Conditioning prices on search behaviour

We consider a market in which �firms can partially observe each consumer's search behavior in the market. In our main model, a �firm knows whether a consumer is visiting it for the �first time or whether she is returning after a previous visit. Firms have an incentive to offer a lower price on a �first visit than a return visit, so that new consumers are offered a "buy-now" discount. The ability to offer such discounts acts to raise all prices in the market. If �firms cannot commit to their buy-later price, in many cases �firms make "exploding" offers, and consumers never return to a previously sampled �rm. Likewise, if �firms must charge the same price to all consumers, regardless of search history, we show that they sometimes have the incentive to make exploding offers. We also consider other ways in which �firms could use information about search behaviour to determine their prices

First-Principles Study of Integer Quantum Hall Transitions in Mesoscopic Samples

We perform first principles numerical simulations to investigate resistance fluctuations in mesoscopic samples, near the transition between consecutive Quantum Hall plateaus. We use six-terminal geometry and sample sizes similar to those of real devices. The Hall and longitudinal resistances extracted from the generalized Landauer formula reproduce all the experimental features uncovered recently. We then use a simple generalization of the Landauer-B\"uttiker model, based on the interplay between tunneling and chiral currents -- the co-existing mechanisms for transport -- to explain the three distinct types of fluctuations observed, and identify the central region as the critical region.Comment: changes to acknowledgements onl

Scalars in the hadron world: the Higgs sector of the strong interaction

Scalar mesons are a key expression of the strong physics regime of QCD and the role condensates, particularly $$, play in breaking chiral symmetry. What new insights have been provided by recent experiments on $D, D_s$ and $J/\psi$ decays to light hadrons is discussed. We need to establish whether all the claimed scalars $\sigma$, $\kappa$, $f_0(1370)$, etc., really exist and with what parameters before we can meaningfully speculate further about which is transiently ${\bar q}q$, ${\bar{qq}} qq$, multi-meson molecule or largely glue.Comment: 10 pages, 4 figures. Invited talk at the International Conference on QCD and Hadronic Physics, Beijing, June 2005. A shortened version will appear in the Proceeding