| In Bose-Einstein condensates with attractive long-range interactions the ground state is not stable. At very low temperatures the main decay process is quantum tunneling but at higher temperatures thermal fluctuations allow classical crossing of the barrier leading to the collapse of the BEC. In analogy to chemical reactions, we describe this process using transition state theory to calculate the thermal decay rates. This requires the knowledge of a classical Hamilton function. We use an extended variational approach with coupled Gaussians with a non-canonical dynamics for the variational parameters. Applying normal form expansions directly to the equations of motion these equations can be integrated and the integrated Hamiltonian can be adapted to the mean-field energy. |
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