6,482 research outputs found
The fate of cooperation during range expansions
Cooperation is beneficial for the species as a whole, but, at the level of an
individual, defection pays off. Natural selection is then expected to favor
defectors and eliminate cooperation. This prediction is in stark contrast with
the abundance of cooperation at all levels of biological systems: from cells
cooperating to form a biofilm or an organism to ecosystems and human societies.
Several explanations have been proposed to resolve this paradox, including
direct reciprocity, kin, and group selection. However, our work builds upon an
observation that selection on cooperators might depend both on their relative
frequency in the population and on the population density. We find that this
feedback between the population and evolutionary dynamics can substantially
increase the frequency of cooperators at the front of an expanding population,
and can even lead to a splitting of cooperators from defectors. After
splitting, only cooperators colonize new territories, while defectors slowly
invade them from behind. Since range expansions are very common in nature, our
work provides a new explanation of the maintenance of cooperation
On the large values of the Riemann zeta-function on short segments of the critical line
In this paper, we obtain a series of new conditional lower bounds for the
modulus and the argument of the Riemann zeta function on very short segments of
the critical line, based on the Riemann hypothesis. In particular, the
conditional solution of one problem of A.A.Karatsuba is given. Some typos of
the previous versions are corrected (in particular, the important remark of
Prof. Yan Fyodorov is taken into account). The reference to the grant of
Russian Scientific Fund is also added.Comment: 40 pages, 4 figure
Quantum Hypercomputation - Hype or Computation?
A recent attempt to compute a (recursion--theoretic) non--computable function using the quantum adiabatic algorithm is criticized and found wanting. Quantum algorithms may outperform classical algorithms in some cases, but so far they retain the classical (recursion--theoretic) notion of computability. A speculation is then offered as to where the putative power of quantum computers may come from
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