Non-normality and non-monotonic dynamics in complex reaction networks

Complex chemical reaction networks, which underlie many industrial and biological processes, often exhibit non-monotonic changes in chemical species concentrations. Such non-monotonic dynamics are in principle possible even in a linear model if the matrix defining the model is non-normal, as charact...

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Main Authors: Zachary G. Nicolaou, Takashi Nishikawa, Schuyler B. Nicholson, Jason R. Green, Adilson E. Motter
Format: Article
Language:English
Published: American Physical Society 2020-10-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.2.043059
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author Zachary G. Nicolaou
Takashi Nishikawa
Schuyler B. Nicholson
Jason R. Green
Adilson E. Motter
author_facet Zachary G. Nicolaou
Takashi Nishikawa
Schuyler B. Nicholson
Jason R. Green
Adilson E. Motter
author_sort Zachary G. Nicolaou
collection DOAJ
description Complex chemical reaction networks, which underlie many industrial and biological processes, often exhibit non-monotonic changes in chemical species concentrations. Such non-monotonic dynamics are in principle possible even in a linear model if the matrix defining the model is non-normal, as characterized by a necessarily non-orthogonal set of eigenvectors. However, the extent to which non-normality is responsible for non-monotonic behavior remains an open question. Here, using a master equation to model the reaction dynamics, we derive a general condition for observing non-monotonic dynamics of individual species, establishing that non-normality promotes non-monotonicity but is not a requirement for it. In contrast, we show that non-normality is a requirement for non-monotonic dynamics to be observed in the Rényi entropy. Using hydrogen combustion as an example application, we demonstrate that non-monotonic dynamics under experimental conditions are supported by a linear chain of connected components, at variance with the dominance of a single giant component observed in typical random reaction networks. The exact linearity of the master equation enables development of a rigorous theory and simulations for dynamical networks of unprecedented sizes (approaching 10^{5} dynamical variables, even for a network of only 20 reactions and involving less than 100 atoms). Our conclusions are expected to hold for other combustion processes, and the general theory we develop is applicable to all chemical reaction networks, including biological ones.
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spelling doaj.art-6e9be1eb827348a1805cd2abd2820d682024-04-12T17:02:12ZengAmerican Physical SocietyPhysical Review Research2643-15642020-10-012404305910.1103/PhysRevResearch.2.043059Non-normality and non-monotonic dynamics in complex reaction networksZachary G. NicolaouTakashi NishikawaSchuyler B. NicholsonJason R. GreenAdilson E. MotterComplex chemical reaction networks, which underlie many industrial and biological processes, often exhibit non-monotonic changes in chemical species concentrations. Such non-monotonic dynamics are in principle possible even in a linear model if the matrix defining the model is non-normal, as characterized by a necessarily non-orthogonal set of eigenvectors. However, the extent to which non-normality is responsible for non-monotonic behavior remains an open question. Here, using a master equation to model the reaction dynamics, we derive a general condition for observing non-monotonic dynamics of individual species, establishing that non-normality promotes non-monotonicity but is not a requirement for it. In contrast, we show that non-normality is a requirement for non-monotonic dynamics to be observed in the Rényi entropy. Using hydrogen combustion as an example application, we demonstrate that non-monotonic dynamics under experimental conditions are supported by a linear chain of connected components, at variance with the dominance of a single giant component observed in typical random reaction networks. The exact linearity of the master equation enables development of a rigorous theory and simulations for dynamical networks of unprecedented sizes (approaching 10^{5} dynamical variables, even for a network of only 20 reactions and involving less than 100 atoms). Our conclusions are expected to hold for other combustion processes, and the general theory we develop is applicable to all chemical reaction networks, including biological ones.http://doi.org/10.1103/PhysRevResearch.2.043059
spellingShingle Zachary G. Nicolaou
Takashi Nishikawa
Schuyler B. Nicholson
Jason R. Green
Adilson E. Motter
Non-normality and non-monotonic dynamics in complex reaction networks
Physical Review Research
title Non-normality and non-monotonic dynamics in complex reaction networks
title_full Non-normality and non-monotonic dynamics in complex reaction networks
title_fullStr Non-normality and non-monotonic dynamics in complex reaction networks
title_full_unstemmed Non-normality and non-monotonic dynamics in complex reaction networks
title_short Non-normality and non-monotonic dynamics in complex reaction networks
title_sort non normality and non monotonic dynamics in complex reaction networks
url http://doi.org/10.1103/PhysRevResearch.2.043059
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