Electroweak tests with τ leptons at LEP

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z⁰ pole. From measurements of the τ polarization in e⁺ e^?→τ ⁺ τ ^?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg _{v e} /g _{a e} =0.066±0.015 andg _{V τ} /g _{A τ} =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG _τ /G _μ =0.996±0.008.     

Standard<Emphasis Type="Italic">SU</Emphasis>(5) supergravity grand unification model and predictions

A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints.     

Amplification of spontaneous emission in Nd~(3 )-doped fiber pumped by Ti: Al_2O_3 tunable laser

Amplification of spontaneous emission(ASE) in 4m Nd~(3 )-doped fiber pumped by Ti : Al~2O_3 tunable laser is studied theoretically and experimentally. The output of 2.64mW from ASE source pumped at 833 nm is obtained and the experimental results of ASE source are compared with that of Nd~(3 )-doped fiber ring laser.     

对称三值代数系统

本文对对称三值格代数与对称三值模代数进行了讨论,提出了任意对称三值函数的格代数规范展开和模代数的一般化展开、最后讨论两种代数之i可的关系,并求出函数展开式系数之间的转换矩阵.     

单调函数的列表判别法

本文讨论了单调函数和函数的最小列表,在此基础上提出单调函数、单调递增函数和单调递减函的列表判别方法,并举例说明了判别过程。     

低温液体无损贮存压力升高的实验与计算

准确、简单地预测低温液体无损贮存时的压力升高具有重要的实用价值。对一低温容器利用液氮为介质进行了多次无损贮存实验,利用多元线性回归方法对实验数据进行分析和检验。分析表明无损贮存时间、初始充满率对压力升高的影响较大,而环境温度的影响可以忽略,并拟合出了压力升高的计算公式。计算结果和实验结果在很大范围内能够较好地吻合。该种计算方法在预测低温液体无损贮存压力升高时有较高的准确性与可靠性。     

Cavity phase matching via an optical parametric oscillator consisting of a dielectric nonlinear crystal sheet

We experimentally demonstrate cavity phase matching for the first time using a sheet optical parametric oscillator which is made of an x-cut KTiOPO(4) crystal sheet. This microcavity presents 220 kW peak power capability for near-frequency-degenerate parametric outputs with up to 23.8% slope efficiency. It also features unique spectral characteristics such as single-longitudinal-mode and narrow linewidth. These attractive properties predict broad applications of such a mini-device, such as terahertz generation, photonic integration, spectroscopy, and quantum information, etc.     

High pulse energy mode-locked multicore photonic crystal fiber laser

A high pulse energy passively mode-locked fiber laser operating in the all-normal dispersion regime is demonstrated. The gain material is an Yb-doped multicore photonic crystal fiber with 18 cores in array-type geometry. Robust and self-starting mode locking is achieved using a fast semiconductor saturable absorber mirror. The laser generates 180?nJ chirped pulses at a 14.48?MHz repetition rate for an average power of 2.6?W. The 1.15?ps output pulses are compressed to 690?fs outside the cavity.     

Free standing modulation doped core–shell GaAs/AlGaAs hetero‐nanowires

Modulation doped AlGaAs/GaAs core–shell nanowire structures were grown by molecular beam epitaxy. A Si delta‐doping was introduced in the AlGaAs shell around the {110} facets of the GaAs core. The wires are typically highly resistive at low temperatures. However, they show a pronounced persistent photoconductivity effect indicating activation of free carriers from the delta‐doped shell to the GaAs core. The n‐type character of the channel is demonstrated by applying a back‐gate voltage. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Physics with large extra dimensions

The recent understanding of string theory opens the possibility that the string scale can be as low as a few TeV. The apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the sub-millimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. In my lecture, I describe briefly this scenario which gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. I also discuss a minimal embedding of the standard model, gauge coupling unification and proton stability. On leave from: Centre de Physique Théorique, Ecole Polytechnique, 91128 Palaiseau, Cedex, France.