NYU Arts & Science
High Energy Physics Seminars
January 24, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Thomas Bachlechner
Columbia

Tunneling in Semi-Classical Gravity

In this seminar I will carefully discuss the solution of the following problem in semi-classical quantum gravity. Consider an object of small mass in a locally Schwarzschild-de Sitter spacetime (Hubble parameter H_A). The object is located in an apparatus that forms a bubble of Hubble parameter H_B, separated via a thin domain wall from the original spacetime. Classically, this domain wall will expand to a finite size and eventually re-collapse. Quantum mechanically, the domain wall can tunnel through a forbidden region and expand indefinitely, leaving the object in a de Sitter region of Hubble parameter H_B, while the apparatus remains unaffected during the quantum transition. The Hamiltonian of a gravitational theory vanishes. I will discuss the quasi-local energy and how it relates to the boundary conditions. I evaluate the probability for tunneling to occur, both for H_A larger and smaller than H_B. The probability can increases with increasing Hubble scale within the bubble. I discuss this naive contradiction with entropy arguments, which would suggest that transitions to a higher entropy (smaller Hubble scale) are favored.


January 31, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Marcus Spradlin
IAS

TBA



February 1, 2018 Thursday 12:30 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Tanguy Pierog
Karlsruhe Inst. of Technology

LHC and Cosmic Rays : the Chicken or the Egg ?

In recent years the interpretation of high energy cosmic ray measurements took another direction. From the astrophysical point of view, it was usually assumed that extra-galactic charged cosmic rays were protons, but mass composition results from the Pierre Auger Observatory, in particular using hadronic interaction models updated with LHC data, point to a mixed composition at energies well above the ankle of the spectrum. Realistic air shower simulation and hadronic interaction models are the key points for a proper interpretation of charged cosmic ray data, and data measured at the LHC are a fundamental ingredient for these models. On the other hand, hadronic models used for cosmic ray analysis have a better predictive power than traditional high energy physics monte-carlo for minimum bias analysis at the LHC. After a first part dedicated to the post-LHC hadronic interaction models and their comparison to LHC data, the latest results from Pierre Auger Observatory will be presented with a focus given on mass composition and constrains on hadronic interactions ... leading to better models to describe LHC data.


February 7, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Surjeet Rajendran
Berkeley

TBA



February 14, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Clay Cordova
IAS

TBA



February 21, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Xi Yin
Harvard U.

TBA



February 28, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Nima Arkani-Hamed
IAS

Marble Statues in the Forest Beyond Quantum Mechanics and Spacetime

I will give an overview of 5 (clearly connected) appearances of ``positive geometries" in physics: (1) the amplituhedron and N=4 SYM, (2) the associahedron and general massless theories in D dimensions, (3) cosmological polytopes, and work-in-progress on (4) the positive geometry of effective field theory (a big generalization of ``positive signs" for operators--where higher dimension operator coefficients are seen to be constrained to live inside "UV/IR polytopes"), and (5) the positive geometry of conformal field theory (which underlies the bootstrap).


March 7, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Anastasia Volovich
Brown U.

TBA



May 9, 2018 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Matthew Lippert
Long Island University

TBA