Editorial: special issue on matching under preferences

This special issue of Algorithms is devoted to the study of matching problems involving ordinal preferences from the standpoint of algorithms and complexit

New and simple algorithms for stable flow problems

Stable flows generalize the well-known concept of stable matchings to markets in which transactions may involve several agents, forwarding flow from one to another. An instance of the problem consists of a capacitated directed network, in which vertices express their preferences over their incident edges. A network flow is stable if there is no group of vertices that all could benefit from rerouting the flow along a walk. Fleiner established that a stable flow always exists by reducing it to the stable allocation problem. We present an augmenting-path algorithm for computing a stable flow, the first algorithm that achieves polynomial running time for this problem without using stable allocation as a black-box subroutine. We further consider the problem of finding a stable flow such that the flow value on every edge is within a given interval. For this problem, we present an elegant graph transformation and based on this, we devise a simple and fast algorithm, which also can be used to find a solution to the stable marriage problem with forced and forbidden edges. Finally, we study the stable multicommodity flow model introduced by Kir\'{a}ly and Pap. The original model is highly involved and allows for commodity-dependent preference lists at the vertices and commodity-specific edge capacities. We present several graph-based reductions that show equivalence to a significantly simpler model. We further show that it is NP-complete to decide whether an integral solution exists

The intertwined role of social and financial remittances in new firms' creation

The paper investigates the role of financial and social remittances in promoting new business creation in migrants’ home countries. By considering a panel of 143 countries during the period 2006–2018, we propose a way to operationalize the complex definition of social remittances and show that both financial and social remittances are positively correlated with the decision to create new firms, even though the effects of financial remittances crucially depend on the level of social remittances. This non-linear relationship points to the fact that countries with better institutions are likely to generate more intense flows of social remittances. However, they also allow for faster socio-economic integration of migrants and may weaken diasporas’ interest and direct financial engagement in entrepreneurial projects in the country of origin. Results obtained on the entire sample are confirmed when looking at the two subsamples of developing and non-OECD countries, respectively

Movement, Habitat Use and Detection Probability of Bridle Shiner Estimated by Patch Occupancy Modeling in a Connecticut Watershed

The bridle shiner (Notropis bifrenatus) is believed to have once been an important prey item throughout its native range; however, recent reports suggest populations have declined significantly and the species is now widely considered as imperiled. Habitats that are associated with this species are typically difficult to sample using traditional methods, making it unclear how much of the observed range reduction could be actual or perceived. My objectives were to estimate detection probability of bridle shiner, evaluate the importance of habitat on their distribution, and determine patterns of movement among habitat patches. I employed a repeated surveys design to estimate detection probability based on capture history and to draw inferences about sites where the species was never encountered. Bridle shiner were batch marked to evaluate among-patch movement distances and frequencies. Movement was infrequent and overall detection probability was high. Detectability was negatively associated with mean water velocity and positively associated with abundance. Occupied habitats tended to have higher springtime macrophyte cover, stable flows over time, and were connected by short distances to similar areas. Among occupied patches, those with shallower mean depths supported bridle shiner in high abundance later in the year, which may be an indication of habitat that is important for recruitment and survival. My findings suggest that false absences are not likely the cause of reported declines in Connecticut and that habitat degradation may be a leading cause of extirpations throughout the state

Movement, Habitat Use and Detection Probability of Bridle Shiner Estimated by Patch Occupancy Modeling in a Connecticut Watershed

The bridle shiner (Notropis bifrenatus) is believed to have once been an important prey item throughout its native range; however, recent reports suggest populations have declined significantly and the species is now widely considered as imperiled. Habitats that are associated with this species are typically difficult to sample using traditional methods, making it unclear how much of the observed range reduction could be actual or perceived. My objectives were to estimate detection probability of bridle shiner, evaluate the importance of habitat on their distribution, and determine patterns of movement among habitat patches. I employed a repeated surveys design to estimate detection probability based on capture history and to draw inferences about sites where the species was never encountered. Bridle shiner were batch marked to evaluate among-patch movement distances and frequencies. Movement was infrequent and overall detection probability was high. Detectability was negatively associated with mean water velocity and positively associated with abundance. Occupied habitats tended to have higher springtime macrophyte cover, stable flows over time, and were connected by short distances to similar areas. Among occupied patches, those with shallower mean depths supported bridle shiner in high abundance later in the year, which may be an indication of habitat that is important for recruitment and survival. My findings suggest that false absences are not likely the cause of reported declines in Connecticut and that habitat degradation may be a leading cause of extirpations throughout the state