Flavor and chiral oscillations with Dirac wave packets

We report about recent results on Dirac wave packets in the treatment of neutrino flavor oscillation where the initial localization of a spinor state implies an interference between positive and negative energy components of mass-eigenstate wave packets. A satisfactory description of fermionic particles requires the use of the Dirac equation as evolution equation for the mass-eigenstates. In this context, a new flavor conversion formula can be obtained when the effects of chiral oscillation are taken into account. Our study leads to the conclusion that the fermionic nature of the particles, where chiral oscillations and the interference between positive and negative frequency components of mass-eigenstate wave packets are implicitly assumed, modifies the standard oscillation probability. Nevertheless, for ultra-relativistic particles and sharply peaked momentum distributions, we can analytically demonstrate that these modifications introduce correction factors proportional to (m12/p0) square which are practically un-detectable by any experimental analysisComment: 16 pages, 2 figure

Digital Start-Up Ecosystems: A Systematic Literature Review and Model Development for South Africa

Digital start-ups play a crucial role in boosting the economies of many countries through technological innovations. Several studies have been conducted assessing digital start-ups or digital entrepreneurship, mainly from the perspective of the Global North. However, gaps exist in the literature regarding digital ecosystems, especially in the context of developing countries (the Global South), such as South Africa. This study fills this gap by exploring the structure as well as highlighting the hindering factors of the start-up ecosystem in South Africa. In addition, the study explores the influential factors of the digital start-up ecosystem and models that can be used to assess upscaling for the growth of new digital start-up ventures. The study conducted a systematic literature review using the PRISMA framework. The Scopus-indexed database was used to source published peer-reviewed papers on digital ecosystems between 2017 and 2023. Key findings of the study pertaining to South Africa’s start-up ecosystem revealed that the country is producing thriving digital start-ups. The current study also identified several challenges that affect the development of digital start-ups in South Africa. Some of the challenges include regulatory barriers, skills shortages, a lack of funding, and a digital infrastructure gap, among others. Furthermore, work is being conducted by ecosystem stakeholders to address these challenges, with a greater collective and cohesive effort needed to effectively address the hindering factors. The study advocates for intervention as well as policy and practitioner implications that could be utilised by ecosystem stakeholders, particularly entrepreneurs in the digital market. The research findings pertain to the South African start-up ecosystem but have greater appeal and relevancy for many developing start-up ecosystems globally, especially in the Global South

Flavor Neutrino Oscillations and Time-Energy Uncertainty Relation

We consider neutrino oscillations as non stationary phenomenon based on Schrodinger evolution equation and mixed states of neutrinos with definite flavors. We show that time-energy uncertainty relation plays a crucial role in neutrino oscillations. We compare neutrino oscillations with $B_{d}^{0}\leftrightarrows\bar B_{d}^{0}$ oscillations.Comment: A report at the 2nd Scandinavian Neutrino Workshop, SNOW 2006, Stockholm, May 2-6, 200

Computational Simulations of the Lateral-Photovoltage-Scanning-Method

The major task for the Lateral-Photovoltage-Scanning-Method is to detect doping striations and the shape of the solid-liquid-interface of an indirect semiconductor crystal. This method is sensitive to the gradient of the charge carrier density. Attempting to simulate the signal generation of the LPS-Method, we are using a three dimensional Finite Volume approach for solving the van Roosbroeck equations with COMSOL Multiphysics in a silicon sample. We show that the simulated LPS-voltage is directly proportional to the gradient of a given doping distribution, which is also the case for the measured LPS-voltage

Diffusion with critically correlated traps and the slow relaxation of the longest wavelength mode

We study diffusion on a substrate with permanent traps distributed with critical positional correlation, modeled by their placement on the perimeters of a critical percolation cluster. We perform a numerical analysis of the vibrational density of states and the largest eigenvalue of the equivalent scalar elasticity problem using the method of Arnoldi and Saad. We show that the critical trap correlation increases the exponent appearing in the stretched exponential behavior of the low frequency density of states by approximately a factor of two as compared to the case of no correlations. A finite size scaling hypothesis of the largest eigenvalue is proposed and its relation to the density of states is given. The numerical analysis of this scaling postulate leads to the estimation of the stretch exponent in good agreement with the density of states result.Comment: 15 pages, LaTeX (RevTeX

Virtual slides in peer reviewed, open access medical publication

<p>Abstract</p> <p>Background</p> <p>Application of virtual slides (VS), the digitalization of complete glass slides, is in its infancy to be implemented in routine diagnostic surgical pathology and to issues that are related to tissue-based diagnosis, such as education and scientific publication.</p> <p>Approach</p> <p>Electronic publication in Pathology offers new features of scientific communication in pathology that cannot be obtained by conventional paper based journals. Most of these features are based upon completely open or partly directed interaction between the reader and the system that distributes the article. One of these interactions can be applied to microscopic images allowing the reader to navigate and magnify the presented images. VS and interactive Virtual Microscopy (VM) are a tool to increase the scientific value of microscopic images.</p> <p>Technology and Performance</p> <p>The open access journal Diagnostic Pathology <url>http://www.diagnosticpathology.org</url> has existed for about five years. It is a peer reviewed journal that publishes all types of scientific contributions, including original scientific work, case reports and review articles. In addition to digitized still images the authors of appropriate articles are requested to submit the underlying glass slides to an institution (DiagnomX.eu, and Leica.com) for digitalization and documentation. The images are stored in a separate image data bank which is adequately linked to the article. The normal review process is not involved. Both processes (peer review and VS acquisition) are performed contemporaneously in order to minimize a potential publication delay. VS are not provided with a DOI index (digital object identifier). The first articles that include VS were published in March 2011.</p> <p>Results and Perspectives</p> <p>Several logistic constraints had to be overcome until the first articles including VS could be published. Step by step an automated acquisition and distribution system had to be implemented to the corresponding article. The acceptance of VS by the reader is high as well as by the authors. Of specific value are the increased confidence to and reputation of authors as well as the presented information to the reader. Additional associated functions such as access to author-owned related image collections, reader-controlled automated image measurements and image transformations are in preparation.</p> <p>Virtual Slides</p> <p>The virtual slide(s) for this article can be found here: <url>http://www.diagnosticpathology.diagnomx.eu/vs/1232133347629819</url>.</p

Extended Source Diffraction Effects Near Gravitational Lens Fold Caustics

Calculations are presented detailing the gravitational lens diffraction due to the steep brightness gradient of the limb of a stellar source. The lensing case studied is the fold caustic crossing. The limb diffraction signal greatly exceeds that due to the disk as a whole and should be detectable for white dwarf sources in our Galaxy and it's satellites with existing telescopes. Detection of this diffraction signal would provide an additional mathematical constraint, reducing the degeneracy among models of the lensing geometry. The diffraction pattern provides pico-arcsecond resolution of the limb profile.Comment: 19 pages including 17 figures, Accepted for publication in ApJ, Minor conceptual change from previous versio

An Analytic Approach to the Wave Packet Formalism in Oscillation Phenomena

We introduce an approximation scheme to perform an analytic study of the oscillation phenomena in a pedagogical and comprehensive way. By using Gaussian wave packets, we show that the oscillation is bounded by a time-dependent vanishing function which characterizes the slippage between the mass-eigenstate wave packets. We also demonstrate that the wave packet spreading represents a secondary effect which plays a significant role only in the non-relativistic limit. In our analysis, we note the presence of a new time-dependent phase and calculate how this additional term modifies the oscillating character of the flavor conversion formula. Finally, by considering Box and Sine wave packets we study how the choice of different functions to describe the particle localization changes the oscillation probability.Comment: 16 pages, 7 figures, AMS-Te

The Physical Range of Majorana Neutrino Mixing Parameters

If neutrinos are Majorana fermions, the lepton mixing parameter space consists of six mixing parameters: three mixing angles and three CP-odd phases. A related issue concerns the physical range of the mixing parameters. What values should these take so that all physically distinguishable mixing scenarios are realized? We present a detailed discussion of the lepton mixing parameter space in the case of two and three active neutrinos, and in the case of three active and N sterile neutrinos. We emphasize that this question, which has been a source of confusion even among "neutrino" physicists, is connected to an unambiguous definition of the neutrino mass eigenstates. We find that all Majorana phases can always be constrained to lie between 0 and pi, and that all mixing angles can be chosen positive and at most less than or equal to pi/2 provided the Dirac phases are allowed to vary between -pi and pi. We illustrate our results with several examples. Finally, we point out that, in the case of new flavor-changing neutrino interactions, the lepton mixing parameter space may need to be enlarged. We properly qualify this statement, and offer concrete examples.Comment: 16 pages, 2 .eps figures, references added, minor typos correcte