full name: tenpy.tools.fit.fit_with_sum_of_exp
fit_with_sum_of_exp(f, n, N=50)¶
Approximate a decaying function f with a sum of exponentials.
MPOs can naturally represent long-range interactions with an exponential decay. A common technique for other (e.g. powerlaw) long-range interactions is to approximate them by sums of exponentials and to include them into the MPOs. This funciton allows to do that.
The algorithm/implementation follows the appendix of [murg2010].
lambdas, prefactors – Such that \(f(k) \approx \sum_i x_i \lambda_i^k\) for (integer) 1 <= k <= N. The function
sum_of_exp()evaluates this for given x.
- Return type