Institute for Gravitation and the Cosmos

2026-01-26

The universe is a mysterious place, and it’s largely composed of mysterious stuff. All of the stuff we can see—galaxies, stars, planets, trees, people—are made of ordinary matter, but this only accounts for about 5 percent of what’s out there. The rest is some combination of so-called “dark matter” and “dark energy.” Scientists have inferred the existence of these mysterious dark entities based on calculations of their gravitational impact on the parts of the universe we can see but have yet to directly observe them. Carlos Blanco, assistant professor of physics and a co-hire of the Institute for Computational and Data Sciences at Penn State, is using AI to develop materials with properties that will hopefully increase our ability to detect dark matter. “Dark matter doesn’t emit, reflect, or absorb light, and the only way that we know it interacts with ordinary matter is through its gravitational impact,” said Blanco. “So, we are trying to develop dark matter detectors that could pick up any faint signals that result from dark matter colliding with an ordinary atom. One way to do this is by identifying materials that might be more likely to produce these signals in ways that we can interpret.” Current dark matter detectors contain some sort of sensor, usually buried deep underground. If a particle of dark matter collides with an atom in the sensor, it might produce a faint signal in the form of light or an excited electron. These events are rare and the signals weak, so the problem becomes how to distinguish a real signal indicating dark matter interacting with the detector and noise in the system resulting from other types of interactions. “The next generation of dark matter detectors have to be cleverer about how they distinguish an actual dark matter signal from the massive amount of noise inherent in these searches,” said Blanco. “One way to do this is if we can determine the directionality of the interaction—did the dark matter particle come in from above the detector, from the side? So, the problem becomes one of materials science. Can we identify a material that would give us this information? Current detectors have been built with materials that are basically off-the-shelf parts, we want some that is purpose built.” To identify these materials, Blanco uses machine learning and generative AI. He is building a model, similar to a large-language model, trained on a large database of small molecules—those with around 30 atoms or less—that have some known properties that indicate how sensitive they may be as detectors. The model “learns” how these properties are related to the structure and composition of the molecules in the training set and can suggest new molecules to try to optimize their ability to detect dark matter. It is analogous to how ChatGPT, for example, is trained on existing text, then can produce original sentences. “As we try to understand the composition and evolution of the universe, our calculations tell us that we are missing as much as 80 percent of the matter; things like galaxies behave like they are five times more massive than what we can detect,” said Blanco. “One of the central problems in particle physics and cosmology is trying to figure out the nature of these missing ingredients in the universe. I studied chemistry as an undergrad and shifted to physics during grad school, but it turns out that this combination of interests allowed me to carve out a niche in this field. Part of the reason I came to Penn State, is that its strengths in materials science make it a playground for folks like me.” Editor's Note: This story is part of a larger feature about artificial intelligence developed for the Winter 2026 issue of the Eberly College of Science Science Journal.

Astrostatistics is the study of how to use astronomical observations, with their associated uncertainties, to constrain models of astrophysics and cosmology. Measurements are made with imperfect instruments and the way in which many objects are observed can be biased by something in their local environment, like dust, that reduces or enhances the emitted signal. Accurately inferring the model from the data requires a careful accounting for all those effects. Visit Penn State's Center for Astrostatistics website to find out more about. [Image Credit: NASA/Ames/JPL-Caltech]

Black holes are regions of spacetime so dense that nothing can escape their gravitational pull - not even light. Researchers at Penn State study black holes theoretically in the context of general relativity and candidate theories for quantum gravity as well as observationally through electromagnetic and gravitational wave surveys.

Cosmic Rays are elementary particles and nuclei, detected on or near the Earth, that originate in energetic processes in the universe. Physicists work to characterize the cosmic ray spectrum: the abundance of different types of particles and their energies. Observations of the primary particles are made in space (e.g., the Alpha Magnetic Spectrometer, AMS, on the International Space Station) and with high-altitude balloons (e.g., the High Energy Light Isotope eXperiment, HELIX). When cosmic rays interact with the Earth's atmosphere, they generate showers of other particles, called secondary cosmic rays, that are detected by instruments on the ground (e.g., the Pierre Auger surface water tanks and fluorescence detectors), and under the ground (e.g., the AMIGA, Auger Muons and Infill for the Ground Array extension for Pierre Auger). Cosmic ray data is used to constrain models for sources that can produce high-energy particles, either extremely energetic astrophysical environments like those around Active Galactic Nuclei (AGN) or extreme events like gamma ray bursts (GRBs).

Cosmological surveys map out the distribution of matter in the universe. Some surveys may target a particular type of object by looking for a very particular spectral signal. For example, the HETDEX survey is designed to find a class of galaxies, Lyman-$\alpha$ emitters, at a time when the universe was about 10-11 billion years younger than it is today. By precisely measuring how those galaxies are receding from us, HETDEX will provide a new constraint on the expansion rate of the universe and the role of dark energy in the past. Other surveys collect light across a wider range of frequencies. For example, the Rubin Observatory Legacy Survey of Space and Time (LSST) will take optical images of a large fraction of the sky, nearly every night. LSST will detect nearly 4 billion galaxies that can be measured so precisely that distortions in galaxy shapes due to gravity can be used, statistically, to map out how both dark and luminous matter are distributed in the Universe. Because LSST will image the same part of the sky so often, it will also capture the variations of light emitted by objects that are changing rapidly, allowing studies of the dynamic universe.

Matter can be detected by its gravitational pull. Many different observations together indicate that about 84% of the gravitating matter in the universe emits no detectable photons. This is the dark matter, and the quest to understand what it is drives the work of large communities in cosmology and particle physics. Experiments like the Large Underground Xenon experiment, LUX, are designed to search for possible interactions between dark matter particles and the particles of the Standard Model. Surveys like the Rubin Observatory Legacy Survey of Space and Time, LSST, will carefully map out the distribution of dark matter, probing for signs that some particle physics interactions was at work along with gravity and affected the evolution of structure. Gravitational wave observations may also reveal something about the nature of dark matter if, for example, the population of detected black holes is inconsistent with the expected astrophysical population.

Many dynamic phenomena in the universe occur over a period of seconds to years. Events with quickly evolving signals include the explosions of Type 1a supernovae, the destruction of stars passing too close to a black hole, and the merger of neutron stars. Some transient phenomena, like Type Ia supernovae, release light in such a reliable way that they can be used as standard reference events to study the evolution of the universe. Other events provide information about matter in extreme environments and at very high energies. These phenomena may be observed not just through their electromagnetic emission, but also through the generation of particles or gravitational waves. For example, a merger of two neutron stars first detected as a gravitational wave event, GW170817, was subsequently observed across the electromagnetic spectrum. Fluctuations in the energetic matter streaming out from the vicinity of a black hole in the center of a galaxy, the flaring blazar TXS 0506+056, produced both neutrinos detected by IceCube and high-energy gamma rays. Several new instruments promise to bring an explosion of data for the study of transient phenomena in the universe. [Image Credit: Illustration: CXC/M. Weiss; X-ray: NASA/CXC/UNH/D. Lin et al, Optical: CFHT. ]

Gravitational waves are tiny ripples in space created by accelerating masses such as the orbit of neutron stars and black holes. As a gravitational wave passes through space it changes the distance between two points. Researchers at Penn State study gravitational waves theoretically as well as observationally through the LIGO and Virgo observatories.

Loop Quantum Gravity is a theory of quantum gravity based on a geometric formulation that predict discrete geometrical phenomena above some minimum length scale (the Planck length).

Physics often advances when crisp mathematical structures are uncovered in a framework developed to describe observed phenomena. For example, in quantum field theory there is a vast discrepancy between the current calculational difficulty in making predictions for experiments and the simple, mathematical form of the end result. The Amplitudes program seeks to explain and exploit this surprising simplicity by reformulating the basic mathematical tools used to make predictions.

Many astrophysical phenomena release not just light (electromagnetic radiation), but also gravitational waves and/or elementary particles including neutrinos and cosmic rays. Each of those signals carries different information about the physics of the source, so collecting more than one enables us to have a deeper understanding of the event that produced them. However, it is an enormous challenge for different types of instruments to coordinate simultaneous observations, and to verify that signals have a common source. Projects like AMON and SciMMA help alert the community to potential multi-messenger events so that an observing program can be coordinated as quickly and efficiently as possible.

Neutrinos are light, electrically-neutral elementary particles that make up the least-understood part of the Standard Model of particle physics. Facilities like DUNE (the Deep Underground Neutrino Experiment) study neutrinos produced in the Fermilab collider as well as neutrinos arriving from cosmic events. Project 8 will measure neutrino mass by looking at neutrinos emitted when tritium decays. The CMB Stage 4 telescopes will use cosmological data to constrain the number of neutrinos and their mass. Many other neutrino facilities focus on detecting neutrinos produced in astrophysical processes, including ANITA, ARA, BEACON, GRAND, IceCube, PUEO, and RNO-G. These cosmic neutrinos can carry key information, along with electromagnetic radiation and gravitational waves, in "multi-messenger" detections of dynamic events in the universe.

Physical mathematics is concerned with mathematics motivated by physics. Prime example of physical mathematics is the pioneering work of Eugene Wigner on the unitary representations of Poincare group which was motivated by his results proving that symmetries of quantum systems must be realized unitarily on their Hilbert spaces. His work opened up the huge field studying the unitary duals of noncompact Lie groups which is still an unfinished chapter of mathematics. In a similar vein, the discovery of supersymmetry by physicists led to the development of the theory of unitary representations of Lie superalgebras. Remarkably, though algebraically more complicated the theory of unitary representations of noncompact Lie superalgebras turned out to be simpler than those of noncompact Lie groups. Furthermore, some of the earliest results on AdS/CFT dualities were obtained, in a true Wignerian sense, within the framework of work on fitting the spectra of Kaluza-Klein supergravities into unitary supermultiplets of their underlying supersymmetry algebras.

All physical systems obey the laws of quantum mechanics, but we have not yet achieved a full understanding of the relationship between quantum mechanics, general relativity, and cosmology. The primordial universe and black holes are two arenas to study these questions in ways that are complementary to research on laboratory quantum systems and quantum information.

Accreting supermassive black holes at the centers of galaxies

The strong force out-competes the electromagnetic force on short distances to hold protons together in atomic nuclei. Nuclear matter can be studied in particle colliders and astrophysical objects like neutron stars. The quantum effects of particles that feel the strong force are important for many measurements in particle physics, including the recently measured anomalous magnetic moment of the muon. Many theoretical predictions of the effects of the strong force rely on the numerically-intensive work that requires supercomputers.