arXiv subjects

Gerhart Seidl

Publications and source records attributed to Gerhart Seidl.

23 records · Page 2Linked to original sources

arXiv2003

Casimir Energy in Deconstruction and the Cosmological Constant

We demonstrate that by employing the correspondence between gauge theories in geometric and in deconstructed extra dimensions, it is possible to transfer the methods for calculating finite Casimir energy densities in higher dimensions to the four-dimensional deconstruction setup. By this means, one obtains an unambiguous and well-defined prescription to determine finite vacuum energy contributions of four-dimensional quantum fields which have a higher-dimensional correspondence. Thereby, large kink masses lead to an exponentially suppressed Casimir effect. For a specific model we hence arrive at a small and positive contribution to the cosmological constant in agreement with observations.

hep-th↗

arXiv2003

Deconstruction and Bilarge Neutrino Mixing

We present a model for lepton masses and mixing angles using the deconstruction setup, based on a non-Abelian flavor symmetry which is a split extension of the Klein group. The symmetries enforce an approximately maximal atmospheric mixing angle theta_{23}, a nearly vanishing reactor mixing angle theta_{13}, and the hierarchy of charged lepton masses. The charged lepton mass spectrum emerges from the Froggatt-Nielsen mechanism interpreted in terms of deconstructed extra dimensions compactified on S^1. A normal neutrino mass hierarchy arises from the coupling to right-handed neutrinos propagating in latticized S^1/Z_2 orbifold extra dimensions. Here, the solar mass squared difference is suppressed by the size of the dynamically generated bulk manifold. Without tuning of parameters, the model yields the solar mixing angle theta_{12} = arctan 1/2^{1/2}. Thus, the obtained neutrino masses and mixing angles are all in agreement with the Mikheyev--Smirnov--Wolfenstein large mixing angle solution of the solar neutrino problem.

hep-ph↗

arXiv2002

A Flavor Symmetry Model for Bilarge Leptonic Mixing and the Lepton Masses

We present a model for leptonic mixing and the lepton masses based on flavor symmetries and higher-dimensional mass operators. The model predicts bilarge leptonic mixing (i.e., the mixing angles theta_{12} and theta_{23} are large and the mixing angle theta_{13} is small) and an inverted hierarchical neutrino mass spectrum. Furthermore, it approximately yields the experimental hierarchical mass spectrum of the charged leptons. The obtained values for the leptonic mixing parameters and the neutrino mass squared differences are all in agreement with atmospheric neutrino data, the Mikheyev--Smirnov--Wolfenstein large mixing angle solution of the solar neutrino problem, and consistent with the upper bound on the reactor mixing angle. Thus, we have a large, but not close to maximal, solar mixing angle theta_{12}, a nearly maximal atmospheric mixing angle theta_{23}, and a small reactor mixing angle theta_{13}. In addition, the model predicts theta_{12} ~= pi/4 - theta_{13}.

hep-ph↗

arXiv2002

Bilarge leptonic mixing from Abelian horizontal symmetries

We construct and present a model for leptonic mixing based on higher-dimensional operators, using the Froggatt-Nielsen mechanism, and Abelian horizontal symmetries (flavor symmetries) of continuous and discrete type. Our model naturally yields bilarge leptonic mixing, coming from both the charged leptons and the neutrinos, and an inverted neutrino mass hierarchy spectrum. The obtained values of the parameters, i.e., the leptonic mixing parameters and the neutrino mass squared differences, are all consistent with the atmospheric neutrino data and the Mikheyev-Smirnov-Wolfenstein large mixing angle solution for the solar neutrino problem.

hep-ph↗

arXiv2001

See-saw Mechanisms for Dirac and Majorana Neutrino Masses

We investigate the see-saw mechanism for generally non-fine-tuned $n \times n$ mass matrices involving both Dirac and Majorana neutrinos. We specifically show that the number of naturally light neutrinos cannot exceed half of the dimension of the considered mass matrix. Furthermore, we determine a criterion for mass matrix textures leading to light Dirac neutrinos with the see-saw mechanism. Especially, we study $4 \times 4$ and $6 \times 6$ mass matrix textures and give some examples in order to highlight these types of textures. Next, we present a model scheme based on non-Abelian and discrete symmetries fulfilling the above mentioned criterion for light Dirac neutrinos. Finally, we investigate the connection between symmetries and the invariants of a mass matrix on a formal level.

hep-ph↗