Big-bang nucleosynthesis (BBN) describes the production of the lightest nuclides via a dynamic interplay among the four fundamental forces during the first seconds of cosmic time. We briefly overview the essentials of this physics, and present new calculations of light element abundances through li6 and li7, with updated nuclear reactions and uncertainties including those in the neutron lifetime. We provide fits to these results as a function of baryon density and of the number of neutrino flavors, N_nu. We review recent developments in BBN, particularly new, precision Planck cosmic microwave background (CMB) measurements that now probe the baryon density, helium content, and the effective number of degrees of freedom, n_eff. These measurements allow for a tight test of BBN and of cosmology using CMB data alone. Our likelihood analysis convolves the 2015 Planck data chains with our BBN output and observational data. Adding astronomical measurements of light elements strengthens the power of BBN. We include a new determination of the primordial helium abundance in our likelihood analysis. New D/H observations are now more precise than the corresponding theoretical predictions, and are consistent with the Standard Model and the Planck baryon density. Moreover, D/H now provides a tight measurement of N_nu when combined with the CMB baryon density, and provides a 2sigma upper limit N_nu < 3.2. The new precision of the CMB and of D/H observations together leave D/H predictions as the largest source of uncertainties. Future improvement in BBN calculations will therefore rely on improved nuclear cross section data. In contrast with D/H and he4, li7 predictions continue to disagree with observations, perhaps pointing to new physics.
We outline the experimental concept and key scientific capabilities of AION (Atom Interferometer Observatory and Network), a proposed experimental programme using cold strontium atoms to search for ultra-light dark matter, to explore gravitational waves in the mid-frequency range between the peak sensitivities of the LISA and LIGO/Virgo/ KAGRA/INDIGO/Einstein Telescope/Cosmic Explorer experiments, and to probe other frontiers in fundamental physics. AION would complement other planned searches for dark matter, as well as probe mergers involving intermediate-mass black holes and explore early-universe cosmology. AION would share many technical features with the MAGIS experimental programme, and synergies would flow from operating AION in a network with this experiment, as well as with other atom interferometer experiments such as MIGA, ZAIGA and ELGAR. Operating AION in a network with other gravitational wave detectors such as LIGO, Virgo and LISA would also offer many synergies.
Primordial nucleosynthesis is one of the three historical evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. Now that the number of neutrino families and the baryonic densities have been fixed by laboratory measurements or CMB observations, the model has no free parameter and its predictions are rigid. Departure from its predictions could provide hints or constraints on new physics or astrophysics in the early universe. Precision on primordial abundances deduced from observations have recently been drastically improved and reach the percent level for both deuterium and helium-4. Accordingly, the BBN predictions should reach the same level of precision. For most isotopes, the dominant sources of uncertainty come from those on the laboratory thermonuclear reactions. This article focuses on helium-4 whose predicted primordial abundance depends essentially on weak interactions which control the neutron-proton ratio. The rates of the various weak interaction processes depend on the experimentally measured neutron lifetime, but also includes numerous corrections that we thoroughly investigate here. They are the radiative, zero-temperature, corrections, finite nucleon mass corrections, finite temperature radiative corrections, weak-magnetism, and QED plasma effects, which are for the first time all included and calculated in a self consistent way, allowing to take into account the correlations between them, and verifying that all satisfy detailed balance. The helium-4 predicted mass fraction is $0.24709\pm0.00017$. In addition, we provide a Mathematica code (PRIMAT) that incorporates, not only these corrections but also a full network of reactions, using the best available thermonuclear reaction rates, allowing the predictions of primordial abundances up to the CNO region.
<p>For the azimuth observation to be made at its magnetic observatories routinely, Japan Meteorological Agency (JMA) has adopted a traditional method based on Polaris sighting. Due to its difficulty to implement under overcast weather conditions and to its demand on observers, for overtime work into the evening, we are motivated to seek for an alternative method based on the Global Navigation Satellite Systems (GNSS) observation that might potentially relieve those two disadvantages. An experiment is made at Kakioka to assess the eligibility and effectiveness of the GNSS method for JMA's unmanned observatories, Memambetsu and Kanoya. The GNSS observations themselves achieve as high a precision as approximately 1 arcsec, as far as they are analyzed with Static mode. Derived from the results of GNSS observation and some supplementary horizontal angle measurements, the azimuth of the azimuth mark for the absolute measurement is determined with a precision of a few arcsecond, which is comparable to the azimuth precision achieved by the Polaris sighting. However, we end up with their significant difference by about 10 arcsec. We discuss this discrepancy to be possibly due to a local geoid gradient. The Polaris observation is made with a theodolite tilted in the gravitational direction, also known as the vertical line deviation, whereas the GNSS observations are based on the azimuth of the compliant ellipsoid plane.</p>
Guilherme W. S. deMelo, Ingo Grevemeyer, Dietrich Lange
et al.
Abstract The rupture behavior of large oceanic strike‐slip earthquakes remains largely unresolved using seismic signals recorded thousands of kilometers away from the source area. Large submarine earthquakes, however, generate hydroacoustic T‐waves propagating through the ocean over long distances. Here, we show that these T‐waves recorded at regional distances on the Ascension hydrophone array of the International Monitoring System can provide critical information on the earthquake location and rupture behavior. We use recordings from 47 events in oceanic transform faults, ranging in magnitude from 5.6 ≤ Mw ≤ 7.1, to investigate the rupture processes. We find that most strike‐slip earthquakes show unilateral rupture behavior, while a few larger events were more complex. Furthermore, earthquakes in oceanic transforms have longer ruptures than events of the same magnitude in continental faults. We argue that differences in the scaling relation of oceanic and continental strike‐slip earthquakes support a lower rigidity in the oceanic lithosphere caused by hydration.
Maria-Eirini Pegia, Bjorn or Jonsson, Anastasia Moumtzidou
et al.
Satellite image change detection, where two images of the same area from different times are compared, is crucial for earth sensing and monitoring applications. Many learning-based detection methods have been proposed for this task, with different performance characteristics. Since these detection methods have been tested under different settings, comparing their performance across a variety of situations is difficult. The goal of this article is therefore to comprehensively compare the state-of-the-art detection methods from the literature, across a variety of dataset parameters. To that end, we analyze the impact of image resolution, training set size, and noise on learning performance. A first set of experiments, using a large set of high-resolution images, reveals that training set resolution should match the resolution of the images the model will be applied to, that larger training sets are beneficial, and that adding Gaussian noise improves performance. A second set of experiments, using a smaller set of low-resolution images, confirms that the training set should also be of the same low resolution, but shows that adding noise does not improve performance in this case. The results also indicate that BiasUNet is the most effective method for detecting changes between image pairs.
Polar snowmelt detection is of great importance for the study of global climate change, and synthetic aperture radar (SAR) images have been widely used for polar snowmelt detection because of its ability to provide round-the-clock, all-weather snowmelt detection. However, conventional snowmelt detection algorithms based on the SAR images have images that are susceptible to interference from coherent speckle noise, which leads to the problems of false pixel and missed change detection. To solve the above-mentioned problems, this article proposed a coherent speckle noise suppression algorithm for the SAR images based on the measure of heterogeneity. That is, the SAR images are divided into homogeneous regions, edge regions, and isolated strong scattering regions by the measure of heterogeneity, and different construction algorithms are used for different regions, which was applied to the Larsen C ice shelf. The results showed that the construction algorithm in this article achieved better results in noise suppression, structure preservation and detail retention, and the comprehensive performance was better in the homogeneous regions and edge regions, which could reduce the false alarm rate and leakage rate, and provided algorithmic support for the study of polar snowmelt detection.
Abstract Continental crust forms in magmatic arcs and transforms through collision, as seen in the Tibetan crust shaped by Neo‐Tethyan subduction and India‐Asia collision. We examine zircons from crustal granulite xenoliths using U‐Pb depth profiling to reveal a 220‐million‐year evolutionary history in southern Tibet. Our data provide age history consistent with the Gangdese magmatic rocks. From 100 Ma, our results show numerous age peaks linked to the arrival of the Indian continent, associated with fast convergence, slab rollback, and eventual slab breakoff. During the post‐collisional stage, the growth of zircon rims indicates a resurgence of metamorphism and anatexis, and contemporaneous shifts in Th/U ratios and (Dy/Yb)N values reflect an increase in crustal thickness. We suggest the capacity of zircon overgrowth to capture geological episodes during crustal evolution. In this case, granulite xenoliths from single areas through zircon depth profiling can offer substantial insights into the geological processes shaping the collisional orogen.
In this contribution, we have investigated the energy spectra of the elemental mass groups of cosmic rays for the Light (H+He), medium (C+O) and heavy (Ne-Fe) components using the High Altitude Water Cherenkov Gamma-Ray observatory (HAWC). The study was carried out in the energy interval from $10$ TeV to $1$ PeV using almost $5$ years of data on hadronic air showers. The energy spectra were unfolded using the bidimensional distribution of the lateral shower age versus the reconstructed primary energy. We have employed the QGSJET-II-04 high-energy hadronic interaction model for the current analysis. The results show the presence of fine structure in the spectra of the light, medium and heavy mass groups of cosmic rays.
Unveiling the dark sector of the Universe is one of the leading efforts in theoretical physics. Among the many models proposed, axions and axion-like particles stand out due to their solid theoretical foundation, capacity to contribute significantly to both dark matter and dark energy, and potential to address the small-scale crisis of ΛCDM. Moreover, these pseudo-scalar fields couple to the electromagnetic sector through a Chern-Simons parity-violating term, leading to a rotation of the plane of linearly polarized waves, namely cosmic birefringence. We explore the impact of the axion-parameters on anisotropic birefringence and study, for the first time, its cross-correlation with the spatial distribution of galaxies, focusing on ultralight axions with masses 10-33 eV ≤ mϕ ≤ 10-28 eV. Through this novel approach, we investigate the axion-parameter space in the mass mϕ and initial misalignment angle θi , within the framework of early dark energy models, and constrain the axion-photon coupling gϕγ required to achieve unity in the signal-to-noise ratio of the underlying cross-correlation, computed with the instrument specifications of Euclid and forthcoming CMB-polarization data. Our findings reveal that for masses below 10-32 eV and initial misalignment angles greater in absolute value than π/4, the signal-to-noise ratio not only exceeds unity but also surpasses that achievable from the auto-correlation of birefringence alone (up to a factor 7), highlighting the informative potential of this new probe. Additionally, given the late-time evolution of these low-mass axions, the signal stems from the epoch of reionization, providing an excellent tool to single out the birefringence generated during this period.
The DArk Matter Particle Explorer (DAMPE) is dedicated to exploring critical scientific domains including the indirect detection of dark matter, cosmic ray physics, and gamma ray astronomy. This study introduces a novel method for calibrating the Point Spread Function (PSF) of DAMPE, specifically designed to enhance the accuracy of gamma-ray observations. By leveraging data from regions near pulsars and bright Active Galactic Nuclei (AGNs), we have refined the PSF calibration process, resulting in an improved angular resolution that closely matches our observational data. This advancement significantly boosts the precision of gamma-ray detection by DAMPE, thereby contributing to its mission objectives in dark matter detection and gamma ray astronomy.
We explore the production of gravitational waves resulting from a first-order phase transition (FOPT) in a non-minimally coupled `Dark Higgs Inflation' model. Utilizing a dark sector scalar field as the inflaton, we demonstrate how inflationary dynamics set the stage for observable FOPT. These transitions, influenced by thermal and quantum effects, generate gravitational wave spectra potentially detectable by observatories such as LISA, DECIGO, the Cosmic Explorer and the Einstein Telescope. Our study highlights the inflaton's dual role in cosmic inflation and early Universe phase transitions, presenting a unified framework to probe physics beyond the Standard Model through gravitational wave astronomy.
Axion-like particles may form a network of cosmic strings in the Universe today that can rotate the plane of polarization of cosmic microwave background (CMB) photons. Future CMB observations with improved sensitivity might detect this axion-string-induced birefringence effect, thereby revealing an as-yet unseen constituent of the Universe and offering a new probe of particles and forces that are beyond the Standard Model of Elementary Particle Physics. In this work, we explore how spherical convolutional neural networks (SCNNs) may be used to extract information about the axion string network from simulated birefringence maps. We construct a pipeline to simulate the anisotropic birefringence that would arise from an axion string network, and we train SCNNs to estimate three parameters related to the cosmic string length, the cosmic string abundance, and the axion-photon coupling. Our results demonstrate that neural networks are able to extract information from a birefringence map that is inaccessible with two-point statistics alone (i.e., the angular power spectrum). We also assess the impact of noise on the accuracy of our SCNN estimators, demonstrating that noise at the level anticipated for Stage IV (CMB-S4) measurements would significantly bias parameter estimation for SCNNs trained on noiseless simulated data, and necessitate modeling the noise in the training data.
New data from ongoing galaxy surveys, such as the $Euclid$ satellite and the Dark Energy Spectroscopic Instrument (DESI), are expected to unveil physics on the largest scales of our universe. Dramatically affected by cosmic variance, these scales are of interest to large-scale structure studies as they exhibit relevant corrections due to general relativity (GR) in the $n$-point statistics of cosmological random fields. We focus on the relativistic, sample-dependent Doppler contribution to the observed clustering of galaxies, whose detection will further confirm the validity of GR in cosmological regimes. Sample- and scale-dependent, the Doppler term is more likely to be detected via cross-correlation measurements, where it acts as an imaginary correction to the power spectrum of fluctuations in galaxy number counts. We present a method allowing us to exploit multi-tracer benefits from a single data set, by subdividing a galaxy population into two sub-samples, according to galaxies' luminosity/magnitude. To overcome cosmic variance we rely on a multi-tracer approach, and to maximise the detectability of the relativistic Doppler contribution in the data, we optimise sample selection. As a result, we find the optimal split and forecast the relativistic Doppler detection significance for both a DESI-like Bright Galaxy Sample and a $Euclid$-like H$\alpha$ galaxy population.
GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite experiment utilizing a LArTPC (Liquid Argon Time Projection Chamber), to simultaneously target astrophysical observations of cosmic MeV gamma-rays and conduct an indirect dark matter search using antimatter. While LArTPCs are widely used in particle physics experiments, they have never been operated at balloon altitudes. An engineering balloon flight with a small-scale LArTPC (eGRAMS) was conducted on July 27th, 2023, to establish a system for safely operating a LArTPC at balloon altitudes and to obtain cosmic-ray data from the LArTPC. The flight was launched from the Japan Aerospace Exploration Agency’s (JAXA) Taiki Aerospace Research Field in Hokkaido, Japan. The total flight duration was 3 hours and 12 minutes, including a level-flight of 44 minutes at a maximum altitude of 28.9 km. The flight system was landed on the sea and successfully recovered. The LArTPC was successfully operated throughout the flight, and about 0.5 million events of the cosmic-ray data including muons, protons, and Compton scattering gamma-ray candidates, were collected. This pioneering flight demonstrates the feasibility of operating a LArTPC in high-altitude environments, paving the way for future GRAMS missions and advancing our capabilities in MeV gamma-ray astronomy and dark matter research.
The structure of the Standard Model (SM) of particle physics points toward grand unified theories (GUTs) where strong and electroweak interactions are unified in a non-Abelian GUT group. The spontaneous breaking of the GUT symmetry to the SM symmetry, together with cosmic inflation, generically leads to metastable topological defects, the most prominent example being cosmic strings. The gravitational-wave background (GWB) produced by a cosmic string network is one of the candidates for an explanation of the GWB recently observed by pulsar timing array (PTA) experiments. We review some properties of the predicted GWB with emphasis on potential implications for GUT model building. The most striking prediction is a GWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.
Cosmic ray muons prove valuable across various fields, from particle physics experiments to non-invasive tomography, thanks to their high flux and exceptional penetrating capability. Utilizing a scintillator detector, one can effectively study the topography of mountains situated above tunnels and underground spaces. The Hankuk Atmospheric-muon Wide Landscaping (HAWL) project successfully charts the mountainous region of eastern Korea by measuring cosmic ray muons with a detector in motion. The real-time muon flux measurement shows a tunnel length accuracy of 6.0 %, with a detectable overburden range spanning from 8 to 400 meter-water-equivalent depth. This is the first real-time portable muon tomography.