Search

Here we study the possible improvements of the existing constraints on the upper bound of graviton mass by the analysis of the stellar orbits around the supermassive black hole (SMBH) at the Galactic Center (GC) in the framework of Yukawa gravity. Main motivation for this study is recent detection of Schwarzschild precession in the orbit of S2 star around the SMBH at the GC by the GRAVITY Collaboration in 2020. They indicated that the orbital precession of the S2 star is close to the General Relativity (GR) prediction, but with possible small deviation from it, and parametrized this effect by introducing an ad hoc factor in the parameterized post-Newtonian (PPN) equations of motion. Here we use the value of this factor presented by GRAVITY in order to perform two-body simulations of the stellar orbits in massive gravity using equations of motion in the modified PPN formalism, as well as to constrain the range of massive interaction $\Lambda$. From the obtained values of $\Lambda$, and assuming that it corresponds to the Compton wavelength of graviton, we then calculated new estimates for the upper bound of graviton mass which are found to be independent, but consistent with the LIGO's estimate of graviton mass from the first gravitational wave (GW) signal GW150914. We also performed Markov chain Monte Carlo (MCMC) simulations in order to constrain the bounds on graviton mass in the case of a small deviation of the stellar orbits from the corresponding GR predictions and showed that our method could further improve previous estimates for upper bounds on the graviton mass. It is also demonstrated that such analysis of the observed orbits of S-stars around the GC in the frame of the Yukawa gravity represents a tool for constraining the upper bound for the graviton mass, as well as for probing the predictions of GR or other gravity theories., Comment: 10 pages, 2 tables, 6 figures. Submitted to Chinese Physics C

In this paper we perform a detailed study of the masses and mixing of the single charmed scalar tetraquarks: $c q \bar{q} \bar{q}$. We also give a systematic analysis of these tetraquark states by weight diagrams, quantum numbers and flavor wave functions. Tetraquark masses are calculated using four different fits. The following SU(3)$_\mathrm{F}$ representations are discussed: $\bar{15}_\mathrm{S}$, $\bar{3}_\mathrm{S}$, $6_\mathrm{A}$ and $\bar{3}_\mathrm{A}$. We use the flavor-spin Glozman-Riska interaction Hamiltonian with SU(3) flavor symmetry breaking. There are 27 different tetraquarks composed of a charm quark $c$ and of the three light flavors $u, d, s$: 11 cryptoexotic (3 D$_\mathrm{s}^{+}$, 4 D$^{+}$, 4 D$^{0}$) and 16 explicit exotic states. We discuss D$_\mathrm{s}$ and its isospin partners in the same multiplet, as well as all the other four-quark states. Some explicit exotic states appear in the spectrum with the same masses as D$_\mathrm{s}^{+}$(2632) in $\bar{15}_\mathrm{S}$ and with the same masses as D$_\mathrm{s}^{+}$(2317) in $6_\mathrm{A}$ representation, which confirm the tetraquark nature of these states., Comment: 10 pages, 6 tables, 6 figures. Accepted for publication in Phys. Rev. D

We show that fundamental plane of elliptical galaxies can be used to obtain observational constraints on metric theories of gravity. Being it connected to global properties of ellipticals, it can fix parameters of modified gravity. Specifically, we use fundamental plane to constrain modified theories of gravity with Yukawa-like corrections which commonly emerge in the post-Newtonian limit. After giving examples on how these corrections are derived, we first analyze the velocity distribution of elliptical galaxies comparing theoretical results of modified gravity with Yukawa-like corrections with astronomical data. According to these results, it is possible to constrain the parameters of the corrections discriminating among classes of models compatible with astronomical observations. We conclude that fundamental plane can be used as a standard tool to probe different theories of gravity in the weak field limit., Comment: 13 pages, 7 figures, to be published in Phys. Dark. Univ. (2020)