arXiv subjects

Hai-Long Huang

Publications and source records attributed to Hai-Long Huang.

13 recordsLinked to original sources

arXiv2026

A fast deep-learning approach to probing primordial black hole populations in gravitational wave events

Primordial black holes (PBHs), envisioned as a compelling dark matter candidate and a window onto early-Universe physics, may contribute to some of the gravitational-wave (GW) signals detected by the LIGO-Virgo-KAGRA network. Traditional hierarchical Bayesian analysis, which relies on precise GW-event posterior estimates to extract information on potential PBH populations from GW events, becomes computationally demanding for catalogs with a large number of events. Here, we present a fast deep-learning framework, leveraging Transformer and normalizing flows, that maps GW-event posterior samples to joint posterior distributions over the hyperparameters of the PBH population. Our approach yields credible intervals with acceptable accuracy while delivering an order-of-magnitude speedup. These results highlight the potential of deep learning for fast and accurate PBH population studies, and its applicability to next-generation GW detectors when combined with appropriate event-level inference models.

gr-qc↗

arXiv2026

Constraining supermassive primordial black hole clustering with the angular auto-correlation of $z\simeq 6$ quasars

High-redshift quasars provide a direct probe of the origin and environment of the earliest supermassive black holes. We use their angular auto-correlation function at $z\simeq 6$ to test scenarios in which supermassive primordial black holes (SMPBHs) are associated with the observed quasar population. The evolved PBH correlation functions, for both Poisson fluctuations and initial PBH clustering, are projected over the quasar redshift window and compared with the measured angular correlation function using Markov chain Monte Carlo inference. It is observed that for the Poisson model, the posterior favors a small abundance, $f_{\rm PBH}\sim 10^{-3}$, and a supermassive effective mass scale, $m_{\rm PBH}\sim 10^{12}M_\odot$, interpreted here as a scale controlling quasar host-halo formation and clustering, and for the initially clustered model, the data prefer an effective clustering amplitude $ξ_{\rm eff}\simeq 2.1$ and a top-hat boundary scale $r_{\rm cl}\simeq 76\,{\rm Mpc}$, corresponding to weak relative contraction of PBH pairs in comoving coordinates.

astro-ph.CO↗

arXiv2026

Search for primordial black holes from gravitational wave populations using deep learning

Gravitational waves (GWs) signals detected by the LIGO/Virgo/KAGRA collaboration might be sourced (partly) by the merges of primordial black holes (PBHs). The conventional hierarchical Bayesian inference methods can allow us to study population properties of GW events to search for the hints for PBHs. However, hierarchical Bayesian analysis require an analytic population model, and becomes increasingly computationally expensive as the number of sources grows. In this paper, we present a novel population analysis method based on deep learning, which enables the direct and efficient estimation of PBH population hyperparameters, such as the PBH fraction in dark matter, $f_{\rm PBH}$. Our approach leverages neural posterior estimation combined with conditional normalizing flows and two embedding networks. Our results demonstrate that inference can be performed within seconds, highlighting the promise of deep learning as a powerful tool for population inference with an increasing number of GW signals for next-generation detectors.

gr-qc↗

arXiv2025

Influence of supermassive primordial black holes on ultraviolet luminosity of high-redshift galaxies

Recently James Webb Space Telescope (JWST) have observed an excess of luminous galaxies at high redshifts ($z \gtrsim 10$). In this work, we investigate whether supermassive primordial black holes (SMPBHs) can explain it by their influence on the ultraviolet luminosity function (UV LF) of high-redshift galaxies. Through Markov Chain Monte Carlo analysis, we constrain the parameters relevant with SMPBHs against current JWST observational data. The results reveal that SMPBHs with masses $M_{\rm PBH} \sim 10^{6.3\text{-}8.3} M_\odot$, abundances $f_{\rm PBH} \sim 10^{-7}\text{-}10^{-5}$, and sub-Eddington ratios $λ_E \ll 1$ can effectively enhance the bright end of the UV LF, consistent with JWST observations.

astro-ph.GA↗

arXiv2025

Broad primordial power spectrum and $μ$-distortion constraints on primordial black holes

Supermassive black holes (SMBHs) might originate from supermassive primordial black holes (PBHs). However, the hypothesis that these PBHs formed through the enhancement of the primordial curvature perturbations has consistently faced significant challenges due to the stringent constraints imposed by $μ$-distortion in the cosmic microwave background (CMB). In this work, we investigate the impact of non-Gaussianity on $μ$-distortion constraint in the context of broad power spectra. Our results show that, under the assumption of non-Gaussian curvature perturbations, a broad power spectrum may lead to weaker $μ$-distortion constraints compared to the Gaussian cases. Our findings highlight the potential of the broad power spectrum to alleviate the $μ$-distortion constraints on supermassive PBHs under large non-Gaussianity.

astro-ph.CO↗

arXiv2024

Sub-Eddington accreting supermassive primordial black holes explain Little Red Dots

The James Webb Space Telescope (JWST) has uncovered an abundant population of compact, extremely red, and X-ray weak objects at $z\gtrsim4$, knows as ``Little Red Dots" (LRDs). These objects exhibit spectral energy distributions that resemble both active galactic nuclei (AGN) and stellar population templates. However, whether dominated by AGN activity or compact star formation, the high redshifts and masses/luminosities of LRDs, coupled with their significant abundance, present potential challenges to the standard $Λ$CDM model. In this work, we proposes a novel cosmic interpretation of this anomaly, suggesting that these LRDs are likely massive galaxies seeded by supermassive primordial black holes (SMPBHs) came into being in the very early universe. We analyze 434 known LRDs from the 0.54 ${\rm deg}^2$ COSMOS-Web survey and test the hypothesis that they originated from SMPBHs assuming sub-Eddington accretion. According to our result, SMPBHs actually could lead to the existence of more LRDs, even at higher redshifts ($z>8$).

astro-ph.GA↗

arXiv2024

Supermassive primordial black holes for the GHZ9 and UHZ1 observed by the JWST

The high redshift ($z>10$) galaxies GHZ9 and UHZ1 observed by the James Webb Space Telescope (JWST) are very massive and have exceptionally high black hole-to-star mass ratios with the central black hole masses $M\gtrsim 10^7\rm~M_\odot$. In this paper, we explore the possibility that they are seeded by the supermassive primordial black holes (SMPBHs), which came into being in the very early universe, with initial masses $\sim 10^7\rm~M_\odot$. We present the self-similar accretion solutions for SMPBHs, and find that the mass growth of SMPBHs during pregalactic era may be negligible. These SMPBHs, when the redshift $z\lesssim 20$, can accelerate seeding high-redshift galaxies and their baryonic content, and consequently explain the central supermassive black holes (SMBHs) of high-redshift massive galaxies through sub-Eddington accretion. According to our results, SMPBHs actually could lead to the existence of more massive SMBHs at higher redshifts compared to other SMBH seed scenarios, specially SMBHs with masses $M\gtrsim 10^7~\rm M_\odot$ at $z>20$ might only origin from SMPBHs, thus the corresponding observation can serve as a potential probe to PBHs.

astro-ph.GA↗

arXiv2024

High-redshift JWST massive galaxies and the initial clustering of supermassive primordial black holes

In this paper, we show that the initial clustering of supermassive primordial black holes (SMPBHs) beyond a Poisson distribution can efficiently enhance the matter power spectrum, and thus the halo mass function. As a result, the population of initially clustered SMPBHs with $M_{\rm PBH}\sim 10^9M_\odot$ and the fraction of energy density $f_{\rm PBH}\sim 10^{-3}$ (consistent with current constraints on SMPBHs) has the potential to naturally explain high-redshift massive galaxies observed by the James Webb Space Telescope.

astro-ph.CO↗

arXiv2024

On primordial universe in anti-de Sitter landscape

How the spacetime evolved non-perturbatively in a landscape with multiple anti-de Sitter (AdS) vacua, which is theoretically well-motivated, has always been a matter of concern. As a step towards this issue, we perform (3+1)D numerical relativity simulations for the inhomogeneous universe in an AdS landscape, and find that large inhomogeneity of scalar field can develop into not only sphere-like bubbles, but also novel tube-like structures. It is observed that the bubble or tube wall (across the potential barrier) likely inflates as a quasi-dS space, while the different regions separated by the walls are in different AdS vacua and will collapse towards singularity.

gr-qc↗

arXiv2024

Primordial extreme mass-ratio inspirals

The coalescence of stellar-mass primordial black holes (PBHs) might explain some of the gravitation waves (GWs) events detected by LIGO-Virgo-KAGRA. On the other hand, observational hints for supermassive PBHs (SMPBHs) have been accumulated. Thus it can be expected that stellar-mass PBHs might be gravitationally bounded to SMPBHs ($\sim10^{6}-10^9M_\odot$) in the early Universe, and both constituted primordial extreme mass-ratio inspirals (EMRIs). In this work, we initiate the study of the merger rate for primordial EMRIs. The corresponding intrinsic EMRI rate at low redshift may be comparable to that of astrophysical model, $10-10^4$yr$^{-1}$, which the space-based detector LISA has the capability to detect, but significantly raises with redshift. Though equal mass binaries also inevitably form, we find that under certain conditions the primordial EMRIs can be the most prevalent GW sources, and thus potentially a new probe to PBH.

astro-ph.CO↗

arXiv2023

Towards supermassive primordial black holes from inflationary bubbles

The bubbles that nucleated during slow-roll inflation can be supercritical, i.e. their radii are larger than the Hubble horizon of de Sitter spacetime inside the bubble (an inflating baby universe inside it), and thus naturally develop to the supermassive primordial black holes (SMPBHs) with a multi-peaks mass function. In this paper, we further investigate relevant phenomenology. After slow-roll inflation ended, the bubbles may be not only supercritical, but also subcritical. It is showed that it seems unlikely for the subcritical bubbles to collapse to SMPBHs. Theoretically, however, before they collapsed such bubbles might have a probability of up-tunnelling to the supercritical ones and thus contribute to SMPBHs. We present a mechanism for the origin of initial clustering of SMPBHs, which can significantly magnify the merger rate of SMPBH binaries, and show the possibility that the merging of such SMPBH binaries explains recent NANOGrav signal.

astro-ph.CO↗

arXiv2023

Merger rate of supermassive primordial black hole binaries

The probability that the primordial black hole (PBH) binaries formed in the early Universe can be affected by the Hubble expansion of background, which is non-negligible when the number density of PBHs is very low (it is actually this case for supermassive PBHs). In this paper, taking into account the effect of cosmic expansion on the comoving distance of PBH pairs, we worked out the merger rate of PBHs with any extended mass function. The torques by all PBHs and linear density perturbations are also considered. It is found that the merger rate of PBH, $M\gtrsim 10^6M_\odot$, binaries is significantly lower for $f_\text{pbh}\lesssim 0.01$ than expected.

astro-ph.CO↗

arXiv2023

Supermassive primordial black holes in multiverse: for nano-Hertz gravitational wave and high-redshift JWST galaxies

Recently, observational hints for supermassive black holes have been accumulating, which has inspired ones to wonder: Can primordial black holes (PBHs) be supermassive, in particular with the mass $M\gtrsim 10^{9}M_\odot$? A supercritical bubble (with an inflating baby universe inside it) that nucleated during inflation can develop into a PBH in our observable Universe. Here, we find that when the inflaton slowly passes by a neighboring vacuum, the nucleating rate of supercritical bubbles would inevitably attain a peak, so the mass distribution of multiverse PBHs, and the mass of peak can be up to $M\gtrsim 10^{11}M_\odot$. Thus our mechanism naturally provides a primordial origin of supermassive BHs.

gr-qc↗