Modern Physics Letters A

This talk discusses the effective field theory view of deep inelastic scattering. In such an approach, the standard factorization formula of a hard coefficient multiplied by a parton distribution function arises from matching of QCD onto an effective field theory. The DGLAP equations can then be viewed as the standard renormalization group equations that determines the cutoff dependence of the nonlocal operator whose forward matrix element is the parton distribution function. As an example, the non-singlet quark splitting function is derived directly from the renormalization properties of the nonlocal operator itself. This approach, although discussed in the literature, does not appear to be well known to the larger high energy community. In this talk we give a pedagogical introduction to this subject.

This paper deals with the confinement mechanism of chiral fermions evolving in a five-dimensional spacetime, with S³ × R four-dimensional slices. To construct the proper Yukawa-type Lagrangian, we must solve the Gordon and Dirac-type equations in the bulk. An intriguing fact that emerges from our analysis is that only the left-handed fermions can be trapped on the brane. Characterizing the wave functions by the quantum number m_ℓ, it turns out that for m_ℓ = 3/2 and m_ℓ ∈ {0, ±1}, once the coupling constant increases, the left-handed modes become more and more dominant in the brane, away from the {z = 0}-singularity.

The AdS/CFT conjecture offers the possibility of a quantum description for a black hole in terms of a CFT. This has led to the study of general AdS₃ type black holes with a view to constructing an explicit toy quantum black hole model. Such a CFT description would be characterized by its central charge and the dimensions of its primary fields. Recently, the expression for the central charges (C_L, C_R) of the CFT dual to the warped AdS₃ have been determined using asymptotic symmetry arguments. The central charges depend, as expected, on the warping factor. We show that topological arguments, used by Witten to constrain central charges for the BTZ black hole, can be generalized to deal with the warped AdS₃ case. Topology constrains the warped factor to be rational numbers while quasi-normal modes are conjectured to give the dimensions of primary fields. We find that in the limit when warping is large or when it takes special rational values, the system tends to Witten's conjectured unique CFTs with central charges that are multiples of 24.

Based on a relativistic Thomas–Fermi model, it is shown that a two-parameter Fermi distribution can be used for describing the neutron density distribution in the ²⁰⁸Pb nucleus.

In the framework of constituent quark model, mass spectra of the ground-state baryons consisting of three or two heavy (b or c) and one light (u, d or s) quarks are calculated by solving three-body Faddeev equations. The results imply that, it is possible to obtain a unified model to describe heavy baryons spectra, as well as meson and SU(3) octet and decuplet baryon spectra. We find that, when taking into account the relativistic correction quark–diquark approximation and three-body Faddeev approach tend to give similar predictions for heavy–light systems. We also study the spin splitting of J^P = (1/2⁺) and J^P = (3/2⁺).

We review some interrelated aspects of thick braneworlds constructed within the framework of 5D gravity coupled to a scalar field depending on the extra dimension. It turns out that when analyzing localization of 4D gravity in this smooth version of the Randall–Sundrum model, a kind of dichotomy emerges. In the first case the geometry is completely smooth and the spectrum of the transverse traceless modes of the metric fluctuations shows a single massless bound state, corresponding to the 4D graviton, and a tower of massive states described by a continuous spectrum of Kaluza–Klein excitations starting from zero mass, indicating the lack of a mass gap. In the second case, there are two bound states, a massless 4D graviton and a massive excitation, separated by a mass gap from a continuous spectrum of massive modes; nevertheless, the presence of a mass gap in the graviton spectrum of the theory is responsible for a naked singularity at the boundaries (or spatial infinity) of the Riemannian manifold. However, the imposition of unitary boundary conditions, which is equivalent to eliminating the continuous spectrum of gravitational massive modes, renders these singularities harmless from the physical point of view, providing the viability of the model.

It is shown that in the high temperature limit, the QED and QCD effective actions differ only in the su(3)-Lie algebra valuation of the gauge fields.

In this paper we consider a class of inflation models on the brane where the dominant part of the inflaton scalar potential does not depend on the inflaton field value during inflation. In particular, we consider supernatural inflation, its hilltop version, A-term inflation, and supersymmetric (SUSY) D- and F-term hybrid inflation on the brane. We show that the parameter space can be broadened, the inflation scale generally can be lowered, and still possible to have the spectral index n_s = 0.96.