2009/06/04 by Christopher Eichler, N. Hasselmann, Nils Hasselmann +1 · 8 citations
Physics and Astronomy · #Boson #Cold Atom Physics and Bose-Einstein Condensates #Density matrix renormalization group #Functional renormalization group #Group (periodic table) #Physics #Quantum Chromodynamics and Particle Interactions #Quantum electrodynamics #Quantum mechanics #Quantum, superfluid, helium dynamics #Renormalization group #cond-mat.quant-gas
paper · pdf · doi:10.1103/physreve.80.051129
published in Physical Review E 80(5), 051129 (American Physical Society) · 9 pages, 6 figures
arxiv created 2009/06/04 · openalex publication_date 2009/11/30 · arxiv updated 2010/03/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We calculate the temperature-dependent condensate density rho0(T) of interacting bosons in three dimensions using the functional renormalization group (FRG). From the numerical solution of suitably truncated FRG flow equations for the irreducible vertices we obtain rho0(T) for arbitrary temperatures. We carefully extrapolate our numerical results to the critical point and determine the order parameter exponent beta approximately 0.32 in reasonable agreement with the expected value 0.345 associated with the XY -universality class. We also calculate the condensate density in two dimensions at zero temperature using a truncation of the FRG flow equations based on the derivative expansion including cubic and quartic terms in the expansion of the effective potential in powers of the density. As compared with the widely used quadratic approximation for the effective potential, the coupling constants associated with the cubic and quartic terms lead to small corrections of the condensate density.