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João Miguel Augusto Penedones Fernandes

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Related publications (32)

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Flux Tube S-Matrix Bootstrap

João Miguel Augusto Penedones Fernandes, Aditya Hebbar

We bootstrap the S matrix of massless particles in unitary, relativistic two dimensional quantum field theories. We find that the low energy expansion of such S matrices is strongly constrained by the existence of a UV completion. In the context of flux tu ...

2019

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

A structural test for the conformal invariance of the critical 3d Ising model

João Miguel Augusto Penedones Fernandes, Pierre Mathieu Yvernay

How can a renormalization group fixed point be scale invariant without being conformal? Polchinski (1988) showed that this may happen if the theory contains a virial current a non-conserved vector operator of dimension exactly (d - 1), whose divergence exp ...

Springer Nature2019

The S-matrix bootstrap. Part III: higher dimensional amplitudes

João Miguel Augusto Penedones Fernandes, Jonathan Campbell Toledo

We consider constraints on the S-matrix of any gapped, Lorentz invariant quantum field theory in 3+1 dimensions due to crossing symmetry, analyticity and unitarity. We extremize cubic couplings, quartic couplings and scattering lengths relevant for the ela ...

Springer Nature2019

Colliders and conformal interfaces

João Miguel Augusto Penedones Fernandes, Marco Meineri

We set up a scattering experiment of matter against an impurity which separates two generic one-dimensional critical quantum systems. We compute the flux of reflected and transmitted energy, thus defining a precise measure of the transparency of the interf ...

Springer Nature2020

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

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

Bootstrapping massive quantum field theories

João Miguel Augusto Penedones Fernandes, Denis Karateev

We propose a new non-perturbative method for studying UV complete unitary quantum field theories (QFTs) with a mass gap in general number of spacetime dimensions. The method relies on unitarity formulated as positive semi-definiteness of the matrix of inne ...

Springer Nature2020

Bootstrapping QCD Using Pion Scattering Amplitudes

João Miguel Augusto Penedones Fernandes

We consider the S-matrix bootstrap of four-dimensional scattering amplitudes with O(3) symmetry and no bound states. We explore the allowed space of scattering lengths which parametrize the interaction strength at threshold of the various scattering channe ...

2019

Bootstrapping the a-anomaly in 4d QFTs

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

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

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

Bounds on photon scattering

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

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

Polarised black holes in ABJM

João Miguel Augusto Penedones Fernandes

We numerically construct asymptotically AdS(4) solutions to Einstein-Maxwell-dilaton theory. These have a dipolar electrostatic potential turned on at the conformal boundary S-2 x R-t. We find two classes of geometries: AdS soliton solutions that encode th ...

Springer Nature2017

Injecting the UV into the bootstrap: Ising Field Theory

João Miguel Augusto Penedones Fernandes, Miguel Alexandre Ribeiro Correia, Antoine Vuignier

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

Numerical tests of the large charge expansion

José Guilherme Boura De Matos, 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

The S-matrix bootstrap IV: multiple amplitudes

João Miguel Augusto Penedones Fernandes, Jonathan Campbell Toledo

We explore the space of consistent three-particle couplings in Z(2)-symmetric two-dimensional QFTs using two first-principles approaches. Our first approach relies solely on unitarity, analyticity and crossing symmetry of the two-to-two scattering amplitud ...

Springer Nature2019

Gravity from quantum mechanics of finite matrices

Noé Pierrot Suchel, Adrien Philippe Martina, João Miguel Augusto Penedones Fernandes, Antoine Vuignier, Xiang Zhao

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

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

Charting the space of 3D CFTs with a continuous global symmetry

João Miguel Augusto Penedones Fernandes, Alessandro Vichi

We study correlation functions of a conserved spin-1 current J in three dimensional Conformal Field Theories (CFTs). We investigate the constraints imposed by permutation symmetry and current conservation on the form of three point functions and the four p ...

Springer Nature2019

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