P&A Colloquium

Physics & Astronomy Colloquium

Title: Final result from the Fermilab Muon g-2 Experiment

Abstract: On June 3, 2025, the Fermilab Muon g-2 Collaboration released its final determination for the muon's magnetic anomaly, a_μ = (g - 2)/2. Our result, after roughly a decade of design and construction and six years of data taking, was a_μ = 116 592 071(15)×10−11. The anomaly a_mu was determined from the ratio of the muon's anomalous precession frequency and the proton's Lamor precession frequency in the magnetic field of a 15 m diameter, 1.5 Tesla, superconducting muon storage ring. In this talk I'll discuss the science that motivated the  g-2 project and the techniques used to reach the 127-ppb precision. I'll also comment on the future work on the muon anomaly and the June 3, New York Times headline that the 'Muon Experiment was Hugely Successful but Clarifed Little'.

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CP 153
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Physics & Astronomy Colloquium

Title: Evidence for Missing Matter in the Inner Solar System: Does the Sun have a Dark Disk?

Abstract: The total mass and distribution of dark matter within the Solar system are poorly known, albeit constraints from measurements of planetary orbits exist. We have discovered, however, that different sorts of determinations of the Sun’s gravitational quadrupole moment can combine to yield new and highly sensitive constraints on the mass distribution close to the Sun. These outcomes provide evidence for a non-luminous disk in this region, nominally coplanar with Mercury’s orbit, and we develop how we can use this finding to limit its mass. The mass estimates associated with its known matter components, although uncertain, point to a prominent dark-matter contribution, which merits further investigation. We describe how existing spacecraft studies of the inner solar system support the existence of a circumsolar dust ring, and we note how continuing observational studies of the inner solar system, including the use of space-based quantum technology, can not only help to refine these constraints but also to identify the nature of and the mass of its dark-matter component.

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CP 153
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Physics & Astronomy Colloquium

Dr. Stephen Taylor, Vanderbilt University

Title: Charting the Gravitational-wave Universe At Light-year Wavelengths

Abstract: The Universe is thrumming with gravitational waves. June 2023 brought the first evidence for an all-sky background of nanohertz-frequency gravitational waves, discovered by collaborations including the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) and groups in Europe, Australia, India, and China. This was an endeavor decades in the making, requiring painstakingly precise timing observations of scores of millisecond pulsars across the Milky Way using flagship radio telescopes. While the results from separate groups are consistent with one another—and the leading interpretation of a population of supermassive black-hole binaries as the source—the observations provoke many new questions. Do the results imply a population of binaries more massive than expected? What are the observational milestones as the first individually resolvable binary signals come into focus? Can we link these signals to their host galaxies or electromagnetic counterparts? In this talk, I will chart the path to discovery, reflect on what we have learned since our announcement, and explore the exciting opportunities and synergies ahead—including the role of next-generation radio instruments and space-borne gravitational-wave missions.

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CP 153
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Physics & Astronomy Colloquium

Dr. Zhoudunming (Kong) Tu, Brookhaven National Laboratory

Title: Exciting the Entangled Vacuum - A New Era in Understanding Visible Matter

Abstract: Not until quite recently was the vacuum recognized as anything more than empty space. Today, we understand it as a dynamic medium, filled with fluctuating fields and virtual particle pairs that shape the very structure of our universe. These invisible pairs break a fundamental symmetry of nature—chiral symmetry—and are thought to generate more than 99% of the mass of the visible universe. Yet, how this hidden mechanism connects to the confinement of quarks inside protons, neutrons, and other particles remains one of the deepest unsolved problems in physics.

In this talk, I will present new insights into this question using high-energy particle collisions at the Relativistic Heavy Ion Collider (RHIC). Such collisions can briefly liberate the virtual quark–antiquark pairs of the vacuum, which then bind together into hadrons such as Λ hyperons. Recent results from these studies open an experimental window into the quantum structure of the vacuum, with far-reaching implications for our understanding of mass, matter, and the strong force described by Quantum Chromodynamics.

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Location:
CP 153
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P&A Colloquium

``Exploring Cosmic Acceleration: Insights from the 3 years of the DESI data'' 

Abstract: The Dark Energy Spectroscopic Instrument (DESI) collaboration is conducting a five-year redshift survey of 40 million extra-galactic sources over 14,000 square degrees of the northern sky up to the redshift of 4 with the Mayall 4-meter telescope at Kitt Peak National Laboratory.  One of its primary goals is to measure the cosmic expansion history precisely and accurately through the measurements of baryon acoustic oscillations (BAO). In this talk, I will present the results of the DESI First and the Third Year Baryon Acoustic Oscillations using the distributions of galaxies and quasars over the redshift range of 0.1-2, the estimates of the relevant systematics, and their intriguing cosmological implications, including the time-evolving dark energy. If time permits,  I will also present how we tackle observational systematics to probe inflation using galaxy surveys robustly. 

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CP 153
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P&A Colloquium

 
Title:
From power generation to quantum information science - material development for enhanced singlet fission
 
Abstract:
Singlet fission is a bi- (or multi- )molecular exciton multiplication process, where one singlet exciton is converted to two triplet excitons of roughly half the energy. For this process to take place, a molecular system must possess (1) appropriate triplet energies relative to the singlet, which is a common property of acenes larger than anthracene, and (2) sufficient intermolecular electronic coupling for Dexter energy transfer to be possible.  Fifteen years ago, our focus was the utilization of this process to enhance the power conversion efficiency of silicon photovoltaics, as a method to break the Shockley-Queisser limit.  This approach requires the correlated triplet state to dissociate into free triplets, which can then be individually harvested for photocurrent generation. More recently, in collaboration with researchers at NREL, we became interested in a different application: By completely re-designing molecular architectures to prevent the triplets from dissociating, systems were developed where the longer-lived triplet pair converted to a correlated quintet state, which can be addressed by microwave irradiation and read-out optically. This talk will cover material design for both applications, along with our current design goals for qubits with µs coherence at room temperature.


 

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CP 153
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P&A Colloquium

 
``The APS Career Talk''
 
Physics degree holders are highly employable in both the private and public sectors. However, students and early career scientists may be unaware of non-academic career pathways that exist within industry. This talk will provide an overview and examples of common career paths taken by physics degree holders, as well as give resources to assist with career exploration and the job search. 
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CP 155
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P&A Colloquium


"Cosmological Constant and Archimedes' Principle"

We investigate the origin of the cosmological constant, which plays a crucial role in the accelerated expansion of the Universe. By analyzing the energy-momentum tensor form factors of hadrons, we find that the QCD trace anomaly balances the pressures from quarks and gluons, thus playing a key role in hadron confinement. The source of this anomaly is traced to the gluon condensate of the vacuum. A similar phenomenon occurs in type II superconductors, where the pressure required to clear the Cooper-pair condensate balances the pressures from the magnetic field and electron supercurrents.

The energy-pressure relations in both hadrons and vortices suggest that the confining pressure originates from their respective condensates: the gluon condensate arises from conformal symmetry breaking, while the superconducting condensate results from gauge symmetry breaking. In both cases, the confining pressure is equal to the negative of the energy density, in accordance with the Archimedes Principle.

We further note that this pressure-energy density relation also applies to the cosmological constant, which Einstein introduced through the metric term. Drawing an analogy with hadrons and superconducting vortices, we speculate that the conformal symmetry breaking in general relativity gives rise to a graviton condensate in the true vacuum, with the cosmological constant emerging as a manifestation of the Archimedes Principle.

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CP 155
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P&A Colloquium

``Observational Benchmarks of Galaxy Evolution from CNO Emission in Extreme Emission Line Galaxies''
 
Emission lines produced by the ionized gas in galaxies encode numerous properties that are important to galaxy evolution, including the current physical conditions and chemical abundances of the emitting gas, the hardness of the stellar radiation field, and the escape of ionizing photons. In turn, these properties are shaped by the star formation history of a galaxy. Since stars produce different metals, e.g., nitrogen, carbon, and oxygen, at different times, the relative abundances of C/O and N/O act as clocks benchmarking important episodes throughout the star formation history. For example, N/O can be interpreted as a tracer of the relative ratio of moderately old stars (>100 Myr) to very young stars (<10 Myr). Recently, high-redshift (z > 6) James Webb Space Telescope (JWST) observations have found galaxies with extremely strong high-energy C, N, and O emission lines that are indicative of high-energy ionizing sources and super-solar relative abundance ratios. This poses a contradiction: how did such young galaxies so early in the universe become enriched with metals from older stars and are they contributing too many ionizing photons? I will discuss our current understanding of these so-called extreme emission line galaxies and what we are learning from rest-UV, optical, and infrared spectra taken with the Hubble Space Telescope (HST) and JWST of low- to high-redshift galaxies. Some of these observations are revising our interpretation of the relative gas abundances and their implications for the chemical evolution, star formation histories, and feedback prescriptions of early galaxies. Such detailed studies of the mechanisms that produce the extreme emission lines are critical to interpreting high-redshift spectroscopic samples and understanding the chemical enrichment of the first galaxies and their contributions to reionization.
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CP 155
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P&A Colloquium

 
``The Discovery of Earth's Third Global Energy Field by NASA’s Endurance Rocketship''
 
This seminar will detail the journey of NASA’s low-cost Endurance sounding rocket mission, which recently discovered Earth’s ambipolar electric field. First theorized over 60 years ago, and thought impossible to measure, this “third” field (as fundamental as gravity and magnetism) is a key driver of Earth’s atmospheric escape mechanisms. Learn how Endurance went from a rough sketch to a rocketship, the enormous challenges and obstacles faced in getting her to space, including global disruptions from a pandemic and war, and what it takes to launch a rocket from the remote and unforgiving Arctic environment. Finally, this colloquium will teach how, with the right team behind you, NASA will build you a rocket mission of your very own.
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CP 155
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