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Role of Atomic Structure Calculations: From Fundamental Physics to Technological Advancements
Bindiya Arora Guru Nanak Dev University
Bound state corrections and high-energy scattering
Ryan Plestid California Institute of Technology (Caltech)
Extending phase spaces at null infinity with the Stueckelberg's trick
Javier Peraza Universidad de la Republica Uruguay
The speed of sound in the EFTofLSS
Caio Bastos de Senna Nascimento University of Washington
Lecture - Relativity, PHYS 604
Ghazal Geshnizjani Perimeter Institute for Theoretical Physics
Lecture - QFT II, PHYS 603
Francois David CEA Saclay
Surface Operators and Exact Holography
Raquel Izquierdo Garcia Perimeter Institute for Theoretical Physics
Symmetric Polynomials of the Weights of a Lie Group Representation
Steven SpalloneICTS:30482Let G be a nice (connected reductive) Lie group. An irreducible representation of G, when restricted to a maximal torus, decomposes into weights with multiplicity. We outline a procedure to compute symmetric polynomials (e.g., power sums) of this multiset of weights in terms of the highest weight. This is joint work with Rohit Joshi.
Conjugacy growth in groups (Online)
Gemma CroweICTS:30484Similar to standard growth of (finitely generated) groups, one can define conjugacy growth of groups which, informally, counts the number of conjugacy classes in a ball of radius n in a Cayley graph. This was first studied by Riven for free groups, and techniques from geometry, combinatorics and formal language theory have proven to be useful for determining information about the conjugacy growth series for a variety of groups.
This talk will provide a survey on the key tools and results about conjugacy growth. Time permitting, I’ll also discuss joint work with Laura Ciobanu, where we studied conjugacy growth in dihedral Artin groups.Role of Atomic Structure Calculations: From Fundamental Physics to Technological Advancements
Bindiya Arora Guru Nanak Dev University
Atomic structure calculations are critical for advancing fundamental physics and driving technological innovation. They provide essential data for experimental design and interpretation, especially when direct measurements are challenging. These calculations are pivotal in areas such as quantum computing, atomic clocks, quantum sensors, and cold atom physics, as well as in fundamental research, including parity non-conservation, dark matter searches, and gravitational wave detection. This presentation will explore how precise atomic property calculations propel both technological advancements and our understanding of nature. I will discuss: Our research group’s contributions to high-precision atomic property calculations for technological developments in cold atom physics, atomic clocks, and other applications. Recent work addressing challenges in atomic structure theory, including basis sets, spurious states, and modeling properties of Rydberg atoms for quantum computing. The design and underlying concepts of the atomic cyberinfrastructure under development in our group.How to learn Pauli noise over a gate set
Senrui ChenUnderstanding quantum noise is an essential step towards building practical quantum information processing systems. Pauli noise is a useful model widely applied in quantum benchmarking, quantum error mitigation, and quantum error correction. Despite previous research, the problem of how to learn a Pauli noise model self-consistently, completely, and efficiently has remained open. In this talk, I will introduce a framework of gate-set Pauli noise learning that aims at addressing this problem. The framework treats initialization, measurement, and a set of quantum gates to suffer from unknown Pauli noise channels, which are allowed to have customized locality constraints. The goal is to learn all the Pauli noise channels using only those noisy operations. I will first introduce a theory on the “learnability” of Pauli noise model, i.e., what information is fundamentally identifiable within the model and what is not. This is established using tools from algebraic graph theory and ideas from gate set tomography; I will then discuss a sample-efficient procedure to learn all learnable information of a Paul noise model to any desired precision; Finally, I will demonstrate how to apply our theoretic framework for concrete practical gate set and noise assumptions, and discuss the potential impact on quantum error mitigation and other applications.
Zeta Functions and applications to twisted conjugacy
Paula LinsICTS:30478In this talk, I will discuss zeta functions that count the number of twisted conjugacy classes of a fixed group.
Twisted conjugacy is a generalisation of the usual conjugacy, where we introduce a twist by an endomorphism. Specifically, given a group G and an automorphism f, we consider the action gx = gx f(g)^{-1}. The orbits of this action are known as twisted conjugacy classes, or Reidemeister classes.
Recent years have seen intensive investigation into the sizes of these classes. A major goal in this area is to classify groups where all classes are infinite. For groups that do not possess this property, the focus shifts to understanding the possible sizes of the classes, among all automorphisms.
In this talk, we will see that, as typical, these zeta functions admit Euler product decompositions with rational local factors, and we will explore how these zeta functions can be utilised to understand twisted conjugacy classes of certain nilpotent groups.
Bound state corrections and high-energy scattering
Ryan Plestid California Institute of Technology (Caltech)
Many fundamental-physics experiments scatter high energy beams off of fixed targets composed of ordinary matter i.e., atoms. When considering the scattering off of atomic electrons we often make the approximation that the electron is free and at rest, however one can ask how good this approximation really is? This becomes especially important in the face of demanding precision goals of certain experiments. For example the planned MuonE experiment will attempt to measure the shape of $\mu e \rightarrow \mu e$ scattering as a function of angle with a precision of 10 ppm. In this talk I will explain how to systematically include bound-state corrections arising from the difference between a free-and-at-rest electron and those bound in atomic orbitals. When the final state of the atom is not measured, a surprisingly simple and elegant formula can be obtained that reduces the leading order corrections to a single atomic matrix element. New developments related to Coulomb corrections for inelastic systems will also be discussed. Based on (arXiv:2403.12184, 2407.21752).
Extending phase spaces at null infinity with the Stueckelberg's trick
Javier Peraza Universidad de la Republica Uruguay
The study of symmetries at null infinity and their connection with soft theorems via Ward identities has been the subject of intense research over the past decade. The organization of the symmetries in a clear - geometric - structure that reflects the subleading infrared effects has led to numerous interesting results, in particular the emergence of the Lw_{1+\infty} algebra of symmetries for gravity. In this talk I will review recent results on an adaptation of Stueckelberg's procedure to extend phase spaces at null infinity, by which gauge symmetry generators are promoted to dynamical degrees of freedom, containing the so-called edge modes. This formalization allows us to obtain charges corresponding to the subleading soft theorems at all orders, and to construct a hierarchy of closed subalgebras that satisfy simple recursion relations. I will show the example of this construction in Yang-Mills theory, and comment on the charge algebra obtained. Finally, I will discuss the application of this construction to gravity, as well as some preliminary results and future directions.
The speed of sound in the EFTofLSS
Caio Bastos de Senna Nascimento University of Washington
The Effective Field Theory of Large Scale Structure (EFTofLSS) has found tremendous success as a perturbative framework for the evolution of large scale structure, and it is now routinely used to compare theoretical predictions against cosmological observations. The model for the total matter field includes one nuisance parameter at 1-loop order, the effective sound speed, which can be extracted by matching the EFT to full N-body simulations. In this talk we explore two different directions related to the effective sound speed. We first show that its emergence can be understood even without effective field theory ingredients, through a perturbative framework that solves the Vlasov-Poisson system of equations directly in phase space. However, we will argue that the EFT is necessary to ensure self-consistency. We then discuss how one can estimate the effective sound speed, via separate universe techniques, with analytic calculations. The estimate is in good agreement with simulation results, and we show it can be used to extract the cosmology dependence of the effective sound speed and to shed light on what cosmic structures shape its value.
Lecture - QFT II, PHYS 603
Francois David CEA Saclay
A construction of irreducible representations of GL_3(O)
Pooja SinglaICTS:30474Let F be a non-Archimedean local field F with ring of integers O and a finite residue field k of characteristic greater than three. While the representations of finite groups of Lie type GL_n(k) and of the p-adic groups GL_n(F) are well studied, the representations of GL_n(O) remain far less understood.
In this talk, we will explore the challenges involved in constructing the complex irreducible representations of GL_n(O), highlighting key differences from the case of GL_n(k). We will then present a method for constructing irreducible representations of GL_3(O). This is based on a recent joint work with Uri Onn and Amritanshu Prasad.
Surface Operators and Exact Holography
Raquel Izquierdo Garcia Perimeter Institute for Theoretical Physics
Non-local operators, supported on submanifolds of spacetime, often encode fascinating physical insights about a theory and can serve as order parameters for phase transitions. In this talk, we will explore various aspects of 1/2 BPS surface operators in N=4 super Yang-Mills. Specifically, I will show how supergravity computes exactly the planar limit of certain correlation functions of surface operators, even though they receive nontrivial quantum corrections. In particular, we will compute correlation functions with Chiral Primary Operators by localizing N = 4 super Yang-Mills on S^4 to a deformed version of 2d Yang-Mills on S^2. These correlation functions, which have a finite number of quantum corrections, can also be computed perturbatively in four dimensions. I will show the exact agreement between these approaches and the corresponding supergravity result. This talk is based on 2406.08541, work in collaboration with Changha Choi and Jaume Gomis.