SciPost Phys. 9, 014 (2020) ·
published 28 July 2020
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We study spin- and mass-imbalanced mixtures of spin-$\tfrac{1}{2}$ fermions
interacting via an attractive contact potential in one spatial dimension.
Specifically, we address the influence of unequal particle masses on the pair
formation by means of the complex Langevin method. By computing the
pair-correlation function and the associated pair-momentum distribution we find
that inhomogeneous pairing is present for all studied spin polarizations and
mass imbalances. To further characterize the pairing behavior, we analyze the
density-density correlations in momentum space, the so-called shot noise, which
is experimentally accessible through time-of-flight imaging. At finite spin
polarization, the latter is known to show distinct maxima at momentum
configurations associated with the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)
instability. Besides those maxima, we find that additional features emerge in
the noise correlations when mass imbalance is increased, revealing the
stability of FFLO-type correlations against mass imbalance and furnishing an
experimentally accessible signature to probe this type of pairing.
SciPost Phys. 6, 056 (2019) ·
published 9 May 2019
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Low-energy effective theories have been used very successfully to study the low-energy limit of QCD, providing us with results for a plethora of phenomena, ranging from bound-state formation to phase transitions in QCD. These theories are consistent quantum field theories by themselves and can be embedded in QCD, but typically have a physical ultraviolet cutoff that restricts their range of validity. Here, we provide a discussion of the concept of renormalization group consistency, aiming at an analysis of cutoff effects and regularization-scheme dependences in general studies of low-energy effective theories. For illustration, our findings are applied to low-energy effective models of QCD in different approximations including the mean-field approximation. More specifically, we consider hot and dense as well as finite systems and demonstrate that violations of renormalization group consistency affect significantly the predictive power of the corresponding model calculations.
