Scientific Series

In this talk, I will show that supergravity on asymptotically flat spaces possesses a (nonlinear) asymptotic symmetry algebra, containing an infinite number of fermionic generators. Starting from the Hamiltonian action for supergravity with suitable boundary conditions on the graviton and gravitino fields, I will derive a graded extension of the BMS_4 algebra at spatial infinity, denoted by SBMS_4. These boundary conditions are not only invariant under the SBMS_4 algebra, but lead to a fully consistent canonical description of the supersymmetries, which have well-defined Hamiltonian generators. One finds, in particular, that the graded brackets between the fermionic generators yield BMS supertranslations, of which they provide therefore “square roots”.  I will comment on some key aspects of extending the asymptotic analysis at spatial infinity to fermions and on the structure of the SBMS_4 algebra in terms of Lorentz representations.

Zoom link: https://pitp.zoom.us/j/95951230095?pwd=eHIwUXB5SUkvd0IvZnVUN3JJMFE1QT09

As a recent combination of two strong global leaders in quantum computing, Honeywell Quantum Solutions and Cambridge Quantum, Quantinuum integrates quantum hardware and software, including solutions for drug discovery, materials science, finance, and other applications. Quantinuum aims to be a center of gravity for quantum computing, supporting collaboration across the ecosystem. For this we have also developed “TKET”, an open-source architecture-agnostic quantum software stack and ‘best in class’ compiler. This enables our partners, collaborators and clients to effortlessly work across multiple platforms and tackle some of the most intriguing and important problems in quantum computing. 

Bio: Dr. Mark Jackson is the Senior Quantum Evangelist at Quantinuum. He received his B.S. in Physics and Mathematics from Duke University and Ph.D. in Theoretical Physics from Columbia University. He then spent 10 years researching superstring theory and cosmology, co-authoring almost 40 technical articles. To promote the public understanding of science, he founded the science crowdfunding platform Fiat Physica and non-profit Science Partnership Fund. He is Adjunct Faculty at Singularity University and a Director of Astronomers Without Borders.

Zoom link: https://pitp.zoom.us/j/98433088425?pwd=UzgwcGpUYnBKNzJmMnQ1ZVNOdGVXZz09

The Entanglement Bootstrap is a program to derive the universal properties of a phase of matter from a single representative wavefunction on a topologically-trivial region.  Much (perhaps all) of the structure of topological quantum field theory can be extracted starting from a state satisfying two axioms that implement the area law for entanglement.  This talk will focus on recent progress (with Bowen Shi and Jin-Long Huang) using this approach to prove remote detectability of topological excitations in various dimensions.  This is an axiom of topological field theory.  Two key ideas are a quantum avatar of Kirby's torus trick to construct states on closed manifolds, and the new concept of pairing manifold, which is a closed manifold associated with a pair of conjugate excitation types that encodes their braiding matrix.  The pairing manifold also produces Verlinde formulae relating the S-matrix to the structure constants of a generalized symmetry algebra of flexible operators.  

Zoom link:  https://pitp.zoom.us/j/92633473610?pwd=eEhqR3BaQXljQm5ScHZvZm81N2FyZz09

The elementary CuO2 plane sustaining cuprate high temperature superconductivity occurs typically at the base of a periodic array of edge-sharing CuO5 pyramids. Virtual transitions of electrons between adjacent planar Cu and O atoms, occurring at a rate t/ℏ and across the charge-transfer energy gap E, generate ‘superexchange’ spin-spin interactions of energy J≈4t4/E3 in an antiferromagnetic correlated-insulator state. However, hole doping this CuO2 plane converts this into a very high temperature superconducting state whose electron-pairing is exceptional. A leading proposal for the mechanism of this intense electron-pairing is that, while hole doping destroys magnetic order it preserves pair-forming superexchange interactions governed by the charge-transfer energy scale E.

To explore this hypothesis directly at atomic-scale, we developed high-voltage single-electron and electron-pair (Josephson) scanning tunneling microscopy, to visualize the interplay of E and the electron-pair density nP in Bi2Sr2CaCu2O8+x. Changing the distance δ between each pyramid’s apical O atom and the CuO2 plane below, should alter the energy levels of the planar Cu and O orbitals and thus vary E.  Hence, the responses of both E and nP to alterations in δ that occur naturally in Bi2Sr2CaCu2O8+x were visualized. These data revealed, directly at atomic scale, the crux of strongly correlated superconductivity in CuO2: the response of the electron-pair condensate to varying the charge transfer energy. Strong concurrence between these observations and recent three-band Hubbard model DMFT predictions for superconductivity in hole-doped Bi2Sr2CaCu2O8+x (PNAS 118, e2106476118 (2021)) indicate that charge-transfer superexchange is the electron-pairing mechanism (PNAS 119, 2207449119 (2022)).

Zoom link:  https://pitp.zoom.us/j/95592484157?pwd=YU56Wno3WnBIUTlyaC9VSHJ3cGxZUT09

Tensor network provides a geometric representation of quantum many-body wave functions. Inspired by holography, we discuss a geometric realization of (one-shot) entanglement distillation for tensor networks including the multi-scale entanglement renormalization ansatz and matrix product states. We evaluate the trace distances between the ‘distilled' states and EPR states step by step and see a trend of distillation. If time permits, I will mention a possible field theoretic generalization of this geometric distillation.

Zoom link: https://pitp.zoom.us/j/98545776462?pwd=b1Z3ZENNRWVITlNOZG1GdzJaMmN1Zz09

Can degrees of freedom in the interior of black holes be responsible for the entropy-area law? If yes, what spacetime appears? In this talk, I answer these questions at the semi-classical level. Specifically, a black hole is considered as a bound state consisting of many semi-classical degrees of freedom which exist uniformly inside and have maximum gravity. The distribution of their information determines the interior metric through the semi-classical Einstein equation. Then, the interior is a continuous stacking of AdS_2 times S^2 without horizon or singularity and behaves like a local thermal state. Evaluating the entropy density from thermodynamic relations and integrating it over the interior volume, the area law is obtained with the factor 1/4 for any interior degrees of freedom. Here, the dynamics of gravity plays an essential role in changing the entropy from the volume law to the area law. This should help us clarify the holographic property of black-hole entropy. [arXiv: 2207.14274]

Zoom link: https://pitp.zoom.us/j/99386433635?pwd=VzlLV2U4T1ZOYmRVbG9YVlFIemVVZz09

The modular commutator is a recently discovered multipartite entanglement measure that quantifies the chirality of the underlying many-body quantum state. In this Letter, we derive a universal expression for the modular commutator in conformal field theories in 1+1 dimensions and discuss its salient features. We show that the modular commutator depends only on the chiral central charge and the conformal cross ratio. We test this formula for a gapped (2+1)-dimensional system with a chiral edge, i.e., the quantum Hall state, and observe excellent agreement with numerical simulations. Furthermore, we propose a geometric dual for the modular commutator in certain preferred states of the AdS/CFT correspondence. For these states, we argue that the modular commutator can be obtained from a set of crossing angles between intersecting Ryu-Takayanagi surfaces.

Zoom link:  https://pitp.zoom.us/j/94069836709?pwd=RlA2ZUsxdXlPTlh2TStObHFDNUY0Zz09

The AdS/CFT correspondence is one of the most important breakthroughs of the last decades in theoretical physics. A recently proposed way to get insights on various features of this duality is achieved by discretizing the Anti-de Sitter spacetime. Within this program, we consider the Poincaré disk and we discretize it by introducing a regular hyperbolic tiling on it. The features of this discretization are expected to be identified in the quantum theory living on the boundary of the hyperbolic tiling. In this talk, we discuss how a class of boundary Hamiltonians can be naturally obtained in this discrete geometry via an inflation rule that allows constructing the tiling using concentric layers of tiles. The models in this class are aperiodic spin chains. Using strong-disorder renormalization group techniques, we study the entanglement entropy of these boundary theories, identifying a logarithmic growth in the subsystem size, with a coefficient depending on the bulk discretization parameters.

Zoom link:  https://pitp.zoom.us/j/95849965965?pwd=eEx5Q0gxR2orR0dzS2pQbG8rR09oUT09

Observations indicate the existence of natural particle accelerators in the Milky Way, capable of producing PeV cosmic rays (“PeVatrons”). Observations also indicate the existence of extreme sources in the Milky Way, capable of producing gamma-ray radiations above 100 TeV. If these gamma-ray sources are hadronic cosmic-ray accelerators, then they must also be neutrino sources. However, no neutrino sources have been detected. How can we consistently understand the observations of cosmic rays, gamma rays, and neutrinos? We point out two extreme scenarios are allowed: (1) the hadronic cosmic-ray accelerators and the gamma-ray sources are the same objects, so that neutrino sources exist and improved telescopes can detect them, versus (2) the hadronic cosmic-ray accelerators and the gamma-ray sources are distinct, so that there are no detectable neutrino sources. We discuss the nature of Milky Way’s highest energy gamma-ray sources and outline future prospects toward understanding the origin of hadronic cosmic rays. 

Zoom link:  https://pitp.zoom.us/j/91390039665?pwd=dGJ2b3VCbVFhUVpSelpjYzJHdk1Gdz09

Weak gravitational lensing by the intervening large-scale structure (LSS) of the Universe is the leading non-linear effect on the anisotropies of the cosmic microwave background (CMB). The integrated line-of-sight gravitational potential that causes the distortion can be reconstructed from the lensed temperature and polarization anisotropies via estimators quadratic in the CMB modes. While previous studies have focused on the lensing power spectrum, upcoming experiments will be sensitive to the bispectrum of the lensing field, sourced by the non-linear evolution of structure. The detection of such a signal would provide additional information on late-time cosmological evolution, complementary to the power spectrum.

Zoom link: https://pitp.zoom.us/j/94880169487?pwd=dzRWcVRwQ2dVdWZ3N2RjOWU2RDUyZz09

The Morita 2-category has as objects associative algebras, 1-morphisms are bimodules and 2-morphisms are given by bimodule homomorphisms. Equivalent objects in this category are exactly Morita equivalent algebras. A vast generalisation of this as a higher category is the so-called higher Morita category, denoted Alg_n. It has two constructions, one due to Haugseng, and one due to Scheimbauer which uses (constructible) factorization algebras. In the latter, Gwilliam-Scheimbauer has proven that every object of Alg_n is n-dualizable. Hence, by the Cobordism Hypothesis, every object gives rise to an n-dimensional (fully extended framed) topological field theory. A natural question to ask is “Which objects of Alg_n are also (n+1)-dualizable?”. This talk is on work in progress (for n=2) to prove a conjecture due to Lurie answering this question. 

Zoom link: https://pitp.zoom.us/j/98595913913?pwd=Vlo1aWtXVlZBVjYxNFlTM2VZY2s3Zz09

Massless particles are always assumed to have Lorentz invariant helicity. However, the generic massless particles allowed by Lorentz invariance and quantum mechanics are "continuous spin particles," whose infinitely many discrete helicity states mix under little group transformations by an amount determined by the spin scale. Previous work at the Perimeter Institute has shown that CSPs have well-behaved soft emission amplitudes, are described by a simple free field theory, and reduce to the photon or graviton at momenta above the spin scale. In this talk, I will show how to couple CSP fields to classical particles. When treating on-shell CSP emission and absorption, the resulting dynamics are causal and readily calculable. Remarkably, they are also unique, depending on only the spin scale. This opens the door to precision experiments which probe the spin scale of the photon and graviton.

Zoom Link:  https://pitp.zoom.us/j/94728811371?pwd=Y3RoRnJuUzNzT0FmRVFiazI5czc5Zz09