Article
Astronomy & Astrophysics
Shyam Balaji, Guillem Domenech, Joseph Silk
Summary: This paper investigates the detection of gravitational waves on the primordial spectrum of fluctuations, particularly during the inflationary phase. It finds that even if the amplitude of the gravitational waves is too small, the effects of cross terms on sharp peaks in the primordial spectrum can still be detected.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Hassan Firouzjahi, Alireza Talebian
Summary: We considered a model of single field inflation containing an intermediate phase of ultra slow-roll and calculated the induced gravitational waves from the enhanced curvature perturbations during this period. The model can accommodate the current observations but has non-trivial predictions for higher frequency ranges that can be tested in future observations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Che-Yu Chen, Yakefu Reyimuaji, Xinyi Zhang
Summary: In this study, slow-roll inflationary models in a class of modified theories of gravity with non-minimal curvature-inflaton couplings were considered. The RT mixing term introduced non-minimal derivative couplings and played a significant role in inflationary dynamics, affecting the predictions for spectral tilt and the tensor-to-scalar ratio. By incorporating this mixing term, chaotic and natural inflation models can better align with observational data.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
Thomas Kite, Jens Chluba, Andrea Ravenni, Subodh P. Patil
Summary: The researchers used numerical methods to explore the energy spectrum characteristics of the primordial gravitational wave background, discussing the effects of different eras in the early universe and their importance in cosmological parameters. Numerical analysis can reveal potential errors in previous literature and describe the effects of gravitational wave backgrounds at different scales.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
C. P. Burgess, R. Holman, Greg Kaplanek, Jerome Martin, Vincent Vennin
Summary: This study computes the rate at which super-Hubble cosmological fluctuations decohere during inflation, due to their gravitational interactions with unobserved shorter-wavelength scalar and tensor modes. The study utilizes Open Effective Field Theory methods to obtain a minimal result, considering only the self-interactions predicted by General Relativity in single-clock models. The findings reveal that decoherence is suppressed by the first slow-roll parameter and the energy density during inflation, but enhanced by the volume within the scale of interest.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Tomasz Krajewski, Krzysztof Turzynski
Summary: We study the post-inflationary evolution in alpha-attractor T-models of inflation, finding that the perturbations of the spectator field are more unstable than the perturbations of the inflaton field, thus dominating the dynamics of the early stages of preheating.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Tomasz Krajewski, Krzysztof Turzynski
Summary: This study focuses on the post-inflationary evolution in alpha-attractor T-models of inflation. By examining the dynamics of the scalar fields present in these models, namely the inflaton and the spectator, it is found that the perturbations of the spectator field are more unstable, thus dominating the dynamics of the early stages of preheating. Additionally, the spectrum of gravitational waves originating from scalar fluctuations is calculated to determine if the alpha-attractor T-models can be constrained or ruled out by current cosmological observations.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Dhiraj Kumar Hazra, Daniela Paoletti, Ivan Debono, Arman Shafieloo, George F. Smoot, Alexei A. Starobinsky
Summary: In this study, constraints on inflationary dynamics and features in the primordial power spectrum of scalar perturbations are presented using Cosmic Microwave Background temperature and polarization data from Planck 2018 data release. Models with suppression and oscillatory features are analyzed and compared with baseline slow-roll potentials. The significance of sharp features has decreased compared to previous data analysis, and bispectra are computed for the best fit candidates obtained from the analysis.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Rongrong Zhai, Hongwei Yu, Puxun Wu
Summary: This paper investigates the influence of the sound speed and rolling speed on the power spectrum of curvature perturbations during inflation. It is found that a sudden decrease in sound speed leads to a change in the scale dependence of the curvature perturbations and alters the growth trend of the power spectrum. In the model where both sound speed and rolling speed decrease, the power spectrum is nearly scale invariant at large scales and enhanced at small scales, resulting in the formation of primordial black holes. Under certain conditions, the power spectrum can exhibit the steepest growth of k^6.
Article
Astronomy & Astrophysics
Arshad Ali, Yungui Gong, Yizhou Lu
Summary: The paragraph discusses the results of studying scalar-induced tensor perturbations during matter domination in various gauges, revealing that the kernel functions in synchronous and comoving gauges are the same and identifying oscillating terms in the perturbations as the secondary gravitational waves induced by scalars. Additionally, it is found that the energy density of these waves is gauge independent and behaves like radiation in the matter-dominated era.
Article
Astronomy & Astrophysics
Shinsuke Kawai, Jinsu Kim
Summary: This study proposes an alternative mechanism for primordial black hole formation based on a scalar field coupled to the Gauss-Bonnet term, which not only leads to the production of primordial black holes but also sources gravitational waves at the second order.
Article
Astronomy & Astrophysics
Mar Bastero-Gil, Antonio Torres Manso
Summary: Investigated the phenomenology of scalar-field interactions with photons and examined the generation of coupled vector particles and calculation of gravitational wave spectra.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Pierre Auclair, Christophe Ringeval
Summary: The next generation of cosmological observations will be able to detect small deviations from a pure power law in the primordial power spectrum of curvature perturbations. These deviations correspond to the running of the spectral index and their measurement would provide as much information as the discovery of deviations from scale invariance. However, accurate parameter inference requires marginalizing over any possible higher-order uncertainties that have not been fully determined.
Article
Astronomy & Astrophysics
Chris Pattison, Vincent Vennin, David Wands, Hooshyar Assadullahi
Summary: The study explores the impact of quantum diffusion on the dynamics of the inflaton during ultra-slow-roll inflation, presenting analytical and numerical techniques. By deriving the characteristic function, the full probability distribution function for the primordial density field is constructed. The numerical results from simulations and a new approach based on iterative Volterra integrals support the possibility of primordial black hole production during ultra-slow-roll inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Oliver Janssen
Summary: The study provides a detailed description of the complex O(4)-symmetric solutions to Einstein's equations on a four-ball in minimally coupled scalar field theories with a slow-roll type potential. The derivation demonstrates an anticipated result, sharpens previous findings in the classical realm of minisuperspace, and uses a complexified slow-roll approximation technique. The technique is applicable to both Hartle-Hawking and Vilenkin wave functions, which predict a family of inflationary universes with different exponential weighting in the semiclassical approximation.
CLASSICAL AND QUANTUM GRAVITY
(2021)
