"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.

``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.

``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.

``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.