Diffractive Interactions

The general framework of diffractive deep inelastic scattering is introduced and reports given in the session on diffractive interactions at the International Workshop on Deep-Inelastic Scattering and Related Phenomena, Rome, April 1996, are presented.Comment: LaTeX with procl.sty, 20 pages. To appear in the Proceedings of the International Workshop on Deep Inelastic Scattering and Related Phenomena, Roma, Italy, April 199

STEM escape rooms for public engagement

Escape rooms are a relatively new cultural phenomenon, attracting a wide range of audiences to test their puzzle-solving skills. While this format has been trialled in an educational context, there has been little exploration of it as a tool for engagement. We ran a STEM-based escape room, open to the public, over five days at a science centre in Malta. This was an exploratory exercise to determine whether escape rooms could be successful in an informal science engagement context. Over seventy players attempted the game and completed our evaluation. Our results suggest that escape rooms can be used in engagement contexts as they provide a positive experience that encourages future interactions with science. They may also draw audiences not normally interested in science and help them engage with scientific content in a more accessible manner. Interestingly, players were able to persist in engaging with content they found difficult while still finding it enjoyable, which has implications for the science communication of complex topics. Finally, players perceived that they were able to learn science through the escape room, which may increase their self-efficacy

A scalable hardware and software control apparatus for experiments with hybrid quantum systems

Modern experiments with fundamental quantum systems - like ultracold atoms, trapped ions, single photons - are managed by a control system formed by a number of input/output electronic channels governed by a computer. In hybrid quantum systems, where two or more quantum systems are combined and made to interact, establishing an efficient control system is particularly challenging due to the higher complexity, especially when each single quantum system is characterized by a different timescale. Here we present a new control apparatus specifically designed to efficiently manage hybrid quantum systems. The apparatus is formed by a network of fast communicating Field Programmable Gate Arrays (FPGAs), the action of which is administrated by a software. Both hardware and software share the same tree-like structure, which ensures a full scalability of the control apparatus. In the hardware, a master board acts on a number of slave boards, each of which is equipped with an FPGA that locally drives analog and digital input/output channels and radiofrequency (RF) outputs up to 400 MHz. The software is designed to be a general platform for managing both commercial and home-made instruments in a user-friendly and intuitive Graphical User Interface (GUI). The architecture ensures that complex control protocols can be carried out, such as performing of concurrent commands loops by acting on different channels, the generation of multi-variable error functions and the implementation of self-optimization procedures. Although designed for managing experiments with hybrid quantum systems, in particular with atom-ion mixtures, this control apparatus can in principle be used in any experiment in atomic, molecular, and optical physics.Comment: 10 pages, 12 figure

Feno e silagem como volumoso para confinamento de bovinos de corte.

bitstream/item/67190/1/CT-49-2001.pd

Modulation instability and conservation of energy:toward a new model

L'articolo analizza la propagazione in regime nonlineare di un segnale ottico CW in presenza di una "piccola" perturbazione. In letteratura sono presenti lavori che specificano i parametri fisici che regolano l'interazione tra il segnale CW e la perturbazione ma non si hanno indicazioni relative ai limiti di applicabilità dei modelli proposti. Obiettivo principale di questo lavoro è rappresentato dalla definizione dei parametri che "attivano" l'instabilità di modulazione e regolano il regime di propagazione nonlineare. A tal fine, il regime di propagazione nonlineare è analizzato vincolandolo al principio di conservazione dell'energia

Dijet Production at Hadron--Hadron Colliders in the BFKL Approach

The production in high-energy hadron collisions of a pair of jets with large rapidity separation is studied in an improved BFKL formalism. By recasting the analytic solution of the BFKL equation as an explicit order-by-order sum over emitted gluons, the effects of phase space constraints and the running coupling are studied. Particular attention is paid to the azimuthal angle decorrelation of the jet pair. The inclusion of sub-leading effects significantly improves the agreement between the theoretical predictions and recent preliminary measurements from the Dzero collaboration.Comment: 19 pages LaTeX; one figure corrected; conclusions unchange

Computation of Mini-Jet Inclusive Cross Sections

We apply the theory of parton-parton total cross sections at large ``s", due to Lipatov and collaborators, to compute the inclusive cross section for jets which accompany a large ``s" parton scattering process.Comment: 13 page

The Impact of Investor Demand on Security Offerings

The studies in this thesis contribute to a growing stream of papers showing that capital structure decisions are not only influenced by corporate determinants, but also by fluctuations in investor tastes and capital available for investment. This is a relatively new way of looking at corporate decisions, but is also given the deserved importance in the literature. This view contrasts with the traditional approach in the literature that largely considered corporate decisions to be distinct from the decision process of investors. Chapters 2 and 3 use convertible debt issuance to analyze the impact of intertemporal variation in investor demand on corporate decisions, and the market reaction to these decisions. Chapter 2 shows that convertible debt issuance, pricing, and design decisions are influenced by demand forces from investors. Chapter 3 finds that a shift in the convertible bond investor base from long-only investors towards convertible arbitrage funds resulted in an increasingly negative stock price reaction, induced by short-selling pressure. Thus, the first two studies in this thesis provide more evidence of corporate opportunism, using data on issuers of convertible debt. The fourth chapter uses data from repeat issuers of equity, and provides evidence in line with the hypothesis that investors take opportunism into account when firms issue new equity. In addition, the paper shows that firms’ choice of capital structure is influenced by their past behavior

Hopf algebras, coproducts and symbols: an application to Higgs boson amplitudes

We show how the Hopf algebra structure of multiple polylogarithms can be used to simplify complicated expressions for multi-loop amplitudes in perturbative quantum field theory and we argue that, unlike the recently popularized symbol-based approach, the coproduct incorporates information about the zeta values. We illustrate our approach by rewriting the two-loop helicity amplitudes for a Higgs boson plus three gluons in a simplified and compact form involving only classical polylogarithms.Comment: 46 page

An Analytic Result for the Two-Loop Hexagon Wilson Loop in N = 4 SYM

In the planar N=4 supersymmetric Yang-Mills theory, the conformal symmetry constrains multi-loop n-edged Wilson loops to be basically given in terms of the one-loop n-edged Wilson loop, augmented, for n greater than 6, by a function of conformally invariant cross ratios. We identify a class of kinematics for which the Wilson loop exhibits exact Regge factorisation and which leave invariant the analytic form of the multi-loop n-edged Wilson loop. In those kinematics, the analytic result for the Wilson loop is the same as in general kinematics, although the computation is remarkably simplified with respect to general kinematics. Using the simplest of those kinematics, we have performed the first analytic computation of the two-loop six-edged Wilson loop in general kinematics.Comment: 17 pages. Extended discussion on how the QMRK limit is taken. Version accepted by JHEP. A text file containing the Mathematica code with the analytic expression for the 6-point remainder function is include