Shallow Potential Research Articles

Bose–Einstein-like condensation due to diffusivity edge under periodic confinement

A generic class of scalar active matter, characterized at the mean field level by the diffusivity vanishing above some threshold density, was recently introduced [Golestanian R 2019 Phys. Rev. E 100 010601(R)]. In the presence of harmonic confinement, such ‘diffusivity edge’ was shown to lead to condensation in the ground state, with the associated transition exhibiting formal similarities with Bose–Einstein condensation (BEC). In this work, the effect of a diffusivity edge is addressed in a periodic potential in arbitrary dimensions, where the system exhibits coexistence between many condensates. Using a generalized thermodynamic description of the system, it is found that the overall phenomenology of BEC holds even for finite energy barriers separating each neighbouring pair of condensates. Shallow potentials are shown to quantitatively affect the transition, and introduce non-universality in the values of the scaling exponents.

Impacts of progressive urban expansion on subsurface temperatures in the city of Amsterdam (The Netherlands)

Subsurface temperatures are substantially higher in urban areas than in surrounding rural environments; the result is a subsurface urban heat island (SUHI). SUHIs and their drivers have received attention in studies world-wide. In this study, a well-constrained data set of subsurface temperatures from Amsterdam, The Netherlands, is presented. The study demonstrates that, through modeling of centuries-long (from fourteenth to twenty-first century) urban development and climate change, along with the history of both the surface urban heat-island temperatures and ground surface temperatures, it is possible to simulate the development and present state of the Amsterdam SUHI. The results provide insight into the drivers of long-term SUHI development, which makes it possible to distinguish subterranean heat sources of more recent times that are localized drivers (such as geothermal energy systems, sewers, boiler basements, subway stations or district heating) from larger-scale drivers (mainly heat loss from buildings and raised ground-surface temperatures due to pavements). Because these findings have consequences for the assessment of the shallow geothermal potential of the SUHIs, it is proposed to distinguish between (1) a regional, long-term SUHI that has developed over centuries due to the larger-scale drivers, and (2) local anomalies caused by anthropogenic heat sources less than one century old.

Uniqueness of static, isotropic low-pressure solutions of the Einstein\u2013Vlasov system

In Beig and Simon (Commun Math Phys 144:373–390, 1992) the authors prove a uniqueness theorem for static solutions of the Einstein–Euler system which applies to fluid models whose equation of state fulfills certain conditions. In this article it is shown that the result of Beig and Simon (1992) can be applied to isotropic Vlasov matter if the gravitational potential well is shallow. To this end we first show how isotropic Vlasov matter can be described as a perfect fluid giving rise to a barotropic equation of state. This Vlasov equation of state is investigated, and it is shown analytically that the requirements of the uniqueness theorem are met for shallow potential wells. Finally the regime of shallow gravitational potential is investigated by numerical means. An example for a unique static solution is constructed, and it is compared to astrophysical objects like globular clusters. Finally we find numerical indications that solutions with deep potential wells are not unique.

Formation of binary black holes in star clusters as gravitational wave sources

Direct detections of gravitational wave suggest that ~ 30 solar mass binary black holes (BBHs) commonly exist in the Universe. One possible formation scenario of such BBHs is dynamical three-body encounters in a dense core of globular clusters, which consist of millions of stars. Compared to globular clusters, open clusters are less dense and less massive but more populous. Because of their shallow potential, they have not been considered to be a formation site of merging BBHs. However, we found a new channel for the formation of BBHs, which is dominant in open clusters. We performed direct N-body simulations of open clusters with a mass of 2500 solar mass for metallicity of Z/Z ⊙ = 0.1. The core-collapse time of open clusters is much shorter than that of globular clusters. Therefore, massive main-sequence stars can form binaries before they evolve to BHs. These main-sequence binaries experience mass transfer evolution, and some of them evolve to BBHs merging within the Hubble time. From our simulations, we estimated the merger rates of BBHs originated from open clusters.

Spatial Segregation of Massive Clusters in Dwarf Galaxies

Abstract The relative average minimum projected separations of star clusters in the Legacy ExtraGalactic UV Survey (LEGUS) and in tidal dwarfs around the interacting galaxy NGC 5291 are determined as a function of cluster mass to look for cluster–cluster mass segregation. Class 2 and 3 LEGUS clusters, which have a more irregular internal structure than the compact and symmetric class 1 clusters, are found to be mass-segregated in low-mass galaxies, which means that the more massive clusters are systematically bunched together compared to the lower-mass clusters. This mass segregation is not present in high-mass galaxies or class 1 clusters. We consider possible causes for this segregation, including differences in cluster formation and scattering in the shallow gravitational potentials of low-mass galaxies.

The (K-, π+)Σ- - hypernuclear production in flight

The in-flight (K-,π+) Σ~-hypernuclear spectra are studied, using a simple interaction model with a square well central part and a delta function spin-orbit Σ-nuclearcore interaction. A comparison is made between the theoretical results and the in-flight (Α'~,π+) experimental data for 12Σ C, 16Σ Ο and 6Σ Li. A shallow potential, with a central potential depth of Vc = (-5 - il5)MeV and a spin-orbit depth of Vao = lbMeV, gives a satisfactory representation of the CERN and BNL in-flight data.

Reversible aggregation of particles with short oligomeric sidechains at the surface studied with Langevin dynamics

We investigate nanoscopic aggregation of asphaltene nanoaggregates by means of Brownian dynamics simulations. Nanoaggregates that represent clusters of 6–10 asphaltene molecules are modelled as spherical particles with an attractive core consisting of polyaromatic hydrocarbons rings and short aliphatic tails that protrude from the surface, as in a spherical brush. As two such nanoaggregates approach each other, the steric repulsion that arises from interactions between the tails, is modelled using Alexander-de Gennes theory and Derjaguin approximation, while the attraction upon contact between polyaromatic cores, caused by van der Waals and other interactions is modelled as a Morse potential. The aggregation occurs when the steric barrier is overcome and the cores come into contact. Our simulations show that, with shallow interaction potentials, that is, with weak attractions and low barriers, the nanoaggregates form small agglomerates with ramified structure that are in metastable equilibrium with uniform solutions. These agglomerates can be described with a fractal dimensions below 1.5, which may represent soluble asphaltenes. The increase in attraction strength promotes aggregation and destabilizes the systems as in the case of dilution with a flocculant, for which several aggregation regimes are observed. Increasing the well-depth and/or barrier for nanoaggregate interaction leads to classical diffusion limited and reaction limited regimes. We find that with high barrier the clusters formed are less close-packed, and may represent the weak gel state typical for bitumen gel.

Detection of Geothermal Potential Zones Using Remote Sensing Techniques

The transition towards a new sustainable energy model—replacing fossil fuels with renewable sources—presents a multidisciplinary challenge. One of the major decarbonization issues is the question of to optimize energy transport networks for renewable energy sources. Within the range of renewable energies, the location and evaluation of geothermal energy is associated with costly processes, such as drilling, which limit its use. Therefore, the present research is aimed at applying different geomatic techniques for the detection of geothermal resources. The workflow is based on free/open access geospatial data. More specifically, remote sensing information (Sentinel-2A and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)), geological information, distribution of gravimetric anomalies, and geographic information systems have been used to detect areas of shallow geothermal potential in the northwest of the province of Orense, Spain. Due to the variety of parameters involved, and the complexity of the classification, a random forest classifier was employed, since this algorithm works well with large sets of data and can be used with categorical and numerical data. The results obtained allowed identifying a susceptible area to be operated on with a geothermal potential of 80 W·m−1 or higher.

Sound-driven single-electron transfer in a circuit of coupled quantum rails

Surface acoustic waves (SAWs) strongly modulate the shallow electric potential in piezoelectric materials. In semiconductor heterostructures such as GaAs/AlGaAs, SAWs can thus be employed to transfer individual electrons between distant quantum dots. This transfer mechanism makes SAW technologies a promising candidate to convey quantum information through a circuit of quantum logic gates. Here we present two essential building blocks of such a SAW-driven quantum circuit. First, we implement a directional coupler allowing to partition a flying electron arbitrarily into two paths of transportation. Second, we demonstrate a triggered single-electron source enabling synchronisation of the SAW-driven sending process. Exceeding a single-shot transfer efficiency of 99%, we show that a SAW-driven integrated circuit is feasible with single electrons on a large scale. Our results pave the way to perform quantum logic operations with flying electron qubits.

Tentative detection of the circumgalactic medium of the isolated low-mass dwarf galaxy WLM

ABSTRACT We report a tentative detection of the circumgalactic medium (CGM) of Wolf–Lundmark–Melotte (WLM), an isolated, low-mass (logM*/M⊙ ≈ 7.6), dwarf irregular galaxy in the Local Group (LG). We analyse an HST/COS archival spectrum of a quasar sightline (PHL2525), which is 45 kpc (0.5 virial radius) from WLM and close to the Magellanic Stream (MS). Along this sightline, two ion absorbers are detected in Si ii, Si iii, Si iv, C ii, and C iv at velocities of ∼−220 km s−1 (Component v-220) and ∼−150 km s−1 (Component v-150). To identify their origins, we study the position–velocity alignment of the components with WLM and the nearby MS. Near the magellanic longitude of PHL2525, the MS-related neutral and ionized gas moves at ≲−190 km s−1, suggesting an MS origin for Component v-220, but not for Component v-150. Because PHL2525 passes near WLM and Component v-150 is close to WLM’s systemic velocity (∼−132 km s−1), it is likely that Component v-150 arises from the galaxy’s CGM. This results in a total Si mass in WLM’s CGM of $M_{\rm Si}^{\rm CGM}\sim (0.2-1.0)\times 10^5~\mathrm{M}_\odot$ using assumption from other COS dwarf studies. Comparing $M_{\rm Si}^{\rm CGM}$ to the total Si mass synthesized in WLM over its lifetime (∼1.3 × 105 M⊙), we find ∼3 per cent is locked in stars, ∼6 per cent in the ISM, ∼15–77 per cent in the CGM, and the rest (∼14–76 per cent) is likely lost beyond the virial radius. Our finding resonates with other COS dwarf galaxy studies and theoretical predictions that low-mass galaxies can easily lose metals into their CGM due to stellar feedback and shallow gravitational potential.

Alternative heating systems for northern remote communities: Techno-economic analysis of ground-coupled heat pumps in Kuujjuaq, Nunavik, Canada

Nunavik is a subarctic remote region covering the northern third of Québec, Canada, where low efficiency and environmentally adverse diesel furnaces are currently used to meet residential heating demand. Studies focusing on building heating alternatives in subarctic climate are limited and hence, this work can help with the development of such systems in remote off-grid communities. Shallow geothermal potential was mapped for Kuujjuaq, the largest village in Nunavik. Four ground-coupled heat pump scenarios were analysed for a simulated 5-occupant residential dwelling, with heating needs of 71 MWh/year. Resulting maps show a relatively high ground potential for such cold region, ranging between 5.8 MWh/year and 22.9 MWh/year per borehole for heat exchanger lengths of 100 m–300 m. A 50-year life-cycle cost analysis of such systems reveal that a compression heat pump with electricity derived from solar photovoltaic panels has a net present cost as low as approximately CAD$179,000, representing the most economically attractive heating option in Kuujjuaq as compared to the currently subsidized, diesel furnace heating at CAD$277,000. This work verifies that shallow geothermal energy through state-of-the-art heat pumps is a financially interesting option in Kuujjuaq. Results can be extended to similar subarctic settings in Canada and worldwide.

Neutron star binary orbits in their host potential: effect on early r-process enrichment

ABSTRACT Coalescing neutron star binary (NSB) systems are primary candidates for r-process enrichment of galaxies. The recent detection of r-process elements in ultrafaint dwarf (UFD) galaxies and the abundances measured in classical dwarfs challenges the NSB merger scenario both in terms of coalescence time-scales and merger locations. In this paper, we focus on the dynamics of NSBs in the gravitational potentials of different types of host galaxies and on its impact on the subsequent galactic enrichment. We find that, for a ∼t−1 delay time distribution, even when receiving a low kick (∼10 km s−1) from the second supernova explosion, in shallow dwarf galaxy potentials NSBs tend to merge with a large off-set from the host galaxy. This results in a significant geometrical dilution of the amount of produced r-process elements that fall back and pollute the host galaxy gas reservoir. The combination of dilution and small number statistics produces a large scatter in the expected r-process enrichment within a single UFD or classical dwarf galaxy. Comparison between our results and observed europium abundances reveals a tension that even a systematic choice of optimistic parameters in our models cannot release. Such a discrepancy could point to the need of additional r-process production sites that suffer less severe dilution or to a population of extremely fast merging binaries.

City-scale solutions for the energy use of shallow urban subsurface resources – Bridging the gap between theoretical and technical potentials

One solution for reducing the current consumption of fossil fuels is a more frequent use of shallow geothermal energy. However, particularly regarding urban subsurface resources, increased use conflicts are predictable. Consequently, reasonable exploitation of subsurface resources requires an assessment of technologically achievable energy potentials with scientific based tools. We present application-oriented management tools which target on deriving shallow subsurface energy potentials. 3D groundwater flow and heat-transport models are used to capture groundwater flow and heat-transport dynamics on the city- and quarter-scale, 2D box models are used to quantify technically feasible extraction rates of well doublets for groundwater heat pump systems.For Basel (Switzerland), prospective large theoretical energy potentials can be derived for areas with high advective heat flux and high temperature gradients. Likewise, single city quarters are suitable for ‘active’ thermal use with well doublets, whereas thermal power potentials reach 1.2 MW. Regarding ‘passive’ installations of energy absorbers in subsurface structures located within the groundwater, energy potentials amount to 4 and up to 40 W m−2.The assessment results can be integrated into urban energy plans and support architects, city planners and potential users to acquire initial site-specific information on the technical feasibility of shallow geothermal energy systems.

Critical Behavior and Fractality in Shallow One-Dimensional Quasiperiodic Potentials.

Quasiperiodic systems offer an appealing intermediate between long-range ordered and genuine disordered systems, with unusual critical properties. One-dimensional models that break the so-called self-dual symmetry usually display a mobility edge, similarly as truly disordered systems in a dimension strictly higher than two. Here, we determine the critical localization properties of single particles in shallow, one-dimensional, quasiperiodic models and relate them to the fractal character of the energy spectrum. On the one hand, we determine the mobility edge and show that it separates the localized and extended phases, with no intermediate phase. On the other hand, we determine the critical potential amplitude and find the universal critical exponent ν≃1/3. We also study the spectral Hausdorff dimension and show that it is nonuniversal but always smaller than unity, hence showing that the spectrum is nowhere dense. Finally, applications to ongoing studies of Anderson localization, Bose-glass physics, and many-body localization in ultracold atoms are discussed.

An improved volumetric method of geothermal resources assessment for shallow ground combining geophysical data

Assessment of available heat capacity in the shallow ground is important to the development of ground source or geothermal heat pumps. A new volumetric method-based approach is proposed for evaluating shallow geothermal potential by combining microtremor survey results. Parameters such as thickness of clay and sandy gravel layers can be achieved by processing the microtremor filed data. The study area was divided into grids based on the different exploration sites. The heat present in each small unit was calculated using the revised volumetric method. This division into small units improved the accuracy of assessment of the geothermal potential and helped plot the distribution map of the available heat amount, which indicated optimal locations for development and utilization of shallow geothermal resources. Jimo, China was used as an example to depict the calculation flow. Since the microtremor survey method can identify the thickness of clay, sandy gravel, and fresh bedrock layers in shallow ground, the amount of shallow geothermal resources present above fresh bedrock was calculated. In Jimo, the amount of exploitable geothermal resources, using the traditional volumetric method, was found to be 4.92 × 1012 kJ. The proposed calculation method not only provided a higher corresponding value of 6.96 × 1012 kJ but also showed the regions with the highest potential of shallow geothermal resources. Hence, this approach provides an alternative method for geothermal potential assessment which can be used globally.

A machine learning approach for mapping the very shallow theoretical geothermal potential

The very shallow geothermal potential (vSGP) is increasingly recognized as a viable resource for providing clean thermal energy in urban and rural areas. This is primarily due to its reliability, low-cost installation, easy maintenance, and little constraints regarding ground-related laws and policies. We propose a methodology to extract the theoretical vSGP (installed in the uppermost 10 m of the ground, and mostly at depths of 1–2 m) at the national scale for Switzerland, based on a combination of Geographic Information Systems, traditional modelling, and machine learning (ML). The theoretical vSGP is based on the estimation of three thermal characteristics of the ground that impact significantly the geothermal potential, namely the monthly temperature at various depths in the surface layer, the thermal conductivity, and the thermal diffusivity. Each of the three variables is estimated separately, to a depth of 1 m below the surface, using the following general strategy: (1) collect significant data related to the variable, (2) if not existing, extract values for the variable at available locations with the help of traditional models and part of the data as input for these models, (3) train a ML model (with the Random Forests algorithm) using the extracted variable values as examples (training output labels) and related information contained in the data as features (training input samples), (4) use the trained ML model to estimate the variable in unknown locations, (5) estimate the uncertainty attached to the estimations. The methodology estimates values for (200 × 200) (m2) pixels forming a grid over Switzerland. The strategy, however, can be generalized to any country with significant data (topographic, weather, and surface layer/soil data) available. The results indicate a very non-negligible potential for very shallow geothermal systems in Switzerland.

Potential model for nuclear astrophysical fusion reactions with a square-well potential

The potential model for nuclear astrophysical reactions requires a considerably shallow nuclear potential when a square-well potential is employed to fit experimental data. We discuss the origin of this apparently different behavior from that obtained with a smooth Woods-Saxon potential, for which a deep potential is often employed. We argue that due to the sharp change of the potential at the boundary the radius parameter tends to be large in the square-well model, which results in a large absorption radius. The wave function then needs to be suppressed in the absorption region, which can eventually be achieved by using a shallow potential. We thus clarify the reason why the square-well potential has been able to reproduce a large amount of fusion data.

Effect of fine-tuning pore structures on the dynamics of confined water

Confinement of water in sub-nanometer pores strongly alters its vibrational dynamics from that of bulk water. The effect of confinement can, furthermore, be finely tuned by small changes in the size and symmetry of the confining pore. Using inelastic neutron scattering (INS), we recently studied the dynamics of water confined in the channels of beryl and cordierite in which, at low temperatures, water shows similar behavior, indicating an absence of hydrogen bonds acting on the water molecule and a shallow water potential in the direction perpendicular to the channels. In addition, we observed multiple tunneling modes (between 0.66 and 14.7 meV) in the INS spectra of beryl due to transitions between the split ground-state of the water protons. Here, we present a study of (i) the effect of pressure on the dynamics of water in beryl, (ii) the dynamics of water in beryl containing alkali metals (which results in changing the orientation of the water molecule in the crystal), and (iii) the dynamics of water in cordierite at low energies. We found a shift in the tunneling and vibrational modes of water in beryl to higher energies at 22 kbar relative to 1 bar. No tunneling modes were observed for water in cordierite and type-II water in beryl. Therefore, we conclude that very small differences in the size and structure of the pores and the orientation of the water molecule in these minerals result in changes in the potential of the water protons and drastic changes in the confined water dynamics.

A framework for assessing the technical and economic potential of shallow geothermal energy in individual and district heating systems: A case study of Slovenia

The deployment of geothermal energy systems can significantly contribute to climate change mitigation and play a part in the transition to a low carbon society. This study proposes a framework for identifying the shallow geothermal energy potential of new individual and district heating (DH) systems. The model accounts for thermal interference between neighbouring wells and borehole heat exchangers, where the main criteria for analysis are ground temperature, thermal conductivity, heat flow, and heat capacity. The paper presents a cost-effective area method for the identification of potential new DH areas, while considering the cost competitiveness of the heat supplied. Economic potential is determined based on the cost-effectiveness of the competing technologies, separately for urban and rural areas. The results show that although 54% of technical DH potential in Slovenia remains untapped, the future of shallow geothermal energy systems lies predominantly in individual systems, which have proven to be the most cost efficient solution on locations with favourable geological or hydro-geological conditions. Where possible, shallow geothermal energy can contribute from 2% to 25% of energy for heat production in analysed existing fossil fuel based DH systems, thus making shallow geothermal energy suitable for supplying base load power in an economical manner.

Techno-Economic Mapping for the Improvement of Shallow Geothermal Management in Southern Switzerland

Cantone Ticino, a mountainous region located in the southern part of Switzerland, is greatly affected by the continuous growth of subsurface exploitation through the use of both closed-loop and open-loop geothermal systems. In this study, techno-economic maps for shallow geothermal potential of Cantone Ticino are produced, considering closed-loop systems. The work starts with the identification of the main parameters affecting the techno-economic potential such as GST and thermal conductivity. Maps for different indicators of techno-economic feasibility are created and compared against real data/measurements. An empirical method is tailored to derive a map of the techno-economic geothermal potential, expressed as meters required to provide 1 kW of installed power. The produced map shows an overall discrepancy from real installed length data of approximately ±23%. Moreover, compared with current regulation, the produced maps show an unoptimized management of the shallow geothermal resource, since high potential zones are commonly located where the installation of BHE is not permitted and often closed-loop systems are installed where the estimated potential is lower, mainly in alluvial fans. In light of these considerations, the authorization process in Cantone Ticino for BHE should be revised taking into account the real techno-economic potential.