119951520
On a difficulty in formulating relativistic partonlike equations
123307684
Hadronic regge sequences as primitive realizations of SL(3,R) symmetry☆
Abstract Four primitive infinite dimensional unitary representations of the group of rotations and deformations - SL(3,R) - are constructed and associated with the four Regge trajectories: π, ϱ, N, Δ. The model predicts E2 transition moments and a power law for E versus j consistent with the Chew-Frautschi relation E∼j 1 2 .
120403374
THREE-TRIPLET MODEL WITH DOUBLE SU(3) SYMMETRY
122507140
Diquark color excitation and the narrow resonances
The new narrow resonances are interpreted in the three-triplet model with integral baryon numbers as diquark color excitations of the qq +- q-barq-bar type. Hadronic decays, ..gamma.. transitions, and coupling to ..gamma.. occur through impurity qq-bar admixtures. Except for the coupling to ..gamma.., all decay rates are suppressed. The enhancements above 4 GeV in hadronic cross sections are attributed to qq-bar color octets or still higher diquark levels. (AIP)
121619492
A possible mechanism for CP nonconservation
120561444
Comment on the paper entitled «On the Poincaré noninvariance of a recent alternative to the Dirac equation»
119174283
Asymptotics of spinfoam amplitude on simplicial manifold: Lorentzian theory
This paper studies the large-j asymptotics of the Lorentzian Engle–Pereira–Rovelli–Livine (EPRL) spinfoam amplitude on a 4D simplicial complex with an arbitrary number of simplices. The asymptotics of the spinfoam amplitude is determined by the critical configurations. Here we show that, given a critical configuration in general, there exists a partition of the simplicial complex into three types of regions and , where the three regions are simplicial sub-complexes with boundaries. The critical configuration implies different types of geometries in different types of regions, i.e. (1) the critical configuration restricted to implies a nondegenerate discrete Lorentzian geometry, (2) the critical configuration restricted to is degenerate of type-A in our definition of degeneracy, but it implies a nondegenerate discrete Euclidean geometry in , (3) the critical configuration restricted to is degenerate of type-B, and it implies a vector geometry in . With the critical configuration, we further make a subdivision of the regions and into sub-complexes (with boundaries) according to their Lorentzian/Euclidean oriented 4-volume V4(v) of the 4-simplices, such that sgn(V4(v)) is a constant sign on each sub-complex. Then in each sub-complex or , the spinfoam amplitude at the critical configuration gives the Regge action in a Lorentzian signature or an Euclidean signature respectively. The Regge action reproduced here contains a sign prefactor sgn(V4(v)) related to the oriented 4-volume of the 4-simplices. Therefore the Regge action reproduced here can be viewed as a discretized Palatini action with an on-shell connection. Finally, the asymptotic formula of the spinfoam amplitude is given by a sum of the amplitudes evaluated at all possible critical configurations, which are the products of the amplitudes associated with different types of geometries.
119715337
Fundamental structure of loop quantum gravity
In the recent twenty years, loop quantum gravity, a background independent approach to unify general relativity and quantum mechanics, has been widely investigated. The aim of loop quantum gravity is to construct a mathematically rigorous, background independent, non-perturbative quantum theory for a Lorentzian gravitational field on a four-dimensional manifold. In the approach, the principles of quantum mechanics are combined with those of general relativity naturally. Such a combination provides us a picture of, so-called, quantum Riemannian geometry, which is discrete on the fundamental scale. Imposing the quantum constraints in analogy from the classical ones, the quantum dynamics of gravity is being studied as one of the most important issues in loop quantum gravity. On the other hand, the semi-classical analysis is being carried out to test the classical limit of the quantum theory. In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help ...
118178605
SL(2,C) Chern–Simons theory, a non-planar graph operator, and 4D quantum gravity with a cosmological constant: Semiclassical geometry
Abstract We study the expectation value of a nonplanar Wilson graph operator in SL ( 2 , C ) Chern–Simons theory on S 3 . In particular we analyze its asymptotic behavior in the double-scaling limit in which both the representation labels and the Chern–Simons coupling are taken to be large, but with fixed ratio. When the Wilson graph operator has a specific form, motivated by loop quantum gravity, the critical point equations obtained in this double-scaling limit describe a very specific class of flat connection on the graph complement manifold. We find that flat connections in this class are in correspondence with the geometries of constant curvature 4-simplices. The result is fully non-perturbative from the perspective of the reconstructed geometry. We also show that the asymptotic behavior of the amplitude contains, at the leading order, an oscillatory part proportional to the Regge action for the single 4-simplex in the presence of a cosmological constant. In particular, the cosmological term contains the full-fledged curved volume of the 4-simplex. Interestingly, the volume term stems from the asymptotics of the Chern–Simons action. This can be understood as arising from the relation between Chern–Simons theory on the boundary of a region, and a theory defined by an F 2 action in the bulk. Another peculiarity of our approach is that the sign of the curvature of the reconstructed geometry, and hence of the cosmological constant in the Regge action, is not fixed a priori, but rather emerges semiclassically and dynamically from the solution of the equations of motion. In other words, this work suggests a relation between 4-dimensional loop quantum gravity with a cosmological constant and SL ( 2 , C ) Chern–Simons theory in 3 dimensions with knotted graph defects.
119099110
Palatini formalism of 5-Dimensional Kaluza-Klein theory
The Einstein field equations can be derived in n dimensions (n > 2) by the variations of the Palatini action. The Killing reduction of 5dimensional Palatini action is studied on the assumption that pentads and Lorentz connections are preserved by the Killing vector field. A Palatini formalism of 4-dimensional action for gravity coupled to a vector field and a scalar field is obtained, which gives exactly the same fields equations in Kaluza-Klein theory.
118376309
Spin-foam fermions: PCT symmetry, Dirac determinant and correlation functions
We discuss fermion coupling in the framework of spin-foam quantum gravity. We analyze the gravity-fermion spin-foam model and its fermion correlation functions. We show that there is a spin-foam analogue of PCT symmetry for the fermion fields on a spin-foam model, which is proved for spin-foam fermion correlation functions. We compute the determinant of the Dirac operator for the fermions, where two presentations of the Dirac determinant are given in terms of diagram expansions. We compute the fermion correlation functions and show that they can be given by Feynman diagrams on the spin-foams, where the Feynman propagators can be represented by a discretized path integral of a world-line action along the edges of the underlying 2-complex.