Article
Astronomy & Astrophysics
Alexandros Karam, Martti Raidal, Eemeli Tomberg
Summary: The study focuses on preheating in plateau inflation in a scenario similar to Higgs inflation, revealing that the oscillating inflaton field repeatedly returns to the plateau, leading to tachyonic production of inflaton particles. Moreover, it is demonstrated that a minimally coupled spectator scalar field can be more efficiently produced through a similar mechanism. The mechanism is solely gravitational and the scalar field mass can be as high as 10^13 GeV, making it a candidate for superheavy dark matter.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Wei Cheng, Xuewen Liu, Ruiyu Zhou
Summary: This paper studies the cosmological inflation and dark matter within a Z3 complex scalar model and finds that the mixing angle, DM mass, and Higgs-like scalar mass are constrained in the low-energy scale. It also suggests that measuring the tensor-to-scalar ratio with higher precision can distinguish between the two forms of inflation in the high-energy scale.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Oleg Lebedev
Summary: Stable scalars can be abundantly produced in the Early Universe even without coupling to other fields. The production and mass scale of these scalars during and after (high scale) inflation are studied, leading to strong constraints. Quantum gravity-induced Planck-suppressed operators significantly affect the abundance of dark matter relics, often resulting in overproduction unless the corresponding Wilson coefficients are very small. The uncontrollable nature of these effects without a quantum gravity theory questions the predictability of many non-thermal dark matter models and has potential implications for string theory constructions with abundant scalar fields.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Mayumi Aoki, Jisuke Kubo, Jinbo Yang
Summary: Utilizing dynamical chiral symmetry breaking in a QCD-like hidden sector to generate the Planck mass and the electroweak scale, the study proposes hidden pions as dark matter candidates. However, due to their super heavy mass (10^9 to 10^12 GeV) and extremely suppressed interaction with the visible sector, direct detection of these hidden pions is not feasible.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Mikhail Shaposhnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell
Summary: The study focuses on inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity, finding that inflation is possible and consistent with observations for a broad range of parameters. The results show that the spectral index is typically given by n(s) = 1-2/N-* and the tensor-to-scalar ratio r can vary between about 10(-10) and 1. This suggests the potential detection of gravitational waves from inflation in certain scenarios of Higgs inflation in the Einstein-Cartan framework.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Alexander B. Balakin, Alexei S. Ilin
Summary: We propose a new self-consistent model that couples cosmic dark energy and dark matter using the rheological approach. This model represents the equations of state as integral operators of the Volterra type. We classify the exact solutions of the model based on the roots of the characteristic polynomial. The pressure, energy density, Hubble function, and acceleration parameter of dark energy and dark matter are expressed explicitly as functions of the dimensionless scale factor. We discuss two intriguing cosmological solutions that describe superexponential expansion and symmetric bounce, as well as new solutions corresponding to quasiperiodic behavior.
Article
Physics, Multidisciplinary
Mikhail Shaposhnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell
Summary: This passage discusses a novel mechanism for producing singlet fermions in the early Universe through gravity-induced interactions. These fermions can act as dark matter particles and are applicable to a wide range of dark matter particle masses. The potential observational consequences of producing keV-scale dark matter in this way, particularly for right-handed neutrinos, are also explored. The authors suggest that determining the momentum distribution of primordial dark matter may shed light on gravity-induced fermionic interactions.
PHYSICAL REVIEW LETTERS
(2021)
Article
Astronomy & Astrophysics
Alberto Salvio
Summary: A new multifield scenario involving both a scalaron and a pseudo Nambu-Goldstone boson as active components, known as natural-scalaron inflation, is investigated. The study shows that there is a robust inflationary attractor even when the masses of the two inflatons are comparable. Additionally, the presence of the scalaron allows for satisfying all observational bounds in a large region of the parameter space, unlike what happens in pure-natural inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Alexandros Karam, Sotirios Karamitsos, Margus Saal
Summary: Attractor inflation is a robust framework for developing inflationary models that are insensitive to potential details. This study classifies the strong coupling limit of inflationary models in both the metric and Palatini approaches using the fl-function formalism, determining the range of non-minimal coupling values that lead to indistinguishable theories within current accuracy. The reconstruction of the Jordan frame potential for-attractors demonstrates the impact of metric or Palatini choice on inflationary observables.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Basabendu Barman, Nicolas Bernal, Ashmita Das, Rishav Roshan
Summary: We study a simple abelian vector dark matter model, where only the dark matter couples non-minimally to the scalar curvature of the background spacetime. By analyzing freeze-out, freeze-in, and scattering scenarios, we show that such non-minimally coupled dark matter can be probed in direct detection experiments, satisfying the observed relic abundance and perturbative unitarity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Mar Bastero-Gil, Jose Santiago, Roberto Vega-Morales, Lorenzo Ubaldi
Summary: We study a mechanism for producing dark photon dark matter at the end of inflation. The rolling inflaton induces a tachyonic instability, leading to the coherent production of dark gauge bosons. We examine the case where the dark photons are relativistic when their mass is generated and calculate the relic abundance today. Furthermore, we analyze the late time power spectrum and find that it preserves the peak generated at the end of inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Alexandros Karam, Eemeli Tomberg, Hardi Veermae
Summary: The study investigates preheating in the Palatini formalism with a quadratic inflaton potential and an additional alpha R-2 term, identifying tachyonic preheating when alpha is greater than or similar to 10^13 and showing that the energy density of the fragmented field grows with a specific rate. The model expands the range of plateau models with similar preheating behavior, suggesting that non-canonical quartic kinetic terms in the Einstein frame can be neglected in the first approximation during preheating and inflation.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Federico Compagnin, Stefano Profumo, Nicolao Fornengo
Summary: This article investigates the cosmology and phenomenology of a dark photon portal with a simple dark sector composed of a single, light, fermionic dark matter particle species with mass in the MeV range. Three possible kinetic mixing structures between a new Abelian gauge group U(1)dark and the visible sector are considered: U(1)e.m., U(1)Y, and T[SU(2)L]. The author assumes the dark photon to have a massive and MeV-scale mass, close to the mass scale of the dark matter candidate. The article calculates the dark matter relic density through freeze-out and freeze-in, taking into account the possibility of a late inflationary period that could dilute the dark matter yield of heavy candidates and additional production modes for models with under-abundant thermal production. The parameter space compatible with various experimental and astrophysical constraints is explored, and prospects for discovery using new CMB probes and MeV gamma-ray telescopes are discussed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Dhong Yeon Cheong, Sung Mook Lee, Seong Chan Park
Summary: Research shows that primordial black holes can be produced in a minimal UV extension of Higgs inflation with an included R-2 term. Parameters consistent with Standard Model measurements and Planck observation results indicate that M-PBH falls within the range of (10^(-16), 10^(-15))M⊙, with significant abundance, potentially making up the majority of dark matter.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Alberto Salvio
Summary: The recent results of the BICEP and Keck collaborations have placed tight constraints on many inflationary models. One possible way to avoid these constraints is by introducing quadratic-in-curvature terms that can UV complete gravity while respecting stability and unitarity. The predictions of quadratic gravity are computed and compared with the BICEP/Keck constraints in two inflationary scenarios, (critical) Higgs inflation and natural inflation, which are already ruled out in Einstein gravity. It is shown that quadratic gravity can restore agreement with the observational constraints in both scenarios.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Enrico Pajer
Summary: The study focuses on the three-point correlators of gravitons and scalar curvature perturbations around a quasi de Sitter space-time and establishes Bootstrap Rules that fully fix the form of these correlators in the asymptotic future at the boundary. The Boostless Bootstrap approach is shown to account for the breaking of de Sitter boosts caused by inflationary backgrounds. Derivations of bispectra involving gravitons in single-clock, canonical inflation are easily derived in this approach, as well as the scalar bispectrum in the Effective Field Theory of inflation to any order in derivatives. In many cases, the derivations are computationally simpler than the corresponding explicit calculations, emphasizing the implications of locality, vacuum choice, and underlying symmetries.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Harry Goodhew, Sadra Jazayeri, Enrico Pajer
Summary: The study shows that in curved spacetime, unitarity has a significant impact on the relationships between coefficients of the wavefunction of the universe, known as the Cosmological Optical Theorem. This theorem strongly constrains the analytic structure and form of correlators, especially in contact diagrams and four-point exchange diagrams. These results provide a new and powerful tool for bootstrapping cosmological correlators.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Harry Goodhew, Sadra Jazayeri, Mang Hei Gordon Lee, Enrico Pajer
Summary: This paper discusses the initial conditions of the universe and the impact of quantum mechanics on late-time observables, deriving a set of single-cut rules, discussing the analytical structure of the wave function, and verifying the applicability of these rules in some specific examples.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Particles & Fields
James Bonifacio, Enrico Pajer, Dong-Gang Wang
Summary: Our understanding of quantum correlators in cosmological spacetimes, including those observed in cosmological surveys, has significantly improved in recent years, leading to the derivation of the most general scalar four-point correlator and the extension of the cosmological bootstrap. By applying techniques from commutative algebra, we have been able to derive these results without assuming Lorentz boosts invariance, further building a new connection between flat and curved spacetime physics.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Sadra Jazayeri, Enrico Pajer, David Stefanyszyn
Summary: In this study, we investigate how final observables can be derived directly from locality, unitarity, and symmetries, without assuming de Sitter boosts. Two new boostless bootstrap tools are introduced to efficiently compute tree-level cosmological correlators/wavefunctions. These tools provide a calculation pipeline without the need for specific assumptions about de Sitter boosts, offering a novel approach to deriving predictions in inflationary cosmology.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Correction
Physics, Particles & Fields
Enrico Pajer, David Stefanyszyn, Jakub Supel
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Giovanni Cabass, Enrico Pajer, David Stefanyszyn, Jakub Supel
Summary: By using gravitational interferometers and cosmological observations, we can investigate the laws of gravity in the early universe. To study and interpret the data, it is important to understand the possible non-Gaussianities of gravitons. In this study, the authors derive the most general tree-level expressions for the three-point functions of massless gravitons, assuming scale invariance.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Aaron Hillman, Enrico Pajer
Summary: This article presents a new differential representation of the perturbative cosmological wavefunction in de Sitter spacetime. It provides a computational advantage by trading nested bulk time integrals for derivatives on boundary kinematical data. This method is applicable to a wide range of phenomenologically relevant theories.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Giovanni Cabass, Sadra Jazayeri, Enrico Pajer, David Stefanyszyn
Summary: We present a set of no-go theorems and yes-go examples for the parity-odd primordial trispectrum of curvature perturbations. Our results show that the presence of scalar fields with arbitrary mass or spinning fields with massless de Sitter mode functions leads to the vanishing of the parity-odd scalar trispectrum and parity-odd scalar correlator. By relaxing certain assumptions, we also provide explicit results for violations of scale invariance, modified dispersion relation, and interactions with massive spinning fields. Our findings demonstrate the sensitivity of the parity-odd trispectrum as a probe for new physics beyond standard inflation.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Physics, Particles & Fields
Santiago Aguei Salcedo, Mang Hei Gordon Lee, Scott Melville, Enrico Pajer
Summary: The wavefunction in quantum field theory is a powerful tool for understanding various aspects of spacetime and boundary observables in different spacetimes. We have investigated the analytic properties of wavefunction coefficients in Minkowski spacetime and found that they are analytic except for singularities on the negative real axis. These singularities are determined by an energy-conservation condition. Our findings have been verified through calculations in scalar field theories, and we have derived new UV/IR sum rules for the wavefunction, which relate the coefficients to integrals of discontinuities in the UV-completion and can constrain total-derivative interactions.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Physics, Particles & Fields
James Bonifacio, Harry Goodhew, Austin Joyce, Enrico Pajer, David Stefanyszyn
Summary: In this study, we compute the tree-level late-time graviton four-point correlation function and quartic wavefunction coefficient for Einstein gravity in de Sitter spacetime. We derive this result using multiple methods, including direct calculation, the in-in formalism, and the wavefunction of the universe. We also find agreement among these different approaches.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Physics, Particles & Fields
Scott Melville, Enrico Pajer
Summary: Research indicates that primordial perturbations in the universe have a quantum origin and can be described by the wavefunction, with unitarity leading to a systematic set of cosmological cutting rules that constrain wavefunction coefficients for different fields and loop orders. These rules have remarkable generality and can be applied to arbitrary interactions of fields with any mass and spin, around a general class of FLRW spacetimes with a Bunch-Davies vacuum. This discovery extends the potential of utilizing unitarity to bootstrap cosmological observables and restrict consistent effective field theories on curved spacetimes.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
