Trident pair production in strong laser pulses

We calculate the trident pair production amplitude in a strong laser background. We allow for finite pulse duration, while still treating the laser fields nonperturbatively in strong-field QED. Our approach reveals explicitly the individual contributions of the one-step and two-step processes. We also expose the role gauge invariance plays in the amplitudes and discuss the relation between our results and the optical theorem.Comment: 4 pages, 1 .eps figure. Version 2: reference added, published versio

Lessons from All Logs Summation in Yukawa Theories

Some features of old results in the total summation of all logarithmic contributions of all diagrams in Yukawa theory are presented. We discuss some lessons from this picture for the description of Pomeron, odderon, etc. in QCD.Comment: 6 pages, 2 figure

Unified Chew-Mandelstam SAID analysis of pion photoproduction data

A unified description of single-pion photoproduction data, together with pion- and eta-hadroproduction data, has been achieved in a Chew-Mandelstam parametrization which is consistent with unitarity at the two-body level. Energy-dependent and single-energy partial wave analyses of pion photoproduction data have been performed and compared to previous SAID fits and multipoles from the Mainz and Bonn-Gatchina groups.Comment: 11 pages, 9 figures, and 2 table

Rapid Divergence of Wing Volatile Profiles Between Subspecies of the Butterfly Pieris rapae (Lepidoptera: Pieridae)

Complex signaling traits such as pheromone profiles can play an important role in the early stages of reproductive isolation between populations. These signals can diverge along multiple trait axes, and signal receivers are often sensitive to subtle differences in signal properties. In the Lepidoptera, prior research has highlighted that natural selection can drive rapid chemical signal divergence, for instance via mate recognition to maintain species boundaries. Much less is known about the occurrence of such changes for predominantly sexually selected chemical signals, such as those released by many male lepidopterans. We evaluated the divergence in male and female wing volatile profiles between two recently isolated subspecies of the pierid butterfly Pieris rapae Linnaeus (Lepidoptera: Pieridae): P. rapae rapae and P. rapae crucivora. In laboratory settings, these subspecies exhibit strong premating isolation, with females rejecting males of the opposite subspecies despite the fact that males direct equivalent courtship effort toward females of either subspecies. Using gas chromatography–mass spectrometry, we analyzed the volatile chemical profiles of individual males and females of each subspecies. We find that males of each subspecies differ in their wing volatile profiles, including quantitative differences in a male sex pheromone, ferrulactone. In contrast, female wing volatiles profiles have diverged significantly less. These sexspecific patterns suggest that male chemical profiles may play a role in the observed premating isolation between these two subspecies, providing support for future investigations of sexually selected chemical traits in population divergence

Quantum memory for squeezed light

We produce a 600-ns pulse of 1.86-dB squeezed vacuum at 795 nm in an optical parametric amplifier and store it in a rubidium vapor cell for 1 us using electromagnetically induced transparency. The recovered pulse, analyzed using time-domain homodyne tomography, exhibits up to 0.21+-0.04 dB of squeezing. We identify the factors leading to the degradation of squeezing and investigate the phase evolution of the atomic coherence during the storage interval.Comment: To appear in PRL. Changes to version 3: we present a larger data set featuring somewhat less squeezing, but also better statistics and a lower margin of error. Some additional revisions are made in response to the referees' comment

Performance evaluation of urban traffic management and ITS: The Rome case study

In order to cope with their growing traffic problems, cities throughout the world deploy Intelligent Transport System (ITS) applications in various fields of urban networks. The decision making process for the installation of ITS is a dialogue between the political instance of the municipalities and the planners. The strategic concept and the detailed planning are undertaken by transportation experts in the respective planning authorities and is based on a vast variety of measurements and evaluations (Reed et al., 1993). The decision for funding the systems however is taken on a political level and is based on the consideration of expected benefits, economic aspects but also public debates and controversies. It is obvious that this dialogue within an inhomogeneous group of stakeholders needs a common basis for the consideration of benefits of ITS as a counterpart to the often obvious costs.In order to deliver this common basis of discussion, a transparent methodology to calculate and present the benefits of ITS has to be elaborated.This methodology should support the decision making process in several aspects:? to identify best practice applications already operational in similar cases in other cities;? to decide on the installation of the system on a technical and a political level;* Technische Universität München† IUAV University of Venice‡ Imperial College London§ Technion, Israel Institute of Technology2. to monitor the performance of the deployed application over a longer period of time;to weigh the investment and operational cost compared to thebenefits of the system. Several solutions to this problem were proposed within the EU FP7 project CONDUITS (2009 - 2011). They included the elaboration of a set of Key Performance Indicators (KPI) targeting different categories of ITS and providing a single, measurable value for their benefit. The following paper gives an overview of the definition process for the KPI, explains their function and gives an example for the calculation of the KPI based on real-life data provided by the city of Rome