Satellite measurements challenge the current understanding of cosmic-ray acceleration and propagation in our Galaxy. Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.
Context. A large proportion of observed white dwarfs show evidence of debris disks, remnants of the former planetary systems, and/or signatures of heavy elements in their atmospheres, induced by the accretion of planetary matter onto their surfaces. The observed abundances are the result of the balance between the accretion flux and the dilution of this planetary material by internal transport processes. A recent study showed that more massive DA white dwarfs are less polluted than smaller mass ones. It was suggested that the reason could be related to the formation of planetary systems when these stars were on the main sequence.
Aims. The aim of this work is to test how internal dilution processes, including thermohaline convection, change with white dwarf masses, and whether such an effect could account for variations in the observed pollution.
Methods. We computed the efficiency of atomic diffusion and thermohaline convection after the accretion of heavy elements onto white dwarfs using static DA models with various masses, effective temperatures, and hydrogen contents.
Results. We confirm that thermohaline convection is always more efficient in diluting accreted elements than atomic diffusion, as previously shown in the literature. However, we find that element dilution by thermohaline convection is less efficient in massive white dwarfs than in smaller mass ones, due to their larger internal density.
Conclusions. We showed that the differences in observed heavy element pollution in white dwarfs according to their masses cannot be explained by the dilution induced by atomic diffusion and thermohaline mixing alone. Indeed, the pollution by planetary system accretion should be more easily detectable in massive white dwarfs than in low-mass ones. We discuss other processes that should be taken into account before drawing any conclusion about the occurrences of planetary systems according to the mass of the star on the main sequence.
The CMS collaboration, V. Chekhovsky, A. Hayrapetyan
et al.
Abstract A search for nonresonant new physics phenomena in high-mass dilepton events produced in association with b-tagged jets is performed using proton-proton collision data collected in 2016–2018 by the CMS experiment at the CERN LHC, at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb −1. The analysis considers two effective field theory models with dimension-six operators; involving four-fermion contact interactions between two leptons (ℓℓ, electrons or muons) and b or s quarks (bbℓℓ and bsℓℓ). Two lepton flavor combinations (ee and μμ) are required and events are classified as having 0, 1, or ≥2 b-tagged jets in the final state. No significant excess is observed over the standard model backgrounds. Upper limits are set on the production cross section of the new physics signals. These translate into lower limits on the energy scale Λ of 6.9 to 9.0 TeV in the bbℓℓ model, depending on model parameters, and on the ratio of energy scale and effective coupling, Λ/g *, of 2.0 to 2.6 TeV in the bsℓℓ model. Lepton flavor universality is also tested by comparing the dielectron (ee) and dimuon (μμ) mass spectra for different b-tagged jet multiplicities. No significant deviation from the standard model expectation of unity is observed.
Nuclear and particle physics. Atomic energy. Radioactivity
Based on the Ca ii H and K lines observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, we employ the photospheric ( ${R}_{{\rm{HK}}}^{{\prime} }$ ) and basal ( ${R}_{{\rm{HK}},L}^{+}$ ) flux-calibrated chromospheric activity indices to examine the relationship between chromospheric activity and the stellar rotation rate. We identify the rotation periods of 11,108 stars observed by Kepler and the Transiting Exoplanet Survey Satellite by crossmatching our chromospheric activity catalog with previous studies. Our statistical results show that chromospheric activity increases with the rotation rate until it reaches a saturation level. As the stellar effective temperature increases from 4950 to 5850 K, the saturation values of the rotation period ( P _rot ) vary correspondingly from 4.38 to 1.23 days for ${R}_{{\rm{HK}}}^{{\prime} }$ and from 9.88 to 1.33 days for ${R}_{{\rm{HK}},L}^{+}$ . Similarly, the corresponding saturation Rossby number (Ro) ranges from 0.200 to 0.032 for ${R}_{{\rm{HK}}}^{{\prime} }$ and from 0.302 to 0.107 for ${R}_{{\rm{HK}},L}^{+}$ . The saturation is also found to be significant in stars with thick convective zones, whereas it is less apparent in stars with higher effective temperatures. For solar-like stars in the T _eff range of 4800–6000 K, the values of chromospheric activity indicators are saturated when P _rot < 1.45 days (Ro < 0.100) and P _rot < 2.85 days (Ro < 0.097) for ${R}_{{\rm{HK}}}^{{\prime} }$ and ${R}_{{\rm{HK}},L}^{+}$ , respectively.
With the increasing global emphasis on sustainable energy, wave energy has gained recognition as a significant renewable marine resource, drawing substantial research attention. However, the efficient conversion of low-frequency, random, and low-energy wave motion into electrical power remains a considerable challenge. In this study, an advanced hybrid generator design is introduced which enhances wave energy harvesting by optimizing wave–body coupling characteristics and incorporating both a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) within the shell. The optimized asymmetric trapezoidal shell (ATS) improves output frequency and energy harvesting efficiency in marine environments. Experimental findings under simulated water wave excitation indicate that the accelerations in the x, y, and z directions for the ATS are 1.9 m·s<sup>−2</sup>, 0.5 m·s<sup>−2</sup>, and 1.4 m·s<sup>−2</sup>, respectively, representing 1.2, 5.5, and 2.3 times those observed in the cubic shell. Under real ocean conditions, a single TENG unit embedded in the ATS achieves a maximum transferred charge of 1.54 μC, a short-circuit current of 103 μA, and an open-circuit voltage of 363 V, surpassing the cubic shell by factors of 1.21, 1.24, and 2.13, respectively. These performance metrics closely align with those obtained under six-degree-of-freedom platform oscillation (0.4 Hz, swing angle range of ±6°), exceeding the results observed in laboratory-simulated waves. Notably, the most probable output frequency of the ATS along the x-axis reaches 0.94 Hz in ocean trials, which is 1.94 times the significant wave frequency of ambient sea waves. The integrated hybrid generator efficiently captures low-quality wave energy to power water quality sensors in marine environments. This study highlights the potential of combining synergistic geometric shell design and generator integration to achieve high-performance wave energy harvesting through improved wave–body coupling.
Abstract The Dirac equation with mass and axial chemical potential is solved analytically, obtaining the mode spinors and the corresponding projection operators, giving the spectral representations of the principal conserved operators. In this framework, the odd partner of the Pryce spin operator is defined for the first time, showing how these operators may be combined for defining the particle and antiparticle spin and polarization operators of Dirac’s theory of massive fermions, either in the free case or in the presence of the axial chemical potential. The quantization procedure is applied in both these cases, obtaining two distinct operator algebras in which the particle and antiparticle spin and polarization operators take canonical forms. In this approach, statistical operators with independent particle and antiparticle vortical chemical potentials may be constructed.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We extend the construction of Alcubierre–Natário class of warp drives to an infinite class of spacetimes with similar properties. This is achieved by utilising the Martel–Poisson charts which closely resembles the Weak Painlevé–Gullstrand form for various background metrics (Mink, AdS, dS). The highlight of this construction is the non-flat intrinsic metric which in three dimensional spacetimes introduce conical singularities at the origin and in higher dimensions generates non-zero Ricci scalar for the spatial hypersurfaces away from the origin. We analyse the expansion/contraction of space and the (NEC) violations associated with these warp drives and find interesting scalings due to the global imprints of the conical defects. Other properties like tilting of light cones, event horizons and several generalisations are also discussed.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Ratovsky Konstantin, Klimenko Maksim, Vesnin Artem
et al.
The paper studies statistical patterns of regional electron content responses to geomagnetic events at high, middle, and equatorial latitudes. The regional electron content is the total electron content averaged over all longitudes in a given latitudinal zone. The statistical analysis includes the following: 1) identification of geomagnetic events based on the AE index and calculation of “reference” geomagnetic storms; 2) calculation of the regional electron content (REC) for five latitudinal zones (equatorial zone, mid-latitude zones of the Northern and Southern hemispheres, and high-latitude zones of the Northern and Southern hemispheres); 3) calculation of REC disturbances (ΔREC), which are relative (percentage) deviations of the observed values, from the 27-day running mean of REC and 4) obtaining the “reference” ionospheric response in the form of the dynamics of average ΔREC, obtained by the superposed epoch method. The superposed epoch method is implemented with the hourly resolution and key moments corresponding to the AE index maximum. Compared with our previous statistical analysis, implemented with daily resolution based on geomagnetic storm identification by the Dst index, the new method leads to a significant increase in the amplitude and the time-focusing of the response. The seasonal behavior of ionospheric responses was analyzed for correspondence to the thermospheric storm concept. The responses of the equatorial and mid-latitude zones of the Southern Hemisphere fit the thermospheric storm concept. In the mid-latitude zone of the Northern Hemisphere, there are a number of exceptions. The responses of the high-latitude zone show the need to take into account the mechanisms behind the formation of positive disturbances, which are absent in the thermospheric storm concept
Ni Putu Audita Placida Emas, Chris Blake, Rossana Ruggeri
et al.
The ratio of the average tangential shear signal of different weak lensing source populations around the same lens galaxies, also known as a shear ratio, provides an important test of lensing systematics and a potential source of cosmological information. In this paper we measure shear ratios of three current weak lensing surveys --KiDS, DES, and HSC-- using overlapping data from the Baryon Oscillation Spectroscopic Survey. We apply a Bayesian method to reduce bias in shear ratio measurement, and assess the degree to which shear ratio information improves the determination of important astrophysical parameters describing the source redshift distributions and intrinsic galaxy alignments, as well as cosmological parameters, in comparison with cosmic shear and full 3x2-pt correlations (cosmic shear, galaxy-galaxy lensing, and galaxy clustering). We consider both Fisher matrix forecasts, as well as full likelihood analyses of the data. We find that the addition of shear ratio information to cosmic shear allows the mean redshifts of the source samples and intrinsic alignment parameters to be determined significantly more accurately. Although the additional constraining power enabled by the shear ratio is less than that obtained by introducing an accurate prior in the mean source redshift using photometric redshift calibration, the shear ratio allows for a useful cross-check. The inclusion of shear ratio data consistently benefits the determination of cosmological parameters such as S_8, for which we obtain improvements up to 34%. However these improvements are less significant when shear ratio is combined with the full 3x2-pt correlations. We conclude that shear ratio tests will remain a useful source of cosmological information and cross-checks for lensing systematics, whose application will be further enhanced by upcoming datasets such as the Dark Energy Spectroscopic Instrument.
A number of stellar astrophysical phenomena, such as tidal novae and planetary engulfment, involve sudden injection of subbinding energy in a thin layer within the star, leading to mass ejection of the stellar envelope. We use a 1D hydrodynamical model to survey the stellar response and mass loss for various amounts ( E _dep ) and locations of the energy deposition. We find that the total mass ejection has a nontrivial dependence on E _dep due to the varying strengths of mass ejection events, which are associated with density/pressure waves breaking out from the stellar surface. The rapid occurrence of multiple breakouts may present a unique observational signature for sudden envelope heating events in stars.
We present JWST NIRCam (F356W and F444W filters) and MIRI (F770W) images and NIRSpec Integral Field Unit (IFU) spectroscopy of the young Galactic supernova remnant Cassiopeia A (Cas A) to probe the physical conditions for molecular CO formation and destruction in supernova ejecta. We obtained the data as part of a JWST survey of Cas A. The NIRCam and MIRI images map the spatial distributions of synchrotron radiation, Ar-rich ejecta, and CO on both large and small scales, revealing remarkably complex structures. The CO emission is stronger at the outer layers than the Ar ejecta, which indicates the re-formation of CO molecules behind the reverse shock. NIRSpec-IFU spectra (3–5.5 μ m) were obtained toward two representative knots in the NE and S fields that show very different nucleosynthesis characteristics. Both regions are dominated by the bright fundamental rovibrational band of CO in the two R and P branches, with strong [Ar vi ] and relatively weaker, variable strength ejecta lines of [Si ix ], [Ca iv ], [Ca v ], and [Mg iv ]. The NIRSpec-IFU data resolve individual ejecta knots and filaments spatially and in velocity space. The fundamental CO band in the JWST spectra reveals unique shapes of CO, showing a few tens of sinusoidal patterns of rovibrational lines with pseudocontinuum underneath, which is attributed to the high-velocity widths of CO lines. Our results with LTE modeling of CO emission indicate a temperature of ∼1080 K and provide unique insight into the correlations between dust, molecules, and highly ionized ejecta in supernovae and have strong ramifications for modeling dust formation that is led by CO cooling in the early Universe.
S-type asymptotic giant branch (AGB) stars are defined by their carbon-to-oxygen (C/O) ratio approaching unity. However, observations of circumstellar molecules in these stars are limited and challenging. In this study, we used the James Clerk Maxwell Telescope to search for cyanide (CN) in 12 selected S-type AGB stars, with only 4 of these stars displaying CN spectral line signals. The column density and fractional abundance of CN were calculated assuming local thermodynamic equilibrium, and the average CN-to-hydrogen-cyanide (HCN) abundance ratio of the four sources is about 0.036. We investigate, for the first time, the relationship between CN and HCN fractional abundances in all types of AGB stars, finding that the ratio is similar in O-rich and S-type stars, while those in C-rich stars are quite different. This result supports the idea that the level of HCN photodissociation plays a crucial role in determining the CN abundance in the circumstellar envelopes of AGB stars at various stages of their evolution.
Marion Pillas, Tito Dal Canton, Cosmin Stachie
et al.
GW170817–GRB 170817A provided the first observation of gravitational waves from a neutron star merger with associated transient counterparts across the entire electromagnetic spectrum. This discovery demonstrated the long-hypothesized association between short gamma-ray bursts and neutron star mergers. More joint detections are needed to explore the relation between the parameters inferred from the gravitational wave and the properties of the gamma-ray burst signal. We developed a joint multimessenger analysis of LIGO, Virgo, and Fermi/GBM data designed for detecting weak gravitational-wave transients associated with weak gamma-ray bursts. As such, it does not start from confident (GWTC-1) events only. Instead, we take the full list of existing compact binary coalescence triggers generated with the PyCBC pipeline from the second Gravitational-Wave Observing Run (O2), and reanalyze the entire set of public Fermi/GBM data covering this observing run to generate a corresponding set of gamma-ray burst candidate triggers. We then search for coincidences between the gravitational-wave and gamma-ray burst triggers without requiring a confident detection in any channel. The candidate coincidences are ranked according to a statistic combining each candidate’s strength in gravitational-wave and gamma-ray data, their time proximity, and the overlap of their sky localization. The ranking is then converted to a false alarm rate using time shifts between the gravitational-wave and gamma-ray burst triggers. We present the results using O2 triggers, which allowed us to check the validity of our method against GW170817–GRB 170817A. We also discuss the different configurations tested to maximize the significance of the joint detection.
We investigated the impact of nonequilibrium conditions on the transmission and recovery of information through noisy channels. By measuring the recoverability of messages from an information source, we demonstrate that the ability to recover information is connected to the nonequilibrium behavior of the information flow, particularly in terms of sequential information transfer. We discovered that the mathematical equivalence of information recoverability and entropy production characterizes the dissipative nature of information transfer. Our findings show that both entropy production (or recoverability) and mutual information increase monotonically with the nonequilibrium strength of information dynamics. These results suggest that the nonequilibrium dissipation cost can enhance the recoverability of noise messages and improve the quality of information transfer. Finally, we propose a simple model to test our conclusions and found that the numerical results support our findings.
Bohdan Slavko, Mikhail Prokopenko, Kirill S. Glavatskiy
We propose a non-equilibrium framework for modelling the evolution of cities, which describes intra-urban migration as an irreversible diffusive process. We validate this framework using the actual migration data for the Australian capital cities. With respect to the residential relocation, the population is shown to be composed of two distinct groups, exhibiting different relocation frequencies. In the context of the developed framework, these groups can be interpreted as two components of a binary fluid mixture, each with its own diffusive relaxation time. Using this approach, we obtain long-term predictions of the cities’ spatial structures, which define their equilibrium population distribution.
Abstract Quintessence fields, introduced to explain the speed-up of the Universe, might affect the geometry of spacetime surrounding black holes, as compared to the standard Schwarzschild and Kerr geometries. In this framework, we study the neutrino pairs annihilation into electron-positron pairs ( $$\nu {\bar{\nu }}\rightarrow e^-e^+$$ ν ν ¯ → e - e + ) near the surface of a neutron star, focusing, in particular, on the Schwarzschild-like geometry in presence of quintessence fields. The effect of the latter is to increase the photon-sphere radius ( $$R_{ph}$$ R ph ), increasing in such a way the maximum energy deposition rate near to $$R_{ph}$$ R ph . The rate turns out to be several orders of magnitude greater than the rate computed in the framework of General Relativity. These results might provide a rising in the GRBs energy emitted from a close binary neutron star system and might be used to constraints the parameters of the quintessence model. Finally we theoretically study the effects of rotation on the neutrino energy deposition.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
A system’s heterogeneity (<i>diversity</i>) is the effective size of its event space, and can be quantified using the Rényi family of indices (also known as Hill numbers in ecology or Hannah–Kay indices in economics), which are indexed by an elasticity parameter <inline-formula><math display="inline"><semantics><mrow><mi>q</mi><mo>≥</mo><mn>0</mn></mrow></semantics></math></inline-formula>. Under these indices, the heterogeneity of a composite system (the <inline-formula><math display="inline"><semantics><mi>γ</mi></semantics></math></inline-formula>-heterogeneity) is decomposable into heterogeneity arising from variation <i>within</i> and <i>between</i> component subsystems (the <inline-formula><math display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>- and <inline-formula><math display="inline"><semantics><mi>β</mi></semantics></math></inline-formula>-heterogeneity, respectively). Since the average heterogeneity of a component subsystem should not be greater than that of the pooled system, we require that <inline-formula><math display="inline"><semantics><mrow><mi>γ</mi><mo>≥</mo><mi>α</mi></mrow></semantics></math></inline-formula>. There exists a multiplicative decomposition for Rényi heterogeneity of composite systems with discrete event spaces, but less attention has been paid to decomposition in the continuous setting. We therefore describe multiplicative decomposition of the Rényi heterogeneity for continuous mixture distributions under parametric and non-parametric pooling assumptions. Under non-parametric pooling, the <inline-formula><math display="inline"><semantics><mi>γ</mi></semantics></math></inline-formula>-heterogeneity must often be estimated numerically, but the multiplicative decomposition holds such that <inline-formula><math display="inline"><semantics><mrow><mi>γ</mi><mo>≥</mo><mi>α</mi></mrow></semantics></math></inline-formula> for <inline-formula><math display="inline"><semantics><mrow><mi>q</mi><mo>></mo><mn>0</mn></mrow></semantics></math></inline-formula>. Conversely, under parametric pooling, <inline-formula><math display="inline"><semantics><mi>γ</mi></semantics></math></inline-formula>-heterogeneity can be computed efficiently in closed-form, but the <inline-formula><math display="inline"><semantics><mrow><mi>γ</mi><mo>≥</mo><mi>α</mi></mrow></semantics></math></inline-formula> condition holds reliably only at <inline-formula><math display="inline"><semantics><mrow><mi>q</mi><mo>=</mo><mn>1</mn></mrow></semantics></math></inline-formula>. Our findings will further contribute to heterogeneity measurement in continuous systems.