Category: Research

Tech Team Tackles Tar Balls’ Impacts On Climate

Research by Claudio Mazzoleni and physics alumni Susan Mathai ’23 and Swarup China ’12 featured in a news article in Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL) by the EMSL. Mazzoleni and a multi-institutional team of researchers set out to determine exactly how solar radiation from the sun interacts with individual tar balls dispersed over a mountainous region in northern Italy.  The research assesses the optical properties of individual tar balls to better understand their influence on climate. 

Tar balls, found in biomass-burning smoke (think smoke from forest fires), impact the Earth’s radiative balance. Understanding the optical properties of tar balls can help reduce uncertainties associated with the contribution of biomass-burning aerosol in current climate models.

The original paper was selected for the cover of the Nov 7th issue of Environmental Science and Technology, and was co-authored by Tyler Capek and Susan Mathai (both Physics); Daniel Veghte of The Ohio State University; Zezhen Cheng, Swarup China ’12 (PhD Atmospheric Sciences), Libor Kovarik, Mazzoleni, and Kuo-Pin Tseng, of the PNNL; and Silvia Bucci and Angela Marinoni, Institute of Atmospheric Sciences and Climate (ISAC)-National Research Council of Italy.

Image of Claudio Mazzoleni
Claudio Mazzoleni
Professor, Physics
Image of Susan Mathai
Susan Mathai ’23
Image of Swarup China
Swarup China ’12

Physicists develop a linear response theory for open systems having exceptional points


Linear analysis plays a central role in science and engineering. Even when dealing with nonlinear systems, understanding the linear response is often crucial for gaining insight into the underlying complex dynamics. In recent years, there has been a great interest in studying open systems that exchange energy with a surrounding reservoir. In particular, it has been demonstrated that open systems whose spectra exhibit non-Hermitian singularities called exceptional points can demonstrate a host of intriguing effects with potential applications in building new lasers and sensors.


At an exceptional point, two or modes become exactly identical. To better understand this, let us consider how drums produce sound. The membrane of the drum is fixed along its perimeter but free to vibrate in the middle. As a result, the membrane can move in different ways, each of which is called a mode and exhibits a different sound frequency. When two different modes oscillate at the same frequency, they are called degenerate. Exceptional points are very peculiar degeneracies in the sense that not only the frequencies of the modes are identical but also the oscillations themselves. These points can exist only in open, non-Hermitian systems with no analog in closed, Hermitian systems.


Over the past years, ad-hoc analysis of the scattering coefficients of non-Hermitian systems having exceptional points has revealed a puzzling result, namely that sometimes their frequency response (the relation between an output and input signals after interacting with the system as a function of the input signal’s frequency) can be Lorentzian or super Lorentzian (i.e. a Lorentzian raised to an integer power). In contrast, the response of a standard linear, isolated oscillator (excluding situations where Fano lineshapes can arise) is always Lorentzian.


Now, an international team of physicists led by Prof. Ramy El-Ganainy from Michigan Technological University, along with several collaborators from Penn State, the Humboldt University in Berlin, and the University of Central Florida, has tackled this problem in their recent Nature Communications article titled “Linear response theory of open systems with exceptional points”. In that work, the team presents a systematic analysis of the linear response of non-Hermitian systems having exceptional points. Importantly, they derive a closed-form expression for the resolvent operator quantifying the system’s response in terms of the right and left eigenvectors and Jordan canonical vectors associated with the underlying Hamiltonian.

A schematic representation of a complex non-Hermitian open system with many degrees of freedom made of coupled optical microdisk cavities. The linear response theory developed in this work provides a full characterization of the relation between output and input signals (indicated by green and yellow arrows, respectively) in terms of the eigenmodes and the canonical states of the underlying non-Hermitian Hamiltonian.


“In contrast to previous expansions of the resolvent operator in terms of the Hamiltonian itself, the formalism developed here provides direct access to the linear response of the system and demonstrates exactly when and how Lorentzian and super-Lorentzian responses arise” says Prof. El-Ganainy. “As it turned out, the nature of the response is determined by the excitation (input) and collection (output) channels” says Amin Hashemi, the first author of the manuscript. The presented theory describes this behavior in detail and is generic enough to apply to any non-Hermitian systems having any number of exceptional points of any order, which makes it instrumental for studying non-Hermitian systems with large degrees of freedom.


Lucas Simonson, physics PhD candidate awarded scholarship to study in Germany

Lucas Simonson is off to study in Germany

Lucas Simonson has been awarded a scholarship by the German Academic Exchange Service (DAAD). He will study at the Max Planck Institute for the Physics of Complex Systems in Dresden.

The German DAAD is a joint organization of the universities and other institutions of higher education in the Federal Republic of Germany, and the world’s largest funding organization of its kind. Supported by public funds, the DAAD promotes international academic cooperation, especially through the exchange of students and academics. DAAD scholarships are awarded by selection committees comprising a panel of independent academics.

He looks forward to studying under Professor Kurt Busch starting October 2022 to the end of April 2023. “The rationale for this trip is that joining my advisor in Germany will allow me to proceed with my research activities at a fast pace without any delay due to his absence. It will also allow me to interact with world-class optics research groups at the Humboldt-Universität Berlin,” he says. “It’s a significant milestone in my academic career and will allow me to experience other cultures outside of those in the US to broaden my worldview,” says Lucas.

Studying in Germany adds another frame of reference in his study of physics. “Lucas is bringing a unique perspective to our group by combining an interdisciplinary education in both electrical engineering and physics,” says Ramy El-Ganainy, associate professor of physics.

Lucas obtained an MS in Applied Physics (back in the spring of 2021). He entered the PhD candidacy at the end of this past spring semester. Upon getting his PhD, Lucas plans to pursue R&D-related work at Ft. Belvoir in Virginia for The Command, Control, Communications, Computers, Cyber, Intelligence, Surveillance and Reconnaissance (C5ISR) Center, the U.S. Army’s information technologies and integrated systems center.

Guest Blog: Uncovering Global Dust-Climate Connections

By Kimberly Geiger, College of Engineering

A satellite photo of a dust storm
“Godzilla” Saharan dust storm in June 2020. Photo courtesy of NASA.

Developed at Michigan Tech, a new global weather station-based dataset named dulSD is enabling long-term, large-scale monitoring of the dust cycle.

As wind shapes the surface of the Earth, it pulls dust from dry, exposed land surfaces into the atmosphere. Xin Xi (GMES) uses observations and models to study the sources, transformation and transport of dust to assess its impact on climate and air quality.

“Airborne dust aerosols impact the Earth in a myriad of ways,” he explained. “Mineral dust interacts with the global energy budget, ocean biogeochemistry, air quality and agriculture.”

Satellite remote sensing, a major source of information to study global dust variability, lacked the specifics Xi needed. He revisited the National Oceanic and Atmospheric Administration’s Integrated Surface Database and set out to create a new dataset for evaluating global dust, which he named duISD.

How much dust is there? Read more on Unscripted, the University’s research blog.

Physics Major Anthony Palmer Wins Best Poster at Computing [MTU] Showcase

Michigan Tech physics and applied and computational mathematics double major Anthony Palmer, along with computer science PhD candidate Elijah Cobb, won the best poster recently in the Computing [MTU] Showcase for “Universal Sensor Description Schema: An extensible metalanguage to support heterogenous, evolving sensor data.”

Image of Anthony Palmer and Elijah Cobb in front of their poster at Michigan Tech’s Computing [MTU] Showcase
Anthony Palmer (left) and Elijah Cobb present their poster at Michigan Tech’s Computing [MTU] Showcase

Collecting and processing underwater sensor data is a critical need for U.S. Navy operations. Differences in sensor data types and forms presents a challenge for complete and accurate use of these data. The Universal Sensor Description Schema (USDS) project seeks to design, evaluate, and deploy a unified, extensible metalanguage for supporting legacy and future sensor data across multiple programming languages and environments. Michigan Tech is collaborating with Applied Research in Acoustics LLC to develop a robust programming environment for development of data-intensive applications.

Anthony came up with the idea for the project while interning at ARiA (a small research-and-development firm serving the Navy, government and industry). It’s been the basis for his senior thesis in physics. Anthony says “This project in particular has helped me learn alot about how programming languages work and are made. It also helped me learn a new functional programming language called “Racket”. Finally, it introduced me to some awesome people in the MTU computer science department including my partner Elijah Cobb and my advisor, Dr. Charles Wallace.”

Eye-opening describes the experience for Anthony.  He says, “I would say that I was surprised by the intricacy of how programming languages are built and function. I would also say that it was unexpected how useful recursion can be for solving problems in computing.” Recursion reduces time complexity, adds clarity and reduces the time needed to write and debug code.

Anthony graduates in a few short weeks. HIs attention will turn to the Navy, where he will be a submarine officer. Eventually he hopes to go into graduate school.

Sunny forecast for Physics Pi Cloud Chamber

Michigan Tech Pi Cloud Chamber
Michigan Tech Pi Cloud Chamber

$4 million in NSF funding makes the Physics Pi Cloud Chamber and extensive supporting instrumentation available to the atmospheric sciences community for investigations of atmospheric processes including aerosols and clouds. The award will also support a 10-week experiential learning program for visiting students through a Pi Chamber laboratory fellowship program and broaden student participation in the physical sciences. Funding will also go towards the design of a larger cloud chamber.

What is the Pi Chamber?

The Pi Chamber at Michigan Technological University simulates cloud conditions within the range of pressures and temperatures occurring in the lower part of the atmosphere (the troposphere). It has a proven record of enabling productive and insightful research in aerosol-cloud interactions, ice nucleation, mixed-phase cloud properties, cloud optical properties, and moist Rayleigh-Bénard convection in the atmospheric sciences.

Design of a larger cloud chamber in the works. 

Current cloud chambers do not allow for collisions between cloud drops as would occur in natural clouds. That’s why the NSF is funding an Aerosol-Cloud-Drizzle Convection Chamber too. NSF support of this project facilitates a cohort of researchers to conduct preliminary design work on a large cloud chamber capable of producing droplets up to the size of drizzle, which is a key transition point for fully understanding the development of precipitation. The proposed chamber would dramatically expand the US and international research community’s ability to conduct laboratory studies of clouds.

Read more about the Pi Chamber.

New Funding

Professor Emeritus David Nitz (Physics/EPSSI) is the principal investigator on a project that has received a $249,804 research and development grant from the National Science Foundation.

This three-year project is titled “WoU-MMA: Enhancing the Neutrino Sensitivity of the Pierre Auger Observatory.”

The Pierre Auger Observatory is used by researchers from across the world to study high energy cosmic rays – high energy particles that can travel through space at speeds approaching the speed of light. This project will support the AugerPrime upgrade to the observatory, increasing the detection efficiency of the observatory’s surface detectors.

New Funding

Raymond Shaw (Physics/EPSSI) is the principal investigator on a project that has received a $2,903,682 research and development grant from the National Science Foundation.

Shaw, co-investigators Will Cantrell, Kartik Iyer, Claudio Mazzoleni, and researchers from institutions across the country will collaborate on the project titled “A Community Laboratory Facility for Exploring and Sensing of Aerosol-Cloud-Drizzle Processes: The Aerosol-Cloud-Drizzle Convection Chamber.”

The proposed ACDC2 cloud chamber will be a world class facility, capable of producing droplets up to the size of drizzle while allowing air motion analogous to that in real clouds.