Uniqueness of solutions for some nonlinear Dirichlet problems

We consider here a class of nonlinear Dirichlet problems, in a bounded domain , of the form

Determination of continuous variable entanglement by purity measurements

We classify the entanglement of two-mode Gaussian states according to their degree of total and partial mixedness. We derive exact bounds that determine maximally and minimally entangled states for fixed global and marginal purities. This characterization allows for an experimentally reliable estimate of continuous variable entanglement based on measurements of purity.     

New far-infrared emissions and frequency measurements in hydrazine

By means of a new CO₂ laser we performed a new investigation of the far-infrared laser emission spectrum of hydrazine excited by the 10P(32) and 10R(8) CO₂ laser lines. We found seven new lines and measured the frequency of four of them; moreover we measured the frequencies of two more lines previously reported in the literature with only wavelength measurements. The frequencies of the far-infrared laser emissions have been measured by means of a frequency-synthesis chain based on new InP Schottky diodes. The detected signal was beat-note generated in a Schottky diode between the far-infrared radiation, the harmonics of a 72 GHz frequency reference and a rf signal. We also characterized all of the observed lines by their polarization relative to the pumping CO₂ laser, the optimum pressure and the offset relative to the CO₂ center frequency. PACS 42.55.Lt; 42.62.Fi     

Boosts in an Arbitrary Direction and Maximal Causal Velocities in a Deformed Minkowski Space

We discuss boosts in a deformed Minkowski space, i.e., a four-dimensional spacetime with metric coefficients depending on nonmetric coordinates (in particular on the energy). The general form of a boost in an arbitrary direction is derived in the case of space anisotropy. Two maximal trivector velocities are mathematically possible, an isotropic and an anisotropic one. However, only the anisotropic velocity has physical meaning, being invariant indeed under deformed boosts.     

Heavy charged Higgs boson production at next generation $\gamma\gamma$ colliders

We investigate the scope of all relevant production modes of charged Higgs bosons in the MSSM, with mass larger than the one of the top quark, at future Linear Colliders operating in mode at the TeV energy scale. Final states with one or two bosons are considered, as produced by both tree- and loop-level interactions. Received: 8 November 2002 / Revised version: 12 February 2003 / Published online: 13 May 2003 RID="a" ID="a" e-mail: stefano.moretti@cern.ch RID="b" ID="b" e-mail: kanemu@post.kek.jp     

Some noncoercive parabolic equations with lower order terms in divergence form

This paper deals with existence and regularity results for the problem $ \cases{u_t-\mathrm{div}(a(x,t,u )\nabla u)=-\mathrm{div}(u\,E) \qquad in \Omega\times (0,T),\cr u=0 \qquad on \partial \Omega\times (0,T), \cr u (0)= u_0 \qquad in \Omega ,\cr} $ under various assumptions on E and $ u_0 $. The main difculty in studying this problem is due to the presence of the term div(uE), which makes the differential operator non coercive on the "energy space" $ L^2 (0, T; H_0^1 (\Omega)) $.AMS Subject Classification: 35K10, 35K15, 35K65.     

Green light generation in a periodically poled Zn-doped LiNbO3 planar waveguide fabricated by He+ implantation

An optical planar waveguide is investigated in ZnO-doped periodically poled lithium niobate formed by He⁺ implantation. Optical losses were found to be 2 dB/cm. Second-harmonic generation is used to produce a green laser beam by quasi-phase matching in the obtained waveguide. The conversion efficiency was found to be 10^-2%/W. Photorefractive resistance properties are reported and discussed relating to un-doped periodically poled lithium niobate. PACS 42.65.-k; 42.65.Wi; 42.82.-m     

On flows of H 3/2-vector fields on the circle

In this paper we study the regularity of flow maps of H ^3/2-vector fields on the circle in terms of fractional Sobolev spaces. This problem is motivated by the understanding of the geometry of Bers’s universal Teichmüller space.