# Nuclear and Particle Theory Seminar

**Mondays, **1**:00pm**

MIT Center for Theoretical Physics**Organizers:** Johannes Michel, Phiala Shanahan, Tracy Slatyer, Xiaojun Yao

January 31, 2022**Mikhail Ivanov**, IAS**Title:** Love and Naturalness**Abstract:** It has been known for a decade that black holes are the most rigid objects in the universe: their tidal deformations (Love numbers) vanish identically in general relativity in four dimensions. This has represented a naturalness problem in the context of classical worldline effective field theory. In my talk I will present a new symmetry of general relativity (Love symmetry) that resolves this naturalness paradox. I will show that perturbations of rotating black holes enjoy an SL(2,R) symmetry in the suitable defined near zone approximation. This symmetry, while approximate in general, in fact yields exact results about static tidal deformations. This symmetry also implies that generic regular black hole perturbations form infinite-dimensional SL(2,R) representations, and in some special cases these are highest weight representations. It is the structure of these highest weight representations that forces the Love numbers to vanish. All other facts about Love numbers also acquire an elegant explanation in terms of SL(2,R) representation theory.

February 7, 2022

TBA

February 14, 2022

Isabel Garcia Garcia, University of California, Santa Barbara

TBA

February 21, President’s Day Holiday No Seminar

February 28, 2022**Siddharth Mishra-Sharma****Title:** Dark photon oscillations in our inhomogeneous Universe and their imprint on CMB, radio, and 21-cm observations**Abstract:** Kinetically-mixed dark photons can oscillate to Standard Model photons, and vice versa. These oscillations can be resonantly enhanced when the plasma mass of the Standard Model photon, which tracks the cosmic electron number density, matches the dark photon mass. I will present an analytic formalism for computing the effect of dark photon oscillations taking into account inhomogeneities in the plasma mass in our Universe and use this to derive new bounds on ultralight dark photons from spectral distortions of the CMB. I will then discuss how dark photon-to-photon oscillations could imprint themselves on observations of the redshifted 21-cm hydrogen line. Finally, I will motivate a possible connection to the long-standing radio background excess measured by ARCADE and low-frequency radio observations.

March 7, 2022**Clara Murgu**i, CalTech

“DarkUnification: a UV complete theory for asymmetric dark matter”.**Abstract:** Motivated by the observed ratio of dark matter to baryon mass densities, which is around a factor 5, we propose a theory of dark-color unification. In this theory, the dark to visible baryon masses are fixed by the ratio of dark to visible confinement scales, which are determined to be nearby in mass through the unification of the dark and visible gauge theories at a high scale. Together with a mechanism for darko-baryo-genesis, which arises naturally from the grand unification sector, the mass densities of the two sectors must be nearby, explaining the observed mass density of dark matter. We focus on the simplest possible example of such a theory, where Standard Model color SU(3)c is unified with dark color SU(2)D into SU(5) at an intermediate scale of around 10^8 -10^9 GeV. The dark baryon consists of two dark quarks in an isotriplet configuration. There are a range of important cosmological, astrophysical and collider signatures to explore, including dark matter self-interactions, early matter domination from the dark hadrons, gravitational wave signatures from the hidden sector phase transition, contributions to flavor observables, as well as Hidden Valley-like signatures at colliders.

March 14, 2022

**Alessandro Lovato**, ANL

Quantum Monte Carlo calculations of atomic nuclei and infinite neutron matter

Abstract

Understanding how the structure and dynamics of nuclei and infinite nuclear matter emerge from the individual interactions between neutrons and protons is a long-standing goal of nuclear theory. Solving the many-body Schrödinger equation involves non-trivial difficulties due to the non-perturbative nature and spin-isospin dependence of nuclear forces. Quantum Monte Carlo methods tackle this problem using stochastic techniques and accurately model short- and long-range nuclear dynamics. In this talk, I will present our recent calculations of the electroweak responses of atomic nuclei and matrix elements relevant to neutrino-less double-beta decay searches. I will then discuss the equation of state of infinite neutron matter, as obtained from local, chiral interactions that explicitly account for the excitation of the Delta resonance. Finally, I will provide some prospects on using artificial neural networks to compactly represent the wave functions of atomic nuclei and translational-invariant systems.

March 21, 2022 Spring Break (no seminar)

March 28, 2022

**Francesca Cuter**i, University of Frankfurt

Lattice insight into the QCD phase diagram at zero and nonzero (isopin) density

April 4, 2022

**Aditya Pathak**, University of Manchester

“A new paradigm for precision top mass measurement: Weighing the top with energy correlators”

April 11, 2022

**Peter Denton**, BNL

Light Dark Matter and Black Holes

April 18,2022 Patriot’s Day (no seminar)

April 25, 2022

**Nobuo Sato**, JLAB

The Next generation of QCD global analysis

May 2, 2022

**Jamie Karthein**, MIT

“Characterizing the Transition Region of the QCD Phase Diagram.”

May 9, 2022

**Adrien Florio**, Stony Brook

Dynamics of the O(4) critical point in QCD