Search Results (92)

The entire classical cosmological history between two extreme de Sitter vacuum solutions is discussed based on Einstein’s equations and non-equilibrium thermodynamics. The initial non-singular de Sitter state is characterised by a very high energy scale, which is equal or smaller than the reduced Planck mass. It is structurally unstable, and all of the continuous created matter, energy, and entropy of the material component comes from the irreversible flow powered by the primeval vacuum energy density. The analytical expression describing the running vacuum is obtained from the thermal approach. It opens a new perspective to solve the old puzzles and current observational challenges plaguing the cosmic concordance model driven by a rigid vacuum. Such a scenario is also modelled through a non-canonical scalar field. It is demonstrated that the resulting scalar field model is shown to be a step-by-step a faithful analytical representation of the thermal running vacuum cosmology. Full article

Côte d’Ivoire has substantially neglected crop residues from farms in rural areas, so this study aimed to provide strategies for the sustainable conversion of these products to hydrogen. The use of existing data showed that, in the Côte d’Ivoire, there were up to 16,801,306 tons of crop residues from 11 crop types in 2019, from which 1,296,424.84 tons of hydrogen could potentially be derived via theoretical gasification and dark fermentation approaches. As 907,497.39 tons of hydrogen is expected annually, the following estimations were derived. The three hydrogen-project implementation scenarios developed indicate that Ivorian industries could be supplied with 9,026,635 gigajoules of heat, alongside 17,910 cars and 4732 buses in the transport sector. It was estimated that 817,293.95 tons of green ammonia could be supplied to farmers. According to the study, 5,727,992 households could be expected to have access to 1718.40 gigawatts of electricity. Due to these changes in the transport, energy, industry, and agricultural sectors, a reduction of 1,644,722.08 tons of carbon dioxide per year could theoretically be achieved. With these scenarios, around 263,276.87 tons of hydrogen could be exported to other countries. The conversion of crop residues to hydrogen is a promising opportunity with environmental and socio-economic impacts. Therefore, this study requires further extensive research. Full article

There is a demand from the scientific, beekeeping and consumer sectors to characterize honey based on its botanical origin, as it provides unique and distinctive properties. Nevertheless, existing studies on the physicochemical properties and the sensorial profile of honey in relation to botanical origin remain insufficient. This study aimed to understand the relationships between sensory profile and various chemical compounds (minerals, sugars, water content and volatiles) of three monofloral honeys (Atractylis serratuloides, Retama sphaerocarpa and Eruca sativa) produced in Algeria using principal component analysis. Crystallization was detected as a distinctive attribute of Eruca and Atractylis honey. A candy aroma and odor with floral nuances, light color, crystallized state and the volatile compounds Alpha-Bisabolol and Beta-eudesmol characterized the Atractylis honey. Eruca honeys were distinguished by an animal and degraded odor, bitter taste, light color and the presence of Dimethyl trisulfide and Dimethyl tetrasulfide. Finally, a vegetal aroma, some saltiness and sourness, dark amber color, lower sugar content, higher K content and Lilac aldehyde and Lilac aldehyde D characterized Retama honeys. Full article

In the frame of exploring the local native biodiversity for new ornamental species, the current study frames pivotal efforts for the ex situ conservation of the vulnerable and protected local Greek endemic plant Campanula laciniata L. and presents its natural requirements, seed germination trial, and first cultivation–fertilization protocol. The temperature and precipitation requirements of C. laciniata prevailing in its natural habitats were explored by using high-spatial-resolution bioclimatic maps in Geographic Information Systems (GIS). The germination of C. laciniata seeds was tested at 15 °C under alternating light and dark conditions as suggested for various Mediterranean Campanula species. However, the germination rate of C. laciniata seeds was low (35%), thus indicating the need for further research. The derived seedlings were used to study the effect of fertilization schemes on C. laciniata growth involving integrated nutrient management (INM), inorganic fertilization (ChF), and control (only water) using a substrate of soil:peat:perlite (4:3:1, v/v/v). After six months of plant growth, specific morphological and physiological characteristics as well as the phenolic content and antioxidant capacity of the plants receiving each fertilization treatment were measured. Fertilization significantly affected the morphological and physiological characteristics of the produced plants. Total phenols and antioxidant capacity were both affected by fertilization treatment but were lower in fertilized plants compared to control ones. After pivotal ex situ conservation, we performed a multifaceted evaluation for the ornamental-horticultural sector showing that C. laciniata holds a noteworthy ornamental potential (52.78%) with feasible value chain creation in the medium term for its sustainable utilization. Full article

The abandonment of inhabited places is a phenomenon widespread on a global scale that has spanned centuries. It has led to the birth of the so-called ‘ghost towns’. These lifeless sites dot the internal Mediterranean and European areas, testifying to the changeability of the human settlements. Through a vision that reverses the paradigm that epitomises the ‘ghost towns’, these places can be transformed from a problem into an opportunity for the development of the territories that host them. The main topic of this article is to present and update investigations performed on three abandoned settlements sited in Portugal, Italy, and Albania in view of their tourist exploitation, considering three different tailored strategies: underwater tourism, dark tourism, and heritage tourism. For each site, we analysed the site history, the abandonment causes, and the territorial-geological features, thus arguing for the possible valorisation and enjoyment approaches with special attention to digital technologies, which are highly underexploited in the sector. This study, which is part of an international research landscape still in the initial stages, falls within the BEGIN project (aBandonment vErsus reGeneratIoN), which aims to develop a multilevel methodological–operational protocol useful in regional, national, EU, and non-EU contexts for the dissemination of knowledge, conservation, regeneration, valorisation, management, and fruition of areas classified as a ‘ghost town’. The research findings can be useful for scholars, practitioners, and local entities entrusted to manage the abandoned towns. Furthermore, the methodological approach followed in this research can supply useful insights into aims to valorise and enjoy worldwide ‘ghost towns’. Full article

Zinc oxide (ZnO) particles have recently received attention in different agriculture sectors as new technologies and practices are entering into force with limited adverse effects on the environment. However, various works have reported both positive or negative effects on plants. The present study focused on an evaluation of the effects of four different new micro- and nano-sized ZnO particles (namely, Desert Roses (DRs), MultiPods (MPs), NanoFlakes (NFs), and NanoParticles (NPs)) on the seed germination traits of Ocimum basilicum L., Lactuca sativa L., and Lepidium sativum L. ZnO particles were applied at concentrations of 12.5 ppm, 25 ppm, and 50 ppm. Seeds moistened with deionized water were used as a control. All the particles were characterized by field emission scanning electron microscopy, and their production of Reactive Oxygen Species (ROS) under seed germination conditions was evaluated through electron paramagnetic resonance spectroscopy. Seeds of each species were put on filter paper under controlled conditions in both dark and light photoperiods. In this bioassay, the final germination percentage (FGP), early root length, and index of germination were evaluated. The results showed a wide variability of response to the type and concentration of ZnO particles and to the applied photoperiod of the three studied species. O. basilicum FGP increased when treated with NPs and DRs already at the lowest concentration and especially in light conditions with values significantly superior to those of the control (71.1%, 69.4%, and 52.2%, respectively). At higher concentrations, phytotoxicity on root length was observed, with a reduction of circa 30% in comparison to untreated seeds. On the contrary, in L. sativum, a phytotoxic effect was seen in radicle length with all the used ZnO particles and concentrations. L. sativa seeds did not show significant effects due to the type of particles, with a reduction in FGP only at higher concentrations and particularly in light conditions. Upon light irradiation, different levels of ROS were counted by the application of ZnO particles. DRs produced the highest amount of DMPO-OH adduct (up to 2.7 × 10⁻⁵ M) followed by the NP type (2.0 × 10⁻⁵ M). Taking together all these findings, the seeds’ coat morphology, their ability to absorb ZnO particles, and the ROS production in light conditions are indeed crucial players in the application of these formulations in seed germination. Full article

During the past few decades, abundant evidence for physics beyond the two standard models of particle physics and cosmology was found. Yet, we are tapping in the dark regarding our understanding of the dark sector. For more than a century, open problems related to the nature of the vacuum remained unresolved. As well as the traditional high-energy frontier and cosmology, technological advancement provides complementary access to new physics via high-precision experiments. Among the latter, the Casimir And Non-Newtonian force EXperiment (Cannex) has successfully completed its proof-of-principle phase and is going to commence operation soon. Benefiting from its plane parallel plate geometry, both interfacial and gravity-like forces are maximized, leading to increased sensitivity. A wide range of dark sector forces, Casimir forces in and out of thermal equilibrium, and gravity can be tested. This paper describes the final experimental design, its sensitivity, and expected results. Full article

Overwhelming astronomical evidence for dark matter and absence of any laboratory evidence for it despite many dedicated searches have fueled speculation that dark matter may reside in a parallel universe interacting with the familiar universe only via gravitational interactions as well as possibly via some ultra-weak forces. In this scenario, we postulate that the visible universe co-exists with a mirror world consisting of an identical duplicate of forces and matter of our world, obeying a mirror symmetry. This picture, motivated by particle physics considerations, not only provides a natural candidate for dark matter but also has the potential to explain the matter dark matter coincidence problem, i.e., why the dark matter content of the universe is only a few times the visible matter content. One requirement for mirror models is that the mirror world must be colder than our world to maintain the success of big bang nucleosynthesis. After a review of the basic features of the model, we present several new results: first is that the consistency between the coldness of the mirror world and the explanation of the matter dark matter coincidence implies an upper bound on the inflation reheat temperature of the universe to be around ${10}^{6.5}$ GeV. We also argue that the coldness implies the mirror world consists mainly of mirror Helium and very little mirror hydrogen, which is the exact opposite of what we see in the visible world. Full article

The present paper is a modest attempt to initiate the research program outlined in this abstract. We propose that general relativity and relativistic MOND (RelMOND) are analogues of broken electroweak symmetry. That is, $SU{\left(2\right)}_R\times U{\left(1\right)}_{YDEM}\to U{\left(1\right)}_{DEM}$ (DEM stands for dark electromagnetism), and GR is assumed to arise from the broken $SU{\left(2\right)}_R$ symmetry and is analogous to the weak force. RelMOND is identified with dark electromagnetism $U{\left(1\right)}_{DEM}$, which is the remaining unbroken symmetry after the spontaneous symmetry breaking of the dark electro-grav sector $SU{\left(2\right)}_R\times U{\left(1\right)}_{YDEM}$. This sector, as well as the electroweak sector, arises from the breaking of an $E_8\times E_8$ symmetry in a recently proposed model of unification of the standard model with pre-gravitation, with the latter based on an $SU{\left(2\right)}_R$ gauge theory. The source charge for the dark electromagnetic force is the square root of mass, motivated by the experimental fact that the ratio of the square roots of the masses of the electron, up-quark, and down-quark is 1:2:3, which is the opposite of the ratio of their electric charges at 3:2:1. The introduction of the dark electromagnetic force helps us understand the peculiar mass ratios of the second and third generations of charged fermions. We also note that in the deep MOND regime, acceleration is proportional to the square root of mass, which motivates us to propose the relativistic $U{\left(1\right)}_{DEM}$ gauge symmetry as the origin of MOND. We explain why the dark electromagnetic force falls inversely with distance, as in MOND, rather than following the inverse square of distance. We conclude that dark electromagnetism effectively mimics cold dark matter, and the two are essentially indistinguishable in cosmological situations where CDM successfully explains observations, such as CMB anisotropies and gravitational lensing. Full article

The notion of a local inertial reference frame is thoroughly analyzed. Dynamics of a field of such frames is derived from the variational principle. It is shown that the resulting theory splits naturally into three sectors, one of which is purely gravitational. Field dynamics in this sector, equivalent to Einstein’s vacuum equations, is obtained unambiguously and admits no ad hoc corrections. The cosmological constant is an essential element of this construction and cannot be removed. It has been shown that the second sector of this theory corresponds to electrodynamics, while the last sector could possibly describe dark matter. Full article

Tensions in the measurements of neutron and kaon weak decays, such as of the neutron lifetime, may speak to the existence of new particles and dynamics not present in the Standard Model (SM). In scenarios with dark sectors, particles that couple feebly to those of the SM appear. We offer a focused overview of such possibilities and describe how the observations of neutron stars, which probe either their structure or dynamics, limit them. In realizing these constraints, we highlight how the assessment of particle processes within dense baryonic matter impacts the emerging picture—and we emphasize both the flavor structure of the constraints and their broader connections to cogenesis models of dark matter and baryogenesis. Full article

While the standard model accurately describes data at the electroweak scale without the inclusion of gravity, beyond the standard model, physics is increasingly intertwined with gravitational phenomena and cosmology. Thus, the gravity-mediated breaking of supersymmetry in supergravity models leads to sparticle masses, which are gravitational in origin, observable at TeV scales and testable at the LHC, and supergravity also provides a candidate for dark matter, a possible framework for inflationary models and for models of dark energy. Further, extended supergravity models and string and D-brane models contain hidden sectors, some of which may be feebly coupled to the visible sector, resulting in heat exchange between the visible and hidden sectors. Because of the couplings between the sectors, both particle physics and cosmology are affected. The above implies that particle physics and cosmology are intrinsically intertwined in the resolution of essentially all of the cosmological phenomena, such as dark matter and dark energy, and in the resolution of cosmological puzzles, such as the Hubble tension and the EDGES anomaly. Here, we give a brief overview of the intertwining and its implications for the discovery of sparticles, as well as the resolution of cosmological anomalies and the identification of dark matter and dark energy as major challenges for the coming decades. Full article

During the winter of 2018, leaf blight on florist’s daisy (Chrysanthemum morifolium L.) was noticed in Egypt. The disease, which was identified as caused by Alternaria alternata, was widely spread and led to serious damage for the exportation sector of this crop. Therefore, a study was conducted to better understand what can be conducted to minimize the problem in the future. Isolates were gathered and evaluated on five chrysanthemum cultivars (i.e., ‘Feeling Green Dark’, ‘Talitha’, ‘Chrystal Regan’, ‘Arctic queen’, and ‘Podolsk Purple’) grown in a greenhouse. The objectives were to isolate and identify the phytopathogen and detect the resistant degree of these cultivars with emphasis on the early growth stages of the crop. The results showed that ‘Podolsk Purple’ was the most resistant cultivar against the different isolates during the rooting and seedling growth stages. ‘Chrystal Regan’ was very susceptible to the different isolates. In addition, the isolate from ‘Feeling Green Dark’ was the strongest, which negatively affected the chlorophyll content and its fluorescence parameters besides other measured vegetative and anatomical features. The findings indicated that the best anatomical characters of the stem and leaf, like the thickness of cuticle and cortex, stem diameter, xylem vessel diameter, and thickness of epidermis as well as lamina thickness were recorded in the ‘Podolsk Purple’ cultivar. This study highlighted that by using the right cultivars, chrysanthemum can be cultivated during the winter season under Egyptian conditions. These results can be a part of solution to overcome the leaf blight caused by A. alternata on chrysanthemum during the early growing stages. Full article

We use Big Bang Nucleosynthesis (BBN) to probe Beyond Standard Model physics in the neutrino sector. Recently, the abundances of primordially produced light elements D and He-4 were determined from observations with better accuracy. The good agreement between the theoretically predicted abundances of primordially produced light elements and those derived from observations allows us to update the BBN constraints on Beyond Standard Model (BSM) physics. We provide numerical analysis of several BSM models of BBN and obtain precise cosmological constraints and indications for new neutrino physics. Namely, we derive more stringent BBN constraints on electron neutrino–sterile neutrino oscillations corresponding to $1\%$ uncertainty of the observational determination of the primordial He-4. The cosmological constraints are obtained both for the zero and non-zero cases of the initial population of the sterile neutrino state. Then, in a degenerate BBN model with neutrino ${\nu }_e\leftrightarrow {\nu }_s$ oscillations, we analyze the change in the cosmological constraints in case lepton asymmetry L is big enough to suppress oscillations. We obtain constraints on the lepton asymmetry L. We discuss a possible solution to the dark radiation problem in degenerate BBN models with ${\nu }_e\leftrightarrow {\nu }_s$ oscillations in case L is large enough to suppress neutrino oscillations during the BBN epoch. Interestingly, the required value of L for solving the DR problem is close to the value of L indicated by the EMPRESS experiment, and also it is close to the value of lepton asymmetry that is necessary to relax Hubble tension. Full article

We show that Einstein’s conformal gravity can explain, simply, and on the geometric ground, galactic rotation curves, without the need to introduce any modification in both the gravitational as well as in the matter sector of the theory. The geometry of each galaxy is described by a metric obtained, making a singular rescaling of Schwarzschild’s spacetime. The new exact solution, asymptotically anti-de Sitter, manifests an unattainable singularity at infinity that cannot be reached in finite proper time; namely, the spacetime is geodetically complete. It deserves to be noticed that, in this paper, we have a different opinion from the usual one. Indeed, instead of making the metric singularity-free, we make it apparently but harmlessly even more singular than Schwarzschild’s. Finally, it is crucial to point out that Weyl’s conformal symmetry is spontaneously broken into the new singular vacuum rather than the asymptotically flat Schwarzschild’s one. The metric is unique according to the null energy condition, the zero acceleration for photons in the Newtonian regime, and the homogeneity of the Universe at large scales. Once the matter is conformally coupled to gravity, the orbital velocity for a probe star in the galaxy turns out to be asymptotically constant consistent with the observations and the Tully–Fisher relation. Therefore, we compare our model with a sample of 175 galaxies and show that our velocity profile very well interpolates the galactic rotation curves after a proper choice of the only free parameter in the metric. The mass-to-luminosity ratios of galaxies turn out to be close to 1, consistent with the absence of dark matter. Full article