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We explore a variety of composite topological structures that arise from the spontaneous breaking of SO(10) to SU(3)c× U(1)em via one of its maximal subgroups SU(5) × U(1)χ, SU(4)c× SU(2)L× SU(2)R, and SU(5) × U(1)X (also known as flipped SU(5)). They include i) a network of ℤ strings which develop monopoles and turn into necklaces with the structure of ℤ2 strings, ii) dumbbells connecting two different types of monopoles, or monopoles and antimonpoles, iii) starfish-like configurations, iv) polypole configurations, and v) walls bounded by a necklace. We display these structures both before and after the electroweak breaking. The appearance of these composite structures in the early universe and their astrophysical implications including gravitational wave emission would depend on the symmetry breaking patterns and scales, and the nature of the associated phase transitions. [ABSTRACT FROM AUTHOR]

We consider non-supersymmetric GUT inflation models in which intermediate mass monopoles may survive inflation because of the restricted number of e-foldings experienced by the accompanying symmetry breaking. Thus, an observable flux of primordial magnetic monopoles, comparable to or a few orders below the Parker limit may be present in the galaxy. The mass scale associated with the intermediate symmetry breaking is 10 13 GeV for an observable flux level, with the corresponding monopoles an order of magnitude or so heavier. Examples based on SO ( 10 ) and E 6 yield such intermediate mass monopoles carrying respectively two and three units of Dirac magnetic charge. For GUT inflation driven by a gauge singlet scalar field with a Coleman–Weinberg or Higgs potential, compatibility with the Planck measurement of the scalar spectral index yields a Hubble constant (during horizon exit of cosmological scales) H ∼ 7 – 9 × 10 13 GeV , with the tensor to scalar ratio r predicted to be ≳0.02. Proton lifetime estimates for decays mediated by the superheavy gauge bosons are also provided. [ABSTRACT FROM AUTHOR]

Abstract: The minimal supersymmetric (or F-term) hybrid inflation is defined by a unique renormalizable superpotential, fixed by a R-symmetry, and it employs a canonical Kähler potential. The inflationary potential takes into account both radiative and supergravity corrections, as well as an important soft supersymmetry breaking term, with a mass coefficient in the range . The latter term assists in obtaining a scalar spectral index close to 0.96, as strongly suggested by the PLANCK and WMAP 9 yr measurements. The minimal model predicts that the tensor-to-scalar r is extremely tiny, of order , while the spectral index running, . If inflation is associated with the breaking of a local symmetry, the corresponding symmetry breaking scale M is with . This scenario is compatible with the bounds on M from cosmic strings, formed at the end of inflation from symmetry breaking. We briefly discuss non-thermal leptogenesis which is readily implemented in this class of models. [Copyright &y& Elsevier]

Abstract: We discuss the important role played during inflation by one of the soft supersymmetry breaking terms in the inflationary potential of supersymmetric hybrid inflation models. With minimal Kähler potential, the inclusion of this term allows the prediction for the scalar spectral index to agree with the value found by WMAP5. In the absence of this soft term, and by taking into account only radiative and supergravity corrections, it is well known that . This same soft term has previously been shown to play a key role in resolving the MSSM μ problem. The tensor to scalar ratio r is quite small in these models, taking on values in the WMAP5 2σ range of . [Copyright &y& Elsevier]

We describe the internal composition of a topologically stable monopole carrying a magnetic charge of 6 π / e that arises from the spontaneous breaking of the trinification symmetry S U (3) c × S U (3) L × S U (3) R (G). Since this monopole carries no color magnetic charge, a charge of 6 π / e is required by the Dirac quantization condition. The breaking of G to the Standard Model occurs in a number of steps and yields the desired topologically stable monopole ("magnetic baryon"), consisting of three confined monopoles. The confined monopoles ("magnetic quarks") each carry a combination of Coulomb magnetic flux and magnetic flux tubes, and therefore they do not exist as isolated states. We also display a more elaborate configuration ("fang necklace") composed of these magnetic quarks. In contrast to the S U (5) monopole which is superheavy and carries a magnetic charge of 2 π / e as well as color magnetic charge, the trinification monopole may have mass in the TeV range, in which case it may be accessible at the LHC and its planned upgrades. [ABSTRACT FROM AUTHOR]

We explore the low energy implications of an F-theory inspired E 6 model whose breaking yields, in addition to the MSSM gauge symmetry, a Z ′ gauge boson associated with a U ( 1 ) symmetry broken at the TeV scale. The zero mode spectrum of the effective low energy theory is derived from the decomposition of the 27 and 27 ‾ representations of E 6 and we parametrise their multiplicities in terms of a minimum number of flux parameters. We perform a two-loop renormalisation group analysis of the gauge and Yukawa couplings of the effective theory model and estimate lower bounds on the new vectorlike particles predicted in the model. We compute the third generation Yukawa couplings in an F-theory context assuming an E 8 point of enhancement and express our results in terms of the local flux densities associated with the gauge symmetry breaking. We find that their values are compatible with the ones computed by the renormalisation group equations, and we identify points in the parameter space of the flux densities where the t − b − τ Yukawa couplings unify. [ABSTRACT FROM AUTHOR]

Abstract: We explore the upper bound on the tensor-to-scalar ratio r in supersymmetric (F-term) hybrid inflation models with the gauge symmetry breaking scale set equal to the value , as dictated by the unification of the MSSM gauge couplings. We employ a unique renormalizable superpotential and a quasi-canonical Kähler potential, and the scalar spectral index is required to lie within the two-sigma interval from the central value found by the Planck satellite. In a sizable region of the parameter space the potential along the inflationary trajectory is a monotonically increasing function of the inflaton, and for this case, , while the spectral index running, , can be as large as 0.01. Ignoring higher order terms which ensure the boundedness of the potential for large values of the inflaton, the upper bound on r is significantly larger, of order 0.01, for subplanckian values of the inflaton, and . [Copyright &y& Elsevier]

We show that if global lepton number symmetry is spontaneously broken in a postinflation epoch, then it can lead to the formation of cosmological domain walls. This happens in the well-known "Majoron paradigm" for neutrino mass generation. We propose some realistic examples that allow spontaneous lepton number breaking to be safe from such domain walls. [ABSTRACT FROM AUTHOR]