Modern Physics Letters A

We review recent advances in the calculation of higher-order soft-gluon corrections for a variety of QCD, Higgs, and SUSY processes in hadron colliders. A unified approach and master formulas for next-to-next-to-leading order soft and virtual corrections are discussed. We present some applications of the formalism to top quark pair production at the Tevatron and the LHC, top production via anomalous couplings in flavor-changing neutral-current processes, W boson hadroproduction at large transverse momentum, and charged Higgs production at the LHC.

The (n + 1)-dimensional Milne universe with extra free directions is used to construct simple FRW cosmological string models in four dimensions, describing expansion in the presence of matter with p= κρ, κ = (4 - n)/3n. We then consider the n = 2 case and make SL(2, ℤ) orbifold identifications. The model is surprisingly related to the null orbifold with an extra reflection generator. The study of the string spectrum involves the theory of harmonic functions in the fundamental domain of SL(2, ℤ). In particular, from this theory one can deduce a bound for the energy gap and the fact that there are an infinite number of excitations with a finite degeneracy. We discuss the structure of wave functions and give examples of physical winding states becoming light near the singularity.

We analyze the electric dipole moment and the Higgs mass constraints on the supersymmetric model which offers dynamical solutions to the μ and strong CP problems. The trilinear coupling phases, and tan β-|μ| are strongly correlated, particularly in the low-tan β regime. Certain values of the phases of the trilinear couplings are forbidden, whereas the CP violating phase from the chargino sector is imprisoned to lie near a CP conserving point, by the Higgs mass and electric dipole moment constraints.

Recent observations of Type Ia supernovae provide evidence for the acceleration of our universe, which leads to the possibility that the universe is entering an inflationary epoch. We simulate it under a "big bounce" model, which contains a time variable cosmological "constant" that is derived from a higher dimension and manifests itself in 4D spacetime as dark energy. By properly choosing the two arbitrary functions contained in the model, we obtain a simple exact solution in which the evolution of the universe is divided into several stages. Before the big bounce, the universe contracts from a Λ-dominated vacuum, and after the bounce, the universe expands. In the early time after the bounce, the expansion of the universe is decelerating. In the late time after the bounce, dark energy (i.e. the variable cosmological "constant") overtakes dark matter and baryons, and the expansion enters an accelerating stage. When time tends to infinity, the contribution of dark energy tends to two thirds of the total energy density of the universe, qualitatively in agreement with observations.

We look at some dynamic geometries produced by scalar fields with both the "right" and the "wrong" signs of the kinetic energy. We start with anisotropic homogeneous universes with closed, open and flat spatial sections. A non-singular solution to the Einstein field equations representing an open anisotropic universe with the ghost field is found. This universe starts collapsing from t→-∞ and then expands to t→∞ without encountering singularities on its way. We further generalize these solutions to those describing inhomogeneous evolution of the ghost fields. Some interesting solutions with the plane symmetry are discussed. These have a property that the same line element solves the Einstein field equations in two mirror regions |t|≥z and |t|≤z, but in one region the solution has the right and in the other, the wrong sign of the kinetic energy. We argue, however, that a physical observer cannot reach the mirror region in a finite proper time. Self-similar collapse/expansion of these fields are also briefly discussed.

We carry out an analysis of the non-universal supersymmetry breaking scalar masses arising in SO(10) supersymmetric unification. By considering patterns of squark and slepton masses, we derive a set of sum rules for the sfermion masses which are independent of the manner in which SO(10) breaks to the Standard Model gauge group via its SU(5) subgroups. The phenomenology arising from such non-universality is unaffected by the symmetry breaking pattern, so long as the breaking occurs via any of the SU(5) subgroups of the SO(10) group.