Inflationary preheating dynamics with two-species condensates

Zache, Torsten V.; Kasper, Valentin; Berges, Jürgen

doi:10.1103/physreva.95.063629

Cited by 6 publications

(10 citation statements)

References 35 publications

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“…Interestingly, a similar sequence of events was recently described in the context of an unstable two-component BEC system, see Ref. [27] and footnote 2.…”

Section: A Parametric Amplification Of Resonant Phonon Modessupporting

confidence: 71%

“…By this we mean that at large n ph ±k , even within the BdG description, when the twomode state (k, −k) is maximally entangled it is already very difficult to verify its nonseparability due to the necessity of taking the difference between two large numbers, namely n ph k n ph −k and c ph k 2 in Eq. (27). One can appreciate the difficulty by examining Figure 3: as n ph ±k increases, the amount of time G…”

Section: B Visibility Of Nonseparability and Effective Dissipationmentioning

confidence: 99%

“…Indeed, sincen 2 k ≥ n k n −k , Eq. (27) implies that a sufficient criterion for nonseparability isη k −η k,th > 0, wherẽ…”

Section: B Visibility Of Nonseparability and Effective Dissipationmentioning

confidence: 99%

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Nonlinearities induced by parametric resonance in effectively 1D atomic Bose condensates

2018

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We present a numerical study of the dynamical effects following a sudden change of the transverse trapping frequency in an elongated Bose-Einstein condensate, which induces periodic oscillations of the radial density. At early times, we observe an exponential growth of the number of resonant longitudinal phonons, in agreement with the predictions of the Bogoliubov-de Gennes treatment. We then observe an ordered sequence of phenomena induced by the nonlinearities of the system. The first is a loss of the nonseparability of the resonant phonon pairs. This is followed by the saturation of the exponential growth and a strong depletion of condensed atoms. Notably, these effects are well-described by effective 1D dynamics, and are hardly affected by the damping of the radial oscillations. Finally, the atomic spectrum becomes broad, featureless and almost incoherent, in agreement with experimental results. The link between this sequence of events and the preheating scenario in inflationary cosmology is striking, as is the similarity of techniques used to study them. arXiv:1802.00739v2 [cond-mat.quant-gas] 3 Sep 2018

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“…Interestingly, a similar sequence of events was recently described in the context of an unstable two-component BEC system, see Ref. [27] and footnote 2.…”

Section: A Parametric Amplification Of Resonant Phonon Modessupporting

confidence: 71%

Section: B Visibility Of Nonseparability and Effective Dissipationmentioning

confidence: 99%

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Nonlinearities induced by parametric resonance in effectively 1D atomic Bose condensates

2018

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“…[55]. The Bose gas is initially prepared in a non-equilibrium state, analogous to the inflationary period of the early universe.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Thermalization of Isolated Bose‐Einstein Condensates by Dynamical Heat Bath Generation

2017

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If and how an isolated quantum system thermalizes despite its unitary time evolution is a long-standing, open problem of many-body physics. The eigenstate thermalization hypothesis (ETH) postulates that thermalization happens at the level of individual eigenstates of a system's Hamiltonian. However, the ETH requires stringent conditions to be validated, and it does not address how the thermal state is reached dynamically from an initial non-equilibrium state. We consider a Bose-Einstein condensate (BEC) trapped in a double-well potential with an initial population imbalance. We find that the system thermalizes although the initial conditions violate the ETH requirements. We identify three dynamical regimes. After an initial regime of undamped Josephson oscillations, the subsystem of incoherent excitations or quasiparticles (QP) becomes strongly coupled to the BEC subsystem by means of a dynamically generated, parametric resonance. When the energy stored in the QP system reaches its maximum, the number of QPs becomes effectively constant, and the system enters a quasi-hydrodynamic regime where the two subsystems are weakly coupled. In this final regime the BEC acts as a grand-canonical heat reservoir for the QP system (and vice versa), resulting in thermalization. We term this mechanism dynamical bath generation (DBG).

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“…B). This can be achieved by starting with a system with unstable internal modes [44,50,[80][81][82][83], or with an inhomogeneous condensate [51-54, 64, 75, 84], and can be technically advantageous.…”

Section: Strong Cooling Quenchmentioning

confidence: 99%

Kinetic theory of nonthermal fixed points in a Bose gas

2019

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We outline a kinetic theory of non-thermal fixed points for the example of a dilute Bose gas, partially reviewing results obtained earlier, thereby extending, complementing, generalizing and straightening them out. We study universal dynamics after a cooling quench, focusing on situations where the time evolution represents a pure rescaling of spatial correlations, with time defining the scale parameter. The non-equilibrium initial condition set by the quench induces a redistribution of particles in momentum space. Depending on conservation laws, this can take the form of a wave-turbulent flux or of a more general self-similar evolution, signaling the critically slowed approach to a non-thermal fixed point. We identify such fixed points using a non-perturbative kinetic theory of collective scattering between highly occupied long-wavelength modes. In contrast, a wave-turbulent flux, possible in the perturbative Boltzmann regime, builds up in a critically accelerated self-similar manner. A key result is the simple analytical universal scaling form of the non-perturbative many-body scattering matrix, for which we lay out the concrete conditions under which it applies. We derive the scaling exponents for the time evolution as well as for the power-law tail of the momentum distribution function, for a general dynamical critical exponent z and an anomalous scaling dimension η. The approach of the non-thermal fixed point is, in particular, found to involve a rescaling of momenta in time t by t β , with β = 1/z, within our kinetic approach independent of η. We confirm our analytical predictions by numerically evaluating the kinetic scattering integral as well as the non-perturbative many-body coupling function. As a side result we obtain a possible finite-size interpretation of wave-turbulent scaling recently measured by Navon et al.

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Inflationary preheating dynamics with two-species condensates

Cited by 6 publications

References 35 publications

Nonlinearities induced by parametric resonance in effectively 1D atomic Bose condensates

Nonlinearities induced by parametric resonance in effectively 1D atomic Bose condensates

Thermalization of Isolated Bose‐Einstein Condensates by Dynamical Heat Bath Generation

Kinetic theory of nonthermal fixed points in a Bose gas

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