74 research outputs found
Lessons from on inflation models: two-scalar theory and Yukawa theory
We demonstrate two properties of the trace of the energy-momentum tensor
in the flat spacetime. One is the decoupling of heavy degrees
of freedom; i.e., heavy degrees of freedom leave no effect for low-energy
-inserted amplitudes. This is intuitively apparent from the
effective field theory point of view, but one has to take into account the
so-called trace anomaly to explicitly demonstrate the decoupling. As a result,
for example, in the inflation model, scalaron decay is insensitive to
heavy degrees of freedom when a matter sector couples to
gravity (up to a non-minimal coupling of a matter scalar field other than the
scalaron). The other property is a quantum contribution to a non-minimal
coupling of a scalar field. The non-minimal coupling disappears from the action
in the flat spacetime, but leaves the so-called improvement term in . We study the renormalization group equation of the non-minimal coupling
to discuss its quantum-induced value and implications for inflation dynamics.
We work it out in the two-scalar theory and Yukawa theory.Comment: 18+9 pages, 5 figures; minor changes to match the version accepted in
PR
Dark matter kinetic decoupling with a light particle
We argue that the acoustic damping of the matter power spectrum is not a
generic feature of the kinetic decoupling of dark matter, but even the
enhancement can be realized depending on the nature of the kinetic decoupling
when compared to that in the standard cold dark matter model. We consider a
model that exhibits a kinetic decoupling and investigate
cosmological perturbations in the cosmological background
numerically in the model. We also give an analytic discussion in a simplified
setup. Our results indicate that the nature of the kinetic decoupling could
have a great impact on small scale density perturbations.Comment: 19 pages, 7 figure
Axion-like particle assisted strongly interacting massive particle
We propose a new realization of strongly interacting massive particles (SIMP)
as self-interacting dark matter, where SIMPs couple to the Standard Model
sector through an axion-like particle. Our model gets over major obstacles
accompanying the original SIMP model, such as a missing mechanism of
kinetically equilibrating SIMPs with the SM plasma as well as marginal
perturbativity of the chiral Lagrangian density. Remarkably, the parameter
region realizing is within the reach of future beam dump experiments such as
the Search for Hidden Particles (SHiP) experiment.Comment: 11 pages, 1 figure. v2: figure updated, discussions improve
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