Search

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 explore t-b-τ Yukawa unification (YU) in a supersymmetric SU(4)c× SU(2)L× SU(2)R model without imposing a discrete left-right (L-R) symmetry. A number of interesting solutions that are compatible with t-b-τ YU, LSP neutralino dark matter (DM), and LHC and other experimental constraints are identified. In particular, they include gluino-neutralino and stau-neutralino coannihilation scenarios, where the NLSP gluino mass can range from 1–3 TeV. Higgsino-like dark matter solutions are also identified for which gluino masses can approach 5 TeV or so. This scenario will be tested at LHC Run-3 and its future upgrades. [ABSTRACT FROM AUTHOR]

We employ a variety of symmetry breaking patterns in SO(10) and E6 Grand Unified Theories to demonstrate the appearance of topological defects including magnetic monopoles, strings, and necklaces. We show that independent of the symmetry breaking pattern, a topologically stable superheavy monopole carrying a single unit of Dirac charge as well as color magnetic charge is always present. Lighter intermediate mass topologically stable monopoles carrying two or three quanta of Dirac charge can appear in SO(10) and E6 models respectively. These lighter monopoles as well as topologically stable intermediate scale strings can survive an inflationary epoch. We also show the ap- pearance of a novel necklace configuration in SO(10) broken to the Standard Model via SU(4)c × SU(2)L × SU(2)R. It consists of SU(4)c and SU(2)R monopoles connected by flux tubes. Necklaces consisting of monopoles and antimonopoles joined together by flux tubes are also identified. Even in the absence of topologically stable strings, a monopole-string system can temporarily appear. This system decays by emitting gravity waves and we provide an example in which the spectrum of these waves is strongly peaked around 10−4 Hz with Ωqwh2 ≃10−12. This spectrum should be within the detection capability of LISA. [ABSTRACT FROM AUTHOR]

We explore proton decay in a class of realistic supersymmetric flipped SU(5) models supplemented by a U(1)R symmetry which plays an essential role in implementing hybrid inflation. Two distinct neutrino mass models, based on inverse seesaw and type I seesaw, are identified, with the latter arising from the breaking of U(1)R by nonrenormalizable superpotential terms. Depending on the neutrino mass model an appropriate set of intermediate scale color triplets from the Higgs superfields play a key role in proton decay channels that include p → (e+, μ+) π0, p → (e+, μ+) K0, p → v ¯ π + , and p → v ¯ K + . We identify regions of the parameter space that yield proton lifetime estimates which are testable at Hyper-Kamiokande and other next generation experiments. We discuss how gauge coupling unification in the presence of intermediate scale particles is realized, and a Z4 symmetry is utilized to show how such intermediate scales can arise in flipped SU(5). Finally, we compare our predictions for proton decay with previous work based on SU(5) and flipped SU(5). [ABSTRACT FROM AUTHOR]

We consider a class of SUSY models in which the MSSM gauge group is supplemented with a gauged U(1)B−L symmetry and a global U(1)R symmetry. This extension introduces only electrically neutral states, and the new SUSY partners effectively double the number of states in the neutralino sector that now includes a blino (from B − L) and singlino from a gauge singlet superfield. If the DM density is saturated by a LSP neutralino, the model yields quite a rich phenomenology depending on the DM composition. The LSP relic density constraint provides a lower bound on the stop and gluino masses of about 3 TeV and 4 TeV respectively, which is testable in the near future collider experiments such as HL-LHC. The chargino mass lies between 0.24 TeV and about 2.0 TeV, which can be tested based on the allowed decay channels. We also find m τ ˜ 1 ≳ 500 GeV, and m e ˜ , m μ ˜ , m v ˜ S , P ≳ 1 TeV. We identify chargino-neutralino coannihilation processes in the mass region 0.24 TeV ≲ m χ ˜ 1 0 ≈ m χ ˜ 1 ± ≲ 1.5 TeV, and also coannihilation processes involving stau, selectron, smuon and sneutrinos for masses around 1 TeV. In addition, A2 resonance solutions are found around 1 TeV, and H2 and H3 resonance solutions are also shown around 0.5 TeV and 1 TeV. Some of the A2 resonance solutions with tan β ≳ 20 may be tested by the A/H → τ+τ− LHC searches.. While the relic density constraint excludes the bino-like DM, it is still possible to realize higgsino, singlino and blino-like DM for various mass scales. We show that all these solutions will be tested in future direct detection experiments such as LUX-Zeplin and Xenon-nT. [ABSTRACT FROM AUTHOR]

We consider magnetic monopoles and strings that appear in non-supersymmetric SO(10) and E6 grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter Gμ spans the range 10−6− 10−30, where G is Newton’s constant and μ is the string tension. We show how intermediate scale monopoles with mass ∼ 1013− 1014 GeV and flux ≲ 2.8 × 10−16 cm−2s−1sr−1, and cosmic strings with Gμ ∼ 10−11− 10−10 survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio r lies between 0.06 and 0.003 depending on the details of the inflationary scenario. [ABSTRACT FROM AUTHOR]