P&A Colloquium

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
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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.


 

Date:
Location:
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. 
Date:
Location:
CP 155
Event Series:

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.

Date:
Location:
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.
Date:
Location:
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.
Date:
Location:
CP 155
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P&A Colloquium

``10,000 Einsteins: AI and the future of theoretical physics''

Machine learning has evolved from a specialized field to a foundational tool in various disciplines, including particle physics. Over the past decade, it has transformed collider physics and is beginning to influence more formal sectors of high-energy theory. An introduction to the use of machine learning in particle physics will be presented, highlighting some recent advances that the speaker has been involved in. Going forward, machine learning will play an increasingly important role in science and education, particularly with the advent of large language models. We are in the early stages of period of rapid change that has been compared to the industrial revolution, the dawn of the internet, or even the inception of writing. Some justification will be given for these bold analogies alongside speculative insights and an optimistic outlook into how machine learning might be essential for continued progress on unraveling the fundamental laws of nature.


 

Date:
Location:
CP 155
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P&A Colloquium

``Visible Matter: Origin and Structure''

In this colloquium, I will discuss recent advancements in understanding the origins and structure of the 5% of visible matter in the universe through the lens of quantum chromodynamics (QCD), with a focus on nucleons and nuclei. I will present the latest experimental findings on the gravitational form factors of the proton, which, when integrated with lattice QCD studies, signal a paradigm shift in our approach to nucleon structure and enhance our comprehension of the strong force that binds nucleons and nuclei.


 

Date:
Location:
CP 155
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