Though individuals prefer to join groups with high quality peers, there are also advantages from being high up in the pecking order within a group. We show that sorting of agents in this environment results in an overlapping interval structure in the type space. Segregation and mixing coexist in a stable equilibrium. When transfers are possible our stable equilibrium corresponds to a competitiv...

Science teaching detached itself from reality and became restricted to the classrooms and textbooks with their overreliance on standardized and repetitive exercises, while students keep their own alternative conceptions. Papert, displeased with this inefficient learning process as early as 1980, championed physics microworlds, where students could experience a variety of laws of motion, from Ar...

The incidence of multifetal pregnancies has increased dramatically over the past two decades, mainly because of the widespread use of ovulation induction agents and assisted reproduction techniques. These techniques have been a matter of concern since twin and higher order pregnancies have long been associated with an increased risk of maternal complications as well as a high prevalence of pren...

The incidence of multifetal pregnancies has increased dramatically over the past two decades, mainly because of the widespread use of ovulation induction agents and assisted reproduction techniques. These techniques have been a matter of concern since twin and higher order pregnancies have long been associated with an increased risk of maternal complications as well as a high prevalence of pren...

We try to answer the question which is the “right” foundation of mathematics, second order logic or set theory. Since the former is usually thought of as a formal language and the latter as a first order theory, we have to rephrase the question. We formulate what we call the second order view and a competing set theory view, and then discuss the merits of both views. On the surface these two vi...