Article
Astronomy & Astrophysics
Hemza Azri, Isaac Bamwidhi, Salah Nasri
Summary: This paper explores two-field inflation in the context of purely affine gravity, introducing a covariant formulation that leads to a curved field space allowing for significant departure from purely metric gravity. By allowing specific noncanonical field kinetic terms, the curved field manifold can be flattened, simplifying inflationary dynamics and enabling new predictions.
Article
Astronomy & Astrophysics
Raphal van Laak, Sam Young
Summary: Primordial black holes are black holes that may have formed in high density regions in the early universe. The fluctuations in their formation rate can be used to constrain the amplitude of non-Gaussianity, especially if primordial black holes make up a significant fraction of dark matter. By extending the calculation to include peaks theory and considering the non-linearities between compaction C and curvature perturbation C, we find that the constraints on quadratic models of non-Gaussianity are largely unchanged, while the constraints on cubic models significantly worsen. If all of the dark matter is composed of primordial black holes, the parameters of non-Gaussianity are -2.9 & BULL; 10-4 < f < 3.8 & BULL; 10-4 and -1.5 & BULL; 10-3 < g < 1.9 & BULL; 10-3 for quadratic and cubic models respectively.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Lei-Hua Liu, Bin Liang, Ya-Chen Zhou, Xiao-Dan Liu, Wu-Long Xu, Ai-Chen Li
Summary: The study on the non-Gaussianity of canonical curvaton scenario using a generalized delta N formalism reveals that most parameter spaces are consistent with observational constraints. The research shows that the well-known parameter values can be accurately recovered in the absence of nonlinear evolution.
Article
Astronomy & Astrophysics
T. Montandon, G. Patanchon, B. van Tent
Summary: By jointly analyzing the power spectrum and bispectrum of CMB temperature and polarization anisotropies, constraints on isocurvature modes can be improved, particularly with significant enhancement for neutrino isocurvature modes. While the joint analysis does not generally improve constraints for Planck data, significant improvements can be achieved by fixing additional parameters in the model. Additionally, the joint analysis can significantly reduce error bars for certain standard cosmological parameters, by breaking degeneracies between adiabatic and isocurvature modes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Pedro Carrilho, Karim A. Malik
Summary: This paper investigates the relationship between the bispectra of the cosmic microwave background and isocurvature modes, as well as the ability of current and future CMB experiments to constrain these modes. Results show that a detectable bispectrum signal can be produced when the compensated isocurvature mode has significant correlation with the adiabatic mode.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Giacomo Ferrante, Gabriele Franciolini, Antonio Junior Iovino, Alfredo Urbano
Summary: We revise the production of primordial black holes (PBHs) in the axion-curvaton model by considering recent developments in the computation of their abundance accounting for nongaussianities (NGs) in the curvature perturbation. We find that the intrinsic NGs generated in such scenarios have a significant impact on the phenomenology associated with PBHs, particularly on the relationship between their abundance and the second order gravitational wave signal. Additionally, we demonstrate that this model can potentially explain the entire dark matter content in the asteroid mass range and the signal reported in the nano-Hz frequency range by the NANOGrav and IPTA collaborations. Along the way, we provide a new explicit computation of the power spectrum of curvature perturbations that goes beyond the sudden decay approximation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
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
Mehrdad Mirbabayi, Andrei Gruzinov
Summary: Sphaleron heating is proposed as a mechanism for warm inflation when the inflaton is coupled to pure Yang-Mills as an axion. The presence of heating introduces a friction coefficient gamma proportional to T-3 in the inflaton's equation of motion, as well as a thermal contribution to cosmological fluctuations. In the absence of knowledge about the inflaton potential, non-Gaussianity is the most promising approach for detecting the signatures of this model. By extending previous work, we compute the scalar three-point correlation function and identify distinct features in the squeezed and folded limits. As a detection strategy, we find that combining the equilateral template with a new template yields a high overlap with the shape of non-Gaussianity for 0.01 <= gamma/H <= 1000, with 0.7 < |f(NL)| < 50 in this range.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
Timo J. Doerries, Ralf Metzler, Aleksei Chechkin
Summary: This article examines the transport of diffusive particles switching between mobile and immobile states with finite rates. The study focuses on the impact of advection on density functions and mean squared displacements (MSDs). Significant anomalous diffusion with cubic scaling in time of the MSD is found at intermediate time scales for high Peclet numbers. This cubic scaling is present for both short and long mean residence times in the immobile state. The study also reveals the newly observed phenomenon of advection-induced subdiffusion for immobilized tracers in the presence of high Peclet numbers. Additionally, the effective advection velocity is reduced in the long-time limit, while the MSD is enhanced by advection. The physical mechanisms behind the emergence of non-Gaussian density functions and the characteristics of the MSD are explored.
NEW JOURNAL OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
Satoshi Iso, Takato Mori, Katsuta Sakai
Summary: This paper extends a previous study on the entanglement entropy of a half space in interacting field theories, introducing a novel calculation method and identifying two specific contributions to the entanglement entropy. Further investigation in more general field theories suggests that non-Gaussian contributions from vertices can be understood as renormalized correlation functions of composite operators.
Article
Astronomy & Astrophysics
Fazlu Rahman, Pravabati Chingangbam, Tuhin Ghosh
Summary: Accurate component separation in full-sky maps at radio and microwave frequencies, like the CMB, requires a deep understanding of the statistical properties of Galactic foreground emissions. Analysis of the statistical properties of Galactic synchrotron using scalar Minkowski functionals and Minkowski tensors reveals high non-Gaussian deviations at the smallest angular scales. Non-Gaussian nature can be explained by perturbative expansion up to second-order terms, with kurtosis terms being dominant over skewness terms.Tests show that the Haslam map becomes increasingly more isotropic at smaller scales.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Sam Young
Summary: In this study, we reassess the impact of local-type non-Gaussianity on the abundance of primordial black holes (PBHs) and find that the effect is much less significant than previously believed. The non-Gaussianity parameters need to be significantly larger to have a similar effect as before, which weakens the constraints on PBH abundance and the primordial power spectrum dependence on non-Gaussianity parameters. Furthermore, we question the existing calculations of PBH abundance due to the correlation between curvature perturbation and compaction.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Maria Mylova, Marianthi Moschou, Niayesh Afshordi, Joao Magueijo
Summary: This paper introduces a thermal bimetric model and explores its non-Gaussian features, providing precise predictions based on the characteristics of the model. These results are of great significance for future cosmological surveys.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Sarvesh Kumar Yadav, Rajib Saha
Summary: This paper examines the validity of the assumption that the temperature field of the Cosmic Microwave Background (CMB) is consistent with a Gaussian random field. A new model-independent method using ordered and non-parametric statistics is proposed and applied to test the uniformity and independence of the CMB spherical harmonic phases (SHP). The results show that there are non-uniform and correlated SHP in the cleaned CMB maps, indicating the presence of non-Gaussian signals.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
L. F. Guimaraes, F. T. Falciano
Summary: This paper presents a method for reconstructing the curvaton potential from a scale-dependent non-Gaussianity parameter, with an example of a weakly self-interacting curvaton model that satisfies observational constraints and explains CMB dipolar modulation. The approach can be extended to reconstruct the curvaton potential from the g(NL) parameter.