
Symmetry in critical random Boolean network dynamics
Hossein, Shabnam; Reichl, Matthew D.; Bassler, Kevin E.
2014-04-01
Using Boolean networks as prototypical examples, the role of symmetry in the dynamics of heterogeneous complex systems is explored. We show that symmetry of the dynamics, especially in critical states, is a controlling feature that can be used both to greatly simplify analysis and to characterize different types of dynamics. Symmetry in Boolean networks is found by determining the frequency at which the various Boolean output functions occur. There are classes of functions that consist of Boolean functions that behave similarly. These classes are orbits of the controlling symmetry group. We find that the symmetry that controls the critical random Boolean networks is expressed through the frequency by which output functions are utilized by nodes that remain active on dynamical attractors. This symmetry preserves canalization, a form of network robustness. We compare it to a different symmetry known to control the dynamics of an evolutionary process that allows Boolean networks to organize into a critical state. Our results demonstrate the usefulness and power of using the symmetry of the behavior of the nodes to characterize complex network dynamics, and introduce an alternative approach to the analysis of heterogeneous complex systems.
Symmetry in Critical Random Boolean Networks Dynamics
Bassler, Kevin E.; Hossein, Shabnam
2014-03-01
Using Boolean networks as prototypical examples, the role of symmetry in the dynamics of heterogeneous complex systems is explored. We show that symmetry of the dynamics, especially in critical states, is a controlling feature that can be used to both greatly simplify analysis and to characterize different types of dynamics. Symmetry in Boolean networks is found by determining the frequency at which the various Boolean output functions occur. Classes of functions occur at the same frequency. These classes are orbits of the controlling symmetry group. We find the nature of the symmetry that controls the dynamics of critical random Boolean networks by determining the frequency of output functions utilized by nodes that remain active on dynamical attractors. This symmetry preserves canalization, a form of network robustness. We compare it to a different symmetry known to control the dynamics of an evolutionary process that allows Boolean networks to organize into a critical state. Our results demonstrate the usefulness and power of using symmetry to characterize complex network dynamics, and introduce a novel approach to the analysis of heterogeneous complex systems. This work was supported by the NSF through grants DMR-0908286 and DMR-1206839, and by the AFSOR and DARPA through grant FA9550-12-1-0405.
On multipartite invariant states III. Rotational symmetry
Chruscinski, D; Chruscinski, Dariusz; Kossakowski, Andrzej
2006-01-01
We construct a class of multipartite states possessing rotational SO(3) symmetry -- these are states of K spin-j_A particles and K spin-j_B particles. The construction of symmetric states follows our two recent papers devoted to unitary and orthogonal multipartite symmetry. We study basic properties of multipartite SO(3) symmetric states: separability criteria and multi-PPT conditions.
On multipartite invariant states II. Orthogonal symmetry
Chruściński, Dariusz; Kossakowski, Andrzej
2006-01-01
We construct a new class of multipartite states possessing orthogonal symmetry. This new class defines a convex hull of multipartite states which are invariant under the action of local unitary operations introduced in our previous paper "On multipartite invariant states I. Unitary symmetry". We study basic properties of multipartite symmetric states: separability criteria and multi-PPT conditions.
Partial dynamical symmetry in a fermion system
Escher; Leviatan
2000-02-28
The relevance of the partial dynamical symmetry concept for an interacting fermion system is demonstrated. Hamiltonians with partial SU(3) symmetry are presented in the framework of the symplectic shell model of nuclei and shown to be closely related to the quadrupole-quadrupole interaction. Implications are discussed for the deformed light nucleus 20Ne.
Partial dynamical symmetry in a fermion system
Escher, J; Escher, Jutta; Leviatan, Amiram
2000-01-01
The relevance of the partial dynamical symmetry concept for an interactingfermion system is demonstrated. Hamiltonians with partial SU(3) symmetry arepresented in the framework of the symplectic shell-model of nuclei and shown tobe closely related to the quadrupole-quadrupole interaction. Implications arediscussed for the deformed light nucleus $^{20}$Ne.
On multipartite invariant states II. Orthogonal symmetry
Chruscinski, D; Chruscinski, Dariusz; Kossakowski, Andrzej
2006-01-01
We construct a new class of multipartite states possessing orthogonal symmetry. This new class defines a convex hull of multipartite states which are invariant under the action of local unitary operations introduced in our previous paper "On multipartite invariant states I. Unitary symmetry". We study basic properties of multipartite symmetric states: separability criteria and multi-PPT conditions.
Dynamical gauge symmetry breaking on the lattice
Energy Technology Data Exchange (ETDEWEB)
Farakos, K.; Koutsoumbas, G.; Zoupanos, G. (National Research Centre for the Physical Sciences Democritos, Athens (Greece))
1990-10-11
We study, using lattice techniques, the dynamical symmetry breaking of a three-dimensional theory that mimics the electroweak sector of the standard model. We show that in the strong coupling limit of a QCD-like theory the fermion condensates which are produced induce dynamical symmetry breaking of the sector corresponding to the electroweak gauge group. (orig.).
Order in the Universe: The Symmetry Principle.
Foundation for Integrative Education, Inc., New York, NY.
The first two papers in this booklet provide a review of the pervasiveness of symmetry in nature and art, discussing how symmetry can be traced through every domain open to our understanding, from all aspects of nature to the special provinces of man; the checks and balances of government, the concept of equal justice, and the aesthetic ordering…
NONLOCAL SYMMETRIES AND NONLOCAL RECURSION OPERATORS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
An expose about covering method on differential equations was given. The general formulae to determine nonlocal symmetries were derived which are analogous to the prolongation formulae of generalized symmetries. In addition, a new definition of nonlocal recursion operators was proposed, which gave a satisfactory explalnation in covering theory for the integro-differcntial recursion operators.
Teaching "Symmetry" in the Introductory Physics Curriculum
Hill, Christopher T; Hill, Christopher T.; Lederman, Leon M.
2000-01-01
Modern physics is largely defined by fundamental symmetry principles and Noether's Theorem. Yet these are not taught, or rarely mentioned, to beginning students, thus missing an opportunity to reveal that the subject of physics is as lively and contemporary as molecular biology, and as beautiful as the arts. We prescribe a symmetry module to insert into the curriculum, of a week's length.
de Leeuw, Marius; Moriyama, Sanefumi; Regelskis, Vidas; Torrielli, Alessandro
2012-01-01
We discuss special quantum group (secret) symmetries of the integrable system associated to the AdS/CFT correspondence. These symmetries have by now been observed in a variety of forms, including the spectral problem, the boundary scattering problem, n-point amplitudes, the pure-spinor formulation and quantum affine deformations.
A nilpotent symmetry of quantum gauge theories
Lahiri, Amitabha
2001-09-01
For the Becchi-Rouet-Stora-Tyutin invariant extended action for any gauge theory, there exists another off-shell nilpotent symmetry. For linear gauges, it can be elevated to a symmetry of the quantum theory and used in the construction of the quantum effective action. Generalizations for nonlinear gauges and actions with higher-order ghost terms are also possible.