arXiv subjects

Dean Miller

Publications and source records attributed to Dean Miller.

4 recordsLinked to original sources

arXiv2026

Ephemeris Refinement for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b with Small Telescope and TESS Observations

We present updated transit timing measurements for three hot Jupiters (Qatar-4 b, HAT-P-18 b, and CoRoT-1 b) by leveraging data collected from the MicroObservatory Telescope Network, a network of small, robotic ground-based telescopes, and the NASA Transiting Exoplanet Survey Satellite (TESS). By combining these data with archival published results, we present the most precise orbital solutions to date for all three systems, allowing for precise transit time predictions for future missions. We report an updated mid-transit time for Qatar-4 b of 2458919.5838 $\pm$ 0.000089 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.80536560 $\pm$ 0.00000021 days. For HAT-P-18 b, we find a mid-transit time of 2459743.85340 $\pm$ 0.000022 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 5.50802957 $\pm$ 0.00000012 days. For CoRoT-1 b, we report a mid-transit time of 2456268.99083 $\pm$ 0.000099 $\mathrm{BJD}_{\mathrm{TDB}}$ and an updated orbital period of 1.50896846 $\pm$ 0.000000071 days. Our results demonstrate improvements over recently published ephemerides, with reductions of 36.4%, 4.35%, and 17.5% in mid-transit time uncertainties and 65.0%, 77.4%, and 16.9% in orbital period uncertainties for Qatar-4 b, HAT-P-18 b, and CoRoT-1 b, respectively. The results of this study improve the precision of future transit predictions and demonstrate the value of coordinated small-telescope monitoring (and citizen science initiatives) when updating the orbital parameters of hot Jupiters.

astro-ph.EP↗

arXiv2022

Morphological Evolution of NMC Secondary Particles Through in situ electrochemical FIB/SEM experiment

Microstructural evolution of NMC secondary particles during the battery operation drives the electrochemical performance and impacts the Li-ion battery lifetime. In this work, we develop an in situ methodology using the FIB/SEM instrument to cycle single secondary particles of NMC active materials while following the modifications of their 3D morphology. Two types of secondary particles, i.e. low and high gradient NMC, were studied alongside morphological investigations in both pristine state and different number of cycles. The quantification of initial inner porosity and cracking evolution upon electrochemical cycling reveals a clear divergence depending on the type of gradient particles. An unexpected enhancement of the discharge capacity is observed during the first cycles concurrently to the appearance of inner cracks. At the first stages, impedance spectroscopy shows a charge transfer resistance reduction that suggests a widening of the crack network connected to the surface, which leads to an increase of contact area between liquid electrolyte and NMC particle. 3D microstructure of individual secondary particles after in situ cycles were investigated using FIB/SEM and nano-XCT. The results suggest a strong impact of the initial porosity shape on the degradation rate.

physics.chem-ph↗

arXiv1994

Finite-element quantum electrodynamics. II. Lattice propagators, current commutators, and axial-vector anomalies

We apply the finite-element lattice equations of motion for quantum electrodynamics given in the first paper in this series to examine anomalies in the current operators. By taking explicit lattice divergences of the vector and axial-vector currents we compute the vector and axial-vector anomalies in two and four dimensions. We examine anomalous commutators of the currents to compute divergent and finite Schwinger terms. And, using free lattice propagators, we compute the vacuum polarization in two dimensions and hence the anomaly in the Schwinger model. A discussion of our choice of gauge-invariant current is provided.

hep-ph↗

arXiv1993

Finite-Element Quantum Electrodynamics

We apply the finite-element lattice equations of motion for quantum electrodynamics to an examination of anomalies in the current operators. By taking explicit lattice divergences of the vector and axial-vector currents we compute the vector and axial-vector anomalies in two and four dimensions. We examine anomalous commutators of the currents to compute divergent and finite Schwinger terms. And, using free lattice propagators, we compute the vacuum polarization in two dimensions and hence the anomaly in the Schwinger model. (To appear in the Proceedings of the International Europhysics Conference on High Energy Physics, Marseille, July 22-28, 1993.)

hep-ph↗