Seminars take place on Wednesdays 12:00-1:00pm in Randall Laboratory #3481
Organizer: Bibhushan Shakya, Uri Kol
Seyda Ipek (Fermilab): "Baryogenesis and Particle--Antiparticle Oscillations" | Jan 13
Our Universe has more matter than antimatter and we cannot explain this asymmetry within the Standard Model. CP violation is crucial to explain the baryon asymmetry of the Universe. We observe the CP violation in the SM in neutral meson oscillations. Can similar (bur beyond the SM) particle--antiparticle oscillations in the early Universe generate the baryon asymmetry? I will show "Yes, they can" and give a specific new physics model as an example.
Joshua Qualls (National Taiwan University): "Exploring spectral bounds from modular invariance" | Jan 20
In contrast with the usual techniques in higher-dimensional CFTs using crossing symmetry of correlators, we focus in this talk on a complementary technique in two dimensions known as the "modular bootstrap"--constraints following from imposing modular invariance of the partition function on the torus. After presenting recent results, we discuss intriguing results from work in progress using toroidal compactification to generate CFTs in order to probe these constraints.
Matthew Dodelson (Stanford): "Drama from Strings" | Feb 3
I will discuss both published and upcoming work by Silverstein and myself on violations of the equivalence principle (or "drama") near black hole horizons in string theory. In particular, we are interested in the longitudinal spreading effect first derived by Susskind. I will review the heuristic derivation of this effect, and then explain how to extract the longitudinal spreading scale from a gauge-invariant six point function in flat spacetime. I will then describe the implications of this effect on the infalling observer and Hawking quanta, and speculate on applications to the information paradox and AdS/CFT.
Mario Martone (Cincinnati): "Expanding the landscape of N=2 Super-conformal field theories" | Feb 17
In this talk I will argue that a systematic classification of 4d N=2 conformal field theories is possible through a careful analysis of the geometry of their Coulomb branches. I will carefully describe this general framework and then carry out the classification explicitly in the rank-1, that is one complex dimensional Coulomb branch, case. We find that the landscape of rank-1 theories is still largely unexplored and make a strong case for the existence of 8 (or up to 12) rank-1 SCFTs in addition to the 11 already known in the literature. De facto doubling the number of known rank-1 N=2 SCFTs. 4 of the 8 have been recently constructed using alternative methods and 3 of them have an intriguing enlarged, N=3, supersymmetry. Finally I will outline how to generalize our construction to higher rank, in particular to the rank-2 case.
Flip Tanedo (UCI): "Dark Photons from the Center of the Earth" | Feb 24
I present a search for dark matter annihilation into dark photons at the center of the Earth, focusing on the present and future reach of IceCube and space-based telescopes. I highlight the effect of low-velocity enhancements to dark matter capture and kinematic features that offer an opportunity for a smoking-gun signal. I also present prospects for an analogous search for dark photons from the center of the sun which may be detected by AMS-02, extending earlier work by modeling the effect of the solar wind.
Chris White (University of Glasgow): "A panoramic view of infrared singularities" | Mar 9
The study of infrared singularities, due to the emission of “soft” (low momentum) gauge bosons, remains a highly active research area in a variety of quantum field theories. After motivating both phenomenological and formal reasons as to why we should care about IR singularities, this talk will review their structure in QED, QCD and quantum gravity, examining the similarities and differences between these three contexts. Finally, I will examine recent work on moving beyond the soft approximation, and why this might be useful.
Yonatan Kahn (Princeton): "A Broadband Approach to Axion Dark Matter Detection" | Mar 23
When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current which follows the magnetic field lines and oscillates at the axion Compton frequency. I will describe a new experiment to detect this axion effective current which, unlike most existing proposals, does not rely on a resonant enhancement of the signal. This broadband approach has advantages at low axion mass, can probe many decades of axion mass simultaneously, and potentially has sensitivity to GUT-scale QCD axions.
Eliot Hijano (UCLA): "Witten diagrams and the geometry of conformal blocks" | Mar 30
The conformal block decomposition of conformal field theory (CFT) correlation functions has recently received renewed attention both due to its central role in the revival of the conformal bootstrap program, and also as a useful way to understand how local physics can emerge in the bulk in examples of AdS/CFT duality. In this talk I will discuss the relation between conformal blocks and anti-de Sitter gravity (AdS) through the AdS/CFT correspondence.
I will describe a new method for decomposing semi-classical gravity Feynman diagrams in AdS (Witten diagrams) intoconformal blocks. Central to this construction is an appealingly simple answer to the question: what object in AdS computes a conformal block? The answer is dubbed a "geodesic Witten diagram," and it provides an intuitive geometric bulk description of a conformal block. I will also present a unified framework for the holographic computation of Virasoroconformal blocks at large central charge.
Yuhsin Tsai (Maryland): "Exotic Signals in The Twin Higgs Model" | Apr 6
Twin Higgs (TH) model gives a naturalness motivation to study the non-SM colored BSM particles, which usually have decay processes relating to the dark-hadronization and displaced signal. In this talk, I will use two examples to discuss these two distinct phenomenology in both collider and astrophysical experiments. In the collider, the exotic twin-quarks, which play a vital role in UV-completing the TH model, can be produced and decay into both the SM and Twin particles. The striking signal allows the reach of twin UV-physics at the LHC and future colliders. For the astrophysical story, I will discuss the Hadrosymmetric TH model. This model provides a WIMP-like DM scenario and dark showers, which can generate the possible galactic center gamma ray excess seen by Fermi-LAT. In order for the twin hadrons to decay before BBN, an additional portal between the SM and twin sector is required, which is within the reach of the LHC or future intensity frontier experiments.
Aitor Lewkowycz (Princeton): "Modular hamiltonians and relative entropies for holographic states" | Apr 13
In this talk, we will use the holographic entanglement entropy formulas to derive a simple expression for the modular hamiltonian in bulk perturbation theory, for an arbitrary state and subregion. This remarkably simple expression has interesting properties such as the equality of bulk and boundary modular flow and relative entropy, to leading order in the gravitational coupling. We will also comment on possible applications of this formula to entanglement wedge reconstruction.
