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New initial condition of the new agegraphic dark energy model

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Chinese Physics B 2013年第3期22卷 561-566页

作者：李云鹤张敬飞张鑫 Department of Physics College of SciencesNortheastern University

The initial condition Ωde（zini）=n^2（1＋zini）^-2/4 at zini = 2000,widely used to solve the differential equation of the density of the new agegraphic dark energy（NADE） Ωde,makes the NADE model a single-parameter dark-energy cosmological ***,we find that this initial condition is only applicable in a flat universe with only dark energy and pressureless *** fact,in order to obtain more information from current observational data,such as the cosmic microwave background（CMB） and the baryon acoustic oscillations（BAO）,we need to consider the contribution of *** this situation,the initial condition mentioned above becomes *** overcome this shortcoming,we investigate the evolutions of dark energy in matter-dominated and radiation-dominated epochs,and obtain a new initial condition de（zini）=n2（1＋zini）-2（1＋F（zini））2/4 at z ini = 2000,where F（z）≡Ωr0（1＋z）/[Ωm0＋Ωr0（1＋z）] with Ωr0 and Ωm0 being the current density parameters of radiation and pressureless matter,*** revised initial condition is applicable for the differential equation of Ωde obtained in the standard Friedmann-Robertson-Walker（FRW） universe with dark energy,pressureless matter,radiation,and even spatial curvature,and can still keep the NADE model as a single-parameter *** the revised initial condition and the observational data of type Ia supernova（SNIa）,CMB,and BAO,we finally constrain the NADE *** results show that the single free parameter n of the NADE model can be constrained tightly.

关键词： new agegraphic dark energy model initial condition single-parameter model observational constraints

Probing the sign-changeable interaction between dark energy and dark matter with current observations

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Science China(Physics,Mechanics & Astronomy) 2018年第3期61卷 1-9页

作者： Juan-Juan Guo Jing-Fei Zhang Yun-He Li Dong-Ze He Xin Zhang Department of Physics College of Sciences Northeastern University Center for High Energy Physics Peking University

We consider the models of vacuum energy interacting with cold dark matter in this study, in which the coupling can change sigh during the cosmological evolution. We parameterize the running coupling b by the form b（a） = boa ＋ be（1 - a）, where at the earlytime the coupling is given by a constant be and today the coupling is described by another constant bo. We explore six specific models with （i） Q = b（a）Hoρo, （ii） Q = b（a）Hoρde, （iii） Q = b（a）Hoρc, （iv） Q = b（a）Hρo, （v） Q = b（a）Hρde, and （vi） Q = b（a）Hρc. The current observational data sets we use to constrain the models include the JLA compilation of type Ia supernova data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements and the Hubble constant direct measurement. We find that, for all the models, we have b0 〈 0 and be 〉 0 at around the lolevel, and b0 and be are in extremely strong anti-correlation. Our results show that the coupling changes sign during the evolution at about the lolevel, i.e., the energy transfer is from dark matter to dark energy when dark matter dominates the universe and the energy transfer is from dark energy to dark matter when dark energy dominates the universe.

关键词： interacting dark energy sign-changeable interaction running coupling observational constraints

constraints on Dark Energy Models from Weak Gravity Conjecture

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Chinese Physics Letters 2008年第8期25卷 3086-3089页

作者：陈希明刘捷龚云贵 College of Mathematics and Physics Chongqing University of Posts and Telecommunications Chongqing 400065

We study the constraints on the dark energy model with constant equation of state parameter w = pip and the holographic dark energy model by using the weak gravity conjecture. The combination of weak gravity conjecture and the observational data gives tu 〈 -0.7 at the 3σ confidence level. The holographic dark energy model realized by a scalar field is in swampland.

关键词： COSMOLOGICAL CONSTANT observational constraints SUPERNOVA DATA IA SUPERNOVAE UNIVERSE REDSHIFT PROBE RECONSTRUCTION ACCELERATION QUINTESSENCE

Constraining the f(R,T)=R+2λT cosmological model using recent observational data

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Chinese Physics C 2023年第11期47卷 167-176页

作者： N.Myrzakulov M.Koussour Alnadhief H.A.Alfedeel E.I.Hassan L.N.Gumilyov Eurasian National University Astana 010008Kazakhstan Ratbay Myrzakulov Eurasian International Centre for Theoretical Physics Astana 010009Kazakhstan Quantum Physics and Magnetism Team LPMCFaculty of Science Ben M'sikCasablanca Hassan II UniversityMorocco Department of Mathematics and Statistics Imam Mohammad Ibn Saud Islamic University(IMSIU)Riyadh 13318Saudi Arabia Department of Physics Faculty of ScienceUniversity of KhartoumP.O.Box 321Khartoum 11115Sudan Centre for Space Research North-West UniversityPotchefstroom 2520South Africa

In this study,we conduct a comprehensive investigation of the cosmological model described by f(R,T)=R+2λT(whereλrepresents a free parameter)in light of the most recent observational *** constraining the model using the Hubble and Pantheon datasets,we determine its compatibility with the observed behavior of the *** this purpose,we adopt a parametric form for the effective equation of state(EoS)*** parametric form allows us to describe the evolution of the EoS parameter with respect to redshift and investigate its behavior during different cosmic *** analysis of the deceleration parameter reveals an accelerating Universe with a present value of q0=−0.64_(−0.03)^(+0.03),indicating the current phase of accelerated *** transition redshift is found to be ztr=0.53_(−0.03)^(+0.04),marking the epoch of transition from deceleration to *** also analyze the evolution of important cosmological parameters,including the density parameter,pressure,effective EoS,and *** findings collectively demonstrate the viability of the f(R,T)cosmological model as a robust candidate capable of engendering the requisite negative pressure,thereby efficiently propelling cosmic ***,the undertaken stability analysis underscores the model's stability within the broader cosmic *** providing the best-fit values for the coupling parameterλ,this approach motivates and encourages further exploration into the extensive landscape of this model and its potential applications across diverse realms of cosmology and astronomy.

关键词： f(R,T)gravity EoS parameter observational constraints dark energy

observational insights into the accelerating universe through reconstruction of the deceleration parameter

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中国物理C:英文版 2023年第8期47卷 184-194页

作者： Devaraja Mallesha Naik N.S.Kavya V.Venkatesha Department of P.G.Studies and Research in Mathematics Kuvempu UniversityShankaraghattaShivamogga 577451KarnatakaINDIA

Recent developments in the exploration of the universe suggest that it is in an accelerated phase of ***,our study aims to probe the current scenario of the universe with the aid of the reconstruction *** primary factor that describes cosmic evolution is the deceleration ***,we provide a physically plausible,newly defined model-independent parametric form of the deceleration ***,we constrain the free parameters through statistical MCMC analysis for different datasets,including the most recent Pantheon+.With the statistically obtained results,we analyze the dynamics of the model through the phase trans-ition,EoS parameter,and energy ***,we make use of the tool Om diagnostic to test our model.

关键词： deceleration parameter parametric reconstruction observational constraints accelerating universe Om diagnostics

Constraining Neutrino Mass in Dynamical Dark Energy Cosmologies with the Logarithm Parametrization and the Oscillating Parametrization

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Journal of High Energy Physics, Gravitation and Cosmology 2023年第4期9卷 1044-1061页

作者： Tian-Ying Yao Rui-Yun Guo Xin-Yue Zhao School of Sciences Xi’an Technological University Xi’an China

We constrain two dynamical dark energy models that are parametrized by the logarithm form of and the oscillating form of . Comparing with the Chevallier-Polarski-Linder (CPL) model, the two parametrizations for dark energy can explore the whole evolution history of the universe properly. Using the current mainstream observational data including the cosmic microwave background data and the baryon acoustic oscillation data as well as the type Ia supernovae data, we perform the X2 statistic analysis to global fit these models, finding that the logarithm parametrization and the oscillating parameterization are almost as well as the CPL scenario in fitting these data. We make a comparison for the impacts of the dynamical dark energy on the cosmological constraints on the total mass of active neutrinos. We find that the logarithm parametrization and the oscillating parameterization can increase the fitting values of Σmv. Looser constraints on Σmv are obtained in the logarithm and oscillating models than those derived in the CPL model. Consideration of the possible mass ordering of neutrinos reveals that the most stringent constraint on Σmv appears in the degenerate hierarchy case.

关键词： Dynamical Dark Energy Neutrino Mass observational constraints