14,407 research outputs found
Quadratic Contributions of Softly Broken Supersymmetry in the Light of Loop Regularization
Loop regularization (LORE) is a novel regularization scheme in modern quantum
field theories. It makes no change to the spacetime structure and respects both
gauge symmetries and supersymmetry. As a result, LORE should be useful in
calculating loop corrections in supersymmetry phenomenology. To demonstrate
further its power, in this article we revisit in the light of LORE the old
issue of the absence of quadratic contributions (quadratic divergences) in
softly broken supersymmetric field theories. It is shown explicitly by Feynman
diagrammatic calculations that up to two loops the Wess-Zumino model with soft
supersymmetry breaking terms (WZ' model), one of the simplest models with the
explicit supersymmetry breaking, is free of quadratic contributions. All the
quadratic contributions cancel with each other perfectly, which is consistent
with results dictated by the supergraph techniques.Comment: 25 pages, 3 figures; accepted versio
The central engines of two unusual radio-intermediate/quiet active galactic nuclei: III Zw 2 and PG 1407+265
We use the accretion disk/corona+jet model to fit the multi-band spectral
energy distributions (SEDs) of two unusual radio-intermediate/quiet quasars. It
is found that the optical/UV emission of III Zw 2 is probably dominated by the
emission from the accretion disk. The X-ray emission should be dominated by the
radiation from the jet, while the contribution of the disk corona is
negligible. The optical/UV component in the SED of PG 1407+265 can be well
modeled as the emission from the accretion disk, while the IR component is
attributed to the thermal radiation from the dust torus with an opening angle ~
50\circ. If the X-ray continuum emission is dominated by the synchrotron
emission of the jet, the source should be a "high peak frequency blazar", which
obviously deviates the normal blazar sequence. The observed SED can also be
fitted quite well by the accretion disk/corona model with the viscosity
parameter ? = 0:5. The spectrum of the accretion disk/corona in PG 1407+265
satisfies the weak line quasar criterion suggested in Laor & Davis.Comment: 26 pages, 5 figures, Accepted by Ap
Quantum Electroweak Symmetry Breaking Through Loop Quadratic Contributions
Based on two postulations that (i) the Higgs boson has a large bare mass GeV at the characteristic energy scale which defines
the standard model (SM) in the ultraviolet region, and (ii) quadratic
contributions of Feynman loop diagrams in quantum field theories are physically
meaningful, we show that the SM electroweak symmetry breaking is induced by the
quadratic contributions from loop effects. As the quadratic running of Higgs
mass parameter leads to an additive renormalization, which distinguishes from
the logarithmic running with a multiplicative renormalization, the symmetry
breaking occurs once the sliding energy scale moves from down to a
transition scale at which the additive renormalized Higgs
mass parameter gets to change the sign. With the input of
current experimental data, this symmetry breaking energy scale is found to be
GeV, which provides another basic energy scale for the
SM besides . Studying such a symmetry breaking mechanism could play an
important role in understanding both the hierarchy problem and naturalness
problem. It also provides a possible way to explore the experimental
implications of the quadratic contributions as lies within the
probing reach of the LHC and the future Great Collider.Comment: 10 pages, 2 figures, published versio
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