International Journal of Modern Physics A

I describe the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tuneable) positive cosmological constant. It utilizes a single chiral multiplet with a gauged shift symmetry, that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms. We also study the question if this model can lead to inflation by identifying the dilaton with the inflaton. We find that this is possible if the Kähler potential is modified by a term that has the form of NS5-brane instantons, leading to an appropriate inflationary plateau around the maximum of the scalar potential, depending on two extra parameters.

In N=1 supergravity the tree-level scalar potential of the hidden sector may have a minimum with broken local supersymmetry (SUSY) as well as a supersymmetric Minkowski vacuum. These vacua can be degenerate, allowing for a consistent implementation of the multiple point principle. The first minimum where SUSY is broken can be identified with the physical phase in which we live. In the second supersymmetric phase, in flat Minkowski space, SUSY may be broken dynamically either in the observable or in the hidden sectors inducing a tiny vacuum energy density. We argue that the exact degeneracy of these phases may shed light on the smallness of the cosmological constant. Other possible phenomenological implications are also discussed. In particular, we point out that the presence of such degenerate vacua may lead to small values of the quartic Higgs coupling and its beta function at the Planck scale in the physical phase.

We show that calculation of a final fermion polarization (for a pure initial state) is equivalent to the problem of looking for complete polarization axis of bispinor. This gives the method for calculation of polarization applicable both for final and intermediate state fermions. We suggest to use fermion propagator (bare or dressed) in form of spectral representation, which gives the orthogonal off-shell energy projectors. This representation leads to covariant separation of particle and antiparticle contributions and gives a natural definition for polarization of intermediate state fermion. The most evident application is related with consistent description of t-quark polarization.

In this paper, we calculate the proton and neutron unpolarized and transversely polarized densities. We use the light-front wave function (LFWF), which at an initial scale is constrained by the soft-wall anti-de Sitter (AdS) QCD model, for calculating the Dirac and Pauli form factors which transverse densities are in terms of these form factors. Also, we use these form factors for calculating the flavor separated results for the proton and neutron electromagnetic form factors and calculate u and d quark unpolarized and transversely polarized densities. Finally, we compare our results with other previous parametrizations.

In this paper, we construct explicit analytical exact solutions to the six and higher-dimensional Einstein–Maxwell theory. In all solutions, a subspace of the metric is the Eguchi–Hanson space where the metric functions are completely determined in terms of known analytical functions. Moreover, we find the solutions can be extended from nonstationary exact solutions to Einstein–Maxwell theory with cosmological constant. We show that the solutions are asymptotically expanding patches of de Sitter space–time.

The Doplicher–Fredenhagen–Roberts (DFR) framework for noncommutative (NC) space–times is considered as an alternative approach to describe the physics of quantum gravity, for instance. In this formalism, the NC parameter, i.e. ${𝜃}^{\mu \nu }$, is promoted to a coordinate of a new extended space–time. Consequently, we have field theory in a space–time with spatial extra-dimensions. This new coordinate has a canonical momentum associated, where the effects of a new physics can emerge in the fields propagation along the extra-dimension. In this paper, we introduce the gauge invariance in the DFR NC space–time by the composite symmetry $U^{\star }(N)\times U^{\star }(N)$. We present the non-Abelian gauge symmetry in DFR formalism and the consequences of this symmetry in the presence of such extra-dimension. The gauge symmetry in this DFR scenario can reveal new gauge fields attached to $𝜃$-extra-dimension. As application, we construct a unification of Strong Interaction with the electromagnetism and a Higgs model to give masses to the NC bosons. We estimate their masses by using some experimental constraints of QCD.

The processes of dielectron production in deuteron–proton collisions at intermediate incident deuteron beam energies are analyzed in the spectator model within the one-pion exchange reggeized approach. We focus mainly on the momentum and angle distributions of the proton-spectator and the proton emitted in quasi-free NN processes at small angles in the laboratory frame. It is shown that the inclusion of many channels in quasi-free NN interaction allows us to describe the HADES data quite satisfactorily at incident deuteron kinetic energies of about 2.5 GeV.

We analyze the De Donder–Weyl covariant field equations for the topologically massive Yang–Mills theory. These equations are obtained through the Poisson–Gerstenhaber bracket described within the polysymplectic framework. Even though the Lagrangian defining the system of our interest is singular, we show that by appropriately choosing the polymomenta one may obtain an equivalent regular Lagrangian, thus avoiding the standard analysis of constraints. Further, our simple treatment allows us to only consider the privileged $(n-1)$-forms in order to obtain the correct field equations, in opposition to certain examples found in the literature.

We discuss dyonic black hole solutions in the case of f(R)-gravity coupled with a dilaton and two gauge bosons. The study of such a model is highly motivated from string theory. Our black hole solutions are extensions of the one firstly studied by Kallosh, Linde, Ortín, Peet and Van Proeyen (KLOPV) in arXiv:hep-th/9205027. We will show that extreme solutions are unstable. In particular, these solutions have Bousso–Hawking–Nojiri–Odintsov (anti)evaporation instabilities.

We discuss experimental signatures relevant for the LHC domain of energies allowing to discriminate possible asymptotic modes of hadron interactions.