Speaker: Javi Serra
Title: Weak Gravity Conjecture from Amplitudes’ Positivity
Host: John Terning
Room: 432
Abstract: In this talk I will show how to derive positivity bounds for scattering amplitudes in theories with a massless graviton in the spectrum in four spacetime dimensions. These new bounds imply that extremal black holes are self-repulsive, M/|Q|<1, once higher-dimensional operators beyond Einstein-Maxwell are taken into account, thus providing an S-matrix proof of the weak gravity conjecture. I will also present applications of these bounds to other gravitational theories, and discuss some future directions of investigation.
Description:
Veterans Day
User:
High-Energy Seminars
Time:
1:30pm - 2:30pm
Send Reminder:
Yes - 0 days 4 hour 0 minutes before start
Description:
Speaker:
Title:
Host:
Room: 432
Abstract:
User:
High-Energy Seminars
Time:
3:30pm - 4:30pm
Description:
Speaker: Karol Kampf
Title: Amplitude method studies of effective field theories
Abstract: Description of low-energy interactions of Goldstone particles of
spontaneously broken symmetries is traditionally done using the most
general action based on the underlying symmetry. The explicitly constructed
Lagrangian can be then used for calculating given scattering amplitudes.
However this process is not very efficient as can be demonstrated already
at the tree-level for relatively small number of external particles. The
modern amplitude methods offer different approach where it is possible to
avoid redundancy stemming from the standard Feynman diagram calculations.
The methods represent not only an efficient way of calculating scattering
amplitudes but can be employed in theoretical studies of their interesting
properties. This allowed among other things to classify the effective
models. Generalization beyond the standard vanishing soft limit, so-called
Adler zero, will be discussed.
Host: Da Liu
Room: 432
User:
High-Energy Seminars
Time:
1:30pm - 2:30pm
Send Reminder:
Yes - 0 days 4 hour 0 minutes before start
Description:
Speaker: Ofri Telem
Title: Gauge Anomalies in an Effective Field Theory, the On-Shell Way
Host: Da Liu
Room: 432
Abstract:
In a seminal paper, John Preskill showed how gauge theories in the Higgs phase can couple consistently to anomalous matter content. This formulation is complementary to the traditional approach in which gauge theories with an anomalous fermion content necessitate gauged-WZW terms that cancel the fermion anomaly. The gauge invariant statement that follows is that anomalous theories in the Higgs phase are completely consistent with unitarity, when considered as EFTs.
In this work we shed more light on the consistency of anomalous gauge theories in the Higgs phase, using the recently discovered, on-shell notion of gauge anomalies as tension between locality and unitarity at 1-loop. We demonstrate how this tension is reconciled in the Higgs phase by calculating the 1-loop contribution of massless chiral fermions to the massive 4-vector amplitude. This is the one of the first full 1-loop calculations that combine the method of generalized unitarity with Nima Arkani-Hamed’s massive amplitude formalism.