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From phase to amplitude oscillators [article]

Pau Clusella, Antonio Politi
2018 arXiv   pre-print
We analyze an intermediate collective regime where amplitude oscillators distribute themselves along a closed, smooth, time-dependent curve C, thereby maintaining the typical ordering of (identical) phase oscillators. This is achieved by developing a general formalism based on two partial differential equations, which describe the evolution of the probability density along C and of the shape of C itself. The formalism is specifically developed for Stuart-Landau oscillators, but it is general
more » ... ugh to be applied to other classes of amplitude oscillators. The main achievements consist in: (i) identification and characterization of a new transition to self-consistent partial synchrony (SCPS), which confirms the crucial role played by higher Fourier hamonics in the coupling function; (ii) an analytical treatment of SCPS, including a detailed stability analysis; (iii) the discovery of a new form of collective chaos, which can be seen as a generalization of SCPS and characterized by a multifractal probability density. Finally, we are able to describe given dynamical regimes both at the macroscopic as well as the microscopic level, thereby shedding further light on the relationship between the two different levels of description.
arXiv:1810.01281v1 fatcat:buyrloelwnbopjodi4n5fhqele

Irregular collective dynamics in a Kuramoto-Daido system [article]

Pau Clusella, Antonio Politi
2020 arXiv   pre-print
We analyse the collective behavior of a mean-field model of phase-oscillators of Kuramoto-Daido type coupled through pairwise interactions which depend on phase differences: the coupling function is composed of three harmonics. We provide convincing evidence of a transient but long-lasting chaotic collective chaos, which persists in the thermodynamic limit. The regime is analysed with the help of clever direct numerical simulations, by determining the maximum Lyapunov exponent and assessing the
more » ... transversal stability to the self-consistent mean field. The structure of the invariant measure is finally described in terms of a resolution-dependent entropy.
arXiv:2010.12801v1 fatcat:gvuaiy2bmjbpxa43iqekkhgu6q

Phase transitions on a class of generalized Vicsek-like models of collective motion [article]

Pau Clusella, Romualdo Pastor-Satorras
2021 arXiv   pre-print
Systems composed of interacting self-propelled particles (SPPs) display different forms of order-disorder phase transitions relevant to collective motion. In this paper we propose a generalization of the Vicsek model characterized by an angular noise term following an arbitrary probability density function, which might depend on the state of the system and thus have a multiplicative character. We show that the well established vectorial Vicsek model can be expressed in this general formalism by
more » ... deriving the corresponding angular probability density function, as well as we propose two new multiplicative models consisting on a bivariate Gaussian and a wrapped Gaussian distributions. With the proposed formalism, the mean-field system can be solved using the mean resultant length of the angular stochastic term. Accordingly, when the SPPs interact globally, the character of the phase transition depends on the choice of the noise distribution, being first-order with an hybrid scaling for the vectorial and wrapped Gaussian distributions, and second order for the bivariate Gaussian distribution. Numerical simulations reveal that this scenario also holds when the interactions among SPPs are given by a static complex network. On the other hand, using spatial short-range interactions displays, in all the considered instances, a discontinuous transition with a coexistence region, consistent with the original formulation of the Vicsek model.
arXiv:2102.04715v1 fatcat:yp6yg7ckcrba5krrfoh5dgsfj4

Irregular collective dynamics in a Kuramoto-Daido system

Antonio Politi, Pau Clusella
2020 Journal of Physics: Complexity  
ORCID iDs Pau Clusella https://orcid.org/0000-0003-2010-7924 Antonio Politi https://orcid.org/0000-0001-8688-1870  ...  Published by IOP Publishing Ltd P Clusella and A Politi Or other 'complications', such as additional degrees of freedom in the oscillator dynamics.  ... 
doi:10.1088/2632-072x/abd3af fatcat:j5q37hwf6bh2lb5dt35qh6jeqq

A minimal model of self-consistent partial synchrony

Pau Clusella, Antonio Politi, Michael Rosenblum
2016 New Journal of Physics  
Phys. 18 (2016) 093037 P Clusella et al This system is equivalent to the van der Pol equation; they are related via the variable substitution  x x 3 .  ... 
doi:10.1088/1367-2630/18/9/093037 fatcat:l3y5w2mqhfbxpibdw4ccxydya4

Amplitude death and restoration in networks of oscillators with random-walk diffusion

Pau Clusella, M. Carmen Miguel, Romualdo Pastor-Satorras
2021 Communications Physics  
AbstractSystems composed of reactive particles diffusing in a network display emergent dynamics. While Fick's diffusion can lead to Turing patterns, other diffusion schemes might display more complex phenomena. Here we study the death and restoration of collective oscillations in networks of oscillators coupled by random-walk diffusion, which modifies both the original unstable fixed point and the stable limit-cycle, making them topology-dependent. By means of numerical simulations we show
more » ... in some cases, the diffusion-induced heterogeneity stabilizes the initially unstable fixed point via a Hopf bifurcation. Further increasing the coupling strength can moreover restore the oscillations. A numerical stability analysis indicates that this phenomenology corresponds to a case of amplitude death, where the inhomogeneous stabilized solution arises from the interplay of random walk diffusion and heterogeneous topology. Our results are relevant in the fields of epidemic spreading or ecological dispersion, where random walk diffusion is more prevalent.
doi:10.1038/s42005-020-00516-w fatcat:git7257pz5gnpemytzeqo3gkja

Pattern invariance for reaction-diffusion systems on complex networks [article]

Giulia Cencetti, Pau Clusella, Duccio Fanelli
2018 Scientific Reports   accepted
Given a reaction-diffusion system interacting via a complex network, we propose two different techniques to modify the network topology while preserving its dynamical behaviour. In the region of parameters where the homogeneous solution gets spontaneously destabilized, perturbations grow along the unstable directions made available across the networks of connections, yielding irregular spatio-temporal patterns. We exploit the spectral properties of the Laplacian operator associated to the graph
more » ... in order to modify its topology, while preserving the unstable manifold of the underlying equilibrium. The new network is isodynamic to the former, meaning that it reproduces the dynamical response (pattern) to a perturbation, as displayed by the original system. The first method acts directly on the eigenmodes, thus resulting in a general redistribution of link weights which, in some cases, can completely change the structure of the original network. The second method uses localization properties of the eigenvectors to identify and randomize a subnetwork that is mostly embedded only into the stable manifold. We test both techniques on different network topologies using the Ginzburg-Landau system as a reference model. Whereas the correlation between patterns on isodynamic networks generated via the first recipe is larger, the second method allows for a finer control at the level of single nodes. This work opens up a new perspective on the multiple possibilities for identifying the family of discrete supports that instigate equivalent dynamical responses on a multispecies reaction-diffusion system.
doi:10.1038/s41598-018-34372-0 pmid:30385860 pmcid:PMC6212431 arXiv:1805.10233v2 fatcat:vkuagpymtvc5jkj6bof7nxasy4

Noise-induced stabilization of collective dynamics

Pau Clusella, Antonio Politi
2017 Physical review. E  
We illustrate a counter-intuitive effect of an additive stochastic force, which acts independently on each element of an ensemble of globally coupled oscillators. We show numerically and semi-analytically that a very small white noise is able to stabilize an otherwise linearly unstable collective periodic regime. Microscopic simulations reveal two noise-induced bifurcations of different nature towards self-consistent partial synchrony. We develop a macroscopic treatment solving the
more » ... nonlinear Fokker-Planck equation by means of a perturbative approach. The associated linear stability analysis confirms the results anticipated by the numerics. We also argue about the generality of the phenomenon.
doi:10.1103/physreve.95.062221 pmid:28709323 fatcat:sdnroi4zmfertce64gyctsrzjm

Amplitude death and restoration in networks of oscillators with random-walk diffusion [article]

Pau Clusella, M. Carmen Miguel, Romualdo Pastor-Satorras
2020 arXiv   pre-print
We study the death and restoration of collective oscillations in networks of oscillators coupled through random-walk diffusion. Differently than the usual diffusion coupling used to model chemical reactions, here the equilibria of the uncoupled unit is not a solution of the coupled ensemble. Instead, the connectivity modifies both, the original unstable fixed point and the stable limit-cycle, making them node-dependent. Using numerical simulations in random networks we show that, in some cases,
more » ... this diffusion induced heterogeneity stabilizes the initially unstable fixed point via a Hopf bifurcation. Further increasing the coupling strength the oscillations can be restored as well. Upon numerical analysis of the stability properties we conclude that this is a novel case of amplitude death. Finally we use a heterogeneous mean-field reduction of the system in order to proof the robustness of this phenomena upon increasing the system size.
arXiv:2009.04740v2 fatcat:brijifnuwbcpdlbgfmg33ucwda

Corrigendum: A minimal model of self-consistent partial synchrony (2016 New J. Phys. 18 093037)

Pau Clusella, Antonio Politi, Michael Rosenblum
2017 New Journal of Physics  
doi:10.1088/1367-2630/aa722b fatcat:deainl3xxredrcazspyk272kiy

Kuramoto model for populations of quadratic integrate-and-fire neurons with chemical and electrical coupling [article]

Pau Clusella, Bastian Pietras, Ernest Montbrió
2021 arXiv   pre-print
We derive the Kuramoto model (KM) corresponding to a population of weakly coupled, nearly identical quadratic integrate-and-fire neurons (QIF) with both electrical and chemical coupling. The ratio of chemical to electrical coupling determines the phase lag of the characteristic sine coupling function of the KM, and critically determines the synchronization properties of the network. We apply our results to investigate chimera states in two coupled populations of identical QIF neurons. We find
more » ... at the presence of both electrical and chemical coupling is a necessary condition for chimera states to exist. Finally, we numerically demonstrate that chimera states gradually disappear as coupling strengths cease to be weak.
arXiv:2110.07665v1 fatcat:q642yvtdqrdf5jvjibvv5xulzu

Immunization and Targeted Destruction of Networks using Explosive Percolation

Pau Clusella, Peter Grassberger, Francisco J. Pérez-Reche, Antonio Politi
2016 Physical Review Letters  
A new method ('explosive immunization' (EI)) is proposed for immunization and targeted destruction of networks. It combines the explosive percolation (EP) paradigm with the idea of maintaining a fragmented distribution of clusters. The ability of each node to block the spread of an infection (or to prevent the existence of a large cluster of connected nodes) is estimated by a score. The algorithm proceeds by first identifying low score nodes that should not be vaccinated/destroyed, analogously
more » ... o the links selected in EP if they do not lead to large clusters. As in EP, this is done by selecting the worst node (weakest blocker) from a finite set of randomly chosen 'candidates'. Tests on several real-world and model networks suggest that the method is more efficient and faster than any existing immunization strategy. Due to the latter property it can deal with very large networks.
doi:10.1103/physrevlett.117.208301 pmid:27886508 fatcat:jqvsxnrtbvgs5cryp6uzxtvccu

Body size variability across habitats in the Brachionus plicatilis cryptic species complex [article]

Aleksandra Walczynska, Manuel Serra
2020 bioRxiv   pre-print
The factors that are noted in the 59 literature as interfering with the general organismal response to temperature, which differs across 60 habitats, are precipitation (Clusella-Trullas, Blackburn & Chown  ...  'Almenara' or B. 160 'Tiscar', both of which are known to occur in the examined study area (Montero-Pau et al., 2011; 161 Gomez et al., 2002). Therefore, we designated this species as SM-X.  ... 
doi:10.1101/2020.04.30.070417 fatcat:rtcn24kkvrczfki2s4wxn5jcwm

MUEBLES E INTERIORES EN CANET DE MAR 1890-1917 Furniture and indoor design in Canet de Mar, 1890-1917

Vicente De la Fuente Bermúdez
2014 Res Mobilis: International Research Journal of Furniture and Decorative Objects  
nº562, 7 de octubre de 1893, p. 634. 2 La Costa de Llevant, Any XVI, nº34, 28 d'agost del 1909, pp. 7-8. 3 La Garriga y la "arquitectura de veraneo" de Raspall está estudiada ampliamente, por ejemplo ver CLUSELLAS  ...  Gargallo o Arturo Mélida, de edificios como: el Seminario Pontificio en Comillas (Fig. 1) ; el Hospital de la Santa Creu i Sant Pau, la Casa Thomas, la Casa lleó Morera o la Fonda España, todos ellos  ... 
doi:10.17811/rm.3.2014.57-73 fatcat:tkzf5eqv55cyveeg2id77ighbm

Body size and climate as predictors of plumage colouration and sexual dichromatism in parrots [article]

Luisana Carballo, Kaspar Delhey, Mihai Valcu, Bart Kempenaers
2020 bioRxiv   pre-print
., 2017) , in support of the thermal melanism hypothesis (Clusella Trullas, van Wyk, & 122 Spotila, 2007) .  ...  This eco-geographical rule proposes that darker animals inhabit colder environments, 123 presumably for thermoregulation reasons (Clusella Trullas et al., 2007; Delhey, 2018) .  ... 
doi:10.1101/2020.05.21.107920 fatcat:wdffynb7ajconiwt2ykqdsxp7e
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