4 papers
Boundary Completion of Vacuum Persistence Probability
Yu Zhou, Hai-Qing Zhang
The vacuum persistence probability, encoded in the imaginary part of the in-out effective action, is a basic measure of vacuum instability and particle production. However, its eva…
On the Imaginary Part of the Effective Action in de Sitter Spacetime with Different Regularization Schemes
Yu Zhou, Hai-Qing Zhang
The imaginary part of the effective action encodes vacuum instability and particle production in the background field. Two standard approaches are commonly used to derive it: the B…
Effective Action and Gravitational Pair Production in (A)dS Spacetime
Yu Zhou, Hai-Qing Zhang
We compute the effective action for a massive scalar field in (A)dS spacetime using the Euclidean heat kernel method. We highlight that in even-dimensional dS spacetimes, the effec…
Is a photon ring invariably a closed structure?
Xiangyu Wang, Xiaobao Wang, Hai-Qing Zhang +1
In this study, we investigate the image of a rotating compact object (CO) illuminated by a geometrically thin, optically thin disk on the equatorial plane. As the radius of the CO'…