Probing High Redshift Radiation Fields with Gamma-Ray Absorption

The next generation of gamma-ray telescopes may be able to observe gamma-ray blazars at high redshift, possibly out to the epoch of reionization. The spectrum of such sources should exhibit an absorption edge due to pair-production against UV photons along the line of sight. One expects a sharp drop in the number density of UV photons at the Lyman edge E_{L}. This implies that the universe becomes transparent after gamma-ray photons redshift below E (m_{e}c^2)^{2}/E_{L} 18 GeV. Thus, there is only a limited redshift interval over which GeV photons can pair produce. This implies that any observed absorption will probe radiation fields in the very early universe, regardless of the subsequent star formation history of the universe. Furthermore, measurements of differential absorption between blazars at different redshifts can cleanly isolate the opacity due to UV emissivity at high redshift. An observable absorption edge should be present for most reasonable radiation fields with sufficient energy to reionize the universe. Ly-alpha photons may provide an important component of the pair-production opacity. Observations of a number of blazars at different redshifts will thus allow us to probe the rise in comoving UV emissivity with time.Comment: ApJ accepted version, minor changes. 19 pages, 5 figure

Graded Contractions of Affine Kac-Moody Algebras

The method of graded contractions, based on the preservation of the automorphisms of finite order, is applied to the affine Kac-Moody algebras and their representations, to yield a new class of infinite dimensional Lie algebras and representations. After the introduction of the horizontal and vertical gradings, and the algorithm to find the horizontal toroidal gradings, I discuss some general properties of the graded contractions, and compare them with the In\"on\"u-Wigner contractions. The example of $\hat A_2$ is discussed in detail.Comment: 23 pages, Ams-Te

Decentralized token economy theory (DeTEcT): token pricing, stability and governance for token economies

This paper presents a pioneering approach for simulation of economic activity, policy implementation, and pricing of goods in token economies. The paper proposes a formal analysis framework for wealth distribution analysis and simulation of interactions between economic participants in an economy. Using this framework, we define a mechanism for identifying prices that achieve the desired wealth distribution according to some metric, and stability of economic dynamics. The motivation to study tokenomics theory is the increasing use of tokenization, specifically in financial infrastructures, where designing token economies is in the forefront. Tokenomics theory establishes a quantitative framework for wealth distribution amongst economic participants and implements the algorithmic regulatory controls mechanism that reacts to changes in economic conditions. In our framework, we introduce a concept of tokenomic taxonomy where agents in the economy are categorized into agent types and interactions between them. This novel approach is motivated by having a generalized model of the macroeconomy with controls being implemented through interactions and policies. The existence of such controls allows us to measure and readjust the wealth dynamics in the economy to suit the desired objectives

Production of Pairs of Sleptoquarks in Hadron Colliders

We calculate the cross section for the production of pairs of scalar leptoquarks (sleptoquarks) in a supersymmetric $E_6$ model, at hadron colliders. We estimate higher order corrections by including $\pi^2$ terms induced by soft-gluon corrections. Discovery bounds on the sleptoquark mass are estimated at collider energies of 1.8, 2, and 4 TeV (Tevatron), and 16 TeV (LHC).Comment: 8 pages, REVTEX, (1 fig. available on request), LAVAL-PHY-94-13/McGILL-94-26/SPhT-94-07

On the electrodynamics of moving bodies at low velocities

We discuss the seminal article in which Le Bellac and Levy-Leblond have identified two Galilean limits of electromagnetism, and its modern implications. We use their results to point out some confusion in the literature and in the teaching of special relativity and electromagnetism. For instance, it is not widely recognized that there exist two well defined non-relativistic limits, so that researchers and teachers are likely to utilize an incoherent mixture of both. Recent works have shed a new light on the choice of gauge conditions in classical electromagnetism. We retrieve Le Bellac-Levy-Leblond's results by examining orders of magnitudes, and then with a Lorentz-like manifestly covariant approach to Galilean covariance based on a 5-dimensional Minkowski manifold. We emphasize the Riemann-Lorenz approach based on the vector and scalar potentials as opposed to the Heaviside-Hertz formulation in terms of electromagnetic fields. We discuss various applications and experiments, such as in magnetohydrodynamics and electrohydrodynamics, quantum mechanics, superconductivity, continuous media, etc. Much of the current technology where waves are not taken into account, is actually based on Galilean electromagnetism

The 0.1-200 keV spectrum of the blazar PKS 2005-489 during an active state

The bright BL Lac object PKS 2005-489 was observed by BeppoSAX on November 1-2, 1998, following an active X-ray state detected by RossiXTE. The source, detected between 0.1 and 200 keV, was in a very high state with a continuum well fitted by a steepening spectrum due to synchrotron emission only. Our X-ray spectrum is the flattest ever observed for this source. The different X-ray spectral slopes and fluxes, as measured by various satellites, are consistent with relatively little changes of the peak frequency of the synchrotron emission, always located below 10^{17} Hz. We discuss these results in the framework of synchrotron self-Compton models. We found that for the BeppoSAX observation, the synchrotron peak frequency is between 10^{15} and 2.5x10^{16} Hz, depending on the model assumptions.Comment: 7 pages, 4 figures, accepted for publication in A&

Traumatic urinary bladder rupture: the usefulness of CT cystography

A 38-year-old male presented at the emergency unit with acute abdominal pain and massive hematuria after a fall in the stairs of his home. At physical examination, tenderness was found in the hypogastric area and in both right and left iliac regions. The first radiological investigation performed was ultrasonography (Fig. A). Free liquid was found in the Morisson pouch, in the perihepatic-space and in the perisplenic fossa. The bladder contained blood clots and there was no liquid in the Douglas pouch. Active bleeding was not excluded. Unenhanced and contrast-enhanced CT of the abdomen in arterial, venous and late phase was performed and large amount of intraperitoneal liquid was confirmed but without evident cause (Fig. B). There were no visceral injuries neither skeletal lesion nor vascular lesion. 60 minutes later, an additional cystography phase was performed and revealed a rupture in the superior aspect of the bladder with intraperitoneal spilling of contrast (Fig. C and D). Consequently, the patient was admitted for surgical repair of the bladder defect

Galilei invariant theories. I. Constructions of indecomposable finite-dimensional representations of the homogeneous Galilei group: directly and via contractions

All indecomposable finite-dimensional representations of the homogeneous Galilei group which when restricted to the rotation subgroup are decomposed to spin 0, 1/2 and 1 representations are constructed and classified. These representations are also obtained via contractions of the corresponding representations of the Lorentz group. Finally the obtained representations are used to derive a general Pauli anomalous interaction term and Darwin and spin-orbit couplings of a Galilean particle interacting with an external electric field.Comment: 23 pages, 2 table