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High-Energy Theory & Cosmology Seminar

Seminars are on Friday, from 12:15pm-1:30pm, in Stevenson 6333.

Monday Sept 17th at 2:00 PM
in room SC-6322
The speaker will be:

Jim Talbert, DESY Hamberg Germany

Title:  A Unified Delta(27) Model of Flavour

Abstract:  Non-Abelian discrete symmetries are frequently used to explain
observed patterns of neutrino mass and mixing.  However, they can also
be employed in unified constructions where the flavour structures of
both quarks and leptons are realized.  In this talk I will first
introduce the flavour problem/puzzle of the Standard Model, and then
briefly motivate the use of discrete symmetries to alleviate it,
before turning to a pedagogical discussion of their implementation in
effective theories. I will then present a simple model based on the
\Delta(27) finite group that is consistent with a stage of Grand
Unification and which implements a `universal texture zero' in the
mass matrices of all fermions, including heavy right-handed Majorana
neutrinos driving a Type-I see-saw mechanism.  The model, upon
considering the continuation of flavour observables to the UV,
realizes extremely successful predictions for the mass, mixing, and CP
violation of all Standard Model fermions.  In addition, the model is
free of discrete gauge anomalies, a feature that I will generically
address with 'simplified formulae' useful for achieving such anomaly
freedom in future model building.  To conclude, I will give some
thoughts on the progress and future of discrete models of flavor.

Friday 21 September 2018 at 12:15pm - 1:30pm. 
room SC-6322

Mahmoud Parvizi

Cosmological Observables via Non-equilibrium Quantum Dynamics in Non-stationary Spacetimes
In nearly all cases cosmological observables associated with quantum matter fields are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a hot, dense environment of quantum fields where far-from-equilibrium interactions manifest expressions for observables with leading terms at higher orders in the coupling. A more rigorous treatment of these cosmological observables may be carried out within the alternative framework of algebraic quantum field theory in curved spacetime, where the field theoretic model of quantum matter is compatible with the classical effects of general relativity. We take the first step towards computing such an observable. We employ the algebraic formalism while considering far-from-equilibrium interactions in a hot, dense environment under the influence of a classical, yet non-stationary, spacetime to derive an expression for the time-dependent energy density as a component of the renormalized stress-energy tensor.