Minimum Potential Research Articles

Plant Hydraulics Improves Predictions of ET and GPP Responses to Drought

AbstractLand surface models typically ignore plant hydraulic processes and use empirical soil moisture stress functions to limit transpiration and photosynthesis. How plant hydraulics impacts the predictions of carbon and water fluxes and their responses to drought remains unclear. Here, we developed an analytical plant hydraulic scheme wherein hydraulic capacitances at the leaf level and stem level were considered, and incorporated it into the vegetation interface processes model (hereafter, VIP‐PHS). Then, we calibrated the VIP‐PHS parameters using a Markov Chain Monte Carlo (MCMC) method and conducted an ecosystem‐scale evaluation of the VIP‐PHS at 30 FLUXNET sites. The results showed that VIP‐PHS improved evapotranspiration (ET) and gross primary production (GPP) simulations across the studied sites, reducing the root mean square error (RMSE) by 0.02–0.27 mm day−1 and 0.04–0.52 g C m−2 day−1 in relation to the empirical soil hydraulic scheme (hereafter, VIP‐SHS). VIP‐PHS decreased the RMSE in ET and GPP by up to 45% and 55% in evergreen needleleaf forests. Compared to VIP‐SHS, VIP‐PHS decreased the sensitivities of ET and GPP to soil moisture stress, and significantly improved ET and GPP predictions under low soil moisture conditions. The sensitivity analysis showed that larger stem hydraulic capacitance better relieved xylem water stress, resulting in greater transpiration and GPP and less‐negative daily minimum stem water potential. These findings highlight the need to incorporate plant hydraulics into the next generation of Earth system models under future drought conditions.

Minimum potential method appropriate to generate 2D RVEs of composites with high fiber volume fraction

This work proposes a novel method, entitled minimum potential method, to generate Representative Volume Elements (RVEs) of unidirectional fibers composites with high fiber volume fractions (FVFs, generally ≥70.0%). In the proposed method, a given VF of random and periodic fibers are initially created within the matrix and the fiber overlap is allowed, and then the fiber overlap is gradually removed by adjusting the fiber centroids based on the principle of the minimum overall potential. In the process of fiber overlap removal, the fiber periodicity and the fibers completely or partly contained in the matrix are preserved. The overall potential of the fibers consists of fiber overlap potential, fiber position potential and fiber periodicity potential, and is minimized using the gradient descent method. The numerical implementation of the proposed method is detailed, and the RVEs of the composites with various FVFs are generated. Through the probability distribution function of the nearest neighbor distance, the cumulative probability distribution function of the nearest neighbor orientation angle, the second-order intensity and pair correlation functions, the fiber distribution in the generated RVEs is analyzed, and the results indicate a completely random distribution of the fibers in the generated RVEs. Comparing with the available experimental test, the literature and the Double-Inclusion model, the proposed method to generate RVEs of the composites with high FVFs is validated.

Evaluating land suitability for Rhus coriaria L. (Sumac) by habitat suitability model

The cultivation of Rhus coriaria has become necessary to preserve their wild populations. To be competitive in the international market, it is important to develop an efficient production chain to reduce costs and improve the quality of the products. The main objective of this study is to provide a method to determine the suitable areas to develop the R. coriaria cultivation with a case study in Gonabad County of Iran. A habitat suitability model (HSM) was applied to survey the distribution of R. coriaria and to identify the best areas the growing of its. Three different main criteria including environmental suitability, agronomic suitability, and social-economical suitability selected for the HSM. Then, each of the three main criteria and their multi-specific indicator was defined in Analytic Hierarchy Process (AHP) and the weights of them were calculated by pairwise comparison matrix. In the next stage, the weights are applied to their layers such as hypsometry, slope, slope aspect, mean annual precipitation, mean annual temperature, soil texture, landuse, water resource type, water resource quality and quantity, road network, and land ownership as roaster layers. The results of the HSM showed a weighted map of land suitability for the R. coriaria that included the maximum and minimum potential of areas for its planting. Based on these results, the areas with the highest suitability for the R. coriaria are strictly associated with precipitation, soil texture, and water resources type.

In-Plane Rotation of Prolate Colloids Adhered to a Planar Substrate in the Presence of Flow.

Micron-size spherical polystyrene colloidal particles are mechanically stretched to a prolate geometry with desirable aspect ratios. The particles in an aqueous medium with specific ionic concentration are then introduced into a microchannel and allowed to settle on a glass substrate. In the presence of unidirectional flow, the loosely adhered particles in the secondary minimum of surface interaction potential are easily washed off, but the remnant in the strong primary minimum preferentially aligns with the flow direction and exercises in-plane rotation. A rigorous theoretical model is constructed to account for filtration efficiency in terms of hydrodynamic drag, intersurface forces, reorientation of prolate particles, and their dependence on flowrate and ionic concentration.

Effect of different irrigation systems on water use partitioning and plant water relations of apple trees growing on deep sandy soils in the Mediterranean climatic conditions, South Africa

All commercial apple fruit (Malus Domestica (Borkh) exported from semi-arid regions are grown under irrigation with drip and micro sprinkler systems being the most widely used. Few studies have directly compared the physiological responses of fruit trees to these systems in detail leading to uncertainties around their performance. This study investigated variations in transpiration rates, tree water status, growth, water use partitioning, fruit yield and quality for trees growing on deep sandy soils under these two systems. Data were collected in a mature Royal Gala orchard in South Africa over three growing seasons. Tree transpiration was quantified using the heat ratio method of monitoring sap flow while the soil water balance approach was used to derive the evapotranspiration (ET) rates. Leaf level results showed that one day after irrigation on hot dry days, the stomatal conductance was, on average, almost double for trees under micro than those under drip irrigation. There was more stress under drip with the minimum midday leaf water potential dropping to under -1.80 MPa compared to only around -1.20 MPa under micro sprinklers. Consequently, the tree transpiration per unit leaf area was substantially higher under micro sprinkler (2.9 L/m2/d) compared to 2.3 L/m2/d under drip (P ≤ 0.05). Canopy growth was slower under drip with peak leaf area index (LAI) around 2.1 compared to 2.7 under the micro sprinkler system. The micro sprinkler system had a more active ground cover than the drip. At peak canopy cover in summer, up to 28% of ET was derived from the orchard floor under micro compared to only 15% under drip. However, fruit size and fruit quality were lower under drip compared to micro sprinkler irrigated trees. The study highlights that while water savings are high under drip irrigated orchards on sandy soils, trees tend to experience considerable water stress culminating in smaller fruit of compromised quality.

Electronic structure and water induced phase transformation in layered perovskite-like K2La2Ti3O10 photocatalyst for water splitting studied by DFT

Layered perovskite-like oxide K2La2Ti3O10 is a perspective photocatalyst for water decomposition at ultraviolet irradiation. In this paper using a density functional theory approach electronic structures of dehydrated and hydrated phases of K2La2Ti3O10 have been studied. It has been found that the water induced phase transformation from I4/mmm to P4/mmm occurs in two steps: at first an increase in the distance between the perovskite layers prevails, and then a shift of the perovskite layers occurs with a moderate changing of the interlayer distance. The band structure calculations have done using the modified Becke-Johnson potential show that K2La2Ti3O10 exhibits indirect band gap of about 3.1 eV. The valence band maximum potential is located at 2.23 eV (vs. normal hydrogen electrode), while the conduction band minimum potential is at −0.91 eV. This confirms the ability of K2La2Ti3O10 both for photocatalytic oxidation of water (producing dioxygen and protons) or pollutants, and to reduce H+ to H2. However, the transfer rate, estimated implicitly from the ratio of the effective masses of the photogenerated holes and electrons in valence and conduction bands, limits photocatalytic performance of K2La2Ti3O10 due to separation ineffectiveness of charge carriers.

Blueprint of a Scalable Spin Qubit Shuttle Device for Coherent Mid-Range Qubit Transfer in Disordered Si/SiGe/SiO2

Silicon spin qubits stand out due to their very long coherence times, compatibility with industrial fabrication, and prospect to integrate classical control electronics. To achieve a truly scalable architecture, a coherent mid-range link that moves the electrons between qubit registers has been suggested to solve the signal fan-out problem. Here, we present a blueprint of such a link of 10 μm length, called a spin qubit shuttle, which is based on connecting an array of gates into a small number of sets. To control these sets, only a few voltage control lines are needed and the number of these sets and thus the number of required control signals is independent of the length of this link. We discuss two different operation modes for the spin qubit shuttle: a qubit conveyor, i.e., a potential minimum that smoothly moves laterally, and a bucket brigade, in which the electron is transported through a series of tunnel-coupled quantum dots by adiabatic passage. We find the former approach more promising considering a realistic Si/SiGe device, including potential disorder from the charged defects at the Si/SiO2 layer, as well as typical charge noise. Focusing on the qubit transfer fidelity in the conveyor shuttling mode, we discuss in detail motional narrowing, the interplay between orbital and valley excitation and relaxation in the presence of g factors that depend on orbital and valley state of the electron, and effects from spin hotspots. We find that a transfer fidelity of 99.9% is feasible in Si/SiGe at a speed of approximately 10m/s, if the average valley splitting and its inhomogeneity stay within realistic bounds. Operation at low global magnetic field approximately equal to 20mT and material engineering towards high valley splitting is favorable for reaching high fidelities of transfer.12 MoreReceived 10 March 2022Revised 18 October 2022Accepted 15 February 2023DOI:https://doi.org/10.1103/PRXQuantum.4.020305Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum information with solid state qubitsQuantum transportSpin coherenceSpin relaxationSurface & interfacial phenomenaPhysical SystemsQuantum dotsSemiconductor compoundsCondensed Matter, Materials & Applied PhysicsQuantum Information

Nonlinear analysis of perforated composite plates under compression by experimental, semi-analytical and numerical methods

The purpose of this paper is to investigate the effects of different cutout shapes on the nonlinear behavior of perforated composite plates using experimental, numerical and semi-analytical methods and to present their capabilities. For analysis, the composite plates are subjected to a compressive load and different out-of-plane boundary conditions are applied to the lateral edges. Investigations are performed by various methods such as experimental tests, finite element method and a semi-analytical technique. For laboratory tests, a fixture has been designed and built that can create different boundary conditions on the lateral edges of perforated plates and can also test laminates up to 6 mm thick. On laminates, three types of openings are created in square, rectangular and elliptical shapes and the perforated laminates are tested with two types of boundary conditions, including clamped on all four edges (CCCC) and simply on two lateral edges and clamped on two ends (SSCC). These experiments are also simulated in the Abaqus finite element package, taking into account the considerations raised and with the nonlinear Riks method. Also, with similar assumptions in experimental and numerical methods, a semi-analytical method has been developed to compare the results and capabilities of different methods in nonlinear analysis of perforated laminates with different boundary conditions. In the last method, the displacement fields are approximated using Legendre functions and assuming the first-order shear deformation theory. Then, the nonlinear system of equilibrium equations governing the perforated plates is obtained through the principle of minimum total potential energy and is solved by the common method of quadratic extrapolation technique. Finally, the capabilities, advantages and disadvantages of each method, especially the fixtures made for this research, are discussed.

Experimental Study On Bird Streamer Flashover for V-Type Insulators of DC Transmission Line in High Altitude Area

In order to obtain the bird streamer flashover characteristics in high altitude areas, the discharge of DC V-type string insulators was studied in high-altitude test base at 4300 m in Tibet. The study results show that medium viscosity bird streamer is easy to form a continuous channel and cause flashover. The flashover probability of positive polarity transmission lines is slightly higher than that of negative. The conductivity of bird excrement almost has no effect on the flashover probability in the range of 1.9∼20.9 mS/cm. To increase the vertical air gap distance can reduce bird streamer flashover probability. Based on the experiment results, the recommended vertical air gap distance values of ±400 kV DC transmission line were proposed. Considering the influence of wind and bird streamer falling angle, the protection radius was set 3.5 m at 3500∼5000 m altitude area. Bird streamer flashover is a mixed discharge of air gap breakdown and the surface discharge along the bird streamer channel, at the altitude of 4300 m area, the minimum breakdown potential gradient is about 2.1 kV/cm, and the discharge between bird streamer and shielding ring can be approximately equivalent to rod-rod gap discharge.

Symmetry restoration in the vicinity of neutron stars with a nonminimal coupling

We propose a new model of scalarized neutron stars (NSs) realized by a self-interacting scalar field ϕ nonminimally coupled to the Ricci scalar R of the form F(ϕ)R. The scalar field has a self-interacting potential and sits at its vacuum expectation value ϕv far away from the source. Inside the NS, the dominance of a positive nonminimal coupling over a negative mass squared of the potential leads to a symmetry restoration with the central field value ϕc close to 0. This allows the existence of scalarized NS solutions connecting ϕv with ϕc whose difference is significant, whereas the field is located in the vicinity of ϕ=ϕv for weak gravitational stars. The Arnowitt-Deser-Misner mass and radius of NSs as well as the gravitational force around the NS surface can receive sizable corrections from the scalar hair, while satisfying local gravity constraints in the Solar system. Unlike the original scenario of spontaneous scalarization induced by a negative nonminimal coupling, the catastrophic instability of cosmological solutions can be avoided. We also study the cosmological dynamics from the inflationary epoch to today and show that the scalar field ϕ finally approaches the asymptotic value ϕv without spoiling a successful cosmological evolution. After ϕ starts to oscillate about the potential minimum, the same field can also be the source for cold dark matter.

Self-assembled nanostructure of copper hydrogen phosphate with catalytic and antibacterial activity

The rapid development of antibiotic resistance poses a huge threat to human health. Copper-based materials is a promising alternative to the traditional antibiotics due to its high efficacy and low resistance potential for bacterial infections. In this work, three-dimensional flower-like copper hydrogen phosphate nanosheet assembled microspheres (CP-NSMSs) are synthesized through a hydrolysis-assisted synthetic method using fructose-1,6-diphosphate (FDP) as the organic phosphate source. The copper hydrogen phosphate nanosheets with high aspect ratio provide a large amount of sharp edges which could penetrate bacterial membranes, resulting in the death of bacteria. Furthermore, the as-prepared CP-NSMSs exhibit the high peroxidase-like activity producing a large amount of reactive oxygen species (ROS) to kill bacteria. Based on the in vitro bacterial growth experiments, our CP-NSMSs show an excellent sterilization effect against both Gram-positive and Gram-negative bacteria. Therefore, the CP-NSMSs synthesized using the FDP as an organic phosphate source is expected to be a promising antibacterial agent with minimum resistance potential.

Domain wall motion across microstructural features in polycrystalline ferroelectric films

This paper describes the effect of microstructural features such as grain boundaries and triple points on the pinning of domain wall motion in perovskite Pb(Zr0.52Ti0.48)O3 (PZT) films on polycrystalline SrRuO3/SrTiO3 substrates. Spatial variability in the collective domain wall dynamics was assessed using non-linearity mapping via Band Excitation Piezoresponse Force Microscopy (BE-PFM). Collocating the non-linearity maps with triple point locations (as visualized by EBSD) allowed for exploration of the effects that local microstructure (e.g., grain boundary) have on domain wall motion. It was found that the extrinsic behavior varied with both the misorientation angle and the proximity to the grain boundary. The width of influence of individual grain boundaries on the motion of domain walls was a function of the character of the grain boundary; random grain boundaries exhibit deeper minima in αd/d33,initial and larger widths of influence (up to 905 nm) compared to coincident site lattice (CSL) boundaries (up to 572 nm). Additionally, triple points containing larger numbers of random boundaries exhibited non-Rayleigh behavior to greater distances, suggesting that the triple point provides either a deep potential minimum or a region where domain wall motion is unfavorable.

On K3-fibred LARGE Volume Scenario with de Sitter vacua from anti-D3-branes

In the context of type IIB superstring compactifications on K3-fibred (weak) Swiss-cheese Calabi Yau (CY) orientifolds, we consider the realisation of de Sitter vacua obtained through the introduction of an overline{D3} -brane at the tip of a highly warped throat of Klebanov-Strassler type. Aiming to have a concrete global realisation, we perform a systematic search for the CY threefolds with 2 < h1,1< 5 arising from the Kreuzer-Skarke database, which satisfy the minimal requirements of being K3-fibred and suitable for moduli stabilisation within the LARGE Volume Scenario (LVS). In this context, after scanning the set of K3-fibred CY threefolds with a so-called diagonal del-Pezzo divisor needed for LVS, we realise that one of the main challenging requirements for having overline{D3} -brane uplifting is to find a suitable orientifold involution which can simultaneously result in a sufficient large D3 tadpole charge along with the presence of suitable O3-planes. In our detailed analysis (limited to) using the CY threefolds with small h1,1, we observe that these topological requirements rule out most of the CY geometries leading to only few possibly suitable candidates for the purpose of overline{D3} -brane uplifting. Subsequently, we present a global model using one such explicit K3-fibred CY threefold with h1,1 = 4 in which all the moduli can be consistently stabilised in a de Sitter minimum of the scalar potential.

Reducing freshwater consumption in pulp and paper industries using pinch analysis and mathematical optimization

The pulp and paper (P&P) industries are classified among the water-intensitive industries. In this work, implementation of the Water Closed-Loop System (WCLS) in a P&P factory to reduce water consumption and wastewater generation was reported. First, the water and steam network of the mill was synthesized, and water sinks and sources along with their flowrates were identified. The key pollutants, including chemical oxygen demand (COD), total suspended solids (TSS), and total dissolved solids (TDS), were pinpointed and acceptable levels for water sinks were acquired. In the second step, by using water pinch analysis with the direct-reuse approach, each limiting pollutant was investigated, and the maximum reduction in freshwater consumption equal to 36.9 % was obtained by considering TSS as the only pollutant. The minimum potential for reducing water consumption belonged to COD (4.0 %) and TDS (18.9 %). In the regeneration-reuse approach, the incomplete performance of the mill's treatment plant in removing COD and TDS resulted in no improvement in the results of the previous step. In the case of TSS alone, the reduction in freshwater consumption increased to 93.3 %. Mathematical optimization was used to study all limiting contaminants simultaneously. The direct-reuse approach achieved a 4.0 % reduction in water consumption, while the regeneration-reuse did not change water consumption compared to the direct-reuse approach, emphasizing the incomplete operation of the treatment plant. Finally, the output contaminants levels of a hypothetical decentralized and modified existing treatment plant were estimated using literature. In this case, the freshwater consumption of the mill declined by 93 %.

Integrated techno-economic and life cycle assessment of shared circular business model based blockchain-enabled dynamic grapevoltaic farm for major grape growing states in India

Grape farms face many climate risks during cultivation, and regulatory and sustainability-related challenges after the harvest. To support the farmers, Government of India (GoI) aims to promote adaptive capacity throughout the grape value chain by improving resilient infrastructure. This paper proposes a novel Grapevoltaics farm design based on shared circular business model principles where resources like energy, water, and land are shared between grape farmer and solar plant operator. The resilience (in the near term) and sustainability (in the long term) of such multifunctional systems may be influenced by the decisions taken by the involved stakeholders in terms of resource sharing and support extension when facing climate risk events. To address stakeholder engagement, the proposed Grapevoltaic farms leverage blockchain smart contract, making them Blockchain-enabled Grapevoltaics (BCeDGVs). To understand the feasibility, 1-ha Grapevoltaic farm is modeled for 12 grape growing regions accross India and analysed using Resilience Performance, Life Cycle Analysis, and Techno-Economic (RePLiCATE) approach. The results show that the solar panels provide resilience support based on the rules of engagement written on blockchain smart contracts. The BCeDGVs has 1295.28–2908.08 kWh/kWp/day electricity generation potential across India with a lifetime average of 15,380.65 MWh even after considering the national average photovoltaic degradation rate of 1.9%. The observed grape yields vary between 2 and 31.25 Mt/ha with an average yield of 45 Mt/ha (table grape) and 40 Mt/ha (wine grape), and the rainwater harvest varies between 1.23 to 7.32 Ml. The economic assessment revealed that grape farmers and photovoltaic plant operators across India under BCeDGVs could have revenues ranging between INR 56.25 to 225 million and INR 29.48–66.19 million, respectively, suggesting to relook into the feed-in tariffs and crop selling prices. The environmental sustainability results suggest that 1.984 ha/MW land-use mitigation and 12–100% reduction in groundwater dependency are possible while maintaining the minimum and maximum national average global warming potentials as 0.074 and 0.088 kg CO2-eq./kg grape, respectively. Overall, the integrated assessments find that the BCeDGVs may promote low carbon, climate resilient grape cultivation in India and has possible integration with GoI's GrapeNet platform. This study highlights a new research direction symbiotic grape farms and energy networks.

Baby diaper's super absorbent polymer derived carbon templated NiCuP@NiCu nanostructures for green hydrogen production

Water electrolysis is considered as the most favorable method to generate hydrogen because of its environmentally friendly approach. As an upgradation of this process, the introduction of urea gives improved energy conversion efficiency and can also be used for the treatment of urea-rich wastewater. Inspired by the above, a bifunctional electrocatalyst, namely NiCuP@NiCu supported on graphitic carbon, is prepared for the first time via high-temperature pyrolysis and in-situ phosphidization process. The carbon support endorses better electron transference, and the presence of mixed active metal redox couples (Mx+/My+, M = Ni&Cu) and their M-O/O–C bonds formation with urea molecule collectively leads to substantial UOR activity. Under alkaline conditions with 0.33 M urea in 1.0 M KOH, the NiCuP@NiCu/C drives 10 mA cm−2 current density with a minimum potential of 1.242 V and overpotential of 98 mV for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER), respectively. What is significant is that NiCuP@NiCu/C is explored as a bifunctional electrocatalyst to construct two electrode electrolyzer, which only requires the minimum potential of 1.313 V to drive 10 mA cm−2 current density. Furthermore, the NiCuP@NiCu/C equipped electrolyzer is used under human urine sample and achieved the maximum H2 production of 0.387 mmol. From the aforementioned outcomes, this works delivers a facile method for exploring an efficient bifunctional electrocatalyst for urea electrolysis and providing a new path to real-time fuel approach enabled H2 production.

Axion dark matter from first-order phase transition, and very high energy photons from GRB 221009A

We study an axion-like particle (ALP) that experiences a first-order phase transition with respect to its mass or potential minimum. This can be realized if the ALP obtains a potential from non-perturbative effects of SU(N) gauge theory that is confined via the first-order phase transition. Similar dynamics are achieved in the so-called trapped misalignment mechanism, where the ALP is trapped in a false vacuum at high temperatures until it begins to oscillate about the true minimum. The resulting ALP abundance is significantly enhanced compared to the standard misalignment mechanism, explaining dark matter in a broader parameter space that is accessible to experiments e.g. IAXO, ALPS-II, and DM-radio. Furthermore, the viable parameter space includes a region of the mass ma≃10−8−10−7eV and the ALP-photon coupling gaγγ≃10−11GeV−1 that can explain the recent observation of very high energy photons from GRB221009A via axion-photon oscillations. The parameter region suggests that the FOPT can generate gravitational waves that explain the NANOGrav hint. If the ALP in this region explains dark matter, then the ALP might have experienced a first-order phase transition. Finally we also discuss cosmological aspects of the dark sector that triggers the FOPT and propose a possible solution to the cooling problem of dark glueballs.

Approximate computational model for the local postbuckling of omega‐stringer‐stiffened composite panels

AbstractTypical thin‐walled structures are found in applications like aircraft, spacecraft and marine vessels. For this type of structure, stability behaviour is crucial. The better this behaviour is understood, the better the full lightweight potential can be exploited. For composite structures especially, new fast analysis tools for preliminary design are required to address this issue. Therefore, the local postbuckling of omega‐stringer‐stiffened composite panels is the subject of a new computational model. The analysis method is computationally highly efficient because it is based on a closed‐form analytical approach. The explicit solution is derived based on the principle of the minimum of the total elastic potential. Furthermore, the solution assumes that the initial eigenform does not substantially change in the early postbuckling regime. In this way, the plates of the skin and stringer can be included explicitly in the analysis. Compared to finite element analysis and a closed‐form computational model found in the literature, the new analysis tool is assessed. The results indicate excellent agreement for panels, where the bay plate is the most critical element of the panel. The new computational model promises to be a highly efficient tool in the preliminary design framework.

Extended analytical solutions of the Bohr Hamiltonian with the sextic oscillator: Pt-Os isotopes

The sextic oscillator adapted to the Bohr Hamiltonian has been used to describe even Pt and Os isotopes from A = 188 to 198 and A = 186 to 192, respectively. The purpose of this study was to investigate the possible transition from the γ-unstable to the spherical vibrator shape phases. In this setup the potential appearing in the Bohr Hamiltonian is independent from the γ shape variable, and the physical observables (energy eigenvalues, B(E2)) can be obtained in closed analytical form within the quasi-exactly solvable formalism for the model space containing 30 of the lowest-lying levels. Experimental energy levels have been associated with the theoretical ones. The available electric quadrupole transition data (B(E2), decay preferences) have been taken into account in matching the experimental and theoretical levels. Special attention has been paid to transitions from the first two excited 0+ levels to the and levels, as these indicate the change of shape phases with spherical and deformed potential minimum. The three parameters of the Hamiltonian have been determined by a weighted least square fit procedure. Trends in the location of states belonging to the ground-state, the K π = 2+ and two excited K π = 0+ bands have been analysed. The trajectory determined by the fitted parameters in the two-dimensional phase space has also been plotted, and it has been found that all the nuclei are characterized by a deformed potential minimum, except for the heaviest Pt isotope (198Pt), for which the transition to the spherical shape phase is realised. Although the spectroscopic information on the next isotopes of the chains (200Pt and 194Os) is far less complete, there are indications that these nuclei are also close to or fall within the domain of spherical potential minimum.

Axion dark matter with thermal friction

Cosmological evolution of axion field in the early universe might be significantly affected by a thermal friction induced by the axion coupling to thermalized hidden sector. We examine the effects of such a thermal friction on axion dark matter density and its perturbation when the thermal friction dominates over the Hubble friction until when the axion field begins to oscillate around the potential minimum. We show that in the presence of sizable thermal friction there can be an exponential decay phase of the axion field before the oscillation phase, during which the axion energy density is efficiently dissipated into hidden thermal bath. Consequently, the previously excluded parameter region due to overclosing relic axion density becomes cosmologically viable with thermal friction. In particular, a QCD axion much lighter than μeV is viable without tuning the initial misalignment angle. We also find that thermal friction can affect the density perturbation of axion dark matter in various ways. For instance, it can alleviate the large-scale isocurvature bound on axion dark matter in the pre-inflationary PQ breaking scenario, which would make the pre-inflationary axion dark matter compatible with high scale inflation over a wide range of model parameters. In the post-inflationary PQ breaking scenario, thermal friction can also significantly change the scaling behavior of axionic strings, and therefore the typical size of the resultant axion miniclusters.