Theory of spin-flip excitations across the ferromagnetic stoner gap in electron energy loss

We present calculations based on a simplified band model of the spin-flip cross section expected in electron energy loss in a ferromagnetic metal. It is shown how direct production of Stoner excitations can lead to observable features in both spin polarized and ordinary EELS spectra. A strong primary electron energy dependence is predicted for all these spin-flip features, in agreement with recent experiments.     

Taming symplectic forms and the Calabi-Yau equation

We study the Calabi–Yau equation on symplectic manifolds.We show that Donaldson's conjecture on estimates for this equationin terms of a taming symplectic form can be reduced to an integralestimate of a scalar potential function. Under a positive curvaturecondition, we show that the conjecture holds.     

Conformationally restricted analogues of both (S)-β-homoserine and (S)-aspartic acid from chiral 3-acylamino pyrrolidin-2-ones

Starting from chiral 3,4-trans-disubstituted pyrrolidin-2-ones 11a and 11b, obtained from a Baylis-Hillman adduct, conformationally restricted analogues of both (S)-β-homoserine, 17, and (S)-aspartic acid, 21, were synthesized, respectively, and these compounds are suitable either for introduction in peptidomimetics or for synthesis of novel β-foldamers.     

Role of the external pressure on the dewetting of soft interfaces

We consider dewetting at soft interfaces, e.g., a rubber ball squeezed in a fluid against a flat hard substrate. We show that the applied squeezing pressure, which was not taken into account in earlier studies of the dewetting transition, may have a big effect on the squeeze-out dynamics.Received: 10 August 2003, Published online: 3 September 2003PACS: 68.15. + e Liquid thin films - 81.40.Pq Friction, lubrication, and wear     

Novel electronically driven surface phase predicted in C/Si(111)

We predict a novel electronically driven phase for the recently created C/Si(111) surface at 1/3 monolayer coverage. Whereas the isoelectronic surface Sn/Ge(111) is a 3 x 3 distorted metal and Si/SiC(0001) is an undistorted magnetic Mott insulator, the new phase combines both features. Two of three adatoms in C/Si(111) should form a distorted (3 x 3) honeycomb sublattice, the third an undistorted insulating and magnetic triangular sublattice. The generally conflicting elements, namely, band energy, favoring distortion, and strong electron correlations favoring a Mott state, actually conspire in this case. This kind of state represents the surface analog of the Fazekas-Tosatti state in the charge density wave compound 1T-TaS2.     

Theoretical evidence for a reentrant phase diagram in ortho-para mixtures of solid H2 at high pressure

We develop a multiorder parameter mean-field formalism for systems of coupled quantum rotors. The scheme is developed to account for systems where ortho-para distinction is valid. We apply our formalism to solid H2 and D2. We find an anomalous reentrant orientational phase transition for both systems at thermal equilibrium. The correlation functions of the order parameter indicate short-range order at low temperatures. As the temperature is increased the correlation increases along the phase boundary. We also find that even extremely small odd-J concentrations (1%) can trigger short-range orientational ordering.     

Excitons and plasmons in wide gaps: Solid rare gases

We develop a model macroscopic response function that describes the electronic response in wide gap insulators. The parameters entering the model, which consists of two coupled oscillators, are fixed by electrostatics. Application is made to both valence and core transitions in solid rare gases. We obtain exciton and plasmon energies in agreement with the available experimental data.