Explore the vast range of titles available.

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.

In this work it is shown how the entropy scaling paradigm introduced by Rosenfeld (Phys Rev A 15:2545–2549, 1977, https://doi.org/10.1103/PhysRevA.15.2545 ) can be extended to calculate the viscosities of branched alkanes by group contribution methods (GCM), making the technique more predictive. Two equations of state (EoS) requiring only a few adjustable parameters (Lee–Kesler–Plöcker and PC-SAFT) were used to calculate the thermodynamic properties of linear and branched alkanes. These EOS models were combined with first-order and second-order group contribution methods to obtain the fluid-specific scaling factor allowing the scaled viscosity values to be mapped onto the generalized correlation developed by Yang et al. (J Chem Eng Data 66:1385–1398, 2021, https://doi.org/10.1021/acs.jced.0c01009 ) The second-order scheme offers a more accurate estimation of the fluid-specific scaling factor, and overall the method yields an AARD of 10 % versus 8.8 % when the fluid-specific scaling factor is fit directly to the experimental data. More accurate results are obtained when using the PC-SAFT EoS, and the GCM generally out-performs other estimation schemes proposed in the literature for the fluid-specific scaling factor.

Hanbury-Brown-Twiss (HBT) correlations for charged pions in central Au+Au collisions at s NN = 2.4 − 7.7 GeV (corresponding to beam kinetic energies in the fixed target frame from E lab = 1.23 to 30 GeV/nucleon) are calculated using the ultra-relativistic quantum molecular dynamics model with different equations of state (EoSs). The effects of a phase transition at high baryon densities are clearly observed in the explored HBT parameters. The results show that the available data on the HBT radii, R O / R S and R O 2 − R S 2 , in the investigated energy region favor a relatively stiff EoS at low beam energies, which then turns into a soft EoS at high collision energies consistent with astrophysical constraints on the high-density EoS of quantum chromodynamics (QCD). The specific effects of two different phase transition scenarios on R O / R S and R O 2 − R S 2 are investigated. A phase transition with a significant softening of the EoS below four times the nuclear saturation density can be excluded using HBT data. Our results highlight that the pion’s R O /R S and R O 2 − R S 2 are sensitive to the stiffness of the EoS and can be used to constrain and understand the QCD EoS in a high baryon density region.

Carbon has been proposed as a major component in the Martian core alongside sulfur for its siderophile behavior during core‐mantle segregation. However, the core C content remains poorly constrained, due to uncertainties in both seismically observed core properties and the equation of state of C‐bearing Fe‐rich liquids. Here we conducted first‐principles molecular dynamics simulations to investigate the equation of state and sound velocity of Fe–S–C liquids under pressures of 10–55 GPa and temperatures of 1,700–3,200 K, conditions relevant to the Martian core. Our results show that the presence of C increases the sound velocity of Fe–S liquids, in contrast to what is observed for other light elements such as S, O, and H. Regardless of the particular seismic model used for the Martian core, we find that about 4.3 ± 1.5 wt% C is required to reproduce the velocity of the core, confirming its role as a major light element.

We trap individual 1D Bose gases and obtain the associated equation of state by combining calibrated confining potentials with in situ density profiles. Our observations agree well with the exact Yang-Yang 1D thermodynamic solutions under the local density approximation. We find that our final 1D system undergoes inefficient evaporative cooling that decreases the absolute temperature, but monotonically reduces a degeneracy parameter.

Two sets of shock compression tests (i.e. conventional and reverse impact) were conducted to determine the shock response of two rock materials using a plate impact facility. Embedded manganin stress gauges were used for the measurements of longitudinal stress and shock velocity. Photon Doppler velocimetry was used to capture the free surface velocity of the target. Experimental data were obtained on a fine-grained marble and a coarse-grained gabbro over a shock pressure range of approximately 1.5-12 GPa. Gabbro exhibited a linear Hugoniot equation of state (EOS) in the pressure-particle velocity (P-up) plane, while for marble a nonlinear response was observed. The EOS relations between shock velocity (US) and particle velocity (up) are linearly fitted as US = 2.62 + 3.319up and US = 5.4 85 + 1.038up for marble and gabbro, respectively. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’.

We review the role and properties of hyperons in finite and infinite nuclear systems. In particular, we present different production mechanisms of hypernuclei, as well as several aspects of hypernuclear γ-ray spectroscopy, and the weak decay modes of hypernuclei. Then we discuss the construction of hyperon–nucleon and hyperon–hyperon interactions on the basis of the meson-exchange and chiral effective field theories. Recent developments based on the so-called Vlow k approach and lattice quantum chromodynamics will also be addressed. Finally, we go over some of the effects of hyperons on the properties of neutron and proto-neutron stars with an emphasis on the so-called ‘hyperon puzzle’, i.e. the problem of the strong softening of the equation of state, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a problem which has become more intriguing and difficult to solve due the recent measurements of approximately 2M⊙ millisecond pulsars. We discuss some of the solutions proposed to tackle this problem. We also re-examine the role of hyperons on the cooling properties of newly born neutron stars and on the development of the so-called r-mode instability.

In order to determine an accurate and reliable high‐pressure and high‐temperature equation of state (EOS) of MgO, unified analyses were carried out for various pressure‐scale‐free experimental data sets measured at 1 atm to 196 GPa and 300–3700 K, which are zero‐pressure thermal expansion data, zero‐pressure and high‐temperature adiabatic bulk modulus (KS) data, room temperature and high‐pressure KS data, and shock compression data. After testing several EOS models based on the Mie‐Grüneisen‐Debye description for the thermal pressures with the Vinet and the third‐order Birch‐Murnaghan equations for the 300‐K isothermal compression, we determined the K′T0 and γ(V) using a new functional form γ = γ0{1 + a[(V/V0)b − 1]} to express the volume dependence of the Grüneisen parameter. Through least squares analyses with prerequisite zero‐pressure and room temperature properties of V0, KS0, α0, and CP0, we simultaneously optimized a set of parameters of K′T0, γ0, a, and b required to represent the P‐V‐T EOS. Determined new EOS models of MgO successfully reproduced all the analyzed P‐V‐T‐KS data up to 196 GPa and 3700 K within the uncertainties, and the total residuals between calculated and observed pressures were found to be 0.8 GPa in root mean squares. These EOS models, even though very simple, are able to reproduce available data quite accurately in the wide pressure‐temperature range and completely independent from other pressure scales. We propose these models for primary pressure calibration standards applicable to quantitative high‐pressure and high‐temperature experiments.

A cluster of astronomical observations emerged that the present Universe is in a phase of accelerated expansion. To examine the accelerated expansion of the Universe, we used the newly proposed gravity in which torsion scalar is responcible for the accelerated expansion. The investigation is carried out using a parameterized effective equation of state with the free parameters α , β , ω 0 and ω 1 . Also, for the analysis we consider the model of the form f ( T ) = m ( - T ) n , where m ≠ 0 and n are the constants. By constraining the model with the combined H ( z ),  SC ,  unCorBAO sample datasets. The model appeared to be in good agreement with the observations, and we were able to determine the parameter values that fit the data the best. Finally, we examined how the deceleration parameter and equation of state parameter behaved in relation to the parameter values that best suited the data.

We present a strangeness-neutral equation of state for QCD that exhibits critical behavior and matches lattice QCD results for the Taylor-expanded thermodynamic variables up to fourth order in μ B / T . It is compatible with the SMASH hadronic transport approach and has a range of temperatures and baryonic chemical potentials relevant for phase II of the Beam Energy Scan at RHIC. We provide an updated version of the software BES-EoS, which produces an equation of state for QCD that includes a critical point in the 3D Ising model universality class. This new version also includes isentropic trajectories and the critical contribution to the correlation length. Since heavy-ion collisions have zero global net-strangeness density and a fixed ratio of electric charge to baryon number, the BES-EoS is more suitable to describe this system. Comparison with the previous version of the EoS is thoroughly discussed.