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Sample records for boson-fermion degeneracy symmetry

  1. Particle-hole symmetry in generalized seniority, microscopic interacting boson (fermion) model, nucleon-pair approximation, and other models

    NASA Astrophysics Data System (ADS)

    Jia, L. Y.

    2016-06-01

    The particle-hole symmetry (equivalence) of the full shell-model Hilbert space is straightforward and routinely used in practical calculations. In this work I show that this symmetry is preserved in the subspace truncated up to a certain generalized seniority and give the explicit transformation between the states in the two types (particle and hole) of representations. Based on the results, I study particle-hole symmetry in popular theories that could be regarded as further truncations on top of the generalized seniority, including the microscopic interacting boson (fermion) model, the nucleon-pair approximation, and other models.

  2. Critical-Point Symmetries in Boson-Fermion Systems: The Case of Shape Transitions in Odd Nuclei in a Multiorbit Model

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Vitturi, A.

    2007-02-02

    We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model [E(5/12)] to describe odd nuclei at the critical point in the transition from the spherical to {gamma}-unstable behavior. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the three single-particle orbitals j=1/2, 3/2, 5/2. Energy spectra and electromagnetic transitions at the critical point compare well with the results obtained within the interacting boson-fermion model, with a boson-fermion Hamiltonian that describes the same physical situation.

  3. Complete Boson-Fermion Model of Superconductivity

    NASA Astrophysics Data System (ADS)

    de Llano, Manuel

    2003-03-01

    The unification of the 1957 BCS theory with that of Bose-Einstein condensation (BEC) that gives roughly good first-principles transition temperature Tc predictions in either 2D or 3D for all of the ``Uemura plot'' ``exotic'' or conventional superconductors without abandoning the much-maligned phonon interaction mechanism has recently been achieved [1]-[3]. The same dynamical mechanism also allows for room-temperature superconductivity. The only condition is that one depart moderately from the perfect electron (e)-/hole (h)-Cooper-pair (CP) symmetry to which BCS (and indeed also the somewhat more general BCS-Bose crossover) theory are restricted by construction. It now becomes feasible to explain, among other things, why largely all superconductors empirically have substantially higher T_c's if their normal-state charge carriers are holes rather than electrons. A complete (in the sense that 2h-CPs are not ignored) boson-fermion model (CBFM) has been developed that reduces in the appropriate special cases to: a) ordinary BCS theory for weak boson-fermion coupling; b) the BCS-Bose ``crossover'' theory dating back to 1967; and, for no 2h-CPs to: c) the 1989 boson-fermion (BF) BEC model by T.D. Lee et al. of superconductors which without 2h-CPs is unrelated to BCS theory; d) an ideal BF binary-gas model [4] predicting nonzero BEC T_c's even in 2D; and finally to e) ordinary BEC (1925). The CBFM is a BF statistical model similar to those developed in the mid-50's by Schafroth, Blatt & Butler but which now includes 2h-CPs on an equal footing with 2e-CPs, and which unlike these models also contains the empirically well-established fermionic energy gap. [1] V.V. Tolmachev, Phys. Lett. A 266, 400 (2000). [2] M. Fortes, M.A. Solis, M. de Llano & V.V. Tolmachev, Physica C 364, 95 (2001). [3] M. de Llano & V.V. Tolmachev, Physica A 317, 546 (2003). [4] M. Casas, N.J. Davidson, M. de Llano, T.A. Mamedov, A. Puente, R.M. Quick, A. Rigo & M.A. Solis, Physica A 295, 146 (2001

  4. General form of the boson-fermion interaction in the interacting boson-fermion model-2

    NASA Astrophysics Data System (ADS)

    Matus, F. A.; Barea, J.

    2017-03-01

    The boson-fermion interaction in the interacting boson-fermion model-2 (IBFM-2) is derived in a systematic and general form from a quadrupole-quadrupole force using several nondegenerate levels. The boson-fermion quadrupole operator employed is obtained from the boson-fermion image of the one nucleon transfer operator which in turn can be calculated following two alternative schemes: the Otsuka-Arima-Iachello and generalized Holstein-Primakoff schemes. Four different terms (two quadrupole and two exchange) were obtained. Application of the new expressions to a single-j model is studied and analyzed.

  5. Evolution of boson-fermion stars

    NASA Astrophysics Data System (ADS)

    Valdez-Alvarado, Susana; Palenzuela, Carlos; Alic, Daniela; Ureña-López, L. Arturo; Becerril, Ricardo

    2012-08-01

    The boson-fermion stars can be modeled with a complex scalar field coupled minimally to a perfect fluid (i.e., without viscosity and non-dissipative). We present a study of these solutions and their dynamical evolution by solving numerically the Einstein-Klein-Gordon-Hydrodynamic (EKGHD) system. It is shown that stable configurations exist, but stability of general configurations depends finely upon the number of bosons and fermions.

  6. Symmetry and degeneracy manifolds in Jahn-Teller molecules

    NASA Astrophysics Data System (ADS)

    Mead, C. A.

    2013-04-01

    We consider problems in dealing with molecular systems of n identical nuclei. One problem is that of finding suitable internal coordinates. For n <= 4, these can be simply the internuclear distances. For n > 4, it is shown that, with perhaps one exception, there is no internal coordinate system that treats all nuclei equivalently. We also consder the properties of conical intersections between two Born-Oppenheimer electronic energy surfaces, in particular the problem of identifying the two coordinates that remove the degeneracy to first order in the near neighborhoods of symmetry manifolds.

  7. Plethystic vertex operators and boson-fermion correspondences

    NASA Astrophysics Data System (ADS)

    Fauser, Bertfried; Jarvis, Peter D.; King, Ronald C.

    2016-10-01

    We study the algebraic properties of plethystic vertex operators, introduced in (2010 J. Phys. A: Math. Theor. 43 405202), underlying the structure of symmetric functions associated with certain generalized universal character rings of subgroups of the general linear group, defined to stabilize tensors of Young symmetry type characterized by a partition of arbitrary shape π. Here we establish an extension of the well-known boson-fermion correspondence involving Schur functions and their associated (Bernstein) vertex operators: for each π, the modes generated by the plethystic vertex operators and their suitably constructed duals, satisfy the anticommutation relations of a complex Clifford algebra. The combinatorial manipulations underlying the results involve exchange identities exploiting the Hopf-algebraic structure of certain symmetric function series and their plethysms.

  8. Plaquette boson-fermion model of cuprates

    NASA Astrophysics Data System (ADS)

    Altman, Ehud; Auerbach, Assa

    2002-03-01

    The strongly interacting Hubbard model on the square lattice is reduced to the low energy plaquette boson fermion model (PBFM). The four bosons (an antiferromagnon triplet and a d-wave hole pair), and the fermions are defined by the lowest plaquette eigenstates. We apply the contractor renormalization method of Morningstar and Weinstein to compute the boson effective interactions. The range-3 truncation error is found to be very small, signaling short hole-pair and magnon coherence lengths. The pair-hopping and magnon interactions are comparable, which explains the rapid destruction of antiferromagnetic order with emergence of superconductivity, and validates a key assumption of the projected SO(5) theory. A vacuum crossing at larger doping marks a transition into the overdoped regime. With hole fermions occupying small Fermi pockets and Andreev coupled to hole pair bosons, the PBFM yields several testable predictions for photoemission, tunneling asymmetry, and entropy measurements.

  9. Symmetry and Degeneracy in Quantum Mechanics. Self-Duality in Finite Spin Systems

    ERIC Educational Resources Information Center

    Osacar, C.; Pacheco, A. F.

    2009-01-01

    The symmetry of self-duality (Savit 1980 "Rev. Mod. Phys. 52" 453) of some models of statistical mechanics and quantum field theory is discussed for finite spin blocks of the Ising chain in a transverse magnetic field. The existence of this symmetry in a specific type of these blocks, and not in others, is manifest by the degeneracy of their…

  10. Pseudo-Hermitian Systems with PT-Symmetry: Degeneracy and Krein Space

    NASA Astrophysics Data System (ADS)

    Choutri, B.; Cherbal, O.; Ighezou, F. Z.; Drir, M.

    2017-02-01

    We show in the present paper that pseudo-Hermitian Hamiltonian systems with even PT-symmetry (P2=1,T2=1) admit a degeneracy structure. This kind of degeneracy is expected traditionally in the odd PT-symmetric systems (P2=1,T2=-1) which is appropriate to the fermions (Scolarici and Solombrino, Phys. Lett. A 303, 239 2002; Jones-Smith and Mathur, Phys. Rev. A 82, 042101 2010). We establish that the pseudo-Hermitian Hamiltonians with even PT-symmetry admit a degeneracy structure if the operator PT anticommutes with the metric operator η σ which is necessarily indefinite. We also show that the Krein space formulation of the Hilbert space is the convenient framework for the implementation of unbroken PT-symmetry. These general results are illustrated with great details for four-level pseudo-Hermitian Hamiltonian with even PT -symmetry.

  11. A rationale for the symmetries by base substitutions of degeneracy in the genetic code.

    PubMed

    Jestin, Jean-Luc

    2010-01-01

    The first symmetry by base substitutions of degeneracy in the genetic code was described by Rumer (1966) and the other symmetries were identified later by Jestin (2006) and Jestin and Soulé (2007). Here, a rationale accounting for these symmetries is reported. The number of non-synonymous substitutions over the replicated coding sequence is written as a function of the substitution matrix, whose elements are the number of substitutions from any codon to any other codon. The p-adic distance used as a similarity measure and applied to this matrix is shown to be biologically relevant. The rationale indicates that symmetries by base substitutions of degeneracy in the genetic code are symmetries of the measures of the number of non-synonymous substitutions for sets of synonymous codons.

  12. Twisted vertex algebras, bicharacter construction and boson-fermion correspondences

    NASA Astrophysics Data System (ADS)

    Anguelova, Iana I.

    2013-12-01

    The boson-fermion correspondences are an important phenomena on the intersection of several areas in mathematical physics: representation theory, vertex algebras and conformal field theory, integrable systems, number theory, cohomology. Two such correspondences are well known: the types A and B (and their super extensions). As a main result of this paper we present a new boson-fermion correspondence of type D-A. Further, we define a new concept of twisted vertex algebra of order N, which generalizes super vertex algebra. We develop the bicharacter construction which we use for constructing classes of examples of twisted vertex algebras, as well as for deriving formulas for the operator product expansions, analytic continuations, and normal ordered products. By using the underlying Hopf algebra structure we prove general bicharacter formulas for the vacuum expectation values for two important groups of examples. We show that the correspondences of types B, C, and D-A are isomorphisms of twisted vertex algebras.

  13. Exceptional points of degeneracy and P T symmetry in photonic coupled chains of scatterers

    NASA Astrophysics Data System (ADS)

    Othman, Mohamed A. K.; Galdi, Vincenzo; Capolino, Filippo

    2017-03-01

    We demonstrate the existence of exceptional points of degeneracy (EPDs) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram at which two or more Bloch eigenstates coalesce, in both their eigenvectors and eigenvalues. We show the emergence of a second-order modal EPD associated with the parity-time (P T ) symmetry condition, at which each particle pair in the double chain exhibits balanced gain and loss. Furthermore, we also demonstrate a fourth-order EPD occurring at the band edge. Such a degeneracy condition was previously referred to as a degenerate band edge in lossless anisotropic photonic crystals. Here, we rigorously show it under the occurrence of gain and loss balance for a discrete guiding system. We identify a more general regime of gain and loss balance showing that P T symmetry is not necessary to attain EPDs. Moreover, we investigate the degree of detuning of the EPD when the geometrical symmetry or balanced condition is broken. Furthermore, we demonstrate a realistic implementation of the EPD in a coupled chain made of pairs of plasmonic nanospheres and active core-shell nanospheres at optical frequencies. These findings open avenues toward superior light localization and transport with application to high-Q resonators utilized in sensors, filters, low-threshold switching and lasing.

  14. Conformal symmetry algebra of the quark potential and degeneracies in the hadron spectra

    NASA Astrophysics Data System (ADS)

    Kirchbach, M.

    2012-10-01

    The essence of the potential algebra concept [Y. Alhassid, F. Gürsey, F. Yachello. Phys. Rev. Lett. 50 (1983)] is that quantum mechanical free motions of scalar particles on curved surfaces of given isometry algebras can be mapped on 1D Schrödinger equations with particular potentials. As long as the Laplace-Beltrami operator on a curved surface is proportional to one of the Casimir invariants of the isometry algebra, free motion on the surface is described by means of the eigenvalue problem of that very Casimir operator. In effect, the excitation modes considered are classified according to the irreducible representations of the algebra of interest and are characterized by typical degeneracies. In consequence, also the spectra of the equivalent Schrödinger operators are classified according to the same irreducible representations and carry the same typical degeneracies. A subtle point concerns the representation of the algebra elements which may or may not be unitarily equivalent to the standard one generating classical groups like SO(n), SO(p,q), etc. To be specific, any similarity transformations of an algebra that underlies, say, an orthogonal group, always conserve the commutators among the elements, but a non-unitarily transformed algebra must not generate same group. One can then consider the parameters of the non-unitary similarity transformation as group symmetry breaking scales and seek to identify them with physical observables. We here use the potential algebra concept as a guidance in the search for an interaction describing conformal degeneracies. For this purpose we subject the so(4) ⊂ so(2,4) isometry algebra of the S3 ball to a particular non-unitary similarity transformation and obtain a deformed isometry copy to S3 such that free motion on the copy is equivalent to a cotangent perturbed motion on S3, and to the 1D Schrödinger operator with the trigonometric Rosen-Morse potential as well. The latter presents itself especially well suited for

  15. Localized modes in arrays of boson-fermion mixtures

    SciTech Connect

    Bludov, Yu. V.; Konotop, V. V.

    2006-10-15

    It is shown that the mean-field description of a boson-fermion mixture with a dominating fermionic component, loaded in a one-dimensional optical lattice, is reduced to the nonlinear Schroedinger equation with a periodic potential and periodic nonlinearity. In such a system there exist localized modes having peculiar properties. In particular, for some regions of parameters there exists a lower bound for a number of bosons necessary for creation of a mode, while for other domains small amplitude gap solitons are not available in the vicinity of either of the gap edges. We found that the lowest branch of the symmetric solution either does not exist or exists only for a restricted range of energies in a gap, unlike in pure bosonic condensates. The simplest bifurcations of the modes are shown and stability of the modes is verified numerically.

  16. The boson fermion resonance model in one dimension

    NASA Astrophysics Data System (ADS)

    Citro, R.; Orignac, E.

    2006-05-01

    We discuss the phase transitions of fermions in one dimension with a narrow Feshbach resonance described by the boson-fermion resonance model. By means of the bosonization technique, we derive a low-energy Hamiltonian of the system and show that a strongly correlated state exists, where the order parameters of the Bose condensation and superfluidity decay with the same critical exponent. We also show that density fluctuations near the Fermi wavevector are strongly suppressed as a consequence of a spin gap and a gap against the formation of phase slips. We find a Luther-Emery point where the phase slips and the spin excitations can be described in terms of pseudofermions, providing closed form expressions of the density-density correlations and the spectral functions. The relevance of our results for experiments with ultracold atomic gases subject to one-dimensional confinement is also discussed.

  17. Collapse in boson-fermion mixtures with all-repulsive interactions

    SciTech Connect

    Prytula, Vladyslav I.; Konotop, Vladimir V.; Perez-Garcia, Victor M.; Vekslerchik, Vadym E.

    2007-10-15

    We describe the collapse of the bosonic component in a boson-fermion mixture due to the pressure exerted on it by a large fermionic component, leading to collapse in a system with all-repulsive interactions. We describe the phenomena of early collapse and superslow collapse of the mixture.

  18. Retarded boson-fermion interaction in atomic systems

    NASA Astrophysics Data System (ADS)

    Datta, Sambhu N.; Misra, Anirban

    2006-08-01

    The retarded interaction between an electron and a spin-0 nucleus is derived from electrodynamical perturbation theory. The contribution of retardation at order v2/c2 mimics the Breit interaction [Phys. Rev. 34, 553 (1929); 36, 388 (1930); 39, 616 (1932)] with the Dirac matrix α2 being replaced by p2/m2c where p2 is the linear momentum operator for the nucleus. An effective one-electron retardation operator is obtained in relative coordinates, and this can be used through all orders in perturbation theory without any problem of infinite degeneracy. A few steps of unitary transformation lead to the nonrelativistic limit. The leading terms in retardation corrections to energy are of order (me/mn)α2Z4(α2mec2). The implications for atomic systems are discussed.

  19. Lifetime measurements in 71Ge and a new interacting boson-fermion model interpretation

    NASA Astrophysics Data System (ADS)

    Ivaşcu, M.; Mărginean, N.; Bucurescu, D.; Căta-Danil, I.; Ur, C. A.; Lobach, Yu. N.

    1999-08-01

    The lifetimes of twelve low spin excited states have been measured in 71Ge using the Doppler shift attenuation method in the 71Ga(p,nγ) reaction at 3.0 and 3.5 MeV incident energy. New interacting boson-fermion model calculations for this nucleus account well for the properties of all its levels known up to about 1.5 MeV excitation.

  20. Internal parity symmetry and degeneracy of Bethe Ansatz strings in the isotropic heptagonal magnetic ring

    NASA Astrophysics Data System (ADS)

    Milewski, J.; Lulek, B.; Lulek, T.; Łabuz, M.; Stagraczyński, R.

    2014-02-01

    The exact Bethe eigenfunctions for the heptagonal ring within the isotropic XXX model exhibit a doubly degenerated energy level in the three-deviation sector at the centre of the Brillouin zone. We demonstrate an explicit construction of these eigenfunctions by use of algebraic Bethe Ansatz, and point out a relation of degeneracy to parity conservation, applied to the configuration of strings for these eigenfunctions. Namely, the internal structure of the eigenfunctions (the 2-string and the 1-string, with opposite quasimomenta) admits generation of two mutually orthogonal eigenfunctions due to the fact that the strings which differ by their length are distinguishable objects.

  1. Transition probabilities and interacting boson-fermion model description of positive parity states in 117Sb

    NASA Astrophysics Data System (ADS)

    Lobach, Yu. N.; Bucurescu, D.

    1998-09-01

    The Doppler shift attenuation method was used to determine lifetimes in the picosecond region for excited states of 117Sb populated with the (α,2nγ) reaction at Eα=27.2 MeV. Interacting boson-fermion model calculations explain reasonably well the main features of the positive parity levels known up to about 2.5 MeV excitation. The mixing of the lowest one-quasiparticle 9/2+ state with the intruder (2p-1h) 9/2+ state, as well as the quadrupole deformation of the intruder band are also discussed.

  2. Comparisons of interacting-boson-fermion approximation and triaxial calculations for odd-mass N =80 nuclei

    SciTech Connect

    Aryaeinejad, R.; Chou, W.; McHarris, W.C. )

    1989-09-01

    The interacting-boson-fermion-approximation and triaxial models were used to calculate excitation energies and mixing ratios for the {ital N}=80 nuclei, {sup 139}Pr, {sup 141}Pm, and {sup 143}Eu. For low-lying negative- and positive-parity states both models yield roughly the same numbers, in good agreement with experimental results. For high-lying states we find that the interacting-boson-fermion-approximation model describes the level structure considerably better than the triaxial model. On the other hand, the triaxial model gives more satisfactory results in predicting the mixing ratios.

  3. Superconductivity in the boson-fermion model with short range fermion repulsion

    NASA Astrophysics Data System (ADS)

    Kostyrko, Tomasz

    1998-03-01

    We consider influence of an on-site Coulomb repulsion U between fermions on superconducting properties of a two-component system of the wide band electrons hybridized with heavy boson-like local electron pairs^1,2. Within an RPA treatment valid for U< fermion bandwidth, we show that U almost completely suppresses superconductivity as long as a boson level stays above a Fermi level (BCS limit), reducing both Tc and a range of stability of an s-wave superconducting phase at T=0 K. In a Bose region, where the chemical potential remains pinned to the boson level, superconductivity is always stable at T=0 K and suppression of Tc is relatively small, especially for finite values of a boson mass. Above results are verified with the conclusions based on an effective t-J like hamiltonian derived by means of a canonical perturbation method from the boson-fermion model in a strong U limit. We show that the on-site boson-fermion hybridization is reduced by a factor of 2t/U (t - fermion hopping) and transforms into an intersite coupling supporting an extended s-wave superconducting order in this limit. [1em] 1. J. Ranninger and Robaszkiewicz, Physica B 135, 468 (1985). 2. R. Friedberg and T.D. Lee, Phys. Rev. B 40, 423 (1989).

  4. Level Density In Interacting Boson-Fermion-Fermion Model (IBFFM) Of The Odd-Odd Nucleus 196Au

    SciTech Connect

    Kabashi, Skender; Bekteshi, Sadik

    2007-04-23

    The level density of the odd-odd nucleus 196Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes.The IBFFM total level density is fitted by Gaussian and its tail is also fitted by Bethe formula and constant temperature Fermi gas model.

  5. One-loop renormalizable Wess-Zumino model on a bosonic-fermionic noncommutative superspace

    NASA Astrophysics Data System (ADS)

    Miao, Yan-Gang; Wang, Xu-Dong

    2014-08-01

    We construct a deformed Wess-Zumino model on the noncommutative superspace where the bosonic and fermionic coordinates are no longer commutative with each other. Using the background field method, we calculate the primary one-loop effective action based on the deformed action. By comparing the two actions, we find that the deformed Wess-Zumino model is not renormalizable. To obtain a renormalizable model, we combine the primary one-loop effective action with the deformed action, and then calculate the secondary one-loop effective action based on the combined action. After repeating this process a third time, we finally give the one-loop renormalizable action up to the second order of bosonic-fermionic noncommutative parameters by using our specific techniques of calculation.

  6. Phase transitions in the interacting boson fermion model: The {gamma}-unstable case

    SciTech Connect

    Alonso, C.E.; Arias, J.M.; Fortunato, L.; Vitturi, A.

    2005-12-15

    The phase transition around the critical point in the evolution from spherical to deformed {gamma}-unstable shapes is investigated in odd nuclei within the interacting boson fermion model. We consider the particular case of an odd j=3/2 particle coupled to an even-even boson core that undergoes a transition from spherical U(5) to {gamma}-unstable O(6) situation. The particular choice of the j=3/2 orbital preserves in the odd case the condition of {gamma}-instability of the system. As a consequence, energy spectrum and electromagnetic transitions, in correspondence of the critical point, display behaviors qualitatively similar to those of the even core. The results are also in qualitative agreement with the recently proposed E(5/4) model, although few differences are present, due to the different nature of the two schemes.

  7. Composite-Particles (Boson, Fermion) Theory of Fractional Quantum Hall Effect

    NASA Astrophysics Data System (ADS)

    Fujita, Shigeji; Suzuki, Akira; Ho, Hung-Cheuk

    2017-02-01

    A theory is developed for fractional quantum Hall effect in terms of composite (c)-bosons (fermions) without useing Laughlin's results about the fractional charge. Here the c-particle (fermion, boson) is defined as a bound composite fermion (boson) containing a conduction electron and an even (odd) number of fluxons (elementary magnetic fluxes). The Bose-condensed c-bosons, each containing an electron and an odd number m of fluxons at the filling factor ν=1/ m is shown to generate the Hall conductivity plateau value m e 2/ h, where the density of c-particles, n_{φ }^{(m)}, either bosonic or fermionic, with m fluxons is given by n_{φ }^{(m)}=ne/m, n e = electron density. The only assumption is that any c-fermion carries a charge magnitude equal to the electron charge e. The quantum Hall state is shown to be more stable at ν=1/3 than at ν=1.

  8. Mixing-demixing transition and collapse of a vortex state in a quasi-two-dimensional boson-fermion mixture

    SciTech Connect

    Adhikari, Sadhan K.; Salasnich, Luca

    2007-05-15

    We investigate the mixing-demixing transition and the collapse in a quasi-two-dimensional degenerate boson-fermion mixture (DBFM) with a bosonic vortex. We solve numerically a quantum-hydrodynamic model based on a new density functional which accurately takes into account the dimensional crossover. It is demonstrated that with the increase of interspecies repulsion, a mixed state of DBFM could turn into a demixed state. The system collapses for interspecies attraction above a critical value which depends on the vortex quantum number. For interspecies attraction just below this critical limit there is almost complete mixing of boson and fermion components. Such mixed and demixed states of a DBFM could be experimentally realized by varying an external magnetic field near a boson-fermion Feshbach resonance, which will result in a continuous variation of interspecies interaction.

  9. From the Hubbard to a Plaquette Boson-Fermion Model for Cuprates

    NASA Astrophysics Data System (ADS)

    Altman, Ehud; Auerbach, Assa

    2002-03-01

    We describe a systematic approach to connect the microscopic physics of the Hubbard model to the phenomena of underdoped High Tc cuprate superconductors. We apply the Contractor Renormalization method of Morningstar and Weinstein to reduce the strongly interacting Hubbard model on the square lattice to the low energy Plaquette Boson Fermion Model (PBFM). The four bosons (an antiferromagnon triplet and a d-wave hole pair), and the fermions are defined by the lowest plaquette eigenstates. We compute the boson effective interactions, and the range-3 truncation error is found to be very small, signaling short hole-pair and magnon coherence lengths. The pair-hopping and magnon interactions are comparable, which explains the rapid destruction of antiferromagnetic order with emergence of superconductivity, and validates a key assumption of the projected SO(5) theory. A vacuum crossing at larger doping marks a transition into the overdoped regime. The PBFM includes hole fermions occupying small Fermi pockets and Andreev coupled to hole pair bosons. In mean field theory it exhibits a pairing gap near the nodes, which grows with Tc and a pseudogap with oposite doping dependence. The PBFM yields several testable predictions for photoemmission, tunneling asymmetry and thermodynamic measurements.

  10. Phase transitions in the boson-fermion resonance model in one dimension

    NASA Astrophysics Data System (ADS)

    Orignac, E.; Citro, R.

    2006-06-01

    We study one-dimensional fermions with photoassociation or with a narrow Fano-Feshbach resonance described by the boson-fermion resonance model. Using the bosonization technique, we derive a low-energy Hamiltonian of the system. We show that at low energy, the order parameters for the Bose condensation and fermion superfluidity become identical, while a spin gap and a gap against the formation of phase slips are formed. As a result of these gaps, charge density wave correlations decay exponentially in contrast with the phases where only bosons or only fermions are present. We find a Luther-Emery point where the phase slips and the spin excitations can be described in terms of pseudofermions. This allows us to provide closed form expressions of the density-density correlations and the spectral functions. The spectral functions of the fermions are gapped, whereas the spectral functions of the bosons remain gapless. The application of a magnetic field results in a loss of coherence between the bosons and the fermion and the disappearance of the gap. Changing the detuning has no effect on the gap until either the fermion or the boson density is reduced to zero. Finally, we discuss the formation of a Mott insulating state in a periodic potential. The relevance of our results for experiments with ultracold atomic gases subject to one-dimensional confinement is also discussed.

  11. Depairing and Bose-Einstein-condensation temperatures in a simple boson-fermion model of superconductors

    NASA Astrophysics Data System (ADS)

    Mamedov, T. A.; de Llano, M.

    2007-03-01

    Starting from the Friedberg-TD Lee Hamiltonian describing a coexisting and dynamically interacting many-particle binary boson-fermion gas mixture with a coupling (λ) -dependent gap 2Δ(λ) in the boson dispersion relation for the s -wave Cooper or BCS model interaction, we deduce several observed characteristic features of high-temperature superconductors at the simplest level. Analytic expressions for both the unpaired-fermion and boson number densities, as well for the fermion chemical potential μ(λ,T) , all of which vary with the degree of bosonization and with temperature T , are derived in detail using two-time, finite-temperature Green function techniques. Simple implicit formulas are then obtained for both two and three dimensions for the pseudogap T* and Bose-Einstein condensation Tc temperatures in terms of μ(λ,T) and 2Δ(λ) . In particular, even at the s -wave level we find a self-consistent description of the generic phase diagram observed in cuprates, including the appearance of a pseudogap and a dome-shaped Tc vs doping behavior both of which hinge on the gapped boson spectrum.

  12. Remove Degeneracy in Relativistic Symmetries for Manning—Rosen Plus Quasi-Hellman Potentials by Tensor Interaction

    NASA Astrophysics Data System (ADS)

    Mousavi, Mohsen; Shojaei, Mohammad Reza

    2016-11-01

    The relativistic Dirac equation under spin and pseudo-spin symmetries is investigated for Manning—Rosen plus quasi-Hellman potentials with tensor interaction. For the first time we consider the Hulthen plus Yukawa for tensor interaction. The Formula method is used to obtain the energy eigen-values and wave functions. We also discuss about the energy eigen-values and the Dirac spinors for the Manning—Rosen plus quasi-Hellman potentials for the spin and pseudo-spin symmetry with Formula method. To show the accuracy of the present model, some numerical results are shown in both pseudo-spin and spin symmetry limits.

  13. Odd-even {sup 147-153}Pm isotopes within the neutron-proton interacting boson-fermion model

    SciTech Connect

    Barea, J.; Alonso, C. E.; Arias, J. M.

    2011-02-15

    Low-lying energy states of the {sup 147-153}Pm isotopic chain are studied within the framework of the neutron-proton interacting boson-fermion model (IBFM-2). The spectra of these isotopes show a transition from a particle coupled to a vibrational core to a particle coupled to a deformed one. The calculation reproduces this behavior. In addition, reduced transition probabilities B(E2) and B(M1) and quadrupole and magnetic moments, as well as spectroscopic factors corresponding to stripping and pickup transfer reactions, are calculated. Obtained results compare well with the available experimental data, which reinforces the reliability of the wave functions obtained within the IBFM-2 model.

  14. On-chip generation of Einstein-Podolsky-Rosen states with arbitrary symmetry

    SciTech Connect

    Gräfe, Markus; Heilmann, René; Nolte, Stefan; Szameit, Alexander

    2015-05-04

    We experimentally demonstrate a method for integrated-optical generation of two-photon Einstein-Podolsky-Rosen states featuring arbitrary symmetries. In our setting, we employ detuned directional couplers to impose a freely tailorable phase between the two modes of the state. Our results allow to mimic the quantum random walk statistics of bosons, fermions, and anyons, particles with fractional exchange statistics.

  15. BEC-polaron gas in a boson-fermion mixture: A many-body extension of Lee-Low-Pines theory

    NASA Astrophysics Data System (ADS)

    Nakano, Eiji; Yabu, Hiroyuki

    2016-05-01

    We investigate the ground state properties of the gaseous mixture of a single species of bosons and fermions at zero temperature, where bosons are major in population over fermions, and form the Bose-Einstein condensate (BEC). The boson-boson and boson-fermion interactions are assumed to be weakly repulsive and attractive, respectively, while the fermion-fermion interaction is absent due to the Pauli exclusion for the low energy s -wave scattering. We treat fermions as a gas of polarons dressed with Bogoliubov phonons, which is an elementary excitation of the BEC, and evaluate the ground state properties with the method developed by Lemmens, Devreese, and Brosens (LDB) originally for the electron polaron gas, and also with a general extension of the Lee-Low-Pines theory for many-body systems (eLLP), which incorporates the phonon drag effects as in the original LLP theory. The formulation of eLLP is developed and discussed in the present paper. The binding (interaction) energy of the polaron gas is calculated in these methods and shown to be finite (negative) for the dilute gas of heavy fermions with attractive boson-fermion interactions, though the suppression by the many-body effects exists.

  16. Semifluxon degeneracy choreography in Aharonov-Bohm billiards

    NASA Astrophysics Data System (ADS)

    Berry, M. V.; Popescu, S.

    2010-09-01

    Every energy level of a charged quantum particle confined in a region threaded by a magnetic flux line with quantum flux one-half must be degenerate for some position of the semifluxon within the boundary B. This is illustrated by computations for which B is a circle and a conformal transformation of a circle without symmetry. As the shape of B is varied, two degeneracies between the same pair of levels can collide and annihilate. Degeneracy of three levels requires three shape parameters, or the positions of three semifluxons; degeneracy of N levels can be generated by int{N(N + 1)/4} semifluxons. The force on the semifluxon is derived.

  17. Giant nonreciprocity near exceptional-point degeneracies

    NASA Astrophysics Data System (ADS)

    Thomas, Roney; Li, Huanan; Ellis, F. M.; Kottos, Tsampikos

    2016-10-01

    We show that gyrotropic structures with balanced gain and loss that respect antilinear symmetries exhibit a giant nonreciprocity at the so-called exact phase where the eigenfrequencies of the isolated non-Hermitian setup are real. The effect occurs in a parameter domain near an exceptional- point (EP) degeneracy, where mode orthogonality collapses. The theoretical predictions are confirmed numerically in the microwave domain, where a nonreciprocal transport above 90 dB is demonstrated, and are further verified using lumped-circuitry modeling. The analysis allows us to speculate the universal nature of the phenomenon for any wave system where EP and gyrotropy can coexist.

  18. The Simplicity of Perfect Atoms: Degeneracies in Supersymmetric Hydrogen

    SciTech Connect

    Rube, Tomas; Wacker, Jay G.; /SLAC /Stanford U., ITP

    2011-08-19

    Supersymmetric QED hydrogen-like bound states are remarkably similar to non-supersymmetric hydrogen, including an accidental degeneracy of the fine structure and which is broken by the Lamb shift. This article classifies the states, calculates the leading order spectrum, and illustrates the results in several limits. The relation to other non-relativistic bound states is explored. Supersymmetric bound states provide a laboratory for studying dynamics in supersymmetric theories. Bound states like hydrogen provide a framework for understanding the qualitative dynamics of QCD mesons, a supersymmetric version of QED can provide a qualitative picture for the symmetries and states of superQCD mesons. Furthermore, recent interest in dark matter as a composite state, leads to asking how supersymmetry acts upon these composite states [4-7]. This article calculates the leading order corrections to a hydrogen-like atoms in an exactly supersymmetric version of QED. Much of the degeneracy is broken by the fine structure and a seminal calculation was performed in [1] for positronium, see [2] for an N = 2 version of positronium. Supersymmetric hydrogen is a similar except for the absence of annihilation diagrams, see [3] for an independent calculation. In the heavy proton mass limit, the supersymmetric interactions of the theory become irrelevant operators, suppressed by powers of the proton mass like the magnetic moment operator in QED and the fine structure is identical to the non-supersymmetric theory. This article finds that fine structure spectrum of supersymmetric spectrum of hydrogen has an accidental degeneracy which is exactly analogous to the accidental degeneracy of the l = 0 and l = 1 levels of the n = 2; j = 1/2 state of hydrogen. The supersymmetric version of the Lamb shift lifts the residual degeneracy and this article computes the logarithmically enhanced breaking.

  19. Spin degeneracy and conductance fluctuations in open quantum dots.

    PubMed

    Folk, J A; Patel, S R; Birnbaum, K M; Marcus, C M; Duruöz, C I; Harris, J S

    2001-03-05

    The dependence of conductance fluctuations on parallel magnetic field is used as a probe of spin degeneracy in open GaAs quantum dots. The variance of fluctuations at high parallel field is reduced from the low-field variance (with broken time-reversal symmetry) by factors ranging from roughly 2 in a 1 microm (2) dot to greater than 4 in 8 microm (2) dots. The factor of 2 is expected for Zeeman splitting of spin-degenerate channels. A possible explanation for the larger suppression based on field-dependent spin-orbit scattering is proposed.

  20. Exactly soluble model of boundary degeneracy

    NASA Astrophysics Data System (ADS)

    Ganeshan, Sriram; Gorshkov, Alexey V.; Gurarie, Victor; Galitski, Victor M.

    2017-01-01

    We investigate the topological degeneracy that can be realized in Abelian fractional quantum spin Hall states with multiply connected gapped boundaries. Such a topological degeneracy (also dubbed as "boundary degeneracy") does not require superconducting proximity effect and can be created by simply applying a depletion gate to the quantum spin Hall material and using a generic spin-mixing term (e.g., due to backscattering) to gap out the edge modes. We construct an exactly soluble microscopic model manifesting this topological degeneracy and solve it using the recently developed technique [S. Ganeshan and M. Levin, Phys. Rev. B 93, 075118 (2016), 10.1103/PhysRevB.93.075118]. The corresponding string operators spanning this degeneracy are explicitly calculated. It is argued that the proposed scheme is experimentally reasonable.

  1. Coexistence of orbital degeneracy lifting and superconductivity in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Miao, H.; Wang, L.-M.; Richard, P.; Wu, S.-F.; Ma, J.; Qian, T.; Xing, L.-Y.; Wang, X.-C.; Jin, C.-Q.; Chou, C.-P.; Wang, Z.; Ku, W.; Ding, H.

    2014-06-01

    We report the angle-resolved photoemission spectroscopy observation of the lifting of symmetry-protected band degeneracy, and consequently the breakdown of local tetragonal symmetry in the superconducting state of Li(Fe1-xCox)As. Supported by theoretical simulations, we analyze the doping and temperature dependences of this band splitting and demonstrate an intimate connection between ferro-orbital correlations and superconductivity.

  2. Nodal surfaces and interdimensional degeneracies

    SciTech Connect

    Loos, Pierre-François; Bressanini, Dario

    2015-06-07

    The aim of this paper is to shed light on the topology and properties of the nodes (i.e., the zeros of the wave function) in electronic systems. Using the “electrons on a sphere” model, we study the nodes of two-, three-, and four-electron systems in various ferromagnetic configurations (sp, p{sup 2}, sd, pd, p{sup 3}, sp{sup 2}, and sp{sup 3}). In some particular cases (sp, p{sup 2}, sd, pd, and p{sup 3}), we rigorously prove that the non-interacting wave function has the same nodes as the exact (yet unknown) wave function. The number of atomic and molecular systems for which the exact nodes are known analytically is very limited and we show here that this peculiar feature can be attributed to interdimensional degeneracies. Although we have not been able to prove it rigorously, we conjecture that the nodes of the non-interacting wave function for the sp{sup 3} configuration are exact.

  3. Decomposition of fractional quantum Hall model states: Product rule symmetries and approximations

    SciTech Connect

    Thomale, Ronny; Bernevig, B. Andrei; Estienne, Benoit; Regnault, Nicolas

    2011-07-15

    We provide a detailed description of a product rule structure of the monomial (Slater) expansion coefficients of bosonic (fermionic) fractional quantum Hall (FQH) states derived recently, which we now extend to spin-singlet states. We show that the Haldane-Rezayi spin-singlet state can be obtained without exact diagonalization through a differential equation method that we conjecture to be generic to other FQH model states. The product rule symmetries allow us to build approximations of FQH states that exhibit increasing overlap with the exact state (as a function of system size) even though our approximation omits more than half of the Hilbert space. We show that the product rule is valid for any FQH state that can be written as an expectation value of parafermionic operators.

  4. Angular-overlap calculation of the Jahn-Teller stabilization energie for f-orbital degeneracies

    SciTech Connect

    Warren, K.D.

    1980-03-01

    The angular-overlap model is applied to the calculation of the linear Jahn-Teller coupling constants for f-orbital degeneracies. The MX/sub 6/, O/sub h/, chromophore is treated as representative of the highest symmetry commonly occurring in the lanthanide and actinide series, and it is shown that, even when spin-orbit effects are taken into account, 5f orbital degeneracies may lead to significant Jahn-Teller stabilization energies. The operation of this effect for F/sup 1/ GAMMA/sub 8/ states is considered. 2 tables.

  5. Degeneracy and complexity in biological systems

    PubMed Central

    Edelman, Gerald M.; Gally, Joseph A.

    2001-01-01

    Degeneracy, the ability of elements that are structurally different to perform the same function or yield the same output, is a well known characteristic of the genetic code and immune systems. Here, we point out that degeneracy is a ubiquitous biological property and argue that it is a feature of complexity at genetic, cellular, system, and population levels. Furthermore, it is both necessary for, and an inevitable outcome of, natural selection. PMID:11698650

  6. Degeneracies in parametrized modified gravity models

    SciTech Connect

    Hojjati, Alireza

    2013-01-01

    We study degeneracies between parameters in some of the widely used parametrized modified gravity models. We investigate how different observables from a future photometric weak lensing survey such as LSST, correlate the effects of these parameters and to what extent the degeneracies are broken. We also study the impact of other degenerate effects, namely massive neutrinos and some of the weak lensing systematics, on the correlations.

  7. Accidental degeneracies in nonlinear quantum deformed systems

    NASA Astrophysics Data System (ADS)

    Aleixo, A. N. F.; Balantekin, A. B.

    2011-09-01

    We construct a multi-parameter nonlinear deformed algebra for quantum confined systems that includes many other deformed models as particular cases. We demonstrate that such systems exhibit the property of accidental pairwise energy level degeneracies. We also study, as a special case of our multi-parameter deformation formalism, the extension of the Tamm-Dancoff cutoff deformed oscillator and the occurrence of accidental pairwise degeneracy in the energy levels of the deformed system. As an application, we discuss the case of a trigonometric Rosen-Morse potential, which is successfully used in models for quantum confined systems, ranging from electrons in quantum dots to quarks in hadrons.

  8. Robust topological degeneracy of classical theories

    NASA Astrophysics Data System (ADS)

    Vaezi, Mohammad-Sadegh; Ortiz, Gerardo; Nussinov, Zohar

    2016-05-01

    We challenge the hypothesis that the ground states of a physical system whose degeneracy depends on topology must necessarily realize topological quantum order and display nonlocal entanglement. To this end, we introduce and study a classical rendition of the Toric Code model embedded on Riemann surfaces of different genus numbers. We find that the minimal ground state degeneracy (and those of all levels) depends on the topology of the embedding surface alone. As the ground states of this classical system may be distinguished by local measurements, a characteristic of Landau orders, this example illustrates that topological degeneracy is not a sufficient condition for topological quantum order. This conclusion is generic and, as shown, it applies to many other models. We also demonstrate that certain lattice realizations of these models, and other theories, display a ground state entropy (and those of all levels) that is "holographic", i.e., extensive in the system boundary. We find that clock and U (1 ) gauge theories display topological (in addition to gauge) degeneracies.

  9. Non-symmorphic band degeneracy at the Fermi level in ZrSiTe

    NASA Astrophysics Data System (ADS)

    Topp, Andreas; Lippmann, Judith M.; Varykhalov, Andrei; Duppel, Viola; Lotsch, Bettina V.; Ast, Christian R.; Schoop, Leslie M.

    2016-12-01

    Non-symmorphic materials have recently been predicted to exhibit many different exotic features in their electronic structures. These originate from forced band degeneracies caused by the non-symmorphic symmetry, which not only creates the possibility to realize Dirac semimetals, but also recently resulted in the prediction of novel quasiparticles beyond the usual Dirac, Weyl or Majorana fermions, which can only exist in the solid state. Experimental realization of non-symmorphic materials that have the Fermi level located at the degenerate point is difficult, however, due to the requirement of an odd band filling. In order to investigate the effect of forced band degeneracies on the transport behavior, a material that has such a degeneracy at or close to the Fermi level is desired. Here, we show with angular resolved photoemission experiments supported by density functional calculations, that ZrSiTe hosts several fourfold degenerate Dirac crossings at the X point, resulting from non-symmorphic symmetry. These crossings form a Dirac line node along XR, which is located almost directly at the Fermi level and shows almost no dispersion in energy. ZrSiTe is thus the first real material that allows for transport measurements investigating Dirac fermions that originate from non-symmorphic symmetry.

  10. Degeneracy Breaking for K2 Microlens Parallaxes

    NASA Astrophysics Data System (ADS)

    Gould, Andrew; Yee, Jennifer; Carey, Sean

    2015-10-01

    By adding Spitzer observations to microlensing targets being observed from Kepler and Earth, we will create the first interplanetary network of microlensing observatories. This 3-observatory configuration has the unique potential to break the famous 4-fold degeneracy for space-based microlensing parallaxes. This is crucial both for the interpretation of some individual events and to rigorously validate the statistical methods that are used when (as is usually the case) this special 3-observatory configuration is not possible. The Kepler K2 C9 microlensing campaign will monitor about 4 square degrees of the Bulge from 6 Apr to 29 Jun, with the aim of measuring microlens parallaxes. Spitzer can observe this K2 field from 18 Jun to 26 Jul. The 11-day overlap between the two campaigns will allow us to break the 4-fold degeneracy of about 50 microlensing events. Some of these events will be well-covered over the peak from K2, with Spitzer observations of the falling wing providing the necessary information to break the degeneracy in the K2-Earth parallax. Others will be the reverse, with K2 observations of the rising event breaking the degeneracy in Spitzer-Earth parallaxes (i.e., for events peaking during the Spitzer campaign). Breaking this degeneracy leads to a definitive measurement of the magnitude of the microlens parallax vector, which will enable measurements of the masses and distances of the lens systems, including events with planets that contribute to the ~12 needed to make a first measurement of the Galactic distribution of planets, binaries, and many single-lens events, some of which could be black holes, brown dwarfs, or other interesting objects. The distance distribution of the ensemble of lenses can serve as a probe of Galactic structure. All lightcurves will be reduced using our customized software and then made public (for unrestricted use), within two months of the completion of observations (as we did for our 2015 observations).

  11. The degeneracy of the free Dirac equation

    SciTech Connect

    Gupta, V. . School of Physics Tata Inst. of Fundamental Research, Bombay ); McKellar, B.H.J. . School of Physics); Wu, D.D. . School of Physics Institute of High Energy Physics, Beijing, BJ . Electron LINAC Dept. General Atomics, San Diego, CA )

    1991-08-01

    Parity-mixed solutions of the free Dirac equation with the same 4-momentum are considered. The first-order EM energy has an electric dipole moment term whose value depends on the mixing angle. Further implications of this degeneracy to perturbative calculations are discussed. It is argued that the properties of the Dirac equation with the Coulomb potential can be used to decide the mixing angle, which should be zero.

  12. Scalar non-degeneracy and flavor unification

    SciTech Connect

    Kojima, Kentaro

    2008-05-13

    Grand unified models of the strong and electroweak forces generally predict some types of flavor unification. The flavor structure in unified theory is probed with superparticle mass spectrum observed in future particle experiments. It is shown that the generation dependence of sfermion mass non-degeneracy provides direct imprints of unification of the standard model matter multiplets. The implication from flavor-violating rare process is also discussed.

  13. Dark degeneracy and interacting cosmic components

    SciTech Connect

    Aviles, Alejandro; Cervantes-Cota, Jorge L.

    2011-10-15

    We study some properties of the dark degeneracy, which is the fact that what we measure in gravitational experiments is the energy-momentum tensor of the total dark sector, and any split into components (as in dark matter and dark energy) is arbitrary. In fact, just one dark fluid is necessary to obtain exactly the same cosmological and astrophysical phenomenology as the {Lambda}CDM model. We work explicitly the first-order perturbation theory and show that beyond the linear order the dark degeneracy is preserved under some general assumptions. Then we construct the dark fluid from a collection of interacting fluids. Finally, we try to break the degeneracy with a general class of couplings to baryonic matter. Nonetheless, we show that these interactions can also be understood in the context of the {Lambda}CDM model as between dark matter and baryons. For this last investigation we choose two independent parametrizations for the interactions, one inspired by electromagnetism and the other by chameleon theories. Then, we constrain them with a joint analysis of CMB and supernovae observational data.

  14. Relativistic symmetries in nuclear single-particle spectra

    NASA Astrophysics Data System (ADS)

    Guo, Jian-You; Liang, Hao Zhao; Meng, Jie; Zhou, Shan-Gui

    Symmetry is a fundamental concept in quantum physics. The quasi-degeneracy between single-particle orbitals (n, l, j = l + 1/2) and (n -1, l + 2, j = l + 3/2) indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry. Since the pseudospin symmetry was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry for anti-nucleons, and many new concepts have been introduced. In this Chapter, we will illustrate the schematic picture of spin and pseudospin symmetries, derive the basic formalism, highlight the recent progress from several different aspects, and discuss selected open issues in this topic.

  15. Hidden Degeneracies in Piecewise Smooth Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Jeffrey, Mike R.

    When a flow suffers a discontinuity in its vector field at some switching surface, the flow can cross through or slide along the surface. Sliding along the switching surface can be understood as the flow along an invariant manifold inside a switching layer. It turns out that the usual method for finding sliding modes — the Filippov convex combination or Utkin equivalent control — results in a degeneracy in the switching layer whenever the flow is tangent to the switching surface from both sides. We derive the general result and analyze the simplest case here, where the flow curves parabolically on either side of the switching surface (the so-called fold-fold or two-fold singularities). The result is a set of zeros of the fast switching flow inside the layer, which is structurally unstable to perturbation by terms nonlinear in the switching parameter, terms such as (signx)2 [where the superscript does mean “squared”]. We provide structurally stable forms, and show that in this form the layer system is equivalent to a generic singularity of a two timescale system. Finally we show that the same degeneracy arises when a discontinuity is smoothed using standard regularization methods.

  16. Neutrino degeneracy and cosmological nucleosynthesis, revisited

    NASA Technical Reports Server (NTRS)

    Olive, K. A.; Schramm, David N.; Thomas, D.; Walker, T. P.

    1991-01-01

    A reexamination of the effects of non-zero degeneracies on Big Bang Nucleosynthesis is made. As previously noted, non-trivial alterations of the standard model conclusions can be induced only if excess lepton numbers L sub i, comparable to photon number densities eta sub tau, are assumed (where eta sub tau is approx. 3 times 10(exp 9) eta sub b). Furthermore, the required lepton number densities (L sub i eta sub tau) must be different for upsilon sub e than for upsilon sub mu and epsilon sub tau. It is shown that this loophole in the standard model of nucleosynthesis is robust and will not vanish as abundance and reaction rate determinations improve. However, it is also argued that theoretically (L sub e) approx. (L sub mu) approx. (L sub tau) approx. eta sub b is much less than eta sub tau which would preclude this loophole in standard unified models.

  17. Defects and degeneracies in supersymmetry protected phases

    NASA Astrophysics Data System (ADS)

    Fokkema, Thessa; Schoutens, Kareljan

    2015-08-01

    We analyse a class of 1D lattice models, known as \\text{M}k models, which are characterised by an order-k clustering of spin-less fermions and by N}=2 lattice supersymmetry. Our main result is the identification of a class of (bulk or edge) defects, that are in one-to-one correspondence with so-called spin fields in a corresponding {Z}k parafermion CFT. In the gapped regime, injecting such defects leads to ground-state degeneracies that are protected by the supersymmetry. The defects, which are closely analogous to quasi-holes over the fermonic Read-Rezayi quantum Hall states, display characteristic fusion rules, which are of Ising type for k = 2 and of Fibonacci type for k = 3.

  18. Quasi-degenerate neutrinos from an abelian family symmetry

    SciTech Connect

    Binetruy, P. |; Lavignac, S.; Petcov, S. |; Ramond, P.

    1996-12-31

    The authors show that models with an abelian family symmetry which accounts for the observed hierarchies of masses and mixings in the quark sector may also accommodate quasi-degeneracies in the neutrino mass spectrum. Such approximate degeneracies are, in this context, associated with large mixing angles. The parameters of this class of models are constrained. The authors discuss their phenomenological implications for present and foreseen neutrino experiments.

  19. Breaking a dark degeneracy with gravitational waves

    SciTech Connect

    Lombriser, Lucas; Taylor, Andy E-mail: ant@roe.ac.uk

    2016-03-01

    We identify a scalar-tensor model embedded in the Horndeski action whose cosmological background and linear scalar fluctuations are degenerate with the concordance cosmology. The model admits a self-accelerated background expansion at late times that is stable against perturbations with a sound speed attributed to the new field that is equal to the speed of light. While degenerate in scalar fluctuations, self-acceleration of the model implies a present cosmological tensor mode propagation at ∼<95 % of the speed of light with a damping of the wave amplitude that is ∼>5 % less efficient than in general relativity. We show that these discrepancies are endemic to self-accelerated Horndeski theories with degenerate large-scale structure and are tested with measurements of gravitational waves emitted by events at cosmological distances. Hence, gravitational-wave cosmology breaks the dark degeneracy in observations of the large-scale structure between two fundamentally different explanations of cosmic acceleration—a cosmological constant and a scalar-tensor modification of gravity. The gravitational wave event GW150914 recently detected with the aLIGO instruments and its potential association with a weak short gamma-ray burst observed with the Fermi GBM experiment may have provided this crucial measurement.

  20. Measures of degeneracy and redundancy in biological networks

    PubMed Central

    Tononi, Giulio; Sporns, Olaf; Edelman, Gerald M.

    1999-01-01

    Degeneracy, the ability of elements that are structurally different to perform the same function, is a prominent property of many biological systems ranging from genes to neural networks to evolution itself. Because structurally different elements may produce different outputs in different contexts, degeneracy should be distinguished from redundancy, which occurs when the same function is performed by identical elements. However, because of ambiguities in the distinction between structure and function and because of the lack of a theoretical treatment, these two notions often are conflated. By using information theoretical concepts, we develop here functional measures of the degeneracy and redundancy of a system with respect to a set of outputs. These measures help to distinguish the concept of degeneracy from that of redundancy and make it operationally useful. Through computer simulations of neural systems differing in connectivity, we show that degeneracy is low both for systems in which each element affects the output independently and for redundant systems in which many elements can affect the output in a similar way but do not have independent effects. By contrast, degeneracy is high for systems in which many different elements can affect the output in a similar way and at the same time can have independent effects. We demonstrate that networks that have been selected for degeneracy have high values of complexity, a measure of the average mutual information between the subsets of a system. These measures promise to be useful in characterizing and understanding the functional robustness and adaptability of biological networks. PMID:10077671

  1. Generalized mass ordering degeneracy in neutrino oscillation experiments

    SciTech Connect

    Coloma, Pilar; Schwetz, Thomas

    2016-09-07

    Here, we consider the impact of neutral-current (NC) nonstandard neutrino interactions (NSI) on the determination of the neutrino mass ordering. We show that in the presence of NSI there is an exact degeneracy which makes it impossible to determine the neutrino mass ordering and the octant of the solar mixing angle θ12 at oscillation experiments. The degeneracy holds at the probability level and for arbitrary matter density profiles, and hence solar, atmospheric, reactor, and accelerator neutrino experiments are affected simultaneously. The degeneracy requires order-1 corrections from NSI to the NC electron neutrino-quark interaction and can be tested in electron neutrino NC scattering experiments.

  2. Analysis and resolution of the ground-state degeneracy of the two-component Bose-Hubbard model.

    PubMed

    Wang, Wei; Penna, Vittorio; Capogrosso-Sansone, Barbara

    2014-08-01

    We study the degeneracy of the ground-state energy E of the two-component Bose-Hubbard model and of the perturbative correction E(1). We show that the degeneracy properties of E and E(1) are closely related to the connectivity properties of the lattice. We determine general conditions under which E is nondegenerate. This analysis is then extended to investigate the degeneracy of E(1). In this case, in addition to the lattice structure, the degeneracy also depends on the number of particles present in the system. After identifying the cases in which E(1) is degenerate and observing that the standard (degenerate) perturbation theory is not applicable, we develop a method to determine the zeroth-order correction to the ground state by exploiting the symmetry properties of the lattice. This method is used to implement the perturbative approach to the two-component Bose-Hubbard model in the case of degenerate E(1) and is expected to be a valid tool to perturbatively study the asymmetric character of the Mott insulator to superfluid transition between the particle and hole side.

  3. Symmetry impedes symmetry discrimination.

    PubMed

    Tjan, Bosco S; Liu, Zili

    2005-12-16

    Objects in the world, natural and artificial alike, are often bilaterally symmetric. The visual system is likely to take advantage of this regularity to encode shapes for efficient object recognition. The nature of encoding a symmetric shape, and of encoding any departure from it, is therefore an important matter in visual perception. We addressed this issue of shape encoding empirically, noting that a particular encoding scheme necessarily leads to a specific profile of sensitivity in perceptual discriminations. We studied symmetry discrimination using human faces and random dots. Each face stimulus was a frontal view of a three-dimensional (3-D) face model. The 3-D face model was a linearly weighted average (a morph) between the model of an original face and that of the corresponding mirror face. Using this morphing technique to vary the degree of asymmetry, we found that, for faces and analogously generated random-dot patterns alike, symmetry discrimination was worst when the stimuli were nearly symmetric, in apparent opposition to almost all studies in the literature. We analyzed the previous work and reconciled the old and new results using a generic model with a simple nonlinearity. By defining asymmetry as the minimal difference between the left and right halves of an object, we found that the visual system was disproportionately more sensitive to larger departures from symmetry than to smaller ones. We further demonstrated that our empirical and modeling results were consistent with Weber-Fechner's and Stevens's laws.

  4. Massive Degeneracy and Goldstone Bosons: A Challenge for the Light Cone

    SciTech Connect

    Weinstein, Marvin; /SLAC

    2010-10-27

    Wherein it is argued that the light front formalism has problems dealing with Goldstone symmetries. It is further argued that the notion that in hadron condensates can explain Goldstone phenomena is false. This talk can be summarized as follows: (1) Exact symmetries can be realized in Wigner or Goldstone mode. (2) When a symmetry is realized in Wigner mode the states of the theory form degenerate irreducible representations of the symmetry group and the lowest energy state is unique. (3) When a symmetry is realized in Goldstone mode the lowest energy state of the theory is infinitely degenerate, the states of the theory do not form irreducible representations of the symmetry group and there are massless particles coupled by the conserved currents to any one of the possible ground states. (4) In finite volume the signal of a Goldstone realization of a symmetry is that the number of nearly degenerate states grows rapidly with increasing volume and the gap between these states shrinks exponentially with the volume. (5) The existence of a condensate such as the magnetization, for a ferromagnet, or the staggered magnetization for an anti-ferromagnet, signals a Goldstone symmetry. This is because this condensate transforms non-trivially under the symmetry transformations and so its existence implies the ground state isn't unique. (6) PCAC means that the pion, kaon and eta are would be Goldstone bosons of the theory where the quark masses are set to zero. This interpretation is overwhelmingly supported by experimental data. This means that these particles are really the wiggling of the order parameter or condensate. (7) Finally, in order for the Goldstone particle to exist there has to be something to wiggle every place where the particle can exist. This means that the condensate that is the order parameter for this Goldstone symmetry cannot be confined to the interior of hadrons. Thus, to reiterate, the challenge for the Light Front is to show how the formalism gives

  5. Ubiquitous symmetries

    NASA Astrophysics Data System (ADS)

    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.

  6. Symmetry breaking around a wormhole

    NASA Astrophysics Data System (ADS)

    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.

  7. Symmetry algebra of a generalized anisotropic harmonic oscillator

    NASA Technical Reports Server (NTRS)

    Castanos, O.; Lopez-Pena, R.

    1993-01-01

    It is shown that the symmetry Lie algebra of a quantum system with accidental degeneracy can be obtained by means of the Noether's theorem. The procedure is illustrated by considering a generalized anisotropic two dimensional harmonic oscillator, which can have an infinite set of states with the same energy characterized by an u(1,1) Lie algebra.

  8. Generalized mass ordering degeneracy in neutrino oscillation experiments

    DOE PAGES

    Coloma, Pilar; Schwetz, Thomas

    2016-09-07

    Here, we consider the impact of neutral-current (NC) nonstandard neutrino interactions (NSI) on the determination of the neutrino mass ordering. We show that in the presence of NSI there is an exact degeneracy which makes it impossible to determine the neutrino mass ordering and the octant of the solar mixing angle θ12 at oscillation experiments. The degeneracy holds at the probability level and for arbitrary matter density profiles, and hence solar, atmospheric, reactor, and accelerator neutrino experiments are affected simultaneously. The degeneracy requires order-1 corrections from NSI to the NC electron neutrino-quark interaction and can be tested in electron neutrinomore » NC scattering experiments.« less

  9. Translational Symmetry and Microscopic Constraints on Symmetry-Enriched Topological Phases: A View from the Surface

    NASA Astrophysics Data System (ADS)

    Cheng, Meng; Zaletel, Michael; Barkeshli, Maissam; Vishwanath, Ashvin; Bonderson, Parsa

    2016-10-01

    The Lieb-Schultz-Mattis theorem and its higher-dimensional generalizations by Oshikawa and Hastings require that translationally invariant 2D spin systems with a half-integer spin per unit cell must either have a continuum of low energy excitations, spontaneously break some symmetries, or exhibit topological order with anyonic excitations. We establish a connection between these constraints and a remarkably similar set of constraints at the surface of a 3D interacting topological insulator. This, combined with recent work on symmetry-enriched topological phases with on-site unitary symmetries, enables us to develop a framework for understanding the structure of symmetry-enriched topological phases with both translational and on-site unitary symmetries, including the effective theory of symmetry defects. This framework places stringent constraints on the possible types of symmetry fractionalization that can occur in 2D systems whose unit cell contains fractional spin, fractional charge, or a projective representation of the symmetry group. As a concrete application, we determine when a topological phase must possess a "spinon" excitation, even in cases when spin rotational invariance is broken down to a discrete subgroup by the crystal structure. We also describe the phenomena of "anyonic spin-orbit coupling," which may arise from the interplay of translational and on-site symmetries. These include the possibility of on-site symmetry defect branch lines carrying topological charge per unit length and lattice dislocations inducing degeneracies protected by on-site symmetry.

  10. Age-Metallicity Degeneracy at mid-UV Wavelengths

    NASA Astrophysics Data System (ADS)

    Bertone, E.; Chavez, M.; Buzzoni, A.

    2009-11-01

    The so-called age-metallicity degeneracy, which affects the optical spectral properties of stellar populations, is also present at mid-ultraviolet wavelengths. We give here the results for two reference objects: the Sun (assumed as representative of the turnoff star of a single stellar population) and M 32. Within a theoretical framework, we have explored the properties of the age-metallicity degeneracy by means of 17 spectroscopic indices from 2100 to 3100 Å: our preliminary results show a metallicity sensitivity parameter value of 1.7±1.2, which is compatible with the Worthey's value of 3/2 in the optical interval.

  11. Boson-fermion confusion: the string path to supersymmetry

    NASA Astrophysics Data System (ADS)

    Ramond, P.

    Reminiscences on the String origins of Supersymmetry are followed by a discussion of the importance of confusing bosons with fermions in building superstring theories in 9 + 1 dimensions. In eleven dimensions, the kinship between bosons and fermions is more subtle, and may involve the exceptional group F4.

  12. Ultracold Superstrings in Atomic Boson-Fermion Mixtures

    SciTech Connect

    Snoek, Michiel; Haque, Masudul; Vandoren, S.; Stoof, H.T.C.

    2005-12-16

    We propose a setup with ultracold atomic gases that can be used to make a nonrelativistic superstring in four spacetime dimensions. In particular, we consider for the creation of the superstring a fermionic atomic gas that is trapped in the core of a vortex in a Bose-Einstein condensate. We explain the required tuning of experimental parameters to achieve supersymmetry between the fermionic atoms and the bosonic modes describing the oscillations in the vortex position. Furthermore, we discuss the experimental consequences of supersymmetry.

  13. Degeneracy of energy levels of pseudo-Gaussian oscillators

    SciTech Connect

    Iacob, Theodor-Felix; Iacob, Felix; Lute, Marina

    2015-12-07

    We study the main features of the isotropic radial pseudo-Gaussian oscillators spectral properties. This study is made upon the energy levels degeneracy with respect to orbital angular momentum quantum number. In a previous work [6] we have shown that the pseudo-Gaussian oscillators belong to the class of quasi-exactly solvable models and an exact solution has been found.

  14. The simplicity of perfect atoms: Degeneracies in supersymmetric hydrogen

    DOE PAGES

    Rube, Tomas; Wacker, Jay G.

    2011-06-07

    In this study, supersymmetric QED hydrogen-like bound states are remarkably similar to nonsupersymmetric hydrogen, including an accidental degeneracy of the fine structure and is broken by the Lamb shift. This article classifies the states, calculates the leading order spectrum, and illustrates the results in several limits. The relation to other nonrelativistic bound states is explored.

  15. The simplicity of perfect atoms: Degeneracies in supersymmetric hydrogen

    SciTech Connect

    Rube, Tomas; Wacker, Jay G.

    2011-06-15

    Supersymmetric QED hydrogen-like bound states are remarkably similar to nonsupersymmetric hydrogen, including an accidental degeneracy of the fine structure and is broken by the Lamb shift. This article classifies the states, calculates the leading order spectrum, and illustrates the results in several limits. The relation to other nonrelativistic bound states is explored.

  16. Symmetry matters.

    PubMed

    Moubayidin, Laila; Østergaard, Lars

    2015-09-01

    985 I. 985 II. 986 III. 987 IV. 988 V. 989 989 References 989 SUMMARY: The development of multicellular organisms depends on correct establishment of symmetry both at the whole-body scale and within individual tissues and organs. Setting up planes of symmetry must rely on communication between cells that are located at a distance from each other within the organism, presumably via mobile morphogenic signals. Although symmetry in nature has fascinated scientists for centuries, it is only now that molecular data to unravel mechanisms of symmetry establishment are beginning to emerge. As an example we describe the genetic and hormonal interactions leading to an unusual bilateral-to-radial symmetry transition of an organ in order to promote reproduction.

  17. Quantification of degeneracy in Hodgkin-Huxley neurons on Newman-Watts small world network.

    PubMed

    Man, Menghua; Zhang, Ya; Ma, Guilei; Friston, Karl; Liu, Shanghe

    2016-08-07

    Degeneracy is a fundamental source of biological robustness, complexity and evolvability in many biological systems. However, degeneracy is often confused with redundancy. Furthermore, the quantification of degeneracy has not been addressed for realistic neuronal networks. The objective of this paper is to characterize degeneracy in neuronal network models via quantitative mathematic measures. Firstly, we establish Hodgkin-Huxley neuronal networks with Newman-Watts small world network architectures. Secondly, in order to calculate the degeneracy, redundancy and complexity in the ensuing networks, we use information entropy to quantify the information a neuronal response carries about the stimulus - and mutual information to measure the contribution of each subset of the neuronal network. Finally, we analyze the interdependency of degeneracy, redundancy and complexity - and how these three measures depend upon network architectures. Our results suggest that degeneracy can be applied to any neuronal network as a formal measure, and degeneracy is distinct from redundancy. Qualitatively degeneracy and complexity are more highly correlated over different network architectures, in comparison to redundancy. Quantitatively, the relationship between both degeneracy and redundancy depends on network coupling strength: both degeneracy and redundancy increase with complexity for small coupling strengths; however, as coupling strength increases, redundancy decreases with complexity (in contrast to degeneracy, which is relatively invariant). These results suggest that the degeneracy is a general topologic characteristic of neuronal networks, which could be applied quantitatively in neuroscience and connectomics.

  18. Extended degeneracy and order by disorder in the square lattice J1-J2-J3 model

    NASA Astrophysics Data System (ADS)

    Danu, Bimla; Nambiar, Gautam; Ganesh, R.

    2016-09-01

    The square lattice antiferromagnet with frustrating next-nearest-neighbor coupling continues to generate tremendous interest, with an elusive quantum disordered phase in the vicinity of J2=J1/2 . At this precise value of frustration, the classical model has a very large degeneracy, which makes the problem difficult to handle. We show that introducing a ferromagnetic J3 coupling partially lifts this degeneracy. It gives rise to a four-site magnetic unit cell with the constraint that the spins on every square must add to zero. This leads to a two-parameter family of ground states and an emergent vector order parameter. We reinterpret this family of ground states as coexistence states of three spirals. Using spin wave analysis, we show that thermal and quantum fluctuations break this degeneracy differently. Thermal fluctuations break it down to a threefold degeneracy with one Néel phase and two stripe phases. This threefold symmetry is restored via a Z3 thermal transition, as we demonstrate using classical Monte Carlo simulations. On the other hand, quantum fluctuations select the Néel state. In the extreme quantum limit of spin 1 /2 , we use exact diagonalization to demonstrate Néel ordering beyond a critical J3 coupling. For weak J3, a variational approach suggests an s -wave plaquette-RVB state. Away from the J2=J1/2 line, we show that quantum fluctuations favor Néel ordering strongly enough to stabilize it within the classical stripe region. Our results shed light on the origin of the quantum disordered phase in the J1-J2 model.

  19. Coulomb analogy for non-Hermitian degeneracies near quantum phase transitions.

    PubMed

    Cejnar, Pavel; Heinze, Stefan; Macek, Michal

    2007-09-07

    Degeneracies near the real axis in a complex-extended parameter space of a Hermitian Hamiltonian are studied. We present a method to measure distributions of such degeneracies on the Riemann sheet of a selected level and apply it in classification of quantum phase transitions. The degeneracies are shown to behave similarly as complex zeros of a partition function.

  20. Epigenomics and the concept of degeneracy in biological systems.

    PubMed

    Maleszka, Ryszard; Mason, Paul H; Barron, Andrew B

    2014-05-01

    Researchers in the field of epigenomics are developing more nuanced understandings of biological complexity, and exploring the multiple pathways that lead to phenotypic expression. The concept of degeneracy-referring to the multiple pathways that a system recruits to achieve functional plasticity-is an important conceptual accompaniment to the growing body of knowledge in epigenomics. Distinct from degradation, redundancy and dilapidation; degeneracy refers to the plasticity of traits whose function overlaps in some environments, but diverges in others. While a redundant system is composed of repeated identical elements performing the same function, a degenerate system is composed of different elements performing similar or overlapping functions. Here, we describe the degenerate structure of gene regulatory systems from the basic genetic code to flexible epigenomic modifications, and discuss how these structural features have contributed to organism complexity, robustness, plasticity and evolvability.

  1. Universal Velocity-Field Characteristics for a Nanowire Arbitrary Degeneracy

    SciTech Connect

    Chek, Desmond C. Y.; Hashim, Abdul Manaf; Tan, Michael Loong Peng; Arora, Vijay K.

    2011-05-25

    The effects of electric field on the carrier motion and drift velocity in nanowire (NW) are presented in this paper. When the electric field is applied in NW, the electron is expected to move in anti-parallel direction to the electric field. This is so-called randomness motion is transformed into streamlined motion in extremely high electric field. The normalized Fermi energy and relative electron population as a function of electric field are examined for various degeneracies. It was found that the electric field has lesser influence on the relative electron population with the increased degeneracy. The drift velocity in NW is shown to increase with electric field until it reaches the saturation velocity. Two approximations have been made to simplify the theoretical equation. It is also shown in this paper that when the quantum emission is taken into account, the drift and saturation velocity degrades.

  2. Topological degeneracy of non-Abelian states for dummies

    NASA Astrophysics Data System (ADS)

    Oshikawa, Masaki; Kim, Yong Baek; Shtengel, Kirill; Nayak, Chetan; Tewari, Sumanta

    2007-06-01

    We present a physical construction of degenerate groundstates of the Moore-Read Pfaffian states, which exhibits non-Abelian statistics, on general Riemann surface with genus g. The construction is given by a generalization of the recent argument [M.O., T. Senthil, Phys. Rev. Lett. 96 (2006) 060601] which relates fractionalization and topological order. The nontrivial groundstate degeneracy obtained by Read and Green [Phys. Rev. B 61 (2000) 10267] based on differential geometry is reproduced exactly. Some restrictions on the statistics, due to the fractional charge of the quasiparticle are also discussed. Furthermore, the groundstate degeneracy of the p + i p superconductor in two dimensions, which is closely related to the Pfaffian states, is discussed with a similar construction.

  3. Black hole state degeneracy in loop quantum gravity

    SciTech Connect

    Agullo, Ivan; Diaz-Polo, Jacobo; Fernandez-Borja, Enrique

    2008-05-15

    The combinatorial problem of counting the black hole quantum states within the isolated horizon framework in loop quantum gravity is analyzed. A qualitative understanding of the origin of the band structure shown by the degeneracy spectrum, which is responsible for the black hole entropy quantization, is reached. Even when motivated by simple considerations, this picture allows to obtain analytical expressions for the most relevant quantities associated to this effect.

  4. A torus bifurcation theorem with symmetry

    NASA Technical Reports Server (NTRS)

    Vangils, S. A.; Golubitsky, M.

    1989-01-01

    Hopf bifurcation in the presence of symmetry, in situations where the normal form equations decouple into phase/amplitude equations is described. A theorem showing that in general such degeneracies are expected to lead to secondary torus bifurcations is proved. By applying this theorem to the case of degenerate Hopf bifurcation with triangular symmetry it is proved that in codimension two there exist regions of parameter space where two branches of asymptotically stable two-tori coexist but where no stable periodic solutions are present. Although a theory was not derived for degenerate Hopf bifurcations in the presence of symmetry, examples are presented that would have to be accounted for by any such general theory.

  5. Breaking the Symmetry in Molecular Nanorings

    PubMed Central

    2016-01-01

    Because of their unique electronic properties, cyclic molecular structures ranging from benzene to natural light-harvesting complexes have received much attention. Rigid π-conjugated templated porphyrin nanorings serve as excellent model systems here because they possess well-defined structures that can readily be controlled and because they support highly delocalized excitations. In this study, we have deliberately modified a series of six-porphyrin nanorings to examine the impact of lowering the rotational symmetry on their photophysical properties. We reveal that as symmetry distortions increase in severity along the series of structures, spectral changes and an enhancement of radiative emission strength occur, which derive from a transfer of oscillator strength into the lowest (k = 0) state. We find that concomitantly, the degeneracy of the dipole-allowed first excited (k = ±1) state is lifted, leading to an ultrafast polarization switching effect in the emission from strongly symmetry-broken nanorings. PMID:26735906

  6. On the degeneracy of the IMRT optimization problem.

    PubMed

    Alber, M; Meedt, G; Nüsslin, F; Reemtsen, R

    2002-11-01

    One approach to the computation of photon IMRT treatment plans is the formulation of an optimization problem with an objective function that derives from an objective density. An investigation of the second-order properties of such an objective function in a neighborhood of the minimizer opens an intuitive access to many traits of this approach. A general finding is that only a small subset of the parameter space has nonzero curvature, while the objective function is entirely flat in a neighborhood of the minimizer in most directions. The dimension of the subspace of vanishing curvature serves as a measure for the degeneracy of the solution. This finding is important both for algorithm design and evaluation of the mathematical model of clinical intuition, expressed by the objective function. The structure of the subspace of great curvature is found to be imposed on the problem by conflicts between objectives of target and critical structures. These conflicts and their corresponding modes of resolution form a common trait between all reasonable treatment plans of a given case. The high degree of degeneracy makes the use of a conjugate gradient optimization algorithm particularly favorable since the number of iterations to convergence is equivalent to the number of different eigenvalues of the curvature tensor and is hence independent from the number of optimization parameters. A high level of degeneracy of the fluence profiles implies that it should be possible to stipulate further delivery-related conditions without causing severe deterioration of the dose distribution.

  7. A backtracking algorithm that deals with particle filter degeneracy

    NASA Astrophysics Data System (ADS)

    Baarsma, Rein; Schmitz, Oliver; Karssenberg, Derek

    2016-04-01

    Particle filters are an excellent way to deal with stochastic models incorporating Bayesian data assimilation. While they are computationally demanding, the particle filter has no problem with nonlinearity and it accepts non-Gaussian observational data. In the geoscientific field it is this computational demand that creates a problem, since dynamic grid-based models are often already quite computationally demanding. As such it is of the utmost importance to keep the amount of samples in the filter as small as possible. Small sample populations often lead to filter degeneracy however, especially in models with high stochastic forcing. Filter degeneracy renders the sample population useless, as the population is no longer statistically informative. We have created an algorithm in an existing data assimilation framework that reacts to and deals with filter degeneracy based on Spiller et al. [2008]. During the Bayesian updating step of the standard particle filter, the algorithm tests the sample population for filter degeneracy. If filter degeneracy has occurred, the algorithm resets to the last time the filter did work correctly and recalculates the failed timespan of the filter with an increased sample population. The sample population is then reduced to its original size and the particle filter continues as normal. This algorithm was created in the PCRaster Python framework, an open source tool that enables spatio-temporal forward modelling in Python [Karssenberg et al., 2010] . The framework already contains several data assimilation algorithms, including a standard particle filter and a Kalman filter. The backtracking particle filter algorithm has been added to the framework, which will make it easy to implement in other research. The performance of the backtracking particle filter is tested against a standard particle filter using two models. The first is a simple nonlinear point model, and the second is a more complex geophysical model. The main testing

  8. Non-Hermitian Hamiltonians with unitary and antiunitary symmetries

    NASA Astrophysics Data System (ADS)

    Fernández, Francisco M.; Garcia, Javier

    2014-03-01

    We analyse several non-Hermitian Hamiltonians with antiunitary symmetry from the point of view of their point-group symmetry. It enables us to predict the degeneracy of the energy levels and to reduce the dimension of the matrices necessary for the diagonalization of the Hamiltonian in a given basis set. We can also classify the solutions according to the irreducible representations of the point group and thus analyse their properties separately. One of the main results of this paper is that some PT-symmetric Hamiltonians with point-group symmetry C2v exhibit complex eigenvalues for all values of a potential parameter. In such cases the PT phase transition takes place at the trivial Hermitian limit which suggests that the phenomenon is not robust. Point-group symmetry enables us to explain such anomalous behaviour and to choose a suitable antiunitary operator for the PT symmetry.

  9. Inherited Symmetry

    ERIC Educational Resources Information Center

    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…

  10. Elementary excitations in magnetically ordered systems with orbital degeneracy

    SciTech Connect

    Joshi, A.; Ma, M. ); Mila, F. ); Shi, D.N. College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, Peoples Republic of ); Zhang, F.C. )

    1999-09-01

    The generalized Holstein-Primakoff transformation is used to develop a quantum flavor wave theory for spin systems with orbital degeneracy. Elementary excitations of ordered ground states consist of spin, orbital, and spin-orbital waves. Spin and spin-orbital waves couple to each other due to orbital anisotropy and Hund[close quote]s rule, resulting in modes observable by inelastic neutron scattering. In the SU(4) limit, flavor waves are dispersionless along one or more directions, and give rise to quantum fluctuations of reduced dimensionality. [copyright] [ital 1999] [ital The American Physical Society

  11. Degeneracy, frequency response and filtering in IMRT optimization.

    PubMed

    Llacer, Jorge; Agazaryan, Nzhde; Solberg, Timothy D; Promberger, Claus

    2004-07-07

    This paper attempts to provide an answer to some questions that remain either poorly understood, or not well documented in the literature, on basic issues related to intensity modulated radiation therapy (IMRT). The questions examined are: the relationship between degeneracy and frequency response of optimizations, effects of initial beamlet fluence assignment and stopping point, what does filtering of an optimized beamlet map actually do and how could image analysis help to obtain better optimizations? Two target functions are studied, a quadratic cost function and the log likelihood function of the dynamically penalized likelihood (DPL) algorithm. The algorithms used are the conjugate gradient, the stochastic adaptive simulated annealing and the DPL. One simple phantom is used to show the development of the analysis tools used and two clinical cases of medium and large dose matrix size (a meningioma and a prostate) are studied in detail. The conclusions reached are that the high number of iterations that is needed to avoid degeneracy is not warranted in clinical practice, as the quality of the optimizations, as judged by the DVHs and dose distributions obtained, does not improve significantly after a certain point. It is also shown that the optimum initial beamlet fluence assignment for analytical iterative algorithms is a uniform distribution, but such an assignment does not help a stochastic method of optimization. Stopping points for the studied algorithms are discussed and the deterioration of DVH characteristics with filtering is shown to be partially recoverable by the use of space-variant filtering techniques.

  12. Low-dimensional relativistic degeneracy in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.; Esfandyari-Kalejahi, A.; Esfandyari-Kalejahi

    2013-12-01

    In this work we investigate the effect of relativistic degeneracy on different properties of low-dimensional quantum plasmas. Using the dielectric response from the conventional quantum hydrodynamic model, including the quantum diffraction effect (Bohm potential) on free electrons, we explore the existence of the Shukla-Eliasson attractive screening and possibility of the ion structure formation in low-dimensional, completely degenerate electron-ion plasmas. A generalized degeneracy pressure expression for arbitrary relativity parameter in two-dimensional case is derived, indicating that change in the polytropic index (change in the equation of state) for the two-dimensional quantum fluid takes place at the electron number-density of n 0 ~= 1.1 × 1020cm-2 whereas this is known to occur for the three-dimensional case in the electron density of n 0 ~= 5.9 × 1029cm-3. Also, a generalized dielectric function valid for all dimensionalities and densities of a degenerate electron gas is calculated, and distinct properties of electron-ion plasmas, such as static screening, structure factor and Thomson scattering, are investigated in terms of plasma dimensionality.

  13. Degeneracy allows for both apparent homogeneity and diversification in populations

    PubMed Central

    Whitacre, James M.; Atamas, Sergei P.

    2013-01-01

    Trait diversity – the substrate for natural selection – is necessary for adaptation through selection, particularly in populations faced with environmental changes that diminish population fitness. In habitats that remain unchanged for many generations, stabilizing selection maximizes exploitation of resources by reducing trait diversity to a narrow optimal range. One might expect that such ostensibly homogeneous populations would have a reduced potential for heritable adaptive responses when faced with fitness-reducing environmental changes. However, field studies have documented populations that, even after long periods of evolutionary stasis, can still rapidly evolve in response to changed environmental conditions. We argue that degeneracy, the ability of diverse population elements to function similarly, can satisfy both the current need to maximize fitness and the future need for diversity. Degenerate ensembles appear functionally redundant in certain environmental contexts and functionally diverse in others. We propose that genetic variation not contributing to the observed range of phenotypes in a current population, also known as cryptic genetic variation (CGV), is a specific case of degeneracy. We argue that CGV, which gradually accumulates in static populations in stable environments, reveals hidden trait differences when environments change. By allowing CGV accumulation, static populations prepare themselves for future rapid adaptations to environmental novelty. A greater appreciation of degeneracy’s role in resolving the inherent tension between current stabilizing selection and future directional selection has implications in conservation biology and may be applied in social and technological systems to maximize current performance while strengthening the potential for future changes. PMID:22910487

  14. Mode-splitting and quasi-degeneracies in circular plate vibration problems: The example of free vibrations of the stator of a traveling wave ultrasonic motor

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwin; Krousgrill, Charles M.

    2012-12-01

    In systems with rotational symmetry, bending modes occur in doubly-degenerate pairs with two independent vibration modes for each repeated natural frequency. In circular plates, the standing waves of two such degenerate bending modes can be superposed with a 1/4 period separation in time to yield a traveling wave response. This is the principle of a traveling wave ultrasonic motor (TWUM), in which a traveling bending wave in a stator drives the rotor through a friction contact. The stator contains teeth to increase the speed at the contact region, and these affect the rotational symmetry of the plate. When systems with rotational symmetry are modified either in their geometry, or by spatially varying their properties or boundary conditions, some mode-pairs split into singlet modes having distinct frequencies. In addition, coupling between some pairs of distinct unperturbed modes also causes quasi-degeneracies in the perturbed modes, which leads their frequency curves to approach and veer away in some regions of the parameter space. This paper discusses the effects of tooth geometry on the behavior of plate modes under free vibration. It investigates mode splitting and quasi-degeneracies and derives analytic expressions to predict these phenomena, using variational methods and a degenerate perturbation scheme for the solution to the plate's discrete eigenvalue problem; these expressions are confirmed by solving the discrete eigenvalue problem of the plate with teeth.

  15. Resolving octant degeneracy at LBL experiment by combining Daya Bay reactor setup

    NASA Astrophysics Data System (ADS)

    Bora, Kalpana; Dutta, Debajyoti

    2014-03-01

    Long baseline Experiment(LBL) have promised to be a very powerful experimental setup to study various issues related to Neutrinos. Some ongoing and planned LBL and medium baseline experiments are- T2K, MINOS, NOvA, LBNE, LBNO etc. But, the long baseline experiments are crippled due to presence of some parameter degeneracies, like the Octant -degeneracy. In this work, we first show the presence of Octant degeneracy in LBL experiments and then combine it with Daya Bay Reactor experiment at different values of CP violation phase. We show that the Octant degeneracy in LBNE can be resolved completely with this proposal.

  16. Broken Symmetry

    ScienceCinema

    None

    2016-07-12

    - Physics, as we know it, attempts to interpret the diverse natural phenomena as particular manifestations of general laws. This vision of a world ruled by general testable laws is relatively recent in the history of mankind. Basically it was initiated by the Galilean inertial principle. The subsequent rapid development of large-scale physics is certainly tributary to the fact that gravitational and electromagnetic forces are long-range and hence can be perceived directly without the mediation of highly sophisticated technical devices. - The discovery of subatomic structures and of the concomitant weak and strong short-range forces raised the question of how to cope with short-range forces in relativistic quantum field theory. The Fermi theory of weak interactions, formulated in terms of point-like current-current interaction, was well-defined in lowest order perturbation theory and accounted for existing experimental data.However, it was inconsistent in higher orders because of uncontrollable divergent quantum fluctuations. In technical terms, in contradistinction to quantum electrodynamics, the Fermi theorywas not “renormalizable”. This difficulty could not be solved by smoothing the point-like interaction by a massive, and therefore short-range, charged “vector” particle exchange: theories with massive charged vector bosons were not renormalizable either. In the early nineteen sixties, there seemed to be insuperable obstacles to formulating a consistent theory with short-range forces mediated by massive vectors. - The breakthrough came from the notion of spontaneous symmetry breaking which arose in the study of phase transitions and was introduced in field theory by Nambu in 1960. - Ferromagnets illustrate the notion in phase transitions. Although no direction is dynamically preferred, the magnetization selects a global orientation. This is a spontaneous broken symmetry(SBS)of rotational invariance. Such continuous SBS imply the existence of

  17. Broken Symmetry

    SciTech Connect

    2011-02-24

    - Physics, as we know it, attempts to interpret the diverse natural phenomena as particular manifestations of general laws. This vision of a world ruled by general testable laws is relatively recent in the history of mankind. Basically it was initiated by the Galilean inertial principle. The subsequent rapid development of large-scale physics is certainly tributary to the fact that gravitational and electromagnetic forces are long-range and hence can be perceived directly without the mediation of highly sophisticated technical devices. - The discovery of subatomic structures and of the concomitant weak and strong short-range forces raised the question of how to cope with short-range forces in relativistic quantum field theory. The Fermi theory of weak interactions, formulated in terms of point-like current-current interaction, was well-defined in lowest order perturbation theory and accounted for existing experimental data.However, it was inconsistent in higher orders because of uncontrollable divergent quantum fluctuations. In technical terms, in contradistinction to quantum electrodynamics, the Fermi theorywas not “renormalizable”. This difficulty could not be solved by smoothing the point-like interaction by a massive, and therefore short-range, charged “vector” particle exchange: theories with massive charged vector bosons were not renormalizable either. In the early nineteen sixties, there seemed to be insuperable obstacles to formulating a consistent theory with short-range forces mediated by massive vectors. - The breakthrough came from the notion of spontaneous symmetry breaking which arose in the study of phase transitions and was introduced in field theory by Nambu in 1960. - Ferromagnets illustrate the notion in phase transitions. Although no direction is dynamically preferred, the magnetization selects a global orientation. This is a spontaneous broken symmetry(SBS)of rotational invariance. Such continuous SBS imply the existence of

  18. Epigenomics and the concept of degeneracy in biological systems

    PubMed Central

    Mason, Paul H.; Barron, Andrew B.

    2014-01-01

    Researchers in the field of epigenomics are developing more nuanced understandings of biological complexity, and exploring the multiple pathways that lead to phenotypic expression. The concept of degeneracy—referring to the multiple pathways that a system recruits to achieve functional plasticity—is an important conceptual accompaniment to the growing body of knowledge in epigenomics. Distinct from degradation, redundancy and dilapidation; degeneracy refers to the plasticity of traits whose function overlaps in some environments, but diverges in others. While a redundant system is composed of repeated identical elements performing the same function, a degenerate system is composed of different elements performing similar or overlapping functions. Here, we describe the degenerate structure of gene regulatory systems from the basic genetic code to flexible epigenomic modifications, and discuss how these structural features have contributed to organism complexity, robustness, plasticity and evolvability. PMID:24335757

  19. Degeneracy measures for the algebraic classification of numerical spacetimes

    SciTech Connect

    Owen, Robert

    2010-06-15

    We study the issue of algebraic classification of the Weyl curvature tensor, with a particular focus on numerical relativity simulations. The spacetimes of interest in this context, binary black hole mergers, and the ringdowns that follow them, present subtleties in that they are generically, strictly speaking, type I, but in many regions approximately, in some sense, type D. To provide meaning to any claims of ''approximate'' Petrov class, one must define a measure of degeneracy on the space of null rays at a point. We will investigate such a measure, used recently to argue that certain binary black hole merger simulations ring down to the Kerr geometry, after hanging up for some time in Petrov type II. In particular, we argue that this hangup in Petrov type II is an artefact of the particular measure being used, and that a geometrically better-motivated measure shows a black hole merger produced by our group settling directly to Petrov type D.

  20. Non-Hermitian Hamiltonians with unitary and antiunitary symmetries

    SciTech Connect

    Fernández, Francisco M. Garcia, Javier

    2014-03-15

    We analyse several non-Hermitian Hamiltonians with antiunitary symmetry from the point of view of their point-group symmetry. It enables us to predict the degeneracy of the energy levels and to reduce the dimension of the matrices necessary for the diagonalization of the Hamiltonian in a given basis set. We can also classify the solutions according to the irreducible representations of the point group and thus analyse their properties separately. One of the main results of this paper is that some PT-symmetric Hamiltonians with point-group symmetry C{sub 2v} exhibit complex eigenvalues for all values of a potential parameter. In such cases the PT phase transition takes place at the trivial Hermitian limit which suggests that the phenomenon is not robust. Point-group symmetry enables us to explain such anomalous behaviour and to choose a suitable antiunitary operator for the PT symmetry. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •PT-symmetric multidimensional oscillators appear to show PT phase transitions. •This transition was conjectured to be a high-energy phenomenon. •We show that point group symmetry is useful for predicting broken PT symmetry in multidimensional oscillators. •PT-symmetric oscillators with C{sub 2v} symmetry exhibit phase transitions at the trivial Hermitian limit.

  1. Nonsymmorphic symmetry-required band crossings in topological semimetals

    NASA Astrophysics Data System (ADS)

    Zhao, Y. X.; Schnyder, Andreas P.

    2016-11-01

    We show that for two-band systems nonsymmorphic symmetries may enforce the existence of band crossings in the bulk, which realize Fermi surfaces of reduced dimensionality. We find that these unavoidable crossings originate from the momentum dependence of the nonsymmorphic symmetry, which puts strong restrictions on the global structure of the band configurations. Three different types of nonsymmorphic symmetries are considered: (i) a unitary nonsymmorphic symmetry, (ii) a nonsymmorphic magnetic symmetry, and (iii) a nonsymmorphic symmetry combined with inversion. For nonsymmorphic symmetries of the latter two types, the band crossings are located at high-symmetry points of the Brillouin zone, with their exact positions being determined by the algebra of the symmetry operators. To characterize these band degeneracies we introduce a global topological charge and show that it is of Z2 type, which is in contrast to the local topological charge of Fermi points in, say, Weyl semimetals. To illustrate these concepts, we discuss the π -flux state as well as the Su-Schrieffer-Heeger model at its critical point and show that these two models fit nicely into our general framework of nonsymmorphic two-band systems.

  2. Cosmological degeneracy versus cosmography: A cosmographic dark energy model

    NASA Astrophysics Data System (ADS)

    Luongo, Orlando; Pisani, Giovanni Battista; Troisi, Antonio

    In this work, we use cosmography to alleviate the degeneracy among cosmological models, proposing a way to parametrize matter and dark energy in terms of cosmokinematics quantities. The recipe of using cosmography allows to expand observable quantities in Taylor series and to directly compare those expansions with data. The strategy involves the expansions of q and j, up to the second-order around a(t) = 1. This includes additional cosmographic parameters which are fixed by current values of q0 and j0. We therefore propose a fully self-consistent parametrization of the total energy density driving the late-time universe speed up. This stratagem does not remove all the degeneracy but enables one to pass from the model-dependent couple of coefficients, ω0 and Ωm,0, to model-independent quantities determined from cosmography. Afterwards, we describe a feasible cosmographic dark energy model, in which matter is fixed whereas dark energy evolves by means of the cosmographic series. Our technique provides robust constraints on cosmokinematic parameters, permitting one to separately bound matter from dark energy densities. Our cosmographic dark energy model turns out to be one parameter only, but differently from the lambda cold dark matter (ΛCDM) paradigm, it does not contain ansatz on the dark energy form. In addition, we even determine the free parameter of our model in suitable 1σ intervals through Monte Carlo analyses based on the Metropolis algorithm. We compare our results with the standard concordance model and we find that our treatment seems to indicate that dark energy slightly evolves in time, reducing to a pure cosmological constant only as z → 0.

  3. Continuous symmetry measures for complex symmetry group.

    PubMed

    Dryzun, Chaim

    2014-04-05

    Symmetry is a fundamental property of nature, used extensively in physics, chemistry, and biology. The Continuous symmetry measures (CSM) is a method for estimating the deviation of a given system from having a certain perfect symmetry, which enables us to formulate quantitative relation between symmetry and other physical properties. Analytical procedures for calculating the CSM of all simple cyclic point groups are available for several years. Here, we present a methodology for calculating the CSM of any complex point group, including the dihedral, tetrahedral, octahedral, and icosahedral symmetry groups. We present the method and analyze its performances and errors. We also introduce an analytical method for calculating the CSM of the linear symmetry groups. As an example, we apply these methods for examining the symmetry of water, the symmetry maps of AB4 complexes, and the symmetry of several Lennard-Jones clusters.

  4. Supersolid formation in a quantum gas breaking a continuous translational symmetry

    NASA Astrophysics Data System (ADS)

    Léonard, Julian; Morales, Andrea; Zupancic, Philip; Esslinger, Tilman; Donner, Tobias

    2017-03-01

    The concept of a supersolid state combines the crystallization of a many-body system with dissipationless flow of the atoms from which it is built. This quantum phase requires the breaking of two continuous symmetries: the phase invariance of a superfluid and the continuous translational invariance to form the crystal. Despite having been proposed for helium almost 50 years ago, experimental verification of supersolidity remains elusive. A variant with only discrete translational symmetry breaking on a preimposed lattice structure—the ‘lattice supersolid’—has been realized, based on self-organization of a Bose–Einstein condensate. However, lattice supersolids do not feature the continuous ground-state degeneracy that characterizes the supersolid state as originally proposed. Here we report the realization of a supersolid with continuous translational symmetry breaking along one direction in a quantum gas. The continuous symmetry that is broken emerges from two discrete spatial symmetries by symmetrically coupling a Bose–Einstein condensate to the modes of two optical cavities. We establish the phase coherence of the supersolid and find a high ground-state degeneracy by measuring the crystal position over many realizations through the light fields that leak from the cavities. These light fields are also used to monitor the position fluctuations in real time. Our concept provides a route to creating and studying glassy many-body systems with controllably lifted ground-state degeneracies, such as supersolids in the presence of disorder.

  5. Degeneracy estimation in interference models on wireless networks

    NASA Astrophysics Data System (ADS)

    McBride, Neal; Bulava, John; Galiotto, Carlo; Marchetti, Nicola; Macaluso, Irene; Doyle, Linda

    2017-03-01

    We present a Monte Carlo study of interference in real-world wireless networks using the Potts model. Our approach maps the Potts energy to discrete interference levels. These levels depend on the configurations of radio frequency allocation in the network. For the first time, we estimate the degeneracy of these interference levels using the Wang-Landau algorithm. The cumulative distribution function of the resulting density of states is found to increase rapidly at a critical interference value. We compare these critical values for several different real-world interference networks and Potts models. Our results show that models with a greater number of available frequency channels and less dense interference networks result in the majority of configurations having lower interference levels. Consequently, their critical interference levels occur at lower values. Furthermore, the area under the density of states increases and shifts to lower interference values. Therefore, the probability of randomly sampling low interference configurations is higher under these conditions. This result can be used to consider dynamic and distributed spectrum allocation in future wireless networks.

  6. Degeneracy, degree, and heavy tails in quantum annealing

    NASA Astrophysics Data System (ADS)

    King, Andrew D.; Hoskinson, Emile; Lanting, Trevor; Andriyash, Evgeny; Amin, Mohammad H.

    2016-05-01

    Both simulated quantum annealing and physical quantum annealing have shown the emergence of "heavy tails" in their performance as optimizers: The total time needed to solve a set of random input instances is dominated by a small number of very hard instances. Classical simulated annealing, in contrast, does not show such heavy tails. Here we explore the origin of these heavy tails, which appear for inputs with high local degeneracy—large isoenergetic clusters of states in Hamming space. This category includes the low-precision Chimera-structured problems studied in recent benchmarking work comparing the D-Wave Two quantum annealing processor with simulated annealing. On similar inputs designed to suppress local degeneracy, performance of a quantum annealing processor on hard instances improves by orders of magnitude at the 512-qubit scale, while classical performance remains relatively unchanged. Simulations indicate that perturbative crossings are the primary factor contributing to these heavy tails, while sensitivity to Hamiltonian misspecification error plays a less significant role in this particular setting.

  7. Another stage of development: Biological degeneracy and the study of bodily ageing.

    PubMed

    Mason, Paul H; Maleszka, Ryszard; Dominguez D, Juan F

    2016-12-21

    Ageing is a poorly understood process of human development mired by a scientific approach that struggles to piece together distributed variable factors involved in ongoing transformations of living systems. Reconfiguring existing research paradigms, we review the concept of 'degeneracy', which has divergent popular and technical definitions. The technical meaning of degeneracy refers to the structural diversity underlying functional plasticity. Degeneracy is a distributed system property that can be observed within individual brains or across different brains. For example, dementias with similar behavioural anomalies can result from a diverse range of cellular "faults", which is an example of degeneracy because the symptoms are similar in spite of different underlying mechanisms. Degeneracy is a valuable epistemological tool that can transformatively enhance scientific models of bodily ageing. We propose that movement science is one of the first areas that can productively integrate degeneracy into models of bodily ageing. We also propose model organisms such as eusocial honey bees in which degeneracy can be studied at the molecular and cellular level. Developing a vocabulary for thinking about how distributed variable factors are interlinked is important if we are to understand bodily ageing not as a single entity, but as the heterogeneous construction of changing biological, social, and environmental processes.

  8. Detecting ground-state degeneracy in many-body systems through qubit decoherence

    NASA Astrophysics Data System (ADS)

    Cui, Hai-Tao; Yi, Xue-Xi

    2017-02-01

    By coupling with a qubit, we demonstrate that qubit decoherence can unambiguously detect the occurrence of ground-state degeneracy in many-body systems. We first demonstrate universality using the two-band model. Consequently, several exemplifications, focused on topological condensed matter systems in one, two, and three dimensions, are presented to validate our proposal. The key point is that qubit decoherence varies significantly when energy bands touch each other at the Fermi surface. In addition, it can partially reflect the degeneracy inside the band. This feature implies that qubit decoherence can be used for reliable diagnosis of ground-state degeneracy.

  9. Lower bounds for the ground-state degeneracies of frustrated systems on fractal lattices

    PubMed

    Curado; Nobre

    2000-12-01

    The total number of ground states for nearest-neighbor-interaction Ising systems with frustrations, defined on hierarchical lattices, is investigated. A simple method is presented, which allows one to factorize the ground-state degeneracy, at a given hierarchy level n, in terms of contributions due to all hierarchy levels. Such a method may yield the exact ground-state degeneracy of uniformly frustrated systems, whereas it works as an approximation for randomly frustrated models. In the latter cases, it is demonstrated that such an approximation yields lower-bound estimates for the ground-state degeneracies.

  10. Symmetry for the nonadiabatic transition in Floquet states

    SciTech Connect

    Hijii, Keigo; Miyashita, Seiji

    2010-01-15

    The frequency of the Rabi oscillation driven by a periodic external field varies with the parameters of the external field, e.g., frequency and amplitude, and it becomes zero at some points of the parameters, which is called coherent destruction of tunneling. This phenomenon is understood as a degeneracy of the Floquet quasienergies as a function of the parameters. We prove that the time-reversal symmetry of the external field is a necessary condition of the degeneracy. We demonstrate the gap opening in the quasienergy spectrum in asymmetrically periodically driven systems. Moreover, an adiabatic transition of the Floquet states is demonstrated and analyzed in the analogy to the Landau-Zener transition.

  11. Linear electronic transport in dense plasmas. II. Finite degeneracy contributions

    NASA Astrophysics Data System (ADS)

    Léger, D.; Deutsch, C.

    1991-06-01

    The formalism described in the first paper in this series is hereafter specialized to a thorough investigation of finite degeneracy contributions to thermoelectronic and mechanical transport coefficients, conveniently expressed as reduced quantities. Temperature corrections are systematically discussed through the analytical properties of the jellium dielectric function. The Thomas-Fermi one appears as a paradigm of regular behavior at q=2k_F while the Lindhard and its T-dependent extension head a singular class characterized by diverging derivatives. Specific methods are developed for these important cases. Results are presented in terms of analytic expansions in the degeneracy parameter α, and exact expressions for the above-mentioned corrections are derived up to order α2. Finally we display a number of numerical results pertaining to fully ionized proton-helium binary mixtures of Astrophysical interest. The connection of the present formalism and its numerical outputs with other previous treatments is also carefully examined. Le formalisme exposé et détaillé dans le premier article de cette série est ici appliqué à la détermination des contributions de dégénérescence partielle aux coefficients de transport thermoélectroniques et mécanique (viscosité), coefficients préalablement exprimés sous forme d'expressions réduites. Les corrections de température finie sont systématiquement analysées en relation avec les propriétés analytiques de la fonction diélectrique du jellium. Alors que celle de Thomas-Fermi fournit l'exemple type de fonction parfaitement régulière en q=2k_F, celle de Lindhard et sa généralisation à T finie sont au contraire caractérisées par des dérivées divergentes en ce point. Des méthodes spécifiques sont développées pour traiter correctement ces cas importants. Nos résultats sont présentés sous forme de développements analytiques en puissance du paramètre de dégénérescence α, et des expressions

  12. Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene

    PubMed Central

    Kim, Youngwook; Park, Jaesung; Song, Intek; Ok, Jong Mok; Jo, Younjung; Watanabe, Kenji; Taniquchi, Takashi; Choi, Hee Cheul; Lee, Dong Su; Jung, Suyong; Kim, Jun Sung

    2016-01-01

    Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states and their transitions due to the interplay of the relative strength of valley, spin and layer polarizations in twisted bilayer graphene. The energy gaps of the broken-symmetry QH states show an electron-hole asymmetric behaviour, and their dependence on the induced displacement field are opposite between even and odd filling factor states. These results strongly suggest that the QH states with broken valley and spin symmetries for individual layer become hybridized via interlayer tunnelling, and the hierarchy of the QH states is sensitive to both magnetic field and displacement field due to charge imbalance between layers. PMID:27905496

  13. Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene

    NASA Astrophysics Data System (ADS)

    Kim, Youngwook; Park, Jaesung; Song, Intek; Ok, Jong Mok; Jo, Younjung; Watanabe, Kenji; Taniquchi, Takashi; Choi, Hee Cheul; Lee, Dong Su; Jung, Suyong; Kim, Jun Sung

    2016-12-01

    Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states and their transitions due to the interplay of the relative strength of valley, spin and layer polarizations in twisted bilayer graphene. The energy gaps of the broken-symmetry QH states show an electron-hole asymmetric behaviour, and their dependence on the induced displacement field are opposite between even and odd filling factor states. These results strongly suggest that the QH states with broken valley and spin symmetries for individual layer become hybridized via interlayer tunnelling, and the hierarchy of the QH states is sensitive to both magnetic field and displacement field due to charge imbalance between layers.

  14. Ground-state degeneracies leave recognizable topological scars in the electronic density.

    PubMed

    Baer, Roi

    2010-02-19

    In Kohn-Sham density functional theory (KS DFT) a fictitious system of noninteracting particles is constructed having the same ground-state (GS) density as the physical system of interest. A fundamental open question in DFT concerns the ability of an exact KS calculation to spot and characterize the GS degeneracies in the physical system. In this Letter we provide theoretical evidence suggesting that the GS density, as a function of position on a 2D manifold of parameters affecting the external potential, is "topologically scarred" in a distinct way by degeneracies. These scars are sufficiently detailed to enable determination of the positions of degeneracies and even the associated Berry phases. We conclude that an exact KS calculation can spot and characterize the degeneracies of the physical system.

  15. Relativistic Pseudospin Symmetry

    SciTech Connect

    Ginocchio, Joseph N.

    2011-05-06

    We show that the pseudospin symmetry that Akito Arima discovered many years ago (with collaborators) is a symmetry of the the Dirac Hamiltonian for which the sum of the scalar and vector potentials are a constant. In this paper we discuss some of the implications of this relativistic symmetry and the experimental data that support these predictions. In his original paper Akito also discussed pseudo-U(3) symmetry. We show that pseudo-U(3) symmetry is a symmetry of the Dirac Hamiltonian for which the sum of harmonic oscillator vector and scalar potentials are equal to a constant, and we give the generators of pseudo-U(3) symmetry. Going beyond the mean field we summarize new results on non relativistic shell model Hamiltonians that have pseudospin symmetry and pseudo-orbital angular momentum symmetry as a dynamical symmetries.

  16. The effect of degeneracy parameter on Weibel instability in dense plasma

    SciTech Connect

    Mahdavi, M.; Khodadadi Azadboni, F.

    2013-12-15

    In this paper, the role of degeneracy parameter, in both directions parallel and perpendicular with propagation direction of the laser beam in plasma, on the growth rate of Weibel instability, is studied. Calculations show that with the temperature anisotropy, β = T{sub ∥}/T{sub ⊥} = 0.2 and a 0.75 times reduction of the degeneracy parameter, the increased rate of the the Weibel instability growth rate is 72%. The degeneracy required for minimal growth rate in interaction laser plasma with a density of 1.2 × 10{sup 32}m{sup −3}, is larger than 3. The reduction of temperature and the degeneracy parameter of plasma in parallel direction will also increase growth rate about 30% more than incrossing degeneracy parameter in transverse direction. With the minimum pressure costs of cold compression, subsequent degeneracy parameters, and the minimum value of electron quiver energy, we can expect growth rate of Weibel instability order 0.01.

  17. Quantification of Degeneracy in Biological Systems for Characterization of Functional Interactions Between Modules

    PubMed Central

    Li, Yao; Dwivedi, Gaurav; Huang, Wen; Yi, Yingfei

    2012-01-01

    There is an evolutionary advantage in having multiple components with overlapping functionality (i.e degeneracy) in organisms. While theoretical considerations of degeneracy have been well established in neural networks using information theory, the same concepts have not been developed for differential systems, which form the basis of many biochemical reaction network descriptions in systems biology. Here we establish mathematical definitions of degeneracy, complexity and robustness that allow for the quantification of these properties in a system. By exciting a dynamical system with noise, the mutual information associated with a selected observable output and the interacting subspaces of input components can be used to define both complexity and degeneracy. The calculation of degeneracy in a biological network is a useful metric for evaluating features such as the sensitivity of a biological network to environmental evolutionary pressure. Using a two-receptor signal transduction network, we find that redundant components will not yield high degeneracy whereas compensatory mechanisms established by pathway crosstalk will. This form of analysis permits interrogation of large-scale differential systems for non-identical, functionally equivalent features that have evolved to maintain homeostasis during disruption of individual components. PMID:22619750

  18. Dynamic symmetries and quantum nonadiabatic transitions

    SciTech Connect

    Li, Fuxiang; Sinitsyn, Nikolai A.

    2016-05-30

    Kramers degeneracy theorem is one of the basic results in quantum mechanics. According to it, the time-reversal symmetry makes each energy level of a half-integer spin system at least doubly degenerate, meaning the absence of transitions or scatterings between degenerate states if the Hamiltonian does not depend on time explicitly. Here we generalize this result to the case of explicitly time-dependent spin Hamiltonians. We prove that for a spin system with the total spin being a half integer, if its Hamiltonian and the evolution time interval are symmetric under a specifically defined time reversal operation, the scattering amplitude between an arbitrary initial state and its time reversed counterpart is exactly zero. Lastly, we also discuss applications of this result to the multistate Landau–Zener (LZ) theory.

  19. Dynamic symmetries and quantum nonadiabatic transitions

    DOE PAGES

    Li, Fuxiang; Sinitsyn, Nikolai A.

    2016-05-30

    Kramers degeneracy theorem is one of the basic results in quantum mechanics. According to it, the time-reversal symmetry makes each energy level of a half-integer spin system at least doubly degenerate, meaning the absence of transitions or scatterings between degenerate states if the Hamiltonian does not depend on time explicitly. Here we generalize this result to the case of explicitly time-dependent spin Hamiltonians. We prove that for a spin system with the total spin being a half integer, if its Hamiltonian and the evolution time interval are symmetric under a specifically defined time reversal operation, the scattering amplitude between anmore » arbitrary initial state and its time reversed counterpart is exactly zero. Lastly, we also discuss applications of this result to the multistate Landau–Zener (LZ) theory.« less

  20. Dynamic symmetries and quantum nonadiabatic transitions

    NASA Astrophysics Data System (ADS)

    Li, Fuxiang; Sinitsyn, Nikolai A.

    2016-12-01

    Kramers degeneracy theorem is one of the basic results in quantum mechanics. According to it, the time-reversal symmetry makes each energy level of a half-integer spin system at least doubly degenerate, meaning the absence of transitions or scatterings between degenerate states if the Hamiltonian does not depend on time explicitly. We generalize this result to the case of explicitly time-dependent spin Hamiltonians. We prove that for a spin system with the total spin being a half integer, if its Hamiltonian and the evolution time interval are symmetric under a specifically defined time reversal operation, the scattering amplitude between an arbitrary initial state and its time reversed counterpart is exactly zero. We also discuss applications of this result to the multistate Landau-Zener (LZ) theory.

  1. Chemical potential and reaction electronic flux in symmetry controlled reactions.

    PubMed

    Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

    2016-07-15

    In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc.

  2. A new method to break the mass-sheet degeneracy using aperture moments

    NASA Astrophysics Data System (ADS)

    Rexroth, Markus; Natarajan, Priyamvada; Kneib, Jean-Paul

    2016-08-01

    Mass determinations from gravitational lensing shear and the higher order estimator flexion are both subject to the mass-sheet degeneracy. Mass sheet degeneracy refers to a transformation that leaves the reduced shear and flexion invariant. In general, this transformation can be approximated by the addition of a constant surface mass density sheet. We propose a new technique to break the mass-sheet degeneracy. The method uses mass moments of the shear or flexion fields in combination with convergence information derived from number counts which exploit the magnification bias. The difference between the measured mass moments provides an estimator for the magnitude of the additive constant that is the mass sheet. For demonstrating this, we derive relations that hold true in general for nth order moments and show how they can be employed effectively to break the degeneracy. We investigate the detectability of this degeneracy parameter from our method and find that the degeneracy parameter can be feasibly determined from stacked galaxy-galaxy lensing data and cluster lensing data. Furthermore, we compare the signal-to-noise ratios of convergence information from number counts with shear and flexion for singular isothermal sphere and Navarro-Frenk-White models. We find that the combination of shear and flexion performs best on galaxy and cluster scales and the convergence information can therefore be used to break the mass-sheet degeneracy without quality loss in the mass reconstruction. In summary, there is power in the combination of shear, flexion, convergence and their higher order moments. With the anticipated wealth of lensing data from upcoming and future satellite missions - EUCLID and WFIRST - this technique will be feasible.

  3. Symmetries in Physics

    NASA Astrophysics Data System (ADS)

    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.

  4. Approximate flavor symmetries

    SciTech Connect

    Rasin, A.

    1994-04-01

    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.

  5. Neurobiological degeneracy: A key property for functional adaptations of perception and action to constraints.

    PubMed

    Seifert, Ludovic; Komar, John; Araújo, Duarte; Davids, Keith

    2016-10-01

    A crucial aspect of understanding human behavior relates to how perception and action sub-systems are integrated during coordinated and controlled movement in goal-directed activity. Here we discuss how a neurobiological system property, degeneracy (i.e., many coordinative structures to achieve one function), can help us understand how skilled individuals functionally adapt perception and action to interacting constraints during performance. Since most research investigating degeneracy has been conducted in neuroanatomy, genetics and theoretical neurobiology, here we clarify how degeneracy is exhibited in perceptual-motor systems. Using an ecological dynamics framework, we highlight how degeneracy underpins the functional role of movement coordination variability in performance of multi-articular tasks. Following that, we discuss how degenerate neurobiological systems are able to exploit system stability and flexibility in their movement coordination. Third, we show how better coupling of information and movement could lead individuals to explore functionally degenerate behaviors. Last, we explore how degeneracy can support pluri-potentiality (i.e., one coordinative structure for many perceptual-motor functions) as a way toward innovation or refinement in performance.

  6. Neutrinos and flavor symmetries

    SciTech Connect

    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.

  7. Polynomial Graphs and Symmetry

    ERIC Educational Resources Information Center

    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…

  8. Chiral symmetry and chiral-symmetry breaking

    SciTech Connect

    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)

  9. Symmetry operation measures.

    PubMed

    Pinsky, Mark; Casanova, David; Alemany, Pere; Alvarez, Santiago; Avnir, David; Dryzun, Chaim; Kizner, Ziv; Sterkin, Alexander

    2008-01-30

    We introduce a new mathematical tool for quantifying the symmetry contents of molecular structures: the Symmetry Operation Measures. In this approach, we measure the minimal distance between a given structure and the structure which is obtained after applying a selected symmetry operation on it. If the given operation is a true symmetry operation for the structure, this distance is zero; otherwise it gives an indication of how different the transformed structure is from the original one. Specifically, we provide analytical solutions for measures of all the improper rotations, S n p, including mirror symmetry and inversion, as well as for all pure rotations, C n p. These measures provide information complementary to the Continuous Symmetry Measures (CSM) that evaluate the distance between a given structure and the nearest structure which belongs to a selected symmetry point-group.

  10. Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path toward Breaking Strong Microlens Degeneracies

    NASA Astrophysics Data System (ADS)

    Bozza, V.; Shvartzvald, Y.; Udalski, A.; Calchi Novati, S.; Bond, I. A.; Han, C.; Hundertmark, M.; Poleski, R.; Pawlak, M.; Szymański, M. K.; Skowron, J.; Mróz, P.; Kozłowski, S.; Wyrzykowski, Ł.; Pietrukowicz, P.; Soszyński, I.; Ulaczyk, K.; OGLE Group; and; Beichman, C.; Bryden, G.; Carey, S.; Fausnaugh, M.; Gaudi, B. S.; Gould, A.; Henderson, C. B.; Pogge, R. W.; Wibking, B.; Yee, J. C.; Zhu, W.; Spitzer Team; Abe, F.; Asakura, Y.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Freeman, M.; Fukui, A.; Hirao, Y.; Inayama, K.; Itow, Y.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Nishioka, T.; Ohnishi, K.; Oyokawa, H.; Rattenbury, N.; Saito, To.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Wakiyama, Y.; Yonehara, A.; MOA Group; Choi, J.-Y.; Park, H.; Jung, Y. K.; Shin, I.-G.; Albrow, M. D.; Park, B.-G.; Kim, S.-L.; Lee, C.-U.; Cha, S.-M.; Kim, D.-J.; Lee, Y.; KMTNet Group; Dominik, M.; Jørgensen, U. G.; Andersen, M. I.; Bramich, D. M.; Burgdorf, M. J.; Ciceri, S.; D'Ago, G.; Evans, D. F.; Figuera Jaimes, R.; Gu, S.-H.; Hinse, T. C.; Kains, N.; Kerins, E.; Korhonen, H.; Kuffmeier, M.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Rasmussen, R. T.; Scarpetta, G.; Skottfelt, J.; Snodgrass, C.; Southworth, J.; Surdej, J.; Unda-Sanzana, E.; von Essen, C.; Wang, Y.-B.; Wertz, O.; MiNDSTEp; Maoz, D.; Friedmann, M.; Kaspi, S.; Wise Group

    2016-03-01

    Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations.

  11. Conformal symmetry and light flavor baryon spectra

    NASA Astrophysics Data System (ADS)

    Kirchbach, M.; Compean, C. B.

    2010-08-01

    The degeneracy among parity pairs systematically observed in the N and Δ spectra is interpreted to hint on a possible conformal symmetry realization in the light flavor baryon sector in line with AdS5/CFT4. The case is made by showing that all the observed N and Δ resonances with masses below 2500 MeV distribute fairly well each over the first levels of a unitary representation of the conformal group, a representation that covers the spectrum of a quark-diquark system, placed directly on a conformally compactified Minkowski spacetime, R1⊗S3, as approached from the AdS5 cone. The free geodesic motion on the S3 manifold is described by means of the scalar conformal equation there, which is of the Klein-Gordon-type. The equation is then gauged by the curved Coulomb potential that has the form of a cotangent function. Conformal symmetry is not exact, this because the gauge potential slightly modifies the conformal centrifugal barrier of the free geodesic motion. Thanks to this, the degeneracy between P11-S11 pairs from same level is relaxed, while the remaining states belonging to same level remain practically degenerate. The model describes the correct mass ordering in the P11-S11 pairs through the spectra as a combined effect of the above conformal symmetry breaking, on the one side, and a parity change of the diquark from a scalar at low masses, to a pseudoscalar at higher masses, on the other. The quality of the wave functions is illustrated by calculations of realistic mean square charge radii and electric charge form factors on the examples of the proton, and the protonic P11(1440), and S11(1535) resonances. The scheme also allows for a prediction of the dressing function of an effective instantaneous gluon propagator from the Fourier transform of the gauge potential. We find a dressing function that is finite in the infrared and tends to zero at infinity.

  12. All Majorana Models with Translation Symmetry are Supersymmetric

    NASA Astrophysics Data System (ADS)

    Hsieh, Timothy H.; Halász, Gábor B.; Grover, Tarun

    2016-10-01

    We establish results similar to Kramers and Lieb-Schultz-Mattis theorems but involving only translation symmetry and for Majorana modes. In particular, we show that all states are at least doubly degenerate in any one- and two-dimensional array of Majorana modes with translation symmetry, periodic boundary conditions, and an odd number of modes per unit cell. Moreover, we show that all such systems have an underlying N =2 supersymmetry and explicitly construct the generator of the supersymmetry. Furthermore, we establish that there cannot be a unique gapped ground state in such one-dimensional systems with antiperiodic boundary conditions. These general results are fundamentally a consequence of the fact that translations for Majorana modes are represented projectively, which in turn stems from the anomalous nature of a single Majorana mode. An experimental signature of the degeneracy arising from supersymmetry is a zero-bias peak in tunneling conductance.

  13. Island of Rare Earth Nuclei with Tetrahedral and Octahedral Symmetries: Possible Experimental Evidence

    SciTech Connect

    Dudek, J.; Dubray, N.; Pangon, V.; Dobaczewski, J.; Olbratowski, P.; Schunck, N.

    2006-08-18

    Calculations using realistic mean-field methods suggest the existence of nuclear shapes with tetrahedral T{sub d} and/or octahedral O{sub h} symmetries sometimes at only a few hundreds of keV above the ground states in some rare earth nuclei around {sup 156}Gd and {sup 160}Yb. The underlying single-particle spectra manifest exotic fourfold rather than Kramers's twofold degeneracies. The associated shell gaps are very strong, leading to a new form of shape coexistence in many rare earth nuclei. We present possible experimental evidence of the new symmetries based on the published experimental results--although an unambiguous confirmation will require dedicated experiments.

  14. Quantization due to breaking the commutativity of symmetries. Wobbling oscillator and anharmonic Penning trap

    NASA Astrophysics Data System (ADS)

    Karasev, M. V.

    2016-10-01

    We discuss two examples of classical mechanical systems which can become quantum either because of degeneracy of an integral of motion or because of tuning parameters at resonance. In both examples, the commutativity of the symmetry algebra is breaking, and noncommutative symmetries arise. Over the new noncommutative algebra, the system can reveal its quantum behavior including the tunneling effect. The important role is played by the creation-annihilation regime for the perturbation or anharmonism. Activation of this regime sometimes needs in an additional resonance deformation (Cartan subalgebra breaking).

  15. Topological semimetals protected by off-centered symmetries in nonsymmorphic crystals

    NASA Astrophysics Data System (ADS)

    Yang, Bohm-Jung; Bojesen, Troels Arnfred; Morimoto, Takahiro; Furusaki, Akira

    2017-02-01

    Topological semimetals have energy bands near the Fermi energy sticking together at isolated points/lines/planes in the momentum space, which are often accompanied by stable surface states and intriguing bulk topological responses. Although it has been known that certain crystalline symmetries play an important role in protecting band degeneracy, a general recipe for stabilizing the degeneracy, especially in the presence of spin-orbit coupling, is still lacking. Here we show that a class of novel topological semimetals with point/line nodes can emerge in the presence of an off-centered rotation/mirror symmetry whose symmetry line/plane is displaced from the center of other symmorphic symmetries in nonsymmorphic crystals. Due to the partial translation perpendicular to the rotation axis/mirror plane, an off-centered rotation/mirror symmetry always forces two energy bands to stick together and form a doublet pair in the relevant invariant line/plane in momentum space. Such a doublet pair provides a basic building block for emerging topological semimetals with point/line nodes in systems with strong spin-orbit coupling.

  16. From physical symmetries to emergent gauge symmetries

    NASA Astrophysics Data System (ADS)

    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.

  17. On the dynamical and geometrical symmetries of Keplerian motion

    NASA Astrophysics Data System (ADS)

    Wulfman, Carl E.

    2009-05-01

    The dynamical symmetries of classical, relativistic and quantum-mechanical Kepler systems are considered to arise from geometric symmetries in PQET phase space. To establish their interconnection, the symmetries are related with the aid of a Lie-algebraic extension of Dirac's correspondence principle, a canonical transformation containing a Cunningham-Bateman inversion, and a classical limit involving a preliminary canonical transformation in ET space. The Lie-algebraic extension establishes the conditions under which the uncertainty principle allows the local dynamical symmetry of a quantum-mechanical system to be the same as the geometrical phase-space symmetry of its classical counterpart. The canonical transformation converts Poincaré-invariant free-particle systems into ISO(3,1) invariant relativistic systems whose classical limit produces Keplerian systems. Locally Cartesian relativistic PQET coordinates are converted into a set of eight conjugate position and momentum coordinates whose classical limit contains Fock projective momentum coordinates and the components of Runge-Lenz vectors. The coordinate systems developed via the transformations are those in which the evolution and degeneracy groups of the classical system are generated by Poisson-bracket operators that produce ordinary rotation, translation and hyperbolic motions in phase space. The way in which these define classical Keplerian symmetries and symmetry coordinates is detailed. It is shown that for each value of the energy of a Keplerian system, the Poisson-bracket operators determine two invariant functions of positions and momenta, which together with its regularized Hamiltonian, define the manifold in six-dimensional phase space upon which motions evolve.

  18. Symmetries in Lagrangian Dynamics

    ERIC Educational Resources Information Center

    Ferrario, Carlo; Passerini, Arianna

    2007-01-01

    In the framework of Noether's theorem, a distinction between Lagrangian and dynamical symmetries is made, in order to clarify some aspects neglected by textbooks. An intuitive setting of the concept of invariance of differential equations is presented. The analysis is completed by deriving the symmetry properties in the motion of a charged…

  19. Symmetry and Interculturality

    ERIC Educational Resources Information Center

    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.

  20. Tensor network decompositions in the presence of a global symmetry

    SciTech Connect

    Singh, Sukhwinder; Pfeifer, Robert N. C.; Vidal, Guifre

    2010-11-15

    Tensor network decompositions offer an efficient description of certain many-body states of a lattice system and are the basis of a wealth of numerical simulation algorithms. We discuss how to incorporate a global symmetry, given by a compact, completely reducible group G, in tensor network decompositions and algorithms. This is achieved by considering tensors that are invariant under the action of the group G. Each symmetric tensor decomposes into two types of tensors: degeneracy tensors, containing all the degrees of freedom, and structural tensors, which only depend on the symmetry group. In numerical calculations, the use of symmetric tensors ensures the preservation of the symmetry, allows selection of a specific symmetry sector, and significantly reduces computational costs. On the other hand, the resulting tensor network can be interpreted as a superposition of exponentially many spin networks. Spin networks are used extensively in loop quantum gravity, where they represent states of quantum geometry. Our work highlights their importance in the context of tensor network algorithms as well, thus setting the stage for cross-fertilization between these two areas of research.

  1. SPIN-PRECESSION: BREAKING THE BLACK HOLE-NEUTRON STAR DEGENERACY

    SciTech Connect

    Chatziioannou, Katerina; Cornish, Neil; Klein, Antoine; Yunes, Nicolás

    2015-01-01

    Mergers of compact stellar remnants are prime targets for the LIGO/Virgo gravitational wave detectors. The gravitational wave signals from these merger events can be used to study the mass and spin distribution of stellar remnants, and provide information about black hole horizons and the material properties of neutron stars. However, it has been suggested that degeneracies in the way that the star's mass and spin are imprinted in the waveforms may make it impossible to distinguish between black holes and neutron stars. Here we show that the precession of the orbital plane due to spin-orbit coupling breaks the mass-spin degeneracy, and allows us to distinguish between standard neutron stars and alternative possibilities, such as black holes or exotic neutron stars with large masses and spins.

  2. Exceptional point and degeneracy of the neutral Higgs boson system H-A

    SciTech Connect

    Felix-Beltran, O.; Gomez-Bock, M.; Hernandez, E.; Mondragon, A.; Mondragon, M.

    2009-04-20

    We analyze the masses and mixings of the isolated neutral and heavy Higgs fields H and A of the Minimal Supersymmetric Standard Model (MSSM) with CP violation, which have opposite CP parities and nearly degenerate masses. At the degeneracy point, the hypersurfaces that represent the physical masses as functions of the system parameters have a rank one algebraic branch point, and the real and imaginary parts have branch cuts, both starting at the same exceptional point but extending in opposite directions in parameter space. Associated with this singularity, the propagator for the mixed neutral Higgs system H-A has a double pole in the non-physical sheet of the squared energy complex plane s. The continuity of the transition amplitude matrix at the exact degeneracy of the masses is examined.

  3. More about the doubling degeneracy operators associated with Majorana fermions and Yang-Baxter equation

    PubMed Central

    Yu, Li-Wei; Ge, Mo-Lin

    2015-01-01

    A new realization of doubling degeneracy based on emergent Majorana operator Γ presented by Lee-Wilczek has been made. The Hamiltonian can be obtained through the new type of solution of Yang-Baxter equation, i.e. -matrix. For 2-body interaction, gives the “superconducting” chain that is the same as 1D Kitaev chain model. The 3-body Hamiltonian commuting with Γ is derived by 3-body -matrix, we thus show that the essence of the doubling degeneracy is due to . We also show that the extended Γ′-operator is an invariant of braid group BN for odd N. Moreover, with the extended Γ′-operator, we construct the high dimensional matrix representation of solution to Yang-Baxter equation and find its application in constructing 2N-qubit Greenberger-Horne-Zeilinger state for odd N. PMID:25631987

  4. Split of Chiral Degeneracy in Mechanical and Structural Properties of Oligopeptide-Polysaccharide Biomaterials

    SciTech Connect

    Taraban, Marc B.; Hyland, Laura L.; Yu, Y. Bruce

    2013-09-23

    Enantiomeric biomaterials which are mirror images of each other are characterized by chiral degeneracy—identical structural characteristics and bulk material properties. The addition of another chiral component, d-polysaccharide, has been shown to split such degeneracy and result in two distinct biomaterials. Dynamic oscillatory rheometry and small-angle X-ray scattering demonstrate that the natural biochirality combination of l-peptides and d-polysaccharides assembles faster, has higher elastic moduli (G'), and is structurally more beneficial as opposed to the alternative d-peptide and d-polysaccharide combination. Chemical modifications of the OH-groups in α-d-glucose units in d-polysaccharides weaken such splitting of chiral degeneracy. These findings form a basis to design novel biomaterials and provide additional insight on why proteins and polysaccharides have oppoiste chirality in the biological world.

  5. More about the doubling degeneracy operators associated with Majorana fermions and Yang-Baxter equation

    NASA Astrophysics Data System (ADS)

    Yu, Li-Wei; Ge, Mo-Lin

    2015-01-01

    A new realization of doubling degeneracy based on emergent Majorana operator Γ presented by Lee-Wilczek has been made. The Hamiltonian can be obtained through the new type of solution of Yang-Baxter equation, i.e. -matrix. For 2-body interaction, gives the ``superconducting'' chain that is the same as 1D Kitaev chain model. The 3-body Hamiltonian commuting with Γ is derived by 3-body -matrix, we thus show that the essence of the doubling degeneracy is due to . We also show that the extended Γ'-operator is an invariant of braid group BN for odd N. Moreover, with the extended Γ'-operator, we construct the high dimensional matrix representation of solution to Yang-Baxter equation and find its application in constructing 2N-qubit Greenberger-Horne-Zeilinger state for odd N.

  6. Vortex degeneracy lifting and Aharonov-Bohm-like interference in deformed photonic graphene.

    PubMed

    Zhang, Peng; Gallardo, Daniel; Liu, Sheng; Gao, Yuanmei; Li, Tongcang; Wang, Yuan; Chen, Zhigang; Zhang, Xiang

    2017-03-01

    Photonic graphene, a honeycomb lattice of evanescently coupled waveguides, has provided a superior platform for investigating a host of fundamental phenomena such as unconventional edge states, synthetic magnetic fields, photonic Landau levels, Floquet topological insulators, and pseudospin effects. Here, we demonstrate both experimentally and numerically, topological vortex degeneracy lifting and Aharonov-Bohm-like interference from local deformation in a photonic honeycomb lattice. When a single valley is excited, lattice deformation leads to the generation of a vortex pair due to the lifting of degeneracy associated with pseudospin states. In the case of double-valley excitation, we observe the Aharonov-Bohm-like interference merely due to the deformation of the graphene lattice, which gives rise to an artificial gauge field. Our results may provide insight into the understanding of similar phenomena in other graphene-like materials and structures.

  7. Large enhancement in thermoelectric efficiency of quantum dot junctions due to increase of level degeneracy

    NASA Astrophysics Data System (ADS)

    Kuo, David M. T.; Chen, Chih-Chieh; Chang, Yia-Chung

    2017-02-01

    It is theoretically demonstrated that the figure of merit (Z T ) of quantum dot (QD) junctions can be significantly enhanced when the degree of degeneracy of the energy levels involved in electron transport is increased. The theory is based on the the Green-function approach in the Coulomb blockade regime by including all correlation functions resulting from electron-electron interactions associated with the degenerate levels (L ). We found that electrical conductance (Ge) as well as electron thermal conductance (κe) are highly dependent on the level degeneracy (L ), whereas the Seebeck coefficient (S ) is not. Therefore, the large enhancement of Z T is mainly attributed to the increase of Ge when the phonon thermal conductance (κp h) dominates the heat transport of the QD junction system. In the serially coupled double-QD case, we also obtain a large enhancement of Z T arising from higher L . Unlike Ge and κe, S is found almost independent on electron interdot hopping strength.

  8. Vacuum degeneracy of a circuit QED system in the ultrastrong coupling regime.

    PubMed

    Nataf, Pierre; Ciuti, Cristiano

    2010-01-15

    We investigate theoretically the quantum vacuum properties of a chain of N superconducting Josephson atoms inductively coupled to a transmission line resonator. We derive the quantum field Hamiltonian for such a circuit QED system, showing that, due to the type and strength of the interaction, a quantum phase transition can occur with a twice degenerate quantum vacuum above a critical coupling. In the finite-size case, the degeneracy is lifted, with an energy splitting decreasing exponentially with increasing values of g{2}N{2}, where g is the dimensionless vacuum Rabi coupling per artificial atom. We determine analytically the ultrastrong coupling asymptotic expression of the two degenerate vacua for an arbitrary number of artificial atoms and of resonator modes. In the ultrastrong coupling regime the degeneracy is protected with respect to random fluctuations of the transition energies of the Josephson elements.

  9. Degeneracy between the dark components resulting from the fact that gravity only measures the total energy-momentum tensor

    SciTech Connect

    Kunz, Martin

    2009-12-15

    Gravity probes only the total energy-momentum tensor, which leads to a perfect degeneracy for generalized dark energy models. Because of this degeneracy, {omega}{sub m} cannot be measured. We demonstrate this explicitly by showing that the combination of cosmic microwave background and supernova data is compatible with very large and very small values of {omega}{sub m} for a specific family of dark energy models. We also show that for the same reason interacting dark energy is always equivalent to a family of noninteracting models. We argue that it is better to face this degeneracy and to parametrize the actual observables.

  10. Transition from {gamma}-rigid to {gamma}-soft dynamics in the interacting boson model: Quasicriticality and quasidynamical symmetry

    SciTech Connect

    Macek, Michal; Cejnar, Pavel; Dobes, Jan

    2009-07-15

    We study the transition from the {gamma}-rigid to {gamma}-soft collective nuclear dynamics across the Casten triangle of the interacting boson model using mean-field techniques and confront the description with the exact diagonalization. We inspect the domain of validity of the SU(3) quasidynamical symmetry inside the Casten triangle and reveal critical behavior within the low-lying excited spectrum due to a degeneracy of {beta} and {gamma} vibrations.

  11. Halogenated benzene radical cations and ground state degeneracy splitting by asymmetric substitution

    USGS Publications Warehouse

    Bondybey, V.E.; Vaughn, C.R.; Miller, T.A.; English, J.H.; Shiley, R.H.

    1981-01-01

    The absorption and laser induced fluorescence of several halogenated benzene radical cations were studied in solid Ne matrices. The spectra of 1,2,4-trifluorobenzene, l,3-dichloro-5-fluorobenzene, and l-chloro-3,5- difluorobenzene radical cations are observed and analyzed. Studies of fluorescence polarization and a photoselection technique were used to examine the splitting of the degeneracy of the benzene cation ground state by asymmetric subsitution. ?? 1981 American Institute of Physics.

  12. Equation of state of the relativistic free electron gas at arbitrary degeneracy

    NASA Astrophysics Data System (ADS)

    Faussurier, Gérald

    2016-12-01

    We study the problem of the relativistic free electron gas at arbitrary degeneracy. The specific heat at constant volume and particle number CV and the specific heat at constant pressure and particle number CP are calculated. The question of equation of state is also studied. Non degenerate and degenerate limits are considered. We generalize the formulas obtained in the non-relativistic and ultra-relativistic regimes.

  13. Degeneracy between primordial tensor modes and cosmic strings in future CMB data from the Planck satellite

    SciTech Connect

    Urrestilla, Jon; Mukherjee, Pia; Liddle, Andrew R.; Hindmarsh, Mark; Kunz, Martin; Bevis, Neil

    2008-06-15

    While observations indicate that the predominant source of cosmic inhomogeneities are adiabatic perturbations, there are a variety of candidates to provide auxiliary trace effects, including inflation-generated primordial tensors and cosmic defects which both produce B-mode cosmic microwave background polarization. We investigate whether future experiments may suffer confusion as to the true origin of such effects, focusing on the ability of Planck to distinguish tensors from cosmic strings, and show that there is no significant degeneracy.

  14. A universal symmetry detection algorithm.

    PubMed

    Maurer, Peter M

    2015-01-01

    Research on symmetry detection focuses on identifying and detecting new types of symmetry. The paper presents an algorithm that is capable of detecting any type of permutation-based symmetry, including many types for which there are no existing algorithms. General symmetry detection is library-based, but symmetries that can be parameterized, (i.e. total, partial, rotational, and dihedral symmetry), can be detected without using libraries. In many cases it is faster than existing techniques. Furthermore, it is simpler than most existing techniques, and can easily be incorporated into existing software. The algorithm can also be used with virtually any type of matrix-based symmetry, including conjugate symmetry.

  15. Dynamical symmetries for fermions

    SciTech Connect

    Guidry, M.

    1989-01-01

    An introduction is given to the Fermion Dynamical Symmetry Model (FDSM). The analytical symmetry limits of the model are then applied to the calculation of physical quantities such as ground-state masses and B(E{sub 2}) values in heavy nuclei. These comparisons with data provide strong support for a new principle of collective motion, the Dynamical Pauli Effect, and suggest that dynamical symmetries which properly account for the pauli principle are much more persistent in nuclear structure than the corresponding boson symmetries. Finally, we present an assessment of criticisms which have been voiced concerning the FDSM, and a discussion of new phenomena and exotic spectroscopy'' which may be suggested by the model. 14 refs., 8 figs., 4 tabs.

  16. Dynamical spacetime symmetry

    NASA Astrophysics Data System (ADS)

    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.

  17. Gauge symmetry from decoupling

    NASA Astrophysics Data System (ADS)

    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.

  18. The Symmetries of QCD

    ScienceCinema

    Sekhar Chivukula

    2016-07-12

    The symmetries of a quantum field theory can be realized in a variety of ways. Symmetries can be realized explicitly, approximately, through spontaneous symmetry breaking or, via an anomaly, quantum effects can dynamically eliminate a symmetry of the theory that was present at the classical level.  Quantum Chromodynamics (QCD), the modern theory of the strong interactions, exemplify each of these possibilities. The interplay of these effects determine the spectrum of particles that we observe and, ultimately, account for 99% of the mass of ordinary matter. 

  19. Animal Gaits and Symmetry

    NASA Astrophysics Data System (ADS)

    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.

  20. Quantum Spectral Symmetries

    NASA Astrophysics Data System (ADS)

    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.

  1. The nuclear symmetry energy

    NASA Astrophysics Data System (ADS)

    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.

  2. Pseudospin symmetry for modified Rosen-Morse potential including a Pekeris-type approximation to the pseudo-centrifugal term

    NASA Astrophysics Data System (ADS)

    Wei, Gao-Feng; Dong, Shi-Hai

    2010-11-01

    By applying a Pekeris-type approximation to the pseudo-centrifugal term, we study the pseudospin symmetry of a Dirac nucleon subjected to scalar and vector modified Rosen-Morse (MRM) potentials. A complicated quartic energy equation and spinor wave functions with arbitrary spin-orbit coupling quantum number k are presented. The pseudospin degeneracy is checked numerically. Pseudospin symmetry is discussed theoretically and numerically in the limit case α rightarrow 0 . It is found that the relativistic MRM potential cannot trap a Dirac nucleon in this limit.

  3. Symmetry and electronic structure of noble-metal nanoparticles and the role of relativity.

    PubMed

    Häkkinen, Hannu; Moseler, Michael; Kostko, Oleg; Morgner, Nina; Hoffmann, Margarita Astruc; von Issendorff, Bernd

    2004-08-27

    We present high resolution UV-photoelectron spectra of cold mass selected Cun-, Agn-, and Aun- with n=53-58. The observed electron density of states is not the expected simple electron shell structure, but is strongly influenced by electron-lattice interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a direct consequence of their icosahedral symmetry, as is confirmed by density functional theory calculations. Neighboring sizes exhibit perturbed electronic structures, as they are formed by removal or addition of atoms to the icosahedron and therefore have lower symmetries. Gold clusters in the same size range show completely different spectra with almost no degeneracy, which indicates that they have structures of much lower symmetry. This behavior is related to strong relativistic bonding effects in gold, as demonstrated by ab initio calculations for Au55-.

  4. Two-particle bosonic-fermionic quantum walk via integrated photonics.

    PubMed

    Sansoni, Linda; Sciarrino, Fabio; Vallone, Giuseppe; Mataloni, Paolo; Crespi, Andrea; Ramponi, Roberta; Osellame, Roberto

    2012-01-06

    Quantum walk represents one of the most promising resources for the simulation of physical quantum systems, and has also emerged as an alternative to the standard circuit model for quantum computing. Here we investigate how the particle statistics, either bosonic or fermionic, influences a two-particle discrete quantum walk. Such an experiment has been realized by exploiting polarization entanglement to simulate the bunching-antibunching feature of noninteracting bosons and fermions. To this scope a novel three-dimensional geometry for the waveguide circuit is introduced, which allows accurate polarization independent behavior, maintaining remarkable control on both phase and balancement.

  5. Transport in thin insulating films close to the Boson-Fermion Crossover

    NASA Astrophysics Data System (ADS)

    Joy, J. C.; Zhang, X.; Hollen, S. M.; Zhao, C.; Fernandes, G.; Xu, J. M.; Valles, J. M., Jr.

    2015-03-01

    In two-dimensional systems, sufficient levels of disorder are known to localize Cooper Pairs into a phase incoherent insulating state. While many theoretical and experimental works have shown this state's existence, its ubiquity close to the disorder tuned Superconductor to Insulator transition is still an open problem. Recent experiments on nanopatterned Pb0.9Bi0.1 films have suggested a crossover from Bosonic to Fermionic transport deep in the insulating phase, indicating that the Cooper Pair Insulator (CPI) only persists to a finite level of microscopic disorder. The normal state resistance at which this crossover occurs is governed by the extent coupling constant inhomogeneities on the scale of the coherence length, which allow the formation of locally phase coherent superconducting islands in the insulating state. By tuning the scale of these inhomogeneities and examining the extent of the CPI state, we argue that the disorder tuned Superconductor to Insulator transition proceeds via pair breaking and Anderson localization of fermions when the level spacing in the islands approaches the size of the mean field gap. This work was supported by the NSF through grants No. DMR-1307290 and DMR-0907357 and by the AFRL, the ONR, and the AFOSR. Currently at the Center for Emergent Materials, Ohio State University.

  6. Tunneling into quantum wires: Regularization of the tunneling Hamiltonian and consistency between free and bosonized fermions

    NASA Astrophysics Data System (ADS)

    Filippone, Michele; Brouwer, Piet W.

    2016-12-01

    Tunneling between a point contact and a one-dimensional wire is usually described with the help of a tunneling Hamiltonian that contains a δ function in position space. Whereas the leading-order contribution to the tunneling current is independent of the way this δ function is regularized, higher-order corrections with respect to the tunneling amplitude are known to depend on the regularization. Instead of regularizing the δ function in the tunneling Hamiltonian, one may also obtain a finite tunneling current by invoking the ultraviolet cutoffs in a field-theoretic description of the electrons in the one-dimensional conductor, a procedure that is often used in the literature. For the latter case, we show that standard ultraviolet cutoffs lead to different results for the tunneling current in fermionic and bosonized formulations of the theory, when going beyond leading order in the tunneling amplitude. We show how to recover the standard fermionic result using the formalism of functional bosonization and revisit the tunneling current to leading order in the interacting case.

  7. Lowering of Boson-Fermion System Energy with a Gapped Cooper Resonant-Pair Dispersion Relation

    NASA Astrophysics Data System (ADS)

    Mamedov, T. A.; de Llano, M.

    Applying two-time Green-function techniques to the Friedberg-T.D. Lee phenomenological Hamiltonian of a many-fermion system, it is shown that positive-energy resonant bosonic pairs associated with four-fermion excitations above the Fermi sea are energetically lower in a ground-state that is a mixture of two coexisting and dynamically interacting many-particle subsystems: a) unpaired fermions and b) composite bosons. It is argued that an interaction between free fermions and bosons excited above the Fermi sea in the mixture, namely, the continuous processes of pair-formation from, and disintegration into, two unpaired electrons, results in a substantially lowering the total system energy. The positive-energy composite bosons begin to appear incoherently below a depairing temperature T* as their coupling- and temperature-dependent number density gradually increases from zero. This leads quite naturally to the pseudogap phenomenon observed in high-Tc cuprates.

  8. Lowering of Boson-Fermion System Energy with a Gapped Cooper Resonant-Pair Dispersion Relation

    NASA Astrophysics Data System (ADS)

    Mamedov, T. A.; de Llano, M.

    2007-09-01

    Applying two-time Green-function techniques to the Friedberg-T.D. Lee phenomenological Hamiltonian of a many-fermion system, it is shown that positive-energy resonant bosonic pairs associated with four-fermion excitations above the Fermi sea are energetically lower in a ground-state that is a mixture of two coexisting and dynamically interacting many-particle subsystems: a) unpaired fermions and b) composite bosons. It is argued that an interaction between free fermions and bosons excited above the Fermi sea in the mixture, namely, the continuous processes of pair-formation from, and disintegration into, two unpaired electrons, results in a substantially lowering the total system energy. The positive-energy composite bosons begin to appear incoherently below a de-pairing temperature T* as their coupling- and temperature-dependent number density gradually increases from zero. This leads quite naturally to the pseudogap phenomenon observed in high-Tc cuprates

  9. Nuclei and Fundamental Symmetries

    NASA Astrophysics Data System (ADS)

    Haxton, Wick

    2016-09-01

    Nuclei provide marvelous laboratories for testing fundamental interactions, often enhancing weak processes through accidental degeneracies among states, and providing selection rules that can be exploited to isolate selected interactions. I will give an overview of current work, including the use of parity violation to probe unknown aspects of the hadronic weak interaction; nuclear electric dipole moment searches that may shed light on new sources of CP violation; and tests of lepton number violation made possible by the fact that many nuclei can only decay by rare second-order weak interactions. I will point to opportunities in both theory and experiment to advance the field. Based upon work supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics and SciDAC under Awards DE-SC00046548 (Berkeley), DE-AC02-05CH11231 (LBNL), and KB0301052 (LBNL).

  10. Hidden symmetries of the Higgs oscillator and the conformal algebra

    NASA Astrophysics Data System (ADS)

    Evnin, Oleg; Nivesvivat, Rongvoram

    2017-01-01

    We give a solution to the long-standing problem of constructing the generators of hidden symmetries of the quantum Higgs oscillator, a particle on a d-sphere moving in a central potential varying as the inverse cosine-squared of the polar angle. This superintegrable system is known to possess a rich algebraic structure, including a hidden SU(d) symmetry that can be deduced from classical conserved quantities and degeneracies of the quantum spectrum. The quantum generators of this SU(d) have not been constructed thus far, except at d  =  2, and naive quantization of classical conserved quantities leads to deformed Lie algebras with quadratic terms in the commutation relations. The nonlocal generators we obtain here satisfy the standard su(d) Lie algebra, and their construction relies on a recently discovered realization of the conformal algebra, which contains a complete set of raising and lowering operators for the Higgs oscillator. This operator structure has emerged from a relation between the Higgs oscillator Schrödinger equation and the Klein-Gordon equation in Anti-de Sitter spacetime. From such a point-of-view, constructing the hidden symmetry generators reduces to manipulations within the abstract conformal algebra so(d, 2).

  11. Lectures on Yangian symmetry

    NASA Astrophysics Data System (ADS)

    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.

  12. Symmetry of priapulids (Priapulida). 2. Symmetry of larvae.

    PubMed

    Adrianov, A V; Malakhov, V V

    2001-02-01

    Larvae of priapulids are characterized by radial symmetry evident from both external and internal characters of the introvert and lorica. The bilaterality appears as a result of a combination of several radial symmetries: pentaradial symmetry of the teeth, octaradial symmetry of the primary scalids, 25-radial symmetry of scalids, biradial symmetry of the neck, and biradial and decaradial symmetry of the trunk. Internal radiality is exhibited by musculature and the circumpharyngeal nerve ring. Internal bilaterality is evident from the position of the ventral nerve cord and excretory elements. Externally, the bilaterality is determined by the position of the anal tubulus and two shortened midventral rows of scalids bordering the ventral nerve cord. The lorical elements define the biradial symmetry that is missing in adult priapulids. The radial symmetry of larvae is a secondary appearance considered an evolutionary adaptation to a lifestyle within the three-dimensional environment of the benthic sediment.

  13. Symmetry in context: salience of mirror symmetry in natural patterns.

    PubMed

    Cohen, Elias H; Zaidi, Qasim

    2013-05-31

    Symmetry is a biologically relevant, mathematically involving, and aesthetically compelling visual phenomenon. Mirror symmetry detection is considered particularly rapid and efficient, based on experiments with random noise. Symmetry detection in natural settings, however, is often accomplished against structured backgrounds. To measure salience of symmetry in diverse contexts, we assembled mirror symmetric patterns from 101 natural textures. Temporal thresholds for detecting the symmetry axis ranged from 28 to 568 ms indicating a wide range of salience (1/Threshold). We built a model for estimating symmetry-energy by connecting pairs of mirror-symmetric filters that simulated cortical receptive fields. The model easily identified the axis of symmetry for all patterns. However, symmetry-energy quantified at this axis correlated weakly with salience. To examine context effects on symmetry detection, we used the same model to estimate approximate symmetry resulting from the underlying texture throughout the image. Magnitudes of approximate symmetry at flanking and orthogonal axes showed strong negative correlations with salience, revealing context interference with symmetry detection. A regression model that included the context-based measures explained the salience results, and revealed why perceptual symmetry can differ from mathematical characterizations. Using natural patterns thus produces new insights into symmetry perception and its possible neural circuits.

  14. Symmetry in context: Salience of mirror symmetry in natural patterns

    PubMed Central

    Cohen, Elias H.; Zaidi, Qasim

    2013-01-01

    Symmetry is a biologically relevant, mathematically involving, and aesthetically compelling visual phenomenon. Mirror symmetry detection is considered particularly rapid and efficient, based on experiments with random noise. Symmetry detection in natural settings, however, is often accomplished against structured backgrounds. To measure salience of symmetry in diverse contexts, we assembled mirror symmetric patterns from 101 natural textures. Temporal thresholds for detecting the symmetry axis ranged from 28 to 568 ms indicating a wide range of salience (1/Threshold). We built a model for estimating symmetry-energy by connecting pairs of mirror-symmetric filters that simulated cortical receptive fields. The model easily identified the axis of symmetry for all patterns. However, symmetry-energy quantified at this axis correlated weakly with salience. To examine context effects on symmetry detection, we used the same model to estimate approximate symmetry resulting from the underlying texture throughout the image. Magnitudes of approximate symmetry at flanking and orthogonal axes showed strong negative correlations with salience, revealing context interference with symmetry detection. A regression model that included the context-based measures explained the salience results, and revealed why perceptual symmetry can differ from mathematical characterizations. Using natural patterns thus produces new insights into symmetry perception and its possible neural circuits. PMID:23729773

  15. Eccentricity Inferences in Multi-planet systems with Transit Timing: Degeneracies and Apsidal Alignment

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel; Van Laerhoven, Christa L.; Ford, Eric B.

    2016-05-01

    Hundreds of multi-transiting systems discovered by the Kepler mission show Transit Timing Variations (TTV). In cases where the TTVs are uniquely attributable to transiting planets, the TTVs enable precise measurements of planetary masses and orbital parameters. Of particular interest are the constraints on eccentricity vectors that can be inferred in systems of low-mass exoplanets.The TTVs in these systems are dominated by a signal caused by near-resonant mean motions. This causes the well-known near-degeneracy between planetary masses and orbital eccentricities. In addition, it causes a degeneracy between the eccentricities of interacting planet pairs.For many systems, the magnitude of individual eccentricities are weakly constrained, yet the data typically provide a tight constraint on the posterior joint distribution for the eccentricity vector components. This permits tight constraints on the relative eccentricity and degree of alignment of interacting planets.For a sample of two and three-planet systems with TTVs, we highlight the effects of these correlations. While the most eccentric orbital solutions for these systems show apsidal alignment, this is often due to the degeneracy that causes correlated constraints on the eccentricity vector components. We compare the likelihood of apsidal alignment for two choices of eccentricity prior: a wide prior using a Rayleigh distribution of scale length 0.1 and a narrower prior with scale length 0.02. In all cases the narrower prior decreased the fraction of samples that exhibited apsidal alignment. However, apsidal alignment persisted in the majority of cases with a narrower eccentricity prior. For a sample of our TTV solutions, we ran simulations of these systems over secular timescales, and decomposed their eccentricity eigenmodes over time, confirming that in most cases, the eccentricities were dominated by parallel eigenmodes which favor apsidal alignment.

  16. Weakly broken galileon symmetry

    SciTech Connect

    Pirtskhalava, David; Santoni, Luca; Trincherini, Enrico; Vernizzi, Filippo

    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.

  17. Baryons and chiral symmetry

    NASA Astrophysics Data System (ADS)

    Liu, Keh-Fei

    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 πNσ 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.

  18. BOOK REVIEW: Symmetry Breaking

    NASA Astrophysics Data System (ADS)

    Ryder, L. H.

    2005-11-01

    One of the most fruitful and enduring advances in theoretical physics during the last half century has been the development of the role played by symmetries. One needs only to consider SU(3) and the classification of elementary particles, the Yang Mills enlargement of Maxwell's electrodynamics to the symmetry group SU(2), and indeed the tremendous activity surrounding the discovery of parity violation in the weak interactions in the late 1950s. This last example is one of a broken symmetry, though the symmetry in question is a discrete one. It was clear to Gell-Mann, who first clarified the role of SU(3) in particle physics, that this symmetry was not exact. If it had been, it would have been much easier to discover; for example, the proton, neutron, Σ, Λ and Ξ particles would all have had the same mass. For many years the SU(3) symmetry breaking was assigned a mathematical form, but the importance of this formulation fell away when the quark model began to be taken seriously; the reason the SU(3) symmetry was not exact was simply that the (three, in those days) quarks had different masses. At the same time, and in a different context, symmetry breaking of a different type was being investigated. This went by the name of `spontaneous symmetry breaking' and its characteristic was that the ground state of a given system was not invariant under the symmetry transformation, though the interactions (the Hamiltonian, in effect) was. A classic example is ferromagnetism. In a ferromagnet the atomic spins are aligned in one direction only—this is the ground state of the system. It is clearly not invariant under a rotation, for that would change the ground state into a (similar but) different one, with the spins aligned in a different direction; this is the phenomenon of a degenerate vacuum. The contribution of the spin interaction, s1.s2, to the Hamiltonian, however, is actually invariant under rotations. As Coleman remarked, a little man living in a ferromagnet would

  19. Symmetry constraint for foreground extraction.

    PubMed

    Fu, Huazhu; Cao, Xiaochun; Tu, Zhuowen; Lin, Dongdai

    2014-05-01

    Symmetry as an intrinsic shape property is often observed in natural objects. In this paper, we discuss how explicitly taking into account the symmetry constraint can enhance the quality of foreground object extraction. In our method, a symmetry foreground map is used to represent the symmetry structure of the image, which includes the symmetry matching magnitude and the foreground location prior. Then, the symmetry constraint model is built by introducing this symmetry structure into the graph-based segmentation function. Finally, the segmentation result is obtained via graph cuts. Our method encourages objects with symmetric parts to be consistently extracted. Moreover, our symmetry constraint model is applicable to weak symmetric objects under the part-based framework. Quantitative and qualitative experimental results on benchmark datasets demonstrate the advantages of our approach in extracting the foreground. Our method also shows improved results in segmenting objects with weak, complex symmetry properties.

  20. Symmetry matters: photodissociation dynamics of symmetrically versus asymmetrically substituted phenols.

    PubMed

    Karsili, Tolga N V; Wenge, Andreas M; Marchetti, Barbara; Ashfold, Michael N R

    2014-01-14

    We report a combined experimental (H (Rydberg) atom photofragment translational spectroscopy) and theoretical (ab initio electronic structure and vibronic coupling calculations) study of the effects of symmetry on the photodissociation dynamics of phenols. Ultraviolet photoexcitation to the bound S1((1)ππ*) state of many phenols leads to some O-H bond fission by tunneling through the barrier under the conical intersection (CI) between the S1 and dissociative S2((1)πσ*) potential energy surfaces in the R(O-H) stretch coordinate. Careful analysis of the total kinetic energy release spectra of the resulting products shows that the radicals formed following S1 ← S0 excitation of phenol and symmetrically substituted phenols like 4-fluorophenol all carry an odd number of quanta in vibrational mode ν(16a), whereas those deriving from asymmetrically substituted systems like 3-fluorophenol or 4-methoxyphenol do not. This contrasting behavior can be traced back to symmetry. Symmetrically substituted phenols exist in two equivalent rotamers, which interconvert by tunneling through the barrier to OH torsional motion. Their states are thus best considered in the non-rigid G4 molecular symmetry group, wherein radiationless transfer from the S1 to S2 state requires a coupling mode of a2 symmetry. Of the three a2 symmetry parent modes, the out-of-plane ring puckering mode ν(16a) shows much the largest interstate coupling constant in the vicinity of the S1/S2 CI. The nuclear motions associated with ν(16a) are orthogonal to the dissociation coordinate, and are thus retained in the radical products. Introducing asymmetry (even a non-linear substituent in the 4-position) lifts the degeneracy of the rotamers, and lowers the molecular symmetry to Cs. Many more parent motions satisfy the reduced (a'') symmetry requirement to enable S1/S2 coupling, the most effective of which is OH torsion. This motion 'disappears' on O-H bond fission; symmetry thus imposes no restriction to

  1. Symmetry in Season.

    ERIC Educational Resources Information Center

    Seidel, Judith Day

    1998-01-01

    Presents activities that demonstrate how technology can help students discover the mathematics in nature. Claims that these experiences can clarify students' vision of the symmetry of beauty that fills the world beyond the computer. Concludes that the use of flexible software tools helps students explore how a shape is affected when they change…

  2. Horror Vacui Symmetry.

    ERIC Educational Resources Information Center

    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)

  3. Degeneracies of particle and nuclear physics uncertainties in neutrinoless β β decay

    NASA Astrophysics Data System (ADS)

    Lisi, E.; Rotunno, A. M.; Šimkovic, F.

    2015-11-01

    Theoretical estimates for the half-life of neutrinoless double beta decay (0 ν β β ) in candidate nuclei are affected by both particle and nuclear physics uncertainties, which may complicate the interpretation of decay signals or limits. We study such uncertainties and their degeneracies in the following context: three 0 ν β β nuclei of great interest for large-scale experiments (Ge 76 , Te 130 , Xe 136 ), two representative particle physics mechanisms (light and heavy Majorana neutrino exchange), and a large set of nuclear matrix elements (NME), computed within the quasiparticle random phase approximation (QRPA). It turns out that the main theoretical uncertainties, associated with the effective axial coupling gA and with the nucleon-nucleon potential, can be parametrized in terms of NME rescaling factors, up to small residuals. From this parametrization, the following QRPA features emerge: (1) the NME dependence on gA is milder than quadratic, (2) in each of the two mechanisms, the relevant lepton number violating parameter is largely degenerate with the NME rescaling factors, and (3) the light and heavy neutrino exchange mechanisms are basically degenerate in the above three nuclei. We comment on the challenging theoretical and experimental improvements required to reduce such particle and nuclear physics uncertainties and their degeneracies.

  4. Open-System Quantum Annealing in Mean-Field Models with Exponential Degeneracy*

    NASA Astrophysics Data System (ADS)

    Kechedzhi, Kostyantyn; Smelyanskiy, Vadim N.

    2016-04-01

    Real-life quantum computers are inevitably affected by intrinsic noise resulting in dissipative nonunitary dynamics realized by these devices. We consider an open-system quantum annealing algorithm optimized for such a realistic analog quantum device which takes advantage of noise-induced thermalization and relies on incoherent quantum tunneling at finite temperature. We theoretically analyze the performance of this algorithm considering a p -spin model that allows for a mean-field quasiclassical solution and, at the same time, demonstrates the first-order phase transition and exponential degeneracy of states, typical characteristics of spin glasses. We demonstrate that finite-temperature effects introduced by the noise are particularly important for the dynamics in the presence of the exponential degeneracy of metastable states. We determine the optimal regime of the open-system quantum annealing algorithm for this model and find that it can outperform simulated annealing in a range of parameters. Large-scale multiqubit quantum tunneling is instrumental for the quantum speedup in this model, which is possible because of the unusual nonmonotonous temperature dependence of the quantum-tunneling action in this model, where the most efficient transition rate corresponds to zero temperature. This model calculation is the first analytically tractable example where open-system quantum annealing algorithm outperforms simulated annealing, which can, in principle, be realized using an analog quantum computer.

  5. Topological Phases on Non-orientable Surfaces: Twisting by Parity Symmetry

    NASA Astrophysics Data System (ADS)

    Chan, Pak On; Teo, Chi Yan; Ryu, Shinsei

    We discuss (2+1)D topological phases on non-orientable spatial surfaces, such as Möbius strip, real projective plane and Klein bottle, etc., which are obtained by twisting the parent topological phases by their underlying pairty symmetries through introducing parity defects. We construct the ground states on arbitrary non-orientable closed manifolds and calculate the ground state degeneracy. Such degeneracy is shown to be robust against continuous deformation of the underlying manifold. We also study the action of the mapping class group on the multiplet of ground states on the Klein bottle. The physical properties of the topological states on non-orientable surfaces are deeply related to the parity symmetric anyons which do not have a notion of orientation in their statistics. For example, the number of ground states on the projective plane equals the root of the number of distinguishable parity symmetric anyons, while the ground state degeneracy on the Klein bottle equals the total number of parity symmetric anyons; In deforming the Klein bottle, the Dehn twist encodes the topological spins whereas the Y-homeomorphism tells the particle-hole relation of the parity symmetric anyons.

  6. Measuring the Degeneracy of Discrete Energy Levels Using a GaAs /AlGaAs Quantum Dot

    NASA Astrophysics Data System (ADS)

    Hofmann, A.; Maisi, V. F.; Gold, C.; Krähenmann, T.; Rössler, C.; Basset, J.; Märki, P.; Reichl, C.; Wegscheider, W.; Ensslin, K.; Ihn, T.

    2016-11-01

    We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs /AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.

  7. Dynamical Symmetries in Classical Mechanics

    ERIC Educational Resources Information Center

    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…

  8. Reflections on Symmetry and Proof

    ERIC Educational Resources Information Center

    Merrotsy, Peter

    2008-01-01

    The concept of symmetry is fundamental to mathematics. Arguments and proofs based on symmetry are often aesthetically pleasing because they are subtle and succinct and non-standard. This article uses notions of symmetry to approach the solutions to a broad range of mathematical problems. It responds to Krutetskii's criteria for mathematical…

  9. PSEUDOSPIN SYMMETRY IN NUCLEI, SPIN SYMMETRY IN HADRONS

    SciTech Connect

    P. PAGE; T. GOLDMAN; J. GINOCCHIO

    2000-08-01

    Ginocchio argued that chiral symmetry breaking in QCD is responsible for the relativistic pseudospin symmetry in the Dirac equation, explaining the observed approximate pseudospin symmetry in sizable nuclei. On a much smaller scale, it is known that spin-orbit splittings in hadrons are small. Specifically, new experimental data from CLEO indicate small splittings in D-mesons. For heavy-light mesons we identify a cousin of pseudospin symmetry that suppresses these splittings in the Dirac equation, known as spin symmetry. We suggest an experimental test of the implications of spin symmetry for wave functions in electron-positron annihilation. We investigate how QCD can give rise to two different dynamical symmetries on nuclear and hadronic scales.

  10. Local Rotational Symmetries.

    DTIC Science & Technology

    1985-08-01

    spanner wrench and the teaspoon, the pointed jaws of the wrench, and the main axes of the gourd , the pear, the squash, and the bowl of the teaspoon...regions such as the handle of the spanner wrench and the main axes of the gourd , squash, and teaspoon, and also pointed regions such as the end of the...Local Symmetry representation does not provide in- tuitively acceptable analyses for round regions, such as the lemon and the round ends of the gourd

  11. Binary-Symmetry Detection

    NASA Technical Reports Server (NTRS)

    Lopez, Hiram

    1987-01-01

    Transmission errors for zeros and ones tabulated separately. Binary-symmetry detector employs psuedo-random data pattern used as test message coming through channel. Message then modulo-2 added to locally generated and synchronized version of test data pattern in same manner found in manufactured test sets of today. Binary symmetrical channel shows nearly 50-percent ones to 50-percent zeroes correspondence. Degree of asymmetry represents imbalances due to either modulation, transmission, or demodulation processes of system when perturbed by noise.

  12. Chiral symmetry and pentaquarks

    SciTech Connect

    Dmitri Diakonov

    2004-07-01

    Spontaneous chiral symmetry breaking, mesons and baryons are illustrated in the language of the Dirac theory. Various forces acting between quarks inside baryons are discussed. I explain why the naive quark models typically overestimate pentaquark masses by some 500 MeV and why in the fully relativistic approach to baryons pentaquarks turn out to be light. I discuss briefly why it can be easier to produce pentaquarks at low than at high energies.

  13. Halting the 'sad degenerationist parade': medical concerns about heredity and racial degeneracy in New Zealand psychiatry, 1853-99.

    PubMed

    Dawson, Maree

    2012-01-01

    Historians have focused on early twentieth-century positive eugenics in New Zealand In this article, I argue that the response came from a tradition of concern about heredity and white racial degeneracy, which extended beyond the British Empire. This article focuses on concerns about heredity at the Auckland Mental Hospital between 1850 and 1899, and contextualises these concerns in New Zealand mental hospital statistics from the late-nineteenth century. This article also considers Australasian, British, North and South American medical and immigration legislation history, and contrasts this with the legislation and medical discourses which formed part of a fear of heredity, racial degeneracy, immigration and mental illness in New Zealand.

  14. Symmetry and Condensed Matter Physics

    NASA Astrophysics Data System (ADS)

    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.

  15. Symmetries in laminated composite plates

    NASA Technical Reports Server (NTRS)

    Noor, A. K.

    1976-01-01

    The different types of symmetry exhibited by laminated anisotropic fibrous composite plates are identified and contrasted with the symmetries of isotropic and homogeneous orthotropic plates. The effects of variations in the fiber orientation and the stacking sequence of the layers on the symmetries exhibited by composite plates are discussed. Both the linear and geometrically nonlinear responses of the plates are considered. A simple procedure is presented for exploiting the symmetries in the finite element analysis. Examples are given of square, skew and polygonal plates where use of symmetry concepts can significantly reduce the scope and cost of analysis.

  16. Invariants of broken discrete symmetries.

    PubMed

    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.

  17. Invariants of Broken Discrete Symmetries

    NASA Astrophysics Data System (ADS)

    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.

  18. Influence of quantum degeneracy on the performance of a gas Stirling engine cycle

    NASA Astrophysics Data System (ADS)

    He, Ji-Zhou; Mao, Zhi-Yuan; Wang, Jian-Hui

    2006-09-01

    Based on the state equation of an ideal quantum gas, the regenerative loss of a Stirling engine cycle working with an ideal quantum gas is calculated. Thermal efficiency of the cycle is derived. Furthermore, under the condition of quantum degeneracy, several special thermal efficiencies are discussed. Ratios of thermal efficiencies versus the temperature ratio and volume ratio of the cycle are made. It is found that the thermal efficiency of the cycle not only depends on high and low temperatures but also on maximum and minimum volumes. In a classical gas state the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal quantum gas state the thermal efficiency of the cycle is smaller than that of the Carnot cycle. This will be significant for deeper understanding of the gas Stirling engine cycle.

  19. Hyperspherical theory of the quantum Hall effect: The role of exceptional degeneracy

    NASA Astrophysics Data System (ADS)

    Daily, K. M.; Wooten, R. E.; Greene, Chris H.

    2015-09-01

    By separating the Schrödinger equation for N noninteracting spin-polarized fermions in two-dimensional hyperspherical coordinates, we demonstrate that fractional quantum Hall (FQH) states emerge naturally from degeneracy patterns of the antisymmetric free-particle eigenfunctions. In the presence of Coulomb interactions, the FQH states split off from a degenerate manifold and become observable as distinct quantized energy eigenstates with an energy gap. This alternative classification scheme is based on an approximate separability of the interacting N -fermion Schrödinger equation in the hyperradial coordinate, which sheds light on the emergence of Laughlin states as well as other FQH states. An approximate good collective quantum number, the grand angular momentum K from K -harmonic few-body theory, is shown to correlate with known FQH states at many filling factors observed experimentally.

  20. Screening charged impurities and lifting the orbital degeneracy in graphene by populating Landau levels.

    PubMed

    Luican-Mayer, Adina; Kharitonov, Maxim; Li, Guohong; Lu, Chih-Pin; Skachko, Ivan; Gonçalves, Alem-Mar B; Watanabe, K; Taniguchi, T; Andrei, Eva Y

    2014-01-24

    We report the observation of an isolated charged impurity in graphene and present direct evidence of the close connection between the screening properties of a 2D electron system and the influence of the impurity on its electronic environment. Using scanning tunneling microscopy and Landau level spectroscopy, we demonstrate that in the presence of a magnetic field the strength of the impurity can be tuned by controlling the occupation of Landau-level states with a gate voltage. At low occupation the impurity is screened, becoming essentially invisible. Screening diminishes as states are filled until, for fully occupied Landau levels, the unscreened impurity significantly perturbs the spectrum in its vicinity. In this regime we report the first observation of Landau-level splitting into discrete states due to lifting the orbital degeneracy.

  1. Edge Modes, Degeneracies, and Topological Numbers in Non-Hermitian Systems

    NASA Astrophysics Data System (ADS)

    Leykam, Daniel; Bliokh, Konstantin Y.; Huang, Chunli; Chong, Y. D.; Nori, Franco

    2017-01-01

    We analyze chiral topological edge modes in a non-Hermitian variant of the 2D Dirac equation. Such modes appear at interfaces between media with different "masses" and/or signs of the "non-Hermitian charge." The existence of these edge modes is intimately related to exceptional points of the bulk Hamiltonians, i.e., degeneracies in the bulk spectra of the media. We find that the topological edge modes can be divided into three families ("Hermitian-like," "non-Hermitian," and "mixed"); these are characterized by two winding numbers, describing two distinct kinds of half-integer charges carried by the exceptional points. We show that all the above types of topological edge modes can be realized in honeycomb lattices of ring resonators with asymmetric or gain-loss couplings.

  2. Very broad gain bandwidth parametric amplification in nonlinear crystals at critical wavelength degeneracy.

    PubMed

    Dabu, R

    2010-05-24

    Gain spectra were calculated at critical wavelength degeneracy (CWD) in a collinear phase-matching geometry optical parametric amplification (OPA) process. The frequency bandwidth available through CWD-OPA is broader compared to the gain bandwidth obtained by the non-collinear OPA geometry. A solution for very broad bandwidth chirped pulse amplification based on partially deuterated DKDP (P-DKDP) crystals, pumped by pulsed green lasers, is proposed. 1.38x10(14) Hz frequency bandwidth and peak intensity gain G approximately 62 were calculated in a 5-mm long 58% deuterated DKDP crystal, pumped by 527-nm wavelength at 64-GW/cm2 intensity. Parametric amplification at CWD in few-mm thin P-DKDP crystals, pumped by picosecond pulses of nearly 100-GW/cm2 intensity, possesses a true potential for generating high energy laser pulses compressible to one-cycle duration.

  3. Partially ferromagnetic electromagnet for trapping and cooling neutral atoms to quantum degeneracy

    SciTech Connect

    Fauquembergue, M.; Riou, J-F.; Guerin, W.; Rangwala, S.; Moron, F.; Villing, A.; Le Coq, Y.; Bouyer, P.; Aspect, A.; Lecrivain, M.

    2005-10-15

    We have developed a compact partially ferromagnetic electromagnet to produce an Ioffe-Pritchard trap for neutral atoms. Our structure permits strong magnetic confinement with low power consumption. Compared to the previous iron-core electromagnet [B. Desruelle, V. Boyer, P. Bouyer, G. Birkl, M. Lecrivain, F. Alves, C. Westbrook, and A. Aspect, Eur. Phys. J. D 1, 255 (1998)], it allows for easy compensation of remnant fields and very high stability, along with cost-effective realization and compactness. We describe and characterize our apparatus and demonstrate trapping and cooling of {sup 87}Rb atoms to quantum degeneracy. Pure Bose-Einstein condensates containing 10{sup 6} atoms are routinely realized on a half-minute cycle. In addition we test the stability of the magnetic trap by producing atom lasers.

  4. Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2.

    PubMed

    Wawrzyńska, E; Coldea, R; Wheeler, E M; Mazin, I I; Johannes, M D; Sörgel, T; Jansen, M; Ibberson, R M; Radaelli, P G

    2007-10-12

    We report a high-resolution neutron diffraction study on the orbitally degenerate spin-1/2 hexagonal metallic antiferromagnet AgNiO2. A structural transition to a tripled unit cell with expanded and contracted NiO6 octahedra indicates sqrt[3]xsqrt[3] charge order on the Ni triangular lattice. This suggests charge order as a possible mechanism of lifting the orbital degeneracy in the presence of charge fluctuations, as an alternative to the more usual Jahn-Teller distortions. A novel magnetic ground state is observed at low temperatures with the electron-rich S=1 Ni sites arranged in alternating ferromagnetic rows on a triangular lattice, surrounded by a honeycomb network of nonmagnetic and metallic Ni ions. We also report first-principles band-structure calculations that explain microscopically the origin of these phenomena.

  5. Dark matter distribution in the Coma cluster from galaxy kinematics: breaking the mass-anisotropy degeneracy

    NASA Astrophysics Data System (ADS)

    Łokas, Ewa L.; Mamon, Gary A.

    2003-08-01

    We study velocity moments of elliptical galaxies in the Coma cluster using Jeans equations. The dark matter distribution in the cluster is modelled by a generalized formula based upon the results of cosmological N-body simulations. Its inner slope (cuspy or flat), concentration and mass within the virial radius are kept as free parameters, as well as the velocity anisotropy, assumed independent of position. We show that the study of line-of-sight velocity dispersion alone does not allow us to constrain the parameters. By a joint analysis of the observed profiles of velocity dispersion and kurtosis, we are able to break the degeneracy between the mass distribution and velocity anisotropy. We determine the dark matter distribution at radial distances larger than 3 per cent of the virial radius and we find that the galaxy orbits are close to isotropic. Due to limited resolution, different inner slopes are found to be consistent with the data and we observe a strong degeneracy between the inner slope α and concentration c; the best-fitting profiles have the two parameters related with c= 19-9.6α. Our best-fitting Navarro-Frenk-White profile has concentration c= 9, which is 50 per cent higher than standard values found in cosmological simulations for objects of similar mass. The total mass within the virial radius of 2.9h-170 Mpc is 1.4 × 1015h-170 Msolar (with 30 per cent accuracy), 85 per cent of which is dark. At this distance from the cluster centre, the mass-to-light ratio in the blue band is 351h70 solar units. The total mass within the virial radius leads to estimates of the density parameter of the Universe, assuming that clusters trace the mass-to-light ratio and baryonic fraction of the Universe, with Ω0= 0.29 +/- 0.1.

  6. Observation of non-Hermitian degeneracies in a chaotic exciton-polariton billiard

    NASA Astrophysics Data System (ADS)

    Gao, T.; Estrecho, E.; Bliokh, K. Y.; Liew, T. C. H.; Fraser, M. D.; Brodbeck, S.; Kamp, M.; Schneider, C.; Höfling, S.; Yamamoto, Y.; Nori, F.; Kivshar, Y. S.; Truscott, A. G.; Dall, R. G.; Ostrovskaya, E. A.

    2015-10-01

    Exciton-polaritons are hybrid light-matter quasiparticles formed by strongly interacting photons and excitons (electron-hole pairs) in semiconductor microcavities. They have emerged as a robust solid-state platform for next-generation optoelectronic applications as well as for fundamental studies of quantum many-body physics. Importantly, exciton-polaritons are a profoundly open (that is, non-Hermitian) quantum system, which requires constant pumping of energy and continuously decays, releasing coherent radiation. Thus, the exciton-polaritons always exist in a balanced potential landscape of gain and loss. However, the inherent non-Hermitian nature of this potential has so far been largely ignored in exciton-polariton physics. Here we demonstrate that non-Hermiticity dramatically modifies the structure of modes and spectral degeneracies in exciton-polariton systems, and, therefore, will affect their quantum transport, localization and dynamical properties. Using a spatially structured optical pump, we create a chaotic exciton-polariton billiard--a two-dimensional area enclosed by a curved potential barrier. Eigenmodes of this billiard exhibit multiple non-Hermitian spectral degeneracies, known as exceptional points. Such points can cause remarkable wave phenomena, such as unidirectional transport, anomalous lasing/absorption and chiral modes. By varying parameters of the billiard, we observe crossing and anti-crossing of energy levels and reveal the non-trivial topological modal structure exclusive to non-Hermitian systems. We also observe mode switching and a topological Berry phase for a parameter loop encircling the exceptional point. Our findings pave the way to studies of non-Hermitian quantum dynamics of exciton-polaritons, which may uncover novel operating principles for polariton-based devices.

  7. Hidden pseudospin and spin symmetries and their origins in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Liang, Haozhao; Meng, Jie; Zhou, Shan-Gui

    2015-03-01

    Symmetry plays a fundamental role in physics. The quasi-degeneracy between single-particle orbitals (n , l , j = l + 1 / 2) and (n - 1 , l + 2 , j = l + 3 / 2) indicates a hidden symmetry in atomic nuclei, the so-called pseudospin symmetry (PSS). Since the introduction of the concept of PSS in atomic nuclei, there have been comprehensive efforts to understand its origin. Both splittings of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with radioactive ion beam facilities. Since the PSS was recognized as a relativistic symmetry in 1990s, many special features, including the spin symmetry (SS) for anti-nucleon, and many new concepts have been introduced. In the present Review, we focus on the recent progress on the PSS and SS in various systems and potentials, including extensions of the PSS study from stable to exotic nuclei, from non-confining to confining potentials, from local to non-local potentials, from central to tensor potentials, from bound to resonant states, from nucleon to anti-nucleon spectra, from nucleon to hyperon spectra, and from spherical to deformed nuclei. Open issues in this field are also discussed in detail, including the perturbative nature, the supersymmetric representation with similarity renormalization group, and the puzzle of intruder states.

  8. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene.

    PubMed

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-14

    Bulk black phosphorus has two optical phonon modes labeled as Ag (2) and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag (2) modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

  9. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene

    NASA Astrophysics Data System (ADS)

    Sun, Yi-Yang; Zhang, Shengbai

    2016-07-01

    Bulk black phosphorus has two optical phonon modes labeled as Ag2 and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag2 modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

  10. Unraveling the origins of conduction band valley degeneracies in Mg2Si(1-x)Sn(x) thermoelectrics.

    PubMed

    Kim, Chang-Eun; Soon, Aloysius; Stampfl, Catherine

    2016-01-14

    To better understand the thermoelectric efficiency of the Mg-based thermoelectrics, using hybrid density-functional theory, we study the microscopic origins of valley degeneracies in the conduction band of the solid solution Mg2Si(1-x)Sn(x) and its constituent components--namely, Mg2Si and Mg2Sn. In the solid solution of Mg2Si(1-x)Sn(x), the sublattices are expected to undergo either tensile or compressive strain in the light of Vegard's law. Interestingly, we find both tensile strain of Mg2Si and compressive strain of Mg2Sn enhance the conduction band valley degeneracy. We suggest that the optimal sublattice strain as one of the origins of the enhanced Seebeck coefficient in the Mg2Si(1-x)Sn(x) system. In order to visualize the enhanced band valley degeneracy at elevated temperatures, the ground state eigenvalues and weights are projected by convolution functions that account for high temperature effects. Our results provide theoretical evidences for the role of sublattice strain in the band valley degeneracy observed in Mg2Si(1-x)Sn(x).

  11. Symmetry-Breaking Motility

    NASA Astrophysics Data System (ADS)

    Lee, Allen; Lee, Ha Youn; Kardar, Mehran

    2005-09-01

    Locomotion of bacteria by actin polymerization and in vitro motion of spherical beads coated with a protein catalyzing polymerization are examples of active motility. Starting from a simple model of forces locally normal to the surface of a bead, we construct a phenomenological equation for its motion. The singularities at a continuous transition between moving and stationary beads are shown to be related to the symmetries of its shape. Universal features of the phase behavior are calculated analytically and confirmed by simulations. Fluctuations in velocity are shown to be generically non-Maxwellian and correlated to the shape of the bead.

  12. Galactic oscillator symmetry

    NASA Technical Reports Server (NTRS)

    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.

  13. Applications of chiral symmetry

    SciTech Connect

    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.

  14. [Symmetries and homologies of Geomerida].

    PubMed

    Zarenkov, N A

    2005-01-01

    The symmetry of Earths life cover (Geomerida) was described generally by L.A. Zenkevich (1948). It coincides with the symmetry of geographic cover. Its symmetry elements are equatorial plane and three meridonal planes corresponded to oceans and continents. The hypsographic curve with point of inflection (symmetry element) on 3 km depth line should be added to these elements. The plankton and benthos communities as well as fauna of taxons are distributed symmetrically according these symmetry elements. Zenkevich model was successfully extrapolated to plankton by K.V. Beklemishev (1967, 1969) and to abyssal benthos by Sokolova M.N. (1986). The plankton communities inhabiting symmetrically located macrocirculations are considered as homologous. The character of circulation determines the trophic structure of plankton and benthos. In the case of high productivity of plankton, benthic grazing animals feed on sedimented particles have bilateral symmetric mouthpart. Otherwise they have to acquire food from water column and use cyclomeric mouthpart. Thus, the symmetry of macrocirculations determines the symmetry distribution of benthic animals with two major symmetries of mouthparts. The peculiarities of organisms' symmetry are discussed in the context of Pierre Curie principle and the ideas of K.V. Beklemishev concerning evolution of morphological axes.

  15. From Molecular Point Group Symmetry to Space Group Symmetry.

    ERIC Educational Resources Information Center

    Hathaway, Brian

    1979-01-01

    Describes undergraduate chemistry curricula in which the student is asked to either build a model of one asymmetric unit in the unit cell and to indicate the positions of the symmetry-related units by putting in key atoms, or to identify on a prebuild model the asymetric and symmetry-related units. (BB)

  16. Symmetry reduction related with nonlocal symmetry for Gardner equation

    NASA Astrophysics Data System (ADS)

    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.

  17. Symmetry and surface symmetry energies in finite nuclei

    SciTech Connect

    Lee, S. J.; Mekjian, A. Z.

    2010-12-15

    A study of the properties of the symmetry energy of nuclei is presented based on density-functional theory. Calculations for finite nuclei are given so that the study includes isospin-dependent surface symmetry considerations as well as isospin-independent surface effects. Calculations are done at both zero and nonzero temperature. It is shown that the surface symmetry energy term is the most sensitive to the temperature while the bulk energy term is the least sensitive. It is also shown that the temperature-dependence terms are insensitive to the force used and even more insensitive to the existence of neutron skin. Results for a symmetry energy with both volume and surface terms are compared with a symmetry energy with only volume terms along the line of {beta} stability. Differences of several MeV are shown over a good fraction of the total mass range in A. Also given are calculations for the bulk, surface and Coulomb terms.

  18. NIF symmetry capsule modeling

    NASA Astrophysics Data System (ADS)

    Weber, S. V.; Casey, D. T.; Pino, J. E.; Rowley, D. P.; Smalyuk, V. A.; Spears, B. K.; Tipton, R. E.

    2013-10-01

    NIF CH ablator symmetry capsules are filled with hydrogen or helium gas. SymCaps have more moderate convergence ratios ~ 15 as opposed to ~ 35 for ignition capsules with DT ice layers, and better agreement has been achieved between simulations and experimental data. We will present modeling of capsules with CD layers and tritium fill, for which we are able to match the dependence of DT yield on recession distance of the CD layer from the gas. We can also match the performance of CH capsules with D3 He fill. The simulations include surface roughness, drive asymmetry, a mock-up of modulation introduced by the tent holding the capsule, and an empirical prescription for ablator-gas atomic mix. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  19. Cognitive Aging and Time Perception: Roles of Bayesian Optimization and Degeneracy

    PubMed Central

    Turgeon, Martine; Lustig, Cindy; Meck, Warren H.

    2016-01-01

    This review outlines the basic psychological and neurobiological processes associated with age-related distortions in timing and time perception in the hundredths of milliseconds-to-minutes range. The difficulty in separating indirect effects of impairments in attention and memory from direct effects on timing mechanisms is addressed. The main premise is that normal aging is commonly associated with increased noise and temporal uncertainty as a result of impairments in attention and memory as well as the possible reduction in the accuracy and precision of a central timing mechanism supported by dopamine-glutamate interactions in cortico-striatal circuits. Pertinent to these findings, potential interventions that may reduce the likelihood of observing age-related declines in timing are discussed. Bayesian optimization models are able to account for the adaptive changes observed in time perception by assuming that older adults are more likely to base their temporal judgments on statistical inferences derived from multiple trials than on a single trial’s clock reading, which is more susceptible to distortion. We propose that the timing functions assigned to the age-sensitive fronto-striatal network can be subserved by other neural networks typically associated with finely-tuned perceptuo-motor adjustments, through degeneracy principles (different structures serving a common function). PMID:27242513

  20. Transient potassium channels augment degeneracy in hippocampal active dendritic spectral tuning

    PubMed Central

    Rathour, Rahul Kumar; Malik, Ruchi; Narayanan, Rishikesh

    2016-01-01

    Hippocampal pyramidal neurons express an intraneuronal map of spectral tuning mediated by hyperpolarization-activated cyclic-nucleotide-gated nonspecific-cation channels. Modeling studies have predicted a critical regulatory role for A-type potassium (KA) channels towards augmenting functional robustness of this map. To test this, we performed patch-clamp recordings from soma and dendrites of rat hippocampal pyramidal neurons, and measured spectral tuning before and after blocking KA channels using two structurally distinct pharmacological agents. Consistent with computational predictions, we found that blocking KA channels resulted in a significant reduction in resonance frequency and significant increases in input resistance, impedance amplitude and action-potential firing frequency across the somato-apical trunk. Furthermore, across all measured locations, blocking KA channels enhanced temporal summation of postsynaptic potentials and critically altered the impedance phase profile, resulting in a significant reduction in total inductive phase. Finally, pair-wise correlations between intraneuronal percentage changes (after blocking KA channels) in different measurements were mostly weak, suggesting differential regulation of different physiological properties by KA channels. Our results unveil a pivotal role for fast transient channels in regulating theta-frequency spectral tuning and intrinsic phase response, and suggest that degeneracy with reference to several coexisting functional maps is mediated by cross-channel interactions across the active dendritic arbor. PMID:27094086

  1. CCDM model with spatial curvature and the breaking of ''dark degeneracy''

    SciTech Connect

    Jesus, J.F.; Andrade-Oliveira, F. E-mail: felipe.oliveira@port.ac.uk

    2016-01-01

    Creation of Cold Dark Matter (CCDM), in the context of Einstein Field Equations, leads to a negative creation pressure, which can be used to explain the accelerated expansion of the Universe. Recently, it has been shown that the dynamics of expansion of such models can not be distinguished from the concordance ΛCDM model, even at higher orders in the evolution of density perturbations, leading at the so called ''dark degeneracy''. However, depending on the form of the CDM creation rate, the inclusion of spatial curvature leads to a different behavior of CCDM when compared to ΛCDM, even at background level. With a simple form for the creation rate, namely, Γ∝1/H , we show that this model can be distinguished from ΛCDM, provided the Universe has some amount of spatial curvature. Observationally, however, the current limits on spatial flatness from CMB indicate that neither of the models are significantly favored against the other by current data, at least in the background level.

  2. Flat band degeneracy and near-zero refractive index materials in acoustic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Shiqiao; Mei, Jun

    2016-01-01

    A Dirac-like cone is formed by utilizing the flat bands associated with localized modes in an acoustic crystal (AC) composed of a square array of core-shell-structure cylinders in a water host. Although the triply-degeneracy seems to arise from two almost-overlapping flat bands touching another curved band, the enlarged view of the band structure around the degenerate point reveals that there are actually two linear bands intersecting each other at the Brillouin zone center, with another flat band passing through the same crossing point. The linearity of dispersion relations is achieved by tuning the geometrical parameters of the cylindrical scatterers. A perturbation method is used to not only accurately predict the linear slopes of the dispersions, but also confirm the linearity of the bands from first principles. An effective medium theory based on coherent potential approximation is developed, and it shows that a slab made of the AC carries a near-zero refractive index around the Dirac-like point. Full-wave simulations are performed to unambiguously demonstrate the wave manipulating properties of the AC structures such as perfect transmission, unidirectional transmission and wave front shaping.

  3. Degeneracies and fluctuations of Néel skyrmions in confined geometries

    NASA Astrophysics Data System (ADS)

    Keesman, Rick; Leonov, A. O.; van Dieten, P.; Buhrandt, Stefan; Barkema, G. T.; Fritz, Lars; Duine, R. A.

    2015-10-01

    The recent discovery of tunable Dzyaloshinskii-Moriya interactions in layered magnetic materials with perpendicular magnetic anisotropy makes them promising candidates for stabilization and manipulation of skyrmions at elevated temperatures. In this article, we use Monte Carlo simulations to investigate the robustness of skyrmions in these materials against thermal fluctuations and finite-size effects. We find that in confined geometries and at finite temperatures skyrmions are present in a large part of the phase diagram. Moreover, we find that the confined geometry favors the skyrmion over the spiral phase when compared to infinitely large systems. Upon tuning the magnetic field through the skyrmion phase, the system undergoes a cascade of transitions in the magnetic structure through states of different number of skyrmions, elongated and half-skyrmions, and spiral states. We consider how quantum and thermal fluctuations lift the degeneracies that occur at these transitions, and find that states with more skyrmions are typically favored by fluctuations over states with less skyrmions. Finally, we comment on electrical detection of the various phases through the topological and anomalous Hall effects.

  4. Degeneracy between θ23 octant and neutrino non-standard interactions at DUNE

    NASA Astrophysics Data System (ADS)

    Agarwalla, Sanjib Kumar; Chatterjee, Sabya Sachi; Palazzo, Antonio

    2016-11-01

    We expound in detail the degeneracy between the octant of θ23 and flavor-changing neutral-current non-standard interactions (NSI's) in neutrino propagation, considering the Deep Underground Neutrino Experiment (DUNE) as a case study. In the presence of such NSI parameters involving the e - μ (εeμ) and e - τ (εeτ) flavors, the νμ →νe and νbarμ →νbare appearance probabilities in long-baseline experiments acquire an additional interference term, which depends on one new dynamical CP-phase ϕeμ/eτ. This term sums up with the well-known interference term related to the standard CP-phase δ creating a source of confusion in the determination of the octant of θ23. We show that for values of the NSI coupling (taken one at-a-time) as small as few % (relative to the Fermi coupling constant GF), and for unfavorable combinations of the two CP-phases δ and ϕeμ/eτ, the discovery potential of the octant of θ23 gets completely lost.

  5. Symmetry in Sign Language Poetry

    ERIC Educational Resources Information Center

    Sutton-Spence, Rachel; Kaneko, Michiko

    2007-01-01

    This paper considers the range of ways that sign languages use geometric symmetry temporally and spatially to create poetic effect. Poets use this symmetry in sign language art to highlight duality and thematic contrast, and to create symbolic representations of beauty, order and harmony. (Contains 8 tables, 14 figures and 6 notes.)

  6. Symmetry in the Car Park

    ERIC Educational Resources Information Center

    Hancock, Karen

    2007-01-01

    In this article, the author presents a lesson on rotational symmetry which she developed for her students. The aim of the lesson was "to identify objects with rotational symmetry in the staff car park" and the success criteria were "pictures or sketches of at least six objects with different orders of rotation". After finding examples of…

  7. Asymptotic symmetries on Killing horizons

    NASA Astrophysics Data System (ADS)

    Koga, Jun-Ichirou

    2001-12-01

    We investigate asymptotic symmetries regularly defined on spherically symmetric Killing horizons in Einstein theory with or without the cosmological constant. These asymptotic symmetries are described by asymptotic Killing vectors, along which the Lie derivatives of perturbed metrics vanish on a Killing horizon. We derive the general form of the asymptotic Killing vectors and find that the group of asymptotic symmetries consists of rigid O(3) rotations of a horizon two-sphere and supertranslations along the null direction on the horizon, which depend arbitrarily on the null coordinate as well as the angular coordinates. By introducing the notion of asymptotic Killing horizons, we also show that local properties of Killing horizons are preserved not only under diffeomorphisms but also under nontrivial transformations generated by the asymptotic symmetry group. Although the asymptotic symmetry group contains the Diff(S1) subgroup, which results from supertranslations dependent only on the null coordinate, it is shown that the Poisson brackets algebra of the conserved charges conjugate to asymptotic Killing vectors does not acquire nontrivial central charges. Finally, by considering extended symmetries, we discuss the fact that unnatural reduction of the symmetry group is necessary in order to obtain the Virasoro algebra with nontrivial central charges, which is not justified when we respect the spherical symmetry of Killing horizons.

  8. Hyperbolic-symmetry vector fields.

    PubMed

    Gao, Xu-Zhen; Pan, Yue; Cai, Meng-Qiang; Li, Yongnan; Tu, Chenghou; Wang, Hui-Tian

    2015-12-14

    We present and construct a new kind of orthogonal coordinate system, hyperbolic coordinate system. We present and design a new kind of local linearly polarized vector fields, which is defined as the hyperbolic-symmetry vector fields because the points with the same polarization form a series of hyperbolae. We experimentally demonstrate the generation of such a kind of hyperbolic-symmetry vector optical fields. In particular, we also study the modified hyperbolic-symmetry vector optical fields with the twofold and fourfold symmetric states of polarization when introducing the mirror symmetry. The tight focusing behaviors of these vector fields are also investigated. In addition, we also fabricate micro-structures on the K9 glass surfaces by several tightly focused (modified) hyperbolic-symmetry vector fields patterns, which demonstrate that the simulated tightly focused fields are in good agreement with the fabricated micro-structures.

  9. Node-surface and node-line fermions from nonsymmorphic lattice symmetries

    NASA Astrophysics Data System (ADS)

    Liang, Qi-Feng; Zhou, Jian; Yu, Rui; Wang, Zhi; Weng, Hongming

    2016-02-01

    We propose a kind of topological quantum state of semimetals in the quasi-one-dimensional (1D) crystal family BaMX 3 (M =V , Nb, or Ta; X =S or Se) by using symmetry analysis and first-principles calculation. We find that in BaVS3 the valence and conduction bands are degenerate in the kz=π /c plane (c is the lattice constant along the z ̂ axis) of the Brillouin zone (BZ). These nodal points form a node surface, and they are protected by a nonsymmorphic crystal symmetry consisting of a twofold rotation about the z ̂ axis and a half-translation along the same z ̂ axis. The band degeneracy in the node surface is lifted in BaTaS3 by including strong spin-orbit coupling (SOC) of Ta. The node surface is reduced into 1D node lines along the high-symmetry paths kx=0 and kx=±√{3 }ky on the kz=π /c plane. These node lines are robust against SOC and guaranteed by the symmetries of the P 63/m m c space group. These node-line states are entirely different from previous proposals which are based on the accidental band touchings. We also propose a useful material design for realizing topological node-surface and node-line semimetals.

  10. Role of cavity degeneracy for high-order mode excitation in end-pumped solid-state lasers.

    PubMed

    Barré, Nicolas; Romanelli, Marco; Brunel, Marc

    2014-02-15

    The possibility of exciting laser modes such as Laguerre-Gaussian (LG) or Ince-Gaussian (IG) modes is discussed on the basis of a gain-matching integral. We reach the conclusion that, using tight pumping and away from degeneracy regions, only the IG(n,n)(e) modes can be excited. Furthermore, pure high-order modes with circular or elliptical nodal lines can never be excited. Only an approximation of such modes, which we call quasi-IG or quasi-LG modes, can be observed and only when the cavity is partially degenerate. We provide experimental results in perfect agreement with the theory and discuss the exact nature of the profiles observed at degeneracy in our experiments and elsewhere in the literature.

  11. PT Symmetry and Spontaneous Symmetry Breaking in a Microwave Billiard

    NASA Astrophysics Data System (ADS)

    Bittner, S.; Dietz, B.; Günther, U.; Harney, H. L.; Miski-Oglu, M.; Richter, A.; Schäfer, F.

    2012-01-01

    We demonstrate the presence of parity-time (PT) symmetry for the non-Hermitian two-state Hamiltonian of a dissipative microwave billiard in the vicinity of an exceptional point (EP). The shape of the billiard depends on two parameters. The Hamiltonian is determined from the measured resonance spectrum on a fine grid in the parameter plane. After applying a purely imaginary diagonal shift to the Hamiltonian, its eigenvalues are either real or complex conjugate on a curve, which passes through the EP. An appropriate basis choice reveals its PT symmetry. Spontaneous symmetry breaking occurs at the EP.

  12. Network, degeneracy and bow tie. Integrating paradigms and architectures to grasp the complexity of the immune system

    PubMed Central

    2010-01-01

    Recently, the network paradigm, an application of graph theory to biology, has proven to be a powerful approach to gaining insights into biological complexity, and has catalyzed the advancement of systems biology. In this perspective and focusing on the immune system, we propose here a more comprehensive view to go beyond the concept of network. We start from the concept of degeneracy, one of the most prominent characteristic of biological complexity, defined as the ability of structurally different elements to perform the same function, and we show that degeneracy is highly intertwined with another recently-proposed organizational principle, i.e. 'bow tie architecture'. The simultaneous consideration of concepts such as degeneracy, bow tie architecture and network results in a powerful new interpretative tool that takes into account the constructive role of noise (stochastic fluctuations) and is able to grasp the major characteristics of biological complexity, i.e. the capacity to turn an apparently chaotic and highly dynamic set of signals into functional information. PMID:20701759

  13. Functional Symmetry of Endomembranes

    PubMed Central

    2007-01-01

    In higher eukaryotic cells pleiomorphic compartments composed of vacuoles, tubules and vesicles move from the endoplasmic reticulum (ER) and the plasma membrane to the cell center, operating in early biosynthetic trafficking and endocytosis, respectively. Besides transporting cargo to the Golgi apparatus and lysosomes, a major task of these compartments is to promote extensive membrane recycling. The endocytic membrane system is traditionally divided into early (sorting) endosomes, late endosomes and the endocytic recycling compartment (ERC). Recent studies on the intermediate compartment (IC) between the ER and the Golgi apparatus suggest that it also consists of peripheral (“early”) and centralized (“late”) structures, as well as a third component, designated here as the biosynthetic recycling compartment (BRC). We propose that the ERC and the BRC exist as long-lived “mirror compartments” at the cell center that also share the ability to expand and become mobilized during cell activation. These considerations emphasize the functional symmetry of endomembrane compartments, which provides a basis for the membrane rearrangements taking place during cell division, polarization, and differentiation. PMID:17267686

  14. Degeneracies when T=0 two body interaction matrix elements are set equal to zero: Talmi's method of calculating coefficients of fractional parentage to states forbidden by the Pauli principle

    NASA Astrophysics Data System (ADS)

    Robinson, Shadow J. Q.; Zamick, Larry

    2001-11-01

    In a previous work [S.J.Q. Robinson and Larry Zamick, Phys. Rev. C 63, 064416 (2001)] we studied the effects of setting all two body T=0 matrix elements to zero in shell model calculations for 43Ti (43Sc) and 44Ti. The results for 44Ti were surprisingly good despite the severity of this approximation. In single-j shell calculations (fn7/2) degeneracies arose between the T=12 I=(12)-1 and (132)-1 states in 43Sc as well as the T=12 I=(132)-2, (172)-1, and (192)-1 in 43Sc. For 44Ti the T=0 states 3+2, 7+2, 9+1, and 10+1 are degenerate as are the 10+2 and 12+1 states. The degeneracies can be explained by certain 6j symbols and 9j symbols either vanishing or being equal as indeed they are. Previously we used Regge symmetries of 6j symbols to explain the vanishing 6j and 9j symbols. In this work a simpler, more physical method is used. This is Talmi's method of calculating coefficients of fractional parentage (cfp) for identical particles to states which are forbidden by the Pauli principle. This is done for both the one particle cfp to handle 6j symbols and the two particle cfp for the 9j symbols. From this we learn that the common thread for the angular momenta I for which the above degeneracies occur is that these angular momenta cannot exist in the calcium isotopes in the f7/2 shell. There are no T=32 f37/2 states with angular momenta 12, 132, 172, and 192. In the same vein there are no T=2 f47/2 states with angular momenta 3, 7, 9, 10, or 12. For these angular momenta, all the states can be classified by the dual quantum numbers (Jπ,Jν).

  15. Symmetry algebras of linear differential equations

    NASA Astrophysics Data System (ADS)

    Shapovalov, A. V.; Shirokov, I. V.

    1992-07-01

    The local symmetries of linear differential equations are investigated by means of proven theorems on the structure of the algebra of local symmetries of translationally and dilatationally invariant differential equations. For a nonparabolic second-order equation, the absence of nontrivial nonlinear local symmetries is proved. This means that the local symmetries reduce to the Lie algebra of linear differential symmetry operators. For the Laplace—Beltrami equation, all local symmetries reduce to the enveloping algebra of the algebra of the conformal group.

  16. Convergence behavior of multireference perturbation theory: Forced degeneracy and optimization partitioning applied to the beryllium atom

    NASA Astrophysics Data System (ADS)

    Finley, James P.; Chaudhuri, Rajat K.; Freed, Karl F.

    1996-07-01

    High-order multireference perturbation theory is applied to the 1S states of the beryllium atom using a reference (model) space composed of the \\|1s22s2> and the \\|1s22p2> configuration-state functions (CSF's), a system that is known to yield divergent expansions using Mo/ller-Plesset and Epstein-Nesbet partitioning methods. Computations of the eigenvalues are made through 40th order using forced degeneracy (FD) partitioning and the recently introduced optimization (OPT) partitioning. The former forces the 2s and 2p orbitals to be degenerate in zeroth order, while the latter chooses optimal zeroth-order energies of the (few) most important states. Our methodology employs simple models for understanding and suggesting remedies for unsuitable choices of reference spaces and partitioning methods. By examining a two-state model composed of only the \\|1s22p2> and \\|1s22s3s> states of the beryllium atom, it is demonstrated that the full computation with 1323 CSF's can converge only if the zeroth-order energy of the \\|1s22s3s> Rydberg state from the orthogonal space lies below the zeroth-order energy of the \\|1s22p2> CSF from the reference space. Thus convergence in this case requires a zeroth-order spectral overlap between the orthogonal and reference spaces. The FD partitioning is not capable of generating this type of spectral overlap and thus yields a divergent expansion. However, the expansion is actually asymptotically convergent, with divergent behavior not displayed until the 11th order because the \\|1s22s3s> Rydberg state is only weakly coupled with the \\|1s22p2> CSF and because these states are energetically well separated in zeroth order. The OPT partitioning chooses the correct zeroth-order energy ordering and thus yields a convergent expansion that is also very accurate in low orders compared to the exact solution within the basis.

  17. Electroweak Symmetry Breaking: With Dynamics

    SciTech Connect

    Chivukula, R. Sekhar

    2005-03-22

    In this note I provide a brief description of models of dynamical electroweak symmetry breaking, including walking technicolor, top-color assisted technicolor, the top-quark seesaw model, and little higgs theories.

  18. Classification of spacetimes with symmetry

    NASA Astrophysics Data System (ADS)

    Hicks, Jesse W.

    Spacetimes with symmetry play a critical role in Einstein's Theory of General Relativity. Missing from the literature is a correct, usable, and computer accessible classification of such spacetimes. This dissertation fills this gap; specifically, we. i) give a new and different approach to the classification of spacetimes with symmetry using modern methods and tools such as the Schmidt method and computer algebra systems, resulting in ninety-two spacetimes; ii) create digital databases of the classification for easy access and use for researchers; iii) create software to classify any spacetime metric with symmetry against the new database; iv) compare results of our classification with those of Petrov and find that Petrov missed six cases and incorrectly normalized a significant number of metrics; v) classify spacetimes with symmetry in the book Exact Solutions to Einstein's Field Equations Second Edition by Stephani, Kramer, Macallum, Hoenselaers, and Herlt and in Komrakov's paper Einstein-Maxwell equation on four-dimensional homogeneous spaces using the new software.

  19. Symmetries from the solution manifold

    NASA Astrophysics Data System (ADS)

    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.

  20. Partial Dynamical Symmetry in Molecules

    NASA Astrophysics Data System (ADS)

    Ping, Jia-Lun; Chen, Jin-Quan

    1997-03-01

    It is shown that any Hamiltonian involving only one- and two-bond interactions for a molecule withnbonds and having a point groupPas its symmetry group may have theSn⊃Ppartial dynamical symmetry, i.e., the Hamiltonian can be solved analytically for a part of the states, called the unique states. For example, theXY6molecule has theS6⊃Ohpartial dynamical symmetry. The model of Iachello and Oss forncoupled anharmonic oscillators is revisited in terms of the partial dynamical symmetry. The energies are obtained analytically for the nine unique levels of theXY6molecule and the structures of the eigenstates are disclosed for the first time, while for non-unique states they are obtained by diagonalizing the Hamiltonian in theS6⊃Ohsymmetry adapted basis with greatly reduced dimension.

  1. Broken Symmetries and Magnetic Dynamos

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2007-01-01

    Phase space symmetries inherent in the statistical theory of ideal magnetohydrodynamic (MHD) turbulence are known to be broken dynamically to produce large-scale coherent magnetic structure. Here, results of a numerical study of decaying MHD turbulence are presented that show large-scale coherent structure also arises and persists in the presence of dissipation. Dynamically broken symmetries in MHD turbulence may thus play a fundamental role in the dynamo process.

  2. Possible violations of spacetime symmetries

    NASA Astrophysics Data System (ADS)

    Urrutia, Luis

    2016-10-01

    The identification of symmetries has played a fundamental role in our understanding of physical phenomena. Nevertheless, in most cases such symmetries constitute only a zeroth-order approximation and they need to be broken so that the predictions of the theory are consistent with experimental observation. In particular, the almost sacred CPT and Lorentz symmetries, which are certainly part of the fundamental ideas of modern physics, need to be probed experimentally. Recently, such efforts have been intensified because different theoretical approaches aiming to understand the microstructure of space-time suggest the possibility that such symmetries could present minute violations. Up to now, and with increasing experimental sensitivities, no signs of violation have been found. Nevertheless, we observe that even the persistence of such negative results will have a profound impact. On one hand, they will provide those symmetries with a firm experimental basis. On the other, they will set stringent experimental bounds to be compared with the possible emergence of such violations in quantum gravity models based upon a discrete structure of space. We present a very general perspective of the research on Lorentz symmetry breaking, together with a review of a few specific topics.

  3. Widening the Scope of a Partial Dynamical Symmetry

    NASA Astrophysics Data System (ADS)

    Pereira, Wesley; Garcia, Ricardo; Zamick, Larry

    2015-10-01

    In a single j shell calculation in which only T = 1(even J) two-particle matrix elements were non-zero there was a partial dynamical symmetry e.g. for 2 protons and 2 neutrons in the f7/2 shell there is a degeneracy of states with angular momenta I = 3,7,9,10. These have non -zero components only for (Jp, Jn) = (4,6) or (6,4). These I's cannot occur for 4 identical partices (44 Ca).We then consider a ``123'' interaction which for J = 0 to 7 is (0,0,1,0,2,0,3,0). Then I = 6 and I = 8 also come into play. Fot these (Jp+Jn) is a good quantum number. One gets an equally spaced multidegerate levels (``vibrational spectra'') with separation of 1.5 MeV. Each of these levels has fixed (Jp+Jn. For(Jp+Jn) equal to 6 we have I = 3 an I = 6 as; for 8 we get 6,7 ,8; for 10,we get 3,7,9,10 and for 12 we get 10,12. In the g9/2 shell with a ``1234'' (Jp+Jn) ranges from 8 to 16 and in h11/2 with ``12345'' from 10 and 20. W.P. Garden State Stokes Alliance for Minorities Participation internship GSISAMP 2. R.G. REU fron NSF PHY-1263280.

  4. Ultracold Fermi gases with emergent SU(N) symmetry

    NASA Astrophysics Data System (ADS)

    Cazalilla, Miguel A.; Rey, Ana Maria

    2014-12-01

    We review recent experimental and theoretical progress on ultracold alkaline-earth Fermi gases with emergent SU(N) symmetry. Emphasis is placed on describing the ground-breaking experimental achievements of recent years. The latter include (1) the cooling to below quantum degeneracy of various isotopes of ytterbium and strontium, (2) the demonstration of optical Feshbach resonances and the optical Stern-Gerlach effect, (3) the realization of a Mott insulator of 173Yb atoms, (4) the creation of various kinds of Fermi-Bose mixtures and (5) the observation of many-body physics in optical lattice clocks. On the theory side, we survey the zoo of phases that have been predicted for both gases in a trap and loaded into an optical lattice, focusing on two and three dimensional systems. We also discuss some of the challenges that lie ahead for the realization of such phases such as reaching the temperature scale required to observe magnetic and more exotic quantum orders. The challenge of dealing with collisional relaxation of excited electronic levels is also discussed.

  5. Control over the Emission Properties of [5]Helicenes Based on the Symmetry and Energy Levels of Their Molecular Orbitals.

    PubMed

    Kubo, Hiromu; Hirose, Takashi; Matsuda, Kenji

    2017-03-30

    The effect of different substituents on the fluorescence properties of [5]helicene derivatives was investigated in terms of molecular orbital symmetry. Unsubstituted [5]helicene is nonemissive due to the symmetry-forbidden S1 → S0 transition. However, the fluorescence emission rate constant (kf) of [5]helicenes is efficiently increased by removing the orbital degeneracy involved in the S1 → S0 transition. As a result, we achieved a [5]helicene derivative exhibiting a high fluorescence quantum yield (Φf = 0.23) and short emission lifetime (⟨τf⟩ = 1.5 ns), which is in marked contrast to unsubstituted [5]helicene (Φf = 0.04 and ⟨τf⟩ = 26 ns).

  6. Effects of time reversal symmetry on phonons in sapphire substrate for ZnO and GaN

    NASA Astrophysics Data System (ADS)

    Kunert, H. W.; Hoffmann, A.; Machatine, A. G. J.; Malherbe, J.; Barnas, J.; Kaczmarczyk, G.; Haboeck, U.; Seguin, R.

    2007-07-01

    Vibrational states in a crystal are classified according to the irreducible representations (irreps) of the corresponding factor group G0k/T. The wave vector k runs over the entire Brillouin zone (BZ). For trigonal BZs, the factor groups are determined by the symmetry points Γ, F, L, T, and the symmetry lines Λ, Σ, Y. When the irreps are complex, the time reversal symmetry has to be taken into account. Using the Frobenuis-Schur criterion adapted to space groups with real and complex irreps, we have investigated high symmetry points and lines of the phonons in trigonal crystals: Cr 2O 3,Fe 2O 3,Ti 2O 3,V 2O 3,FeCO 3,CaCO 3,CdCO 3,MgCO 3,MnCO 3,NaCO 3 and ZnCO 3, with the common space group D3d6( R3¯c). We have found several phonons which are influenced by the time reversal symmetry. Therefore, an extra degeneracy of phonons arises. The theoretical results are also compared with available experimental data.

  7. Polarization properties and disorder effects in H{sub 3} photonic crystal cavities incorporating site-controlled, high-symmetry quantum dot arrays

    SciTech Connect

    Surrente, Alessandro; Felici, Marco; Gallo, Pascal; Dwir, Benjamin; Rudra, Alok; Kapon, Eli; Biasiol, Giorgio

    2015-07-20

    We report on the effects of optical disorder on breaking the symmetry of the cavity modes of H{sub 3} photonic crystal cavities incorporating site-controlled pyramidal quantum dots (QDs) as the internal light source. The high in-plane symmetry of the polarization states of the pyramidal QDs simplifies the analysis of the polarization states of the H{sub 3} cavities. It is shown that the optical disorder induced by fabrication imperfections lifts the degeneracy of the two quadrupole cavity modes and tilts the elongation axes of the cavity mode patterns with respect to the ideal, hexagonal symmetry case. These results are useful for designing QD-cavity structures for polarization-entangled photon sources and few-QD lasers.

  8. Revising the solution of the neutrino oscillation parameter degeneracies at neutrino factories

    SciTech Connect

    Gago, A. M.; Jones Perez, J.

    2007-02-01

    In the context of neutrino factories, we review the solution of the degeneracies in the neutrino oscillation parameters. In particular, we have set limits to sin{sup 2}2{theta}{sub 13} in order to accomplish the unambiguous determination of {theta}{sub 23} and {delta}. We have performed two different analysis. In the first, at a baseline of 3000 km, we simulate a measurement of the channels {nu}{sub e}{yields}{nu}{sub {mu}}, {nu}{sub e}{yields}{nu}{sub {tau}}, and {nu}{sub {mu}}{yields}{nu}{sub {mu}}, combined with their respective conjugate ones, with a muon energy of 50 GeV and a running time of five years. In the second, we merge the simulated data obtained at L=3000 km with the measurement of {nu}{sub e}{yields}{nu}{sub {mu}} channel at 7250 km, the so-called 'magic baseline.' In both cases, we have studied the impact of varying the {nu}{sub {tau}} detector efficiency-mass product ({epsilon}{sub {nu}{tau}xM{tau}}), at 3000 km, keeping unchanged the {nu}{sub {mu}} detector mass and its efficiency. At L=3000 km, we found the existence of degenerate zones, that correspond to values of {theta}{sub 13}, which are equal or almost equal to the true ones. These zones are extremely difficult to discard, even when we increase the number of events. However, in the second scenario, this difficulty is overcome, demonstrating the relevance of the 'magic baseline'. From this scenario, the best limits of sin{sup 2}2{theta}{sub 13}, reached at 3{sigma}, for sin{sup 2}2{theta}{sub 23}=0.95, 0.975, and 0.99 are: 0.008, 0.015, and 0.045, respectively, obtained at {delta}=0, and considering ({epsilon}{sub {nu}{tau}xM{tau}}){approx_equal}125, which is 5 times the initial efficiency-mass combination.

  9. Symmetry in polarimetric remote sensing

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Yueh, S. H.; Kwok, R.

    1993-01-01

    Relationships among polarimetric backscattering coefficients are derived from the viewpoint of symmetry groups. For both reciprocal and non-reciprocal media, symmetry encountered in remote sensing due to reflection, rotation, azimuthal, and centrical symmetry groups is considered. The derived properties are general and valid to all scattering mechanisms, including volume and surface scatterings and their interactions, in a given symmetrical configuration. The scattering coefficients calculated from theoretical models for layer random media and rough surfaces are shown to obey the symmetry relations. Use of symmetry properties in remote sensing of structural and environmental responses of scattering media is also discussed. Orientations of spheroidal scatterers described by spherical, uniform, planophile, plagiothile, erectophile, and extremophile distributions are considered to derive their polarimetric backscattering characteristics. These distributions can be identified from the observed scattering coefficients by comparison with theoretical symmetry calculations. A new parameter is then defined to study scattering structures in geophysical media. Observations from polarimetric data acquired by the Jet Propulsion Laboratory airborne synthetic aperture radar over forests, sea ice, and sea surface are presented. Experimental evidences of the symmetry relationships are shown and their use in polarimetric remote sensing is illustrated. For forests, the coniferous forest in Mt. Shasta area (California) and mixed forest near Presque Isle (Maine) exhibit characteristics of the centrical symmetry at C-band. For sea ice in the Beaufort Sea, multi-year sea ice has a cross-polarized ratio e close to e(sub 0), calculated from symmetry, due to the randomness in the scattering structure. First-year sea ice has e much smaller than e(sub 0) due to the preferential alignment of the columnar structure of the ice. From polarimetric data of a sea surface in the Bering Sea, it is

  10. Topological phases on non-orientable surfaces: twisting by parity symmetry

    NASA Astrophysics Data System (ADS)

    Chan, AtMa P. O.; Teo, Jeffrey C. Y.; Ryu, Shinsei

    2016-03-01

    We discuss (2 + 1)D topological phases on non-orientable spatial surfaces, such as Möbius strip, real projective plane and Klein bottle, etc, which are obtained by twisting the parent topological phases by their underlying parity symmetries through introducing parity defects. We construct the ground states on arbitrary non-orientable closed manifolds and calculate the ground state degeneracy (GSD). Such degeneracy is shown to be robust against continuous deformation of the underlying manifold. We also study the action of the mapping class group on the multiplet of ground states on the Klein bottle. The physical properties of the topological states on non-orientable surfaces are deeply related to the parity symmetric anyons which do not have a notion of orientation in their statistics. For example, the number of ground states on the real projective plane equals the root of the number of distinguishable parity symmetric anyons, while the GSD on the Klein bottle equals the total number of parity symmetric anyons; in deforming the Klein bottle, the Dehn twist encodes the topological spins whereas the Y-homeomorphism tells the particle-hole relation of the parity symmetric anyons.

  11. Topological semimetal: a probable new state of quantum optical lattice gases protected by D4 symmetry

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Liu, W. Vincent; Das Sarma, S.

    2011-03-01

    We demonstrate that a novel topological semimetal emerges as a parity-protected critical theory for fermionic atoms loaded in the p and d orbital bands of a two-dimensional optical lattice. The new quantum state is characterized by a parabolic band-degeneracy point with Berry flux 2 π , in sharp contrast to the π flux of Dirac points as in graphene. We prove that this topological liquid is a universal property for all lattices of D4 point group symmetry and the band degeneracy is protected by odd parity. Turning on interparticle repulsive interaction, the system undergoes a phase transition to a topological insulator, whose experimental signature includes chiral gapless domain-wall modes, reminiscent of quantum Hall edge states. KS and SDS acknowledge the support of JQI-NSF-PFC, AFOSR-MURI, ARO-DARPA-OLE and ARO-MURI. W.V.L. is supported by ARO and ARO-DARPA-OLE. We thank the KITP at UCSB for its hospitality where this research is supported in part by NSF Grant No. PHY05-51164.

  12. Quantum graphs: PT -symmetry and reflection symmetry of the spectrum

    NASA Astrophysics Data System (ADS)

    Kurasov, P.; Majidzadeh Garjani, B.

    2017-02-01

    Not necessarily self-adjoint quantum graphs—differential operators on metric graphs—are considered. Assume in addition that the underlying metric graph possesses an automorphism (symmetry) P . If the differential operator is P T -symmetric, then its spectrum has reflection symmetry with respect to the real line. Our goal is to understand whether the opposite statement holds, namely, whether the reflection symmetry of the spectrum of a quantum graph implies that the underlying metric graph possesses a non-trivial automorphism and the differential operator is P T -symmetric. We give partial answer to this question by considering equilateral star-graphs. The corresponding Laplace operator with Robin vertex conditions possesses reflection-symmetric spectrum if and only if the operator is P T -symmetric with P being an automorphism of the metric graph.

  13. Structure and Properties of High Symmetry Composites

    DTIC Science & Technology

    1990-07-27

    utilizing a 4-directional reinforcement. Reducing the close-to-cubic symmetry concept into practice in our laboratory by a three-dimensional braiding...modelled by utilizing the different elastic strain energy expressions produced by different combinations of symmetry elements. Symmetry in Materials The...rings is insignmicant. Utilizing the above assumptions, numerous textile structures possess holosymmetric cubic symmetry. This symmetry state is found in

  14. Particle-hole symmetry, many-body localization, and topological edge modes

    NASA Astrophysics Data System (ADS)

    Vasseur, Romain; Friedman, Aaron J.; Parameswaran, S. A.; Potter, Andrew C.

    We study the excited states of interacting fermions in one dimension with particle-hole symmetric disorder (equivalently, random-bond XXZ chains) using a combination of renormalization group methods and exact diagonalization. Absent interactions, the entire many-body spectrum exhibits infinite-randomness quantum critical behavior with highly degenerate excited states. We show that though interactions are an irrelevant perturbation in the ground state, they drastically affect the structure of excited states: even arbitrarily weak interactions split the degeneracies in favor of thermalization (weak disorder) or spontaneously broken particle-hole symmetry, driving the system into a many-body localized spin glass phase (strong disorder). In both cases, the quantum critical properties of the non-interacting model are destroyed, either by thermal decoherence or spontaneous symmetry breaking. This system then has the interesting and counterintuitive property that edges of the many-body spectrum are less localized than the center of the spectrum. We argue that our results rule out the existence of certain excited state symmetry-protected topological orders. Supported by the Gordon and Betty Moore Foundation's EPiQS Initiative (Grant GBMF4307 (ACP), the Quantum Materials Program at LBNL (RV), NSF Grant DMR-1455366 and UCOP Research Catalyst Award No. CA-15-327861 (SAP).

  15. Structural Symmetry in Membrane Proteins.

    PubMed

    Forrest, Lucy R

    2015-01-01

    Symmetry is a common feature among natural systems, including protein structures. A strong propensity toward symmetric architectures has long been recognized for water-soluble proteins, and this propensity has been rationalized from an evolutionary standpoint. Proteins residing in cellular membranes, however, have traditionally been less amenable to structural studies, and thus the prevalence and significance of symmetry in this important class of molecules is not as well understood. In the past two decades, researchers have made great strides in this area, and these advances have provided exciting insights into the range of architectures adopted by membrane proteins. These structural studies have revealed a similarly strong bias toward symmetric arrangements, which were often unexpected and which occurred despite the restrictions imposed by the membrane environment on the possible symmetry groups. Moreover, membrane proteins disproportionately contain internal structural repeats resulting from duplication and fusion of smaller segments. This article discusses the types and origins of symmetry in membrane proteins and the implications of symmetry for protein function.

  16. Symmetry Guide to Ferroaxial Transitions

    NASA Astrophysics Data System (ADS)

    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 .

  17. The relationship between noise correlation and the Green's function in the presence of degeneracy and the absence of equipartition

    USGS Publications Warehouse

    Tsai, V.C.

    2010-01-01

    Recent derivations have shown that when noise in a physical system has its energy equipartitioned into the modes of the system, there is a convenient relationship between the cross correlation of time-series recorded at two points and the Green's function of the system. Here, we show that even when energy is not fully equipartitioned and modes are allowed to be degenerate, a similar (though less general) property holds for equations with wave equation structure. This property can be used to understand why certain seismic noise correlation measurements are successful despite known degeneracy and lack of equipartition on the Earth. No claim to original US government works Journal compilation ?? 2010 RAS.

  18. Demonstration of CW mode locked Cr:forsterite laser using self-shortening and transverse mode degeneracy driven mode locking.

    PubMed

    George, J; Thakur, P; Bindra, K S; Oak, S M

    2014-11-10

    This paper reports a nearly Fourier transform limited CW mode locked Cr:forsterite laser at 1282 nm, with 131 fs pulse duration, based on self-shortening and transverse mode degeneracy (TMD) driven mode locking, operating near the point of fourth-order TMD. The cavity employs a combination of instantaneous intensity driven self-shortening, and operation on the right side of the fourth-order TMD, to generate the self-amplitude modulation necessary for self-mode locking.

  19. Resonantly amplified vibronic symmetry breaking

    NASA Astrophysics Data System (ADS)

    Poliakoff, E. D.; Rathbone, G. J.; Bozek, J. D.; Lucchese, R. R.

    2002-05-01

    In photoelectron spectroscopy, it is normally assumed that excitation of a single quantum of a non-totally symmetric vibrational mode is forbidden owing to symmetry constraints. Using vibrationally resolved photoelectron spectroscopy over a broad spectral range, we have shown that a previously overlooked mechanism can lead to these nominally forbidden transitions. Specifically, the photoelectron can mediate the oscillator strength for such a transition via resonantly amplified vibronic symmetry breaking, and this effect results from intrachannel rather than interchannel coupling. In our first experiments, we focused on bending excitation accompanying CO2 photoionization. Photoelectron spectroscopy on the CO_2^+(C^2Σ_g^+) state showed that the excitation of the (010) vibrational mode is mediated by a shape resonant continuum electron. The degree of vibrational excitation can be substantial, and extensions to other types of symmetry breaking are currently being investigated.

  20. Shape phase transitions in odd-A nuclei

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2008-11-11

    We investigate shape phase transitions in odd nuclei within the Interacting Boson Fermion Model. Special attention is given to the case of the transition from the vibrational behaviour to the stable axial deformation. The odd particle is assumed to be moving in the three single particle orbitals j = 1/2,3/2,5/2 with a boson-fermion Hamiltonian that leads to the occurrence of the SU{sup BF}(3) boson-fermion symmetry when the boson part approaches the SU(3) condition. Both energy spectra and electromagnetic transitions show characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The role of the additional particle in characterizing the properties of the critical points in finite quantal systems is investigated by resorting to the formalism based on the intrinsic frame.

  1. U{sup BF}(5) to SU{sup BF}(3) shape phase transition in odd nuclei for j=1/2, 3/2, and 5/2 orbits: The role of the odd particle at the critical point

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-01-15

    We investigate the phase transition in odd nuclei within the Interacting Boson Fermion Model in correspondence with the transition from spherical to stable axially deformed shape. The odd particle is assumed to be moving in the single-particle orbitals with angular momenta j=1/2,3/2,5/2 with a boson-fermion Hamiltonian that leads to the occurrence of the SU{sup BF}(3) boson-fermion symmetry when the boson part approaches the SU(3) condition. Both energy spectra and electromagnetic transitions show characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The role of the additional particle in characterizing the properties of the critical points in finite quantal systems is investigated by resorting to the formalism based on the intrinsic frame.

  2. Symmetries of coupled harmonic oscillators

    NASA Technical Reports Server (NTRS)

    Han, D.; Kim, Y. S.

    1993-01-01

    It is shown that the system of two coupled harmonic oscillators possesses many interesting symmetries. It is noted that the symmetry of a single oscillator is that of the three-parameter group Sp(2). Thus two uncoupled oscillator exhibits a direct product of two Sp(2) groups, with six parameters. The coupling can be achieved through a rotation in the two-dimensional space of two oscillator coordinates. The closure of the commutation relations for the generators leads to the ten-parameter group Sp(4) which is locally isomorphic to the deSitter group O(3,2).

  3. Iterates of maps with symmetry

    NASA Technical Reports Server (NTRS)

    Chossat, Pascal; Golubitsky, Martin

    1988-01-01

    Fixed-point bifurcation, period doubling, and Hopf bifurcation (HB) for iterates of equivariant mappings are investigated analytically, with a focus on HB in the presence of symmetry. An algebraic formulation for the hypotheses of the theorem of Ruelle (1973) is derived, and the case of standing waves in a system of ordinary differential equations with O(2) symmetry is considered in detail. In this case, it is shown that HB can lead directly to motion on an invariant 3-torus, with an unexpected third frequency due to drift of standing waves along the torus.

  4. The Broken Symmetry of Time

    SciTech Connect

    Kastner, Ruth E.

    2011-11-29

    This paper seeks to clarify features of time asymmetry in terms of symmetry breaking. It is observed that, in general, a contingent situation or event requires the breaking of an underlying symmetry. The distinction between the universal anisotropy of temporal processes and the irreversibility of certain physical processes is clarified. It is also proposed that the Transactional Interpretation of quantum mechanics offers an effective way to explain general thermodynamic asymmetry in terms of the time asymmetry of radiation, where prior such efforts have fallen short.

  5. Quantum Symmetries and Exceptional Collections

    NASA Astrophysics Data System (ADS)

    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.

  6. Symmetry analysis of cellular automata

    NASA Astrophysics Data System (ADS)

    García-Morales, V.

    2013-01-01

    By means of B-calculus [V. García-Morales, Phys. Lett. A 376 (2012) 2645] a universal map for deterministic cellular automata (CAs) has been derived. The latter is shown here to be invariant upon certain transformations (global complementation, reflection and shift). When constructing CA rules in terms of rules of lower range a new symmetry, “invariance under construction” is uncovered. Modular arithmetic is also reformulated within B-calculus and a new symmetry of certain totalistic CA rules, which calculate the Pascal simplices modulo an integer number p, is then also uncovered.

  7. Chiral symmetry in quarkyonic matter

    SciTech Connect

    Kojo, T.

    2012-05-15

    The 1/N{sub c} expansion classifies nuclear matter, deconfined quark matter, and Quarkyonic matter in low temperature region. We investigate the realization of chiral symmetry in Quarkyonic matter by taking into account condensations of chiral particle-hole pairs. It is argued that chiral symmetry and parity are locally violated by the formation of chiral spirals, <{psi}-bar exp (2i{mu}{sub q} z{gamma}{sup 0} {gamma}{sup z}){psi}> . An extension to multiple chiral spirals is also briefly discussed.

  8. Bell Inequalities and Group Symmetry

    NASA Astrophysics Data System (ADS)

    Bolonek-Lasoń, Katarzyna

    2017-03-01

    Recently the method based on irreducible representations of finite groups has been proposed as a tool for investigating the more sophisticated versions of Bell inequalities (V. Ugǔr Gűney, M. Hillery, Phys. Rev. A90, 062121 ([2014]) and Phys. Rev. A91, 052110 ([2015])). In the present paper an example based on the symmetry group S 4 is considered. The Bell inequality violation due to the symmetry properties of regular tetrahedron is described. A nonlocal game based on the inequalities derived is described and it is shown that the violation of Bell inequality implies that the quantum strategies outperform their classical counterparts.

  9. Nonsupersymmetric Dualities from Mirror Symmetry

    NASA Astrophysics Data System (ADS)

    Kachru, Shamit; Mulligan, Michael; Torroba, Gonzalo; Wang, Huajia

    2017-01-01

    We study supersymmetry breaking perturbations of the simplest dual pair of (2 +1 )-dimensional N =2 supersymmetric field theories—the free chiral multiplet and N =2 super QED with a single flavor. We find dual descriptions of a phase diagram containing four distinct massive phases. The equivalence of the intervening critical theories gives rise to several nonsupersymmetric avatars of mirror symmetry: we find dualities relating scalar QED to a free fermion and Wilson-Fisher theories to both scalar and fermionic QED. Thus, mirror symmetry can be viewed as the multicritical parent duality from which these nonsupersymmetric dualities directly descend.

  10. Chiral symmetry on the lattice

    SciTech Connect

    Creutz, M.

    1994-11-01

    The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model.

  11. Accidental degeneracy in the spiropyran radical cation: charge transfer between two orthogonal rings inducing ultra-efficient reactivity.

    PubMed

    Mendive-Tapia, David; Kortekaas, Luuk; Steen, Jorn D; Perrier, Aurélie; Lasorne, Benjamin; Browne, Wesley R; Jacquemin, Denis

    2016-11-16

    Photochromism of the spiropyran radical cation to the corresponding merocyanine form is investigated by a combination of electrochemical oxidation, UV/vis absorption spectroscopy, spectroelectrochemistry and first-principles calculations (TD-DFT, CAS-SCF and CAS-PT2). First, we demonstrate that the ring-opening of mono-spiropyrans occurs upon one-electron oxidation and that it can be driven photochemically as well as thermally, with trapping of the merocyanine by protonation. Second, in order to explain this experimentally observed spectroelectrochemical behaviour we suggest a theoretical mechanism based on the reactivity of the two lowest electronic excited-states, which promotes effective electron transfer from the indoline (nitrogen-ring) to the pyran (oxygen-ring) moieties (and vice versa) through a conical intersection seam of degeneracy. Characterisation of the minimum energy conical intersection on this crossing revealed that it presents a rare diabatic trapping topology. The excited state molecule cannot escape from crossing the intersection seam due to the presence of only one degeneracy-lifting coordinate that efficiently channels into the formation of the merocyanine photoproduct, so giving rise to a "kitchen sink" funnel-like effect. Therefore, assuming rapid relaxation after vertical excitation to a higher electronic state, photoconversion cannot be avoided in the D1 electronic state, which rationalises the remarkably efficient visible light driven excited-state reactivity observed experimentally.

  12. Charge 2 e /3 Superconductivity and Topological Degeneracies without Localized Zero Modes in Bilayer Fractional Quantum Hall States

    NASA Astrophysics Data System (ADS)

    Barkeshli, Maissam

    2016-08-01

    It has been recently shown that non-Abelian defects with localized parafermion zero modes can arise in conventional Abelian fractional quantum Hall (FQH) states. Here we propose an alternate route to creating, manipulating, and measuring topologically protected degeneracies in bilayer FQH states coupled to superconductors, without the creation of localized parafermion zero modes. We focus mainly on electron-hole bilayers, with a ±1 /3 Laughlin FQH state in each layer, with boundaries that are proximity coupled to a superconductor. We show that the superconductor induces charge 2 e /3 quasiparticle-pair condensation at each boundary of the FQH state, and that this leads to (i) topologically protected degeneracies that can be measured through charge sensing experiments and (ii) a fractional charge 2 e /3 ac Josephson effect. We demonstrate that an analog of non-Abelian braiding is possible, despite the absence of a localized zero mode. We discuss several practical advantages of this proposal over previous work, and also several generalizations.

  13. Spin symmetry in the antinucleon spectrum.

    PubMed

    Zhou, Shan-Gui; Meng, Jie; Ring, P

    2003-12-31

    We discuss spin and pseudospin symmetry in the spectrum of single nucleons and single antinucleons in a nucleus. As an example we use relativistic mean field theory to investigate single antinucleon spectra. We find a very well developed spin symmetry in single antineutron and single antiproton spectra. The dominant components of the wave functions of the spin doublet are almost identical. This spin symmetry in antiparticle spectra and the pseudospin symmetry in particle spectra have the same origin. However, it turns out that the spin symmetry in antinucleon spectra is much better developed than the pseudospin symmetry in normal nuclear single particle spectra.

  14. Charge symmetry at the partonic level

    SciTech Connect

    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.

  15. Super no-scale models in string theory

    NASA Astrophysics Data System (ADS)

    Kounnas, Costas; Partouche, Hervé

    2016-12-01

    We consider "super no-scale models" in the framework of the heterotic string, where the N = 4 , 2 , 1 → 0 spontaneous breaking of supersymmetry is induced by geometrical fluxes realizing a stringy Scherk-Schwarz perturbative mechanism. Classically, these backgrounds are characterized by a boson/fermion degeneracy at the massless level, even if supersymmetry is broken. At the 1-loop level, the vacuum energy is exponentially suppressed, provided the supersymmetry breaking scale is small, m3/2 ≪Mstring. We show that the "super no-scale string models" under consideration are free of Hagedorn-like tachyonic singularities, even when the supersymmetry breaking scale is large, m3/2 ≃Mstring. The vacuum energy decreases monotonically and converges exponentially to zero, when m3/2 varies from Mstring to 0. We also show that all Wilson lines associated to asymptotically free gauge symmetries are dynamically stabilized by the 1-loop effective potential, while those corresponding to non-asymptotically free gauge groups lead to instabilities and condense. The Wilson lines of the conformal gauge symmetries remain massless. When stable, the stringy super no-scale models admit low energy effective actions, where decoupling gravity yields theories in flat spacetime, with softly broken supersymmetry.

  16. Turning Students into Symmetry Detectives

    ERIC Educational Resources Information Center

    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…

  17. Platonic Symmetry and Geometric Thinking

    ERIC Educational Resources Information Center

    Zsombor-Murray, Paul

    2007-01-01

    Cubic symmetry is used to build the other four Platonic solids and some formalism from classical geometry is introduced. Initially, the approach is via geometric construction, e.g., the "golden ratio" is necessary to construct an icosahedron with pentagonal faces. Then conventional elementary vector algebra is used to extract quantitative…

  18. Concomitant Ordering and Symmetry Lowering

    ERIC Educational Resources Information Center

    Boo, William O. J.; Mattern, Daniell L.

    2008-01-01

    Examples of concomitant ordering include magnetic ordering, Jahn-Teller cooperative ordering, electronic ordering, ionic ordering, and ordering of partially-filled sites. Concomitant ordering sets in when a crystal is cooled and always lowers the degree of symmetry of the crystal. Concomitant ordering concepts can also be productively applied to…

  19. Symmetry-protected topological entanglement

    NASA Astrophysics Data System (ADS)

    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.

  20. Circular codes, symmetries and transformations.

    PubMed

    Fimmel, Elena; Giannerini, Simone; Gonzalez, Diego Luis; Strüngmann, Lutz

    2015-06-01

    Circular codes, putative remnants of primeval comma-free codes, have gained considerable attention in the last years. In fact they represent a second kind of genetic code potentially involved in detecting and maintaining the normal reading frame in protein coding sequences. The discovering of an universal code across species suggested many theoretical and experimental questions. However, there is a key aspect that relates circular codes to symmetries and transformations that remains to a large extent unexplored. In this article we aim at addressing the issue by studying the symmetries and transformations that connect different circular codes. The main result is that the class of 216 C3 maximal self-complementary codes can be partitioned into 27 equivalence classes defined by a particular set of transformations. We show that such transformations can be put in a group theoretic framework with an intuitive geometric interpretation. More general mathematical results about symmetry transformations which are valid for any kind of circular codes are also presented. Our results pave the way to the study of the biological consequences of the mathematical structure behind circular codes and contribute to shed light on the evolutionary steps that led to the observed symmetries of present codes.

  1. Baryon and chiral symmetry breaking

    SciTech Connect

    Gorsky, A.; Krikun, A.

    2014-07-23

    We briefly review the generalized Skyrmion model for the baryon recently suggested by us. It takes into account the tower of vector and axial mesons as well as the chiral symmetry breaking. The generalized Skyrmion model provides the qualitative explanation of the Ioffe’s formula for the baryon mass.

  2. From symmetries to number theory

    SciTech Connect

    Tempesta, P.

    2009-05-15

    It is shown that the finite-operator calculus provides a simple formalism useful for constructing symmetry-preserving discretizations of quantum-mechanical integrable models. A related algebraic approach can also be used to define a class of Appell polynomials and of L series.

  3. The Symmetry of Natural Laws.

    ERIC Educational Resources Information Center

    Brown, Laurie M.

    This document is a monograph intended for advanced undergraduate students, or beginning graduate students, who have some knowledge of modern physics as well as classical physics, including the elementary quantum mechanical treatment of the hydrogen atom and angular momentum. The first chapter introduces symmetry and relates it to the mathematical…

  4. Resonantly amplified vibronic symmetry breaking

    NASA Astrophysics Data System (ADS)

    Rathbone, G. J.; Poliakoff, E. D.; Bozek, John D.; Lucchese, R. R.

    2001-05-01

    The energy dependence of the vibrational branching ratio for exciting one quantum of bending is determined for CO2 4σg-1 photoionization. This nominally forbidden transition becomes allowed for a photoionization transition as a result of instantaneous symmetry breaking due to zero point motion, and is strongly enhanced by a continuum shape resonance.

  5. Hidden local symmetry and beyond

    NASA Astrophysics Data System (ADS)

    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)”.

  6. Monster symmetry and extremal CFTs

    NASA Astrophysics Data System (ADS)

    Gaiotto, Davide

    2012-11-01

    We test some recent conjectures about extremal selfdual CFTs, which are the candidate holographic duals of pure gravity in AdS 3. We prove that no c = 48 extremal selfdual CFT or SCFT may possess Monster symmetry. Furthermore, we disprove a recent argument against the existence of extremal selfdual CFTs of large central charge.

  7. Superdeformations and fermion dynamical symmetries

    SciTech Connect

    Wu, Cheng-Li . Dept. of Physics and Atmospheric Science Tennessee Univ., Knoxville, TN . Dept. of Physics and Astronomy Joint Inst. for Heavy Ion Research, Oak Ridge, TN )

    1990-01-01

    In this talk, I will present a link between nuclear collective motions and their underlying fermion dynamical symmetries. In particular, I will focus on the microscopic understanding of deformations. It is shown that the SU{sub 3} of the one major shell fermion dynamical symmetry model (FDSM) is responsible for the physics of low and high spins in normal deformation. For the recently observed phenomena of superdeformation, the physics of the problem dictates a generalization to a supershell structure (SFDSM), which also has an SU{sub 3} fermion dynamical symmetry. Many recently discovered feature of superdeformation are found to be inherent in such an SU{sub 3} symmetry. In both cases the dynamical Pauli effect plays a vital role. A particularly noteworthy discovery from this model is that the superdeformed ground band is not the usual unaligned band but the D-pair aligned (DPA) band, which sharply crosses the excited bands. The existence of such DPA band is a key point to understand many properties of superdeformation. Our studies also poses new experimental challenge. This is particularly interesting since there are now plans to build new and exciting {gamma}-ray detecting systems, like the GAMMASPHERE, which could provide answers to some of these challenges. 34 refs., 11 figs., 5 tabs.

  8. Theory of nodal s±-wave pairing symmetry in the Pu-based 115 superconductor family

    SciTech Connect

    Das, Tanmoy; Zhu, Jian -Xin; Graf, Matthias J.

    2015-02-27

    The spin-fluctuation mechanism of superconductivity usually results in the presence of gapless or nodal quasiparticle states in the excitation spectrum. Nodal quasiparticle states are well established in copper-oxide, and heavy-fermion superconductors, but not in iron-based superconductors. Here, we study the pairing symmetry and mechanism of a new class of plutonium-based high-Tc superconductors and predict the presence of a nodal s⁺⁻ wave pairing symmetry in this family. Starting from a density-functional theory (DFT) based electronic structure calculation we predict several three-dimensional (3D) Fermi surfaces in this 115 superconductor family. We identify the dominant Fermi surface “hot-spots” in the inter-band scattering channel, which are aligned along the wavevector Q = (π, π, π), where degeneracy could induce sign-reversal of the pairing symmetry. Our calculation demonstrates that the s⁺⁻ wave pairing strength is stronger than the previously thought d-wave pairing; and more importantly, this pairing state allows for the existence of nodal quasiparticles. Finally, we predict the shape of the momentum- and energy-dependent magnetic resonance spectrum for the identification of this pairing symmetry.

  9. Theory of nodal s±-wave pairing symmetry in the Pu-based 115 superconductor family

    DOE PAGES

    Das, Tanmoy; Zhu, Jian -Xin; Graf, Matthias J.

    2015-02-27

    The spin-fluctuation mechanism of superconductivity usually results in the presence of gapless or nodal quasiparticle states in the excitation spectrum. Nodal quasiparticle states are well established in copper-oxide, and heavy-fermion superconductors, but not in iron-based superconductors. Here, we study the pairing symmetry and mechanism of a new class of plutonium-based high-Tc superconductors and predict the presence of a nodal s⁺⁻ wave pairing symmetry in this family. Starting from a density-functional theory (DFT) based electronic structure calculation we predict several three-dimensional (3D) Fermi surfaces in this 115 superconductor family. We identify the dominant Fermi surface “hot-spots” in the inter-band scattering channel,more » which are aligned along the wavevector Q = (π, π, π), where degeneracy could induce sign-reversal of the pairing symmetry. Our calculation demonstrates that the s⁺⁻ wave pairing strength is stronger than the previously thought d-wave pairing; and more importantly, this pairing state allows for the existence of nodal quasiparticles. Finally, we predict the shape of the momentum- and energy-dependent magnetic resonance spectrum for the identification of this pairing symmetry.« less

  10. Theory of nodal s±-wave pairing symmetry in the Pu-based 115 superconductor family

    PubMed Central

    Das, Tanmoy; Zhu, Jian-Xin; Graf, Matthias J.

    2015-01-01

    The spin-fluctuation mechanism of superconductivity usually results in the presence of gapless or nodal quasiparticle states in the excitation spectrum. Nodal quasiparticle states are well established in copper-oxide, and heavy-fermion superconductors, but not in iron-based superconductors. Here, we study the pairing symmetry and mechanism of a new class of plutonium-based high-Tc superconductors and predict the presence of a nodal s+− wave pairing symmetry in this family. Starting from a density-functional theory (DFT) based electronic structure calculation we predict several three-dimensional (3D) Fermi surfaces in this 115 superconductor family. We identify the dominant Fermi surface “hot-spots” in the inter-band scattering channel, which are aligned along the wavevector Q = (π, π, π), where degeneracy could induce sign-reversal of the pairing symmetry. Our calculation demonstrates that the s+− wave pairing strength is stronger than the previously thought d-wave pairing; and more importantly, this pairing state allows for the existence of nodal quasiparticles. Finally, we predict the shape of the momentum- and energy-dependent magnetic resonance spectrum for the identification of this pairing symmetry. PMID:25721375

  11. Field theory representation of mixed gauge-gravity symmetry-protected topological invariants, group cohomology and beyond

    NASA Astrophysics Data System (ADS)

    Wang, Juven; Gu, Zheng-Cheng; Wen, Xiao-Gang

    The challenge of identifying symmetry-protected topological states (SPTs) is due to their lack of symmetry-breaking order parameters and intrinsic topological orders. For this reason, it is impossible to formulate SPTs under Ginzburg-Landau theory or probe SPTs via fractionalized bulk excitations and topology-dependent ground state degeneracy. However, the partition functions from path integrals with various symmetry twists are universal SPT invariants, fully characterizing SPTs. In this work, we use gauge fields to represent those symmetry twists in closed spacetimes of any dimensionality and arbitrary topology. This allows us to express the SPT invariants in terms of continuum field theory. We show that SPT invariants of pure gauge actions describe the SPTs predicted by group cohomology, while the mixed gauge-gravity actions describe the beyond-group-cohomology SPTs, recently observed by Kapustin. We find new examples of mixed gauge-gravity actions for U(1) SPTs in 3+1D and 4+1D via the Stiefel-Whitney class and the gravitational Chern-Simons term. [Work based on Phys. Rev. Lett. 114, 031601 (2015) arXiv:1405.7689

  12. Symmetry Breaking During Drosophila Oogenesis

    PubMed Central

    Roth, Siegfried; Lynch, Jeremy A.

    2009-01-01

    The orthogonal axes of Drosophila are established during oogenesis through a hierarchical series of symmetry-breaking steps, most of which can be traced back to asymmetries inherent in the architecture of the ovary. Oogenesis begins with the formation of a germline cyst of 16 cells connected by ring canals. Two of these 16 cells have four ring canals, whereas the others have fewer. The first symmetry-breaking step is the selection of one of these two cells to become the oocyte. Subsequently, the germline cyst becomes surrounded by somatic follicle cells to generate individual egg chambers. The second symmetry-breaking step is the posterior positioning of the oocyte within the egg chamber, a process mediated by adhesive interactions with a special group of somatic cells. Posterior oocyte positioning is accompanied by a par gene-dependent repolarization of the microtubule network, which establishes the posterior cortex of the oocyte. The next two steps of symmetry breaking occur during midoogenesis after the volume of the oocyte has increased about 10-fold. First, a signal from the oocyte specifies posterior follicle cells, polarizing a symmetric prepattern present within the follicular epithelium. Second, the posterior follicle cells send a signal back to the oocyte, which leads to a second repolarization of the oocyte microtubule network and the asymmetric migration of the oocyte nucleus. This process again requires the par genes. The repolarization of the microtubule network results in the transport of bicoid and oskar mRNAs, the anterior and posterior determinants, respectively, of the embryonic axis, to opposite poles of the oocyte. The asymmetric positioning of the oocyte nucleus defines a cortical region of the oocyte where gurken mRNA is localized, thus breaking the dorsal–ventral symmetry of the egg and embryo. PMID:20066085

  13. Structure and Degeneracy of Vortex Lattice Domains in Pure Superconducting Niobium: A Small-Angle Neutron Scattering Study

    SciTech Connect

    Laver, M.; Bowell, C.; Forgan, E. M.; Abrahamsen, A. B.; Fort, D.; Dewhurst, C. D.; Muhlbauer, S.; Christen, David K; Kohlbrecher, J.; Cubitt, R.; Ramos, S.

    2009-01-01

    High-purity niobium exhibits a surprisingly rich assortment of vortex lattice (VL) structures for fields applied parallel to a fourfold symmetry axis, with all observed VL phases made up of degenerate domains that spontaneously break some crystal symmetry. Yet a single regular hexagonal VL domain is observed at all temperatures and fields parallel to a threefold symmetry axis. We report a detailed investigation of the transition between these lush and barren VL landscapes, discovering new VL structures and phase transitions at high fields. We show that the number and relative population of VL domains is intrinsically tied to the underlying crystal symmetry. We discuss how subtle anisotropies of the crystal may generate the remarkable VLs observed.

  14. A valence bond analysis of electronic degeneracies in Jahn-Teller systems: low-lying states of the cyclopentadienyl radical and cation.

    PubMed

    Zilberg, Shmuel; Haas, Yehuda

    2002-09-11

    The lowest doublet electronic state of the cyclopentadienyl radical (CPDR) and the lowest singlet state of the cyclopentadienyl cation (CPDC) are distorted from the highly symmetric D(5h) structure due to the Jahn-Teller effect. A valence bond analysis based on the phase-change rule of Longuet-Higgins reveals that in both cases the distortion is due to the first-order Jahn-Teller effect. It is shown that, while for the radical an isolated Jahn-Teller degeneracy is expected, in the case of the cation the main Jahn-Teller degeneracy is accompanied by five satellite degeneracies. The method offers a chemically oriented way for identifying the distortive coordinates.

  15. Space-based Microlens Parallax Observation as a Way to Resolve the Severe Degeneracy between Microlens-parallax and Lens-orbital Effects

    NASA Astrophysics Data System (ADS)

    Han, C.; Udalski, A.; Lee, C.-U.; Gould, A.; Bozza, V.; Szymański, M. K.; Soszyński, I.; Skowron, J.; Mróz, P.; Poleski, R.; Pietrukowicz, P.; Kozłowski, S.; Ulaczyk, K.; Wyrzykowski, Ł.; Pawlak, M.; OGLE Collaboration; Albrow, M. D.; Chung, S.-J.; Kim, S.-L.; Cha, S.-M.; Jung, Y. K.; Kim, D.-J.; Lee, Y.; Park, B.-G.; Ryu, Y.-H.; Shin, I.-G.; Yee, J. C.; KMTNet Collaboration

    2016-08-01

    In this paper, we demonstrate the severity of the degeneracy between the microlens-parallax and lens-orbital effects by presenting the analysis of the gravitational binary-lens event OGLE-2015-BLG-0768. Despite the obvious deviation from the model based on the linear observer motion and the static binary, it is found that the residual can be almost equally well explained by either the parallactic motion of the Earth or the rotation of the binary-lens axis, resulting in the severe degeneracy between the two effects. We show that the degeneracy can be readily resolved with the additional data provided by space-based microlens parallax observations. By enabling us to distinguish between the two higher-order effects, space-based microlens parallax observations will not only make it possible to accurately determine the physical lens parameters but also to further constrain the orbital parameters of binary lenses.

  16. Universal Formulation For Symmetries In Computed Flows

    NASA Technical Reports Server (NTRS)

    Pao, S. Paul; Abdol-Hamid, Khaled S.

    1995-01-01

    Universal formulation for high-order symmetries in boundary conditions on flows devised. Eliminates need for special procedures to incorporate symmetries and corresponding boundary conditions into computer codes solving Navier-Stokes and Euler equations of flow.

  17. An Elementary Course in Mathematical Symmetry.

    ERIC Educational Resources Information Center

    Rose, Bruce I.; Stafford, Robert D.

    1981-01-01

    A college course designed to teach students about the mathematics of symmetry using pieces of wallpaper and cloth designs is presented. Mathematical structures and the symmetry of graphic designs provide the starting point for instruction. (MP)

  18. Symmetry perception in humans and macaques.

    PubMed

    Beck, Diane M; Pinsk, Mark A; Kastner, Sabine

    2005-09-01

    The human ability to detect symmetry has been a topic of interest to psychologists and philosophers since the 19th century, yet surprisingly little is known about the neural basis of symmetry perception. In a recent fMRI study, Sasaki and colleagues begin to remedy this situation. By identifying the neural structures that respond to symmetry in both humans and macaques, the authors lay the groundwork for understanding the neural mechanisms underlying symmetry perception.

  19. Flavored Peccei-Quinn symmetry

    NASA Astrophysics Data System (ADS)

    Ahn, Y. H.

    2015-03-01

    In an attempt to uncover any underlying physics in the standard model (SM), we suggest a μ - τ power law in the lepton sector, such that relatively large 13 mixing angle with bilarge ones can be derived. On the basis of this, we propose a neat and economical model for both the fermion mass hierarchy problem of the SM and a solution to the strong charge parity (C P ) problem, in a way that no domain wall problem occurs, based on A4×U (1 )X symmetry in a supersymmetric framework. Here we refer to the global U (1 )X symmetry that can explain the above problems as "flavored Peccei-Quinn symmetry." In the model, a direct coupling of the SM gauge singlet flavon fields responsible for spontaneous symmetry breaking to ordinary quarks and leptons, both of which are charged under U (1 )X, comes to pass through Yukawa interactions, and all vacuum expectation values breaking the symmetries are connected to each other. So the scale of Peccei-Quinn symmetry breaking is shown to be roughly located around the 1 012 GeV section through its connection to the fermion masses. The model predictions are shown to lie on the testable regions in the very near future through on-going experiments for neutrino oscillation, neutrinoless double beta decay, and the axion. We examine the model predictions, arisen from the μ - τ power law, on leptonic C P violation, neutrinoless double beta decay, and atmospheric mixing angle, and show that the fermion mass and mixing hierarchies are in good agreement with the present data. Interestingly, we show the model predictions on the axion mass ma≃2.53 ×1 0-5 eV and the axion coupling to photon ga γ γ≃1.33 ×1 0-15 GeV-1 . And subsequently the square of the ratio between them is shown to be one or two orders of magnitude lower than that of the conventional axion model.

  20. Generalized partial dynamical symmetry in nuclei.

    PubMed

    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.

  1. Noether symmetries and duality transformations in cosmology

    NASA Astrophysics Data System (ADS)

    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.

  2. Superalgebra and fermion-boson symmetry

    PubMed Central

    Miyazawa, Hironari

    2010-01-01

    Fermions and bosons are quite different kinds of particles, but it is possible to unify them in a supermultiplet, by introducing a new mathematical scheme called superalgebra. In this article we discuss the development of the concept of symmetry, starting from the rotational symmetry and finally arriving at this fermion-boson (FB) symmetry. PMID:20228617

  3. Symmetry Breaking for Black-Scholes Equations

    NASA Astrophysics Data System (ADS)

    Yang, Xuan-Liu; Zhang, Shun-Li; Qu, Chang-Zheng

    2007-06-01

    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.

  4. CP symmetry in optical systems

    NASA Astrophysics Data System (ADS)

    Dana, Brenda; Bahabad, Alon; Malomed, Boris A.

    2015-04-01

    We introduce a model of a dual-core optical waveguide with opposite signs of the group-velocity dispersion 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 symmetry, while the addition of the intracore 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.

  5. Facial symmetry in robust anthropometrics.

    PubMed

    Kalina, Jan

    2012-05-01

    Image analysis methods commonly used in forensic anthropology do not have desirable robustness properties, which can be ensured by robust statistical methods. In this paper, the face localization in images is carried out by detecting symmetric areas in the images. Symmetry is measured between two neighboring rectangular areas in the images using a new robust correlation coefficient, which down-weights regions in the face violating the symmetry. Raw images of faces without usual preliminary transformations are considered. The robust correlation coefficient based on the least weighted squares regression yields very promising results also in the localization of such faces, which are not entirely symmetric. Standard methods of statistical machine learning are applied for comparison. The robust correlation analysis can be applicable to other problems of forensic anthropology.

  6. Broken symmetries in multilayered perceptrons

    NASA Astrophysics Data System (ADS)

    Barkai, E.; Hansel, D.; Sompolinsky, H.

    1992-03-01

    The statistical mechanics of two-layered perceptrons with N input units, K hidden units, and a single output unit that makes a decision based on a majority rule (Committee Machine) are studied. Two architectures are considered. In the nonoverlapping case the hidden units do not share common inputs. In the fully connected case each hidden unit is connected to the entire input layer. In both cases the network realizes a random dichotomy of P inputs. The statistical properties of the space of solutions as a function of P is studied, using the replica method, and by numerical simulations, in the regime where N>>K. In the nonoverlapping architecture with continuously varying weights the capacity, defined as the maximal number of P per weight, (αc) is calculated under a replica-symmetric (RS) ansatz. At large K, αc diverges as K1/2 in contradiction with the rigorous upper bound, αcsymmetry-breaking effect. The instability of the RS solution is shown to occur at a value of α which remains finite in the large-K limit. A one-step replica-symmetry-breaking (RSB) ansatz is studied for K=3 and in the limit K goes to infinity. The results indicate that αc(K) diverges with K, probably logarithmically. The occurrence of RSB far below the capacity limit is confirmed by comparison of the theoretical results with numerical simulations for K=3. This symmetry breaking implies that unlike the single-layer perceptron case, the space of solutions of the two-layer perceptron breaks, beyond a critical value of α, into many disjoint subregions. The entropies of the connected subregions are almost degenerate, their relative difference being of order 1/N. In the case of a nonoverlapping Committee Machine with binary, i.e., +/-1 weights, αc<=1 is an upper bound for all K. The RS theory predicts αc=0.92 for K=3 and αc=0.95 for the large-K limit

  7. Symmetry of cardiac function assessment

    PubMed Central

    Bai, Xu-Fang; Ma, Amy X

    2016-01-01

    Both right and left ventricles are developed from two adjacent segments of the primary heart tube. Though they are different with regard to shape and power, they mirror each other in terms of behavior. This is the first level of symmetry in cardiac function assessment. Both cardiac muscle contraction and relaxation are active. This constructs the second level of symmetry in cardiac function assessment. Combination of the two levels will help to find some hidden indexes or approaches to evaluate cardiac function. In this article, four major indexes from echocardiography were analyzed under this principal, another seventeen indexes or measurement approaches came out of the shadow, which is very helpful in the assessment of cardiac function, especially for the right cardiac function and diastolic cardiac function. PMID:27582768

  8. Electronic Degeneracy and Intrinsic Magnetic Properties of EpitaxialNb: SrTiO3 Thin Films Controlled by Defects.

    PubMed

    Sarantopoulos, A; Ferreiro-Vila, E; Pardo, V; Magén, C; Aguirre, M H; Rivadulla, F

    2015-10-16

    We report thermoelectric power experiments in e-doped thin films of SrTiO3 (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and nonlinear Hall effect. Ab initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this Letter for tetragonally distorted e-doped STO thin films, is similar to that observed in LaAlO3/STO interfaces and magnetic STO quantum wells.

  9. The Valley-Degeneracy-Breaking Induced Arbitrary-Chern Number Insulator on Square Lattice and the Quantum Hall Effect

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Xiang; Li, Fu-Xiang; Cao, Jie

    2015-02-01

    The arbitrary-Chern number (ACN) insulator describes the system with Chern number C that may be modulated beyond 0 and ±1. In this work, we take the two-orbit square lattice as an example to study the universal behavior of the Chern insulator under external magnetic field. The two-orbit square lattice may support the ACN phase when different types of hopping integrals are introduced to break the valley degeneracy. We will investigate the quantum Hall effect of the ACN phase, including the rule of the Hall steps and the Hall conductance around the charge neutral point. The results are further demonstrated by the ribbon dispersions and the corresponding edge states. We also try to detect the topological phase transition with the laser pulse by analyzing the excitation fraction and the corresponding valley polarization. Our studies may provide new routes to devise the novel valleytronics.

  10. Electronic Degeneracy and Intrinsic Magnetic Properties of EpitaxialNb : SrTiO3 Thin Films Controlled by Defects

    NASA Astrophysics Data System (ADS)

    Sarantopoulos, A.; Ferreiro-Vila, E.; Pardo, V.; Magén, C.; Aguirre, M. H.; Rivadulla, F.

    2015-10-01

    We report thermoelectric power experiments in e -doped thin films of SrTiO3 (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and nonlinear Hall effect. Ab initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this Letter for tetragonally distorted e -doped STO thin films, is similar to that observed in LaAlO3 /STO interfaces and magnetic STO quantum wells.

  11. Symmetries in Lagrangian Field Theory

    NASA Astrophysics Data System (ADS)

    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.

  12. Fermion mass without symmetry breaking

    NASA Astrophysics Data System (ADS)

    Catterall, Simon

    2016-01-01

    We examine a model of reduced staggered fermions in three dimensions interacting through an SO (4) invariant four fermion interaction. The model is similar to that considered in a recent paper by Ayyer and Chandrasekharan [1]. We present theoretical arguments and numerical evidence which support the idea that the system develops a mass gap for sufficiently strong four fermi coupling without producing a symmetry breaking fermion bilinear condensate. Massless and massive phases appear to be separated by a continuous phase transition.

  13. Explaining quantum spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    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.

  14. Dark matter and global symmetries

    NASA Astrophysics Data System (ADS)

    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.

  15. Symmetry analysis of talus bone

    PubMed Central

    Islam, K.; Dobbe, A.; Komeili, A.; Duke, K.; El-Rich, M.; Dhillon, S.; Adeeb, S.; Jomha, N. M.

    2014-01-01

    Objective The main object of this study was to use a geometric morphometric approach to quantify the left-right symmetry of talus bones. Methods Analysis was carried out using CT scan images of 11 pairs of intact tali. Two important geometric parameters, volume and surface area, were quantified for left and right talus bones. The geometric shape variations between the right and left talus bones were also measured using deviation analysis. Furthermore, location of asymmetry in the geometric shapes were identified. Results Numerical results showed that talus bones are bilaterally symmetrical in nature, and the difference between the surface area of the left and right talus bones was less than 7.5%. Similarly, the difference in the volume of both bones was less than 7.5%. Results of the three-dimensional (3D) deviation analyses demonstrated the mean deviation between left and right talus bones were in the range of -0.74 mm to 0.62 mm. It was observed that in eight of 11 subjects, the deviation in symmetry occurred in regions that are clinically less important during talus surgery. Conclusions We conclude that left and right talus bones of intact human ankle joints show a strong degree of symmetry. The results of this study may have significance with respect to talus surgery, and in investigating traumatic talus injury where the geometric shape of the contralateral talus can be used as control. Cite this article: Bone Joint Res 2014;3:139–45. PMID:24802391

  16. A direct measurement of the mean occupation function of quasars: Breaking degeneracies between halo occupation distribution models

    SciTech Connect

    Chatterjee, Suchetana; Nguyen, My L.; Myers, Adam D.; Zheng, Zheng

    2013-12-20

    Recent work on quasar clustering suggests a degeneracy in the halo occupation distribution constrained from two-point correlation functions. To break this degeneracy, we make the first empirical measurement of the mean occupation function (MOF) of quasars at z ∼ 0.2 by matching quasar positions with groups and clusters identified in the MaxBCG sample. We fit two models to the MOF, a power law and a four-parameter model. The number distribution of quasars in host halos is close to Poisson, and the slopes of the MOF obtained from our best-fit models (for the power-law case) favor an MOF that monotonically increases with halo mass. The best-fit slopes are 0.53 ± 0.04 and 1.03 ± 1.12 for the power-law model and the four-parameter model, respectively. We measure the radial distribution of quasars within dark matter halos and find it to be adequately described by a power law with a slope –2.3 ± 0.4. We measure the conditional luminosity function (CLF) of quasars and show that there is no evidence that quasar luminosity depends on host halo mass, similar to the inferences drawn from clustering measurements. We also measure the conditional black hole mass function (CMF) of our quasars. Although the results are consistent with no dependence on halo mass, we observe a slight indication of downsizing of the black hole mass function. The lack of halo mass dependence in the CLF and CMF shows that quasars residing in galaxy clusters have characteristic luminosity and black hole mass scales.

  17. The mass-sheet degeneracy and time-delay cosmography: analysis of the strong lens RXJ1131-1231

    NASA Astrophysics Data System (ADS)

    Birrer, Simon; Amara, Adam; Refregier, Alexandre

    2016-08-01

    We present extended modelling of the strong lens system RXJ1131-1231 with archival data in two HST bands in combination with existing line-of-sight contribution and velocity dispersion estimates. Our focus is on source size and its influence on time-delay cosmography. We therefore examine the impact of mass-sheet degeneracy and especially the degeneracy pointed out by Schneider & Sluse (2013) [1] using the source reconstruction scale. We also extend on previous work by further exploring the effects of priors on the kinematics of the lens and the external convergence in the environment of the lensing system. Our results coming from RXJ1131-1231 are given in a simple analytic form so that they can be easily combined with constraints coming from other cosmological probes. We find that the choice of priors on lens model parameters and source size are subdominant for the statistical errors for H0 measurements of this systems. The choice of prior for the source is sub-dominant at present (2% uncertainty on H0) but may be relevant for future studies. More importantly, we find that the priors on the kinematic anisotropy of the lens galaxy have a significant impact on our cosmological inference. When incorporating all the above modeling uncertainties, we find H0 = 86.6+6.8-6.9 km s-1 Mpc-1, when using kinematic priors similar to other studies. When we use a different kinematic prior motivated by Barnabè et al. (2012) [2] but covering the same anisotropic range, we find H0 = 74.5+8.0-7.8 km s-1 Mpc-1. This means that the choice of kinematic modeling and priors have a significant impact on cosmographic inferences. The way forward is either to get better velocity dispersion measures which would down weight the impact of the priors or to construct physically motivated priors for the velocity dispersion model.

  18. Generalization of Friedberg-Lee symmetry

    NASA Astrophysics Data System (ADS)

    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.

  19. Enhanced Facial Symmetry Assessment in Orthodontists.

    PubMed

    Jackson, Tate H; Clark, Kait; Mitroff, Stephen R

    2013-01-01

    Assessing facial symmetry is an evolutionarily important process, which suggests that individual differences in this ability should exist. As existing data are inconclusive, the current study explored whether a group trained in facial symmetry assessment, orthodontists, possessed enhanced abilities. Symmetry assessment was measured using face and non-face stimuli among orthodontic residents and two control groups: university participants with no symmetry training and airport security luggage screeners, a group previously shown to possess expert visual search skills unrelated to facial symmetry. Orthodontic residents were more accurate at assessing symmetry in both upright and inverted faces compared to both control groups, but not for non-face stimuli. These differences are not likely due to motivational biases or a speed-accuracy tradeoff-orthodontic residents were slower than the university participants but not the security screeners. Understanding such individual differences in facial symmetry assessment may inform the perception of facial attractiveness.

  20. Symmetry constraints on many-body localization

    NASA Astrophysics Data System (ADS)

    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.

  1. Symmetries in nuclei: New methods and applications

    NASA Astrophysics Data System (ADS)

    Caprio, Mark A.

    2011-04-01

    When a symmetry is a ``good'' symmetry of the nuclear system, as in the dynamical symmetries of the shell model and interacting boson model, this symmetry can directly give the spectroscopic properties of the nucleus, without the need for involved calculations. However, even if a symmetry is strongly broken, it nonetheless provides a calculational tool, classifying the basis states used in a full computational treatment of the many-body problem and greatly simplifying the underlying computational machinery. The symmetry then serves as the foundation for a physically meaningful truncation scheme for the calculation. This talk will provide an introduction to new applications of symmetry approaches to the nuclear problem, including the required mathematical developments. Supported by the US DOE under grant DE-FG02-95ER-40934 and by the Research Corporation for Science Advancement under a Cottrell Scholar Award.

  2. Enhanced Facial Symmetry Assessment in Orthodontists

    PubMed Central

    Jackson, Tate H.; Clark, Kait; Mitroff, Stephen R.

    2013-01-01

    Assessing facial symmetry is an evolutionarily important process, which suggests that individual differences in this ability should exist. As existing data are inconclusive, the current study explored whether a group trained in facial symmetry assessment, orthodontists, possessed enhanced abilities. Symmetry assessment was measured using face and non-face stimuli among orthodontic residents and two control groups: university participants with no symmetry training and airport security luggage screeners, a group previously shown to possess expert visual search skills unrelated to facial symmetry. Orthodontic residents were more accurate at assessing symmetry in both upright and inverted faces compared to both control groups, but not for non-face stimuli. These differences are not likely due to motivational biases or a speed-accuracy tradeoff—orthodontic residents were slower than the university participants but not the security screeners. Understanding such individual differences in facial symmetry assessment may inform the perception of facial attractiveness. PMID:24319342

  3. Symmetry breaking and wake instabilities

    NASA Astrophysics Data System (ADS)

    Sengupta, Raja

    A numerical technique has been developed in the context of spatio-temporal stability analysis. The convective/absolute nature of instability determines the time-asymptotic response of a linearly unstable flow, either in the form an oscillator or in the form of a noise amplifier. This depends on the location of pinch point singularities of the dispersion relations obtained via linear stability analyses. A new and efficient approach to locate such singularities is presented. Local analyticity of the dispersion relations was exploited via the Cauchy-Riemann equations in a quasi-Newton's root- finding procedure employing numerical Jacobians. Initial guesses provided by temporal stability analyses have been shown to converge to the pinch points even in the presence of multiple saddle points for various Falkner- Skan wedge profiles. This effort was motivated by the phenomenon of spontaneous symmetry breaking in flow over a cone. At large enough incidence, a pair of vortices develop on the leeward side of the cone which eventually become asymmetric as the angle of attack is increased further. A conical, thin-layer Navier-Stokes solver was employed to investigate the effect of flowfield saddles in this process. The approximate factorization scheme incorporated in the solver was shown analytically to be symmetric to eliminate possible sources of asymmetry. Local grid resolution studies were performed to demonstrate the importance of correctly computing the leeside saddle point and the secondary separation and reattchment points. Topological studies of the flow field as it loses symmetry agreed well with previous qualitative experimental observations. However, the original goal of this study, to settle an ongoing controversy regarding the nature of the instability responsible for symmetry breaking, could not be realized due to computational inadequacy. It is conjectured that the process is governed by an absolute instability similar to that observed in a flow over a circular

  4. Duality symmetries and G+++ theories

    NASA Astrophysics Data System (ADS)

    Riccioni, Fabio; Steele, Duncan; West, Peter

    2008-02-01

    We show that the nonlinear realizations of all the very extended algebras G+++, except the B and C series which we do not consider, contain fields corresponding to all possible duality symmetries of the on-shell degrees of freedom of these theories. This result also holds for G+++2 and we argue that the nonlinear realization of this algebra accounts precisely for the form fields present in the corresponding supersymmetric theory. We also find a simple necessary condition for the roots to belong to a G+++ algebra.

  5. History of electroweak symmetry breaking

    NASA Astrophysics Data System (ADS)

    Kibble, T. W. B.

    2015-07-01

    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.

  6. Contact symmetries and Hamiltonian thermodynamics

    SciTech Connect

    Bravetti, A.; Lopez-Monsalvo, C.S.; Nettel, F.

    2015-10-15

    It has been shown that contact geometry is the proper framework underlying classical thermodynamics and that thermodynamic fluctuations are captured by an additional metric structure related to Fisher’s Information Matrix. In this work we analyse several unaddressed aspects about the application of contact and metric geometry to thermodynamics. We consider here the Thermodynamic Phase Space and start by investigating the role of gauge transformations and Legendre symmetries for metric contact manifolds and their significance in thermodynamics. Then we present a novel mathematical characterization of first order phase transitions as equilibrium processes on the Thermodynamic Phase Space for which the Legendre symmetry is broken. Moreover, we use contact Hamiltonian dynamics to represent thermodynamic processes in a way that resembles the classical Hamiltonian formulation of conservative mechanics and we show that the relevant Hamiltonian coincides with the irreversible entropy production along thermodynamic processes. Therefore, we use such property to give a geometric definition of thermodynamically admissible fluctuations according to the Second Law of thermodynamics. Finally, we show that the length of a curve describing a thermodynamic process measures its entropy production.

  7. Symmetry properties in polarimetric remote sensing

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Yueh, S. H.; Kwok, R.; Li, F. K.

    1992-01-01

    This paper presents the relations among polarimetric backscattering coefficients from the viewpoint of symmetry groups. Symmetry of geophysical media encountered in remote sensing due to reflection, rotation, azimuthal, and centrical symmetry groups is considered for both reciprocal and nonreciprocal cases. On the basis of the invariance under symmetry transformations in the linear polarization basis, the scattering coefficients are related by a set of equations which restrict the number of independent parameters in the polarimetric covariance matrix. The properties derived under these transformations are general and apply to all scattering mechanisms in a given symmetrical configuration. The scattering coefficients calculated from theoretical models for layer random media and rough surfaces are shown to obey the derived symmetry relations. Use of symmetry properties in remote sensing of structural and environmental responses of scattering media is discussed. As a practical application, the results from this paper provide new methods for the external calibration of polarimetric radars without the deployment of man-made calibration targets.

  8. Symmetry energy of dilute warm nuclear matter.

    PubMed

    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.

  9. Classification of topological phases with reflection symmetry

    NASA Astrophysics Data System (ADS)

    Yoshida, Tsuneya; Morimoto, Takahiro; Furusaki, Akira

    2015-03-01

    In Z2 topological band insulators, the time-reversal symmetry protects their topological structure. In these years such a notion is extended to correlated systems including bosonic systems, and these nontrivial phases are referred to as symmetry protected topological (SPT) phases. Parallel to this progress, a topological crystalline insulator, protected by spatial symmetry, is found for SnTe. Thus, SPT phases protected by this type of symmetry are naturally expected, and classifications of such phases are desired. In this article, we address this issue by focusing on a reflection symmetry. Our analysis based on the Chern-Simons approach proposes periodic tables for bosonic and fermionic SPT phases in two dimensions. Besides that, we show an SPT phase with the reflection symmetry is stabilized in a spin model of honeycomb lattice.

  10. Dynamics-dependent symmetries in Newtonian mechanics

    NASA Astrophysics Data System (ADS)

    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 Noether's 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 Schrödinger equation.

  11. Dynamical symmetries of the Kepler problem

    NASA Astrophysics Data System (ADS)

    Cariglia, Marco; Silva Araújo, Eduardo

    2013-09-01

    This paper comes from a first-year undergraduate research project on hidden symmetries of the dynamics for classical Hamiltonian systems. 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 the basic elements of many important physics subjects in the same project, including the Hamiltonian formalism, hidden symmetries, integrable systems, group theory and the use of manifolds.

  12. Atomic Tests of Symmetry Principles.

    NASA Astrophysics Data System (ADS)

    Davies, I. O. G.

    Available from UMI in association with The British Library. Requires signed TDF. Parity non-conserving effects in atoms due to the neutral weak current interaction can be enhanced in two ways: by exploiting the Z-dependence and by using a near degeneracy between opposite parity states. In this thesis a case where both enhancements are simultaneously present is considered: samarium has Z = 62 and the states 4f^66s6p ^7G_sp{1} {0} and 4f^66d5d ^7F_1 are only 320 GHz apart. A calculation by Gongora and Sandars (1986) yields a value for R = Im ^{rm PNC}/ of 10^{-4}. To assess the feasibility of utilizing this gain to detect PNC effects a number of exploratory experiments have been performed and a new type of optical rotation experiment, involving crossed electric and magnetic fields, has been considered. Results are presented for the E1 transition 4f^6 6s^2 ^7F _0 - 4f^66s6p ^7G_1 at 639 nm which include analyses of the absorption spectrum (both Doppler-broadened and Doppler-free), the Faraday and the Stark induced rotation. The data include measurements of isotope shifts and hyperfine structure constants, the oscillator strength (from the deduced natural linewidth) and the broadening constant for the He-Sm system. Zeeman and optical coherences were discovered to be important in the analysis of the rotation spectra and a theoretical treatment involving density matrix equations is presented. In addition, for the odd isotopes, effects of optical pumping have also been considered. The Stark rotation was analysed giving |(4f^66s5d ^7F_1|er |4f^66s6p ^7G_1| = 0cdot85(5) e a_0 . The M1 resonance was located by Stark mixing and the background Faraday rotation in this region investigated. It is concluded that because of observed background, the low E1 transition amplitude measured and the low work function of samarium making the application of high electrical fields in the oven difficult that a PNC optical rotation experiment is unlikely to offer any advantage over

  13. The near-symmetry of proteins.

    PubMed

    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.

  14. Lie symmetry analysis of the Heisenberg equation

    NASA Astrophysics Data System (ADS)

    Zhao, Zhonglong; Han, Bo

    2017-04-01

    The Lie symmetry analysis is performed on the Heisenberg equation from the statistical physics. Its Lie point symmetries and optimal system of one-dimensional subalgebras are determined. The similarity reductions and invariant solutions are obtained. Using the multipliers, some conservation laws are obtained. We prove that this equation is nonlinearly self-adjoint. The conservation laws associated with symmetries of this equation are constructed by means of Ibragimov's method.

  15. Symmetry-protected single-photon subradiance

    NASA Astrophysics Data System (ADS)

    Cai, Han; Wang, Da-Wei; Svidzinsky, Anatoly A.; Zhu, Shi-Yao; Scully, Marlan O.

    2016-05-01

    We study the protection of subradiant states by the symmetry of the atomic distributions in the Dicke limit, in which collective Lamb shifts cannot be neglected. We find that antisymmetric states are subradiant states for distributions with reflection symmetry. 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.

  16. Discrete flavor symmetries for degenerate solar neutrino pair and their predictions

    NASA Astrophysics Data System (ADS)

    Joshipura, Anjan S.; Patel, Ketan M.

    2014-08-01

    Flavor symmetries appropriate for describing a neutrino spectrum with degenerate solar pair and a third massive or massless neutrino are discussed. We demand that the required residual symmetries of the leptonic mass matrices be subgroups of some discrete symmetry group Gf. Gf can be a subgroup of SU(3) if the third neutrino is massive and we derive general results on the mixing angle predictions for various discrete subgroups of SU(3) divided into the two classes, called type C and D in Miller et al. [Theory and Applications of Finite Groups (John Wiley & Sons, New York, 1916)]. The main results are (a) All the SU(3) subgroups of type C fail in simultaneously giving correct θ13 and θ23. (b) All the groups of type D can predict a relation cos2θ13sin2θ23=1/3 among the mixing angles which appears to be a good zeroth order approximation. Among these, various Δ(6n2) groups with n ≥8 can simultaneously lead also to sin2θ13 in agreement with global fit at 3σ. (c) The group Σ(168)≅PSL(2,7) predicts near to the best fit value for θ13 and θ23 within the 1σ range. All discrete subgroups of U(3) with order <512 and having three-dimensional irreducible representation are considered as possible Gf when the third neutrino is massless. Only seven of them are shown to be viable and three of these can correctly predict θ13 and/or θ23. The solar angle remains undetermined at the leading order in all the cases due to degeneracy in the masses. A class of general perturbations which can correctly reproduce all the observables is discussed in the context of several groups which offer good leading order predictions.

  17. Functional ferroic heterostructures with tunable integral symmetry.

    PubMed

    Becher, C; Trassin, M; Lilienblum, M; Nelson, C T; Suresha, S J; Yi, D; Yu, P; Ramesh, R; Fiebig, M; Meier, D

    2014-07-02

    The relation between symmetry and functionality was pinpointed by Pierre Curie who stated that it is the symmetry breaking that creates physical properties. This fundamental principle is nowadays used for engineering heterostructures whose integral symmetry leads to exotic phenomena such as one-way transparency. For switching devices, however, such symmetry-related functionalities cannot be used because the symmetry in conventional heterostructures is immutable once the material has been synthesized. Here we demonstrate a concept for post-growth symmetry control in PbZr0.2Ti0.8O3 and BiFeO3-based heterostructures. A conducting oxide is sandwiched between two ferroelectric layers, and inversion symmetry is reversibly switched on or off by layer-selective electric-field poling. The generalization of our approach to other materials and symmetries is discussed. We thus establish ferroic trilayer structures as device components with reversibly tunable symmetry and demonstrate their use as light emitters that can be activated and deactivated by applying moderate electric voltages.

  18. Discrete gauge symmetry in continuum theories

    SciTech Connect

    Krauss, L.M.; Wilczek, F.

    1989-03-13

    We point out that local symmetries can masquerade as discrete global symmetries to an observer equipped with only low-energy probes. The existence of the underlying local gauge invariance can, however, result in observable Aharonov-Bohm-type effects. Black holes can therefore carry discrete gauge charges: a form of nonclassical ''hair.'' Neither black-hole evaporation, wormholes, nor anything else can violate discrete gauge symmetries. In supersymmetric unified theories such discrete symmetries can forbid proton-decay amplitudes that might otherwise be catastrophic.

  19. Fake conformal symmetry in unimodular gravity

    NASA Astrophysics Data System (ADS)

    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.

  20. Nonlinear (super)symmetries and amplitudes

    NASA Astrophysics Data System (ADS)

    Kallosh, Renata

    2017-03-01

    There is an increasing interest in nonlinear supersymmetries in cosmological model building. Independently, elegant expressions for the all-tree amplitudes in models with nonlinear symmetries, like D3 brane Dirac-Born-Infeld-Volkov-Akulov theory, were recently discovered. Using the generalized background field method we show how, in general, nonlinear symmetries of the action, bosonic and fermionic, constrain amplitudes beyond soft limits. The same identities control, for example, bosonic E 7(7) scalar sector symmetries as well as the fermionic goldstino symmetries.

  1. Competing instabilities, orbital ordering, and splitting of band degeneracies from a parquet renormalization group analysis of a four-pocket model for iron-based superconductors: Application to FeSe

    NASA Astrophysics Data System (ADS)

    Xing, Rui-Qi; Classen, Laura; Khodas, Maxim; Chubukov, Andrey V.

    2017-02-01

    We report the results of a parquet renormalization group (RG) study of competing instabilities in the full 2D four-pocket, three-orbital low-energy model for iron-based superconductors. We derive and analyze the RG flow of the couplings, which describes all symmetry-allowed interactions between low-energy fermions. Despite that the number of the couplings is large, we argue that there are only two stable fixed trajectories of the RG flow and one weakly unstable fixed trajectory with a single unstable direction. Each fixed trajectory has a finite basin of attraction in the space of initial system parameters. On the stable trajectories, either interactions involving only dx z and dy z or only dx y orbital components on electron pockets dominate, while on the weakly unstable trajectory interactions involving dx z (dy z) and dx y orbital states on electron pockets remain comparable. The behavior along the two stable fixed trajectories has been analyzed earlier [Chubukov, Khodas, and Fernandes, Phys. Rev. X 6, 041045 (2016), 10.1103/PhysRevX.6.041045]. Here we focus on the system behavior along the weakly unstable trajectory and apply the results to FeSe. We find, based on the analysis of susceptibilities along this trajectory, that the leading instability upon lowering the temperature is towards a three-component d -wave orbital nematic order. Two components are the differences between fermionic densities on dx z and dy z orbitals on hole pockets and on electron pockets, and the third one is the difference between the densities of dx y orbitals on the two electron pockets. We argue that this order is consistent with the splitting of band degeneracies, observed in recent photoemission data on FeSe by Fedorov et al. [Sci. Rep. 6, 36834 (2016), 10.1038/srep36834].

  2. PREFACE: Symmetries in Science XV

    NASA Astrophysics Data System (ADS)

    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

  3. K-mixing in the doubly mid-shell nuclide 170Dy and the role of vibrational degeneracy

    NASA Astrophysics Data System (ADS)

    Söderström, P.-A.; Walker, P. M.; Wu, J.; Liu, H. L.; Regan, P. H.; Watanabe, H.; Doornenbal, P.; Korkulu, Z.; Lee, P.; Liu, J. J.; Lorusso, G.; Nishimura, S.; Phong, V. H.; Sumikama, T.; Xu, F. R.; Yagi, A.; Zhang, G. X.; Ahn, D. S.; Alharbi, T.; Baba, H.; Browne, F.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Estrade, A.; Fukuda, N.; Griffin, C. J.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kanaoka, H.; Kanaya, S.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; Lee, E. J.; Lee, C. S.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Niţă, C. R.; Odahara, A.; Patel, Z.; Podolyák, Zs.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Shand, C. M.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Valiente-Dòbon, J. J.; Xu, Z. Y.

    2016-11-01

    A detailed study of the structure of the doubly mid-shell nucleus 104 166 170Dy has been carried out, following isomeric and β decay. We have measured the yrast band up to the spin-parity Jπ =6+ state, the K = 2γ-vibration band up to the 5+ state, a low-lying negative-parity band based on a 2- state that could be a candidate for the lowest energy octupole vibration state within this nucleus, and a candidate for the Kπ =6+ two quasi-particle isomer. This state was determined to have an excitation energy of 1643.91(23) keV and a half life of 0.99(4) μs, with a reduced hindrance for its decay to the ground-state band an order of magnitude lower than predicted by NpNn systematics. This is interpreted as being due to γ-vibrational mixing from a near degeneracy of the isomer and the 6+ state of the γ band. Furthermore, the parent nucleus 170Tb has been determined to have a half-life of 0.91 (- 13 + 18 ) s with a possible spin-parity of 2-.

  4. Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number

    SciTech Connect

    Levy, Mel E-mail: mlevy@tulane.edu; Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W. E-mail: mlevy@tulane.edu

    2014-05-14

    Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.

  5. Tunable transmission of quantum Hall edge channels with full degeneracy lifting in split-gated graphene devices.

    PubMed

    Zimmermann, Katrin; Jordan, Anna; Gay, Frédéric; Watanabe, Kenji; Taniguchi, Takashi; Han, Zheng; Bouchiat, Vincent; Sellier, Hermann; Sacépé, Benjamin

    2017-04-13

    Charge carriers in the quantum Hall regime propagate via one-dimensional conducting channels that form along the edges of a two-dimensional electron gas. Controlling their transmission through a gate-tunable constriction, also called quantum point contact, is fundamental for many coherent transport experiments. However, in graphene, tailoring a constriction with electrostatic gates remains challenging due to the formation of p-n junctions below gate electrodes along which electron and hole edge channels co-propagate and mix, short circuiting the constriction. Here we show that this electron-hole mixing is drastically reduced in high-mobility graphene van der Waals heterostructures thanks to the full degeneracy lifting of the Landau levels, enabling quantum point contact operation with full channel pinch-off. We demonstrate gate-tunable selective transmission of integer and fractional quantum Hall edge channels through the quantum point contact. This gate control of edge channels opens the door to quantum Hall interferometry and electron quantum optics experiments in the integer and fractional quantum Hall regimes of graphene.

  6. Chemical potentials and thermodynamic characteristics of ideal Bose- and Fermi-gases in the region of quantum degeneracy

    NASA Astrophysics Data System (ADS)

    Sotnikov, A. G.; Sereda, K. V.; Slyusarenko, Yu. V.

    2017-01-01

    Calculations of chemical potentials for ideal monatomic gases with Bose-Einstein and Fermi-Dirac statistics as functions of temperature, across the temperature region that is typical for the collective quantum degeneracy effect, are presented. Numerical calculations are performed without any additional approximations, and explicit dependences of the chemical potentials on temperature are constructed at a fixed density of gas particles. Approximate polynomial dependences of chemical potentials on temperature are obtained that allow for the results to be used in further studies without re-applying the involved numerical methods. The ease of using the obtained representations is demonstrated on examples of deformation of distribution for a population of energy states at low temperatures, and on the impact of quantum statistics (exchange interaction) on the equations of state for ideal gases and some of the thermodynamic properties thereof. The results of this study essentially unify two opposite limiting cases in an intermediate region that are used to describe the equilibrium states of ideal gases, which are well known from university courses on statistical physics, thus adding value from an educational point of view.

  7. AS ABOVE, SO BELOW: EXPLOITING MASS SCALING IN BLACK HOLE ACCRETION TO BREAK DEGENERACIES IN SPECTRAL INTERPRETATION

    SciTech Connect

    Markoff, Sera; Silva, Catia V.; Nowak, Michael A.; Gallo, Elena; Plotkin, Richard M.; Hynes, Robert; Wilms, Jörn; Maitra, Dipankar; Drappeau, Samia E-mail: C.V.DeJesusSilva@uva.nl E-mail: egallo@umich.edu E-mail: joern.wilms@sternwarte.uni-erlangen.de E-mail: samia.drappeau@irap.omp.eu

    2015-10-20

    Over the past decade, evidence has mounted that several aspects of black hole (BH) accretion physics proceed in a mass-invariant way. One of the best examples of this scaling is the empirical “fundamental plane of BH accretion” relation linking mass, radio, and X-ray luminosity over eight orders of magnitude in BH mass. The currently favored theoretical interpretation of this relation is that the physics governing power output in weakly accreting BHs depends more on relative accretion rate than on mass. In order to test this theory, we explore whether a mass-invariant approach can simultaneously explain the broadband spectral energy distributions from two BHs at opposite ends of the mass scale but that are at similar Eddington accretion fractions. We find that the same model, with the same value of several fitted physical parameters expressed in mass-scaling units to enforce self-similarity, can provide a good description of two data sets from V404 Cyg and M81*, a stellar and supermassive BH, respectively. Furthermore, only one of several potential emission scenarios for the X-ray band is successful, suggesting it is the dominant process driving the fundamental plane relation at this accretion rate. This approach thus holds promise for breaking current degeneracies in the interpretation of BH high-energy spectra and for constructing better prescriptions of BH accretion for use in various local and cosmological feedback applications.

  8. Paramagnetic-based NMR restraints lift residual dipolar coupling degeneracy in multidomain detergent-solubilized membrane proteins.

    PubMed

    Shi, Lei; Traaseth, Nathaniel J; Verardi, Raffaello; Gustavsson, Martin; Gao, Jiali; Veglia, Gianluigi

    2011-02-23

    Residual dipolar couplings (RDCs) are widely used as orientation-dependent NMR restraints to improve the resolution of the NMR conformational ensemble of biomacromolecules and define the relative orientation of multidomain proteins and protein complexes. However, the interpretation of RDCs is complicated by the intrinsic degeneracy of analytical solutions and protein dynamics that lead to ill-defined orientations of the structural domains (ghost orientations). Here, we illustrate how restraints from paramagnetic relaxation enhancement (PRE) experiments lift the orientational ambiguity of multidomain membrane proteins solubilized in detergent micelles. We tested this approach on monomeric phospholamban (PLN), a 52-residue membrane protein, which is composed of two helical domains connected by a flexible loop. We show that the combination of classical solution NMR restraints (NOEs and dihedral angles) with RDC and PRE constraints resolves topological ambiguities, improving the convergence of the PLN structural ensemble and giving the depth of insertion of the protein within the micelle. The combination of RDCs with PREs will be necessary for improving the accuracy and precision of membrane protein conformational ensembles, where three-dimensional structures are dictated by interactions with the membrane-mimicking environment rather than compact tertiary folds common in globular proteins.

  9. Inflation, symmetry, and B-modes

    NASA Astrophysics Data System (ADS)

    Hertzberg, Mark P.

    2015-05-01

    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 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 typically

  10. Wormhole dynamics in spherical symmetry

    SciTech Connect

    Hayward, Sean A.

    2009-06-15

    A dynamical theory of traversable wormholes is detailed in spherical symmetry. Generically a wormhole consists of a tunnel of trapped surfaces between two mouths, defined as temporal outer trapping horizons with opposite senses, in mutual causal contact. In static cases, the mouths coincide as the throat of a Morris-Thorne wormhole, with surface gravity providing an invariant measure of the radial curvature or ''flaring-out''. The null energy condition must be violated at a wormhole mouth. Zeroth, first, and second laws are derived for the mouths, as for black holes. Dynamic processes involving wormholes are reviewed, including enlargement or reduction, and interconversion with black holes. A new area of wormhole thermodynamics is suggested.

  11. Electroweak symmetry breaking via QCD.

    PubMed

    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.

  12. Mirror symmetry for Enriques surfaces

    NASA Astrophysics Data System (ADS)

    Lakuriqi, Enkeleida

    In this thesis, we investigate three separate but related projects. In the first one, we describe the geometric backgrounds of Type II string theory which are given by Enriques surfaces and their mirrors. We also study the effect of various string dualities on such backgrounds, in particular phase change in Gauged Linear Sigma Models and mirror symmetry. In the second project, we investigate special Kahler geometry in order to find canonical coordinates on the moduli of generalised Calabi-Yau spaces and the associated (2, 2) superconformal field theories. In the third project, we develop a general technique for computing the massless spectrum of (0, 2) quantum field theory compactified on a proper stack or an orbifold. We produce general formulas for the contribution of the twisted sectors and compute specific examples of compactifications on gerbes on projective spaces and Calabi-Yau threefolds.

  13. Permutation symmetry for theta functions

    SciTech Connect

    Carlson, B.C.

    2011-01-21

    This paper does for combinations of theta functions most of what Carlson (2004) [1] did for Jacobian elliptic functions. In each case the starting point is the symmetric elliptic integral R{sub F} of the first kind. Its three arguments (formerly squared Jacobian elliptic functions but now squared combinations of theta functions) differ by constants. Symbols designating the constants can often be used to replace 12 equations by three with permutation symmetry (formerly in the letters c, d, n for the Jacobian case but now in the subscripts 2, 3, 4 for theta functions). Such equations include derivatives and differential equations, bisection and duplication relations, addition formulas (apparently new for theta functions), and an example of pseudoaddition formulas.

  14. Rare Isotopes and Fundamental Symmetries

    NASA Astrophysics Data System (ADS)

    Brown, B. Alex; Engel, Jonathan; Haxton, Wick; Ramsey-Musolf, Michael; Romalis, Michael; Savard, Guy

    2009-01-01

    Experiments searching for new interactions in nuclear beta decay / Klaus P. Jungmann -- The beta-neutrino correlation in sodium-21 and other nuclei / P. A. Vetter ... [et al.] -- Nuclear structure and fundamental symmetries/ B. Alex Brown -- Schiff moments and nuclear structure / J. Engel -- Superallowed nuclear beta decay: recent results and their impact on V[symbol] / J. C. Hardy and I. S. Towner -- New calculation of the isospin-symmetry breaking correlation to superallowed Fermi beta decay / I. S. Towner and J. C. Hardy -- Precise measurement of the [symbol]H to [symbol]He mass difference / D. E. Pinegar ... [et al.] -- Limits on scalar currents from the 0+ to 0+ decay of [symbol]Ar and isospin breaking in [symbol]Cl and [symbol]Cl / A. Garcia -- Nuclear constraints on the weak nucleon-nucleon interaction / W. C. Haxton -- Atomic PNC theory: current status and future prospects / M. S. Safronova -- Parity-violating nucleon-nucleon interactions: what can we learn from nuclear anapole moments? / B. Desplanques -- Proposed experiment for the measurement of the anapole moment in francium / A. Perez Galvan ... [et al.] -- The Radon-EDM experiment / Tim Chupp for the Radon-EDM collaboration -- The lead radius Eexperiment (PREX) and parity violating measurements of neutron densities / C. J. Horowitz -- Nuclear structure aspects of Schiff moment and search for collective enhancements / Naftali Auerbach and Vladimir Zelevinsky -- The interpretation of atomic electric dipole moments: Schiff theorem and its corrections / C. -P. Liu -- T-violation and the search for a permanent electric dipole moment of the mercury atom / M. D. Swallows ... [et al.] -- The new concept for FRIB and its potential for fundamental interactions studies / Guy Savard -- Collinear laser spectroscopy and polarized exotic nuclei at NSCL / K. Minamisono -- Environmental dependence of masses and coupling constants / M. Pospelov.

  15. Neutrino properties and fundamental symmetries

    SciTech Connect

    Bowles, T.J.

    1996-07-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). There are two components to this work. The first is a development of a new detection scheme for neutrinos. The observed deficit of neutrinos from the Sun may be due to either a lack of understanding of physical processes in the Sun or may be due to neutrinos oscillating from one type to another during their transit from the Sun to the Earth. The Sudbury Neutrino Observatory (SNO) is designed to use a water Cerenkov detector employing one thousand tonnes of heavy water to resolve this question. The ability to distinguish muon and tau neutrinos from electron neutrinos is crucial in order to carry out a model-independent test of neutrino oscillations. We describe a developmental exploration of a novel technique to do this using {sup 3}He proportional counters. Such a method offers considerable advantages over the initially proposed method of using Cerenkov light from capture on NaCl in the SNO. The second component of this work is an exploration of optimal detector geometry for a time-reversal invariance experiment. The question of why time moves only in the forward direction is one of the most puzzling problems in modern physics. We know from particle physics measurements of the decay of kaons that there is a charge-parity symmetry that is violated in nature, implying time-reversal invariance violation. Yet, we do not understand the origin of the violation of this symmetry. To promote such an understanding, we are developing concepts and prototype apparatus for a new, highly sensitive technique to search for time-reversal-invariance violation in the beta decay of the free neutron. The optimized detector geometry is seven times more sensitive than that in previous experiments. 15 refs.

  16. Flavor symmetries and fermion masses

    SciTech Connect

    Rasin, Andrija

    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, Vub/Vcb = √mu/mc and Vtd/Vts = √md/ms, 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 β → sγ constrains the parameter space when the ratio of the vacuum expectation values of the two Higgs doublets, tanβ, 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.

  17. Cubic Icosahedra? A Problem in Assigning Symmetry

    ERIC Educational Resources Information Center

    Lloyd, D. R.

    2010-01-01

    There is a standard convention that the icosahedral groups are classified separately from the cubic groups, but these two symmetry types have been conflated as "cubic" in some chemistry textbooks. In this note, the connection between cubic and icosahedral symmetries is examined, using a simple pictorial model. It is shown that octahedral and…

  18. Symmetry in critical random Boolean network dynamics.

    PubMed

    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.

  19. Symmetry is less than meets the eye.

    PubMed

    Apthorp, Deborah; Bell, Jason

    2015-03-30

    Symmetry is a ubiquitous feature in the visual environment and can be detected by a variety of species, ranging from insects through to humans [1,2]. Here we show it can also bias estimates of basic scene properties. Mirror (reflective) symmetry can be detected in as little as 50 ms, in both natural and artificial visual scenes, and even when embedded within cluttered backgrounds [1]. In terms of its biological relevance, symmetry is a key determinant in mate selection; the degree of symmetry in a face is positively associated with perceived healthiness and attractiveness ratings [3]. In short, symmetry processing mechanisms are an important part of the neural machinery of vision. We reveal that the importance of symmetry extends beyond the processing of shape and objects. Mirror symmetry biases our perception of scene content, with symmetrical patterns appearing to have fewer components than their asymmetric counterparts. This demonstrates an interaction between two fundamental dimensions of visual analysis: symmetry [1] and number [4]. We propose that this numerical underestimation results from a processing bias away from the redundant information within mirror symmetrical displays, extending existing theories regarding redundancy in visual analysis [5,6].

  20. Symmetry in Critical Random Boolean Networks Dynamics

    NASA Astrophysics Data System (ADS)

    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.

  1. Symmetry in critical random Boolean network dynamics

    NASA Astrophysics Data System (ADS)

    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.

  2. Order in the Universe: The Symmetry Principle.

    ERIC Educational Resources Information Center

    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…

  3. Partial dynamical symmetry in a fermion system

    PubMed

    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.

  4. Teaching symmetry in the introductory physics curriculum

    SciTech Connect

    Hill, C. T.; Lederman, L. 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.

  5. Broken chiral symmetry on a null plane

    SciTech Connect

    Beane, Silas R.

    2013-10-15

    On a null-plane (light-front), all effects of spontaneous chiral symmetry breaking are contained in the three Hamiltonians (dynamical Poincaré generators), while the vacuum state is a chiral invariant. This property is used to give a general proof of Goldstone’s theorem on a null-plane. Focusing on null-plane QCD with N degenerate flavors of light quarks, the chiral-symmetry breaking Hamiltonians are obtained, and the role of vacuum condensates is clarified. In particular, the null-plane Gell-Mann–Oakes–Renner formula is derived, and a general prescription is given for mapping all chiral-symmetry breaking QCD condensates to chiral-symmetry conserving null-plane QCD condensates. The utility of the null-plane description lies in the operator algebra that mixes the null-plane Hamiltonians and the chiral symmetry charges. It is demonstrated that in a certain non-trivial limit, the null-plane operator algebra reduces to the symmetry group SU(2N) of the constituent quark model. -- Highlights: •A proof (the first) of Goldstone’s theorem on a null-plane is given. •The puzzle of chiral-symmetry breaking condensates on a null-plane is solved. •The emergence of spin-flavor symmetries in null-plane QCD is demonstrated.

  6. Continuous point symmetries in group field theories

    NASA Astrophysics Data System (ADS)

    Kegeles, Alexander; Oriti, Daniele

    2017-03-01

    We discuss the notion of symmetries in non-local field theories characterized by integro-differential equations of motion, from a geometric perspective. We then focus on group field theory (GFT) models of quantum gravity and provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them.

  7. Topological symmetry breaking by quantum wormholes

    SciTech Connect

    Mignemi, S.; Moss, I. )

    1993-10-15

    In multiply connected spacetimes which contain quantum wormholes it may be possible to break gauge symmetries without the usual Higgs fields. In a simple model, symmetry breaking is favored by the quantum effects of Dirac Fermions and leads to vector boson masses related to the wormhole separation.

  8. The role of symmetry in nuclear physics

    NASA Astrophysics Data System (ADS)

    Iachello, Francesco

    2015-02-01

    The role of discrete symmetries in nuclear physics is briefly reviewed within the context of the algebraic cluster model (ACM). The symmetries D3 (triangle) for 3α and Td (tetrahedron) for 4α are discussed and evidence shown for their occurrence in 12C (D3) and 16O (Td).

  9. Symmetries in flat space-times

    SciTech Connect

    Duncan, D.C.

    1989-01-01

    In the following flat spacetimes with a high degree of symmetry are studied. The first part completes the classification of all homogeneous flat spacetimes begun by Wolf. The second part explores classification of flat spacetimes with symmetry groups having codimension one orbits. In this case attention is restricted to spacetimes which model a centrally symmetric gravitational field.

  10. A nilpotent symmetry of quantum gauge theories

    NASA Astrophysics Data System (ADS)

    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.

  11. NOTE: Circular symmetry in topologically massive gravity

    NASA Astrophysics Data System (ADS)

    Deser, S.; Franklin, J.

    2010-05-01

    We re-derive, compactly, a topologically massive gravity (TMG) decoupling theorem: source-free TMG separates into its Einstein and Cotton sectors for spaces with a hypersurface-orthogonal Killing vector, here concretely for circular symmetry. We then generalize the theorem to include matter; surprisingly, the single Killing symmetry also forces conformal invariance, requiring the sources to be null.

  12. Electroweak symmetry breaking: Top quard condensates

    SciTech Connect

    Bardeen, W.A.

    1990-12-01

    The fundamental mechanisms for the dynamical breaking of the electroweak gauge symmetries remain a mystery. This paper examines the possible role of heavy fermions, particularly the top quark, in generating the observed electroweak symmetry breaking, the masses of the W and Z bosons and the masses of all observed quarks and leptons. 27 refs., 10 figs., 4 tabs.

  13. Teaching Point-Group Symmetry with Three-Dimensional Models

    ERIC Educational Resources Information Center

    Flint, Edward B.

    2011-01-01

    Three tools for teaching symmetry in the context of an upper-level undergraduate or introductory graduate course on the chemical applications of group theory are presented. The first is a collection of objects that have the symmetries of all the low-symmetry and high-symmetry point groups and the point groups with rotational symmetries from 2-fold…

  14. Ermakov's Superintegrable Toy and Nonlocal Symmetries

    NASA Astrophysics Data System (ADS)

    Leach, P. G. L.; Karasu Kalkanli, A.; Nucci, M. C.; Andriopoulos, K.

    2005-11-01

    We investigate the symmetry properties of a pair of Ermakov equations. The system is superintegrable and yet possesses only three Lie point symmetries with the algebra sl(2, R). The number of point symmetries is insufficient and the algebra unsuitable for the complete specification of the system. We use the method of reduction of order to reduce the nonlinear fourth-order system to a third-order system comprising a linear second-order equation and a conservation law. We obtain the representation of the complete symmetry group from this system. Four of the required symmetries are nonlocal and the algebra is the direct sum of a one-dimensional Abelian algebra with the semidirect sum of a two-dimensional solvable algebra with a two-dimensional Abelian algebra. The problem illustrates the difficulties which can arise in very elementary systems. Our treatment demonstrates the existence of possible routes to overcome these problems in a systematic fashion.

  15. Natural Electroweak Breaking from a Mirror Symmetry

    SciTech Connect

    Chacko, Z.; Goh, Hock-Seng; Harnik, Roni

    2006-06-16

    We present ''twin Higgs models,'' simple realizations of the Higgs boson as a pseudo Goldstone boson that protect the weak scale from radiative corrections up to scales of order 5-10 TeV. In the ultraviolet these theories have a discrete symmetry which interchanges each standard model particle with a corresponding particle which transforms under a twin or a mirror standard model gauge group. In addition, the Higgs sector respects an approximate global symmetry. When this global symmetry is broken, the discrete symmetry tightly constrains the form of corrections to the pseudo Goldstone Higgs potential, allowing natural electroweak symmetry breaking. Precision electroweak constraints are satisfied by construction. These models demonstrate that, contrary to the conventional wisdom, stabilizing the weak scale does not require new light particles charged under the standard model gauge groups.

  16. Bilateral symmetry breaking in nonlinear circular cylinders.

    PubMed

    Yuan, Lijun; Lu, Ya Yan

    2014-12-01

    Symmetry breaking is a common phenomenon in nonlinear systems, it refers to the existence of solutions that do not preserve the original symmetries of the underlying system. In nonlinear optics, symmetry breaking has been previously investigated in a number of systems, usually based on simplified model equations or temporal coupled mode theories. In this paper, we analyze the scattering of an incident plane wave by one or two circular cylinders with a Kerr nonlinearity, and show the existence of solutions that break a lateral reflection symmetry. Although symmetry breaking is a known phenomenon in nonlinear optics, it is the first time that this phenomenon was rigorously studied in simple systems with one or two circular cylinders.

  17. Symmetries in geology and geophysics

    PubMed Central

    Turcotte, Donald L.; Newman, William I.

    1996-01-01

    Symmetries have played an important role in a variety of problems in geology and geophysics. A large fraction of studies in mineralogy are devoted to the symmetry properties of crystals. In this paper, however, the emphasis will be on scale-invariant (fractal) symmetries. The earth’s topography is an example of both statistically self-similar and self-affine fractals. Landforms are also associated with drainage networks, which are statistical fractal trees. A universal feature of drainage networks and other growth networks is side branching. Deterministic space-filling networks with side-branching symmetries are illustrated. It is shown that naturally occurring drainage networks have symmetries similar to diffusion-limited aggregation clusters. PMID:11607719

  18. On Gauging Symmetry of Modular Categories

    NASA Astrophysics Data System (ADS)

    Cui, Shawn X.; Galindo, César; Plavnik, Julia Yael; Wang, Zhenghan

    2016-12-01

    Topological order of a topological phase of matter in two spacial dimensions is encoded by a unitary modular (tensor) category (UMC). A group symmetry of the topological phase induces a group symmetry of its corresponding UMC. Gauging is a well-known theoretical tool to promote a global symmetry to a local gauge symmetry. We give a mathematical formulation of gauging in terms of higher category formalism. Roughly, given a UMC with a symmetry group G, gauging is a 2-step process: first extend the UMC to a G-crossed braided fusion category and then take the equivariantization of the resulting category. Gauging can tell whether or not two enriched topological phases of matter are different, and also provides a way to construct new UMCs out of old ones. We derive a formula for the {H^4}-obstruction, prove some properties of gauging, and carry out gauging for two concrete examples.

  19. Symmetries, weak symmetries, and related solutions of the Grad-Shafranov equation

    SciTech Connect

    Cicogna, G.; Pegoraro, F.; Ceccherini, F.

    2010-10-15

    We discuss a new family of solutions of the Grad-Shafranov (GS) equation that describes D-shaped toroidal plasma equilibria with sharp gradients at the plasma edge. These solutions have been derived by exploiting the continuous Lie symmetry properties of the GS equation and in particular a special type of 'weak' symmetries. In addition, we review the continuous Lie symmetry properties of the GS equation and present a short but exhaustive survey of the possible choices for the arbitrary flux functions that yield GS equations admitting some continuous Lie symmetry. Particular solutions related to these symmetries are also discussed.

  20. Coulomb Correlations in 4d and 5d Oxides from First Principles - or How Spin-Orbit Materials choose their Effective Orbital Degeneracies.

    PubMed

    Martins, Cyril; Aichhorn, Markus; Biermann, Silke

    2017-03-06

    The interplay of spin-orbit coupling and Coulomb correlations has become a hot topic in condensed matter theory and is especially at stake in 4d and 5d transition metal oxides, like iridates or rhodates. Here, we review recent advances in dynamical mean-field theory(DMFT)-based electronic structure calculations for treating such compounds, introducing all necessary implementation details. We also discuss the evaluation of Hubbard interactions in spin-orbit materials. As an example, we perform DMFT calculations on insulating strontium iridate (Sr2IrO4) and its 4d metallic counterpart strontium rhodate (Sr2RhO4). While a Mott-insulating state is obtained for Sr2IrO4 in its paramagnetic phase, the obtained spectral properties and Fermi surfaces for Sr2RhO4 show excellent agreement with available experimental data. We finally discuss the electronic structure of these two compounds by introducing the notion of effective spin-orbital degeneracy as the key quantity that determines the correlation strength. We stress that effective spin-orbital degeneracy introduces an additional axis into the conventional picture of a phase diagram based on filling and on the ratio of interactions to bandwidth, in analogy with the degeneracy controled Mott transition in d1 perovskites.

  1. Natural quasicrystal with decagonal symmetry

    PubMed Central

    Bindi, Luca; Yao, Nan; Lin, Chaney; Hollister, Lincoln S.; Andronicos, Christopher L.; Distler, Vadim V.; Eddy, Michael P.; Kostin, Alexander; Kryachko, Valery; MacPherson, Glenn J.; Steinhardt, William M.; Yudovskaya, Marina; Steinhardt, Paul J.

    2015-01-01

    We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al71Ni24Fe5, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal to be identified, was found in the same meteorite. The new quasicrystal was found associated with steinhardtite (Al38Ni32Fe30), Fe-poor steinhardtite (Al50Ni40Fe10), Al-bearing trevorite (NiFe2O4) and Al-bearing taenite (FeNi). Laboratory studies of decagonal Al71Ni24Fe5 have shown that it is stable over a narrow range of temperatures, 1120 K to 1200 K at standard pressure, providing support for our earlier conclusion that the Khatyrka meteorite reached heterogeneous high temperatures [1100 < T(K) ≤ 1500] and then rapidly cooled after being heated during an impact-induced shock that occurred in outer space 4.5 Gya. The occurrences of metallic Al alloyed with Cu, Ni, and Fe raises new questions regarding conditions that can be achieved in the early solar nebula. PMID:25765857

  2. PREFACE: Symmetries in Science XIV

    NASA Astrophysics Data System (ADS)

    Schuch, Dieter; Ramek, Michael

    2010-04-01

    Symmetries Logo This volume of the proceedings "Symmetries in Science XIV" is dedicated to the memory of our colleagues and dear friends Marcos Moshinsky and Yuriĭ Smirnov who regularly participated in these Symposia and were a great inspiration to many. We shall miss them. Dieter Schuch and Michael Ramek The international symposium "Symmetries in Science XIV" held at Collegium Mehrerau in Bregenz, Austria from July 19-24, 2009, attended by 32 scientists from 11 countries, was an experiment, performed by theoreticians. Aim of this experiment was to find out if the desire to revive or even continue this conference series was stronger than the very restricted pecuniary boundary conditions. It obviously was! After its establishment by Bruno Gruber in 1979, the biennial series settled in the very stimulating atmosphere of the monastery Mehrerau, which provided the ideal environment for a limited number of invited participants to exchange ideas, without parallel sessions, and pursue deeper discussions (at the latest in the evening at "Gasthof Lamm"). When the conference series terminated in 2003, former participants were quite disappointed. Meeting again at several (larger) conferences in subsequent years, there were repeated expressions of "the lack of a Bregenz-type meeting in our field nowadays" and the question of a possible "revitalization", even without external funding. After some hesitation, but also driven by our own desire to reinstate the series, we consulted Bruno who not only approved wholeheartedly but also offered his full support. It all finally led to the symposium in July 2009. The atmosphere was really like in the "good old days" and the interesting and thought-provoking presentations culminated in the publication of these Proceedings. We are grateful to Carl Bender for establishing contact with IOP making it possible for us to publish these Proceedings in the Journal of Physics Conference Series. A majority of the participants contributed to these

  3. PREFACE: Symmetries in Science XVI

    NASA Astrophysics Data System (ADS)

    2014-10-01

    This volume of the proceedings ''Symmetries in Science XVI'' is dedicated to the memory of Miguel Lorente and Allan Solomon who both participated several times in these Symposia. We lost not only two great scientists and colleagues, but also two wonderful persons of high esteem whom we will always remember. Dieter Schuch, Michael Ramek There is a German saying ''all good things come in threes'' and ''Symmetries in Science XVI'', convened July 20-26, 2013 at the Mehrerau Monastery, was our third in the sequel of these symposia since taking it over from founder Bruno Gruber who instigated it in 1988 (then in Lochau). Not only the time seemed to have been perfect (one week of beautiful sunshine), but also the medley of participants could hardly have been better. This time, 34 scientists from 16 countries (more than half outside the European Union) came together to report and discuss their latest results in various fields of science, all related to symmetries. The now customary grouping of renowned experts and talented newcomers was very rewarding and stimulating for all. The informal, yet intense, discussions at ''Gasthof Lamm'' occurred (progressively later) each evening till well after midnight and finally till almost daybreak! However, prior to the opening ceremony and during the conference, respectively, we were informed that Miguel Lorente and Allan Solomon had recently passed away. Both attended the SIS Symposia several times and had many friends among present and former participants. Professor Peter Kramer, himself a long-standing participant and whose 80th birthday commemoration prevented him from attending SIS XVI, kindly agreed to write the obituary for Miguel Lorente. Professors Richard Kerner and Carol Penson (both also former attendees) penned, at very short notice, the tribute to Allan Solomon. The obituaries are included in these Proceedings and further tributes have been posted to our conference website. In 28 lectures and an evening poster

  4. Bilateral symmetry across Aphrodite Terra

    NASA Technical Reports Server (NTRS)

    Crumpler, L. S.; Head, J. W.; Campbell, D. B.

    1987-01-01

    There are three main highland areas on Venus: Beta Regio, Ishtar Terra and Aphrodite Terra. The latter is least known and the least mapped, yet existing analyses of Aphrodite Terra based on available Pioneer-Venus orbiter data suggest that it may be the site of extensive rifting. Some of the highest resolution (30 km) PV data (SAR) included most of the western half of Aphrodite Terra. Recent analysis of the SAR data together with Arecibo range-doppler topographic profiling (10 X 100 km horizontal and 10 m vertical resolution) across parts of Aphrodite, further characterized the nature of possible tectonic processes in the equatorial highlands. The existence of distinct topographic and radar morphologic linear discontinuities across the nearly east-west strike of Aphrodite Terra is indicated. Another prominent set of linear features is distinctly parallel to and orthogonal to the ground tracks of the PV spacecraft and are not included because of the possibility that they are artifacts. Study of the northwest trending cross-strike discontinuities (CSD's) and the nature of topographic and morphologic features along their strike suggest the presence of bilateral topographic and morphologic symmetry about the long axis of Aphrodite Terra.

  5. Symmetry and range limits in importance indices.

    PubMed

    Seifan, Tal; Seifan, Merav

    2015-10-01

    Recently, Mingo has analyzed the properties of I imp, an importance index, and demonstrated that its range is not symmetrical. While agreeing with this comment, we believe that more light needs to be shed on the issue of symmetry in relation to such indices. Importance indices are calculated using three values: performance of the organism in the absence and in the presence of neighbors and maximum performance of the organism in ideal conditions. Because of this structure, importance indices can hardly ever achieve symmetry along the whole range of potential performances. We discuss the limitation of the symmetry range for different symmetry types and for both additive and multiplicative indices. We conclude that importance indices, as other interactions indices, are practical tools for interpreting ecological outcomes, especially while comparing between studies. Nevertheless, the current structure of importance indices prevents symmetry along their whole range. While the lack of "perfect" symmetry may call for the development of more sophisticated importance metrics, the current indices are still helpful for the understanding of biological systems and should not be discarded before better alternatives are well established. To prevent potential confusion, we suggest that ecologists present the relevant index symmetry range in addition to their results, thus minimizing the probability of misinterpretation.

  6. Symmetries in fluctuations far from equilibrium.

    PubMed

    Hurtado, Pablo I; Pérez-Espigares, Carlos; del Pozo, Jesús J; Garrido, Pedro L

    2011-05-10

    Fluctuations arise universally in nature as a reflection of the discrete microscopic world at the macroscopic level. Despite their apparent noisy origin, fluctuations encode fundamental aspects of the physics of the system at hand, crucial to understand irreversibility and nonequilibrium behavior. To sustain a given fluctuation, a system traverses a precise optimal path in phase space. Here we show that by demanding invariance of optimal paths under symmetry transformations, new and general fluctuation relations valid arbitrarily far from equilibrium are unveiled. This opens an unexplored route toward a deeper understanding of nonequilibrium physics by bringing symmetry principles to the realm of fluctuations. We illustrate this concept studying symmetries of the current distribution out of equilibrium. In particular we derive an isometric fluctuation relation that links in a strikingly simple manner the probabilities of any pair of isometric current fluctuations. This relation, which results from the time-reversibility of the dynamics, includes as a particular instance the Gallavotti-Cohen fluctuation theorem in this context but adds a completely new perspective on the high level of symmetry imposed by time-reversibility on the statistics of nonequilibrium fluctuations. The new symmetry implies remarkable hierarchies of equations for the current cumulants and the nonlinear response coefficients, going far beyond Onsager's reciprocity relations and Green-Kubo formulas. We confirm the validity of the new symmetry relation in extensive numerical simulations, and suggest that the idea of symmetry in fluctuations as invariance of optimal paths has far-reaching consequences in diverse fields.

  7. Symmetries in fluctuations far from equilibrium

    PubMed Central

    Hurtado, Pablo I.; Pérez-Espigares, Carlos; del Pozo, Jesús J.; Garrido, Pedro L.

    2011-01-01

    Fluctuations arise universally in nature as a reflection of the discrete microscopic world at the macroscopic level. Despite their apparent noisy origin, fluctuations encode fundamental aspects of the physics of the system at hand, crucial to understand irreversibility and nonequilibrium behavior. To sustain a given fluctuation, a system traverses a precise optimal path in phase space. Here we show that by demanding invariance of optimal paths under symmetry transformations, new and general fluctuation relations valid arbitrarily far from equilibrium are unveiled. This opens an unexplored route toward a deeper understanding of nonequilibrium physics by bringing symmetry principles to the realm of fluctuations. We illustrate this concept studying symmetries of the current distribution out of equilibrium. In particular we derive an isometric fluctuation relation that links in a strikingly simple manner the probabilities of any pair of isometric current fluctuations. This relation, which results from the time-reversibility of the dynamics, includes as a particular instance the Gallavotti–Cohen fluctuation theorem in this context but adds a completely new perspective on the high level of symmetry imposed by time-reversibility on the statistics of nonequilibrium fluctuations. The new symmetry implies remarkable hierarchies of equations for the current cumulants and the nonlinear response coefficients, going far beyond Onsager’s reciprocity relations and Green–Kubo formulas. We confirm the validity of the new symmetry relation in extensive numerical simulations, and suggest that the idea of symmetry in fluctuations as invariance of optimal paths has far-reaching consequences in diverse fields. PMID:21493865

  8. Relativity symmetries and Lie algebra contractions

    SciTech Connect

    Cho, Dai-Ning; Kong, Otto C.W.

    2014-12-15

    We revisit the notion of possible relativity or kinematic symmetries mutually connected through Lie algebra contractions under a new perspective on what constitutes a relativity symmetry. Contractions of an SO(m,n) symmetry as an isometry on an m+n dimensional geometric arena which generalizes the notion of spacetime are discussed systematically. One of the key results is five different contractions of a Galilean-type symmetry G(m,n) preserving a symmetry of the same type at dimension m+n−1, e.g. a G(m,n−1), together with the coset space representations that correspond to the usual physical picture. Most of the results are explicitly illustrated through the example of symmetries obtained from the contraction of SO(2,4), which is the particular case for our interest on the physics side as the proposed relativity symmetry for “quantum spacetime”. The contractions from G(1,3) may be relevant to real physics.

  9. Sufficient symmetry conditions for Topological Quantum Order.

    PubMed

    Nussinov, Zohar; Ortiz, Gerardo

    2009-10-06

    We prove sufficient conditions for Topological Quantum Order at zero and finite temperatures. The crux of the proof hinges on the existence of low-dimensional Gauge-Like Symmetries, thus providing a unifying framework based on a symmetry principle. These symmetries may be actual invariances of the system, or may emerge in the low-energy sector. Prominent examples of Topological Quantum Order display Gauge-Like Symmetries. New systems exhibiting such symmetries include Hamiltonians depicting orbital-dependent spin exchange and Jahn-Teller effects in transition metal orbital compounds, short-range frustrated Klein spin models, and p+ip superconducting arrays. We analyze the physical consequences of Gauge-Like Symmetries (including topological terms and charges) and show the insufficiency of the energy spectrum, topological entanglement entropy, maximal string correlators, and fractionalization in establishing Topological Quantum Order. General symmetry considerations illustrate that not withstanding spectral gaps, thermal fluctuations may impose restrictions on suggested quantum computing schemes. Our results allow us to go beyond standard topological field theories and engineer systems with Topological Quantum Order.

  10. Discrete symmetries and de Sitter spacetime

    SciTech Connect

    Cotăescu, Ion I. Pascu, Gabriel

    2014-11-24

    Aspects of the ambiguity in defining quantum modes on de Sitter spacetime using a commuting system composed only of differential operators are discussed. Discrete symmetries and their actions on the wavefunction in commonly used coordinate charts are reviewed. It is argued that the system of commuting operators can be supplemented by requiring the invariance of the wavefunction to combined discrete symmetries- a criterion which selects a single state out of the α-vacuum family. Two such members of this family are singled out by particular combined discrete symmetries- states between which exists a well-known thermality relation.

  11. Exploring Symmetry to Assist Alzheimer's Disease Diagnosis

    NASA Astrophysics Data System (ADS)

    Illán, I. A.; Górriz, J. M.; Ramírez, J.; Salas-Gonzalez, D.; López, M.; Padilla, P.; Chaves, R.; Segovia, F.; Puntonet, C. G.

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder first affecting memory functions and then gradually affecting all cognitive functions with behavioral impairments and eventually causing death. Functional brain imaging as Single-Photon Emission Computed Tomography (SPECT) is commonly used to guide the clinician's diagnosis. The essential left-right symmetry of human brains is shown to play a key role in coding and recognition. In the present work we explore the implications of this symmetry in AD diagnosis, showing that recognition may be enhanced when considering this latent symmetry.

  12. Duality and symmetry lost in solid mechanics

    NASA Astrophysics Data System (ADS)

    Bui, Huy Duong

    2008-01-01

    Some conservation laws in Solids and Fracture Mechanics present a lack of symmetry between kinematic and dynamic variables. It is shown that Duality is the right tool to re-establish the symmetry between equations and variables and to provide conservation laws of the pure divergence type which provide true path independent integrals. The loss of symmetry of some energetic expressions is exploited to derive a new method for solving some inverse problems. In particular, the earthquake inverse problem is solved analytically. To cite this article: H.D. Bui, C. R. Mecanique 336 (2008).

  13. Homogeneous sphere packings with triclinic symmetry.

    PubMed

    Fischer, W; Koch, E

    2002-11-01

    All homogeneous sphere packings with triclinic symmetry have been derived by studying the characteristic Wyckoff positions P -1 1a and P -1 2i of the two triclinic lattice complexes. These sphere packings belong to 30 different types. Only one type exists that has exclusively triclinic sphere packings and no higher-symmetry ones. The inherent symmetry of part of the sphere packings is triclinic for 18 types. Sphere packings of all but six of the 30 types may be realized as stackings of parallel planar nets.

  14. Symmetry energy III: Isovector skins

    NASA Astrophysics Data System (ADS)

    Danielewicz, Paweł; Singh, Pardeep; Lee, Jenny

    2017-02-01

    Isoscalar density is a sum of neutron and proton densities and isovector is a normalized difference. Here, we report the experimental evidence for the displacement of the isovector and isoscalar surfaces in nuclei, by ∼ 0.9 fm from each other. We analyze data on quasielastic (QE) charge exchange (p,n) reactions, concurrently with proton and neutron elastic scattering data for the same target nuclei, following the concepts of the isoscalar and isovector potentials combined into Lane optical potential. The elastic data largely probe the geometry of the isoscalar potential and the (p,n) data largely probe a relation between the geometries of the isovector and isoscalar potentials. The targets include 48Ca, 90Zr, 120Sn and 208Pb and projectile incident energy values span the range of (10-50) MeV. In our fit to elastic and QE charge-exchange data, we allow the values of isoscalar and isovector radii, diffusivities and overall potential normalizations to float away from those in the popular Koning and Delaroche parametrization. We find that the best-fit isovector radii are consistently larger than isoscalar and the best-fit isovector surfaces are steeper. Upon identifying the displacement of the potential surfaces with the displacement of the surfaces for the densities in the Skyrme-Hartree-Fock calculations, and by supplementing the results with those from analyzing excitation energies to isobaric analog states in the past, we arrive at the slope and value of the symmetry energy at normal density of 70 < L < 101 MeV and 33.5 < aaV < 36.4 MeV, respectively.

  15. Symmetry and the Cosmic Microwave Background

    NASA Technical Reports Server (NTRS)

    Wollock, Edward J.

    2012-01-01

    A brief historical introduction to the development of observational astronomy and cosmology will be presented. The close relationship between the properties of light, symmetry, and our understanding the contents of our universe will be explored.

  16. Personal recollections on chiral symmetry breaking

    NASA Astrophysics Data System (ADS)

    Kobayashi, Makoto

    2016-07-01

    The author's work on the mass of pseudoscalar mesons is briefly reviewed. The emergence of the study of CP violation in the renormalizable gauge theory from consideration of chiral symmetry in the quark model is discussed.

  17. FJRW-Rings and Mirror Symmetry

    NASA Astrophysics Data System (ADS)

    Krawitz, Marc; Priddis, Nathan; Acosta, Pedro; Bergin, Natalie; Rathnakumara, Himal

    2010-05-01

    The Landau-Ginzburg Mirror Symmetry Conjecture states that for an invertible quasi-homogeneous singularity W and its maximal group G of diagonal symmetries, there is a dual singularity W T such that the orbifold A-model of W/ G is isomorphic to the B-model of W T . The Landau-Ginzburg A-model is the Frobenius algebra {fancyscript{H}_{W,G}} constructed by Fan, Jarvis, and Ruan, and the B-model is the orbifold Milnor ring of W T . We verify the Landau-Ginzburg Mirror Symmetry Conjecture for Arnol’d’s list of unimodal and bimodal quasi-homogeneous singularities with G the maximal diagonal symmetry group, and include a discussion of eight axioms which facilitate the computation of FJRW-rings.

  18. Spontaneous chiral symmetry breaking in metamaterials.

    PubMed

    Liu, Mingkai; Powell, David A; Shadrivov, Ilya V; Lapine, Mikhail; Kivshar, Yuri S

    2014-07-18

    Spontaneous chiral symmetry breaking underpins a variety of areas such as subatomic physics and biochemistry, and leads to an impressive range of fundamental phenomena. Here we show that this prominent effect is now available in artificial electromagnetic systems, enabled by the advent of magnetoelastic metamaterials where a mechanical degree of freedom leads to a rich variety of strong nonlinear effects such as bistability and self-oscillations. We report spontaneous symmetry breaking in torsional chiral magnetoelastic structures where two or more meta-molecules with opposite handedness are electromagnetically coupled, modifying the system stability. Importantly, we show that chiral symmetry breaking can be found in the stationary response of the system, and the effect is successfully demonstrated in a microwave pump-probe experiment. Such symmetry breaking can lead to a giant nonlinear polarization change, energy localization and mode splitting, which provides a new possibility for creating an artificial phase transition in metamaterials, analogous to that in ferrimagnetic domains.

  19. Space and time from translation symmetry

    SciTech Connect

    Schwarz, A.

    2010-01-15

    We show that the notions of space and time in algebraic quantum field theory arise from translation symmetry if we assume asymptotic commutativity. We argue that this construction can be applied to string theory.

  20. Noether symmetries and the Swinging Atwood Machine

    NASA Astrophysics Data System (ADS)

    Moreira, I. C.; Almeida, M. A.

    1991-07-01

    In this work we apply the Noether theorem with generalised symmetries for discussing the integrability of the Swinging Atwood Machine (SAM) model. We analyse also the limitations of this procedure and compare it with the Yoshida method.

  1. Soliton surfaces in the generalized symmetry approach

    NASA Astrophysics Data System (ADS)

    Grundland, A. M.

    2016-09-01

    We investigate some features of generalized symmetries of integrable systems aiming to obtain the Fokas-Gel'fand formula for the immersion of two-dimensional soliton surfaces in Lie algebras. We show that if there exists a common symmetry of the zero-curvature representation of an integrable partial differential equation and its linear spectral problem, then the Fokas-Gel'fand immersion formula is applicable in its original form. In the general case, we show that when the symmetry of the zero-curvature representation is not a symmetry of its linear spectral problem, then the immersion function of the two-dimensional surface is determined by an extended formula involving additional terms in the expression for the tangent vectors. We illustrate these results with examples including the elliptic ordinary differential equation and the C P N-1 sigma-model equation.

  2. Magnetohydrodynamic equilibria with incompressible flows: Symmetry approach

    SciTech Connect

    Cicogna, G.; Pegoraro, F.

    2015-02-15

    We identify and discuss a family of azimuthally symmetric, incompressible, magnetohydrodynamic plasma equilibria with poloidal and toroidal flows in terms of solutions of the Generalized Grad Shafranov (GGS) equation. These solutions are derived by exploiting the incompressibility assumption, in order to rewrite the GGS equation in terms of a different dependent variable, and the continuous Lie symmetry properties of the resulting equation and, in particular, a special type of “weak” symmetries.

  3. Spontaneously broken spacetime symmetries and Goldstone's theorem.

    PubMed

    Low, Ian; Manohar, Aneesh V

    2002-03-11

    Goldstone's theorem states that there is a massless mode for each broken symmetry generator. It has been known for a long time that the naive generalization of this counting fails to give the correct number of massless modes for spontaneously broken spacetime symmetries. We explain how to get the right count of massless modes in the general case, and discuss examples involving spontaneously broken Poincaré and conformal invariance.

  4. Noether symmetries in the phase space

    NASA Astrophysics Data System (ADS)

    Díaz, Bogar; Galindo-Linares, Elizabeth; Ramírez-Romero, Cupatitzio; Silva-Ortigoza, Gilberto; Suárez-Xique, Román; Torres del Castillo, Gerardo F.; Velázquez, Mercedes

    2014-09-01

    The constants of motion of a mechanical system with a finite number of degrees of freedom are related to the variational symmetries of a Lagrangian constructed from the Hamiltonian of the original system. The configuration space for this Lagrangian is the phase space of the original system. The symmetries considered in this manner include transformations of the time and may not be canonical in the standard sense.

  5. Leptogenesis with Friedberg-Lee Symmetry

    NASA Astrophysics Data System (ADS)

    Araki, Takeshi; Geng, C. Q.

    We consider the µ - τ symmetric Friedberg-Lee (FL) symmetry for the neutrino sector and show that a specific FL translation leads to the tribimaximal mixing pattern of the Maki-Nakagawa-Sakata (MNS) matrix. We also apply the symmetry to the type-I seesaw framework and address the baryon asymmetry of the universe through the leptogenesis mechanism. We try to establish a relation between the net baryon asymmetry and CP phases included in the MNS matrix.

  6. Symmetry breaking of quasihelical stellarator equilibria

    SciTech Connect

    Weening, R.H. )

    1993-04-01

    A mean-field Ohm's law is used to determine the effects of the bootstrap current on quasihelically symmetric stellarator equilibria. The Ohm's law leads to the conclusion that the effects of the bootstrap current break the quasihelical stellarator symmetry at second order in an inverse aspect ratio expansion of the magnetic field strength. The level of symmetry breaking suggests that good approximations to quasihelical stellarator fusion reactors may not be attainable.

  7. Density dependence of nuclear symmetry energy

    NASA Astrophysics Data System (ADS)

    Behera, B.; Routray, T. R.; Tripathy, S. K.

    2016-10-01

    High density behavior of nuclear symmetry energy is studied on the basis of the stiffest density dependence of asymmetric contribution to energy per nucleon in charge neutral n + p + e + μ matter under beta equilibrium. The density dependence of nuclear symmetry energy obtained in this way is neither very stiff nor soft at high densities and is found to be in conformity with recent observations of neutron stars.

  8. Fluency Expresses Implicit Knowledge of Tonal Symmetry

    PubMed Central

    Ling, Xiaoli; Li, Fengying; Qiao, Fuqiang; Guo, Xiuyan; Dienes, Zoltan

    2016-01-01

    The purposes of the present study were twofold. First, we sought to establish whether tonal symmetry produces processing fluency. Second, we sought to explore whether symmetry and chunk strength express themselves differently in fluency, as an indication of different mechanisms being involved for sub- and supra-finite state processing. Across two experiments, participants were asked to listen to and memorize artificial poetry showing a mirror symmetry (an inversion, i.e., a type of cross serial dependency); after this training phase, people completed a four-choice RT task in which they were presented with new artificial poetry. Participants were required to identify the stimulus displayed. We found that symmetry sped up responding to the second half of strings, indicating a fluency effect. Furthermore, there was a dissociation between fluency effects arising from symmetry vs. chunk strength, with stronger fluency effects for symmetry rather than chunks in the second half of strings. Taken together, we conjecture a divide between finite state and supra-finite state mechanisms in learning grammatical sequences. PMID:26869960

  9. Symmetry calculation for molecules and transition states.

    PubMed

    Vandewiele, Nick M; Van de Vijver, Ruben; Van Geem, Kevin M; Reyniers, Marie-Françoise; Marin, Guy B

    2015-01-30

    The symmetry of molecules and transition states of elementary reactions is an essential property with important implications for computational chemistry. The automated identification of symmetry by computers is a very useful tool for many applications, but often relies on the availability of three-dimensional coordinates of the atoms in the molecule and hence becomes less useful when these coordinates are a priori unavailable. This article presents a new algorithm that identifies symmetry of molecules and transition states based on an augmented graph representation of the corresponding structures, in which both topology and the presence of stereocenters are accounted for. The automorphism group order of the graph associated with the molecule or transition state is used as a starting point. A novel concept of label-stereoisomers, that is, stereoisomers that arise after labeling homomorph substituents in the original molecule so that they become distinguishable, is introduced and used to obtain the symmetry number. The algorithm is characterized by its generic nature and avoids the use of heuristic rules that would limit the applicability. The calculated symmetry numbers are in agreement with expected values for a large and diverse set of structures, ranging from asymmetric, small molecules such as fluorochlorobromomethane to highly symmetric structures found in drug discovery assays. The new algorithm opens up new possibilities for the fast screening of the degree of symmetry of large sets of molecules.

  10. A new paradigm for animal symmetry.

    PubMed

    Holló, Gábor

    2015-12-06

    My aim in this article is to soften certain rigid concepts concerning the radial and bilateral symmetry of the animal body plan, and to offer a more flexible framework of thinking for them, based on recent understandings of how morphogenesis is regulated by the mosaically acting gene regulatory networks. Based on general principles of the genetic regulation of morphogenesis, it can be seen that the difference between the symmetry of the whole body and that of minor anatomical structures is only a question of a diverse timing during development. I propose that the animal genome, as such, is capable of expressing both radial and bilateral symmetries, and deploys them according to the functional requirements which must be satisfied by both the anatomical structure and body as a whole. Although it may seem paradoxical, this flexible view of symmetry, together with the idea that symmetry is strongly determined by function, bolsters the concept that the presence of the two main symmetries in the animal world is not due to chance: they are necessary biological patterns emerging in evolution.

  11. Fluency Expresses Implicit Knowledge of Tonal Symmetry.

    PubMed

    Ling, Xiaoli; Li, Fengying; Qiao, Fuqiang; Guo, Xiuyan; Dienes, Zoltan

    2016-01-01

    The purposes of the present study were twofold. First, we sought to establish whether tonal symmetry produces processing fluency. Second, we sought to explore whether symmetry and chunk strength express themselves differently in fluency, as an indication of different mechanisms being involved for sub- and supra-finite state processing. Across two experiments, participants were asked to listen to and memorize artificial poetry showing a mirror symmetry (an inversion, i.e., a type of cross serial dependency); after this training phase, people completed a four-choice RT task in which they were presented with new artificial poetry. Participants were required to identify the stimulus displayed. We found that symmetry sped up responding to the second half of strings, indicating a fluency effect. Furthermore, there was a dissociation between fluency effects arising from symmetry vs. chunk strength, with stronger fluency effects for symmetry rather than chunks in the second half of strings. Taken together, we conjecture a divide between finite state and supra-finite state mechanisms in learning grammatical sequences.

  12. Exploring symmetry in near-vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Berzak Hopkins, L.; Le Pape, S.; Divol, L.; Meezan, N.; MacKinnon, A.; Ho, D. D.; Jones, O.; Khan, S.; Ma, T.; Milovich, J.; Pak, A.; Ross, J. S.; Thomas, C.; Turnbull, D.; Amendt, P.; Wilks, S.; Zylstra, A.; Rinderknecht, H.; Sio, H.; Petrasso, R.

    2015-11-01

    Recent experiments with near-vacuum hohlraums, which utilize a minimal but non-zero helium fill, have demonstrated performance improvements relative to conventional gas-filled (0.96 - 1.6 mg/cc helium) hohlraums: minimal backscatter, reduced capsule drive degradation, and minimal suprathermal electron generation. Because this is a low laser-plasma interaction platform, implosion symmetry is controlled via pulse-shaping adjustments to laser power balance. Extending this platform to high-yield designs with high-density carbon capsules requires achieving adequate symmetry control throughout the pulse. In simulations, laser propagation is degraded suddenly by hohlraum wall expansion interacting with ablated capsule material. Nominal radiation-hydrodynamics simulations have not yet proven predictive on symmetry of the final hotspot, and experiments show more prolate symmetry than preshot calculations. Recent efforts have focused on understanding the discrepancy between simulated and measured symmetry and on alternate designs for symmetry control through varying cone fraction, trade-offs between laser power and energy, and modifications to case-to-capsule ratio. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  13. Symmetry energy in cold dense matter

    NASA Astrophysics Data System (ADS)

    Jeong, Kie Sang; Lee, Su Houng

    2016-01-01

    We calculate the symmetry energy in cold dense matter both in the normal quark phase and in the 2-color superconductor (2SC) phase. For the normal phase, the thermodynamic potential is calculated by using hard dense loop (HDL) resummation to leading order, where the dominant contribution comes from the longitudinal gluon rest mass. The effect of gluonic interaction on the symmetry energy, obtained from the thermodynamic potential, was found to be small. In the 2SC phase, the non-perturbative BCS paring gives enhanced symmetry energy as the gapped states are forced to be in the common Fermi sea reducing the number of available quarks that can contribute to the asymmetry. We used high density effective field theory to estimate the contribution of gluon interaction to the symmetry energy. Among the gluon rest masses in 2SC phase, only the Meissner mass has iso-spin dependence although the magnitude is much smaller than the Debye mass. As the iso-spin dependence of gluon rest masses is even smaller than the case in the normal phase, we expect that the contribution of gluonic interaction to the symmetry energy in the 2SC phase will be minimal. The different value of symmetry energy in each phase will lead to different prediction for the particle yields in heavy ion collision experiment.

  14. A new paradigm for animal symmetry

    PubMed Central

    Holló, Gábor

    2015-01-01

    My aim in this article is to soften certain rigid concepts concerning the radial and bilateral symmetry of the animal body plan, and to offer a more flexible framework of thinking for them, based on recent understandings of how morphogenesis is regulated by the mosaically acting gene regulatory networks. Based on general principles of the genetic regulation of morphogenesis, it can be seen that the difference between the symmetry of the whole body and that of minor anatomical structures is only a question of a diverse timing during development. I propose that the animal genome, as such, is capable of expressing both radial and bilateral symmetries, and deploys them according to the functional requirements which must be satisfied by both the anatomical structure and body as a whole. Although it may seem paradoxical, this flexible view of symmetry, together with the idea that symmetry is strongly determined by function, bolsters the concept that the presence of the two main symmetries in the animal world is not due to chance: they are necessary biological patterns emerging in evolution. PMID:26640644

  15. Dynamical symmetry group and quantum splittings for a free particle on the group manifold AdS{sub 3}

    SciTech Connect

    Chenaghlou, A.; Fakhri, H.

    2005-08-01

    It is shown that the set of all quantum states corresponding to the motion of a free particle on the group manifold AdS{sub 3} as the bases with two different labels, constitute a Hilbert space. The second label is bounded by the first one however, the first label is semibounded. The Casimir operator corresponding to the simultaneous and agreeable shifting generators of both labels along with the Cartan subalgebra generator describe the Hamiltonian of a free particle on AdS{sub 3} with dynamical symmetry group U(1,1) and infinite-fold degeneracy for the energy spectrum. The Hilbert space for the Lie algebra of the dynamical symmetry group is a reducible representation space. But the Hilbert subspaces constructed by all the bases which have a given constant value for the difference of two their labels, constitute an irreducible representation for it. It is also shown that the irreducible representation subspaces of the Lie algebras u(1,1) and u(2) are separately spanned by the bases which have the same value for the second and first labels, respectively. These two bunches of Hilbert subspaces present two different types of quantum splittings on the Hilbert space.

  16. as the flavor symmetry in a non-minimal SUSY model

    NASA Astrophysics Data System (ADS)

    Gómez-Izquierdo, J. C.; González-Canales, F.; Mondragon, M.

    2015-05-01

    We present a non-minimal renormalizable SUSY model, with extended Higgs sector and right-handed neutrinos, where the flavor sector exhibits a flavor symmetry. We analyzed the simplest version of this model, in which R-parity is conserved and the right-handed neutrino masses in the flavor doublet are considered with and without degeneracy. We find the generic form of the mass matrices both in the quark and lepton sectors. We reproduce, according to current data, the mixing in the CKM matrix. In the leptonic sector, in the general case where the right-handed neutrino masses are not degenerate, we find that the values for the solar, atmospheric, and reactor mixing angles are in very good agreement with the experimental data, both for a normal and an inverted hierarchy. In the particular case where the right-handed neutrinos masses are degenerate, the model predicts a strong inverted hierarchy spectrum and a sum rule among the neutrino masses. In this case the atmospheric and solar angles are in very good agreement with experimental data, and the reactor one is different from zero, albeit too small (). This value constitutes a lower bound for in the general case. We also find the range of the values for the neutrino masses in each case.

  17. [Types and systems of symmetry and their multiplicity in the adenovirus protein coat. I. Symmetry networks and general symmetry motives].

    PubMed

    Nász, István; Adám, Eva

    2005-10-09

    Each of the more than 1500 polypeptide molecules of 7 different types building up the adenovirus capsid--probably even those of their amino acids--are in symmetrical location. Every kind of polypeptide forms also a separately symmetrical network in the capsid distributed according to their functions in the inner and outer side and inside of the facets and edges, but always in compliance with the icosahedral symmetry. Therefore, each different polypeptide also means a general symmetry motif in the capsid in its own symmetry network. Hexons can be considered as general symmetry motifs in some special association that is because of their environmental position four kinds of hexon types can be found, which are on every facet, next to one another, like three identical groups of four hexons according to the three-fold rotational symmetry. Two polypeptides of a peripentonal hexon of each group of four hexons orient towards the penton and the third toward the other penton located further on the same edge. There are two versions of the arrangement of the group of four hexons: the hexons surround either a polypeptide IX or a polypeptide IIIa. The two versions of group of four hexons on 20 facets symmetrically recurring 60 times as general hexon symmetry motifs form the capsid in combination with the network of other polypeptides. Ideally, the surface of the hexon trimer shows three-fold rotational and three-fold reflexional symmetries. In the arrangement of the hexons in the facets the translational, rotational, horizontal and vertical reflexional symmetry and the combination of these, as well as the glide reflexion and the anti-symmetry can be found. Each hexon has six nearest neighbours and every hexon takes part in the construction of three hexon rows. Every facet and every vertex made up of five facets has an anti-symmetrical pair located on the opposite side of the capsid. Every triangular facet participates in forming three vertices and every facet has three nearest

  18. Perception of Mirror Symmetry in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Falter, Christine M.; Bailey, Anthony J.

    2012-01-01

    Gestalt grouping in autism spectrum disorders (ASD) is selectively impaired for certain organization principles but for not others. Symmetry is a fundamental Gestalt principle characterizing many biological shapes. Sensitivity to symmetry was tested using the Picture Symmetry Test, which requires finding symmetry lines on pictures. Individuals…

  19. Generalized Gross-Pitaevskii equation adapted to the U (5 ) ⊃ SO (5 ) ⊃ SO (3 ) symmetry for spin-2 condensates

    NASA Astrophysics Data System (ADS)

    He, Y. Z.; Liu, Y. M.; Bao, C. G.

    2015-03-01

    A generalized Gross-Pitaevskii equation adapted to the U(5 )⊃SO(5 )⊃SO(3 ) symmetry has been derived and solved for the spin-2 condensates. The spin-textile and the degeneracy of the ground state (g.s.) together with the factors affecting the stability of the g.s., such as the gap and the level density in the neighborhood of the g.s., have been studied. Based on a rigorous treatment of the spin-degrees of freedom, the spin-textiles can be understood in an N -body language. In addition to the ferro, polar, and cyclic phases, the g.s. might in a mixture of them when |M | is not equal to 0 and 2 N (M is the total magnetization). The great difference in the stability and degeneracy of the g.s. caused by varying φ (which marks the features of the interaction) and M is notable. Since the root-mean-square radius Rrms is an observable, efforts have been made to derive a set of formulas to relate Rrms and N ,ω (frequency of the trap), and φ . These formulas provide a way to check the theories with experimental data.

  20. Symmetry types, systems and their multiplicity in the structure of adenovirus capsid. I. Symmetry networks and general symmetry motifs.

    PubMed

    Nász, I; Adám, Eva

    2006-03-01

    Each of the more than 1500 polypeptide molecules of 7 different types building up the adenovirus capsid--probably even those of their amino-acids--are in symmetrical location. Every kind of polypeptide forms a separately also symmetrical network in the capsid distributed according to their functions in the inner and outer side and the inside of the facets and edges, but always in compliance with the icosahedral symmetry. Therefore, each different polypeptide also means a general symmetry motif in the capsid in its own symmetry network. Hexons can be considered as general symmetry motifs in some special association that is because of their environmental position four kinds of hexon types can be found, which are on every facet, next to one another, like three identical groups of four (GOF) according to the three-fold rotational symmetry. Two polypeptides of a peripentonal hexon of each GOF orient toward the penton and the third toward the other penton located further on the same edge. There are two versions of the arrangement of the GOFs: the hexons surround either a polypeptide IX or a polypeptide IlIa. The two versions of GOFs on 20 facets symmetrically recurring 60 times as general hexon symmetry motifs form the capsid in combination with the network of other polypeptides. Ideally, the surface of the hexon trimer shows three-fold rotational and three-fold reflexional symmetries. In the arrangement of hexons in the facets the translational, rotational, horizontal and vertical reflexional symmetry and the combination of these, as well as the glide reflexion and the antisymmetry can be found. Each hexon has six nearest neighbours and every hexon takes part in the construction of three hexon rows. Every facet and every vertex made up of five facets has an antisymmetrical pair located on the opposite side of the capsid. Every triangular facet participates in forming three vertices and every facet has three nearest neighbouring facets. In the facets, the polypeptide

  1. Discovering Symmetry in Everyday Environments: A Creative Approach to Teaching Symmetry and Point Groups

    ERIC Educational Resources Information Center

    Fuchigami, Kei; Schrandt, Matthew; Miessler, Gary L.

    2016-01-01

    A hands-on symmetry project is proposed as an innovative way of teaching point groups to undergraduate chemistry students. Traditionally, courses teaching symmetry require students to identify the point group of a given object. This project asks the reverse: students are instructed to identify an object that matches each point group. Doing so…

  2. Group Parametrized Tunneling and Local Symmetry Conditions

    NASA Astrophysics Data System (ADS)

    Harter, William; Mitchell, Justin

    2010-06-01

    Recently, Hougen showed an ad hoc symmetry-based parameterization scheme for analyzing tunneling dynamics and high resolution spectra of fluxional molecular structure similar to S-parameter analysis of superfine structure in SF_6 or NH_3 maser inversion dynamics by Feynman et.al. The problem is that ad hoc parametrization, like path integration in general, can lead to logjams of parameters or ``paths'' with no way to pick out the relevant ones. We show a way to identify and use relevant parameters for a tunneling Hamiltonian H having global G-symmetry-defined bases by first expressing H as a linear combination bar γ ^i {bar g}_i of operators in dual symmetry group bar G. The coefficients bar γ ^i are parameters that define a complete set of allowed paths for any H with G-symmetry and are related thru spectral decomposition of G to eigensolutions of H. Quantum G vs.bar G duality generalizes lab -vs. -body and state -vs. -particle. The number of relevant bar γ ^i-parameters is reduced if a system tends to stick in states of a local symmetry subgroup LsubsetG so the H spectrum forms level clusters labeled by induced representations d(ℓ)(L)\\uparrowG. A cluster-(ℓ) has one E(epsilon)-level labeled by G species (epsilon) for each L species (ℓ) in Depsilon(G)downarrowL by Frobenius reciprocity. Then we apply local symmetry conditions to each irrep Depsilon(bar γ ^i {bar g}_i) that has already been reduced with respect to local symmetry L. This amounts to setting each off-diagonal component Dj,kepsilon(H) to zero. Local symmetry conditions may tell which bar γ ^i-parameters are redundant or zero and directly determine d(ℓ)\\uparrowG tunneling matrix eigenvalues that give E(epsilon)-levels as well as eigenvectors. Otherwise one may need to choose a particular localizing subgroup chain LsubsetL_1subsetL_2...G and further reduce the number of path parameters to facilitate spectral fitting. J.T. Hougen, 2009 MSS RJ01, {J Mol Spect 123, 197 (1987) W.G. Harter and

  3. The symmetries of the Carroll superparticle

    NASA Astrophysics Data System (ADS)

    Bergshoeff, Eric; Gomis, Joaquim; Parra, Lorena

    2016-05-01

    Motivated by recent applications of Carroll symmetries we investigate, using the method of nonlinear realizations, the geometry of flat and curved (AdS) Carroll space and the symmetries of a particle moving in such a space both in the bosonic as well as in the supersymmetric case. In the bosonic case we find that the Carroll particle possesses an infinite-dimensional symmetry which only in the flat case includes dilatations. The duality between the Bargmann and Carroll algebra, relevant for the flat case, does not extend to the curved case. In the supersymmetric case we study the dynamics of the { N }=1 AdS Carroll superparticle. Only in the flat limit we find that the action is invariant under an infinite-dimensional symmetry that includes a supersymmetric extension of the Lifshitz Carroll algebra with dynamical exponent z = 0. We also discuss in the flat case the extension to { N }=2 supersymmetry and show that the flat { N }=2 superparticle is equivalent to the (non-moving) { N }=1 superparticle and that therefore it is not BPS unlike its Galilei counterpart. This is due to the fact that in this case kappa-symmetry eliminates the linearized supersymmetry. In an appendix we discuss the { N }=2 curved case in three-dimensions only and show that there are two { N }=2 theories that are physically different.

  4. Symmetry in social exchange and health

    NASA Astrophysics Data System (ADS)

    Siegrist, Johannes

    2005-10-01

    Symmetry is a relevant concept in sociological theories of exchange. It is rooted in the evolutionary old norm of social reciprocity and is particularly important in social contracts. Symmetry breaking through violation of the norm of reciprocity generates strain in micro-social systems and, above all, in victims of non-symmetric exchange. In this contribution, adverse healthconsequences of symmetry breaking in contractual social exchange are analysed, with a main focus on the employment contract. Scientific evidence is derived from prospective epidemiological studies testing the model of effort-reward imbalance at work. Overall, a twofold elevated risk of incident disease is observed in employed men and women who are exposed to non-symmetric exchange. Health risks include coronary heart disease, depression and alcohol dependence, among others. Preliminary results suggest similar effects on health produced by symmetry breaking in other types of social relationships (e.g. partnership, parental roles). These findings underline the importance of symmetry in contractual social exchange for health and well-being.

  5. Axisymmetric photonic structures with PT-symmetry

    NASA Astrophysics Data System (ADS)

    Ahmed, Waqas W.; Herrero, Ramon; Botey, Muriel; Staliunas, Kestutis

    2016-09-01

    PT-symmetric structures in photonic crystals, combining refractive index and gain-loss modulations is becoming a research field with increasing interest due to the light directionality induced by these particular potentials. Here, we consider PT-symmetric potentials with axial symmetry to direct light to the crystal central point obtaining a localization effect. The axial and PT-symmetric potential intrinsically generates an exceptional central point in the photonic crystal by the merge of both symmetries. This particular point in the crystal lattice causes field amplitude gradients with exponential slopes around the crystal center. The field localization strongly depends on the phase of the central point and on the complex amplitude of the PT-potential. The presented work analyzes in a first stage 1D linear PT-axisymmetric crystals and the role of the central point phase that determines the defect character, i.e. refractive index defect, gain-loss defect or a combination of both. The interplay of the directional light effect induced by the PT-symmetry and the light localization around the central point through the axial symmetry enhances localization and allows higher field concentration for certain phases. The linearity of the studied crystals introduces an exponential growth of the field that mainly depends on the complex amplitude of the potential. The work is completed by the analysis of 2D PT-axisymmetric potentials showing different spatial slopes and growth rates caused by symmetry reasons.

  6. Graph fibrations and symmetries of network dynamics

    NASA Astrophysics Data System (ADS)

    Nijholt, Eddie; Rink, Bob; Sanders, Jan

    2016-11-01

    Dynamical systems with a network structure can display remarkable phenomena such as synchronisation and anomalous synchrony breaking. A methodology for classifying patterns of synchrony in networks was developed by Golubitsky and Stewart. They showed that the robustly synchronous dynamics of a network is determined by its quotient networks. This result was recently reformulated by DeVille and Lerman, who pointed out that the reduction from a network to a quotient is an example of a graph fibration. The current paper exploits this observation and demonstrates the importance of self-fibrations of network graphs. Self-fibrations give rise to symmetries in the dynamics of a network. We show that every network admits a lift with a semigroup or semigroupoid of self-fibrations. The resulting symmetries impact the global dynamics of the network and can therefore be used to explain and predict generic scenarios for synchrony breaking. Also, when the network has a trivial symmetry groupoid, then every robust synchrony in the lift is determined by symmetry. We finish this paper with a discussion of networks with interior symmetries and nonhomogeneous networks.

  7. Seiberg duality versus hidden local symmetry

    NASA Astrophysics Data System (ADS)

    Abel, Steven; Barnard, James

    2012-05-01

    It is widely believed that the emergent magnetic gauge symmetry of SQCD is analogous to a hidden local symmetry (HLS). We explore this idea in detail, deriving the entire (spontaneously broken) magnetic theory by applying the HLS formalism to spontaneously broken SU( N) SQCD. We deduce the Kähler potential in the HLS description, and show that gauge and flavour symmetry are smoothly restored along certain scaling directions in moduli space. We propose that it is these symmetry restoring directions, associated with the R-symmetry of the theory, that allow full Seiberg duality. Reconsidering the origin of the magnetic gauge bosons as the ρ-mesons of the electric theory, colour-flavour locking allows a simple determination of the parameter a. Its value continuously interpolates between a = 2 on the baryonic branch of moduli space — corresponding to "vector meson dominance" — and a = 1 on the mesonic branch. Both limiting values are consistent with previous results in the literature. The HLS formalism is further applied to SO and Sp groups, where the usual Seiberg duals are recovered, as well as adjoint SQCD. Finally we discuss some possible future applications, including (naturally) the unitarisation of composite W scattering, blended Higgs/technicolour models, real world QCD and non-supersymmetric dualities.

  8. Direct calculation of the linear thermal expansion coefficients of MoS2 via symmetry-preserving deformations

    NASA Astrophysics Data System (ADS)

    Gan, Chee Kwan; Liu, Yu Yang Fredrik

    2016-10-01

    Using density-functional perturbation theory and the Grüneisen formalism, we directly calculate the linear thermal expansion coefficients (TECs) of a hexagonal bulk system MoS2 in the crystallographic a and c directions. The TEC calculation depends critically on the evaluation of a temperature-dependent quantity Ii(T ) , which is the integral of the product of heat capacity and Γi(ν ) , of frequency ν and strain type i , where Γi(ν ) is the phonon density of states weighted by the Grüneisen parameters. We show that to determine the linear TECs we may use minimally two uniaxial strains in the z direction and either the x or y direction. However, a uniaxial strain in either the x or y direction drastically reduces the symmetry of the crystal from a hexagonal one to a base-centered orthorhombic one. We propose to use an efficient and accurate symmetry-preserving biaxial strain in the x y plane to derive the same result for Γ (ν ) . We highlight that the Grüneisen parameter associated with a biaxial strain may not be the same as the average of Grüneisen parameters associated with two separate uniaxial strains in the x and y directions due to possible preservation of degeneracies of the phonon modes under a biaxial deformation. Large anisotropy of TECs is observed where the linear TEC in the c direction is about 1.8 times larger than that in the a or b direction at high temperatures. Our theoretical TEC results are compared with experiment. The symmetry-preserving approach adopted here may be applied to a broad class of two lattice-parameter systems such as hexagonal, trigonal, and tetragonal systems, which allows many complicated systems to be treated on a first-principles level.

  9. Preserving Symmetry in Preconditioned Krylov Subspace Methods

    NASA Technical Reports Server (NTRS)

    Chan, Tony F.; Chow, E.; Saad, Y.; Yeung, M. C.

    1996-01-01

    We consider the problem of solving a linear system Ax = b when A is nearly symmetric and when the system is preconditioned by a symmetric positive definite matrix M. In the symmetric case, one can recover symmetry by using M-inner products in the conjugate gradient (CG) algorithm. This idea can also be used in the nonsymmetric case, and near symmetry can be preserved similarly. Like CG, the new algorithms are mathematically equivalent to split preconditioning, but do not require M to be factored. Better robustness in a specific sense can also be observed. When combined with truncated versions of iterative methods, tests show that this is more effective than the common practice of forfeiting near-symmetry altogether.

  10. The geometry of spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    Abud, M.; Sartori, G.

    1983-10-01

    The problem of classifying the theoretically allowed patterns of spontaneous symmetry breading, in theories where the ground state is determined as a minimum of a G-invariant potential ( G a compact group of transformations), is analyzed. A detailed, complete, and rigorous justification of a recently proposed approach to the determination of the minima of G-invariant potentials (M. Abud and G. Sartori, Phys. Lett. B104 (1981), 147) is presented. The results are obtained through an analysis of the geometry of the finite-dimensional representations of G, which leads to a complete characterization of the structure of orbit space and its partition in subsets (strata) formed by orbits with the same symmetry under G-transformations (orbit type), and to a new theorem stating that the gradients of complex analytic G-invariant functions annihilate on one-dimensional strata. Polynomial potentials in particular are studied. Conditions for instability of the residual symmetry (second-order phase transitions) are determined.

  11. Symmetry-breaking oscillations in membrane optomechanics

    NASA Astrophysics Data System (ADS)

    Wurl, C.; Alvermann, A.; Fehske, H.

    2016-12-01

    We study the classical dynamics of a membrane inside a cavity in the situation where this optomechanical system possesses a reflection symmetry. Symmetry breaking occurs through supercritical and subcritical pitchfork bifurcations of the static fixed-point solutions. Both bifurcations can be observed through variation of the laser-cavity detuning, which gives rise to a boomerang-like fixed-point pattern with hysteresis. The symmetry-breaking fixed points evolve into self-sustained oscillations when the laser intensity is increased. In addition to the analysis of the accompanying Hopf bifurcations we describe these oscillations at finite amplitudes with an ansatz that fully accounts for the frequency shift relative to the natural membrane frequency. We complete our study by following the route to chaos for the membrane dynamics.

  12. Geometric symmetries in superfluid vortex dynamics

    SciTech Connect

    Kozik, Evgeny; Svistunov, Boris

    2010-10-01

    Dynamics of quantized vortex lines in a superfluid feature symmetries associated with the geometric character of the complex-valued field, w(z)=x(z)+iy(z), describing the instant shape of the line. Along with a natural set of Noether's constants of motion, which - apart from their rather specific expressions in terms of w(z) - are nothing but components of the total linear and angular momenta of the fluid, the geometric symmetry brings about crucial consequences for kinetics of distortion waves on the vortex lines, the Kelvin waves. It is the geometric symmetry that renders Kelvin-wave cascade local in the wave-number space. Similar considerations apply to other systems with purely geometric degrees of freedom.

  13. Cylindrical polarization symmetry for nondestructive nanocharacterization

    NASA Astrophysics Data System (ADS)

    Zhan, Qiwen

    2003-07-01

    Recently there is an increasing interest in laser beams with radial symmetry in polarization. Due to the cylindrical symmetry in polarization, these beams have unique focusing properties, which may find wide applications in a variety of nanometer scale applications, including high-resolution metrology, high-density data storage, and multi-functional optical microtool. In this paper, simple method of generating cylindrically polarized beams is presented and their potential applications to nondestructive nano-characterization are discussed. A high resolution surface plasmon microscope and a surface plasmon enhanced apertureless near-field scanning optical microscope are proposed. An automatic scanning microellipsometer that uses the cylindrical symmetry to enhance the signal-to-noise-ratio in high-spatial-resolution ellipsometric measurement will also be presented.

  14. Arbitrary lattice symmetries via block copolymer nanomeshes

    PubMed Central

    Majewski, Pawel W.; Rahman, Atikur; Black, Charles T.; Yager, Kevin G.

    2015-01-01

    Self-assembly of block copolymers is a powerful motif for spontaneously forming well-defined nanostructures over macroscopic areas. Yet, the inherent energy minimization criteria of self-assembly give rise to a limited library of structures; diblock copolymers naturally form spheres on a cubic lattice, hexagonally packed cylinders and alternating lamellae. Here, we demonstrate multicomponent nanomeshes with any desired lattice symmetry. We exploit photothermal annealing to rapidly order and align block copolymer phases over macroscopic areas, combined with conversion of the self-assembled organic phase into inorganic replicas. Repeated photothermal processing independently aligns successive layers, providing full control of the size, symmetry and composition of the nanoscale unit cell. We construct a variety of symmetries, most of which are not natively formed by block copolymers, including squares, rhombuses, rectangles and triangles. In fact, we demonstrate all possible two-dimensional Bravais lattices. Finally, we elucidate the influence of nanostructure on the electrical and optical properties of nanomeshes. PMID:26100566

  15. Discrete Abelian gauge symmetries and axions

    NASA Astrophysics Data System (ADS)

    Honecker, Gabriele; Staessens, Wieland

    2015-07-01

    We combine two popular extensions of beyond the Standard Model physics within the framework of intersecting D6-brane models: discrete ℤn symmetries and Peccei-Quinn axions. The underlying natural connection between both extensions is formed by the presence of massive U(1) gauge symmetries in D-brane model building. Global intersecting D6-brane models on toroidal orbifolds of the type T6/ℤ2N and T6/ℤ2 × ℤ2M with discrete torsion offer excellent playgrounds for realizing these extensions. A generation-dependent ℤ2 symmetry is identified in a global Pati-Salam model, while global left-right symmetric models give rise to supersymmetric realizations of the DFSZ axion model. In one class of the latter models, the axion as well as Standard Model particles carry a non-trivial ℤ3 charge.

  16. Approximate flavor symmetries in the lepton sector

    SciTech Connect

    Rasin, A. ); Silva, J.P. )

    1994-01-01

    Approximate flavor symmetries in the quark sector have been used as a handle on physics beyond the standard model. Because of the great interest in neutrino masses and mixings and the wealth of existing and proposed neutrino experiments it is important to extend this analysis to the leptonic sector. We show that in the seesaw mechanism the neutrino masses and mixing angles do not depend on the details of the right-handed neutrino flavor symmetry breaking, and are related by a simple formula. We propose several [ital Ansa]$[ital uml]---[ital tze] which relate different flavor symmetry-breaking parameters and find that the MSW solution to the solar neutrino problem is always easily fit. Further, the [nu][sub [mu]-][nu][sub [tau

  17. Approximate gauge symmetry of composite vector bosons

    NASA Astrophysics Data System (ADS)

    Suzuki, Mahiko

    2010-08-01

    It can be shown in a solvable field theory model that the couplings of the composite vector bosons made of a fermion pair approach the gauge couplings in the limit of strong binding. Although this phenomenon may appear accidental and special to the vector bosons made of a fermion pair, we extend it to the case of bosons being constituents and find that the same phenomenon occurs in a more intriguing way. The functional formalism not only facilitates computation but also provides us with a better insight into the generating mechanism of approximate gauge symmetry, in particular, how the strong binding and global current conservation conspire to generate such an approximate symmetry. Remarks are made on its possible relevance or irrelevance to electroweak and higher symmetries.

  18. Spontaneous Symmetry Breaking in Interdependent Networked Game

    NASA Astrophysics Data System (ADS)

    Jin, Qing; Wang, Lin; Xia, Cheng-Yi; Wang, Zhen

    2014-02-01

    Spatial evolution game has traditionally assumed that players interact with direct neighbors on a single network, which is isolated and not influenced by other systems. However, this is not fully consistent with recent research identification that interactions between networks play a crucial rule for the outcome of evolutionary games taking place on them. In this work, we introduce the simple game model into the interdependent networks composed of two networks. By means of imitation dynamics, we display that when the interdependent factor α is smaller than a threshold value αC, the symmetry of cooperation can be guaranteed. Interestingly, as interdependent factor exceeds αC, spontaneous symmetry breaking of fraction of cooperators presents itself between different networks. With respect to the breakage of symmetry, it is induced by asynchronous expansion between heterogeneous strategy couples of both networks, which further enriches the content of spatial reciprocity. Moreover, our results can be well predicted by the strategy-couple pair approximation method.

  19. Workshop on electroweak symmetry breaking: proceedings

    SciTech Connect

    Hinchliffe, I.

    1984-10-01

    A theoretical workshop on electroweak symmetry breaking at the Superconducting Supercollider was held at Lawrence Berkeley Laboratory, June 4-22, 1984. The purpose of the workshop was to focus theoretical attention on the ways in which experimentation at the SSC could reveal manifestations of the phenomenon responsible for electroweak symmetry breaking. This issue represents, at present, the most compelling scientific argument for the need to explore the energy region to be made accessible by the SSC, and a major aim of the workshop was to involve a broad cross section of particle theorists in the ongoing process of sharpening the requirements for both accelerator and detector design that will ensure detection and identification of meaningful signals, whatever form the electroweak symmetry breaking phenomenon should actually take. Separate entries were prepared for the data base for the papers presented.

  20. Mutual information and spontaneous symmetry breaking

    NASA Astrophysics Data System (ADS)

    Hamma, A.; Giampaolo, S. M.; Illuminati, F.

    2016-01-01

    We show that the metastable, symmetry-breaking ground states of quantum many-body Hamiltonians have vanishing quantum mutual information between macroscopically separated regions and are thus the most classical ones among all possible quantum ground states. This statement is obvious only when the symmetry-breaking ground states are simple product states, e.g., at the factorization point. On the other hand, symmetry-breaking states are in general entangled along the entire ordered phase, and to show that they actually feature the least macroscopic correlations compared to their symmetric superpositions is highly nontrivial. We prove this result in general, by considering the quantum mutual information based on the two-Rényi entanglement entropy and using a locality result stemming from quasiadiabatic continuation. Moreover, in the paradigmatic case of the exactly solvable one-dimensional quantum X Y model, we further verify the general result by considering also the quantum mutual information based on the von Neumann entanglement entropy.

  1. Supersymmetric defect models and mirror symmetry

    SciTech Connect

    Hook, Anson; Kachru, Shamit; Torroba, Gonzalo

    2013-11-01

    We study supersymmetric field theories in three space-time dimensions doped by various configurations of electric charges or magnetic fluxes. These are supersymmetric avatars of impurity models. In the presence of additional sources such configurations are shown to preserve half of the supersymmetries. Mirror symmetry relates the two sets of configurations. We discuss the implications for impurity models in 3d NN = 4 QED with a single charged hypermultiplet (and its mirror, the theory of a free hypermultiplet) as well as 3d NN = 2 QED with one flavor and its dual, a supersymmetric Wilson-Fisher fixed point. Mirror symmetry allows us to find backreacted solutions for arbitrary arrays of defects in the IR limit of NN = 4 QED. Our analysis, complemented with appropriate string theory brane constructions, sheds light on various aspects of mirror symmetry, the map between particles and vortices and the emergence of ground state entropy in QED at finite density.

  2. Nonlinear realization and hidden local symmetries

    NASA Astrophysics Data System (ADS)

    Bando, Masako; Kugo, Taichiro; Yamawaki, Koichi

    1988-07-01

    The idea of dynamical gauge bosons of hidden local symmetries in nonlinear sigma models is reviewed. Starting with a fresh look at the Goldstone theorem and low energy theorems, we present a modern review of the general theory of nonlinear realization both in nonsupersymmetric and supersymmetric cases. We then show that any nonlinear sigma model based on the manifold G/ H is gauge equivalent to a “linear” model possessing a Gglobal × Hlocal symmetry, Hlocal being a hidden local symmetry. The corresponding supersymmetric formulation is also presented. The above gauge equivalence can be extended to a model having a larger symmetry Gglobal × Glocal. Also reviewed are dynamical calculatio ns showing that in some two-, three- and four-dimensional models, the gauge bosons of the hidden local symmetries acquire the kinetic terms via quantum effects, thus becoming “dynamical”. We suggest that such a dynamical gauge boson may be a rather common phenomenon realized in Nature. As a realistic example, we examine the QCD case where we identify the vector mesons (ϱ,ω,ф,K ∗) with the dynamical gauge bosons of the hidden U(3) v local symmetry in the U(3) L × U(3) R/U(3) V nonlinear sigma model. The totality of the vector meson phenomenology seems to support our basic idea. The axial-vector mesons are also incorporated into our framework. Also given is a brief sketch of some applications of this formalism to unified models beyond the standard model, such as technicolor, composite W/Z boson and supergravity models.

  3. Broken symmetry in ideal magnetohydrodynamic turbulence

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1993-01-01

    A numerical study of the long-time evolution of a number of cases of inviscid, isotropic, incompressible, three-dimensional fluid, and magneto-fluid turbulence has been completed. The results confirm that ideal magnetohydrodynamic turbulence is non-ergodic if there is no external magnetic field present. This is due essentially to a canonical symmetry being broken in an arbitrary dynamical representation. The broken symmetry manifests itself as a coherent structure, i.e., a non-zero time-averaged part of the turbulent magnetic field. The coherent structure is observed, in one case, to contain about eighteen percent of the total energy.

  4. Routh symmetry in the Chaplygin's rolling ball

    NASA Astrophysics Data System (ADS)

    Kim, Byungsoo

    2011-12-01

    The Routh integral in the symmetric Chaplygin's rolling ball has been regarded as a mysterious conservation law due to its interesting form of sqrt {I_1 I_3 + m< {I_s ,s} rangle } Ω _3 . In this paper, a new form of the Routh integral is proposed as a Noether's pairing form of a conservation law. An explicit symmetry vector for the Routh integral is proved to associate the conserved quantity with the invariance of the Lagrangian function under the rollingly constrained nonholonomic variation. Then, the form of the Routh symmetry vector is discussed for its origin as the linear combination of the configurational vectors.

  5. Weak Lie symmetry and extended Lie algebra

    SciTech Connect

    Goenner, Hubert

    2013-04-15

    The concept of weak Lie motion (weak Lie symmetry) is introduced. Applications given exhibit a reduction of the usual symmetry, e.g., in the case of the rotation group. In this context, a particular generalization of Lie algebras is found ('extended Lie algebras') which turns out to be an involutive distribution or a simple example for a tangent Lie algebroid. Riemannian and Lorentz metrics can be introduced on such an algebroid through an extended Cartan-Killing form. Transformation groups from non-relativistic mechanics and quantum mechanics lead to such tangent Lie algebroids and to Lorentz geometries constructed on them (1-dimensional gravitational fields).

  6. The Scalar Mesons and Z(3) Symmetry

    SciTech Connect

    Toernqvist, Nils A.

    2007-02-27

    It is pointed out that the det{sigma} + det{sigma}{dagger} term, which resolves the UA(1) problem in effective theories, gives rise to three classical minima along the UA(1) circle when Nf = 3. The three minima are related to the center Z(3) of SU(3). This Z(3) symmetry can be retained if the SU(3)L x SU(3)R symmetry breaking is assumed to be trilinear in the fields. The three vacua suggests a connection to the strong CP problem and confinement.

  7. Neutron matter, symmetry energy and neutron stars

    NASA Astrophysics Data System (ADS)

    Gandolfi, S.; Steiner, A. W.

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron- rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.

  8. Neutron matter, symmetry energy and neutron stars

    SciTech Connect

    Stefano, Gandolfi; Steiner, Andrew W

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron-rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.

  9. Partial restoration of chiral symmetry inside hadrons

    SciTech Connect

    Iritani, Takumi; Cossu, Guido; Hashimoto, Shoji

    2016-01-22

    We investigate the spatial distribution of the chiral condensate around static color sources for both quark-antiquark and three-quark systems. In the QCD vacuum a tube-like structure of chromo fields appears between color sources, which leads to a linearly confining potential. We show that the magnitude of the condensate is reduced inside the flux-tube, which suggests that chiral symmetry is partially restored inside the hadrons. By using a static baryon source in a periodic box as a model of the nuclear matter, we estimate the restoration of chiral symmetry with finite baryon number density.

  10. Hopf bifurcation in the presence of symmetry

    NASA Technical Reports Server (NTRS)

    Golubitsky, M.; Stewart, I.

    1985-01-01

    Group theory is applied to obtain generalized differential equations from the Hopf bifurcation theory on branching to periodic solutions. The conditions under which the symmetry group will admit imaginary eigenvalues are delimited. The action of the symmetry group on the circle group are explored and the Liapunov-Schmidt reduction is used to prove the Hopf theorem in the symmetric case. The emphasis is on simplifying calculations of the stability of bifurcating branches. The resulting general theory is demonstrated in terms of O(2) acting on a plane, O(n) in n-space, and O(3) and an irreducible model for spherical harmonics.

  11. Wormholes and Peccei-Quinn symmetries

    SciTech Connect

    Choi, K.; Holman, R. )

    1990-01-08

    We show how wormholes and Peccei-Quinn symmetries are in fact complementary in solving the strong {ital CP} problem. On the one hand, Peccei-Quinn symmetries are shown to provide us with a wormhole parameter that couples only to the QCD anomaly. This then allows us to implement the wormhole solution to the strong {ital CP} problem constructed previously by the present authors as well as by Preskill, Trivedi, and Wise. On the other hand, wormholes are shown to drive the axion mass to zero or to the wormhole scale, thus avoiding the axion-energy-density crisis in either case.

  12. Coupled oscillators with parity-time symmetry

    NASA Astrophysics Data System (ADS)

    Tsoy, Eduard N.

    2017-02-01

    Different models of coupled oscillators with parity-time (PT) symmetry are studied. Hamiltonian functions for two and three linear oscillators coupled via coordinates and accelerations are derived. Regions of stable dynamics for two coupled oscillators are obtained. It is found that in some cases, an increase of the gain-loss parameter can stabilize the system. A family of Hamiltonians for two coupled nonlinear oscillators with PT-symmetry is obtained. An extension to high-dimensional PT-symmetric systems is discussed.

  13. Conformal and projective symmetries in Newtonian cosmology

    NASA Astrophysics Data System (ADS)

    Duval, C.; Gibbons, G. W.; Horváthy, P. A.

    2017-02-01

    Definitions of non-relativistic conformal transformations are considered both in the Newton-Cartan and in the Kaluza-Klein-type Eisenhart/Bargmann geometrical frameworks. The symmetry groups that come into play are exemplified by the cosmological, and also the Newton-Hooke solutions of Newton's gravitational field equations. It is shown, in particular, that the maximal symmetry group of the standard cosmological model is isomorphic to the 13-dimensional conformal-Newton-Cartan group whose conformal-Bargmann extension is explicitly worked out. Attention is drawn to the appearance of independent space and time dilations, in contrast with the Schrödinger group or the Conformal Galilei Algebra.

  14. Symmetry energy II: Isobaric analog states

    NASA Astrophysics Data System (ADS)

    Danielewicz, Pawel; Lee, Jenny

    2014-02-01

    Using excitation energies to isobaric analog states (IAS) and charge invariance, we extract nuclear symmetry coefficients, representing a mass formula, on a nucleus-by-nucleus basis. Consistently with charge invariance, the coefficients vary weakly across an isobaric chain. However, they change strongly with nuclear mass and range from aa˜10 MeV at mass A˜10 to aa˜22 MeV at A˜240. Variation with mass can be understood in terms of dependence of nuclear symmetry energy on density and the rise in importance of low densities within nuclear surface in smaller systems. At A≳30, the dependence of coefficients on mass can be well described in terms of a macroscopic volume-surface competition formula with aaV≃33.2 MeV and aaS≃10.7 MeV. Our further investigation shows, though, that the fitted surface symmetry coefficient likely significantly underestimates that for the limit of half-infinite matter. Following the considerations of a Hohenberg-Kohn functional for nuclear systems, we determine how to find in practice the symmetry coefficient using neutron and proton densities, even when those densities are simultaneously affected by significant symmetry-energy and Coulomb effects. These results facilitate extracting the symmetry coefficients from Skyrme-Hartree-Fock (SHF) calculations, that we carry out using a variety of Skyrme parametrizations in the literature. For the parametrizations, we catalog novel short-wavelength instabilities. In our further analysis, we retain only those parametrizations which yield systems that are adequately stable both in the long- and short-wavelength limits. In comparing the SHF and IAS results for the symmetry coefficients, we arrive at narrow (±2.4 MeV) constraints on the symmetry-energy values S(ρ) at 0.04≲ρ≲0.13 fm. Towards normal density the constraints significantly widen, but the normal value of energy aaV and the slope parameter L are found to be strongly correlated. To narrow the constraints, we reach for the

  15. Non-standard symmetries and quantum anomalies

    SciTech Connect

    Visinescu, Anca; Visinescu, Mihai

    2008-08-31

    Quantum anomalies are investigated on curved spacetimes. The intimate relation between Killing-Yano tensors and non-standard symmetries is pointed out. The gravitational anomalies are absent if the hidden symmetry is associated to a Killing-Yano tensor. The axial anomaly in a background gravitational field is directly related with the index of the Dirac operator. In the Dirac theory on curved spaces, Killing-Yano tensors generate Dirac-type operators involved in interesting algebraic structures. The general results are applied to the 4-dimensional Euclidean Taub-NUT space.

  16. Black Hole Thermodynamics and Lorentz Symmetry

    NASA Astrophysics Data System (ADS)

    Jacobson, Ted; Wall, Aron C.

    2010-08-01

    Recent developments point to a breakdown in the generalized second law of thermodynamics for theories with Lorentz symmetry violation. It appears possible to construct a perpetual motion machine of the second kind in such theories, using a black hole to catalyze the conversion of heat to work. Here we describe and extend the arguments leading to that conclusion. We suggest the inference that local Lorentz symmetry may be an emergent property of the macroscopic world with origins in a microscopic second law of causal horizon thermodynamics.

  17. A symmetry principle for topological quantum order

    SciTech Connect

    Nussinov, Zohar Ortiz, Gerardo

    2009-05-15

    We present a unifying framework to study physical systems which exhibit topological quantum order (TQO). The major guiding principle behind our approach is that of symmetries and entanglement. These symmetries may be actual symmetries of the Hamiltonian characterizing the system, or emergent symmetries. To this end, we introduce the concept of low-dimensional Gauge-like symmetries (GLSs), and the physical conservation laws (including topological terms, fractionalization, and the absence of quasi-particle excitations) which emerge from them. We prove then sufficient conditions for TQO at both zero and finite temperatures. The physical engine for TQO are topological defects associated with the restoration of GLSs. These defects propagate freely through the system and enforce TQO. Our results are strongest for gapped systems with continuous GLSs. At zero temperature, selection rules associated with the GLSs enable us to systematically construct general states with TQO; these selection rules do not rely on the existence of a finite gap between the ground states to all other excited states. Indices associated with these symmetries correspond to different topological sectors. All currently known examples of TQO display GLSs. Other systems exhibiting such symmetries include Hamiltonians depicting orbital-dependent spin-exchange and Jahn-Teller effects in transition metal orbital compounds, short-range frustrated Klein spin models, and p+ip superconducting arrays. The symmetry based framework discussed herein allows us to go beyond standard topological field theories and systematically engineer new physical models with finite temperature TQO (both Abelian and non-Abelian). Furthermore, we analyze the insufficiency of entanglement entropy (we introduce SU(N) Klein models on small world networks to make the argument even sharper), spectral structures, maximal string correlators, and fractionalization in establishing TQO. We show that Kitaev's Toric code model and Wen

  18. Quregisters, Symmetry Groups and Clifford Algebras

    NASA Astrophysics Data System (ADS)

    Cervantes, D.; Morales-Luna, G.

    2016-03-01

    Natural one-to-one and two-to-one homomorphisms from SO(3) into SU(2) are built conventionally, and the collection of qubits, is identified with a subgroup of SU(2). This construction is suitable to be extended to corresponding tensor powers. The notions of qubits, quregisters and qugates are translated into the language of symmetry groups. The corresponding elements to entangled states in the tensor product of Hilbert spaces reflect entanglement properties as well, and in this way a notion of entanglement is realised in the tensor product of symmetry groups.

  19. Dual technicolor with hidden local symmetry

    SciTech Connect

    Belitsky, A. V.

    2010-08-15

    We consider a dual description of the technicolor-like gauge theory within the D4/D8-brane configuration with varying confinement and electroweak symmetry breaking scales. Constructing an effective truncated model valid below a certain cutoff, we identify the particle spectrum with Kaluza-Klein modes of the model in a manner consistent with the hidden local symmetry. Integrating out heavy states, we find that the low-energy action receives nontrivial corrections stemming from the mixing between standard model and heavy gauge bosons, which results in reduction of oblique parameters.

  20. Shape phase transitions and critical points

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-05-04

    We investigate different aspects connected with shape phase transitions in nuclei and the possible occurrence of dynamical symmetries at the critical points. We discuss in particular the behaviour of the neighbour odd nuclei at the vicinity of the critical points in the even nuclei. We consider both the case of the transition from the vibrational behaviour to the gamma-unstable deformation (characterized within the collective Bohr hamiltonian by the E(5) critical point symmetry) and the case of the transition from the vibrational behaviour to the stable axial deformation (characterized by the X(5) symmetry). The odd particle is assumed to be moving in the three single particle orbitals j = 1/2,3/2,5/2, a set of orbitals that is known to lead to possible supersymmetric cases. The coupling of the odd particle to the Bohr hamiltonian does lead in fact in the former case at the critical point to the E(5/12) boson-fermion dynamical symmetry. An alternative approach to the two shape transitions is based on the Interacting Boson Fermion Model. In this case suitably parametrized boson-fermion hamiltonians can describe the evolution of the odd system along the shape transitions. At the critical points both energy spectra and electromagnetic transitions were found to display characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The behaviour of the odd nuclei can therefore be seen as necessary complementary signatures of the occurrence of the phase transitions.

  1. Symmetry, winding number, and topological charge of vortex solitons in discrete-symmetry media

    SciTech Connect

    Garcia-March, Miguel-Angel; Zacares, Mario; Sahu, Sarira; Ceballos-Herrera, Daniel E.

    2009-05-15

    We determine the functional behavior near the discrete rotational symmetry axis of discrete vortices of the nonlinear Schroedinger equation. We show that these solutions present a central phase singularity whose charge is restricted by symmetry arguments. Consequently, we demonstrate that the existence of high-charged discrete vortices is related to the presence of other off-axis phase singularities, whose positions and charges are also restricted by symmetry arguments. To illustrate our theoretical results, we offer two numerical examples of high-charged discrete vortices in photonic crystal fibers showing hexagonal discrete rotational invariance.

  2. Identical Wells, Symmetry Breaking, and the Near-Unitary Limit

    NASA Astrophysics Data System (ADS)

    Harshman, N. L.

    2017-03-01

    Energy level splitting from the unitary limit of contact interactions to the near unitary limit for a few identical atoms in an effectively one-dimensional well can be understood as an example of symmetry breaking. At the unitary limit in addition to particle permutation symmetry there is a larger symmetry corresponding to exchanging the N! possible orderings of N particles. In the near unitary limit, this larger symmetry is broken, and different shapes of traps break the symmetry to different degrees. This brief note exploits these symmetries to present a useful, geometric analogy with graph theory and build an algebraic framework for calculating energy splitting in the near unitary limit.

  3. Dynamics symmetries of Hamiltonian system on time scales

    SciTech Connect

    Peng, Keke Luo, Yiping

    2014-04-15

    In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

  4. Dynamics symmetries of Hamiltonian system on time scales

    NASA Astrophysics Data System (ADS)

    Peng, Keke; Luo, Yiping

    2014-04-01

    In this paper, the dynamics symmetries of Hamiltonian system on time scales are studied. We study the symmetries and quantities based on the calculation of variation and Lie transformation group. Particular focus lies in: the Noether symmetry leads to the Noether conserved quantity and the Lie symmetry leads to the Noether conserved quantity if the infinitesimal transformations satisfy the structure equation. As the new application of result, at end of the article, we give a simple example of Noether symmetry and Lie symmetry on time scales.

  5. Symmetry groups associated with tilings on a flat torus.

    PubMed

    Loyola, Mark L; De Las Peñas, Ma Louise Antonette N; Estrada, Grace M; Santoso, Eko Budi

    2015-01-01

    This work investigates symmetry and color symmetry properties of Kepler, Heesch and Laves tilings embedded on a flat torus and their geometric realizations as tilings on a round torus in Euclidean 3-space. The symmetry group of the tiling on the round torus is determined by analyzing relevant symmetries of the planar tiling that are transformed to axial symmetries of the three-dimensional tiling. The focus on studying tilings on a round torus is motivated by applications in the geometric modeling of nanotori and the determination of their symmetry groups.

  6. The numerical measure of symmetry for 3D stick creatures.

    PubMed

    Jaśkowski, Wojciech; Komosinski, Maciej

    2008-01-01

    This work introduces a numerical, continuous measure of symmetry for 3D stick creatures and solid 3D objects. Background information about the property of symmetry is provided, and motivations for developing a symmetry measure are described. Three approaches are mentioned, and two of them are presented in detail using formal mathematical language. The best approach is used to sort a set of creatures according to their symmetry. Experiments with a mixed set of 84 individuals originating from both human design and evolution are performed to examine symmetry within these two sources, and to determine if human designers and evolutionary processes prefer symmetry or asymmetry.

  7. Tri-bimaximal mixing from twisted Friedberg-Lee symmetry

    NASA Astrophysics Data System (ADS)

    Araki, Takeshi; Takahashi, Ryo

    2009-10-01

    We investigate the Friedberg-Lee (FL) symmetry and its promotion to include the μ- τ symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation of the FL symmetry. The second one is based on the S 3 permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each scheme are also presented.

  8. Qudit quantum computation on matrix product states with global symmetry

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Sheng; Stephen, David T.; Raussendorf, Robert

    2017-03-01

    Resource states that contain nontrivial symmetry-protected topological order are identified for universal single-qudit measurement-based quantum computation. Our resource states fall into two classes: one as the qudit generalizations of the one-dimensional qubit cluster state, and the other as the higher-symmetry generalizations of the spin-1 Affleck-Kennedy-Lieb-Tasaki (AKLT) state, namely, with unitary, orthogonal, or symplectic symmetry. The symmetry in cluster states protects information propagation (identity gate), while the higher symmetry in AKLT-type states enables nontrivial gate computation. This work demonstrates a close connection between measurement-based quantum computation and symmetry-protected topological order.

  9. Equilibria with incompressible flows from symmetry analysis

    SciTech Connect

    Kuiroukidis, Ap E-mail: gthroum@cc.uoi.gr; Throumoulopoulos, G. N. E-mail: gthroum@cc.uoi.gr

    2015-08-15

    We identify and study new nonlinear axisymmetric equilibria with incompressible flow of arbitrary direction satisfying a generalized Grad Shafranov equation by extending the symmetry analysis presented by Cicogna and Pegoraro [Phys. Plasmas 22, 022520 (2015)]. In particular, we construct a typical tokamak D-shaped equilibrium with peaked toroidal current density, monotonically varying safety factor, and sheared electric field.

  10. The Symmetry Group of the Permutahedron

    ERIC Educational Resources Information Center

    Crisman, Karl-Dieter

    2011-01-01

    Although it can be visualized fairly easily and its symmetry group is easy to calculate, the permutahedron is a somewhat neglected combinatorial object. We propose it as a useful case study in abstract algebra. It supplies concrete examples of group actions, the difference between right and left actions, and how geometry and algebra can work…

  11. Automatic procedure for generating symmetry adapted wavefunctions.

    PubMed

    Johansson, Marcus; Veryazov, Valera

    2017-01-01

    Automatic detection of point groups as well as symmetrisation of molecular geometry and wavefunctions are useful tools in computational quantum chemistry. Algorithms for developing these tools as well as an implementation are presented. The symmetry detection algorithm is a clustering algorithm for symmetry invariant properties, combined with logical deduction of possible symmetry elements using the geometry of sets of symmetrically equivalent atoms. An algorithm for determining the symmetry adapted linear combinations (SALCs) of atomic orbitals is also presented. The SALCs are constructed with the use of projection operators for the irreducible representations, as well as subgroups for determining splitting fields for a canonical basis. The character tables for the point groups are auto generated, and the algorithm is described. Symmetrisation of molecules use a projection into the totally symmetric space, whereas for wavefunctions projection as well and partner function determination and averaging is used. The software has been released as a stand-alone, open source library under the MIT license and integrated into both computational and molecular modelling software.Graphical abstract.

  12. Carbon Nanotubes: From Symmetry to Applications

    NASA Astrophysics Data System (ADS)

    Damnjanović, M.

    In this chapter, we show how the concept of symmetry gives theoretical explanation of the properties, which made carbon nanotubes (NTs) one of the most interesting materials of nanotechnology. First, in Sect. 3.1, we consider basic facts on single-wall carbon nanotubes (SWCNTs), including their configuration and symmetry. Then, we discuss double-wall nanotubes.Next, Sect. 3.2 is devoted to elementary symmetry-based physical properties. More precisely, we explain the energy spectrum of electrons and phonons, showing that as the consequence of the symmetry, energies must be arranged in the so-called bands. Elementary properties of these band structures may be a priory discussed, yielding easily famous conducting law, showing strong dependence of conductivity on the type of nanotube. Conserved quantum numbers enable us to extract selection rules for various physical processes. This way, radial breathing mode appears to be very important for the characterization of the samples by Raman spectroscopy. Also, optical properties are derived.Finally, in Sect. 3.3, mutual interaction between the walls of double-wall nanotubes is discussed. It is explained why this interaction is very weak, which is used to propose nanomachines with almost superslippery parts.

  13. Geometry and symmetries in lattice spinor gravity

    SciTech Connect

    Wetterich, C.

    2012-09-15

    Lattice spinor gravity is a proposal for regularized quantum gravity based on fermionic degrees of freedom. In our lattice model the local Lorentz symmetry is generalized to complex transformation parameters. The difference between space and time is not put in a priori, and the euclidean and the Minkowski quantum field theory are unified in one functional integral. The metric and its signature arise as a result of the dynamics, corresponding to a given ground state or cosmological solution. Geometrical objects as the vierbein, spin connection or the metric are expectation values of collective fields built from an even number of fermions. The quantum effective action for the metric is invariant under general coordinate transformations in the continuum limit. The action of our model is found to be also invariant under gauge transformations. We observe a 'geometrical entanglement' of gauge- and Lorentz-transformations due to geometrical objects transforming non-trivially under both types of symmetry transformations. - Highlights: Black-Right-Pointing-Pointer We formulate the geometrical aspects of a proposal for a lattice regularized model of quantum gravity. Black-Right-Pointing-Pointer The vierbein shows an entanglement between Lorentz symmetry and gauge symmetry. Black-Right-Pointing-Pointer Euclidean and Minkowski signatures of the collective metric and the vierbein are described within the same functional integral.

  14. Correlators with sℓ2 Yangian symmetry

    NASA Astrophysics Data System (ADS)

    Fuksa, J.; Kirschner, R.

    2017-01-01

    Correlators based on sℓ2 Yangian symmetry and its quantum deformation are studied. Symmetric integral operators can be defined with such correlators as kernels. Yang-Baxter operators can be represented in this way. Particular Yangian symmetric correlators are related to the kernels of QCD parton evolution. The solution of the eigenvalue problem of Yangian symmetric operators is described.

  15. Large Hierarchies from Approximate R Symmetries

    SciTech Connect

    Kappl, Rolf; Ratz, Michael; Schmidt-Hoberg, Kai; Nilles, Hans Peter; Ramos-Sanchez, Saul; Vaudrevange, Patrick K. S.

    2009-03-27

    We show that hierarchically small vacuum expectation values of the superpotential in supersymmetric theories can be a consequence of an approximate R symmetry. We briefly discuss the role of such small constants in moduli stabilization and understanding the huge hierarchy between the Planck and electroweak scales.

  16. Folded Fashions: Symmetry in Clothing Design.

    ERIC Educational Resources Information Center

    Evered, Lisa J.

    1992-01-01

    Fashion design is a field perceived as both a female and male domain that utilizes mathematics. Presents creative activities to teach the concept of symmetry as applied in fashion designs in the style of the famous French designer Madeleine Vionnet. (MDH)

  17. Enhanced gauge symmetries on elliptic K3

    NASA Astrophysics Data System (ADS)

    Bonora, L.; Reina, C.; Zampa, A.

    1999-04-01

    We show that the geometry of K3 surfaces with singularities of type A-D-E contains enough information to reconstruct a copy of the Lie algebra associated to the given Dynkin diagram. We apply this construction to explain the enhancement of symmetry in F and IIA theories compactified on singular K3's.

  18. The symmetry properties of planetary magnetic fields

    SciTech Connect

    Raedler, K.H. ); Ness, N.F. )

    1990-03-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of Earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For Earth, Jupiter, and Saturn the centered dipole, quadrupole, and octupole contributions are included, while at Uranus, only the dipole and quadrupole contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. It is found that there are a number of common features of the magnetic fields of Earth and Jupiter. Compared to Earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis, by now rather well known, but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

  19. Disordered cold atoms in different symmetry classes

    NASA Astrophysics Data System (ADS)

    Pinheiro, Fernanda; Larson, Jonas

    2015-08-01

    We consider an experimentally realizable model of noninteracting but randomly coupled atoms in a two-dimensional optical lattice. By choosing appropriate real or complex-valued random fields and species-dependent energy offsets, this system can be used to analyze effects of disorder in four different symmetry classes: the chiral BDI and AIII and the nonchiral A and AI. These chiral classes are known to support a metallic phase at zero energy, which here, due to the inevitable finite size of the system, should also persist in a neighborhood of nonzero energies. As we discuss, this is of particular interest for experiments involving quenches. Away from the center of the spectrum, we find that excitations appear as domain walls in the cases with time-reversal symmetry or as vortices in the cases where time-reversal symmetry is absent. Therefore, a quench in a system with uniform density would lead to the formation of either vortices or domain walls depending on the symmetry class. For the nonchiral models in classes A and AI, a population imbalance between the two atomic species naturally occurs. In these cases, one of the two species is seen to favor a more uniform density. We also study the onset of localization as the disorder strength is increased for the different classes, and by deriving an effective model for the nonchiral cases we show how their eigenstates remain extended for larger values of the coupling with the disorder when compared to the nonchiral ones.

  20. Bilarge neutrino mixing and Abelian flavor symmetry

    NASA Astrophysics Data System (ADS)

    Ding, Gui-Jun; Morisi, S.; Valle, J. W. F.

    2013-03-01

    We explore two bilarge neutrino mixing Anzätze within the context of Abelian flavor symmetry theories: (BL1) sin⁡θ12˜λ, sin⁡θ13˜λ, sin⁡θ23˜λ, and (BL2) sin⁡θ12˜λ, sin⁡θ13˜λ, sin⁡θ23˜1-λ. The first pattern is proposed by two of us and is favored if the atmospheric mixing angle θ23 lies in the first octant, while the second one is preferred for the second octant of θ23. In order to reproduce the second texture, we find that the flavor symmetry should be U(1)×Zm, while for the first pattern the flavor symmetry should be extended to U(1)×Zm×Zn with m and n of different parity. Explicit models for both mixing patterns are constructed based on the flavor symmetries U(1)×Z3×Z4 and U(1)×Z2. The models are extended to the quark sector within the framework of SU(5) grand unified theory in order to give a successful description of quark and lepton masses and mixing simultaneously. Phenomenological implications are discussed.

  1. Test of Lorentz symmetry with trapped ions

    NASA Astrophysics Data System (ADS)

    Pruttivarasin, Thaned

    2016-05-01

    The outcome of an experiment should not depend on the orientation of the apparatus in space. This important cornerstone of physics is deeply engrained into the Standard Model of Physics by requiring that all fields must be Lorentz invariant. However, it is well-known that the Standard Model is incomplete. Some theories conjecture that at the Planck scale Lorentz symmetry might be broken and measurable at experimentally accessible energy scales. Therefore, a search for violation of Lorentz symmetry directly probes physics beyond the Standard model. We present a novel experiment utilizing trapped calcium ions as a direct probe of Lorentz-violation in the electron-photon sector. We monitor the energy between atomic states with different orientations of the electronic wave-functions as they rotate together with the motion of the Earth. This is analogous to the famous Michelson-Morley experiment. To remove magnetic field noise, we perform the experiment with the ions prepared in the decoherence-free states. Our result improves on the most stringent bounds on Lorentz symmetry for electrons by 100 times. The experimental scheme is readily applicable to many ion species, hence opening up paths toward much improved test of Lorentz symmetry in the future. (Ph. D. Advisor: Hartmut Haeffner, University of California, Berkeley).

  2. Neutrino mass and mixing with discrete symmetry.

    PubMed

    King, Stephen F; Luhn, Christoph

    2013-05-01

    This is a review paper about neutrino mass and mixing and flavour model building strategies based on discrete family symmetry. After a pedagogical introduction and overview of the whole of neutrino physics, we focus on the PMNS mixing matrix and the latest global fits following the Daya Bay and RENO experiments which measure the reactor angle. We then describe the simple bimaximal, tri-bimaximal and golden ratio patterns of lepton mixing and the deviations required for a non-zero reactor angle, with solar or atmospheric mixing sum rules resulting from charged lepton corrections or residual trimaximal mixing. The different types of see-saw mechanism are then reviewed as well as the sequential dominance mechanism. We then give a mini-review of finite group theory, which may be used as a discrete family symmetry broken by flavons either completely, or with different subgroups preserved in the neutrino and charged lepton sectors. These two approaches are then reviewed in detail in separate chapters including mechanisms for flavon vacuum alignment and different model building strategies that have been proposed to generate the reactor angle. We then briefly review grand unified theories (GUTs) and how they may be combined with discrete family symmetry to describe all quark and lepton masses and mixing. Finally, we discuss three model examples which combine an SU(5) GUT with the discrete family symmetries A₄, S₄ and Δ(96).

  3. Multipartite invariant states. II. Orthogonal symmetry

    SciTech Connect

    Chruscinski, Dariusz; Kossakowski, Andrzej

    2006-06-15

    We construct a class of multipartite states possessing orthogonal symmetry. This new class contains multipartite states which are invariant under the action of local unitary operations introduced in our preceding paper [Phys. Rev. A 73, 062314 (2006)]. We study basic properties of multipartite symmetric states: separability criteria and multi-PPT conditions.

  4. Einstein-Yang-Mills theory: Asymptotic symmetries

    NASA Astrophysics Data System (ADS)

    Barnich, Glenn; Lambert, Pierre-Henry

    2013-11-01

    Asymptotic symmetries of the Einstein-Yang-Mills system with or without cosmological constant are explicitly worked out in a unified manner. In agreement with a recent conjecture, one finds a Virasoro-Kac-Moody type algebra not only in three dimensions but also in the four-dimensional asymptotically flat case.

  5. Theory overview of testing fundamental symmetries

    NASA Astrophysics Data System (ADS)

    Mavromatos, Nick E.

    2014-04-01

    I review first some theoretical motivations for violation of Lorentz and/or CPT Invariance. Although the latter symmetries may be violated in a quantum gravity setting, nevertheless there are situations in which these violations are due to a given classical background geometry that may characterised early epochs of our Universe, and in fact be responsible for the observed dominance of matter over antimatter in the Universe. In this way I estimate some of the coefficients of the Standard Model Extension (SME), which is a framework for a field theoretic study of such a breakdown of fundamental symmetries. Then I describe briefly some tests of these symmetries, giving emphasis in low-energy antiproton physics and electric dipole moment measurements, of interest to this conference. I also mention the rôle of entangled states of neutral mesons in providing independent measurements of T(ime reversal) and CP Violation, thus providing independent tests of CPT symmetry, as well as novel ("smoking-gun" type) tests of decoherence-induced CPT violation, which may characterise some models of quantum gravity.

  6. Movement Symmetries and the Mammalian Vestibular System

    NASA Astrophysics Data System (ADS)

    McCollum, Gin; Boyle, Richard

    2000-03-01

    Unity of movement requires vertebrates to have an ability to symmetrize along the midline. For example, human erect stance involves symmetry with respect to gravity. The mammalian vestibular system provides a mechanism for maintaining symmetries, which is also open to influence and adaptation by the rest of the organism. The vestibular system includes the inner ear endorgans and central nuclei, along with projections to oculomotor, cerebellar, thalamic, and spinal motor centers. The vestibular endorgans - the semicircular canals and the otoliths - use sensory hairs to register inertia. The vestibular endorgans are right-left symmetric and the semicircular canals form an approximately orthogonal coordinate system for angular motion. Primary afferent axons project from the endorgans to the vestibular nuclei (and a few other places). The vestibular nuclei integrate vestibular, visual, and somatosensory signals, along with a proposed copy of the voluntary motor command and signals from other central structures. The relationship between the canals and the otoliths gives rise to symmetries among neurons, in the organization among the several vestibular nuclei, and in the projections from the vestibular nuclei. These symmetries organize the space of body movements so that functional relationships are maintained in spite of the many free variables of body movement. They also provide a foundation for adaptive reinterpretation of the relationship between canal and otolith signals, for example in freefall.

  7. Gender Symmetry, Sexism, and Intimate Partner Violence

    ERIC Educational Resources Information Center

    Allen, Christopher T.; Swan, Suzanne C.; Raghavan, Chitra

    2009-01-01

    This study of a predominantly Hispanic sample of 92 male and 140 female college students examines both gender symmetry in intimate partner violence (IPV) and inconsistent relationships found in previous studies between sexist attitudes and IPV. Results indicate that although comparable numbers of men and women perpetrate and are victimized in…

  8. BRST symmetry in the general gauge theories

    NASA Astrophysics Data System (ADS)

    Hyuk-Jae, Lee; Jae, Hyung, Yee

    1994-01-01

    By using the residual gauge symmetry interpretation of BRST invariance we have constructed a new BRST formulation for general gauge theories including those with open algebras. For theories with open gauge algebra the formulation leads to a BRST invariant effective action which does not contain any higher order terms in the ghost fields.

  9. Golden Probe of Electroweak Symmetry Breaking

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Lykken, Joe; Spiropulu, Maria; Stolarski, Daniel; Vega-Morales, Roberto

    2016-12-01

    The ratio of the Higgs couplings to W W and Z Z pairs, λW Z, is a fundamental parameter in electroweak symmetry breaking as well as a measure of the (approximate) custodial symmetry possessed by the gauge boson mass matrix. We show that Higgs decays to four leptons are sensitive, via tree level or one-loop interference effects, to both the magnitude and, in particular, overall sign of λW Z. Determining this sign requires interference effects, as it is nearly impossible to measure with rate information. Furthermore, simply determining the sign effectively establishes the custodial representation of the Higgs boson. We find that h →4 ℓ (4 ℓ≡2 e 2 μ , 4 e , 4 μ ) decays have excellent prospects of directly establishing the overall sign at a high luminosity 13 TeV LHC. We also examine the ultimate LHC sensitivity in h →4 ℓ to the magnitude of λW Z. Our results are independent of other measurements of the Higgs boson couplings and, in particular, largely free of assumptions about the top quark Yukawa couplings which also enter at one loop. This makes h →4 ℓ a unique and independent probe of electroweak symmetry breaking and custodial symmetry.

  10. Aspects of Chiral Symmetry Breaking in Lattice QCD

    NASA Astrophysics Data System (ADS)

    Horkel, Derek P.

    In this thesis we describe two studies concerting lattice quantum chromodynamics (LQCD): first, an analysis of the phase structure of Wilson and twisted-mass fermions with isospin breaking effects, second a computational study measuring non-perturbative Greens functions. We open with a brief overview of the formalism of QCD and LQCD, focusing on the aspects necessary for understanding how a lattice computation is performed and how discretization effects can be understood. Our work in Wilson and twisted-mass fermions investigates an increasingly relevant regime where lattice simulations are performed with quarks at or near their physical masses and both the mass difference of the up and down quarks and their differing electric charges are included. Our computation of a non-perturbative Greens functions on the lattice serves as a first attempt to validate recent work by Dine et. al. [24] in which they calculate Greens functions which vanish in perturbation theory, yet have a contribution from the one instanton background. In chapter 2, we determine the phase diagram and pion spectrum for Wilson and twisted-mass fermions in the presence of non-degeneracy between the up and down quark and discretization errors, using Wilson and twisted-mass chiral perturbation theory. We find that the CP-violating phase of the continuum theory (which occurs for sufficiently large non-degeneracy) is continuously connected to the Aoki phase of the lattice theory with degenerate quarks. We show that discretization effects can, in some cases, push simulations with physical masses closer to either the CP-violating phase or another phase not present in the continuum, so that at sufficiently large lattice spacings physical-point simulations could lie in one of these phases. In chapter 3, we extend the work in chapter 2 to include the effects of electromagnetism, so that it is applicable to recent simulations incorporating all sources of isospin breaking. For Wilson fermions, we find that the

  11. Symmetry and random sampling of symmetry independent configurations for the simulation of disordered solids.

    PubMed

    D'Arco, Philippe; Mustapha, Sami; Ferrabone, Matteo; Noël, Yves; De La Pierre, Marco; Dovesi, Roberto

    2013-09-04

    A symmetry-adapted algorithm producing uniformly at random the set of symmetry independent configurations (SICs) in disordered crystalline systems or solid solutions is presented here. Starting from Pólya's formula, the role of the conjugacy classes of the symmetry group in uniform random sampling is shown. SICs can be obtained for all the possible compositions or for a chosen one, and symmetry constraints can be applied. The approach yields the multiplicity of the SICs and allows us to operate configurational statistics in the reduced space of the SICs. The present low-memory demanding implementation is briefly sketched. The probability of finding a given SIC or a subset of SICs is discussed as a function of the number of draws and their precise estimate is given. The method is illustrated by application to a binary series of carbonates and to the binary spinel solid solution Mg(Al,Fe)2O4.

  12. Infinite dimensional symmetries of self-dual Yang-Mills

    NASA Astrophysics Data System (ADS)

    Mansfield, Paul; Wardlow, Adam

    2009-08-01

    We construct symmetries of the Chalmers-Siegel action describing self-dual Yang-Mills theory using a canonical transformation to a free theory. The symmetries form an infinite dimensional Lie algebra in the group algebra of isometries.

  13. Symmetry-induced anyon breeding in fractional quantum Hall states

    NASA Astrophysics Data System (ADS)

    Lu, Yuan-Ming; Fidkowski, Lukasz

    2014-03-01

    An exotic feature of the fractional quantum Hall effect is the emergence of anyons, which are quasiparticle excitations with fractional statistics. In the presence of a symmetry, such as U (1) charge conservation, it is well known that anyons can carry fractional symmetry quantum numbers. In this paper we reveal a different class of symmetry realizations, i.e., anyons can "breed" in multiples under symmetry operation. We focus on the global Ising (Z2) symmetry and show examples of these unconventional symmetry realizations in Laughlin-type fractional quantum Hall states. One remarkable consequence of such an Ising symmetry is the emergence of anyons on the Ising symmetry domain walls. We also provide a mathematical framework which generalizes this phenomenon to any Abelian topological orders.

  14. Unity of quark and lepton interactions with symplectic gauge symmetry

    SciTech Connect

    Rajpoot, S.

    1982-07-01

    Properties of symplectic groups are reviewed and the gauge structure of Sp(2n) derived. The electroweak unification of leptons within Sp(8) gauge symmetry and grand unification of quarks and leptons within Sp(10) gauge symmetry are discussed.

  15. The construction of symmetry in children and adults.

    PubMed

    Zingrone, William A

    2014-01-01

    The development of the concept of symmetry is important to an overall understanding of cognitive development in children and to spatial cognition in particular. Age differences in the construction of the 3 types of symmetry (bilateral, translational, and radial) were investigated in children and adults engaged in block construction. Children 2-4.5 years old produced bilateral symmetry in low frequencies independent of their precise vertical alignment of blocks. Children 4-12 years old and adults produced all 3 types of symmetry. The hypothesis predicting the sequence and frequency of the 3 types of symmetry based on an analysis of spatial complexity was partially supported. Bilateral symmetry was produced at significantly higher frequencies than the other 2 types across all age groups. Children 5-12 years old produced adult levels of bilateral symmetry while children 9-12 years old reached adult levels of construction of translational and radial symmetry.

  16. Relativistic pseudospin symmetry and shell model Hamiltonians that conserve pseudospin symmetry

    SciTech Connect

    Ginocchio, Joseph N

    2010-09-21

    Professor Akito Arima and his colleagues discovered 'pseudospin' doublets forty-one years ago in spherical nuclei. These doublets were subsequently discovered in deformed nuclei. We show that pseudospin symmetry is an SU(2) symmetry of the Dirac Hamiltonian which occurs when the scalar and vector potentials are opposite in sign but equal in magnitude. This symmetry occurs independent of the shape of the nucleus: spherical, axial deformed, triaxial, and gamma unstable. We survey some of the evidence that pseudospin symmetry is approximately conserved for a Dirac Hamiltonian with realistic scalar and vector potentials by examining the energy spectra, the lower components of the Dirac eigenfunctions, the magnetic dipole and Gamow-Teller transitions in nuclei, the upper components of the Dirac eigenfunctions, and nucleon-nucleus scattering. We shall also suggest that pseudospin symmetry may have a fundamental origin in chiral symmetry breaking by examining QCD sum rules. Finally we derive the shell model Hamiltonians which conserve pseudospin and show that they involve tensor interactions.

  17. Goodness of regularity in dot patterns: global symmetry, local symmetry, and their interactions.

    PubMed

    Nucci, Massimo; Wagemans, Johan

    2007-01-01

    Goodness is a classic Gestalt notion defined as salience or perceptual strength of a given pattern. All operational models of goodness have assigned a central role to mirror symmetry but not much attention has been paid to the distinction between global and local mirror symmetry, and their possible interactions. We designed eight different types of dot patterns (all consisting of 80 dots), combining different numbers (0, 1, and 2) and relative orientations (parallel or orthogonal to each other) of local and global axes of symmetry (affecting 50% or 100% of the dots, respectively) at different absolute orientations (vertical and horizontal). Each of 640 trials consisted of a short presentation of a new dot pattern, which subjects had to classify as regular or random. We hypothesised that the overall goodness of patterns is not the simple sum of the amount of regularity present in them but depends on the cooperation and competition between symmetries. The results confirmed our hypothesis, showing that performance in this regularity-detection task did not increase in a linear way when some symmetries were added to other symmetries.

  18. Neutrino Mixing:. from the Broken μ-τ Symmetry to the Broken Friedberg-Lee Symmetry

    NASA Astrophysics Data System (ADS)

    Xing, Zhi-Zhong

    I argue that the observed flavor structures of leptons and quarks might imply the existence of certain flavor symmetries. The latter should be a good starting point to build realistic models towards deeper understanding of the fermion mass spectra and flavor mixing patterns. The μ-τ permutation symmetry serves for such an example to interpret the almost maximal atmospheric neutrino mixing angle (θ23 ~ 45°) and the strongly suppressed CHOOZ neutrino mixing angle (θ13 < 10°). In this talk I like to highlight a new kind of flavor symmetry, the Friedberg-Lee symmetry, for the effective Majorana neutrino mass operator. Luo and I have shown that this symmetry can be broken in an oblique way, such that the lightest neutrino remains massless but an experimentally-favored neutrino mixing pattern is achievable. We get a novel prediction for θ13 in the CP-conserving case: sinθ13 = tanθ12|(1 - tanθ23)/(1 + tanθ23)|. Our scenario can simply be generalized to accommodate CP violation and be combined with the seesaw mechanism. Finally I stress the importance of probing possible effects of μ-τ symmetry breaking either in terrestrial neutrino oscillation experiments or with ultrahigh-energy cosmic neutrino telescopes.

  19. Partial dynamical symmetry at critical points of quantum phase transitions.

    PubMed

    Leviatan, A

    2007-06-15

    We show that partial dynamical symmetries can occur at critical points of quantum phase transitions, in which case underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of partial dynamical symmetries are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape phases in nuclei.

  20. Black hole entropy from conformal symmetry on the horizon

    NASA Astrophysics Data System (ADS)

    Carlip, Steven

    2017-01-01

    The idea that black hole entropy might be governed by a conformal symmetry is an old one, but until now most efforts have focused on either asymptotic symmetries or symmetries on a ``stretched horizon. For two-dimensional dilaton gravity, I show the existence of a well-behaved conformal symmetry that is on the horizon, with a central charge that correctly determines the black hole entropy. Supported by Department of Energy grant DE-FG02-91ER40674.