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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 study the low energy implications of a trinification model based on the gauge symmetry G = S U (3) c × S U (3) L × S U (3) R , without imposing gauge coupling unification. A minimal model requires two Higgs multiplets that reside in the bi-fundamental representation of G, and this is shown to be adequate for accommodating the Standard Model (SM) fermion masses and generate, via loop corrections and seesaw mechanism, suitable masses for the heavy neutral leptons as well as the observed SM neutrinos. We estimate a lower bound of around 15 TeV for the masses of the new down- type quarks that are required by the S U (3) L × S U (3) R symmetry. We examine the resonant production at the LHC of the new gauge bosons, which leads to a lower bound of 16 TeV for the symmetry breaking scale of G. We also show how the muon g - 2 anomaly can be resolved in the presence of these new gauge bosons and the heavy charged leptons present in the model. Finally, the model predicts the presence of a topologically stable monopole carrying three quanta (6 π / e) of Dirac magnetic charge and mass ≳ 160 TeV. If new matter fields lying in the fundamental representations of G are included, the model predicts the presence of exotic leptons, mesons and baryons carrying fractional electric charges such as ± e / 3 and ± 2 e / 3 , fully compatible with the Dirac quantization condition. [ABSTRACT FROM AUTHOR]

We explore the implications of resolving the muon g - 2 anomaly in a S U (4) c × S U (2) L × S U (2) R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 σ resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass m τ ~ ≲ 400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon g - 2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accommodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. Although a light stau can be compatible with the stability of the scalar potential, the Higgs boson mass constraint has a strong impact on the solutions with tan β bounded from above, namely tan β ≲ 20 . The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau–neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino–neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of 10 - 13 pb which hopefully, can be expected to be tested in the near future. [ABSTRACT FROM AUTHOR]

We discuss E 6 based extensions of the Standard Model (SM) containing two varieties of superheavy metastable cosmic strings (CSs) that respectively have neutral and electrically charged current carriers. We employ an extended version of the velocity-dependent one-scale (VOS) model, recently discussed by some authors, to estimate the gravitational wave (GW) spectrum emitted by metastable strings with a dimensionless string tension G μ ≈ 10 − 6 that carry a right-handed neutrino (RHN) current. We find that with a low to moderate amount of current, the spectrum is compatible with the LIGO O3 run and also consistent at the 1 σ level with the recent PTA signals. [ABSTRACT FROM AUTHOR]

We explore the gravitational wave spectrum generated by string-wall structures in an S O (10) (S p i n (10)) based scenario of pseudo-Goldstone boson dark matter (pGDM) particle. This dark matter candidate is a linear combination of the Standard Model (SM) singlets present in the 126 and 16 dimensional Higgs fields. The Higgs 126-plet vacuum expectation value (VEV) 〈 126 H 〉 leaves unbroken the Z 2 subgroup of Z 4 , the center of S O (10). Among other things, this yields topologically stable cosmic strings with a string tension μ ∼ 〈 126 H 〉 2. The subsequent (spontaneous) breaking of Z 2 at a significantly lower scale by the 16-plet VEV 〈 16 H 〉 leads to the appearance of domain walls bounded by the strings produced earlier. We display the gravitational wave spectrum for Gμ values varying between 10 − 15 and 10 − 9 (〈 126 H 〉 ∼ 10 11 - 1014 GeV), and 〈 16 H 〉 ∼ 0.1 - 102 TeV range (G denotes Newton's constant.) These predictions can be tested, as we show, by a variety of (proposed) experiments including LISA, ET, CE and others. [ABSTRACT FROM AUTHOR]

We consider a U (1) B - L model with a Z ′ portal Dirac fermion dark matter (DM) χ of low mass which couples very weakly to the B - L gauge boson Z ′ . An arbitrary B - L charge Q ≠ ± 1 , ± 3 of the DM χ ensures its stability. Motivated by the sensitivity reach of forthcoming "Lifetime Frontier" experiments, we focus on the Z ′ mass, m Z ′ , in the sub-GeV to few GeV range. To evaluate the DM relic abundance, we examine both the freeze-out and freeze-in DM scenarios. For the freeze-out scenario, we show that the observed DM abundance is reproduced near the Z ′ resonance, m χ ≃ m Z ′ / 2 , where m χ is the DM mass. For the freeze-in scenario, we focus on m χ ≪ m Z ′ . We show that for a fixed value of m Z ′ , g BL values roughly scale as 1/Q to reproduce the observed DM abundance. For various Q values in the range between 10 - 6 and 10 2 , we show that the gauge coupling values g BL needed to reproduce the observed DM abundance lie in the search reach of future planned and/or proposed experiments such as FASER, Belle-II, LDMX, and SHiP. In the freeze-in case, the Q values to realize observable g BL values are found to be much smaller than that in the freeze-out case. [ABSTRACT FROM AUTHOR]

Motivated by the recently reported measurement of the W boson mass M W = 80.4335 ± 0.0094 GeV by the CDF collaboration, we propose a type III seesaw extension of the minimal supersymmetric standard model (MSSM) which also includes an R-parity violating term. Without taking potential SUSY radiative corrections into account, we show that the CDF measurement of M W and the LEP measurement of the ρ parameter can be simultaneously accommodated at the 2 σ level. A long-lived gravitino in a few GeV mass range is a unique viable dark matter candidate in this framework. [ABSTRACT FROM AUTHOR]