Article
Astronomy & Astrophysics
Jessica L. Cook
Summary: This paper considers the formation of primordial black holes (PBHs) sourced by an increase in the power spectrum. Two background inflaton models, natural inflation and hilltop inflation, are examined. Instead of a peaked power spectrum, this paper explores the formation of PBHs from perturbations closer to the end of inflation, ensuring that the PBHs are too small to violate bounds. Understanding PBHs sourced from an inflationary power spectrum would provide valuable evidence for inflation on a different energy scale from the cosmic microwave background (CMB), shedding light on what occurred during inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Sugumi Kanno, Ann Mukuno, Jiro Soda, Kazushige Ueda
Summary: Dark gauge fields have been proposed as potential candidates for dark matter, and if they exist, primordial dark magnetic fields would have existed during inflation. It is believed that primordial gravitational waves arise from quantum fluctuations during inflation. This study investigates the conversion of gravitons into dark photons in the presence of background primordial dark magnetic fields and finds that this process induces a tachyonic instability in the primordial gravitational waves, leading to a peak in their power spectrum. The height of the peak depends on the observation direction, and the peak frequency can range from 10-5 to 103 Hertz for GUT scale inflation, suggesting that the observation of primordial gravitational waves could be a new way to probe primordial dark magnetic fields.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Sugumi Kanno, Ann Nakato, Jiro Soda, Kazushige Ueda
Summary: There is observational evidence for the existence of primordial magnetic fields generated during inflation. We investigate primordial gravitational waves during inflation in the presence of magnetic fields sustained by a gauge kinetic coupling. In this model, both gravitons as excitations of primordial gravitational waves, and photons as excitations of electromagnetic fields are strongly squeezed, and become entangled through graviton to photon conversion. We calculate the entanglement entropy of the gravitons and find that their state is a mixed state rather than a squeezed state.
Article
Astronomy & Astrophysics
Hai-Jun Li
Summary: This paper investigates the stochastic oscillations between axion-like particles (ALPs) and photons in the cosmic magnetic field. Numerical results of ALP-photon oscillation probability distributions are presented for different magnetic field scenarios. These oscillations may have effects on phenomena such as the cosmic microwave background, the cosmic X-ray background, and the extragalactic gamma-ray background.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Tomohiro Fujita, Kyohei Mukaida, Yuichiro Tada
Summary: In this study, we develop a stochastic formalism for U(1) gauge fields coupled with a rolling pseudo-scalar field during inflation. We derive the Langevin equations for the physical electromagnetic fields and study their analytic solutions. Through numerical simulation, we demonstrate that the averaged electromagnetic fields over the Hubble scale continuously change their direction and fluctuate around the analytically obtained expectation values. While the isotropy is spontaneously broken in each local Hubble patch, it is globally preserved by averaging all the Hubble patches.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Rajeev Kumar Jain, P. Jishnu Sai, Martin S. Sloth
Summary: This study calculates the primordial correlation between gravitons and a non-minimally coupled abelian gauge field in the early universe, and finds that this correlation satisfies new consistency relations in the three-point cross-correlation functions. The study shows that the interaction between gravitons and gauge fields may have implications for cosmological observables today.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Massimo Giovannini
Summary: This article investigates the large-scale magnetic fields generated by the quantum mechanical fluctuations of hypercharge, combined with the evolution of gauge coupling during a long inflationary stage. The results show that the magnetic power spectra can be amplified when the post-inflationary expansion rate is slower than radiation. Furthermore, the study emphasizes that the modulations of the gauge power spectra freeze when the relevant wavelengths reenter the Hubble radius, and the late-time values of the magnetic power spectra can be accurately computed based on these observations.
Article
Astronomy & Astrophysics
V. K. Oikonomou
Summary: We investigate the effects of short axion kination eras on the energy spectrum of primordial gravitational waves. Our findings indicate a characteristic shape in the energy spectrum that can be observed in future gravitational wave experiments.
Article
Astronomy & Astrophysics
Andreas Ringwald, Ken'ichi Saikawa, Carlos Tamarit
Summary: This paper analyzes the spectrum of primordial gravitational waves predicted in the SMASH model, which addresses multiple fundamental problems in particle physics and cosmology. The unique prediction for the critical temperature of the PQ phase transition in the model leads to a drastic change in the universe's equation of state. Future high sensitivity GW experiments, like DECIGO, are expected to detect the nontrivial features resulting from the PQ phase transition in this model.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Fuminobu Takahashi, Wen Yin
Summary: The study explores the possibility of heavy QCD axions inducing slow roll inflation to solve the strong CP problem through the Peccei-Quinn mechanism. It requires fine-tuning between contributions to achieve hilltop inflation, leading to potential challenges in experiments for validation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Maxim Dvornikov
Summary: This study focuses on the system of interacting axions and magnetic fields in the early universe after the quantum chromodynamics phase transition. Both axions and magnetic fields are assumed to be spatially inhomogeneous. By solving the equations numerically, the evolution of the magnetic field is compared between cases with inhomogeneous and homogeneous axions. It is found that the instability of the magnetic field can be suppressed by considering the inhomogeneity of axions.
Article
Astronomy & Astrophysics
V. P. Pomakov, S. P. O'Sullivan, M. Brueggen, F. Vazza, E. Carretti, G. H. Heald, C. Horellou, T. Shimwell, A. Shulevski, T. Vernstrom
Summary: Faraday rotation studies of distant radio sources provide valuable insights into the evolution and origin of cosmic magnetism. This study uses data from the LOFAR Two-Metre Sky Survey to investigate the relationship between Faraday rotation measure (RM) and redshift. By analyzing random pairs of radio sources, the researchers were able to isolate the extragalactic contribution to the RM difference and estimate the comoving magnetic field strength and redshift evolution. The results suggest an upper limit for the magnetic field strength and support certain magnetogenesis scenarios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Multidisciplinary
Radhika Achikanath Chirakkara, Christoph Federrath, Pranjal Trivedi, Robi Banerjee
Summary: The study shows that in the highly subsonic regime, the saturation efficiency of magnetic field amplification by the turbulent dynamo increases as the Mach number decreases. Even with purely longitudinal forcing modes, a high saturation efficiency can be achieved.
PHYSICAL REVIEW LETTERS
(2021)
Article
Astronomy & Astrophysics
Soichiro Hashiba, Kohei Kamada, Hiromasa Nakatsuka
Summary: By studying the Chern-Simons coupling between the pseudoscalar inflaton and the gauge field, and examining the subsequent pair-particle production induced by the amplified gauge field known as the Schwinger effect during the kination era, we find that successful reheating of the Universe can be achieved through the domination of the pair-produced particles over the kinetic energy of the inflaton.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Kohei Kamada, Fumio Uchida, Jun'ichi Yokoyama
Summary: The decay of hypermagnetic helicity at electroweak symmetry breaking may have produced baryon asymmetry, however, fully helical magnetic field may not be strong enough to explain the origin of intergalactic magnetic field; the combination of helical and nonhelical primordial magnetic fields may explain both, but is ruled out by the constraint on amplitude of baryon isocurvature perturbations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Oksana Iarygina, Evangelos Sfakianakis, Dong-Gang Wang, Ana Achucarro
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Astronomy & Astrophysics
Tomohiro Fujita, Evangelos I. Sfakianakis, Maresuke Shiraishi
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Physics, Particles & Fields
Peter Adshead, Pranjal Ralegankar, Jessie Shelton
JOURNAL OF HIGH ENERGY PHYSICS
(2019)
Article
Astronomy & Astrophysics
Peter Adshead, Lauren Pearce, Marco Peloso, Michael A. Roberts, Lorenzo Sorbo
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Physics, Multidisciplinary
Rachel Nguyen, Jorinde van de Vis, Evangelos Sfakianakis, John T. Giblin, David Kaiser
PHYSICAL REVIEW LETTERS
(2019)
Article
Astronomy & Astrophysics
Perseas Christodoulidis, Diederik Roest, Evangelos I. Sfakianakis
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2019)
Article
Physics, Multidisciplinary
Peter Adshead, John T. Giblin, Mauro Pieroni, Zachary J. Weiner
PHYSICAL REVIEW LETTERS
(2020)
Article
Astronomy & Astrophysics
Perseas Christodoulidis, Diederik Roest, Evangelos Sfakianakis
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2020)
Article
Astronomy & Astrophysics
Mary Gerhardinger, John T. Jr Jr Giblin, Andrew J. Tolley, Mark Trodden
Summary: The Galileon scalar field theory, which exhibits the Vainshtein screening mechanism, has implications for predictions of gravitational waves and tests of gravity. The derivative nature of their interactions poses a challenge in effective field theories but can be overcome through numerical simulations.
Article
Astronomy & Astrophysics
Chi Tian, Stefano Anselmi, Matthew F. Carney, John T. Giblin, James Mertens, Glenn Starkman
Summary: This study examines the behavior of curvature modes on hypersurfaces of an inhomogeneous spacetime in a nonperturbative numerical relativistic setting, and compares it with the curvature inferred by observers. The observations become sensitive to the impact of curvature sourced by inhomogeneities on inferred average properties, showing general agreement with past literature.
Article
Astronomy & Astrophysics
Zachary J. Weiner, Peter Adshead, John T. Giblin
Summary: Simulation of the nonperturbative decay of ultralight scalars into Abelian gauge bosons reveals an excess of gravitational-wave signals beyond constraints across the entire parameter space under consideration, suggesting that gravitational-wave production from the decay of early dark energy may offer a unique probe of these models.
Article
Astronomy & Astrophysics
Jorinde van de Vis, Rachel Nguyen, Evangelos Sfakianakis, John T. Giblin, David Kaiser
Article
Astronomy & Astrophysics
Peter Adshead, John T. Giblin, Mauro Pieroni, Zachary J. Weiner
Article
Astronomy & Astrophysics
John T. Giblin, Avery J. Tishue