I will speak about my work with Zechuan Zheng on the numerical bootstrap method for large N matrix models and lattice Yang-Mills theory. First I will demonstrate the method on analytically solvable one matrix model and an "unsolvable" two-matrix model, where this approach appears to be superior in efficiency over Monte Carlo. Then I explain how to study by this method the SU(Nc) lattice...
Excited state contamination is one of the most challenging sources of systematics to tackle in the determination of nucleon matrix elements and form factors. The signal-to-noise problem prevents one from considering large source-sink time separations. Instead, state-of-the-art analyses consider multi-state fits. Excited state contributions to the correlation functions are particularly...
The low energy contribution to ∆S = 2 transitions beyond the standard model is described by five B-parameters. Lattice results from different research teams, as reviewed by FLAG, show tension between two of these parameters. After reviewing this situation, we describe an alternative proposal for a completely non-perturbative determination of these quantities, based on SF and $\chi$-SF ...
$𝑉_{𝑢𝑏}$ is the smallest and least known of all CKM matrix elements; it's currently determined primarily through the exclusive process $B \to \pi \ell \bar{\nu}$, and additional channels to determine it are welcomed by the community. I will present progress toward a lattice QCD determination of the $𝑉_{𝑢𝑏}$ matrix from the $B \to \pi \pi \ell \bar{\nu}$ process, where the $\pi\pi$ system is...
The tension between the inclusive and exclusive determinations of |Vxb| (x=c or u) persists more than 10 years. I discuss what is needed to solve the problem including possible lattice calculation of the inclusive decay rate.
Simulations of lattice QCD have emerged as the most reliable tool for making predictions of the low energy properties of hadrons and of quarks and gluons composing them with control over all systematic uncertainties. In this review, I will cover the status of the calculations of quantities that are needed in the analysis of neutrinos off nuclear targets. These include the axial charge and the...
After a brief introduction, I present the status of hadronic vacuum polarization (HVP) and light-by-light (HLbL) contributions to the muon anomalous magnetic moment. The focus will be on the most important piece, the connected light quark HVP, but all contributions will be covered. Comparisons with experiment and data-driven theory are also addressed.
The decreasing uncertainties in theoretical predictions and experimental measurements of several hadronic observables related to weak processes, which in many cases are now smaller than O(1%), require theoretical calculations to include subleading corrections that were neglected so far. Precise determinations of weak decay rates, including QED and strong isospin-breaking effects, can play a...
Lattice QCD determinations of hadronic matrix elements required for precision tests of the Standard Model are now approaching an accuracy where the electromagnetic interactions of the quarks can no longer be neglected. In particular, the electric charge of the sea quarks cannot be ignored a priori without introducing an uncontrolled systematic uncertainty. In this talk I will outline the...
Determination of the CKM matrix elements |Vcb| and |Vub| reached the stage that full lattice QCD calculations are available to compare with the experimental data including their kinematical distributions. I briefly summarize the situation and discuss the remaining problems to be understood/solved. That include $b \to c$, $b \to u$ as well as $b \to s$
decays such as $B \to K \ell \ell$.
We discuss how to perform interpolations between relativistic and static computations in order to extract heavy-light B-physics observables in the continuum.
This strategy can be carried out entirely in large volume, but its predictivity is enhanced by the following step scaling approach.
Relativistic computations are carried out at the physical b-quark mass using the Schrödinger...
The observed baryon asymmetry in the universe cannot be reconciled with the current form of the Standard Model (SM) of particle physics. The amount of CP-violation stemming from the Cabibbo-Kobayashi-Maskawa matrix is not sufficient to explain the observed matter-antimatter asymmetry. Historically, one of the initial systems investigated in the search for discrete symmetries violations was the...
We present preliminary results for the $K^*(892)$ and $\rho(770)$ resonances extracted from lattice QCD data using Lüscher's finite-volume formalism. We review the theory and techniques involved in our computation of correlation functions and extraction of energy levels from an RBC-UKQCD $N_f=2+1$ domain-wall fermion lattice with a physical pion mass. We consider lattice irreducible...
In this talk we describe two frameworks for computing spectral densities from lattice correlators: Bayesian and Backus-Gilbert methods. We show that despite being built upon very different assumptions, they share many similarities. The resulting analogy can be exploited to improve aspects of the computation. We also show how smeared spectral densities can be used to compute hadronic masses.
When designing lattice actions, gauge field smearing is frequently used to define the lattice Dirac operator. One wants to avoid the situation when too much smearing leads to uncontrolled continuum extrapolations as the short distance behaviour of the lattice theory is modified. We focus on the gradient flow formalism as it allows to study both smearing and physical flow. We investigate the...
A strong fermion sign problem prohibits direct lattice simulations of QCD at finite baryon density, so that knowledge of the phase diagram is limited to small chemical potentials. On the other hand, the phase diagram is severely constrained by information on the chiral limit. I discuss recent lattice results at vanishing density, which show the chiral phase transition for Nf=2-7 degenerate...
Critical points are categorized based on the number of relevant variables. The standard critical point in systems like the Ising model involves two relevant variables, namely temperature and external magnetic field. On the other hand, a tricritical point is characterized by four such variables. The protocritical point, widely known as the Yang-Lee edge singularity (YLE), is the simplest form...
I describe some recent mathematical developments in the search for optimal methods of extrapolation and analytic continuation, based on ideas from the theory of resurgent asymptotics. I will illustrate some of the ideas with applications to examples in quantum field theory. The underlying goal is to be able to quantify errors precisely, and to devise flexible numerical schemes.
Understanding phase transitions from limited data generated from finite volume simulations is one of the important challenges one faces today. Analysis of Lee Yang zeros in finite volumes has recently re-emerged as a promising tool in addressing this challenge. In this talk we will see two methods of extracting these zeros from lattice simulations of QCD, the Ising model and O(N) theories. The...
While approximations of trivializing field transformations for lattice path integrals were considered already by early practitioners, more recent efforts aimed at ergodicity restoration and thermodynamic integration formulate trivialization as a variational generative modeling problem. This enables the application of modern machine learning algorithms for optimization over expressive...
We present the implementation of inverse renormalization group transformations with the use of machine learning algorithms to generate, in absence of the critical slowing down effect, configurations of increasing lattice size. We conclude by discussing research directions, pertinent to computationally hard problems, which utilize the inverse renormalization group to obtain configurations for...
To understand how well online advertising works (or if it works at all), we design geographically-based randomized experiments in which ads are shown to people in some regions, but not in other regions. The design of these regions, which form the randomizable units of the experiments, can be seen as a process of unsupervised learning about the underlying geographical structure of a country,...
[Slides available on request]
I discuss some trends, topics, open issues around Analytics, Privacy, Reliable AI with some potential business applications, e.g. in Anti Money Laundering.
To study QCD resonances within lattice QCD one needs as a first step correlation functions computed from a large basis of single- and multi-hadron interpolators. A particularly efficient method to compute these correlation functions is distillation. In this talk, I am presenting the state of the art of the distillation technique and will also cover recent new developments. As an outlook for...
In this talk we give an overview of the open source C++ package Hadrons, which is a Grid-based workflow management system for lattice field theory simulations. Hadrons utilises the dataflow programming paradigm to break potentially large calculations into a series of composable elementary modules (e.g. Dirac operator inversions, contractions, IO, etc.). This gives the user the flexibility to...
The $D$ and $D_s$ decay constants are important inputs
for the determination of the CKM matrix elements $V_{cd}$ and $V_{cs}$
and precision tests of the Standard Model. With lattice determinations
of these quantities reaching the sub-percent level, it is important
to demonstrate control over all sources of systematic uncertainty, and
in particular, those arising from disretisation effects...
The symmetries of a conformal system are sometimes enough to determine correlators without knowing the microscopic details of a theory. The analytic conformal bootstrap provides a consistent roadmap for this approach. This poster will go through this process and apply it to the case of defect correlators in holographic theories. In the case of the 1/2 BPS-Wilson-line defect theory, the...
We are improving one of the available lattice software packages HiRep by crucially adding GPU acceleration. This development is accompanied by an overall software quality improvement in the build system, testing, and documentation, adding features for both CPUs and GPUs. The software is available under https://github.com/claudiopica/HiRep in the branch HiRep-CUDA and will soon be merged into master.
We discuss the phase diagram of QCD and in particular the vicinity of the Roberge-Weiss transition, the chiral transition and the QCD critical end point. We argue that the universal location of the Lee-Yang edge singularity can be used to determine the exact locations of these transitions. In order to calculate the Lee-Yang edge from lattice QCD data we discuss two methods, which includes the...
The axial charge of the nucleon, $g_A$, has been computed extensively on the lattice. However, the axial charges for other octet baryons (hyperons) such as the $\Sigma$ and $\Xi$ baryons are less well known experimentally and theoretically. Here we present results for the isovector axial, scalar and tensor charges, as well as for the second Mellin moments of isovector PDFs. The scalar charges...
Workflow management has become an important topic in many research communities. Here, we focus on the particular aspect of provenance tracking. We follow the W3C PROV standard and formulate a provenance model for Lattice QCD that includes the ensemble-generation and the measurement parts of the Lattice QCD workflow. Since many important provenance questions in our community require extensions...
The ``Sphaleron Rate'' (imaginary linear-in-frequency part of the topological density retarded Green's function) determines the real-time relaxation rate of axial quark number for light quarks in a hot medium, and is relevant in heavy-ion collisions and electroweak baryogenesis. We recently showed how it can be determined in pure-glue QCD via standard Euclidean simulations, via a novel...
