Modern Physics Letters A

Recently, we extracted the strong coupling, ${\alpha }_s(m_{\tau }^2)$, from the revised ALEPH data for non-strange hadronic tau decays. Our analysis is based on a method previously used for the determination of the strong coupling from OPAL data. In our strategy, we employ different moments of the spectral functions both with and without pinching, including duality violations, in order to obtain fully self-consistent analyses that do not rely on untested assumptions (such as the smallness of higher dimension contributions in the operation product expansion (OPE)). Here we discuss the ${\alpha }_s$ values obtained from the ALEPH and the OPAL data, the robustness of the analysis, as well as non-perturbative contributions from DVs and the OPE. We show that, although the ${\alpha }_s$ determination is sound, non-perturbative effects limit the accuracy with which one can extract the strong coupling from tau decay data. Finally, we discuss the compatibility of the data sets and the possibility of a combined analysis.

Recently reported diboson and diphoton excesses at LHC are interpreted to be connected with heavy WW zero spin resonances. The resonances appears due to the would-be anomalous triple interaction of the weak bosons, which is defined by well-known coupling constant $\lambda$. The 2 TeV anomaly, tentatively corresponds to weak isotopic spin-2 scalar state and the $\gamma \gamma$ 750 GeV anomaly corresponds to weak isotopic spin-0 pseudoscalar state. We obtain estimates for the effect, which qualitatively agree with ATLAS data. Effects are predicted in a production of W${}^{+}$ W${}^{-}$, (Z, $\gamma$)(Z, $\gamma$) via resonance $X_{\mathrm{\text{PS}}}$ with $M_{\mathrm{\text{PS}}}\simeq$ 750 GeV, which could be reliably checked at the upgraded LHC at $\sqrt{s}=$ 13 TeV. In the framework of an approach to the spontaneous generation of the triple anomalous interaction its coupling constant is estimated to be $\lambda =-0.02\pm 0.005$ in an agreement with existing restrictions. Specific predictions of the hypothesis are significant effects in decay channels $X_{\mathrm{\text{PS}}}\to \gamma l^{+}{l}^{-}$, $X_{\mathrm{\text{PS}}}\to l^{+}{l}^{-}{l}^{+}{l}^{-}(l=e,\mu )$.

We develop an alternative Ashtekar formalism in eight dimensions. In fact, using a MacDowell–Mansouri physical framework and a self-dual curvature symmetry, we propose an action in eight dimensions in which the Levi-Civita tenor with eight indices plays a key role. We explicitly show that such an action contains number of linear, quadratic and cubic terms in the Riemann tensor, Ricci tensor and scalar curvature. In particular, the linear term is reduced to the Einstein–Hilbert action with cosmological constant in eight dimensions. We prove that such a reduced action is equivalent to the Lovelock action in eight dimensions.

We propose a gravitational energy–momentum (GEMT) tensor of the general relativity obtained using Noether’s theorem. It transforms as a tensor under general coordinate transformations. One of the two indices of the GEMT labels a local Lorentz frame that satisfies the energy–momentum conservation law. The energies for a gravitational wave, a Schwarzschild black hole and a Friedmann–Lemaitre–Robertson–Walker (FLRW) universe are calculated as examples. The gravitational energy of the Schwarzschild black hole exists only outside the horizon, its value being the negative of the black hole mass.

ATLAS and CMS observe deviations from the expected background in the diphoton invariant mass searches of new resonances around 750 GeV. We show that a simple realization in terms of a new pseudoscalar state can accommodate the observations. The model leads to further footprints that can be soon observed. The new state can be interpreted both as an axion or as a highly natural composite state arising from minimal models of dynamical electroweak (EW) symmetry breaking. We further show how to disentangle the two scenarios. Beyond the possible explanation of the diphoton excess, the results show that it is possible to directly test and constrain composite dynamics via processes stemming from its distinctive topological sector.

The theory of special relativity derives from the Lorentz transformation. The Lorentz transformation implies differential simultaneity and light speed isotropy. Experiments to probe differential simultaneity should be able to distinguish the Lorentz transformation from a kinematically-similar alternate transformation that predicts absolute simultaneity, the absolute Lorentz transformation. Here, we describe how published optical tests of light speed isotropy/anisotropy cannot distinguish between the two transformations. We show that the shared equations of the two transformations, from the perspective of the “stationary” observer, are sufficient to predict null results in optical resonator experiments and in tests of frequency changes in one-way light paths. In an influential 1910 exposition on differential simultaneity, Comstock described how a “stationary” observer would observe different clock readings for spatially-separated “moving” clocks. The difference in clock readings is an integral aspect of differential simultaneity. We derive the equation for the difference in clock readings and show that it is equivalent to the Sagnac correction that describes light speed anisotropies in satellite communications. We describe an experimental strategy that can measure the differences in spatially-separated clock times to allow a direct probe of the nature of simultaneity.

The observation of gravitational waves from the Laser Interferometer Gravitational-Wave Observatory (LIGO) event GW150914 may be used to constrain the possibility of Lorentz violation in graviton propagation, and the observation by the Fermi Gamma-Ray Burst Monitor (GBM) of a transient source in apparent coincidence may be used to constrain the difference between the velocities of light and gravitational waves: $c_g-c_{\gamma }<10^{-17}$.