stable sets
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2021 ◽  
Vol 288 (1962) ◽  
Author(s):  
D. W. Kikuchi ◽  
K. Reinhold

Animals exhibit extensive intraspecific variation in behaviour. Causes of such variation are less well understood. Here, we ask when competition leads to the maintenance of multiple behavioural strategies. We model variability using the timing of bird migration as an example. Birds often vary in when they return from non-breeding grounds to establish breeding territories. We assume that early-arriving birds (counting permanent residents as ‘earliest’) select the best territories. But arriving before the optimal (frequency-independent) breeding date incurs a fitness penalty. Using simulations, we find stable sets of return dates. When year-round residency is viable, the greatest between-individual variation occurs when a small proportion of permanent residents is favoured, and the rest of the population varies in their return times. However, when fitness losses due to year-round residency exceed the benefits of breeding in the worst territory, all individuals migrate, although their return dates often vary continuously. In that case, individual variation is inversely related to fitness risks and positively related to territory inequality. This result is applicable across many systems: when there is more to gain through competition, or when its risks are small, a diversity of individual strategies prevails. Additionally, stability can depend upon the distribution of resources.


2021 ◽  
Vol 6 (3) ◽  
pp. 138-160
Author(s):  
Elena V. Novoselova

The article is dedicated to the analysis of Peruvian travelogues of German-speaking travelers in the second half of 19th — early 20th centuries. Until now, this material has not attracted the attention of americanists. In the present analysis the author sets the following tasks: identifying the place of Peru in the German social and cultural discourse of the corresponding period; describing the social portrait of the German traveler in Peru; highlighting the main patterns underlying the image of Peru created by travelers; analyzing factors that influenced the creation of these patterns. The analysis shows the following results. First, the place of Peru in German discourse can be described as insignificant. Secondly, the typical German traveler to Peru was an educated middle-class person with a certain background concerning the Peruvian theme. Third, the author identifies the following patterns — stable sets of ideas about Peru: exoticism, mostly negative image of local habitants, dichotomy of the Peruvian past and present, in which the past acts as an era of glory, and the present — as the time of decline; view of the landscape as a reflection of the political and economic state of the country. The author also characterizes the main descriptive model of Peru for German travelers as “realistic”. Finally, the author identifies some factors that influenced the formation of the image of this country, in particular, the colonial discourse and the racial theory, as well as the political sympathies of the travelers themselves.


Synthese ◽  
2021 ◽  
Author(s):  
Samuli Reijula

AbstractReal kinds, both natural and social categories, are characterized by rich inductive potential. They have relatively stable sets of conceptually independent projectable properties. Somewhat surprisingly, even some purely social categories (e.g., ethnicity, gender, political orientation) show such multiple projectability. The article explores the origin of the inductive richness of social categories and concepts. I argue that existing philosophical accounts provide only a partial explanation, and mechanisms of boundary formation and stabilization must be brought into view for a more comprehensive account of inductively rich social categories.


2021 ◽  
Author(s):  
Jumei Yue ◽  
Yongyi Yan ◽  
Zengqiang Chen

2021 ◽  
Author(s):  
Jadder Bismarck de Sousa Cruz ◽  
Cândida Nunes da Silva ◽  
Orlando Lee

Let $k$ be a positive integer. A \emph{partial $k$-coloring} of a digraph $D$ is a set $\calC$ of $k$ disjoint stable sets and has \emph{weight} defined as $\sum_{C \in \calC} |C|$. An \emph{optimal} $k$-coloring is a $k$-coloring of maximum weight. A \emph{path partition} of a digraph $D$ is a set $\calP$ of disjoint paths of $D$ that covers its vertex set and has \emph{$k$-norm} defined as $\sum_{P \in \mathcal{P}} \min\{|P|,k\}$. A path partition $\calP$ is \emph{$k$-optimal} if it has minimum $k$-norm. A digraph $D$ is \emph{matching-spine} if its vertex set can be partitioned into sets $X$ and $Y$, such that $D[X]$ has a Hamilton path and the arc set of $D[Y]$ is a matching. Linial (1981) conjectured that the $k$-norm of a $k$-optimal path partition of a digraph is at most the weight of an optimal partial $k$-coloring. We present some partial results on this conjecture for matching-spine digraphs.


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