93 research outputs found
Non-minimal coupling in Higgs-Yukawa model with asymptotically safe gravity
We study the fixed point structure of the Higgs-Yukawa model, with its scalar
being non-minimally coupled to the asymptotically safe gravity, using the
functional renormalization group. We have obtained the renormalization group
equations for the cosmological and Newton constants, the scalar mass-squared
and quartic coupling constant, and the Yukawa and non-minimal coupling
constants, taking into account all the scalar, fermion, and graviton loops. We
find that switching on the fermionic quantum fluctuations makes the non-minimal
coupling constant irrelevant around the Gaussian-matter fixed point with the
asymptotically safe gravity.Comment: typos corrected; Accepted for publication in Class. and Quantum
Grav.; 50 pages, 5 figures; typos corrected in Eqs. (61), (62), and (79); the
last paragraph of Sec. 5.4 added; references added; other minor revision
Hillclimbing Higgs inflation
We propose a realization of cosmic inflation with the Higgs field when the
Higgs potential has degenerate vacua by employing the recently proposed idea of
hillclimbing inflation. The resultant inflationary predictions exhibit a
sizable deviation from those of the ordinary Higgs inflation.Comment: 5 pages, 3 figures, 1 table (v1); published version, references and
footnotes added (v2
Minimal Higgs inflation
We consider a possibility that the Higgs field in the Standard Model (SM)
serves as an inflaton when its value is around the Planck scale. We assume that
the SM is valid up to an ultraviolet cutoff scale \Lambda, which is slightly
below the Planck scale, and that the Higgs potential becomes almost flat above
\Lambda. Contrary to the ordinary Higgs inflation scenario, we do not assume
the huge non-minimal coupling, of O(10^4), of the Higgs field to the Ricci
scalar. We find that \Lambda must be less than 5*10^{17}GeV in order to explain
the observed fluctuation of the cosmic microwave background, no matter how we
extrapolate the Higgs potential above \Lambda. The scale 10^{17}GeV coincides
with the perturbative string scale, which suggests that the SM is directly
connected with the string theory. For this to be true, the top quark mass is
restricted to around 171GeV, with which \Lambda can exceed 10^{17}GeV. As a
concrete example of the potential above \Lambda, we propose a simple log type
potential. The predictions of this specific model for the e-foldings N_*=50--60
are consistent with the current observation, namely, the scalar spectral index
is n_s=0.977--0.983 and the tensor to scalar ratio 0<r<0.012--0.010. Other
parameters, dn_s/dlnk, n_t, and their derivatives, are also consistent.Comment: 25 pages, 9 figures; references added(v2); Version to appear in
PTEP(v3
QCD Effects in the Decays of TeV Black Holes
In models with ``large'' and/or warped extra dimensions, the
higher-dimensional Planck scale may be as low as a TeV. In that case black
holes with masses of a few TeV are expected to be produced copiously in
multi-TeV collisions, in particular at the LHC. These black holes decay through
Hawking radiation into typically O(20) Standard Model particles. Most of these
particles would be strongly interacting. Naively this would lead to a final
state containing 10 or so hadronic jets. However, it has been argued that the
density of strongly interacting particles would be so large that they
thermalize, forming a ``chromosphere'' rather than well-defined jets. In order
to investigate this, we perform a QCD simulation which includes parton-parton
scattering in addition to parton showering. We find the effects of parton
scattering to remain small for all cases we studied, leading to the conclusion
that the decays of black holes with masses within the reach of the LHC will not
lead to the formation of chromospheres.Comment: LaTeX with equation.sty (included), 26 pages, 4 figures. Added a few
references and one footnot
Diagonal Kaluza-Klein expansion under brane localized potential
We clarify and study our previous observation that, under a compactification
with boundaries or orbifolding, vacuum expectation value of a bulk scalar field
can have different extra-dimensional wave-function profile from that of the
lowest Kaluza-Klein mode of its quantum fluctuation, under presence of
boundary-localized potentials which would be necessarily generated through
renormalization group running. For concreteness, we analyze the Universal Extra
Dimension model compactified on orbifold , with brane-localized Higgs
potentials at the orbifold fixed points. We compute the Kaluza-Klein expansion
of the Higgs and gauge bosons in an -like gauge by treating the
brane-localized potential as a small perturbation. We also check that the
parameter is not altered by the brane localized potential.Comment: 22 pages, published versio
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