arXiv subjects

Hongxing Chen

Publications and source records attributed to Hongxing Chen.

At least 19 recordsLinked to original sources

arXiv2026

Bounded $t$-structures on the category of strongly bounded objects

Strongly bounded objects in a weakly approximable triangulated category are known to relate closely to global dimension and to play a significant role in the uniqueness problem for triangulated enhancements. In this paper, we investigate when the full subcategory of strongly bounded objects admits a bounded $t$-structure. Our main result, under a finiteness condition termed the finite strong finitistic dimension, states that this happens exactly when the subcategory agrees with the full subcategory of bounded objects in the ambient triangulated category. In that case, the bounded $t$-structure is unique up to equivalence; even more, the uniqueness holds unconditionally on the full subcategory of bounded objects.

math.RT↗

arXiv2026

The GASKAP-HI Survey towards the Magellanic Clouds: Cold Atomic Gas Survival and Evolution in the Large Magellanic Cloud

We use atomic hydrogen (HI) absorption detections from the GASKAP-HI survey to investigate the properties of cold atomic gas in the Large Magellanic Cloud (LMC). Using the radiative transfer method, we decompose 155 sightlines into 330 cold neutral medium (CNM), 2 thermally unstable neutral medium (UNM), and 310 warm neutral medium (WNM) components. We find that the CNM in the LMC exhibits higher optical depths (median 0.46), lower spin temperatures (median $\sim$37 K), broader linewidths (median $\sim$4.9 km s$^{-1}$), and slightly lower CNM fractions (median $\sim$23%) than in the Milky Way. We examine the connection between the CNM, molecular gas, and star formation, finding that CNM correlates more closely with molecular gas than WNM, while molecular gas shows a tighter relation with star formation. Molecular hydrogen (H$_2$) formation begins near $N{_\mathrm{HI,CNM}}\sim10^{20}~\mathrm{cm^{-2}}$, and nearly all sightlines with $N_{\mathrm{HI,CNM}}>10^{21}~\mathrm{cm^{-2}}$ contain molecular gas. The CNM fraction increases with visual extinction ($A_V$), and the LMC maintains CNM fractions comparable to those in the Milky Way at substantially lower $A_V$, likely due to higher local densities and a longer line-of-sight depth. Sightlines near expanding shells tend to show higher CNM fractions, although this is partly driven by higher total HI column densities. Finally, the CNM kinematics generally follow the HI disk rotation, with about 7% of components showing velocity offsets greater than $25~\mathrm{km~s^{-1}}$, likely tracing inflows or outflows driven by stellar feedback or large-scale interactions within the Magellanic System.

astro-ph.GA↗

arXiv2026

ICME 2026 Grand Challenge on Cross-Scenario Defect Detection and Fine-Grained Severity Grading for High-Precision Manufacturing

This paper presents the IEEE International Conference on Multimedia and Expo (ICME) 2026 Grand Challenge on Cross-Scenario Defect Detection and Fine-Grained Severity Grading for High-Precision Manufacturing. The challenge is motivated by two key limitations of existing industrial defect inspection systems: (1) current deep learning-based methods often suffer significant performance degradation when deployed in unseen production scenarios, and (2) most benchmarks neglect severity-aware assessment, which is critical for risk control and yield optimization. To address these limitations, we design two complementary tracks: Track 1 (Cross-Scenario Defect Detection) targets accurate defect detection, localization, and classification across diverse unseen production environments; Track 2 (Fine-Grained Severity Grading) requires assigning each detected defect an industry-standard severity level, including Acceptable, Marginal NG, NG, and Gross NG. We construct a large-scale industrial dataset of high-resolution microscopic images spanning seven representative defect categories, comprising over 3,800 images with pixel-level instance annotations for Track 1 and over 2,600 images with severity-grade labels for Track 2. The challenge attracted 86 registered participants with 130 submissions; during the final testing phase, 21 teams submitted results and 12 teams provided models with technical reports. The resulting benchmark, together with the diverse and effective solutions contributed by participating teams, sets a new standard for industrial defect analysis research.

cs.CV↗

arXiv2026

Finiteness of homological dimensions in triangulated categories

In a general triangulated category, the finiteness of the finitistic dimension serves as a prerequisite for a categorical obstruction, via the singularity category, to the existence of bounded $t$-structures. In this paper, we investigate the finitistic, big finitistic, and global dimensions, and establish explicit inequalities that relate these dimensions of the middle category in a recollement of triangulated categories to those of the outer categories. This provides a unified framework for extending some known results on the homological dimensions of ordinary rings to weakly approximable triangulated categories.

math.RT↗

arXiv2026

Quasi-projective dimensions of complexes over rings

Quasi-projective dimension of modules over associative rings is generalized in this paper to the one of complexes of modules. Basic properties of this dimension are established, including a comparison result with projective dimension and a derived Auslander-Buchsbaum formula for complexes of finite quasi-projective dimension. Several sufficient conditions are provided for a commutative noetherian local ring to be a complete intersection under the assumption that each finitely generated module has finite quasi-projective dimension. This provides some positive answers to an open question on quasi-projective dimension proposed by Gheibi-Jorgensen-Takahashi. Moreover, the behavior of quasi-projective dimension under taking the quotient of a commutative ring modulo a regular sequence is investigated, and some partial results toward the change-of-rings question on quasi-projective dimension are given.

math.RA↗

arXiv2025

The Local Group L-band Survey: Probing Cold Atomic Gas in IC10 with Neutral Hydrogen Absorption

We present the first localized detections of the cold neutral medium (CNM) in IC10, offering a rare view of dense atomic gas in a low-metallicity (0.27 solar metallicity) dwarf galaxy. As a low-metallicity starburst, IC10's interstellar medium conditions could reflect small-scale physical conditions that mirror those of early galaxies, providing a unique window into the heating and cooling processes that shaped the interstellar medium in early-Universe environments. Leveraging the high angular (<5'' ~ 15pc) and spectral (0.4 km/s) resolution of the Local Group L-band Survey, we searched for HI absorption against nine continuum radio sources and detected absorption along three sightlines corresponding to internal radio emission sources within IC10. Using Gaussian decomposition and radiative transfer, we characterize the CNM, deriving spin temperatures of ~30-55 K, column densities of (0.6-3.0)x 1$0^{21}$ cm$^{-2}$, cold HI fractions of ~ 21-37%, and line widths of ~ 5.6-13.6 km/s. For each individual detection of HI absorption, we find corresponding molecular emission from 12CO (J=1-0), HCO+ (J=1-0), and HCN (J=1-0) at similar velocities and with comparable linewidths, indicating a well-mixed cold atomic and molecular medium. In IC10, the CNM shows a clear kinematic connection to the high-density ISM, implying a stronger dynamical coupling with molecular gas than in the Milky Way, in line with expectations for low-metallicity environments. At the ~ 15 pc scales probed by slightly extended HII regions in IC10, unresolved CNM clouds likely contribute to line blending, so the observed broad HI linewidths may partly reflect spatial and kinematic averaging.

astro-ph.GA↗

arXiv2025

Properties of quasi-projective dimension over abelian categories

Quasi-projective dimension was introduced by Gheibi, Jorgensen and Takahashi to generalize the Auslander-Buchsbaum formula and the depth formula in commutative algebra. In this paper, we establish some basic properties of quasi-projective dimensions of objects in abelian categories. Analogous to global dimension of rings, we also introduce the concept of quasi-global dimension for left Noetherian rings, and then compare quasi-global dimension with global dimension for a class of Nakayama algebras. This provides new examples of finite-dimensional algebras with finite quasi-global dimensions but infinite global dimensions.

math.RA↗

arXiv2025

Virtually Gorenstein algebras of infinite dominant dimension

Motivated by understanding the Nakayama conjecture which states that algebras of infinite dominant dimension should be self-injective, we study self-orthogonal modules with virtually Gorenstein endomorphism algebras and prove the following result: Given a finitely generated, self-orthogonal module over an Artin algebra with an orthogonal condition on its Nakayama translation, if its endomorphism algebra is virtually Gorenstein, then the module is projective. As a consequence, we re-obtain a recent result: the Nakayama conjecture holds true for the class of strongly Morita, virtually Gorenstein algebras. Finally, we show that virtually Gorenstein algebras can be constructed from Frobenius extensions.

math.RT↗

arXiv2025

The Karl G. Jansky Very Large Array Local Group L-band Survey (LGLBS)

We present the Local Group L-Band Survey (LGLBS), a Karl G. Jansky Very Large Array (VLA) survey producing the highest quality 21-cm and 1-2 GHz radio continuum images to date for the six VLA-accessible, star-forming, Local Group galaxies. Leveraging the VLA's spectral multiplexing power, we simultaneously survey the 21-cm line at high 0.4 km/s velocity resolution, the 1-2 GHz polarized continuum, and four OH lines. For the massive spiral M31, the dwarf spiral M33, and the dwarf irregular galaxies NGC6822, IC10, IC1613, and the Wolf-Lundmark-Melotte Galaxy (WLM), we use all four VLA configurations and the Green Bank Telescope to reach angular resolutions of $< 5''$ ($10{-}20$~pc) for the 21-cm line with $<10^{20}$~cm$^{-2}$ column density sensitivity, and even sharper views ($< 2''$; $5{-}10$~pc) of the continuum. Targeting these nearby galaxies ($D\lesssim1$ Mpc) reveals a sharp, resolved view of the atomic gas, including 21-cm absorption, and continuum emission from supernova remnants and HII regions. These datasets can be used to test theories of the abundance and formation of cold clouds, the driving and dissipation of interstellar turbulence, and the impact of feedback from massive stars and supernovae. Here, we describe the survey design and execution, scientific motivation, data processing, and quality assurance. We provide a first look at and publicly release the wide-field 21-cm HI data products for M31, M33, and four dwarf irregular targets in the survey, which represent some of the highest physical resolution 21-cm observations of any external galaxies beyond the LMC and SMC.

astro-ph.GA↗

arXiv2025

A neutral hydrogen absorption study of cold gas in the outskirts of the Magellanic Clouds using the GASKAP-HI survey

Cold neutral hydrogen (HI) is a crucial precursor for molecular gas formation and can be studied via HI absorption. This study investigates HI absorption in low column density regions of the Small and Large Magellanic Clouds (SMC and LMC) using the Galactic-ASKAP HI (GASKAP-HI) survey, conducted by the Australian Square Kilometer Array Pathfinder (ASKAP). We select 10 SMC directions in the outer regions and 18 LMC directions, with 4 in the outskirts and 14 within the main disk. Using the radiative transfer method, we decompose the emission and absorption spectra into individual cold neutral medium (CNM) and warm neutral medium (WNM) components. In the SMC, we find HI peak optical depths of 0.09-1.16, spin temperatures of ~20-50 K, and CNM fractions of 1-11%. In the LMC, optical depths range from 0.03 to 3.55, spin temperatures from ~10 to 100 K, and CNM fractions from 1% to 100%. The SMC's low CNM fractions likely result from its low metallicity and large line-of-sight depth. Additionally, the SMC's outskirts show lower CNM fractions than the main body, potentially due to increased CNM evaporation influenced by the hot Magellanic Corona. Shell motions dominate the kinematics of the majority of CNM clouds in this study and likely supply cold HI to the Magellanic Stream. In the LMC, high CNM fraction clouds are found near supergiant shells, where thermal instability induced by stellar feedback promotes WNM-to-CNM transition. Although no carbon monoxide (CO) has been detected, enhanced dust shielding in these areas helps maintain the cold HI.

astro-ph.GA↗

arXiv2024

The Local Group L-Band Survey: The First Measurements of Localized Cold Neutral Medium Properties in the Low-Metallicity Dwarf Galaxy NGC 6822

Measuring the properties of the cold neutral medium (CNM) in low-metallicity galaxies provides insight into heating and cooling mechanisms in early Universe-like environments. We report detections of two localized atomic neutral hydrogen (HI) absorption features in NGC 6822, a low-metallicity (0.2 Z$_{\odot}$) dwarf galaxy in the Local Group. These are the first unambiguous CNM detections in a low-metallicity dwarf galaxy outside the Magellanic Clouds. The Local Group L-Band Survey (LGLBS) enabled these detections due to its high spatial (15 pc for HI emission) and spectral (0.4 \kms) resolution. We introduce LGLBS and describe a custom pipeline to search for HI absorption at high angular resolution and extract associated HI emission. A detailed Gaussian decomposition and radiative transfer analysis of the NGC 6822 detections reveals five CNM components, with key properties: a mean spin temperature of 32$\pm$6 K, a mean CNM column density of 3.1$\times$10$^{20}$ cm$^{-2}$, and CNM mass fractions of 0.33 and 0.12 for the two sightlines. Stacking non-detections does not reveal low-level signals below our median optical depth sensitivity of 0.05. One detection intercepts a star-forming region, with the HI absorption profile encompassing the CO (2$-$1) emission, indicating coincident molecular gas and a depression in high-resolution HI emission. We also analyze a nearby sightline with deep, narrow HI self-absorption dips, where the background warm neutral medium is attenuated by intervening CNM. The association of CNM, CO, and H$\alpha$ emissions suggests a close link between the colder, denser HI phase and star formation in NGC 6822.

astro-ph.GA↗

arXiv2024

Environmental effects on satellite galaxies from the perspective of cold gas

Environment plays a pivotal role in shaping the evolution of satellite galaxies. Analyzing the properties related to the cold gas phase of satellites provides insights into unravelling the complexity of environmental effects. We use the hydro-dynamical simulations Illustris TNG and Eagle, and the semi-analytic models (SAMs) GAEA and L-Galaxies, in comparison with recent observations from the Westerbork Synthesis Radio Telescope (WSRT), to investigate the properties of satellite galaxies hosted by halos with mass $M_{200}>10^{12.8}M_\odot$, and within projected regions $\le 1.1$ virial radius $R_{200}$. Generally, satellite galaxies selected from semi-analytic models have more HI than those selected from hydro-dynamical simulations across all projected radii, e.g. more than 30% of satellites in the two hydro-simulations are HI depleted, while this fraction is almost zero in SAMs. Furthermore, both hydro-dynamical simulations and SAMs reproduce the observed decrease of HI content and specific star-formation rate (sSFR) towards the halo centre. However, the trend is steeper in two hydro-dynamical simulations TNG and EAGLE, resulting in a better agreement with the observational data, especially in more massive halos. By comparing the two version of GAEA, we find that the inclusion of ram-pressure stripping of cold gas significantly improves the predictions on HI fractions. The refined hot gas stripping method employed in one of the two L-Galaxies models also yields improved results.

astro-ph.GA↗

arXiv2023

Bounded $t$-structures, finitistic dimensions, and singularity categories of triangulated categories

Recently, Amnon Neeman settled a bold conjecture by Antieau, Gepner, and Heller regarding the relationship between the regularity of finite-dimensional noetherian schemes and the existence of bounded $t$-structures on their derived categories of perfect complexes. In this paper, using different methods, we prove some very general results about the existence of bounded $t$-structures on (not necessarily algebraic or topological) triangulated categories and their invariance under completion. We show that if the opposite category of an essentially small triangulated category has finite finitistic dimension in our sense, then the existence of a bounded t-structure on it forces it to be equal to its completion. We also prove a parallel result regarding the equivalence of all bounded t-structures on any intermediate triangulated category between the starting category and its completion. Our general treatment, when specialized to the case of schemes, immediately gives us Neeman's theorem as an application and significantly generalizes another remarkable theorem by Neeman about the equivalence of bounded $t$-structures on the bounded derived categories of coherent sheaves. When specialized to other cases like associative rings, nonpositive DG-rings, connective $\mathbb{E}_1$-rings, triangulated categories without models, etc., we get many other applications. Under mild finiteness assumptions, these results not only give a categorical obstruction (the singularity category in our sense) to the existence of bounded $t$-structures on a triangulated category, but also provide plenty of triangulated categories on which all bounded $t$-structures are equivalent. The strategy used in our treatment is introducing a new concept of finitistic dimension for triangulated categories and lifting $t$-structures along completions of triangulated categories.

math.RA↗

arXiv2023

Derived equivalences for mirror-reflective algebras

We show that the construction of mirror-reflective algebras inherits derived equivalences of gendo-symmetric algebras. More precisely, suppose A and B are gendo-symmetric algebras with both Ae and Bf faithful projective-injective left ideals generated by idempotents e in A and f in B, respectively. If A and B are derived equivalent, then the mirror-reflective algebras of (A,e) and (B,f) are derived equivalent.

math.RT↗

arXiv2022

Mirror-reflective algebras and Tachikawa's second conjecture

Given an algebra with an idempotent, we introduce two procedures to construct families of new algebras, termed mirror-reflective algebras and reduced mirror-reflective algebras. We then establish connections among these algebras by recollements of derived module categories. In case of given algebras being gendo-symmetric, we show that the (reduced) mirror-reflective algebras are symmetric and provide new methods to construct systematically both higher dimensional (minimal) Auslander-Gorenstein algebras and gendo-symmetric algebras of higher dominant dimensions. This leads to a new formulation of Tachikawa's second conjecture for symmetric algebras in terms of idempotent stratifications.

math.RT↗

arXiv2022

Resolving dualities and applications to homological invariants

Dualities of resolving subcategories of finitely generated modules over Artin algebras are characterized as dualities with respect to Wakamatsu tilting bimodules. By restriction of these dualities to resolving subcategories of finitely generated modules with finite projective or Gorenstein-projective dimensions, Miyashita's duality and Huisgen-Zimmermann's correspondence on tilting modules as well as their Gorenstein version are obtained. Applications include constructing triangle equivalences of derived categories of finitely generated Gorenstein-projective modules and showing the invariance of higher algebraic $K$-groups and semi-derived Ringel-Hall algebras of finitely generated Gorenstein-projective modules under tilting.

math.RA↗

arXiv2022

Homological theory of orthogonal modules

Tachikawa's second conjecture predicts that a finitely generated, orthogonal module over a finite-dimensional self-injective algebra is projective. This conjecture is an important part of the Nakayama conjecture. Our principal motivation of this work is a systematic understanding of finitely generated, orthogonal generators over a self-injective Artin algebra from the view point of stable module categories. As a result, for an orthogonal generator M, we establish a recollement of the M-relative stable categories, describe compact objects of the right term of the recollement, and give equivalent characterizations of Tachikawa's second conjecture in terms of M-Gorenstein categories. Further, we introduce Gorenstein-Morita algebras and show that the Nakayama conjecture holds true for them.

math.RT↗

arXiv2021

Symmetric subcategories, tilting modules and derived recollements

For any good tilting module $T$ over a ring $A$, there exists an $n$-symmetric subcategory $\mathscr{E}$ of a module category such that the derived category of the endomorphism ring of $T$ is a recollement of the derived categories of $\mathscr{E}$ and $A$ in the sense of Beilinson-Bernstein-Deligne. Thus the kernel of the total left-derived tensor functor induced by the tilting module is triangle equivalent to the derived category of $\mathscr{E}$.

math.RT↗