Talks

Magnetars are exceptional neutron stars with the highest magnetic
fields ( 10^15 gauss) in the universe, an unusual quasi steady X
radiation (10^35 ergs/sec) and also produce flares which are some of
the brightest events (10^46 ergs in one fifth of a second) to be
recorded. There is no satisfactory model of magnetars.
The talk will cover neutron stars and a new model for the origin of
the magnetic fields in which magnetars arise from a high baryon
density ( phase transition) magnetized core which forms when they are
born. The core magnetic field is initially shielded by the ambient
high conductivity plasma. With time the shielding currents dissipate
transporting the core field out, first to the crust and then breaking
through the crust to the surface of the star. Recent observations
provide support for this model which accounts for several properties
of magnetars and also enables us to identify new magnetars.

Atomic clocks are the most precise timekeepers ever built. If you could keep an advanced atomic clock running long enough, it would neither gain nor lose a single second over the entire lifespan of the universe. With the availability of spectrally pure lasers and the ability to precisely measure optical frequencies, it appears the era of optical atomic clocks has begun. Advances in atomic clocks are expected to be important in a range of emerging technological applications, including quantum computers. Dr. David Wineland, 2012 Nobel Laureate in Physics, will explore the theoretical and technological know-how needed to build these ultra-precise timepieces during his Perimeter Institute Public Lecture on Wednesday, Nov. 4. 

Topological phases of matter are phases of matter which are not characterized
by classical local order parameters of some sort. Instead, it is the global properties
of quantum many-body ground states which distinguish one topological phase from
another. One way to detect such global properties is to put the system on a topologically
non-trivial space (spacetime). For example, topologically ordered phases in (2+1)
dimensions exhibit ground state degeneracy which depends on the topology of the spatial manifold.
In this talk, I will discuss how one can use a {\it unoriented} space (spacetime)
to detect non-trivial properties of topological phases of matter in the presence
of discrete spacetime symmetry, such as time-reversal or reflection symmetry.
In particular, I will show how interaction effects on topological insulators and
superconductors can be understood using quantum anomalies on unoriented spacetime.

The Reeh-Schlieder theorem says, roughly, that, in any reasonable quantum field theory,  for any bounded region of spacetime R, any state can be approximated arbitrarily closely by operating on the vacuum state (or any state of bounded energy) with operators formed by smearing polynomials in the field operators with functions having support in R.  This strikes many as counterintuitive, and Reinhard Werner has glossed the theorem as saying that “By acting on the vacuum with suitable operations in a terrestrial laboratory, an experimenter can create the Taj Mahal on (or even behind) the Moon!” This talk has two parts.  First, I hope to convince listeners that the theorem is not counterintuitive,  and that it follows immediately from facts that are already familiar fare to anyone who has digested the opening chapters of any standard introductory textbook of QFT.  In the second, I will discuss what we can learn from the theorem about how relativistic causality is implemented in quantum field theories.