Correlation Widths in Quantum--Chaotic Scattering

An important parameter to characterize the scattering matrix S for quantum-chaotic scattering is the width Gamma_{corr} of the S-matrix autocorrelation function. We show that the "Weisskopf estimate" d/(2pi) sum_c T_c (where d is the mean resonance spacing, T_c with 0 <= T_c <= 1 the "transmission coefficient" in channel c and where the sum runs over all channels) provides a very good approximation to Gamma_{corr} even when the number of channels is small. That same conclusion applies also to the cross-section correlation function

Microcomputer network

The microcomputer network is a powerful processing machine that is constructed using a number of small microcomputers. ach microcomputer is based on a single chip microcomputer supplemented with memory and peripherals. The network was designed to be a general purpose machine to model the interactions of several programs running asynchronously. The requirements of such a model are easily met by the microcomputer network, sufficient memory space is available, the basic execution rate is variable, and a random number generator is included. The microcomputer network is general enough for a wide range of applications, therefore a section on programming the network is included. The next chapter is an overview of the network. Chapter three covers the design and construction of the network hardware. The software that runs on the network is discussed in chapter four along with a section on programming the network. A list of references is included for specific information on devices used in the design

Effective Coupling for Open Billiards

We derive an explicit expression for the coupling constants of individual eigenstates of a closed billiard which is opened by attaching a waveguide. The Wigner time delay and the resonance positions resulting from the coupling constants are compared to an exact numerical calculation. Deviations can be attributed to evanescent modes in the waveguide and to the finite number of eigenstates taken into account. The influence of the shape of the billiard and of the boundary conditions at the mouth of the waveguide are also discussed. Finally we show that the mean value of the dimensionless coupling constants tends to the critical value when the eigenstates of the billiard follow random-matrix theory

The generalised relativistic Lindhard functions

We present here analytic expressions for the generalised Lindhard function, also referred to as Fermi Gas polarisation propagator, in a relativistic kinematic framework and in the presence of various resonances and vertices. Particular attention is payed to its real part, since it gives rise to substantial difficulties in the definition of the currents entering the dynamics.Comment: 48 pages, 2 figures, to be published in EPJ

Non-Surgical Endodontic Management of Type II Dens Invaginatus with Closed and Open Apex

Dens invaginatus (DI) is a developmental anomaly that poses a significant challenge to the clinician if endodontic treatment is required. The type II (as per Oehlers) form exhibits complex internal anatomy and is frequently associated with incomplete root and apex formation. The purpose of this study is to present two cases of type II DI in the maxillary lateral incisors. In the first case, non-surgical endodontic therapy was performed utilizing calcium hydroxide as an intracanal dressing, showing significant periapical healing of the apical radiolucent area at the six month follow-up. In the second case, the development of the root and apex were affected by pulp necrosis, and the revascularization procedure was performed. Complete resolution of the pre-existing apical radiolucency, apical closure, thickening of the root canal walls, and increase in root length, after 32 months was observed. Early detection of teeth with DI type II and proper exploration of their internal anatomy are key factors for their successful management. As demonstrated in this report, conservative non-surgical endodontic treatment should be the first line of treatment for these cases. The use of revascularization protocols in teeth that develop pulp necrosis and exhibit early stage of root development could be a better alternative than traditional apexification techniques.Keywords: Calcium Hydroxide; Close Apex; Dens Invaginatus; Open Apex; Revascularizatio

The Rarita--Schwinger field: renormalization and phenomenology

We discuss renormalization of propagator of interacting Rarita--Schwinger field. Spin-3/2 contribution after renormalization takes usual resonance form. For non-leading spin-1/2 terms we found procedure, which guarantees absence of poles in energy plane. The obtained renormalized propagator has one free parameter and is a straight generalization of the famous free propagator of Moldauer and Case. Application of this propagator for production of $\Delta^{++}(1232)$ in \pi^{+}\particle{p}\to \pi^{+}\particle{p} leads to good description of total cross-section and to reasonable agreement with results of partial wave analysis.Comment: 19 pages, 3 figures, revtex4; misprints, min editorial change

Redundance of Δ\Delta-isobar Parameters in Effective Field Theories

It is shown that the off-shell parameters in the interaction Lagrangian of pions, nucleons, and $\Delta$-isobars are redundant in the framework of effective field theories. Our results also suggest the necessity of including the $\Delta$ as an explicit dynamical degree of freedom.Comment: 11 pages, RevTex, no figures, a minor error corrected, to appear in PL

Spin 3/2 Beyond the Rarita-Schwinger Framework

We employ the two independent Casimir operators of the Poincare group, the squared four--momentum, P^2, and the squared Pauli-Lubanski vector, W^2, in the construction of a covariant mass-m, and spin-3/2 projector in the four-vector-spinor, \psi_{\mu}. This projector provides the basis for the construction of an interacting Lagrangian that describes a causally propagating spin-3/2} particle coupled to the electromagnetic field by a gyromagnetic ratio of g_{3/2}=2.Comment: 20 page

Statistics of S-matrix poles in Few-Channel Chaotic Scattering: Crossover from Isolated to Overlapping Resonances

We derive the explicit expression for the distribution of resonance widths in a chaotic quantum system coupled to continua via M equivalent open channels. It describes a crossover from the $\chi^2$ distribution (regime of isolated resonances) to a broad power-like distribution typical for the regime of overlapping resonances. The first moment is found to reproduce exactly the Moldauer-Simonius relation between the mean resonance width and the transmission coefficient. This fact may serve as another manifestation of equivalence between the spectral and the ensemble averaging.Comment: 4 two-column pages, RevTex. text is slightly modified; some misprints are correcte

Micro-CT study of the root canal anatomy of maxillary canines

Background: This study aimed to describe the anatomy of maxillary canines from a Western Mexican sub-population using micro-computed tomography (micro-CT). Material and methods: Maxillary canines (n=32) were scanned at 19.6?m voxel resolution. Number and location of canals, the distance between the cemento-enamel junction and apex, occurrence of accessory and lateral canals, presence of oval canals, number of foraminas as well as two- (area, perimeter, roundness, aspect ratio, major and minor diameters) and three-dimensional (volume, surface area, and SMI) analysis were performed. Data of two- dimensional analyses at 5 different apical levels was statistically compared using Kruskal-Wallis tests (?=0.05). Results: Overall, 31 specimens had one root with a main canal (Vertucci type I). Mean distance from the apex to the cemento-enamel junction was 16.32±2.27. Apical foraminas were present in 14 specimens (43.75%). No statistical differences were found in the two-dimensional analyses between the foramen and the 1 and 2mm apical levels ( P >0.05). Conclusions: Maxillary canines presenting one root canal were present in a high percentage of cases (96%). The prevalence of long oval canals was <12% at the apical third and at least 37% of the sample showed more than one point of exit in the last apical 3m