Dense Medium Research Articles

Jet quenching: From theory to simulation

With the explosion of data on jet-based observables in relativistic heavy-ion collisions at the Large Hadron Collider and the Relativistic Heavy-Ion Collider, perturbative Quantum Chromodynamics (pQCD)-based simulations of these processes, often interacting with an expanding viscous fluid dynamical background, have taken center stage. This review is meant to bridge the gap between theory, simulation and phenomenology of jet modification in a dense medium. We will demonstrate how the existence of such end-to-end event generators with semi-realistic or even fully realistic final states allows for the most rigorous comparisons between pQCD-based jet modification theory and experiment. State-of-the-art calculations of several jet-based observables are presented. Extensions of this theory to jets in the small systems of p–A and e–A collisions are discussed.

Jet angularities in dijet production in proton-proton and heavy-ion collisions at RHIC

We study jet angularities for dijet production at the Relativistic Heavy Ion Collider (RHIC) in proton-proton (pp) and nucleus-nucleus (AA) collisions at 200 GeV nucleon-nucleon center-of-mass collision energy. In particular, we provide NLL resummed predictions for angularity observables of groomed and ungroomed jets produced in pp collisions matched to next-to-leading order QCD calculations resulting in NLO + NLL′ accuracy. Our parton-level predictions are corrected for non-perturbative effects, such as hadronization and underlying event, using parton-to-hadron level transfer matrices obtained with the Sherpa event generator. Furthermore, we use the Q-Pythia and Jewel generators to estimate the impact of the interaction between quarks and gluons produced by the parton shower with the dense medium formed in heavy-ion collisions on the considered jet angularities.

Oxidation of benzene with N2O on ZSM-5 zeolite: A comparison of gas-phase and supercritical conditions

The catalytic oxidation of benzene with nitrous oxide (N2O) over ZSM-5 zeolite has been carried out in a continuous-flow reactor under supercritical conditions and compared with the results of the gas-phase reaction. Aromatic substrates and nitrous oxide under the conditions of supercritical experiments (300–435 °C, 6.0–18.0 MPa) are both reagents and the supercritical medium. It has been established that the productivity of the supercritical oxidation of benzene into phenol significantly exceeds the productivity of the gas-phase process owing to the limited reversible deactivation of the catalyst under supercritical conditions and the in situ removal of the coke precursors by the dense reaction medium. In addition, it has been demonstrated that a successful in situ regeneration of the deactivated oxidation catalyst can be carried out during the transition from gas-phase reaction conditions to supercritical conditions in one experiment.

Absorption of ultrashort laser pulses in medium with account for propagation effects

The absorption of ultrashort laser pulses in an optically dense medium is theoretically studied based on the total absorption coefficient over the entire duration of the pulse, taking into account the effects of propagation and reflection of pulse from vacuum/medium interface. The approach is the generalization of our previous work (available at: www.nobelprize.org/prizes/physics/2023/summary), which traced a ‘bridge’ between the micro- and macro-description of radiation processes in a medium induced by electromagnetic pulses of arbitrary duration. The expression for the total absorption coefficient is obtained in terms the complex refractive index of the medium. Various limits of this expression are considered. Numerical calculations of the dependence of the total absorption coefficient on the parameters of the laser pulses and the thickness of the medium layer were carried out and the results obtained were discussed.

Dependent scattering and plasmon coupling in concentrated suspensions of optically hard nanoparticles

This study establishes the accuracy and efficacy of the recently developed radiative transfer with reciprocal transactions (R2T2) method for quickly simulating radiation transfer through concentrated thick suspensions of optically hard nanoparticles featuring a large mismatch in refractive and/or absorption indices compared with their surrounding medium. Concentrated suspensions of optically hard nanoparticles exhibit strong light scattering and dependent scattering effects including both near-field interactions among particles and interferences of scattered waves in the far-field. Concentrated suspensions of metallic nanoparticles also exhibit plasmon coupling effect that leads to widening of absorption peak and red-shift in the peak surface plasmon resonance wavelength. However, predicting these complex interactions between EM waves and particles in thick and concentrated suspensions by explicitly solving Maxwell's equations is computationally intensive, if not impossible. Conventional solutions like Lorenz–Mie theory combined with independent scattering approximation do not account for dependent scattering and plasmon coupling. Furthermore, the dense medium radiative transfer theory is a far-field approximation that does not account for near-field effects, leading to significant errors in predictions, as illustrated in this study. By contrast, the R2T2 method's predictions showed excellent agreement with the solutions of Maxwell's equations obtained using the superposition T-matrix method for thin films containing optically hard particles. The method also rigorously accounted for multiple scattering as well as plasmon coupling in thick concentrated suspensions. These results could facilitate the design of plasmonic suspensions used in various energy and environmental applications.

Dynamical properties of mildly relativistic ejecta produced by the mass-loading of gamma-ray burst jets in dense ambient media

Abstract We present the results of a series of 3D special relativistic hydrodynamic simulations of a gamma-ray burst (GRB) jet in a massive circumstellar medium (CSM) surrounding the progenitor star. Our simulations reproduce the jet morphology transitioning from a well-collimated state to a thermal pressure-driven state for a range of CSM masses and outer radii. The jet–CSM interaction redistributes the jet energy to materials expanding into a wide solid angle and results in a quasi-spherical ejecta with four-velocities from $\Gamma \beta \simeq 0.1$ to 10. The mass and kinetic energy of the ejecta with velocities faster than $0.1c$ are typically of the order of $0.1\, M_{\odot }$ and $10^{51}\:\mbox{erg}$ with only a weak dependence on the CSM mass and radius for the explored CSM parameter ranges. We find that the numerically obtained density structure of the mildly relativistic ejecta is remarkably universal. The radial density profile is well approximated as a power-law function of the radial velocity with an index of $-5$, $\rho \propto v^{-5}$, in agreement with our previous simulations and other studies, as well as those suggested from recent studies on early-phase spectra of supernovae associated with GRBs. Such fast ejecta rapidly becomes transparent following its expansion. Gradually releasing the trapped thermal photons, the ejecta gives rise to bright UV–optical emission within ${\sim} 1\:$d. We discuss the potential link of the relativistic ejecta resulting from jet–CSM interaction to GRB-associated supernovae as well as fast and blue optical transients.

Revisiting primordial black hole capture by neutron stars

A sub-solar mass primordial black hole (PBH) passing through a neutron star, can lose enough energy through interactions with the dense stellar medium to become gravitationally bound to the star. Once captured, the PBH would sink to the core of the neutron star, and completely consume it from the inside. In this paper, we improve previous energy-loss calculations by considering a realistic solution for the neutron star interior, and refine the treatment of the interaction dynamics and collapse likelihood. We then consider the effect of a sub-solar PBH population on neutron stars near the Galactic center. We find that it is not possible to explain the lack of observed pulsars near the galactic center through dynamical capture of PBHs, as the velocity dispersion is too high. We then show that future observations of old neutron stars close to Sgr A* could set stringent constraints on the PBHs abundance. These cannot however be extended in the currently unconstrained asteroid-mass range, since PBHs of smaller mass would lose less energy in their interaction with the neutron star and end up in orbits that are too loosely bound and likely to be disrupted by other stars in the Galactic center.

Solid–liquid–gas-like phase transition in electric field driven dense granular media

The polarization induced by an external electric field significantly influences the contact charge of particles. It can easily cause solid–liquid–gas-like phase transitions in dense granular media, which are the key factors leading to environmental and safety disasters such as sandstorms, volcanic eruptions, and spacecraft emergencies. In this letter, our investigation focused on a densely packed granular system with different thicknesses subjected to bottom excitation and an external electric field. Using the discrete element method (DEM), we proposed conditions for the first- and second-order phase transitions and revealed the mechanism of electrical signal transformation. We presented the physical characteristics of charge and polarization diffusion coefficients for charged particles, and introduced a theoretical Turing model to predict critical phase transitions. Additionally, this phase transition model was extended to the application of electrostatic dust removal, quantitatively predicting the relationship between dust removal efficiency, particle layer thickness, and electric field intensity.

Mechanical resistance of the environment affects root hair growth and nucleus dynamics

Root hair (RH) cells are important for the growth and survival of seedlings. They favor plant–microbe interactions and nutrients uptake. When invading the soil, RH cells have to penetrate a dense medium exhibiting a variety of physical properties, such as mechanical resistance, that impact the growth and survival of plants. Here we investigate the effect of the mechanical resistance of the culture medium on RH-physical and phenotypical parameters such as length, time, and speed of growth. We also analyze the impact of the environment on nuclear dynamics. We show that the RH growth rate and the nucleus speed decrease similarly as mechanical resistance increases while the time of growth of RH cells is invariable. Moreover, during RH growth, the nucleus-to-tip distance was found to decrease when the stiffness of the environment was increased. Along this line, using Latrunculin B treatment in liquid growth media, we could internally slow down RH growth to reach speeds similar to those observed in stiff solid media while the nucleus-to-tip distance was only slightly affected, supporting thus the idea of a specific effect of mechanical resistance of the environment on nucleus dynamics.

Study on water transfer characteristics and desulfurization effect during the separation of fine low rank lignite in the dry dense medium fluidized bed

Coal is an important support for the development of the national economy. Lignite has high utilization value. This paper utilizes a dry dense medium fluidized bed for separation of low rank high sulfur lignite across the size range of 6–0 mm. The study focuses on the spatial diffusion and transfer characteristics of material moisture in the fluidized bed, systematically analyzes the influence of material moisture on the bed fluidization characteristics and the bed density spatial uniform stability, explores the diffusion and separation characteristics of the material in the bed, and determines the material separation time domain. The experimental results indicate that when t = 60 s, the high concentration area of the whole bed is distributed in the center, and the low concentration area is distributed in the side wall At when t = 360 s, the high concentration area of the upper bed is distributed near the side wall, and the high concentration area of the middle and lower layers are distributed in the center of the bed. At t = 420 s, the high concentration area in the upper layer gradually disappears, and the separation of high and low-density particles is completed in the middle layer, achieving stratification. When the bed layer moisture content is 0.5 % and the air flow is 16.3 cm/s, the bed pressure drop tends to stabilize, and the bed fluidization effect is better, reaching its peak moisture content. The fluctuation in bed layer spatial density distribution is significant, especially in the central area of the upper layer (within the circular area 0 ≤ R ≤ 3 cm), where the density distribution fluctuation is most pronounced, with an average density of 1.67 g/cm3. The fluctuation amplitude of the middle bed density is relatively low, with an average density of 1.65 g/cm3. The fluctuation amplitude of the lower bed density is the smallest, with an average density of 1.53 g/cm3. When t = 0–120 s, the ash content of each layer along the bed height is close to the raw coal, which belongs to the material diffusion distribution time domain. When t = 120–240 s, the material is stratified locally, which belongs to the material initial stratification time domain. When t = 240–420 s, the high and low density particles achieve orderly stratification, which belongs to the material sorting time domain The results show that the clean coal yield was 74.68 %, sulfur content is 0.98 %, ash content is 9.96 %, gangue yield is 25.32 %, sulfur content is 18.69 %, ash content is 58.32 %, Ep is 0.65 g/cm3. The high-precision dry separation of fine grained low rank high sulfur lignite was realized.

Mycotic flora characteristics of the endontic flora in patients affected by COVID-19

BACKGROUND: Owing to the fact that, presently, at a dental appointment, it is possible to observe a wide range of consequences arising after COVID-19, among which are observed lesions of the pulp and periodontium of the tooth, additional diagnostic methods should be introduced before choosing treatment tactics. In our previous study, we analyzed the contents of root canals of teeth in patients who had COVID-19 using bacterioscopy. Coccus flora was detected in all cases and elements of Candida yeast-like fungi were recorded in 89 cases (76.1%). Based on the obtained data, it was advantageous to perform microbiological examination of the endodontium in this group of patients to further study their physical and chemical properties and correct the treatment regimen in gangrenous form of chronic pulpitis and aggravated forms of periodontitis, which determined the relevance of the present study. AIM: To reveal the characteristics of the mycotic flora of the endodontium in patients who previously had COVID-19. MATERIALS AND METHODS: A bacteriologic study of root canal contents in patients who had previously undergone a new coronavirus infection at different times, diagnosed as “exacerbation of chronic periodontitis”, “chronic gangrenous pulpitis”, and “acute suppurative periodontitis”, was conducted to detect fungi of the genus Candida in the tooth root canal system, which was obtained during mechanical treatment with a sterile endodontic instrument. The patients (n=49) were divided into groups according to their final diagnosis: group 1, chronic gangrenous pulpitis (27 patients); group 2, acute purulent periodontitis (9 patients); and group 3, exacerbation of chronic periodontitis (13 patients). Then, the collected material was placed in a tube with Amies transport medium and sent to the laboratory. Seeding of the material was performed in sterile Petri dishes on Sabouraud agar by rubbing with a plastic spatula. Further, Petri dishes were placed in the thermostat for 24–48 hours of incubation at 37±10 °C. Then, the study was carried out according to the generally accepted scheme: the obtained cultures were identified to species by the character of growth on dense medium. RESULTS: The given bacteriological study of the patients’ endontic contents confirmed the data of bacterioscopy and concretized the previously obtained results. On final examination, black colonies of Candida albicans were observed in 95.92% of cases. No growth of Candida albicans colonies was observed in two cases (4.08%). CONCLUSION: The bacteriologic study performed after bacterioscopy of diagnosis confirmed the presence of fungi of the genus Candida in the root canals of teeth in patients who previously had COVID-19. The study showed that when treating similar patients, the high risk of infection of periodontal complex tissues by Candida fungi should be considered. It is advisable to supplement the standard protocols of endodontic treatment with physical exposure, for example, laser radiation, or additional medication with antifungal drugs, such as fluconazole.

A possible direct exposure of the Earth to the cold dense interstellar medium 2–3 Myr ago

Cold, dense clouds in the interstellar medium of our Galaxy are 4–5 orders of magnitude denser than their diffuse counterparts. Our Solar System has most likely encountered at least one of these dense clouds during its lifetime. However, evidence for such an encounter has not been studied in detail yet. Here we derive the velocity field of the Local Ribbon of Cold Clouds (LRCC) by modelling the 21 cm data from the HI4PI survey, finding that the Solar System may have passed through the LRCC in the constellation Lynx 2–3 million years ago. Using a state-of-the-art simulation of the heliosphere, we show that during the passage, the heliosphere shrinks to a scale of 0.22 au, smaller than the Earth’s orbit around the Sun. This would have put the Earth in direct contact with the dense interstellar medium for a period of time and exposed it to a neutral hydrogen density above 3,000 cm−3. Such a scenario agrees with geological evidence from 60Fe and 244Pu isotopes. The encounter and related increased radiation from Galactic cosmic rays might have had a substantial impact on the Earth’s system and climate.

The dense and non-homogeneous circumstellar medium revealed in radio wavelengths around the Type Ib SN 2019oys

Context. Mass loss from massive stars, especially towards the end of their lives, plays a key role in their evolution. Radio emission from core-collapse supernovae (SNe) serves as a probe of the interaction of the SN ejecta with the circumstellar medium (CSM) and can reveal the mass-loss history of the progenitor. Aims. We aim to present broadband radio observations of the CSM-interacting SN 2019oys. SN 2019oys was first detected in the optical and was classified as a Type Ib SN. Then, ~100 days after discovery, it showed an optical rebrightening and a spectral transition to a spectrum dominated by strong narrow emission lines, which suggests strong interaction with a distant, dense, CSM shell. Methods. We modelled the broadband, multi-epoch radio spectra, covering 2.2 to 36 GHz and spanning from 22 to 1425 days after optical discovery, as a synchrotron emitting source. Using this modelling, we characterised the shockwave and the mass-loss rate of the progenitor. Results. Our broadband radio observations show strong synchrotron emission. This emission, as observed 201 and 221 days after optical discovery, exhibits signs of free–free absorption from the material in front of the shock travelling in the CSM. In addition, the steep power law of the optically thin regime points towards synchrotron cooling of the radiating electrons. Analysing these spectra in the context of the SN-CSM interaction model gives a shock velocity of 11 000 km s−1 (for a radius evolution of ~∆t0.8, where ∆t is the time since optical discovery) and an electron number density of 4.1 × 105 cm−3 at a distance of 2.6 × 1016 cm. This translates to a high mass-loss rate from the progenitor massive star of 10−3 M⊙ yr−1 for an assumed wind of 100 km s−1 (assuming a constant mass-loss rate in steady winds). The late-time radio spectra, 392 and 557 days after optical discovery, show broad spectral peaks. We show that this can be explained by introducing a non-homogeneous CSM structure.

Can preconcentration of cassiterite from its pegmatite ore reduce processing costs and improve operational sustainability?

Different concentration techniques were evaluated for preconcentration of a mineral ore at a coarser size to avoid energy and resource wastage. Specifically, the aim was to reduce milling costs and energy required in the beneficiation of tin. In this study, cassiterite (0.17% Sn) was the mineral of interest in a pegmatite ore body associated with quartz (SiO2 > 60%) and alumina (Al2O3 > 20%). Three concentration techniques, namely dense media, shaking table, and flotation, coupled with characterization analysis, were used to assess the concentration response. The results confirmed that particle size and mineral liberation impact the separation process. High recovery and grade were obtained with gravity concentration methods (dense media and shaking table) for coarser (+300 to +212 μm) and intermediate (+150 to +53 μm) particle sizes. Lower recovery and grade were identified for much finer sizes (-53 to -38 μm). Flotation produced a high-grade product at a relatively low recovery and appeared to be only applicable to finer grains. Separation efficiency based on Schulz's equation measured a segregation performance of 74.8% for dense medium separation and 60.7% for the shaking table for the coarse and intermediate particle sizes. Flotation only achieved a separation of 30%-40%. The results suggest that use of dense media separation as a rough preconcentration method prior to further grinding, and the utilization of a more advanced concentration technique for mineral recovery and upgrade, constitute a successful approach to improve process economics.

Separation density prediction of geldart A– dense medium in gas-solid fluidized bed coal beneficiators

Gas-solid Fluidized Bed Coal Beneficiator (GFBCB) process is a crucial dry coal beneficiation fluidization technology. The work employs the GFBCB process alongside a novel Geldart A– dense medium, consisting of Geldart A magnetite particles and Geldart C ultrafine coal, to separate small-size separated objects in the GFBCB. The effects of various operational conditions, including the volume fraction of ultrafine coal, the gas velocity, the separated objects size, and the separation time, were investigated on the GFBCB's separation performance. The results indicated that the probable error for 6∼3 mm separated objects could be controlled within 0.10 g/cm3. Compared to the traditional Geldart B/D dense medium, the Geldart A/A– dense medium exhibited better size-dependent separation performance with an overall probable error 0.04∼0.12 g/cm3. Moreover, it achieved a similar separation accuracy to the Geldart B/D dense medium fluidized bed with different external energy for the small-size object beneficiation. The work furthermore validated a separation density prediction model based on theoretical derivation, available for both Geldart B/D dense medium and Geldart A/A– dense medium at different operational conditions.

Probing Relativistic Heavy-Ion Collisions via Photon Anisotropic Flow Ratios. A Brief Review

The anisotropic flow of photons produced in relativistic nuclear collisions is known as a promising observable for studying the initial state and the subsequent evolution of the hot and dense medium formed in such collisions. The investigation of photon anisotropic flow coefficients, vn, has attracted high interest over the last decade, involving both theory and experiment. The thermal emission of photons and their anisotropic flow are found to be highly sensitive to the initial state of the fireball, where even slight modifications can lead to significant variations in the final state results. In contrast, the ratio of photon anisotropic flow stands out as a robust observable, exhibiting minimal sensitivity to the initial conditions. Here, we briefly review the studies of the individual elliptic and triangular flow parameters of photons as well as their ratios and how these parameters serve as valuable probes for investigating the intricacies of the initial state and addressing the challenges posed by the direct photon puzzle.

Radiative corrections for factorized jet observables in heavy ion collisions

I look at the renormalization of the medium structure function and a medium induced jet function in a factorized cross section for jet substructure observables in Heavy Ion collisions. This is based on the formalism developed in [1], which uses an Open quantum system approach combined with the Effective Field Theory (EFT) for forward scattering to derive a factorization formula for jet observables which work as hard probes of a long lived dilute Quark Gluon Plasma (QGP) medium. I show that the universal medium structure function that captures the observable independent physics of the QGP has both rapidity and UV anomalous dimensions that appear due to medium induced Bremsstrahlung. The resulting Renormalization Group (RG) equations correspond to the BFKL equation and the running of the QCD coupling respectively. I present the first results for the numerical impact of resummation using these RG equations on the mean free path of the jet in the medium. I also briefly discuss the prospects of extending this formalism for a short lived dense medium.

Effects of Size Polydispersity and Dense Media on Quantitative Ultrasound Estimates.

Quantitative ultrasound (QUS) techniques based on the backscatter coefficient (BSC) aim to characterize the scattering properties of biological tissues. A scattering model is fit to the measured BSC, and the fitted QUS parameters can provide local tissue microstructure, namely, scatterer size and acoustic concentration. However, these techniques may fail to provide a correct description of tissue microstructure when the medium is polydisperse and/or dense. The objective of this study is to investigate the effects of scatterer size polydispersity in sparse or dense media on the QUS estimates. Four scattering models (i.e., the monodisperse and polydisperse sparse models, and the monodisperse and polydisperse concentrated models based on the structure factor) are compared to assess their accuracy and reliability in quantifying the QUS estimates. Simulations are conducted with different scatterer size distributions for sparse, moderately dense, and dense media (volume fractions of 1%, 20%, and 73%, respectively). The QUS parameters are estimated by using model-based inverse methods at different center frequencies between 8 and 50 MHz. Experimental data are also analyzed using colon adenocarcinoma HT29 cell pellet biophantoms to further validate the results obtained from simulations at the volume fraction of 73%. Our findings reveal that the choice of scattering model has a significant impact on the accuracy of QUS estimates. For sufficiently high frequencies and dense media, the polydisperse concentrated model outperforms the other models and enables more accurate quantification. Furthermore, our results contribute to advancing our understanding of the complexities associated with scatterer size polydispersity and dense media in spectral-based QUS techniques.

Symmetry breaking due to multi-angle matter-neutrino resonance in neutron star merger remnants

Neutron star merger remnants are unique sites for exploring neutrino flavor conversion in dense media. Because of the natural excess of ν̅e over νe , the neutrino-neutrino potential can cancel the matter potential, giving rise to matter-neutrino resonant flavor conversion. Under the assumption of two (anti)neutrino flavors and spatial homogeneity, we solve the neutrino quantum kinetic equations to investigate the occurrence of the matter-neutrino resonance within a multi-angle framework. We find that isotropy is broken spontaneously, regardless of the mass ordering. Relying on a hydrodynamical simulation of a binary neutron star merger remnant with a black hole of 3 M ⊙ and an accretion torus of 0.3 M ⊙, we find that complete flavor conversion caused by the matter-neutrino resonance is unlikely, although the matter and neutrino potentials cancel at various locations above the disk. Importantly, the matter-neutrino resonant flavor conversion crucially depends on the shape of the neutrino angular distributions. Our findings suggest that an accurate modeling of the neutrino angular distributions is necessary to understand flavor conversion physics in merger remnants, its implications on the disk physics and synthesis of the elements heavier than iron.

Observational evidence to support a dense ambient medium shaping the jet in 3C 84

Highly collimated relativistic jets are a defining feature of certain active galactic nuclei (AGN), yet their formation mechanism remains elusive. Previous observations and theoretical models have proposed that the ambient medium surrounding the jets could exert pressure, playing a crucial role in shaping the jets. However, a direct observational confirmation of such a medium has been lacking. In this study, we present very long baseline interferometric (VLBI) observations of 3C 84 (NGC 1275), located at the center of the Perseus Cluster. Through monitoring observations with the Very Long Baseline Array (VLBA) at 43 GHz, a jet knot was detected to have been ejected from the sub-parsec scale core in the late 2010s. Intriguingly, this knot propagated in a direction significantly offset from the parsec-scale jet direction. To delve deeper into the matter, we employed follow-up VLBA 43 GHz observations, tracing the knot’s trajectory until the end of 2022. We discovered that the knot abruptly changed its trajectory in the early 2020s, realigning itself with the parsec-scale jet direction. Additionally, we present results from an observation of 3C 84 with the Global VLBI Alliance (GVA) at 22 GHz, conducted near the monitoring period. By jointly analyzing the GVA 22 GHz image with a VLBA 43 GHz image observed about one week apart, we generated a spectral index map, revealing an inverted spectrum region near the edge of the jet where the knot experienced deflection. These findings suggest the presence of a dense, cold ambient medium characterized by an electron density exceeding ∼105 cm−3, which guides the jet’s propagation on parsec scales and significantly contributes to the overall shaping of the jet.