arXiv subjects

Peng-Cheng Chu

Publications and source records attributed to Peng-Cheng Chu.

At least 19 recordsLinked to original sources

arXiv2026

Quark matter at finite temperature and proto-quark stars with the axion effects in SU(3) Nambu-Jona-Lasinio model

We investigate the thermodynamical properties of strange quark matter (SQM) and proto-quark stars (PQSs) within the SU(3) Nambu-Jona-Lasinio (NJL) model at finite temperature, specifically incorporating the effects of axion fields and vector interactions. Our results demonstrate that these interactions significantly influence the equation of state (EoS), constituent quark masses, entropy density, and the maximum star mass of PQSs at the isentropic stages along the star evolution line. Furthermore, we reveal a distinct thermodynamic signature in the early evolution: the presence of trapped neutrinos leads to a substantial increase in electron number density while simultaneously suppressing the core temperature compared to the neutrino-free case. These findings may highlight the crucial role of the axion effects, flavor-dependent vector interactions, and particle composition in determining the observable properties of compact stars at finite temperature.

nucl-th↗

arXiv2026

Temperature fluctuations in a realistic Polyakov-loop extended Nambu--Jona-Lasinio Model along the freeze-out line

We extend and reparameterize the Polyakov--Nambu--Jona-Lasinio (PNJL) model to reproduce lattice simulation data at zero baryon chemical potential and to position its critical endpoint (CEP) within the BES-II experimental energy range. Using this realistic PNJL model, we investigate the behavior of the second-order temperature cumulant $C_2$ along the freeze-out line, aiming to understand the non-monotonic energy dependence of the two-particle transverse momentum correlation $C_{p_T}$ observed by the STAR Collaboration. Our results show a distinct dip structure in $C_2$ near the CEP and the first-order phase boundary on the phase diagram. Along the experimentally extracted freeze-out line, the dip minimum occurs around 7.7 GeV, and its trend is consistent with that observed by STAR, suggesting that the non-monotonic dependence of $C_{p_T}$ may be related to the CEP. Our results also indicate that cumulant ratios such as $C_3/C_2^2$ or $C_4/C_2^3$ eliminate the influence of initial volume fluctuations and may better reveal the underlying critical fluctuations. Further verification could be pursued through hydrodynamic or transport simulations that incorporate critical dynamics. These results and predictions might provide an a priori theoretical basis for future experimental measurements of higher-order event-mean transverse momentum fluctuations.

nucl-th↗

arXiv2026

Dynamics of potential-free warm $\mathbf{k}$-inflation with nonminimal derivative coupling

In contrast to potential-driven warm inflation models, this paper presents a new inflationary scenario driven purely by noncanonical kinetic terms. We derive the evolution equations and the associated slow-roll approximations specific to the kinetic case. The model incorporates a nonminimal derivative coupling that enhances gravitational friction; when combined with thermal damping, this leads to a significantly slower evolution of the pure kinetic inflaton. The resulting slow-roll approximations differ fundamentally from those of potential-driven inflation. The attractor behavior of this warm $k$-inflation with nonminimal derivative coupling is explored, confirming that slow-roll solutions can approach a strict exponential expansion attractor under relaxed slow-roll conditions. We further calculate the density fluctuation equations and obtain analytic expressions for the power spectrum, spectral index, and tensor-to-scalar ratio. Compared to standard inflation in general relativity, the energy scale at horizon crossing is lower, and the tensor-to-scalar ratio is significantly reduced due to the combined effects of thermal damping and nonminimal derivative coupling. The field excursion remains comfortably sub-Planckian. The model's predictions are in excellent agreement with the latest Planck 2018 data, offering a novel and successful extension of the warm inflation paradigm.

gr-qc↗

arXiv2026

Dynamics and observational signatures of warm Dirac-Born-Infeld inflation with nonminimal derivative coupling

This paper investigates a warm Dirac-Born-Infeld (DBI) inflationary model with nonminimal derivative coupling (NMDC) to gravity, where the inflaton kinetic term interacts with the Einstein tensor, thereby improving the effective gravitational friction. This model seamlessly integrates the noncanonical DBI kinetic structure, the NMDC-induced gravitational friction, and thermal dissipation. We formulate the background evolution equations along with the corresponding slow-roll stability conditions, leading to analytic results for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $R$. By applying these results to power-law potentials with $n=2$ and $n=4$, the model parameter space is constrained using the \emph{Planck} 2018 data. The findings indicate that the interaction between NMDC-induced gravitational friction and thermal dissipation effectively modulates $n_s$ and significantly expands the viable parameter space. In the $(n_s,R)$ plane, the predictions for $N=50$ fall within the 95\% confidence-level region, while those for $N=60$ extend into the 68\% confidence-level region and approach the observationally preferred central values. For the representative parameter choices examined, the tensor-to-scalar ratio is notably suppressed, generally within the range $10^{-8}\lesssim R\lesssim10^{-5}$. Moreover, the combined damping mechanism relaxes the slow-roll condition related to $\eta$ and limits the inflaton field excursion, thus addressing the $\eta$ problem without incurring super-Planckian field variations. These results indicate that warm DBI inflation with NMDC offers a theoretically coherent and observationally viable inflationary model, showcasing the complementary effects of thermal dissipation and enhanced gravitational friction in the context of modified gravity.

gr-qc↗

arXiv2025

Fluctuations of Temperature in the Polyakov-loop extended Nambu--Jona-Lasinio Model

We investigate temperature fluctuations in hot QCD matter using a 3-flavor Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. The high-order cumulant ratios $R_{n2}$ ($n>2$) exhibit non-monotonic variations across the chiral phase transition, characterized by slight fluctuations in the chiral crossover region and significant oscillations around the critical point. In contrast, distinct peak and dip structures are observed in the cumulant ratios at low baryon chemical potential. These structures gradually weaken and eventually vanish at high chemical potential as they compete with the sharpening of the chiral phase transition, particularly near the critical point and the first-order phase transition. Our results indicate that these non-monotonic peak and dip structures in high-order cumulant ratios are associated with the deconfinement phase transition. This study quantitatively analyzes temperature fluctuation behavior across different phase transition regions, and the findings are expected to be observed and validated in heavy-ion collision experiments through measurements of event-by-event mean transverse momentum fluctuations.

nucl-th↗

arXiv2025

Primordial non-Gaussianity in noncanonical warm inflation with nonminimal derivative coupling

This paper presents and investigates non-Gaussian perturbations for the warm k-inflation model that is driven by pure kinetic energy. The two complementary components of the overall non-Gaussianity are the three-point and four-point correlations. The intrinsic non-Gaussian component, denoted as the nonlinear parameter f_{NL}^{int}, is rooted in the three-point correlation for the inflaton field. Meanwhile, the \delta N part non-Gaussianity, denoted as f_{NL}^{\delta N}, is the contribution attributed to the four-point correlation function of the inflaton field. In this paper, the above two components in warm k-inflation are individually computed and analyzed. Then, comparisons and discussions between them are conducted, and the non-Gaussian theoretical results are compared with experimental observations to determine the range of model parameters within the allowable range of observation.

gr-qc↗

arXiv2025

Dark matter effects on the properties of quark stars and the implications for the peculiar objects

We systematically investigate the observable properties of dark matter-admixed quark stars (DQSs) using the confined-isospin-density-dependent-mass model in combination with the generic bosonic self-interacting dark matter model. Our results show that the dark matter (DM) can significantly influence the properties of quark stars including the mass, radius, and the central pressure at the maximum mass configurations. Moreover, we observe that the mass of DMparticles and the DMfraction significantly affect the types of stellar configurations, and we study these configurations in detail under various scenarios and predict the possibility that two recently observed peculiar objects HESS J1731-347 and PSR J014-4002E are DQSs.

nucl-th↗

arXiv2024

Effects of a first-order QCD phase transition on light nucleus production

Using an extended Polyakov-looped Nambu--Jona-Lasinio (PNJL) model to describe the baryon density fluctuations of quark matter along the isentropic trajectories corresponding to different $s/\rho_B$ values extracted from Au+Au collisions at energies $\sqrt{s_{NN}} = 7.7-200$ GeV, we investigate the effects of the first-order phase transition on the light nucleus yield ratio $N_t \times N_p/N_d^2$. The results indicate that the second-order scaled density moment $y_2$, used to quantify density fluctuations, rapidly increases to form a peak when the isentropic trajectories pass through the phase coexistence region. We extract the yield ratios $N_t\times N_p/N_d^2$ at chemical freeze-out from the isentropic trajectories at different collision energies and found significant enhancements at 19.6 GeV and 27 GeV. This is similar to the trends observed by the STAR experiment, suggesting that the enhancements in the yield ratios $N_t\times N_p/N_d^2$ observed in the STAR experiment could be explained by the density fluctuations generated in the first-order phase transition region.

nucl-th↗

arXiv2024

Axion effects on quark matter and quark-matter cores in massive hybrid stars

Using a three-flavor Nambu--Jona-Lasinio model to describe the charge-parity violating effects through axion field, we investigate the axion effects on quark matter and quark-matter cores in massive hybrid stars. The properties of quark matter vary with the scaled axion field $a/f_a$ in a periodic manner, with a period of $2\pi$. Within the range from 0 to $\pi $, axion field decrease the baryon chemical potential of the first-order phase transition, leading to an increase in normalized pressure and stiffening of the quark matter equation of state. The effect of axions on hybrid star matter that includes the hadron-quark phase transition is contrary to expectations. The axion field shifts the onset of the hadron-quark mixed phase to lower densities but slightly softens the equation of state of the mixed phase matter, which also results in a slight decrease in the maximum mass and corresponding radius of the hybrid stars. However, we also find that the lowering of the onset of the mixed phase significantly increases the radius and mass of the quark-matter core in the hybrid star. Therefore, our results indicate with axion effects, a sizable quark-matter core can appear in $2M_{\odot}$ massive neutron stars.

nucl-th↗

arXiv2024

Noncanonical warm inflation with nonminimal derivative coupling

This study extended noncanonical warm inflation to the nonminimal derivative coupling scenario. The fundamental equations, including the evolution equations and the slow roll equations of this new framework, were derived. The enlarged damping term, which encompasses both gravitationally enhanced friction and thermal damping, resulted in a well overdamped inflationary process, ensuring that the slow roll approximations can be satisfactorily satisfied. A linear stability analysis corroborated the viability of this approach, yielding significantly relaxed slow roll conditions within the context of noncanonical warm inflation with nonminimal derivative coupling. Subsequently, the density fluctuations in this new framework were analyzed, leading to approximately analytic results for the power spectrum, spectral index, and related quantities. Both the energy scale at horizon crossing and the tensor-to-scalar ratio decreased considerably because of the effects of thermal damping and nonminimal derivative coupling. The upper bound for field excursion remained safely sub-Planckian in this inflationary scenario. Thus we reached a successful and meaningful model to broad the scope of warm inflation.

gr-qc↗

arXiv2024

Cluster radioactivity preformation probability of trans-lead nuclei in the scheme of NpNn

In the present work, the cluster radioactivity preformation probability Pc in the scheme of NpNn for the effective number of the valence particles (holes) in trans-lead nuclei has been systematically investigated. This quantity has been explored in the simplified parametrization of NpNn as well as the multiplication NpNnI of this product with the isospin asymmetry I. The calculations for Pc are both performed in microscopic and model-dependent way. Within the microscopic approach, based on our previous work [Chin. Phys. C 47,014101 (2023)], Pc is calculated in cluster formation model (CFM) combined with the exponential relationship of Pc to the alpha decay preformation probability P alpha when the mass number of the emitted cluster Ac less than 28. While Ac greater than 28, Pc is obtained through the charge-number dependence of Pc on the decay products proposed by Ren et al. [Phys. Rev. C 70,034304 (2004)]. In the model-dependent approach, Pc is extracted through the ratios from calculated cluster radioactivity half-lives in the framework of unified fission model (UFM) proposed by Dong et al. [Eur. Phys. J. A 41,197 (2009)] to experimental ones. Both of the results show Pc in logarithmic form are linear to NpNn as well as NpNnI. For comparison, the parent-mass-number dependence analytical formula as well as the model proposed by K. Wei and H. F. Zhang [Phys. Rev. C 96,021601(R)(2017)] are also used. Furthermore, the preformation mechanic for cluster radioactivity has also been discussed.

nucl-th↗

arXiv2023

The mixed phase quark core in massive hybrid stars

We investigate the properties of hybrid star and the mixed phase core to explore the radius ratio of the mixed phase in hybrid star. In the context of observed massive neutron stars (NSs), we examine the internal structure, phase transitions, and the impacts of the equation of state (EOS) in maximum hybrid star. We investigate the stiffness changes in the EOS during the hadron-quark phase transition within the hybrid stars. The relativistic mean-field (RMF) model is used to describe hadronic matter, while to the represent quark matter, the Nambu-Jona-Lasinio (NJL) model is applied. We explore the strength of vector coupling in quark matter, which delays the onset density of the mixed phase and reduces the size of the mixed-phase core in a hybrid star, but does not exhibit a clear correlation with the central density. In a hybrid star with a maximum mass of approximately 2 solar masses ($M_\odot$), a mixed-phase core of $\sim$5 km may exist, comprising about $40\%$ of the total radius. However, our results do not support the existence of a sizable quark core containing the mixed phase ($R_{\rm{MP}}>1/2~R_{\rm{total}}$) for the maximum-mass hybrid star or for a 2~$M_\odot$ massive star.

nucl-th↗

arXiv2023

Speed of sound and polytropic index in QCD matter

We investigate the speed of sound and polytropic index of quantum chromodynamics (QCD) matter in the full phase diagram based on a 3-flavor Polyakov-looped Nambu-Jona-Lasinio (pNJL) model. The speed of sound and polytropic index in isothermal and adiabatic cases all have a dip structure at the low chemical potential side of the chiral phase transition boundary, and these quantities reach their global minimum values at the critical endpoint (CEP) but are not completely zero, where the values in adiabatic are lightly greater than those in isothermal. Different from the speed of sound, the polytropic index also exists a peak around the chiral phase transition boundary. Along the hypothetical chemical freeze-out lines, the speed of sound rapidly decreases near the CEP, followed by a small spinodal behavior, while the polytropic index, especially in isothermal, exhibits a more pronounced and nearly closed to zero dip structure as it approaches the CEP.

hep-ph↗

arXiv2023

The effect of gluon condensate on the entanglement entropy in a holographic model

In this study, we examine the impact of the gluon condensate on holographic entanglement entropy within an Einstein-Dilaton model at both zero and finite temperatures. A critical length exists for the difference in entanglement entropy between connected and disconnected surfaces in this model, which is typically interpreted as an indicator of phase transition. As the gluon condensate increases, the critical length decreases, suggesting that confinement strengthens at zero temperature. Additionally, the entropic C-function abruptly drops to zero at the critical length, indicating the absence of entangled states. At finite temperatures, the results show that the effect of the gluon condensate on the critical length is qualitatively similar to that at zero temperature. We observe that the entropic C-function increases as a function of $L$ at finite temperature, though it exhibits competitive behaviors when the gluon condensate is large.

hep-ph↗

arXiv2023

Properties of quark-matter cores in massive hybrid stars

Using the constraints from astrophysical observations and heavy-ion experiments, we investigate the equation of state (EOS) of hybrid star matter and the properties of quark-matter cores in hybrid stars. The quark matter interactions in hybrid stars are described based on 3-flavor Nambu-Jona-Lasinio model with various vector and vector-isovector coupling constants. In this work, we find that the hybrid star matter EOS is more sensitive to the strength of the vector interaction, and the EOS becomes stiffer with increasing vector strength $R_V$. The vector-isovector interaction characterized by the coupling constant $R_{IV}$ make main contribution to the hadron-quark mixed phase. Meanwhile, we note that a step change of both the sound velocity and the polytropic index $\gamma$ occurs in the hadron-quark phase transition, and it is restored with the decrease of nucleon and lepton degrees of freedom in the high density quark phase. Although the coupling constants increase the hybrid star maximum mass up to $2.08M_{\odot}$, they also decrease the mass and radius of the quark core and the mixed core. With different quark coupling constants, we also find that the maximum mass and radius of the quark matter core in a stable hybrid star can reach $0.80M_{\odot}$ and 6.95 km, which are close to half of the maximum mass and radius of the complete star. However, properties of quark matter have no effect on the $M = 1.4M_{\odot}$ hybrid star as a result of no quark matter inner core, which can also be confirmed by the criterion of the polytropic index, and thus our results also indicate that the quark interactions have no effect on the tidal deformability $\Lambda_{1.4}$ of hybrid stars.

nucl-th↗

arXiv2023

Properties of quark matter and hybrid stars from a quasiparticle model

We investigate the properties of hybrid stars with the hadron-quark phase transition by using a quasiparticle model. Results from our study indicate that the coupling constant $g$ can stiffen the EOS of hybrid star matter and thus increase the hybrid star maximum mass and its tidal deformability, whereas it also decreases the mass and radius of the pure quark core. In addition, we find that a step change of the sound velocity occurs in the hadron-quark mixed phase, and it is restored with the decrease of nucleon and lepton degrees of freedom in the high density quark phase. The approximate rule that the polytropic index $\gamma \leq 1.75$ can also be used as a criterion for separating hadronic from quark matter in our work. The hypothesis of absolutely stable SQM (or "Witten hypothesis") suggests that a hybrid star containing a sufficient amount of SQM in its core will rapidly convert into a strange quark star. The SQM in hybrid stars therefore should break the absolutely stable condition, and the energy per nucleon ($E/A$) of both $ud$QM and SQM must exceed the lowest energy per nucleon 930 MeV. As a result, we provide the maximum mass, minimum radius $R_{1.4}$ and minimum tidal deformation $\Lambda_{1.4}$ of the hybrid stars as well as the maximum mass and radius of the quark matter core with different $g$ values within the allowable regions ($E/A>930$ MeV) on the $g-B^{1/4}$ plane. Using the constraints from astrophysical observations and heavy-ion experiments for comparison, our results indicate that the recently discovered massive neutron stars be well described as hybrid stars in the quasiparticle model, and confirm that the sizable quark-matter cores ($R_{QC}>6.5$ km) containing the mixed phase can appear in $2M_{\odot}$ massive stars.

nucl-th↗

arXiv2023

Non-Gaussianity in the warm k-inflation

This paper presents and investigates non-Gaussian perturbations for the warm k-inflation model that is driven by pure kinetic energy. The two complementary components of the overall non-Gaussianity are the three-point and four-point correlations. The intrinsic non-Gaussian component, denoted as the nonlinear parameter f_{NL}^{int}, is rooted in the three-point correlation for the inflaton field. Meanwhile, the δN part non-Gaussianity, denoted as f_{NL}^{δN}, is the contribution attributed to the four-point correlation function of the inflaton field. In this paper, the above two components in warm k-inflation are individually computed and analyzed. Then, comparisons and discussions between them are conducted, and the non-Gaussian theoretical results are compared with experimental observations to determine the range of model parameters within the allowable range of observation.

gr-qc↗

arXiv2022

GW190814: Circumstantial Evidence for Up-Down Quark Star

Within a confining quark matter model which considers phenomenologically the quark confinement and asymptotic freedom as well as the chiral symmetry restoration and quark deconfinement at high baryon density, we find that if the up-down quark matter ($ud$QM) is more stable than nuclear matter and strange quark matter (SQM), the maximum mass of static quark stars with $ud$QM is $2.87M_{\odot}$ under agreement with both the constraints on star tidal deformability from gravitational wave signal GW170817 and the mass-radius of PSR J0030+0451 and PSR J0740+6620 measured by NICER. In contrast, the conventional strange quark star with the SQM that is more stable than nuclear matter while the nuclear matter is more stable than $ud$QM, has a maximum static mass of only $1.87M_{\odot}$ and its radius significantly deviates from NICER's constraint. Our results thus provide circumstantial evidence suggesting the recently reported GW190814's secondary component with a mass of $2.59^{+0.08}_{-0.09}M_\odot$ could be an up-down quark star.

astro-ph.HE↗