1,032 research outputs found
Innovation rather than improvement: a solvable high-dimensional model highlights the limitations of scalar fitness
Much of our understanding of ecological and evolutionary mechanisms derives
from analysis of low-dimensional models: with few interacting species, or few
axes defining "fitness". It is not always clear to what extent the intuition
derived from low-dimensional models applies to the complex, high-dimensional
reality. For instance, most naturally occurring microbial communities are
strikingly diverse, harboring a large number of coexisting species, each of
which contributes to shaping the environment of others. Understanding the
eco-evolutionary interplay in these systems is an important challenge, and an
exciting new domain for statistical physics. Recent work identified a promising
new platform for investigating highly diverse ecosystems, based on the classic
resource competition model of MacArthur. Here, we describe how the same
analytical framework can be used to study evolutionary questions. Our analysis
illustrates how, at high dimension, the intuition promoted by a one-dimensional
(scalar) notion of fitness can become misleading. Specifically, while the
low-dimensional picture emphasizes organism cost or efficiency, we exhibit a
regime where cost becomes irrelevant for survival, and link this observation to
generic properties of high-dimensional geometry.Comment: 8 pages, 4 figures + Supplementary Materia
Power-law spin correlations in a perturbed honeycomb spin model
We consider spin- model on the honeycomb lattice~\cite{Kitaev06}
in presence of a weak magnetic field . Such a perturbation
destroys exact integrability of the model in terms of gapless fermions and
\textit{static} fluxes. We show that it results in appearance of a
long-range tail in the irreducible dynamic spin correlation function: , where is
proportional to the density polarization function of fermions
Energy-ordered resource stratification as an agnostic signature of life
The search for extraterrestrial life hinges on identifying biosignatures,
often focusing on gaseous metabolic byproducts as indicators. However, most
such biosignatures require assuming specific metabolic processes. It is widely
recognized that life on other planets may not resemble that of Earth, but
identifying biosignatures ``agnostic'' to such assumptions has remained a
challenge. Here, we propose a novel approach by considering the generic outcome
of life: the formation of competing ecosystems. We use a minimal model to argue
that the presence of ecosystem-level dynamics, characterized by ecological
interactions and resource competition, may yield biosignatures independent of
specific metabolic activities. Specifically, we propose the emergent
stratification of chemical resources in order of decreasing energy content as a
candidate new biosignature. While likely inaccessible to remote sensing, this
signature could be relevant for sample return missions, or for detection of
ancient signatures of life on Earth itself.Comment: 5 pages, 3 figure
Generalized end-product feedback circuit senses high dimensional environmental fluctuations
Understanding computational capabilities of simple biological circuits, such
as the regulatory circuits of single-cell organisms, remains an active area of
research. Recent theoretical work has shown that a simple regulatory
architecture based on end-product inhibition can exhibit predictive behavior by
learning fluctuation statistics of one or two environmental parameters. Here we
extend this analysis to higher dimensions. We show that as the number of inputs
increases, a generalized version of the circuit can learn not only the dominant
direction of fluctuations, as shown previously, but also the subdominant
fluctuation modes.Comment: 8 pages, 6 figure
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