Format results
Quantum Field Theory II - Lecture 221130
PIRSA:22110011Statistical Physics - Lecture 221130
PIRSA:22110019QFT2 - Quantum Electrodynamics - Afternoon Lecture
Cliff Burgess McMaster University
Shapes of non-Gaussianity in warm inflation
Mehrdad Mirbabayi Institute for Advanced Study (IAS)
Exactly solvable model for a deconfined quantum critical point in 1D
Carolyn Zhang University of Chicago
TBD
Asu Ozdaglar (MIT) *Presenting VirtuallyInstructions to join the fully virtual workshop session in the academic metaverse: https://immorlica.com/workshop.htm **Recording Notice** Once you enter Gathertown, you consent to being recorded. If do you do not wish to be recorded, you can: Make yourself anonymous Not enter the Gathertown spaceNon-Isometric Quantum Error Correction in Gravity
In the holographic approach to quantum gravity, quantum information theory plays a fundamental role in understanding how semiclassical gravity emerges from the microscopic description. The map (sometimes called the dictionary) between these two descriptions has the structure of a quantum error correcting code. In the context of an evaporating black hole, this code can be arbitrarily far from an isometry. Such codes are novel from a quantum information standpoint, and their properties are not yet well understood. I will describe a simple toy model of an evaporating black hole which allows for an explicit construction of the dictionary using the Euclidean gravity path integral. I will also describe the sense in which this dictionary is a non-isometric code, explain its basic properties, and comment on implications for semiclassical physics in the black hole interior.
Zoom link: https://pitp.zoom.us/j/94869738394?pwd=dGNBWXpmTTZaRSs3c0NQUDA1UkZCZz09
Quantum Field Theory II - Lecture 221130
PIRSA:22110011Statistical Physics - Lecture 221130
PIRSA:22110019Learning through the Grapevine
Suraj Malladi (Cornell)We examine how well someone learns when information from original sources only reaches them after repeated person-to-person noisy relay. We characterize how many independent chains a learner needs to access in order to accurately learn, as these chains grow long. In the presence of random mutation of message content and trans- mission failures, there is a sharp threshold such that a receiver fully learns if they have access to more chains than the threshold number, and learn nothing if they have fewer. Moreover, we show that as the distance to primary sources grows, all learning comes from either the frequency or content of received messages, so learning only from the more informative dimension is equivalent to full Bayesian learning. However, even slight uncertainty over the relative rates of mutations makes learning from long chains impossible, no matter how many distinct sources information trickles down from. This suggests that forces which lengthen chains of communication can severely disrupt social learning, even if they increase the frequency of communication.Social Connectedness and Information Markets
Rachel Kranton (Duke)This paper introduces a simple model of contemporary information markets: Consumers prefer high-quality information, judiciously sharing stories and posts. High-quality stories are costly to produce, and overall quality is endogenous. When suppliers' payoffs derive from how many consumers view their stories, quality is highest when social connectedness is neither too high nor too low. Third-party misinformation can increase high-quality output, since consumers share more judiciously. In highly-connected markets, low-quality stories are widely seen and dominate. However, when suppliers' payoffs derive solely on consumer actions (e.g, votes or purchases) based on their stories and consumers are highly connected, consumers perfectly infer quality and quality is highest.Learning from Viral Content
Kevin He (Penn)(This work is joint with Krishna Dasaratha.) We study learning on social media with an equilibrium model of users interacting with shared news stories. Rational users arrive sequentially and each observes an original story (i.e., a private signal) and a sample of predecessors' stories in a news feed, then decides which stories to share. The observed sample of stories depends on what predecessors share as well as the sampling algorithm, which represents a design choice of the platform. We focus on how much the algorithm relies on virality (how many times a story has been previously shared) when generating news feeds. Showing users more viral stories can increase information aggregation, but it can also generate steady states where most shared stories are wrong. Such misleading steady states self-perpetuate, as users who observe these wrong stories develop wrong beliefs, and thus rationally continue to share them. We find that these bad steady states appear discontinuously, and even a benevolent platform designer either accepts these misleading steady states or induces fragile learning outcomes in the optimal design.QFT2 - Quantum Electrodynamics - Afternoon Lecture
Cliff Burgess McMaster University
This course uses quantum electrodynamics (QED) as a vehicle for covering several more advanced topics within quantum field theory, and so is aimed at graduate students that already have had an introductory course on quantum field theory. Among the topics hoped to be covered are: gauge invariance for massless spin-1 particles from special relativity and quantum mechanics; Ward identities; photon scattering and loops; UV and IR divergences and why they are handled differently; effective theories and the renormalization group; anomalies.
Words to Describe a Black Hole
Ying Lin Harvard University
We revamp the constructive enumeration of 1/16-BPS states in the maximally supersymmetric Yang-Mills in four dimensions, and search for ones that are not of multi-graviton form. A handful of such states are found for gauge group SU(2) at relatively high energies, resolving a decade-old enigma. Along the way, we clarify various subtleties in the literature, and prove a non-renormalization theorem about the exactness of the cohomological enumeration in perturbation theory. We point out a giant-graviton-like feature in our results, and envision that a deep analysis of our data will elucidate the fundamental properties of black hole microstates.
Zoom link: https://pitp.zoom.us/j/96037678536?pwd=eGdhTWF3UVN1em5uZVpJbWYyM2tzUT09
Shapes of non-Gaussianity in warm inflation
Mehrdad Mirbabayi Institute for Advanced Study (IAS)
Sphaleron heating has been recently proposed as a mechanism to realize warm inflation when inflaton is an axion coupled to pure Yang-Mills. As a result of heating, there is a friction coefficient γ\propto T^3 in the equation of motion for the inflaton, and a thermal contribution to cosmological fluctuations. Without the knowledge of the inflaton potential, non-Gaussianity is the most promising way of searching for the signatures of this model. Building on an earlier work by Bastero-Gil, Berera, Moss and Ramos, we compute the scalar three-point correlation function and point out some distinct features in the squeezed and folded limits. As a detection strategy, we show that the combination of the equilateral template and one new template has a large overlap with the shape of non-Gaussianity over the range 0.01 <= γ/Η <= 1000 and in this range 0.7<|f_NL|<50.
Zoom link: https://pitp.zoom.us/j/95921707772?pwd=NUNhU1QrRm5HaDJNMEYyaTJXQmZnQT09
QFT2 - Quantum Electrodynamics - Morning Lecture
This course uses quantum electrodynamics (QED) as a vehicle for covering several more advanced topics within quantum field theory, and so is aimed at graduate students that already have had an introductory course on quantum field theory. Among the topics hoped to be covered are: gauge invariance for massless spin-1 particles from special relativity and quantum mechanics; Ward identities; photon scattering and loops; UV and IR divergences and why they are handled differently; effective theories and the renormalization group; anomalies.
Exactly solvable model for a deconfined quantum critical point in 1D
Carolyn Zhang University of Chicago
We construct an exactly solvable lattice model for a deconfined quantum critical point (DQCP) in (1+1) dimensions. This DQCP occurs in an unusual setting, namely at the edge of a (2+1) dimensional bosonic symmetry protected topological phase (SPT) with ℤ2×ℤ2 symmetry. The DQCP describes a transition between two gapped edges that break different ℤ2 subgroups of the full ℤ2×ℤ2 symmetry. Our construction is based on an exact mapping between the SPT edge theory and a ℤ4 spin chain. This mapping reveals that DQCPs in this system are directly related to ordinary ℤ4 symmetry breaking critical points. Based on arXiv:2206.01222.
Zoom link: https://pitp.zoom.us/j/93794543360?pwd=Y3lidGZhRFNrUjEyMVpaNEgwTnE3QT09