Particle Mass Research Articles

Dynamics of massive and massless particles in the spacetime of a wiggly cosmic dislocation

AbstractIn this paper, we investigate the spacetime containing both small-scale structures (wiggles) and spatial dislocation, forming a wiggly cosmic dislocation. We study the combined effects of these features on the dynamics of massive and massless particles. Our results show that while wiggles alone lead to bound states and dislocation introduces angular momentum corrections, their coupling produces more complex effects, influencing both particle motion and wave propagation. Notably, this coupling significantly modifies radial solutions and eigenvalues, with the direction of motion or propagation becoming a critical factor in determining the outcomes. Numerical solutions reveal detailed aspects of particle dynamics as functions of dislocation and string parameters, including plots of trajectories, probability densities, and energy levels. These findings deepen our understanding of how a wiggly cosmic dislocation shapes particle dynamics, suggesting new directions for theoretical exploration in cosmological models.

Dark sector tunneling field potentials for a dark big bang

All of the significant evidence for dark matter observed thus far has been through its gravitational interactions. After 40 years of direct detection experiments, the parameter space for weakly interacting massive particles (WIMPs) as dark matter candidates is rapidly approaching the neutrino floor. Moreover, there have been no signs of WIMPs in any particle production experiments so far. In this light, we consider a dark sector that is strongly decoupled from the visible sector, interacting exclusively through gravity. In this model, proposed by Freese and Winkler [Dark matter and gravitational waves from a dark big bang, ], dark matter can be produced through a first-order phase transition in the dark sector dubbed “the dark big bang.” We fully determine the allowed region of parameter space for the tunneling potential that leads to the realization of a dark big bang and is consistent with all experimental bounds available. Published by the American Physical Society 2024

Any way the wind blows: quantifying superbubbles and their outflows in simulated galaxies across z ≈ 0 − 3

Abstract We present an investigation of clustered stellar feedback in the form of superbubbles identified within eleven galaxies from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, at both cosmic noon (1 < z < 3) and in the local Universe. We study the spatially-resolved multiphase outflows that these supernovae drive, comparing our findings with recent theory and observations. These simulations consist of five LMC-mass galaxies and six Milky Way-mass progenitors (with a minimum baryonic particle mass of mb.min = 7, 100M⊙). For all galaxies, we calculate the local and galaxy-averaged mass and energy loading factors from the identified outflows. We also characterize the multiphase morphology and properties of the identified superbubbles, including the ‘shell’ of cool (T < 105 K) gas and break out of energetic hot (T > 105 K) gas when the shell bursts. We find that these simulations, regardless of redshift, have mass-loading factors and momentum fluxes in the cool gas that largely agree with recent observations. Lastly, we also investigate how methodological choices in measuring outflows can affect loading factors for galactic winds.

Suffusion of irregular concave gap-graded sand with resolved CFD-DEM

The complex morphologies of particles are a crucial factor influencing suffusion in gap-graded granular soils. However, the micro-mechanism of soil suffusion composed of irregular concave particles remains unclear. To this end, a systematic numerical simulation that considers particle concavity and aspect ratio is performed with the resolved discrete element method (DEM) and computational fluid dynamics (CFD) approach. The macro responses of suffusion of particles with varying morphologies, e.g., cumulative eroded particle mass and sample profile, are revealed and interpreted from a microscopic view, e.g., particle rotation, coordination number, and moment. It is found that the rotation of irregularly shaped particles during suffusion requires overcoming the moment applied by the surrounding particles. Particles with bigger contact force or irregularity require a higher moment to be overcome, thus significantly increasing their suffusion resistance. Irregularly shaped particles can adjust their orientation to reduce the moment and drag force applied to them. At the same aspect ratio, particles with larger concavity are more likely to interlock with each other, with increasing the coordination number of the soil packing and shrinking the pore channel for particle migration. A shape parameter considering both concavity and aspect ratio is finally proposed to characterise the influence on suffusion.

Lyapunov exponents and phase transition of Hayward AdS black hole

AbstractIn this paper, we study the relationship between the phase transition and Lyapunov exponents for 4D Hayward anti-de Sitter (AdS) black hole. We consider the motion of massless and massive particles around an unstable circular orbit of the Hayward AdS black hole in the equatorial plane and calculate the corresponding Lyapunov exponents. The phase transition is found to be well described by the multivaled Lyapunov exponents. It is also found that different phases of Hayward AdS black hole coincide with different branches of the Lyapunov exponents. We also study the discontinuous change in the Lyapunov exponents and find that it can serve as an order parameter near the critical point. The critical exponent of change in Lyapunov exponent near the critical point is found to be 1/2.

Effects of Titanate on Brake Wear Particle Emission Using a Brake Material Friction Test Dynamometer

We investigated the effect of lepidocrocite-type layered titanate, which is compounded in brake pads, to reduce brake particle emissions. The dust reduction effect of titanate was evaluated using a small-scale inertial brake material friction test dynamometer. The results suggested that brake particle emissions are related to the microphysical structure of the pad surface, such as the uniformity of the friction film and secondary plateau formation, and that friction materials containing titanate contribute significantly to reducing both particle mass (PM) and particle number (PN) emissions of brake particles in both non-asbestos organic (NAO) and low-steel (LS) pads. In particular, LS pads generally have a problem of having more brake particles than NAO pads, but this study found that brake particles can be significantly reduced by compounding titanate instead of tin sulfide.

Dark matter limits from the tip of the red giant branch of globular clusters

Capture and annihilation of weakly interacting massive particle (WIMP)-like dark matter in red giant stars can lead to faster-than-expected ignition of the helium core, and thus a lower tip of the red giant branch (TRGB) luminosity. We use data to place constraints on the dark matter-nucleon cross section using 22 globular clusters with measured TRGB luminosities, and place projections on the sensitivity resulting from 161 clusters with full phase space distributions observed by . Although limits remain weaker than those from Earth-based direct detection experiments, they represent a constraint that is fully independent of dark matter properties in the solar neighborhood, probing its properties across the entire Milky Way galaxy. Based on our findings, it is likely that the use of the TRGB as a standard candle in H0 measurements is very robust against the effects of dark matter. Published by the American Physical Society 2024

Generalized uncertainty principle from the regularized self-energy

We use the Schrödinger–Newton equation to calculate the regularized self-energy of a particle using a regular self-gravitational and electrostatic potential derived in string T-duality. The particle mass M is no longer concentrated into a point but is diluted and described by a quantum-corrected smeared energy density resulting in corrections to the energy of the particle, which is interpreted as a regularized self-energy. We extend our results and find corrections to the relativistic particles using the Klein–Gordon, Proca and Dirac equations. An important finding is that we extract a form of the generalized uncertainty principle (GUP) from the corrected energy. This form of the GUP is shown to depend on the nature of particles; namely, for bosons (spin 0 and spin 1) we obtain a quadratic form of the GUP, while for fermions (spin 1/2) we obtain a linear form. The correlation we find between spin and GUP may offer insights for investigating quantum gravity.

The multidimensional coagulation and collisional breakage equation with unbounded kernel

Many scientific and technical fields have benefited from the understanding of the Coagulation and Collisional Breakage Equation (CCBE). In one-dimensional CCBE, only one property of the particle (like size or mass of the particle) is considered. However, there are other factors (like including volume, enthalpy, porosity, mole number, binder content, and more) that affect how particle ensembles behave. Therefore the study of multidimensional CCBE is more accurate. For the multi-dimensional (CCBE), we denote the property characteristics vector as x → = ( x 1 , x 2 , … , x d ) ∈ R + d . In this research work, the existence of a continuous solution is investigated where collision rate satisfies C ( x → , y → ) ≤ c ∏ i = 1 d ( 1 + x i ) ν ( 1 + y i ) ν , where c>0 is a constant, 0 ≤ ν ≤ θ and the coagulation kernel satisfies the following, K ( x → , y → ) ≤ k ∏ i = 1 d ( 1 + x i ) α ( 1 + y i ) α , where k is a positive constant, 0 ≤ α ≤ θ and 0 < θ ≤ 1 . Additionally, the uniqueness of the solution is shown. To prove the result, we have defined a new norm and examined the equicontinuity with respect to time and the property characteristics vector and Arzelà–Ascoli theorem is used.

Momentum shift and on-shell constructible massive amplitudes

We construct tree-level amplitude for massive particles using on-shell recursion relations based on two classes of momentum shifts: an all-line transverse shift that deforms momentum by its transverse polarization vector, and a massive Britto-Cachazo-Feng-Witten-type shift. We illustrate that these shifts allow us to correctly calculate four-point and five-point amplitudes in massive QED, without an ambiguity associated with the contact terms that may arise from a simple “gluing” of lower-point on-shell amplitudes. We discuss various aspects and applicability of the two shifts, including the large-z behavior and complexity scaling. We show that there exists a “good” all-line transverse shift for all possible little group configurations of the external particles, which can be extended to a broader class of theories with massive particles such as massive QCD and theories with massive spin-1 particles. The massive Britto-Cachazo-Feng-Witten-type shift enjoys more simplicity, but a “good” shift does not exist for all the spin states due to the specific choice of spin axis. Published by the American Physical Society 2024

Determination of Nanoparticles and Elements in Blue Mussels (Mytilus edulis) along the Norwegian Coastline.

Our work aimed to examine nanoparticle levels in 69 distinct pooled mussel samples along the Norwegian coastline, considering samples from different environmental contexts, including natural locations, potentially polluted hotspots, and mussel farms. Single-particle ICP-MS was utilized to determine particle mass and number concentrations at environmentally relevant levels in addition to the total content of 11 elements: aluminum, barium, cerium, copper, iron, manganese, lead, silicon, silver, titanium, and zirconium. Results showed nanoparticle mass concentrations of few ng/g up to tens of μg/g and number concentrations of 106 to 109 particles/g (wet weight). Certain urban and industrially impacted locations were linked to increased levels of, e.g., silver, lead, cerium, zirconium, and titanium NPs. Farmed mussels exhibited lower concentrations. However, natural variations were considerable, and impacted locations mostly did not differ from the highest levels in pristine areas. The study presents the first extensive survey of NPs of 11 different elements in marine biota and provides evidence of increased levels of NPs in areas with anthropogenic activities.

Correlations and Signaling in the Schrödinger-Newton Model

Abstract The Schrödinger-Newton model is a semi-classical theory in which, in addition to mutual attraction, massive quantum particles interact with their own gravitational fields. While there are many studies on the phenomenology of single particles, correlation dynamics in multipartite systems is largely unexplored. Here, we show that the Schrödinger-Newton interactions preserve the product form of the initial state of a many-body system, yet on average agreeing with classical mechanics of continuous mass distributions. This leads to a simple test of the model, based on verifying bipartite gravitational evolution towards non-product states. We show using standard quantum mechanics that, with currently accessible single-particle parameters, two masses released from harmonic traps get correlated well before any observable entanglement is accumulated. Therefore, the Schrödinger-Newton model can be tested with setups aimed at observation of gravitational entanglement with significantly relaxed requirements on coherence time. We also present a mixed-state extension of the model that avoids superluminal signaling.

A fully coupled solid-particle microphysics scheme for stratospheric aerosol injections within the aerosol–chemistry–climate model SOCOL-AERv2

Abstract. Recent studies have suggested that injection of solid particles such as alumina and calcite particles for stratospheric aerosol injection (SAI) instead of sulfur-based injections could reduce some of the adverse side effects of SAI such as ozone depletion and stratospheric heating. Here, we present a version of the global aerosol–chemistry–climate model SOCOL-AERv2 and the Earth system model (ESM) SOCOLv4 which incorporate a solid-particle microphysics scheme for assessment of SAI of solid particles. Microphysical interactions of the solid particle with the stratospheric sulfur cycle were interactively coupled to the heterogeneous chemistry scheme and the radiative transfer code (RTC) for the first time within an ESM. Therefore, the model allows simulation of heterogeneous chemistry at the particle surface as well as feedbacks between microphysics, chemistry, radiation and climate. We show that sulfur-based SAI results in a doubling of the stratospheric aerosol burden compared to the same mass injection rate of calcite and alumina particles with a radius of 240 nm. Most of the sulfuric acid aerosol mass resulting from SO2 injection does not need to be lifted to the stratosphere but is formed after in situ oxidation and subsequent water uptake in the stratosphere. Therefore, to achieve the same radiative forcing, larger injection rates are needed for calcite and alumina particle injection than for sulfur-based SAI. The stratospheric sulfur cycle would be significantly perturbed, with a reduction in stratospheric sulfuric acid burden by 53 %, when injecting 5 Mt yr−1 (megatons per year) of alumina or calcite particles of 240 nm radius. We show that alumina particles will acquire a sulfuric acid coating equivalent to about 10 nm thickness if the sulfuric acid is equally distributed over the whole available particle surface area in the lower stratosphere. However, due to the steep contact angle of sulfuric acid on alumina particles, the sulfuric acid coating would likely not cover the entire alumina surface, which would result in available surface for heterogeneous reactions other than the ones on sulfuric acid. When applying realistic uptake coefficients of 1.0, 10−5 and 10−4 for H2SO4, HCl and HNO3, respectively, the same scenario with injections of calcite particles results in 94 % of the particle mass remaining in the form of CaCO3. This likely keeps the optical properties of the calcite particles intact but could significantly alter the heterogeneous reactions occurring on the particle surfaces. The major process uncertainties of solid-particle SAI are (1) the solid-particle microphysics in the injection plume and degree of agglomeration of solid particles on the sub-ESM grid scale, (2) the scattering properties of the resulting agglomerates, (3) heterogeneous chemistry on the particle surface, and (4) aerosol–cloud interactions. These uncertainties can only be addressed with extensive, coordinated experimental and modelling research efforts. The model presented in this work offers a useful tool for sensitivity studies and incorporating new experimental results on SAI of solid particles.

Effect of soft magnetic particles content on multi-physics field of magnetorheological composite gel clutch with complex flow channel excited by Halbach array arrangement

In this paper we investigate the influence of soft magnetic particle mass fraction on the multi-physics field of proposed magnetorheological (MR) gel clutch. A novel MR gel clutch with complex cup-shaped gap is described, whose performance is based on the relative placement between Halbach array arrangement and MR gel. Smart MR gel with 40 wt%, 50 wt%, 60 wt%, 70 wt% and 80 wt% of soft magnetic particles used as the transfer medium and Halbach array is adopted as magnetic excitation system. Its magnetic/mechanical analysis is carried out based on Bingham-plastics model using COMSOL Multiphysics software, which takes into account the variation of dynamic viscosity with magnetic flux density. The distribution of the magnetic flux density, shear yield stress, post-yield viscosity, shear stress and torque in the four flow channels during the transition from engagement state to disengagement state are obtained and analyzed in detail. Multi-physics field characteristics of proposed MR gel clutch with five kinds of MR gels are studied and compared in order to give some useful suggestions in the design phase. Finally, the dynamic torque of the MR clutch with different MR gel is experimentally evaluated.

JWST lensed quasar dark matter survey – II. Strongest gravitational lensing limit on the dark matter free streaming length to date

ABSTRACT This is the second in a series of papers in which we use JWST Mid Infrared Instrument multiband imaging to measure the warm dust emission in a sample of 31 multiply imaged quasars, to be used as a probe of the particle nature of dark matter. We present measurements of the relative magnifications of the strongly lensed warm dust emission in a sample of nine systems. The warm dust region is compact and sensitive to perturbations by populations of haloes down to masses $\sim 10^6$ M$_{\odot }$. Using these warm dust flux-ratio measurements in combination with five previous narrow-line flux-ratio measurements, we constrain the halo mass function. In our model, we allow for complex deflector macromodels with flexible third- and fourth-order multipole deviations from ellipticity, and we introduce an improved model of the tidal evolution of subhaloes. We constrain a WDM model and find an upper limit on the half-mode mass of $10^{7.6}\, {\rm M}_\odot$ at posterior odds of 10:1. This corresponds to a lower limit on a thermally produced dark matter particle mass of 6.1 keV. This is the strongest gravitational lensing constraint to date, and comparable to those from independent probes such as the Ly $\alpha$ forest and Milky Way satellite galaxies.

The next galactic supernova can uncover mass and couplings of particles decaying to neutrinos

Many particles predicted by extensions of the Standard Model feature interactions with neutrinos, e.g., Majoron-like bosons ϕ. If the mass of ϕ is larger than about 10 keV, they can be produced abundantly in the core of the next galactic core-collapse supernova through neutrino coalescence, and leave it with energies of around 100 MeV. Their subsequent decay to high-energy neutrinos and anti-neutrinos provides a distinctive signature at Earth. Ongoing and planned neutrino and dark matter experiments allow us to reconstruct the energy, flavor, and time of arrival of these high-energy neutrinos. For the first time, we show that these measurements can help pinpointing the mass of ϕ and its couplings to neutrinos of different flavor. Our results can be generalized in a straightforward manner to other hypothetical feebly interacting particles, like novel gauge bosons or heavy neutral leptons, that decay into neutrinos.

Potential human exposure and risks of incidental nanoparticles released during rotary dry cutting of ceramic tiles

Rotary dry cutting and rectifying of ceramic tiles are sources of fine particulate matter (PM2.5) and nanoparticles (NPs). These activities are typically carried out inside industrial facilities during the manufacturing process, as well as outdoors and in residential indoor spaces during the installation phase, where mitigation measures are seldom implemented. This work aimed to understand the particle formation and release mechanisms, as well as particle properties (physical, chemical, and toxicological) and potential impacts on human health and the environment, for particles generated during ceramic tile rotary dry cutting operations. Aerosols were characterised in terms of particle number and mass concentrations, chemical composition, morphology and in vitro cytotoxicity. Two types of commercially available and representative tiles were tested in controlled chamber experiments: porous and non-porous ceramic body tiles (referred to in this work as A and B types, respectively). Results evidenced the release of fine particles and NPs during dry cutting of both materials, in comparable concentrations (20.000-45.000/cm3, 1-min average). However, the particle size distribution was significantly finer from A tiles (70% of the particle number concentration was nanosized (<100 nm)) in comparison to B tiles (<20%). While airborne particle chemical profiles were similar for both types of materials in the coarser size fractions (>0.6μm), in the smaller size fractions (<0.6μm) larger differences were observed. The chemical composition of airborne aerosols was consistent with that of the deposited dust. In vitro cytotoxicity responses evidenced statistically significant differences between exposure to aerosols from both types of tiles: cell viability was lower after exposure to aerosols from A tiles (50% at the original concentration) compared to those from B tiles, which exhibited high cell viability regardless of the aerosol concentration. Overall, results evidenced NP formation and release during rotary dry cutting of ceramic tiles, varying physical-chemical and cytotoxic profiles as a function of the material being processed, and highlight this activity as a potential health hazard in scenarios where prevention and mitigation measures are not implemented.

Gravitational lensing around dark matter in galactic halo region

The presence of dark matter in the galactic region has decisively confirmed by astronomical observations , however, the characteristics of dark matter yet to be recognized correctly. Utilizing the Einstein’s general theory of relativity and the observed rotational curve profile as input, we point out some features of galactic dark matter. Usually, dark matter is not directly visible but affects the lensing. In this paper, the deflection of a massive particle by galactic dark matter is studied using the Jacobi metric approach. We also provide a brief analysis of the image features of the deflection angle.

A model of light pseudoscalar dark matter

The EW-νR model was constructed in order to provide a seesaw scenario operating at the Electroweak scale ΛEW∼246 GeV, keeping the same SM gauge structure. In this model, right-handed neutrinos are non-sterile and have masses of the order ΛEW. They can be searched for at the LHC along with heavy mirror quarks and leptons, the lightest of which has large decay lengths. The model also incorporates a rich scalar sector, consistent with various experimental constraints, predicts a ∼125 GeV scalar with the SM Higgs characteristics satisfying the current LHC Higgs boson data. The seesaw mechanism requires the existence of a complex scalar which is singlet under the SM gauge group. The imaginary part of this complex scalar denoted by As0 is proposed to be the sub-MeV dark matter candidate in this manuscript. We find that the sub-MeV scalar can serve as a viable non-thermal feebly interacting massive particle (FIMP)-DM candidate. This As0 can be a naturally light sub-MeV DM candidate due to its nature as a pseudo-Nambu-Goldstone (PNG) boson in the model. We show that the well-studied freeze out mechanism falls short in this particular framework producing DM overabundance. We identify that the freeze in mechanism produce the correct order of relic density for the sub-MeV DM candidate satisfying all applicable constraints. We also discuss the allowed parameter space arising from the current indirect search bounds for this sub-MeV DM.

Design and Characterization of a New Quartz Smog Chamber System for Studying the Atmospheric Effects of Vehicle Emissions on Plateaus

Since the 1960s, smog chambers have been an important tool for studying air pollution, and many indoor and outdoor smog chambers have been developed both domestically and internationally. However, all of these chambers are located at altitudes below 1500 meters, only simulating atmospheric conditions in low-altitude plains. Moreover, most are made of polytetrafluoroethylene (PTFE), resulting in a higher wall deposition effect. To simulate the evolution of atmospheric pollution in high-altitude regions, we developed the world's highest-altitude quartz smog chamber, located in Kunming at an elevation of 1900 meters. The chamber is a 3.375m³ cube constructed from 5mm quartz glass and features controlled temperature (0°C to 40°C) and relative humidity (2%-95%). We conducted a comprehensive characterization of the chamber, including tests for temperature and humidity stability, mixing stability, pressure resistance and sealing, light intensity measurement and environmental light matching, and background pollutant and wall loss assessments. The characterization results indicate excellent performance in simulating sunlight and controlling background pollutants. The NO2 photolysis rate is adjustable, ranging from 2.03×10⁻³s⁻1 to 5.87×10⁻³s⁻1. Under dry conditions, after 6 hours of photooxidation, the detected O3 formation rate was approximately 1.05 ppb/h, with a particulate mass concentration around 0.12 μg/m³. The reactor withstands pressures exceeding 1.5 bar, and at this pressure, the leak rate was measured at 1.1‰. Validation using the toluene-NO₂ system showed that indoor mixing reached equilibrium in about four minutes. The wall loss rate for SWFU-HAP particles at 25°C and RH <10% was 0.066 h⁻1, which is 70% lower compared to other chambers, while at RH = 50%, the wall loss rate was 0.137 h⁻1. These results demonstrate the superior performance of our system, meeting the high standards required for high-altitude vehicle exhaust aerosol emissions research and the investigation of the formation mechanisms of vehicle exhaust in high-altitude atmospheric environments.