Angular fractals in thermal CFT

• Nathan Benjamin (USC)

Room: Inamori Center I will discuss universal properties of partition functions at high temperature and large angular fugacity in d>2 conformal field theories (CFTs). This provides spin-refined information -- namely the statistics of spins of local operators -- valid for all CFTs, that in some sense generalizes modular invariance of d=2 CFTs. As an example application, I will show that the effective free energy of even-spin minus odd-spin operators at high temperature is smaller than the usual free energy by a factor of 1/2^d.

Short talks Room: Inamori Center

Taming Asymptotic Freedom with Anti-de-Sitter

• Shota Komatsu (CERN)

Room: Inamori Center Anti-de-Sitter space acts as an infra-red cut off for asymptotically free theories, allowing interpolation between a weakly-coupled small-sized regime and a strongly-coupled flat-space regime. We scrutinize the interpolation for theories in two dimensions from the perspective of boundary conformal theories. We show that the appearance of a singlet marginal operator destabilizes a gapless phase existing at a small size, triggering a boundary renormalization group flow to a gapped phase that smoothly connects to flat space. We conjecture a similar mechanism for confinement in gauge theories.

Short talks Room: Inamori Center

Infinitely many new renormalization group flows between Virasoro minimal models from non-invertible symmetries

• Yu Nakayama (YITP)

Room: Inamori Center We discuss the role of non-invertible symmetries in RG flows between Virasoro minimal models. They give infinitely many new constraints by generalizing the notion of anomaly matching to non-invertible symmetries, leading to the predictions of infinitely many new RG flows. Our general classification includes the old flows such as Zamolldchikov's unitary flows, but also all the examples known including the recent sporadic one e.g. proposed by Klebanov et al.

Pinning Defects, Fusion and Factorization

• Yifan Wang (NYU)

Room: Inamori Center I'll discuss recent results on the dynamics of defects in conformal field theory. In particular, I'll describe the phenomena of defect fusion and the factorization of spacetime under renormalization group flows on defects. I'll illustrate these phenomena with the so-called pinning field defects which have simple definitions in quantum field theory and also comment on the broader implications for understanding extended operators.

Holographic Entanglement, Pseudo Entropy and Wormholes

• Tadashi Takayanagi (YITP)

Room: Inamori Center The idea of holographic duality in string theory provides a simple geometric computation of entanglement entropy. This generalizes the celebrated Bekenstein-Hawking formula of black hole entropy and strongly suggests that a gravitational spacetime consists of many qubits with quantum entanglement. Recently, a new extension of entanglement entropy, called pseudo entropy, which depends on both an initial and a final state, was introduced. This quantity turned out to have a clear geometric dual via the holography and also plays a role of a new order parameter of quantum phases. In this talk, after reviewing the above mentioned developments, we would like to point out that pseudo entropy becomes a useful probe in traversable wormhole geometries, where non-hermitian density matrices naturally appear in their CFT duals.

Short talks Room: Inamori Center

Topological symmetries and their gaugings in 2dCFT and 3dTFT

• Ingo Runkel (Hamburg U.)

Room: Inamori Center The study of topological defects in quantum field theory has seen a wealth of activity recently leading to many interesting insights, for example the explicit realisation of non-invertible topological defects in higher dimensional QFTs via the gauging of higher form symmetries, or the description of the higher algebraic structures inherent in these topological defects. In this talk, I would like to focus on low-dimensional examples, where such defects and their properties have been investigated for some time already. I would like to exhibit some of the properties of topological defects in two-dimensional conformal field theory and in three-dimensional topological field theory, and show some of the structural insights into 2dCFT and 3dTFT one can gain with the help of defects. In this way, the well-understood low-dimensional case might serve as a source of ideas and as a test-case for higher dimensional constructions.

Short talks Room: Inamori Center

No-go theorems for higher-spin charges in AdS_2

• Marco Meineri (U. Turin)

Room: Inamori Center Higher-spin conserved currents and charges feature prominently in integrable 2d QFTs in flat space. Motivated by the question of integrable field theories in Anti de-Sitter space, we consider the consequences of higher-spin currents for QFTs in AdS2, and find that their effect is much more constraining than in flat space. Specifically, it is impossible to preserve:(a) any higher-spin charges when deforming a massive free field by interactions, or (b) any spin-4 charges when deforming a CFT by a Virasoro primary. Along the way, we explain how higher-spin charges lead to integer spacing in the spectrum of primaries and constraints on correlation functions.

Short talks Room: Inamori Center

From Weyl Anomaly to Defect Supersymmetric R\'enyi Entropy and Casimir Energy

• Yang Zhou (Fudan U.)

Room: Inamori Center We present a closed-form expression for the contribution of surface defects to the supersymmetric Rényi entropy in six-dimensional (2,0) theories. Our results show that this defect contribution is a linear function of 1/n and is directly proportional to 2b-d_2, where b and d_2 are the surface defect Weyl anomaly coefficients. We also derive a closed-form expression for the defect contribution to the supersymmetric Casimir energy, which simplifies to -d_2 (up to a proportionality constant) in the chiral algebra limit. This talk is based on arXiv:2501.09498 with Zixiao Huang and Ma-Ke Yuan.

Short talks Room: Inamori Center

Localized RG flows on composite defects and C-theorem

• Dongsheng Ge (Osaka U.)

Room: Inamori Center We consider a composite defect system where a lower-dimensional defect (sub-defect) is embedded to a higher-dimensional one, and examine renormalization group (RG) flows localized on the defect. A composite defect is constructed in the (3 − ϵ)-dimensional free O(N) vector model with line and surface interactions by triggering localized RG flows to non-trivial IR fixed points. Focusing on the case where the symmetry group O(N) is broken to a subgroup O(m) × O(N − m) on the line defect, there is an O(N) symmetric fixed point for all N, while two additional O(N) symmetry breaking ones appear for N ≥ 23. We also examine a C-theorem for localized RG flows along the sub-defect and show that the C-theorem holds in our model by perturbative calculations.

Non-Invertible Symmetry and Entanglement Entropy

• Yichul Choi (IAS)

Room: Inamori Center Given a quantum field theory with a global symmetry, it is important to understand how the various observables organize into representations of the symmetry. In this talk, we focus on 2d conformal field theories with non-invertible global symmetries described by fusion categories. We will discuss how the boundary local operators connecting two potentially different conformal boundary conditions organize themselves under the action of non-invertible symmetries, using 3d topological field theory techniques. We then explain how this can be used to compute the sub-leading constant contribution to the non-invertible symmetry-resolved entanglement entropy of a single interval, which is somewhat analogous to the topological entanglement entropy of TQFTs.

Short talks Room: Inamori Center

Non-Supersymmetric Heterotic Branes

• Justin Kaidi (Kyushu U.)

Room: Inamori Center The common statement that any consistent quantum gravity theory contains dynamical objects with all possible charges suggests that there are still a number of hitherto-unidentified branes in string theory. In this talk I will discuss four of these new branes, focusing on heterotic string theories. The talk will cover aspects such as exact worldsheet descriptions of the branes, their relation to ten-dimensional non-supersymmetric heterotic string theories, and connections to the theory of topological modular forms.