87 research outputs found
Revised and Improved Value of the QED Tenth-Order Electron Anomalous Magnetic Moment
In order to improve the theoretical prediction of the electron anomalous
magnetic moment we have carried out a new numerical evaluation of the 389
integrals of Set V, which represent 6,354 Feynman vertex diagrams without
lepton loops. During this work, we found that one of the integrals, called
, was given a wrong value in the previous calculation due to an incorrect
assignment of integration variables. The correction of this error causes a
shift of to the Set~V contribution, and hence to the tenth-order
universal (i.e., mass-independent) term . The previous evaluation
of all other 388 integrals is free from errors and consistent with the new
evaluation. Combining the new and the old (excluding ) calculations
statistically, we obtain as the best estimate of
the Set V contribution. Including the contribution of the diagrams with fermion
loops, the improved tenth-order universal term becomes
. Adding hadronic and electroweak contributions leads
to the theoretical prediction . From this and the best measurement of
, we obtain the inverse fine-structure constant . The theoretical prediction of the muon anomalous
magnetic moment is also affected by the update of QED contribution and the new
value of , but the shift is much smaller than the theoretical
uncertainty.Comment: 32 pages, 1 figure, references adde
Higher Order Terms of Improved Mean Field Approximation for IIB Matrix Model and Emergence of Four-dimensional Space-time
The spontaneous breakdown of SO(10) symmetry of the IIB matrix model has been
studied by using the improved mean field approximation (IMFA). In this report,
the eighth-order contribution to the improved perturbative series is obtained,
which involves evaluation of 20410 planar two-particle irreducible vacuum
diagrams. We consider SO(d)-preserving configurations as ansatz (d=4,7). The
development of plateau, the solution of self-consistency condition, is seen in
both ansatz. The large ratio of the space-time extent of d-dimensional part
against the remaining (10-d)-dimensional part is obtained for SO(4) ansatz
evaluated at the representative points of the plateau. It would be interpreted
as the emergence of four-dimensional space-time in the IIB matrix model.Comment: 13 page
potential in the HAL QCD method with all-to-all propagators
In this paper, we perform the first application of the hybrid method (exact
low modes plus stochastically estimated high modes) for all-to-all propagators
to the HAL QCD method. We calculate the HAL QCD potentials in the
scattering in order to see how statistical fluctuations of the
potential behave under the hybrid method. All of the calculations are performed
with the 2+1 flavor gauge configurations on lattice at the
lattice spacing fm and MeV. It is
revealed that statistical errors for the potential are enhanced by stochastic
noises introduced by the hybrid method, which, however, are shown to be reduced
by increasing the level of dilutions, in particular, that of space dilutions.
From systematic studies, we obtain a guiding principle for a choice of dilution
types/levels and a number of eigenvectors to reduce noise contaminations to the
potential while keeping numerical costs reasonable. We also confirm that we can
obtain the scattering phase shifts for the system by the hybrid
method within a reasonable numerical cost, which are consistent with the result
obtained with the conventional method. The knowledge we obtain in this study
will become useful to investigate hadron resonances which require quark
annihilation diagrams such as the meson by the HAL QCD potential with
the hybrid method.Comment: 20 pages, 10 figures, published version in PTE
Configuration sampling in multi-component multi-sublattice systems enabled by ab Initio Configuration Sampling Toolkit (abICS)
Simulation of the intermediate levels of disorder found in multi-component
multi-sublattice systems in various functional materials is a challenging
issue, even for state-of-the-art methodologies based on first-principles
calculation. Here, we introduce our open-source package ab Initio Configuration
Sampling Toolkit (abICS), which combines high-throughput first-principles
calculations, machine learning, and parallel extended ensemble sampling in an
active learning setting to enable such simulations. The theoretical background
is reviewed in some detail followed by brief notes on usage of the software. In
addition, our recent applications of abICS to multi-component ionic systems and
their interfaces for energy applications are reviewed as demonstration of the
power of this approach.Comment: 25 pages, 6 figure
Tenth-Order QED Contribution to the Electron g-2 and an Improved Value of the Fine Structure Constant
This paper presents the complete QED contribution to the electron g-2 up to
the tenth order. With the help of the automatic code generator, we have
evaluated all 12672 diagrams of the tenth-order diagrams and obtained 9.16
(58)(\alpha/\pi)^5. We have also improved the eighth-order contribution
obtaining -1.9097(20)(\alpha/\pi)^4, which includes the mass-dependent
contributions. These results lead to a_e(theory)=1 159 652 181.78 (77) \times
10^{-12}. The improved value of the fine-structure constant \alpha^{-1} =
137.035 999 174 (35) [0.25 ppb] is also derived from the theory and measurement
of a_e.Comment: 4 pages, 2 figures. Some numbers are slightly change
Exploring walking behavior in SU(3) gauge theory with 4 and 8 HISQ quarks
We present the report of the LatKMI collaboration on the lattice QCD
simulation for the cases of 4 and 8 flavors. The Nf=8 in particular is
interesting from the model-building point of view: The typical walking
technicolor model with the large anomalous dimension is the so-called
one-family model (Farhi-Susskind model). Thus we explore the walking behavior
in LQCD with 8 HISQ quarks by comparing with the 4-flavor case (in which the
chiral symmetry is spontaneously broken). We report preliminary results on the
spectrum, analyzed through the chiral perturbation theory and the finite-size
hyperscaling, and we discuss the availability of the Nf=8 QCD to the
phenomenology.Comment: 7 pages, Proceedings of 30th International Symposium on Lattice Field
Theory, June 24-29, 2012, Cairns, Australi
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