There is currently a (possible) tension between various measurements of the Hubble expansion rate. I will give a recap of this issue, and describe how we use the Cosmic Microwave Background to infer the local expansion rate.

# Events Archive

## Events Archive

### Pheno & Vino Seminar | Jo Dunkley, Princeton University | "How fast is the universe growing?" | Jadwin 303

### HET Seminar - Radu Roiban - Pennsylvania State University

### HET Seminar | Radu Roiban, Penn State | “Perspectives on the Generally-Relativistic Two-Body Problem from Double Copy & EFT”| Bloomberg Lecture Hall

While the flat space two-body problem is integrable, the generally-relativistic one is not starting at the next-to-leading order.

### Gravity Initiative Lunch, Elena Giorgi | PGI, "The Teukolsky equations in Kerr-Newman spacetime"

Abstract:

### Biophysics Seminar: Melike Lakadamyali, UPENN: Super-resolution imaging of chromatin structure and dynamics|Joseph Henry Room

### Gravity Group Lunch Seminar, Andrew Chael | PCTS "The black hole-jet connection in M87: linking simulations to VLBI images"

The Event Horizon Telescope (EHT) has produced the first image of the 1.3 mm-wavelength emission around the black hole "shadow" at the heart of M87.

### Hamilton Colloquium Series, Michal Lipson, Columbia University, "The Revolution of Silicon Photonics" Jadwin A-10

We are now experiencing a revolution in optical technologies, where one can print and control massive optical circuits, on a microelectronic chip. This revolution is enabling a whole range of applications that are in need for scalable optical technologies and it is opening the door to areas that only a decade ago were unimaginable.

### Special Condensed Matter Seminar | Han Yan, OIST, Japan, | "Universal picture of holographic toy models from Rank-2 U(1) theory (or Lifshitz gravity)" | PCTS Seminar Room 407

In this talk, we address two points connecting holographic toy models and fracton states of matter. First, we show that there is a unified picture behind different holographic toy models based on tensor-networks, bit threads, and fracton model: a web of bit threads on a hyperbolic lattice.

### HET Seminar | Edgar Shaghoulian, Cornell | "Integrable deformations in quantum mechanics, T-Tbar, and SYK" | Jadwin A06

The Wilsonian paradigm suggests universality of quantum field theory in the infrared. Interestingly, it also suggests universality of quantum mechanics (d=1 quantum field theory) in the ultraviolet. This suggests a study of the landscape of the infrared and the robustness of the ultraviolet.

### HET Seminar | Adam Levine, IAS | “On a Quantum Penrose Inequality” | Bloomberg Hall Physics Library

**Description:** Suggested reading:

Marc Mars, Present Status of the Penrose Inequality, arXiv:0906.5566

Netta Engelhardt and Gary Horowitz, A Holographic Argument for the Penrose Inequality in AdS, arXiv:1903.00555

Quantum Penrose Inequality, arXiv:1908.02755

### Condensed Matter Seminar | Andrey Chubukov, U of Minnesota "Interplay between superconductivity and non-Fermi liquid above a quantum critical point in a metal" | Joseph Henry Room, Jadwin Hall

I discuss the interplay between non-Fermi liquid behaviour and superconductivity near a quantum-critical point (QCP) in a metal. The tendencies towards superconductivity and non-Fermi liquid behaviour compete: fermionic incoherence destroys the Cooper logarithm, while superconductivity eliminates scattering at low energies and restores...

### Pheno & Vino Seminar | Jack Setford, Toronto | "Signatures of Mirror Stars" | Jadwin 303

Motivated by theories of neutral naturalness, I will argue that Mirror Stars are a generic possibility in any hidden sector with analogues of Standard Model electromagnetism and nuclear physics.

### HET Seminar | Theo Johnson-Freyd, Perimeter Institute | “TMF and SQFT” | Bloomberg Lecture Hall

I will describe my work, all joint with D. Gaiotto and some also joint with E. Witten, to understand the homotopy type of the space of (1+1)d N=(0,1) SQFTs --- what a condensed matter theorist would call "phases" of SQFTs. Our motivating hypothesis (due in large part to Stolz and Teichner) is that this space models the spectrum called "...

### Gravity Initiative Lunch, Baoyi Chen | Caltech "Probing near-horizon physics via gravitational wave echoes"

Abstract: Because of the Black-Hole Information Paradox, and the singularity, many physicists believed that GR must be modified to incorporate quantum effects, and that such modifications may affect black-hole spacetimes. The additional near-horizon structure might modify the boundary conditions for incoming gravitational waves, and lead to...

### Biophysics Seminar: Marija Zanic, Vanderbilt University: Dynamic Architecture of the Microtubule Cytoskeleton| Joseph Henry Room

Microtubules are active biological polymers known to stochastically switch between phases of growth and shrinkage, a behavior termed ‘dynamic instability’. Microtubule treadmilling, in which the microtubule plus end grows while the minus end shrinks, is also observed in cells.

### HET Seminar | Si Li, IAS; Tsinghua University | “Deforming Holomorphic Chern-Simons at Large N” | Bloomberg Lecture Hall

We describe the coupling of holomorphic Chern-Simons theory at large N with Kodaira-Spencer gravity. This gives a complete description of open-closed string field theory in the topological B-model. We explain an anomaly cancellation mechanism at all loops in perturbation theory in this model.

### Gravity Group Seminar, Rachael Beaton | Princeton

Following up on Adam Riess's talk last month, **Rachael Beaton**, a Hubble and Carnegie-Princeton postdoctoral fellow in Astrophysical Sciences, will present the latest results from the Carnegie-Chicago Hubble program, published last summer, that provide for a determination of the...

### Hamilton Colloquium Series, Michelle Simmons, University of New South Wales, Australia, "Atomic Qubits in Silicon"

Building a quantum computer in the highly manufacturable material silicon offers many advantages. Phosphorus atom qubits in silicon in particular have demonstrated extremely long (up to 35 s) coherence times with >99.9% fidelity.

### Math Physics Seminar | Paul Bourgade, NYU | "Branching processes in random matrix theory and analytic number theory" | Jadwin A06

Fyodorov, Hiary and Keating have conjectured that the maximum of the characteristic polynomial of random matrices behaves like extremes of log-correlated Gaussian fields. This allowed them to predict the size of local maxima of L-function along the critical axis.

### Pheno & Vino Seminar | Jessie Shelton, U of Ilinois | "Dark Thermal Histories" | Jadwin 303

One generic scenario for the dark matter of our universe is that it resides in a hidden sector: it talks to other dark fields more strongly than it talks to the Standard Model. I'll discuss some minimal cosmological origin scenarios for this class of models and explore their consequences for the observability of dark states today. Some...