arXiv subjects

Anna Zakharova

Publications and source records attributed to Anna Zakharova.

At least 37 records · Page 2Linked to original sources

arXiv2022

Impact of the ligand deformation on the $\mathcal{P}$,$\mathcal{T}$-violation effects in the YbOH molecule

The ytterbium monohydroxide is a promising molecule for a new physics searches. It is well known that levels of the opposite parity, separated by the energy split, so-called $l$-doublets, define the experimental electric field strength required for the molecule polarization. In addition, in our previous paper [Phys.Rev. A 105, L050801 (2022)] we have shown that the value of $l$-doubling directly influences the sensitivity of linear triatomic molecules to the $\mathcal{P}$,$\mathcal{T}$-odd effects. In our work [The JCP 155, 164301 (2021)] we have calculated the value of $l$-doubling for the YbOH molecule with approximation of fixed O-H bond length. Accounting the importance of this property, in the present study we consider the additional degree of freedom corresponding to the ligand (OH) deformation.

physics.atom-ph↗

arXiv2022

Rotating and vibrating symmetric top molecule RaOCH$_3$ in the fundamental $\mathcal{P}$, $\mathcal{T}$-violation searches

We study the influence of the rotations and vibrations of the symmetric top RaOCH$_3$ molecule on its effectiveness as a probe for the $\mathcal{P}$ and $\mathcal{T}$-violating effects, such as the electron electric dipole moment (eEDM) and the scalar-pseudoscalar electron-nucleon interaction (Ne-SPS). The corresponding enhancement parameters $E_{\rm eff}$ and $E_{\rm s}$ are computed for the ground and first excited rovibrational states with different values of the angular momentum component $K$. For the lowest $K$-doublet with $v_\perp=0$ and $K=1$ the values are $E_{\rm eff}=47.647\,\mathrm{GV/cm}$ and $E_{\rm s}=62.109\,\mathrm{kHz}$. The results show larger deviation from the equilibrium values than in triatomic molecules.

physics.atom-ph↗

arXiv2022

Sensitivity of the YbOH molecule to $\mathcal{P}$,$\mathcal{T}$-odd effects in the external electric field

Electron electric dipole moment (eEDM) search using lasercoolable triatomics like YbOH is one of the most sensitive probes for physics beyond the Standard Model. The eEDM-induced energy shift is proportional to polarization ($P$) of the molecule. Similarly to diatomics with $Ω-$doubling structure it was assumed that for triatomics with $l-$doubling structure, related to the vibrational angular momentum, $P$ can easily be saturated to almost 100\% value with moderate external electric field. We developed the method for calculation of properties of triatomic molecules and applied it to calculation of $P$ of $^{174}$YbOH in the first excited $v=1$ bending mode. Calculations showed that the most of the levels reach less than 50\% efficiency. We showed that this fact is related to the Hund's case $b$ coupling scheme of YbOH. As coupling scheme (for $Ω=1/2$ molecules) approaches $a$ (or $c$) case polarization increases up to 100\% value. Results of our calculations should be used for correct extracting of eEDM value from YbOH experiment and similar calculations are required for other molecules.

physics.atom-ph↗

arXiv2021

Coupling-induced periodic windows in networked discrete-time systems

Networked nonlinear systems present a variety of emergent phenomena as a result of the mutual interactions between their units. An interesting feature of these systems is the presence of stable periodic behavior even when each unit oscillates chaotically if in isolation. Surprisingly, the mechanism in which the network interaction replaces chaos by periodicity is still poorly understood. Here, we show that such an onset of regularity can occur via replication of periodic windows. This phenomenon multiplies the stability domains in the system parameter space, not only suppressing chaos but also making the network less vulnerable to external disturbances such as shocks and noise. Moreover, we observe that the network cluster synchronizes for the parameters corresponding to the replica periodic windows. To confirm these observations, we employ the formalism of the master stability function demonstrating that the complete synchronized state is indeed transversally unstable in the replica windows.

nlin.AO↗

arXiv2021

Sparsity-driven synchronization in oscillators networks

The emergence of synchronized behavior is a direct consequence of networking dynamical systems. Naturally, strict instances of this phenomenon, such as the states of complete synchronization are favored, or even ensured, in networks with a high density of connections. Conversely, in sparse networks, the system state-space is often shared by a variety of coexistent solutions. Consequently, the convergence to complete synchronized states is far from being certain. In this scenario, we report the surprising phenomenon in which completely synchronized states are made the sole attractor of sparse networks by removing network links, the sparsity-driven synchronization. This phenomenon is observed numerically for nonlocally coupled Kuramoto networks and verified analytically for locally coupled ones. In addition, we reduce the network equations to a one-dimension dynamical system to unravel the bifurcation scenario underlying the network transition to completely synchronized behavior. Furthermore, we present a simple procedure, based on the bifurcations in the thermodynamic limit, that determines the minimum number of links to be removed in order to ensure complete synchronization. Finally, we propose an application of the reported phenomenon as a control scheme to drive complete synchronization in high connectivity networks.

nlin.AO↗

arXiv2021

Rovibrational structure of the Ytterbium monohydroxide molecule and the $\mathcal{P}$,$\mathcal{T}$-violation searches

The spectrum of triatomic molecules with close rovibrational opposite parity levels is sensitive to the $\mathcal{P}$,$\mathcal{T}$-odd effects. This makes them a convenient platform for the experimental search of a new physics. Among the promising candidates one may distinguish the YbOH as a non-radioactive compound with a heavy atom. The energy gap between levels of opposite parity, $l$-doubling, is of a great interest as it determines the electric field strength required for the full polarization of the molecule. Likewise, the influence of the bending and stretching modes on the sensitivities to the $\mathcal{P}$,$\mathcal{T}$-violation requires a thorough investigation since the measurement would be performed on the excited vibrational states. This motivates us to obtain the rovibrational nuclear wavefunctions, taking into account the anharmonicity of the potential. As a result, we get the values of the $E_{\rm eff}$ and $E_s$ for the lowest excited vibrational state and determine the $l$-doubling

physics.atom-ph↗

arXiv2021

Asymmetry-induced order in multilayer networks

Symmetries naturally occur in real-world networks and can significantly influence the observed dynamics. For instance, many synchronization patterns result from the underlying network symmetries, and high symmetries are known to increase the stability of synchronization. Yet, here we find that general macroscopic features of network solutions such as regularity can be induced by breaking their symmetry of interactions. We demonstrate this effect in an ecological multilayer network where the topological asymmetries occur naturally. These asymmetries rescue the system from chaotic oscillations by establishing stable periodic orbits and equilibria. We call this phenomenon asymmetry-induced order and uncover its mechanism by analyzing both analytically and numerically the suppression of dynamics on the system's synchronization manifold. Moreover, the bifurcation scenario describing the route from chaos to order is also disclosed. We demonstrate that this result also holds for generic node dynamics by analyzing coupled paradigmatic Rössler and Lorenz systems.

nlin.AO↗

arXiv2021

Edges of inter-layer synchronization in multilayer networks with time-switching links

We investigate the transition to synchronization in a two-layer network with time-switching inter-layer links. We focus on the role of the number of inter-layer links and the time-scale of topological changes. Initially, we observe a smooth transition to complete synchronization for the static inter-layer topology by increasing the number of inter-layer links. Next, for a dynamic topology with the existent inter-layer links randomly changing among identical units in the layers, we observe a significant improvement in the system synchronizability, i.e., the layers synchronize with lower inter-layer connectivity. More interestingly, we find that, for a critical switching-time, the transition to synchronization occurs abruptly as the number of inter-layer links increases. We interpret this phenomenon as the shrinking, and ultimately, the disappearance of the basin of attraction of a desynchronized network state.

nlin.AO↗

arXiv2021

Unbalanced clustering and solitary states in coupled excitable systems

We demonstrate the mechanisms of emergence and the link between two types of symmetry-broken states, the unbalanced periodic two-cluster states and solitary states, in coupled excitable systems with prevalent repulsive interactions. Solitary states in non-locally coupled arrays inherit their dynamical features from unbalanced cluster states in globally coupled networks. Apart from self-organization based on phase-locked synchrony, interplay of excitability and local multiscale dynamics also gives rise to leap-frog states involving alternating order of spiking. Noise suppresses multistability of cluster states and induces pattern homogenization, transforming solitary states into patterns of patched

nlin.AO↗

arXiv2020

$\mathcal{P}$,$\mathcal{T}$-odd effects for RaOH molecule in the excited vibrational state

Triatomic molecule RaOH combines the advantages of laser-coolability and the spectrum with close opposite-parity doublets. This makes it a promising candidate for experimental study of the $\mathcal{P}$,$\mathcal{T}$-violation. Previous studies concentrated on the calculations for different geometries without the averaging over the rovibrational wave function and stressed the possibility that the dependence of the $\mathcal{P}$, $\mathcal{T}$ parameters on the bond angle may significantly alter the observed value. We obtain the rovibrational wave functions of RaOH in the ground electronic state and excited vibrational state using the close-coupled equations derived from the adiabatic Hamiltonian. The potential surface is constructed based on the two-component relativistic CCSD(T) computation employing the generalized relativistic effective core potential (GRECP) for the Radium atom. The averaged values of the parameters $E_{\rm eff}$ and $E_s$ describing the sensitivity of the system to the electron electric dipole moment and the scalar-pseudoscalar nucleon-electron interaction are calculated and the value of $l$-doubling is obtained.

physics.atom-ph↗

arXiv2020

Solitary states in multiplex neural networks: onset and vulnerability

We investigate solitary states in a two-layer multiplex network of FitzHugh-Nagumo neurons in the oscillatory regime. We demonstrate how solitary states can be induced in a multiplex network consisting of two non-identical layers. More specifically, we show that these patterns can be introduced via weak multiplexing into a network that is fully synchronized in isolation. We show that this result is robust under variations of the inter-layer coupling strength and largely independent of the choice of initial conditions. Moreover, we study the vulnerability of solitary states with respect to changes in the inter-layer topology. In more detail, we remove links that connect two solitary nodes of each layer and evaluate the resulting pattern. We find a highly non-trivial dependence of the survivability of the solitary states on topological (position in the network) and dynamical (phase of the oscillation) characteristics.

nlin.AO↗

arXiv2020

Coherence resonance in neuronal populations: mean-field versus network model

The counter-intuitive phenomenon of coherence resonance describes a non-monotonic behavior of the regularity of noise-induced oscillations in the excitable regime, leading to an optimal response in terms of regularity of the excited oscillations for an intermediate noise intensity. We study this phenomenon in populations of FitzHugh-Nagumo (FHN) neurons with different coupling architectures. For networks of FHN systems in excitable regime, coherence resonance has been previously analyzed numerically. Here we focus on an analytical approach studying the mean-field limits of the locally and globally coupled populations. The mean-field limit refers to the averaged behavior of a complex network as the number of elements goes to infinity. We derive a mean-field limit approximating the locally coupled FHN network with low noise intensities. Further, we apply mean-field approach to the globally coupled FHN network. We compare the results of the mean-field and network frameworks for coherence resonance and find a good agreement in the globally coupled case, where the correspondence between the two approaches is sufficiently good to capture the emergence of anticoherence resonance. Finally, we study the effects of the coupling strength and noise intensity on coherence resonance for both the network and the mean-field model.

nlin.AO↗

arXiv2019

Delay engineered solitary states in complex networks

We present a technique to engineer solitary states by means of delayed links in a network of neural oscillators and in coupled chaotic maps. Solitary states are intriguing partial synchronization patterns, where a synchronized cluster coexists with solitary nodes displaced from this cluster and distributed randomly over the network. We induce solitary states in the originally synchronized network of identical nodes by introducing delays in the links for a certain number of selected network elements. It is shown that the extent of displacement and the position of solitary elements can be completely controlled by the choice (values) and positions (locations) of the incorporated delays, reshaping the delay engineered solitary states in the network.

nlin.AO↗

arXiv2019

Taming Chimeras in Networks through Multiplexing Delays

Chimera referring to a coexistence of coherent and incoherent states, is traditionally very difficult to control due to its peculiar nature. Here, we provide a recipe to construct chimera states in the multiplex networks with the aid of multiplexing-delays. The chimera state in multiplex networks is produced by introducing heterogeneous delays in a fraction of inter-layer links, referred as multiplexing-delay, in a sequence. Additionally, the emergence of the incoherence in the chimera state can be regulated by making appropriate choice of both inter- and intra-layer coupling strengths, whereas the extent and the position of the incoherence regime can be regulated by appropriate placing and {strength} of the multiplexing delays. The proposed technique to construct such {engineered} chimera equips us with multiplex network's structural parameters as tools in gaining both qualitative- and quantitative-control over the incoherent section of the chimera states and, in turn, the chimera. Our investigation can be of worth in controlling dynamics of multi-level delayed systems and attain desired chimeric patterns.

nlin.AO↗

arXiv2019

Partial synchronization in empirical brain networks as a model for unihemispheric sleep

We analyze partial synchronization patterns in a network of FitzHugh-Nagumo oscillators with empirical structural connectivity measured in healthy human subjects. We report a dynamical asymmetry between the hemispheres, induced by the natural structural asymmetry. We show that the dynamical asymmetry can be enhanced by introducing the inter-hemispheric coupling strength as a control parameter for partial synchronization patterns. We specify the possible modalities for existence of unihemispheric sleep in human brain, where one hemisphere sleeps while the other remains awake. In fact, this state is common among migratory birds and mammals like aquatic species.

nlin.AO↗

arXiv2019

Relay synchronization in multiplex networks of discrete maps

Complex multiplex networks consist of several subnetwork layers, which interact via pairwise inter-layer connections. Relay synchronization between distant layers which are not directly connected, but only via a relay layer, can be observed in multiplex networks. We study three-layer networks of discrete logistic maps, where each individual layer is a nonlocally coupled ring, and demonstrate scenarios of relay synchronization of complex patterns in the outer layers which interact via an intermediate layer. We find regimes of relay synchronization for chimera states, i.e., patterns of coexisting coherent and incoherent domains, and a transition from phase chimeras to amplitude chimeras for increasing inter-layer coupling. We determine analytically the approximate critical coupling strengths for the existence of phase chimeras.

nlin.AO↗

arXiv2018

Networks of coupled oscillators: from phase to amplitude chimeras

We show that amplitude-mediated phase chimeras and amplitude chimeras can occur in the same network of nonlocally coupled identical oscillators. These are two different partial synchronization patterns, where spatially coherent domains coexist with incoherent domains and coherence/incoherence refer to both amplitude and phase or only the amplitude of the oscillators, respectively. By changing the coupling strength the two types of chimera patterns can be induced. We find numerically that the amplitude chimeras are not short-living transients but can have a long lifetime. Also, we observe variants of the amplitude chimeras with quasiperiodic temporal oscillations. We provide a qualitative explanation of the observed phenomena in the light of symmetry breaking bifurcation scenarios. We believe that this study will shed light on the connection between two disparate chimera states having different symmetry-breaking properties.

nlin.AO↗

arXiv2018

Weak multiplexing in neural networks: Switching between chimera and solitary states

We investigate spatio-temporal patterns occurring in a two-layer multiplex network of oscillatory FitzHugh-Nagumo neurons, where each layer is represented by a nonlocally coupled ring. We show that weak multiplexing, i.e., when the coupling between the layers is smaller than that within the layers, can have a significant impact on the dynamics of the neural network. We develop control strategies based on weak multiplexing and demonstrate how the desired state in one layer can be achieved without manipulating its parameters, but only by adjusting the other layer. We find that for coupling range mismatch weak multiplexing leads to the appearance of chimera states with different shapes of the mean velocity profile for parameter ranges where they do not exist in isolation. Moreover, we show that introducing a coupling strength mismatch between the layers can suppress chimera states with one incoherent domain (one-headed chimeras) and induce various other regimes such as in-phase synchronization or two-headed chimeras. Interestingly, small intra-layer coupling strength mismatch allows to achieve solitary states throughout the whole network.

nlin.CD↗