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P&A Colloquium

Physics & Astronomy Colloquium

Title: Free boundary problems for Euler flows

Abstract: Free boundary problems are very interesting but also very challenging problems in fluid dynamics, where the boundary of the fluid is also freely moving along with the fluid flow. 

I will discuss two such models, governed by the compressible, respectively the incompressible Euler equations, including also MHD flows.  This is joint work with Mihaela Ifrim, and in part with Benjamin Pineau and Mitchell Taylor.

Date:
-
Location:
CP 153
Event Series:

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'.

Date:
-
Location:
CP 153
Event Series:

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.

Date:
-
Location:
CP 153
Event Series:

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. 

Date:
Location:
CP 153
Event Series:

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.


 

Date:
Location:
CP 153
Event Series: