Quantum resonant activation

Magazzù, Luca; Hänggi, Peter; Spagnolo, Bernardo; Valenti, Davide

doi:10.1103/physreve.95.042104

Cited by 18 publications

(8 citation statements)

References 52 publications

(150 reference statements)

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“…A number of studies have suggested a spatially distributed older population of stars in Taurus. X-ray studies using ROSAT detected a very widely dispersed stellar population, ≈ 50 pc (≈ 20 • ) away from the central molecular clouds in Taurus (Neuhäeuser et al 1995a,b;Briceño et al 1997;Carkner et al 1997;Magazzù et al 1999). One explanation is that these objects formed tens of million years before the well-studied young population.…”

Section: Zhang Et Almentioning

confidence: 99%

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

Zhang

Liu

Best

et al. 2018

ApJ

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We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3π Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370 deg 2 ) and deeper (down to ≈3 M Jup ) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution (R ≈ 100) nearinfrared spectra to quantify reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (≈ 100 − 3 M Jup in Taurus). We have discovered 25 low-gravity (VL-G) and the first 11 intermediate-gravity (INT-G) substellar (M6-L1) members of Taurus, constituting the largest single increase of Taurus brown dwarfs to date. We have also discovered 1 new Pleiades member and 13 new members of the Perseus OB2 association, including a candidate very wide separation (58 kAU) binary. We homogeneously reclassify the spectral types and extinctions of all previously known Taurus brown dwarfs. Altogether our discoveries have thus far increased the substellar census in Taurus by ≈ 40% and added three more L-type members (≈ 5 − 10 M Jup ). Most notably, our discoveries reveal an older (>10 Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. The mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes.

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Section: Zhang Et Almentioning

confidence: 99%

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

Zhang

Liu

Best

et al. 2018

ApJ

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“…Thanks to theorems due to Bourret-Frisch [38] which provide a factorization for the multi-time correlation functions of dichotomous process and Loginov-Shapiro [39] which relates the average of time evolution operator of the noise with that of the system operators, Eqs. ( 9)-( 12) can be averaged exactly over the RTN [40]. The averaging process effectively doubles the number of correlation functions by coupling the correlations of the noise signal α(t) with the system operator correlations.…”

Section: Stochastic Averagingmentioning

confidence: 99%

Two-time correlation functions beyond quantum regression theorem: Effect of external noise

Kurt

2021

Preprint

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We present the results of a study of the two-time correlation functions of a dichotomously driven two-level system in contact with a thermal bath by using corrections beyond quantum regression theorem. In the strong system-environment coupling regime, it is found that the noise parameters could be tuned to control the magnitude of corrections at low environmental temperatures. Motional averaging and narrowing effect of the external noise were observed on the absorption and emission spectra of the two-state system. Furthermore, effects similar to the destruction of tunneling and noise enhancement of transport are observed in the dynamics of the two-time correlations.

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“…The frequencies for which

is maximized (or no escape occurs, depending on the amplitude) roughly correspond to the energy separations

, and

, showing that a resonance phenomenon between the external driving and these frequencies occurs. For

, a minimum of

is visible, which is akin to the quantum resonant activation phenomenon [ 95 ] and noise suppression effect [ 24 , 25 ]. However, these noise-induced effects and the related relaxation dynamics have been observed by fixing the initial condition for the system in the metastable well.…”

Section: Driven Quantum Dissipative Dynamicsmentioning

confidence: 99%

Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System

Spagnolo

Carollo

Valenti

2018

Entropy

Self Cite

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Abstract:The stabilizing effect of quantum fluctuations on the escape process and the relaxation dynamics from a quantum metastable state are investigated. Specifically, the quantum dynamics of a multilevel bistable system coupled to a bosonic Ohmic thermal bath in strong dissipation regime is analyzed. The study is performed by a non-perturbative method based on the real-time path integral approach of the Feynman-Vernon influence functional. We consider a strongly asymmetric double well potential with and without a monochromatic external driving, and with an out-of-equilibrium initial condition. In the absence of driving we observe a nonmonotonic behavior of the escape time from the metastable region, as a function both of the system-bath coupling coefficient and the temperature. This indicates a stabilizing effect of the quantum fluctuations. In the presence of driving our findings indicate that, as the coupling coefficient γ increases, the escape time, initially controlled by the external driving, shows resonant peaks and dips, becoming frequency-independent for higher γ values. Moreover, the escape time from the metastable state displays a nonmonotonic behavior as a function of the temperature, the frequency of the driving, and the thermal-bath coupling, which indicates the presence of a quantum noise enhanced stability phenomenon. Finally, we investigate the role of different spectral densities, both in sub-Ohmic and super-Ohmic dissipation regime and for different cutoff frequencies, on the relaxation dynamics from the quantum metastable state. The results obtained indicate that, in the crossover dynamical regime characterized by damped intrawell oscillations and incoherent tunneling, the spectral properties of the thermal bath influence non-trivially the short time behavior and the time scales of the relaxation dynamics from the metastable state.

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Quantum resonant activation

Cited by 18 publications

References 52 publications

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

Two-time correlation functions beyond quantum regression theorem: Effect of external noise

Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System

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