We study, within the spin-boson dynamics, synchronization of a quantum tunneling system with an external, time-periodic driving signal. As main result, we find that at sufficiently large system-bath coupling strength (i.e., for friction alpha > 1) thermal noise plays constructive role in yielding forced synchronization. This noise-induced can occur when frequency is larger than zero-temperature rate. application evidencing effect, consider charge transfer dynamics molecular complexes.

We present a theory of solvent effects on the rate intramolecular proton-transfer (IPT) reactions. The proton tunnels between two vibrational levels double minimum potential. proton’s coupling to is modeled with an oscillator bath, appropriate reactions where charge interacts many molecules. evaluated by use Golden Rule; perturbation level splitting. IPT constant has several limiting expressions, one which activated form. activation energy related medium reorganization energy, and provides...

We present a theory of proton transfer reactions which incorporate the modulation proton’s potential surface by intermolecular vibrations and effect coupling to solvent degrees freedom. The tunnels between states corresponding it being localized in wells double minimum potential. resulting tunnel splitting depends on separation. response charge is modeled as that damped oscillator, allowing introduction friction effects dynamics. rate evaluated perturbation level splitting. find typically...

Previously derived expressions for the characteristic function of work performed on a quantum system by classical external force are generalized to arbitrary initial states considered and Hamiltonians with degenerate spectra. In particular case microcanonical states, explicit corresponding probability density formulated. Their limit as well their relations canonical discussed. A fluctuation theorem is that expresses ratio probabilities process its time reversal densities equilibrium systems...

An amenable, analytical two-state description of the nonlinear population dynamics a noisy bistable system driven by rectangular subthreshold signal is put forward. Explicit expressions for dynamics, correlation function (its coherent and incoherent parts), signal-to-noise ratio (SNR), stochastic resonance (SR) gain are obtained. Within suitably chosen range parameter values this reduced yields anomalous SR gains exceeding unity and, simultaneously, gives rise to nonmonotonic behavior SNR vs...

Work performed on a system in microcanonical state by changes control parameter is characterized terms of its statistics. The transition probabilities between eigenstates the Hamiltonians at beginning and end change obey detailed balance-like relation from which various forms fluctuation theorem are obtained. As an example, sudden deformations two-dimensional harmonic oscillator potential considered, validity Jarzynski equality connecting degrees degeneracy energy eigenvalues before after confirmed.

We study the long-time response of a stochastic system formed by very many interacting subsystems coupled mean-field interaction and subject to time periodic external field. In absence driving field; shows an order-disorder phase transition its evolution is well described Fokker-Planck equation which nonlinear in probability density. carry out analysis dynamics case weak field means perturbation (linear theory). The then given terms generalized susceptibility. Its evaluation that phenomenon...

The possibility of controlling the tunneling a proton in condensed phase with use static or time varying external fields, which couple to transition dipole moment proton, is investigated. Starting from Hamiltonian, an equation motion describing tunnel dynamics as stochastically modulated, externally driven, two-level system derived under suitable restrictions. For fields that satisfy precise connection between frequency and amplitude, whereby resulting Floquet eigenvalues (quasienergies) are...

We address the phenomenon of stochastic resonance in a noisy bistable system driven by time-dependent periodic force (not necessarily sinusoidal) and its two-state approximation. Even for driving forces with subthreshold amplitudes, behavior response might require nonlinear description. introduce analytical numerical tools to analyze power spectral amplification signal-to-noise ratio regime. Our analysis shows importance effects on fluctuations These can be usefully exploited achieve high...

In the context of phenomenon stochastic resonance (SR), we study correlation function, signal-to-noise ratio (SNR), and output over input SNR, i.e., gain, which is associated to nonlinear response a bistable system driven by time-periodic forces white Gaussian noise. These quantifiers for SR are evaluated using techniques linear theory (LRT) beyond usually employed two-mode approximation scheme. We analytically demonstrate within such an extended LRT description that gain can indeed not...

We analyze the transition from nonadiabatic to solvent controlled adiabatic electron transfer kinetic behavior with emphasis on inverted regime. By viewing process as dynamical motion a donor surface followed by possible crossing acceptor surface, we are able obtain simple consecutive reaction expression for overall rate in terms of constants surfaces and motion. When between is not localized point, find that there frictional effects this constant, contrast case. Use typical parameters shows...

A finite-difference method for solving a general class of linear and nonlinear time-dependent Fokker-Planck equations, which is based on K-point Stirling interpolation formula, suggested. It has fifth-order convergence in time 2Kth-order space allows one to achieve given level accuracy with slow (or even without) increase the number grid points. The most appealing features are perhaps that it norm conserved, equilibrium preserving sense every solution analytic equations also an discretized...

The main objective of this work is to explore aspects stochastic resonance (SR) in noisy bistable, symmetric systems driven by subthreshold periodic rectangular external signals possessing a large duty cycle unity. Using precise numerical solution the Langevin equation, we carry out detailed analysis behavior first two cumulant averages, correlation function, and its coherent incoherent parts. We also depict nonmonotonic versus noise strength several SR quantifiers such as average output...

We explore stochastic resonance effects in the response of a complex system formed by finite number interacting, identical subunits driven time-periodic force. The driving force alone cannot induce sustained oscillations between different attractors dynamics absence noise. focus on global variable defined as arithmetic mean relevant each subunit. construct numerical approximations to its first two long time cumulant moments and correlation function. also compute output signal-to-noise ratio...

We investigate the role of noise in phenomenon stochastic synchronization switching events a rocked, overdamped bistable potential driven by white Gaussian noise, archetype description resonance. present an approach to counting process noise-induced events: starting from Markovian dynamics nonstationary, continuous particle dynamics, one finds upon contraction onto two states non-Markovian renewal dynamics. A proper definition output discrete phase is given, and time rate change its average...

Comb-like poly(β-aspartate)s that adopt layered arrangements with well-defined phase transitions are revealed here. Outstanding thermochromic effects displayed by these materials under polarized light, a rapid, fully reversible color response is highly sensitive to temperature (see Figure) and can be adjusted copolymerization.

The tunneling of a particle between two states, as influenced by coupling the to an external field, is investigated. A spin-boson Hamiltonian used describe tunnel system and its interaction with medium augmented term dipole moment field. projection operator method introduced that provides equations motion for particle's density matrix permits discussion field effects on even at very low temperatures. These can exhibit solutions characterized population relaxation rate constant average over...

We consider the kinetics of electron transfer reactions in condensed media with different reorganization energies for forward and backward processes. The starting point our analysis is an extension well-known Zusman equations to case parabolic diabatic curves curvatures. A generalized master equation populations as well formal expressions their long-time limit derived. discuss conditions under which time evolution reactants products can be described at all times by a single exponential law....

The stochastic amplification of a periodic signal in truly nonlinear Fokker-Planck model, whose drift coefficient exhibits functional dependence on the distribution function, is analyzed numerically by means finite-difference method. Our aim to check validity basic concepts widely used studying linear and/or undriven systems. A perturbation approach evaluate generalized susceptibility model response theory tested and found be adequate for weak driving fields. We also Floquet H theorem which...

The response of a nonlinear stochastic system driven by an external sinusoidal time-dependent force is studied variety numerical and analytical approximations. validity linear theory put to critical test comparing its predictions with solutions over extended parameter regime driving amplitudes frequencies. relevance the frequency for applicability explored.

The role of solvent dynamics on low temperature nonadiabatic electron transfer reactions is explored. degrees freedom orthogonal to the nuclear motion reaction coordinate are represented by a frictional term. Thus, along described damped quantum oscillator equation motion. This used construct rate constant which describes long range phenomena such as occurs in biological oxidation-reduction reactions. correctly even for temperatures lower than characteristic frequencies and friction. We...