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Author(s): L. Tanzi [sup.1] [sup.2] [sup.3] , S. M. Roccuzzo [sup.4] [sup.5] , E. Lucioni [sup.1] [sup.2] [sup.3] , F. Famà [sup.1] , A. Fioretti [sup.1] , C. Gabbanini [sup.1] [...], Supersolids are exotic materials combining the frictionless flow of a superfluid with the crystal-like periodic density modulation of a solid. The supersolid phase of matter was predicted 50 years ago.sup.1-3 for solid helium.sup.4-8. Ultracold quantum gases have recently been made to exhibit periodic order typical of a crystal, owing to various types of controllable interaction.sup.9-13. A crucial feature of a D-dimensional supersolid is the occurrence of D + 1 gapless excitations, reflecting the Goldstone modes associated with the spontaneous breaking of two continuous symmetries: the breaking of phase invariance, corresponding to the locking of the phase of the atomic wave functions at the origin of superfluid phenomena, and the breaking of translational invariance due to the lattice structure of the system. Such modes have been the object of intense theoretical investigations.sup.1,14-18, but they have not yet been observed experimentally. Here we demonstrate supersolid symmetry breaking through the appearance of two distinct compressional oscillation modes in a harmonically trapped dipolar Bose-Einstein condensate, reflecting the gapless Goldstone excitations of the homogeneous system. We observe that the higher-frequency mode is associated with an oscillation of the periodicity of the emergent lattice and the lower-frequency mode characterizes the superfluid oscillations. This work also suggests the presence of two separate quantum phase transitions between the superfluid, supersolid and solid-like configurations. Two distinct compressional oscillation modes are characterized in a dipolar Bose-Einstein condensate; this demonstrates the breaking of two symmetries owing to the coexisting superfluid and crystal properties of a supersolid.

Three series of dibenzo[a,c]phenazines were prepared in an order to assess the impact of side chain position on the phase stability of columnar liquid crystals. Each series was composed of four isomeric compounds differing only in the disposition of hexyloxy and decyloxy chains around the central aromatic core, giving rise to electronically similar compounds with varying shapes and symmetries. The substitution pattern was found to have a moderate effect on the clearing transition of the liquid crystal but a larger impact on the melting temperatures. These observations suggest a viable strategy for controlling the phase range of liquid crystals via judicious choice of peripheral chain structure and location. Key words: liquid crystals, self-assembly, symmetry, organic synthesis. Nous avons prepare trois series de dibenzo[a,c]phenazines en vue d'evaluer les effets de la position de la chaine laterale sur la stabilite de phase de cristaux liquides colonnaires. Chaque serie comptait quatre composes isomeriques qui se distinguaient uniquement par la disposition des chaines hexyloxy et decyloxy autour du noyau aromatique central, ce qui donnait lieu a des composes similaires sur le plan electronique et dont la forme et la symetrie variaient. Nous avons observe que l'arrangement des substituants avait un effet modere sur la transition nematique-isotrope du cristal liquide, mais un effet plus important sur les temperatures de fusion. Ces observations permettent d'envisager une strategie pratique permettant de moduler l'intervalle de transition de phase des cristaux liquides par un choix judicieux de la structure et de la position des chaines peripheriques. [Traduit par la Redaction] Mots-cles : cristaux liquides, autoassemblage, symetrie, synthese organique., Introduction The unique ability of liquid crystals (LCs) to simultaneously exhibit both order and fluidity has been exploited in an enormous variety of applications, including display devices, (1,2) holography, (3) [...]

Author(s): R. M. Roettenbacher (corresponding author) [1]; J. D. Monnier [1]; H. Korhonen [2, 3]; A. N. Aarnio [1]; F. Baron [1, 4]; X. Che [1]; R. O. Harmon [5]; [...]

Author(s): Silvia Pascoli, Jessica Turner Author Affiliations: Matter-antimatter symmetry violated All visible matter in the Universe is made of fundamental building blocks, the elementary particles. The group of particles known [...], In a mirror world, antiparticles should behave in the same way as particles. But it emerges that leptons -- neutrinos, electrons and their more exotic cousins -- might not obey this expected pattern. Signs that neutrinos break CP symmetry.

Author(s): Toshio Miyamachi [sup.1] [sup.2] , Tobias Schuh [sup.1] , Tobias Märkl [sup.1] , Christopher Bresch [sup.1] , Timofey Balashov [sup.1] , Alexander Stöhr [sup.1] [sup.3] , Christian Karlewski [sup.4] [...], Single magnetic atoms on non-magnetic surfaces have magnetic moments that are usually destabilized within a microsecond, too speedily to be useful, but here the magnetic moments of single holmium atoms on a highly conductive metallic substrate can reach lifetimes of the order of minutes. Memory in a moment The magnetic moments of individual magnetic atoms are attractive components for both memory and quantum computing applications. But interactions between such atoms and the substrates on which they are mounted tend to destabilize the magnetic moments, giving them lifetimes of typically less than a few milliseconds. Toshio Miyamachi and colleagues have now identified a system consisting of single atoms of the lanthanide series rare earth element holmium on a highly conductive surface, in which intrinsic symmetries related to the properties of both the atom and the substrate combine to minimize these destabilizing interactions. As a result, the magnetic moments of the atoms can achieve lifetimes of several minutes. Single magnetic atoms, and assemblies of such atoms, on non-magnetic surfaces have recently attracted attention owing to their potential use in high-density magnetic data storage and as a platform for quantum computing.sup.1,2,3,4,5,6,7,8. A fundamental problem resulting from their quantum mechanical nature is that the localized magnetic moments of these atoms are easily destabilized by interactions with electrons, nuclear spins and lattice vibrations of the substrate.sup.3,4,5. Even when large magnetic fields are applied to stabilize the magnetic moment, the observed lifetimes remain rather short.sup.5,6 (less than a microsecond). Several routes for stabilizing the magnetic moment against fluctuations have been suggested, such as using thin insulating layers between the magnetic atom and the substrate to suppress the interactions with the substrate's conduction electrons.sup.2,3,5, or coupling several magnetic moments together to reduce their quantum mechanical fluctuations.sup.7,8. Here we show that the magnetic moments of single holmium atoms on a highly conductive metallic substrate can reach lifetimes of the order of minutes. The necessary decoupling from the thermal bath of electrons, nuclear spins and lattice vibrations is achieved by a remarkable combination of several symmetries intrinsic to the system: time reversal symmetry, the internal symmetries of the total angular momentum and the point symmetry of the local environment of the magnetic atom.

In this technical note, we give a geometrical framework for the design of observers on finite-dimensional Lie groups for systems which possess some specific symmetries. The design and the error (between true and estimated state) equation are explicit and intrinsic. We consider also a particular case: left-invariant systems on Lie groups with right equivariant output. The theory yields a class of observers such that the error equation is autonomous. The observers converge locally around any trajectory, and the global behavior is independent from the trajectory, which is reminiscent of the linear stationary case. Index Terms--Inertial navigation, invariance, Lie group, nonlinear asymptotic observer, symmetry.

The ground, excited and ionized states of P450CO were studied by performing five different calculations with the SAC (symmetry adapted cluster)/SAC-CI method. The effect of proteins on the spectrum by using the point charge model for environmental proteins is examined.

Research is presented describing the methods used to observe a specific HIV protease and discover its quantitative structure symmetry.

Thermophysical algebraic invariance formulation is a robust method for interpretation of invariant features of radiometrically uncalibrated infrared (IR) imagery for ATR and site change detection. The approach focuses on internal object composition and thermophysical properties of imaged objects. Invariance to ambient scene conditions, ability to classify objects and focus on phenomena affecting long-wave IR imagery are the special features of the method. Symmetric alphastable models can adequately model all these features. Results of real IR imagery and ground truth data are presented.

A new renormalization group (RG) theory has been developed applicable to Ginzburg-Landau-Wilson arbitrary anisotropic systems. It contains invariants of all orders with nonlocal vertices. It is difficult to work with exact RG equations, because of the infinite number of redundant operators, however the new exact RG equation obtained, is free of redundant operators.

Penrose tiling in quasicrystal structures can be forced using one type of tile and following the matching rule, or using more than one type of tile and violating the matching rule. The quasiperiodic tiling using decagons inscribed by a fat rhombus tile produces overlapping of the tiles. The central fat tile can be surrounded by other tiles in 11 ways, which is the number given by the Penrose arrow rules. Tiling can also be forced by minimizing the free energy of a tile-cluster. This maximizes the tile density and is a simple physically driven mechanism for quasicrystals formation.

The breaking of symmetry in superfluid helium-3 (He-3) and the formation of defects is used to model the dynamics of cosmological phase transitions. Superfluid He-3 is heated and rapidly cooled to make it non-superfluid. Below the critical temperature, the symmetry of He-3 is broken. A gradient in the phase produces a flow pattern whose energy defines the superfluid analogues of cosmic strings, vortex lines. Superfluids are a good medium for studying the defects caused by symmetry breaking.

A fourth type of subatomic particle shows imperfect symmetry with its antiparticle. Charge conjugation parity symmetry holds that an experiment should be indistinguishable from its reflection in a mirror if [...]

X-ray measurements and Mossbauer spectrum analysis of the iron carbonyl compound, Fe3(CO)12, show that between 100 and 320 K, an excellent agreement exists between the temperature dependences of the calculated and experimental values of the doublet area ratio. The recoil-free fractions and the line area ratio also have linear relationships with temperature. These observations confirm the anisotropic vibration for the two sites, Fe(sub A) and Fe(sub B). The results also support the Goldanskii-Karyagin asymmetry in the compound and reject the possibility of 60 degrees rotational disorder.

The difference in reactivity for the anion radical cleavage and the coupling of radicals with nucleophiles is due to the orbital symmetry restrictions. The overlap is restricted between the pie orbital in the benzene ring and between the sp3 orbital having the unpaired electron in the cleaved radical. A supplementary orbital symmetry restriction is created by the electronic factor of the reaction. This restriction effect causes a decrease of the magnitude of the cleavage rate constant by 3 and a 1/2 order.