Publications

@article{Wontchui2022,
title = {Intermingled attractors in an asymmetrically driven modified Chua oscillator},
author = {T T Wontchui and M E Sone and S R Ujjwal and J Y Effa and H P E Fouda and R Ramaswamy},
url = {https://pubs.aip.org/aip/cha/article/32/1/013106/2835551/Intermingled-attractors-in-an-asymmetrically},
doi = {10.1063/5.0069232},
issn = {1054-1500},
year = {2022},
date = {2022-01-03},
journal = {Chaos},
volume = {32},
number = {1},
abstract = {Understanding the asymptotic behavior of a dynamical system when system parameters are varied remains a key challenge in nonlinear dynamics. We explore the dynamics of a multistable dynamical system (the response) coupled unidirectionally to a chaotic drive. In the absence of coupling, the dynamics of the response system consists of simple attractors, namely, fixed points and periodic orbits, and there could be chaotic motion depending on system parameters. Importantly, the boundaries of the basins of attraction for these attractors are all smooth. When the drive is coupled to the response, the entire dynamics becomes chaotic: distinct multistable chaos and bistable chaos are observed. In both cases, we observe a mixture of synchronous and desynchronous states and a mixture of synchronous states only. The response system displays a much richer, complex dynamics. We describe and analyze the corresponding basins of attraction using the required criteria. Riddled and intermingled structures are revealed.},
keywords = {Chaos, Lorenz, Lyapunov exponent, Multistability},
pubstate = {published},
tppubtype = {article}
}

@article{Manchanda2017,
title = {Collective dynamics in heterogeneous networks of neuronal cellular automata},
author = {K Manchanda and A Bose and R Ramaswamy},
url = {https://ramramaswamy.org/papers/167.pdf},
doi = {10.1016/j.physa.2017.06.021},
issn = {0378-4371},
year = {2017},
date = {2017-01-01},
journal = {Physica A: Statistical Mechanics and its Applications},
volume = {487},
pages = {111},
publisher = {Elsevier B.V.},
abstract = {We examine the collective dynamics of heterogeneous random networks of model neuronal cellular automata. Each automaton has b active states, a single silent state and r‚àíb‚àí1 refractory states, and can show ‚Äòspiking’ or ‚Äòbursting’ behavior, depending on the values of b. We show that phase transitions that occur in the dynamical activity can be related to phase transitions in the structure of Erdõs‚ÄìRényi graphs as a function of edge probability. Different forms of heterogeneity allow distinct structural phase transitions to become relevant. We also show that the dynamics on the network can be described by a semi-annealed process and, as a result, can be related to the Boolean Lyapunov exponent.},
keywords = {Binary Mixtures, Cellular automata, Discrete Dynamics, Lyapunov exponent, Network Motif},
pubstate = {published},
tppubtype = {article}
}

@article{Negi2001,
title = {Plethora of strange nonchaotic attractors},
author = {Surendra Singh Negi and Ramakrishna Ramaswamy},
url = {https://ramramaswamy.org/papers/079.pdf},
doi = {10.1007/s12043-001-0140-7},
issn = {03044289},
year = {2001},
date = {2001-01-01},
journal = {Pramana – Journal of Physics},
volume = {56},
number = {1},
pages = {47–56},
abstract = {We show that it is possible to devise a large class of skew-product dynamical systems which have strange nonchaotic attractors (SNAs): the dynamics is asymptotically on fractal attractors and the largest Lyapunov exponent is non-positive. Furthermore, we show that quasiperiodic forcing, which has been a hallmark of essentially all hitherto known examples of such dynamics is not necessary for the creation of SNAs.},
keywords = {10, 42, 45, b, Fractals, Lyapunov exponent, nonchaotic, pacs nos 05, strange attractors},
pubstate = {published},
tppubtype = {article}
}

@article{Negi2000,
title = {Bifurcations and transitions in the quasiperiodically driven logistic map},
author = {Surendra Singh Negi and Awadhesh Prasad and Ramakrishna Ramaswamy},
url = {https://ramramaswamy.org/papers/078.pdf},
doi = {10.1016/S0167-2789(00)00110-X},
issn = {01672789},
year = {2000},
date = {2000-01-01},
journal = {Physica D: Nonlinear Phenomena},
volume = {145},
number = {1-2},
pages = {1–12},
abstract = {We discuss several bifurcation phenomena that occur in the quasiperiodically driven logistic map. This system can have strange nonchaotic attractors (SNAs) in addition to chaotic and regular attractors; on SNAs the dynamics is aperiodic, but the largest Lyapunov exponent is nonpositive. There are a number of different transitions that occur here, from periodic attractors to SNAs, from SNAs to chaotic attractors, etc. We describe some of these transitions by examining the behavior of the largest Lyapunov exponent, distributions of finite time Lyapunov exponents and the invariant densities in the phase space. textcopyright 2000 Elsevier Science B.V.},
keywords = {Lyapunov exponent, Quasiperiodically driven logistic map, Strange nonchaotic attractors},
pubstate = {published},
tppubtype = {article}
}

@article{Mehra1996,
title = {Maximal Lyapunov exponent at crises},
author = {V Mehra and R Ramaswamy
},
url = {https://link.aps.org/doi/10.1103/PhysRevE.53.3420},
doi = {10.1103/PhysRevE.53.3420},
year = {1996},
date = {1996-04-01},
journal = {Physical Review E},
volume = {53},
number = {4},
pages = {3420-3424},
abstract = {We study the variation of Lyapunov exponents of simple dynamical systems near attractor-widening and attractor-merging crises. The largest Lyapunov exponent has universal behavior, showing abrupt variation as a function of the control parameter as the system passes through the crisis point, either in the value itself, in the case of an attractor-widening crisis, or in the slope, for an attractor-merging crisis. The distribution of local Lyapunov exponents is very different for the two cases: the fluctuations remain constant through a merging crisis, but there is a dramatic increase in the fluctuations at a widening crisis.},
keywords = {Chaos Theory, Lyapunov exponent},
pubstate = {published},
tppubtype = {article}
}

@article{Tiwari1996b,
title = {Nos´e-Hoover dynamics of a nonintegrable Hamiltonian},
author = {S Tiwari and R Ramaswamy
},
url = {https://www.sciencedirect.com/science/article/pii/0166128095043098},
doi = {10.1016/0166-1280(95)04309-8},
issn = {0166-1280},
year = {1996},
date = {1996-01-15},
journal = {Journal of Molecular Structure: THEOCHEM},
volume = {361},
number = {1},
pages = {111-116},
abstract = {We study the dynamics of a hamiltonian system with two degrees of freedom coupled to a Nosé-Hoover thermostat. In the absence of the thermostat, the system is quasi-integrable: at low energies, most of the motion is on two-dimensional tori, while at higher energies, the motion is mainly chaotic. Upon coupling to the thermostat the system becomes more chaotic, as evidenced by the magnitude of the largest Lyapunov exponent. In contrast to the case of isotropic oscillator systems coupled to thermostats, there is no evidence for a regime of integrable behaviour, even for large values of Q.},
keywords = {Lyapunov exponent, Nonintegrable Hamiltonian Systems},
pubstate = {published},
tppubtype = {article}
}

@article{Nayak1995b,
title = {The maximal Lyapunov exponent in small atomic clusters},
author = {S K Nayak, R Ramaswamy and C Chakravarty},
url = {https://link.aps.org/doi/10.1103/PhysRevE.51.3376},
doi = {10.1103/PhysRevE.51.3376},
year = {1995},
date = {1995-04-01},
journal = {Physical Review E},
volume = {51},
number = {4},
pages = {3376–3380},
abstract = {We study small clusters of atomic argon,
Ar7 Ar13, and Ar55, in the temperature range where they undergo a transition from a solidlike phase to a liquidlike phase. The signature of the phase transition is clearly seen as a dramatic increase in the largest Lyapunov exponent as the cluster ‘‘melts.},
keywords = {Atomic Clusters, Lyapunov exponent},
pubstate = {published},
tppubtype = {article}
}