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Quan Cheng

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astro-ph.HE astro-ph.SR Computer Vision hep-ph Machine Learning

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preprint2026arXiv

Exploring Superfluid Angular Momentum Reservoir Effect on Pulsar Glitches and Forecasting Next Glitches of the Crab Pulsar

Pulsar glitches are generally viewed as stochastic events driven by sudden angular momentum transfer from the neutron star's superfluid interior to its crust. Except two peculiar pulsars with quasi-periodic glitches, this stochastic view has prevailed. Here, by clustering temporally proximate small glitches of the Crab pulsar, we uncover clear evidence of an underlying quasi-periodic modulation, challenging the paradigm of purely random behavior. Furthermore, our correlation analyses reveal a strong positive relationship between glitch cluster size and waiting time since the preceding clusters. These findings demonstrate the effect of angular momentum reservoir operating over long-term scales and enable the predictions of next glitching window. Remarkably, two minor glitches detected in July and August 2025, which align with our initial prediction made in June, should be confirmed as the onset of this predicted activity. Inspired by the initial success, we forecast the occurrence of a major glitch from now until August 2026, with possible glitch size up to a relative change in rotational frequency of $697.2 \times 10^{-9}$. Physically, the observed long-term quasi-periodicity and cluster size-waiting time correlations imply that each glitch event releases only a fraction of the stored superfluid angular momentum. This partial-release mechanism provides a unified framework for both stochastic and quasi-periodic glitch behaviors across different pulsars, underscoring the universality of the superfluid angular momentum reservoir effect. As the most intensively monitored object, the Crab pulsar serves as a natural laboratory for studying angular momentum inside neutron stars.

preprint2026arXiv

Stable Routing for Mixture-of-Experts in Class-Incremental Learning

Class-incremental learning (CIL) requires models to learn new classes sequentially while preserving prior knowledge. Recently, approaches that combine pre-trained models with mixture-of-experts (MoE) have received increasing attention in CIL: they typically expand experts during learning and employ a router to assign weights across experts. However, existing MoE methods often overlook routing drift induced by expert expansion. Once new experts are introduced, the router may reassign samples from earlier classes to newly added experts, thereby perturbing previously established expert compositions and causing interference even when old experts remain frozen. We argue that expandable MoE in CIL requires two complementary properties: stable old-class routing for knowledge preservation and sufficient capacity utilization for new-class adaptation. To this end, we propose Stable Routing for MoE (StaR-MoE), a routing-level framework for expandable MoE in CIL. By incorporating sensitivity-aware routing alignment, StaR-MoE aligns current old-class routing behavior with historical routing distributions through sensitivity-guided constraints. Complementarily, StaR-MoE introduces asymmetric capacity regularization to encourage effective utilization of the expanded expert pool without compromising class-specific routing specialization. Extensive experiments across four standard CIL benchmarks demonstrate that StaR-MoE consistently improves both average and last accuracy over state-of-the-art methods, highlighting the importance of stable routing.

preprint2015arXiv

Stochastic gravitational wave background from magnetic deformation of newly born magnetars

Newly born magnetars are promising sources for gravitational wave (GW) detection due to their ultra-strong magnetic fields and high spin frequencies. Within the scenario of a growing tilt angle between the star's spin and magnetic axis, due to the effect of internal viscosity, we obtain improved estimates of the stochastic gravitational wave backgrounds (SGWBs) from magnetic deformation of newly born magnetars. We find that the GW background spectra contributed by the magnetars with ultra-strong toroidal magnetic fields of 10^{17} G could roughly be divided into four segments. Most notably, in contrast to the background spectra calculated by assuming constant tilt angles χ=π/2, the background radiation above 1000 Hz are seriously suppressed. However, the background radiation at the frequency band \sim100-1000 Hz are moderately enhanced, depending on the strengths of the dipole magnetic fields. We suggest that if all newly born magnetars indeed have toroidal magnetic fields of 10^{17} G, the produced SGWBs should show sharp variations with the observed frequency at several tens to about 100 hertz. If these features could be observed through sophisticated detection of the SGWB using the proposed Einstein Telescope, it will provide us a direct evidence of the tilt angle evolutions and further some deep understandings about the properties of newly born magnetars.

preprint2014arXiv

How can newly born rapidly rotating neutron stars become magnetars?

In a newly born (high-temperature and Keplerian rotating) neutron star, r-mode instability can lead to stellar differential rotation, which winds the seed poloidal magnetic field ($\sim 10^{11}$ G) to generate an ultra-high ($\sim 10^{17}$ G) toroidal field component. Subsequently, by succumbing to the Tayler instability, the toroidal field could be partially transformed into a new poloidal field. Through such dynamo processes, the newly born neutron star with sufficiently rapid rotation could become a magnetar on a timescale of $\sim 10^{2-3}$ s, with a surface dipolar magnetic field of $\sim10^{15}$ G. Accompanying the field amplification, the star could spin down to a period of $\sim5$ ms through gravitational wave radiation due to the r-mode instability and, in particular, the non-axisymmetric stellar deformation caused by the toroidal field. This scenario provides a possible explanation for why the remnant neutron stars formed in gamma-ray bursts and superluminous supernovae could be millisecond magnetars.

preprint2013arXiv

Could strange stars be in the color-flavor-locked phase: Tested by their thermal evolutions

The thermal evolution of strange stars in both normal and color-flavor-locked (CFL) phases are investigated together with the evolutions of the stellar rotation and the r-mode instability. The heating effects due to the deconfinement transition of the stellar crust and the dissipation of the r-modes are considered. As a result, the cooling of the stars in the normal phase is found to be not very different from the standard one. In contrast, for the stars in the CFL phase, a big bump during the first hundred years and a steep decay ($\sim$7% in ten years) at the ages of $\sim10^{4-6}$ yrs are predicted in their thermal evolution curves. These unique features provide an effective observational test for determining whether or not the CFL phase is reached in strange stars. This thermal test method is independent of and complementary to the rotational test method, which is a direct consequence of the r-mode instability.