Selected Publications

We investigate four-dimensional near-conformal dynamics by means of the large-charge limit. We first introduce and justify the formalism in which near-conformal invariance is insured by adding a dilaton and then determine the large-charge spectrum of the theory. The dilaton can also be viewed as the radial mode of the EFT. We calculate the two-point functions of charged operators. We discover that the mass of the dilaton, parametrising the near-breaking of conformal invariance, induces a novel term that is logarithmic in the charge. One can therefore employ the large-charge limit to explore near-conformal dynamics and determine dilaton-related properties.

We study the $O(4)$ Wilson–Fisher fixed point in $2+1$ dimensions in fixed large-charge sectors identified by products of two spin-$j$ representations $(j_L,j_R)$. Using effective field theory we derive a formula for the conformal dimensions $D(j_L, j_R)$ of the leading operator in terms of two constants, $c_{ 3 / 2}$ and $c_{ 1 / 2}$, when the sum $j_L + j_R$ is much larger than the difference $|j_L-j_R|$. We compute $D(j_L,j_R)$ when $j_L= j_R$ with Monte Carlo calculations in a discrete formulation of the $O(4)$ lattice field theory, and show excellent agreement with the predicted formula and estimate $c_{ 3 / 2}=1.068(4)$ and $c_{ 1 / 2}=0.083(3)$.
in PRL, 2019

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

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

More Publications

. Near-Conformal Dynamics at Large Charge. 2019.


. Large charge at large N. 2019.


. O(d,d) transformations preserve classical integrability. 2019.


. A safe CFT at large charge. in JHEP, 2019.


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


. SUSY and the bi-vector. In Phys.Scripta, 2018.


Selected Talks

We apply the large-charge expansion to O(N) vector models starting from first principles. We focus on the Wilson–Fisher point in three dimensions. We compute conformal dimensions and energies on generic Riemann surfaces at zero and finite temperature, at fixed charge Q in the regime 1 ≪ N ≪ Q. Our approach places the earlier effective field theory treatment on firm ground and extends its predictions.

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.

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.

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

More Talks

A large charge to tame strong coupling
Tue, 8 Oct, 2019
Large charge at large N
Tue, 27 Aug, 2019
Large charge: advanced applications
Tue, 2 Jul, 2019
Compensating strong coupling with large charge
Thu, 17 Jan, 2019
The unreasonable effectiveness of the large charge expansion
Tue, 16 Jan, 2018