Forthcoming events in this series
An introduction to asymptotic safety
Abstract
I define what it means for a quantum
field theory to be asymptotically safe and
discuss possible applications to theories
of gravity and matter.
Quantum communication in Rindler spacetime
Abstract
Communication between observers in a relativistic scenario has proved to be
a setting for a fruitful dialogue between quantum field theory and quantum
information theory. A state that an inertial observer in Minkowski space
perceives to be the vacuum will appear to an accelerating observer to be a
thermal bath of radiation. We study the impact of this Davies-Fulling-Unruh
noise on communication, particularly quantum communication from an inertial
sender to an accelerating observer and private communication between two
inertial observers in the presence of an accelerating eavesdropper. In both
cases, we establish compact, tractable formulas for the associated
communication capacities assuming encodings that allow a single excitation
in one of a fixed number of modes per use of the communications channel.
Lattice String Field Theory: The 1d linear dilaton
Abstract
String field theory is a candidate for a full non-perturbative definition
of string theory. We aim to define string field theory on a space-time
lattice to investigate its behaviour at the quantum level. Specifically, we
look at string field theory in a one dimensional linear dilaton background,
using level truncation to restrict the theory to a finite number of fields.
I will report on our preliminary results at level-0 and level-1.
Asymmetric dark matter
Abstract
Much effort has been devoted to the study of weak scale particles, e.g. supersymmetric neutralinos, which have a relic abundance from thermal equilibrium in the early universe of order what is inferred for dark matter. This does not however provide any connection to the comparable abundance of baryonic matter, which must have a non-thermal origin. However "dark baryons" of mass ~5 GeV from a new strongly interacting sector would naturally provide dark matter and are consistent with recent putative signals in experiments such as CoGeNT and DAMA. Such particles would accrete in the Sun and affect heat transport in the interior so as to affect low energy neutrino fluxes and can possibly resolve the current conflict between helioseismological data and the Standard Solar Model.
Analytic torsion for twisted de Rham complexes
Abstract
I will define and discuss the properties of the analytic torsion of
twisted cohomology and briefly of Z_2-graded elliptic complexes
in general, as an element in the graded determinant line of the
cohomology of the complex, generalizing most of the variants of Ray-
Singer analytic torsion in the literature. IThe definition uses pseudo-
differential operators and residue traces. Time permitting, I will
also give a couple of applications of this generalized torsion to
mathematical physics. This is joint work with Siye Wu.
Axions, Inflation and the Anthropic Principle
Abstract
The QCD axion is the leading solution to the strong-CP problem, a
dark matter candidate, and a possible result of string theory
compactifications. However, for axions produced before inflation, high
symmetry-breaking scales (such as those favored in string-theoretic axion
models) are ruled out by cosmological constraints unless both the axion
misalignment angle and the inflationary Hubble scale are extremely
fine-tuned. I will discuss how attempting to accommodate a high-scale axion
in inflationary cosmology leads to a fine-tuning problem that is worse than
the strong-CP problem the axion was originally invented to solve, and how
this problem is exacerbated when additional axion-like fields from string
theory are taken into account. This problem remains unresolved by anthropic
selection arguments commonly applied to the high-scale axion scenario.
Toposes in algebraic quantum theory
Abstract
Topology can be generalised in at least two directions: pointless
topology, leading ultimately to topos theory, or noncommutative
geometry. The former has the advantage that it also carries a logical
structure; the latter captures quantum settings, of which the logic is
not well understood generally. We discuss a construction making a
generalised space in the latter sense into a generalised space in the
former sense, i.e. making a noncommutative C*-algebra into a locale.
This construction is interesting from a logical point of view,
and leads to an adjunction for noncommutative C*-algebras that extends
Gelfand duality.
Exact probes of boundary conditions and flows in two-dimensional quantum field theories
Locally covariant quantum field theory in curved spacetime
Abstract
A recent innovation in quantum field theory is the locally covariant
framework developed by Brunetti, Fredenhagen and Verch, in which quantum
field theories are regarded as functors from a category of spacetimes to a
category of *-algebras. I will review these ideas and particularly discuss
the extent to which they correspond to the intuitive idea of formulating the
same physics in all spacetimes.