arXiv subjects

Ming-chung Chu

Publications and source records attributed to Ming-chung Chu.

14 recordsLinked to original sources

arXiv2026

Radial velocity statistics of cosmic voids as a probe of interacting dark energy

Due to their vast sizes and extremely low densities, the dynamics of cosmic voids are largely decoupled from complex, small-scale baryonic physics and are highly sensitive to the background expansion of the Universe. This makes them clean and sensitive probes of dark energy's properties. Using N-body simulations, we show that the void radial velocity and velocity dispersion profiles are sensitive to the Type 3 interacting dark energy model parameters, the momentum coupling $β$ ($<0$) and the scalar field parameter $λ$. Within the $1σ$ range of the best-fit values of $β$ and $λ$ constrained by Planck CMB, DESI BAO, and DES-Y5 supernova data, we find up to $\sim 30\%$ deviations in the void radial-velocity and velocity-dispersion profile spans relative to the uncoupled scenario, which can be well-approximated by a 4-parameter quadratic regression model. This demonstrates that the void radial velocity statistics provide an independent and observationally accessible probe of the dark-sector interaction in the Type 3 model.

astro-ph.CO↗

arXiv2026

Measuring neutrino mass and asymmetry through galaxy pairwise peculiar velocity

Cosmic neutrinos are among the most abundant fermions in the Universe, yet the values of their masses and chemical potentials remain uncertain. In this Letter, we present the first constraints on the total neutrino mass $M_ν$ and the neutrino asymmetry parameter $η^2$ derived from the mean galaxy pairwise peculiar velocity in the quasi-linear and nonlinear regimes. We develop a simulation-based analysis pipeline that connects neutrino properties to predictions of galaxy pairwise velocity, and apply it to galaxy data from the Cosmicflows-4 grouped catalog. Our analysis is performed within two independent cosmological frameworks, based on cosmological parameters derived from Cosmic microwave background (CMB) and local distance ladder measurements, respectively. By performing fits to the galaxy pairwise velocity, we obtain consistent constraints from both frameworks. Quoting posterior means with 68% CL, we find $M_ν= 0.24^{+0.34}_{-0.18}\ \mathrm{eV}$ and $η^2 = 2.14^{+0.30}_{-0.32}$ in the CMB framework, and $M_ν= 0.37^{+0.34}_{-0.26}\ \mathrm{eV}$ and $η^2 = 2.4^{+2.1}_{-1.6}$ in the local framework. In particular, we find a 7$σ$ measurement of a non-zero neutrino asymmetry in the CMB framework. These neutrino parameters are consistent with those, in our previous work, obtained from the Planck CMB temperature power spectrum. These results demonstrate that galaxy pairwise velocities provide an independent and sensitive probe of neutrino properties, opening a new avenue for testing neutrino physics with large-scale structure observations.

astro-ph.CO↗

arXiv2026

Probing the Type 3 interacting dark-energy model using matter pairwise velocity

Dark sector interactions can be explored via the so-called Type 3 model where dark matter and dark energy exchange momentum only, so as to minimize deviations from the $Λ$CDM background expansion history. Using N-body simulations, we analyze the imprint of Type 3 model parameters, the momentum exchange coupling constant $β$ and the slope of scalar field potential $λ$, on large-scale structure observables, particularly the matter pairwise velocity statistics. We find that the effects of $β$ ($<0$) and $λ$ on the mean matter peculiar pairwise velocity and velocity dispersion are degenerate. Our results highlight the potential of velocity statistics as a probe of dark sector interactions and underscore the importance of disentangling $β$ and $λ$ in cosmological analyses.

astro-ph.CO↗

arXiv2025

Measuring the Low-Energy Weak Mixing Angle with Supernova Neutrinos

The weak mixing angle $θ_W$ is a fundamental parameter in the electroweak theory with a value running according to the energy scale, and its precision measurement in the low-energy regime is still ongoing. We propose a method to measure the low-energy $\sin{^2θ_W}$ by taking advantage of Argo, a future ton-scale liquid argon dark matter detector, and the neutrino flux from a nearby core-collapse supernova (CCSN). We evaluate the expected precision of this measurement through the coherent elastic neutrino-nucleus scattering (CE$ν$NS) channel. We show that Argo is potentially capable of achieving a few percent determination of $\sin{^2θ_W}$, at the momentum transfer of $q \sim 20$ MeV, in the observation of a CCSN within $\sim 3$ kpc from the Earth. Such a measurement is valuable for both the precision test of the electroweak theory and searching for new physics beyond the standard model in the neutrino sector.

hep-ph↗

arXiv2025

Measuring neutrino mass and asymmetry with matter pairwise velocities

Neutrinos are believed to be the most abundant fermions in the Universe, but their masses are unknown, except for being non-zero but much smaller than other fermions. Cosmological relic neutrinos could also have non-zero chemical potentials (or asymmetries). Using neutrino-involved N-body simulations, we investigate the neutrino effects on the matter pairwise velocity, which itself is an interesting probe of cosmology. We find that for light-halo ($[10^{11},10^{13}]\ M_\odot$) mean pairwise velocity, in the transition range ($[4,15]\ \mathrm{Mpc}$), the effects of neutrino masses overwhelm the effects of neutrino asymmetries, while in the two-halo-group range ($[25,50]\ \mathrm{Mpc}$), for both light and heavy haloes ($[10^{13},10^{15}]\ M_\odot$), the effects of neutrino asymmetries dominate, making it possible to disentangle the two effects. We provide fitting formulae to quantify the effects of neutrino mass and asymmetry on halo-halo pairwise velocities.

astro-ph.CO↗

arXiv2025

Refitting cosmological data with neutrino mass and degeneracy

A simple and natural extension of the standard Lambda cold dark matter ($Λ$CDM) model is to allow relic neutrinos to have finite chemical potentials. We confront this $Λ$CDM$ξ$ model, a $Λ$CDM with neutrino mass $M_ν$ and degeneracy $ξ_3$ as additional parameters, with various cosmological data sets. We find that the $H_0$ and $S_8$ tensions become significant only in the presence of the cosmic microwave background (CMB) polarization data. Specifically, the global and local measurements agree to within 0.8$σ$ and 1.6$σ$ for the $H_0$ and $S_8$ tensions, respectively, when the CMB polarization data are not included. Therefore, the $H_0$ and $S_8$ tensions exist between CMB temperature and polarization data, both being global measurements. Fitting the $Λ$CDM$ξ$ model to the CMB temperature data, we find 3$σ$ evidence for nonzero neutrino mass ($M_ν=0.57^{+0.17}_{-0.13}\,\mathrm{eV}$) and degeneracy ($ξ_3=1.13^{+0.41}_{-0.19}$), and the O(1) neutrino degeneracy parameter is compatible with Big Bang nucleosynthesis data. The scalar index $n_s$ exceeds 1 slightly, which is compatible with some hybrid inflation models. Furthermore, the recent DESI baryon acoustic oscillation data prefer the $Λ$CDM$ξ$ model to the Planck $Λ$CDM model. Similar results are obtained when including additional supernova data, while the inclusion of the Atacama Cosmology Telescope $τ$ prior shifts the preferred $M_ν$ and $ξ_3$ values closer to zero and brings $n_s$ back to the values favored when the polarization data are included.

hep-ph↗

arXiv2025

Impact of light sterile neutrinos on cosmological large scale structure

Sterile neutrinos with masses on the $\mathrm{eV}$ scale are promising candidates to account for the origin of neutrino mass and the reactor neutrino anomalies. The mixing between sterile and active neutrinos in the early universe could result in a large abundance of relic sterile neutrinos, which depends on not only their physical mass $m_{\rm phy}$ but also their degree of thermalization, characterized by the extra effective number of relativistic degrees of freedom $ΔN_{\rm eff}$. Using neutrino-involved N-body simulations, we investigate the effects of sterile neutrinos on the matter power spectrum, halo pairwise velocity, and halo mass and velocity functions. We find that the presence of sterile neutrinos suppress the matter power spectrum and halo mass and velocity functions, but enhance the halo pairwise velocity. We also provide fitting formulae to quantify these effects.

astro-ph.CO↗

arXiv2025

Phase-transition-induced collapse of proto-compact stars and its implication for supernova explosions

A hadron-quark phase transition (PT) may trigger supernova explosions during stellar core collapse. However, both success and failure have occurred in previous attempts to explode dying stars via this mechanism. We systematically explore the outcomes of the PT-induced collapse of mock proto-compact stars (PCSs) with a constant entropy and lepton fraction, with spherically symmetric general relativistic hydrodynamic simulations and a controlled series of hybrid equations of state. Our results reveal the qualitative dependence of successful and failed explosions on the PT and quark matter characteristics. A small portion ($\sim\!0.04\%\!-\!1\%$) of the released binding energy $ΔE_B$ transforms into the diagnostic explosion energy $E_{\rm exp,diag}$, which saturates at $\sim\!6\times10^{51}$ erg near the black hole formation. Note that our $E_{\rm exp,diag}$ represents an upper limit of the final explosion energies in realistic supernova simulations. We draw the phase diagrams indicative of the possible fates of supernova explosions driven by hadron-quark PTs, where the control parameters are the onset density, energy gap of the PT, and the quark matter speed of sound. Our findings can guide further self-consistent investigations on PT-driven core-collapse supernovae and help identify hadron-quark PT-induced PCS collapse from future observations.

astro-ph.HE↗

arXiv2024

Measuring the Hubble constant through the galaxy pairwise peculiar velocity

The Hubble constant $H_0$, the current expansion rate of the universe, is one of the most important parameters in cosmology. The cosmic expansion regulates the mutually approaching motion of a pair of celestial objects due to their gravity. Therefore, the mean pairwise peculiar velocity of celestial objects, which quantifies their relative motion, is sensitive to both $H_0$ and the dimensionless total matter density $Ω_m$. Based on this, using the Cosmicflows-4 data, we measured $H_0$ for the first time via the galaxy pairwise velocity in the nonlinear and quasi-linear range. Our results yield $H_0=75.5\pm1.4$ km s$^{-1}$ Mpc$^{-1}$ and $Ω_m=0.311^{+0.029}_{-0.028}$ . The uncertainties of $H_0$ and $Ω_m$ can be improved to around 0.6% and 2%, respectively, if the statistical errors become negligible in the future.

astro-ph.CO↗

arXiv2023

Accretion-induced Collapse of Dark Matter-admixed Rotating White Dwarfs: Dynamics and Gravitational-wave Signals

We present two-dimensional hydrodynamic simulations of the accretion-induced collapse (AIC) of rotating white dwarfs admixed with an extended component of dark matter (DM) comprising of sub-GeV degenerate fermionic DM particles. We find that the DM component would follow the collapse of the normal matter (NM) component to become a bound DM core. Thus, we demonstrate how a DM-admixed neutron star could form through DM-admixed AIC (DMAIC) for the first time, with the dynamics of DM taken into account. The gravitational-wave (GW) signature from the DMAIC shows distinctive features. In the diffusive DM limit, the DM admixture indirectly suppresses the post-bounce spectral peak of the NM GWs. In the compact DM limit, the collapse dynamics of the DM in a Milky Way event generate GWs that are strong enough to be detectable by Advanced LIGO as continuous low-frequency ($< 1000$ Hz) signals after the NM core bounce. Our study not only is the first-ever computation of GW from a collapsing DM object but also provides the key features to identify DM in AIC events through future GW detections.

astro-ph.HE↗

arXiv2022

Effects of Neutrino Masses and Asymmetries on Dark Matter Halo Assembly

Massive cosmological neutrinos suppress the Large-Scale Structure (LSS) in the Universe by smoothing the cosmic over-densities, and hence structure formation is delayed relative to that in the standard Lambda-Cold Dark Matter ($Λ$CDM) model. We characterize the merger and mass accretion history of dark matter halos with the halo formation time $a_{1/2}$, tree entropy $s$ and halo leaf function $\ell(X)$ and measure them using neutrino-involved N-body simulations. We show that a non-zero sum of neutrino masses $M_ν$ delays the $a_{1/2}$ for halos with virial mass between $10^{13} M_\odot$ and $3\times 10^{13} M_\odot$, whereas a non-zero neutrino asymmetry parameter $η^2$ has the opposite effect. While the mean tree entropy $\bar s$ does not depend significantly on either $M_ν$ or $η^2$, the halo leaf function does. Furthermore, the dependencies of $\ell$ on $M_ν$ and $η^2$ have significant evolution in redshift $z$, with the relative contributions of $M_ν$ and $η^2$ showing a sigmoid-like transition as a function of $z$ around $z \approx 0.6$. Together with the matter power spectrum, these halo parameters allow us to break the parameter degeneracy between $M_ν$ and $η^2$ so that they can both be constrained in principle.

astro-ph.CO↗

arXiv2021

Gravitational-wave Signature of a First-order Quantum Chromodynamics Phase Transition in Core-Collapse Supernovae

A first-order quantum chromodynamics (QCD) phase transition (PT) may take place in the protocompact star (PCS) produced by a core-collapse supernova (CCSN). In this work, we study the consequences of such a PT in a non-rotating CCSN with axisymmetric hydrodynamic simulations. We find that the PT leads to the collapse of the PCS and results in a loud burst of gravitational waves (GWs). The amplitude of this GW burst is $\sim30$ times larger than the post-bounce GW signal normally found for non-rotating CCSN. It shows a broad peak at high frequencies ($\sim2500-4000$ Hz) in the spectrum, has a duration of $\lesssim5 {\rm ms}$, and carries $\sim3$ orders of magnitude more energy than the other episodes. Also, the peak frequency of the PCS oscillation increases dramatically after the PT-induced collapse. In addition to a second neutrino burst, the GW signal, if detected by the ground-based GW detectors, is decisive evidence of the first-order QCD PT inside CCSNe and provides key information about the structure and dynamics of the PCS.

astro-ph.HE↗

arXiv2021

Can the GW190814 secondary component be a bosonic dark matter admixed compact star?

We investigate whether the recently observed 2.6 $M_\odot$ compact object in the gravitational-wave event GW190814 can be a bosonic dark matter admixed compact star. By considering the three constraints in mass, radius and stability of such an object, we find that if the dark matter is made of QCD axions, their particle mass $m$ is constrained to a range that has already been ruled out by the independent constraint imposed by the stellar-mass black hole superradiance process. The 2.6 $M_\odot$ object can still be a neutron star admixed with at least 2.0 $M_\odot$ of dark matter made of axion-like particles (or even a pure axion-like particle star) if $2 \times 10^{-11}$ eV $\leq m \leq 2.4 \times 10^{-11}$ eV ($2.9 \times 10^{-11}$ eV $\leq m \leq 3.2 \times 10^{-11}$ eV) and with decay constant $f \geq 8 \times 10^{17}$ GeV.

astro-ph.HE↗

arXiv2017

Precise Clustering and Density Evolution of redMaPPer Galaxy Clusters versus MXXL Simulation

We construct a large, redshift complete sample of distant galaxy clusters by correlating Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12) redshifts with clusters identified with the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) algorithm. Our spectroscopic completeness is 97% for ~ 7,000 clusters within the redMaPPer selection limit, $z \leqslant$ 0.325, so that our cluster correlation functions are much more precise than earlier work and not suppressed by photometric redshifts. We derive an accurate power-law mass-richness relation from the observed abundance with respect to the mass function from Millennium XXL (MXXL) simulation, adjusted to the Planck weighted cosmology. The number density of clusters is found to decline by 20% over the range 0.1 $< z <$ 0.3, in good agreement with the evolution predicted by MXXL. Our projected three-dimensional correlation function scales with richness, $λ$, rising from $r_0=$ 14 h$^{-1}$ Mpc at $λ\simeq$ 25, to $r_0=$ 22 h$^{-1}$ Mpc at $λ\simeq$ 60, with a gradient that matches MXXL when applying our mass-richness relation, whereas the observed amplitude of the correlation function at $\left =$ 0.24 exceeds the MXXL prediction by 20% at the $\simeq$ 2.5$σ$ level. This tension cannot be blamed on spurious, randomly located clusters as this would reduce the correlation amplitude. Full consistency between the correlation function and the abundances is achievable for the pre-Planck values of $σ_8=$ 0.9, $Ω_m=$ 0.25, and h = 0.73, matching the improved distance ladder estimate of the Hubble constant.

astro-ph.CO↗