arXiv subjects

Anna Zakharova

Publications and source records attributed to Anna Zakharova.

At least 19 recordsLinked to original sources

arXiv2026

Rovibrational structure and electric dipole moments of the AcOCH$_3$+ ion

The possibility of laser cooling and the presence of closely spaced rovibrational doublets make polyatomic molecules an attractive platform for the $\mathcal{P}$, $\mathcal{T}$-violation searches. We study the spectrum of the lowest rovibrational state of the AcOCH$_3+$ symmetric top molecule. The electronic structure full-electron computation was performed within a relativistic coupled cluster method with double and perturbative triple excitations. The rovibrational wavefunctions are obtained using a coupled channel technique, taking into account all rovibrational effects and anharmonicities of the potential. As a result, the vibrational frequencies, as well as the values of the electric dipole moments for the rovibrational states, were computed.

physics.atom-ph↗

arXiv2026

Axion electron-electron interaction in the RaOH molecule to search for Dark matter

Axions are promising candidates for the role of Dark matter particles. In this paper, the question of the suitability of the RaOH molecule for the experimental detection of electron-electron interactions through the exchange of axions is studied. To take into account an impact of the rotations and vibrations a computation must be performed for a large number of molecular configurations. In this work we study this problem using a combination of the Generalized relativistic effective core potential and One-center restoration technique of the correct four-component spinors.

hep-ph↗

arXiv2026

Axion-mediated electron-electron interaction in RaOCH_3 molecule

We study the parity-violating electron-electron interaction mediated by the axion-like in the hexatomic molecule of a symmetric top type. The rich rovibrational behavior require electronic computations for multiple molecular configurations which can be reduced using Generalized Relativistic Effective Core Potential. To restore the correct behavior in the core region we use a one-center restoration technique generalized by us earlier to the two-electron properties. The property is averaged on the lowest-lying rovibrational states.

physics.atom-ph↗

arXiv2026

$\mathcal{P}$, $\mathcal{T}$-violating axion-mediated interactions in RaOH molecule

If axion simultaneously has the scalar couplings to the nucleons and pseudo-scalar couplings to the electrons, it may mediate a $\mathcal{P}$, $\mathcal{T}$-violating interaction between the electronic shell and nuclei in the molecules. The polyatomic molecule RaOH, which is considered as a promising platform for the $\mathcal{P}$, $\mathcal{T}$ violation searches, is studied for its sensitivity to such interactions. Due to the long-range nature (on molecular scales) of the axion-mediated interaction, it is important whether the enhancement parameter would be sensitive to the vibration of the molecule. Our results imply that the impact of the vibrations on the axion-mediated electron-nucleon interaction in the molecule is similar to the impact on the short-range electron-nucleon scalar-pseudoscalar interaction studied earlier.

hep-ph↗

arXiv2025

Solitary states in spiking oscillators with higher-order interactions

We study a system of globally coupled FitzHugh-Nagumo oscillators, showing that the presence of higher-order interactions affects the character of the transition between synchronous and asynchronous states. In particular, we demonstrate that, around the synchronization transition, solitary states emerge due to the presence of second-order interactions. In difference to the phenomenology observed in systems of phase oscillators, we show that, at low coupling strengths, solitary states appear for both transition directions, whereas for higher couplings they only occur in the forward direction, with the backwards one characterized by explosive desynchronization.

nlin.AO↗

arXiv2025

Breakdown of stochastic resonance in complex networks

In networked systems, stochastic resonance occurs as a collective phenomenon where the entire stochastic network resonates with a weak applied periodic signal. Beyond the interplay among the network coupling, the amplitude of the external periodic signal, and the intensity of stochastic fluctuations, the maintenance of stochastic resonance also crucially depends on the resonance capacity of each oscillator composing the network. This scenario raises the question: Can local defects in the ability of oscillators to resonate break down the stochastic resonance phenomenon in the entire network? Here, we investigate this possibility in complex networks of prototypical bistable oscillators in a double-well potential. We test the sustainability of stochastic resonance by considering a fraction of network oscillators with nonresonant potential landscapes. We find that the number of nonresonant oscillators depends nonlinearly on their dissimilarity from the rest of the network oscillators. In addition, we unravel the role of the network topology and coupling strength in maintaining, or suppressing, the stochastic resonance for different noise levels and number of nonresonant oscillators. Finally, we obtain a low-dimensional deterministic model confirming the results observed for the networks.

nlin.AO↗

arXiv2024

Delayed-feedback oscillators replicate the dynamics of multiplex networks: wavefront propagation and stochastic resonance

The widespread development and use of neural networks have significantly enriched a wide range of computer algorithms and promise higher speed at lower cost. However, the imitation of neural networks by means of modern computing substrates is highly inefficient, whereas physical realization of large scale networks remains challenging. Fortunately, delayed-feedback oscillators, being much easier to realize experimentally, represent promising candidates for the empirical implementation of neural networks and next generation computing architectures. In the current research, we demonstrate that coupled bistable delayed-feedback oscillators emulate a multilayer network, where one single-layer network is connected to another single-layer network through coupling between replica nodes, i.e. the multiplex network. We show that all the aspects of the multiplexing impact on wavefront propagation and stochastic resonance identified in multilayer networks of bistable oscillators are entirely reproduced in the dynamics of time-delay oscillators. In particular, varying the coupling strength allows suppressing and enhancing the effect of stochastic resonance, as well as controlling the speed and direction of both deterministic and stochastic wavefront propagation. All the considered effects are studied in numerical simulations and confirmed in physical experiments, showing an excellent correspondence and disclosing thereby the robustness of the observed phenomena.

nlin.AO↗

arXiv2024

Lévy noise-induced coherence resonance: numerical study versus experiment

Using the FitzHugh-Nagumo system in the excitable regime, we investigate the influence of the L{é}vy noise properties on the effect of coherence resonance. In particular, we demonstrate that the L{é}vy noise can be a constructive or destructive factor providing for enhancement or suppression of noise-induced coherence. We show that the positive or negative role of the L{é}vy noise impact is dictated by the noise stability index and skewness parameter. The correlation time and the deviation of interspike intervals used in this analysis are shown to be maximized or minimized for an appropriate choice of the noise parameters. Numerical simulations are combined with experiments on an electronic circuit showing an excellent qualitative correspondence and proving thereby the robustness of the observed phenomena.

nlin.AO↗

arXiv2024

Symmetric top molecule YbOCH$_3$ in the fundamental $\mathcal{P}$, $\mathcal{T}$-violation searches

The symmetric top molecule YbOCH$_3$ is studied for its potential to $\mathcal{P}$, $\mathcal{T}$-violation searches. The influence of the rotations and vibrations of the YbOCH$_3$ on such violating effects as the electron electric dipole moment (eEDM) and the scalar-pseudoscalar electron-nucleon interaction (Ne-SPS) is studied using the coupled channels method. The corresponding sensitivity parameters $E_{\rm eff}$ and $E_{\rm s}$ are computed.

quant-ph↗

arXiv2023

States localized on a boundary of the time-dependent parity-breaking medium

We consider the massive vector field propagating in the inhomogeneous parity-breaking medium, such as the dense hot hadronic matter with chiral imbalance. The transition between the regions with approximately constant values of the parity-breaking parameter allows for the states localized on such boundary to occur. The adiabatic change of the background introduces either decay or the amplification of the localized states. We also discuss the non-adiabatic destruction of these bound states.

hep-th↗

arXiv2023

Scale-free avalanches in arrays of FitzHugh-Nagumo oscillators

The activity in the brain cortex remarkably shows a simultaneous presence of robust collective oscillations and neuronal avalanches, where intermittent bursts of pseudo-synchronous spiking are interspersed with long periods of quiescence. The mechanisms allowing for such a coexistence are still a matter of an intensive debate. Here, we demonstrate that avalanche activity patterns can emerge in a rather simple model of an array of diffusively coupled neural oscillators with multiple timescale local dynamics in vicinity of a canard transition. The avalanches coexist with the fully synchronous state where the units perform relaxation oscillations. We show that the mechanism behind the avalanches is based on an inhibitory effect of interactions, which may quench the spiking of units due to an interplay with the maximal canard. The avalanche activity bears certain heralds of criticality, including scale-invariant distributions of event sizes. Furthermore, the system shows an increased sensitivity to perturbations, manifested as critical slowing down and a reduced resilience.

nlin.AO↗

arXiv2023

The impact of the near-surface region on the interpretation of x-ray absorption spectroscopy

Transition metal oxides (TMOs) exhibit a broad spectrum of electronic, magnetic, and optical properties, making them intriguing materials for various technological applications. Soft x-ray absorption spectroscopy (XAS) is widely used to study TMOs, shedding light on their chemical state, electronic structure, orbital polarization, element-specific magnetism, and more. Different XAS acquisition modes feature different information depth regimes in the sample. Here, we employ two XAS acquisition modes, having surface-sensitive versus bulk probing depths, on the prototypical TMO SrVO3. We illustrate and elucidate a strong apparent discrepancy between the different modes, emphasizing the impact of the near-surface region on the interpretation of XAS data. These findings highlight the importance of the acquisition mode selection in XAS analysis. Moreover, the results highlight the role of the near-surface region not only in the characterization of TMOs, but also in the design of future nanoscale oxide electronics.

cond-mat.mtrl-sci↗

arXiv2023

Multiplexing-based control of wavefront propagation: the interplay of inter-layer coupling, asymmetry and noise

We show how multiplexing influences propagating fronts in multilayer networks of coupled bistable oscillators. Using numerical simulation, we investigate both deterministic and noise-sustained propagation. In particular, we demonstrate that the multiplexing allows to reduce the intra-layer dynamics to a common regime where the front propagation speed in all the interacting layers attains the same fixed value. In the presence of noise the dynamics is more complicated and is characterized by the ability of the system to adjust to the common propagation speed for varying the multiplexing strength. In addition, we find that the noise-induced stabilization of wavefront propagation in multilayer networks allows to obtain less pronounced deviations of the wavefront compared to the stabilization achieved in the isolated layer. Finally, we demonstrate that the reduction of the wavefront deviations can be enhanced by increasing the number of interacting layers.

nlin.AO↗

arXiv2023

Bandwidth Control and Symmetry Breaking in a Mott-Hubbard Correlated Metal

In Mott materials strong electron correlation yields a spectrum of complex electronic structures. Recent synthesis advancements open realistic opportunities for harnessing Mott physics to design transformative devices. However, a major bottleneck in realizing such devices remains the lack of control over the electron correlation strength. This stems from the complexity of the electronic structure, which often veils the basic mechanisms underlying the correlation strength. Here, we present control of the correlation strength by tuning the degree of orbital overlap using picometer-scale lattice engineering. We illustrate how bandwidth control and concurrent symmetry breaking can govern the electronic structure of a correlated $SrVO_3$ model system. We show how tensile and compressive biaxial strain oppositely affect the $SrVO_3$ in-plane and out-of-plane orbital occupancy, resulting in the partial alleviation of the orbital degeneracy. We derive and explain the spectral weight redistribution under strain and illustrate how high tensile strain drives the system towards a Mott insulating state. Implementation of such concepts will drive correlated electron phenomena closer towards new solid state devices and circuits. These findings therefore pave the way for understanding and controlling electron correlation in a broad range of functional materials, driving this powerful resource for novel electronics closer towards practical realization.

cond-mat.str-el↗

arXiv2022

Stochastic control of spiking activity bump expansion: monotonic and resonant phenomena

We consider spatially localized spiking activity patterns, so-called bumps, in ensembles of bistable spiking oscillators. The bistability consists in the coexistence of self-sustained spiking dynamics and quiescent steady-state regime. We show numerically that the processes of growth or contraction of such patterns can be controlled by varying the intensity of multiplicative noise. In particular, the effect of the noise is monotonic in an ensemble of the coupled Hindmarsh-Rose oscillators. On the other hand, in another model proposed by V. Semenov et al. in 2016 (see Ref. [V. Semenov et al., Phys. Rev. E 93, 052210 (2016)]), a resonant noise effect is observed. In that model, stabilization of the activity bump expansion is achieved at an appropriate noise level, and the noise effect reverses with a further increase in noise intensity. Moreover, we show the constructive role of nonlocal coupling which allows to save domains and fronts being totally destroyed due to the action of noise in the case of local coupling.

nlin.AO↗

arXiv2022

Solitary routes to chimera states

We show how solitary states in a system of globally coupled FitzHugh-Nagumo oscillators can lead to the emergence of chimera states. By a numerical bifurcation analysis of a suitable reduced system in the thermodynamic limit we demonstrate how solitary states, after emerging from the synchronous state, become chaotic in a period-doubling cascade. Subsequently, states with a single chaotic oscillator give rise to states with an increasing number of incoherent chaotic oscillators. In large systems, these chimera states show extensive chaos. We demonstrate the coexistence of many of such chaotic attractors with different Lyapunov dimensions, due to different numbers of incoherent oscillators.

nlin.CD↗

arXiv2022

Multiplexing-based control of stochastic resonance

We show that multiplexing allows to control noise-induced dynamics of multilayer networks in the regime of stochastic resonance. We illustrate this effect on an example of two- and multi-layer networks of bistable overdamped oscillators. In particular, we demonstrate that multiplexing suppresses the effect of stochastic resonance, if the periodic forcing is present in only one layer. In contrast, the multiplexing allows to enhance the stochastic resonance, if the periodic forcing and noise are present in all the interacting layers. In such a case the impact of multiplexing has a resonant character: the most pronounced effect of stochastic resonance is achieved for an appropriate intermediate value of coupling strength between the layers. Moreover, multiplexing-induced enhancement of the stochastic resonance can become more pronounced for increasing number of coupled layers. To visualize the revealed phenomena, we use the evolution of the dependence of the signal-to-noise ratio on the noise intensity for varying strength of coupling between the layers.

nlin.AO↗

arXiv2022

Solitary states in complex networks: impact of topology

The dynamical behavior of networked systems is expected to reflect the features of their coupling structure. Yet, symmetry-broken solutions often occur in symmetrically coupled networks. An example is provided by the so-called solitary states where the dynamics of one network node is different from the entire symmetric network. Here, we investigate the structural constraints of networks for the appearance of solitary states in their dynamics. By performing a large number of numerical simulations, we find that such states occur with high probability in asymmetric networks, such as the ones exhibiting the scale-free property. Next, we analyze the structural features of the networks demonstrating solitary states to reveal that the minimum number of connections in the adjacent nodes of a solitary one is crucial for the appearance of the solitary states. Finally, we perform bifurcation analysis of a dimension-reduced system, confirming the influence of the connectivity of the neighboring nodes on the solitary ones.

nlin.PS↗