Internal symmetries and bootstrap models

Chapter 1 serves ms a brief introduction to the ideas which form the subject of this thesis, internal symmetry, bootstraps, duality and the quark model. In Chapters 2 and 3 we survey predictions for internal symmetries made from (^N)/D bootstraps and the duality hypothesis respectively. Both approaches predict a Lie group structure and predict the meson representations. In addition the duality equations imply that the baryons transform as two-quark composites. A phenomenological choice of a subset of the duality constraints can be made which has a physical three-quark solution. Symmetry breaking is discussed in both cases. In Chapter 4 we contrast the predictions surveyed in the previous two chapters. Duality requires exchange degeneracies among trajectories of different multiplet8 but these do not result from (^N)/D models. In the dual case the even-signature, isosinglet trajectories are identified with mixed f, f' states, degenerate with the W,Ѳ respectively, whereas bootstrap models always produce a high-lying singlet trajectory which is most naturally identified with the Pomeron. It is argued that these differences make it unlikely that dual models can be deduced in any simple way from the bootstrap hypothesis. An (^N)/D quark model with meson exchanges is examined in Chapter 5. With the assumption that the quark mass is much larger than the meson mass, a singlet meson trajectory is obtained which lies an order of magnitude above the octet trajectories. This result is unaltered if symmetry breaking of any order is allowed. These difficulties are not removed by treating the particle exchange forces as perturbations to a background term. It is concluded that these results together with the known difficulties of obtaining physical slopes and intercepts imply that this type of quark model should probably be discarded

Letter from Elizabeth P. Hutt to James B. Finley

Elizabeth Pelham Finley Hutt writes to her uncle James B. Finley from Little Rock Arkansas. She and her family have recently moved from The Springs, a God-forsaken community where she was very unhappy. She thanks her uncle for the books and letter, and asks him to write again soon. Abstract Number - 496https://digitalcommons.owu.edu/finley-letters/1694/thumbnail.jp

Generation of acoustic emission from the running-in and subsequent micropitting of a mixed-elastohydrodynamic contact

This paper presents the use of Acoustic Emission to study the running-in and subsequent micropitting of a pair of hardened steel surfaces under mixed lubrication conditions. These surfaces were loaded together under rolling/sliding conditions typical of heavily loaded gearing. Relocation profilometry was used to measure the rapid running-in process and the development of micropits. Acoustic emission (AE) was found to be highly sensitive to both the initial changes in surface topography during the running-in process, and to subsequent changes caused by micropit formation. However, AE appears to be sensitive to changes in asperity interaction rather than the underlying mechanisms of plastic deformation, crack growth and fracture. It is concluded that AE can provide considerable insight into conditions in mixed-elastohydrodynamic contacts

Finding in Commercial-Engineer Controversy

Finding concerning a controversy between the commercial and engineer departments at Utah Agricultural College

Synchronous and Asynchronous Evaluation of Dynamic Neural Fields

International audienceIn \cite{rougier:2006}, we've introduced a dynamic model of visual attention based on the Continuum Neural Field Theory \cite{Taylor:1999} that explained attention as being an emergent property of a dynamic neural field. The fundamental property of the model is its facility to select a single stimulus out of several perfectly identical input stimuli by applying asynchronous computation. In the absence of external noise and with a zero initial state, the theoretical mathematical solution of the field equation predicts the final equilibrium state to equally represent all of the input stimuli. This finding is valid for synchronous numerical computation of the system dynamics where elements of the spatial field are computed all together at each time point. However, asynchronous computation, where elements of the spatial field are iterated in time one after the other yields different results leading the field to move towards a single stable input pattern. This behavior is in fact quite similar to the effect of noise on dynamic fields. The present work aims at studying this phenomenom in some details and characterizes the relation between noise, synchronous evaluation (the ``regular'' mathematical integration) and asynchronous evaluation in the case of a simple dual particle system. More generally, we aim at explaining the behavior of a general differential equation system when it is considered as a set of particles that may or may not iterated by synchronous computations

Flavoured jets with exact anti-ktk_t kinematics and tests of infrared and collinear safety

We propose extensions of the anti-$k_t$ and Cambridge/Aachen hierarchical jet clustering algorithms that are designed to retain the exact jet kinematics of these algorithms, while providing an infrared-and-collinear-safe definition of jet flavour at any fixed order in perturbation theory. Central to our approach is a new technique called Interleaved Flavour Neutralisation (IFN), whereby the treatment of flavour is integrated with, but distinct from, the kinematic clustering. IFN allows flavour information to be meaningfully accessed at each stage of the clustering sequence, which enables a consistent assignment of flavour both to individual jets and to their substructure. We validate the IFN approach using a dedicated framework for fixed-order tests of infrared and collinear safety, which also reveals unanticipated issues in earlier approaches to flavoured jet clustering. We briefly explore the phenomenological impact of IFN with anti-$k_t$ jets for benchmark tasks at the Large Hadron Collider.Comment: 36 pages, 27 figures, 1 table, code available from https://github.com/jetflav/IFNPlugi

The acoustic emission from asperity interactions in mixed lubrication

Gears typically operate in mixed lubrication conditions, where the lubricant film is too thin to prevent opposing surface asperities from interacting with each other. The likelihood/intensity of interactions is indicated by the Λ ratio: the ratio of smooth surface film thickness to surface roughness. Researchers have asserted that asperity interactions are the predominant cause of acoustic emission (AE) in healthy gear contacts. However, direct experiments on gears have yet to yield a clear relationship between the Asperity AE (AAE) and Λ ratio, this is in part due to the complexity of gear tooth contacts. In this paper, a disc rig was used to simulate a simplified gear contact so that the fundamental relationship between AAE and Λ could be investigated more effectively. By varying oil temperature and entrainment speed, a wide spectrum of lubrication conditions was generated. In contrast to other published studies, an independent measurement technique, the contact voltage (CV), was used to verify the amount of interactions, and repeated roughness measurements were used to confirm minimal surface wear. A simple, consistent and precise relationship between AAE amplitude and Λ was identified and defined for changes from full-film to mixed lubrication. Within the mixed lubrication regime, the AAE amplitude increased exponentially as Λ decreased at all speeds tested. It was also observed that an increase in speed always resulted in an increase in AAE amplitude, independently of any changes in Λ. This direct effect of speed was modelled so that the AAE could be predicted for any combination of speed and Λ within the tested envelope. This paper links gear contact tribology and AE with new precision and clearly demonstrates the potential of using AAE as a sensitive monitoring technique for the lubrication condition of gears