Prof. Dr. Ralf S. Klessen, Universität Heidelberg

The First Stars: Formation, Properties, and Impact

The first generation of stars, often called Population III (or Pop III), form from metal-free primordial gas at redshifts z ~ 30 and below. They dominate the cosmic star formation history until z ~ 20-15, at which point the formation of metal-enriched Pop II stars takes over. I review current theoretical models for the formation, properties and impact of Pop III stars, and discuss observational constraints. I argue that primordial gas is highly susceptible to fragmentation and Pop III stars form as members of small clusters with a logarithmically flat mass function. Feedback from massive Pop III stars plays a central role in regulating subsequent star formation, but major uncertainties remain regarding its immediate impact. Direct observations of Pop III stars in the early Universe remain extremely challenging, whereas stellar archeological surveys allow us to constrain both the low-mass and the high-mass ends of the Pop III mass distribution. Observations suggest that most massive Pop III stars end their lives as core-collapse supernovae rather than as pair-instability supernovae. I also speculate about the formation of supermassive stars, which under very specific circumstances can get as massive as several 100.000 solar masses and can become the seeds of the supermassive black holes observed in the high-redshift universe.

Dr. Maxim Pospelov, University of Minnesota

Dark Matter snooker

Despite enormous experimental investment in searches of particle dark matter, certain well-motivated corners of parameter space remain to be elusive “blind spots” for direct detection. In my talk I will address two of such exceptions: light particles that simply do not have enough kinetic energy to detect, and strongly-interacting particles that quickly thermalize and also become sub-threshold for direct detection. I show that both blind spots can be probed through double collisions of Dark matter – first with some energetic Standard model particles (solar electrons, cosmic rays, particles in a beam, neutrons in nuclear reactors etc) that bring DM to energies above thresholds followed by the scattering inside a detector. This way, I derive novel constraints on light dark matter, as well as strongly-interacting dark matter models, using existing dark matter and neutrino experiments. 

Dr. Maxim Pospelov, University of Minnesota

New developments in EDM theory

Over the last 10 years there has been a large progress in experiments testing the coupling of electron spin to electric field. These experiments are often referred to as “electron dipole moment experiments” (or EDMs). In my talk I will show how the Standard Model CP-violation leads to the coupling of electron spin to the electric field, and argue that the most important mechanism is related to the spin interaction with the nucleus. I will finish the talk with some comments on lattice attempts to calculate neutron EDM induced by theta QCD.

Dr. Rebecca Larson, Rochester Institute of Technology

Advancements in Exploring the Early Universe: Unlocking the Mysteries of Galaxies During the Reionization Era

The history of galaxies in the early Universe remains substantially unknown. The mystery surrounding these galaxies is primarily a result of the epoch in which they existed. During the epoch of reionization (z>6), the Universe experienced its last major phase change, where the neutral gas permeating the intergalactic medium [IGM] became ionized. Light emitted from early galaxies was often blocked by this neutral gas (or “cosmic fog”), preventing restframe ultraviolet [UV] spectroscopic studies of this epoch except for faint traces of light detectable in the near-infrared [NIR] from the brightest sources. Before 2022, the high-redshift field was restricted due to limited ground- and space-based instrumentation probing NIR wavelengths and beyond. Much of what we learned spectroscopically about these galaxies during this time came from a handful of bright UV metal emission lines or far-infrared [FIR] emission (generally with only 1-2 lines detected in individual galaxies). These data only came after fighting for hours using the most massive telescopes on the ground and in space. Since the advent of JWST, the high-redshift field has exploded with new science probing wavelengths and redshifts previously inaccessible. Using the advanced spectroscopic NIR capabilities of the JWST, we have found increasingly distant galaxies and characterized these sources within the heart of the epoch of reionization [EoR] for the first time. In this talk, I will discuss the state of the high-redshift field before and after the launch of JWST – highlighting our work from the Cosmic Evolution and Early Release Science [CEERS] survey, among other key early release science [ERS] & Cycle 1-3 programs. These new data have led to the discovery of an unexpected abundance of bright galaxies and active galactic nuclei [AGN] in the EoR, providing insights into the roles that the nature of these early galaxies and the nurturing from their environments played in the reionization of the Universe.

Prof. Felix Ringer, Stony Brook University

From Qubits to Quarks: Quantum Computing Meets Nuclear Physics

The strong force in nature, described by the theory of quantum chromodynamics (QCD), governs the interaction of quarks and gluons, which constitute the main building blocks of the visible universe. Since its development over five decades ago, various fundamental questions have remained unanswered despite significant theoretical and experimental efforts: How do the dynamics of quarks and gluons give rise to emergent structures such as nucleons and nuclei? What is the phase diagram of nuclear matter, and what are the real-time and non-equilibrium dynamics at collider experiments and in the early universe? While significant progress has been made on the theory side using perturbative techniques and lattice QCD, the answers to some of the most challenging questions are expected to be beyond the capabilities of classical computing. Advances in quantum computing coupled with the development of innovative algorithms motivate the exploration of quantum simulations to address these questions. In this talk, I will discuss recent progress toward quantum simulations for fundamental particle and nuclear physics, covering both discrete (qubit) and continuous variable (qumode) approaches.