``Shocking tales of structure formation: Evolving galaxies and black holes in evolving environments''

Abstract: Understanding the interplay between galaxy evolution, star formation, and black hole activity from the perspective of structure formation remains one of the most fascinating challenges in modern astrophysics. On the largest scales, pairs of galaxy clusters colliding drive the growth of structure. Cluster mergers are the most energetic events since the Big Bang, which release 10^64 ergs over 1-2 billion years and produce dramatic, long-lasting effects. By bringing together panchromatic observations, I will discuss how the merger of galaxy clusters can trigger star formation and black hole activity in cluster galaxies, shape the evolution of cluster galaxies, and reverse typical environmental trends observed in relaxed clusters at low redshift. With approximately half the galaxy clusters in the local Universe undergoing mergers, this recent work has revealed gaps in our understanding of the growth of structure in the Universe and showed the potential for discovery in this understudied field. I will draw parallels between the fundamental drivers of galaxy and black hole evolution in low-redshift clusters and the processes relevant in the context of proto-clusters and high-redshift clusters, where mergers and associated non-thermal phenomena were far more common than in the nearby Universe. I will conclude by discussing how the treasure trove of cluster samples at increasingly large redshifts delivered by a new generation of instruments will help guide discoveries in the field of gas, galaxy, and black hole evolution at the epoch when structures first formed.

``Quantum Field Theory, Separation of Scales, and Beyond''

 We will review the role of Quantum Field Theory (QFT) in modern physics.  We will highlight how QFT uses a reductionist perspective as a powerful quantitative tool relating phenomena at different length and energy scales.  We will then discuss various examples motivated by string theory and lattice models that challenge this separation of scales and seem outside the standard framework of QFT.  These lattice models include theories of fractons and other exotic systems.

``Codes, CFTs, and ensemble holography''

Holographic correspondence is a duality between gravity in (d+1)-dimensional curved AdS space and non-gravitational d-dimensional QFT “living” on the boundary. More recently a substantial evidence emerged that perhaps a more fundamental version of holographic duality would be between gravity in (d+1)-dimensions and a boundary ensemble of many QFTs. Details and microscopic picture behind this duality is still largely unclear. I will show that ensemble duality emerges naturally in the context of the relation between classical and quantum codes and conformal field theories in 2d. This relation was identified back in the 90s and revised recently, leading to surprising connections with higher form symmetries and quantum information. The emerging picture is that boundary CFTs are labeled by quantum codes, such that the statement of holographic duality becomes a quantum information theoretic identity between different families of stabilizer states.   

``Pulsars as Laboratories for Fundamental Physics"

Pulsars — rapidly rotating neutron stars emitting regular electromagnetic pulses — are pivotal in astrophysical tests of fundamental physics. Their pulse timing precision allows the detection of subtle disturbances from gravitational waves, while their extreme density offers unique insights into theories beyond the Standard Model, especially those predicting baryon number violation (BNV).  Stringent constraints on BNV, arising from its non-observation in experiments, motivate the search for its astrophysical consequences. This talk examines how slow BNV processes, leading to quasi-equilibrium evolution, influence pulsar orbital and spin dynamics. Observations of binary pulsar orbital periods, coupled with the effects of dense matter in neutron star cores, can place severe constraints on BNV. We propose that BNV in pulsars could manifest as anomalies in the second derivative of the spin frequency, transitions between states of spinning down and up, and a spectrum of braking indices. The talk concludes by exploring the potential for detecting these effects, particularly in the context of advancements in pulsar timing arrays and the broader implications for our understanding of fundamental physics.

``Pulsed, Polarized and Sliced – Fundamental Ingredients in Neutron Precision Physics"

The neutron represents a versatile tool in the realm of fundamental particle physics at low energies. In my research group, we focus on the development of novel precision devices and experiments with the goal to search for signals of new physics beyond the standard model of particle physics. In this seminar, I will introduce a few such activities currently pursued at the University of Bern and carried out at national and international neutron research centers. The projects comprise the hunt for a neutron electric dipole moment using a pulsed beam, the search for axion-like particles, and the development of a high-sensitivity grating interferometer to measure the neutron electric charge.

``Opening up the Gravitational Wave Spectrum''

The historic discovery of gravitational waves by LIGO has initiated a new era of astronomy, permitting us to observe the universe through new eyes. LIGO is sensitive to gravitational waves at frequencies above 40 Hz. Much like the case of electromagnetism, there is a strong science case to observationally probe other parts of the gravitational wave spectrum. Significant advances on this front have been made in the mHz band by the LISA collaboration and the nHz range by the NanoGRAV collaboration. How might be probe other gravitational wave frequencies? In this talk, I will discuss the use of atom interferometers to probe gravitational waves in the 1 Hz band. I will also explore the potential use of asteroids as test masses to detect gravitational waves at micro Hz frequencies and the possible use of astrometry in the nHz - micro Hz regime.  

``Experimental Study of the Time Reversal Invariance in Polarized Epithermal Neutron Optics (J-PARC E99 : NOPTREX)''

The visibility of parity violating effects in nuclear interactions is extremely enhanced in the resonant neutron absorption via compound nuclear states for some of medium-heavy nuclei. The enhancement is explained as a result of the interference between parity-unfavored partial amplitudes of the compound nuclear process, which is referred to as "s-p mixing". The "s-p mixing" is expected to enhance the visibility of the effect of the breaking of both parity and time-reversal symmetry (P-odd T-odd).
Based on these consideration, an experimental approach to search for the P-odd T-odd effects to activate a novel type of new physics search beyond the standard model is in progress using the pulsed neutron beam from the pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) under the collaboration "Neutron Optical Parity and Time-Reversal EXperiment (NOPTREX)" as the program number J-PARC P99. P-odd T-odd effects will be studied in neutron optics in which fake T-violating effects can be controlled, with the enhanced sensitivity biased to chromo-EDM. We discuss the studies of the "s-p mixing" in 139La(n,gamma)140La and the plan of T-violation search with polarized lanthanum target.
(We also introduce other neutron fundamental physics on-going at the J-PARC.)

``Electroweak interactions of nuclei''

Abstract: Electroweak interactions provide us with wonderful opportunities and challenges in nuclear physics, and this colloquium focuses on three recent advances regarding the modeling, computation, and understanding of such processes. (i) The neutron distribution of atomic nuclei can be probed via elastic neutrino scattering and via parity-violating electron scattering. Such experiments test virtual Z-boson exchange at very low momentum transfers and the inferred size of the neutron distribution (when compared with easy-to-measure charge distribution) constrains the nuclear equation of state, linking nuclei to neutron stars. (ii) Beta decays of nuclei happen at slower rates than what is expected from the beta decay of the free neutron. Ab initio computations of such processes show that this “quenching” of beta-decay rates is due to two-body currents and correlations, i.e. interaction effects between the decaying neutron and nearby nucleons. (iii) Neutrino-less double beta decay is probed world wide in experiments that search for physics beyond the standard model. If observed, a nuclear matrix element connects the lifetime of this decay with the neutrino-mass scale. The colloquium presents the challenges and advances in computations of this matrix element. 

``The Electron-Ion Collider : The Next QCD Frontier''

The Electron-Ion Collider (EIC) is a pioneering new particle accelerator that will be built on the current site of the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. It will provide high energy collisions of polarized electrons with polarized protons and ions, allowing for experiments that probe the nature of strong interactions to unprecedented precision. The EIC Project has grown and evolved rapidly since the official launch by the U.S. Department of Energy in 2020. This talk will discuss the primary physics themes driving the EIC effort, the recent milestones achieved by the project and the efforts to establish two complementary detectors at adjacent interaction regions. 

Dr. Kyle Leach

Associate Professor

Department of Physics

Colorado School of Mines

Host: Korsch

Title: Hunting for Ghosts using Rare-Isotope Doped Superconducting and Optomechanical Sensors

Abstract: Nuclear beta and electron capture (EC) decay serve as sensitive probes of the structure and symmetries at the microscopic scale of our Universe. As such, precision measurements of the final-state products in these processes can be used as powerful laboratories to search for new physics from the meV to TeV scale. Significant advances in “rare isotope” availability and quality, coupled with decades of sensing technique development from the AMO community have led us into a new era of fundamental tests of nature using unstable nuclei. For the past few years, we have taken the approach of embedding radioisotopes in thin-film superconducting tunnel junctions (STJs) to precisely measure the recoiling atom that gets an eV-scale “kick” from the neutrino following EC decay. These recoils are encoded with the fundamental quantum information of the neutrino and decay process, as well as carrying unique signatures of weakly coupled beyond standard model (BSM) physics; including neutrino mass, exotic weak currents, and potential “dark” particles created within the energy-window of the decay. These measurements provide a complimentary and (crucially) model-independent portal to the dark sector with sensitivities that push towards synergy between laboratory and cosmological probes. In this talk, I will discuss the broad program we have developed to provide leading limits in these areas as well as the technological advances across several sub-disciplines of science required to enable this work, including subatomic physics, quantum engineering, atomic theory, and materials science. Finally, I will discuss future prospects of extending this work using macroscopic amounts of harvested exotic atoms from the Facility for Rare Isotope Beams (FRIB) in optically levitated nanospheres for direct momentum measurements of the decay recoils.