Imaginary Polarization as a Way to Surmount the Sign Problem in Ab Initio Calculations of Spin-Imbalanced Fermi Gases

Jens Braun, Jiunn-Wei Chen, Jian Deng, Joaquín E. Drut, Bengt Friman, Chen-Te Ma, and Yu-Dai Tsai
Phys. Rev. Lett. 110, 130404 – Published 26 March 2013


From ultracold atoms to quantum chromodynamics, reliable ab initio studies of strongly interacting fermions require numerical methods, typically in some form of quantum Monte Carlo calculation. Unfortunately, (non)relativistic systems at finite density (spin polarization) generally have a sign problem, such that those ab initio calculations are impractical. It is well-known, however, that in the relativistic case imaginary chemical potentials solve this problem, assuming the data can be analytically continued to the real axis. Is this feasible for nonrelativistic systems? Are the interesting features of the phase diagram accessible in this manner? By introducing complex chemical potentials, for real total particle number and imaginary polarization, the sign problem is avoided in the nonrelativistic case. To give a first answer to the above questions, we perform a mean-field study of the finite-temperature phase diagram of spin-1/2 fermions with imaginary polarization.

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  • Received 1 October 2012


© 2013 American Physical Society

Authors & Affiliations

Jens Braun1, Jiunn-Wei Chen2, Jian Deng3, Joaquín E. Drut4, Bengt Friman5, Chen-Te Ma2, and Yu-Dai Tsai6,7

  • 1Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, D-64289 Darmstadt, Germany
  • 2Department of Physics, National Center for Theoretical Sciences and Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan
  • 3School of Physics, Shandong University, Shandong 250100, People’s Republic of China
  • 4Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
  • 5GSI Helmholtzzentrum für Schwerionenforschung, D-64291 Darmstadt, Germany
  • 6Department of Physics, Tsing-Hua University, Hsinchu, Taiwan 300, Republic of China
  • 7Department of Physics, University of California, Berkeley, California 94720, USA

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Vol. 110, Iss. 13 — 29 March 2013

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