Modern Physics Letters A

The high parton density regime of the quantum chromodynamics (QCD), where the physics of parton saturation is expected to be dominant, is briefly discussed. Some phenomenological aspects of saturation are described, mainly focusing on possible signatures of the nonlinear QCD dynamics in the heavy quark production in electron–proton/nucleus collisions. Implications of these effects in the heavy quark production in ultraperipheral heavy-ion collisions are also presented.

Superimposed D-branes have matrix-valued functions as their transverse coordinates, since the latter take values in the Lie algebra of the gauge group inside the stack of coincident branes. This leads to considering a classical dynamics where the multiplication law for coordinates and/or momenta, being given by matrix multiplication, is non-Abelian. Quantization further introduces noncommutativity as a deformation in powers of Planck's constant ℏ. Given an arbitrary simple Lie algebra and an arbitrary Poisson manifold ℳ, both finite-dimensional, we define a corresponding C⋆-algebra that can be regarded as a non-Abelian Poisson manifold. The latter provides a natural framework for a matrix-valued classical dynamics.

A study of the one-loop dilatation operator in the scalar sector of SYM is presented. The dilatation operator is analyzed from the point of view of Hamiltonian matrix models. A Lie algebra underlying operator mixing in the planar large-N limit is presented, and its role in understanding the integrability of the planar dilatation operator is emphasized. A classical limit of the dilatation operator is obtained by considering a contraction of this Lie algebra, leading to a new way of constructing classical limits for quantum spin chains. An infinite tower of local conserved charges is constructed in this classical limit purely within the context of the matrix model. The deformation of these charges and their relation to the charges of the spin chain is also elaborated upon.

A set of N three-component unit scalar fields in (3+1) Minkowski spacetime is investigated. The highly nonlinear coupling between them is chosen to omit the scaling instabilities. The multi-soliton static configurations with arbitrary Hopf numbers are found. Moreover, the generalized version of the Vakulenko–Kapitansky inequality is obtained. The possibility of attractive as well as repulsive interaction between hopfions is shown. A noninteracting limit is also discussed.

We demonstrate that an SU(2)_L×U(1)_Y model with the same particle content as Standard Model (SM) and discrete reflection symmetry between second and third generations of leptons gives rise to charged lepton and neutrino mass matrices which can accommodate the present solar, atmospheric, WMAP neutrino experimental results. The model predicts the value of |U₁₃| which could be tested in neutrino factories and the effective Majorana neutrino mass <m_ee> which is at the lower end of the present experimental value. Neutrino masses are generated through dim=5 operators and the scale of which are constrained by the value of <m_ee>. If, in future neutrinoless double beta decay experiments namely, MOON, EXO, GENIUS shift the lower bound on <m_ee> by one order, the present model will fail to accommodate the solar neutrino mixing angle due to LMA solution.

We analyze the Unruh effect from the point of view of quantum entanglement. We introduce the entangled state representation in Rindler space and show that the Minkowski vacuum state is an entangled state in Rindler space. The corresponding squeezing operator, which is related to the acceleration of the detector, is obtained naturally. The excitation representation and number state–phase state representations are also introduced in Rindler space. The number-phase commutative relation is established.