Embedding generalized thimble HMC into worldvolume HMC improves ergodicity and phase-space exploration for sign-problem mitigation in 2D doped Hubbard model simulations, enabling larger lattices and controlled extrapolations.
Monte Carlo study of Lefschetz thimble structure in one-dimensional Thirring model at finite density
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abstract
We consider the one-dimensional massive Thirring model formulated on the lattice with staggered fermions and an auxiliary compact vector (link) field, which is exactly solvable and shows a phase transition with increasing the chemical potential of fermion number: the crossover at a finite temperature and the first order transition at zero temperature. We complexify its path-integration on Lefschetz thimbles and examine its phase transition by hybrid Monte Carlo simulations on the single dominant thimble. We observe a discrepancy between the numerical and exact results in the crossover region for small inverse coupling $\beta$ and/or large lattice size $L$, while they are in good agreement at the lower and higher density regions. We also observe that the discrepancy persists in the continuum limit keeping the temperature finite and it becomes more significant toward the low-temperature limit. This numerical result is consistent with our analytical study of the model's thimble structure. And these results imply that the contributions of subdominant thimbles should be summed up in order to reproduce the first order transition in the low-temperature limit.
representative citing papers
WV-HMC successfully simulates the doped 2D Hubbard model on 8x8 lattices at U/t=8 and T/t≈0.156 with controlled statistical errors.
WV-HMC computes number and energy densities for the doped 2D Hubbard model on 6x6 and 8x8 lattices at U/t=8 and T/t≈0.156, showing effectiveness where standard DQMC fails.
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Enhancing the ergodicity of Worldvolume HMC via embedding generalized thimble HMC
Embedding generalized thimble HMC into worldvolume HMC improves ergodicity and phase-space exploration for sign-problem mitigation in 2D doped Hubbard model simulations, enabling larger lattices and controlled extrapolations.
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Analyzing the two-dimensional doped Hubbard model with the Worldvolume HMC method
WV-HMC successfully simulates the doped 2D Hubbard model on 8x8 lattices at U/t=8 and T/t≈0.156 with controlled statistical errors.
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Applying the Worldvolume Hybrid Monte Carlo method to the Hubbard model away from half filling
WV-HMC computes number and energy densities for the doped 2D Hubbard model on 6x6 and 8x8 lattices at U/t=8 and T/t≈0.156, showing effectiveness where standard DQMC fails.