Energy Slope Research Articles

Constraining Hadron-quark Phase Transition Parameters within the Quark-mean-field Model Using Multimessenger Observations of Neutron Stars

Abstract We extend the quark mean-field (QMF) model for nuclear matter and study the possible presence of quark matter inside the cores of neutron stars. A sharp first-order hadron-quark phase transition is implemented combining the QMF for the hadronic phase with “constant-speed-of-sound” parameterization for the high-density quark phase. The interplay of the nuclear symmetry energy slope parameter, L, and the dimensionless phase transition parameters (the transition density n trans/n 0, the transition strength Δε/ε trans, and the sound speed squared in quark matter ) are then systematically explored for the hybrid star properties, especially the maximum mass M max and the radius and the tidal deformability of a typical 1.4 M ⊙ star. We show the strong correlation between the symmetry energy slope L and the typical stellar radius R 1.4, similar to that previously found for neutron stars without a phase transition. With the inclusion of phase transition, we obtain robust limits on the maximum mass (M max < 3.6 M ⊙) and the radius of 1.4 M ⊙ stars (R 1.4 ≳ 9.6 km), and we find that a phase transition that is too weak (Δε/ε trans ≲ 0.2) taking place at low densities ≲1.3–1.5 n 0 is strongly disfavored. We also demonstrate that future measurements of the radius and tidal deformability of ∼1.4 M ⊙ stars, as well as the mass measurement of very massive pulsars, can help reveal the presence and amount of quark matter in compact objects.

Analytic insights on the information content of new observables

Uncertainty quantification has emerged as a rapidly growing field in nuclear science. Theoretical predictions of physical observables often involve extrapolations to regions that are poorly constrained by laboratory experiments and astrophysical observations. Without properly quantified theoretical errors, such model predictions are of limited value. Also, one often deals with theoretical constructs that involve fundamental quantities that are not accessible to experiment or observation. Particularly relevant in this context is the pressure of pure neutron matter. In this contribution we develop an analytic framework to answer the question of "How can new data reduce uncertainties of current theoretical models?" [P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C81, 051303(R) (2010)]. Simple and insightful expressions are obtained to quantify the impact of one or two new observables on theoretical uncertainties in two critical quantities: the slope of the symmetry energy at saturation density and the pressure of pure neutron matter at twice nuclear matter saturation density.

Constraining the equation of state of dense nuclear matter using thermal emission of neutron stars

In this work, the equation of state (EoS) of the dense matter in the core of neutron stars (NSs) is based on a recently proposed meta-modeling of nuclear matter composed of nucleons, which can be parametrized by empirical quantities such as the energy density at saturation density or the nuclear incompressibility modulus. We use a set of recent observations of the thermal emission of seven NSs in quiescent low-mass X-ray binaries (qLMXBs) in order to find some constraints on the parameters of the meta-model, and thus on the nuclear EoS. This is done in a Bayesian statistical framework using Markov Chain Monte Carlo (MCMC) methods, to perform a simultaneous analysis over the seven sources. For the first time, the theoretical modeling of the EoS is directly implemented in the data analysis. We obtain constraints on the slope of the symmetry energy, MeV, and give the first estimation of its curvature, MeV, and on the isoscalar skewness parameter, MeV. Radii of about 12 km are preferred with a good fit statistic, yielding a nuclear EoS that is consistent with observational data and recent gravitational waves signals from NSs coalescence.

Approximate solutions of the Schrödinger equation with energy-dependent screened Coulomb potential in D – dimensions

Within the framework of the conventional Nikiforov-Uvarov method and a new form of Greene-Aldrich approximation scheme, we solved the Schrödinger equation with the energy-dependent screened Coulomb potential. Energy eigenvalues and energy eigenfunctions were obtained both approximately and numerically at different dimensions. The energy variations with different potential parameters, quantum numbers and energy slope parameter, respectively were also discussed graphically. The major finding of this research is the effect of the energy slope parameter on the energy spectra, which is seen in the existence of two simultaneous energy values for a particular quantum state. Our special cases also agree with the results obtained from literature, when the energy slope parameter is zero.

Rapidly rotating Δ-resonance-admixed hypernuclear compact stars

We use a set of hadronic equations of state derived from covariant density functional theory to study the impact of their high-density behavior on the properties of rapidly rotating Δ-resonance-admixed hyperonic compact stars. In particular, we explore systematically the effects of variations of the bulk energy isoscalar skewness, Qsat, and the symmetry energy slope, Lsym, on the masses of rapidly rotating compact stars. With models for equation of state satisfying all the modern astrophysical constraints, excessively large gravitational masses of around 2.5M⊙ are only obtained under three conditions: (a) strongly attractive Δ-resonance potential in nuclear matter, (b) maximally fast (Keplerian) rotation, and (c) parameter ranges Qsat≳500 MeV and Lsym≲50 MeV. These values of Qsat and Lsym have a rather small overlap with a large sample (total of about 260) parametrizations of covariant nucleonic density functionals. The extreme nature of requirements (a)-(c) reinforces the theoretical expectation that the secondary object involved in the GW190814 event is likely to be a low-mass black hole rather than a supramassive neutron star.

Interaction of Jets and Submesoscale Dynamics Leads to Rapid Ocean Ventilation

ABSTRACTOcean ventilation is the process by which climatically important tracers such as heat and carbon are exchanged between the atmosphere and ocean interior. In this paper a series of numerical simulations are used to study the interaction of submesoscales and a topographically steered jet in driving rapid ventilation. The ventilation is found to increase both as a function of wind stress and model resolution, with a submesoscale-resolving 1/120° model exhibiting the largest ventilation rate. The jet in this simulation is found to be persistently unstable to submesoscale instabilities, which are known to feature intense vertical circulations. The vertical tracer transport is found to scale as a function of the eddy kinetic energy and mean isopycnal slope, whose behaviors change as a function of the wind stress and due to the emergence of a strong potential vorticity gradient due to the lateral shear of the jet. These results highlight the importance of jet–submesoscale interaction as a bridge between the atmosphere and the ocean interior.

Neutron star inner crust: Effects of rotation and magnetic fields

We study the role of the pasta phases on the properties of rotating and magnetized neutron stars. In order to investigate such systems, we make use of two different relativistic mean-field unified inner-crust--core equations of state, with a different density dependence of the symmetry energy, and an inner crust computed within a Thomas-Fermi calculation. Special attention is given to the crust-core transition density, and the pasta phases effects on the global properties of stars. The effects of strong magnetic fields and fast rotation are computed by solving the Einstein-Maxwell equations self-consistently, taking into account anisotropies induced by the centrifugal and the Lorentz force. The location of the magnetic field neutral line and the maximum of the Lorentz force on the equatorial plane are calculated. The conditions under which they fall inside the inner crust region are discussed. We verified that models with a larger symmetry energy slope show more sensitivity to the variation of the magnetic field. One of the maxima of the Lorentz force, as well as the neutral line, and for a certain range of frequencies, fall inside the inner crust region. This may have consequences in the fracture of the crust, and may help explain phenomena associated with star quakes.

Quantifying separation energy with a modified Capillary Break-up Extensional Rheometer (CaBER) to study polymer solutions

ABSTRACT A Capillary Break-up Extensional Rheometer (CaBER) was modified to enable measurements of the axial force in combination with the related displacement. This makes it possible to determine the separation energy , the tackiness, of a polymer solution between two parallel plates with the CaBER. Separation energies of solutions of linear polystyrene, comb polystyrene and linear poly(methyl methacrylate) in dimethylformamide were measured as model systems. For linear polymers at a critical polymer concentration, there was a drastic change in slope of the separation energy . This critical concentration was shown to be the minimum concentration at which continuous bead-free fibers could be electrospun.

Nuclear pasta in hot and dense matter and its influence on the equation of state for astrophysical simulations

We explore the properties of nuclear pasta appearing in supernova matter, i.e., matter at finite temperature with a fixed proton fraction. The pasta phases with a series of geometric shapes are studied using the compressible liquid-drop (CLD) model, where nuclear matter separates into a dense liquid phase of nucleons and a dilute gas phase of nucleons and $\alpha$ particles. The equilibrium conditions for two coexisting phases are derived by minimization of the total free energy including the surface and Coulomb contributions, which are clearly different from the Gibbs conditions for phase equilibrium due to the finite-size effects. Compared to the results considering only spherical nuclei, the inclusion of pasta phases can delay the transition to uniform matter and enlarge the region of nonuniform matter in the phase diagram. The thermodynamic quantities obtained in the present calculation with the CLD model are consistent with those in the realistic equation of state table for astrophysical simulations using the Thomas--Fermi approximation. It is found that the density ranges of various pasta shapes depend on both the temperature $T$ and the proton fraction $Y_p$. Furthermore, the nuclear symmetry energy and its density dependence may play crucial roles in determining the properties of pasta phases. Our results suggest that the pasta phase diagram is most sensitively dependent on the symmetry energy slope $L$ especially in the low-$Y_p$ and high-$T$ region.

Investigation of optical polarization characteristics for an AlGaN-based quantum well structure

The anisotropic optical properties of an AlGaN-based quantum well (QW) structure are investigated by using the effective-mass theory. Firstly, the crystal-field bowing parameter (bcr = −0.087) and the slope (bs = 8) of the crystal-field splitting energy (∆cr) — in-plane strain (εxx) curve are obtained by comparing the calculated degree of polarization (DOP) of the AlGaN alloy with the experimental values. Then, the DOP of Al0.35Ga0.65N/AlxGa1-xN single QW structures with various Al-content (x = 0.5, 0.45, 0.55) in the barrier layer is calculated by employing the obtained parameters. The DOP is enhanced from −43.15% to −4.47% with increasing Al-content at J = 100 A cm−2. By increasing the injection current density or the residual strain in the active region, the DOP can be increased/decreased by modulating the Al component of the barrier layer due to the different polarization characteristics of the transition levels. In addition, the AlGaN-based QW structure with lower Al-content in the barrier layer shows the larger spontaneous emission rate.

Bootstrap analysis of the correlation between neutron skin thickness and the slope of symmetry energy

This work illustrates the use of bootstrap methods to quantify the statistical uncertainties on the correlation coefficients between the slope of the symmetry energy and the neutron skin thickness in heavy nuclei. By using several energy density functionals, I discuss the density dependence of such a correlation and its evolution with isospin asymmetry. In particular, I observe that the correlation between the slope of the symmetry energy and the neutron skin is present not only at saturation density, but over a much larger density range.

Near-Surface Ocean Kinetic Energy Spectra and Small-Scale Intermittency from Ship-Based ADCP Data in the Bay of Bengal

AbstractHorizontal currents in the Bay of Bengal were measured on eight cruises covering a total of 8600 km using a 300-kHz acoustic Doppler current profiler (ADCP). The cruises are distributed over multiple seasons and regions of the Bay. Horizontal wavenumber spectra of these currents over depths of 12–54 m and wavelengths from 2 to 400 km were decomposed into rotational and divergent components assuming isotropy. An average of across- and along-track spectra over all cruises shows that the spectral slope of horizontal kinetic energy for wavelengths of 10–80-km scales with an exponent of −1.7 ± 0.05, which transitions to a steeper slope for wavelengths above 80 km. The rotational component is significantly larger than the divergent component at scales greater than 80 km, while the ratio of the two is nearly constant with a mean of 1.16 ± 0.4 between 10 and 80 km. The measurements show a fair amount of variability and spectral levels vary between cruises by about a factor of 5 over 10–100 km. Velocity differences over 10–80 km show probability density functions and structure functions with stretched exponential behavior and anomalous scaling. Comparisons with the Garrett–Munk internal wave spectrum indicate that inertia–gravity waves account for only a modest fraction of the kinetic energy between 10 and 80 km. These constraints suggest that the near-surface flow in the Bay is primarily balanced and follows a forward enstrophy transfer quasigeostrophic regime for wavelengths greater than approximately 80 km, with a larger role for unbalanced rotating stratified turbulence and internal waves at smaller scales.

Particle‐Based Lagrangian Filtering for Locating Wave‐Generated Thermal Refugia for Coral Reefs

AbstractTides and tidally generated waves play a key role in modulating the heat budget of the nearshore environment, which can significantly affect the ecology of the coastal and reef zones. The high spatial resolution required to resolve such waves in numerical models means that diagnosing wave‐generated heat fluxes (WHFs) has so far only been possible over very limited areas. Because many marine ecosystems that are affected by WHFs, such as coral reefs, are patchily distributed within domains of hundreds of kilometers, an alternative to fully wave‐resolving models is needed to identify thermal refugia and guide conservation efforts over larger regions. In this study, a one‐way nested series of regional ocean simulations has been conducted to study the role of waves in driving high‐frequency temperature variations in the Coral Triangle and to develop a method for identifying WHF in coarser‐resolution models. A filtering method using Lagrangian particles is used to separate the wave component of the flow, which is used to diagnose the wave energy and to identify locations experiencing large, high‐frequency temperature variability. These locations are shown to possess three key characteristics: large time‐mean wave kinetic energy, shallow depth, and a steep bathymetric gradient that gives access to a nearby source of cold, subthermocline water. A function of the wave kinetic energy and bathymetric slope is found to closely correlate with areas of maximal temperature variance, suggesting its use as a convenient and readily calculable metric to locate thermal refugia in observations or numerical experiments over large spatial domains.

Evaluation of the sand trap performance of the Pengasih weir during the operational period

Sedimentation is the main trigger in reducing the capacity of the irrigation channel. The weir is equipped with a sand trap, to withstand the volume of sediments originating from the upstream area, some of which enter the irrigation intake. The sand trap is designed with sufficient width and sloping energy slope, allowing sediment to settle. The Pengasih Weir, located in Kulonprogo Regency, is one of the weirs that is equipped with a sand trap building. The Pengasih Weir and the sand trap were built-in 1972. With the development of current conditions, it is necessary to evaluate the performance of the sand trap of The Pengasih Weir. In this study, the evaluation of sand trap performance is reviewed during the operational (settling) period. The result showed that the Meyer-Peter Muller formula can be used as an approach in the calculation of the amount of sediment transport and also to estimate the settled volume. It is recommended to flush the sand trap in between 184.922 days. The average value of trap efficiency was 0.89%. It can be concluded that the Pegasih Weir sand trap design still has good performance in settling the sediment inflow.

Isospin dependence of projectile fragmentation at hundreds of MeV/u * * Supported by the National Natural Science Foundation of China (11875328, 11605296, 11635003)

By modeling the fragmentation process using a dynamic model and permitting only evaporation in the statistical code, the main features of a projectile fragmentation at 600 MeV/u were considered in our previous study [Phys. Rev. C, 98: 014610 (2018)]. In this study, we extend this to the isospin dependence of a projectile fragmentation at several hundreds of MeV/u. We searched for isospin observables related to the isospin fractionation to extract the symmetry energy, and found that at the pre-equilibrium stage of the collisions an isospin diffusion will take place and affect the isospin of the final fragments. The isospin fractionation plays a part during the fragmenting stage. Compared to the soft symmetry energy, the stiff symmetry energy provides a smaller repulsive force for neutrons and an attractive force for the protons in a neutron-rich system at a subnormal density, and hence causes a smaller isospin asymmetry of the gas phase, leaving a more neutron-rich liquid phase. An observable robust isospin is proposed to extract the slope of the symmetry energy at normal density based on the isospin dependence of the projectile fragmentation at hundreds of MeV/u.

Fracture properties of reclaimed asphalt pavement mixtures with rejuvenator

Reclaimed asphalt pavement (RAP) technology has been extensively promoted to conserve depleting virgin materials for asphalt mixtures. High RAP content is desirable from economic and environmental standpoints. However, RAP mixtures become too stiff and require modification such as rejuvenator. This paper presents the evaluation on the fracture characteristics of mixtures prepared with 50% and 70% RAP, with and without rejuvenator that were subjected to indirect tensile strength (ITS) and notched semi-circular bending (SCB) tests. The fractured surfaces of the tested specimens were quantified using geospatial imaging technique to identify the proportion contribution to failure, namely cohesive, adhesive and broken aggregates. The results showed that the fractured rejuvenated mixtures were predominantly of the cohesive type when compared with the non-rejuvenated mixtures. On the other hand, the failure modes of non-rejuvenated mixtures were of the adhesive and aggregate failure types. The measured ITS at two temperatures corresponded with the expected damage trends. Similar behaviour was found in the derived fracture energy and pre-peak slope that were obtained from the SCB pure tensile and tensile-shear load–displacement curves. The findings showed that the fracture properties of rejuvenated mixtures performed comparably with virgin mixtures in terms of fracture toughness, tensile strength and proportion of damage contribution.

Beyond-mean-field effects on the symmetry energy and its slope from the low-lying dipole response of Ni68

We study low-energy dipole excitations in the unstable nucleus $^{68}$Ni with the beyond-mean-field (BMF) subtracted second random-phase-approximation (SSRPA) model based on Skyrme interactions. First, strength distributions are compared with available experimental data and transition densities of some selected peaks are analyzed. The so-called isospin splitting is also discussed by studying the isoscalar/isovector character of such excitations. We estimate then in an indirect way BMF effects on the symmetry energy of infinite matter and on its slope starting from the BMF SSRPA low-lying strength distribution. For this, several linear correlations are used, the first one being a correlation existing between the contribution (associated with the low-energy strength) to the total energy-weighted sum rule (EWSR) and the slope of the symmetry energy. BMF estimates for the slope of the symmetry energy can be extracted in this way. Correlations between such a slope and the neutron-skin thickness of $^{68}$Ni and correlations between the neutron-skin thickness of $^{68}$Ni and the electric dipole polarizability times the symmetry energy are then used to deduce BMF effects on the symmetry energy.

Tunable in the range of 4.5-6.8 µm room temperature single-crystal Fe:CdTe laser pumped by Fe:ZnSe laser.

We report a laser operation from a Fe:CdTe single crystal, pumped by 40-ns pulses of a 4.12-µm Fe:ZnSe laser. The maximum output energy of 5.8 mJ was produced at 5.4 µm with 30% absorbed energy slope efficiency. A record 2300-nm-wide smooth and continuous wavelength tunability over 4.5-6.8 µm range was demonstrated, being the longest wavelength tuning achieved for Fe2+-doped chalcogenide lasers. We also discuss the features of the oscillation spectra.

Key factor for determining relation between radius and tidal deformability of neutron stars: Slope of symmetry energy * * This work is partly Supported by the Shandong Natural Science Foundation (JQ201701), the Natural Science Foundation of China (11622540, 11675094, 11705102, 11775133), the China Postdoctoral Science Foundation (2019M652358), the Young Scholars Program of Shandong University, Weihai (2015WHWLJH01), and the Fundamental Research

The constraints on tidal deformability of neutron stars were first extracted from GW170817 by LIGO and Virgo Collaborations. However, the relationship between the radius and tidal deformability is still under debate. Using an isospin-dependent parameterized equation of state (EOS), we study the relation between and and its dependence on parameters of symmetry energy and EOS of symmetric nuclear matter when the mass is fixed at , , and . We find that, although the changes of high order parameters of and can shift individual values of and , the relation remains approximately at the same fitted curve. The slope of the symmetry energy plays the dominant role in determining the relation. By investigating the mass dependence of the relation, we find that the well fitted relation for 1.4 is broken for massive neutron stars.

Discriminating surface soil inorganic nitrogen cycling under various land uses in a watershed with simulations of energy balanced temperature and slope introduced moisture

Surface soil under various land uses/covers plays an important pool of N discharge in a watershed. Soil temperature and moisture drive soil N cycling, especially important for the watersheds with anthropogenic manipulations. Not all of the ongoing process-based models consider topographic factors of known importance when simulating soil moisture but most of them simulate soil temperature typically derived from empirical relations with air temperature. These assumptions might lead to underestimate the N discharge in the watersheds. This study employed an energy balanced soil temperature module and a slope introduced soil moisture module in coupling with a conceptual model of hydro-bio-geochemical process-based watershed life cycle analysis, i.e. the Watershed Inorganic Nitrogen Dynamic (WIND), to simulate soil N cycling across forest land, farmland, and urban bare land in an urbanizing watershed in southern China. The model was calibrated and validated by two individual survey events in 2013 and 2016–17 respectively using moisture and inorganic N in surface soil (0–10 cm) of the watershed with determination coefficients (R2) above 0.7. Significantly higher soil temperature arose when using the energy balanced module in comparison to the air temperature module. Meanwhile, soil moisture declining with land slope became significant above 15° steepness. Estimates of surface soil N cycling across all land uses were significantly altered. Importantly, land uses determined the extents of their alterations. The WIND provides insights into drivers of hot - spot/hot - moment hydro-bio-geochemical processes of soil inorganic N for land uses in the watershed. More generally, as the findings inform a better constraint of parameters in other physics-based watershed-scale water quality models they also potentially directly contribute to improved strategies for sustainable management of inorganic N discharges under the predicted climate changes.