arXiv subjects

Christopher L. Duston

Publications and source records attributed to Christopher L. Duston.

6 recordsLinked to original sources

arXiv2026

Using Gemini and LuaLaTeX to transcribe physics videos into PDF/UA-2 and ISO 32005 math-accessible PDFs

We present an AI transcription workflow that uses freely available tools to transcribe instructional physics videos with substantial mathematical content into math-accessible PDFs. Guided by our carefully crafted system instructions, Google Gemini transcribes linked or uploaded videos into LaTeX output. Importantly, all board-written or screen-presented equations are transcribed into LaTeX math and incorporated into the verbal flow or presented in descriptive segments, which also describe graphs, diagrams, and pedagogically important actions and interactions. Gemini's LaTeX output is appended to a prewritten SE tagging-enabled preamble and compiled by a LuaLaTeX engine; the resulting PDF transcripts routinely compile without errors and pass PDF/UA-2 and ISO 32005 validation tests. We provide a balanced performance assessment using numerous examples from test transcriptions. The publicly available supplementary resources contain complete transcripts corresponding to all presented examples, and also contain our well-tested system instructions and preamble so that others can use, adapt, study, and further develop our transcription framework.

physics.ed-ph↗

arXiv2026

Size, shape, density, and atmospheric limit of (50000) Quaoar revealed from 14 years of stellar occultation

We present results from 28 stellar occultations by the large Trans-Neptunian Object (50000) Quaoar registered between 2018 and 2025. By performing a joint analysis of this occultation data-set, along with other 9 published events, we were able to fit an oblate ellipsoid shape, with equatorial semi-axes, a and b of 566.1+2.5-2.2 km, and a polar semi-axis, c, of 511.2+3.6-3.7 km. It provides an equivalent volumetric diameter of 1094.4 +/- 4.6 km and polar oblateness of 0.097 +/- 0.011. Considering an absolute magnitude of H = 2.79 +/- 0.35, we derive a geometric albedo of pV = 0.125 +/- 0.038. We have derived new upper limits to the surface pressure of a CH4 atmosphere of 0.15 nbar (1-sigma) and 0.65 nbar (3-sigma). We also provide a table with the 36 new astrometric positions for Quaoar. Using the new system mass derived from Weywot's orbit around Quaoar, we calculated a density of 1.760 +/- 0.109 g/cm3. Moreover, from the derived size and rotation period (8.8394 +/- 0.0002 hours (Ortiz et al. 2003)), we calculate that, if Quaoar is in Maclaurin hydrostatic equilibrium state, it would have a density of 1.859 +/- 0.200 g/cm3. This result, within the error bars, is compatible with the value we found. Therefore, this work shows that Quaoar can be a Maclaurin object, being eligible as a dwarf planet.

astro-ph.EP↗

arXiv2025

The 2017 Merrimack College Mobile Lightboard: Personalized Office-Based Lightboarding on a Shared Mobile Board

We present and evaluate the Merrimack College Mobile Lightboard, which we built in 2017 and which is still in use in 2025. Our design was closely based on that of the groundbreaking 2014 Duke University Lightboard but with a smaller glass pane, 5 feet wide instead of 6 feet wide. The resulting scaled-down board is small enough to move in and out of individual faculty offices, but large enough to make detailed videos. An updated construction cost estimate is provided, and recent upgrades are briefly discussed. We believe that personalized office-based lightboarding represents an attractive option for many faculty members, with strengths that complement those of centralized installations. Our successful build suggests that this option is technically and financially feasible at many if not most higher education institutions.

physics.ed-ph↗

arXiv2015

Using Cosmic Strings to Relate Local Geometry to Spatial Topology

In this paper we will discuss how cosmic strings can be used to bridge the gap between the local geometry of our spacetime model and the global topology. The primary tool is the theory of foliations and surfaces, and together with observational constraints we can isolate several possibilities for the topology of the spatial section. This implies that the discovery of cosmic strings would not just be significant for an understanding of structure formation in the early universe, but also for the global properties of the spacetime model.

math-ph↗

arXiv2013

Semiclassical Partition Functions for Gravity with Cosmic Strings

In this paper we describe an approach to construct semiclassical partition functions in gravity which are complete in the sense that they contain a complete description of the differentiable structures of the underlying 4-manifold. In addition, we find our construction naturally includes cosmic strings. We discuss some possible applications of the partition functions in the fields of both quantum gravity and topological string theory

gr-qc↗

arXiv2012

Topspin Networks in Loop Quantum Gravity

We discuss the extension of loop quantum gravity to topspin networks, a proposal which allows topological information to be encoded in spin networks. We will show that this requires minimal changes to the phase space, C*-algebra and Hilbert space of cylindrical functions. We will also discuss the area and Hamiltonian operators, and show how they depend on the topology. This extends the idea of "background independence" in loop quantum gravity to include topology as well as geometry. It is hoped this work will confirm the usefulness of the topspin network formalism and open up several new avenues for research into quantum gravity.

gr-qc↗