Article
Astronomy & Astrophysics
Nahuel Miron-Granese
Summary: This study examines the impact of viscous effects of the primordial plasma on the evolution of the primordial gravitational waves (pGW) spectrum, using a second-order theory framework. Two main contributions are identified: the viscous evolution of pGW and the GW production due to initial spin-2 fluctuations of the fluid. The former effect is characterized by a relative amplitude decrease of about 1 to 10% compared to the GW free evolution spectrum.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
William Giare, Matteo Forconi, Eleonora Di Valentino, Alessandro Melchiorri
Summary: This paper analyzes the inflationary gravitational waves, which act as additional radiation in the Early Universe and can increase the effective number of relativistic species (N-eff) through a correction based on the integrated energy-density in gravitational waves across all scales. The study demonstrates that the calculation is dominated by the behavior of the tensor spectrum on scales corresponding to modes that cross the horizon very close to the end of inflation, making it strongly model dependent. The researchers use a theoretical Monte Carlo approach within the framework of the Effective Field Theory of inflation to investigate the observable predictions of various models, proving that accurate analyses are necessary to obtain reliable information on the inflationary Universe.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Guillem Domenech, Chunshan Lin, Misao Sasaki
Summary: We calculate the gravitational waves induced by density fluctuations from the distribution of primordial black holes, finding that most of the waves are generated after the black holes evaporate. The strongest constraint on the produced gravitational waves comes from big bang nucleosynthesis, and some of the waves could potentially be detected by LIGO and DECIGO in the future.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Yoelsy Leyva, Giovanni Otalora
Summary: This article studies inflation and the generation of primordial fluctuations in f (R) gravity's rainbow. The cosmological perturbations and the scalar and tensor primordial power spectrum are calculated. The predictions of the model are contrasted with current observational data from PLANCK and BICEP/Keck. New results for the scalar spectral index ns and the tensor-to-scalar ratio r are found, along with new observational constraints on the rainbow functions.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Konstantinos Dimopoulos
Summary: In this study, a toy-model is used to investigate the situation where two flat directions meet at an enhanced symmetry point and realize the usual hybrid inflation mechanism. The kinetic term of the waterfall field has a pole at its vacuum expectation value (VEV), similar to alpha-attractors. Therefore, after the phase transition that terminates hybrid inflation, the waterfall field does not roll to its VEV but instead drives a stiff period, resulting in a peak in the spectrum of primordial gravitational waves with a barotropic parameter w approximately equal to 1/2. This peak can be observed by the upcoming LISA mission and Advanced LIGO.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Xuce Niu, Moinul Hossain Rahat, Karthik Srinivasan, Wei Xue
Summary: This study extends the reach of the cosmological collider for massive gauge boson production during inflation from the CMB scales to the interferometer scales. By considering a Chern-Simons coupling between the gauge bosons and the pseudoscalar inflaton, the authors show that the presence of massive gauge fields during inflation can be detected from characteristic gravitational wave signals encompassing the whole range of current and planned interferometers.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ema Dimastrogiovanni, Matteo Fasiello, Lucas Pinol
Summary: For the first time, this study derives the explicit form of the anisotropies induced by the scalar(tensor)-tensor-tensor type of primordial non-Gaussianities in the stochastic gravitational wave background using the in-in formalism. The method is applied to both single-field slow-roll and multi-field models, providing examples at tree-level and one-loop. The results are compared to previous findings on anisotropies during inflation and offer the potential for detection of the induced gravitational wave anisotropy atop a gravitational signal.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Sebastian Garcia-Saenz, Lucas Pinol, Sebastien Renaux-Petel, Denis Werth
Summary: We demonstrate that the contribution of the primordial trispectrum to the scalar-induced stochastic gravitational wave background is limited in conventional inflationary scenarios. Scale-invariant theories with regular or local trispectrum shapes cannot significantly contribute due to their smallness compared to the relative one-loop correction of the scalar power spectrum. Additionally, a toy model for a scale-dependent scalar spectrum confirms the robustness of our no-go result.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
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
Ameek Malhotra, Ema Dimastrogiovanni, Matteo Fasiello, Maresuke Shiraishi
Summary: The study explores and confirms the effectiveness of cross-correlating stochastic gravitational wave background anisotropies with CMB temperature fluctuations to establish the primordial nature of a given gravitational wave signal. It considers gravitational wave anisotropies induced by scalar-tensor-tensor primordial non-Gaussianity and calculates the expected uncertainty on the non-linearity parameter F-NL for various proposed experiments. Additionally, it calculates the theoretical, cosmic-variance-limited, error on the non-linearity parameter as a benchmark for future survey planning.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Sayantan Choudhury, Sudhakar Panda, M. Sami
Summary: In this study, we provide a detailed analysis of the formation of Primordial Black Holes (PBHs) during Slow Roll (SR) to Ultra Slow Roll (USR) sharp transitions in the framework of single-field inflation using an effective field theory (EFT) approach. Our results show that the prospects for PBH formation are severely limited in a single-field inflationary framework when renormalizing the power spectrum to one loop order in P(X, phi) theories. We also demonstrate that the addition of an SR regime after USR before the end of inflation does not significantly change our conclusions. Moreover, our findings strictly rule out the possibility of generating large masses of PBHs from all possible models of single field inflation (canonical and non-canonical).
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ki-Young Choi, Su-beom Kang, Rathul Nath Raveendran
Summary: In this paper, the authors demonstrate how a potential of multi scalar fields can be reconstructed from a given power spectrum to generate a peak in the power spectrum on small scales. The slow-roll of the second field in the curved trajectory is responsible for the generation of this peak through the isocurvature perturbation. The reconstructed potential from multi scalar fields may not be unique and different potentials can be derived from a given power spectrum.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Chloe Gowling, Mark Hindmarsh
Summary: This study investigates LISA's sensitivity to the thermodynamic parameters encoded in the stochastic background produced by a phase transition using the sound shell model to characterize the gravitational wave power spectrum and the Fisher matrix to estimate uncertainties. The power spectrum in the sound shell model can be well approximated by a four-parameter double broken power law, and the peak power and frequency can be measured to approximately 10% accuracy for signal-to-noise ratios (SNRs) above 20. The phase boundary speed is found to be the best constrained parameter, with potential for good prospects in combinations of parameters.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Sandeep Aashish, Abhijith Ajith, Sukanta Panda, Rahul Thakur
Summary: This study investigates classes of inflation models driven by antisymmetric tensor field, with minimal and nonminimal couplings to gravity, and proposes solutions to known issues of such models. The study shows that by choosing a different background structure for the antisymmetric tensor field, inflation can still be supported in the minimal model with a quadratic potential, contrary to previous results. The study also analyzes the impact of nonminimal coupling to gravity on perturbations to the antisymmetric tensor and the tensor modes of perturbed metric. Furthermore, the study explores the behavior of tensor modes in the two models, finding that the speed of gravitational waves can be tuned to c in the latter model. The power spectrum and spectral index exhibit slight scale dependence. Finally, the study considers a quartic potential motivated by the graceful exit to the reheating phase, which requires a nonminimal coupling to support inflation. The evolution of the two tensor modes of the perturbed metric differs in this model, resulting in a highly scale-dependent power spectrum.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Jacopo Fumagalli, Mauro Pieroni, Sebastien Renaux-Petel, Lukas T. Witkowski
Summary: In this study, the detection prospects of oscillations in the frequency profile of the stochastic gravitational wave background are investigated using the upcoming space-based gravitational wave observatory LISA. It is found that the oscillations can be reconstructed with LISA, and it is confirmed that they are a worthwhile target for future detection efforts and offer a key for experimentally testing inflation at small scales.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
