Relaxation time of water's high-density amorphous ice phase

Dielectric relaxation spectroscopy of pressure amorphized hexagonal ice shows that water's high-density amorphous form relaxes in approximately 1 s at 140 K and 1 GPa and that the relaxation is virtually unaffected by pressure. This indicates that the amorph is an ultraviscous liquid above 140 K, the same as would be obtained by supercooling water at 1 GPa through its ice VI phase boundary, and that the glass transition temperature is independent of pressure and close to that of amorphous solid water produced at atmospheric pressure.     

Are pulsar glitches triggered by a superfluid two-stream instability?

Mature neutron stars are expected to have several superfluid components. Strong evidence for this is provided by the glitches that have been observed in dozens of pulsars. We describe a superfluid analog of the two-stream instability that is well known in plasma physics and provide arguments that this instability is likely to be relevant for neutron stars. This is a new physical mechanism which may play a key role in explaining the glitch mechanism and which could also prove to be relevant in laboratory experiments on various superfluid systems.     

First-principle calculations of the experimental vibrational spectrum of a surface adsorbate: anharmonic resonance coupling between fundamental and binary modes

By including relevant physical properties in our modeling of a surface adsorbate system we can, from first principles, correctly calculate all experimentally observed features in the vibrational spectrum of CH3CH2O- and CD3CH2O- adsorbed on Cu(100). That is, we reproduce the number of observed modes, the vibrational frequencies, and intensities of the modes including the presence/absence of binary overtone and combination modes. No scaling was performed. Our calculations show that the anharmonic terms of the potential energy surface of free ethanol are transferrable to the corresponding surface adsorbate, ethoxy, while the harmonic terms are not.     

Almost holomorphic extensions of ultradifferentiable functions

For a smooth functionf on ℝ ⁿ , we construct an extensionF to ℂ ⁿ with vanishing to a high order on ℝ ⁿ and give precise estimates of how the degree of smothness is reflected in the degree of vanishing. This analysis is used to define the operator on (n,n−1) forms with singularities on ℝ ⁿ .     

On soft gluon emission and the transverse momentum properties of final state particles

We discuss the infrared problem in a theory with confined quarks and gluons. In QED, the infrared cutoff depends on the adjustable experimental energy resolution. For QCD, the physical observables of the asymptotic final state are the hadron momenta whereas the gluon momenta do not correspond to observable quantities. Thus the energy resolution of a “gluon detector” is determined by the hadronic mass scale. In particular, we study the effect of soft gluon emission on the transverse momentum of the hadrons.     

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Book reviews

     

A maximal distance result of interest in robotic simulation

Given two hyper-rectangles inE ⁿ with sides having surface normals in the directions of the axes, and given a connected set in each that touches all 2n sides of its containing hyper-rectangle, it is important to have an easily calculated upper bound on the distance between the two connected sets. A result giving such a bound, necessary in branch and bound algorithms used for collision avoidance in robotic simulation, is stated and proved here.The work of the second and third authors was supported in part by the Natural Sciences and Engineering Research Council of Canada.     

Pesticide residues in fresh fruit and vegetables on the Swedish market, January 1985–December 1989

Conclusion Compared with the previous investigation in 1981–1984, the frequency of samples of fruit and vegetables with excessive amounts of pesticides has decreased from 3.9% to 3.4%.     

Two simple models for gravitational-wave modes of compact stars

Two simple model problems relevant for the gravitational-wave modes of relativistic stars are discussed. It is shown that the entire mode-spectrum can be obtained if one considers the modes as arising because of the trapping of gravitational waves by the spacetime curvature. The stellar fluid need play no dynamic role. Furthermore, it is shown that two distinct families of gravitational-wave modes exist. The first corresponds to waves trapped inside the star, while the second is similar to acoustic waves scattered off a hard sphere. An infinite number of the first kind of modes exist, but the latter family will only have a few members.     

Monolayer K-films on Ni(100) — II. Electronic excitations

Electronic excitations in a K layer adsorbed on Ni(100) have been observed by means of electron energy loss spectroscopy. The observed excitation energy depends on the density of K atoms in the layer. In the low density range the loss energy decreases from 3.5 to 1.5 eV as the density increases from 6.10¹³ to 3.10¹⁴ K atoms per cm². This loss is interpreted to be due to an excitation from below the Fermi level to the shifted K valence level Increasing the density further from 3.10¹⁴ to 6.10¹⁴ K atoms per cm² yields a loss peak that increases in energy from 1.5 to 2.3 eV. This loss peak merges into the surface-bulk plasmon complex for a thick K film and the energy vs density dependence is compatible with a plasmon excitation in the K layer.