Extra Matter Research Articles

Generalising axion-like particle as the curvaton: sourcing primordial density perturbation and non-Gaussianities

We investigate the non-perturbatively generated axion-like particle (ALP) potential, involving fermions in the dark sector that couple to the ALP, in an early universe cosmological inflationary stage with the ALP being a spectator field. The potential here deviates from the standard cosine nature due to the presence of the two dark sector fermion masses mu\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u$$\\end{document} and md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_d$$\\end{document} which couple to the ALP. The ALP is a spectator field during inflation but it starts to oscillate and dominates the energy density of the universe after inflation ends, thereby sourcing isocurvature perturbations, while standard curvature fluctuations from the inflaton are assumed to be sub-dominant. Subsequently the ALP decays converting the isocurvature perturbations to adiabatic perturbations thereby acting as the origin of the primordial density perturbations. We identify the parameter space involving the axion decay constant fϕ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{\\phi }$$\\end{document}, scale of confinement Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}, ALP mass m and the masses of the fermions, mu\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u$$\\end{document} and md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_d$$\\end{document} where it can satisfactorily behave as the curvaton and source the observed primordial density perturbation. We also predict local non-Gaussianity signals for bi-spectrum and tri-spectrum fNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{NL}$$\\end{document} and gNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{NL}$$\\end{document}, as a function of the ratio mu/md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u/m_d$$\\end{document}, which are within the allowed range in the latest Planck observations and are detectable with future observations. Particularly we find that the value of fNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{NL}$$\\end{document} and gNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{NL}$$\\end{document} are dependent on the ratio of mu\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u$$\\end{document} and md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_d$$\\end{document}: fNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{NL}$$\\end{document} is more or less positive for all scenarios except mu=md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u = m_d$$\\end{document} and gNL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g_{NL}$$\\end{document} is always positive irrespective of the ratio between mu\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u$$\\end{document} and md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_d$$\\end{document}. The results of our analysis in the limit mu=md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u = m_d$$\\end{document} resembles vanilla curvaton scenario while in the limit mu≫md\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_u \\gg m_d$$\\end{document} resembles pure axion cosine potential. This is because the model has the unique feature where the extra matter in the dark sector determines the nature and shape of the potential.

Accelerated manganese(II) removal by in situ mine drainage treatment system without organic substrate amendment: Metagenomic insights into chemolithoautotrophic manganese oxidation via extracellular electron transfer

Mine drainage waters often contain elevated concentrations of toxic metals and can be a source of environmental pollution. Manganese (Mn)-oxidizing bacteria (MnOB), which can oxidize soluble Mn(II) to insoluble Mn(III, IV) under neutral pH conditions, are expected to be a promising biological agent in passive mine drainage remediation. However, the diversity, functionality and applicability of MnOB for mine drainage treatment remain mostly unknown. Given that many mine environments are poor in organic substances, it is necessary to elucidate the functions of MnOB communities that contribute to metal removal without supplementation with extra organic matter. Here, we constructed in situ continuous-flow bioreactors for treating mine drainage containing approximately 20 mg L−1 Mn(II) and 6 mg L−1 zinc (Zn) (II) and operated these bioreactors without amended organic matter. The removal of Mn(II) and Zn(II) ions reached more than 98 % at a hydraulic retention time of 0.5 days. The X-ray diffraction pattern of Mn oxides deposited on the surface of limestone carriers indicated woodruffite-like mineral accumulation in the reactors. Several heterotrophic MnOB were isolated from the bioreactor, and metagenomic analysis revealed a predominance of diverse lineages of heterotrophs, including Elusimicrobiota, which harbored MoxA-like multicopper oxidase genes. Furthermore, the metagenomic analysis also suggested the involvement of gammaproteobacterial species that possessed putative genes for extracellular electron uptake and CO2 fixation. Our findings offer the first insights into the potential for chemolithoautotrophic Mn(II) oxidation processes via electron transfer from Mn(II/III) and application of chemolithoautotrophic and heterotrophic MnOB in mine drainage remediation without supplying organic materials.

Cosmology on a gravitational wave background

ABSTRACT It is a fact that the universe lives on a gravitational wave background (GWB), which is extra space–time energy that is not contained in Einstein’s field equations. In a previous work, this energy is treated as a property of space–time and not as a source. With this in mind, a new model was developed that incorporates this energy to explain the current accelerated expansion of the universe where the GWB was incorporated by extending Einstein’s equations to $R_{\mu \nu }-\frac{1}{2}Rg_{\mu \nu }+\frac{2\pi ^2}{{\lambda }^2}g_{\mu \nu }= \kappa ^2 T_{\mu \nu }$, where λ is the Compton wavelength of the cosmological scale graviton. In the present work, we show that this extended form agrees very well with the observations of cosmic chronometers, baryon acoustic oscillations, and Pantheon SN Type Ia, reproducing the observational data with a Δχ2 = 3.26 in favour of the current model compared to the ΛCDM. The favoured values by these observations are Ω0m = 0.311 ± 0.065, H0 = 68.3 ± 1.4 km s−1 Mpc−1, and Ω0k = 0.001 ± 0.011. We also find excellent agreement of this model with the cosmic microwave background and the mass power spectrum. We conclude that this model is an excellent alternative to explain the accelerated expansion of the universe without incorporating the cosmological constant or any type of extra matter.

Ultra-stretchable and conductive polyacrylamide/carboxymethyl chitosan composite hydrogels with low modulus and fast self-recoverability as flexible strain sensors

There is a great demand for the fabrication of soft electronics using hydrogels due to their biomimetic structures and good flexibility. However, conventional hydrogels have poor mechanical properties, which restricts their applications as stretchable sensors. Herein, a facile one-step strategy is proposed to fabricate tough and conductive hydrogels by making use of the graftability of carboxymethyl chitosan without extra conductive matter and crosslinking agent. The obtained polyacrylamide/carboxymethyl chitosan composite hydrogels possess outstanding transmittance and excellent mechanical performances, with tensile breaking stress of 630 kPa, breaking strain of 4560 %, toughness of 8490 kJ/m3. These hydrogels have low modulus of 5–20 kPa, fast recoverability after unloading, high conductivity of ∼0.85 S/m without the addition of other conductive substances and good biocompatibility. The ionic conductivity of the gels originates from the counterions of carboxymethyl chitosan, affording the hydrogels as resistive-type sensors. The resultant hydrogel sensors demonstrate a broad strain window (0.12–1500 %), excellent linear response, high sensitivity with the gauge factor reaching 11.72, and great durability, capable of monitoring diverse human motions. This work provides a new strategy to develop stretchable conductive hydrogels with promising applications in the fields of artificial intelligence and flexible electronics.

Soil disturbance, amelioration and rehabilitation affect forest growth, health, soil carbon and chemistry on five long-term soil productivity (LTSP) sites in southeastern British Columbia

Soil disturbance amelioration affected tree survival, growth, health, mineral soil chemistry, and their covariation on five Long-Term Soil Productivity (LTSP) sites in southeastern British Columbia. The two most different LTSP treatments (baseline disturbance of no compaction / all organic matter left, versus most severe of heavy compaction / forest floor removed) were compared to five amelioration treatments: rehabilitation of most severe LTSP treatment (soil tillage with or without incorporation of removed forest floor [Rehab + FF]), root disease (Armillaria ostoyae (Romagn.) Herink) amelioration treatments (stump removal or biological with Hypholoma fasiculare), and enhancement of soil organic matter (tilling extra forest floor into mineral soil). Treatment significantly (p < 0.05) affected 10-year mineral soil carbon, nitrogen, sulfur, mineralizable nitrogen, and potassium, which were lower on forest floor removal treatments and higher on forest floor addition treatments (27 to 97% of baseline versus 78 to 183% of baseline, respectively). Western white pine (Pinus monticola Dougl. ex D.Don) 15-year productivity (m3/ha) was significantly affected by treatment (Rehab + FF yielding a 10 fold increase in productivity versus the poorly growing baseline treatment), with treatment also significant when total disease was a covariate and for average and total volume when mineral soil Ca:Al ratio was a marginally significant (p < 0.1) covariate, and for survival when the incidence of total disease or white pine blister rust (Cronartium ribicola) were significant covariates; or with mineral soil C:N ratio as a significant covariate. The incidence of blister rust and total disease were significantly influenced by treatment when C:N was a significant covariate. For 20-year lodgepole pine (Pinus contorta Dougl. Ex Loud) there were no direct relationships apparent, but western gall rust (Endocronartium harknessii) had treatment significant when total sulfur was a significant covariate. Fifteen- and twenty-year Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) had no significant relationships. Results demonstrate that restoring or adding extra organic matter (forest floor) into mineral soil increased soil carbon and related nutrients and can increase above ground carbon (forest productivity). Conversely, removing forest floor lowered mineral soil carbon and generally lowered tree volume. Varied effects due to growth limiting factors like frost and competing vegetation affected results on a few plots. Recommendations include leaving or enhancing organic matter onsite for soil carbon, nutrients, forest health and site productivity. Further analysis with the larger LTSP dataset and ongoing monitoring is encouraged to determine if the results persist in the long-term and to better understand the significant covariate relationships.

Moduli trapping mechanism in modular flavor symmetric models

We discuss how the moduli in modular flavor symmetric models dynamically select enhanced symmetry points at which the residual modular symmetry renders extra matter fields massless. The moduli dynamics non-perturbatively produces the extra matter particles, which gives (time-dependent) effective potential that traps the moduli to enhanced symmetry points. We show analytic estimates of particle production rate consistent with numerical results, and the dynamics of moduli based on the analytic estimates.

Bubbleless Air Shapes Biofilms and Facilitates Natural Organic Matter Transformation in Biological Activated Carbon.

The biodegradation in the middle and downstream of slow-rate biological activated carbon (BAC) is limited by insufficient dissolved oxygen (DO) concentrations. In this study, a bubbleless aerated BAC (termed ABAC) process was developed by installing a hollow fiber membrane (HFM) module within a BAC filter to continuously provide aeration throughout the BAC system. The BAC filter without an HFM was termed NBAC. The laboratory-scale ABAC and NBAC systems operated continuously for 426 days using secondary sewage effluent as an influent. The DO concentrations for NBAC and ABAC were 0.78 ± 0.27 and 4.31 ± 0.44 mg/L, respectively, with the latter providing the ABAC with greater electron acceptors for biodegradation and a microbial community with better biodegradation and metabolism capacity. The biofilms in ABAC secreted 47.3% less EPS and exhibited greater electron transfer capacity than those in NBAC, resulting in enhanced contaminant degradation efficiency and long-term stability. The extra organic matter removed by ABAC included refractory substances with a low elemental ratio of oxygen to carbon (O/C) and a high elemental ratio of hydrogen to carbon (H/C). The proposed ABAC filter provides a valuable, practical example of how to modify the BAC technology to shape the microbial community, and its activity, by optimizing the ambient atmosphere.

Leptonic cascade decays of a heavy Higgs boson through vectorlike leptons at the LHC

We demonstrate the potential of fully leptonic cascade decays of a heavy neutral Higgs boson through vectorlike leptons as a simultaneous probe for extended Higgs sectors and extra matter particles at the LHC. The processes we explore are unique in that their event topologies lead to di-boson-like leptonic final states with a lepton pair which does not reconstruct the mass of a gauge boson. By recasting existing 2ell +{E}_R^{textrm{miss}} and 3/4ℓ searches channels using run2 data from the LHC we obtain model independent bounds on the masses of heavy scalars and vectorlike leptons and use these results to explore future prospects at the HL-LHC. Our results can be directly applied to any kind of new physics scenarios sharing the final states and the event topology. For concreteness, we apply our results to a benchmark scenario: a two Higgs doublet model type-II augmented with vectorlike leptons. Remarkably, even with current data the sensitivity of our analysis shows a reach for masses of a heavy neutral Higgs and vectorlike leptons up to 2 TeV and 1.5 TeV, respectively. Even for low tan β ≳ 1, the analysis retains sensitivity to heavy Higgs masses slightly above 1 TeV. The future sensitivities at the HL-LHC extend the reach for heavy Higgses and new leptons to 2.7 TeV and 2 TeV, respectively.

The dark (BPS) side of thermodynamics in Minkowski4

We explore the BPS limit of asymptotically flat black hole thermodynamics, drawing analogies with recent studies of black holes in anti-de Sitter space. Although ultimately motivated by supersymmetry and quantum gravity, the BPS limit is classically well-defined for the dyonic Kerr-Newman black holes in pure Einstein-Maxwell theory and various generalizations with additional scalars and gauge fields that admit embedding in mathcal{N} = 2 supergravity (for concreteness we consider the STU model). This limit is manifestly different from extremality as it includes a family of rotating Euclidean saddles that represent a (fictitious) thermal branch, smoothly connected with the extremal static Reissner-Nordström black hole and its generalizations with extra matter. We are able to evaluate unambiguously all BPS chemical potentials, finding constant imaginary angular velocity as a consequence of Wick rotation. In the mixed ensemble of fixed magnetic and varying electric charges, we derive the OSV formula that is crucial for the microscopic understanding of the system, and provide evidence that it should be interpreted as a fixed-point formula.

The role of nitrogen fixation and crop N dynamics on performance and legacy effects of maize-grain legumes intercrops on smallholder farms in Tanzania

Maize-grain legume intercrops form an important component of the cropping systems of smallholder farmers in many parts of sub-Saharan Africa. However, the effects of cropping system and fertilizer use on nitrogen fixation and nitrogen uptake of component crops in maize-legume intercrops are not well understood. Our study addressed the questions: (i) What is the capacity of pigeonpea and lablab to fix atmospheric nitrogen (N2) in sole crop and when intercropped with maize on smallholder farms across different agro-ecological conditions?; (ii) How does productivity and N-uptake by sole and intercropped maize and legumes respond to N and P fertilizer?; and (iii) What are the residual effects of the sole crops, intercrops and fertilizer treatments on the productivity of a succeeding maize crop? We studied additive intercropping systems on eight farms in Babati, Tanzania: maize-long duration pigeonpea, maize-medium duration pigeonpea and maize-lablab, with separate sole crops, at three fertilizer rates: no fertilizer; 40 kg P ha−1; and 90 kg N ha−1 + 40 kg P ha−1. Whereas P fertilizer was applied on maize and the legumes, the N fertilizer was only applied on maize. Maize and pigeonpea were sown simultaneously, while lablab was relay-planted one month later. N2-fixation was quantified using the 15N natural abundance method. N2-fixation differed among the legume species. Sole long-duration pigeonpea fixed significantly more N2 (20–63 kg ha−1 more) than all other cropping systems, corresponding to the greater shoot dry matter and N yield of this system. The combined N uptake of maize and legume in intercrops was consistently larger than that of sole maize or the legume. Application of fertilizer resulted in enhanced N uptake both in the current season (up to 40 kg N ha−1 more) and in a succeeding maize crop (up to 71 kg N ha−1 more). We observed positive associations between grain yield, dry matter production and total N uptake of a succeeding maize crop, and the N-fixed by legume species in the preceding season. Each kg of legume shoot N yield was associated with up to 14 kg ha−1 extra grain yield, 29 kg ha−1 extra dry matter and 0.5 kg ha−1 extra total N uptake of the succeeding maize crop. Our results show that maize-legume intercrops enhance N-uptake. Furthermore, N2-fixation by sole or intercropped legumes confers strong residual benefits on productivity of a succeeding maize crop.

Charged anisotropic decoupled compact objects in f(R) gravity

In this paper, we aim to formulate anisotropic solutions that represent charged self-gravitating static spheres in [Formula: see text] gravity. We introduce the effects of anisotropy in the domain of an isotropic solution by including an extra matter source. The spherical configuration is deformed by transforming radial as well as temporal metric functions. As a result of these transformations, the isotropic and anisotropic matter sources can be decoupled from each other. The system of field equations is disintegrated into two arrays such that the first set corresponds to the isotropic source while the second comprises the new gravitational source. The charged Krori–Barua spacetime is employed to specify the first set in the background of [Formula: see text] Starobinsky model. Two solutions of the other system are determined by incorporating a barotropic equation of state along with additional constraints on the anisotropic source. The matching conditions are imposed at the hypersurface to determine the values of unknown constants. Different features of the constructed models are inspected by using the mass and radius of Her X-I. One of the constructed solutions agrees with the viability and stability conditions for specific values of charge and the decoupling parameter.

Ice-templated additive-free porous starches with tuned morphology and properties

Biodegradable anisotropic neat porous starch materials without any additional cross-linking, plasticizer or any extra matter have been fabricated via facile ice-templating method. Waxy maize was dissolved in water followed by unidirectional freezing and ice sublimation. The influence of process parameters (starch concentration and retrogradation time) on the morphology, density, mechanical properties under the uniaxial compression and thermal conductivity were investigated. The internal morphology and the shape of the pores, from lamellar to sponge-like, was shown to be governed by starch concentration. All porous starches have very low density (0.07–0.15 g/cm3), anisotropic mechanical properties and low thermal conductivity, in particular in transverse direction (0.037–0.048 W/(m·K)). Interestingly, when compressing the ice-templated starches in the transverse direction, the thermal conductivity was further decreased reaching the values of 0.033 W/(m·K). This work provides the guidelines for making fully biobased porous starch materials with controlled morphology and properties.

The response of the natural and sewage-impacted intertidal mussel community of the SW Atlantic to pulse (before / after summer) and chronic sewage discharges in the 1997 - 2014 period

Until 2014 Mar del Plata city discharged its untreated sewage effluents to the intertidal sector. This city has a marked seasonality in the urban discharge, varying between 2.8 and 3.5 m3.sec.-1 of effluents before/after summer. The effect on the intertidal benthic community was evaluated in both spatially, in sewage-impacted and reference sites, and temporarily in both the short term, before/after summer, and in long term along nine periods between 1997 - 2014. The bivalve Brachidontes rodriguezii, the ecosystem engineer, reach the maximum dominance and frequency in reference areas. Spatially the presence of opportunistic and tolerant species characterized the impacted areas, while in reference sites sensitive species were prevalent. The opportunistic polychaete species Capitella "capitata" sp. and Alitta succinea were dominant near the sewage discharge in firsts periods. In other periods the indicator species were Rhynchospio glutaea or Boccardia spp. From 2008 the invader Boccardia proboscidea characterized the sewage-impacted sites building massive reefs. The crustaceans Jassa falcata and Caprella sp. were very abundant at intermediate distances from the sewage discharge, while Monocorophium insidiosum was very abundant in sewage-impacted areas. The tolerant and opportunistic species are favored after the summer due to the extra organic matter input. All community parameters showed lower values after the summer, and also a trend to diminish along the studied period.

The response of the natural and sewage-impacted intertidal mussel community of the SW Atlantic to pulse (before / after summer) and chronic sewage discharges in the 1997 - 2014 period

Until 2014 Mar del Plata city discharged its untreated sewage effluents to the intertidal sector. This city has a marked seasonality in the urban discharge, varying between 2.8 and 3.5 m3.sec.-1 of effluents before/after summer. The effect on the intertidal benthic community was evaluated in both spatially, in sewage-impacted and reference sites, and temporarily in both the short term, before/after summer, and in long term along nine periods between 1997 - 2014. The bivalve Brachidontes rodriguezii, the ecosystem engineer, reach the maximum dominance and frequency in reference areas. Spatially the presence of opportunistic and tolerant species characterized the impacted areas, while in reference sites sensitive species were prevalent. The opportunistic polychaete species Capitella "capitata" sp. and Alitta succinea were dominant near the sewage discharge in firsts periods. In other periods the indicator species were Rhynchospio glutaea or Boccardia spp. From 2008 the invader Boccardia proboscidea characterized the sewage-impacted sites building massive reefs. The crustaceans Jassa falcata and Caprella sp. were very abundant at intermediate distances from the sewage discharge, while Monocorophium insidiosum was very abundant in sewage-impacted areas. The tolerant and opportunistic species are favored after the summer due to the extra organic matter input. All community parameters showed lower values after the summer, and also a trend to diminish along the studied period.

Can quantum mechanics breed negative masses?

The Casimir effect realizes the existence of static negative energy densities in quantum field theory. We establish physically reasonable conditions for the non-negativity of the total mass of a Casimir apparatus held in equilibrium in the Minkowski background, irrespective of any condensed matter consideration. Specifically, the dynamical equilibrium requires the presence of additional matter to hold the system apart. As long as this extra matter satisfies the dominant energy condition, the mass of the combined system is positive. Thus, the very same reason why energy cannot travel backward in time could be the underlying mechanism behind the positivity of the mass. We discuss the takeaways from the Casimir setting to more general circumstances.

Geochemical Study of the Iron Age Settlement Occupational Layer and the Early Roman Time Agricultural Layer at Voorthuizen, The Netherlands

The application of geochemical analysis in archaeology provides a better understanding of ancient human activities. This paper presents the results of geochemical multi-element, LOI, MS, and geochronological analyses of a cultural layer at the Voorthuizen (The Netherlands) archaeological site. The study has revealed a difference in the geochemical composition of an occupational surface in the Iron Age settlement and an early Roman Time agricultural horizon. The former is enriched in Ba, Sr, Rb, Th, Cl, and Mg, while the latter displays elevated P, Pb, Ni, Mn, and V values. The study has provided a deeper insight into the agricultural techniques applied at the Voorthuizen site and on the so-called Celtic Fields, known as ancient field systems dating from the same period and widespread throughout north-west Europe. It seems that household waste was not used as a fertilizer at Voorthuizen, while the application of manure is characteristic of Celtic Fields. However, phosphorous values in the Voorthuizen agricultural horizon are comparable to those in the Celtic Fields, suggesting similar sources of P in both cases. Elevated Si and “mobile” Fe, Mn, V, Pb, As, and Sn, along with higher MS measurements, are indicative of the use of extra mineral matter for the fertilization of the Voorthuizen ancient arable field.

E6 GUT and Baryon Asymmetry Generation in the E6CHM

Grand unified theories (GUTs) may result in the E6-inspired composite Higgs model (E6CHM) at low energies, almost stabilizing the electroweak scale. We consider an orbifold GUT in 6 dimensions in which the E6-gauge group is broken to the gauge symmetry of the standard model (SM) while different multiplets of the SM fermions come from different 27-plets. The strongly coupled sector of the E6CHM is confined on the brane where E6 is broken down to its SU(6) subgroup. Near the scale of f≳5TeV, this approximate SU(6) symmetry is expected to be further broken down to its SU(5) subgroup, which contains the SM-gauge group. Such a breakdown leads to a set of pseudo-Nambu–Goldstone bosons (pNGBs) that includes an SM-like Higgs doublet. The approximate gauge coupling unification in the E6CHM takes place at high energies when the right-handed top quark is a composite fermion. To ensure anomaly cancellation, the weakly coupled sector of this model contains extra exotic matter beyond the SM. We discuss the mechanism of the generation of matter–antimatter asymmetry within the variant of the E6CHM in which the baryon number and CP invariance are violated.

Nonperturbative effects in the Standard Model with gauged 1-form symmetry

We study the Standard Model with gauged {mathrm{mathbb{Z}}}_{N=2,3,6}^{(1)} subgroups of its {mathrm{mathbb{Z}}}_6^{(1)} 1-form global symmetry, making the gauge group frac{mathrm{SU}(3)times mathrm{SU}(2)times mathrm{U}(1)}{{mathrm{mathbb{Z}}}_N} . We show that, on a finite {mathbbm{T}}^3 , there are self-dual instantons of fractional topological charge. They mediate baryon- and lepton-number violating processes. We compare their amplitudes to the ones due to the usual BPST-instantons. We find that the small hypercharge coupling suppresses the fractional-instanton contribution, unless the torus size is taken sub-Planckian, or extra matter is added above the weak scale. We also discuss these results in light of the cosmological bounds on the torus size.

Anomaly-free Abelian gauge symmetries with Dirac seesaws

We perform a systematic analysis of Standard Model extensions with an additional anomaly-free gauge U(1) symmetry, to generate tree-level Dirac neutrino masses. An anomaly-free symmetry demands nontrivial conditions on the charges of the unavoidable new states. An intensive scan was performed, looking for solutions generating neutrino masses by the type-I and type-II tree-level Dirac seesaw mechanism, via operators with dimension 5 and 6, that correspond to active or dark symmetries. Special attention was paid to the cases featuring no extra massless chiral fermions or multicomponent dark matter with unconditional stability.

Thick branes in the scalar\u2013tensor representation of f(R,\xa0T) gravity

Braneworld scenarios consider our observable universe as a brane embedded in a five-dimensional bulk. In this work, we consider thick braneworld systems in the recently proposed dynamically equivalent scalar–tensor representation of f(R, T) gravity, where R is the Ricci scalar and T the trace of the stress–energy tensor. In the general fleft( R,Tright) case we consider two different models: a brane model without matter fields where the geometry is supported solely by the gravitational fields, and a second model where matter is described by a scalar field with a potential. The particular cases for which the function fleft( R,Tright) is separable in the forms Fleft( Rright) +T and R+Gleft( Tright) , which give rise to scalar–tensor representations with a single auxiliary scalar field, are studied separately. The stability of the gravitational sector is investigated and the models are shown to be stable against small perturbations of the metric. Furthermore, we show that in the fleft( R,Tright) model in the presence of an extra matter field, the shape of the graviton zero-mode develops internal structure under appropriate choices of the parameters of the model.