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  • 1.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Blennow, Mattias
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hällgren, Tomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Stability and leptogenesis in the left-right symmetric seesaw mechanism2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 4, p. 022-1-022-25Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Garbrecht, Björn
    et al.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hybrid inflation exit through tunneling2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, p. 033-Article in journal (Refereed)
    Abstract [en]

    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).

  • 3. Hernandez, Andres
    et al.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Schmidt, Michael G.
    Effective action in a general chiral model: Next to leading order derivative expansion in the worldline method2008In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 793, no 3, p. 425-450Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Huber, S. J.
    et al.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Prokopec, T.
    Schmidt, M. G.
    Baryogenesis in the MSSM, nMSSM and NMSSM2007In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 785, no 1-2, p. 206C-209CArticle in journal (Refereed)
  • 5. Huber, Stephan J.
    et al.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Production of gravitational waves in the nMSSM2008In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 5, p. 017-Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Huber, Stephan J.
    et al.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Prokopec, Tomislav
    Schmidt, Michael G.
    Electroweak phase transition and baryogenesis in the nMSSM2006In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 757, no 1-2, p. 172-196Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Hällgren, Tomas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Triplet leptogenesis in left-right symmetric seesaw models2008In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, Vol. 2008, no 01, p. 014-Article in journal (Refereed)
    Abstract [en]

    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.

  • 8.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Electroweak baryogenesis in the nMSSM2007In: SUSY06: The 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions / [ed] Feng, JL, 2007, Vol. 903, p. 689-692Conference paper (Refereed)
    Abstract [en]

    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.

  • 9.
    Konstandin, Thomas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Huber, Stephan J.
    Numerical approach to multi-dimensional phase transitions2006In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 6, p. 021-Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Konstandin, Thomas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    The effective matter potential for highly relativistic neutrinos2006In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 634, no 03-feb, p. 267-271Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Blennow, MattiasKTH, School of Engineering Sciences (SCI), Theoretical Physics.Badelek, BarbaraEdsjö, JoakimHällgren, TomasKonstandin, ThomasPearce, MarkKTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    The 2nd Scandinavian NeutrinO Workshop2006Conference proceedings (editor) (Refereed)
    Abstract [en]

    The first Scandinavian NeutrinO Workshop (SNOW) was held in Uppsala, Sweden, in February 2001. About five years passed until the next SNOW took place—this time in Stockholm, Sweden between 2 May 2006 and 6 May 2006. The aim of the workshop was to cover a variety of topics in neutrino physics with leading researchers in the field as speakers. The Royal Swedish Academy of Sciences (KVA) awarded SNOW 2006 a grant for inviting such speakers. The workshop was mainly directed towards phenomenology and theory with connections to experiments and gave an opportunity for theorists and experimentalists to work together, discuss the latest results, and combine the different branches of neutrino physics. The different topics discussed were: solar and atmospheric neutrinos, reactor and accelerator neutrinos, neutrinos in astrophysics and cosmology, phenomenology of neutrino data, neutrino oscillations, theory and model building, fundamental properties of neutrinos, neutrinoless double beta decay, and flavor physics.

    Around 70 scientists (spanning from graduate students to world-leading researchers) in the field of neutrino physics participated in SNOW 2006 and 44 talks were presented in plenary sessions. Out of the 44 talks, 37 have been contributed to these proceedings.

    The talks of SNOW 2006 took place in the Oskar Klein Auditorium at the AlbaNova University Center in Stockholm. The AlbaNova University Center is a joint endeavour between the Royal Institute of Technology (KTH) and Stockholm University. The social program included a welcome reception at KVA, an excursion to the Royal Armoury at the Royal Palace in Stockholm as well as a boat trip in the archipelago of Stockholm, a reception at the City Hall of Stockholm arranged by the city, and finally, a workshop dinner at Häringe Castle south of Stockholm.

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