3,711 research outputs found
Eighth-Order Vacuum-Polarization Function Formed by Two Light-by-Light-Scattering Diagrams and its Contribution to the Tenth-Order Electron g-2
We have evaluated the contribution to the anomalous magnetic moment of the
electron from six tenth-order Feynman diagrams which contain eighth-order
vacuum-polarization function formed by two light-by-light scattering diagrams
connected by three photons. The integrals are constructed by two different
methods. In the first method the subtractive counter terms are used to deal
with ultraviolet (UV) singularities together with the requirement of
gauge-invariance. In the second method, the Ward-Takahashi identity is applied
to the light-by-light scattering amplitudes to eliminate UV singularities.
Numerical evaluation confirms that the two methods are consistent with each
other within their numerical uncertainties. Combining the two results
statistically and adding small contribution from the muons and/or tau leptons,
we obtain . We also evaluated the
contribution to the muon from the same set of diagrams and found .Comment: 27 page
Valley Instanton versus Constrained Instanton
Based on the new valley equation, we propose the most plausible method for
constructing instanton-like configurations in the theory where the presence of
a mass scale prevents the existence of the classical solution with a finite
radius. We call the resulting instanton-like configuration as valley instanton.
The detail comparison between the valley instanton and the constrained
instanton in theory and the gauge-Higgs system are carried out. For
instanton-like configurations with large radii, there appear remarkable
differences between them. These differences are essential in calculating the
baryon number violating processes with multi bosons.Comment: 37 pages, 8 eps figures, LaTeX, uses epsf.sty, citesort.sty and
wrapfig2.sty. Minor modification
Dynamical Generation of Non-Abelian Gauge Group via the Improved Perturbation Theory
It was suggested that the massive Yang-Mills-Chern-Simons matrix model has
three phases and that in one of them a non-Abelian gauge symmetry is
dynamically generated. The analysis was at the one-loop level around a
classical solution of fuzzy sphere type. We obtain evidences that three phases
are indeed realized as nonperturbative vacua by using the improved perturbation
theory. It also gives a good example that even if we start from a trivial
vacuum, the improved perturbation theory around it enables us to observe
nontrivial vacua.Comment: 31 pages, published versio
Improved Taylor Expansion method in the Ising model
We apply an improved Taylor expansion method, which is a variational scheme
to the Ising model in two dimensions. This method enables us to evaluate the
free energy and magnetization in strong coupling regions from the weak coupling
expansion, even in the case of a phase transition. We determine the approximate
value of the transition point using this scheme. In the presence of an external
magnetic field, we find both stable and metastable physical states.Comment: 13 pages, 9 figure
Proper Eighth-Order Vacuum-Polarization Function and its Contribution to the Tenth-Order Lepton g-2
This paper reports the Feynman-parametric representation of the
vacuum-polarization function consisting of 105 Feynman diagrams of the eighth
order, and its contribution to the gauge-invariant set called Set I(i) of the
tenth-order lepton anomalous magnetic moment. Numerical evaluation of this set
is carried out using FORTRAN codes generated by an automatic code generation
system gencodevpN developed specifically for this purpose. The contribution of
diagrams containing electron loop to the electron g-2 is 0.017 47 (11)
(alpha/pi)^5. The contribution of diagrams containing muon loop is 0.000 001 67
(3) (alpha/pi)^5. The contribution of tau-lepton loop is negligible at present.
The sum of all these terms is 0.017 47 (11) (alpha/pi)^5. The contribution of
diagrams containing electron loop to the muon g-2 is 0.087 1 (59) (alpha/pi)^5.
That of tau-lepton loop is 0.000 237 (1) (alpha/pi)^5. The total contribution
to a_mu, the sum of these terms and the mass-independent term, is 0.104 8 (59)
(alpha/pi)^5.Comment: 48 pages, 6 figures. References are correcte
Recent Developments in the Theory of Tunneling
Path-integral approach in imaginary and complex time has been proven
successful in treating the tunneling phenomena in quantum mechanics and quantum
field theories. Latest developments in this field, the proper valley method in
imaginary time, its application to various quantum systems, complex time
formalism, asympton theory for the large order analysis of the perturbation
theory, are reviewed in a self-contained manner.Comment: 100 pages, LaTeX, PTPTeX.sty, 36 eps figures, To be published in
Progress of Theoretical Physics Supplimen
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