355 research outputs found
Hyperon Electromagnetic Properties in Two-Flavor Chiral Perturbation Theory
The pion mass dependence of hyperon electromagnetic properties is determined
using two-flavor heavy baryon chiral perturbation theory. Specifically we
compute chiral corrections to the charge radii, magnetic moments, and magnetic
radii of the spin one-half hyperons, as well as the charge radii, magnetic
moments, magnetic radii, electric quadrupole moments, and quadrupole radii of
the spin three-half hyperons. Results for the nucleon and delta are also
included. Efficacy of the two-flavor theory is investigated by analyzing the
role played by virtual kaons. For the electromagnetic properties of spin
one-half hyperons, kaon loop contributions are shown to be well described by
terms analytic in the pion mass squared. Similarly kaon contributions to the
magnetic moments of spin three-half hyperons are well described in the
two-flavor theory. The remaining electromagnetic properties of spin three-half
resonances can be described in two-flavor chiral perturbation theory, however,
this description fails just beyond the physical pion mass. For the case of
experimentally known hyperon magnetic moments and charge radii, we demonstrate
that chiral corrections are under reasonable control, in contrast to the
behavior of these observables in the three-flavor chiral expansion. The
formulae we derive are ideal for performing the pion mass extrapolation of
lattice QCD data obtained at the physical strange quark mass.Comment: 29 pages, 7 figures, v3: published versio
Hyperon Axial Charges in Two-Flavor Chiral Perturbation Theory
We use two-flavor heavy baryon chiral perturbation theory to investigate the
isovector axial charges of the spin one-half hyperons. Expressions for these
hyperon axial charges are derived at next-to-leading order in the chiral
expansion. We utilize phenomenological and lattice QCD inputs to assess the
convergence of the two-flavor theory, which appears to be best for cascades.Comment: 4 pages, 1 figures, published versio
Real-time simulation of non-equilibrium transport of magnetization in large open quantum spin systems driven by dissipation
Using quantum Monte Carlo, we study the non-equilibrium transport of
magnetization in large open strongly correlated quantum spin
systems driven by purely dissipative processes that conserve the uniform or
staggered magnetization. We prepare both a low-temperature Heisenberg
ferromagnet and an antiferromagnet in two parts of the system that are
initially isolated from each other. We then bring the two subsystems in contact
and study their real-time dissipative dynamics for different geometries. The
flow of the uniform or staggered magnetization from one part of the system to
the other is described by a diffusion equation that can be derived
analytically.Comment: 6 pages, 5 figures. Revised version: Discussion extended and
references adde
Chiral Corrections to Hyperon Axial Form Factors
We study the complete set of flavor changing hyperon axial current matrix
elements at small momentum transfer. Using partially quenched heavy baryon
chiral perturbation theory, we derive the chiral and momentum behavior of the
axial and induced pseudoscalar form factors. The meson pole contributions to
the latter posses a striking signal for chiral physics. We argue that the study
of hyperon axial matrix elements enables a systematic lattice investigation of
the efficacy of three flavor chiral expansions in the baryon sector. This can
be achieved by considering chiral corrections to SU(3) symmetry predictions,
and their partially quenched generalizations. In particular, despite the
presence of eight unknown low-energy constants, we are able to make
next-to-leading order symmetry breaking predictions for two linear combinations
of axial charges.Comment: 23 pages, 3 figures, typos corrected and a new NLO prediction adde
Flavor Twisted Boundary Conditions in the Breit Frame
We use a generalization of chiral perturbation theory to account for the
effects of flavor twisted boundary conditions in the Breit frame. The relevant
framework for two light flavors is an SU(6|4) partially quenched theory, where
the extra valence quarks differ only by their boundary conditions. Focusing on
the pion electromagnetic form factor, finite volume corrections are calculated
at next-to-leading order in the chiral expansion and are estimated to be small
on current lattices.Comment: 4 pages, 1 figure, discussion and citations altere
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