The 2023 Andrew Chamblin Memorial Colloquium

http://andrewchamblin.org/lecture.html

Speaker:  Dr. Vijay Balasubramanian

Professor

University of Pennsylvania

Title:  The entropy of black holes

Abstract:  One of the most famous results of twentieth-century physics states that black holes carry an entropy proportional to the area of their horizons. This entropy formula is universal in general relativity: it applies to black holes with any mass, charge, or rotation, and in any spacetime dimension.  I will describe a recent proposal explaining the microscopic origin and universality of this formula.  The proposal exploits new developments in the study of many-body chaos, thermalization, and quantum dynamics, along with concepts of complexity and information from theoretical computer science, communications theory, and cryptography.  These developments also suggest that the interior of a black hole is causally accessible to external observers, but only if they can perform egregiously complex measurements that are inaccessible under normal conditions.

Speaker: Patricia Rankin

Professor and Department Chair

Arizona State University

Department of Physics

Host: Plaster

Title: Physics is Fun! Everyone should do it

Abstract: Patricia Rankin became a physicist because she enjoyed it. She still enjoys it. She remembers being asked as a student why more women didn’t study physics. She can now give a much better answer to that question. This talk looks at how physicists solve problems, and why how we think impacts the demographics of our field. She will discuss how our understanding of what makes people leave physics has evolved and why the focus is now on a process driven approach. She will argue that while the field would benefit from more diversity, what matters to an individual is that they get to do what they enjoy and feel welcome.

Dr. NandiniTrivedi

Professor

Ohio State University

Host: Murthy

Title: Fractionalized excitations in Quantum Spin Liquids and their Detection

Abstract: The 2022 Nobel prize celebrates the detection of entanglement between two photons. Quantum spin liquids (QSLs) are long-range entangled states of matter of billions of interacting qubits or spins that develop in a Mott insulator. The fate of the interacting spins can progress along two paths as the temperature is lowered: the spins can undergo long range ordering, spontaneously breaking the continuous symmetries, leading to a magnetic phase; or the spins can remain disordered but get quantum mechanically entangled with long range patterns of many-body entanglement in the resultant QSL. The possibility of obtaining QSL phases is enhanced by having a low spin and enhanced quantum fluctuations, and frustration arising from the lattice geometry and/or competing spin-spin interactions. Remarkably QSLs harbor fractionalized excitations rather than the conventional spin waves of ordered magnets that carry integer units of angular momentum. In my talk I will identify detectable signatures of these fractionalized excitations in experiments using light and neutrons. These fractionalized excitations are promising candidates to create logical qubits for quantum computation. 

Dr. Heidi Wu

Assistant Professor

Boise State University

Host: Su

Title: Probing Cosmic Acceleration with Galaxy Clusters

Abstract: The accelerated expansion of the Universe is one of the biggest puzzles in physics: Why is gravity repulsive rather than attractive on distance scales larger than a few million lightyears? Cosmic acceleration slows down the growth of structure, and we can use galaxy clusters — the largest gravitationally bound objects in the Universe — to probe the nature of cosmic acceleration.  In this talk, I will first introduce our current understanding of the Universe.  I will then discuss how we use sky surveys of galaxy clusters to measure cosmic acceleration and how several ambitious ground- and space-based missions will revolutionize our understanding of the Universe.

Speaker: Geoff Greene

Professor Emeritus

University of Tennessee

Host: Crawford

Title: The Life and Death of the Free Neutron

Abstract:  The decay of the free neutron is the simplest example of nuclear beta decay and, as such, is the archetype for a wide variety of Weak Interaction processes. These include radioactivity, Big Bang Nucleosynthesis, and energy production in the sun. Additionally, The precise value of the free neutron lifetime, can, along with other data, be used to test the consistency of the Standard Model. Remarkably, the value of neutron lifetime can also help determine the atmospheric composition of Venus. Given the breadth of physics involved, it is  disconcerting to note that, at present, measurements of the neutron lifetime by different methods are inconsistent. In this talk, I will discuss the physics of neutron decay and will review the strategies for the experimental determination of the neutron lifetime. I will discuss some of the experimental challenges and will attempt to provide some illumination of the current discrepant situation. 

Title: Electrify Everything!

Abstract: Making everything run on electricity is a necessary step in the transition from fossil fuels.    Starting that process immediately  is also necessary, and  helpful both to the process and the environment.

Host: Korsch

Title: Trapped-ion optical clocks: Telling time and testing physics at the quantum limit

Abstract: Optical transitions in trapped, laser-cooled ions can provide an extremely well-controlled frequency reference for atomic clocks.  The most stable and accurate atomic clocks now make measurements with total uncertainty approaching 1×10^-18.  The Ion Storage Group at NIST develops optical clocks based on the ¹S₀-³P₀ resonance in ²⁷Al⁺.  To perform precision spectroscopy on this atomic system we use the basic building block of a quantum computer, the two-qubit gate, which transfers information from ²⁷Al⁺ to a second ion species held in the same trap.  I will introduce these systems and present recent frequency comparisons between them and other optical clocks at NIST.   These comparisons provide valuable data for international time/frequency standards and can test our fundamental theories including relativity and the Standard Model.  I will also describe quantum metrology techniques that have allowed us to approach the quantum limit for stability in a ²⁷Al⁺ single-ion clock.

Host: Murthy
Title:  Dynamics at the edge: charge fractionalization and near-stationary high energy state 

Title: Quantum Codes from Condensed Matter to Quantum Gravity

Abstract: I will explore the appearance of quantum codes in diverse contexts, from the toric code of condensed matter physics to holographic codes  in quantum gravity.   The contexts and implementations of these codes  vary widely, but their structures have much in common and suggest a deeper connection between them. 

Host: Su

Title: Combining Galaxy and CMB Surveys — all the science that “comes for free”

Abstract: The LCDM model has been extraordinarily successful. In the past 20 years, the cosmology community has worked hard to make ever more precise measurements of the LCDM parameters using large datasets from cosmic surveys. As error bars shrink and several tensions arise, we are eager to look for new and different ways of making robust statements of the LCDM paradigm. In this talk I like to focus on one particular direction where we can get new information to help this effort — by combining different cosmic surveys, in particular galaxy and CMB surveys. I will first describe the latest cosmological analysis using the Dark Energy Survey (DES) and CMB lensing from the South Pole Telescope (SPT) and Planck. Then I will talk about combining DES galaxies and the thermal Sunyaev Zel'dovich (tSZ) effect measured from SPT and Planck to learn about the baryonic feedback in our galaxies. These analyses will highlight the power of combining different datasets to tackle some of the most pressing issues in observational cosmology today.