50,156 research outputs found
Meson Masses and Mixing Angles in 2+1 Flavor Polyakov Quark Meson Sigma Model and Symmetry Restoration Effects
The meson masses and mixing angles have been calculated for the scalar and
pseudoscalar sector in the framework of the generalized 2+1 flavor Polyakov
loop augmented quark meson linear sigma model. We have given the results for
two different forms of the effective Polyakov loop potential. The comparison of
results with the existing calculations in the bare 2+1 quark meson linear sigma
model, shows that the restoration of chiral symmetry becomes sharper due to the
influence of the Polyakov loop potential. We find that inclusion of the
Polyakov loop in quark meson linear sigma model together with the presence of
axial anomaly, triggers an early and significant melting of the strange
condensate. We have examined how the inclusion of the Polyakov loop
qualitatively and quantitatively affects the convergence in the masses of the
chiral partners in pseudoscalar (, , , ) and scalar
(, , ,) meson nonets as the temperature is varied on
the reduced temperature scale. The role of anomaly in determining the
isoscalar masses and mixing angles for the pseudoscalar ( and )
and scalar ( and )meson complex, has also been investigated in the
Polyakov quark meson linear sigma model. The interplay of chiral symmetry
restoration effects and the setting up of restoration trend has been
discussed and analyzed in the framework of the presented model calculations.Comment: 15 pages, 8 figures, 4 table
Exact spin-orbital separation in a solvable model in one dimension
A one-dimensional model of coupled spin-1/2 spins and pseudospin-1/2 orbitals
with nearest-neighbor interaction is rigorously shown to exhibit spin-orbital
separation by means of a non-local unitary transformation. On an open chain,
this transformation completely decouples the spins from the orbitals in such a
way that the spins become paramagnetic while the orbitals form the soluble XXZ
Heisenberg model. The nature of various correlations is discussed. The more
general cases, which allow spin-orbital separation by the same method, are
pointed out. A generalization for the orbital pseudospin greater than 1/2 is
also discussed. Some qualitative connections are drawn with the recently
observed spin-orbital separation in Sr2CuO3.Comment: 5 page
Shear-strain-induced Spatially Varying Super-lattice Structures on Graphite studied by STM
We report on the Scanning Tunneling Microscope (STM) observation of linear
fringes together with spatially varying super-lattice structures on (0001)
graphite (HOPG) surface. The structure, present in a region of a layer bounded
by two straight carbon fibers, varies from a hexagonal lattice of 6nm
periodicity to nearly a square lattice of 13nm periodicity. It then changes
into a one-dimensional (1-D) fringe-like pattern before relaxing into a
pattern-free region. We attribute this surface structure to a shear strain
giving rise to a spatially varying rotation of the affected graphite layer
relative to the bulk substrate. We propose a simple method to understand these
moire patterns by looking at the fixed and rotated lattices in the Fourier
transformed k-space. Using this approach we can reproduce the spatially varying
2-D lattice as well as the 1-D fringes by simulation. The 1-D fringes are found
to result from a particular spatial dependence of the rotation angle.Comment: 14 pages, 6 figure
Global satellite triangulation and trilateration for the National Geodetic Satellite Program (solutions WN 12, 14 and 16)
A multi-year study and analysis of data from satellites launched specifically for geodetic purposes and from other satellites useful in geodetic studies was conducted. The program of work included theoretical studies and analysis for the geometric determination of station positions derived from photographic observations of both passive and active satellites and from range observations. The current status of data analysis, processing and results are examined
Geometric phase for a dimerized disordered continuum: Topological shot noise
Geometric phase shift associated with an electron propagating through a
dimerized-disordered continuum is shown to be 0, or (modulo 2),
according as the associated circuit traversed in the two-dimensional parameter
space excludes, or encircles a certain singularity. This phase-shift is a
topological invariant. Its discontinuous dependence on the electron energy and
disorder implies a statistical spectral and conductance fluctuation in a
corresponding mesoscopic system. Inasmuch as the fluctuation derives from the
discreteness of the phase shift, it may aptly be called a topological
shot-noise.Comment: 10 pages(LATEX) + 1 figure, (revised version). Will appear in
Europhys. Let
Phase field modelling of grain boundary premelting using obstacle potentials
We investigate the multi-order parameter phase field model of Steinbach and
Pezzolla [I. Steinbach, F. Pezzolla, A generalized field method for multiphase
transformations using interface fields, Physica D 134 (1999) 385-393]
concerning its ability to describe grain boundary premelting. For a single
order parameter situation solid-melt interfaces are always attractive, which
allows to have (unstable) equilibrium solid-melt-solid coexistence above the
bulk melting point. The temperature dependent melt layer thickness and the
disjoining potential, which describe the interface interaction, are affected by
the choice of the thermal coupling function and the measure to define the
amount of the liquid phase. Due to the strictly finite interface thickness also
the interaction range is finite. For a multi-order parameter model we find
either purely attractive or purely repulsive finite-ranged interactions. The
premelting transition is then directly linked to the ratio of the grain
boundary and solid-melt interfacial energy.Comment: 12 page
Elucidating the structural composition of a Fe-N-C catalyst by nuclear and electron resonance techniques
Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands
Ample consumption period available until use-by dates: a potential, marketing position for store brands
Traditionally store brands in Australia are viewed with suspicion in regard to their quality and are usually purchased because of the "value for money" that they offer. Australian supermarket majors are considering introducing a new suite of store brands in the higher price brackets. The danger of moving upscale however is that these store brands are relinquishing their value for money appeal and will come head to head with the manufactured brands. Store brands will now require some quality dimension to compete. This paper after studying the attitudes and behavioural response of grocery shoppers to use by dates, is proposing that that the promise of "generous" use-by dates as a surrogate for quality, could be considered as a positioning plank to promote store brands as alternatives to manufactured brands. Logit analysis is employed to explain shoppers' perception and response to use-by dates, of products that they regularly buy, and of alternative products which they have never bought before if the use-by dates of their regular items are perceived to be too shor
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