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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]

Abstract We propose a novel reformulation of supersymmetric (more precisely μ -) hybrid inflation based on a local U(1) or any suitable extension of the minimal supersymmetric standard model (MSSM) which also resolves the μ problem. We employ a suitable Kahler potential which effectively yields quartic inflation with non-minimal coupling to gravity. Imposing the gravitino Big Bang Nucleosynthesis (BBN) constraint on the reheat temperature (T r ≲ 10 6 GeV) and requiring a neutralino LSP, the tensor to scalar ratio (r) has a lower bound r ≳ 0.004. The U(1) symmetry breaking scale lies between 108 and 1012 GeV. We also discuss a scenario with gravitino dark matter whose mass is a few GeV. [ABSTRACT FROM AUTHOR]

We consider μ -term hybrid inflation which, in its minimal format with gravity mediated supersymmetry breaking, leads to split supersymmetry. The MSSM μ -term in this framework is larger than the gravitino mass m G , and successful inflation requires m G (and hence also | μ | ) ≳ 5 × 10 7 GeV, such that the gravitino decays before the LSP neutralino freezes out. Assuming universal scalar masses of the same order as m G , this leads to split supersymmetry. The LSP wino with mass ≃ 2 TeV is a plausible dark matter candidate, the gluino may be accessible at the LHC, and the MSSM parameter tan ⁡ β ≃ 1.7 in order to be compatible with the measured Higgs boson mass. The tensor-to-scalar ratio r , a canonical measure of gravity waves, can be as high as 0.001. [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]

We explore the dark matter and LHC implications of t − b − τ quasi Yukawa unification in the framework of supersymmetric models based on the gauge symmetry G = SU ( 4 ) c × SU ( 2 ) L × SU ( 2 ) R . The deviation from exact Yukawa unification is quantified by a dimensionless parameter C ( | C | ≲ 0.2 ), such that the Yukawa couplings at M GUT are related by y t : y b : y τ = | 1 + C | : | 1 − C | : | 1 + 3 C | . In contrast to earlier studies which focused on universal gaugino masses, we consider non-universal gaugino masses at M GUT that are compatible with the gauge symmetry G . Our results reveal a variety of neutralino dark matter scenarios consistent with the observations. These include stau and chargino coannihilation scenarios, the A -resonance scenario, as well as Higgsino dark matter solutions which are more readily probed by direct detection searches. The gluino mass is found to be ≲ 4 TeV , the stop mass is ≳ 2 TeV , while the first two family squarks and sleptons are of order 4–5 TeV and 3 TeV respectively. [ABSTRACT FROM AUTHOR]

We present an inflationary model in which the Standard Model Higgs doublet field with non-minimal coupling to gravity drives inflation, and the effective Higgs potential is stabilized by new physics which includes a dark matter particle and right-handed neutrinos for the seesaw mechanism. All of the new particles are fermions, so that the Higgs doublet is the unique inflaton candidate. With central values for the masses of the top quark and the Higgs boson, the renormalization group improved Higgs potential is employed to yield the scalar spectral index n s ≃ 0.968 , the tensor-to-scalar ratio r ≃ 0.003 , and the running of the spectral index α = d n s / d ln ⁡ k ≃ − 5.2 × 10 − 4 for the number of e-folds N 0 = 60 ( n s ≃ 0.962 , r ≃ 0.004 , and α ≃ − 7.5 × 10 − 4 for N 0 = 50 ). The fairly low value of r ≃ 0.003 predicted in this class of models means that the ongoing space and land based experiments are not expected to observe gravity waves generated during inflation. [ABSTRACT FROM AUTHOR]

Motivated by the reported discovery of inflationary gravity waves by the Bicep2 experiment, we propose an inflationary scenario in supergravity, based on the standard superpotential used in hybrid inflation. The new model yields a tensor-to-scalar ratio r ≃ 0.14 and scalar spectral index n s ≃ 0.964 , corresponding to quadratic (chaotic) inflation. The important new ingredients are the high-scale, ( 1.6 – 10 ) ⋅ 10 13 GeV , soft supersymmetry breaking mass for the gauge singlet inflaton field and a shift symmetry imposed on the Kähler potential. The end of inflation is accompanied, as in the earlier hybrid inflation models, by the breaking of a gauge symmetry at ( 1.2 – 7.1 ) ⋅ 10 16 GeV , comparable to the grand-unification scale. [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 consider the low energy implications including particle spectroscopy of SO(10) inspired t-b-τ Yukawa coupling unification with , where μ is the coefficient of the bilinear Higgs mixing term of the minimal supersymmetric standard model (MSSM). We employ non-universal MSSM gaugino masses induced by SO(10) invariant dimension five operators, such that the total number of fundamental parameters is precisely the same as in Yukawa unified supersymmetric SO(10) models with universal gaugino masses and . We find that t-b-τ Yukawa unification with is compatible with the current experimental bounds, including the WMAP bound on neutralino dark matter and the measured value of the muon anomalous magnetic moment. We present a variety of benchmark points which include relatively light squarks () of the first two families and an example in which the bottom and top squarks are lighter than the gluino. This is quite distinct from Yukawa unification with and universal gaugino masses in which the gluino is the lightest colored sparticle and the squarks of the first two families have masses in the multi-TeV range. [Copyright &y& Elsevier]

Abstract: We identify models of supersymmetric hybrid inflation in which the tensor-to-scalar ratio, a canonical measure of gravity waves produced during inflation, can be as large as 0.03 or so, which will be tested by the Planck satellite experiment. The parameter space achieving this result is found to correspond to an intermediate-scale soft mass for the inflaton. The scalar spectral index lies within the WMAP one sigma bounds, while . [Copyright &y& Elsevier]

Abstract: Minimal supersymmetric hybrid inflation utilizes a canonical Kähler potential and a renormalizable superpotential which is uniquely determined by imposing a U(1) R-symmetry. In computing the scalar spectral index we take into account modifications of the tree level potential caused by radiative and supergravity corrections, as well as contributions from the soft supersymmetry breaking terms with a negative soft mass-squared term allowed for the inflaton. All of these contributions play a role in realizing values in the range 0.96–0.97 preferred by WMAP. The U(1) R-symmetry plays an important role in flipped by eliminating the troublesome dimension five proton decay. The proton decays into via dimension six operators arising from the exchange of superheavy gauge bosons with a lifetime of order years. [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]

Abstract: We employ chaotic ( and ) inflation to illustrate the important role radiative corrections can play during the inflationary phase. Yukawa interactions of ϕ, in particular, lead to corrections of the form , where and μ is a renormalization scale. For instance, chaotic inflation with radiative corrections looks compatible with the most recent WMAP (5 year) analysis, in sharp contrast to the tree level case. We obtain the 95% confidence limits , and , where and r respectively denote the scalar spectral index and scalar to tensor ratio. The limits for inflation are , and . The next round of precision experiments should provide a more stringent test of realistic chaotic and inflation. [Copyright &y& Elsevier]

Abstract: We construct a supersymmetric model in which a discrete symmetry (C-parity) implements strict left–right symmetry in the scalar (Higgs) sector. Although two electroweak bidoublets are introduced to accommodate the observed fermion masses and mixings, a natural missing partner mechanism insures that a single pair of MSSM Higgs doublets survives below the left–right symmetry breaking scale. If this scale happens to lie in the TeV range, several new particles potentially much lighter than the charged gauge bosons will be accessible at the LHC. [Copyright &y& Elsevier]

Abstract: We construct supersymmetric models with spontaneously broken left–right symmetry (C-parity). The minimal supersymmetric standard model (MSSM) can be recovered at low scales by exploiting the missing partner mechanism. The field content is compatible with realistic fermion masses and mixings, proton lifetime is close to or exceeds the current experimental bounds, and supersymmetric hybrid inflation can be implemented to take care of C-parity domain walls as well as magnetic monopoles, and to realize the observed baryon asymmetry via non-thermal leptogenesis. [Copyright &y& Elsevier]

Abstract: We introduce a flavor symmetry à la Froggat–Nielsen to explain the magnitude of the CKM mixing angles as well bilarge mixing in the neutrino sector. In the framework of GUTs we also estimate the magnitude of the third leptonic mixing angle . Estimates for rare leptonic decays such as are also provided. Finally, leptogenesis is exploited for estimating the magnitude of leptonic CP violation. [Copyright &y& Elsevier]

Abstract: We discuss hybrid inflation in supersymmetric flipped model such that the cosmic microwave anisotropy is essentially proportional to , where M denotes the symmetry breaking scale and () is the reduced Planck mass. The magnitude of M determined from measurements can be consistent with the value inferred from the evolution of and gauge couplings. In other words, one could state that flipped predicts (more precisely ‘postdicts’) . The scalar spectral index , the scalar to tensor ratio satisfies , while . [Copyright &y& Elsevier]

Abstract: We present a predictive scheme for fermion masses and mixings based on supersymmetric which provides an understanding of the observed hierarchies in the charged fermion sector including CKM mixings. In the neutrino sector bi-large mixing can be realized, while the third leptonic mixing angle . [Copyright &y& Elsevier]

Abstract: We explore a realistic supersymmetric model spontaneously broken at around . The presence of D- and F-flat directions gives rise to TeV mass doubly charged particles which can be found at the LHC. We implement TeV scale leptogenesis and employing both type I and II seesaw, the three light neutrinos are partially degenerate with masses in the 0.02–0.1 eV range. The effective mass parameter for neutrinoless double beta decay is 0.03–0.05 eV. We also find the interesting relation . [Copyright &y& Elsevier]

Abstract: It has been suggested that the dark energy density in the universe is associated with a metastable (false) vacuum, while the true vacuum has a vanishing cosmological constant. By including supergravity corrections we show how this is naturally realized in realistic supersymmetric hybrid inflation models. With a fundamental supersymmetry breaking scale , the LSP is not a suitable candidate for cold dark matter. We consider axion physics to overcome this and simultaneously provide a resolution of the MSSM μ problem. [Copyright &y& Elsevier]

Abstract: We implement inflation in a supersymmetric model with R-symmetry such that the cosmic microwave anisotropy is proportional to , where –, the breaking scale, and . The presence of a global symmetry, spontaneously broken also at scale , provides an upper bound on the masses of singlet right-handed neutrinos, which explains the mass scale associated with atmospheric neutrino oscillations. The monopoles and cosmic strings are inflated away. Although the doublet–triplet splitting requires fine-tuning, the MSSM μ problem is resolved and dimension five proton decay is strongly suppressed. [Copyright &y& Elsevier]

Within a democratic approach based on discrete symmetries, we show how the charged lepton mass hierarchies and bilarge neutrino mixings can be realized. For the third mixing angle we find θ13∼√ of Δmsol2/Δmatm2∼0.1–0.2. [Copyright &y& Elsevier]

We present a five-dimensional supersymmetric SO(10) model compactified on an orbifold S(1)/Z2×Z2′. The gauge symmetry G422≡SU(4)c×SU(2)L×SU(2)R, realized on one of the fixed points (branes), is spontaneously broken to the MSSM via the Higgs mechanism. Employing a flavor U(1) symmetry and suitably extending the ‘matter’ sector enables us to understand large mixings in the neutrino sector via a democratic approach, vs. the small CKM mixings. A residual R-symmetry on G422 brane helps eliminate the troublesome dimension five nucleon decay, while the U(1) symmetry plays an essential role in suppressing dimension six decay. For rare leptonic decays we expect BR(μ→eγ)∼BR(τ→μγ)∼BR(τ→eγ). [Copyright &y& Elsevier]

We discuss a five-dimensional inflationary scenario based on a supersymmetric SO(10) model compactified on S1/(Z2×Z2′). Inflation is implemented through scalar potentials on four-dimensional branes, and a brane-localized Einstein–Hilbert term is essential to make both brane vacuum energies positive during inflation. The orbifold boundary conditions break the SO(10) gauge symmetry to SU(4)c×SU(2)L×SU(2)R (≡H). The inflationary scenario yields δT/T∝(M/MPlanck)2, which fixes M, the symmetry breaking scale of H to be close to the SUSY GUT scale of 1016 GeV. The scalar spectral index n is 0.98–0.99, while the gravitational wave contribution to the quadrupole anisotropy is negligible (≲1%). The inflaton decay into the lightest right-handed neutrinos yields the observed baryon asymmetry via leptogenesis. [Copyright &y& Elsevier]

Working with a U(1) flavor symmetry, we show how the hierarchical structure in the charged fermion sector and a democratic approach for neutrinos that yields large solar and atmospheric neutrino mixings can be simultaneously realized in the MSSM framework. However, in SU(5) due to the unified multiplets we encounter difficulties. Namely, democracy for the neutrinos leads to a wrong hierarchical pattern for charged fermion masses and mixings. We discuss how this is overcome in flipped SU(5). [Copyright &y& Elsevier]

We consider neutrino oscillations and neutrinoless double beta decay in a five-dimensional standard model with warped geometry. Although the see-saw mechanism in its simplest form cannot be implemented because of the warped geometry, the bulk standard model neutrinos can acquire the desired (Majorana) masses from dimension five interactions. We discuss how large mixings can arise, why the large mixing angle MSW solution for solar neutrinos is favored, and provide estimates for the mixing angle Ue3. Implications for neutrinoless double beta decay are also discussed. [Copyright &y& Elsevier]

We discuss a brane based inflationary scenario in which an initially non-supersymmetric configuration involving a D4 brane is dynamically transformed into a supersymmetric one in a background space–time geometry determined by a stack of D6 branes. Inflation is realized in the effective four-dimensional theory and ends after reaching a stable BPS configuration. The scalar spectral index turns out to be 0.98. Under some simplifying assumption the reheat temperature, Hubble constant and the string scale are estimated to be of order 108 GeV, 1012 GeV and 1016 GeV, respectively. [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]