Events at Physics |
Events on Thursday, April 17th, 2025
- R. G. Herb Condensed Matter Seminar
- Field theory of monitored, interacting fermions with charge-conservation
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Matthew Foster, Rice University
- Abstract: The dynamics of entanglement in monitored quantum circuits has opened up a new chapter in far-from-equilibrium, quantum many-body physics. Charge-conserving dynamics of 1D free fermions monitored by local charge measurements are known to possess only an area-law entangled phase, with no measurement-induced phase transition (MIPT). We formulate the more interesting problem for monitored dynamics of interacting fermions, using the Keldysh formalism. We derive a simple effective statistical mechanics model for the system. We show that, as soon as local density interactions are turned on, the volume-law entangled phase and the MIPT into an area-law phase appear, the latter described by a separatrix in the weak-coupling RG flow. Invoking general symmetry principles, our theory also naturally exhibits the “charge-fuzzy” and “‘charge-sharpened” phases, as well as the “charge-sharpening” transition of KT type, identified in previous work. We explain how the simple effective stat. mech. model that we obtain is made possible by the heating effects of the measurements, which trivialize the fermion distribution function whilst still admitting a panoply of dynamical phases and transitions.
- Host: Alex Levchenko
- High Energy Seminar
- Measuring the nucleon axial form factor in deuterium and hydrogen can’t be that hard?
- Time: 2:30 pm - 3:30 pm
- Place: CH 5280 /
- Speaker: Rik Gran, Professor Physics and Astronomy University of Minnesota Duluth, Co-spokesperson MINERvA experiment
- Abstract: In a recent paper in Nature, the MINERvA neutrino cross section experiment presented a measurement of the axial form factor of the nucleon using anti-neutrino reactions on protons (hydrogen nuclei). This is the first new nucleon data since the 1980’s bubble chamber measurements that used neutrino + neutron (in deuterium) reactions. Phenomenological nucleon form factors are essential information for two customers. They are used in the calculation of the baseline event rates for neutrino + nucleus interactions used in the search of other phenomena, such as neutrino oscillation parameters and CP violation. They can also be calculated using QCD lattice techniques, where calculations may in principle be more precise than the existing measurements. This talk will split between celebrating the 50 year history of the deuterium measurements and describing the new MINERvA measurement, with implications for current and upcoming neutrino experiments such as T2K, NOvA, SBN, and DUNE.
- Host: Brian Rebel
- Astronomy Colloquium
- New Views of Exoplanet Atmosphere Physics and Chemistry from JWST
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Jonathan Fortney, University of California, Santa Cruz
- Abstract: Giant planets and brown dwarfs are astrophysical objects with different formation locations – planets in disks and brown dwarfs (we think) in giant molecular clouds. These different objects transition across the very same range of Teff, with planets strongly influenced by their parent star’s heating from “above,” while brown dwarfs inexorably cool from their interior, which warms their atmospheres from “below.” This major energy difference can drive important differences between atmospheres. JWST has been revolutionizing our understanding of these cool atmospheres, and in this talk I will discuss a range of modeling work that aims to confront a variety of high signal-to-noise spectral observations, in particular for objects below Teff = 1000 K, where a number of major chemical transitions in these atmospheres occur. Our work uncovers a wide range of physical processes, including vertical mixing, photochemistry, and tidal heating, which can all affect the structure and chemistry of cool atmospheres. The significant diversity in spectra stress-test our models in unique ways.
- Host: Melinda Soares-Furtado