On knottings in the physical Hilbert space of LQG as given by the EPRL model

We consider the EPRL spin foam amplitude for arbitrary embedded two-complexes. Choosing a definition of the face- and edge amplitudes which lead to spin foam amplitudes invariant under trivial subdivisions, we investigate invariance properties of the amplitude under consistent deformations, which are deformations of the embedded two-complex where faces are allowed to pass through each other in a controlled way. Using this surprising invariance, we are able to show that in the physical Hilbert space as defined by the sum over all spin foams contains no knotting classes of graphs anymore.Comment: 22 pages, 14 figure

Projected Wavefunctions and High Temperature Superconductivity

We study the Hubbard model with parameters relevant to the cuprates, using variational Monte Carlo with projected d-wave states. For doping 0 < x < 0.35 we obtain a superconductor whose order parameter tracks the observed nonmonotonic Tc(x). The variational parameter Delta_{var}(x) scales with the (pi,0) ``hump'' and T* seen in photoemission. Projection leads to incoherence in the spectral function, and from the singular behavior of its moments we obtain the nodal quasiparticle weight Z which vanishes linearly in x, though the Fermi velocity remains finite as x approaches zero. The Drude weight D_{low} and superfluid density are consistent with experiments, and D_{low} scales with Z.Comment: 4 pages, 5 EPS figures. (1) Many improvements including discussion of n(k) and superfluid density. (2) Added comparison with slave boson mean field theory. (3) Added new reference

Alterações do teor de nitrogênio na folha e pecíolo, na produção e composição da uva pela adubação nitrogenada em videiras no Planalto do Rio Grande do Sul.

O trabalho objetivou avaliar como a aplicação de N afeta o seu teor na folha inteira e pecíolo, usados para a recomendação de N à videira no RS e SC, e sobre a produção e composição da uva.bitstream/CNPUV/10104/1/cot087.pd

Pure rotational spectra of TiO and TiO_2 in VY Canis Majoris

We report the first detection of pure rotational transitions of TiO and TiO_2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational temperature, T_rot, of about 250 K was derived for TiO_2. Although T_rot was not well constrained for TiO, it is likely somewhat higher than that of TiO_2. The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO_2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow.Comment: to appear in Astronomy and Astrophysic

The Fermi surface of Bi2Sr2CaCu2O8

We study the Fermi surface of Bi2Sr2CaCu2O8 (Bi2212) using angle resolved photoemission (ARPES) with a momentum resolution of ~ 0.01 of the Brillouin zone. We show that, contrary to recent suggestions, the Fermi surface is a large hole barrel centered at (pi,pi), independent of the incident photon energy.Comment: 4 pages (revtex), 4 figures (eps, 2 color

Momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals measured by angle resolved photoemission spectroscopy

We use angle resolved photoemission spectroscopy (ARPES) to study the momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals. We find that the Gamma hole pocket is fully gapped below the superconducting transition temperature. The value of the superconducting gap is 15 +- 1.5 meV and its anisotropy around the hole pocket is smaller than 20% of this value. This is consistent with an isotropic or anisotropic s-wave symmetry of the order parameter or exotic d-wave symmetry with nodes located off the Fermi surface sheets. This is a significant departure from the situation in the cuprates, pointing to possibility that the superconductivity in the iron arsenic based system arises from a different mechanism.Comment: 4 pages, 3 figure