1,550 research outputs found
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
Prospects for single-photon sideband cooling of optically trapped neutral atoms
We propose a cooling scheme for realizing single-photon sideband cooling on particles trapped in a state-dependent optical potential. We develop a master rate equation from an ab initio model and find that in experimentally feasible conditions it is possible to reduce the average occupation number of the vibrational levels in one dimension by more than 90% by applying a frequency sweep on the cooling laser that sequentially cools all the motional states. Notably, this cooling scheme works also when a particle experiences a deeper trap in its internal ground state than in its excited state, a condition for which conventional single-photon sideband cooling does not work. In our analysis, we consider two cases: a two-level particle confined in an optical tweezer, and Li atoms confined in an optical lattice, and we find conditions for efficient cooling in both cases. The results from the model are confirmed by a full quantum Monte Carlo simulation of the system Hamiltonian. Our findings provide an alternative cooling scheme that can be applied in principle to any particle, e.g., atoms, molecules, or ions, confined in a state-dependent optical potential
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
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
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
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
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