Selected Publications

A safe CFT at large charge

We apply the large-charge limit to the first known example of a four-dimensional gauge-Yukawa theory featuring an ultraviolet interacting fixed point in all couplings. We determine the energy of the ground state in presence of large fixed global charges and deduce the global symmetry breaking pattern. We show that the fermions decouple at low energy leaving behind a confining Yang–Mills theory and a characteristic spectrum of type I (relativistic) and type II (non-relativistic) Goldstone bosons. Armed with the knowledge acquired above we finally arrive at establishing the conformal dimensions of the theory as a triple expansion in the large-charge, the number of flavors and the controllably small inverse gauge coupling constant at the UV fixed point. Our results unveil a number of noteworthy properties of the low-energy spectrum, vacuum energy and conformal properties of the theory. They also allow us to derive a new consistency condition for the relative sizes of the couplings at the fixed point.
2019

Conformal dimensions via large charge expansion

We construct an efficient Monte Carlo algorithm that overcomes the severe signal-to-noise ratio problems and helps us to accurately compute the conformal dimensions of large-$Q$ fields at the Wilson-Fisher fixed point in the $O(2)$ universality class. Using it we verify a recent proposal that conformal dimensions of strongly coupled conformal field theories with a global $U(1)$ charge can be obtained via a series expansion in the inverse charge $1/Q$. We find that the conformal dimensions of the lowest operator with a fixed charge $Q$ are almost entirely determined by the first few terms in the series.
in PRL, 2017

Generalized type IIB supergravity equations and non-Abelian classical r-matrices

We study some examples of Yang-Baxter deformations of the $AdS_5 \times S^5$ superstring with non-Abelian classical $r$-matrices which satisfy the homogeneous classical Yang-Baxter equation (CYBE). All of the resulting backgrounds satisfy the generalized type IIB supergravity equations. For some of them, we derive “T-dualized” backgrounds and show that these satisfy the usual type IIB supergravity equations. Remarkably, some of them are locally identical to undeformed $AdS_5 \times S^5$.
Journal of Physics A Highlight, 2016

On the CFT Operator Spectrum at Large Global Charge

We calculate the anomalous dimensions of operators with large global charge $J$ in certain strongly coupled conformal field theories in three dimensions, such as the $O(2)$ model and the supersymmetric fixed point with a single chiral superfield and a $W = \Phi^3$ superpotential. Working in a $1/J$ expansion, we find that the large-$J$ sector of both examples is controlled by a conformally invariant effective Lagrangian for a Goldstone boson of the global symmetry. For both these theories, we find that the lowest state with charge $J$ is always a scalar operator whose dimension is $\Delta(J) = a J^{3 / 2} + b J^{1 / 2} - 0.093$, up to corrections that vanish at large $J$.
In JHEP, 2015

Recent Publications

. A safe CFT at large charge. 2019.

. Conformal dimensions in the large charge sectors at the $O(4)$ Wilson-Fisher fixed point. 2019.

. SUSY and the bi-vector. 2018.

. The large-charge expansion for Schrödinger systems. In JHEP, 2018.

. Killing spinors from classical r-matrices. in J.Phys.A, 2018.

. An AdS/EFT correspondence at large charge. in Nucl.Phys. B, 2018.

Selected Talks

I will discuss some advanced applications of the large charge expansion for systems with special properties. I will show how to prove some of the general conjectures for the vector models in the limit of large N and show how to completely resum the large-charge perturbative expansion for (non-Lagrangian) N=2 supersymmetric theories in four dimensions.

The unreasonable effectiveness of effective field theory

We compute conformal dimensions and other physical quantities for strongly coupled conformal field theories in three dimensions with global symmetries. We show how in sectors of large global charge $Q$, the charge acts as a controlling parameter and physical quantities can be explicitly computed in a $1/Q$ perturbative expansion. In the case of the $O(2)$ model we show how the predictions of this approach are in very good agreement with lattice measurements.

Boundaries, Lattices and the Gravitational Anomaly

I discuss a general proof of the following two facts regarding two-dimensional local quantum field theories with non-vanishing gravitational anomaly: 1. these theories do not admit a lattice regularization (this generalizes the renowned Nielsen-Ninomiya theorem); 2. their Hilbert space does not factorize into Hilbert spaces in complementary regions. Fact 2 implies in particular that, in the presence of a non-vanishing gravitational anomaly, the usual definitions of quantum entanglement break down.

Recent & Upcoming Talks

Tue, 2 Jul, 2019
Thu, 23 May, 2019
Compensating strong coupling with large charge
Thu, 17 Jan, 2019
The unreasonable effectiveness of the large charge expansion
Tue, 16 Jan, 2018
The unreasonable effectiveness of the large charge expansion
Fri, 5 Jan, 2018
Deformations, defects and a noncommutative spectral curve
Tue, 5 Sep, 2017