Combinatorics of tight geodesics and stable lengths

We give an algorithm to compute the stable lengths of pseudo-Anosovs on the curve graph, answering a question of Bowditch. We also give a procedure to compute all invariant tight geodesic axes of pseudo-Anosovs. Along the way we show that there are constants $1<a_1<a_2$ such that the minimal upper bound on `slices' of tight geodesics is bounded below and above by $a_1^{\xi(S)}$ and $a_2^{\xi(S)}$, where $\xi(S)$ is the complexity of the surface. As a consequence, we give the first computable bounds on the asymptotic dimension of curve graphs and mapping class groups. Our techniques involve a generalization of Masur--Minsky's tight geodesics and a new class of paths on which their tightening procedure works.Comment: 19 pages, 2 figure

Antidumping mechanisms and safeguards in Peru

Peru's experience in the application of antidumping and safeguard measures is characterized by a radical change in the philosophy and procedures of trade at the beginning of the 1990s, and by an increasing use of these mechanisms. Trade liberalization was accompanied by the liberalization of foreign currency transactions and of financial and labor markets. Also, the internal revenue administration was modernized, institutions for regulation and competition defense were created, and state enterprises were transferred to private owners or concessionaires. New laws and institutions were created to regulate markets, including INDECOPI, a novel government agency charged with antimonopoly regulation and consumer defense, and which houses the Antidumping and Subsidies Commission. This highly autonomous and technical Commission became the central player in the implementation of WTO rules and procedures for fair trade. Since the reform was launched, a total of 81 trade protection cases have been presented, of which 57 were followed by a dumping investigation. The application of antidumping duties was approved for 29 of the cases investigated. Only two cases of safeguard investigations were recorded, one of which (Chinese textile clothing articles) is still in the negotiation phase. This paper reviews that case experience in detail, concluding that Peru has clearly differentiated between unfair competition and dumping on the one hand, and damage and safeguards on the other, and has applied strict technical criteria to the former and broader political considerations to the latter. Despite recent indications of a partial retreat from those principles, the decade-old reform is expected to last.

Beyond the IMF

A consensus has developed that the International Monetary Fund (IMF) is not fulfilling its role, prompting multiple proposals for reform. However, this paper argues that the focus on reform should be complemented with an exploration of alternatives outside the IMF which hold the potential to not only give developing countries greater bargaining leverage with the Fund but also, by increasing competition, spurring the institution to better performance. The paper argues that most of the IMF’s functions are being carried out in part through alternative institutional arrangements. It focuses in particular on the insurance role of the Fund and argues that developing countries are developing alternative insurance mechanisms, from a higher level of reserves, to regional co-insurance facilities to remittances as a counter-cyclical source of foreign exchange. The de facto exit of its clientele has been driven by the high political costs associated with Fund borrowing and now poses unprecedented challenges for the Fund, in particular pressures on its income. The paper argues for a rapid restructuring and significant cuts of the Fund’s administrative budget with the budget savings instead directed to lower the interest rates charged to borrowers.IMF, reform, developing countries, insurance, foreign exchange, remittances,

The goal dependent automaticity of drinking habits

In recent treatments of habitual social behaviour, habits are conceptualised as a form of goal-directed automatic behaviour that are mentally represented as goal-action links. Three experiments tested this conceptualisation in the context of students’ drinking (alcohol consumption) habits. Participants were randomly assigned to conditions where either a goal related to drinking behaviour (socialising) was activated, or an unrelated goal was activated. In addition, participants’ drinking habits were measured. The dependent variable in Experiments 1 and 2 was readiness to drink, operationalised by speed of responding to the action concept “drinking” in a verb verification task. Experiment 3 used uptake of a voucher to measure drinking behaviour. Findings supported the view that when habits are established, simply activating a goal related to the focal behaviour automatically elicits that behaviour. These findings are consistent with a goal-dependent conception of habit. Possibilities for interventions designed to attenuate undesirable habitual behaviours are considered

Coherent control of nanomagnet dynamics via ultrafast spin torque pulses

The magnetization orientation of a nanoscale ferromagnet can be manipulated using an electric current via the spin transfer effect. Time domain measurements of nanopillar devices at low temperatures have directly shown that magnetization dynamics and reversal occur coherently over a timescale of nanoseconds. By adjusting the shape of a spin torque waveform over a timescale comparable to the free precession period (100-400 ps), control of the magnetization dynamics in nanopillar devices should be possible. Here we report coherent control of the free layer magnetization in nanopillar devices using a pair of current pulses as narrow as 30 ps with adjustable amplitudes and delay. We show that the switching probability can be tuned over a broad range by timing the current pulses with the underlying free-precession orbits, and that the magnetization evolution remains coherent for more than 1 ns even at room temperature. Furthermore, we can selectively induce transitions along free-precession orbits and thereby manipulate the free magnetic moment motion. We expect this technique will be adopted for further elucidating the dynamics and dissipation processes in nanomagnets, and will provide an alternative for spin torque driven spintronic devices, such as resonantly pumping microwave oscillators, and ultimately, for efficient reversal of memory bits in magnetic random access memory (MRAM).Comment: 4 pages, 3 figures, submitted to Nature Physic