Triangle Seminars

Abstract:
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.

Abstract:
Within supersymmetric grand unified theories, cosmic strings are
generically formed at the end of a hybrid inflationary era.
However, cosmic microwave background measurements imply
severe constraints on the allowed cosmic strings contribution to the
temperature anisotropies.
In the framework of supersymmetry, I will study F- and D-term inflation
and I will set constraints on the free parameters (mass scales and
couplings) of the models, so that there is compatibility between
mixed models (inflation + cosmic strings) and current measurements.
Recently there is a revival in interest for cosmic strings, since ina
ddition,
superstrings could play the role of cosmic strings in theories with large
extra dimensions and moreover it may be that cosmic strings have been
already seen in the sky.

Abstract:
The IIB supersymmetry algebra in d=10 can be extended including 10-forms. One of these is the RR 10-form, which takes part in the tadpole cancellation mechanism of the type-I string. D9-branes are electrically charged with respect to this 10-form. IIB supergravity possesses a global
SL(2,R) symmetry, which the quantum theory breaks to SL(2,Z). Even if 10-forms have no dynamics, since their field-strength vanishes identically, it is possible to study their behaviour under SL(2,Z) transformations. We determine all the possible independent 10-forms as representations of
SL(2,Z), and in particular we show in which multiplet the RR 10-form lies. Finally, we perform the same analysis for the IIA supersymmetry algebra, and interpret the results in terms of T-duality.

Abstract:
I will start by introducing a scheme for quantum communication using an unmodulated and unmeasured spin chain. It presents an alternative to converting between static and flying qubits in order to connect up distinct quantum processors. I present some approaches to accomplish perfect quantum communication through a spin chain despite the dispersion of quantum information in the chain. I also discuss the accomplishment of gates between distant spins thorough a spin chain. Apart from transfer, a chain can also be used to simultaneously generate and distribute a maximally entangled state between distant sites, as I illustrate through a chain of coupled qutrits.