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Theophilus Dwamena Frimpong

Publications and source records attributed to Theophilus Dwamena Frimpong.

2 recordsLinked to original sources

Extremal and global-time statistics of sluggish random walks with stochastic resetting

We study the extremal and global-time statistics of a one-dimensional sluggish random walk, whose diffusivity decays as a power law of the distance from the origin, under Poissonian resetting to the origin. A change of variable maps the process onto a signed Bessel process, so that renewal theory applies. We obtain the exact Laplace transform of the distribution of the maximum over a finite window. At long times the centered maximum of the transformed process follows the Gumbel law, and in physical space the typical maximum grows as a power of the logarithm of the window length. The far-tail rate function does not depend on $α$ in the Bessel variable, so the second-order dynamical transition known for Brownian resetting, between maxima produced by a single anomalously long inter-reset interval and maxima produced by an interval occupying essentially the whole window, holds for every $α$. The time of the maximum is uniformly distributed in the bulk of the window, with boundary layers that shift its mean above the midpoint logarithmically in the window length. The last-passage time through the origin has an exact density, and the time elapsed since it converges to a Gamma law. Reflection symmetry makes the occupation time of the positive half-line and the last-passage time uncorrelated. The results reduce to the Brownian case and agree with simulations.

cond-mat.stat-mech↗

Sluggish random walks with resetting: nonequilibrium aspects

We derive exact analytical expressions for the fixed-time probability distribution and the Laplace transform of the distribution of the first-passage time to reach a target for a sluggish random walk in one dimension subject to two different types of stochastic resetting: stochastic resetting at random Poisson-distributed times, and resetting implemented whenever a position threshold is reached. The optimal resetting rate that minimises the mean first-passage time is obtained as a function of the sluggishness parameter, while under threshold resetting the mean first-passage time to the origin is found to increase monotonically with the threshold. We also characterise the occupation-time statistics, retrieving a Lamperti-type distribution under free dynamics and under Poissonian resetting at rate for short observation times, a Gaussian distribution centred at half for long observation times, and a distinct deterministic limit under threshold resetting. To further characterise nonequilibrium aspects of resetting, we evaluate the distribution and mean of the cost incurred per reset under Poissonian resetting, and the cost rate under threshold resetting, for different (linear, power-law, exponential) cost functions, and find the same critical behaviour of the cost rate in the limits of a vanishing resetting rate and an infinite threshold, respectively. Numerical simulations validate with excellent accuracy our analytical formulae.

cond-mat.stat-mech↗