International Journal of Modern Physics A

Some new results are presented and recent developments are reviewed on the study of Time in quantum physics as an observable, canonically conjugate to energy. Operators for the observable Time are investigated in particle and photon quantum theory. In particular, this paper deals with the Hermitian (more precisely, maximal Hermitian, but non-self-adjoint) operator for Time which appears: (i) for particles, in ordinary nonrelativistic quantum mechanics; and (ii) for photons (i.e. in first-quantization quantum electrodynamics). In conclusion, various recent and possible future applications of the time quantum analysis for tunnelling processes, nuclear collisions and systems with (quasi)discrete energy spectra are indicated.

The one-loop contribution to the superpotential, in particular the Veneziano–Yankielowicz potential in supersymmetric Yang–Mills model is discussed from an elementary field theory method and the matrix model point of view. Both approaches are based on the renormalization group variation of the superconformal supersymmetric Yang–Mills model.

We point out that the notion of an unparticle, recently introduced by Georgi, can be interpreted as a particular case of a field with continuously distributed mass considered in Phys. Lett. B325, 430 (1994). We also point out that the simplest renormalizable extension of the SU_c(3) ⊗ SU_L(2) ⊗ U(1) Standard Model is the extension with the replacement of the U(1) gauge propagator with .

Experimental studies on gold–gold collisions at RHIC at have produced a vast amount of data and results to be analyzed in the light of various competing models in the domain of multiparticle production scenario. We have chosen to analyze here the measured data on the p_T-spectra of various light and nonstrange secondaries and some of their very important ratio-behaviors at the various centralities of the collision in the light of a version of the sequential chain model. The agreements between measured data and theoretical plots are found to be modestly satisfactory.

Non-Abelian higher gauge theory has recently emerged as a generalization of standard gauge theory to higher-dimensional (two-dimensional in the present context) connection forms, and as such, it has been successfully applied to the non-Abelian generalizations of the Yang–Mills theory and 2-form electrodynamics. (2+1)-dimensional gravity, on the other hand, has been a fertile testing ground for many concepts related to classical and quantum gravity, and it is therefore only natural to investigate whether we can find an application of higher gauge theory in this latter context. In the present paper we investigate the possibility of applying the formalism of higher gauge theory to gravity in 2+1 dimensions, and we show that a nontrivial model of (2+1)-dimensional gravity coupled to scalar and tensorial matter fields — the ΣΦEA model — can be formulated as a higher gauge theory (as well as a standard gauge theory). Since the model has a very rich structure — it admits as solutions black-hole BTZ-like geometries, particle-like geometries as well as Robertson–Friedman–Walker cosmological-like expanding geometries — this opens a wide perspective for higher gauge theory to be tested and understood in a relevant gravitational context. Additionally, it offers the possibility of studying gravity in 2+1 dimensions coupled to matter in an entirely new framework.

Taking the self-gravitation interaction and unfixed background space–time into account, we study the Hawking radiation of Kerr–Newman–Kasuya black holes using Hamilton–Jacobi method. The result shows that the tunneling rate is related to the change of Bekenstein–Hawking entropy and the radiation spectrum deviates from the purely thermal one, which is accordant with that obtained using Parikh and Wilczek's method and gives a correction to the Hawking radiation of the black hole.

In this paper we review Klimčík's construction of noncommutative gauge theory on the fuzzy supersphere. This theory has an exact SUSY gauge symmetry with a finite number of degrees of freedom and thus in principle it is amenable to the methods of matrix models and Monte Carlo numerical simulations. We also write down in this paper a novel fuzzy supersymmetric scalar action on the fuzzy supersphere.

In this paper we suggest a new model of preons–dyons making composite quark–leptons and bosons, described by the supersymmetric string-inspired flipped gauge group of symmetry. This approach predicts the possible extension of the Standard Model to the family replicated gauge group model of type G^N_fam, where N_fam is the number of families and G is the symmetry group: G = SMG, SU(5), SO(10), E₆, etc. Here E₆ and are nondual and dual sectors of theory with hyperelectric g and hypermagnetic charges, respectively. Starting with an idea that the most realistic model leading to the unification of all fundamental interactions (including gravity) is the "heterotic" string-derived flipped model, we have assumed that at high energies μ > 10¹⁶GeV there exists the following chain of the flipped models:

The black hole entropy due to spin fields are calculated by using brick-wall model. The appearance of the logarithmic terms is demonstrated and we specially deal with the subleading logarithmic term which exists for any spin fields. It is shown that the subleading logarithmic term is related to the use of WKB approximation but it usually includes not only a quadratic term and a linear term of the spin but also a zero-power term of the spin.