Final Abundance Research Articles

Photonuclear Reaction Rates of 157,159Ho and 163,165Tm and Their Impact in the γ-process

Reliable photonuclear reaction rates in stellar conditions are essential for understanding the origin of the heavy stable neutron-deficient isotopes between 74Se and 196Hg, i.e., p-nuclei. However, many reaction rates of relevance still have to rely on the Hauser–Feshbach (HF) model due to the rarity of experimental progress. One such case is in the mass range of 160 for Dy, Er, Ho, and Tm isotopes. In this work we attempt to constrain the HF model in the TALYS package by reproducing the available experimental data on 160Dy(p, γ)161Ho and 162Er(p, γ)163Tm in the A ∼ 160 mass region, and examine the effects of level density, gamma strength function, and the optical model potential. The constrained model then allows us to calculate the reaction rates of 157,159Ho(γ, p) and 163,165Tm(γ, p) for the γ-process nucleosynthesis in a carbon-deflagration model for Type Ia supernovae. Our recommended rates differ from the JINA REACLIB by more than one order of magnitude in the temperature range 2–3 GK. This results in changes in the final abundance of p-nuclei in the A ∼ 160 mass range by −5.5% to 3% from those with JINA, which means that the uncertainty of (γ, p) reactions is not predominant for the synthesis of these nuclei.

Corrections of the Distribution of Nuclei Due to Neutron Degeneracy and Their Effects in the R-Process in Neutron Stars—Black Hole Mergers

The r-process is one of the processes that produces heavy elements in the Universe. One of its possible astrophysical sites is the neutron star–black hole (NS-BH) merger. We first show that the neutrons can degenerate before and during the r-process in these mergers. Previous studies assumed neutrons were non-degenerate and the related rates were calculated under Maxwell–Boltzmann approximations. Hence, we corrected the related rates with neutron degeneracy put in the network code and calculated with the trajectories of NS-BH mergers. We show that there are differences in the nuclei distributions. The heating rates and the temperature at most can be two times larger. The change in heating rates and temperature can affect the light curves of the kilonovae. However, this has little effect on the final abundances.

Chemical abundances for a sample of FGK dwarfs in the Pleiades open cluster from APOGEE

ABSTRACT This paper presents chemical abundances of 12 elements (C, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe) for 80 FGK dwarfs in the Pleiades open cluster, which span a temperature range of $\sim$2000 K in T$_{\rm eff}$, using the high-resolution (R$\sim$22 500) near-infrared SDSS (Sloan Digital Sky Survey)-IV/APOGEE (Apache Point Observatory Galactic Evolution Experiment) spectra ($\lambda$1.51–1.69 $\mu$m). Using a 1D local thermodynamic equilibrium abundance analysis, we determine an overall metallicity of [Fe/H] = +0.03 $\pm$ 0.04 dex, with the elemental ratios [$\alpha$/Fe] = +0.01 $\pm$ 0.05, [odd-z/Fe] = –0.04 $\pm$ 0.08, and [iron peak/Fe] = –0.02 $\pm$ 0.08. These abundances for the Pleiades are in line with the abundances of other open clusters at similar galactocentric distances as presented in the literature. Examination of the abundances derived from each individual spectral line revealed that several of the stronger lines displayed trends of decreasing abundance with decreasing $T_{\rm eff}$. The list of spectral lines that yield abundances that are independent of $T_{\rm eff}$ are presented and used for deriving the final abundances. An investigation into possible causes of the temperature-dependent abundances derived from the stronger lines suggests that the radiative codes and the APOGEE line list we employ may inadequately model van der Waals broadening, in particular in the cooler K dwarfs.

Antibiotic resistomes and ecological risk elimination in field-scale constructed wetland revealed by integrated metagenomics and metatranscriptomics

Constructed wetlands (CWs) are identified as significant ecological systems for the potential control of antibiotic resistance genes (ARGs) in the environment. However, the precise mechanisms governing removal, persistence, expression, and associated risks of ARGs during wetland treatment remain poorly understood. In this study, the distribution, mobility, expression, and hosts of ARGs in water, sediments, and plants of a field-scale CW and its parallel natural river were systematically investigated through metagenomic and metatranscriptomic approaches. Results showed that both the abundance and diversity of ARGs in water gradually decreased along the way of CW, reaching a final abundance removal rate of 72.28 % in the effluent. Source tracking analysis indicted that the reduction of ARGs in water was mainly achieved by the dynamic accumulation of ARGs in sediments and plants of the CW. Proteobacteria were identified as primary hosts for ARGs, particularly in sediments and plants during CW treatment. Moreover, although ESKAPE pathogens carrying multiple ARGs persisted in all media throughout the CW treatment, ARG expression levels and risk of water were also significantly decreased after CW treatment. Collectively, our comprehensive multi-omics study would enhance the understanding of ARG removal by CWs, offering insights for controlling antimicrobial resistance in wastewater treatment system.

Element Formation in Radiation-hydrodynamics Simulations of Kilonovae

Understanding the details of r-process nucleosynthesis in binary neutron star merger (BNSM) ejecta is key to interpreting kilonova observations and identifying the role of BNSMs in the origin of heavy elements. We present a self-consistent, two-dimensional, ray-by-ray radiation-hydrodynamic evolution of BNSM ejecta with an online nuclear network (NN) up to a timescale of days. For the first time, an initial numerical relativity ejecta profile composed of the dynamical component and spiral-wave and disk winds is evolved including detailed r-process reactions and nuclear heating effects. A simple model for the jet energy deposition is also included. Our simulation highlights that the common approach of relating in postprocessing the final nucleosynthesis yields to the initial thermodynamic profile of the ejecta can lead to inaccurate predictions. Moreover, we find that neglecting the details of the radiation-hydrodynamic evolution of the ejecta in nuclear calculations can introduce deviations of up to 1 order of magnitude in the final abundances of several elements, including very light and second r-process peak elements. The presence of a jet affects element production only in the innermost part of the polar ejecta, and it does not alter the global nucleosynthesis results. Overall, our analysis shows that employing an online NN improves the reliability of nucleosynthesis and kilonova light-curve predictions.

Targeted whole-genome recovery of single viral species in a complex environmental sample

Characterizing unknown viruses is essential for understanding viral ecology and preparing against viral outbreaks. Recovering complete genome sequences from environmental samples remains computationally challenging using metagenomics, especially for low-abundance species with uneven coverage. We present an experimental method for reliably recovering complete viral genomes from complex environmental samples. Individual genomes are encapsulated into droplets and amplified using multiple displacement amplification. A unique gene detection assay, which employs an RNA-based probe and an exonuclease, selectively identifies droplets containing the target viral genome. Labeled droplets are sorted using a microfluidic sorter, and genomes are extracted for sequencing. We demonstrate this method's efficacy by spiking two known viral genomes, Simian virus 40 (SV40, 5,243 bp) and Human Adenovirus 5 (HAd5, 35,938 bp), into a sewage sample with a final abundance in the droplets of around 0.1% and 0.015%, respectively. We achieve 100% recovery of the complete sequence of the spiked-in SV40 genome with uniform coverage distribution. For the larger HAd5 genome, we cover approximately 99.4% of its sequence. Notably, genome recovery is achieved with as few as one sorted droplet, which enables the recovery of any desired genomes in complex environmental samples, regardless of their abundance. This method enables single-genome whole-genome amplification and targeting characterizations of rare viral species and will facilitate our ability to access the mutational profile in single-virus genomes and contribute to an improved understanding of viral ecology.

Monte Carlo simulation of UV-driven synthesis of complex organic molecules on icy grain surfaces

Context. Complex organic molecules (COMs) have been widely observed in molecular clouds and protostellar environments. One of the formation mechanisms of COMs is radical reactions on the icy grain surface driven by UV irradiation. While many experiments have reported that various COMs (including biomolecules) can be synthesized under such ice conditions, the majority of the reaction processes are unclear. Complementary numerical simulations are necessary to unveil the synthetic process behind the formation of COMs. Aims. In this study, we develop a chemical reaction simulation using a Monte Carlo method. To explore the complex reaction network of COM synthesis, the model was designed to eliminate the need to prepare reaction pathways in advance and to keep computational costs low. This allows for broad parameter surveys and a global investigation of COM synthesis reactions. With this simulation, we investigate the chemical reactions occurring on icy dust surfaces during and after UV irradiation, assuming a protoplanetary disk environment. We aim to reveal the types of organic molecules produced in a disk and the formation mechanisms of COMs, in particular, amino acids and sugars. Methods. The Monte Carlo method we developed here produces reaction sequences by selecting a reaction from all candidate reactions at each calculation step, based on Arrhenius-type weighting. For our purpose, we significantly accelerated the calculation by adopting an approximate estimation of activation energy without expensive quantum chemical calculations. Results. The results show that photodissociation and subsequent radical-radical reactions cause random rearrangement of the covalent bonds in the initial molecules composed of methanol, formaldehyde, ammonia, and water. Consequently, highly complex molecules such as amino acids and sugars were produced in a wide range of the initial conditions. We found that the final abundances of amino acids and sugars have extremely similar dependence on the atomic ratios of the initial molecules, which peak at C/H ~ 0.1–0.3 and O/H ~ 0.3–0.5, although the amino acids abundance is usually more than ten times higher than that of sugars. To understand this dependence, a semi-analytical formula was derived. Additionally, parameter surveys of temperature, photon energy, and other factors have suggested that the decomposition reactions of amino acids and sugars undergo a rapid transition within the threshold of a given parameter.

Chemical evolution of complex organic molecules in turbulent protoplanetary discs: effect of stochastic ultraviolet irradiation

ABSTRACT We investigate the chemical evolution of complex organic molecules (COMs) in turbulent discs using gas-ice chemical reaction network simulations. We trace trajectories of dust particles considering advection, turbulent diffusion, gas drag, and vertical settling, for 10$^6$ yr in a protoplanetary disc. Then, we solve a gas-ice chemical reaction network along the trajectories and obtain the temporal evolution of molecular abundances. We find that the COM abundances in particles can differ by more than two orders of magnitude even when the ultraviolet (UV) fluence (i.e. the time integral of UV flux) received by the particles are similar, suggesting that not only the UV fluence but also the time variation of the UV flux does matter for the evolution of COMs in discs. The impact of UV fluence on molecular abundances differs between oxygen-bearing and nitrogen-bearing COMs. While higher UV fluence results in oxygen being locked into CO$_2$, leading to reduced abundances of oxygen-bearing COMs such as CH$_3$OCH$_3$, mild UV exposure can promote their formation by supplying the precursor radicals. On the other hand, nitrogen is not locked up into specific molecules, allowing the formation of nitrogen-bearing COMs, particularly CH$_3$NH$_2$, even for the particle that receives the higher UV fluence. We also find that the final COM abundances are mostly determined by the inherited abundances from the protostellar core when the UV fluence received by dust particles is less than a critical value, while they are set by both the inherited abundances and the chemistry inside the disc at higher UV fluence.

The 2024 BBN baryon abundance update

We revisit the state of the light element abundances from big bang nucleosynthesis in early 2024 with particular focus on the derived baryon abundance. We find that the largest differences between the final baryon abundances are typically driven by the assumed Deuterium burning rates, characterized in this work by the underlying code. The rates from theoretical ab-initio calculations favor smaller baryon abundances, while experimentally-determined rates prefer higher abundances. Through robust marginalization over a wide range of nuclear rates, the recently released PRyMordial code allows for a conservative estimate of the baryon abundance at Ω bh 2 = 0.02218 ± 0.00055 (using PDG-recommended light element abundances) in ΛCDM and Ω bh 2 = 0.02196 ± 0.00063 when additional ultra-relativistic relics are considered (ΛCDM + N eff). These additional relics themselves are constrained to ΔN eff = -0.10 ± 0.21 by light element abundances alone.

Collapsing domain wall networks: impact on pulsar timing arrays and primordial black holes

Unstable domain wall (DW) networks in the early universe are cosmologically viable and can emit a large amount of gravitational waves (GW) before annihilating. As such, they provide an interpretation for the recent signal reported by Pulsar Timing Array (PTA) collaborations. A related important question is whether such a scenario also leads to significant production of Primordial Black Holes (PBH).We investigate both GW and PBH production using 3D numerical simulations in an expanding background, with box sizes up to N = 3240,including the annihilation phase. We find that:i) the network decays exponentially, i.e. the false vacuum volume drops as ∼ exp(-η 3), with η the conformal time;ii) the GW spectrum is larger than traditional estimates by more than one order of magnitude, due to a delay between DW annihilation and the sourcing of GWs. We then present a novel semi-analytical method to estimate the PBH abundances: rare false vacuum pockets of super-Hubble size collapse to PBHs if their energy density becomes comparable to the background when they cross the Hubble scale. Smaller (but more abundant) pockets will instead collapse only if they are close to spherical. This introduces very large uncertainties in the final PBH abundance. The first phenomenological implication is that the DW interpretation of the PTA signal is compatible with observational constraints on PBHs, within the uncertainties. Second, in a different parameter region, the dark matter can be entirely in the form of asteroid-mass PBHs from the DW collapse. Remarkably, this would also lead to a GW background in the observable range of LIGO-Virgo-KAGRA and future interferometers, such as LISA and Einstein Telescope.

New insights on waste mixing for enhanced fermentative hydrogen production

Co-fermentation can differently impact H2 production, with positive or negative interactions observed. Positive interactions were usually attributed to a balanced composition and improved buffer capacity. However, the impact of co-fermentation on microbial communities (H2-producing and H2-consuming bacteria) remains unexplored. This work aimed to deepen the interaction mechanisms observed in co-fermentation targeting microbial communities with an innovative focus on H2-consuming bacteria (homoacetogens). The H2 production of seven mixtures (food waste fractions and rye silage) and individual performances were compared by Biochemical Hydrogen Potential (BHP). Final microbial communities were characterized by sequencing and qPCR. A positive correlation between H2 yield and Soluble and Easily Extractible Sugars (SEES) content was observed for all the substrates (R² = 0.79), confirming this correlation not only for individual substrates but also mixtures. Positive interactions were observed for most of the mixtures, with a H2 yield significantly higher (16–37 %) than expected. The faster H2 production observed in mixtures (2.6 times faster) was correlated to the selection of Clostridiaceae_1 family (final relative abundance of 90–98 %) and decline of homoacetogens. It is therefore essential to further understand the microbial communities’ dynamics in co-fermentation to develop efficient fermentation systems.

Vector dark matter, inflation, and non-minimal couplings with gravity

We propose a cosmological dark matter production mechanism in the form of a longitudinal massive vector boson. We build upon the work [1] including non-minimal couplings of the massive vector with gravity, developing a well motivated set-up from an effective field theory perspective. We carefully track the dynamics of vector field in passing from inflation to radiation dominated universe to show that the late time abundance of longitudinal modes — excited initially by the quantum fluctuations during inflation — can provide the observed dark matter abundance for sufficiently weak non-minimal coupling and wide range of vector masses 5 × 10-7 ≲ m [eV] ≲ 5 × 103. The final abundance of dark matter depends on two parameter, the vector mass and its non-minimal coupling with gravity. We discuss experimental venues to probe this framework, including the production of a stochastic gravitational wave background. The latter is especially interesting, as the same mechanism that generates dark matter can potentially lead to the production of gravitational waves in the LISA frequency band, through the second-order effects of large dark matter iso-curvature perturbations at small scales. We take a first step in this direction, identifying the potential information that gravitational wave experiments can provide on the parameter space of dark matter within this scenario.

Combined effect of light and glyphosate herbicide on growth rate of marine diatom algae.

The effect of glyphosate herbicide at concentrations of 25, 100, 150 and 200 μg.L-1 on growth characteristics of diatoms C. caspia and T. weissflogii under accumulative growth conditions was investigated. Increasing herbicide concentration in the medium resulted in growth suppression of both species and decreased the final abundance of the cultures in the stationary growth phase. The calculated concentrations of herbicide EC10 and EC50 (10 and 90 μg.L-1 for C. caspia and 7 and 25 μg·L-1 for T. weissflogii, respectively) led to a 10 and 50% reduction in the abundance of the studied cultures relative to the control, are ecologically significant and correspond to the values recorded in aquatic areas. The combined effect of light (in the range of 20-250 µE.m-2.s-1) and glyphosate (calculated concentrations of EC10 and EC50) on the growth characteristics of microalgae was evaluated. An increase in algal sensitivity to light was observed with glyphosate exposure. In both species, the increase in the concentration of glyphosate in the medium led to a decrease in the initial angle of slope of the light curve of growth under conditions of light limitation, a reduction in the value of light saturation of growth, narrowing of the boundaries of the light optimum and an increase in the degree of light inhibition. It is shown that the effect of the combined action of light and glyphosate exceeds the sum of the effects of each factor. This fact should be taken into account in ecotoxicological monitoring when assessing the risks of glyphosate ingress into aquatic ecosystems. An increase in glyphosate concentration in water during periods with high values of solar insolation is potentially dangerous due to a decrease in the photosynthetic activity of algae and a reduction in diatom algae abundance.

The evolution and impact of ∼3000 M⊙ stars in the early Universe

We present evolutionary models of massive, accreting population III stars with constant and variable accretion rates until the end of silicon burning, with final masses of ~ 1000–3000 M⊙. In all our models, after the core-hydrogen-burning phase, the star expands towards the red side of the Hertzsprung-Russell diagram is where it spends the rest of its evolution. During core helium burning, the models exhibit an outer convective envelope as well as many large intermediate convective zones. These intermediate zones allow for strong internal mixing to occur which enriches the surface in helium. The effect of increasing metallicity at a constant accretion rate of 10−3 M⊙yr−1 shows an increase in the lifetime, final mass and distribution of helium in the envelope. Our fiducial model with mass of 3000 M⊙ has a final surface helium abundance of 0.74 and 9% of its total mass or 50% of the core mass, has a value of Γ1 < 4/3 at the end of core silicon burning. If the collapse of the core is accompanied by the ejection of the envelope above the carbon-oxygen core, this could have a significant impact on the chemical evolution of the surroundings and subsequent stellar generations. The model has a final log(N/O) ≈ 0.45, above the lower limit in the recently detected high-redshift galaxy GN-z11. We discuss the impact of a single 3000 M⊙ star on chemical, mechanical and radiative feedback, and present directions for future work.

Analysis of the fermentation kinetics and gut microbiota modulatory effect of dried chicory root reveals the impact of the plant-cell matrix rationalizing its conversion in the distal colon.

Aim: The cell matrix of plant foods has received little attention in prebiotic fiber research. We aimed to understand the impact of the plant cell matrix in dried chicory root on its breakdown in the human gut to explain its reported beneficial effects on gut and metabolic health. Methods: We applied in vitro digestion and fermentation models together with an ex vivo gut barrier integrity model. Plant cell matrix intactness in the upper gastrointestinal tract was investigated by scanning electron microscopy. Colonic breakdown of inulin, and chicory root cubes and powder was assessed by gut microbiota analysis using 16S rRNA gene amplicon sequencing and determining the kinetics of changes in pH, gas, and short-chain fatty acid (SCFA) production. Finally, effects on gut barrier integrity were explored by exposing colonic biopsies to fermentation supernatants in an Ussing chamber model. Results: The plant cell matrix of dried chicory root cubes remained intact throughout upper gastrointestinal transit. Dried chicory root fermentation resulted in higher final relative abundances of pectin-degrading Monoglobus and butyrate-producing Roseburia spp. compared to inulin and a seven-fold increase in Bifidobacterium spp. in donors where these species were present. Dried chicory root cubes yielded similar total SCFAs but higher final butyrate levels than chicory root powder or isolated inulin with less gas produced. No uniform but donor-specific effects of fermentation supernatants on the maintenance of gut barrier integrity were detected. Conclusion: The intact plant cell matrix of dried chicory root affected its colonic breakdown kinetics and microbiota, underpinning its beneficial effect in vivo.

Cooperation between autotrophic and heterotrophic denitrifiers under low C/N ratios revealed by individual-based modelling

Denitrifying biofilms, in which autotrophic denitrifiers (AD) and heterotrophic denitrifiers (HD) coexist, play a crucial role in removing nitrate from water or wastewater. However, it is difficult to elucidate the interactions between HD and AD through sequencing-based experimental methods. Here, we developed an individual-based model to describe the interspecies dynamics and priority effects between sulfur-based AD (Thiobacillus denitrificans) and HD (Thauera phenylcarboxya) under different C/N ratios. In test I (coexistence simulation), AD and HD were initially inoculated at a ratio of 1:1. The simulation results showed excellent denitrification performance and a coaggregation pattern of denitrifiers, indicating that cooperation was the predominant interaction at a C/N ratio of 0.25 to 1.5. In test II (invasion simulation), in which only one type of denitrifier was initially inoculated and the other was added at the invasion time, denitrifiers exhibited a stratification pattern in biofilms. When HD invaded AD, the final HD abundance decreased with increasing invasion time, indicating an enhanced priority effect. When AD invaded HD, insufficient organic carbon sources weakened the priority effect by limiting the growth of HD populations. This study reveals the interaction between autotrophic and heterotrophic denitrifiers, providing guidance for optimizing wastewater treatment process.

Mottled ducks, feral mallards, and their hybrids in Florida

AbstractThe nonmigratory and endemic Florida mottled duck (Anas fulvigula fulvigula) is facing conservation threats from the combined effects of urbanization and introgressive hybridization with feral mallards (Anas platyrhynchos) and mallard x mottled duck hybrids. In the past, the status of the Florida mottled duck population was assessed during annual aerial surveys and most brown ducks (mottled ducks, mallards, and hybrids of them) detected during the survey would have been mottled ducks. But the release of domesticated mallards for aesthetic purposes has led to increases in the prevalence of mallards‐hybrids (mallards or mallard x mottled duck hybrids) throughout peninsular Florida, USA, and because it is impossible to differentiate among mottled ducks, female mallards, and hybrids during aerial surveys, helicopter surveys were halted in 2009 until state researchers could conduct a range‐wide study to determine what proportion of brown ducks are mottled ducks versus mallards‐hybrids. We used plumage keys and high‐resolution photography to categorize brown ducks from 557 wetland grid points as either mottled ducks or mallards‐hybrids. Of the 5,179 brown ducks categorized, 40.1% were mottled ducks and 59.9% were mallards‐hybrids. We used logistic regression analysis to model the interactive effect of a site's latitude and level of urbanization (urban gradient value within a 2‐km buffer) to generate a predictive raster surface (1‐km resolution) of the study area with values corresponding to the probability that a brown duck observed within a cell is a pure mottled duck. Predicted values will be used as correction factors when estimating final mottled duck population abundance from brown‐duck survey data. Additionally, the predictive raster surface will be used to identify wetlands where mottled ducks remain predominant so that these sites can be targeted for preservation. Overall, mallards‐hybrids outnumbered mottled ducks throughout most of peninsular Florida, especially in more urbanized regions, and their current prevalence rate presents a serious conservation threat, via hybridization, to extant mottled duck populations.

Resonant pseudo-Dirac dark matter as a sub-GeV thermal target

Dark matter (DM) could be a pseudo-Dirac thermal relic with a small mass splitting that is coupled off diagonally to a kinetically mixed dark photon. This model, particularly in the sub-GeV mass range, is a key benchmark for accelerator searches and direct detection experiments. Typically, the presence of even a tiny fraction of pseudo-Dirac DM in the excited state around the time of recombination would be excluded by DM annihilation bounds from the cosmic microwave background (CMB); thus, viable thermal histories must typically feature an exponential suppression of the excited state. We revisit assumptions about the thermal history in the resonant regime, where the dark photon mass is slightly more than twice the DM mass (to within ∼10%), leading to an s-channel resonance in the annihilation cross section. This resonance substantially reduces the couplings required for achieving the observed relic abundance, implying that in much of the parameter space, the DM kinetically decouples from the Standard Model well before the final DM relic abundance is achieved. We find that the excited state is not thermally depopulated in this regime. In spite of this, we find that the presence of the excited state does violate CMB bounds, even for arbitrarily small mass splittings. The present-day abundance of the excited state opens up the possibility of signatures that are usually not relevant for pseudo-Dirac DM, including indirect detection, direct detection, and self-interacting DM signatures. Published by the American Physical Society 2024

Non-thermal WIMP production from higher order moduli decay

In a non-standard cosmological scenario heavy, long-lived particles, which we call moduli, dominate the energy density prior to Big Bang Nucleosynthesis. Weakly Interacting Massive Particles (WIMPs) may be produced non-thermally from moduli decays. The final relic abundance then depends on additional parameters such as the branching ratio of moduli to WIMPs and the modulus mass. This is of interest for WIMP candidates, such as a bino-like neutralino, where thermal production in standard cosmology leads to an overdensity. Previous works have shown that the correct dark matter (DM) relic density can then still be obtained if the moduli, with mass less than 107 GeV, decay to WIMPs with a branching ratio of less than 10-4. This upper bound could easily be violated once higher order corrections, involving final states with more than two particles, are included. We compute the branching ratios of three- and four-body decays of a modulus into final states involving two DM particles for general couplings. We then apply these expressions to sparticle production within the Minimal Supersymmetric Standard Model (MSSM) with neutralino DM. We find that this upper bound on the branching ratio can be satisfied in simplified models through an appropriate choice of as yet undetermined couplings. However, in the MSSM, it requires sparticle masses to be very close to half the modulus mass, in contrast to the idea of weak-scale supersymmetry.

Photon to axion conversion during Big Bang Nucleosynthesis

We investigate how the resonant conversion at a temperature T̅ = 25–65 keV of a fraction of the CMB photons into an axion-like majoron affects BBN. The scenario, that assumes the presence of a primordial magnetic field and the subsequent decay of the majorons into neutrinos at T ≈ 1 eV, has been proposed to solve the H 0 tension. We find two main effects. First, since we lose photons to majorons at T̅, the baryon to photon ratio is smaller at the beginning of BBN (T > T̅) than during decoupling and structure formation (T ≪ T̅). This relaxes the 2σ mismatch between the observed deuterium abundance and the one predicted by the standard ΛCDM model. Second, since the conversion implies a sudden drop in the temperature of the CMB during the final phase of BBN, it interrupts the synthesis of lithium and beryllium and reduces their final abundance, possibly alleviating the lithium problem.