12,147 research outputs found
Electrodynamics Modified by Some Dimension-five Lorentz Violating Interactions: Radiative Corrections
We study radiative corrections to massless quantum electrodynamics modified
by two dimension-five LV interactions and in
the framework of effective field theories. All divergent
one-particle-irreducible Feynman diagrams are calculated at one-loop order and
several related issues are discussed. It is found that massless quantum
electrodynamics modified by the interaction alone is one-loop renormalizable and the result can be
understood on the grounds of symmetry. In this context the one-loop
Lorentz-violating beta function is derived and the corresponding running
coefficients are obtained.Comment: 13 pages, 1 figure. Version to appear in EPJ
Ergodicity and Mixing in Quantum Dynamics
After a brief historical review of ergodicity and mixing in dynamics,
particularly in quantum dynamics, we introduce definitions of quantum
ergodicity and mixing using the structure of the system's energy levels and
spacings. Our definitions are consistent with usual understanding of ergodicity
and mixing. Two parameters concerning the degeneracy in energy levels and
spacings are introduced. They are computed for right triangular billiards and
the results indicate a very close relation between quantum ergodicity (mixing)
and quantum chaos. At the end, we argue that, besides ergodicity and mixing,
there may exist a third class of quantum dynamics which is characterized by a
maximized entropy.Comment: 10 pages, 6 figures and 1 tabl
Constraints on the Brans-Dicke gravity theory with the Planck data
Based on the new cosmic CMB temperature data from the Planck satellite, the 9
year polarization data from the WMAP, the BAO distance ratio data from the SDSS
and 6dF surveys, we place a new constraint on the Brans-Dicke theory. We adopt
a parametrization \zeta=\ln(1+1/\omega}), where the general relativity (GR)
limit corresponds to . We find no evidence of deviation from general
relativity. At 95% probability, , correspondingly,
the region is excluded. If we restrict ourselves to
the (i.e. ) case, then the 95% probability interval is
. We can also translate this
result to a constraint on the variation of gravitational constant, and find the
variation rate today as yr ( error bar), the integrated change since the epoch of
recombination is ( error
bar). These limits on the variation of gravitational constant are comparable
with the precision of solar system experiments.Comment: 7 pages, 5 figures, 2 table
The Importance of Proper Renormalization Scale-Setting for Testing QCD at Colliders
A primary problem for perturbative QCD analyses is how to set the
renormalization scale of the QCD running coupling in order to achieve maximally
precise fixed-order predictions for physical observables. The Principle of
Maximum Conformality (PMC) eliminates the ambiguities associated with the
conventional renormalization scale-setting procedure, giving predictions which
are independent of the choice of renormalization scheme. The scales of the QCD
couplings and the effective number of quark flavors are set order by order in
the pQCD series. The PMC has a solid theoretical foundation, satisfying the
standard renormalization group invariance and all of the the self-consistency
conditions derived from the renormalization group......In this brief report, we
summarize the results of our recent PMC applications for a number of collider
processes, emphasizing their generality and applicability....... These results
demonstrate that the application of the PMC systematically eliminates a major
theoretical uncertainty for pQCD predictions, thus increasing the sensitivity
of the colliders to possible new physics beyond the Standard Model.Comment: 10 pages, 4 figures. The title has been changed. This review,
submitted to Frontiers of Physics, is based on a contribution by S.J.B. at
the Conference {\it Workshop on Physics at a Future High Intensity Collider @
2-7 GeV in China} Hefei, China January 14-16, 201
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