264,721 research outputs found
An Abundance of Heterotic Vacua
We explicitly construct the largest dataset to date of heterotic vacua
arising from stable vector bundles on Calabi-Yau threefolds. Focusing on
elliptically fibered Calabi-Yau manifolds with spectral cover bundles, we show
that the number of heterotic models with non-zero number of generations is
finite. We classify these models according to the complex base of their
Calabi-Yau threefold and to the unification gauge group that they preserve in
four dimensions. This database of the order of models, which includes
potential Standard Model candidates, is subjected to some preliminary
statistical analyses. The additional constraint that there should be three net
generations of particles gives a dramatic reduction of the number of vacua.Comment: 27 pages, 12 figures, added reference
On dynamics of fermion generations
The hierarchy of fermion masses and EW symmetry breaking without elementary
Higgs is studied on the basis of strong gauge field distributions governing the
EW dynamics. The mechanism of symmetry breaking due to quark bilinears
condensation is generalized to the case, when higher field correlators are
present in the EW vacuum. Resulting wave functional yields several minima of
quark bilinears, giving masses of three (or more) generations. Mixing is
suggested to be due to kink solutions of the same wave functional. For a
special form of this mixing ("coherent mixing") a realistic hierarhy of masses
and of CKM coefficients is obtained and arguments in favor of the fourth
generation are given. Possible important role of topological charges for CP
violating phases and small masses of the first generation is stressed.Comment: 31 pages, typos corrected, references adde
On The Potential of Minimal Flavour Violation
Assuming the Minimal Flavour Violation hypothesis, we derive the general
scalar potential for fields whose background values are the Yukawa couplings.
We analyze the minimum of the potential and discuss the fine-tuning required to
dynamically generate the mass hierarchies and the mixings between different
quark generations. Two main cases are considered, corresponding to Yukawa
interactions being effective operators of dimension five or six (or,
equivalently, resulting from bi-fundamental and fundamental scalar fields,
respectively). At the renormalizable and classical level, no mixing is
naturally induced from dimension five Yukawa operators. On the contrary, from
dimension six Yukawa operators one mixing angle and a strong mass hierarchy
among the generations result.Comment: 33 pages, 6 figures; Note added in proof on the stability of the
minima of the scalar potential; results unchanged; references adde
N=1 supersymmetric SU(4)xSU(2)LxSU(2)R effective theory from the weakly coupled heterotic superstring
In the context of the free-fermionic formulation of the heterotic
superstring, we construct a three generation N=1 supersymmetric
SU(4)xSU(2)LxSU(2)R model supplemented by an SU(8) hidden gauge symmetry and
five Abelian factors. The symmetry breaking to the standard model is achieved
using vacuum expectation values of a Higgs pair in (4bar,2R)+(4,2R) at a high
scale. One linear combination of the Abelian symmetries is anomalous and is
broken by vacuum expectation values of singlet fields along the flat directions
of the superpotential. All consistent string vacua of the model are completely
classified by solving the corresponding system of F- and D-flatness equations
including non-renormalizable terms up to sixth order. The requirement of
existence of electroweak massless doublets further restricts the
phenomenologically viable vacua. The third generation fermions receive masses
from the tree-level superpotential. Further, a complete calculation of all
non-renormalizable fermion mass terms up to fifth order shows that in certain
string vacua the hierarchy of the fermion families is naturally obtained in the
model as the second and third generation fermions earn their mass from fourth
and fifth order terms. Along certain flat directions it is shown that the ratio
of the SU(4) breaking scale and the reduced Planck mass is equal to the up
quark ratio m_c/m_t at the string scale. An additional prediction of the model,
is the existence of a U(1) symmetry carried by the fields of the hidden sector,
ensuring thus the stability of the lightest hidden state. It is proposed that
the hidden states may account for the invisible matter of the universe.Comment: Latex2e file, 50 pages, uses rotating.st
Bimaximal mixing from the leptonic new texture for triangular mass matrices
An analysis of the leptonic texture for the new triangular mass matrices has
been carried out. In particular, it is shown that both bimaximal and nearly
bimaximal solutions for solar and atmospheric neutrino anomalies can be
generated within this pattern. We have also derived exact and compact
parametrization of the leptonic mixing matrix in terms of the lepton masses and
the parameters and . A consistency with the CHOOZ
reactor result for and a smallness of the Jarlskog's invariant
parameter are obtained.Comment: 16 pages, late
Preon Model and Family Replicated E_6 Unification
Previously we suggested a new preon model of composite quark-leptons and
bosons with the 'flipped' gauge symmetry group. We
assumed that preons are dyons having both hyper-electric and hyper-magnetic
charges, and these preons-dyons are confined by hyper-magnetic
strings which are an supersymmetric non-Abelian flux tubes created
by the condensation of spreons near the Planck scale. In the present paper we
show that the existence of the three types of strings with tensions
producing three (and only three) generations of composite
quark-leptons, also provides three generations of composite gauge bosons
('hyper-gluons') and, as a consequence, predicts the family replicated
unification at the scale GeV. This group of
unification has the possibility of breaking to the group of symmetry: which
undergoes the breakdown to the Standard Model at lower energies. Some
predictive advantages of the family replicated gauge groups of symmetry are
briefly discussed.Comment: This is a contribution to the Proc. of the Seventh International
Conference ''Symmetry in Nonlinear Mathematical Physics'' (June 24-30, 2007,
Kyiv, Ukraine), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA
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