Quantum Zeno Effect and Light-Dark Periods for a Single Atom

The quantum Zeno effect (QZE) predicts a slow-down of the time development of a system under rapidly repeated ideal measurements, and experimentally this was tested for an ensemble of atoms using short laser pulses for non-selective state measurements. Here we consider such pulses for selective measurements on a single system. Each probe pulse will cause a burst of fluorescence or no fluorescence. If the probe pulses were strictly ideal measurements, the QZE would predict periods of fluorescence bursts alternating with periods of no fluorescence (light and dark periods) which would become longer and longer with increasing frequency of the measurements. The non-ideal character of the measurements is taken into account by incorporating the laser pulses in the interaction, and this is used to determine the corrections to the ideal case. In the limit, when the time between the laser pulses goes to zero, no freezing occurs but instead we show convergence to the familiar macroscopic light and dark periods of the continuously driven Dehmelt system. An experiment of this type should be feasible for a single atom or ion in a trapComment: 16 pages, LaTeX, a4.sty; to appear in J. Phys.

Gender, risk and the Wall Street alpha male

From the outset, analyses of the 2008 financial crisis, in mainstream as well as feminist discussions, have been gendered. In particular, rampant risk taking in an unregulated environment, widely deemed to be a principle cause of the crash, has been associated with masculine characteristics. In this article I explore how the concepts of gender and risk entwine in two films on the financial crisis – The Other Guys and Margin Call. By looking at how gender is used to dramatise financial risk, I explore how understandings of high risk behaviour are gendered, and the implications this has in the context of finance. Fictional representations mediate public understanding of this notoriously complex field, as the number of films and documentaries on the crisis demonstrates. Exploring how gender is used to communicate risk reminds us that risk taking is part of a performance of masculinity that needs to be established by constructing a feminine, risk-averse other. The contention of this paper is that to address gender bias in finance and the economy, gendered meanings of risk need to be openly challenged, and cultural and material analyses of gendered inequality brought into dialogue

Axions And Other Very Light Bosons

L ` = CITATION: K. Hagiwara et al. (Particle Data Group), Phys. Rev. D 66, 010001 (2002) (URL: http://pdg.lbl.gov) -- 2-- ` eff is so small (` eff . 10 ) as required by the current limits on the neutron electric dipole moment, even though ` eff O(1) is perfectly allowed by the QCD gauge invariance. Here, ` eff is the effective ` parameter after the diagonalization of the quark masses, and F is the gluon field strength and = 2 ffl aeoe F aeoea . An axion is a pseudoNG boson of a spontaneously broken Peccei--Quinn symmetry, which is an exact symmetry at the classical level, but is broken quantum mechanically due to the triangle anomaly with the gluons. The definition of the Peccei--Quinn symmetry is model dependent. As a result of the triangle anomaly, the axion acquires an effective coupling to gluons ` ` eff \Gamma OE A f A ' ; (2) where OE A is the axion field. It is often convenient to define the axion decay constant f A with this Lagrangian [6]

The Stability of Spike Solutions to the One-Dimensional Gierer-Meinhardt Model

The stability properties of an N-spike equilibrium solution to a simpli ed form of the GiererMeinhardt activator-inhibitor model in a one-dimensional domain is studied asymptotically in the limit of small activator diusivity ". The equilibrium solution consists of a sequence of spikes of equal height. The two classes of eigenvalues that must be considered are the O(1) eigenvalues and the O(" ) eigenvalues, which are referred to as the large and small eigenvalues, respectively