Black Holes and Sub-millimeter Dimensions
ArXiv hep-th/9808138 (1998)
Abstract:
Recently, a new framework for solving the hierarchy problem was proposed which does not rely on low energy supersymmetry or technicolor. The fundamental Planck mass is at a TeV and the observed weakness of gravity at long distances is due the existence of new sub-millimeter spatial dimensions. In this letter, we study how the properties of black holes are altered in these theories. Small black holes---with Schwarzschild radii smaller than the size of the new spatial dimensions---are quite different. They are bigger, colder, and longer-lived than a usual $(3+1)$-dimensional black hole of the same mass. Furthermore, they primarily decay into harmless bulk graviton modes rather than standard-model degrees of freedom. We discuss the interplay of our scenario with the holographic principle. Our results also have implications for the bounds on the spectrum of primordial black holes (PBHs) derived from the photo-dissociation of primordial nucleosynthesis products, distortion of the diffuse gamma-ray spectrum, overclosure of the universe, gravitational lensing, as well as the phenomenology of black hole production. For example, the bound on the spectral index of the primordial spectrum of density perturbations is relaxed from 1.25 to 1.45-1.60 depending on the epoch of the PBH formation. In these scenarios PBHs provide interesting dark matter candidates; for 6 extra dimensions MACHO candidates with mass $\sim 0.1M_\odot$ can arise. For 2 or 3 extra dimensions PBHs with mass $\sim 2000 M_\odot$ can occur and may act as both dark matter and seeds for early galaxy and QSO formation.Implications of generalized Z-Z ' mixing
PHYS REV D 57:11 (1998) 6788-6792
Abstract:
We discuss experimental implications of extending the gauge structure of the standard model to include an additional U(1) interaction broken at or near the weak scale. We work with the most general, renormalizable Lagrangian for the SU(2)x U(1)x U(1) sector, with emphasis on the phenomenon of gauge kinetic mixing between the two U(1) gauge fields, and do not restrict ourselves to any of the "canonical" Z' models often discussed in the literature. Low-energy processes and Z(0)-pole precision measurements an specifically addressed.CP Violation, Higgs Couplings, and Supersymmetry
ArXiv hep-ph/9804355 (1998)
Abstract:
Supersymmetric extensions of the standard model generically contain additional sources of CP violation. We discuss how at one loop a potentially large CP violating coupling of the lightest Higgs, h^0, to leptons is induced in the minimal supersymmetric standard model (MSSM). The CP violating couplings of h^0 in extensions of the MSSM, such as the next-to-minimal supersymmetric standard model (NMSSM) are also considered. We indicate how this CP violation might be observed; in particular a polarization-dependent production asymmetry, in the context of a muon collider, provides a means to access this coupling cleanly. In the MSSM, existing limits on the electric dipole moment (EDM) of the electron, coupled with standard universality assumptions, severly constrains any such signal. Nevertheless, extensions of the MSSM, such as the NMSSM, allow CP-violating signals as large as 100%.Supersymmetric D-term Inflation, Reheating and Affleck-Dine Baryogenesis
ArXiv hep-ph/9802358 (1998)
Abstract:
The phenomenology of supersymmetric models of inflation, where the inflationary vacuum energy is dominated by D-terms of a U(1), is investigated. Particular attention is paid to the questions of how to arrange for sufficient e-folds of inflation to occur, what kind of thermal history is expected after the end of inflation, and how to implement successful baryogenesis. Such models are argued to require a more restrictive symmetry structure than previously thought. In particular, it is non-trivial that the decays of the fields driving D-inflation can reheat the universe in such a way as to avoid the strong gravitino production constraints. We also show how the initial conditions for Affleck-Dine baryogenesis can arise in these models and that the simplest flat directions along which baryon number is generated can often be ruled out by the constraints coming from decoherence of the condensate in a hot environment. At the end, we find that successful reheating and baryogenesis can take place in a large subset of D-inflationary models.Building models of gauge-mediated supersymmetry breaking without a messenger sector
NUCL PHYS B 509:1-2 (1998) 3-32