| 1. |
- Akhmedov, Evgeny, et al.
(författare)
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Stability and leptogenesis in the left-right symmetric seesaw mechanism
- 2007
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; 4, s. 022-1-022-25
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the left-right symmetric type I+II seesaw mechanism, where an eight-fold degeneracy among the mass matrices of heavy right-handed neutrinos M-R is known to exist. Using the stability property of the solutions and their ability to lead to successful baryogenesis via leptogenesis as additional criteria, we discriminate among these eight solutions and partially lift their eight-fold degeneracy. In particular, we find that viable leptogenesis is generically possible for four out of the eight solutions.
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| 2. |
- Garbrecht, Björn, et al.
(författare)
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Hybrid inflation exit through tunneling
- 2007
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; :1, s. 033-
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Tidskriftsartikel (refereegranskat)abstract
- For hybrid inflationary potentials, we derive the tunneling rate from field configurations along the flat direction towards the waterfall regime. This process competes with the classically rolling evolution of the scalar fields and needs to be strongly subdominant for phenomenologically viable models. Tunneling may exclude models with a mass scale below 10(12) GeV, but can be suppressed by small values of the coupling constants. We find that tunneling is negligible for those models, which do not require fine tuning in order to cancel radiative corrections, in particular for GUT-scale SUSY inflation. In contrast, electroweak scale hybrid inflation is not viable, unless the inflaton-waterfall field coupling is smaller than approximately 10(-11).
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| 3. |
- Hernandez, Andres, et al.
(författare)
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Effective action in a general chiral model : Next to leading order derivative expansion in the worldline method
- 2008
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213 .- 1873-1562. ; 793:3, s. 425-450
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Tidskriftsartikel (refereegranskat)abstract
- We present a formalism to determine the imaginary part of a general chiral model in the derivative expansion. Our formalism is based on the worldline path integral for the covariant current that can be given in an explicit chiral and gauge covariant form. The effective action is then obtained by integrating the covariant current, taking account of the anomaly.
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| 4. |
- Huber, S. J., et al.
(författare)
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Baryogenesis in the MSSM, nMSSM and NMSSM
- 2007
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 785:1-2, s. 206C-209C
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Huber, Stephan J., et al.
(författare)
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Electroweak phase transition and baryogenesis in the nMSSM
- 2006
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Ingår i: Nuclear Physics B. - : Elsevier BV. - 0550-3213 .- 1873-1562. ; 757:1-2, s. 172-196
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the nMSSM with CP violation in the singlet sector. We study the static and dynamical properties of the electroweak phase transition. We conclude that electroweak baryogenesis in this model is generic in the sense that if the present limits on the mass spectrum are applied, no severe additional tuning is required to obtain a strong first-order phase transition and to generate a sufficient baryon asymmetry. For this we determine the shape of the nucleating bubbles, including the profiles of CP-violating phases. The baryon asymmetry is calculated using the advanced transport theory to first and second order in gradient expansion presented recently. Still, first and second generation sfermions must be heavy to avoid large electric dipole moments.
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| 6. |
- Huber, Stephan J., et al.
(författare)
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Production of gravitational waves in the nMSSM
- 2008
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :5, s. 017-
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Tidskriftsartikel (refereegranskat)abstract
- During a strongly first-order phase transition gravitational waves are produced by bubble collisions and turbulent plasma motion. We analyze the relevant characteristics of the electroweak phase transition in the nMSSM to determine the generated gravitational wave signal. Additionally, we comment on correlations between the production of gravitational waves and baryogenesis. We conclude that the gravitational wave relic density in this model is generically too small to be detected in the near future by the LISA experiment. We also consider the case of a 'standard model' with dimension-six Higgs potential, which leads to a slightly stronger signal of gravitational waves.
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| 7. |
- Hällgren, Tomas, et al.
(författare)
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Triplet leptogenesis in left-right symmetric seesaw models
- 2008
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing / SISSA. - 1475-7516. ; 2008:01, s. 014-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss scalar triplet leptogenesis in a specific left-right symmetric seesaw model. We show that the Majorana phases that are present in the model can be effectively used to saturate the existing upper limit on the CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and analyze the viability of triplet leptogenesis. It is known for this kind of scenario that the efficiency of leptogenesis is maximal if there exists a hierarchy between the branching ratios of the triplet decays into leptons and Higgs particles. We show that triplet leptogenesis typically favors branching ratios with not too strong hierarchies, since maximal efficiency can only be obtained at the expense of suppressed CP-asymmetries.
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| 8. |
- Konstandin, Thomas
(författare)
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Electroweak baryogenesis in the nMSSM
- 2007
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Ingår i: SUSY06. - : AIP. - 9780735404106 ; , s. 689-692
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Konferensbidrag (refereegranskat)abstract
- In this talk, electroweak baryogenesis in the nMSSM is discussed following Ref [1]. We focus on differences compared to the MSSM. We conclude that electroweak baryogenesis in the nMSSM is rather generic. Still, sfermions of the first two generations are required to be heavy to evade constraints from electric dipole moments.
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| 9. |
- Konstandin, Thomas, et al.
(författare)
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Numerical approach to multi-dimensional phase transitions
- 2006
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :6, s. 021-
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Tidskriftsartikel (refereegranskat)abstract
- We present an algorithm for numerically analysing the bounce solution for first-order phase transitions. Our approach is well suited to treating phase transitions with several fields. The algorithm consists of two parts. In the first part the bounce solution without damping is determined; in this case energy is conserved. In the second part the continuation to the physically relevant case with damping is performed. The approach presented is numerically stable and easily implemented.
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| 10. |
- Konstandin, Thomas, et al.
(författare)
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The effective matter potential for highly relativistic neutrinos
- 2006
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Ingår i: Physics Letters B. - : Elsevier B.V.. - 0370-2693 .- 1873-2445. ; 634:03-feb, s. 267-271
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Tidskriftsartikel (refereegranskat)abstract
- We investigate matter effects on highly relativistic neutrinos. The self-energy of neutrinos is determined in an electron or neutrino background taking into account resonance and finite width effects of the gauge bosons. We find minor changes compared to the formerly used formula for the propagator function and large deviations of the effective width from the decay width of the gauge bosons considering higher moments of the electron or neutrino distribution function.
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