Bi-local baryon interpolating fields with two flavours

We construct bi-local interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We use the restrictions following from the Pauli principle to derive relations/identities among the baryon operators with identical quantum numbers. Such relations that follow from the combined spatial, Dirac, color, and isospin Fierz transformations may be called the (total/complete) Fierz identities. These relations reduce the number of independent baryon operators with any given spin and isospin. We also study the Abelian and non-Abelian chiral transformation properties of these fields and place them into baryon chiral multiplets. Thus we derive the independent baryon interpolating fields with given values of spin (Lorentz group representation), chiral symmetry ($U_L(2) \times U_R(2)$ group representation) and isospin appropriate for the first angular excited states of the nucleon.Comment: 15 pages, 4 tables, accepted by EPJ

Chiral Baryon Fields in the QCD Sum Rule

We study the structure of local baryon fields using the method of QCD sum rule. We only consider the single baryon fields and calculate their operator product expansions. We find that the octet baryon fields belonging to the chiral representations [(3,3*)+(3*,3)] and [(8,1)+(1,8)] and the decuplet baryon fields belonging to the chiral representations [(3,6)+(6,3)] lead to the baryon masses which are consistent with the experimental data of ground baryon masses. We also calculate their decay constants, check our normalizations for baryon fields in PRD81:054002(2010) and find that they are well-defined.Comment: 12 pages, 6 figure, 1 table, accepted by EPJ

Baryon Tri-local Interpolating Fields

We systematically investigate tri-local (non-local) three-quark baryon fields with U_L(2)*U_R(2) chiral symmetry, according to their Lorentz and isospin (flavor) group representations. We note that they can also be called as "nucleon wave functions" due to this full non-locality. We study their chiral transformation properties and find all the possible chiral multiplets consisting J=1/2 and J=3/2 baryon fields. We find that the axial coupling constant |g_A| = 5/3 is only for nucleon fields belonging to the chiral representation (1/2,1)+(1,1/2) which contains both nucleon fields and Delta fields. Moreover, all the nucleon fields belonging to this representation have |g_A| = 5/3.Comment: 8 pages, 3 tables, accepted by EPJ

Twist-3 Distribute Amplitude of the Pion in QCD Sum Rules

We apply the background field method to calculate the moments of the pion two-particles twist-3 distribution amplitude (DA) $\phi_p(\xi)$ in QCD sum rules. In this paper,we do not use the equation of motion for the quarks inside the pion since they are not on shell and introduce a new parameter $m_0^p$ to be determined. We get the parameter $m_0^p\approx1.30GeV$ in this approach. If assuming the expansion of $\phi_p(\xi)$ in the series in Gegenbauer polynomials $C_n^{1/2}(\xi)$, one can obtain its approximate expression which can be determined by its first few moments.Comment: 12 pages, 3 figure

On the Black-Hole/Qubit Correspondence

The entanglement classification of four qubits is related to the extremal black holes of the 4-dimensional STU model via a time-like reduction to three dimensions. This correspondence is generalised to the entanglement classification of a very special four-way entanglement of eight qubits and the black holes of the maximally supersymmetric N = 8 and exceptional magic N = 2 supergravity theories.Comment: 32 pages, very minor changes at the start of Sec. 4.1. Version to appear in The European Physical Journal - Plu

De novo design of proteins housing excitonically coupled chlorophyll special pairs

Natural photosystems couple light harvesting to charge separation using a ‘special pair’ of chlorophyll molecules that accepts excitation energy from the antenna and initiates an electron-transfer cascade. To investigate the photophysics of special pairs independently of the complexities of native photosynthetic proteins, and as a first step toward creating synthetic photosystems for new energy conversion technologies, we designed C2-symmetric proteins that hold two chlorophyll molecules in closely juxtaposed arrangements. X-ray crystallography confirmed that one designed protein binds two chlorophylls in the same orientation as native special pairs, whereas a second designed protein positions them in a previously unseen geometry. Spectroscopy revealed that the chlorophylls are excitonically coupled, and fluorescence lifetime imaging demonstrated energy transfer. The cryo-electron microscopy structure of a designed 24-chlorophyll octahedral nanocage with a special pair on each edge closely matched the design model. The results suggest that the de novo design of artificial photosynthetic systems is within reach of current computational methods

On the Catalytic Role of High Baroclinic Modes in Eddy-driven Large-Scale Circulations.

International audienceThis paper investigates the tridimensional consistency of the resolution of eddy scales in simulating large-scale flows. The generation of classical wind-forced, eddy-driven double-gyre circulation is investigated with a multilayered quasi-geostrophic model. Six-layers on the vertical have been chosen to assure the convergence of the baroclinic instability. Emphasis is on the resolution of the high baroclinic modes and its effects on the dynamics of the midlatitude jet. Several eddy-resolving experiments, identical except for the horizontal resolution, which can be low (20 km) or high (10 km), are compared. In every experiment, the scales associated with the first and second baroclinic modes are well resolved, but those associated with the third and higher baroclinic modes are so only in 10-km experiments For a better illustration of the importance of the high vertical modes, three-layer experiments having configurations equivalent to that of the six-layer experiments have been conducted. Note that in the three-layer experiments, all the baroclinic radii of deformation that are explicitly present (the first and second) are well resolved with both 10-km or 20-km grid resolutions. The major effect of fine resolution is to amplify the inertial mode and consequently increase the penetration scale of the midlatitude jet (by almost 40% in six-layer cases, and only 20% in three-layer cases), whereas the other indexes related to the large-scale flow are not modified by more than 10%. Our analyses show that fine (10-km) resolution produces a larger excitation of the inertial mode, and reverses the effect of numerical hyperviscosity on the stability of the jet stream, (less subgrid-scale dissipation yields a longer jet, the contrary happens when the resolution is 20-km). These latter effects are significantly more important when the vertical resolution is six-layered. Global and local energetics indicate that the coupling between the layers is more efficient in high-resolution experiments, due to a better representation of the dynamics related to vortex stretching. Energy transfer rates show much larger amplitudes for the instability and rectification processes, which affect the large-scale flow toward a stronger jet and recirculation. Wavenumber spectra for all vertical modes show that when the resolution is six-layered, the fine resolution yields a better representation of the energy and enstrophy cascades. The physics missing in 20-krn grid simulations can be cast in terms of a scale-dependent eddy viscosity that is negative at large-scales. The analysis of the effects of negative viscosity demonstrates the dynamical impact of the resolution of the high vertical modes; the low-resolution experiment shows a deficit in negative viscosity at large wavenumbers, because the truncation of the 20-km grid interferes with the stratified inverse cascade. This artificially damps the large scales in the low-resolution experiments, and reduces the barotropic inertial circulation. In conclusion, the high baroclinic modes appear to play a catalytic role in eddy-driven circulations: despite their low kinetic energy level, they are strongly involved in energy transfers and are essential pathways for determining the large-scale response of turbulent ocean models. However, our calculations show that if the fine horizontal resolution significantly modifies the quantitative impact of the second and third baroclinic modes on the mean circulation, the contribution of the fourth and fifth baroclinic modes remains negligible. Therefore, the tridimensional consistency of model resolution appears to be of crucial importance in the simulation eddy-driven large-scale flows, but the number of vertical modes that require a fine resolution seems to be limited

Audio properties of perceived boundaries in music

Data mining tasks such as music indexing, information retrieval, and similarity search, require an understanding of how listeners process music internally. Many algorithms for automatically analyzing the structure of recorded music assume that a large change in one or another musical feature suggests a section boundary. However, this assumption has not been tested: while our understanding of how listeners segment melodies has advanced greatly in the past decades, little is known about how this process works with more complex, full-textured pieces of music, or how stable this process is across genres. Knowing how these factors affect how boundaries are perceived will help researchers to judge the viability of algorithmic approaches with different corpora of music. We present a statistical analysis of a large corpus of recordings whose formal structure was annotated by expert listeners. We find that the acoustic properties of boundaries in these recordings corroborate findings of previous perceptual experiments. Nearly all boundaries correspond to peaks in novelty functions, which measure the rate of change of a musical feature at a particular time scale. Moreover, most of these boundaries match peaks in novelty for several features at several time scales. We observe that the boundary-novelty relationship can vary with listener, time scale, genre, and musical feature. Finally, we show that a boundary profile derived from a collection of novelty functions correlates with the estimated salience of boundaries indicated by listeners. © 1999-2012 IEEE

Relativistic configuration interaction calculations on K

In this work, the multi-configuration Dirac-Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used to calculate the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα X-ray from Mg III to Mg XI. We also take the contributions from the Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels, into account. The present values for Mg X and Mg XI were in good agreement with the previous experimental and theoretical results. The new data in this work provide reference values for the level lifetimes, charge state distributions, and average charge of magnesium plasmas