Search Results (111)

A maximum entropy (ME) methodology was used to infer the Hubble constant from the temperature anisotropies in cosmic microwave background (CMB) measurements, as measured by the Planck satellite. A simple cosmological model provided physical insight and afforded robust statistical sampling of a parameter space. The parameter space included the spectral tilt and amplitude of adiabatic density fluctuations of the early universe and the present-day ratios of dark energy, matter, and baryonic matter density. A statistical temperature was estimated by applying the equipartition theorem, which uniquely specifies a posterior probability distribution. The ME analysis inferred the mean value of the Hubble constant to be about 67 km/sec/Mpc with a conservative standard deviation of approximately 4.4 km/sec/Mpc. Unlike standard Bayesian analyses that incorporate specific noise models, the ME approach treats the model error generically, thereby producing broader, but less assumption-dependent, uncertainty bounds. The inferred ME value lies within 1σ of both early-universe estimates (Planck, Dark Energy Signal Instrument (DESI)) and late-universe measurements (e.g., the Chicago Carnegie Hubble Program (CCHP)) using redshift data collected from the James Webb Space Telescope (JWST). Thus, the ME analysis does not appear to support the existence of the Hubble tension. Full article

The composition and physical state of dark matter remain among the most pressing unresolved questions in modern physics. Addressing these questions is crucial to our understanding of the Universe’s structure. In this work, we explore the hypothesis that massive scalar bosons, such as axions, constitute the majority of dark matter. We focus on two key aspects of axion physics: (i) the role of axion–neutrino coupling in generating neutrino mass and (ii) the thermodynamic properties of axion dark matter. We propose that the interaction between neutrinos and axions in the early Universe, prior to hadronic formation, could provide a mechanism for finite neutrino masses. Furthermore, to account for the observed large-scale distribution of dark matter, we extend the Bose–Einstein condensation framework and derive the critical temperature $T_c$ that defines the onset of the condensate phase. Our calculations suggest that this temperature ranges from a few ${10}^{-3}$ degrees Kelvin to approximately one Kelvin, depending on the axion scale factor $f_a$. These findings support the plausibility of axions as viable dark matter candidates and emphasize the importance of future experimental searches for axion–neutrino interactions. Additional astrophysical and laboratory investigations could further refine axion mass constraints and shed light on the role of axion condensates in the evolution of the early Universe. Full article

Nitrification is the key process linking the oxidized and reduced forms of reactive nitrogen, playing an important role in the nitrogen biogeochemical cycle. Quantifying the nitrification rate and evaluating its environmental regulators in different aquatic environments at both regional and global scales has received increasing attention. However, the spatiotemporal variations in nitrification rates in coastal waters, particularly with different trophic states, remain unclear. By using the ¹⁵N-labeling technique, here, we quantified the nitrification rates under dark and light conditions in the surface waters of Shenzhen Bay and Dapeng Bay, representing eutrophic and oligotrophic environments, respectively. The nitrification rates were 2–3 orders of magnitude higher in Shenzhen Bay (eutrophic) than those in Dapeng Bay (oligotrophic). The concentrations of ammonium and total suspended matter play key roles in regulating the spatiotemporal distribution and difference in nitrification in these two coastal bays. The nitrification rate under the dark condition (0.13–49.37 nmol N L⁻¹ h⁻¹) was greater than that under light incubation (0–10.15 nmol N L⁻¹ h⁻¹), indicating light inhibition of 33–100% in the surface water. Such results imply that daily integrated nitrification based on the rates under dark incubation may have been overestimated. An environment with high turbidity is preferable for nitrification, as it reduces the damage caused by light to ammonia-oxidizing microbes. Collectively, the differences in nitrification rates further result in a distinct composition of dissolved inorganic nitrogen, with Shenzhen Bay dominated by nitrate and Dapeng Bay dominated by ammonium. Our results provide scientific references for the mitigation of nitrogen pollution in different trophic coastal bays. Full article

Thermal relics with masses in the GeV to TeV range remain possible candidates for the Universe’s dark matter (DM). These neutral particles are often assumed to have vanishing electric and magnetic dipole moments so that they do not interact with single real photons, but the anapole moment, a static electromagnetic property whose features are akin to that of a classical toroidal solenoid, can still be non-zero, permitting interactions with single virtual photons. In some models, DM predominantly annihilates into charged standard model particles through a p-wave process mediated by the anapole moment. The anapole moment is also responsible for another interaction of interest. If a DM medium were subjected to an electric current, a DM particle whose anapole moment was aligned with the current would have lower energy than the state with an antialigned anapole moment. Given these interactions, if a collection of initially unpolarized DM particles were subjected to an electric current, then the DM medium would become partially polarized, according to the Boltzmann distribution. In such a polarized medium, DM annihilation into photons, a subdominant s-wave process realizable through higher order interactions, would be somewhat suppressed. If the local electric current existed during a time in which the DM begins to drop out of thermal equilibrium with the rest of the Universe, the suppressed annihilation could lead to a small local excess in the relic DM density relative to a current-free region. This mechanism by which the local DM density can be perturbed is novel. Using effective interactions to model a DM particle’s anapole moment and polarizabilities (responsible for s-wave annihilation into two photons), we compute the changes in the DM density produced by long- and short-lived currents around freeze out. If we employ the most stringent constraints on DM annihilation into two photons, we find that long-lived currents can result in a fractional change in the DM density on the order of ${10}^{-17}$ for DM masses around 100 GeV; for short-lived currents, this fractional change in local DM density is on the order of ${10}^{-23}$ for the same DM mass. Full article

It has long been known that the observed mass surface density of cored dark matter (DM) halos is approximately constant, independently of the galaxy mass (i.e., ${\rho }_c{r}_c\simeq \mathrm{constant}$, with ${\rho }_c$ and $r_c$ being the central volume density and the radius of the core, respectively). Here, we review the evidence supporting this empirical fact as well as its theoretical interpretation. It seems to be an emergent law resulting from the concentration–halo mass relation predicted by the current cosmological model, where the DM is made of collisionless cold DM particles (CDM). We argue that the prediction ${\rho }_c{r}_c\simeq \mathrm{constant}$ is not specific to this particular model of DM but holds for any other DM model (e.g., self-interacting) or process (e.g., stellar or AGN feedback) that redistributes the DM within halos conserving its CDM mass. In addition, the fact that ${\rho }_c{r}_c\simeq \mathrm{constant}$ is shown to allow the estimate of the core DM mass and baryon fraction from stellar photometry alone is particularly useful when the observationally expensive conventional spectroscopic techniques are unfeasible. Full article

It has been recently argued that numerous enigmatic observations remain challenging to explain within the framework of conventional physics. These anomalies include unexpected correlations between temperature variations in the stratosphere, the total electron content of the Earth’s atmosphere, and earthquake activity on one hand and the positions of planets on the other. Decades of collected data provide statistically significant evidence for these observed correlations. These works suggest that these correlations arise from strongly interacting “streaming invisible matter” which gets gravitationally focused by the solar system bodies including the Earth’s inner mass distribution. Here, we propose that some of these, as well as other anomalies, may be explained by rare yet energetic events involving the so-called axion quark nuggets (AQNs) impacting the Earth. In other words, we identify the “streaming invisible matter” conjectured in that works with AQNs, offering a concrete microscopic mechanism to elucidate the observed correlations. It is important to note that the AQN model was originally developed to address the observed similarity between the dark matter and visible matter densities in the Universe, i.e., ${\mathrm{\Omega }}_{\mathrm{DM}}\sim {\mathrm{\Omega }}_{\mathrm{visible}}$, and not to explain the anomalies discussed here. Nonetheless, we support our proposal by demonstrating that the intensity and spectral characteristics of AQN-induced events are consistent with the aforementioned puzzling observations. Full article

The recent astrometric data of hundreds of millions of stars from Gaia DR3 has allowed for a precise determination of the Milky Way rotation curve up to 28 kpc. The data suggest a rapid decline in the density of dark matter beyond 19 kpc. We fit the whole rotation curve with four components (gas, disk, bulge, and halo), and compute the microlensing optical depth to the Large Magellanic Cloud. With this model of the galaxy we reanalyse the microlensing events of the MACHO and EROS-2 Collaborations. Using the published MACHO efficiency function for the duration of their survey, together with the rate of expected events according to the new density profile, we find that the Dark Matter halo could be composed of up to 20% of massive compact halo objects for any mass between $0.001$ to $1M_{\odot }$. For the EROS-2 survey, using a modified efficiency curve for consistency with the MACHO analysis, we also find compatibility with a MACHO halo, but with a tighter constraint around $0.005M_{\odot }$ where the halo fraction cannot be larger than ∼10%. This result assumes that all the lenses have the same mass. If these were distributed in an extended mass function like that of the Thermal History Model, the constraints are weakened, allowing 100% of all DM in the form of Primordial Black Holes. Full article

Based on organic carbon content measurement, kerogen microscopic examination, and the analysis of source rock maturity and major/trace elements, this study restores the sedimentary paleoenvironment of the Ying 4 Member in the southern Shuangcheng area, Songliao Basin, and determines the main controlling factors of the region’s organic matter enrichment. The results indicate that the organic carbon content of the source rock in the study area is 0.51%–8.29%, with a mean value of 2.48%. The average total organic carbon (TOC) value of the source rock reaches 2.35%, and the kerogen type index (KTI) is mainly distributed between 1.6 and 39.5, with an average of 21.5. The organic matter type is II₂. The rock core test shows that the vitrinite reflectance (Ro) is 0.83%–0.97%, with an average of 0.90%, demonstrating that the source rock in the study area has entered the peak hydrocarbon-generation stage. During the deposition of Ying 4 Member, the paleoclimate was warm and humid, and the corresponding sedimentary paleoenvironment was brackish water, having a typical reducing condition with low oxygen content and good primary productivity. In addition, intense volcanic activity have occurred, and the generated volcanic ash and hydrothermal fluids have transported substantial nutrients to the lake basin, promoting the development of algae in the water. The crossplot of the TOC content of dark shale against multiple paleoenvironment indexes shows that the organic matter enrichment in the Ying 4 Member is mainly controlled by paleoproductivity and the paleoclimate, but not associated with redox conditions and paleosalinity. Only warm conditions with high paleoproductivity can lead to organic matter enrichment, and regional volcanic activity plays a significant role in increasing paleoproductivity. Overall, the organic matter enrichment in the study area can be described by the productivity model. Full article

According to some theoretical models, primordial black holes with masses of more than 10⁸ solar masses could be born in the early universe, and their possible observational manifestations have been investigated in a number of works. Dense dark matter and baryon halos could form around such primordial black holes even at the pre-galactic stage (in the cosmological Dark Ages epoch). In this paper, the distribution and physical state of the gas in the halo are calculated, taking into account the radiation transfer from the central accreting primordial black hole. This made it possible to find the ionization radius, outside of which there are regions of neutral hydrogen absorption in the 21 cm line. The detection of annular absorption regions at high redshifts in combination with a central bright source may provide evidence of the existence of supermassive primordial black holes. We also point out the fundamental possibility of observing absorption rings with strong gravitational lensing on galaxy clusters, which weakens the requirements for the angular resolution of radio telescopes. Full article

The Large and Small Magellanic Clouds (LMC and SMC) form the closest interacting galactic system to the Milky Way, therewith providing a laboratory to test cosmological models in the local Universe. We quantify the likelihood for the Magellanic Clouds (MCs) to be observed within the $\mathsf{\Lambda }$CDM model using hydrodynamical simulations of the IllustrisTNG project. The orbits of the MCs are constrained by proper motion measurements taken by the Hubble Space Telescope and Gaia. The MCs have a mutual separation of $d_{\mathrm{MCs}}=24.5\mathrm{kpc}$ and a relative velocity of $v_{\mathrm{MCs}}=90.8\mathrm{km}{\mathrm{s}}^{-1}$, implying a specific phase-space density of $f_{\mathrm{MCs},\mathrm{obs}}\equiv {(d_{\mathrm{MCs}}·v_{\mathrm{MCs}})}^{-3}=9.10\times {10}^{-11}{\mathrm{km}}^{-3}{\mathrm{s}}^3{\mathrm{kpc}}^{-3}$. We select analogues to the MCs based on their stellar masses and distances in MW-like halos. None of the selected LMC analogues have a higher total mass and lower Galactocentric distance than the LMC, resulting in >3.75$\sigma$ tension. We also find that the $f_{\mathrm{MCs}}$ distribution in the highest resolution TNG50 simulation is in $3.95\sigma$ tension with observations. Thus, a hierarchical clustering of two massive satellites like the MCs in a narrow phase-space volume is unlikely in $\mathsf{\Lambda }$CDM, presumably because of short merger timescales due to dynamical friction between the overlapping dark matter halos. We show that group infall led by an LMC analogue cannot populate the Galactic disc of satellites (DoS), implying that the DoS and the MCs formed in physically unrelated ways in $\mathsf{\Lambda }$CDM. Since the ${20}^{\circ }$ alignment of the LMC and DoS orbital poles has a likelihood of $P=0.030$ ($2.17\sigma$), adding this ${\chi }^2$ to that of $f_{\mathrm{MCs}}$ gives a combined likelihood of $P=3.90\times {10}^{-5}$ ($4.11\sigma$). Full article

The vertical distribution patterns of daily primary production and dark carbon fixation were investigated at three stations in the East/Japan Sea (hereafter East Sea), a semi-enclosed marginal sea in the northwest Pacific Ocean. Our results displayed consistent vertical patterns of daily primary production at two of the stations, while the third station exhibited a markedly different distribution pattern, highlighting localized variations in production dynamics. In contrast, dark carbon fixations displaying varying vertical patterns among the stations are not specific enough to have much meaning. Water column-integral values showed differences in the contribution of dark carbon fixation to total primary production, ranging from 4.5% to 27.1%. These variations may reflect environmental parameters such as nutrient concentrations. However, our study is limited by the lack of direct data on the microbial community structure and chemoautotrophic activities, which are crucial for a more comprehensive understanding of these patterns. Understanding the environmental drivers of dark carbon fixation is crucial for elucidating carbon cycling dynamics in the East Sea. Notably, dark carbon fixation could contribute up to one-third of primary production in the region as an additional source of newly produced organic matter, highlighting the need for further investigation into this previously overlooked process. Full article

The spin-torsion theory is a gauge theory approach to gravity that expands upon Einstein’s general relativity (GR) by incorporating the spin of microparticles. In this study, we further develop the spin-torsion theory to examine spherically symmetric and static gravitational systems that involve free-falling macroscopic particles. We posit that the quantum spin of macroscopic matter becomes noteworthy at cosmic scales. We further assume that the Dirac spinor and Dirac equation adequately capture all essential physical characteristics of the particles and their associated processes. A crucial aspect of our approach involves substituting the constant mass in the Dirac equation with a scale function, allowing us to establish a connection between quantum effects and the scale of gravitational systems. This mechanism ensures that the quantum effect of macroscopic matter is scale-dependent and diminishes locally, a phenomenon not observed in microparticles. For any given matter density distribution, our theory predicts an additional quantum term, the quantum potential energy (QPE), within the mass expression. The QPE induces time dilation and distance contraction, and thus mimics a gravitational well. When applied to cosmology, our theory yields a static cosmological model. The QPE serves as a counterpart to the cosmological constant introduced by Einstein to balance gravity in his static cosmological model. The QPE also offers a plausible explanation for the origin of Hubble redshift (traditionally attributed to the universe’s expansion). The predicted luminosity distance–redshift relation aligns remarkably well with SNe Ia data from the cosmological sample of SNe Ia. In the context of galaxies, the QPE functions as the equivalent of dark matter. The predicted circular velocities align well with rotation curve data from the SPARC (Spitzer Photometry and Accurate Rotation Curves database) sample. Importantly, our conclusions in this paper are reached through a conventional approach, with the sole assumption of the quantum effects of macroscopic matter at large scales, without the need for additional modifications or assumptions. Full article

The axion anti-quark nugget (A$\overline{\mathrm{Q}}$N) model was developed to explain in a natural way the asymmetry between matter and antimatter in Universe. In this hypothesis, a similitude between the dark and the visible components exists. The lack of observability of any type of dark matter up to now, in particular A$\overline{\mathrm{Q}}$Ns, requires finding new ways of detecting these particles, if they exist. In spite of strong interaction with visible matter, for such objects a very small ratio of cross section to mass is expected and thus huge detector systems are necessary. This paper presents a new idea for the direct detection of the A$\overline{\mathrm{Q}}$Ns using minerals as natural rock deposits acting as paleo-detectors, where the latent signals of luminescence produced by interactions of A$\overline{\mathrm{Q}}$Ns are registered and can be identified as an increased and symmetrical deposited dose. The estimates were made for minerals widely distributed on Earth, for which the thermoluminescence (TL) signal is intense and if the thermal conditions are constant and with low temperatures, the lifetime of the latent signals is kept for geological time scales. Full article

Agriculture in Central Asia and in the Fergana Valley in general strongly depends on irrigation and drainage of agricultural lands. The Fergana Valley includes about 45% of the irrigated area in the Syr Darya River basin. Active use of irrigation in agriculture can lead to changes in the soil’s natural composition, as well as pollution and changes in the soil’s physical and chemical properties. Soil degradation in the process of irrigation can lead to a decrease in crop yields and, as a consequence, to a decrease in food security in the region. In this study, a comparative analysis of three main types of Calcisols (Dark, Light, and Typical) before (uncultivated soil) and after agricultural use (surface-irrigated agricultural soil) was carried out. Irrigation leads to increment of SOC stocks in Typical (from 113.8 to 126.3 t/ha) and Light (from 62.8 to 100.1 t/ha) Calcisols and to decreasing of SOC stocks in Dark Calcisols (from 160.1 to 175.3 t/ha). In general, the content of biophilic elements (SOC and TN) is lower in irrigated soils, and their distribution in the soil profile is close to the functional relationship (r² 0.98 to 0.99). In uncultivated Calcisols, the profile distribution of SOC and TN is more heterogeneous (r² 0.67 to 0.97). Changes in the humification processes of soil organic matter are also identified; in soils after irrigation the carbon ratio of humic/fulvic acids (CHA/CFA) is lower (<1) compared to their uncultivated counterparts (~1). The alteration of the soil water regime also resulted in transformation of the individual compositions of amino acids. All studied types of Calcisols are characterized by changes in particle-size distribution of soils especially in the number of the silt fraction (0.01–0.05 mm) and the difference between uncultivated and irrigated soils, 10–20%, which is associated with the processes of colmatage by accumulation of a fine fraction and replacement of sub-fractions in the fraction of sand. The highest concentrations of nutrients are characteristic of the upper soil horizons (P up to 231, K up to 2350 mg/kg), which indicate their pedogenic and agrogenic origins rather than inheritance from the parent material. Soil P and K availability is rather high, with non-labile forms prevailing, although of near reserve. The surface irrigation results in apparent accumulation of water-soluble Mg²⁺ (1.6–2.1 meq/100 g) and K⁺ (0.6–0.9 meq/100 g), but the cation of Ca²⁺ predominates in the base cations’ composition, which is the most favorable in terms of soil agrogenic property formation. Data obtained will be useful for development of strategies for effective land use in arid, subtropical, overpopulated regions of Central Asia that have deficient water sources and intensive soil degradation. Full article

We present an analysis of the ellipticities of galaxy groups, derived from the spatial distribution of member galaxies, revealing a notable incongruity between the observed local galaxy groups and their counterparts in the Lambda cold dark matter cosmology. Specifically, our investigation reveals a substantial disparity in the ellipticities of observed groups with masses ${10}^{13.0}<M_{\mathrm{h}}<{10}^{14.5}{\mathrm{M}}_{\odot }{h}^{-1}$ exhibiting significantly higher ellipticities (at a confidence level of approximately $4\sigma$) compared to their simulated counterparts. Notably, the consistent use of the same group finder for identifying galaxy groups in both observational and simulated datasets underscores the robustness of this result. This observation may imply a potential incongruence between the inferred age of the Universe from observations and the predictions of the model, which aligns with the younger Universe hypothesis suggested by the elevated fraction of observed satellite pairs with correlated line-of-sight relative velocities compared to simulations. Our findings significantly strengthen the plausibility of a younger age for our Universe. Full article