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SUMMARY:Four-Fermi-Theories in 3 dimensions: Critical flavour number of th
e massless Thirring model
DTSTART;VALUE=DATE-TIME:20170622T134000Z
DTEND;VALUE=DATE-TIME:20170622T140000Z
DTSTAMP;VALUE=DATE-TIME:20200220T045503Z
UID:indico-contribution-331@cern.ch
DESCRIPTION:Speakers: Dr. WELLEGEHAUSEN\, Björn (JLU Giessen)\nThe Thirri
ng model is a Four-Fermi-Theory with a current-current interaction and $U(
2N_\\text{f})$ chiral symmetry. It is closely related to three-dimensional
QED\nand other models used to describe properties of graphene. In additio
n it serves as a toy model to study chiral symmetry breaking.\nIn the limi
t of flavour-number $N_\\text{f} \\to 1/2$ it is connected to the Gross-Ne
veau model\, which shows a parity-breaking discrete chiral phase transitio
n\nwhile in the limit of large $N_\\text{f}$\, chiral symmetry is not spon
taneously broken. The critical flavour number\, below which the model show
s chiral symmetry breaking\, has been obtained with different methods over
the last years but so far\, the results are not conclusive ranging from $
N_\\text{f\,c}=2$ to $\\infty$.\n\nIn the talk\, we employ fierz transform
ations to derive an effective potential for an order parameter for chiral
symmetry breaking and discuss its properties. Via lattice simulations with
exactly chiral fermions we can relate at first undetermined parameters of
the potential to chirally invariant observables.\nWith this approach we s
how that there is no spontaneous chiral symmetry breaking in the Thirring
model for integer flavour numbers. For half-integer flavour numbers the mo
del shows a discrete parity-breaking phase transition up to some critical
flavour number which we present in the talk.\n\nhttps://makondo.ugr.es/eve
nt/0/session/101/contribution/331
LOCATION: Seminarios 1+2
URL:https://makondo.ugr.es/event/0/session/101/contribution/331
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