arXiv subjects

Jingdong Shao

Publications and source records attributed to Jingdong Shao.

6 recordsLinked to original sources

arXiv2026

Gravitational wave spectrum from first-order QCD phase transitions based on a parity doublet model

We investigate the gravitational wave spectrum from first-order QCD phase transitions using the parity doublet model at finite baryon chemical potential. The model incorporates the chiral invariant mass $m_0$, representing the portion of nucleon mass that persists even when chiral symmetry is restored. Within the model, we identify two first-order phase transition regions: the nuclear liquid--gas transition and the chiral phase transition. By solving the bounce equation and computing the Euclidean action $S_3/T$, we obtain the gravitational wave spectra from both transitions. The liquid--gas transition yields $α\sim \mathcal{O}(1)$ and $β/H \sim \mathcal{O}(10)$--$\mathcal{O}(100)$ near the endpoint of the first-order line, producing signals with peak frequencies from the millihertz to the nanohertz band that can fit the existing data. In contrast, the chiral transition produces signals suppressed by approximately five orders of magnitude, well below the sensitivity of all current and planned detectors. These results connect the chiral invariant mass to the gravitational wave spectrum, offering a novel probe of the origin of nucleon mass through gravitational wave astronomy.

nucl-th↗

arXiv2026

Primordial Quark Stars Made of Long-lived False Vacuum

A false vacuum could be a profound ingredient of fundamental physics, yet its direct detection in laboratories is hindered when the lifetime is exponentially long. Conventional static phase diagrams often discard metastable false vacuum, we show that, however, in a dynamical treatment of a first-order QCD phase transition at large quark chemical potential that strongly suppresses tunneling, cosmologically long-lived, and thus indispensable false vacuum naturally arises, and makes nontrivial contribution to constituting primordial quark objects. We identify two distinct branches of such primordial quark objects: quark star crusted with false vacuum, and nugget specifically referring to quark star in global false vacuum, which may account for a population of small compact stars. Some long-lived primordial objects may have survived until the late Universe, and hopefully sow the seeds of high red-shift galaxies. Its false vacuum decay can power ultra-energetic long $γ$-ray bursts and kHz gravitational waves within multi-messenger facilities, rendering itself an astrophysical and thus testable phenomenon.

hep-ph↗

arXiv2025

Transition rate and gravitational wave spectrum from first-order QCD phase transitions

We investigate the gravitational wave spectrum induced by first-order QCD phase transitions including the deconfinement phase transition in the pure gluon system and Friedberg-Lee model, and chiral phase transition in the quark-meson model and Polyakov quark-meson model. The gravitational wave power spectra are sensitive to the phase transition rate $β/H$. All QCD models predict a rather large phase transition rate in the order of $β/H\sim10^4$ at high temperature region, and the produced gravitational waves lie in the peak frequency region of $10^{-4}-0.01 {\rm Hz}$, corresponding to an energy spectrum in the range of $10^{-8}-10^{-7}$, which can be detected by LISA and Taiji. If a high baryon density is generated through Affleck-Dine baryogenesis or other mechanisms, the baryon chemical potential significantly reduces the phase transition rate, potentially dropping it to the order of $β/H\sim 10^1$, leading to the production of nanohertz gravitational waves. Furthermore, a critical quark chemical potential exists with a zero phase transition rate $β/H=0$, indicating that the false vacuum will not decay, thus supporting the formation of primordial quark nuggets in the early universe.

hep-ph↗

arXiv2024

Nanohertz gravitational waves and primordial quark nuggets from dense QCD matter in the early universe

The first-order QCD phase transition at high temperature features a large transition rate in the magnitude of $β/H \sim 10^4$ with induced stochastic gravitational waves typically lying in the LISA range. High baryon density in the early universe can be generated through Affleck-Dine baryogenesis. The baryon chemical potential enhances the potential barrier and significantly reduces the transition rate, which decreases from infinity at the critical end point (CEP) to zero at the critical nucleation point (CNP). Nanohertz gravitational waves can be produced in a narrow window of high baryon chemical potential with transition rate in the order of $β/H \sim 10^1$. When the phase transition rate reaches zero, the false vacuum of high baryon density quark matter is unlikely to decay and can persist over cosmological time scales. Therefore the primordial quark nuggets (PQN) can form and survive in the early universe as the seeds of compact stars, thereby dramatically accelerating the evolution of compact stars and the formation of galaxies, which may explain the high red-shift massive galaxies observed by the James Webb Space Telescope.

hep-ph↗

arXiv2024

Chiral phase transition and spin alignment of vector meson in the Polarized-Polyakov-loop Nambu-Jona-Lasinio model under rotation

By using the extrapolation method, a polarized Polykov-loop potential at finite real angular velocity is constructed from the lattice results at finite imaginary angular velocity. The chiral and deconfinement phase transitions under rotation have been simultaneously investigated in the Polarized-Polyakov-loop Nambu-Jona-Lasinio (PPNJL) model. It is observed that both critical temperatures of deconfinement and chiral phase transition increase with the angular velocity, which is in consistent with lattice results. The spin alignment of vector meson has the negative deviation of $ρ_{00} -1/3$ under rotation, and the deviation in the PPNJL model is much more significant than that in the NJL model and the quark coalescence model, which revealing the important role of rotating gluons on the quark polarization.

hep-ph↗

arXiv2023

Gravitational waves and primordial black holes from chirality imbalanced QCD first-order phase transition with $\mathcal {P}$ and $\mathcal {CP}$ violation

The chirality imbalance in QCD is spontaneously induced by a repulsive axial-vector interaction from the instanton anti-instanton pairing at high temperature above the chiral phase transition, and vanishes at low temperature. The chiral chemical potential $μ_5$ is in the same magnitude as estimated from the sphaleron transition. Phase transition of the chirality imbalance is always a first-order one in the early universe with $\mathcal {P}$ and $\mathcal {CP}$ violation. The spectra of gravitational waves and the formation of the primordial black holes from this first-order phase transition is investigated in this work, and the effect of a strong magnetic field is also analyzed. The gravitational waves produced by chirality imbalance can be detected by LISA, Taiji and DECIGO, with the peak energy density locating in the range of $10^{-11}$ to $10^{-9}$ and the peak frequencies lying in the range of $10^{-5}$ Hz to $10^{-2}$ Hz. The spectrum with larger axial vector coupling strength and stronger magnetic field has higher peak energy density and lower peak frequency. According to this trend, the gravitational waves spectra might also be able to be detected by SKA, IPTA and EPTA. The Phase transition inverse duration $β/H_*$ calculated from the bounce solution is in the order of $10^4$, which is much higher than typical value $10-100$ from electroweak phase transitions. Based on the mechanism of postponement of the false vacuum decay, it is found that the formation of the primordial black hole is not favored because the phase transition completes in an extreme short time due to the large value of $β/H_*$ and thus the false vacuum energy density decays sharply.

hep-ph↗