Modern Physics Letters A

The basic ideas of k_t-factorization and CCFM parton evolution is discussed. The unintegrated gluon densities, obtained from CCFM fits to the proton structure function data at HERA are used to predict hadronic final state cross-sections like jet production at HERA, but also comparisons with recent measurements of heavy quark production at the Tevatron are presented. Finally, the k_t-factorization approach is applied to Higgs production at high energy hadron–hadron colliders and the transverse momentum spectrum of Higgs production at the LHC is calculated.

Using Clifford algebraic methods we describe how to generalize Maxwell theory of Electrodynamics associated with ordinary point-charges to a generalized Maxwell theory in Clifford spaces involving extended charges and p-forms of arbitrary rank. Clifford algebras contain the appropriate algebraic-geometric features to implement the principle of polydimensional transformations (branes of different dimensionality are rotated into each other) that could possibly lead to a proper formulation of string and M theory.

We consider an anti de Sitter universe filled by quantum CFT with classical phantom matter and perfect fluid. The model represents the combination of a trace-anomaly annihilated and a phantom driven anti de Sitter universes. The influence exerted by the quantum effects and phantom matter on the AdS space is discussed. Different energy conditions in this type of universe are investigated and compared with those for the corresponding model in a de Sitter universe.

We calculate the linearized metric perturbations in the five-dimensional two-brane model of Randall and Sundrum. In a carefully chosen gauge, we write down and decouple Einstein equations for the perturbations and get the final and simple perturbative metric ansatz. This ansatz turns out to be equal to the linear expansion of the metric solution of Charmousis et al.¹ We show that this ansatz, the metric ansatz of Boos et al.² and the one of Das and Mitov³ are not incompatible, as it appears on the surface, but completely equivalent by an allowed gauge transformation that we give.

A massless spinor particle is considered in the background spacetimes generated by a moving mass current and by a spinning cosmic string. In the weak field approximation it is shown that the solution of the Weyl equations depends on the velocity of the source, which does not affect the curvature in this approximation in the case of a moving mass current. In the case of a spinning cosmic string, the solution of the Weyl equations depends on the deficit angle and on the angular momentum of the string. These effects may be viewed as examples of the gravitational analogues of the Aharonov–Bohm effect in electrodynamics.

The loop variable method that has been developed for the U(1) bosonic open string is generalized to include non-Abelian gauge invariance by incorporating "Chan–Paton" gauge group indices. The scale transformation symmetry k(s)→λ(s)k(s) that was responsible for gauge invariance in the U(1) case continues to be a symmetry. In addition there is a non-Abelian "rotation" symmetry. Both symmetries crucially involve the massive modes. However, it is plausible that only a linear combination, which is the usual Yang–Mills transformation on massless fields, has a smooth (worldsheet) continuum limit. We also illustrate how an infinite number of terms in the equation of motion in the cutoff theory add up to give a term that has a smooth continuum limit, and thus contributes to the low energy Yang–Mills equation of motion.

A generalization of the thermodynamic uncertainty relations is proposed. It is done by introducing an additional term proportional to the interior energy into the standard thermodynamic uncertainty relation that leads to existence of the lower limit of inverse temperature. In our opinion the approach proposed may lead to the proofs of these relations. To this end, the statistical mechanics deformation at Planck scale. The statistical mechanics deformation is constructed by analogy to the earlier quantum mechanical results. As previously, the primary object is a density matrix, but now the statistical one. The obtained deformed object is referred to as a statistical density pro-matrix. This object is explicitly described, and it is demonstrated that there is a complete analogy in the construction and properties of quantum mechanics and statistical density matrices at Planck scale (i.e. density pro-matrices). It is shown that an ordinary statistical density matrix occurs in the low-temperature limit at temperatures much lower than the Planck's. The associated deformation of a canonical Gibbs distribution is given explicitly.