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
Xuce Niu, Moinul Hossain Rahat, Karthik Srinivasan, Wei Xue
Summary: The four-point correlation function of primordial scalar perturbations has both even and odd contributions, and the odd signal provides a new way to search for new physics during inflation in cosmological observations. We study the distinctive predictions of even and odd parity from the axion inflation model, where the inflaton is coupled to a vector field via a Chern-Simons interaction. The numerical studies show that the massive and massless vector fields have significant even signals, while the odd contribution is about one to two orders of magnitude smaller.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
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
Astronomy & Astrophysics
Arunoday Sarkar, Chitrak Sarkar, Buddhadeb Ghosh
Summary: By defining the k-modes of quantum fluctuations during inflation through the dynamical horizon crossing condition k = aH, and solving the equations of cosmological first-order perturbations self-consistently with chaotic alpha-attractor type potentials, we were able to study the behavior of various parameters in k-space. Comparison with Planck data in the low-k regime constrained the values of the alpha parameter through microscopic calculations. The calculated results matched the Planck-2018 data with 68% or near 95% CL for various values of alpha.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Marios Bounakis, Ian G. Moss, Gerasimos Rigopoulos
Summary: The study provides a concise treatment of the evolution in a Hyperinflation model, finding that the adiabatic spectral index severely restricts the values of the potential's slope.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Aliakbar Abolhasani, Harry Goodhew
Summary: We present a systematic prescription for calculating cosmological correlation functions for models with derivative interactions and compare it with the in-in formalism. By performing path integrals, we show that our method recovers the classical action and includes additional contributions to cancel other divergences.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Anamaria Hell
Summary: This study compares the massive Kalb-Ramond and Proca fields with a quartic self-interaction, and shows that they have the same strong coupling scale. However, the different modes in these theories behave differently beyond the strong coupling scale, indicating a potential contradiction with claims in the literature about their duality.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Nina K. Stein, William H. Kinney
Summary: We have constructed a family of simple single-field inflation models that are consistent with Planck/BICEP Keck bounds. These models have a small tensor amplitude and no running of the scalar spectral index. The construction involves a constant-roll hilltop inflaton potential, with the end of inflation being a free parameter induced by dominant higher-order operators. This construction directly demonstrates that there is no lower bound on the tensor/scalar ratio for simple single-field inflation models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Abineet Parichha, Shiv Sethi
Summary: This study proposes a decaying WIMP model that can address the issues with the CDM model at small scales. By comparing the predictions of this model with CMB and galaxy clustering data, the effectiveness of the model is demonstrated and constraints on certain parameters are obtained.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Panagiotis Christeas, Logan Thomas
Summary: The next decade will bring abundant new cosmological data, while fundamental questions about inflation still remain. Therefore, efficient calculations are needed, especially in non-standard scenarios for the early Universe. In this work, we demonstrate that a small adjustment to Weinberg's perturbation series can yield agreement with standard in-in calculations at every order of perturbation theory for commonly studied spins and masses in de Sitter spacetime, and we extend the result to a large class of cosmological spacetimes, including slow roll spacetimes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Cesar Gomez, Raul Jimenez
Summary: The most robust prediction of inflation driven by a single field is the existence of a red tilt for the spectrum of curvature fluctuations that is experimentally of order 0.04. This is derived by solving the exact equation for quantum fluctuations in a quasi de Sitter background with a small but non-vanishing first slow-roll parameter. The lack of scale invariance associated with the tilt is classical in essence and parametrized by the slow roll parameter of the inflaton potential. A purely quantum mechanical and model independent derivation of the tilt is presented based on two observations: the correlator for the Mukhanov-Sasaki gauge invariant variables is related to the quantum Fisher function, and this quantum Fisher function has a non-vanishing scale dependent red tilt that fits the effective quasi de Sitter prediction and experimental value at the energy scales of interest.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Markus R. Mosbech, Celine Boehm, Steen Hannestad, Olga Mena, Julia Stadler, Yvonne Y. Y. Wong
Summary: Research found that interactions between massive neutrinos and dark matter significantly change the lower bounds on sigma 8 inferred from Planck data, leading to agreement within 1-2 sigma with weak lensing estimates of sigma 8, while barely affecting the value of the Hubble constant H-0.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Suvedha Suresh Naik, Kazuyuki Furuuchi, Pravabati Chingangbam
Summary: This paper analyzes a class of inflationary models involving particle productions and compares their predictions with the CMB data from Planck 2018. It is found that the multi-bump model with multiple bursts of particle production provides a better fit to the data compared to the concordance ACDM model.
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
I. G. Marian, U. D. Jentschura, N. Defenu, A. Trombettoni, I Nandori
Summary: This paper investigates the evolution of the constant term in nonperturbative renormalization group methods and proposes a subtraction method to recover the correct results. The constant term has different physical meanings in models with different dimensions, being associated with the ground-state energy in quantum mechanical models and playing a role in cosmic inflation. These findings have important applications in cosmological models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Particles & Fields
Ali Akil, Xi Tong
Summary: The study emphasizes the necessity of resolving apparent gauge dependence in quantum corrections for Higgs-like inflation models and offers a practical shortcut to gauge-independent inflationary observables. By using an effective potential obtained from a specific background current choice, gauge-independent predictions of inflationary observables can be achieved. Furthermore, the use of gauge-invariant current terms can lead to gauge-independent effective potentials and ultimately gauge-invariant inflationary observables in any theory to all orders.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Mitsuhiro Kato, Kanji Nishii, Toshifumi Noumi, Toshiaki Takeuchi, Siyi Zhou
Summary: In de Sitter space, semiclassical spiky strings and the corresponding Regge trajectories are studied, showing that each trajectory has a maximum spin due to de Sitter acceleration similar to the folded string. This leads to the question of how to maintain mild high-energy string scattering, which is familiar in flat space and anti-de Sitter space. Analysis suggests that achieving infinitely many higher spin states requires considering infinitely many Regge trajectories with increasing folding numbers.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Chon Man Sou, Xi Tong, Yi Wang
Summary: This study analyzes gravitational particle production assisted by chemical potential, using the uniformly smoothed Stokes-line method and Borel summation. Analytic/semi-analytic formulae describing the production of spin-1 and spin-1/2 particles in various FRW spacetimes are obtained. The work serves as a concrete demonstration of the uniformly smoothed Stokes-line method applied to cosmology.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Suro Kim, Toshifumi Noumi, Keito Takeuchi, Siyi Zhou
Summary: The study indicates that non-Gaussianities with vertical bar f(NL)vertical bar greater than or similar to 1 cannot be realized without interactions that violate unitarity. It also finds that for the Hubble scale H greater than or similar to 6 x 10(9) GeV, Planck suppressed operators can easily generate too large non-Gaussianities, requiring a mechanism to suppress quantum gravity corrections.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Xi Tong, Yi Wang, Hui-Yu Zhu
Summary: The transitions between energy levels of a gravitational atom system in a pulsar-black hole system are more likely to be detected, especially the fine and hyperfine structure transitions, which can be better analytically calculated and serve as ideal probes for gravitational collider signals.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Particles & Fields
Xi Tong, Yi Wang, Yuhang Zhu
Summary: This study reveals that the evolution of interacting massive particles in the de Sitter bulk can be understood as a series of resonant decay and production events. Based on this perspective, the cosmological collider signals are classified into local and nonlocal categories with different physical origins. Furthermore, a cutting rule is derived for efficient extraction of these signals through analytical methods, which can be easily implemented as symbolic computational packages in the future.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Nuclear
Haipeng An, Kun-Feng Lyu, Lian-Tao Wang, Siyi Zhou
Summary: We investigate the characteristics of gravitational wave (GW) signals generated by first-order phase transitions during the inflation era, revealing that the power spectrum of GW oscillates with its wave number. These signals can be observed directly by future terrestrial and spatial GW detectors and indirectly through the B-mode spectrum in the CMB. The oscillatory feature of GW is distinct from those generated by phase transitions after inflation and contains important information about the scale of the phase transition and the subsequent evolution of the universe.
Article
Physics, Particles & Fields
Haipeng An, Kun-Feng Lyu, Lian-Tao Wang, Siyi Zhou
Summary: Large excursion of the inflaton field can trigger interesting dynamics, including first-order phase transitions that result in the production of gravitational waves (GWs). This work demonstrates that the oscillatory feature of GWs is generic for sources in eras of accelerated expansion. The shape of the GW signal provides information about the evolution of the early universe following the phase transition and can be used to distinguish different models of evolution during and after inflation. This study highlights the importance of GW signals as a powerful probe for understanding early universe dynamics.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Yong Cai, Ji Xu, Shuai Zhao, Siyi Zhou
Summary: This article investigates the perturbative unitarity for stable violations of the null energy condition (NEC) in the contexts of Galileon and beyond Horndeski genesis cosmology. The findings suggest that unknown new physics may be needed to explain the phenomena beyond what is represented by the Horndeski operators.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Xi Tong, Zhong-Zhi Xianyu
Summary: In this study, we investigate the theory and phenomenology of massive spin-2 fields during inflation with a nonzero background chemical potential, and extend the application of cosmological collider physics to tensor modes. By identifying a unique dimension-5 and parity-violating chemical potential operator, we successfully construct a ghost-free linear theory propagating one scalar mode and two tensor modes. The introduction of the chemical potential greatly enhances the production of one tensor mode, even for heavy spin-2 particles, resulting in large and distinct cosmological collider signals observed in both the curvature trispectrum and the tensor-curvature mixed bispectrum.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
Robert Caldwell, Yanou Cui, Huai-Ke Guo, Vuk Mandic, Alberto Mariotti, Jose Miguel No, Michael J. Ramsey-Musolf, Mairi Sakellariadou, Kuver Sinha, Lian-Tao Wang, Graham White, Yue Zhao, Haipeng An, Ligong Bian, Chiara Caprini, Sebastien Clesse, James M. Cline, Giulia Cusin, Bartosz Fornal, Ryusuke Jinno, Benoit Laurent, Noam Levi, Kun-Feng Lyu, Mario Martinez, Andrew L. Miller, Diego Redigolo, Claudia Scarlata, Alexander Sevrin, Barmak Shams Es Haghi, Jing Shu, Xavier Siemens, Daniele A. Steer, Raman Sundrum, Carlos Tamarit, David J. Weir, Ke-Pan Xie, Feng-Wei Yang, Siyi Zhou
Summary: This white paper discusses the significance of detecting gravitational-wave signals of non-astrophysical origin in answering fundamental scientific questions about the Universe, and highlights the connections between early-Universe mechanisms and fundamental physics.
GENERAL RELATIVITY AND GRAVITATION
(2022)
Article
Astronomy & Astrophysics
Haipeng An, Xi Tong, Siyi Zhou
Summary: We propose a scenario where superheavy dark matter (DM) can be produced via symmetry restoration first-order phase transition during inflation triggered by the evolution of the inflaton field. The phase transition happens in a spectator sector coupled to the inflaton field. The massive particles produced after bubble collisions are protected against decaying by the restored symmetry and may serve as a DM candidate in the later evolution of the Universe. We show that the latent heat released during the phase transition can be sufficient to produce the DM relic abundance observed today. In addition, accompanied with the superheavy DM, this first-order phase transition also produces gravitational waves detectable via future gravitational wave detectors.
Article
Astronomy & Astrophysics
Xi Tong, Yi Wang, Hui -Yu Zhu
Summary: The study shows that the impact of a binary companion on black hole superradiance mainly weakens the superradiance rate through tidal perturbation. Once the binary separation distance reaches a critical value, the superradiance rate becomes negative and the boson cloud is absorbed by the black hole. Different mass ratios of companions impose strict constraints on resonant transitions of the cloud, and the backreaction force manifests as changes in the binary orbit.
Article
Astronomy & Astrophysics
Xi Tong, Yi Wang, Yuhang Zhu
Summary: We study semiclassical communication in positivity-violating k-essence scalar field theories, where the self-interactions due to the nonlinear nature of these theories constrain the rate of superluminal information transfer. By deriving a novel bit rate bound on superluminal communication within a conceptual model, we reveal the possibility that, even without a maximal information propagation speed, there is still an upper bound on the rate of information transfer.
Article
Astronomy & Astrophysics
Qianhang Ding, Xi Tong, Yi Wang
Summary: The study proposes using pulsar-black hole binaries to probe gravitational collider physics by measuring the Romer delay in pulsar arrival times caused by atomic transitions of the boson cloud around the black hole affecting orbital motion. Results show that the pulsar timing accuracy is almost always sufficient to capture resonance phenomenon if the transitions occur within the observable window.
ASTROPHYSICAL JOURNAL
(2021)
