Talks

According to the Asymptotic Safety conjecture, a (non-perturbatively)
renormalizable quantum field theory of gravity could be constructed
based on the existence of a non-trivial fixed point of the
renormalization group flow.
The existence of this fixed point can be established, e.g., via the
non-perturbative methods of the functional renormalization group (FRG).
In practice, the use of the FRG methods requires to work within
truncations of the gravitational action, and higher-derivative operators
naturally lead to the presence of several poles in the propagator. The
question is whether these poles represent a real problem for the
unitarity of the theory.

Using QED as a working example, in this talk I will discuss some aspects
of non-perturbative unitarity in Quantum Field Theory. I will show that
the inclusion of quantum effects at all scales is of crucial importance
to assess unitarity of field theories. In particular, poles appearing in
truncations of the action could correspond to fake degrees of freedom of
the theory. Possible conditions to determine, within truncations,
whether a pole represents a fake or a genuine degree of freedom of the
theory will also be discussed.

Cosmological simulations of galaxy formation have evolved significantly over the last years.
In my talk I will describe recent efforts to model the large-scale distribution
of galaxies with cosmological hydrodynamics simulations. I will focus on the
Illustris simulation, and our new simulation campaign, the IllustrisTNG
project. After demonstrating the success of these simulations in terms of
reproducing an enormous amount of observational data, I will also talk about
their limitations and directions for further improvements over the next couple
of years.

The first part of this talk will introduce generalized Jordan–Wigner
transformation on arbitrary triangulation of any simply connected
manifold in 2d, 3d and general dimensions. This gives a duality
between all fermionic systems and a new class of Z2 lattice gauge
theories. This map preserves the locality and has an explicit
dependence on the second Stiefel–Whitney class and a choice of spin
structure on the manifold. In the Euclidean picture, this mapping is
exactly equivalent to introducing topological terms (Chern-Simon term
in 2d or the Steenrod square term in general) to the Euclidean action.
We can increase the code distance of this mapping, such that this
mapping can correct all 1-qubit and 2-qubits errors and is useful for
the simulation of fermions on the quantum computer. The second part of
my talk is about SPT phases. By the boson-fermion duality, we are able
to show the equivalent between any supercohomology fermionic SPT and
some higher-group bosonic SPT phases. Particularly in (3+1)D, we have
constructed a unitary quantum circuit for any supercohomology
fermionic SPT state with gapped boundary construction. This fermionic
SPT state is derived by gauging higher-form Z2 symmetry in the
higher-group bosonic SPT and apply the boson-fermion duality.

A superoscillatory function is a bandlimited function that, on some interval, oscillates faster than the highest frequency component shown in the function's Fourier transform. Superoscillations can be arbitrarily fast and of arbitrarily long duration but come at the expense of requiring a correspondingly large dynamic range. I will review how superoscillatory wave forms can be constructed and I will discuss the unusual behavior of wave functions that superoscillate. For example, they can describe particles that automatically strongly accelerate when passing through a slit. A postselected stream of them represents a ray that cools the slit walls, raising foundational and thermodynamic questions. Superoscillatory wave forms are already being used for practical applications such as spatial resolution beyond the diffraction limit. 

The LHC bear great potential in seeking for hidden sector particles, such as a high-quality QCD axion, glueballs, and heavy neutrinos. 

In this talk, I will present my recent studies on how to probe these hidden sector particles through the novel but challenging long-lived particle searches.