Publications by João Miguel Augusto Penedones Fernandes

Hilbert space of quantum field theory in de Sitter spacetime

João Miguel Augusto Penedones Fernandes, Kamran Salehi Vaziri

We study the decomposition of the Hilbert space of quantum field theory in (d+1)-dimensional de Sitter spacetime into unitary irreducible representations (UIRs) of its isometry group SO(1,d+1). First, we consider multiparticle states in free theories start ...

2025

Gravity from quantum mechanics of finite matrices

Xiang Zhao, João Miguel Augusto Penedones Fernandes

We revisit the Berenstein-Maldacena-Nastase (BMN) conjecture relating M-theory on a PP-wave background and Matrix Quantum Mechanics (MQM) of N x N matrices. In particular, we study the BMN MQM at strong coupling and finite N and derive an effective Hamilto ...

SPRINGER2025

Renormalization group flows in AdS and the bootstrap program

João Miguel Augusto Penedones Fernandes

We study correlation functions of the bulk stress tensor and boundary operators in Quantum Field Theories (QFT) in Anti-de Sitter (AdS) space. In particular, we derive new sum rules from the two-point function of the stress tensor and its three-point funct ...

Springer Nature2024

Bounds on photon scattering

Kelian Philippe Häring, João Miguel Augusto Penedones Fernandes, Marco Meineri, Denis Karateev, Aditya Hebbar

We study 2-to-2 scattering amplitudes of massless spin one particles in d = 4 space-time dimensions, like real world photons. We define a set of non-perturbative observables (Wilson coefficients) which describe these amplitudes at low energies. We use full ...

SPRINGER2024

Trace anomalies and the graviton-dilaton amplitude

João Miguel Augusto Penedones Fernandes, Biswajit Sahoo

We consider 3+1 dimensional Quantum Field Theories (QFTs) coupled to the dilaton and the graviton. We show that the graviton-dilaton scattering amplitude receives a universal contribution which is helicity flipping and is proportional to ∆c − ∆a along any ...

Springer Nature2024

Numerical tests of the large charge expansion

João Miguel Augusto Penedones Fernandes

We perform Monte-Carlo measurements of two and three-point functions of charged operators in the critical O(2) model in 3 dimensions. Our results are compatible with the predictions of the large charge superfluid effective field theory. To obtain reliable ...

Springer Nature2024

Where is M-theory in the space of scattering amplitudes?

João Miguel Augusto Penedones Fernandes, Andrea Guerrieri

We use the S-matrix bootstrap to carve out the space of unitary, analytic, crossing symmetric and supersymmetric graviton scattering amplitudes in nine, ten and eleven dimensions. We extend and improve the numerical methods of our previous work in ten dime ...

Springer Nature2023

The Källén-Lehmann representation in de Sitter spacetime

João Miguel Augusto Penedones Fernandes, Kamran Salehi Vaziri, Manuel Loparco

We study two-point functions of symmetric traceless local operators in the bulk of de Sitter spacetime. We derive the Kallen-Lehmann spectral decomposition for any spin and show that unitarity implies its spectral densities are nonnegative. In addition, we ...

Springer Nature2023

Towards the non-perturbative cosmological bootstrap

João Miguel Augusto Penedones Fernandes, Kamran Salehi Vaziri, Matthijs Jan Hogervorst

We study quantum field theory on a de Sitter spacetime dS(d+1) background. Our main tool is the Hilbert space decomposition in irreducible unitary representations of its isometry group SO(d + 1, 1). As the first application of the Hilbert space formalism, ...

Springer Nature2023

Injecting the UV into the bootstrap: Ising Field Theory

Miguel Alexandre Ribeiro Correia, João Miguel Augusto Penedones Fernandes

We merge together recent developments in the S-matrix bootstrap program to develop a dual setup in 2 space-time dimensions incorporating scattering amplitudes of massive particles and matrix elements of local operators. In particular, the stress energy ten ...

Springer Nature2023

Spinning S-matrix bootstrap in 4d

João Miguel Augusto Penedones Fernandes, Denis Karateev, Aditya Hebbar

We review unitarity and crossing constraints on scattering amplitudes for particles with spin in four dimensional quantum field theories. As an application we study two to two scattering of neutral spin 1/2 fermions in detail. Assuming Mandelstam analytici ...

Springer Nature2022

Bootstrapping the a-anomaly in 4d QFTs

João Miguel Augusto Penedones Fernandes, Jan Krzysztof Marucha, Biswajit Sahoo

We study gapped 4d quantum field theories (QFTs) obtained from a relevant deformation of a UV conformal field theory (CFT). For simplicity, we assume the existence of a Z(2) symmetry and a single Z2-odd stable particle and no Z(2)-even particles at low ene ...

Springer Nature2022

Numerical data for scattering amplitudes of photon in d=4

João Miguel Augusto Penedones Fernandes, Marco Meineri, Denis Karateev, Aditya Hebbar

Numerical data for scattering amplitudes of photons in d=4 obtained by solving various optimisation problems. The data is stored in .txt files. Mathematica notebook is provided for loading and plotting the data. ...

2022

Searching for continuous phase transitions in 5D SU(2) lattice gauge theory

José Pedro Gamito de Saldanha Calado Matos, Adrien Florio, João Miguel Augusto Penedones Fernandes

We study the phase diagram of 5-dimensional SU(2) Yang-Mills theory on the lattice. We consider two extensions of the fundamental plaquette Wilson action in the search for the continuous phase transition suggested by the 4 + epsilon expansion. The extensio ...

Springer Nature2021

S-matrix bootstrap for effective field theories: massless pions

João Miguel Augusto Penedones Fernandes, Andrea Guerrieri

We use the numerical S-matrix bootstrap method to obtain bounds on the two leading Wilson coefficients (or low energy constants) of the chiral lagrangian controlling the low-energy dynamics of massless pions. This provides a proof of concept that the numer ...

Springer Nature2021

Where Is String Theory in the Space of Scattering Amplitudes?

João Miguel Augusto Penedones Fernandes, Andrea Guerrieri

We use the S-matrix bootstrap to carve out the space of unitary, crossing symmetric and supersymmetric graviton scattering amplitudes in ten dimensions. We focus on the leading Wilson coefficient a controlling the leading correction to maximal supergravity ...

AMER PHYSICAL SOC2021

Hamiltonian truncation in Anti-de Sitter spacetime

João Miguel Augusto Penedones Fernandes, Marco Meineri, Kamran Salehi Vaziri, Matthijs Jan Hogervorst

Quantum Field Theories (QFTs) in Anti-de Sitter (AdS) spacetime are often strongly coupled when the radius of AdS is large, and few methods are available to study them. In this work, we develop a Hamiltonian truncation method to compute the energy spectrum ...

Springer Nature2021

Towards bootstrapping RG flows: sine-Gordon in AdS

João Miguel Augusto Penedones Fernandes

The boundary correlation functions for a Quantum Field Theory (QFT) in an Anti-de Sitter (AdS) background can stay conformally covariant even if the bulk theory undergoes a renormalization group (RG) flow. Studying such correlation functions with the numer ...

Springer Nature2021

Applications of dispersive sum rules: epsilon-expansion and holography

João Miguel Augusto Penedones Fernandes, João Pedro Alves Da Silva, Din Carmi, Alexander Zhiboedov

We use Mellin space dispersion relations together with Polyakov conditions to derive a family of sum rules for Conformal Field Theories (CFTs). The defining property of these sum rules is suppression of the contribution of the double twist operators. First ...

SCIPOST FOUNDATION2021

A scattering amplitude in Conformal Field Theory

Marc Gillioz, João Miguel Augusto Penedones Fernandes, Marco Meineri

We define form factors and scattering amplitudes in Conformal Field Theory as the coefficient of the singularity of the Fourier transform of time-ordered correlation functions, as p(2) -> 0. In particular, we study a form factor F(s, t, u) obtained from a ...

Springer Nature2020