arXiv subjects

John Belz

Publications and source records attributed to John Belz.

4 recordsLinked to original sources

arXiv2022

Boundary dynamics in competing critical black hole formation

Expanding upon our previous study of competing critical phenomena in black hole formation, we numerically investigate the behavior of dominant exponents across the boundary separating asymptotically dispersing and collapsing regions in a two-dimensional configuration space of initial data. We find that across the Type II boundary section the dominant exponent remains constant, equal to the reciprocal of Choptuik's well-known quasi-universal value, whereas across the Type I section the exponent noticeably varies. We postulate that this change reflects the existence of a third critical solution in addition to the two primary competing solutions, possibly another member of the family of metastable soliton stars constituting the Type I attractor.

gr-qc↗

arXiv2020

Investigation into Length Scale Dominance in Critical Black Hole Formation

The critical formation of low-mass black holes is a historical cornerstone of numerical General Relativity, with important implications in cosmology for censorship conjectures and the production of primordial black holes (PBHs). Concurrent with the surge in black hole observational physics in recent years has been an increased interest in these subjects. Critical formation is often suggested as a mechanism for PBH production, but it is possible that the existence of different types of critical processes potentially accompanying more realistic scenarios may affect this conclusion more than has been considered thus far. This paper numerically investigates, as a toy model, the interplay of multiple near-critical fields in the collapse of spherically symmetric scalar fields. It is found that a combination of type~I and type~II near-critical fields results in a kind of competition between their respective critical evolutions and propose. A heuristic explanation for this phenomenon is given employing ideas from the theory of dynamical systems.

gr-qc↗

arXiv2019

Depth of maximum of air-shower profiles: testing the compatibility of measurements performed at the Pierre Auger Observatory and the Telescope Array experiment

At the Pierre Auger Observatory and the Telescope Array, the measurements of depths of maximum of air-shower profiles, $X_\mathrm{max}$, are performed using direct observations of the longitudinal development of showers with the help of the fluorescence telescopes. Though the same detection technique is used at both installations, the straightforward comparison of the characteristics of the measured $X_\mathrm{max}$ distributions is not possible due to the different approaches to the analysis of the recorded events. In this work, the Auger-Telescope Array composition working group presents a technique to compare the $X_\mathrm{max}$ measurements from the Auger Observatory and the Telescope Array. Applying this technique the compatibility of the first two moments of the measured $X_\mathrm{max}$ distributions is qualitatively tested for energies $10^{18.2}~{\rm eV} < E < 10^{19.0}~{\rm eV}$ using the recently published Telescope Array data from the Black Rock Mesa and Long Ridge fluorescence detector stations. For a quantitative comparison, simulations of air showers with EPOS-LHC, folded with effects of the Telescope Array detector, are required along with the inclusion in the analysis of the systematic uncertainties in the measurements of $X_\mathrm{max}$ and the energies of the events.

astro-ph.HE↗

arXiv1999

Study of the Decays KL -> pi+ pi- gamma and KL -> pi+ pi- e+ e- at KTeV

We present new results on the related rare KL decay modes KL -> pi+ pi- gamma and KL -> pi+ pi- e+ e-. KTeV has performed the first direct measurement of the form factor for the "direct emission" component of KL -> pi+ pi- gamma decays, a quantity with ramifications for particular chiral models. In addition, the form factor and direct emission/inner bremsstrahlung branching ratio - also presented here - are important input parameters for the understanding of the planar-angle distribution of KL -> pi+ pi- e+ e- decays. Preliminary results indicating the presence of a T-violating asymmetry in the KL -> pi+ pi- e+ e- angular distribution are presented.

hep-ex↗