Wigner islands with electrons over helium

We present here the first experimental study of Wigner islands formed by electrons floating over helium. Electrons are trapped electrostatically in a mesoscopic structure covered with a helium film, behaving as a quantum dot. By removing electrons one by one, we are able to find the addition spectrum, i.e. the energy required to add (or extract) one electron from the trap with occupation number $N$. Experimental addition spectra are compared with Monte Carlo simulations for the actual trap geometry, confirming the ordered state of electrons over helium in the island.Comment: 12 pages, 13 figures, draft pape

What does the Web of Science five-year synchronous impact factor have to offer?

With a random sample of 10 JCR (Science) subject areas it is shown that the 2-year and the 5-year impact factor of journals lead statistically to the same ranking per category. Yet in a majority of cases, the 5-year impact factor is larger than the 2-year one.</p

Die probleem van die versnellende verandering in die wêreld

Die versnelling waaraan tegnologiese vordering in ons tyd onderhewig is, bring sulke ingrypende veranderings mee dat die aanpassing by daardie veranderings en die noodsaaklik- heid om die implikasies van die veranderings te interpreteer, een van die belangrikste verantwoordelikhede van ons tydvak word. Soos 'n Amerikaanse skrywer dit stel — ,,Everything nailed down is coming loose”

Using off-diagonal confinement as a cooling method

In a recent letter [Phys. Rev. Lett. 104, 167201 (2010)] we proposed a new confining method for ultracold atoms on optical lattices, based on off-diagonal confinement (ODC). This method was shown to have distinct advantages over the conventional diagonal confinement (DC) that makes use of a trapping potential, including the existence of pure Mott phases and highly populated condensates. In this paper we show that the ODC method can also lead to temperatures that are smaller than with the conventional DC method, depending on the control parameters. We determine these parameters using exact diagonalizations for the hard-core case, then we extend our results to the soft-core case by performing quantum Monte Carlo (QMC) simulations for both DC and ODC systems at fixed temperatures, and analysing the corresponding entropies. We also propose a method for measuring the entropy in QMC simulations.Comment: 6 pages, 6 figure

Polaron relaxation in ferroelectric thin films

We report a dielectric relaxation in ferroelectric thin films of the ABO3 family. We have compared films of different compositions with several growth modes: sputtering (with and without magnetron) and sol-gel. The relaxation was observed at cryogenic temperature (T<100K) for frequencies from 100Hz up to 10MHz. This relaxation activation energy is always lower than 200meV. It is very similar to the polaron relaxation that we reported in the parent bulk perovskites. Being independent of the materials size, morphology and texture, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shapin

Trapping electrons in electrostatic traps over the surface of helium

We have observed trapping of electrons in an electrostatic trap formed over the surface of liquid helium-4. These electrons are detected by a Single Electron Transistor located at the centre of the trap. We can trap any desired number of electrons between 1 and $\sim 30$. By repeatedly ($\sim 10^3-10^4$ times) putting a single electron into the trap and lowering the electrostatic barrier of the trap, we can measure the effective temperature of the electron and the time of its thermalisation after heating up by incoherent radiation.Comment: Presented at QFS06 - Kyoto, to be published in J. Low Temp. Phys., 6 pages, 3 figure

Little Higgs studies in ATLAS

Study of the possible discovery in Atlas of the new particles predicted by Little Higgs models are presented. Different heavy bosons W_H/Z_H/A_H final states have been studied, with, when relevant, two Higgs mass hypotheses mH=120 GeV and mH=200 GeV. The heavy top T, and the new higgs boson phi++ have also been searched for. The discovery potential of ATLAS is shown to cover a significant portion of the parameter space. This paper is part of the 2006 CERN yellow report : CP studies and non-standard Higgs physics

Effective algebraic degeneracy

We prove that any nonconstant entire holomorphic curve from the complex line C into a projective algebraic hypersurface X = X^n in P^{n+1}(C) of arbitrary dimension n (at least 2) must be algebraically degenerate provided X is generic if its degree d = deg(X) satisfies the effective lower bound: d larger than or equal to n^{{(n+1)}^{n+5}}