arXiv subjects

Yue-Lin Sming Tsai

Publications and source records attributed to Yue-Lin Sming Tsai.

At least 19 recordsLinked to original sources

arXiv2026

A Common $\sim$55 GeV Inelastic Dark Matter Origin of the LZ, Fermi-LAT, and AMS-02 Excesses and Paleo-Detector Prospects

We investigate the 248~keV nuclear recoil excess reported by LUX-ZEPLIN (LZ) in a leptophobic inelastic dark matter framework, in which the mass splitting naturally suppresses low-energy recoils. We find two viable branches, including the endothermic solution with a high dark matter mass $m_χ\gtrsim400$~GeV and the exothermic one with a mass of tens GeV. Remarkably, the exothermic dark matter scenario with $m_χ\sim55$~GeV can simultaneously account for the LZ excess, the Galactic Center GeV gamma-ray excess, and the AMS-02 antiproton excess. The favored annihilation cross-section is slightly below the one required for the observed relic abundance, resulting in an overabundant relic in the minimal setup. An additional neutrino-portal mediator can provide the required depletion while leaving the gamma-ray and antiproton signals essentially unchanged. We further show that paleo-detectors provide a powerful probe of the inelastic interpretation, requiring exposures of $\sim10$ and $\sim100$~mg Gyr for the endothermic and exothermic scenarios, respectively.

hep-ph↗

arXiv2026

Raising the Optical Depth to Reionization with Dark Matter Decay

DESI DR2 baryon acoustic oscillation measurements have sharpened a discrepancy with cosmic microwave background (CMB) inferences that can be recast as a preference for a reionization optical depth of $τ_{\rm reio}\simeq 0.09$, well above the $\simeq 0.06$ inferred from large-scale CMB polarization measurements. Here we test whether electromagnetic energy injection from dark matter (DM) decaying through $χ\rightarrow e^{+}e^{-}$ can provide this additional optical depth. Adopting a Gompertzian model for astrophysical reionization, which provides an asymmetric, simulation-calibrated description of cosmic reionization, we derive $τ_{\rm reio}$ self-consistently from the evolution of the free-electron fraction, including the contribution from DM decay. We jointly constrain cosmological and reionization parameters and the DM decay rate using ACT+Planck CMB temperature and polarization anisotropies, CMB lensing, BAO measurements, and quasar damping-wing observations. For $m_χ=1\,{\rm GeV}$, DM decay raises the marginalized optical depth from $τ_{\rm reio}=0.064$ to $0.072$, but does not significantly improve the fit. The additional optical depth arises primarily from a broad ionization tail extending through the cosmic dark ages, rather than from an earlier onset of astrophysical reionization. Across $m_χ=2\,{\rm MeV}$--$7\,{\rm GeV}$, the central $68\%$ credible intervals remain below the $τ_{\rm reio}\simeq 0.08$ level previously found sufficient to bring both the neutrino-mass tension and the exclusion of $Λ$CDM below the $2σ$ level. The corresponding DM lifetime constraints are complementary to cosmic-ray and gas-heating bounds and competitive with previous CMB limits. Decaying DM therefore shifts the inferred optical depth in the direction required to ease the CMB--BAO discrepancy, but the allowed increase remains insufficient to alleviate it substantially.

astro-ph.CO↗

arXiv2026

The impact of primordial magnetic fields on the formation of galaxies

Primordial magnetic fields (PMFs), potentially generated during cosmic inflation or early-universe phase transitions, can modify cosmic structure formation by enhancing the post-recombination matter power spectrum. In this work, we investigate the impact of PMFs on galaxy formation using a suite of high-resolution cosmological hydrodynamical simulations evolved to $z=0$. Our simulations are initialized with PMF-induced enhancements to the matter power spectrum and include more comprehensive baryonic subgrid models than previous work, incorporating both stellar and AGN feedback. We find that PMFs systematically accelerate early structure formation, producing more abundant halos and galaxies, higher baryon fractions, enhanced star formation rates, and rapid growth of supermassive black holes at high redshifts ($z \sim 10$). However, the resulting enhanced stellar and AGN feedback efficiently processes and expels gas, reducing the late-time differences between PMF and standard $Λ$CDM models. The PMF signatures are therefore strongest at high redshift and gradually weaken toward low redshift as nonlinear evolution and baryonic feedback dominate over the initial PMF-induced enhancements. The impact of PMFs depends strongly on the characteristic peak scale, $k_{\rm peak}$, of the initial power enhancement, with models yielding similar non-linear evolution if they share a similar $k_{\rm peak}$, even when other PMF parameters differ. Our results highlight the critical role of comprehensive baryonic physics in accurately quantifying PMF signatures.

astro-ph.GA↗

arXiv2026

Challenges in Binary Pulsar Timing Detection of Dark Matter Subhalos

Recently, binary pulsar timing has been proposed as a viable probe of dark matter subhalos with masses of $\sim 10^7\,M_{\odot}$ in the solar neighborhood. We present a comprehensive analytical framework that incorporates the subhalo mass function, projection effects of line-of-sight acceleration, and the spatiotemporal geometric requirements for joint detection by binary systems, enabling a quantitative evaluation of the detectability of nearby subhalos. Applying this framework to the current binary pulsar sample, we find a probability $\leq 1.7 \times 10^{-4}$ of detecting at least one subhalo within the effective volume. An independent timing residual analysis shows no statistically significant excess in line-of-sight accelerations beyond predictions from data-driven Galactic gravitational potential models. These results place stringent constraints on detecting $<10^8~M_{\odot}$ dark matter subhalos with existing pulsar timing data, aligning with the theoretical expectation that such subhalos have a low survival probability in the solar neighborhood. A low detection prospect still holds even for future Square Kilometre Array observations.

astro-ph.HE↗

arXiv2026

Milky Way Dynamics Favor Dark Matter over Modified Gravity Models

Modified gravity theories such as Modified Newtonian Dynamics (MOND) and Scalar-Tensor-Vector Gravity (STVG) have been proposed as alternatives to dark matter, but decisive tests have been hindered by degeneracies between baryonic structure and gravitational laws. Here we break this degeneracy using independent, high-precision constraints: the Milky Way radial rotation curve, vertical phase-space spirals from Gaia, and a broken-exponential stellar disk. A joint reconstruction of the radial and vertical gravitational fields reveals a structural inconsistency in modified gravity -- no model can simultaneously reproduce both observations. Our results strongly disfavor MOND at $>13σ$ and STVG at $>4σ$. In contrast, dark matter halo models naturally explain the observations, providing a self-consistent test of gravity on galactic scales.

astro-ph.GA↗

arXiv2026

Cosmology of Inelastic Self-Interacting Dark Matter: Linear Evolution and Observational Constraints

We study the linear cosmological evolution of inelastic self-interacting dark matter in a two-component dark sector with a small mass splitting, assuming thermal initial conditions for the two species. We derive the coupled background and perturbation equations for inelastic conversion between the two species, considering both power-law and low-velocity saturation cross sections. Exothermic conversion injects kinetic energy into the light component, generating pressure support that suppresses small-scale structure and produces dark acoustic oscillations in the matter power spectrum. The resulting cutoff at scale $k > 1\,h\,\mathrm{Mpc}^{-1}$ depends on the normalization and velocity dependence of the cross section, the dark matter mass and the mass splitting. Using linear power spectra computed with a modified Boltzmann solver, we apply recast constraints from Lyman-$α$ forest data and high-redshift UV luminosity functions, finding non-monotonic but closed exclusion regions driven by the competition between efficient conversion and rapid depletion of the heavy component. These results show that the internal thermodynamics of a secluded multi-component dark sector can leave observable imprints on structure formation, providing a complementary probe of secluded dark matter.

astro-ph.CO↗

arXiv2026

Probing Cosmic-Ray-Boosted and Supernova-Sourced Sub-GeV Dark Matter with Paleo-Detectors

Astrophysical dark matter particles with masses well below GeV-scale can be difficult to detect using conventional nuclear recoil experiments due to their low velocities in our Milky Way halo. Elastic scattering with high-energy cosmic rays or thermal production inside core-collapse supernovae can accelerate sub-GeV DM to (semi-)relativistic velocities, producing nuclear recoil energies above the keV threshold that paleo-detectors can record over geological timescales. Using olivine as the target with 100$\,$g$\cdot$Gyr exposure, we compute track length distributions from such (semi-)relativistic dark matter fluxes, incorporating all major backgrounds (neutrinos, uranium-chain neutrons, thorium recoils) with a statistical analysis on an Asimov dataset. We derive 95 C.L. projected sensitivity of paleo-detectors to the DM-nucleon cross section for dark matter masses between a few MeV and hundreds of MeV. Our results show that paleo-detectors are able to probe large parameter regions that are not covered by current and near-future experiments designed to detect dark matter and neutrinos. In particular, paleo-detectors offer a unique ability to record the dark matter flux from Galactic supernova events over geological times. Such cumulative exposure enables sensitivity gains of a few orders of magnitude compared to conventional experiments.

hep-ph↗

arXiv2026

Self-Interacting Dark Matter with Mass Segregation: A Unified Explanation of Dwarf Cores and Small-Scale Lenses

In two-component self-interacting dark matter (SIDM) models with inter-species interactions, mass segregation arises naturally from collisional relaxation, enhancing central densities and gravothermal evolution. We demonstrate that models with velocity-dependent interactions, both within and between species, can connect several small-scale observations while remaining consistent with cluster-scale constraints. This combination enables core formation in dwarf halos, where the presence of baryons increases the inner densities and enhances the predicted strong lensing signatures. Using cosmological and controlled simulations alongside an accurate parametric model, we present proof-of-principle examples showing that this framework can explain the structure of dark perturbers observed in strong lensing systems, and can enhance the efficiency of small-scale lenses by a factor of a few, in line with the excess reported in galaxy-galaxy strong-lensing observations. Importantly, mass segregation can enhance the Einstein radii of SIDM halos relative to their cold dark matter (CDM) counterparts, overcoming a key challenge in one-component SIDM scenarios. Our results present mass segregation in two-component SIDM as a self-consistent, testable framework with the potential to address multiple small-scale challenges in structure formation.

astro-ph.CO↗

arXiv2026

Flux-ratio anomalies in cusp quasars reveal dark matter beyond CDM

Strongly lensed quasars in cusp configurations provide a uniquely sensitive probe of small-scale dark matter structure. Using the largest microlensing-free flux ratios for 17 quadruply imaged cusps, we combine these with extensive Monte Carlo simulations of mock lens realizations under cold dark matter (CDM), self-interacting dark matter (SIDM), and fuzzy dark matter (FDM) scenarios. Building on this, we propose a region (minor-axis and narrow major-axis cusp lenses) where flux-ratio anomalies persist even under globally parameterized models ("macromodels") with multipole freedom (capturing disk, asymmetric, or merger-driven structures). Within this region, J1042+1641 is $>3σ$ incompatible with both CDM and SIDM. Our results yield a Bayes factor exceeding $100$, providing very strong evidence for FDM over even the most optimistic CDM and SIDM scenarios. As only 11 cusp lenses lie within this region, extending to larger samples will be essential for assessing its statistical generality and for decisively confirming these findings with future microlensing-free flux ratio data.

astro-ph.CO↗

arXiv2026

A solution to the S8 tension through neutrino-dark matter interactions

Neutrinos and dark matter (DM) are two of the least understood components of the Universe, yet both play crucial roles in cosmic evolution. Clues about their fundamental properties may emerge from discrepancies in cosmological measurements across different epochs of cosmic history. Possible interactions between them could leave distinctive imprints on cosmological observables, offering a rare window into dark sector physics beyond the standard $Λ$CDM framework. We present compelling evidence that DM-neutrino interactions can resolve the persistent structure growth parameter discrepancy, $S_8 = σ_8\,\sqrt{Ω_m/0.3}$, between early and late universe observations. By incorporating cosmic shear measurements from current Weak Lensing surveys, we demonstrate that an interaction strength of $u \sim 10^{-4}$ not only provides a coherent explanation for the high-multipole observations from the Atacama Cosmology Telescope (\texttt{ACT}), but also alleviates the $S_8$ discrepancy. Combining early universe constraints with \texttt{DES Y3 cosmic shear} data yields a nearly $3σ$ preference for non-zero DM neutrino interactions. This strengthens previous observational claims and provides a clear path toward a significant breakthrough in cosmological research. Our findings challenge the standard $Λ$CDM paradigm and highlight the potential of future large-scale structure surveys, which can rigorously test this interaction and unveil the fundamental properties of DM.

astro-ph.CO↗

arXiv2026

Dark-Matter-Deficient Galaxies from Collisions: A New Probe of Bursty Feedback and Dark Matter Physics

High-velocity collisions between gas-rich ultra-diffuse galaxies present a promising formation channel for dark-matter-deficient galaxies (DMDGs). Using hydrodynamical simulations, we show that the progenitors' baryonic binding energy, $|E_{\rm bind}|$, critically controls the outcome. Repeated potential fluctuations, e.g., from bursty feedback, inject energy and reduce $|E_{\rm bind}|$ by $\approx 15\%$, yielding fewer but substantially more massive DMDGs. By contrast, elastic self-interacting dark matter (SIDM) produces comparable cores without lowering $|E_{\rm bind}|$, perturbing DMDG masses without clear enhancement. This differs from what happens in host halos, where SIDM-induced cores enhance dark matter tidal stripping while keeping baryons compact and resilient to tidal effects. The contrasting roles of SIDM may provide a means to distinguish feedback-formed halo cores from those created by SIDM. Among 15 paired simulation runs, 13 show higher DMDG masses in the weakened-binding case, and about two thirds exhibit $>100\%$ mass enhancements. The simulations also predict systematically lower gas fractions due to sustained post-collision star formation, yielding a clean observational signature. Upcoming wide-field imaging (CSST, LSST), HI surveys (FAST), and kinematic follow-up will be crucial to test this scenario.

astro-ph.GA↗

arXiv2026

Current Status of Inert Higgs Dark Matter with Dark Fermions

The precision measurements of the muon magnetic moment and the $W$ boson mass have sparked interest in the potential deviations from standard model (SM) predictions. While it may be premature to attribute any excesses in these precision measurements to new physics, they do offer a valuable indication of potential directions for physics beyond the SM. Additionally, the particle nature of dark matter (DM) remains a crucial enigma. Despite the absence of any definitive DM signal in direct detection and collider experiments, the Galactic Center GeV $γ$-ray excess and the AMS-02 antiproton ($\overline{p}$) excess could potentially offer hints related to the evidence of DM. Motivated by these observations, we propose a simple DM model that addresses all these issues. This model extends the SM by incorporating singlet and doublet Dirac fermion fields, along with a doublet complex scalar field. For the viable parameter regions in this model, we find that future upgrades of the Large Hadron Collider and DM direct detection experiments can only partially probe them, while future high-energy muon colliders hold promise for exploring the unexplored parameter space.

hep-ph↗

arXiv2025

Prospects for Probing Sub-GeV Leptophilic Dark Matter with the Future VLAST

The proposed Very Large Area Space Telescope (VLAST), with its expected unprecedented sensitivity in the MeV-GeV range, can also address the longstanding "MeV Gap" in gamma-ray observations. We explore the capability of VLAST to detect sub-GeV leptophilic dark matter (DM) annihilation, focusing on scalar and vector mediators and emphasizing the resonance region where the mediator mass is approximately twice the DM mass. While $s$-wave annihilation is tightly constrained by relic density and cosmic microwave background observations, $p$-wave and mixed $(s+p)$-wave scenarios remain viable, particularly near resonance. Additionally, direct detection experiments, especially those probing DM-electron scattering, significantly constrain nonresonance parameter space but are less effective in the resonance regime. VLAST can uniquely probe this surviving region, outperforming existing and planned instruments, and establishing itself as a crucial tool for indirect detection of thermal relic DM.

hep-ph↗

arXiv2025

Constraints on axionlike particles from 16.5 years of Fermi-LAT data and prospects for VLAST

Axionlike particles (ALPs), hypothetical particles beyond the Standard Model, are considered as promising dark matter candidates. ALPs can convert into photons and vice versa in a magnetic field via the Primakoff effect, potentially generating detectable oscillation in $γ$-ray spectra. This study analyzes 16.5 years of data from the Fermi Large Area Telescope (Fermi-LAT) on NGC 1275, the brightest galaxy in the Perseus cluster, to constrain the ALP parameter space. Our results improve the previous 95\% exclusion limits of the photon-ALP coupling $g_{aγ}$ by a factor of 2 in the ALP mass range of $4\times 10^{-10}\,\mathrm{eV}\lesssim m_{a}\lesssim 5\times 10^{-9}\,\mathrm{eV}$. Moreover, we investigate the projected sensitivity of the future Very Large Area $γ$-ray Space Telescope (VLAST) on searching for ALPs. We find that (i) the expected sensitivity on the ALP-photon coupling can be stronger than that from the upcoming International Axion Observatory (IAXO) in the ALP mass range of $2\times 10^{-11}\,\mathrm{eV}\lesssim m_{a}\lesssim 1\times 10^{-7}\,\mathrm{eV}$, with the best sensitivity of $g_{aγ}\sim 7\times 10^{-13}\,\mathrm{GeV^{-1}}$ at $m_{a}\sim 2\times 10^{-10}\,\mathrm{eV}$; (ii) VLAST can extend the sensitivity of the ALP masses below $5\times 10^{-12}\,\mathrm{eV}$, where the ALP-photon coupling $g_{aγ}\gtrsim 1.5\times 10^{-11}\,\mathrm{GeV^{-1}}$ will be excluded; (iii) the entire parameter space of ALP accounting for TeV transparency can be fully tested. These results demonstrate that VLAST will offer an excellent opportunity for ALPs searches.

hep-ph↗

arXiv2025

Scrutinizing the impact of the solar modulation on AMS-02 antiproton excess

This study examines the impact of solar modulation on the antiproton excess observed by AMS-02, which may indicate dark matter (DM) annihilation. We analyze three solar modulation models: the force-field approximation (FFA), a time-, charge-, and rigidity-dependent FFA, and a three-dimensional numerical simulation based on the Parker transport equation. Based on AMS-02 latest antiproton data (2025), our results show that the significance of the DM signal is sensitive to the chosen modulation model, with a 2$σ$ signal for the FFA (4$σ$ if including data from H, He, C, O, B/C, and B/O) and a reduced significance for more complex models. We also address systematic uncertainties using two methods: the add-in-quadrature method, which assumes uncorrelated uncertainties between energy bins, and the nuisance parameter method, which treats systematic uncertainties as nuisance parameters during the fitting process. Fitted to AMS-02 antiproton data, DM annihilation to the $b\bar{b}$ scenario with three different solar modulation models shows that the add-in-quadrature method causes overfitting, whereas the nuisance parameters approach leads to underfitting. Statistically, the signal region of the FFA model using the add-in-quadrature method is the most reliable. This work highlights the need for refined solar modulation models and a better treatment of uncertainties for a conclusive interpretation of the AMS-02 data.

astro-ph.CO↗

arXiv2025

Exploring sub-GeV dark matter via $s$-wave, $p$-wave, and resonance annihilation with CMB data

We revisit constraints on sub-GeV dark matter (DM) annihilation via $s$-wave, $p$-wave, and resonance processes using current and future CMB data from Planck, FIRAS, and upcoming experiments such as LiteBIRD, CMB-S4, PRISTINE, and PIXIE. For $s$-wave annihilation, we provide updated limits for both $e^{+}e^{-}$ and $ππ$ channels, with the profile likelihood method yielding stronger constraints than the marginal posterior method. In the $p$-wave case, we comprehensively present a model-independent inequality for the $95\%$ upper limits from FIRAS, PRISTINE, and PIXIE, with future experiments expected to surpass current BBN limits. For resonance annihilation, we report -- for the first time -- the $95\%$ upper limits on the decay branching ratio of the mediator particle, when the resonance peaks during the recombination epoch. Overall, our study highlights the complementary strengths of $μ$-distortion and CMB anisotropies in probing sub-GeV DM annihilation.

hep-ph↗

arXiv2025

Diversifying halo structures in two-component self-interacting dark matter models via mass segregation

Self-interacting dark matter (SIDM), through gravothermal evolution driven by elastic self-scatterings, offers a compelling explanation for the observed diversity of inner halo densities. In this work, we investigate SIDM dynamics in a two-component dark matter model with mass ratios of order unity, motivated by an asymmetric dark matter framework that naturally evades constraints from relic abundance and mediator decay, while enabling strong, velocity-dependent self-interactions. We show that cross-component scatterings significantly enhance mass segregation, driving the formation of dense, core collapsed-like halos. This effect couples naturally to SIDM-induced diversity, introducing a new mechanism for generating structural variations beyond those arising from gravothermal evolution alone. Our results reveal a novel mechanism for reconciling SIDM with small-scale observational tensions by enabling shifts in central densities while preserving the flexibility to generate diverse halo structures. We further highlight that halo structural diversity may serve as a diagnostic of dark sector composition, opening a new observational window into the particle nature of SIDM.

astro-ph.CO↗

arXiv2025

Searching for Axion-Like Particles with X-ray Observations of Alpha Centauri

We investigate the production of axion-like particles (ALPs) in stellar cores, where they interact with electromagnetic fields and electrons, with typical masses between $\mathcal O(0.1)$ and $\mathcal O(10)$ keV. These low-energy ALPs are gravitationally trapped in the orbits of stars and subsequently decay into two photons that we detect as monochromatic X-ray lines. We propose to search for these gravitationally trapped ALPs in the Alpha Centauri binary system, our closest stellar neighbor, using sensitive X-ray detectors like Chandra and eROSITA. Our search for ALP decay signals in the energy range of $0.2$ keV to $10$ keV yielded null results, thus establishing the most stringent limits on ALP interactions to date. In the case of ALP-electron coupling $g_{aee}\leq 10^{-15}$, we have improved the limits on the ALP-photon coupling $g_{aγγ}$ in ALP mass range between $0.25~\keV$ and $5~\keV$, compared to previous measurements, including those from GW170817, SN 2023ixf, and other sources, and specially the improvement reaches about 2 orders of magnitude at the mass of 2 keV. Even tighter constraints are set for larger $g_{aee}$.

astro-ph.HE↗