arXiv subjects

Hao-Ran Cui

Publications and source records attributed to Hao-Ran Cui.

3 recordsLinked to original sources

arXiv2026

Extraordinary boundary correlations at deconfined quantum critical points

Recent years have seen a growing appreciation for the effects of quantum critical fluctuations on gapless boundary degrees of freedom. Here we consider the boundary dynamics of the non-compact $\mathbb{CP}^{N-1}$ (NCCP$^{N-1}$) model in two spatial dimensions, with $N$ complex boson species coupled to a fluctuating $\mathrm{U}(1)$ gauge field. These models describe quantum phase transitions beyond the Landau paradigm, such as the deconfined quantum critical point between superconducting (SC) and quantum spin Hall (QSH) phases. We show that, in a large-$N$ limit and with the bulk tuned to criticality, boundaries of the NCCP$^{N-1}$ model display logarithmically decaying, or ``extraordinary-log,'' correlations. In particular, when monopole operators exhibit quasi-long-ranged order at the boundary, we find that the extraordinary-log exponent of the NCCP$^{N-1}$ model in the large-$N$ limit is $q=N/4$, signifying a new family of boundary universality classes parameterized by $N$. In the context of the QSH -- SC transition, the quantum critical point inherits helical edge modes from the QSH phase, and this extraordinary-log behavior manifests in their Cooper pair correlations.

cond-mat.str-el↗

arXiv2025

Modeling frequency instability in high-quality resonant experiments

Modern resonant sensing tools can achieve increasingly high quality factors, which correspond to extremely narrow linewidths. In such systems, time-variation of the resonator's natural frequency can potentially impact its ability to accumulate power and its resulting sensitivity. One such example is the Dark SRF experiment, which utilizes superconducting radio frequency (SRF) cavities with quality factors of $Q\sim10^{10}$. Microscopic deformations of the cavity lead to stochastic jittering of its resonant frequency with amplitude 20 times its linewidth. Naively, one may expect this to lead to a large suppression in accumulated power. In this work, we study in detail the effects of frequency instability on high-quality resonant systems, utilizing the Dark SRF experiment as a case study. We show that the timescale of jittering is crucial to determining its effect on power accumulation. Namely, when the resonant frequency varies sufficiently quickly, the system accumulates power as if there were no jittering at all. This implies that the sensitivity of a jittering resonator is comparable to that of a stable resonator. In the case of Dark SRF, we find that jittering only induces a $\sim 10\%$ loss in power. Our results allow the dark-photon exclusion bound from Dark SRF's pathfinder run to be refined, leading to a constraint that is an order of magnitude stronger than previously reported (corresponding to a signal-to-noise ratio which is four orders of magnitude larger). This result represents the world-leading constraint on dark photons over a wide range of masses below $6\,\rm \mu eV$ and translates to the best laboratory-based limits on the photon mass $m_\gamma<2.9\times 10^{-48}\,\rm g$.

physics.ins-det↗

arXiv2024

Hawking Radiation of Nonrelativistic Scalars: Applications to Pion and Axion Production

In studying secondary gamma-ray emissions from Primordial Black Holes (PBHs), the production of scalar particles like pions and axion-like particles (ALPs) via Hawking radiation is crucial. While previous analyses assumed relativistic production, asteroid-mass PBHs, relevant to upcoming experiments like AMEGO-X, likely produce pions and ALPs non-relativistically when their masses exceed 10 MeV. To account for mass dependence in Hawking radiation, we revisit the greybody factors for massive scalars from Schwarzschild black holes, revealing significant mass corrections to particle production rates compared to the projected AMEGO-X sensitivity. We highlight the importance of considering non-relativistic $\pi^0$ production in interpreting PBH gamma-ray signals, essential for determining PBH properties. Additionally, we comment on the potential suppression of pion production due to form factor effects when producing extended objects via Hawking radiation. We also provide an example code for calculating the Hawking radiation spectrum of massive scalar particles.

hep-ph↗