Narrow Results

A program to compute the gluon self-energy diagram in class III nonrelativistic gauges has been constructed. It succeeded to show that axial gauges do not exhibit nonlocal counterterms. The high complexity of the calculations, the need to be able to control intermediate steps of calculations and the necessity to work inside a limited memory of a few Mbytes led us to give it special features which may serve outside the specific application for which it has been designed.

The structure of the program and its salient working features are described. It is divided into four modules, which are almost independent except that they are linked by their respective output. Files containing intermediate results of calculations are automatically generated. The amount of algebraic manipulations has been greatly reduced thanks to a careful choice of the representation of the expression adapted to each stage of the calculation. The adaptative character of this program is discussed as well as the generalization it needs to cover other types of Feynman diagram calculations.

The purpose of this study is to extend the concept of a generalized Lie 3-algebra, known to the divisional algebra of the octonions 𝕆, to split-octonions 𝕊𝕆, which is non-divisional. This is achieved through the unification of the product of both of the algebras in a single operation. Accordingly, a notational device is introduced to unify the product of both algebras. We verify that 𝕊𝕆 is a Malcev algebra and we recalculate known relations for the structure constants in terms of the introduced structure tensor. Finally we construct the manifestly supersymmetric affine superalgebra. An application of the split Lie 3-algebra for a Bagger and Lambert gauge theory is also discussed.

In this paper, the Maxwell extension of the special-affine algebra is obtained and corresponding nonlinear realization is constructed. We give also the differential realization of the generators of the extended symmetry. Moreover, we present the gauge theory of the Maxwell special-affine algebra and the topological gravity action in four dimensions. As a conclusion, we show that the Bianchi identities can be found by using the solution of the equations of motion.

Cosmological solutions for covariant canonical gauge theories of gravity are presented. The underlying covariant canonical transformation framework invokes a dynamical spacetime Hamiltonian consisting of the Einstein–Hilbert term plus a quadratic Riemann tensor invariant with a fundamental dimensionless coupling constant $g_1$. A typical time scale related to this constant, $\tau =\sqrt{8\pi G{g}_1}$, is characteristic for the type of cosmological solutions: for $t\ll \tau$, the quadratic term is dominant, the energy–momentum tensor of matter is not covariantly conserved, and we observe modified dynamics of matter and spacetime. On the other hand, for $t\gg \tau$, the Einstein term dominates and the solution converges to classical cosmology. This is analyzed for different types of matter and dark energy with a constant equation of state. While for a radiation-dominated universe solution, the cosmology does not change, we find for a dark energy universe the well-known de-Sitter space. However, we also identify a special bouncing solution (for $k=0$) which for large times approaches the de-Sitter space again. For a dust-dominated universe (with no pressure), deviations are seen only in the early epoch. In late epoch, the solution asymptotically behaves as the standard dust solution.

The group embeddings used in orbifolding the AdS/CFT correspondence to arrive at quiver gauge field theories are studied for both supersymmetric and nonsupersymmetric cases. For an orbifold AdS₅×S⁵/Γ the conditions for embeddings of the finite group Γ in the SU(4)~O(6) isotropy of S⁵ are stated in the form of consistency rules, both for Abelian and non-Abelian Γ.

The standard model of particle physics is generalized with a horizontal symmetry so that all its results are successfully reproduced without inducing any unphysical modes of existence. Two stage breakdowns of symmetries result in mass matrices of Majorana and Dirac types for fundamental fermions and predict rich physical modes of boson fields, some of which might be observed by the LHC experiment.

In this paper, a semi-simple and Maxwell extension of the (anti) de Sitter algebra is constructed. Then, a gauge-invariant model has been presented by gauging the Maxwell semi-simple extension of the (anti) de Sitter algebra. We firstly construct a Stelle–West-like model action for five-dimensional spacetime in which the effects of spontaneous symmetry breaking have been taken into account. In doing so, we get an extended version of Einstein’s field equations. Next, we decompose the five-dimensional extended Lie algebra and establish a MacDowell–Mansouri-like action that contains the Einstein–Hilbert term, the cosmological term as well as new terms coming from Maxwell extension in four-dimensional spacetime where the torsion-free condition is assumed. Finally, we have shown that both models are equivalent for an appropriately chosen gauge condition.

The generic form of space-time dynamics as a classical gauge field theory has recently been derived, based on only the action principle and on the principle of general relativity. It was thus shown that Einstein’s general relativity is the special case where (i) the Hilbert Lagrangian (essentially the Ricci scalar) is supposed to describe the dynamics of the “free” (uncoupled) gravitational field, and (ii) the energy–momentum tensor is that of scalar fields representing real or complex structureless (spin-$0$) particles. It followed that all other source fields — such as vector fields representing massive and nonmassive spin-$1$ particles — need careful scrutiny of the appropriate source tensor. This is the subject of our actual paper: we discuss in detail the coupling of the gravitational field with (i) a massive complex scalar field, (ii) a massive real vector field, and (iii) a massless vector field. We show that different couplings emerge for massive and nonmassive vector fields. The massive vector field has the canonical energy–momentum tensor as the appropriate source term — which embraces also the energy density furnished by the internal spin. In this case, the vector fields are shown to generate a torsion of space-time. In contrast, the system of a massless and charged vector field is associated with the metric (Hilbert) energy–momentum tensor due to its additional $\mathrm{\text{U}}(1)$ symmetry. Moreover, such vector fields do not generate a torsion of space-time. The respective sources of gravitation apply for all models of the dynamics of the “free” (uncoupled) gravitational field — which do not follow from the gauge formalism but must be specified based on separate physical reasoning.

In this paper we present the central ideas and results of a rigorous theory of the Chern–Simons functional integral. In particular, we show that it is possible to define the Wilson loop observables (WLOs) for pure Chern–Simons models with base manifold M = ℝ³ rigorously as infinite dimensional oscillatory integrals by exploiting an "axial gauge fixing" and applying certain regularization techniques like "loop-smearing" and "framing". The (values of the) WLOs can be computed explicitly. If the structure group G of the model is Abelian one obtains well-known linking number expressions for the WLOs. If G is Non-Abelian one obtains expressions which are similar but not identical to the state model representations for the Homfly and Kauffman polynomials given in [19, 21, 31].

The model for effective QCD Hamiltonian, describing bound states of “constituent” quark and antiquark, is proposed, using the Light Front (LF) formulation of QCD in the LF gauge. Zero mode of gluon field becomes independent canonical variable in this model unlike the known canonical formulations on the LF. This mode forms the “string” between quark and antiquark and bounds them. As quark and antiquark are separated by the “string”, the interaction term, related to the interaction of fermion currents in the Hamiltonian, gives zero due to locality of this interaction. We introduce the nonlocal modification of this term and investigate the resulting spectral equation for mass squared. This equation is solved analytically in the large quark mass limit. However the rotation invariance turns out to be violated with our choice of modified interaction term. We show the way to restore the invariance and discuss the possibility to obtain the spectrum describing the experimental one.

Gauge field theory of a horizontal symmetry of the group G_H = SU(2)_H × U(1) is developed so as to generalize the standard model of particle physics. All fermion and scalar fields are assumed to belong to doublets and singlets of the group in high energy regime. Mass matrices with four texture zeros of Dirac and Majorana types are systematically derived. In addition to seven scalar particles, the theory predicts existence of one peculiar vector particle which seems to play important roles in astrophysics and particle physics.