Spacetime inversion symmetries such as parity and time reversal play a central role in physics, but they are usually treated as global symmetries.
In quantum gravity there are no global symmetries, so any spacetime inversion symmetries must be gauge symmetries.
In particular this includes CRT symmetry (in even dimensions usually combined with a rotation to become CPT), which in quantum field theory is always a symmetry and seems likely to be a symmetry of quantum gravity as well.
In this talk, we will discuss what it means to gauge a spacetime inversion symmetry and explain some of the more unusual consequences of doing this.
In particular, I will argue that the gauging of CRT is automatically implemented by the sum over topologies in the Euclidean gravity path integral, that in a closed universe the Hilbert space of quantum gravity must be a real vector space, and that in Lorentzian signature manifolds which are not time-orientable must be included as valid configurations of the theory.

In high-energy collision experiments, the momentum distribution of hadron pairs reveals correlations arising from hadron interactions and quantum statistics. Traditionally, femtoscopy has been used to derive emission source information from these correlations. Recently, these techniques have also facilitated new methods to assess hadron
interactions, as exemplified by the ALICE collaboration’s significant advancements at the LHC. This talk will cover the fundamental theoretical methods for calculating momentum correlation functions and discuss recent applications to antikaon-nucleon systems and hypernuclei, with a look toward future research at J-PARC.

References:
[1] S. Cho et al., ExHIC collaboration, Prog. Part. Nucl. Phys. 95, 279 (2017).
[2] Y. Kamiya, T. Hyodo, K. Morita, A. Ohnishi, W. Weise, Phys. Rev. Lett. 124, 132501 (2020).
[3] A. Jinno, Y. Kamiya, T. Hyodo, A. Ohnishi, arXiv:2403.09126 [nucl-th]

We discuss analogy between statistical mechanics and quantum field theory from the point of view of fine-tuning problem. In the former, (first-order) phase transition (PT) point spans a finite parameter space in micro-canonical ensemble, while it is literally a point and looks like a fine-tuning of parameters in canonical ensemble.
In this talk, I would like to point out that similar picture holds in quantum field theory. As concrete examples, we discuss free scalar theory and \phi^4 theory and show that gapless point (m^2=0) is typically realized in micro- canonical ensemble. Then, as a phenomenological application, we show that the Higgs alignment in the two Higgs doublet model can be realized in the micro-canonical picture without imposing any symmetries.

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 simulation of lattice gauge theories is expected to become a major application of quantum computers in the future. So far, most efforts have focused on the scheme based on quantum circuits. In this talk, I will advocate an alternative scheme inspired by measurement-based quantum computation. The Trotterized discrete time evolution of a Hamiltonian lattice gauge theory is driven by adaptive single-qubit measurements on an entangled resource state tailored for the simulated theory. The resource state itself has interesting physical properties and is in a symmetry-protected topological (SPT) phase protected by higher-form symmetries. We demonstrate an anomaly inflow mechanism between the simulated theory and the resource state by computing the gauge transformations of defect-dependent partition functions. The resource state can also be used to prove Kramers-Wannier-Wegner dualities of various lattice models. Based on arXiv:2210.10908 and 2402.08720 with Sukeno and Parayil Mana.

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].