arXiv subjects

Nadav Shnerb

Publications and source records attributed to Nadav Shnerb.

6 recordsLinked to original sources

arXiv2023

Stability and Fluctuations in Complex Ecological Systems

From 08-12 August, 2022, 32 individuals participated in a workshop, Stability and Fluctuations in Complex Ecological Systems, at the Lorentz Center, located in Leiden, The Netherlands. An interdisciplinary dialogue between ecologists, mathematicians, and physicists provided a foundation of important problems to consider over the next 5-10 years. This paper outlines eight areas including (1) improving our understanding of the effect of scale, both temporal and spatial, for both deterministic and stochastic problems; (2) clarifying the different terminologies and definitions used in different scientific fields; (3) developing a comprehensive set of data analysis techniques arising from different fields but which can be used together to improve our understanding of existing data sets; (4) having theoreticians/computational scientists collaborate closely with empirical ecologists to determine what new data should be collected; (5) improving our knowledge of how to protect and/or restore ecosystems; (6) incorporating socio-economic effects into models of ecosystems; (7) improving our understanding of the role of deterministic and stochastic fluctuations; (8) studying the current state of biodiversity at the functional level, taxa level and genome level.

q-bio.PE↗

arXiv2020

Alternative states in plant communities driven by a life-history tradeoff and demographic stochasticity

Life-history tradeoffs among species are major drivers of community assembly. Most studies investigate how tradeoffs promote deterministic coexistence of species. It remains unclear how tradeoffs may instead promote historically contingent exclusion of species, where species dominance is affected by initial abundances, causing alternative community states. Focusing on the establishment-longevity tradeoff, we study the transient dynamics and equilibrium outcomes of competitive interactions in a simulation model of plant community assembly. We show that, in this model, the establishment-longevity tradeoff is a necessary but not sufficient condition for alternative stable equilibria that require also low fecundity for both species. An analytical approximation of our simulation model demonstrates that alternative stable equilibria are driven by demographic stochasticity in the number of seeds arriving at each establishment site. This site-scale stochasticity is only affected by fecundity and therefore occurs even in infinitely large communities. In many cases where the establishment-longevity tradeoff does not cause alternative stable equilibria, it still decreases the rate of convergence toward the single equilibrium, resulting in decades of transient dynamics that can appear indistinguishable from alternative stable equilibria in empirical studies.

q-bio.PE↗

arXiv2014

Simultaneous first and second order percolation transitions in interdependent networks

In a system of interdependent networks, an initial failure of nodes invokes a cascade of iterative failures that may lead to a total collapse of the whole system in a form of an abrupt first order transition. When the fraction of initial failed nodes $1-p$ reaches criticality, $p=p_c$, the abrupt collapse occurs by spontaneous cascading failures. At this stage, the giant component decreases slowly in a plateau form and the number of iterations in the cascade, $τ$, diverges. The origin of this plateau and its increasing with the size of the system remained unclear. Here we find that simultaneously with the abrupt first order transition a spontaneous second order percolation occurs during the cascade of iterative failures. This sheds light on the origin of the plateau and on how its length scales with the size of the system. Understanding the critical nature of the dynamical process of cascading failures may be useful for designing strategies for preventing and mitigating catastrophic collapses.

cond-mat.stat-mech↗

arXiv2008

Transition Phenomena Induced by Internal Noise and Quasi-absorbing State

We study a simple chemical reaction system and effects of the internal noise. The chemical reaction system causes the same transition phenomenon discussed by Togashi and Kaneko [Phys. Rev. Lett. 86 (2001) 2459; J. Phys. Soc. Jpn. 72 (2003) 62]. By using the simpler model than Togashi-Kaneko's one, we discuss the transition phenomenon by means of a random walk model and an effective model. The discussion makes it clear that quasi-absorbing states, which are produced by the change of the strength of the internal noise, play an important role in the transition phenomenon. Stabilizing the quasi-absorbing states causes bifurcation of the peaks in the stationary probability distribution discontinuously.

cond-mat.stat-mech↗

arXiv1995

The Quantization process for the Driven Quantum Well - Perturbative Expansion and the Classical Limit

We consider the quantum mechanical behavior of a driven particle in an infinite 1D potential well. We show that the time dependent perturbation series is induced by the delicate non-trivial properties of the momentum operator in this case, namely, its non-self-adjointness. Using this expansion, we calculate the first order contribution to the cross section and the energy gain, and discuss their classical limit. In this limit the one-period energy gain converges to its classical analog - the classical local (momentum space) diffusion coefficient. Both the classical and quantum mechanical results are compared with numerical simulations.

cond-mat↗

arXiv1995

Traces of a Quantum Anti-Resonance in a Driven System

It has been previously shown, that classically chaotic kicked systems, whose unperturbed spectrum posseses one energy scale, admits a quantum anti-resonance (QAR) behavior. In this study we extend the conditions under which which this QAR occurs for the case of a two-sided kicked 1D infinite potential well. It is then shown by a perturbative argument that this QAR effects the behavior of the equivalent driven well, i.e., the number of periods needed to leave the initial state has a sharp peak around the QAR. We give a numerical evidence that the anti resonance persists even for large values of the perturbation parameter.

cond-mat↗