Article
Astronomy & Astrophysics
Karim P. Y. Thebault
Summary: We evaluate various criteria for resolving big bang singularities in quantum cosmology, considering their physical viability and logical strength. Based on this evaluation, we propose a consistent set of constitutive conditions that jointly define the resolution of "global dynamics" and "local curvature" big bang singularities. Although this article focuses on finite dimensional models of quantum cosmology, we believe our analysis can be extended to a broader examination of criteria for resolving quantum singularities in cosmology and black hole physics.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Paola C. M. Delgado, Ruth Durrer, Nelson Pinto-Neto
Summary: In this paper, the CMB bispectrum for bouncing models motivated by Loop Quantum Cosmology was computed. Despite the decay of the primordial bispectrum above a large pivot scale, it was found that the cumulative signal-to-noise ratio of the bispectrum induced in the CMB from scales t < 30 is larger than 10 in all cases of interest, indicating the potential for detection in the Planck data.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Review
Astronomy & Astrophysics
Valerio Bozza
Summary: This paper reviews the evolution of perturbations in bouncing cosmologies and discusses significant attempts to reconcile predicted spectra with observations. Bouncing cosmologies, particularly the pre-Big Bang scenario, are viable alternatives to inflation that can help address current theoretical and observational tensions.
Article
Astronomy & Astrophysics
C. Wetterich
Summary: The study shows that crossing the Big Bang singularity in a simple scalar field and gravity model requires tuning of model parameters, rather than being a generic phenomenon. This singularity crossing does not lead to physical singularities, but the model is not a realistic description of the Universe as it fails to capture acceptable inhomogeneities.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
D. Jackson, R. Bufalo
Summary: In this work, the improved Deser-Woodard non-local gravity over five different cosmological models is analyzed, aiming to avoid the initial singular state of the universe. The numerical solution for the non-local distortion function is developed using the reconstruction procedure, providing viable cosmological solutions. The physical aspects and outcomes of the distortion function evolution at the bouncing point for each model are discussed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Jinyi Liu, Zeyang Sun, Jiakang Han, Julien Carron, Jacques Delabrouille, Siyu Li, Yang Liu, Jing Jin, Shamik Ghosh, Bin Yue, Pengjie Zhang, Chang Feng, Zhi-Qi Huang, Hao Liu, Yi-Wen Wu, Le Zhang, Zi-Rui Zhang, Wen Zhao, Bin Hu, Hong Li, Xinmin Zhang
Summary: AliCPT-1 is the first Chinese cosmic microwave background experiment aiming for high-precision measurement of CMB B-mode polarization. This study forecasts the signal-to-noise ratio of CMB lensing reconstruction, lensing-galaxy, and lensing-cosmic infrared background cross-correlations for AliCPT-1. The results show that the measurement significance increases with longer observation times and optimizing frequency data can improve the signal-to-noise ratio.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Astronomy & Astrophysics
Micol Benetti, Salvatore Capozziello, Gaetano Lambiase
Summary: Researchers conducted a detailed study on viable f(T) teleparallel cosmological models, including power law, exponential, and square-root exponential, analyzing their evolution at different scales. Through a combination of measurements, they obtained narrow constraints on the free parameters of these models, indicating a preference for extended gravity models in observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Karthik Rajeev, Vikramaditya Mondal, Sumanta Chakraborty
Summary: In this paper, we investigate the impact of introducing anisotropy on bouncing models of cosmology. We find that quantum effects can enable a bounce, even when classical bouncing is forbidden due to large anisotropic stress. By solving the Wheeler-deWitt equation, we observe a phase transition-like behavior in the probability of a bouncing universe, which sharply decreases as the shear density increases beyond a critical value. Our findings are supported by Lorentzian quantum cosmology and the Picard-Lefschetz theory.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Norman Cruz, Esteban Gonzalez, Jose Jovel
Summary: This paper explores the different types of singularities in the ΛCDM model with dissipative processes, considering viscous cold dark matter and early-time viscous radiation domination. Future singularities like Big Rip are allowed, as well as Big Crunch singularities when a negative cosmological constant is present. The negative pressure of viscosity also allows for de Sitter and even Big Rip types of singularities, opening the possibility of accelerated expansion in anti-de Sitter cosmologies.
Article
Astronomy & Astrophysics
Tsung-Han Yeh, Keith A. Olive, Brian D. Fields
Summary: The effect of neutron lifetime and its uncertainty on standard big bang nucleosynthesis (BBN) is explored in this study. It is found that the uncertainties in neutron lifetime dominate the predicted errors in He-4 abundance. However, these theory errors are still smaller than the uncertainties in He-4 observations. For the predictions of other light elements, neutron lifetime contributes negligibly to their error budget.
Article
Physics, Multidisciplinary
Latham Boyle, Kieran Finn, Neil Turok
Summary: We investigate the idea that the universe before the Big Bang is the CPT reflection of the universe after the bang to explain how the universe does not violate CPT symmetry. We show that CPT symmetry selects a preferred vacuum state for quantum fields on a CPT-invariant cosmological background spacetime. The theory also predicts a universe/anti-universe pair emerging into the radiation-dominated era and offers insights into dark matter and cosmological perturbations.
Review
Multidisciplinary Sciences
M. Gasperini
Summary: This article presents a non-standard cosmological scenario based on the duality symmetries of string theory, replacing the big bang singularity with a 'big bounce' at high but finite curvature. The bouncing epoch is prepared by a long phase of cosmic evolution starting from an initial state asymptotically approaching the string perturbative vacuum.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Physics, Particles & Fields
Abdul Malik Sultan, Abdul Jawad
Summary: This paper investigates the implications of Einstein-Aether and modified Horava-Lifshitz theories of gravity on big bang nucleosynthesis. By comparing the models with observational bounds, it is found that the chosen gravity models satisfy the constraints of big bang nucleosynthesis, making them viable cosmological models.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Correction
Astronomy & Astrophysics
Nashwan Sabti, James Alvey, Miguel Escudero, Malcolm Fairbairn, Diego Blas
Summary: The new measurement of the d+p -> He-3+gamma reaction rate has important implications for predicting the primordial deuterium abundance during the time of BBN, but has little impact on constraints on dark sector parameters. Constraints on neutrino-like particles are not significantly affected, while constraints on electrophilic dark sector states may vary moderately. With updated results for light dark sector states, the combination of BBN and CMB observations can lead to some variation in bounds on electrophilic dark sectors.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Review
Astronomy & Astrophysics
Enrique Gaztanaga
Summary: This passage discusses an alternative model for cosmic expansion, suggesting that it originates from gravitational collapse and bounce. The model proposes that a massive black hole formed and rebounded, resulting in the Big Bang expansion. It offers an explanation for cosmic acceleration without the need for inflation or dark energy.
Article
Astronomy & Astrophysics
Zihan Zhou, Jun Yan, Andrea Addazi, Yi-Fu Cai, Antonino Marciano, Roman Pasechnik
Summary: This study introduces a novel phenomenon in particle cosmology, where specific cosmological phase transitions are triggered by quantum tunneling through multiple vacua. This mechanism predicts a potentially significant new source of gravitational waves with distinct energy spectrum patterns, which could be detected by future gravitational wave interferometers.
Article
Astronomy & Astrophysics
Pierre Zhang, Guido D'Amico, Leonardo Senatore, Cheng Zhao, Yifu Cai
Summary: By analyzing the Full Shape of the BOSS Correlation Function and combining it with other measurements, we have determined the present day Hubble constant, matter fraction, and parameters of the primordial power spectrum. We have also placed constraints on the total neutrino mass. These results are consistent with previous studies and show no tension or inconsistency.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Pierre Zhang, Yifu Cai
Summary: The study re-analyzed the full shape of the BOSS galaxy two-point function within Lambda-CDM, with results constraining various cosmological parameters. The effect of redshift selection on the results was discussed, emphasizing the importance of systematic assessments for ongoing and future large-volume surveys.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Xin Ren, Sheng-Feng Yan, Yaqi Zhao, Yi-Fu Cai, Emmanuel N. Saridakis
Summary: In this study, we investigate the effective field theory formulation of torsional gravity in a cosmological framework and reconstruct the f(T) form in a model-independent way. By considering observational data and performing fitting using polynomial functions, we find an analytic expression that describes the cosmological evolution in great agreement with observations.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Yi-Fu Cai, Xiao-Han Ma, Misao Sasaki, Dong-Gang Wang, Zihan Zhou
Summary: This study reports a novel prediction from single-field inflation that a tiny step in the inflaton potential can alter our understanding of primordial non-Gaussianities of the curvature perturbation. By analyzing the tail of the probability distribution generated by an upward step transition between two stages of slow-roll evolution, it is found that a highly non-Gaussian tail can be generated even when the conventional nonlinearity parameters remain small. This research demonstrates for the first time the sensitive dependence of non-perturbative effects on the tail of the probability distribution and proposes potential applications to primordial black holes.
Article
Astronomy & Astrophysics
Yi-Fu Cai, Xiao-Han Ma, Misao Sasaki, Dong-Gang Wang, Zihan Zhoua
Summary: This paper investigates the relationship between deviations from Gaussian statistics in primordial perturbations and non-perturbative effects. It presents specific examples where the tail of the distribution becomes highly non-Gaussian despite remaining almost Gaussian in the perturbative regime. The study reveals the rich phenomenology of non-Gaussian tails, which has been overlooked in conventional analyses.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Editorial Material
Physics, Multidisciplinary
Yi-Fu Cai
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Physics, Multidisciplinary
Guan-Wen Yuan, Lei Zu, Lei Feng, Yi-Fu Cai, Yi-Zhong Fan
Summary: This study investigates new particles and fields to explain the excess in W-boson mass. The interpretations of axion-like particle and dark photon have been significantly narrowed down by global electroweak fits. The possibility of attributing the W-boson mass anomaly to chameleon dark energy is ruled out by other experiments.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Multidisciplinary Sciences
Hang Liang, Man Jiao, Yue Huang, Pei Yu, Xiangyu Ye, Ya Wang, Yijin Xie, Yi-Fu Cai, Xing Rong, Jiangfeng Du
Summary: Laboratory search for exotic interactions is crucial for exploring physics beyond the standard model. We report new experimental constraints on two exotic spin-dependent interactions at the micrometer scale based on ensembles of nitrogen-vacancy (NV) centers in diamond. Our results establish new bounds for these exotic spin interactions at the micrometer scale.
NATIONAL SCIENCE REVIEW
(2023)
Article
Astronomy & Astrophysics
Dongdong Zhang, Jia-Rui Li, Jiaqi Yang, Yufei Zhang, Yi-Fu Cai, Wenjuan Fang, Chang Feng
Summary: We use the Ali Cosmic Microwave Background Polarization Telescope (AliCPT) to forecast the constraints on neutrino physics parameters using the Cosmic Microwave Background (CMB) temperature, E-mode polarization, and lensing spectra. Our numerical simulations show that AliCPT can achieve a precision of sigma(N (eff)) = 0.56 and M (nu) < 1.10 eV (95% CL.) for the first year of observation, based on TT, TE, EE, and CMB lensing power spectra. We also investigate how instrumental parameters such as noise level, FWHM, and sky coverage affect these constraints on neutrino parameters.
ASTROPHYSICAL JOURNAL
(2023)
Article
Physics, Multidisciplinary
Tinggui Wang, Guilin Liu, Zhenyi Cai, Jinjun Geng, Min Fang, Haoning He, Ji-an Jiang, Ning Jiang, Xu Kong, Bin Li, Ye Li, Wentao Luo, Zhizheng Pan, Xuefeng Wu, Ji Yang, Jiming Yu, Xianzhong Zheng, Qingfeng Zhu, Yi-Fu Cai, Yuanyuan Chen, Zhiwei Chen, Zigao Dai, Lulu Fan, Yizhong Fan, Wenjuan Fang, Zhicheng He, Lei Hu, Maokai Hu, Zhiping Jin, Zhibo Jiang, Guoliang Li, Fan Li, Xuzhi Li, Runduo Liang, Zheyu Lin, Qingzhong Liu, Wenhao Liu, Zhengyan Liu, Wei Liu, Yao Liu, Zheng Lou, Han Qu, Zhenfeng Sheng, Jianchun Shi, Yiping Shu, Zhenbo Su, Tianrui Sun, Hongchi Wang, Huiyuan Wang, Jian Wang, Junxian Wang, Daming Wei, Junjie Wei, Yongquan Xue, Jingzhi Yan, Chao Yang, Ye Yuan, Yefei Yuan, Hongxin Zhang, Miaomiao Zhang, Haibin Zhao, Wen Zhao
Summary: The Wide Field Survey Telescope (WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China (USTC) and the Purple Mountain Observatory (PMO). It is equipped with a 2.5-meter diameter primary mirror and a mosaic CCD camera, and it will scan the northern sky in four optical bands to detect transient phenomena and study the variability of Galactic and extragalactic objects.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Lei-Hua Liu, Mian Zhu, Wentao Luo, Yi-Fu Cai, Yi Wang
Summary: We systematically investigate the microlensing effect of a charged spherically symmetric wormhole, where the light source is remote from the throat. The numerical result shows that the range of total magnification is from 105 to 10-2 depending on various metrics. Our theoretical investigation could shed new light on exploring the wormhole with the microlensing effect.
Article
Astronomy & Astrophysics
Yu-Min Hu, Yaqi Zhao, Xin Ren, Bo Wang, Emmanuel N. Saridakis, Yi-Fu Cai
Summary: This study investigates the scalar perturbations and possible strong coupling issues of f(T) gravity using the effective field theory (EFT) approach. The generalized EFT framework of modified teleparallel gravity is revisited and applied to examine both linear and second-order perturbations in f(T) theory. The results suggest that there is no new scalar mode present in f(T) gravity, indicating a strong coupling problem. However, an estimation of the strong coupling scale based on the ratio of cubic to quadratic Lagrangians shows that the strong coupling problem can be avoided for certain modes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Yiqi Huang, Jiajun Zhang, Xin Ren, Emmanuel N. Saridakis, Fuyu Dong, Yi-Fu Cai
Summary: In this study, we perform N-body simulations to investigate the structure formation process in f(T) gravity. By comparing with ACDM cosmology, we find clear observational differences due to the modifications brought about by f(T) gravity in the evolution of the Hubble function and the effective Newton's constant. We extract several physical quantities and observe differences in the matter density distribution, matter power spectrum, counts-in-cells, halo mass function, and excess surface density around low-density positions.
Article
Physics, Particles & Fields
Yi-Fu Cai, Chao Chen, Qianhang Ding, Yi Wang
Summary: A novel class of celestial objects called stellar bubbles, dominated by primordial black holes, is proposed, which can be generated through phase transitions in the primordial Universe. The radiations emitted by these stellar bubbles have distinct features in the gamma-ray spectra and gravitational waves.
EUROPEAN PHYSICAL JOURNAL C
(2022)