Nuclear Theory·nucl-th
7 papers—2 primary·5 cross-listed
[Submitted on 25 Jun 2024] (cross-list from physics.soc-ph)
Contribution to the volume "In Memory of Steven Weinberg" to appear in Nuclear Physics B.
[Submitted on 11 Jul 2024] (cross-list from hep-ph)
Adrian Dumitru🇺🇸 · Heikki Mäntysaari🇫🇮 · Yossathorn Tawabutr🇫🇮
The recently revised small- helicity evolution, resumming the double-logarithmic factor, , allows for the study of helicity distributions of quarks and gluons at small Bjorken , corresponding to high center-of-mass energy. In this work, we calculate the moderate- initial conditions in the regime, , for the small- helicity evolution using a light-front valence quark model of the proton, which provides additional physical information about the target. The perturbative emission and absorption of a gluon by the valence quarks are also included. The results, given in Eqs. (35), provide a new set of initial conditions with a significantly reduced number of free parameters than conventional models. Consequently, the predictive power of small- helicity evolution is expected to improve once the initial conditions from this work are incorporated.
[Submitted on 12 Jul 2024] (cross-list from hep-lat)
Ryo Ashikawa🇯🇵 · Masakiyo Kitazawa🇯🇵 · Shinji Ejiri🇯🇵 · Kazuyuki Kanaya🇯🇵
Binder-cumulant analysis of the critical point in the heavy-quark region of QCD is performed by Monte-Carlo simulations with the hopping-parameter expansion at . We extend our previous analysis at to finer lattices and perform high-precision analyses on large spatial volumes up to the aspect ratio . Higher order terms in the hopping-parameter expansion are incorporated effectively up to 14th order. The numerical results show that the violation of the finite-size scaling becomes more prominent on the finer lattice at a given aspect ratio.
[Submitted on 12 Jul 2024] (cross-list from hep-lat)
Harshit Pandey🇮🇳 · Ravi Shanker🇮🇳 · Sayantan Sharma🇮🇳
We study some interesting aspects of the spectral properties of SU(3) gauge theory, both with and without dynamical quarks (QCD) at thermal equilibrium using lattice gauge theory techniques. By calculating the eigenstates of a massless overlap Dirac operator on the gauge configurations, we implement a gauge-invariant method to study spectral properties of non-Abelian gauge theories. We have unambiguously categorized Dirac eigenvalues into different regimes based on a quantity defined in terms of the ratios of nearest neighbor spacings. While majority of these eigenstates below the magnetic scale are similar to those of random matrices belonging to the Gaussian Unitary ensemble at temperatures much higher than the chiral crossover transition in QCD, a few among them start to become prominent only near the crossover. These form fractal-like clusters with the median value for their fractal dimensions hinting at the universality class of the chiral transition in QCD. We further demonstrate that momentum modes below the magnetic scale in a particular non-equilibrium state of QCD are classically chaotic and estimate an upper bound on the thermalization time fm/c by matching this magnetic scale with that of a thermal state at MeV.
[Submitted on 12 Jul 2024] (cross-list from astro-ph.HE)
Sudipta Hensh🇯🇵 · Yong-Jia Huang🇨🇳 · Toru Kojo🇯🇵 · Luca Baiotti🇯🇵 · Kentaro Takami🇯🇵 · Shigehiro Nagataki🇯🇵 · Hajime Sotani🇯🇵
We investigate binary neutron star (BNS) mergers using general-relativistic numerical simulations with hadronic and hybrid equations of state (EOSs), incorporating the latest observations and theoretical constraints. We address two viable scenarios for the transition to quark matter: a quark-hadron crossover (QHC) or a strong first-order phase transition (1PT). To distinguish between different models, we define neutron-quark stars (NQS) as configurations where quark effects emerge at masses below the lowest observed neutron-star mass. While traditional "hybrid stars" may be distinguished by purely hadronic configurations through mass-radius measurements, the mass-radius relations of NQSs resemble those of purely hadronic models, with no sharp boundary between hadrons and quarks. The name NQS effectively captures the absence of a phase boundary between hadrons and quarks in QHC scenarios. Our results indicate that QHC models can be distinguished from hadronic ones if both the inspiral and postmerger gravitational waves (GWs) are observed. In particular, the dominant postmerger frequency () tends to be lower than in hadronic models with the same tidal deformability (). We also present the first general-relativistic simulations of BNS mergers where the stars already contain quark matter before merging. These involve a strong first-order phase transition (1PT) at 1.8 times nuclear saturation density, followed by a stiff quark EOS. Finally, we identify a robust linear correlation between the total GW energy emitted after the merger and the frequency. Remarkably, this relation holds regardless of the quark presence.
first authorsco-authorsvia INSPIRE