Thursdays 4:00 p.m. 104 Physics. Colloquium organizer: Dr. Hyunsoo Kim hyunsoo.kim@mst.edu

Link to main colloquium page

**Integrability and action-angle variables of binary black holes at second post-Newtonian order**

Accurate and efficient modeling of binary black holes (BBHs) is crucial for the detection of gravitational waves (GWs) emitted by them. Closed-form solutions to these systems when they are in the initial inspiral phase are highly sought after and have been worked out by many groups in the post-Newtonian (PN) approximation. Most of these worked-out solutions are valid only in certain limits (small eccentricity, no spins, equal mass, etc). Establishing the integrable nature of PN BBHs opens up the possibility of constructing closed-form solutions since integrability precludes chaos and guarantees the existence of action-angle variables. In this talk, against the backdrop of the PN Hamiltonian framework, I will discuss our series of efforts in establishing the integrable nature of the most general BBH system (arbitrary masses, spins, and eccentricity) as per the Liouville-Arnold theorem at 2PN order. I will also discuss our recently derived action-angle-based solution for these systems at 1.5PN order.

Quantum Computing, Quantum Teleportation and Time Crystals

Quantum Computing is parallel computing and is nonlocal in nature. Geometry, physics, and computing are triangularly interrelated. There exist four new fundamental nonlocal operator-state relations for an entangled atomic chain. Computation states are then cyclic. There exists a minimum focus distance for the entanglement between two atoms. Any addition of four times of that focus distance provides the foundation for quantum teleportation in a piece-wise Euclidean chain. Time crystals are the direct computation results that an entangled atomic chain is capable of computing. There are four interacting planar time crystals with the same Poincare cycle, but only half of them are observable as we predict, and quantum computing is irreversible. When the geometry changes, there exist “spherical time crystals” from the rotational symmetry breaking. Thus, we predict that “time” can be “curved” in Fourier space, the space we observe all the computation results. In a long chain, it is possible to have “birth-and-death” of time crystals elsewhere in the chain. Sierpinski triangle with self-similar features provides the foundation for true artificial intelligence and the larger-scale operator-state relations to emerge.

**An introduction to the quantum vacuum**

*One of the most fascinating predictions of quantum field theory is that quantum fluctuations induce nonlinearities in the quantum vacuum. These nonlinearities lead to a number of surprising phenomena: the vacuum behaves like a polarising material, it acts to screen electric charge, and is even unstable to the application of electric fields, "decaying" via the Schwinger pair-creation mechanism.*

* *

*This talk will provide a pedagogical introduction to the quantum vacuum in quantum electrodynamics. I will discuss vacuum polarisation and charge screening in standard QFT, and will then describe the richer structure of the vacuum in the presence of external electromagnetic fields. Finally I will describe some experimental facilities currently under construction that are aiming to probe the nonlinear structure of the vacuum for the first time. Comments and questions will be welcome throughout!*

What carries the current in metals and superconductors?

Assa Auerbach, Technion

The Hall coefficient has long been used to characterize the charge carriers as Fermi surface quasiparticles. However, unexpected Hall coefficient sign reversals and divergences (a.k.a. ``Hall anomalies’’) are commonly observed in strongly correlated metals and flux flowing superconductors. The validity of band theory and Boltzmann equation is called into question.

I will describe recent advances in quantum transport theory which allows us to calculate the Hall coefficients from models of strong interactions, and to identify the “moving parts” which give rise to these Hall anomalies.

Classification of the universal dynamics in two-dimensional strongly ferromagnetic superfluids

Scale invariance and self-similarity in physics provide a unified framework to classify phases of matter and dynamical properties of near- and far-from-equilibrium many-body systems. To address universality, we monitor the non equilibrium dynamics of a two-dimensional ferromagnetic spinor gas subjected to quenches of the quadratic Zeeman coefficient. This allows to dynamically cross the underlying second-order magnetic phase transitions triggering spin-mixing. Within the short time-evolution we observe the spontaneous nucleation of topological defects (gauge or spin vortices) which annihilate through their interaction giving rise to magnetic domains for longer timescales where the gas enters the universal coarsening regime. This is characterized by the spatiotemporal scaling of the spin correlation functions and structure factor allowing to measure corresponding scaling exponents which depend crucially on the symmetry of the order parameter and belong to distinct universality classes. Our experimental observations are in excellent agreement with the predictions of the truncated Wigner method accounting both for quantum and thermal fluctuations in the initial state. These results represent a paradigmatic example of categorizing far-from-equilibrium dynamics in quantum many-body systems and reveal the interplay of topological defects for the emergent universality class.

**An introduction to the quantum vacuum**

*One of the most fascinating predictions of quantum field theory is that quantum fluctuations induce nonlinearities in the quantum vacuum. These nonlinearities lead to a number of surprising phenomena: the vacuum behaves like a polarising material, it acts to screen electric charge, and is even unstable to the application of electric fields, "decaying" via the Schwinger pair-creation mechanism.*

* *

*This talk will provide a pedagogical introduction to the quantum vacuum in quantum electrodynamics. I will discuss vacuum polarisation and charge screening in standard QFT, and will then describe the richer structure of the vacuum in the presence of external electromagnetic fields. Finally I will describe some experimental facilities currently under construction that are aiming to probe the nonlinear structure of the vacuum for the first time. Comments and questions will be welcome throughout!*

**A PHYSICIST’S JOURNEY THROUGH THE EVER-CHANGING WORLD OF HIGH-TECHNOLOGY**

Kul B. Bhasin, PhD, CEO, Comsat Architects, Cleveland, Ohio

A passionate technologist for over four decades, Dr. Kul Bhasin, uncovers how his PhD Physics training at Missouri S&T fueled, and continues to fuel, his achievements in high technology. The academic and cultural environments at M S&T, in retrospect, played a fundamental role in his successful entry into the micro-electronics industry, his illustrious thirty year career at NASA, into entrepreneurship of creating his own space communications company. Successful students who learn to be cognizant of the influences and experiences offered them, can gather, and translate those experiences into their future careers.

Particle Physics in Computing Frontier

Our knowledge of the fundamental particles and their interactions is summarized by the standard model of particle physics. Mathematically, the theory describes these forces and particles as the dynamics of elegant geometric objects. Now advancing our understanding in this field has required experiments that operate at higher energies and intensities, which produce extremely large and information-rich data samples. The use of machine-learning techniques and quantum algorithms is revolutionizing how we interpret these data samples, greatly increasing the discovery potential of present and future experiments. In this talk, I will provide a brief overview of the standard model, and introduce simple examples where quantum algorithms could be useful.

**Anderson localization of light in three dimensions**

**or how to solve a problem in under forty years**

*Alexey Yamilov, Missouri S&T*

Anderson localization marks a halt of diffusive wave propagation in disordered systems. Despite extensive studies over the past 40 years, Anderson localization of light in three dimensions (3D) had remained elusive, leading to questions of its very existence. Recent orders-of-magnitude speed-up of finite-difference time-domain calculations has finally allowed to conduct ab-initio brute-force numerical simulations of light transport in fully disordered 3D systems with unprecedented dimension and refractive index contrast. It is demonstrated that 3D localization of vector electromagnetic waves is indeed possible in random packings of metallic spheres, in sharp contrast to its absence in the dielectric systems [Yamilov *et al*, Nat. Phys. 19, 1308 (2023)]. In this talk, I will describe the long perilous path towards the discovery, dotted with multiple high-profile retractions and false starts. This result brings new life to a field, which was at the point of despair just few years ago.

**Fragility of life or what would happen if the speed of light were smaller**

The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants. We show that anthropic arguments can set powerful constraints on transient variations of the fine-structure constant alpha (or, colloquially, speed of light) over the past 4 billion years since the appearance of lifeforms on Earth. The regime of transient variation of fundamental constants is characteristic of clumpy dark matter models. We argue that the passage through Earth of a macroscopic dark matter clump with a value of alpha inside differing substantially from its nominal value would make Earth uninhabitable. We demonstrate that in the regime of extreme variation of alpha, the periodic table of elements is truncated, and water fails to serve as a universal solvent. Thereby, the anthropic principle constrains the likelihood of such encounters on a 4-billion-year timescale. This enables us to improve existing astrophysical bounds on certain dark matter model couplings by several orders of magnitude.

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