371 research outputs found
A note on the predictions of models with modular flavor symmetries
Models with modular flavor symmetries have been thought to be highly predictive. We point out that these predictions are subject to corrections from non–holomorphic terms in the Lagrangean. Specifically, in the models discussed in the literature, the Kähler potential is not fixed by the symmetries, for instance. The most general Kähler potential consistent with the symmetries of the model contains additional terms with additional parameters, which reduce the predictive power of these constructions. We also comment on potential ways of how one may conceivably retain the predictivity
Mirage Torsion
Z_NxZ_M orbifold models admit the introduction of a discrete torsion phase.
We find that models with discrete torsion have an alternative description in
terms of torsionless models. More specifically, discrete torsion can be 'gauged
away' by changing the shifts by lattice vectors. Similarly, a large class of
the so-called generalized discrete torsion phases can be traded for changing
the background fields (Wilson lines) by lattice vectors. We further observe
that certain models with generalized discrete torsion are equivalent to
torsionless models with the same gauge embedding but based on different
compactification lattices. We also present a method of classifying heterotic
Z_NxZ_M orbifolds.Comment: 26 pages, 3 figures, v2: matches version published in JHE
Violation from String Theory
We identify a natural way to embed symmetry and its violation
in string theory. The symmetry of the low energy effective
theory is broken by the presence of heavy string modes.
violation is the result of an interplay of and flavor symmetry.
violating decays of the heavy modes could originate a
cosmological matter-antimatter asymmetry.Comment: 7 pages, 4 figure
A note on discrete R symmetries in Z6-II orbifolds with Wilson lines
We re-derive the R symmetries for the Z6-II orbifold with non-trivial Wilson
lines and find expressions for the R charges which differ from those in the
literature.Comment: 13 pages, 3 figure
Anomaly-safe discrete groups
We show that there is a class of finite groups, the so-called perfect groups,
which cannot exhibit anomalies. This implies that all non-Abelian finite simple
groups are anomaly-free. On the other hand, non-perfect groups generically
suffer from anomalies. We present two different ways that allow one to
understand these statements.Comment: 11 page
Asymptotic symmetries on Kerr--Newman horizon without anomaly of diffeomorphism invariance
We analyze asymptotic symmetries on the Killing horizon of the
four-dimensional Kerr--Newman black hole. We first derive the asymptotic
Killing vectors on the Killing horizon, which describe the asymptotic
symmetries, and find that the general form of these asymptotic Killing vectors
is the universal one possessed by arbitrary Killing horizons. We then construct
the phase space associated with the asymptotic symmetries. It is shown that the
phase space of an extreme black hole either has the size comparable with a
non-extreme black hole, or is small enough to exclude degeneracy, depending on
whether or not the global structure of a Killing horizon particular to an
extreme black hole is respected. We also show that the central charge in the
Poisson brackets algebra of these asymptotic symmetries vanishes, which implies
that there is not an anomaly of diffeomorphism invariance. By taking into
account other results in the literature, we argue that the vanishing central
charge on a black hole horizon, in an effective theory, looks consistent with
the thermal feature of a black hole. We furthermore argue that the vanishing
central charge implies that there are infinitely many classical configurations
that are associated with the same macroscopic state, while these configurations
are distinguished physically.Comment: 14 pages, v2: references added, minor corrections, v3: new pars and
refs. added and corresponding correction
Singlet Extensions of the MSSM with Z(4)(R) Symmetry
We discuss singlet extensions of the MSSM with Z(4)(R) symmetry. We show that holomorphic zeros can avoid a potentially large coefficient of the term linear in the singlet. The emerging model has both an effective mu term and a supersymmetric mass term for the singlet mu(N) which are controlled by the gravitino mass. The mu term turns out to be suppressed against mu(N) by about one or two orders of magnitude. We argue that this class of models might provide us with a solution to the little hierarchy problem of the MSSM
Gauged Discrete Symmetries and Proton Stability
We discuss the results of a search for anomaly free Abelian Z_N discrete
symmetries that lead to automatic R-parity conservation and prevents dangerous
higher-dimensional proton decay operators in simple extensions of the minimal
supersymmetric extension of the standard model (MSSM) based on the left-right
symmetric group, the Pati-Salam group and SO(10). We require that the
superpotential for the models have enough structures to be able to give correct
symmetry breaking to MSSM and potentially realistic fermion masses. We find
viable models in each of the extensions and for all the cases, anomaly freedom
of the discrete symmetry restricts the number of generations.Comment: 8 pages, 2 figures; v2 : typos fixed, references adde
- …