arXiv subjects

Jin-Jun Zhang

Publications and source records attributed to Jin-Jun Zhang.

3 recordsLinked to original sources

arXiv2018

Observational constraints on running vacuum model

We investigate the power spectra of the CMB temperature and matter density in the running vacuum model (RVM) with the time-dependent cosmological constant of $Λ= 3 νH^2 + Λ_0$, where $H$ is the Hubble parameter. In this model, dark energy decreases in time and decays to both matter and radiation. By using the Markov chain Monte Carlo method, we constrain the model parameter $ν$ as well as the cosmological observables. Explicitly, we obtain $ν\leq 1.54 \times 10^{-4}$ (68\% confidence level) in the RVM with the best-fit $χ^2_{\mathrm{RVM}} = 13968.8$, which is slightly smaller than $χ^2_{Λ\mathrm{CDM}} = 13969.8$ in the $Λ$CDM model of $ν=0$.

astro-ph.CO↗

arXiv2018

Cosmological constraints on $Λ(α)$CDM models with time-varying fine structure constant

We study the $Λ(α)$CDM models with $Λ(α)$ being a function of the time-varying fine structure constant $α$. We give a close look at the constraints on two specific $Λ(α)$CDM models with one and two model parameters, respectively, based on the cosmological observational measurements along with 313 data points for the time-varying $α$. We find that the model parameters are constrained to be around $10^{-4}$, which are similar to the results discussed previously but more accurately.

astro-ph.CO↗

arXiv2018

Flavor Violating Higgs Couplings in Minimal Flavor Violation

Motivated by the rencent LHC data on the lepton-flavor violating (LFV) decays $h\to \ell_1 \ell_2$ and $B_{s,d}\to \ell_1 \ell_2$, we study the Higgs-mediated flavor-changing neutral current (FCNC) interactions in the effective field theory (EFT) approach without and with the minimal flavor violation (MFV) hypothesis, and concentrate on the later. After considering the $B$ and $K$ physics data, the various LFV processes, and the LHC Higgs data, severe constraints on the Higgs FCNC couplings are derived, which are dominated by the LHC Higgs data, the $B_s - \bar B_s$ mixing, and the $μ\to e γ$ decay. In the general case and the MFV framework, allowed ranges of various observables are obtained, such as $\mathcal B (B_s\to \ell_1 \ell_2)$, $\mathcal B (h\to \ell_1 \ell_2)$, $\mathcal B (h\to q_1 q_2)$, and the branching ratio of $μ\to e$ conversion in Al. Future prospects of searching for the Higgs FCNC interactions at the low-energy experiments and the LHC are discussed.

hep-ph↗