Search Talks

Bosonic ultra-light dark matter (ULDM) would form cored density distributions at the centres of galaxies. These cores admit analytic description as the lowest energy bound state solution ("soliton") of the Schrödinger-Poisson equations. Numerical simulations of ULDM galactic halos found empirical scaling relations between the mass of the large-scale host halo and the mass of the central soliton. 
We connect the simulation results of different groups to basic properties of the soliton. Importantly, simulations imply that the specific kinetic energy in the soliton and in the host halo should be approximately equal. This relation predicts that the peak circular velocity, measured for the host halo in the outskirts of the galaxy, should repeat itself in the central region. Contrasting this prediction to the measured rotation curves of low surface-brightness galaxies, we show that ULDM in the mass range m ~ 10⁻²²-10⁻²¹ eV, which has been invoked as a possible solution of small-scale puzzles of ΛCDM, is in tension with the data. We discuss the potential of detailed dynamical modelling of the Milky Way and other well-resolved galaxies to probe ULDM up to m ~ 10⁻¹⁹ eV.

Magnetohydrodynamics (MHD) describes the low-energy physics of electromagnetically conducting plasmas. In the conventional formulation of MHD, one introduces dynamical electromagnetic fields on top of the usual hydrodynamic setup by hand. In this talk, we will explore an alternate effective view of MHD purely based on symmetries, as a "string fluid" of magnetic field lines, without any assumption about the underlying microscopic field content. We will argue that MHD is described by a novel theory of superfluidity with a partially broken one-form symmetry. We will also discuss the implications of this broken symmetry for constructing hydrostatic partition functions describing MHD. The talk is based on [arXiv:1808.01939, arXiv:1811.04913]. 

The discovery of a Higgs like boson at LHC in 2012 was a development of fundamental importance in particle physics. With this newly discovered state included in theoretical predictions of scattering events,  the Standard Model can be extrapolated  to much higher experimental energies. This implies that a degree of scale separation will be present between the discovered particles of the Standard Model, and any new particles required to address the outstanding mysteries that the Standard Model leaves unanswered. As a result, interest in treating the Standard Model as a consistent Effective Field Theory (the SMEFT) has dramatically increased. This powerful theory is the state of the art in studying experimental results model independently, up to energies that LHC probes in a robust fashion experimentally. Rather remarkably, as interest in this theory has increased in recent years, a number of subtleties has also been discovered in the physics of the SMEFT.  In this talk, I will review this rapidly advancing area.

I will give a holographic argument in favor of the AdS Penrose inequality, which conjectures a lower bound on the total mass in terms of the area of apparent horizons. This inequality is often viewed as a test of cosmic censorship. Time permitting, I’ll also discuss a generalization to charged black holes and connections with a quasi-local energy and the second law for apparent horizons.  

I will introduce my recent works on the phenomenology of solutions to the strong CP problem, QCD axion and Parity. I will first describe the production of the QCD axion in the early universe and show that the dark matter abundance is naturally reproduced for a wide range of the parameter space. I will then show a tight relation between the Parity solution, dark matter direct detection, the proton decay, and the precise measurements of the standard model parameters.

In the first part of the talk, I will mention the ongoing numerical efforts using lattice calculations to understand the holographic dualities relating the super Yang-Mills (SYM) theories in various dimensions and their conjectured Type II supergravity theories in the decoupling limit. In the second part, I will discuss the tensor renormalization group study of the SU(2) gauge-Higgs model in two dimensions using the higher-order tensor renormalization group (HOTRG) algorithm and compare the results with the Monte Carlo simulations. 

The 21st century may come to be known as the Age of Photonics, as we exploit our ability to make and manipulate light as an amazing carrier of energy and information. From quantum computing and entanglement to eye surgery and solar energy, humans are already reaping the benefits of our own endeavours to understand and control light.

In her public lecture webcast at Perimeter on March 6, Cather Simpson from the University of Auckland will highlight her research in exploring how recent advances in the physics of light are transforming our ability to feed the planet safely and sustainably.

Simpson moved from Case Western Reserve University in the USA to the University of Auckland’s Physics and Chemistry Departments in 2007. There, she started the Photon Factory, a laser centre whose mission is to exploit exotic, ultrashort pulsed lasers to enable cross-disciplinary research from the very fundamental to the applied and entrepreneurial.

Simpson’s research explores the interaction of light with matter, particularly how materials can convert light into more useful forms of energy. A relatively recent area of focus is in agriculture, where her work has led to two international award-winning spinout companies. Her many recent accolades include a National Tertiary Teaching Excellence Award, the 2016 Silicon Valley Forum 1st-place AgTech medal, and election as a Fellow of the Royal Society of New Zealand Te Apārangi.

It is known that there is a relationship between conformal Carroll transformations and BMS symmetry. In this talk I will explore the geometry of generic Carroll structures which may be thought of as the basic underlying geometric structure on null hypersurfaces. A Carroll structure can be thought of as a fibre bundle with Ehresmann connection, and one finds that (generalized) BMS symmetry emerges as the conformal symmetry of this bundle and connection. I’ll briefly also describe how this story fits into the physics of ’soft modes.’

Mirror sectors -- hidden sectors that are approximate copies of the Standard Model -- are a generic prediction of many models, notably the Mirror Twin Higgs model. Such models can have a rich cosmology and many interesting detection signatures beyond the realm of colliders. In this talk, I will focus on the possibility that mirror matter can form stars which undergo mirror nuclear fusion in their cores. I will discuss the mechanisms by which these objects can emit Standard Model light and estimate their luminosity and prospects for their detection.

An assessment of the particle standard model and an alternative formulation of
the model are presented. An ultraviolet complete particle model is constructed
for the observed particles of the standard model. The quantum field theory
associates infinite derivative entire functions with propagators and vertices, which
make perturbative quantum loops finite and maintain Poincaré invariance and
unitarity of the model. The electroweak model SU(2) X U(1) group is treated as a
broken symmetry group with non-vanishing experimentally determined boson
and fermion masses. A spontaneous symmetry breaking of the vacuum by a
scalar Higgs field is not invoked to restore boson and fermion masses to the
initially massless SU(2) X U(1) Lagrangian of the standard model. The hierarchy
naturalness problem of the Higgs boson mass is resolved and the model
contains only experimentally observed masses and coupling constants. The
renormalization group features of the scalar Higgs field are investigated and the
model is shown to be asymptotically safe and free from the triviality problem. It is
demonstrated that the finite nonlocal quantum field theory satisfies
microcausality. The model can predict a stable vacuum evolution. Experimental
tests to distinguish the standard model from the alternative model are proposed.
The finite quantum field theory can be extended to quantum gravity.