Nuclear Theory·nucl-th

Tuesday·May 10, 2022

11 papers—6 primary·5 cross-listed

01
A new class of hybrid EoS with multiple critical endpoints for simulations of supernovae, neutron stars and their mergers
Oleksii Ivanytskyi🇵🇱 · David Blaschke🇵🇱
We introduce a family of equations of state (EoS) for hybrid neutron star (NS) matter that is obtained by a two-zone parabolic interpolation between a soft hadronic EoS at low densities and a stiff quark matter EoS with color superconductivity at high densities within a finite region of baryonic chemical potentials $μ_{B}^{h} < μ_{B} < μ_{B}^{q}$ . We consider two scenarios corresponding to a cross-over and a strong first-order transition between quark and hadron phases considered at finite and zero temperatures. This allows us to analyze the effects of finite entropy on the EoS and mass-radius relation of NS. We demonstrate that the formation of a color superconducting state of quark matter drives the evolution of matter in supernovae explosions under the condition of entropy conservation to higher temperatures than in the case of deconfinement to normal quark matter. Within the presented hybrid EoS scenario, regions of the QCD phase diagram may be accessible to supernovae and NS mergers that can be reached also in terrestrial experiments with relativistic heavy ion collisions.
nucl-thastro-ph.HEhep-phEPJA(2022)·28 citations
02
Phases of Quench Dynamics in the Presence of Fluctuation
Chang Lei🇨🇳 · Shu Lin🇨🇳
We study the effect of thermal fluctuations on a sourced quench in a system with $Z_{2}$ symmetry. By ignoring the fluctuation of finite momentum modes and tracing the dynamics of zero momentum mode driven by a spatially homogeneous source near the critical point, we map out a phase diagram for the quench dynamics. The phase diagram consists of three different phases. Phase I occurs for large fluctuations with the relaxation time set by fluctuation induced inverse effective mass square. Phase II occurs for small fluctuation and slow quench rate. The dynamics is characterized by a modified Kibble-Zurek scaling. Phase III corresponds to small fluctuations and rapid quench rate. The relaxation time tends to a finite value in the rapid quench limit. We also estimate the fluctuations of finite momentum modes, finding significant enhancement of the effective mass square. We speculate the qualitative features of the phase diagram may remain the same, but enhanced fluctuations can lead to shrinkage of phase II and III.
nucl-thcond-mat.supr-conhep-phPRResearch(2023)·0 citations
03
Spectral function for $^{4}$ He using the Chebyshev expansion in coupled-cluster theory
J. E. Sobczyk🇩🇪 · S. Bacca🇩🇪 · G. Hagen🇺🇸 · T. Papenbrock🇺🇸
We compute spectral function for $^{4}$ He by combining coupled-cluster theory with an expansion of integral transforms into Chebyshev polynomials. Our method allows to estimate the uncertainty of spectral reconstruction. The properties of the Chebyshev polynomials make the procedure numerically stable and considerably lower in memory usage than the typically employed Lanczos algorithm. We benchmark our predictions with other calculations in the literature and with electron scattering data in the quasi-elastic peak. The spectral function formalism allows one to extend ab-initio lepton-nucleus cross sections into the relativistic regime. This makes it a promising tool for modeling this process at higher energy transfers. The results we present open the door for studies of heavier nuclei, important for the neutrino oscillation programs.
nucl-thhep-phPRC(2022)·12 citations
04
The Big Bang Nucleosynthesis abundances of the light elements using improved thermonuclear reaction rates
Chen Wu
Big Bang Nucleosynthesis (BBN) is an important stage of a homogeneous and isotropic expanding universe. The results of calculation of the synthesis of light elements during this epoch can then be compared with the abundances of the light elements. The theoretical calculation of the BBN model depends on the initial conditions of the early universe and reaction cross sections measured by the nuclear physics experiment. Recently, an update of the NACRE (Nuclear Astrophysics Compilation of REactions) database is presented. This improved compilation comprises thermonuclear reaction rates for 34 two-body reactions on light nuclides (fifteen are particle transfer reactions and nineteen are radiative capture reactions). In this work, we calculate the BBN abundances by using these updated thermonuclear reaction rates in the framework of the code \texttt{AlterBBN}. Our results suggest that the new numerical result of the primordial Lithium abundance is 7.1 percent larger than the previous calculation.
nucl-thGen.Rel.Grav.(2023)·2 citations
05
Azimuthal-sensitive three-dimensional HBT radius in Au-Au collisions at $E_{b e am} = 1.23$ $A$ GeV by the IQMD model
Ling-Meng Fang🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳
We used an Isospin dependent Quantum Molecular Dynamics (IQMD) model to simulate Au + Au collisions at beam energy $E_{b e am}$ = 1.23 $A$ GeV, which corresponds to center of mass energy $s_{N N} = 2.4$ GeV. Firstly, we obtained reasonable rapidity and transverse mass spectra of $π^{-}$ and $π^{+}$ as well as "apparent" temperature parameters in comparison with the HADES data. Then by calculating three-dimensional Hanbury Brown and Twiss (HBT) radius of same charged pion-pairs, we obtained the square difference of outward radius and sideward radius, i.e. $R_{o u t}^{2} - R_{s i d e}^{2}$ , as well as the freeze-out volume ( $V_{f o}$ ), which were basically consistent with the trend of HADES experimental results. The azimuthal dependence of the HBT radii was also calculated by a matrix method, and corrected by the rotation matrix. In addition, the eccentricities of the $x y$ - and $z y$ - planes of pion-pair emissions were also extracted for different pair transverse momentum and collision centrality, which show that the $x y$ -eccentricity increases with pair transverse momentum as well as centrality but not for $z y$ -eccentricity, indicating a more asymmetric transverse emission of particle-pairs with higher transverse momentum in off-central collisions.
nucl-thnucl-exEPJA(2022)·8 citations
06
$S O (3)$ quadratures in angular-momentum projection
Noritaka Shimizu · Yusuke Tsunoda
While the angular-momentum projection is a common tool for theoretical nuclear structure studies, a large amount of computations are required particularly for triaxially deformed states. In the present work, we clarify the conditions of the exactness of quadratures in the projection method. For efficient computation, the Lebedev quadrature and spherical $t$ -design are introduced to the angular-momentum projection. The accuracy of the quadratures is discussed in comparison with the conventional Gauss-Legendre and trapezoidal quadratures. We found that the Lebedev quadrature is the most efficient among them and the necessary number of sampling points for the quadrature, which is often proportional to the computation time, is reduced by a factor 3/2 in comparison with the conventional method.
nucl-thComput.Phys.Commun.(2023)·3 citations
07
Conformal Colliders Meet the LHC
Kyle Lee🇺🇸 · Bianka Meçaj🇺🇸 · Ian Moult🇺🇸
The remarkably high energies of the Large Hadron Collider (LHC) have allowed for the first measurements of the shapes and scalings of multi-point correlators of energy flow operators, $⟨ Ψ∣ E (n_{1}) E (n_{2}) \dots E (n_{k}) ∣Ψ ⟩$ , providing new insights into the Lorentzian dynamics of quantum chromodynamics (QCD). In this Letter, we use recent advances in effective field theory to derive a rigorous factorization theorem for the light-ray density matrix, $ρ = ∣Ψ ⟩ ⟨ Ψ∣$ , inside high transverse momentum jets at the LHC. Using the light-ray operator product expansion, the scaling behavior of multi-point correlators can be computed from the expectation value of the twist-2 spin- $J$ light-ray operators, $O^{[J]}$ , in this state, $Tr [ρ O^{[J]}]$ . We compute the light-ray density matrix at next-to-leading order, and combine this with results for the next-to-leading logarithmic scaling behavior of the correlators up to six-points, comparing with CMS Open Data. This theoretical accuracy allows us to resolve the quantum scaling dimensions of QCD light-ray operators inside jets at the LHC. Our factorization theorem for the light-ray density matrix at the LHC completes the link between recent developments in the study of energy correlators and LHC phenomenology, opening the door to a wide variety of precision jet substructure studies.
↳ hep-phhep-exnucl-exnucl-thPRD(2025)·133 citations
08
Nonparametric Representation of Neutron Star Equation of State Using Variational Autoencoder
Ming-Zhe Han · Shao-Peng Tang · Yi-Zhong Fan
We introduce a new nonparametric representation of the neutron star (NS) equation of state (EoS) by using the variational autoencoder (VAE). As a deep neural network, the VAE is frequently used for dimensionality reduction since it can compress input data to a low-dimensional latent space using the encoder component and then reconstruct the data using the decoder component. Once a VAE is trained, one can take the decoder of the VAE as a generator. We employ 100,000 EoSs that are generated using the nonparametric representation method based on \citet{2021ApJ...919...11H} as the training set and try different settings of the neural network, then we get an EoS generator (trained VAE's decoder) with four parameters. We use the mass\textendash{}tidal-deformability data of binary neutron star (BNS) merger event GW170817, the mass\textendash{}radius data of PSR J0030+0451, PSR J0740+6620, PSR J0437-4715, and 4U 1702-429, and the nuclear constraints to perform the joint Bayesian inference. The overall results of the analysis that includes all the observations are $R_{1.4} = 12.5 9_{- 0.42}^{+ 0.36} km$ , $Λ_{1.4} = 48 9_{- 110}^{+ 114}$ , and $M_{max} = 2.2 0_{- 0.19}^{+ 0.37} M_{⊙}$ ( $90%$ credible levels), where $R_{1.4}$ / $Λ_{1.4}$ are the radius/tidal-deformability of a canonical $1.4 M_{⊙}$ NS, and $M_{max}$ is the maximum mass of a non-rotating NS. The results indicate that the implementation of the VAE techniques can obtain the reasonable results, while accelerate calculation by a factor of $\sim$ 3\textendash10 or more, compared with the original method.
↳ astro-ph.HEastro-ph.IMnucl-thApJ(2023)·19 citations
09
Gravitational Wave Signal for Quark Matter with Realistic Phase Transition
Yuki Fujimoto🇯🇵 · Kenji Fukushima🇯🇵 · Kenta Hotokezaka🇯🇵 · Koutarou Kyutoku🇯🇵
The cores of neutron stars (NSs) near the maximum mass realize the most highly compressed matter in the universe where quark degrees of freedom may be liberated. Such a state of dense matter is hypothesized as quark matter (QM) and its presence has awaited to be confirmed for decades in nuclear physics. Gravitational waves from binary NS mergers are expected to convey useful information called the equation of state (EOS). However, the signature for QM with realistic EOS is not yet established. Here, we show that the gravitational wave in the post-merger stage can distinguish the theory scenarios with and without a transition to QM. Instead of adopting specific EOSs as studied previously, we compile reliable EOS constraints from the ab initio approaches. We demonstrate that early collapse to a black hole after NS merger signifies softening of the EOS associated with the onset of QM in accord with ab initio constraints. Nature of hadron-quark phase transition can be further constrained by the condition that electromagnetic counterparts need to be energized by the material left outside the remnant black hole.
↳ astro-ph.HEgr-qcnucl-thPRL(2023)·87 citations
10
Mixing effects on 1S and 2S state heavy mesons in the light-front quark model
Ahmad Jafar Arifi🇰🇷 · Ho-Meoyng Choi🇰🇷 · Chueng-Ryong ji🇺🇸 · Yongseok Oh🇰🇷
The mass spectra and wave functions of both $1 S$ and $2 S$ state heavy pseudoscalar ( $P$ ) and vector ( $V$ ) mesons are analyzed within the light-front quark model. Important empirical constraints employed in our analysis of the mass spectra and wave functions are the experimental mass-gap relation, $Δ M_{P} > Δ M_{V}$ , where $Δ M_{P (V)} = M_{P (V)}^{2 S} - M_{P (V)}^{1 S}$ and the hierarchy of the decay constants, $f_{1 S} > f_{2 S}$ , between $1 S$ and $2 S$ meson states. We maintain the orthogonality of the trial wave functions of the $1 S$ and $2 S$ states in our variational calculation of the Hamiltonian with the Coulomb plus confining potentials and treat the hyperfine interaction perturbatively for the heavy-heavy and heavy-light $P$ and $V$ mesons due to the nature of the heavy quark symmetry. Realizing that the empirical constraints cannot be satisfied without mixing of the $1 S$ and $2 S$ states, we find the lower bound of the mixing angle $θ$ between $1 S$ and $2 S$ states as $θ_{c} = cot^{- 1} (26) /2 ≃ 6^{\circ}$ and obtain the optimum value of the mixing angle around $1 2^{\circ}$ to cover both the charm and bottom flavors of the heavy quark. The mixing effects are found to be more significant to the $2 S$ state mesons than to the $1 S$ state mesons. The properties of $1 S$ and $2 S$ state mesons including the mass spectra, decay constants, twist-2 distribution amplitudes, and electromagnetic form factors are computed. Our results are found to be in a good agreement with the available data and lattice simulations. In particular, the $2 S$ state pseudoscalar $D_{s}$ meson is predicted to have a mass of $2600$ MeV, which is very close to the mass of the newly discovered $D_{s 0} (2590)^{+}$ meson by the LHCb Collaboration. This supports the interpretation of the observed state as a radial excitation of the $D_{s}^{+}$ meson.
↳ hep-phnucl-thPRD(2022)·48 citations
11
In-medium polarization tensor in strong magnetic fields (I): Magneto-birefringence at finite temperature and density
Koichi Hattori🇨🇳 · Kazunori Itakura🇯🇵
We investigate in-medium polarization effects of the fermion and antifermion pairs at finite temperature and density in strong magnetic fields within the lowest Landau level approximation. Inspecting the integral representation of the polarization tensor by analytic and numerical methods, we provide both the real and imaginary parts of the polarization tensor obtained after delicate interplay between the vacuum and medium contributions essentially due to the Pauli-blocking effect. Especially, we provide a complete analytic form of the polarization tensor at zero temperature and finite density that exhibits an exact cancellation and associated relocation of the singular threshold behaviors for a single photon decay to a fermion and antifermion pair. As a physical application of the in-medium polarization tensor, we discuss the magneto-birefringence that is polarization-dependent dispersion relations of photons induced by the strong magnetic fields.
↳ hep-phastro-ph.HEnucl-thAnnals Phys.(2022)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE