International Journal of Modern Physics A

We review the recent developments in obtaining accelerating cosmologies and/or inflation from higher-dimensional gravitational theories, in particular superstring theories in ten dimensions and M-theory in 11 dimensions. We first discuss why it is difficult to obtain inflationary behavior in the effective low-energy theories of superstring/M-theory, i.e. supergravity theories. We then summarize interesting solutions including S-branes that give rise to accelerating cosmologies and inflationary solutions in M-theory with higher order corrections. Other approaches to inflation in the string context are also briefly discussed.

Systems of neutral interacting mesons are investigated, concerning in particular their description by an effective Hamiltonian, with a special emphasis on discrete symmetries. Several ambiguities are pointed out. First, the connection to quantum field theory, in which the physical masses and are the poles of the full renormalized propagator, shows that, for mass-split binary systems, two mass matrices rather than a single effective one are at work; they correspond to the two values and of the momentum squared. Transformation properties of the physical eigenstates by discrete symmetries may not reflect the ones of these two mass matrices (and those of the Lagrangian at any given p²). Then, after showing that a bi-orthogonal basis has to be used to diagonalize the complex mass matrix of such unstable systems, and not a bi-unitary transformation, we turn to the ambiguity linked to the commutation of the fields of the K⁰ and of its charge conjugate : any constant effective mass matrix is defined, in the basis, up to arbitrary diagonal antisymmetric terms; I use this freedom to deform it in various ways, in both the and (K_L,K_S) basis, and I study the consequences on the spectrum. CPT symmetry is specially concerned. An effective mass matrix can always be cast into a CPT invariant form, and only T violating eigenstates can never be cast into CP eigenstates. The dual formalism of |in> and <out| states and bi-orthogonal basis, suitable for nonnormal matrices, is used. In a subsequent work, the fundamental roles played by the normality of the mass matrix and CPT symmetry in the framework of quantum field theory will be investigated in connection with experimental results.

Unification ideas motivate the formulation of field equations on an extended matrix-spin space. Demanding that the Poincaré symmetry be maintained, one derives scalar symmetries that are associated with flavor and gauge groups. Boson and fermion solutions are obtained with a fixed representation. A field theory can be equivalently written and interpreted in terms of elements of such a space and is similarly constrained. At 5+1 dimensions, one obtains isospin and hypercharge SU(2)_L×U(1) symmetries, their vector carriers, two-flavor charged and chargeless leptons, and scalar particles. Mass terms produce breaking of the symmetry to an electromagnetic U(1), a Weinberg's angle with sin²(θ_W)=0.25, and additional information on the respective coupling constants. The particles' underlying spin symmetry gives information on their masses; one reproduces the Standard Model ratio M_Z/M_W, and predicts possible Higgs masses of M_H≈114 and M_H≈161 GeV, at tree level.

A systematic error in the extraction of sin²θ_W from nuclear deep inelastic scattering of neutrinos and antineutrinos arises from higher-twist effects arising from nuclear shadowing. We explain that these effects cause a correction to the results of the recently reported significant deviation from the Standard Model that is potentially as large as the deviation claimed, and of a sign that cannot be determined without an extremely careful study of the data set used to model the input parton distribution functions.

A string in four dimensions is constructed by supplementing it with 44 Majorana fermions. The later are represented by 11 vectors in the bosonic representation SO(D-1,1). The central charge is 26. The fermions are grouped in such a way that the resulting action is worldsheet supersymmetric. The energy–momentum and current generators satisfy the super-Virasoro algebra. GSO projections are necessary for proving modular invariance. Space–time supersymmetry algebra is deduced and is substantiated for specific modes of zero mass. The symmetry group of the model can descend to the low energy standard model group SU(3)×SU_L(2)×U_Y(1) through the Pati–Salam group.

An energy–momentum carried by electromagnetic field produced by two point-like charged particles is calculated. Integration region considered in the evaluation of the bound and emitted quantities produced by all points of world-lines up to the end points at which particles' trajectories puncture an observation hyperplane y⁰=t. Radiative part of the energy–momentum contains, apart from usual integrals of Larmor terms, also the sum of work done by Lorentz forces of point-like charges acting on one another. Therefore, the combination of wave motions (retarded Liénard–Wiechert solutions) leads to the interaction between the sources.

In the model III 2HDM there are new CP violating phases which would affect the mixing. In this paper, we calculate the new physics contributions to the neutral B meson mass splitting ΔM_Bq (q=d,s) at the next-to-leading order (NLO) level. Using the high accuracy data and other relevant data, we draw the constraints on the parameter space of the model III 2HDM. Moreover, we calculate the new physics corrections to the ratio q/p. It is found that the phase of (q/p)_n for B_d which is due to the new contributions is very small and consequently in agreement with the measurements of the time dependent CP asymmetry S_J/ψK in B→J/ψK_S. On the contrary, the phase of (q/p)_n for B_s is large enough to give significant effects on CP violation in the neutral B_s system.

We propose a spinorial approach to the unified electroweak interactions, in which no use is made of spontaneous symmetry breakdown. No scalar particles are needed in order to break the symmetry. No reference is made to gauge symmetry. Our approach stresses the role of space–time and isospin symmetries in the build up of the electroweak model. Internal degrees of freedom, such as isospin, are incorporated in the theory by using spinors carrying isospin indices. All vector bosons are described by a rank 2 field in the spinorial and the isospinorial indices. Leptons are accomodated in a rank 1 spinor field and in a rank 2 isospin field as well. The dynamical variables of the theory are the chiral and isochiral components of these fields.