Time-resolved hot luminescence and resonant Raman scattering: Cu2O revisited

Time-resolved resonant scattering of both one-phonon and two-phonon Raman modes at the 1s ortho-exciton state of the yellow series in Cu₂O is reported. From the time dependence of the one-phonon mode we determine the scattering rate among the triply degenerate ortho-exciton states to be 2.5 × 10⁸sec^-1. From the two-phonon modes we directly determine the exciton lifetime as a function of its kinetic energy. In both cases the resonant scattering is found to be dominated by hot luminescence.     

Multiplicity distributions in hadronic and heavy ion reactions

It is shown that the study of multiplicity distributionsP(n) can provide valuable information about the reaction mechanism of strong interactions. The relation betweenP(n) and Bose-Einstein correlations is discussed and the recent Na³⁵ results are interpreted as possible evidence for the existence of a chaotic and a coherent component inP(n). An experiment to test the coherent nature of pion beams is proposed.     

Asymmetric Wiener-Poisson control

A one-dimensional Wiener plus independent Poisson noise control problem, with asymmetric control bounds and integral discounted quadratic cost over an infinite horizon, is considered. The resultant Bellman equations are solved, allowing the optimal control to be expressed explicitly in closed-loop form.     

Coherence and self-induced transparency in high-energy hadronic collisions

Two consequences of coherence of mesonic fields have been tested in proton-nucleus collisions. Multiplicity fluctuations measured in finite rapidity intervals are found to obey a Poisson distribution at large rapidities where nuclear transparency occurs. In close analogy to quantum optics we present a quark-parton model in which this link between coherence and transparency is realized via the phenomenon of self-induced transparency.     

On large minimal blocking sets in PG(2,q)

The size of large minimal blocking sets is bounded by the Bruen–Thas upper bound. The bound is sharp when q is a square. Here the bound is improved if q is a non‐square. On the other hand, we present some constructions of reasonably large minimal blocking sets in planes of non‐prime order. The construction can be regarded as a generalization of Buekenhout's construction of unitals. For example, if q is a cube, then our construction gives minimal blocking sets of size q^4/3 + 1 or q^4/3 + 2. Density results for the spectrum of minimal blocking sets in Galois planes of non‐prime order is also presented. The most attractive case is when q is a square, where we show that there is a minimal blocking set for any size from the interval . © 2004 Wiley Periodicals, Inc. J Combin Designs 13: 25–41, 2005.     

From Dyck Paths to Standard Young Tableaux

Annals of Combinatorics - We present nine bijections between classes of Dyck paths and classes of standard Young tableaux (SYT). In particular, we consider SYT of flag and rectangular shapes, we...     

Minimal Model Fusion Rules From 2-Groups

The fusion rules for the (p,q)-minimal model representations of the Virasoro algebra are shown to come from the group in the following manner. There is a partition into disjoint subsets and a bijection between and the sectors of the (p,q)-minimal model such that the fusion rules correspond to where .     

Dispersion-free fiber transmission for femtosecond pulses by use of a dispersion-compensating fiber and a programmable pulse shaper

We demonstrate nearly distortionless 2.5-km fiber transmission of sub-500-fs pulses, using a combination of standard single-mode fiber, dispersion-compensating fiber, and a programmable pulse shaper for simultaneous quadratic and cubic dispersion compensation. The dispersion-compensating fiber corrects the bulk of the quadratic and the cubic phases for the single-mode fiber, and the fiber-pigtailed programmable pulse shaper exactly compensates the residual dispersion terms. Together these elements permit complete recompression of pulses, which first broaden by ~400 times in the single-mode fiber.