STATISTICAL PROPERTIES OF RANKINGS IN SPORTS AND GAMES

Any collection can be ranked. Sports and games are common examples of ranked systems: players and teams are constantly ranked using different methods. The statistical properties of rankings have been studied for almost a century in a variety of fields. More recently, data availability has allowed us to study rank dynamics: how elements of a ranking change in time. Here, we study the rank distributions and rank dynamics of 12 datasets from different sports and games. To study rank dynamics, we consider measures that we have defined previously: rank diversity, change probability, rank entropy, and rank complexity. We also introduce a new measure that we call “system closure” that reflects how many elements enter or leave the rankings in time. We use a random walk model to reproduce the observed rank dynamics, showing that a simple mechanism can generate similar statistical properties as the ones observed in the datasets. Our results show that while rank distributions vary considerably for different rankings, rank dynamics have similar behaviors, independently of the nature and competitiveness of the sport or game and its ranking method. Our results also suggest that our measures of rank dynamics are general and applicable for complex systems of different natures.

The Coming of the Drawloom: A Chapter in the Technological Transmission between Iran and India

In the history of technology, the loom has come to occupy an important place. While the horizontal handloom has a comparatively simple mechanism, this is not true of the vertical drawloom, which through centuries has developed complex forms. The question of the latter’s presence in India in early times has aroused some controversy. The case is made in this article that it arrived in the thirteenth century from Iran but failed to supplant the handloom in most areas of textile production, except for carpet weaving, mainly in Kashmir.

Unsupervised temporal consistency improvement for microscopy video segmentation with Siamese networks

We introduce a simple mechanism by which a CNN trained to perform semantic segmentation of individual images can be re-trained - with no additional annotations - to improve its performance for segmentation of videos. We put the segmentation CNN in a Siamese setup with shared weights and train both for segmentation accuracy on annotated images and for segmentation similarity on unlabelled consecutive video frames. Our main application is live microscopy imaging of membrane-less organelles where the fluorescent groundtruth for virtual staining can only be acquired for individual frames. The method is directly applicable to other microscopy modalities, as we demonstrate by experiments on the Cell Segmentation Benchmark. Our code is available at https://github.com/kreshuklab/ learning-temporal-consistency.

Light dark matter from inflaton decay

We propose a simple mechanism of light dark matter (DM) production from the decay of the oscillating inflaton condensation. If the reheating temperature after inflation is higher than the inflaton mass, which is of the same order of the momentum of the DM at the time of the production, the DM momentum can be suppressed compared to the temperature of the thermal plasma if the interaction of the DM is weak enough. Consequently, the DM can be cold enough to avoid the observational constraints on the warm DM, like the Lyman-α bound even if the DM mass is small. We study the bosonic and fermionic DM production from the inflaton decay, taking into account the effect of the stimulated emission and Pauli blocking, respectively. In both cases, the DM can be cold and abundant enough to be a viable candidate of the DM. We also apply our mechanism to the production of isocurvature-problem-free axion DM and Dirac sea DM of right-handed neutrino consistent the seesaw relation for the active neutrino masses.

On-Chip Micro Mixer Driven by Elastic Wall with Virtual Actuator

In this paper, we propose an on-chip micromixer driven by an elastic wall with a virtual actuator. The on-chip micro mixer is composed of a circular chamber surrounded by a ring-shaped channel under isolation with an elastic wall. When vibrational pressure is put on the driving channel by an actuator, the volume of the circular chamber changes through the deformation of the elastic wall, as if there exists a virtual actuator near the wall. As a result, the liquid in the circular chamber is pushed out and pulled through the neck channel. This action creates a swirling flow in the circular chamber while maintaining isolation from the driving channel. Through experiments, we confirmed the swirling flow under an isolated environment using an air-based valve. The advantage of this approach is that the micromixer can be designed with a single layer having a simple mechanism.

Freedom to choose between public resources promotes cooperation

As cooperation incurs a cost to the cooperator for others to benefit, its evolution seems to contradict natural selection. How evolution has resolved this obstacle has been among the most intensely studied questions in evolutionary theory in recent decades. Here, we show that having a choice between different public resources provides a simple mechanism for cooperation to flourish. Such a mechanism can be at work in many biological or social contexts where individuals can form different groups or join different institutions to perform a collective action task, or when they can choose between collective actions with different profitability. As a simple evolutionary model suggests, defectors tend to join the highest quality resource in such a context. This allows cooperators to survive and out-compete defectors by sheltering in a lower quality resource. Cooperation is maximized, however, when the qualities of the two highest quality resources are similar, and thus, they are almost interchangeable.

Competition Between Public Resources Promotes Cooperation

As cooperation incurs a cost to the cooperator for others to benefit, its evolution seems to contradict natural selection. How evolution has resolved this obstacle, has been among the most intensely studied questions in the evolutionary theory in recent decades. Here, by showing that competition between public resources provides a simple mechanism for cooperation to flourish, we uncover a novel road to the evolution of cooperation. Such a mechanism can be at work in many biological or social contexts where individuals can form different groups or join different institutions to perform a collective action task, or when they can choose between different collective actions, with different profitability. As a simple evolutionary model suggests, in such a context, defectors tend to join the highest quality resource. This allows cooperators to survive and out-compete defectors by sheltering in a lower quality resource. Cooperation level is maximized however, when the qualities of the two highest quality resources are similar, and thus, they can perform the most competitively to attract individuals.