Radial quantization would be the ideal formalism for studying strongly-coupled near-conformal quantum field theories but it requires the ability to perform lattice calculations on static, curved manifolds, specifically a very long cylinder whose cross section is a sphere. Smoothly discretizing the surface of a sphere requires a graph with unequal edge lengths. The geometry of such graphs is well understood since 1961 using Regge Calculus. But, lattice quantum field theories are defined in terms of couplings which appear in the action rather than edge lengths and so the relationship between couplings and lengths must be determined dynamically. A simple example is computing the ratio of spatial to temporal lattice spacings in anisotropic lattice QCD. I will discuss our conjecture that computing anisotropic lattice spacing ratios on affine transformations of regular flat lattices is sufficient to determine coupling assignments on curved lattices.

Quantum field theories (QFTs) describe a lot of physical phenomena in our world. And giving a mathematical definition of QFTs is a long-standing problem. There are several mathematical formulations: Wightman formulation, Osterwalder–Schrader formulation and Atiya-Segal formulation. And each of them cover different aspects of QFTs. Recently, Costello and their collabolators formulate QFTs by using factorization algbras. This formulaion cover a lot of classes of QFTs: TQFTs, 2d CFTs and perturbative QFTs. And they reproduce various results such as asymptotic freedom in non-Abelian gauge theories. Factorization algbras can be given by Batalin–Vilkovisky quantization (BV quantization) of the Lagrangian. However the original BV quantizations are perturbative and they do not have non-perturbative effects like instanton. In this talk, we propose BV quantizations which include instanton effects in compact scalar theory. In modern language, it is a BV formulation of ℤ gauging.

In this talk we identify a Z3 discrete gravitational theta angle in the non-supersymmetric SO(16) x SO(16) heterotic string, which is detected by a 10D spacetime manifold that is an Sp(2) group manifold. In the first part, we explain the string theory computation that identifies this Z3 theta angle, involving non-perturbative anomaly on the instantonic NS5 branes. In the second part, we motivate our endeavor by Stolz-Teichner conjecture which relates 2D (0,1) SQFT to Topological modular forms. Our result identifies two generators of torsional classes in TMF of specific degrees by explicit 2D (0,1) theories: one begins a 2D (0,1) sigma model to Sp(2), the other being the SO(16) x SO(16) chiral fermionic SCFT. Based on 2403.08861 with Yuji Tachikawa.

The quantum theories of both gravity and electromagnetism require a recipe to specify how the constraint equations of the theory are implemented. Recently we argued that the standard procedure for implementing the Hamiltonian and momentum constraints in gravity and Gauss’ law in electromagnetism is unnecessarily restrictive. With a looser approach to quantization we find that, in the classical limit, a source for the non-dynamical parts of the field is generically present. These sources mimic the existence of pressureless dust -providing an explanation for the perceived dark matter in the universe.

The current precision on determining CKM matrix elements is below a per cent in several cases, and tensions between results are present, for example, in the Vus/Vud plane. Investigating that problem is essential for searching for new physics through weak decays. At this level of precision, a crucial ingredient is the determination of radiative corrections to pseudoscalar meson weak decays. Those have been computed mainly through effective field theories, which can have uncontrolled uncertainties. It is, therefore, important for lattice QCD+QED simulations to provide accurate predictions from first principles. In this talk, I will present various results, mainly from the UKQCD collaboration, illustrating several challenges faced when performing such calculations. The first calculation at physical quark masses of radiative corrections to kaon and pion was published in [1] after the pioneering work from [2]. A feature of [1] is an uncomfortably sizeable systematic error due to theoretical uncertainties on higher-order finite-size corrections. I will present our result and detail this issue based on the formalism established in [3]. I will conclude with future possible directions to address this problem.
[1]: https://doi.org/10.1007/JHEP02(2023)242
[2]: https://doi.org/10.1103/PhysRevD.100.034514
[3]: https://doi.org/10.1103/PhysRevD.105.074509

Light particles beyond the Standard Model may be produced in electron and positron beam dumps of the International Linear Collider (ILC).
We study capability of the ILC beam dump experiment to search for new physics, comparing the performance of the electron and positron beam dumps.
Firstly, the dark photon, axion-like particles, and light scalar bosons are considered as new physics scenarios. We find that the ILC beam dump experiment has higher sensitivity than past beam dump experiments, with the positron beam dump having slightly better performance for new physics particles which are produced by the electron-positron pair-annihilation.
We also propose an experimental setup to search for sub-GeV dark matter, the Beam-Dump eXperiment at the ILC (ILC-BDX). We study the production, decay and scattering of sub-GeV dark matter particles in several models with a dark photon mediator. Taking into account beam-related backgrounds due to neutrinos produced in the beam dump as well as the cosmic-ray background, we evaluate the sensitivity reach of the ILC-BDX experiment. We find that the ILC-BDX will be able to probe interesting regions of the model parameter space and, in many cases, reach well below the relic target.
This talk is based on the following papers: arXiv: 2105.13768 [hep-ph] and 2301.03816 [hep-ph].

Preserving the symmetries of massless fermions is a well-known challenge in lattice field theory. I’ll discuss symmetry-preserving lattice regularizations of 2d QED with one and two flavors of Dirac fermions, as well as the `3450′ chiral gauge theory. The construction leverages bosonization and recently-proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum, the anomalies are reproduced at finite lattice spacing, and in each case we’ve found a sign-problem-free dual formulation.

In this talk, after reviewing the basics of the massive spinor helicity formalism, we introduce a momentum shift based on the helicity basis. This momentum shift allows an on-shell reconstruction of renormalizable theories with particles of any mass. As a demonstration of our method, we compute $e^+ e^- \to \mu^+ \mu^-$ and $W^+W^- \to W^+W^ $ amplitudes. An issue was raised on the former amplitude in literature and we see that, with our momentum shift, we can resolve the issue. In the latter case, we recover the correct amplitude, which contains the four-point contact interaction in terms of the Feynman diagrams, solely from the three-point amplitude. We see that this result is closely related to the Ward identity.

In this seminar, I will talk about how temperature observations of neutron stars provide a unique window to explore physics beyond the Standard Model of particle physics. Neutron stars, with their extreme environments, serve as natural laboratories for testing the limits of our physical understanding. The standard cooling theory, which accounts for the cooling of isolated neutron stars through neutrino and electromagnetic radiation, generally aligns with observational data. However, the presence of hypothetical particles such as axions and dark matter, predicted by theories that extend the Standard Model, could alter this cooling behavior. Axions, for example, increase cooling rates, while dark matter interactions could lead to additional heating. By comparing revised theoretical predictions with observed temperature evolution, we might explore signs of these elusive particles. This talk is based on the following papers: arXiv:2309.02633, 2308.16066, 2204.
02413, 2204.02238, 2008.03924, 1905.02991, 1904.04667, 1806.07151.

Particulate dark matter (DM), completely isolated from the Standard Model particle sector, can be produced in the early Universe from primordial black hole (PBH) evaporation. However, big bang nucleosynthesis (BBN) observations put an upper bound on the initial mass of PBH requiring the PBH to evaporate completely before the advent of BBN. DM particles in the mass range ∼(1–10^9)GeV cannot explain the observed relic abundance for an early matter dominated universe due to this BBN constraint. However, this assumes the presence of only one monochromatic PBH mass distribution in the early Universe. In this talk, we will explore the simple possibility of achieving the observed relic with DM masses from the above mentioned range for an early matter dominated era with two monochromatic evaporating PBH mass distributions and demonstrate that the fermionic DM masses consistent with BBN change slightly.