Connecting Angular Momentum and Galactic Dynamics: The complex Interplay between Spin, Mass, and Morphology

The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use the Magneticum simulations. We successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40 percent smaller than the specific angular momentum of the total DM halo and shows a significant scatter.Comment: 25 pages, accepted by ApJ, www.magneticum.or

Achieving Strong Magnon Blockade through Magnon Squeezing in a Cavity Magnetomechanical System

We propose a scheme to achieve magnon (photon) blockade by using magnon squeezing within a cavity magnomechanical system under weak pump driving. Under ideal conditions, we observe a substantial magnon blockade effect, as well as simultaneous photon blockade. Moreover, both numerical and analytical results match perfectly, providing robust evidence of consistency. In addition to calculating optimal parametric gain and detuning values, we can improve the second-order correlation function. The proposed scheme will be a pioneering approach towards magnon (photon) blockade in experimental cavity magnomechanical systems.Comment: 6 page

Quantum Probes for the Characterization of Nonlinear Media

Active optical media leading to interaction Hamiltonians of the form $H = \tilde{\lambda}\, (a + a^{\dagger})^{\zeta}$ represent a crucial resource for quantum optical technology. In this paper, we address the characterization of those nonlinear media using quantum probes, as opposed to semiclassical ones. In particular, we investigate how squeezed probes may improve individual and joint estimation of the nonlinear coupling $\tilde{\lambda}$ and of the nonlinearity order $\zeta$. Upon using tools from quantum estimation, we show that: i) the two parameters are compatible, i.e. the may be jointly estimated without additional quantum noise; ii) the use of squeezed probes improves precision at fixed overall energy of the probe; iii) for low energy probes, squeezed vacuum represent the most convenient choice, whereas for increasing energy an optimal squeezing fraction may be determined; iv) using optimized quantum probes, the scaling of the corresponding precision with energy improves, both for individual and joint estimation of the two parameters, compared to semiclassical coherent probes. We conclude that quantum probes represent a resource to enhance precision in the characterization of nonlinear media, and foresee potential applications with current technology

An improved SPH scheme for cosmological simulations

We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations of galaxies and the large-scale structure. In particular, we combine, implement, modify and test a vast majority of SPH improvement techniques in the latest instalment of the GADGET code. We use the Wendland kernel functions, a particle wake-up time-step limiting mechanism and a time-dependent scheme for artificial viscosity, which includes a high-order gradient computation and shear flow limiter. Additionally, we include a novel prescription for time-dependent artificial conduction, which corrects for gravitationally induced pressure gradients and largely improves the SPH performance in capturing the development of gas-dynamical instabilities. We extensively test our new implementation in a wide range of hydrodynamical standard tests including weak and strong shocks as well as shear flows, turbulent spectra, gas mixing, hydrostatic equilibria and self-gravitating gas clouds. We jointly employ all modifications; however, when necessary we study the performance of individual code modules. We approximate hydrodynamical states more accurately and with significantly less noise than standard SPH. Furthermore, the new implementation promotes the mixing of entropy between different fluid phases, also within cosmological simulations. Finally, we study the performance of the hydrodynamical solver in the context of radiative galaxy formation and non-radiative galaxy cluster formation. We find galactic disks to be colder, thinner and more extended and our results on galaxy clusters show entropy cores instead of steadily declining entropy profiles. In summary, we demonstrate that our improved SPH implementation overcomes most of the undesirable limitations of standard SPH, thus becoming the core of an efficient code for large cosmological simulations.Comment: 21 figures, 2 tables, accepted to MNRA

Analysis of water delivery performance of smallholder irrigation schemes in Ethiopia: Diversity and lessons across schemes, typologies and reaches

Irrigation systems consist of three interdependent components involving: the irrigation scheme, the on-farm management and the organizations. The irrigation scheme refers to the infrastructure for water acquisition and distribution (water delivery). This study focused on water delivery performance of 10 smallholders irrigation schemes in four regions of Ethiopia, representing diverse water sources, distribution systems, command areas (50–6000 ha) and number of beneficiary farmers (233–500 farm households) and across agro-ecologies as represented by elevation ranges (1500–2725 masl). Relative irrigation supply (RIS), irrigation intensity (Ii), cropping intensity (CI), farm level adequacy (FLA), sustainability of irrigated land (SIL), and equity and field application efficiency were employed as performance indicators. The study involved focus group discussions, household surveys and measurements of water flow across selected points of water delivery systems during 2014/2015 cropping season. More than 300 sample farmers were selected randomly from different reaches (head, mid and tail) of the schemes and before the analysis the 10 irrigation schemes were clustered into three typologies (modern, semi-modern and traditional schemes) using seven comprehensive and weighted indicators. The result showed that irrigation typology developed in this study enabled to identify three relatively homogeneous irrigation schemes typologies: modern, semi-modern and traditional. There was apparent diversity of the study schemes in terms of indicators used. At typology level, as illustrated by the RIS, the highest amount of water was diverted for semi-modern schemes (RIS of 3.84); while the highest water delivery at farm relative delivery (FRD) was recorded for the modern schemes (FRD 2.21). Traditional schemes consistently showed lower value for both RIS and FRD. Regardless of their typologies, all study schemes suffer from mismatch of water demand and supply. The lower the RIS and FRD values, the stronger was the water supply disparities between irrigation reaches. Assessment of farmers’ perception on fairness of irrigation water delivery substantiate these arguments. Implicitly, it is important to track the fate of diverted excess water. Field observation and empirical evidences show divergent points of losses of excess water indicating focus areas of improved water conservation on smallholder irrigation schemes. For example the largest proportion of over supplied water (~100%) in the semimodern schemes and in traditional schemes was lost in the conveyance and distribution systems. For modern schemes water losses in the processes of conveyance was low (26%), while the significant proportion of water (76%) was lost on farm. In view of this evidence, we concluded that irrigation schemes in Ethiopia, regardless of their typology, have low water delivery performance. As every scheme has shown its own strength and weakness, concluding sustainability in terms of typology is misleading and this suggests that policy directions should be based on composite sustainability indices

Appraisal of the Sesame production opportunities and constraints, and farmer-preferred varieties and traits, in eastern and southwestern Ethiopia

Open access article; Published online: 11 Oct 2021Sesame (Sesamum indicum L.) is an important oilseed crop with well-developed value chains. It is Ethiopia’s most valuable export commodity after coffee (Coffea arabica L.), contributing to socioeconomic development. The productivity of the crop is low and stagnant in Ethiopia and other major sesame growing regions in sub-Saharan Africa (<0.6 t/ha) due to a multitude of production constraints. The objective of this study was to document sesame production opportunities and constraints, as well as farmer- and market-preferred varieties and traits, in eastern and southwestern Ethiopia as a guide for large-scale production and breeding. A participatory rural appraisal (PRA) study was conducted in two selected sesame growing regions and four districts in Ethiopia. Data were collected from 160 and 46 sesame farmers through semistructured questionnaires and focus group discussions. Sesame is grown by all respondent farmers in the study areas for food and as a source of cash. Most respondent farmers (56%) reported cultivating sesame using seeds of unknown varieties often sourced from the informal seed sector. About 83% of the respondents reported lack of access to improved seeds as the most important production constraint, followed by low yield gains from cultivating the existing varieties (reported by 73.8% of respondents), diseases (69.4%), and low market price (68.8%). Other production constraints included insect pests (59.4%), lack of market information (55%), and high cost of seed (50%). The above constraints were attributed to the absence of a dedicated breeding programme, lack of a formal seed sector, poor extension services, and underdeveloped pre- and postharvest infrastructures. The most important market-preferred traits of sesame included true-to-type seed (reported by 36.3% of respondents), white seed colour (28.8%), and high seed oil content (23.8%). The vital farmer-preferred attributes included reasonable market price (reported by 11.3% of respondents), resistance to crop diseases (10.9%), drought tolerance (10.3%), resistance to crop insect pests (9.2%), higher seed yield (8.9%), higher thousand-seed weight (7.2%), higher oil content (6.3%), white seed colour (6.1%), early maturity (6.1%), and good oil qualities such as aroma and taste (5.7%). Therefore, there is a need for a dedicated sesame genetic improvement programme by integrating the above key production constraints and market- and farmer-preferred traits to develop and deploy new generation varieties to enhance the production, productivity, and adoption of sesame cultivars in Ethiopia

The effect of physical water quality and water level changes on the occurrence and density of <i>Anopheles</i> mosquito larvae around the shoreline of the Koka reservoir, central Ethiopia

Entomological studies to determine the effect of the physical characteristics of mosquito larval breeding water bodies and reservoir water level changes on the occurrence of Anopheles mosquito larvae were conducted in two villages at Koka reservoir in central Ethiopia between August and December 2007. Of the two study villages, Ejersa is located close to the reservoir, and Kuma is 5 km away from it. Data on the type, number and physical characteristics of Anopheles larval breeding habitat, species composition and densities of anopheles mosquitoes in and around the study villages were investigated and recorded. Meteorological and reservoir water level data were compared with availability of Anopheles larval breeding sites and densities. Entomological data, derived from weekly larval collections, showed that Anopheles pharoensis Theobald, Anopheles gambiae s.l. Giles, Anopheles coustani Laveran and Anopheles squamosus Theobald were breeding in the study area. The mean larval density of An. gambiae s.l. in this study was higher in slightly turbid and shallow aquatic habitat than in turbid and relatively deep aquatic habitat. The density of An. pharoensis in habitat with floating vegetation and with relatively shady conditions was significantly higher than that of less shaded aquatic habitat and greater emergent vegetation. There was also a positive correlation between the occurrence of Anopheles larvae with the water and daily minimum atmospheric temperature. Similarly at Ejersa, over the sampling period, there was a positive correlation between falling reservoir water levels and the number of positive breeding habitats. These results confirm that physical characteristics of the water bodies play an important role in the species composition, total Anopheles larval count, and the density of Anopheles mosquitoes. Suitable breeding habitat in the vicinity of the reservoir village was strongly associated with the reservoir. This is particularly important for An. pharoensis and An. gambiae s.l. which are important vectors of malaria in the area