199 research outputs found
Stringy Origin of Discrete R-symmetries
Discrete symmetries play a crucial role in particle physics. They appear
abundantly in string model constructions. We focus here on the case of discrete
-symmetries which are intrinsically connected to the Lorentz group in extra
dimensions and the appearance of -extended supersymmetry. In that sense,
discrete -symmetries can be understood as "fractionally" extended
supersymmetry. These symmetries reveal insight about the location of fields in
extra dimensions (in particular the Higgs boson). Applications can be found in
the solution of the -problem, suppression of proton decay and the
structure of the soft terms of broken supersymmetry.Comment: Proceedings of the Corfu Summer Institute 2016 "School and Workshops
on Elementary Particle Physics and Gravity",31 August - 23 September, 2016,
Corfu, Greec
Five golden rules for superstring phenomenology
Recent measurements of the values of gauge coupling constants as well as
neutrino properties support the idea of a grand unified (GUT) description of
particle physics at a large scale of GeV. We discuss a
strategy to incorporate this picture in the framework of superstring theory. In
such a scheme successful predictions of GUTs can be realized while some of the
more problematic aspects of grand unification might be avoided. The most
promising models are expected in the framework of the heterotic
string theory.Comment: Based on talks given at the conference on ``String Phenomenology
2004, Ann Arbor, and ``Pascos04-NathFest Symposium'', Boston, August 200
Anomalous U(1) gauge symmetries and heterotic-typeI/II string duality
Anomalous U(1) gauge symmetries can appear both in heterotic and type I
string theories. In the heterotic case we find a single anomalous U(1), while
in open string theories several such symmetries can appear. Nonetheless, there
is a conjectured duality symmetry that might connect these two theories. We
review the properties of anomalous gauge symmetries in various string theories
as well as the status of this heterotic-type I/II duality. We also comment on
the possible phenomenological applications of anomalous gauge symmetries in
string theory.Comment: 7 pages, Latex, JHEP, Contribution to the Proceedings of TMR99,
European Program Meeting on Quantum Aspects of Gauge Theories, Supersymmetry
and Unification, Paris, September 199
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