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Inflationary cosmology with Quantum Gravitational Effects and Swampland Conjectures

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Communications in Theoretical Physics 2019年第9期71卷 1115-1120页

作者： Qiang Wu Tao Zhu institute for Theoretical Physics and cosmology Zhejiang University of Technology

Recently proposed two swampland criteria that arising from string theory landscape leads to the important challenge of the realization of single-field inflationary models. Especially one of swampland criteria which implies a large tensor-to-scalar ratio is strongly in tension with recent observational results. In this paper, we explore the possibility the swampland conjectures could be compatible with single-field inflationary scenarios if the effects due to the quantum theory of gravity are considered. We show that the quantum gravitational effects due to the nonlinear dispersion relation provides significant modifications on the amplitude of both the scalar and tensor perturbation spectra. Such modifications could be either raise or reduce the perturbation spectra depending on the values of the parameters in the nonlinear terms of the dispersion relations. Therefore, these effects can reduce the tensor-to-scalar ratio to a smaller value, which helps to relax the tension between the swampland conjecture and observational data.

关键词： inflation quantum gravitational effects swampland conjectures uniform asymptotic approximation

Dark energy constraints from joint analysis of standard rulers and standard candles

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Research in Astronomy and Astrophysics 2011年第6期11卷 641-654页

作者： Marek Biesiada Beata Malec Aleksandra Piórkowska Department of Astrophysics and cosmology Institute of PhysicsUniversity of Silesia Copernicus Center for Interdisciplinary Studies

We performed joint analysis of five cosmological models invoked to explain the accelerating expansion of the *** used the data from strong gravitational lensing systems,locations of cosmic microwave background acoustic peaks and baryon acoustic oscillation data in combination with supernova Ia data（Union2 compilation）.The observables we used came from both standard rulers and standard candles,so they had different parameter degeneracies and different restrictive powers in the parameter spaces of cosmological *** best fits we obtained for the model parameters in joint analysis turned out to prefer cases effectively equivalent to the ΛCDM *** were also in agreement with other combined studies performed by other authors on different sets of diagnostic *** theoretic methods used to assess which model is most supported by the data lead to the conclusion that the concordance model ΛCDM is clearly preferred in joint *** quintessence（both having constant or time varying equation of state） and Chaplygin gas get considerably less support from the data while the brane world（DGP） scenario is practically ruled out.

关键词： cosmology:observations-cosmological parameters-gravitational lensing-supernovae

What do parameterized Om(z) diagnostics tell us in light of recent observations?

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Research in Astronomy and Astrophysics 2018年第6期18卷 49-58页

作者： Jing-Zhao Qi Shuo Cao Marek Biesiada Teng-Peng Xu Yan Wu Si-Xuan Zhang Zong-Hong Zhu Department of Astronomy Beijing Normal University Department of Astrophysics and cosmology Institute of Physics University of Silesia

In this paper, we propose a new parametrization for Om(z) diagnostics and show how the most recent and significantly improved observations concerning the H(z) and SN Ia measurements can be used to probe the consistency or tension between the ΛCDM model and observations. Our results demonstrate that H0 plays a very important role in the consistency test of ΛCDM with H(z)data. Adopting the Hubble constant priors from Planck 2013 and Riess, one finds considerable tension between the current H(z) data and ΛCDM model and confirms the conclusions obtained previously by others. However, with the Hubble constant prior taken from WMAP9, the discrepancy between H(z) data and ΛCDM disappears, i.e., the current H(z) observations still support the cosmological constant scenario. This conclusion is also supported by the results derived from the Joint Lightcurve Analysis(JLA) SN Ia sample. The best-fit Hubble constant from the combination of H(z)+JLA(H00 = 68.81+1.5-1.49 km s-1 Mpc-1) is very consistent with results derived both by Planck 2013 and WMAP9, but is significantly different from the recent local measurement by Riess.

关键词： cosmology: theory cosmology: observations cosmology: cosmological parameters

Holographic dark energy from acceleration of particle horizon

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Chinese Physics C 2023年第3期47卷 218-224页

作者： H.R.Fazlollahi institute of Gravitation and cosmology Peoples Friendship University of Russia(RUDNUniversity)Moscow117198RussianFederation

Following the holographic principle,which suggests that the energy density of dark energy may be inversely proportional to the area of the event horizon of the Universe,we propose a new energy density of dark energy through the acceleration of the particle horizon scaled by the length of this *** proposed model depends only on one free parameter:β=*** values of β near zero,the deviation between the proposed model and the ∧ CDM model is significant,while forβ-→1.99,the suggested model has no conflict with the ∧ CDM *** of the value of β,the model considers dark energy to behave as matter with positive pressure in high redshifts,wx 0.33,while for present and near-future Universe,it is considered to behave similar to that in the cosmological constant model and phantom *** the model with the Ricci dark energy model,we show that our model reduces the errors of the Ricci dark energy model concerning the calculation of the age of old supernovae and evolution of different cosmic components in high ***,we calculated matter structure formation parameters such as the CMB temperature and matter power spectrum of the model to consider the effects of matter-like dark energy during the matter-dominated era.

关键词： cosmology holographic principle dark energy

Enhanced search sensitivity to the double beta decay of ^(136)Xe to excited states with topological signatures

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Science China(Physics,Mechanics & Astronomy) 2021年第6期64卷 41-50页

作者： Chen Xie Kaixiang Ni Ke Han Shaobo Wang institute of Nuclear and Paricle Physics(INPAC) Shanghai Laboratory for Particle Physics and CosmologyKey Laboratory for Partic le Astrophysics and Cosmology(MOE)School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China ParisTech Elite institute of Technology Shanghai Jiao Tong UniversiryShanghai 200240China

The double beta decay of ^(136)Xe to excited states of 136Ba(DBD-ES)has not yet been discovered *** experimental signature of such decays,one or two gamma rays following the beta signals,can be identified more effectively in a gaseous detector with the help of topological *** have investigated key parameters of particle trajectories of DBD-ES with Monte Carlo simulation data of the proposed PandaX-III detector as an *** background rates can be reduced by about one order of magnitude while keeping more than half of signals with topological *** estimated half-life sensitivity of DBD-ES can be improved by 1.8 times to 4.1×10^(23) year(90%C.L.).Similarly,the half-life sensitivity of neutrinoless double beta decay of ^(136)Xe to excited states of 136Ba can be improved by a factor of 4.8 with topological signatures.

关键词： neutrino double beta decay topological signatures background suppression

Einstein Probe discovery of EP240408a: A peculiar X-ray transient with an intermediate timescale

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 222-240页

作者： Wenda Zhang Weimin Yuan Zhixing Ling Yong Chen Nanda Rea Arne Rau Zhiming Cai Huaqing Cheng Francesco Coti Zelati Lixin Dai Jingwei Hu Shumei Jia Chichuan Jin Dongyue Li Paul O’Brien Rongfeng Shen Xinwen Shu Shengli Sun Xiaojin Sun Xiaofeng Wang Lei Yang Bing Zhang Chen Zhang Shuang-Nan Zhang Yonghe Zhang Jie An David Buckley Alexis Coleiro Bertrand Cordier Liming Dou Rob Eyles-Ferris Zhou Fan Hua Feng Shaoyu Fu Johan P.U.Fynbo Lluis Galbany Saurabh W.Jha Shuaiqing Jiang Albert Kong Erik Kuulkers Weihua Lei Wenxiong Li Bifang Liu Mingjun Liu Xing Liu Yuan Liu Zhu Liu Chandreyee Maitra Alessio Marino Itumeleng Monageng Kirpal Nandra Jeremy Sanders Roberto Soria Lian Tao Junfeng Wang Song Wang Tinggui Wang Zhongxiang Wang Qingwen Wu Xuefeng Wu Dong Xu Yanjun Xu Suijian Xue Yongquan Xue Zijian Zhang Zipei Zhu Hu Zou Congying Bao Fansheng Chen Houlei Chen Tianxiang Chen Wei Chen Yehai Chen Yifan Chen Chenzhou Cui Weiwei Cui Yanfeng Dai Dongwei Fan Ju Guan Dawei Han Dongjie Hou Haibo Hu Maohai Huang Jia Huo Zhenqing Jia Bowen Jiang Ge Jin Chengkui Li Junfei Li Longhui Li Maoshun Li Wei Li Zhengda Li Tianying Lian Congzhan Liu Heyang Liu Huaqiu Liu Fangjun Lu Laidan Luo Jia Ma Xuan Mao Haiwu Pan Xin Pan Liming Song Hui Sun Yunyin Tan Qingjun Tang Yihan Tao Hao Wang Juan Wang Lei Wang Wenxin Wang Yilong Wang Yusa Wang Qinyu Wu Haitao Xu Jingjing Xu Xinpeng Xu Yunfei Xu Zhao Xu Changbin Xue Yulong Xue Ailiang Yan Haonan Yang Xiongtao Yang Yanji Yang Juan Zhang Mo Zhang Wenjie Zhang Zhen Zhang Zhen Zhang Ziliang Zhang Donghua Zhao Haisheng Zhao Xiaofan Zhao Zijian Zhao Hongyan Zhou Yilin Zhou Yuxuan Zhu Zhencai Zhu National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Sciences University of Chinese Academy of Sciences Key Laboratory of Particle Astrophysics institute of High Energy Physics Chinese Academy of Sciences institute of Space Sciences (ICE) CSIC Institut d’Estudis Espacials de Catalunya (IEEC) Max Planck institute for Extraterrestrial Physics Innovation Academy for Microsatellites Chinese Academy of Sciences Department of Physics University of Hong Kong School of Physics and Astronomy University of Leicester School of Physics and Astronomy Sun Yat-sen University Department of Physics Anhui Normal University Shanghai institute of Technical Physics Chinese Academy of Sciences Physics Department Tsinghua University Nevada Center for Astrophysics University of Nevada Las Vegas Department of Physics and Astronomy University of Nevada Las Vegas South African Astronomical Observatory Department of Astronomy University of Cape Town Department of Physics University of the Free State Université Paris Cité CNRS Astroparticule et Cosmologie Université Paris Cité CEA Paris-Saclay IRFU/DAp-AIM Department of Astronomy Guangzhou University Cosmic Dawn Center (DAWN) Niels Bohr institute University of Copenhagen Department of Physics and Astronomy Rutgers the State University of New Jersey institute for Cosmic Ray Research The University of Tokyo ESA/ESTEC Department of Astronomy School of Physics Huazhong University of Science and Technology INAF-Osservatorio Astrofisico di Torino Sydney institute for Astronomy School of Physics The University of Sydney Department of Astronomy Xiamen University institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Department of Astronomy University of Science and Technology School of Astronomy and Space Sciences University of Science and Technology of China institute of Deep Space Sciences Deep Space Exploration Laboratory Department of Astronomy School of Physics and Astronomy Yunnan University Shanghai Astronomical Observatory Chi

We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe （EP） and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength *** new transient was first detected with Wide-field X-ray Telescope （WXT） on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for *** flare reached a peak flux of 3.9×10-9erg cm-2s-1in 0.5-4 ke V,～300 times brighter than the underlying X-ray emission detected throughout the *** and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new *** X-ray spectrum is non-thermal in 0.5-10 ke V,with a power-law photon index varying *** X-ray light curve shows a plateau lasting for ～4 d,followed by a steep decay till becoming undetectable ～10 d after the initial *** on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term *** counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these *** demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical *** nature of EP240408a thus remains an *** suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of～10 *** detection and follow-ups of more of such objects are essential for revealing their origin.

关键词： X-ray transients ${\bm~{Einstein~~Probe}}$

Holographic dark energy in non-conserved gravity theory

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Communications in Theoretical Physics 2024年第4期76卷 126-133页

作者： H R Fazlollahi institute of Gravitation and cosmology Peoples Friendship University of Russia(RUDN University)6 Miklukho-Maklaya StMoscow117198Russia

Recently, reconsidering the Rastall idea T_(μ;νν)^(v)=α_(,μ) through relativistic thermodynamics gives a new form for the scalar field α which led us to construct modern modified theory of gravity debugged ‘non-conserved gravity theory’ Fazlollahi 2023 Euro. Phys. J. C 83 923. This theory unlike other modified theories of gravity cannot directly explain the current acceleration expansion in the absence of the cosmological constant and or existence of other forms of dark energy. Hence, in this study we have reinvestigated holographic dark energy Ρ_(X)~H^(2) in the non-conserved theory of gravity. In this context, the density and pressure of dark energy depend on the non-conserved term and density of the dust matter field. As shown, due to non-conservation effects on large-scale structures, unlike the original holographic model, our model onsets an acceleration epoch for the current Universe satisfies observations. Moreover, the interaction and viscous scenarios are studied for this model.

关键词： non-conserved gravity covariant form of thermodynamics holographic dark energy

Gravitational Equivalence Theorem and Double-Copy for Kaluza-Klein Graviton Scattering Amplitudes

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Research 2022年第4期2022卷 411-420页

作者： Yan-Feng Hang Hong-Jian He Tsung-Dao Lee institute and School of Physics and Astronomy Key Laboratory for Particle Astrophysics and Cosmology(MOE)Shanghai Key Laboratory for Particle Physics and CosmologyShanghai Jiao Tong UniversityShanghaiChina institute of Modern Physics and Department of Physics Tsinghua UniversityBeijingChina Center for High Energy Physics Peking UniversityBeijingChina

We analyze the structure of scattering amplitudes of the Kaluza-Klein (KK) gravitons and of the KK gravitational Goldstone bosons in the compactified 5d general relativity (GR). Using a general Rξ gauge fixing, we study the geometric Higgs mechanism for the massive spin-2 KK gravitons. We newly propose and prove a gravitational equivalence theorem (GRET) to connect the scattering amplitudes of longitudinal KK gravitons to that of the KK gravitational Goldstone bosons, which formulates the geometric gravitational Higgs mechanism at the scatteringS-matrix level. We demonstrate that the GRET provides a general energy cancellation mechanism guaranteeing the N-point longitudinal KK graviton scattering amplitudes to have their leading energy dependence cancelled down by a large power factor of E^(2N)(N≥4) up to any loop level. We propose an improved double-copy approach to construct the massive KK graviton (Goldstone) amplitudes from the KK gauge boson (Goldstone) amplitudes. With these, we establish a new correspondence between the two types of energy cancellations in the four-point longitudinal KK amplitudes at tree level: E^(4)→E0 in the KK gauge theory and E^(10)→E^(2) in the KK GR theory.

关键词： theory gauge guarantee

Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at Large Liquid Scintillator Detectors

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Chinese Physics Letters 2021年第11期38卷 18-22页

作者： Ziping Ye Feiyang Zhang Donglian Xu Jianglai Liu Tsung-Dao Lee institute Shanghai 200240China INPAC and School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Laboratory for Particle Physics and cosmology Key Laboratory for Particle Physics and Cosmology(MOE)Shanghai 200240China

Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μ_(v) = 2.1 × 10^(-11)μ_(B).However, tritium backgrounds or solar axion interaction in this energy window are equally plausible *** multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton·year exposure of liquid scintillator to solar neutrinos, a sensitivity of μ_(v) < 10^(-11)μ_(B) can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.

关键词： Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at Large Liquid Scintillator Detectors