Nuclear Theory·nucl-th

Tuesday·November 22, 2022

21 papers—8 primary·13 cross-listed

01
Pre-hydrodynamic evolution in large and small systems
Tiago Nunes da Silva🇧🇷 · David D. Chinellato🇧🇷 · André V. Giannini🇧🇷 · Maurício N. Ferreira🇪🇸 · Gabriel S. Denicol🇧🇷 · Maurício Hippert🇺🇸 · Matthew Luzum🇧🇷 · Jorge Noronha🇺🇸 · Jun Takahashi🇧🇷
We extend our previous investigation of the effects of pre-hydrodynamic evolution on final-state observables in heavy-ion collisions to smaller systems. We use a state-of-the-art hybrid model for the numerical simulations with optimal parameters obtained from a previous Bayesian study. By studying p-Pb collisions, we find that the effects due to the assumption of a conformal evolution in the pre-hydrodynamical stage are even more important in small systems. We also show that this effect depends on the time duration of the pre-equilibrium stage, which is further enhanced in small systems. Finally, we show that the recent proposal of a free-streaming with subluminal velocity for the pre-equilibrium stage, thus effectively breaking conformal invariance, can alleviate the contamination of final state observables. Our study further reinforces the need for moving beyond conformal approaches in pre-equilibrium dynamics modeling, especially when extracting transport coefficients from hybrid models in the high-precision era of heavy-ion collisions.
nucl-thhep-phPRC(2023)·21 citations
02
Effect of the $σ$ -cut potential on the properties of neutron stars with or without a hyperonic core
N. K. Patra · B. K. Sharma · A. Reghunath · A. K. H. Das · T. K. Jha
Motivated by the recent observation of high-mass pulsars ( $M ≃ 2 M_{⊙}$ ), we employ the $σ$ -cut potential on the equation of state (EOS) of high-density matter and the properties of neutron stars within the relativistic mean-field (RMF) model using TM1 $^{*}$ parameter set. The $σ$ -cut potential is known to reduce the contributions of the $σ$ field, resulting in a stiffer EOS at high densities and hence leading to larger neutron star masses without affecting the properties of nuclear matter at normal saturation density. We also analyzed the effect of the same on pure neutron matter and also on the neutron star matter with and without hyperonic core and compared it with the available theoretical, experimental, and observational data. The corresponding tidal deformability ( $Λ_{1.4}$ ) is also calculated. With the choice of meson-hyperon coupling fixed to hypernuclear potentials, we obtain $\approx 10 %$ increase in mass by employing the $σ$ -cut potential for $f_{s} = 0.6$ . Our results are in good agreement with various experimental constraints and observational data, particularly with the GW170817 data.
nucl-thastro-ph.HEgr-qchep-phPRC(2022)·14 citations
03
Soft dipole resonance in neutron-rich $^{8}$ He
Takayuki Myo · Myagmarjav Odsuren · Kiyoshi Kato
In neutron-rich $^{8}$ He, we study the soft dipole resonance, which is regarded as a dipole oscillation of four valence neutrons against the $^{4}$ He core, and its effect on the low-energy electric dipole strength with a $^{4}$ He+ $n$ + $n$ + $n$ + $n$ five-body cluster model. This work is an extended study of an earlier letter [T. Myo and K. Katō, Phys. Rev. C106, L021302 (2022)]. The five-body unbound $1^{-}$ states of $^{8}$ He are obtained with the complex energy eigenvalues by using the complex scaling method and the dipole strength is calculated in terms of the complex-scaled Green's function. Two kinds of the dominant excitation modes are confirmed in the dipole strength below 20 MeV of the excitation energy. The strengths below 10 MeV are exhausted by the $^{7}$ He+ $n$ channel, which sequentially decays to $^{6}$ He+ $n$ + $n$ . Above 10 MeV, the strengths arise from the soft dipole mode of four neutrons ( $4 n$ ) oscillating against the $^{4}$ He core. We further explore the possibility of the soft dipole resonance for this state by carefully searching for the resonance pole and finally predict the corresponding resonance with the excitation energy of 14 MeV and the decay width of 21 MeV. The soft dipole resonance exhausts about half of the dipole strength in the relative motion between the $^{4}$ He core and $4 n$ .
nucl-thnucl-exPTEP(2022)·8 citations
04
An expedition to the islands of stability in the first-order causal hydrodynamics
Rajesh Biswas · Sukanya Mitra · Victor Roy
The recently proposed connection between the Lorentz invariance of stability and the speed of signal propagation has been tested for a first-order relativistic dissipative hydrodynamic theory. The fact that the stability situation in different reference frames agrees with each other only as long as the signal propagation respects causality, has been explicitly established for the theory, which is microscopically derived from the covariant kinetic equation in general hydrodynamic frames with arbitrary momentum-dependent interactions.
nucl-thhep-phPLB(2023)·14 citations
05
Kaon-meson condensation and $Δ$ resonance in hyperonic stellar matter within a relativistic mean-field model
Fu Ma🇨🇳 · Chen Wu🇨🇳 · Wenjun Guo🇨🇳
We study the equation of state of dense baryon matter within the relativistic mean-field model, and we include $Δ$ (1232) isobars into IUFSU model with hyperons and consider the possibility of kaon meson condensation. We find that it is necessary to consider the $Δ$ resonance state inside the massive neutron star. The critical density of Kaon mesons and hyperons is shifted to a higher density region, in this respect an early appearance of $Δ$ resonances is crucial to guarantee the stability of the branch of hyperonized star with the difference of the coupling parameter $x_{σ Δ}$ constrained based on the QCD rules in nuclear matter. The $Δ$ resonance produces a softer equation of state in the low density region, which makes the tidal deformability and radius consistent with the observation of GW170817. As the addition of new degrees of freedom will lead to a softening of the equation of state, the $σ$ -cut scheme, which states the decrease of neutron star mass can be lowered if one assumes a limited decrease of the $σ$ -meson strength at $ρ_{B}$ ( $ρ_{B} > ρ_{0}$ ), finally we get a maximum mass neutron star with $Δ$ resonance heavier than 2 $M_{⊙}$ .
nucl-thPRC(2023)·14 citations
06
Toy model to understand oscillatory behavior in timelike nucleon form factors
Ri-Qing Qian🇨🇳 · Zhan-Wei Liu🇨🇳 · Xu Cao🇨🇳 · Xiang Liu🇨🇳
To understand the oscillatory behavior exhibited in the timelike electromagnetic form factors of nucleons, we propose a toy model based on the Jost function of the $N N ˉ$ pair into the timelike form factors with the help of the distorted-wave Born approximation. By constructing a simple square-well potential reflecting the final-state interaction of $N N ˉ$ , we naturally represent the damped oscillatory phenomenon in the timelike electromagnetic form factors of nucleons. Especially, our study reveals that the ``period" of the oscillation is approximately determined by the Yukawa interaction range $1/ m_{π}$ . Other possible potentials are also discussed. The threshold enhancements of the cross sections for $e^{+} e^{-} \to n n ˉ$ , $Λ Λ ˉ$ , and $Λ_{c} Λ ˉ_{c}$ can also be understand within this scenario.
nucl-thhep-exhep-phnucl-exPRD(2023)·17 citations
07
Probing the Non-exponential Decay Regime in Open Quantum Systems
S. M. Wang · W. Nazarewicz · A. Volya · Y. G. Ma
The most important law of radioactivity is that of the exponential decay. In the realm of quantum mechanics, however, this decay law is neither rigorous nor fundamental. The deviations from the exponential decay have been observed experimentally at the early stage of a decay process, but there is little evidence for non-exponential behavior at long times. Yet such long-term non-exponentiality is expected theoretically to probe the non-resonant background components of the initial wave function which preserve the structural interference and the memory of how the state was created. In this paper, we propose new observables that can be used for experimental investigations of the post-exponential decay regime, including the decay of threshold resonances, particle correlations in three-body decays, and interference between near-lying resonances. While the specific examples presented in this work pertain to atomic nuclei, the properties of non-exponential decay are generic, i.e., they apply to other many-body open quantum systems, such as hadrons, atoms, molecules, and nanostructures.
nucl-thnucl-exquant-phPRResearch(2023)·24 citations
08
QCD Equation of State of Dense Nuclear Matter from a Bayesian Analysis of Heavy-Ion Collision Data
Manjunath Omana Kuttan🇩🇪 · Jan Steinheimer🇩🇪 · Kai Zhou🇩🇪 · Horst Stoecker🇩🇪
Bayesian methods are used to constrain the density dependence of the QCD Equation of State (EoS) for dense nuclear matter using the data of mean transverse kinetic energy and elliptic flow of protons from heavy ion collisions (HIC), in the beam energy range $s_{NN} = 2 - 10 G e V$ . The analysis yields tight constraints on the density dependent EoS up to 4 times the nuclear saturation density. The extracted EoS yields good agreement with other observables measured in HIC experiments and constraints from astrophysical observations both of which were not used in the inference. The sensitivity of inference to the choice of observables is also discussed.
hep-phhep-exnucl-exnucl-thPRL(2023)·65 citations
09
How does dark matter affect compact star properties and high density constraints of strongly interacting matter
Violetta Sagun🇵🇹 · Edoardo Giangrandi🇵🇹 · Oleksii Ivanytskyi🇵🇱 · Costança Providência🇵🇹 · Tim Dietrich🇩🇪
We study the impact of asymmetric bosonic dark matter on neutron star properties, including possible changes of tidal deformability, maximum mass, radius, and matter distribution inside the star. The conditions at which dark matter particles tend to condensate in the star's core or create an extended halo are presented. We show that dark matter condensed in a core leads to a decrease of the total gravitational mass and tidal deformability compared to a pure baryonic star, which we will perceive as an effective softening of the equation of state. On the other hand, the presence of a dark matter halo increases those observable quantities. Thus, observational data on compact stars could be affected by accumulated dark matter and, consequently, constraints we put on strongly interacting matter at high densities. To confirm the presence of dark matter in the compact star's interior, and to break the degeneracy between the effect of accumulated dark matter and strongly interacting matter properties at high densities, several astrophysical and GW tests are proposed.
↳ astro-ph.HEgr-qchep-phnucl-thEPJ Web Conf.(2022)·15 citations
10
Projection algorithm for state preparation on quantum computers
I. Stetcu🇺🇸 · A. Baroni🇺🇸 · J. Carlson🇺🇸
We present an efficient method to prepare states of a many-body system on quantum hardware, first isolating individual quantum numbers and then using time evolution to isolate the energy. Our method in its simplest form requires only one additional auxiliary qubit. The total time evolved for an accurate solution is proportional to the ratio of the spectrum range of the trial state to the gap to the lowest excited state, and the accuracy increases exponentially with the time evolved. Isolating the quantum numbers is efficient because of the known eigenvalues, and increases the gap thus shortening the propagation time required. The success rate of the algorithm, or the probability of producing the desired state, is a simple function of measurement times and phases and is dominated by the square overlap of the original state to the desired state. We present examples from the nuclear shell model and the Heisenberg model. We compare this algorithm to previous algorithms for short evolution times and discuss potential further improvements.
↳ quant-phnucl-thPRC(2023)·38 citations
11
Open-quantum-systems approach to in-medium heavy quarkonium dynamics
Alexander Rothkopf🇳🇴
Heavy quarkonium continues to play a central role in the study of nuclear matter under extremes of temperature and density in relativistic heavy-ion collisions. In this talk I report on recent developments in the theoretical description of quarkonium in-medium dynamics using the open-quantum systems approach. Not only does it provide a clear interpretation of the imaginary part of the complex heavy-quark potential but also reveals that a subtle interplay between screening and wavefunction decoherence is responsible for the melting of heavy quarkonium states.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2023)·0 citations
12
Seebeck and Nernst coefficients of a magnetized hot QCD medium with number conserving kernel
Salman Ahamad Khan🇮🇳 · Binoy Krishna Patra🇮🇳
We have studied the thermoelectric response of a hot and magnetized QCD medium created in the noncentral events at heavy-ion collider experiments. The collisional aspects of the medium have been embedded in the relativistic Boltzmann transport equation (RBTE) using Bhatnagar-Gross-Krook (BGK) collision integral, which insures the particle number conservation, unlike the commonly used relaxation time approximation (RTA). We have incorporated the thermal medium effects in the guise of a quasiparticle model, where the interaction among the partons is embodied in the medium dependent mass of the quark, which has been evaluated using the framework of the perturbative thermal QCD with a magnetic field in the background. In the absence of $B$ , the Seebeck coefficient for individual quark flavors gets slightly reduced in the BGK term in comparison to naive RTA, while it gets enhanced for the composite partonic medium. In the presence of strong magnetic field ( $B$ ), the BGK term enhances the Seebeck coefficient for the individual flavors as well as that for medium. The medium Seebeck coefficient rises with the strength of quark chemical potential ( $μ$ ) in the absence as well as that in the strong $B$ . We observe chirality dependence in the Seebeck and Nernst coefficients in the weak magnetic field as the degeneracy in the masses of left- and right-handed chiral modes gets lifted in the weak $B$ . Seebeck coefficient is larger for left-handed modes contrary to the Nernst coefficient which is higher for the right-handed modes. Seebeck coefficient is almost similar in the weak field for both the collision term, while Nernst coefficient gets reduced (enhanced) for $L$ ( $R$ ) modes considerably in the BGK collision term.
↳ hep-phnucl-thPRD(2023)·7 citations
13
$η$ meson in strange magnetized matter
Shivanshi Tiwari · Rajesh Kumar🇺🇸 · Manisha Kumari · Arvind Kumar
The in-medium properties of $η$ mesons are studied in hot and dense isospin asymmetric strange magnetized matter using the chiral SU(3) hadronic mean-field model. The scalar and vector density of baryons are expressed in terms of thermal distribution functions at finite temperature and magnetic field and have dependence on the scalar fields $σ$ , $ζ$ , and $δ$ through the effective mass of baryons and the dependence on the vector fields $ω, ρ$ , and $ϕ$ through the effective chemical potential. The properties of $η$ mesons get modified in a hot and dense magnetized environment through the medium-modified nucleons and hyperons. The negative mass shift obtained gives rise to optical potential, which is attractive in the medium and suggests a possibility of $η$ -mesic bound states formation. The addition of hyperons in the medium enhances the attractive interactions and causes an increased negative mass shift for $η$ mesons.
↳ hep-phnucl-thEur.Phys.J.Plus(2024)·2 citations
14
Anomalous dimension of transverse momentum broadening in planar $N = 4$ SYM
Paul Caucal🇫🇷
The typical transverse momentum $Q_{s} (t)$ (or "saturation" momentum) acquired by a hard particle propagating through a $N = 4$ SYM plasma increases over time like $t^{γ}$ , with an anomalous exponent $γ > 1/2$ characteristic of super-diffusion. This anomalous exponent is a function of the 't Hooft coupling $λ = g^{2} N_{c}$ . Recently, a method has been proposed to systematically compute the perturbative series of $γ (λ)$ at weak coupling. This method relies on the traveling wave interpretation of the time evolution of $Q_{s} (t)$ and on the dominance of soft-collinear radiative corrections at large times. In this paper, we compute $γ (λ)$ up to $O (λ^{2})$ using the double logarithmic behaviour of the BFKL equation in planar $N = 4$ SYM at three loops. This calculation allows us to discuss the transition towards the strong coupling regime where AdS/CFT calculations predict $γ \to 1$ .
↳ hep-phhep-thnucl-thEPJ Web Conf.(2022)·0 citations
15
Equation of state for strange quark matter: Linking the Nambu--Jona-Lasinio model to perturbative QCD
Marcus Benghi Pinto🇧🇷
Neutron star constraints and {\it ab initio} pQCD evaluations require the EoS representing cold quark matter to be stiff at intermediate baryonic densities and soft at high- $n_{B}$ . Here, I suggest that the three flavor NJL model with a density dependent repulsive coupling, $G_{V} (μ)$ , can generate an EoS which interpolates between these two regimes. Such an interpolation requires repulsion to start decreasing with the chemical potential just after chiral transition takes place. The conjecture behind this mechanism is that repulsion should be necessary only as long as the quark condensates, which dress the effective masses, have non-vanishing values. This assumption guarantees that an initially hard EoS suffers a conspicuous change of slope at $E ≃ 0.7 GeVf m^{- 3}$ converging to the pQCD results at higher energy densities. Then, the speed of sound naturally reaches a non-conformal maximum at $n_{B} = 3.23 n_{0} = 0.52 fm^{- 3}$ while the trace anomaly remains positive for all densities, in agreement with recent investigations. These non-trivial results {\it cannot} be simultaneously obtained when $G_{V}$ vanishes or has a fixed value. Therefore, the simple model proposed here is able to link the (non-perturbative) region of intermediate densities to the region where pQCD becomes reliable.
↳ hep-phnucl-thPRC(2023)·10 citations
16
Anomalous magnetohydrodynamics with temperature-dependent electric conductivity and application to the global polarization
Hao-Hao Peng🇨🇳 · Sihao Wu🇨🇳 · Ren-jie Wang🇨🇳 · Duan She🇨🇳 · Shi Pu🇨🇳
We have derived the solutions of the relativistic anomalous magnetohydrodynamics with longitudinal Bjorken boost invariance and transverse electromagnetic fields in the presence of temperature or energy density dependent electric conductivity. We consider the equations of states in a high temperature limit or in a high chiral chemical potential limit. We obtain both perturbative analytic solutions up to the order of \hbar and numerical solutions in our configurations of initial electromagnetic fields and Bjorken flow velocity. Our results show that the temperature or energy density dependent electric conductivity plays an important role to the decaying of the energy density and electromagnetic fields. We also implement our results to the splitting of global polarization for \Lambda and \bar{\Lambda} hyperons induced by the magnetic fields. Our results for the splitting of global polarization disagree with the experimental data in low energy collisions, which implies that the contribution from gradient of chemical potential may dominate in the low energy collisions.
↳ hep-phnucl-thPRD(2023)·23 citations
17
Chiral instabilities & the fate of chirality imbalance in non-Abelian plasmas
Sören Schlichting🇩🇪 · Sayantan Sharma🇮🇳
We present a first principles study of chiral plasma instabilities and axial charge transfer in non-Abelian plasmas with a strong gauge-matter coupling $g^{2} N_{f} = 64$ , by performing $3 + 1$ D real-time classical-statistical lattice simulation with dynamical fermions. We explicitly demonstrate for the first time that -- unlike in an Abelian plasma -- the transfer of chirality from the matter sector to the gauge fields occurs predominantly due to topological sphaleron transitions. We elaborate on the similarities and differences of the axial charge dynamics in cold Abelian $U (1)$ and non-Abelian $S U (2)$ plasmas, and comment on the implications of our findings for the study of anomalous transport phenomena, such as the chiral magnetic effect in QCD matter.
↳ hep-phhep-latnucl-thPRL(2023)·14 citations
18
Thoughts about the utility of perturbative QCD in the cores of neutron stars
Aleksi Kurkela🇳🇴
In this contribution, I discuss the utility that perturbative QCD offers in studying the matter in the cores of neutron stars. I discuss the reasons why perturbative QCD can constrain the equation of state at densities far below the densities where we can perform controlled calculations. I discuss how perturbative QCD can inform nuclear modelling of neutron stars and how it influences equation-of-state inference. And finally, I discuss the implications to the QCD phase diagram and argue that interesting features in the equation of state revealed by the QCD input may be used to argue for the existence of quark-matter cores in most massive neutron stars.
↳ hep-phastro-ph.HEnucl-thEPJ Web Conf.(2022)·9 citations
19
Probing phase transition in neutron stars via the crust-core interfacial mode
Jiaxiang Zhu · Chuming Wang · Chengjun Xia · Enping Zhou · Yiqiu Ma
Gravitational waves emitted from the binary neutron star (BNS) systems can carry information about the dense matter phase in these compact stars. The crust-core interfacial mode is an oscillation mode in a neutron star and it depends mostly on the equation of the state of the matter in the crust-core transition region. This mode can be resonantly excited by the tidal field of an inspiraling-in BNS system, thereby affecting the emitted gravitational waves, and hence could be used to probe the equation of state in the crust-core transition region. In this work, we investigate in detail how the first-order phase transition inside the neutron star affects the properties of the crust-core interfacial mode, using a Newtonian fluid perturbation theory on a general relativistic background solution of the stellar structure. Two possible types of phase transitions are considered: (1) the phase transitions happen in the fluid core but near the crust-core interface, which results in density discontinuities; and (2) the strong interaction phase transitions in the dense core (as in the conventional hybrid star case). These phase transitions' impacts on interfacial mode properties are discussed. In particular, the former phase transition has a minor effect on the M-R relation and the adiabatic tidal deformability, but can significantly affect the interfacial mode frequency and thereby could be probed using gravitational waves. For the BNS systems, we discuss the possible observational signatures of these phase transitions in the gravitational waveforms and their detectability. Our work enriches the exploration of the physical properties of the crust-core interfacial mode and provides a promising method for probing the phase transition using the seismology of a compact star.
↳ astro-ph.HEgr-qcnucl-thPRD(2023)·19 citations
20
On chiral spin symmetry and the QCD phase diagram
Owe Philipsen🇩🇪 · Leonid Ya. Glozman🇩🇪 · Peter Lowdon🇦🇹 · Robert D. Pisarski🇺🇸
Recently, an approximate $S U (4)$ chiral spin-flavour symmetry was observed in multiplet patterns of QCD meson correlation functions, in a temperature range above the chiral crossover. This symmetry is larger than the chiral symmetry of massless QCD, and can only arise effectively when colour-electric quark-gluon interactions dynamically dominate the quantum effective action. At temperatures about three times the crossover temperature, these patterns disappear again, indicating the screening of colour-electric interactions, and the expected chiral symmetry is recovered. In this contribution we collect independent evidence for such an intermediate temperature range, based on screening masses and the pion spectral function. Both kinds of observables behave non-perturbatively in this window, with resonance-like peaks for the pion and its first excitation disappearing gradually with temperature. Using symmetry arguments and the known behaviour of screening masses at small densities, we discuss how this chiral spin symmetric band continues into the QCD phase diagram.
↳ hep-lathep-phnucl-thPoS(2023)·7 citations
21
On-shell versus curvature mass parameter fixing schemes in the three flavor quark-meson model with vacuum fluctuations
Vivek Kumar Tiwari🇮🇳
The vacuum effective potential and phase diagram for the three (2+1) flavor quark-meson model have been computed and compared in an extended mean-field approximation (e-MFA) where the model parameters are fixed by using different renormalization prescriptions after including quark one-loop vacuum fluctuations. When the vacuum one-loop divergence is regularized in the minimal subtraction scheme and the curvature masses of the scalar and pseudo-scalar mesons are used for fixing the parameters, the setting of the quark-meson model with the vacuum term (QMVT) turns out to be inconsistent as one notes that the curvature masses are defined by the evaluation of self-energy at zero momentum. This work constitutes the first application of the consistent on-shell parameter fixing scheme to the three flavor quark-meson (QM) model. In this setting of the renormalized quark-meson (RQM) model, the physical (pole) masses of the $π, K, η$ and $η^{'}$ pseudo-scalar mesons and the scalar $σ$ meson,the pion decay constant and kaon decay constant are put into the relation of the running mass parameter and couplings by using the on-shell and the minimal subtraction renormalization schemes. The nonstrange direction normalized vacuum effective potential plots for both the RQM model and QMVT model, are exactly identical for the $m_{σ} =$ 658.8 MeV while the nonstrange direction order parameter temperature variations and phase diagrams for both the models RQM and PQMVT are identical when the $m_{σ}$ value is smaller by 10 MeV i.e. $m_{σ} =$ 648 MeV. This happens because the normalized vacuum effective potential variation in the nonstrange direction is somewhat influenced by its variation in the strange direction.
↳ hep-phnucl-thPRD(2023)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE