Publications

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Entangled universes

Divij Gupta, Matthew Headrick, Martin Sasieta

SciPost Phys. 19, 143 (2025) · published 1 December 2025 | · pdf

We propose a generalization of the RT and HRT holographic entanglement entropy formulas to spacetimes with asymptotically Minkowski as well as asymptotically AdS regions. We postulate that such spacetimes represent entangled states in a tensor product of Hilbert spaces, each corresponding to one asymptotic region. We show that our conjectured formula has the same general properties and passes the same general tests as the standard HRT formula. We provide further evidence for it by showing that in many cases the Minkowski asymptotic regions can be replaced by AdS ones using a domain wall. We illustrate the use of our formula by calculating entanglement entropies between asymptotic regions in Brill-Lindquist spacetimes, finding phase transitions similar to those known to occur in AdS. We construct networks of universes by gluing together Brill-Lindquist spaces along minimal surfaces. Finally, we discuss a variety of possible extensions and generalizations, including to universes with asymptotically de Sitter regions; in the latter case, we identify an ambiguity in the homology condition, leading to two different versions of the HRT formula which we call "orthodox" and "heterodox", with different physical interpretations.
Universal thermalization dynamics in (1+1)d QFTs

Richard A. Davison, Luca V. Delacretaz

SciPost Phys. 18, 177 (2025) · published 4 June 2025 | · pdf

We identify the universal mechanism behind the thermalization of (1+1)d QFTs at high and low temperatures. Viewing these theories as CFTs perturbed by relevant or irrelevant deformations, we show that conformal perturbation theory in the thermal state breaks down at late times allowing for the emergence of hydrodynamics. This breakdown occurs universally due to the unsuppressed exchange of stress tensors near the lightcone. Furthermore, for theories with central charge $c→∞$ we solve for the emergent hydrodynamic theory to all orders in the gradient expansion by arguing that all transport parameters appearing in two-point functions have universal expressions in terms of the scaling dimension $\Delta$ of the perturbation. The radius of convergence of the hydrodynamic dispersion relations provides an early time cutoff for hydrodynamics, which agrees with the time scale at which conformal perturbation theory breaks down.
Classical weight-four L-value ratios as sums of Calabi-Yau invariants

Philip Candelas, Xenia de la Ossa, Joseph McGovern

SciPost Phys. 18, 181 (2025) · published 6 June 2025 | · pdf

We revisit the series solutions of the attractor equations of 4d $\mathcal{N}=2$ supergravities obtained by Calabi–Yau compactifications previously studied in [P. Candelas et al., J. High Energy Phys. 11, 032 (2021)]. While only convergent for a restricted set of black hole charges, we find that they are summable with Padé resummation providing a suitable method. By specialising these solutions to rank-two attractors, we obtain many conjectural identities of the type discovered in [P. Candelas et al., J. High Energy Phys. 11, 032 (2021)]. These equate ratios of weight-four special L-values with an infinite series whose summands are formed out of genus-0 Gromov–Witten invariants. We also present two new rank-two attractors which belong to moduli spaces each interesting in their own right. Each of these moduli spaces possess two points of maximal unipotent monodromy. One has already been studied by Hosono and Takagi, and we discuss issues stemming from the associated L-function having nonzero rank.
A family of vertex algebras from Argyres-Douglas theory

Heeyeon Kim, Jaewon Song

SciPost Phys. 19, 144 (2025) · published 2 December 2025 | · pdf

We find that multiple vertex algebras can arise from a single 4d $\mathcal{N}=2$ superconformal field theory (SCFT). The connection is given by the BPS monodromy operator $M$, which is a wall-crossing invariant quantity that captures the BPS spectrum on the Coulomb branch. For a class of low-rank Argyres-Douglas theories, we find that the trace of the multiple powers of the monodromy operator Tr$M^N$ yield modular functions that can be identified with the vacuum characters of certain vertex algebra for each $N$. In particular, we realize unitary VOAs of the Deligne-Cvitanović exceptional series type $(A_2)_1$, $(G_2)_1$, $(D_4)_1$, $(F_4)_1$, $(E_6)_1$ from Argyres-Douglas theories. We also find the modular invariant characters of the 'intermediate vertex algebras' $(E_{7\frac{1}{2}})_1$ and $(X_1)_1$. Our analysis allows us to construct 3d $\mathcal{N}=2$ gauge theories that flow to $\mathcal{N}=4$ SCFTs in the IR, whose specialized half-index can be identified with these modular invariant characters.
BV formalism and partition functions

Pietro Antonio Grassi, Ondrej Hulik

SciPost Phys. 18, 202 (2025) · published 23 June 2025 | · pdf

The BV formalism is a well-established method for analyzing symmetries and quantizing field theories. In this paper, we use BV formalism to derive partition functions and the space of gauge invariant operators implementing the equations of motions and their redundancies for selected theories. We discuss various interpretations of the results, some dualities, and relation to the first quantized models.
Generalized symmetry enriched criticality in (3+1)d

Benjamin Moy

SciPost Phys. 19, 145 (2025) · published 3 December 2025 | · pdf

We construct two classes of continuous phase transitions in 3+1 dimensions between gapped phases that break distinct generalized global symmetries. Our analysis focuses on $SU(N)/\mathbb{Z}_N$ gauge theory coupled to $N_f$ flavors of Majorana fermions in the adjoint representation. For $N$ even and sufficiently large odd $N_f$, upon imposing time-reversal symmetry and an $SO(N_f)$ flavor symmetry, the massless theory realizes a quantum critical point between a gapped phase in which a $\mathbb{Z}_N$ one-form symmetry is completely broken and a phase where it is broken to $\mathbb{Z}_2$, leading to $\mathbb{Z}_{N/2}$ topological order. We characterize the possible patterns of symmetry fractionalization in these phases and provide an explicit lattice model that exhibits the transition. The critical point has an enhanced symmetry, which includes non-invertible analogues of time-reversal symmetry. Enforcing a non-invertible time-reversal symmetry and the $SO(N_f)$ flavor symmetry, for $N$ and $N_f$ both odd, we demonstrate that this critical point can appear between a topologically ordered phase and a phase that spontaneously breaks the non-invertible time-reversal symmetry, furnishing an analogue of deconfined quantum criticality for generalized symmetries.
Graviton mass and entanglement islands in low spacetime dimensions

Hao Geng

SciPost Phys. 19, 146 (2025) · published 4 December 2025 | · pdf

It has been conjectured and proven that entanglement island is not consistent with long-range (massless) gravity in a large class of spacetimes, including typical asymptotically anti-de Sitter spacetimes, in high spacetime dimensions. The conjecture and its proof are motivated by the observation that existing constructions of entanglement islands in high dimensions are all in gravitational theories where the graviton is massive for which the standard gravitational Gauss' law doesn't apply. In this letter, we show that this observation persists to lower dimensional cases. We achieve this goal by providing a unified description of the gravitational Gauss' law violation in island models that can work in any dimensions. This unified description teaches us new lessons on entanglement islands and subregion physics in quantum gravity. We focus on the case of the (1+1)-dimensional Jackiw-Teitelboim (JT) gravity for the purpose of demonstration.
The fermionic double smeared null energy condition

Duarte Fragoso, Lihan Guo

SciPost Phys. Core 8, 045 (2025) · published 26 June 2025 | · pdf

Energy conditions are crucial for understanding why exotic phenomena such as traversable wormholes and closed timelike curves remain elusive. In this paper, we prove the Double Smeared Null Energy Condition (DSNEC) for the fermionic free theory in 4-dimensional flat Minkowski spacetime, extending previous work on the same energy condition for the bosonic case [J. R. Fliss and B. Freivogel, SciPost Phys. 12, 084 (2022); J. R. Fliss et al., SciPost Phys. 14, 024 (2023)] by adapting Fewster and Mistry's method [C. J. Fewster and B. Mistry, Phys. Rev. D 68, 105010 (2003)] to the energy-momentum tensor $T_{++}$. A notable difference from previous works lies in the presence of the $\gamma_0 \gamma_+$ matrix in $T_{++}$, causing a loss of symmetry. This challenge is addressed by making use of its square-root matrix. We provide explicit analytic results for the massless case as well as numerical insights for the mass-dependence of the bound in the case of Gaussian smearing.
Area law and OPE blocks in conformal field theory

Jiang Long

SciPost Phys. Proc. 4, 013 (2021) · published 13 August 2021 | · pdf

This is an introduction to the relationship between area law and OPE blocks in conformal field theory.
Monte Carlo Event Generator updates, for tau pair events at Belle II energies

Sw. Banerjee, D. Biswas, T. Przedzinski, Z. Was

SciPost Phys. Proc. 16, 003 (2025) · published 14 July 2025 | · pdf

The Monte Carlo for lepton pair production and $\tau$ decays consist of KKMC for lepton pair production, tauola for $\tau$ lepton decays and photos for radiative corrections in decays. An effort for adaptation of the system for precision data to be collected at Belle II experiment lead to extension of phase space generation modules both in photos and tauola to enable decays and/or radiative corrections of additional light lepton pairs. The phase-space and matrix element parts of the programs are separated, that is why extension to processes where lepton pair is produced through narrow resonances, like dark photon, was straight forward. In the present version of tauola, the list of $\tau$ decay channels is enriched with multitude of exotic ones, useful for searches of new physics. The hadronic currents parametrization of main decay channels is prepared for basic simulation in the experiment. The basis for future work on precise fits of hadronic currents including Machine Learning is retained, but development of necessary software solutions is left for the forthcoming years. Presented programs versions are available in stand-alone format from GitLab or through the basf2 system of Belle II software. Official distribution web pages, documenting programs tests, are retained but not necessarily up to date.

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