Schwarzschild-like Wormholes in Asymptotically Safe Gravity

In this paper, we analyze the Schwarzschild-like wormhole in the Asymptotically Safe Gravity(ASG) scenario. The ASG corrections are implemented via renormalization group methods, which, as consequence, provides a new tensor Xμν as a source to improved field equations, and promotes the Newton’s constant into a running coupling constant. In particular, we check whether the radial energy conditions are satisfied and compare with the results obtained from the usual theory. We show that only in the particular case of the wormhole being asymptotically flat(Schwarzschild Wormholes) that the radial energy conditions are satisfied at the throat, depending on the chosen values for its radius r0. In contrast, in the general Schwarzschild-like case, there is no possibility of the energy conditions being satisfied nearby the throat, as in the usual case. After that, we calculate the radial state parameter, ω(r), in r0, in order to verify what type of cosmologic matter is allowed at the wormhole throat, and we show that in both cases there is the possibility of the presence of exotic matter, phantom or quintessence-like matter. Finally, we give the ω(r) solutions for all regions of space. Interestingly, we find that Schwarzschild-like Wormholes with excess of solid angle of the sphere in the asymptotic limit have the possibility of having non-exotic matter as source for certain values of the radial coordinate r. Furthermore, it was observed that quantum gravity corrections due the ASG necessarily imply regions with phantom-like matter, both for Schwarzschild and for Schwarzschild-like wormholes. This reinforces the supposition that a phantom fluid is always present for wormholes in this context.

Ellis–Bronnikov Wormholes in Asymptotically Safe Gravity

In this paper, we investigate the simplest wormhole solution—the Ellis–Bronnikov one—in the context of the asymptotically safe gravity (ASG) at the Planck scale. We work with three models, which employ the Ricci scalar, Kretschmann scalar, and squared Ricci tensor to improve the field equations by turning the Newton constant into a running coupling constant. For all the cases, we check the radial energy conditions of the wormhole solution and compare them with those that are valid in general relativity (GR). We verified that asymptotic safety guarantees that the Ellis–Bronnikov wormhole can satisfy the radial energy conditions at the throat radius, r0, within an interval of values of the latter, which is quite different from the result found in GR. Following this, we evaluate the effective radial state parameter, ω(r), at r0, showing that the quantum gravitational effects modify Einstein’s field equations in such a way that it is necessary to have a very exotic source of matter to generate the wormhole spacetime–phantom or quintessence-like matter. This occurs within some ranges of the throat radii, even though the energy conditions are or are not violated there. Finally, we find that, although at r0 we have a quintessence-like matter, upon growing r, we inevitably came across phantom-like regions. We speculate whether such a phantom fluid must always be present in wormholes in the ASG context or even in more general quantum gravity scenarios.

The Debye length and the running coupling of QCD: A potential and phenomenological approach

In this paper, one uses a damped potential to present a description of the running coupling constant of QCD in the confinement phase. Based on a phenomenological perspective for the Debye screening length, one compares the running coupling obtained here with both the Brodsky–de Téramond–Deur and the Richardson approaches. The results seem to indicate the model introduced here corroborate the Richardson approach. Moreover, the Debye screening mass in the confinement phase depends on a small parameter, which tends to vanish in the nonconfinement phase of QCD.

A new variational approach and its application toheavy quarkonia

By combining the variational principle with Heisenberg uncertaintyprinciple in an effective Hamiltonian for heavy flavored mesons, we in-troduce a framework to estimate masses and radii of these states froman analytical constraint. In a novel manner, a model for quark velocityand a model for quark momentum width are introduced. These kinemat-ical model parameters are obtained as analytical functions of inter quarkseparation in heavy quarkonia. The values of such quark parameters arethen used in the calculation of S-wave annihilation decay rates of \bar{c}c and\bar{b} b. To test the accuracy of our technique we first calculate the spin averaged masses, scalar radii and annihilation decay rates of charmoniumand bottomonium without and with relativistic corrections by solving theSchrödinger wave equation with the appropriate parametrization of the Song-Lin potential. The Schrödinger wave equation is solved numericallywith the matrix Numerov method and we observe a good agreement withthe experimental measurements and other theoretical calculations and extract strong running coupling constant for \bar{c}c and \bar{b}b systems. In non rel-ativistic settings, heavy meson spectra have been obtained and extended to rather higher excited states within our framework by using bare masses of c and b quarks which we have extracted from analysis of experimentaldata

Status of Measurement of R Value at BESIII

The R value is important for muon magnetic moment aµ and QED running coupling constant evaluated at Z pole, is useful to extract resonance parameters. BESIII experiment collected about 130 energy points between 2.0GeV and 4.6GeV for a precise measurement of R value. The status of R measurement at BESIII is reported in this paper.

Muon-electron scattering at next-to-leading order accuracy

The next-to-leading order electro-weak radiative corrections to the µ±e- → µ±e- process are reviewed and their relevance is discussed for the MUonE experiment, proposed at CERN. The aim of MUonE is the high precision measurement of the QED running coupling constant in the space-like region, from which the full hadronic contribution can be extracted and used to provide a new and independent determination of the leading-order hadronic correction to the muon g − 2. In this context, the required accuracy demands that radiative corrections are accounted for at the highest level of precision and implemented into a Monte Carlo event generator for data analysis. The first step towards the final goal of theoretical precision, which will require the full set of NNLO corrections and resummation of higher orders, is the inclusion of NLO electro-weak corrections.

Absolute Position and Energy

In this paper we will develop further the absolute position of a particle defined in (1), (2) which involves the particle's decay time or when relevant internal time and the particle's velocity with respect to the expanding universe. We will refine the previous definition to give two separate absolute position definitions, one termed the absolute position at rest and the other termed the absolute position which includes also a contribution of the particle's velocity with respect to the velocity of the expanding universe. Next we will discuss how we may define the particle's absolute energy from the particle's absolute position definition. We will show, how the absolute energy definition may help us to identify a dependence between the particle's decay time, as measured in its rest frame, and its velocity with respect to the expanding universe. Consequently, we will relate the above to the particle's mean lifetime and discuss the affect and relationship of the running coupling constant and the possible mean lifetime dependence on velocity. Finally, experimental ways by which one may investigate and test the above are presented.