628 research outputs found
The epsilon expansion at next-to-next-to-leading order with small imaginary chemical potential
We discuss chiral perturbation theory for two and three quark flavors in the
epsilon expansion at next-to-next-to-leading order (NNLO) including a small
imaginary chemical potential. We calculate finite-volume corrections to the
low-energy constants and and determine the non-universal
modifications of the theory, i.e., modifications that cannot be mapped to
random matrix theory (RMT). In the special case of two quark flavors in an
asymmetric box we discuss how to minimize the finite-volume corrections and
non-universal modifications by an optimal choice of the lattice geometry.
Furthermore we provide a detailed calculation of a special version of the
massless sunset diagram at finite volume.Comment: 21 pages, 5 figure
Overlap/Domain-wall reweighting
We investigate the eigenvalues of nearly chiral lattice Dirac operators
constructed with five-dimensional implementations. Allowing small violation of
the Ginsparg-Wilson relation, the HMC simulation is made much faster while the
eigenvalues are not significantly affected. We discuss the possibility of
reweighting the gauge configurations generated with domain-wall fermions to
those of exactly chiral lattice fermions.Comment: 7 pages, 3 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July-3 August 2013, Mainz, German
Chiral behavior of decay form factors in lattice QCD with exact chiral symmetry
We calculate the form factors of the semileptonic decays in
three-flavor lattice QCD, and study their chiral behavior as a function of the
momentum transfer and the Nambu-Goldstone boson masses. Chiral symmetry is
exactly preserved by using the overlap quark action, which enables us to
directly compare the lattice data with chiral perturbation theory (ChPT). We
generate gauge ensembles at a lattice spacing of 0.11fm with four pion masses
covering 290-540 MeV and a strange quark mass m_s close to its physical value.
By using the all-to-all quark propagator, we calculate the vector and scalar
form factors with high precision. Their dependence on m_s and the momentum
transfer is studied by using the reweighting technique and the twisted boundary
conditions for the quark fields. We compare the results for the semileptonic
form factors with ChPT at next-to-next-to leading order in detail. While many
low-energy constants appear at this order, we make use of our data of the light
meson electromagnetic form factors in order to control the chiral
extrapolation. We determine the normalization of the form factors as f_+(0) =
0.9636(36)(+57/-35), and observe reasonable agreement of their shape with
experiment.Comment: 34 pages, 13 figure
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