11,667 research outputs found
One loop renormalization for the axial Ward-Takahashi identity in Domain-wall QCD
We calculate one-loop correction to the axial Ward-Takahashi identity given
by Furman and Shamir in domain-wall QCD. It is shown perturbatively that the
renormalized axial Ward-Takahashi identity is satisfied without fine tuning and
the ``conserved'' axial current receives no renormalization, giving .
This fact will simplify the calculation of the pion decay constant in numerical
simulations since the decay constant defined by this current needs no lattice
renormalization factor.Comment: 16 pages, 3 axodraw.sty figure
Domain Wall Fermions in Quenched Lattice QCD
We study the chiral properties and the validity of perturbation theory for
domain wall fermions in quenched lattice QCD at beta=6.0. The explicit chiral
symmetry breaking term in the axial Ward-Takahashi identity is found to be very
small already at Ns=10, where Ns is the size of the fifth dimension, and its
behavior seems consistent with an exponential decay in Ns within the limited
range of Ns we explore. From the fact that the critical quark mass, at which
the pion mass vanishes as in the case of the ordinary Wilson-type fermion,
exists at finite Ns, we point out that this may be a signal of the parity
broken phase and investigate the possible existence of such a phase in this
model at finite Ns. The rho and pi meson decay constants obtained from the
four-dimensional local currents with the one-loop renormalization factor show a
good agreement with those obtained from the conserved currents
The Lattice Parameter in Domain Wall QCD
We evaluate the ratio of the scale parameter in domain wall QCD to
the one in the continuum theory at one loop level incorporating the effect of
massless quarks. We show that the Pauli-Villars regulator is required to
subtract the unphysical massive fermion modes which emerge in the fermion loop
contributions to the gluon self energy. Detailed results are presented as a
function of the domain wall height .Comment: 16 pages, 1 figure as eps-file, some references adde
Magnetic order in Ce0.95Nd0.05CoIn5: the Q-phase at zero magnetic field
We report neutron scattering experiment results revealing the nature of the
magnetic order occurring in the heavy fermion superconductor Ce0.95Nd0.05CoIn5,
a case for which an antiferromagnetic state is stabilized at a temperature
below the superconducting transition one. We evidence an incommensurate order
and its propagation vector is found to be identical to that of the magnetic
field induced antiferromagnetic order occurring in the stoichiometric
superconductor CeCoIn5, the so-called Q-phase. The commonality between these
two cases suggests that superconductivity is a requirement for the formation of
this kind of magnetic order and the proposed mechanism is the enhancement of
nesting condition by d-wave order parameter with nodes in the nesting area.Comment: submitted to Phys. Rev. Lett. on June 30th, 201
Spontaneous Parity Violation in QCD At Finite Temperature: On the Inapplicability of the Vafa-Witten Theorem
The generalization of the Vafa-Witten theorem ruling out parity violation to
QCD at finite temperature is considered. It is shown that this generalization
of the theorem rules out Lorentz-invariant parity violating operators from
spontaneously acquiring vacuum expectation values. However, it does not rule
out Lorentz-noninvariant parity-violating operators from acquiring expectation
values. Other situations where the theorem is inapplicable are also discussed.Comment: Minor typos correcte
A numerical reinvestigation of the Aoki phase with N_f=2 Wilson fermions at zero temperature
We report on a numerical reinvestigation of the Aoki phase in lattice QCD
with two flavors of Wilson fermions where the parity-flavor symmetry is
spontaneously broken. For this purpose an explicitly symmetry-breaking source
term was added to the fermion action.
The order parameter was computed with
the Hybrid Monte Carlo algorithm at several values of on
lattices of sizes to and extrapolated to . The existence of a
parity-flavor breaking phase can be confirmed at and 4.3, while we
do not find parity-flavor breaking at and 5.0.Comment: 8 pages, 5 figures, Revised version as to be published in Phys.Rev.
Exact supersymmetry in the relativistic hydrogen atom in general dimensions -- supercharge and the generalized Johnson-Lippmann operator
A Dirac particle in general dimensions moving in a 1/r potential is shown to
have an exact N = 2 supersymmetry, for which the two supercharge operators are
obtained in terms of (a D-dimensional generalization of) the Johnson-Lippmann
operator, an extension of the Runge-Lenz-Pauli vector that relativistically
incorporates spin degrees of freedom. So the extra symmetry (S(2))in the
quantum Kepler problem, which determines the degeneracy of the levels, is so
robust as to accommodate the relativistic case in arbitrary dimensions.Comment: 4 pages, 1 figur
Dynamical scaling analysis of the optical Hall conductivity in the quantum Hall regime
Dynamical scaling analysis is theoretically performed for the ac (optical)
Hall conductivity as a function of Fermi
energy and frequency for the two-dimensional electron
gas and for graphene. In both systems, results based on exact diagonalization
show that displays a well-defined dynamical
scaling, for which the dynamical critical exponent as well as the localization
exponent are fitted and plugged in. A crossover from the dc-like bahavior to
the ac regime is identified. The dynamical scaling analysis has enabled us to
quantify the plateau in the ac Hall conductivity previously obtained, and to
predict that the plateaux structure in ac is robust enough to be observed in
the THz regime.Comment: 5 pages, 3 figure
Efimov effect from functional renormalization
We apply a field-theoretic functional renormalization group technique to the
few-body (vacuum) physics of non-relativistic atoms near a Feshbach resonance.
Three systems are considered: one-component bosons with U(1) symmetry,
two-component fermions with U(1)\times SU(2) symmetry and three-component
fermions with U(1) \times SU(3) symmetry. We focus on the scale invariant
unitarity limit for infinite scattering length. The exact solution for the
two-body sector is consistent with the unitary fixed point behavior for all
considered systems. Nevertheless, the numerical three-body solution in the
s-wave sector develops a limit cycle scaling in case of U(1) bosons and SU(3)
fermions. The Efimov parameter for the one-component bosons and the
three-component fermions is found to be approximately s=1.006, consistent with
the result of Efimov.Comment: 21 pages, 6 figures, minor changes, published versio
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