Modern Physics Letters A

This Brief Review presents a new, analytic, gauge-invariant, non-perturbative and rigorous approach to the calculation of QCD phenomena. In this formulation a basic distinction between the conventional description of QCD and a more "realistic" description, taking into account that asymptotic quarks exist only in bound states, is brought into focus by the evaluation of the Schwinger solution for the QCD generating functional (GF) in terms of the exact Fradkin representations of the Green's functional G₀(x, y|A) and the vacuum functional L[A]. A new and simplifying output called "Effective Locality" appears, in which the interactions between quarks by the exchange of a "gluon bundle" (GB) (which "bundle" contains an infinite number of gluons, including cubic and quartic gluon interactions) display an exact locality property that reduces the several functional integrals of the formulation down to a set of ordinary integrals, susceptible to desktop-computer computation. As an example of the power of these methods we offer as a first pencil-and-paper calculation the quark–antiquark binding potential of a pion, and the corresponding three-quark binding potentials of a nucleon, obtained in a simple way from relevant eikonal scattering approximations. This example is followed by the estimation of a nucleon–nucleon binding potential to form a model deuteron, which may have relevance to the origin of the nuclear shell model and nuclear binding in general.

We propose Lagrangian formulation for the particle with value of spin fixed within the classical theory. The Lagrangian is invariant under non-Abelian group of local symmetries. On this reason, all the initial spin variables turn out to be unobservable quantities. As the gauge-invariant variables for description of spin we can take either the Frenkel tensor or the Bargmann–Michel–Telegdi (BMT) vector. Fixation of spin within the classical theory implies O(ℏ)-corrections to the corresponding equations of motion.

We investigate a spatially flat Friedmann–Robertson–Walker (FRW) universe where dark matter exchanges energy with a self-interacting holographic dark energy (SIHDE). Using the χ²-statistical method on the Hubble function, we obtain a critical redshift that seems to be consistent with both BAO and CMB data. We calculate the theoretical distance modulus for confronting with the observational data of SNe Ia for small redshift z ≤ 0.1 and large redshift 0.1 ≤ z ≤ 1.5. The model gets accelerated faster than the ΛCDM one and it can be a good candidate to alleviate the coincidence problem. We also examine the age crisis at high redshift associated with the old quasar APM 08279+5255.

We construct a class of closed time-like curves (CTCs) using a compactified extra dimension u. A nonzero metric element g_tu(u) enables particles to travel backwards in global time t. The compactified dimension guarantees that the geodesic curve closes in u. The effective 2D (t and u) nature of the metric ensures that spacetime is flat, therein satisfying all the classical stability conditions as expressed by the energy conditions. Finally, stationarity of the metric guarantees that a particle's energy is conserved. The pathologies that plague many hypothesized metrics admitting CTCs, e.g., an infinite cylinder of matter, a negative energy-distribution, particle acceleration/blue-shifting along the CTC, do not occur within our metric class.

This paper is the completion of an earlier work arXiv:1207.4867 which involves the derivation of oblique corrections in the MSSM at one-loop. In terms of the two-component spinor formalism, which is new in comparison with those used in the literature, the contributions arising from the fermion superpartners, i.e. neutralino-chargino sector to self-energy of Standard Model electroweak gauge bosons are calculated. Corresponding descendants the S, T and U parameters are presented. The validity of our results is examined in two ways, which are then followed by detailed analysis on the results in the literature.