41 research outputs found
Criticality and Inflation of the Gauged B-L Model
We consider the multiple point principle (MPP) and the inflation of the
gauged B-L extension of the Standard Model (SM) with a classical conformality.
We examine whether the scalar couplings and their beta functions can become
simultaneously zero at GeV by using the
two-loop renormalization group equations (RGEs). We find that we can actually
realize such a situation and that the parameters of the model are uniquely
determined by the MPP. However, as discussed in \cite{Iso:2012jn}, if we want
to realize the electroweak symmetry breaking by the radiative B-L symmetry
breaking, the self coupling of a newly introduced SM singlet
complex scalar must have a non-zero value at ,
which means the breaking of the MPP. We find that the GeV
electroweak symmetry breaking can be achieved even if this breaking is very
small; . Within this
situation, the mass of the B-L gauge boson is predicted to be \begin{equation}
M_{B-L}=2\sqrt{2}\times\sqrt{\frac{\lambda(v_{h})}{0.10}}\times v_{h}\simeq
696\hspace{1mm}\text{GeV},\nonumber\end{equation} where is the Higgs
self coupling and is the Higgs expectation value. This is a remarkable
prediction of the (slightly broken) MPP. Furthermore, such a small
opens a new possibility: plays a roll of the inflaton
\cite{Okada:2011en}. Another purpose of this paper is to investigate the
inflation scenario with the non-minimal gravitational
coupling based on the two-loop RGEs.Comment: 28 pages, 8 figures; some typos are corrected, Eq.(11) is corrected,
the predicted mass of M_{B-L} has changed, RGEs are corrected, footnotes
added, references added (v2); some typos are corrected, Eq.(26) is added,
references added, version to appear in PTEP(v3
Reconsideration of the Coleman's Baby Universe
We reconsider the Coleman's mechanism that solves the Cosmological Constant
Problem by the baby universes. We use the Lorentzian path integral and allow
each universe has a different effective field theory and a vacuum. By using the
probability distribution of coupling constants, it is shown that the
cosmological constant of our universe does not necessary become small due to
the effects of other universes.Comment: 13 pages, 3 figures; typos are corrected, and references are added
(v3
RG-improvement of the effective action with multiple mass scales
Improving the effective action by the renormalization group (RG) with several
mass scales is an important problem in quantum field theories. A method based
on the decoupling theorem was proposed in \cite{Bando:1992wy} and
systematically improved \cite{Casas:1998cf} to take threshold effects into
account. In this paper, we apply the method to the Higgs-Yukawa model,
including wave-function renormalizations, and to a model with two real scalar
fields . In the Higgs-Yukawa model, even at one-loop level,
Feynman diagrams contain propagators with different mass scales and decoupling
scales must be chosen appropriately to absorb threshold corrections. On the
other hand, in the two-scalar model, the mass matrix of the scalar fields is a
function of their field values and the resultant running
couplings obey different RGEs on a different point of the field space. By
solving the RGEs, we can obtain the RG improved effective action in the whole
region of the scalar fields.Comment: 22 pages, 6 figure
Reheating-era leptogenesis
We propose a novel leptogenesis scenario at the reheating era. Our setup is
minimal in the sense that, in addition to the standard model Lagrangian, we
only consider an inflaton and higher dimensional operators. The lepton number
asymmetry is produced not by the decay of a heavy particle, but by the
scattering between the standard model particles. After the decay of an
inflaton, the model is described within the standard model with higher
dimensional operators. The Sakharov's three conditions are satisfied by the
following way. The violation of the lepton number is realized by the
dimension-5 operator. The complex phase comes from the dimension-6 four lepton
operator. The universe is out of equilibrium before the reheating is completed.
It is found that the successful baryogenesis is realized for the wide range of
parameters, the inflaton mass and reheating temperature, depending on the
cutoff scale. Since we only rely on the effective Lagrangian, our scenario can
be applicable to all mechanisms to generate neutrino Majorana masses.Comment: 5 pages, 3 figures; published version(v2
Hillclimbing saddle point inflation
Recently a new inflationary scenario was proposed in arXiv:1703.09020 which
can be applicable to an inflaton having multiple vacua. In this letter, we
consider a more general situation where the inflaton potential has a (UV)
saddle point around the Planck scale. This class of models can be regarded as a
natural generalization of the hillclimbing Higgs inflation (arXiv:1705.03696).Comment: 5 pages, 3 figures; Report number added (v2
Note on general functional flows in equilibrium systems
We study the response of generating functionals to a variation of parameters
(couplings) in equilibrium systems i.e. in quantum field theory (QFT) and
equilibrium statistical mechanics. These parameters can be either physical ones
such as coupling constants or artificial ones which are intentionally
introduced such as the renormalization scale in field theories. We first derive
general functional flow equations for the generating functional
(grand-canonical potential) of the connected diagrams. Then, we obtain
functional flow equations for the one-particle irreducible (PI) vertex
functional (canonical potential) by performing the Legendre
transformation. By taking the functional derivatives of the flow equations, we
can obtain an infinite hierarchical equations for the PI vertices. We also
point out that a Callan-Symanzik type equation holds among the vertices when
partition function is invariant under some changes of the parameters. After
discussing general aspects of parameter response, we apply our formalism to
several examples and reproduce the well-known functional flow equations. Our
response theory provides us a systematic and general way to obtain various
functional flow equations in equilibrium systems.Comment: 24 page
Multiple Point Principle of the Standard Model with Scalar Singlet Dark Matter and Right Handed Neutrinos
We consider the multiple point principle (MPP) of the Standard Model (SM)
with the scalar singlet Dark Matter (DM) and three heavy right-handed neutrinos
at the scale where the beta function of the effective Higgs
self coupling becomes zero. We make the two-loop
analysis and find that the top quark mass and the Higgs portal coupling
are strongly related each other. One of the good points in this model
is that the larger is allowed. This fact is
consistent with the recent experimental value \cite{ATLAS:2014wva}
GeV, which corresponds to the DM mass
.Comment: 16 pages, 4 figures; references added, Version to appear in PTEP(v2