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Third order equations of motion and the Ostrogradsky instability
Hayato Motohashi, Teruaki Suyama
It is known that any nondegenerate Lagrangian containing time derivative terms higher than first order suffers from the Ostrogradsky instability, pathological excitation of positiv…
Primordial black holes from temporally enhanced curvature perturbation
Teruaki Suyama, Yi-Peng Wu, Jun'ichi Yokoyama
Scalar field with generalized kinetic interactions metamorphoses depending on its field value, ranging from cosmological constant to stiff matter. We show that such a scalar field…
Testing scenarios of primordial black holes being the seeds of supermassive black holes by ultracompact minihalos and CMB -distortions
Kazunori Kohri, Tomohiro Nakama, Teruaki Suyama
Supermassive black holes and intermediate mass black holes are believed to exist in the Universe. There is no established astrophysical explanation for their origin and considerati…
Reheating the Universe Once More: The Dissipation of Acoustic Waves as a Novel Probe of Primordial Inhomogeneities on Even Smaller Scales
Tomohiro Nakama, Teruaki Suyama, Jun'ichi Yokoyama
We provide a simple but robust bound on the primordial curvature perturbation in the range , which has not been constrained so far un…
Black hole perturbation in the most general scalar-tensor theory with second-order field equations II: the even-parity sector
Tsutomu Kobayashi, Hayato Motohashi, Teruaki Suyama
We perform a fully relativistic analysis of even-parity linear perturbations around a static and spherically symmetric solution in the most general scalar-tensor theory with second…
Loop contribution to inflationary magnetic field
Hayato Motohashi, Teruaki Suyama
Within the framework of the standard quantum electrodynamics, we compute contribution of vacuum polarization at one-loop order to the power spectrum of the magnetic field on inflat…