### Abstract

Language | English |
---|---|

Article number | 023032 |

Number of pages | 13 |

Journal | New Journal of Physics |

Volume | 15 |

Issue number | 2 |

DOIs | |

Publication status | Published - 19 Feb 2013 |

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### Keywords

- discrete breathers
- optical waveguides
- BEC
- negative temperatures

### Cite this

*New Journal of Physics*,

*15*(2), [023032]. https://doi.org/10.1088/1367-2630/15/2/023032

}

*New Journal of Physics*, vol. 15, no. 2, 023032. https://doi.org/10.1088/1367-2630/15/2/023032

**Discrete breathers and negative-temperature states.** / Iubini, Stefano; Franzosi, Roberto; Livi, Roberto; Oppo, Gian-Luca; Politi, Antonio.

Research output: Contribution to journal › Letter

TY - JOUR

T1 - Discrete breathers and negative-temperature states

AU - Iubini, Stefano

AU - Franzosi, Roberto

AU - Livi, Roberto

AU - Oppo, Gian-Luca

AU - Politi, Antonio

PY - 2013/2/19

Y1 - 2013/2/19

N2 - We explore the statistical behaviour of the discrete nonlinear Schrödinger equation as a test bed for the observation of negative-temperature (i.e. above infinite temperature) states in Bose–Einstein condensates in optical lattices and arrays of optical waveguides. By monitoring the microcanonical temperature, we show that there exists a parameter region where the system evolves towards a state characterized by a finite density of discrete breathers and a negative temperature. Such a state persists over very long (astronomical) times since the convergence to equilibrium becomes increasingly slower as a consequence of a coarsening process. We also discuss two possible mechanisms for the generation of negative-temperature states in experimental setups, namely, the introduction of boundary dissipations and the free expansion of wavepackets initially in equilibrium at a positive temperature.

AB - We explore the statistical behaviour of the discrete nonlinear Schrödinger equation as a test bed for the observation of negative-temperature (i.e. above infinite temperature) states in Bose–Einstein condensates in optical lattices and arrays of optical waveguides. By monitoring the microcanonical temperature, we show that there exists a parameter region where the system evolves towards a state characterized by a finite density of discrete breathers and a negative temperature. Such a state persists over very long (astronomical) times since the convergence to equilibrium becomes increasingly slower as a consequence of a coarsening process. We also discuss two possible mechanisms for the generation of negative-temperature states in experimental setups, namely, the introduction of boundary dissipations and the free expansion of wavepackets initially in equilibrium at a positive temperature.

KW - discrete breathers

KW - optical waveguides

KW - BEC

KW - negative temperatures

U2 - 10.1088/1367-2630/15/2/023032

DO - 10.1088/1367-2630/15/2/023032

M3 - Letter

VL - 15

JO - New Journal of Physics

T2 - New Journal of Physics

JF - New Journal of Physics

SN - 1367-2630

IS - 2

M1 - 023032

ER -