165 citations · 2.5k across the 85 of their papers we have counts for
86 papers
Tunneling from a Slowly Rolling Multifield Background Using Tadpole Subtraction
Masaki Yamada
We study semiclassical tunneling in scalar field theories with slowly evolving homogeneous backgrounds. We formulate the problem by combining tadpole subtraction with an adiabatic…
Formation and scaling of strings for global symmetry
Masaki Yamada
We numerically investigate networks of global strings with multi-string junctions in a scalar field model whose vacuum manifold is $\mathrm{PSU}(N)=\mathrm{SU}(N)/\m…
Dark baryon from pure Yang-Mills theory and its GW signature from cosmic strings
Masaki Yamada, Kazuya Yonekura
We point out that SO() pure Yang-Mills theory provides a candidate for dark matter (DM) without the explicit need to impose any additional symmetry. The DM candidate is a parti…
Can baryon asymmetry be explained by a large initial value before inflation?
Kai Murai, Fuminobu Takahashi, Masaki Yamada +1
We show that the baryon asymmetry of the Universe cannot be explained by a large initial value before inflation because it inevitably predicts correlated baryon isocurvature pertur…
Quantum decay of scalar and vector boson stars and oscillons into gravitons
Kazunori Nakayama, Fuminobu Takahashi, Masaki Yamada
We point out that a soliton such as an oscillon or boson star inevitably decays into gravitons through gravitational interactions. These decay processes exist even if there are no…
Stochastic dynamics of multi-waterfall hybrid inflation and formation of primordial black holes
Yuichiro Tada, Masaki Yamada
We show that a hybrid inflation model with multiple waterfall fields can result in the formation of primordial black hole (PBH) with an astrophysical size, by using an advanced alg…
On the primordial black hole formation in hybrid inflation
Yuichiro Tada, Masaki Yamada
We revisit the scenario of primordial black hole (PBH) formation from large curvature perturbations generated during the waterfall phase transition in hybrid inflation models. In a…
Axion dark matter from first-order phase transition, and very high energy photons from GRB 221009A
Shota Nakagawa, Fuminobu Takahashi, Masaki Yamada +1
We study an axion-like particle (ALP) that experiences the first-order phase transition with respect to its mass or potential minimum. This can be realized if the ALP obtains a pot…
Wash-in leptogenesis after axion inflation
Valerie Domcke, Kohei Kamada, Kyohei Mukaida +2
CP violation and the violation of baryon-minus-lepton number B-L do not necessarily have to occur simultaneously in order to accomplish successful leptogenesis. Instead, it suffice…
Formation of hot spots around small primordial black holes
Minxi He, Kazunori Kohri, Kyohei Mukaida +1
In this paper, we investigate the thermalization of Hawking radiation from primordial black holes (PBHs) in the early Universe, taking into account the interference effect on therm…
Cascades of high-energy SM particles in the primordial thermal plasma
Kyohei Mukaida, Masaki Yamada
High-energy standard model (SM) particles in the early Universe are generated by the decay of heavy long-lived particles. The subsequent thermalization occurs through the splitting…
A new constraint on primordial lepton flavour asymmetries
Valerie Domcke, Kohei Kamada, Kyohei Mukaida +2
A chiral chemical potential present in the early universe can source helical hypermagnetic fields through the chiral plasma instability. If these hypermagnetic fields survive until…
Gravitational production of dark photon dark matter with mass generated by the Higgs mechanism
Takanori Sato, Fuminobu Takahashi, Masaki Yamada
We study the gravitational production of dark photon dark matter during inflation, when dark photons acquire mass by the Higgs mechanism. In the previous study, it was assumed that…
Cosmic F- and D-strings from pure Yang-Mills theory
Masaki Yamada, Kazuya Yonekura
We discuss the formation of cosmic strings or macroscopic color flux tubes after the deconfinement/confinement phase transition in the pure Yang-Mills theory. Based on holographic…
Cosmic strings from pure Yang-Mills theory
Masaki Yamada, Kazuya Yonekura
We discuss the formation of cosmic strings or macroscopic color flux tubes at the phase transition from the deconfinement to confinement phase in pure Yang-Mills (YM) theory, such…
Early-Universe Model Building
Pouya Asadi, Saurabh Bansal, Asher Berlin +37
Theoretical investigations into the evolution of the early universe are an essential part of particle physics that allow us to identify viable extensions to the Standard Model as w…
Baryon Asymmetric Universe from Spontaneous CP Violation
Kohei Fujikura, Yuichiro Nakai, Ryosuke Sato +1
Spontaneous CP violation, such as the Nelson-Barr (NB) mechanism, is an attractive scenario for addressing the strong CP problem while realizing the observed phase of the Cabibbo-K…
Leptoflavorgenesis: baryon asymmetry of the Universe from lepton flavor violation
Kyohei Mukaida, Kai Schmitz, Masaki Yamada
Charged-lepton flavor violation (CLFV) is a smoking-gun signature of physics beyond the Standard Model. The discovery of CLFV in upcoming experiments would indicate that CLFV proce…
Semiclassical analysis of axion-assisted and axion-driven pair production
Hiroyuki Kitamoto, Masaki Yamada
We study the pair production of fermions in a time dependent axion background with and without an electric background. We construct the adiabatic mode functions which incorporate t…
Cosmic Birefringence Triggered by Dark Matter Domination
Shota Nakagawa, Fuminobu Takahashi, Masaki Yamada
Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination. We show that this naturally happens if the ALP is coupled to the dark matter densit…
A natural and simple UV completion of the QCD axion model
Masaki Yamada, Tsutomu T. Yanagida
The novel PQ mechanism replaces the strong CP problem with some challenges in a model building. In particular, the challenges arise regarding i) the origin of an anomalous global s…
Trapping Effect for QCD Axion Dark Matter
Shota Nakagawa, Fuminobu Takahashi, Masaki Yamada
In the early universe, the potential of a scalar field can be significantly modified, and the scalar field may be trapped for a long time in a different location than the current v…
Wash-In Leptogenesis
Valerie Domcke, Kohei Kamada, Kyohei Mukaida +2
We present a leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino masses as low as a few 100 TeV. This mechanism, wh…
Gravitational Waves and Dark Radiation from Dark Phase Transition: Connecting NANOGrav Pulsar Timing Data and Hubble Tension
Yuichiro Nakai, Motoo Suzuki, Fuminobu Takahashi +1
Recent pulsar timing data reported by the NANOGrav collaboration may indicate the existence of a stochastic gravitational wave background around Hz. We explore a p…