## Events at Physics |

### Events on Monday, February 12th, 2024

**Atomic Physics Seminar****Quantum metrology with an optical lattice atom interferometer interrogated for one minute****Time:**12:00 pm - 1:00 pm**Place:**5310 Chamberlin Hall**Speaker:**Cristian Panda, UC Berkeley**Abstract:**Exceptional levels of quantum control and coherence are instrumental in quantum metrology and sensing. Atom interferometers are powerful in both probing fundamental physics and everyday sensing but have been limited to measurement times of a few seconds by using atoms in free fall. I will describe how we realize interferometers with atoms suspended for an unprecedented 70 seconds in an optical lattice. This method is particularly well suited for probing localized potentials. I will show how, for the first time, we (1) optimize the gravitational sensitivity of the lattice interferometer and (2) use a system of signal inversions and switches to suppress and quantify systematic effects. This enables us to measure the attraction of a miniature source mass with record accuracy of 6.2 nm/s2, less than a billionth of Earth’s gravity and four times as good as the best similar measurements with freely falling atoms. This performance demonstrates the advantages of lattice interferometry in fundamental physics measurements. I will then show how the lattice atom interferometer can overcome the limits of current atomic gravimeters for applications in the field. Finally, I will discuss prospects for next-generation lattice atom interferometers and applications in precision measurement and quantum inertial sensing.**Host:**Thad Walker**Plasma Physics (Physics/ECE/NE 922) Seminar****"Stellarator optimization through coil shaping"****Time:**12:00 pm - 1:15 pm**Place:**1227 Engineering Hall**Speaker:**Hiroyuki Yamaguchi, National Institute for Fusion Studies**Abstract:**Stellarators/heliotrons are plasma devices that can confine plasma in a toroidal shape primarily by a magnetic field produced by external magnets. In the field of magnetic confinement fusion research, one of the challenges is the optimization of stellarators/heliotrons. In this seminar, stellarator/heliotron optimization techniques developed at National Institute for Fusion Science (NIFS, Japan) and their recent application will be explained. Optimization applying a free-form curve and the genetic algorithm will be highlighted as a very unique aspect of this technique. Interestingly, it has been found that the numerically-optimized magnetic configurations that are usually generated by crowded modular coils can be reproduced well even by a small number of helical coils.**Host:**Prof. Adelle Wright**Theory Seminar (High Energy/Cosmology)****Mapping New Physics from the UV to the IR****Time:**4:00 pm - 5:00 pm**Place:**5280 Chamberlin Hall**Speaker:**Grant Remmen, NYU**Abstract:**Using a combination of techniques spanning the modern amplitudes program, string theory, effective field theory, cosmology, and particle physics, I will show how the space of possibilities for new physics can be constrained—from both top-down and bottom-up perspectives—in a variety of contexts, ranging from quantum gravity, to predictions for colliders, to cosmic inflation.

In the first part of the talk, we will ask a bedrock question of quantum gravity: Is string theory unique? String amplitudes famously accomplish several extraordinary and interrelated mathematical feats, including an infinite spin tower, tame UV behavior, and dual resonance. I will demonstrate that it is possible to construct infinite new classes of tree-level, dual resonant amplitudes with customizable, nonlinear mass spectra. The construction generalizes naturally to n-point scattering and allows for a worldsheet integral representation. However, these constructions can be strongly constrained using multiparticle factorization, which provides a powerful new set of tools for building consistent amplitudes. In the case of a Regge spectrum, I will investigate whether string amplitudes can be bootstrapped from first principles, finding extra freedom in the dynamics that allows for a new class of dual resonant hypergeometric amplitudes.

In the second part of the talk, I will take a particle physics-driven approach, constraining effective field theories using unitarity and causality. We will construct analytic dispersion relations for the effective field theory of the standard model, bounding the size and sign of higher-dimension operators, with significant implications for CP and flavor violation. These positivity bounds allow us to connect qualitatively different experiments, including predictions for the LHC and precision measurements. I will then apply these tools in a cosmological context, building positivity bounds for the theory of multifield inflation and extracting predictions for non-Gaussianities in the cosmic microwave background.

Taken together, these two complementary initiatives comprise a program unifying phenomenological, formal, and cosmological approaches to high energy physics, bringing together powerful tools bridging fields to map the possibilities of future physics.**Host:**Lisa Everett