Colloquium

Simon Corrodi

Argonne National Laboratory

The Muon’s Wobble: Measuring Muon g-2 to Test the Standard Model

The study of magnetic moments, or "g-factors," has a long history of testing fundamental theories, from early measurements of the electron's anomaly providing stringent tests of QED to modern precision probes of the Standard Model. The muon's g-factor is particularly compelling: its larger mass, compared to the electron, renders it significantly more sensitive to virtual contributions from undiscovered particles. The Muon g-2 Experiment at Fermilab recently concluded its mission, measuring the anomalous magnetic moment to 127 parts-per-billion, a four-fold improvement over the historic Brookhaven result. This talk will describe the evolution of these measurements, explain the "wobble" technique, present the final results from Fermilab, and discuss future prospects.

Tzu-Chieh Wei

Stony Brook University

From Haldane’s “conjecture” to entangled gapped ground states for quantum computation

Haldane in 1981 argued that any integer antiferromagnetic Heisenberg chain has a unique ground state with a nonzero gap above it. This seemed to be at odds with known results from spin-1/2 Heisenberg chain that has gapless excitations from the Bethe ansatz solution and Lieb-Schultz-Mattis theorem. But his results paved the way for recent development of symmetry-protected topological order in early 2000s. One of the exact results supporting Haldane's claim is the construction of a spin-1 rotation-symmetric chain by Affleck, Kennedy, Lieb and Tasaki (AKLT) in 1987 that has an exactly known unique ground state and a provable nonzero spectral gap. AKLT’s construction can be extended to any lattice, such as the hexagonal and square lattices, already presented in one of their original works. The corresponding wave functions display no magnetic ordering and exponentially decaying correlations, but whether the models have nonzero gap was not known at that time. Motivated by the quest for universal quantum computation, we were able to show that these AKLT wave functions can be used to perform universal quantum computation. Moreover, we also rigorously established the existence of nonzero spectral gap in some of the two- and three-dimensional AKLT models, including the one on the hexagonal lattice and another one on the decorated diamond lattice. These developments will be covered in this talk. As of the present, it was not known whether one could prepare these higher-dimensional AKLT wave functions efficiently and deterministically on quantum computers. We will also present schemes for efficient (constant-time) preparation of an ensemble of random-bond AKLT states on any finite lattice.

John Beggs

Indiana University

The Cortex and the Critical Point

Condensed matter physics provides a framework for understanding experiments on ensembles of neurons. Within this framework, cascades of activity among cortical neurons follow the same equations that govern avalanches in granular materials, complete with power laws, an exponent relation, and a universal scaling function. These “neuronal avalanches” also show that the cerebral cortex operates near a critical point where many of its information processing functions are optimized, analogous to peaks in susceptibility and correlation length seen at a continuous phase transition. I will review progress in this field over the past 20 years and point to the new frontiers it has opened in human health and deep learning.

Kenneth Lanzetta

Stony Brook University

Cosmology with the Condor Array Telescope

Most of the baryonic matter of the Universe is predicted to reside not in galaxies but rather in diffuse gas that traces the dark-matter filaments that make up the “cosmic web” underlying large-scale structure. The gas is heated by gravitational collapse and ionized by the metagalactic radiation field, producing faint emission that illuminates the otherwise invisible dark-matter scaffolding. Detecting such emission requires sensitivity to surface-brightness levels far below those accessible to conventional astronomical instruments and has therefore remained a major observational challenge for decades. To meet this challenge, we developed the Condor Array Telescope, a purpose-built optical telescope array optimized specifically for ultra–low–surface-brightness imaging of diffuse, extended emission. In this talk, I describe the Condor Array Telescope and its prospects for directly imaging the cosmic web in emission across most of cosmic time.

--

No Colloquium

David Weiss

Penn State University

Exciting 1D gases

1D gases with point contact interactions are special because they are integrable many-body systems, which means that they have many extra conserved quantities, beyond the usual few (energy, momentum, etc.).  I will explain the previous sentence in more detail and then show how we make bundles of 1D Bose gases in the lab, the various ways we excite them out of equilibrium, and how we use them as model systems for studying quantum dynamics. Perhaps especially notable to the Stony Brook physics community, certain insights we achieve are surprisingly applicable to the early time dynamics of relativistic heavy ion collisions.

Jo Dunkley

Princeton University

The Start of the Simons Observatory

The Simons Observatory is a new millimeter-wave observatory in Chile that recently started observations. Its largest 6-meter telescope is measuring the cosmic microwave background (CMB), the earliest image we have of the universe, over half the sky. Its smaller telescopes are seeking a signal imprinted by gravitational waves from the early universe. The large-telescope survey overlaps with many optical surveys and provides a route to mapping the cosmic web of gas and dark matter. By surveying half the sky every couple of days, we also hope to see new types of transient astronomical events in millimeter-wavelengths, and track the light-curves of thousands of active galactic nuclei. In this talk I will describe the observatory and its science plans, and show some early data.

--

Spring Break (No Colloquium)

--

No Colloquium

Frederick Walter

Stony Brook University

The Dark Side of the Sun

Solar flares and their accompanying coronal mass ejections have had only minimal effect on life on our planet for the past 4 billion years. But today secondary effects of energetic solar events  can have devastating consequences for our electrical infrastructure and communications systems. The September 1859 Carrington event, the first recorded solar flare, remains one of the strongest on record. The geomagnetic storm which struck the next day weakened the Earth's magnetic field by over 900 nT (nearly 1%), produced an aurora seen as far south as Cuba and Tahiti, and induced currents in telegraph wires. Weaker events today wreak havoc with the electrical grid, upset GPS navigation, and displace satellites from their intended orbits.

Following an overview of stellar magnetism and flaring mechanisms, I will discuss the known large solar events and their consequences. Solar astronomers are not yet able to predict energetic solar events, and the small number of historical events limits our ability to predict statistically when the next major flare might be expected. Data from the Kepler and TESS missions now let us explore flare rates and strengths from a large sample of stars. I shall discuss how stellar data are improving our understanding of large solar events and their risks to today's society.

• Zachary Cheslog
• Rose Hoffren
• Rojae Mighty
• Maria Sazonova

Stony Brook University

Undergraduate Colloquium

• Current and Future Constraints on the Primordial Power Spectrum
• Double-detonation of oxygen-neon white dwarfs
• Geometric Scaling and Gluon Saturation at EIC
• Buffer gas cooling of charged fullerenes

--

 No Colloquium

Juan Estrada

Brookhaven National Laboratory

Dark Sector Exploration with Low-Noise Silicon Detectors

I will discuss current ideas and experimental efforts to explore the dark sector using a new generation of ultra-low-noise silicon detectors. Technologies such as Skipper-CCDs, SiSeRO devices, Skipper-CMOS sensors, and MAS-CCDs enable the measurement of extremely small ionization signals in silicon, reaching sensitivities at the level of single electron–hole pairs. These capabilities open new opportunities to search for light dark matter and other weakly interacting particles. This talk will review the detector concepts and recent progress in direct dark matter searches using low noise CCDs. I will also discuss how these low-threshold sensors are being deployed in underground experiments, particle beams, and astronomical observations, and how scaling these technologies to larger detectors may allow us to probe previously inaccessible regions of dark sector parameter space. 

John Parmentola

RAND Corporation

How Could Sea Levels Fall by 400 Feet During an Ice Age?

Sea levels fell by about 400 feet (120 meters) during the great ice ages of the past million years as enormous continental ice sheets grew across Greenland, North America, and Eurasia. Explaining how such vast quantities of ocean water could be transferred to land as ice remains one of the central questions of climate science.

Although the Earth’s orbit geometry slowly changes over time, the planet receives nearly the same total solar energy each year. Ice ages, therefore, cannot be explained simply by small changes in the Sun’s annual energy supply. Instead, orbital geometry redistributes solar energy across latitudes and seasons. The Arctic climate system is governed primarily by summer melt energy, while the tropical oceans respond to the cumulative storage of solar energy through evaporation, ocean heat content, and the transport of moisture toward higher latitudes.

In this talk, I will describe a mechanism I call the Countervailing Obliquity–Precession Effect (COPE). COPE arises from changes in orbital geometry that reduce summer heating in the Arctic while simultaneously increasing seasonal energy accumulation in the tropical zone. This redistribution alters the balance between high-latitude ice melt and tropical evaporation, potentially influencing the growth of continental-scale ice sheets.

Satellite observations of the Earth’s radiation budget show that a measurable fraction of this redistributed energy persists in the tropical climate system today. The COPE predicts that the tropical zone absorbs different amounts of solar energy during two halves of the Earth’s annual orbit. Satellite measurements from the CERES mission reveal a persistent net tropical zone asymmetry of roughly 1 W/m² over the past two decades, indicating that part of the redistributed orbital energy remains within the climate system rather than being fully offset by cloud reflection and thermal emission to space.

Evidence suggests that COPE operated during Marine Isotope Stage 19c (MIS 19c), an interglacial about 800,000 years ago that closely resembles the present Holocene (MIS 1). For both intervals, the energy accumulated in the tropical zone exceeds—by many times—the energy required to evaporate enough ocean water to lower sea levels by 400 feet, independent of climate feedback mechanisms.

Taken together, these results suggest that the redistribution of orbital energy through the Earth system may play an important role in explaining how ice ages begin and how sea levels can fall by hundreds of feet over geological timescales.

Derek Teaney

Stony Brook University

Graduate Colloquium