463 research outputs found
Print Culture and Visual Interpretation in Eighteenth-Century German Editions of Thomson's The Seasons
S3 x Z2 model for neutrino mass matrices
We propose a model for lepton mass matrices based on the seesaw mechanism, a
complex scalar gauge singlet and a horizontal symmetry S_3 \times
\mathbbm{Z}_2. In a suitable weak basis, the charged-lepton mass matrix and
the neutrino Dirac mass matrix are diagonal, but the vacuum expectation value
of the scalar gauge singlet renders the Majorana mass matrix of the
right-handed neutrinos non-diagonal, thereby generating lepton mixing. When the
symmetry is not broken in the scalar potential, the effective
light-neutrino Majorana mass matrix enjoys -- interchange symmetry,
thus predicting maximal atmospheric neutrino mixing together with .
A partial and less predictive form of -- interchange symmetry is
obtained when the symmetry is softly broken in the scalar potential.
Enlarging the symmetry group S_3 \times \mathbbm{Z}_2 by an additional
discrete electron-number symmetry \mathbbm{Z}_2^{(e)}, a more predicitive
model is obtained, which is in practice indistinguishable from a previous one
based on the group .Comment: 13 pages, 3 figures, final version for publication in JHE
Derivative corrections to the Born-Infeld action through beta-function calculations in N=2 boundary superspace
We calculate the beta-functions for an open string sigma-model in the
presence of a U(1) background. Passing to N=2 boundary superspace, in which the
background is fully characterized by a scalar potential, significantly
facilitates the calculation. Performing the calculation through three loops
yields the equations of motion up to five derivatives on the fieldstrengths,
which upon integration gives the bosonic sector of the effective action for a
single D-brane in trivial bulk background fields through four derivatives and
to all orders in alpha'. Finally, the present calculation shows that demanding
ultra-violet finiteness of the non-linear sigma-model can be reformulated as
the requirement that the background is a deformed stable holomorphic U(1)
bundle.Comment: 25 pages, numerous figure
Harmonising Basel III and the Dodd Frank Act Through International Accounting Standards – Reasons Why International Accounting Standards Should Serve as 'Thermostats'
A model realizing the Harrison-Perkins-Scott lepton mixing matrix
We present a supersymmetric model in which the lepton mixing matrix
obeys, at the seesaw scale, the Harrison--Perkins--Scott
\textit{Ansatz}--vanishing , maximal atmospheric neutrino mixing, and
( is the solar mixing angle). The
model features a permutation symmetry among the three lepton multiplets
of each type--left-handed doublets, right-handed charged leptons, and
right-handed neutrinos--and among three Higgs doublets and three
zero-hypercharge scalar singlets; a fourth right-handed neutrino, a fourth
Higgs doublet, and a fourth scalar singlet are invariant under . In
addition, the model has seven \mathbbm{Z}_2 symmetries, out of which six do
not commute with . Supersymmetry is needed in order to eliminate some
quartic terms from the scalar potential, quartic terms which would make
impossible to obtain the required vacuum expectation values of the three Higgs
doublets and three scalar singlets. The Yukawa couplings to the charged leptons
are flavour diagonal, so that flavour-changing neutral Yukawa interactions only
arise at loop level.Comment: 16 pages, plain LaTeX, no figures; some clarifying remarks in the
conclusions and references added, version accepted for publication in JHE
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