Search Talks

Quantum decay of false vacuum states via the nucleation of bubbles may 
have played an important role in the early history of our Universe.  For 
example, in multiverse models that utilize false vacuum eternal 
inflation, the Big Bang of our observable Universe corresponds to one of 
these bubble nucleation events.  Further, our observable Universe may 
have undergone a series of symmetry-breaking first-order phase 
transitions as it cooled, which may have produced a remnant background 
of gravitational waves.

I will present results from a new real-time picture of false vacuum 
decay which, in contrast to existing semiclassical techniques, does not 
rely on classically forbidden tunneling paths.  Lattice simulations are 
used to evolve initial realizations of fluctuations around the false 
vacuum forward in time via the classical equations of motion.  In these 
simulations, we observe the false vacuum decay via the formation and 
subsequent expansion and coalescence of true vacuum bubbles.  By 
sampling initial field realizations, we build up ensembles of these 
decay histories and empirically determine the bubble nucleation rate.  
The rates agree well with standard Euclidean techniques, which cannot 
provide a time-dependent description of the decay.  Some novel 
applications of our new approach include investigation of bubble-bubble 
correlation functions, decay of time-evolving metastable states, decay 
of non-vacuum initial states, and the regime of rapid decays.

In this talk I will set out two new contributions to the study of operational tasks in a relativistic quantum setting. First, I will present a generalisation of the task known as ‘summoning,’ in which an unknown quantum state is supplied to an agent and must be returned at a specified point when a corresponding call is made. I will show that when this task is generalised to allow for more than one call to be made, an apparent paradox arises: the extra freedom makes it strictly harder to complete the task. Second, I will describe a quantum generalisation of the classic cryptographic task known as ‘zero-knowledge-proving.’ I will show that there exists no perfectly secure quantum relativistic protocol for this task, and I will then set out a protocol which is conjectured to be close to optimal in security for this task. These results have practical applications for distributed quantum computing and cryptography and also interesting implications for our understanding of relativistic quantum information and its localisation in spacetime.

The Heisenberg algebra plays an important role in many areas of mathematics and physics. Khovanov constructed a categorical analogue of this algebra which emphasizes its connections to representation theory and combinatorics. Recently, Brundan, Savage, and Webster have shown that the Grothendieck group of this category is isomorphic to the Heisenberg algebra. However, applying an alternative decategorification functor called the trace to the Heisenberg category yields a richer structure: a W-algebra, an infinite-dimensional Lie algebra related to conformal field theory. In this talk, we will describe recent work extending this latter result to a generalized version of the Heisenberg category associated to an arbitrary graded Frobenius algebra F. The decategorifications of this Frobenius Heisenberg category conjecturally provide connections to alternative Heisenberg algebras and W-algebras associated to the algebra F. This is joint work with Alistair Savage (University of Ottawa).

Sexual harassment and sexual assault in the workplace is almost always a severe betrayal of trust.  I will describe research and theory that my students and I have developed over the last 25 years regarding interpersonal and institutional betrayals of trust.  My presentation will include an explanation of betrayal trauma theory and information about institutional betrayal.   I will present data from some of our research studies, including results from a study of sexual harassment of graduate students.   Included will be research-based recommendations for how to respond well to disclosures of harassment and sexual violence as well as steps individuals and institutions can take to constructively address sexual violence and promote institutional courage.  

Jennifer J. Freyd, PhD, is a Fellow at the Center for Advanced Study in the Behavioral Sciences at Stanford University and a Professor of Psychology at the University of Oregon.