Article
Astronomy & Astrophysics
Kazuhiro Kogai, Kazuyuki Akitsu, Fabian Schmidt, Yuko Urakawa
Summary: This study systematically investigates the sensitivity of galaxy shapes to new physics in the initial conditions by decomposing the galaxy shape function into spin components and computing their contributions. It demonstrates that a galaxy imaging survey essentially functions as a spin-sensitive detector of such particles in the early universe, providing valuable insights into the primordial non-Gaussianity generated from higher spin particles.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Gabriele Montefalcone, Vikas Aragam, Luca Visinelli, Katherine Freese
Summary: This study examines the effect of the original cosine potential on warm natural inflation. The presence of a radiation bath during inflation introduces a dissipation rate in the equation of motion for the inflaton field, potentially reducing the necessary field excursion for a viable period of inflation. We investigate whether this dissipation can avoid the requirement of a large decay constant in cold cosine natural inflation. However, we find that accommodating a significantly sub-Planckian decay constant in the presence of temperature-dependent dissipation is challenging.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Guillem Domenech, Roya Mohayaee, Subodh P. Patil, Subir Sarkar
Summary: In this study, the tension between the dipole anisotropy of number counts of cosmologically distant sources and the cosmic microwave background (CMB) is investigated. It is found that primordial perturbations with wavelength comparable to or exceeding the Hubble radius can induce a number count dipole, but smaller modes are too small to reconcile the dipole tension.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Tingqi Cai, Jie Jiang, Yi Wang
Summary: This study presents the first lattice simulation to investigate the nature of multi-stream inflation. The simulation confirms the physical picture of multi-stream inflation and reveals new findings in parameter space and field behaviors. It shows that gradient energy plays a significant role in multi-stream inflation. The bifurcation probability in a double field potential with a shifted Gaussian barrier is controlled by the shift distance with an error function relation. The bubbles created by bifurcation tend to be more spherical as bifurcation probability decreases. Furthermore, bifurcation is more likely to introduce oscillations of field values inside the bubbles than outside.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Jason Kristiano, Jun'ichi Yokoyama
Summary: By calculating the one-loop correction to the two-point functions of curvature perturbation in single-field inflation generated by cubic self-interaction, we find that the correction is finite and inversely proportional to the spectral tilt. Requiring the correction to be much smaller than the tree-level contribution leads to an upper bound on primordial non-Gaussianity. Observationally, the allowed region of non-Gaussian parameter space is entirely included by the region where the one-loop correction is smaller than the tree-level contribution, but there exists a significantly large region where the one-loop correction is larger than 1% or even 10% of the latter. If future observations confirm non-Gaussianity falling within such a region, it would be important to incorporate higher-order corrections to the spectrum in order to achieve precise cosmology. In some extreme cases, where the one-loop correction has a comparable magnitude to the tree-level contribution, it might indicate a breakdown of the cosmological perturbation theory in the context of single-field inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Guido D'Amico, Nemanja Kaloper
Summary: Inflation does not have to occur all at once, and can be solved by a series of short bursts of cosmic acceleration interrupted by brief periods of decelerated expansion. This allows for more flexibility in theory and can lead to interesting predictions regarding scalar and tensor spectra of perturbations at short wavelengths. Future CMB spectroscopy searches and primordial gravity probes may help test these features and reveal potential populations of rare particles or primordial black holes as dark matter.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Fengge Zhang, Yungui Gong, Jiong Lin, Yizhou Lu, Zhu Yi
Summary: The study of non-Gaussianities of primordial curvature perturbations in G-inflation models reveals that even though f(NL) becomes large at certain scales, it remains to be small at peak scales. This suggests that the contributions of non-Gaussianity to scalar induced secondary gravitational waves and primordial black hole abundance are expected to be negligible.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Mio Kubota, Kin-ya Oda, Stanislav Rusak, Tomo Takahashi
Summary: Double inflation can occur when a spectator field is non-minimally coupled to gravity. The non-minimal coupling results in the growth of the spectator field, which drives the second stage of inflation in a significant region of parameter space. The non-minimal coupling of the spectator field can modify the predictions for the spectral index and the tensor-to-scalar ratio.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Jerome Martin, Lucas Pinol
Summary: The robustness of multi-field inflation to the physics of reheating is investigated, establishing equations of motion for background and perturbative quantities and emphasizing the importance of tracking perturbations through numerical calculations for precision. Illustrating a physical prediction affected by micro-physics of reheating, the study finds significant differences when ignoring fine-structure of reheating, highlighting the necessity of considering detailed reheating processes in multi-field inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Lei-Hua Liu, Tomislav Prokopec
Summary: This study investigates scalar cosmological perturbations generated through nonminimal coupling in two-field inflationary models with a focus on curvaton scenarios. It shows that small, negative nonminimal couplings can contribute to a redder curvature spectrum, potentially saving some curvaton scenarios that would otherwise be ruled out. The study also highlights the impact of nonminimal coupling on the postinflationary growth of the spectator perturbation and the effectiveness of the curvaton mechanism.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
William L. Matthewson, Dennis Stock, Ruth Durrer
Summary: In this paper, we introduce the concept of "redshift fluctuation" as a gauge-invariant cosmological observable and provide its fully relativistic expression. The angular power spectrum of this variable is analyzed to study the relevance of different relativistic contributions and to compare it with conventional observable galaxy number count fluctuations. Fisher forecasts are performed to investigate the utility of this variable for future spectroscopic surveys, with a focus on the dependence of the results on the size of the redshift bins and the analysis cutoff.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Ki-Young Choi, Jinn-Ouk Gong, Su-beom Kang, Rathul Nath Raveendran
Summary: This article suggests a new method to reconstruct the inflaton potential directly from the primordial power spectrum within canonical single-field inflation. It introduces a more generalized slow-roll approximation to reliably probe the properties of the inflaton potential. The validity of this method is discussed through several examples.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
C. P. Burgess, S. P. de Alwis, F. Quevedo
Summary: The primordial fluctuations revealed by CMB align closely with quantum fluctuations stretched across the sky due to accelerated cosmic expansion. However, this stretching could introduce uncontrolled theoretical errors into late-time cosmological calculations. Speculations like the Trans-Planckian Censorship Conjecture have been proposed to address this issue, but the consistency of Effective Field Theory governing late-time cosmology may not necessarily be threatened by the descent of modes due to universal expansion.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jinn-Ouk Gong, Maria Mylova
Summary: In this study, we examine the validity of the classical approximation of the waterfall phase transition in hybrid inflation from an effective field theory perspective. By integrating out the fluctuations of the waterfall field up to one-loop order, an effective field theory is constructed. Assuming slow-roll conditions are satisfied, we find that the backreaction of the waterfall field fluctuations can significantly impact the evolution of the system, rendering the classical approximation invalid. We derive the necessary constraint to ensure the validity of the effective field theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Danilo Artigas, Julien Grain, Vincent Vennin
Summary: The separate-universe approach provides an effective description of cosmological perturbations, simplifying the analysis of large-scale fluctuations by considering the universe as a collection of independent homogeneous and isotropic regions. This study formulates the separate-universe approach in the Hamiltonian formalism, analyzing the full phase-space structure of perturbations. The research shows that, as long as the wavelengths are larger than a certain lower bound, the separate-universe approach reproduces the same phase-space dynamics as the full cosmological perturbation theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
