It has long been known that smooth crossovers between “Higgs” regimes and “confining” regimes are possible in some gauge theories with fundamental representation matter, leading to a notion of Higgs/confinement “complementarity”.  But the validity, or otherwise, of such complementarity can be subtle, especially in massless phases with Goldstone bosons.  This talk will examine the presence or absence of Higgs/confinement phase transitions, when there are no distinguishing local order parameters, in both instructive models and in dense QCD.

Abstract: The Deep Underground Neutrino Experiment (DUNE) will be the leading next-generation particle project in the US.  It aims to measure CP violation in the neutrino sector and determine the mass ordering of neutrinos.  These measurements are straightforward conceptually but challenging practically.  One outstanding issue is the modeling of GeV neutrino-nucleus interaction.  With a lack of a proper theoretical framework, it is not only difficult to simulate neutrino events in the detector accurately but also difficult to assess its impact on the physics measurements.  I will discuss our attempts at understanding how cross-section uncertainties impact oscillation measurements and new physics searches.

String Theory modifies general relativity with Chern-Simons terms.  In this talk we show how this theory naturally encodes a graviaxion dark matter particle, baryogenesis during cosmic inflation, and leaves imprints on gravitational wave signals in compact binary systems.

After introducing the Taylor expansion method for lattice QCD calculations at non-vanishing baryon chemical potential, I will scrutinize the limitations of the method arising from the presence of Yang-Lee edge singularities in the QCD phase diagram. I will discuss a newly introduced resummation scheme for the Taylor expansion to overcome this limitation and show the efficacy of this scheme using a simple solvable model. I will present some results from realistic lattice QCD calculations utilizing this resummation scheme. I will conclude by introducing a generalized version of the scheme that can resum the recently proposed multi-parameter Taylor expansion. 

Scattering amplitudes are the arena where quantum field theory directly meets collider experiments. An excellent model for scattering in QCD is provided by N=4 super-Yang-Mills theory, particularly in the planar limit of a large number of colors, where the theory becomes integrable, and amplitudes become dual to light-like polygonal Wilson-loop expectation values. The first nontrivial case is the 6-gluon amplitude (hexagonal Wilson loop), which can be computed to 7 loops using a bootstrap which is based on the rigidity of the function space of multiple polylogarithms, together with a few other conditions. It is also possible to bootstrap a particular form factor for the chiral stress-tensor operator to produce 3 gluons, through 8 loops. Remarkably, the two sets of results are related by a mysterious “antipodal” duality, which exchanges the role of branch cuts and derivatives. I will describe how the bootstrapping works and what we know about this new duality.

I’ll review a new, simpler explanation for the large scale geometry of spacetime, presented in our recent preprint arXiv:2201.07279. The basic ingredients are elementary and well-known, namely Einstein’s theory of gravity and Hawking’s method of computing gravitational entropy. The new twist is provided by the boundary conditions we proposed for big bang-type singularities, allowing conformal zeros but imposing CPT symmetry and analyticity at the bang. These boundary conditions allow gravitational instantons for universes with positive Lambda, massless radiation and positive or negative space curvature. Using them, we are able to infer the gravitational entropy for a complete set of quasi-realistic, four-dimensional cosmologies. If the total entropy in radiation exceeds that of Einstein’s static universe, the gravitational entropy exceeds the de Sitter entropy. As the total entropy is increased,  the most probable large-scale geometry for the universe becomes increasingly flat, homogeneous and isotropic. I’ll briefly summarize recent progress towards elaborating this picture into a fully predictive cosmological theory.

Electroweak interactions assign a central role to the gauge group 𝑆𝑈(2)𝐿×𝑈(1)𝑌 , which is either realized linearly (SMEFT) or nonlinearly (e.g., HEFT) in the effective theory obtained when new physics above the electroweak scale is integrated out. Although the discovery of the Higgs boson has made SMEFT the default assumption, nonlinear realization remains possible.

I will discuss how the two can be distinguished through their predictions for the size of certain low-energy dimension-6 four-fermion operators. Future measurements can therefore tell us if non-SMEFT new physics is really necessary.

We present a QCD analysis of the effective weak Hamiltonian at hadronic energy scales for strangeness-nonchanging (∆S = 0) hadronic processes. Performing a leading-order renormalization group analysis in QCD from the weak to the O(2 GeV) energy scale, we derive the pertinent effective Hamiltonian for hadronic parity violation, including the effects of both neutral and charged weak currents. We compute the complete renormalization group evolution of all isosectors and the evolution through heavy-flavor thresholds for the first time. We show that the additional four-quark operators that enter below the electroweak scale from QCD operator mixing effects form a closed set, and they result in a 12×12 anomalous dimension matrix. We use the resulting effective Hamiltonian to determine the parity-violating meson-nucleon coupling constants, h^1_π , h^{ 0,1,2}_ ρ , h^{0,1}_ ω , employing the factorization Ansatz and assessments of the pertinent quark charges of the nucleon in lattice QCD at the 2 GeV scale. On this basis, we connect to earlier calculations of low-energy, hadronic parity-violating observables in few-nucleon systems to make theoretical predictions that we compare with recent experimental results, for a global view of the relative importance of the various isosectors. 

The observed baryon asymmetry in the universe cannot be reconciled with the current form of the Standard Model (SM) of particle physics. The amount of CP-violation stemming from the Cabibbo-Kobayashi-Maskawa matrix is not sufficient to explain the observed matter-antimatter asymmetry. Historically, one of the first systems to be studied in the search for CP-violation is the electric dipole moment (EDM) of the neutron. The contribution to the neutron EDM coming from the SM is several order of magnitudes smaller than the current experimental bound, thus providing a unique background-free window for potential discovery of physics Beyond the Standard Model (BSM). Beside all the CP-violating effective operators describing the contributions from BSM, the neutron EDM can potentially be induced by the strong CP-violating theta term.

After a brief summary of the current status for experimental searches of a neutron EDM, I describe the different CP-violating sources and the challenges of a lattice QCD calculation of the corresponding hadronic matrix elements. I then proceed detailing recent results obtained, with my collaborators, on the neutron EDM with a specific focus on the the main theoretical and numerical tool used: the gradient flow. I conclude with near-term goals, challenges and an optimistic view into the future.

Stars have the potential to be excellent dark matter detectors; dark matter could heat them up, destroy them by forming black holes, or modify heat transport. To predict when and how this might happen, we need to compute the scattering rate of dark matter inside stars. In this talk, I will describe how, for a wide range of dark matter models, this requires taking into account collective effects - that is, coherent scattering with many particles inside the star. These effects have been neglected in many previous treatments; I will show how they can enhance or suppress naive predictions for dark matter scattering rates by orders of magnitude. Calculations can be performed systematically by computing in-medium effective propagators, using the apparatus of thermal field theory.