Triangle Seminars

Abstract:
Machine learning is transforming the way many many aspect of particle physics research is pursued. In this talk I will show a few different ways in which neural networks can be leveraged to make theoretical calculations more efficient and allow it to leverage the newest hardware and software developments.

Abstract:
The development in quantum technologies is matched by an equal energetic activity in formulations of quantum field theories, especially as quantum many-body Hamiltonians, suitable for implementation in quantum simulation and computers. In this talk, we discuss the quantum link formulation of lattice gauge theories, which has not only enabled successful synergy between particle and condensed matter physics, but have also pointed towards the existence of quantum scars which violate the eigenstate thermalization hypothesis and resist thermalization under unitary dynamics. Abelian quantum link models have also been implemented in quantum simulators and computers.

Abstract:
The 1+1-dimensional adjoint QCD theory (namely SU(N) gauge theory coupled to a Majorana fermion in the adjoint representation of the gauge group) has the curious property that at a certain non-zero ratio of the fermion mass to the gauge coupling, it exhibits (1, 1) supersymmetry. I will shed some new light onto the supersymmetry of 2d adjoint QCD using several analytical and numerical methods, including the construction of a gauge-invariant, Lorentz-covariant supercurrent, whose conservation relies on the presence of a quantum anomaly. Lastly, I will discuss generalizations of the adjoint QCD theory that exhibit supersymmetric sectors.

Abstract:
I will discuss precision holography for the non-conformal SYM theories arising on the worldvolume of coincident Dp-branes. I will show how the free energy of the planar SYM theory on the round sphere and the expectation values of fundamental BPS Wilson loops can be computed explicitly by utilizing supersymmetric localization. I will then present a class of supergravity backgrounds that capture the backreaction of spherical Dp-branes and provide a holographic description of the SYM theory. I will show that the supergravity calculations of the free energy and the Wilson loop expectation value are in precise agreement with the supersymmetric localization results. Finally, I will exploit the scaling similarity property of the Dp-brane supergravity solutions to derive simple Witten diagram rules for the calculation of n-point correlation functions and will show how to explicitly compute 2pt- and 3pt-functions. This leads to explicit results of the 2pt- and 3pt-functions of scalar BPS operators in the planar strongly-coupled SYM theory, including the cases of the BFSS model and the 3d maximally supersymmetric YM theory, that could be tested using lattice QFT methods.

Abstract:
Symmetry is a powerful organizing principle, allowing for all-order predictions about the behaviour of quantum systems. In this talk I explain how (generalized) symmetries act on boundary conditions and defects, and use these ideas to constrain fundamental properties of (1+1)d scattering amplitudes, such as crossing symmetry, and screening of UV defects by bulk degrees of freedom.

Abstract:
Gravity is derived from an entropic action coupling matter fields with geometry called Gravity from Entropy action [1]. The fundamental idea is to relate the metric of Lorentzian spacetime to a quantum operator, playing the role of a renormalizable effective density matrix and to describe the matter fields topologically, according to a Dirac-Kähler formalism, as the direct sum of a 0-form, a 1-form and a 2-form. While the geometry of spacetime is defined by its metric, the matter fields can be used to define an alternative metric, the metric induced by the matter fields and curvature. The proposed Gravity from Entropy (GfE) action is associated to a Lagrangian given by a novel geometric quantum relative entropy (GQRE) between the metric of spacetime and the metric induced by the matter fields and curvature which capture the entanglement between geometric degrees of freedom of spacetime. The modified Einstein equations obtained from this action reduce to the Einstein equations with zero cosmological constant in the regime of low coupling. By introducing the G-field, which acts as a set of Lagrangian multipliers, and interpreting it a physical and measurable field, the proposed entropic action reduces to a dressed Einstein-Hilbert action with an emergent positive cosmological constant only dependent on the G-field. The obtained equations of modified gravity remain second order in the metric and in the G-field. Interestingly the GfE action when calculated on Schwarzschild metric allows us to derive from first principles the area law for black holes with large Schwarzschild radius [2]. A canonical quantization of this field theory could bring new insights into quantum gravity while further research might clarify the role that the G-field could have for dark matter.

[1] Bianconi, G., 2025. Gravity from entropy. Physical Review D, 111(6), p.066001.
[2] Bianconi, G., 2025. The quantum relative entropy of the Schwarzschild black hole and the area law. Entropy, 27(3), p.266.

Abstract:
In the later part of his life, Grothendieck became fascinated by the fact that certain simple graphs can encode holomorphic maps to the sphere. He called them dessins d’enfants — “children’s drawings.”
Meanwhile, over fifty years ago, ’t Hooft observed that the 1/N expansion in gauge theory closely mirrors the genus expansion in string theory, suggesting a relation between Feynman diagrams and string worldsheets.
I will discuss how recent efforts to derive the AdS/CFT correspondence unite these two perspectives: Grothendieck’s surprise emerges as the simplest instance of gauge/string duality.

Abstract:
We study the dynamics and phase structure of Abelian gauge theories in d=1+1 dimensions. These include U(1) gauge theory coupled to a scalar and a fermion, as well as the two-flavour Schwinger model with different charges. Both theories exhibit a surprisingly rich phase diagram as masses are varied, with both c=1 and c=1/2 critical lines or points. We build up to the study of 2d chiral gauge theories, which hold particular interest because they provide a mechanism for symmetric mass generation, a phenomenon in which fermions become gapped without breaking chiral symmetries.